112 entries, last updated 18-Oct-2000
plain text bibtex file with keywords and annotations:
biped.bib
@ARTICLE{AdolphK95,
AUTHOR = {K. E. Adolph},
TITLE = {Psychophysical Assessment of Toddlers Ability To
Cope With Slopes},
JOURNAL = {Journal of Experimental Psychology-Human Perception
and Performance},
VOLUME = {21},
NUMBER = {4},
PAGES = {734--750},
YEAR = {1995},
ABSTRACT = {This research examined how infants in early stages
of walking determine whether a hill is safe or risky
for locomotion. A psychophysical staircase procedure
provided estimates of infants' physical ability to
walk up and down slopes (2-degrees to 36-degrees),
and a 'go ratio' indexed the accuracy of their
perceptual judgments. On average, perceptual
judgments were scaled to walking ability on
slopes. Children walked on safe slopes and balked on
risky ones. For ascent, perceptual judgments were
related to length of walking experience and walking
skill on flat ground. Better walkers were also
better perceivers. For descent, judgments neatly
mirrored exploratory activity. Better perceivers
explored hills more efficiently by hesitating,
touching, and testing different positions on hills
around the limits of their physical ability.},
ANNOTE = {The main points of this paper are summarized nicely
in the abstract. Infants tend to charge at uphill
slopes and 'learn by doing' whereas they use
perceptual cues to gauge the affordances of downhill
slopes (learn by exploration). Sometimes exploration
confirmed that the slope was safe to walk; other
times exploration resulted in an alternative
strategy (e.g., crawling, sliding). The go-ratio
(one minus the fraction of trials where the child
refused to make an attempt) shows that on slopes
shallower than the walking boundary, children almost
always make an attempt, but as the slope increases
beyond the empirically defined boundary, attemps
drop off rapidly to zero at the steepest slopes.},
KEYWORDS = {child locomotion, development}
}
@ARTICLE{AdolphK97,
AUTHOR = {K. E. Adolph},
YEAR = 1997,
TITLE = {Learning in the development of infant locomotion},
JOURNAL = {Monographs of The Society For Research in Child Development},
VOLUME = 62,
NUMBER = 3,
ANNOTE = {KeyWords Plus: 1ST 6 MONTHS, OPTICAL-FLOW, MOTOR DEVELOPMENT,
YOUNG WALKERS, ORIENTATION DISCRIMINATION, INTERLIMB COORDINATION,
AUTONOMOUS WALKING, POSTURAL RESPONSES, SCALED INFORMATION, OBJECT
PROPERTIES}
}
@ARTICLE{AdolphK98,
AUTHOR = {K. E. Adolph and M. A. Eppler},
YEAR = 1998,
TITLE = {Development of visually guided locomotion},
JOURNAL = {Ecological Psychology},
VOLUME = 10,
NUMBER = {(3-4)},
PAGES = {303--321},
ABSTRACT = {This article presents a developmental account of changes in the
visual guidance of locomotion. In contrast to the impressive
efficiency of adult locomotion, locomotor activity is not under
prospective control at the onset of human mobility. Infants
require extensive crawling and walking experience before
responding adaptively to variations in the terrain. At the same
time that they are learning to navigate in increasingly varied
environments, their bodies and skills are rapidly changing.
Learning generalizes from safe, flat ground to novel surfaces but
it does not transfer to new methods of locomotion. We account for
these patterns of generality and specificity of learning by
focusing on the role of exploratory behavior in detecting threats
to balance control.},
KEYWORDS = {child locomotion, development}
}
@ARTICLE{AssaianteC93,
AUTHOR = {C. Assaiante and B. Amblard},
YEAR = 1993,
TITLE = {Ontogenesis of Head Stabilization In Space During Locomotion In
Children: Influence of Visual Cues},
JOURNAL = {Experimental Brain Research},
VOLUME = 93,
NUMBER = 3,
PAGES = {499--515},
ABSTRACT = {The main purpose of this study was to investigate the
development of the head stabilization in space strategy (HSSS)
during various locomotor tasks in 3- to 8-year-old children and
adults. The contribution of visual factors to the HSSS was also
examined by applying peripheral visual restriction, stroboscopic
visual motion cue restriction, and darkness. The kinematics of
the head and trunk rotations (pitch, yaw, and roll) were analyzed
by means of an optical TV-image processor (ELITE system). For
each of the three angular components, an appropriate ''head
anchoring index'' was defined in order to compare the HSSS with a
head stabilization on the trunk strategy. Head-trunk correlation
rates were also calculated for each angular component in order to
evaluate the head-trunk stiffness. The development of head-trunk
coordinations during locomotion under normal vision can be said
to involve at least three main periods. The first period occurs
from the age of 3 to 6 years, when the HSSS is adopted only while
walking on the flat ground. While walking on narrow supports,
children in this age-group rather tend to increase the head-trunk
stiffness, especially at 6 years of age. The second period
includes 7- to 8-year-old children. Children of this age become
able to adopt the HSSS while walking on narrow supports. During
this period, the HSSS is associated with a large decrease in the
head-trunk correlations. Lastly, in adulthood the HSSS is
commonly adopted but specifically involves the roll component
associated with the lateral body oscillations while walking.
Vision was found to have little influence on children's HSSS
while walking, whatever their age. Moreover, darkness induces an
increase in the efficiency of the HSSS in adults. This confirms
that the HSSS is the most appropriate strategy available for
dealing with an increase in the level of equilibrium difficulty
and may reflect a ''top-down'' organization of the postural
control while walking. These results also suggest that the HSSS
may be mainly of vestibular origin and presumably serves to
facilitate the visual input processing, particularly that of the
motion and peripheral visual cues which are involved in the
control of body equilibrium during locomotion.},
KEYWORDS = {child locomotion, development}
}
@ARTICLE{AssaianteC95,
AUTHOR = {C. Assaiante and B. Amblard},
YEAR = 1995,
TITLE = {An Ontogenic Model For The Sensorimotor Organization of Balance
Control In Humans},
JOURNAL = {Human Movement Science},
VOLUME = 14,
NUMBER = 1,
PAGES = {13--43},
ABSTRACT = {On the basis of a review of the literature including the
authors' own experimental studies, a model for the ontogenesis of
balance control in children was developed. This qualitative
ontogenetic model has to do with the equilibrium strategies built
up by children in situations which are difficult but within the
scope of their abilities. The model involves two functional
principles. First: The stable reference frame on which the
balance control is based can be either the support on which the
subject is standing or the vertical gravity. When the frame of
reference is the support surface, balance control is temporally
organized either from the feet to the head (posture) or from the
hip to the head (locomotion) (ascending organization). When the
frame of reference is the vertical gravity, balance control is
temporally organized from the head to the feet (descending
organization). Secondly: Children gradually become able to master
the various degrees of freedom which have to be controlled
simultaneously during movement. For example, the head can be
stabilized either on the trunk with the neck structures blocked
(the en bloc mode of operation) or in space with the neck
structures loose (the articulated model). Four main periods can
be said to occur during the human life span. The first extends
from birth up to the acquisition of the upright stance. This
period is characterized by the development of postural responses
along a cephalocaudal gradient. This chronological cephalocaudal
progression with age of the ability to control several body
segments may correspond to a descending temporal organization of
unperturbed postural control, associated with an articulated
operation of the head-trunk unit. The second period takes place
from the acquisition of the upright stance up to around the age
of 6. During this period, our experimental results are consistent
with an ascending organization of balance control, from the feet
to the head in postural stance and from the hips to the head in
locomotion. This ascending organization is associated with an en
bloc mode of head-trunk operation, which serves to minimize the
degrees of freedom. The third period begins at around the age of
7 and continues up to an upper age-limit which is as yet unknown.
It is characterized by the return to an articulated mode of
head-trunk operation, whereby the head stabilization necessary
for the descending temporal organization of balance control is
ensured. Lastly, the fourth period, which is reached during
adulthood, combines the main features of the third period with a
new skill involving the articulated operation of the head-trunk
unit along with a selective control of the degrees of freedom at
the neck level.},
KEYWORDS = {child locomotion, development, balance}
}
@ARTICLE{AssaianteC96,
AUTHOR = {C. Assaiante and B. Amblard},
YEAR = 1996,
TITLE = {Visual factors in the child's gait: Effects on locomotor skills},
JOURNAL = {Perceptual and Motor Skills},
VOLUME = 83,
NUMBER = 3,
PAGES = {1019--1041},
ABSTRACT = {This kinematic study investigated the effects of visual factors
on the angular oscillations of the head and trunk during various
locomotor tasks in 3- to 8-yr.-old children and adults. The
oscillations of the head under normal vision were limited and
changed little across ages. Oscillations of both head and trunk
about the roll axis were the most sensitive to difficulty in
maintaining lateral equilibrium. On narrow supports, the lateral
oscillations of the trunk increased between the ages of 3 and 6
years, with a maximum amplitude at the latter age and then
decreased up to adulthood, suggesting a transition phase around
the age of 6 years. Visual restriction had little effect on the
control of angular oscillations of the head in children or
adults. On a narrow support in darkness, adults increased
oscillations of the trunk but reduced oscillations of the head.
It can be concluded that, regardless of the age, control of
locomotor equilibrium aims at limiting the angular oscillations
of the head. Vision seems to contribute little to stabilization
of the head.},
KEYWORDS = {child locomotion, development}
}
@ARTICLE{AssaianteC98,
AUTHOR = {C. Assaiante and B. Thomachot R. Aurenty and B. Amblard},
YEAR = 1998,
TITLE = {Organization of lateral balance control in toddlers during the
first year of independent walking},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 30,
NUMBER = 2,
PAGES = {114--129},
ABSTRACT = {The authors of the present study tested the hypothesis that
toddlers initiate lateral body stabilization first at the hip
level in order to better control the center of gravity (CG),
minimize the upper body destabilization induced by the movement
of the feet, and prevent falls. Intersegmental coordination among
the hip, the shoulder, and the head was investigated in toddlers
during their Ist year of independent walking. The efficiency of
locomotor balance control was examined in the frontal plane. An
automatic optical TV image processor (ELITE system) was used in
analyzing the kinematics of foot, hip, shoulder, and head
rotations. For the hip, the shoulder, and the head, appropriate
anchoring indices were defined so that comparisons could be made
concerning the stabilization of a given body segment with respect
to its external space and to the adjacent supporting anatomical
segment. Cross-correlation functions were also used for
extracting the temporal patterns of the body segments that
occurred during locomotion and for obtaining some information
about the coupling of 2 consecutive segments such as the
head-shoulder and the shoulder-hip. First, hip stabilization in
space appeared from the Ist week of independent walking and
clearly preceded those of the shoulder and the head, suggesting
an ascending progression, with age, in the ability of new walkers
to control lateral balance during locomotion. Second, the hip
movements occurred before the shoulder movements and the shoulder
movements before the head movements, indicating that locomotor
balance control is organized temporally in an ascending fashion,
from the hip to the head. Third, the high values of the
correlation coefficients, mainly between the head and the
shoulder, were consistent with a global en bloc operation of the
head-trunk unit.},
KEYWORDS = {child locomotion, development}
}
@ARTICLE{AssaianteC98b,
AUTHOR = {C. Assaiante},
YEAR = 1998,
TITLE = {Development of locomotor balance control in healthy children},
JOURNAL = {Neuroscience and Biobehavioral Reviews},
VOLUME = 22,
NUMBER = 4,
PAGES = {527--532},
ABSTRACT = {A set of experimental studies showing how inter-segmental
coordination develops during childhood in various locomotor tasks
is reviewed. On the basis of these results and two functional
principles (stable reference frame and control of the degrees of
freedom of the body joints), we recently proposed an ontogenetic
model for the sensorimotor organization of balance control in
humans (5). In this model, the hypothesis was put forward that
the two main modes of equilibrium control (ascending vs
descending temporal organization) operate alternatively and are
associated with either of two modes of head-trunk linkage ('en
bloc' vs articulated) during four successive periods in the
course of ontogenesis. The advantage of this model is that it is
heuristic and therefore open to further improvements, including
the generalization of these balance strategies to most of the
posture-kinetic activities, the comparison between unperturbed
natural balance and reactions to postural disturbances. Some
improvements are suggested, and are illustrated by the studies of
intersegmental coordination in new experimental tasks such as
hops using one foot or two feet and the initiation of gait. These
new results are consistent with the idea that mastery of the
degrees of freedom to be controlled simultaneously during the
movement improves gradually with age. Moreover, they support the
concept of multiple reference frames which operate in a
complementary manner or in concert to permit the most appropriate
organization of balance control, depending on the environmental
requirements.},
KEYWORDS = {child locomotion, development, balance}
}
@PHDTHESIS{BenbrahimH96,
AUTHOR = {Hamid Benbrahim},
YEAR = 1996,
TITLE = {Biped Dynamic Walking Using Reinforcement Learning},
SCHOOL = {University of New Hampshire},
ANNOTE = {RL approach to walking with a real robot that's not quite bipedal
because it's attached to a four-wheeled cart.},
ABSTRACT = {This thesis presents a study of biped dynamic walking using
reinforcement learning. Ahardware biped robot was built. It uses
low gear ratio DC motors in order to provide freeleg movements.
The Self Scaling Reinforcement learning algorithm was developed
inorder to deal with the problem of reinforcement learning in
continuous action domains. Anew learning architecture was
designed to solve complex control problems. It usesdifferent
modules that consist of simple controllers and small neural
networks. Thearchitecture allows for easy incorporation of
modules that represent new knowledge, ornew requirements for the
desired task. Control experiments were carried out using
asimulator and the physical biped. The biped learned dynamic
walking on flat surfaceswithout any previous knowledge about its
dynamic model.},
KEYWORDS = {Robotics, RL, Biped Locomotion}
}
@ARTICLE{BenbrahimH97,
AUTHOR = {Hamid Benbrahim and Judy A. Franklin},
YEAR = 1997,
TITLE = {Biped Dynamics Walking Using Reinforcement Learning},
JOURNAL = {Robotics and Autonomous Systems},
VOLUME = 22,
PAGES = {283--302},
ANNOTE = {Short, journal version of Benbrahim's PhD thesis.},
ABSTRACT = {This paper presents some results from a study of biped dynamic
walking usingreinforcement learning. During this study a hardware
biped robot was built, a newreinforcement learning algorithm as
well as a new learning architecture were developed.The biped
learned dynamic walking without any previous knowledge about its
dynamicmodel. The Self Scaling Reinforcement learning algorithm
was developed in order to dealwith the problem of reinforcement
learning in continuous action domains. The learningarchitecture
was developed in order to solve complex control problems. It uses
differentmodules that consist of simple controllers and small
neural networks. The architectureallows for easy incorporation of
new modules that represent new knowledge, or newrequirements for
the desired task.},
KEYWORDS = {Robotics, RL, Biped Locomotion}
}
@ARTICLE{BreniereY89,
AUTHOR = {Y. Breniere and B. Bril and R. Fontaine},
YEAR = 1989,
TITLE = {Analysis of the transition from upright stance to steady-state
locomotion in children with under 200 days of autonomous walking},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 21,
NUMBER = 1,
PAGES = {20-37},
ANNOTE = {In contrast to adults, who adjust their gait initiation to match
the target velocity, infants appear to use one general gait
initiation "program" which takes more than one step. Also in
contrast to adults, who shift their COP toward the heels in
anticipation of the start of the first step, infants do not use
this strategy as part of gait initiation. [They haven't mastered
their postural control and so they don't expolit the natural
dynamics as adults do.]},
ABSTRACT = {The aim of this paper was to study, from a developmental
perspective, the transient phase of gait during the period
between the standing posture and the achievement of steady gait,
using temporal and biomechanical parameters. Eight children who
had been walking autonomously for 64 to 200 days were observed. A
total of 64 sequences of steps were analyzed. A sequence of steps
began with the child standing still and was executed on a large
force plate. From the determination of the instantaneous velocity
of center of gravity results establish that, unlike adults,
progression velocity in children is not reached at the end of the
first step, but after two to four steps. The gait initiation
process does not depend on the steady state velocity, but results
from an initial fall. The duration of the movement up to the end
of the first step is independent of the progression velocity but
depends only upon the body mass and moment of inertia of the
children.},
KEYWORDS = {Biomech, Child Locomotion, Development, Gait Initiation}
}
@ARTICLE{BreniereY96,
AUTHOR = {Y. Breniere},
YEAR = 1996,
TITLE = {Why we walk the way we do},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 28,
NUMBER = 4,
PAGES = {291--298},
ABSTRACT = {By using inverse dynamics and forceplate recordings, this study
established the principle of oscillating systems and the
influence of gravity and body parameters on the programming of
the gait parameters, step frequency and length. Calculation of
the ratio of the amplitude of the center of mass (CM) and the
center of foot pressure (CP) oscillations yielded an equation and
established a biomechanical constant, the natural body frequency
(NBF). NBF appears to be an absolute invariant parameter,
specific to human standing posture and gait in terrestrial
gravity, which influences the relative positions of CM and CP and
whose value separates the frequency bands of standing posture
from those for gait. This equation was tested by using the
experimental paradigm of stepping in place and then used in
calculating the magnitude of CM oscillations during gait. The
biomechanical analysis of the experimental observations allows
one to establish the relationships between body parameters and
gravity and the central programming of locomotor parameters.},
KEYWORDS = {biomech, locomotion, development}
}
@ARTICLE{BrilB98,
AUTHOR = {B. Bril and A. Ledebt},
YEAR = 1998,
TITLE = {Head coordination as a means to assist sensory integration in
learning to walk},
JOURNAL = {Neuroscience and Biobehavioral Reviews},
VOLUME = 22,
NUMBER = 4,
PAGES = {555--563},
ABSTRACT = {After a brief presentation of the development of free walking
interpreted as learning dynamical equilibrium, the problem of
sensory integration in the process of walking development is
discussed. A critical review of the role of vision in the
development of posture-locomotor task is presented, along with
recent test results on the development of the vestibular system.
A final section presents the development of head stabilization
and coordination as a necessary means to assist sensory
integration. It is suggested that if sensory information is
necessary to enhance posture-locomotor skills, a good mastery of
walking is in turn necessary to increase the efficiency of
sensory integration.},
KEYWORDS = {child locomotion, development}
}
@ARTICLE{BrilB92,
AUTHOR = {Blandine Bril and Yvon Breniere},
YEAR = 1992,
TITLE = {Postural Requirements and Progression Velocity in Young Walkers},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 24,
NUMBER = 1,
PAGES = {105--116},
ANNOTE = {The authors are interested in the way static postural control and
dynamic walking control bootstrap each other as infants acquire
independent locomotion. They assume (as does Thelen) that the basic
ability to walk is present yet masked by the demands of postural
control (primarily strength). The authors interpret the result of
decreasing BOS width in two ways. First, a wider BOS is needed for
new walkers because this gives greater stability in the lateral
direction. Second, a wider BOS early on helps with gait initiation;
new walkers use fewer degrees of freedom by rocking back-and-forth
as they walk, but then free up degrees of freedom by falling
forward as they gain experience (cf. Bernstein). The authors also
speculate that learning to walk is a two-stage process because
there's an initial fast change in gait parameters (the integration
phase) followed by a slow change --- and more importantly, by a
change in interrelationships -- in the gait parameters (the tuning
phase).},
ABSTRACT = {This article describes developmental changes in gait velocity
and relates these changes to gait parameters that index postural
stability (step width and lateral acceleration) and two
components of velocity (cadence and step length).... From a
developmental point of view, the data lead us to interpret early
walking (the first 5 months) as a process of integration of
postural constraints into the dynamic necessities of gait
movement. A second phase, beginning after 4 to 5 months of
independent walking, is considered to be a tuning phase
characterized by a more precise adjustment of the gait
parameters.},
KEYWORDS = {Biomech, Child Locomotion, Development}
}
@ARTICLE{CalancieB94,
AUTHOR = {B. Calancie and B. Needhamshropshire and P. Jacobs and K. Willer
and G. Zych and B. A. Green},
YEAR = 1994,
TITLE = {Involuntary Stepping After Chronic Spinal-Cord Injury --- Evidence
For a Central Rhythm Generator For Locomotion In Man},
JOURNAL = {Brain},
VOLUME = 117,
NUMBER = 5,
PAGES = {1143--1159},
ABSTRACT = {We investigated a pattern of involuntary lower extremity
stepping-like movements which recently appeared in a subject with
a 17-year history of neurologically incomplete injury to the
cervical spinal cord. The movements were rhythmic, alternating
and forceful, involved all muscles of the lower extremities and
could be reliably evoked by lying the subject down (supine) and
extending his hips. Once in this position, the movements
continued spontaneously in the absence of external sensory
perturbations, with a step-cycle duration of similar to 3.5 s
(0.3 Hz). This rate could be either increased or temporarily
halted by specific sensory inputs. Anaesthetizing the subject's
tight hip joint, in which we found evidence of pathology, led to
a marked attenuation of the stepping movements for a period of
similar to 15 min. We believe that a combination of (i) preserved
but limited supraspinal tonic facilitation, and (ii) abnormal,
perhaps noxious afferent in flow from the subject's right hip to
the spinal cord may underlie the appearance of this highly
unusual and involuntary movement pattern. The striking similarity
between the movement and EMG patterns in this subject and those
described in many reports using the surgically reduced cat model
suggests that we were witnessing the first well-defined example
of a central rhythm generator for stepping in the adult human.},
KEYWORDS = {neuro, CPG, locomotion}
}
@INPROCEEDINGS{CaoM98,
AUTHOR = {M. Cao and A. Kawamura},
YEAR = 1998,
TITLE = {A Design Method of Neural Oscillatory Networks for Generation of
Humanoid Biped Walking Patterns},
BOOKTITLE = {Proceedings of the {IEEE} International Conference on Robotics
and Automation},
PAGES = {2357--2362},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway}
}
@ARTICLE{ChangT93,
AUTHOR = {T. H. Chang and Y. Hurmuzlu},
YEAR = 1993,
TITLE = {Sliding Control Without Reaching Phase and Its Application To
Bipedal Locomotion},
JOURNAL = {Journal of Dynamic Systems Measurement and Control ---
Transactions of the {ASME}},
VOLUME = 115,
NUMBER = 3,
PAGES = {447--455},
ABSTRACT = {A new variable structure control law based on the Lyapunov's
second method that can be used in trajectory planning problems of
robotic systems is developed. A modified approach to the
formulation of the sliding domain equations in terms of tracking
errors has been presented. This approach possesses three distinct
advantages: (i) it eliminates the reaching phase, (ii) it
provides means to predict the entire motion and directly control
the evolution of tracking errors, (iii) it facilitates the
trajectory planning process in the joint and/or cartesian spaces.
A planar, five-link bipedal locomotion model has been developed.
Five constraint relations that cast the motion of the biped in
terms of four parameters are developed. The new control method is
applied to regulate the locomotion of the system according to the
five constraint relations. Numerical simulation performed to
verify the ability of the controller to achieve steady gait by
applying the proposed control scheme. Bifurcation diagrams of the
periodic motions of the biped are used to demonstrate the
improvements in controller performance that arise from the
application of the proposed method.},
KEYWORDS = {robotics, biped locomotion, Lyapunov}
}
@ARTICLE{ChengM97,
AUTHOR = {M. Y. Cheng and C. S. Lin},
YEAR = 1997,
TITLE = {Genetic algorithm for control design of biped locomotion},
JOURNAL = {Journal of Robotic Systems},
VOLUME = 14,
NUMBER = 5,
PAGES = {365--373},
ABSTRACT = {Dynamic biped walking is a difficult control problem. The design
involves that of the controller as well as the gait. A typical
design procedure involves tedious analysis, careful planning, and
testing. The procedure is time consuming and the analysis is
often based on some linearized model. Selection of control
parameters and nominal trajectory determines the quality of
control and in typical designs, some or all of the parameters are
selected intuitively. The result is often not the best. If some
special goal (such as to walk as fast as possible) is desirable,
the design may become even harder. While the analytical approach
is not easy, one possible alternative is to obtain the optimal or
near-optimal design through parameter search. This study explores
this approach. The design of the biped controller and gait is
formulated as a parameter search problem, and a genetic algorithm
is applied to help obtain the optimal design. Designs to achieve
different goals, such as being able to walk on an inclined
surface, walk at a high speed, or walk with a specified step size
have been evolved with the use of the genetic algorithm.
Simulation results show that the genetic algorithm (GA) is
capable of finding good solutions.},
KEYWORDS = {robotics, biped locomotion, AI, simulation}
}
@INPROCEEDINGS{ChevallereauC98,
AUTHOR = {C. Chevallereau and A. M. {Formal'sky} and B. Perrin},
YEAR = 1998,
TITLE = {Low Energy Cost Reference Trajectories for a Biped Robot},
BOOKTITLE = {Proceedings of the {IEEE} International Conference on Robotics
and Automation},
PAGES = {1398--1404},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway}
}
@ARTICLE{ChouL97,
AUTHOR = {L. Chou and L. F. Draganich and S. M. Song},
YEAR = 1997,
TITLE = {Minimum energy trajectories of the swing ankle when stepping over
obstacles of different heights},
JOURNAL = {Journal of Biomechanics},
VOLUME = 30,
NUMBER = 2,
PAGES = {115--120},
ANNOTE = {The authors use DP to find optimal ankle trajectories for stepping
over obstacles. Humans appear to minimize energy expenditure when
walking on level ground but not when stepping over obstacles.
(Humans use larger-than-necessary obstacle clearance.) See also
Chou et al., J. Biomech 28(4):377, 1995.},
ABSTRACT = {This study was performed to test the hypothesis that the motion
of the lower extremities when stepping over obstacles is governed
by the criterion of minimum mechanical energy. The trajectories
of the swing ankle during level walking and when stepping over
obstacles of 51, 102, 153, and 204 mm heights were predicted and
measured for eight healthy young adults. The predictions were
made with a planar, seven-link linkage model based on the
criterion of minimum mechanical energy using the method of
dynamic programming. When stepping over obstacles, the predicted
trajectories of the swing ankle were just high enough for the
swing toe to clear the obstacles. The clearances measured between
the obstacle and toe were significantly larger than those
predicted. When stepping over obstacles the levels of work
required to generate the measured trajectories were significantly
larger (p less than or equal to 0.002) than those required to
produce the predicted trajectories. The amount of work necessary
to generate the measured or predicted trajectories increased
linearly (significant at p less than or equal to 0.022) with
obstacle height and, except when predicting the trajectory for
the lowest obstacle, was significantly greater than that required
when walking on level ground (p < 0.02). Thus, conservation of
energy was found to become a less dominant criterion for
governing the motion of the body when crossing obstacles than
when walking on level ground.},
KEYWORDS = {biomech, obstacle avoidance, DP, RL, optimal control}
}
@ARTICLE{ColemanM98,
AUTHOR = {Michael J. Coleman and Andy Ruina},
YEAR = 1998,
TITLE = {An Uncontrolled Walking Toy That Cannot Stand Still},
JOURNAL = {Physical Review Letters},
VOLUME = 80,
NUMBER = 16,
PAGES = {3658--3661},
ANNOTE = {The authors extend McGeer's work with passive walkers and show the
construction of a Tinker Toy device that is dynamically stable in
side-to-side motion as well as fore-aft motion.},
ABSTRACT = {We built a simple two-leg toy that can walk stably with no
control system. It walks downhill powered only by gravity. It
seems to be the first McGeer-like passive-dynamic walker that is
statically unstable in all standing positions, yet is stable in
motion. It is one of a few known mechanical devices that are
stable near a statically unstable configuration but do not depend
on spinning parts. Its design is loosely based on simulations
which do not predict its observed stability. Its motion
highlights the possible role of uncontrolled nonholonomic
mechanics in balance.},
KEYWORDS = {Biomech, NLD, passive locomotion}
}
@ARTICLE{CollinsJ94,
AUTHOR = {J. J. Collins and S. A. Richmond},
YEAR = 1994,
TITLE = {Hard-wired central pattern generators for quadrupedal locomotion},
JOURNAL = {Biological Cybernetics},
VOLUME = 71,
NUMBER = 5,
PAGES = {375--385},
ABSTRACT = {Animal locomotion is generated and controlled, in part, by a
central pattern generator (CPG), which is an intraspinal network
of neurons capable of producing rhythmic output. In the present
work, it is demonstrated that a hard-wired CPG model, made up of
four coupled nonlinear oscillators, can produce multiple
phase-locked oscillation patterns that correspond to three common
quadrupedal gaits - the walk, trot, and bound. Transitions
between the different gaits are generated by varying the
network's driving signal and/or by altering internal oscillator
parameters. The above in numero results are obtained without
changing the relative strengths or the polarities of the system's
synaptic interconnections, i.e., the network maintains an
invariant coupling architecture. It is also shown that the
ability of the hard-wired CPG network to produce and switch
between multiple gait patterns is a model-independent phenomenon,
i.e., it does not depend upon the detailed dynamics of the
component oscillators and/or the nature of the inter-oscillator
coupling. Three different neuronal oscillator models - the Stein
neuronal model, the Van der Pol oscillator, and the
FitzHugh-Nagumo model - and two different coupling schemes are
incorporated into the network without impeding its ability to
produce the three quadrupedal gaits and the aforementioned gait
transitions.},
KEYWORDS = {}
}
@ARTICLE{CymbalyukG98,
AUTHOR = {G. S. Cymbalyuk and R. M.Borisyuk and U. Mueller-{W}ilm and H.
Cruse},
YEAR = 1998,
TITLE = {Oscillatory network controlling six-legged locomotion. Optimization
of model parameters},
JOURNAL = {Neural Networks},
VOLUME = 11,
NUMBER = {(7-8)},
PAGES = {1449--1460},
ANNOTE = {The paper describes a model of six-legged walking, with a sort of
reinforcement learning based on the FLSS cost (frequency of the
loss of static stability). The authors use a GA to minimize FLSS to
the vicinity of the global minimum and then use a Monte Carlo
method to search a smaller space of solutions.},
ABSTRACT = {The model of a legged locomotory system is optimized to ensure
stable motion, reliable with respect to different initial
conditions. The cost function suggested is based on the frequency
of the model's loss of stability evaluated for randomly chosen
initial leg positions. The optimized model can start from the
majority of allowed leg configurations, demonstrating stable
walking at low and moderate speeds. Furthermore, an acceleration
procedure is designed to permit the model to pick up practically
every speed and then walk successfully.},
KEYWORDS = {Biomech, locomotion, RL}
}
@ARTICLE{DavyD87,
AUTHOR = {D. T. Davy and M. L. Audu},
YEAR = 1987,
TITLE = {A Dynamic Optimization Technique For Predicting Muscle Forces In
The Swing Phase of Gait},
JOURNAL = {Journal of Biomechanics},
VOLUME = 20,
NUMBER = 2,
PAGES = {187--201},
ANNOTE = {The authors describe the use use of optimal control techniques as
a means for estimating muscle forces from gait kinematics (no
invasive measurements). They place particular emphasis of
approaches that account for musculoskeletal dynamics which, in
contrast to "static" optimization techniques, successfully predict
features like the lag between motor command and torque generation.
(See also a Letter to the Editor by Herbert Hatze in J. Biomech
21(10), 1988.)},
ABSTRACT = {The muscle force sharing problem was solved for the swing phase
of gait using a dynamic optimization algorithm. For comparison
purposes the problem was also solved using a typical static
optimizaton algorithm. The objective function for the dynamic
optimization algorithm was a combination of the tracking error
and the metabolic energy consumption....},
KEYWORDS = {Biomech, Optimal Control, Locomotion}
}
@ARTICLE{DiedrichF98,
AUTHOR = {F. J. Diedrich and W. H. Warren},
YEAR = 1998,
TITLE = {The dynamics of gait transitions: Effects of grade and load},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 30,
NUMBER = 1,
PAGES = {60--78},
ABSTRACT = {Diedrich and Warren (1995a) proposed that gait transitions
behave like bifurcations between attractors, with the relative
phase of the leg segments as an order parameter and stride
frequency and stride length as control parameters. In the present
experiments, the authors tested the prediction that manipulation
of the attractor layout, either through the addition of load to
the ankles or through an increase in the grade of the treadmill,
induces corresponding changes in the walk-run transition. As
predicted, the load manipulation shifted the most stable walk and
the transition to lower stride frequencies. In contrast, the
grade manipulation shifted the most stable walk and the
transition to shorter stride lengths. Other features of the
dynamic theory were also replicated, including enhanced
fluctuations of phase and systematic changes in stride length and
frequency at the transition. Overall, in these experiments a
shift of the attractors in control parameter space yielded a
corresponding shift of the transition.},
KEYWORDS = {biomech, locomotion, NLD}
}
@ARTICLE{DimitrijevicM98,
AUTHOR = {M. R. Dimitrijevic and Y. Gerasimenko and M. M. Pinter},
YEAR = 1998,
TITLE = {Evidence for a spinal central pattern generator in humans},
JOURNAL = {Annals of the New York Academy of Sciences},
VOLUME = 860,
PAGES = {360--376},
ABSTRACT = {Non-patterned electrical stimulation of the posterior structures
of the lumbar spinal cord in subjects with complete,
long-standing spinal cord Injury, can induce patterned,
locomotor-like activity, We show that epidural spinal cord
stimulation can elicit step-like EMG activity and locomotor
synergies in paraplegic subjects. An electrical train of stimuli
applied over the second lumbar segment with a frequency of 25 to
60 Hz and an amplitude of 5-9 V was effective in inducing
rhythmic, alternating stance and swing phases of the lower limbs.
This finding suggests that spinal circuitry in humans has the
capability of generating locomotor-like activity even when
isolated from brain control, and that externally controlled
sustained electrical stimulation of the spinal cord can replace
the tonic drive generated by the brain.},
KEYWORDS = {neuro, CPG, locomotion}
}
@ARTICLE{DuysensJ98,
AUTHOR = {J. Duysens and H. {{V}an de {C}rommert}},
YEAR = 1998,
TITLE = {Neural control of locomotion; Part 1. The central pattern generator
from cats to humans},
JOURNAL = {Gait & Posture},
VOLUME = 7,
PAGES = {131--141},
ABSTRACT = {In the last years it has become possible to regain some
locomotor activity in patients suffering from an incomplete
spinal cord injury (SCI) through intense training on a treadmill.
The ideas behind this approach owe much to insights derived from
animal studies. Many studies showed that cats with complete
spinal cord transection can recover locomotor function. These
observations were at the basis of the concept of the central
pattern generator (CPG) located at spinal level. The evidence for
such a spinal CPG in cats and primates (including man) is
reviewed in part 1, with special emphasis on some very recent
developments which support the view that there is a human spinal
CPG for locomotion.},
KEYWORDS = {neuro, CPG, locomotion}
}
@ARTICLE{EngJ97,
AUTHOR = {J. J. Eng and D. A. Winter and A. E. Patla},
YEAR = 1997,
TITLE = {Intralimb dynamics simplify reactive control strategies during
locomotion},
JOURNAL = {Journal of Biomechanics},
VOLUME = 30,
NUMBER = 6,
PAGES = {581--588},
ANNOTE = {The authors show that in normal walking and in trip situations,
the nervous system still exploits the passive dynamics of the legs.
They also show that active control of the knee leads to control of
the ankle and hip and that energy cost, which may be a factor for
normal walking, is not optimized during a trip of slip.},
ABSTRACT = {The utilization of passive dynamics to control the swing
trajectory is one mechanism which serves to minimize energy costs
during locomotion, in addition to reducing the complexity of the
neural control. In a reactive situation (e.g. trip or slip during
walking), the energy cost may not be a major determinant of the
locomotor activity as there is a need for quick corrective action
under the threat of a fall. Therefore, we addressed the following
question: does the nervous system utilize passive dynamics during
the reactive control of locomotion? An unexpected mechanical
perturbation was applied to the foot during early and late swing
during walking. Video data were input into an inverse dynamics
routine to obtain the joint moment and mechanical power profiles
and to partition the joint moments into active and passive
components. The nervous system still utilized the passive
dynamics of the effector system; active control of a single
joint, the knee joint, passively facilitated the flexor action at
the proximal hip and distal ankle joint following the early swing
perturbation. The minimization of the mechanical energy cost was
not a major determinant for this task since the total mechanical
work during the perturbed steps was greater than during normal
steps. A neuromuscular constraint was observed following the late
swing perturbation; the active control of the hip and knee joints
were increased but the magnitude of the hip extensor/knee flexor
moment was invariant and equal to 1.6. The intralimb dynamics
identified during these responses may serve to simplify the
complexity of the active control of the nervous system.},
KEYWORDS = {biomech, biped locomotion, passive dynamics, optimal control}
}
@ARTICLE{EpplerM96,
AUTHOR = {M. A. Eppler and K. E. Adolph and T. Weiner},
YEAR = 1996,
TITLE = {The developmental relationship between infants' exploration and
action on slanted surfaces},
JOURNAL = {Infant Behavior & Development},
VOLUME = 19,
NUMBER = 2,
PAGES = {259--264},
ABSTRACT = {This research provides converging evidence that infants use
exploratory activity to differentiate slant around a horizontal
axis before they relate information about slant to consequences
for locomotion. In Experiment 1, 14-month-old toddlers walked
down safe, shallow 10 degrees hills and slid down or avoided
risky, steep 36 degrees hills when height of the hills was held
constant. Results indicate that judgments were based an slant. In
Experiment 2, 9-month-old crawling infants explored shallow 10
degrees and steep 30 degrees slopes differentially in a
nonlocomotor task. Exploration was similar to previous locomotor
research with full-size hills, even though crawlers plunged
headlong over both shallow and steep hills in the earlier study.},
KEYWORDS = {child locomotion, development}
}
@ARTICLE{ErmentroutB94,
AUTHOR = {B. Ermentrout and N. Kopell},
YEAR = 1994,
TITLE = {Learning of Phase Lags in Coupled Neural Oscillators},
JOURNAL = {Neural Computation},
VOLUME = 6,
NUMBER = 2,
PAGES = {225--241},
ABSTRACT = {If an oscillating neural circuit is forced by another such
circuit via a composite signal, the phase lag induced by the
forcing can be changed by changing the relative strengths of
components of the coupling. We consider such circuits, with the
forced and forcing oscillators receiving signals with some given
phase lag. We show how such signals can be transformed into an
algorithm that yields connection strengths needed to produce that
lag. The algorithm reduces the problem of producing a given phase
lag to one of producing a kind of synchrony with a ''teaching''
signal; the algorithm can be interpreted as maximizing the
correlation between voltages of a cell and the teaching signal.
We apply these ideas to regulation of phase lags in chains of
oscillators associated with undulatory locomotion.},
KEYWORDS = {CPG, learning}
}
@ARTICLE{FerrisD99,
AUTHOR = {Daniel P. Ferris and Kailine Liang and Claire T. Farley},
YEAR = 1999,
TITLE = {Runners Adjust Leg Stiffness for their First Step on a New Running
Surface},
JOURNAL = {Journal of Biomechanics},
VOLUME = 32,
PAGES = {787--794},
ANNOTE = {The authors assume that the leg and running surface can be modeled
as two linear springs in series. They use simulation results as
well as human data to show that runners quickly adapt their
effective leg stiffness to suit the terrain stiffness.},
ABSTRACT = {Human runners adjust the stiffness of their stance leg to
accommodate surface stiffness during steady state running. This
adjustment allows runners to maintain similar center of mass
movement (e.g., ground contact time and stride frequency)
regardless of surface stiffness....},
KEYWORDS = {Biomech, Gait, Stiffness}
}
@ARTICLE{FujimotoY98,
AUTHOR = {Y. Fujimoto and A. Kawamura},
YEAR = 1998,
TITLE = {Simulation of an autonomous biped walking robot including
environmental force interaction},
JOURNAL = {{IEEE} Robotics & Automation Magazine},
VOLUME = 5,
NUMBER = 2,
PAGES = {33--42},
ABSTRACT = {This autonomous biped walking control system is based on
reactive force interaction at the foothold. The precise 3D
dynamic simulation presented includes: 1) a posture controller
which accommodates the physical constraints of the reactive
force/torque on the foot with quadratic programming. 2) a
real-time COM (center of mass) tracking controller for foot
placement, with a discrete inverted pendulum model. 3) a 3D
dynamic simulation scheme with precise contact with the
environment. The proposed approach realizes robust biped
locomotion because environmental interaction is directly
controlled. The proposed method is applied to a 20 axes
simulation model, and stable biped locomotion with velocity of
0.25 m/sec and a stepping time of 0.5 sec/step is realized.},
KEYWORDS = {robotics, biped locomotion}
}
@ARTICLE{GarciaM98,
AUTHOR = {M. Garcia and A. Chatterjee and A. Ruina and M. Coleman},
YEAR = 1998,
TITLE = {The simplest walking model: Stability, complexity, and scaling},
JOURNAL = {Journal of Biomechanical Engineering --- Transactions of the ASME},
VOLUME = 120,
NUMBER = 2,
PAGES = {281--288},
ABSTRACT = {We demonstrate that an irreducibly simple, uncontrolled
two-dimensional two-link model, vaguely resembling human legs,
can walk down a shallow slope, powered only by gravity. This
model is the simplest special case of the passive-dynamic models
pioneered by McGeer (1990a). It has two rigid massless legs
hinged at the hip, a point-mass at the hip, and infinitesimal
point-masses at the feet. The feet have plastic (no-slip,
no-bounce) collisions with the slope surface, except during
forward swinging, when geometric interference (foot scuffing) is
ignored. After nondimensionalizing the governing equations, the
model has only one free parameter the ramp slope gamma. This
model shows stable walking modes similar to more elaborate
models, bur allows some use of analytic methods to study ifs
dynamics. The analytic calculations find initial conditions and
stability estimates for period-one gait limit cycles. The model
exhibits two period-one gait cycles, one of which is stable when
0 < gamma < 0.015 rad. With increasing gamma, stable cycles of
higher periods appear, and the walking-like motions apparently
become chaotic through a sequence of period doublings. Scaling
laws for the model predict that walking speed is proportional to
stance angle, stance angle is proportional to gamma(1/3), and
that the gravitational power used is proportional to upsilon(4)
where upsilon is the velocity along the slope.},
KEYWORDS = {robotics, biped locomotion}
}
@ARTICLE{GoddardR92,
AUTHOR = {R. E. Goddard and Y. P. Zheng and H. Hemami},
YEAR = 1992,
TITLE = {Control of the Heel-Off to Toe-Off Motion of a Dynamic Biped Gait},
JOURNAL = {IEEE Transactions on Systems, Man, and Cybernetics},
VOLUME = 22,
NUMBER = 1,
PAGES = {92--102}
}
@INPROCEEDINGS{GorceP98,
AUTHOR = {P. Gorce and F. {E}l Hafi},
YEAR = 1998,
TITLE = {Modelling of Human Body Control Scheme and Learning in Stepping
Motion Over an Obstacle},
BOOKTITLE = {Proceedings of the {IEEE/RSJ} International Conference on
Intelligent Robots and Systems},
PAGES = {64--69},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway, NJ},
ANNOTE = {The authors start by capturing motion information for human
subjects stepping over boxes with different heights (0.2-0.7 m).
They identify a minimum "security" distance to the obstacle such
that clearance of the box is possible as well as a maximum
"influence" distance such that the current gait is altered to step
over the obstacle. They also assume that the trajectory of the lead
leg is symmetric wrt the box when deriving the desired joint
trajectories. By "learning" the authors refer to minimization of
the leg distances to the box -- the distance from the obstacle to
the nearest part of each leg (roughly the knee of the stance leg)
-- but they give no other details.},
ABSTRACT = {The aim of our study is to bettern understand the decision
mechanisms of human body during the stepping motion over an
obstacle.... this approach constitute decision module based on
learning process to realize stepping motion. We compare
simulation results to experimental data.},
KEYWORDS = {Robotics, Biomech, Bipedal Locomotion, Simulation}
}
@ARTICLE{GorceP98b,
AUTHOR = {P. Gorce and M. Guihard},
YEAR = 1998,
TITLE = {On dynamic control of pneumatic bipeds},
JOURNAL = {Journal of Robotic Systems},
VOLUME = 15,
NUMBER = 7,
PAGES = {421--433},
ABSTRACT = {Some fundamental properties must be verified when dealing with
the dynamic control of legged robots. Actually, to make the robot
follow a given gait, the control strategy has to ensure dynamic
stability in real time. Moreover, to make the supervisor
efficient, the control of each leg has to be highly reliable.
Accuracy robustness, and rapidly are then required to follow
dynamic motions. To verify these properties, we propose a general
control architecture designed for pneumatic legged robots and
develop it for a biped. This control architecture is composed of
two main levels. The upper one, called the "Coordinator" level,
maintains the robot stability by correcting on line its center of
mass acceleration and distributing correctly the forces on each
limb. The lower level, called the "Limb" level, is devoted to the
control of each limb according to the desired position and force
trajectories given by the Coordinator level. The chosen
trajectories are derived from biomechanical results, and a
dynamic model that takes into account mechanical and pneumatic
effects is presented. We propose to deal with the setting and the
raising phases, using a continuous nonlinear joint impedance
controller. The asymptotic stability is ensured by using Popov
criteria. Simulation results of this new controller are
presented, leading to a good behavior of the leg during the two
phases at relatively high velocities.},
KEYWORDS = {robotics, biped locomotion}
}
@ARTICLE{GrassoR98,
AUTHOR = {R. Grasso and C. Assaiante and P. Prevost and A. Berthoz},
YEAR = 1998,
TITLE = {Development of anticipatory orienting strategies during locomotor
tasks in children},
JOURNAL = {Neuroscience and Biobehavioral Reviews},
VOLUME = 22,
NUMBER = 4,
PAGES = {533--539},
ABSTRACT = {Some basic problems related to the development of goal-directed
locomotion in humans are reviewed here. A preliminary study is
presented which was aimed at investigating the emergence of
anticipatory head orienting strategies during goal-directed
locomotion in children. Eight children ranging from 3.5 to 8
years had to walk along a 90 degrees right corner trajectory to
reach a goal, both in light and in darkness. The instantaneous
orientation in space of the head, trunk, hips and left foot
antero/posterior axes was computed by means of an ELITE four-TV
camera, 100 Hz system. The results showed that predictive head
orienting movements can occur also in the youngest children. The
head starts to rotate toward the goal before the corner point of
the trajectory is reached. In children, the head peak rotation
coincides with the trajectory corner while in adults the peak is
attained before. In children, the walking speed is largely
decreased in darkness. The results suggest that feedforward
control of goal-directed locomotion appears very early in gait
development and becomes increasingly important afterwards.},
KEYWORDS = {child locomotion, development}
}
@INPROCEEDINGS{HaseK98,
AUTHOR = {K. Hase and N. Yamazaki},
YEAR = 1998,
TITLE = {Computational Evolution of Human Bipedal Walking by a
Neuro-Musculo-Skeletal Model},
BOOKTITLE = {Proceedings of the Third International Symposium on Artificial
Life and Robotics},
PAGES = {174--177},
ANNOTE = {The authors use an interesting design for a simulated biped robot
inspired by human locomotion. They use a genetic algorithm to show
that a human-like body could evolve from a chimpanzee-shaped body
based on a fitness measure that accounts for things like energy
consumption, muscular fatigue and skeletal load.},
ABSTRACT = {The acquisition process of bipedal walking in humans was
simulated using a neuro-musculo-skeletal model and genetic
algorithms, based on the assumption that the shape of the body
has been adapted for locomotion. The model was constructed as 10
two-dimensional rigid links with 26 muscles and 18 neural
oscillators....},
KEYWORDS = {robotics, CPG, biped locomotion, GA}
}
@ARTICLE{HemamiH84,
AUTHOR = {Hooshang Hemami and Yuan F. Zheng},
YEAR = 1984,
TITLE = {Dynamics and control of motion on the ground and in the air with
application to biped robots},
JOURNAL = {J. of Robotic Systems},
VOLUME = 1,
NUMBER = 1,
PAGES = {101--116}
}
@ARTICLE{HillS99,
AUTHOR = {Stephen W. Hill and Aftab E. Patla and M. G. Ishac and A. L. Adkin
and T. J. Supan and D. G. Barth},
YEAR = 1999,
TITLE = {Altered kinetic strategy for the control of swing limb elevation
over obstacles in unilateral below-knee amputee gait},
JOURNAL = {Journal of Biomechanics},
VOLUME = 32,
NUMBER = 5,
ANNOTE = {The authors show that as obstacle height increases, knee flexion
on the prosthetic side is increased by using a hip strategy (in
contrast to the sound side which uses a knee strategy). They
discuss the exploitation of intersegmental dynamics and conclude
that amputees adjust their gait to exploit the change in leg
dynamics. See also Patla & Prentice, Exp. Brain Res. 106:499-504,
1995; Ghez & Sainburg, Canadian J. of Physiol. Pharm. 73:273, 1995.},
ABSTRACT = {Our goal was to document the kinetic strategies for obstacle
avoidance in below-knee amputees. Kinematic data were collected
as unilateral below-knee traumatic amputees stepped over
obstacles of various heights in the walking path. Inverse
dynamics were employed to calculate power profiles and work
during the limb-elevation and limb-lowering phases. Limb
elevation was achieved by employing a different strategy of
intra-limb interaction for elevation of the prosthetic limb than
for the sound limb, which was similar to that seen in healthy
adult non-amputees. As obstacle height increased, prosthetic side
knee flexion was increased by modulating the work done at the
hip, and not the knee, as seen on the sound side. Although the
strength of the muscles about the residual knee was preserved,
the range of motion of that knee had previously been found to be
somewhat limited. Perhaps more importantly, potential instability
of the interface between the stump and the prosthetic socket, and
associated discomfort at the stump could explain the altered
limb-elevation strategy. Interestingly, the limb-lowering
strategy seen in the sound limb and in non-amputees already
features modulation of rotational and translational work at the
hip: so an alternate strategy was not required. Thus, following a
major insult to the sensory and neuromuscular system, the CNS is
able to update the internal model of the locomotor apparatus as
the individual uses the new limb in a variety of movements, and
modify control strategies as appropriate.},
KEYWORDS = {biomech, biped locomotion, adaptation, obstacle avoidance}
}
@INPROCEEDINGS{HuJ98,
AUTHOR = {Jianjuen Hu and Jerry Pratt and Gill Pratt},
YEAR = 1998,
TITLE = {Adaptive Dynamic Control of a Bipedal Walking Robot with Radial
Basis Function Neural Networks},
BOOKTITLE = {Proceedings of the {IEEE/RSJ} International Conference on
Intelligent Robots and Systems},
PAGES = {400--405},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway, NJ},
ANNOTE = {The authors describe a control scheme for bipedal robots. First,
they use virtual spring-damper components to design a virtual
controller that achieves things like upright posture and constant
forward velocity; forces in virtual space are mapped to joint
torques in physical space. Second, they use a finite state machine
to represent the switching of the spring-damper components on and
off. Third, they use RBF networks to capture higher-order
nonlinearities not accounted for by their basic linear
(spring-damper) model of the robot dynamics in virtual space. The
RBF network is updated by an unsupervised learning approach based
on Lyapunov theory [Sanner and Slotine, IEEE Trans. Neur. Nets
3(6), 1992].},
ABSTRACT = {The robustness of bipedal walking can be enhanced by the use of
adaptive control and learning. This paper describes one such
approach, Radial Basis Function (RBF) Neural Network Adaptive
Control (NNAC). The adaptive control mechanism is designed in a
virtual space utilizing the Virtual Model Control paradigm [3].
The neural network is parameterized and trained in an
unsupervised learning mode. There are two advantages to this
approach. First, the NNAC can identify the unmodelled dynamics of
the robot and ensure asymptotic system stability in a Lyapunov
sense. Second, the controller can better accommodate unexpected
external disturbances. This system's design is described in this
paper and simulation results are presented.},
KEYWORDS = {Robotics, Bipedal Locomotion, Control}
}
@ARTICLE{IbidapoObeO95,
AUTHOR = {O. Ibidapo-Obe and A. B. Alonge and Adedeji Badiru},
YEAR = 1995,
TITLE = {On Active Controls for a Biped Mechanism},
JOURNAL = {Applied Mathematics and Computation},
VOLUME = 69,
NUMBER = {2-3},
PAGES = {159--??}
}
@ARTICLE{ItoS98,
AUTHOR = {Satoshi Ito and Hideo Yuasa and Zhi-wei Luo and Masami Ito and Dai
Yanagihara},
YEAR = 1998,
TITLE = {A Mathematical Model of Adaptive Behavior In Quadruped Locomotion},
JOURNAL = {Biological Cybernetics},
VOLUME = 78,
PAGES = {337--347},
ABSTRACT = {Locomotion involves repetitive movementsand is often executed
unconsciously and automatically.In order to achieve smooth
locomotion, the coordina-tion of the rhythms of all physical
parts is important.Neurophysiological studies have revealed that
basic rhythms are produced in the spinal network called, the
central pattern generator (CPG), where some neural oscillators
interact to self-organize coordinated rhythms.We present a model
of the adaptation of locomotion patterns to a variable
environment, and attempt to elucidate how the dynamics of
locomotion pattern generation are adjusted by the environmental
changes. Recent experimental results indicate that decerebrate
cats have the ability to learn new gait patterns in a changed
environment. In those experiments, a decere-brate cat was set on
a treadmill consisting of three moving belts. This treadmill
provides a periodic pertur-bation to each limb through variation
of the speed ofeach belt. When the belt for the left forelimb is
quickened, the decerebrate cat initially loses interlimb
coordination and stability, but gradually recovers themand -nally
walks with a new gait. Based on the abovebiological facts, we
propose a CPG model whoserhythmic pattern adapts to periodic
perturbation fromthe variable environment. First, we design the
oscillatorinteractions to generate a desired rhythmic pattern.In
our model, oscillator interactions are regardedas the forces that
generate the desired motion pattern.If the desired pattern has
already been realized, then theinteractions are equal to zero.
However, this rhythmicpattern is not reproducible when there is
an environ-mental change. Also, if we do not adjust the
rhythmicdynamics, the oscillator interactions will not be
zero.Therefore, in our adaptation rule, we adjust the mem-orized
rhythmic pattern so as to minimize the oscillatorinteractions.
This rule can describe the adaptive behav-ior of decerebrate cats
well. Finally, we propose amathematical framework of an
adaptation in rhythmicmotion. Our framework consists of three
types of dynamics: environmental, rhythmic motion, and
adap-tation dynamics. We conclude that the time scale
ofadaptation dynamics should be much larger than that ofrhythmic
motion dynamics, and the repetition of rhyth-mic motions in a
stable environment is important for theconvergence of adaptation.},
KEYWORDS = {biomech, neuro, CPGs, locomotion, robotics}
}
@ARTICLE{JengS96,
AUTHOR = {S. F. Jeng and K. G. Holt and L. Fetters and C. Certo},
YEAR = 1996,
TITLE = {Self-optimization of walking in nondisabled children and children
with spastic hemiplegic cerebral palsy},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 28,
NUMBER = 1,
PAGES = {15--27},
ABSTRACT = {Children voluntarily adopt a frequency and movement pattern for
walking. The force-driven harmonic oscillator (FDHO) model was
used in this study for accurate prediction of the preferred
walking frequency of nondisabled children and children with
spastic hemiplegic cerebral palsy. Four potential optimality
criteria with which the preferred walking pattern was forced to
comply were examined: minimization of physiological costs,
maximization of mechanical energy conservation, minimization of
asymmetry in lower limb movements and minimization of variability
of interlimb and intralimb coordination. Age and gender-matched
nondisabled children (n = 6) and children with spastic hemiplegic
cerebral palsy (n = 6) were tested under six frequency conditions
of walking at a constant speed on a treadmill. For the
nondisabled children, the results indicated that their preferred
walking frequency could be accurately predicted by the FDHO
model. They freely adopted a walking pattern that minimized
physiological costs, asymmetry, and variability of inter- and
intralimb coordination. For the children with spastic hemiplegic
cerebral palsy, the prediction of preferred overground walking
frequency required that the FDHO model be modified to account for
muscle mass and leg length discrepancies between limbs and
increased stiffness. Most of the children achieved the same
optimality goals as the nondisabled when walking at the preferred
frequency. However, the children were found to use different
mechanisms to attain these goals: for example, a steeper increase
observed in physiological cost at higher frequencies; a lowered
center of gravity Of the body, which allowed for angular
symmetry; and greater variability of between-joint coordination
in the nonaffected limb and less variability in the affected
limb.},
KEYWORDS = {child locomotion, optimal control}
}
@ARTICLE{JensenJ94,
AUTHOR = {Jody L. Jensen and Beverly D. Ulrich and Esther Thelen and Klaus
Schneider and Ronald F. Zernicke},
YEAR = 1994,
TITLE = {Adaptive Dynamics of the Leg Movement Patterns of Human Infants: I.
The Effects of Posture on Spontaneous Kicking},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 26,
NUMBER = 4,
PAGES = {303--312},
ABSTRACT = {This is the first of two articles in which we describe how
infants adapt their spontanteous leg movements to changes in
posture or to elicitation of behaviors by a mechanical
treadmill.... This increased correlation between muscle torques
at the hip and knee implicates anatomical and energetic
constraints --- the intrinsic limb dynamics --- in creating
coordinated limb behavior out of nonspecific muscle activations.},
KEYWORDS = {Biomech, Child Locomotion, Development}
}
@ARTICLE{JensenJ95,
AUTHOR = {Jody. L. Jensen and E. Thelen and B. D. Ulrich and K. Schneider
and R. F. Zernicke},
YEAR = 1995,
TITLE = {Adaptive Dynamics of the Leg Movement Patterns of Human Infants.
{III}. Age-Related Differences in Limb Control},
JOURNAL = {Journal of Motor Behavior},
VOLUME = 27,
NUMBER = 4,
PAGES = {366--374},
ABSTRACT = {In this article, the development of the increasingly
differentiated control of the joints necessary to transform the
spontaneous leg movements of early infancy into adaptive and
functional actions is described. The hypothesis-that increasing
joint control requires the capability for disassociation of joint
action, the active modulation of joint stiffness, and a
transition from proximal to distal control of the joints-is
proposed. Kinematic and kinetic analyses of the vertical kicks of
infants 2 weeks, 3 months, and 7 months of age (as well as a
comparative group of adults) indicated increasing joint
independence as well as phase-dependent dent and joint-dependent
control modifications. The kicks of the younger infants were
dominated by a proximal control strategy and minimal adjustments
of the limb energetics during the flexion and extension phases of
the kick. By 7 months of age, much larger modulations of the kick
phases were observed as well as increasing evidence of distal
control. These results revealed kinematic and kinetic patterns of
emerging limb control between 2 weeks and 7 months of age.}
}
@ARTICLE{JonicS99,
AUTHOR = {S. Jonic and T. Jankovic and V. Gajic and D. Popovic},
YEAR = 1999,
TITLE = {Three machine learning techniques for automatic determination of
rules to control locomotion},
JOURNAL = {{IEEE} Transactions on Biomedical Engineering},
VOLUME = 46,
NUMBER = 3,
PAGES = {300--310},
ABSTRACT = {Automatic prediction of gait events (e.g., heel contact, flat
foot, initiation of the swing, etc.) and corresponding profiles
of the activations of muscles is important for realtime control
of locomotion. This paper presents three supervised machine
learning (ML) techniques for prediction of the activation
patterns of muscles and sensory data, based on the history of
sensory data, for walking assisted by a functional electrical
stimulation (FES), Those ML's are: 1) a multilayer perceptron
with Levenberg-Marquardt modification of backpropagation learning
algorithm; 2) an adaptive-network-based fuzzy inference system
(ANFIS); and 3) a combination of an entropy minimization type of
inductive learning (IL) technique and a radial basis function
(RBF) type of artificial neural network with orthogonal least
squares learning algorithm. Here we show the prediction of the
activation of the knee flexor muscles and the knee joint angle
for seven consecutive strides based on the history of the knee
joint angle and the ground reaction forces, The data used for
training and testing of ML's was obtained from a simulation of
walking assisted with an FES system [39], The ability of
generating rules for an FES controller was selected as the most
important criterion when comparing the ML's. Other criteria such
as generalization of results, computational complexity, and
learning rate were also considered, The minimal number of rules
and the most explicit and comprehensible rules were obtained by
ANFIS. The best generalization was obtained by the IL and RBF
network.},
KEYWORDS = {biomech, AI, EMG, locomotion}
}
@ARTICLE{KeijzerF98,
AUTHOR = {F. A. Keijzer},
YEAR = 1998,
TITLE = {Doing without representations which specify what to do},
JOURNAL = {Philosophical Psychology},
VOLUME = 11,
NUMBER = 3,
PAGES = {269--302},
ANNOTE = {author keywords mentioned dynamics and biped locomotion},
ABSTRACT = {A discussion is going on in cognitive science about the use of
representations to explain how intelligent behavior is generated.
In the traditional view, an organism is thought to incorporate
representations. These provide an internal model that is used by
the organism to instruct the motor apparatus so that the adaptive
and anticipatory characteristics of behavior come about.
So-called interactionists claim that this representational
specification of behavior raises more problems than it solves. In
their view, the notion of internal representational models is to
be dispensed with. Instead, behavior is to be explained as the
intricate interaction between an embodied organism and the
specific make up of an environment. The problem with a
non-representational interactive account is that it has severe
difficulties with anticipatory, future oriented behavior. The
present paper extends the interactionist conceptual framework by
drawing on ideas derived from the study of morphogenesis. This
extended interactionist framework is based on an analysis of
anticipatory behavior as a process which involves multiple
spatio-temporal scales of neural, bodily and environmental
dynamics. This extended conceptual framework provides the
outlines for an explanation of anticipatory behavior without
involving a representational specification of future goal states.}
}
@ARTICLE{KeppleT98,
AUTHOR = {T. M. Kepple and H. J. Sommer and K. L. Siegel and S. J. Stanhope},
YEAR = 1998,
TITLE = {A three-dimensional musculoskeletal database for the lower
extremities},
JOURNAL = {Journal of Biomechanics},
VOLUME = 31,
NUMBER = 1,
PAGES = {77--80},
ANNOTE = {The authors examined the muscle attachments from 52 skeletons.},
ABSTRACT = {A three-dimensional musculoskeletal database of the lower
extremities has been developed for use in human musculoskeletal
models. The locations of idealized muscle attachments on the
pelvis, both femurs, both tibias and fibulas, and both feet were
accurately digitized for 52 dried skeletal specimens. The mean
specimen heights were 177.5 cm (male) and 166.2 cm (female) and
the mean specimen age at the time of death was 48.8 yr.
Statistical accumulation and scaling techniques were used to
generate highly representative normative models, which were
divided into groups and tested for differences based on gender
and race. From the test results, the pelvis was divided into a
male model(RMS = 8.6 mm), a black female model(RMS = 7.0 mm) and
a white female model (RMS = 7.3 mm). The foot was separated into
black (RMS = 3.7 mm) and white models (RMS = 3.6 mm). Single
models were used for the femur (RMS = 6.5 mm) and the
tibia/fibula (RMS = 3.7). Containing over 12000 anatomical
landmarks digitized from 52 dried skeletons, this study
represents an improvement over previous databases by an order of
magnitude.},
KEYWORDS = {biomech, anthropometry, leg model}
}
@ARTICLE{KimS98,
AUTHOR = {Seunghwan Kim and Hyubgtae Kook and Sand Gui Lee and Myung-Han
Park},
YEAR = 1998,
TITLE = {Synchronization and Clustering in a Network of Three Globally
Coupled Neural Oscillators},
JOURNAL = {International Journal of Bifurcation and Chaos},
VOLUME = 8,
NUMBER = 4,
PAGES = {731--739},
ABSTRACT = {Collective dynamics of three globally coupled Hodgkin-Huxley
neurons with a symmetric synap-tic coupling has been studied as a
paradigm of one of the simplest but nontrivial example
ofphysiology-based coupled oscillator networks capable of
displaying synchrony and clustering.Rich phase dynamics have been
observed and the phase diagram for various phase states,
inparticular the synchronized state and clustered states, have
been constructed by direct numer-ical simulations of the full
system. We find that the computed phase diagram in the
synapticparameter space of the reversal potential and the signal
propagation time delay reveals a richbifurcation structure and
agrees with one from bifurcation analysis of the reduced phase
model.Implication of our findings in connection with two-coupled
neurons and larger neural networksis discussed.},
KEYWORDS = {NLD, CPG, Neuro}
}
@ARTICLE{KoH96,
AUTHOR = {Hyeongseok Ko and Norman I. Badler},
YEAR = 1996,
TITLE = {Animating Human Locomotion with Inverse Dynamics},
JOURNAL = {IEEE Computer Graphics and Applications},
VOLUME = 16,
NUMBER = 2,
PAGES = {50--59}
}
@ARTICLE{KojimaN98,
AUTHOR = {N. Kojima and K. Nakazawa and S. I. Yamamoto and H. Yano},
YEAR = 1998,
TITLE = {Phase-dependent electromyographic activity of the lower-limb
muscles of a patient with clinically complete spinal cord injury
during orthotic gait},
JOURNAL = {Experimental Brain Research},
VOLUME = 120,
NUMBER = 1,
PAGES = {139--142},
ANNOTE = {The authors present EMG data from a paraplegic patient while
walking with the help of an orthotic device. This device includes a
rigid exoskeleton with the knee and ankle joints fixed, a pair of
crutches, and a CO2 powered device to make the sole of the stance
shoe thicker and that of the swing shoe thinner. The results show
locomotor EMG patterns despite supraspinal input, although the
observed patterns are somewhat different from normal EMG. (For
instance, the tibialis anterior is active during stance.) The
authors point to several other papers that speculate about the
interaction between afferent signals and CPGs for generating
locomotion without suprapinal input: (1) Brooke et al., J.
Neurophys. 73:102-111, 1995 has a study that illustrates the
effects of passive stepping movements (i.e., the stretch reflex);
(2) Harkema et al., J. Neurophys. 77:797-811, 1997 has a study that
interprets weight loading as an important cue for the spinal cord;
(3) Calancie et al.,Brain 117:1143-1159, 1994 has a study that
shows the hip extension modulates a spinal CPG. (Also see Dietz et
al., Ann. Neurol. 37:574-582, 1995 and Dobkin et al., J. Neurol.
Rehab. 9:183-190, 1995 for studies on weight unloading and
treadmill walking.)},
ABSTRACT = {We examined the lower-limb electromyographic (EMG) activity from
a patient with clinically complete spinal cord injury during
orthotic gait. A newly developed gait orthosis was used to obtain
bipedal locomotion. The surface EMG data during the gait together
with the biomechanical variables were collected by way of a radio
EMG system. A cyclic EMG activation pattern corresponding to the
gait cycles were observed in each of the paralyzed lower-limb
muscles during the orthotic gait. Although the EMG activation did
not seem to contribute toward generating the gait, it showed some
similarities to that of the infant stepping or immature gait.
These results might be regarded as one of the indirect pieces of
evidence that suggest the existence of a spinally originating
motor mechanism underlying human locomotion.},
KEYWORDS = {biomech, neuro, CPG, locomotion}
}
@ARTICLE{KopellN91,
AUTHOR = {N. Kopell and G. B. Ermentrout and T. L. Williams},
YEAR = 1991,
TITLE = {On Chains of Oscillators Forced at One End},
JOURNAL = {SIAM Journal on Applied Mathematics},
VOLUME = 51,
NUMBER = 5,
PAGES = {1397--1417}
}
@ARTICLE{LedebtA94,
AUTHOR = {A. Ledebt and Y. Breniere},
YEAR = 1994,
TITLE = {Dynamical Implication of Anatomical and Mechanical Parameters In
Gait Initiation Process In Children},
JOURNAL = {Human Movement Science},
VOLUME = 13,
NUMBER = 6,
PAGES = {801--815},
ABSTRACT = {This study analyses the incidence of anatomical (mass, height,
inertia) and mechanical (gravity) parameters on the duration of
gait initiation, from a standing posture, in children. Twenty-one
children, aged 4, 6 and 8 years, participated in the study.
Experimental and theoretical values of the duration of gait
initiation are compared. The experimental data are computed from
children's gait executed on a force plate. The theoretical data
are computed by using an inverted-pendulum model. The results
show that (1) duration of gait initiation is independent of gait
velocity, as it is in adults; (2) the experimental values are
very close to the theoretical values. These findings suggest that
children's biomechanical constants are determining factors for
initiating movement. It is hypothesized that the capacity to
combine and adapt properties of the body with dynamics of the
context is acquired through practice of independent walking.},
KEYWORDS = {biomech, child locomotion, NLD}
}
@ARTICLE{LedebtA98,
AUTHOR = {Annick Ledebt and B. Bril and Y. Breniere},
YEAR = 1998,
TITLE = {The build-up of anticipatory behaviour - An analysis of the
development of gait initiation in children},
JOURNAL = {Experimental Brain Research},
VOLUME = 120,
NUMBER = 1,
PAGES = {9--17},
ANNOTE = {As summarized in the abstract, the authors looked at COP
trajectories during gait initiation. They hypothesize that adult
anticipatory movements --- while not essential for gait yet lead to
more efficient walking --- are the result of tuning of the
premature movements observed in children after about one year of
independent walking. The authors conclude that experience my play a
large role in motor skill learning in children, in addition to
neural maturation which is often viewed as the primary factor.},
ABSTRACT = {This study analyses the anticipatory postural adjustments during
the gait initiation process in children aged 2.5, 4, 6 and 8
years. In adults, anticipation during gait initiation includes a
shift in the centre of foot pressure (CP) both backwards and
towards the stepping foot. Backward displacement and the duration
of the anticipation phase covary with the gait progression
velocity reached by the subject at the end of the first step. In
the present study, the children walked on a force plate that
allowed us to calculate the acceleration of the centre of mass
and the displacements of the CP. The results showed three main
characteristics of the development of anticipatory behaviour: (1)
The occurrence of anticipatory displacements of the CP increased
progressively with age. Systematic backward anticipation was
found for all children except one of the youngest, whereas the
lateral displacement was systematically observed later, in the
6-year group; (2) the amplitude of the spatial parameters showed
a significant increase with age; (3) contrary to the adult, the
amplitude of the backward shift did not covary with the
forthcoming velocity in the youngest groups. This covariation
became significant at 6 years and remained significant at 8
years. The results showed that even if anticipatory behaviour was
present in 2.5-year-old children it is only later that the child
is able of more accurate tuning of feedforward control, probably
due to better control of the overall postural adjustments.},
KEYWORDS = {biomech, child locomotion, development}
}
@ARTICLE{LerouxA99,
AUTHOR = {Alain Leroux and J. Fung and H. Barbeau},
YEAR = 1999,
TITLE = {Adaptation of the walking pattern to uphill walking in normal and
spinal-cord injured subjects},
JOURNAL = {Experimental Brain Research},
VOLUME = 126,
NUMBER = 3,
PAGES = {359--368},
ANNOTE = {The authors observe that patients with incomplete spinal cord
injuries (SCI) are able to adapt to uphill walking. Normal subjects
show a progressive decrease in hip, knee, and ankle angles with
increasing grade, whereas SCI subjects adopt one of several
possible movement strategies.},
ABSTRACT = {Lower-limb movements and muscle-activity patterns were assessed
from seven normal and seven ambulatory subjects with incomplete
spinal-cord injury (SCI) during level and uphill treadmill
walking (5, 10 and 15 degrees). Increasing the treadmill grade
from 0 degrees to 15 degrees induced an increasingly flexed
posture of the hip, knee and ankle during initial contact in all
normal subjects, resulting in a larger excursion throughout
stance. This adaptation process actually began in mid-swing with
a graded increase in hip flexion and ankle dorsiflexion as well
as a gradual decrease in knee extension. In SCI subjects, a
similar trend was found at the hip joint for both swing and
stance phases, whereas the knee angle showed very limited changes
and the ankle angle showed large variations with grade throughout
the walking cycle. A distinct coordination pattern between the
hip and knee was observed in normal subjects, but not in SCI
subjects during level walking. The same coordination pattern was
preserved in all normal subjects and in five of seven SCI
subjects during uphill walking. The duration of electromyographic
(EMG) activity of thigh muscles was progressively increased
during uphill walking, whereas no significant changes occurred in
leg muscles. In SCI subjects, EMG durations of both thigh and leg
muscles, which were already active throughout stance during level
walking, were not significantly affected by uphill walking. The
peak amplitude of EMG activity of the vastus lateralis, medial
hamstrings, soleus, medial gastrocnemius and tibialis anterior
was progressively increased during uphill walking in normal
subjects. In SCI subjects, the peak amplitude of EMG activity of
the medial hamstrings was adapted in a similar fashion, whereas
the vastus lateralis, soleus and medial gastrocnemius showed very
limited adaptation during uphill walking. We conclude that SCI
subjects can adapt to uphill treadmill walking within certain
limits, but they use different strategies to adapt to the
changing locomotor demands.},
KEYWORDS = {biomech, locomotion, adaptation, spinal injury}
}
@ARTICLE{LiG99,
AUTHOR = {G. Li and K. R. Kaufman and E. Chao and H. E. Rubash},
YEAR = 1999,
TITLE = {Prediction of antagonistic muscle forces using inverse dynamic
optimization during flexion extension of the knee},
JOURNAL = {Journal of Biomechanical Engineering --- Transactions of the
{ASME}},
VOLUME = 121,
NUMBER = 3,
PAGES = {316--322},
ABSTRACT = {This paper examined the feasibility of using different
optimization criteria in inverse dynamic optimization to predict
antagonistic muscle forces and joint reaction forces during
isokinetic flexion/extension and isometric extension exercises of
the knee. Both quadriceps and hamstrings muscle groups were
included in this study. The knee joint motion included
flexion/extension, varus/valgus, and internal/external rotations.
Four linear, nonlinear, and physiological optimization criteria
were utilized in the optimization procedure. All optimization
criteria adopted in this paper were shown to be able to predict
antagonistic muscle contraction during flexion and extension of
the knee. The predicted muscle forces were compared in temporal
patterns with EMG activities (averaged data measured from five
subjects). Joint reaction forces were predicted to be similar
using all optimization criteria. In comparison with previous
studies, these results suggested that the kinematic information
involved in the inverse dynamic optimization plays an important
role in prediction of the recruitment of antagonistic muscles
rather than the selection of a particular optimization criterion.
Therefore, it might be concluded that a properly formulated
inverse dynamic optimization procedure should describe the knee
joint rotation in three orthogonal planes.},
KEYWORDS = {biomech, EMG, optimal control}
}
@ARTICLE{LoebG99,
AUTHOR = {G. E. Loeb and I. E. Brown and E. J. Cheng},
YEAR = 1999,
TITLE = {A hierarchical foundation for models of sensorimotor control},
JOURNAL = {Experimental Brain Research},
VOLUME = 126,
NUMBER = 1,
PAGES = {1--18},
ABSTRACT = {Successful performance of a sensorimotor task arises from the
interaction of descending commands from the brain with the
intrinsic properties of the lower levels of the sensorimotor
system, including the dynamic mechanical properties of muscle,
the natural coordinates of somatosensory receptors, the
interneuronal circuitry of the spinal cord, and computational
noise in these elements. Engineering models of biological motor
control often oversimplify or even ignore these lower levels
because they appear to complicate an already difficult problem.
We modeled three highly simplified control systems that reflect
the essential attributes of the lower levels in three tasks:
acquiring a target in the face of random torque-pulse
perturbations, optimizing fusimotor gain for the same
perturbations, and minimizing postural error versus energy
consumption during low- versus high-frequency perturbations. The
emergent properties of the lower levels maintained stability in
the face of feedback delays, resolved redundancy in over-complete
systems, and helped to estimate loads and respond to
perturbations. We suggest a general hierarchical approach to
modeling sensorimotor systems, which better reflects the real
control problem faced by the brain, as a first step toward
identifying the actual neurocomputational steps and their
anatomical partitioning in the brain.},
KEYWORDS = {neuro, hierarchical control}
}
@ARTICLE{McFadyenB97,
AUTHOR = {B. J. McFadyen and H. Carnahan},
YEAR = 1997,
TITLE = {Anticipatory locomotor adjustments for accommodating versus
avoiding level changes in humans},
JOURNAL = {Experimental Brain Research},
VOLUME = 114,
NUMBER = 3,
PAGES = {500--506},
ANNOTE = {The authors examine "anticipatory locomotor adjustments" (ALA) for
human gait under the conditions of avoiding and accommodating to
changes in terrain height. For avoidance, humans use an active
knee-flexion strategy (with passive hip flexion), and for
accommodation, humans use an active hip-flexion strategy (with
passive knee flexion). In a compound environments involving both
avoidance and accommodation, a combined strategy is used with
active flexion at both hip and knee. The authors then argue that
these strategies arise as a "more effiecient exploitation of
intersegmental dynamics of the lower limb for foot transport and
orientation...."},
ABSTRACT = {The control of locomotion has been studied from various
perspectives related to the tasks of pattern generation,
equilibrium control or adaptation to the environment. The last of
these locomotor components has received comparably less
attention, specifically pertaining to anticipatory adjustments.
Continuing the work which has been conducted on both humans and
cats, the present paper explores the nature of the differences in
anticipatory locomotor adjustments for obstacle avoidance versus
the accommodation to level changes. Six subjects walked in six
different environments including no obstructions, a simple
obstacle, two different level changes (a platform and stairs),
and a combination of an obstacle with each respective level
change. Full dynamic analyses allowed comparison of muscle
torques as well as muscle power generated and absorbed at the
lower limb joints across conditions. It was found that the
previously shown robust lower limb reorganization characterized
by a knee flexor generation strategy was upheld in all conditions
when the obstacle was present. Pure level changes involved an
augmentation of the ongoing hip strategy inherent In normal level
walking. In the compound environment of obstructed level changes,
subjects chose to combine an augmentation of hip flexor power
with a reorganization to active knee flexion. The results are
discussed from the point of view of general principles of
mechanical coordination and the exploitation of intersegmental
dynamics for foot transport.},
KEYWORDS = {biomech, locomotion, dynamics}
}
@BOOK{McMahonT84,
AUTHOR = {Thomas A. Mc{M}ahon},
YEAR = 1984,
TITLE = {Muscles, Reflexes, and Locomotion},
PUBLISHER = {Princeton University Press},
ADDRESS = {Princeton, New Jersey},
ANNOTE = {This book is a classic that starts with muscle mechanics and
muscle physiology and moves quicly to modeling and neural control
of locomotion. The book concludes with an interesting chapter on
effects of scale.},
KEYWORDS = {Biomech, Locomotion, Neuro}
}
@ARTICLE{MillerW94,
AUTHOR = {W. T. Miller},
YEAR = 1994,
TITLE = {Real-Time Neural Network Control of a Biped Walking Robot},
JOURNAL = {IEEE Control Systems},
VOLUME = 14,
PAGES = {41--48}
}
@MASTERSTHESIS{MishraS93,
AUTHOR = {Sanjay Mishra},
YEAR = 1993,
TITLE = {Control of Biped Locomotion Using Oscillators},
NOTE = {Also available as Institute for Systems Research technical report
MS_93-12.},
SCHOOL = {University of Maryland},
KEYWORDS = {biomech, CPGs, locomotion, robotics}
}
@INPROCEEDINGS{MiyakoshiS98,
AUTHOR = {Seiichi Miyakoshi and Gentaro Taga and Yasuo Kuniyoshi and Akihiko
Nagakubo},
YEAR = 1998,
TITLE = {Three Dimensional Bipedal Stepping Motion Using Neural Oscillators
--- Towards Humanoid Motion in the Real World},
BOOKTITLE = {Proceedings of {IEEE/RSJ} International Conference on
Intelligent Robots and Systems},
PAGES = {84--89},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway, NJ},
ANNOTE = {The authors target problem is "To achieve a robust and adaptive
behavior while coordinating a redundant high DOF system under the
strong effect of physical body dynamics". They extend Taga's
simulation work from 2D to 3D and also simplify the CPG control
mechanism. CPGs are based on Matsuoka oscillators (Biol. Cybern.
52:367, 1985). One CPG controls the roll of the pelvis wrt the
trunk and two other CPGs control the "stamping" motion of the legs.
The flexor units of each leg CPG excite the hip, knee, and ankle
flexors of the ipsilateral leg and inhibit the flexor unit for the
contralateral leg. (There's a similar arrangement for the externsor
units and extensor muscles.) The authors also use a weak PD
controller to bias the model into an upright posture. Entrainment
is achieved with the help of touch sensors on the feet and
orientation sensors for the thighs that provide feedback to the
CPG's. The author's devise the CPG coupling so the initial upright
posture converges to a stable limit cycle.},
ABSTRACT = {CPG (central pattern generator) and entrainment dynamics
together form a promising framework for robust and adaptive
behavior generation for a high degree of freedom system in
unstructured environment. This paper investigates its possibility
in the domain of biped robot locomotion....},
KEYWORDS = {Robotics, Biped Locomotion, CPG, Simulation}
}
@ARTICLE{MiyazakiF80,
AUTHOR = {Fumio Miyazaki and Suguru Arimoto},
YEAR = 1980,
TITLE = {A control theoretic study of dynamical biped locomotion},
JOURNAL = {J. Dynamic Systems, Meas. and Control, ASME Trans},
VOLUME = 102,
PAGES = {233--239}
}
@INPROCEEDINGS{MorimotoJ98,
AUTHOR = {Jun Morimoto and Kenji Doya},
YEAR = 1998,
TITLE = {Reinforcement Learning of Dynamic Motor Sequence: Learning to Stand
Up},
BOOKTITLE = {Proceedings of the {IEEE/RSJ} International Conference on
Intelligent Robots and Systems},
PAGES = {1721--1726},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway, NJ},
ANNOTE = {The authors use an actor-critic architecture and TD learning to
make a simulated three-link robot stand up. They specify three
subgoals (joint configurations) that break the overall problem into
three smaller RL problems. A normalized RBF network serves as the
function approximator. Actual joint torques are implemented with a
PD controller based on the actor's target joint angles and
velocities. The critic supplies the reward as a function of the
deviation from the subgoal configuration.},
ABSTRACT = {In this paper, we propose a learning method for implementing
human-like sequential movements in robots. As an example of
dynamic sequential movement, we consider the "stand-up" task for
a two-joint, three-link robot. In contrast to the case of steady
walking or standing, the desired trajecory for such a transient
behavior is very difficult to derive....},
KEYWORDS = {RL, Function Approximation, RBF, Biped Locomotion}
}
@ARTICLE{MullerwilmU93,
AUTHOR = {U. Mullerwilm},
YEAR = 1993,
TITLE = {A Neuron-Like Network With The Ability to Learn Coordinated
Movement Patterns},
JOURNAL = {Biological Cybernetics},
VOLUME = 68,
NUMBER = 6,
PAGES = {519--526},
ABSTRACT = {A model calculation is presented simulating the coordinated
interaction between the walking legs of a multi-legged animal.
The neural network consists of separate modules with oscillatory
capabilities. It has the ability to adjust the necessary
parameters for producing a coordinated interaction between the
modules in a self-organizing fashion. Some sort of reinforcement
comparison learning is used to train the network. It starts
oscillations in a completely uncoupled state. After about 100
learning steps, the generation of a stable alternating pattern is
usually terminated. Then, the network is able to maintain
synchronization, even when disturbances are applied to single
agents or to the network as a whole.},
KEYWORDS = {RL, CPG, locomotion}
}
@ARTICLE{NiggB87,
AUTHOR = {B. M. Nigg and H. A. Bahlsen and S. M. Lueth and S. Stokes},
YEAR = 1987,
TITLE = {The Influence of Running Velocity and Midsole Hardness on External
Impact Forces in Heel-Toe Running},
JOURNAL = {Journal of Biomechanics},
VOLUME = 20,
NUMBER = 10,
PAGES = {951--959},
ANNOTE = {The paper provides some data which suggest that runners tune their
leg stiffness to match running velocity and compensate for changes
in midsole stiffness (cf. FerrisD99). Changes in midsole stiffness
don't influence the external impact forces but do affect the
internal distribution of those forces. (Softer midsoles reduce
ligament forces and increase joint forces.)},
ABSTRACT = {The purpose of this study was to investigate the influence of
midsole hardness and running velocity on external impact forces
in heel-toe running.... The result showed that running velocity
does influence external impact force peaks (linear connection)
and that midsole hardness does not influence magnitude and
loading rate of the external vertical impact forces. Changes in
kinematic and kinetic data can be used to explain this result
mechanically. However, the neuromuscular control mechanism to
keep external impact forces constant are not known.},
KEYWORDS = {Biomech, Locomotion, Leg Stiffness}
}
@ARTICLE{NikolicZ98,
AUTHOR = {Z. M. Nikolic and D. B. Popovic},
YEAR = 1998,
TITLE = {Predicting quadriceps muscle activity during gait with an automatic
rule determination method},
JOURNAL = {{IEEE} Transactions on Biomedical Engineering},
VOLUME = 45,
NUMBER = 8,
PAGES = {1081--1085},
ABSTRACT = {It has been suggested that control using a skill-based expert
system can be applicable to gait restoration. Rule-based systems
have several advantages for this application: they generate a
fast response (they are not computationally intensive) and they
are easy to comprehend and implement. A major problem with using
such systems is the inability of users to determine its rules. In
this study, an automatic method for obtaining the production
rules from a set of examples is described, The rule base was
automatically induced from a model which used external sensor
signals as inputs and electromyogram (EMG) patterns as outputs.
The method is based on the minimization of entropy. A production
rule estimated the muscle activity pattern using the sensor
information. The algorithm was tested using data recorded from
six able-bodied individuals during ground level walking, with and
without ankle-foot orthoses. The data show ed that gait
variability will increase in able-bodied subjects when the motion
of ankle joints is restricted, thus, providing a good test for
generalization. The experimental results illustrate performance
of the production rule that estimates quadriceps muscle group
activity pattern for ground level walking in able-bodied
subjects.},
KEYWORDS = {biomech, AI, EMG, locomotion}
}
@ARTICLE{NishiiJ98,
AUTHOR = {Jun Nishii},
YEAR = 1998,
TITLE = {A Learning Model For Oscillatory Networks},
JOURNAL = {Neural Networks},
VOLUME = 11,
PAGES = {249--257},
ABSTRACT = {A learning model for coupled oscillators is proposed. The
proposed learning rule takes a simple form by which the intrinsic
frequencies ofthe component oscillators and the coupling strength
between them are changed according to the effects of the input
signals on the dynamicsof the oscillator. In the learning mode,
each component oscillator receives a teacher signal of desired
phase and frequency, and a desiredparameter set for generating
the desired pattern is acquired by the proposed learning rule. It
is known that the basic locomotor patterns ofmany living bodies
are generated by coupled neural oscillators. The proposed
learning rule could be a learning model used by such
neuralsystems to acquire an adequate parameter set for generating
a desired locomotor pattern.},
KEYWORDS = {biomech, CPGs, locomotion, robotics}
}
@ARTICLE{PaiY99,
AUTHOR = {Yi-Chung Pai and Kamran Iqbal},
YEAR = 1999,
TITLE = {Simulated movement termination for balance recovery: can movement
strategies be sought to maintain stability in the presence of
slipping or forced sliding?},
JOURNAL = {Journal of Biomechanics},
VOLUME = 32,
NUMBER = 8,
PAGES = {779--786},
ANNOTE = {The authors use simulation and numerical optimization to find
ranges of horizontal velocity where the subject can maintain the
COM above the BOS. They found overlap in these ranges for slipping
and non-slipping conditions. They speculate that adaptation will
cause subjects to seek the overlap region as a strategy for dealing
with uncertain surface conditions.},
ABSTRACT = {Slipping during various kinds of movement often leads to
potentially dangerous incidents of falling. The purpose of this
study was to determine whether there was evidence to support the
theory that movement strategies could be used by individuals to
regain stability during an episode of slipping and whether forced
sliding from a moving platform accurately simulated the effect of
slipping on stability and balance. A single-link-plus-foot
biomechanical model was used to mathematically simulate base of
support (BOS) translation and body segment rotation during
movement termination in sagittal plane. An optimization routine
was used to determine region of stability [defined at given COM
locations as the feasible range of horizontal velocities of the
center of mass (COM) of human subject that can be reduced to zero
with respect to the BOS while still allowing the COM to traverse
within the BOS limits]. We found some 30% overlap in the region
of stability for slipping and non-slipping conditions. This
finding supports the theory that movement strategies can be
sought for restoring stability and balance even if slipping
unexpectedly occurs. We also found that forced sliding produces
effects on stability that are similar to those of slipping,
indicated by over 50% overlap in the regions of stability for the
two conditions. In addition, forced sliding has distinctive
effects on stability, including a "shift" of the region of
stability extended beyond the BOS in the direction of sliding.
These findings may provide quantifiable guidance for balance
training aimed at reducing fall incidents under uncertain floor
surface conditions.},
KEYWORDS = {biomech, biped locomotion, balance, adaptation}
}
@ARTICLE{PandyM88,
AUTHOR = {Marcus G. Pandy and Necip Berme},
YEAR = 1988,
TITLE = {A Numerical Method for Simulating the Dynamics of Human Walking},
JOURNAL = {Journal of Biomechanics},
VOLUME = 21,
NUMBER = 12,
PAGES = {1043--1051},
ANNOTE = {This paper describes important background work for any endeavor in
simulating human gait. The authors present the recursive
Newton-Euler inverse dynamics algorithm as it applies to
simulations of human locomotion. (See also the paper by the same
authors in the current issue.)},
ABSTRACT = {This paper presents a general method for simulating the movement
of the lower extremity during human walking. It is based upon two
separate algorithms: one for single support (am open kinematic
chain), and the other for the double support phase (a closed-loop
linkage).... The attractiveness of the method is that it offers a
compact alternative to manually deriving the equations defining a
mathematical model for human gait.},
KEYWORDS = {Biomech, Locomotion, Simulation, Newton-Euler}
}
@INPROCEEDINGS{ParkJ98,
AUTHOR = {Jong H. Park and Yong K. Rhee},
YEAR = 1998,
TITLE = {{ZMP} Trajectory Generation for Reduced Trunk Motions of Biped
Robots},
BOOKTITLE = {Proceedings of the {IEEE/RSJ} International Conference on
Intelligent Robots and Systems},
PAGES = {90--95},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway, NJ},
ANNOTE = {The authors use the ZMP to compute the desired trunk posture given
a predetermined leg trajectory. (These trajectories are the input
to a controller.) The novel part is that fuzzy logic is used to
determine the desired trajectory of the ZMP. The rules are meant to
capture the idea that the hip and ankle positions play a large role
in the heel-to-toe movement of the ZMP for humans.},
ABSTRACT = {Trunk motions are typically used to stabilize the motions of
biped robots, which can be very large in some leg trajectories.
This paper proposes a method to reduce the motion range of the
trunk by generating a desired trajectory of the ZMP [zero-moment
point]. The trajectory is determined by a fuzzy logic based on
the leg trajectories that are arbitrarily selected. The resulting
ZMP trajectory is similar to human's one and the ZMP continuously
moves forward. The proposed scheme is simulated on a
7-degree-of-freedom biped robot. Its results indicate that the
proposed ZMP trajectory increases the stability of the locomotion
and thus resulting in reduction of motion range of the trunk.},
KEYWORDS = {Robotics, Biomech, Simulation}
}
@ARTICLE{PrattG00,
AUTHOR = {G. A. Pratt},
TITLE = {Legged Robots at MIT: What's New Since Raibert},
JOURNAL = {IEEE Robotics and Automation Magazine},
VOLUME = {7},
NUMBER = {3},
PAGES = {15--19},
YEAR = {2000},
ABSTRACT = {The MIT Leg Lab is best known for the seminal work
of Marc Raibert, who showed in the 1980s that
robotic running could be accomplished using a few
simple, decoupled control laws.... The question
was: what to do next?},
ANNOTE = {The paper gives a nice overview of work at the MIT
Leg Lab and describes two basic lines of research:
improved actuators and improved walking control
algorithms. Research on actuator design has focused
on the series elastic actuator, which improves the
characterisitcs of electric motors for natural
robotic walking movements. On the control front,
research focused on virtual model control which
builds a complex control law out of simple virtual
components that have intuitive physical meaning.},
KEYWORDS = {robotics, actuator, control}
}
@ARTICLE{PrenticeS98,
AUTHOR = {S. D. Prentice and A. E. Patla and D. A. Stacey},
YEAR = 1998,
TITLE = {Simple artificial neural network models can generate basic muscle
activity patterns for human locomotion at different speeds},
JOURNAL = {Experimental Brain Research},
VOLUME = 123,
NUMBER = 4,
PAGES = {474--480},
ANNOTE = {The authors describe a neural network model for generating EMG
patterns observed in human walking. The network has two components.
First, a recurrent network that receives tonic input is responsible
for generating sine and cosine waveforms with the proper frequency.
These waveforms are then shaped by a second feedforward network to
give the actual EMG patterns for specific muscles. No
speed-dependent patterns are possible without a fundamental change
to this model, although the model does illustrate an interesting
decomposition of CPGs into a self-sustaining oscillatory component
and a shaping component.},
ABSTRACT = {A neural network model has been developed to represent the
shaping function of a central pattern generator (CPG) for human
locomotion. The model was based on cadence and electromyographic
data obtained from a single human subject who walked on a
treadmill. The only input to the model was the fundamental timing
of the gait cycle (stride rate) in the form of sine and cosine
waveforms whose period was equal to the stride duration. These
simple signals were then shaped into the respective muscle
activation patterns of eight muscles of the lower limb and trunk.
A network with a relatively small number of hidden units trained
with back-propagation was able to produce an excellent
representation of both the amplitude and timing characteristics
of the EMGs over a range of walking speeds. The results are
further discussed with respect to the dependence of some muscles
upon sensory feedback anti other inputs not explicitly presented
to the model.},
KEYWORDS = {biomech, CPG, biped locomotion, EMG}
}
@ARTICLE{ProkopT95,
AUTHOR = {T. Prokop and W. Berger and W. Zijlstra and V. Dietz},
YEAR = 1995,
TITLE = {Adaptational and Learning-Processes During Human Split-Belt
Locomotion --- Interaction Between Central Mechanisms and Afferent
Input},
JOURNAL = {Experimental Brain Research},
VOLUME = 106,
NUMBER = 3,
PAGES = {449--456},
ANNOTE = {This paper illustrates that humans can adapt to walking where the
legs move at different speeds. The learning effect persists to
later trials but does not transfer to the mirrored condition. The
authors view these results as evidence for separate leg CPGs with
relatively little learning by the cerebellum (in contrast to
previous research on uppper limb coordination).},
ABSTRACT = {Split-belt locomotion (i.e., walking with unequal leg speeds)
requires a rapid adaptation of biomechanical parameters and
therefore of leg muscle electromyographic (EMG) activity. This
adaptational process during the first strides of asymmetric gait
as well as learning effects induced by repetition were studied in
11 healthy volunteers. Subjects were switched from slow (0.5 m/s)
symmetric gait to split-belt locomotion with speeds of 0.5 m/s
and 1.5 m/s, respectively. All subjects were observed to adapt in
a similar way: (1) during the first trial, adaptation required
about 12-15 strides. This was achieved by an increase in stride
cycle duration, i.e., an increase in swing duration on the fast
side and an increase in support duration on the slow side. (2)
Adaptation of leg extensor and flexor EMG activity paralleled the
changes of biomechanical parameters. During the first strides,
muscle activity was enhanced with no increase in coactivity of
antagonistic leg muscles. (3) A motor learning effect was seen
when the same paradigm was repeated a few minutes later -
interrupted by symmetric locomotion - as adaptation to the
split-belt speeds was achieved within 1-3 strides. (4) This
short-time learning effect did not occur in the ''mirror''
condition when the slow and fast sides were inverted. In this
case adaptation again required 12-15 strides. A close link
between central and proprioceptive mechanisms of interlimb
coordination is suggested to underlie the adaptational processes
during split-belt conditions. It can be assumed that, as in
quadrupedal locomotion of the cat, human bipedal locomotion
involves separate locomotor generators to provide the flexibility
demanded. The present results suggest that side-specific
proprioceptive information regarding the dynamics of the movement
is necessary to adjust the centrally generated locomotor activity
for both legs to the actual needs for controlled locomotion.
Although the required pattern is quickly learned, this learning
effect cannot be transferred to the contralateral side.},
KEYWORDS = {biomech, neuro, CPG, locomotion}
}
@INPROCEEDINGS{RostamiM,
AUTHOR = {M. Rostami and G. Bessonnet},
YEAR = 1998,
TITLE = {Impactless Sagittal Gait of a Biped Robot During the Single Support
Phase},
BOOKTITLE = {Proceedings of the {IEEE} International Conference on Robotics
and Automation ({ICRA}-98)},
PAGES = {1385--1391},
PUBLISHER = {IEEE Computer Society},
ADDRESS = {Piscataway}
}
@ARTICLE{SalatianA97,
AUTHOR = {A. W. Salatian and K. Y. Yi and Y. F. Zheng},
YEAR = 1997,
TITLE = {Reinforcement learning for a biped robot to climb sloping surfaces},
JOURNAL = {Journal of Robotic Systems},
VOLUME = 14,
NUMBER = 4,
PAGES = {283--296},
ABSTRACT = {A neural network mechanism is proposed to modify the gait of a
biped robot that walks on sloping surfaces using sensory inputs.
The robot climbs a sloping surface from a level surface with no
priori knowledge of the inclination of the surface. By training
the neural network while the robot is walking, the robot adjusts
its gait and finally forms a gait that is as stable as when it
walks on the level surface. The neural network is trained by a
reinforcement learning mechanism while proportional and integral
(PI) control is used for position control of the robot joints.
Experiments of static and pseudo dynamic learning are performed
to show the validity of the proposed reinforcement learning
mechanism.},
KEYWORDS = {robotics, biped locomotion, RL}
}
@ARTICLE{Sardain98,
AUTHOR = {P. Sardain and H. Rostami and G. Bessonnet},
YEAR = 1998,
TITLE = {An anthropomorphic biped robot: Dynamic concepts and technological
design},
JOURNAL = {{IEEE} Transactions on Systems Man and Cybernetics Part {A}},
VOLUME = 28,
NUMBER = 6,
PAGES = {823--838},
ABSTRACT = {The authors of this study are a part of a joint project,
involving four French laboratories, whose goal is the design and
construction of a mechanical biped robot with anthropomorphic
characteristics. Motivations for this project, named BIP, are
addressed in [7], In the first section of this paper, we will
examine mechanical architectures of some representatives of
state-of-the art biped robots by focusing on their kinematic
arrangement. It is widely known that the existence of natural
gaits is close