Biped robot walking control on inclined planes with fuzzy parameter adaptation

The bipedal structure is suitable for a robot functioning in the human environment, and assuming assistive roles. However, the bipedal walk is a poses a difficult control problem. Walking on even floor is not satisfactory for the applicability of a humanoid robot. This paper presents a study on bipedal walk on inclined planes. A Zero Moment Point (ZMP) based reference generation technique is employed. The orientation of the upper body is adjusted online by a fuzzy logic system to adapt to different walking surface slopes. This system uses a sampling time larger than the one of the joint space position controllers. A newly defined measure of the oscillatory behavior of the body pitch angle and the average value of the pelvis pitch angle are used as inputs to the fuzzy adaptation system. A 12-degrees-of-freedom (DOF) biped robot model is used in the full-dynamics 3-D simulations. Simulations are carried out on even floor and inclined planes with different slopes. The results indicate that the fuzzy adaptation algorithms presented are successful in enabling the robot to climb slopes of 5.6 degrees (10 percent)

Locomotor-like leg movements evoked by rhythmic arm movements in humans

Motion of the upper limbs is often coupled to that of the lower limbs in human bipedal locomotion. It is unclear, however, whether the functional coupling between upper and lower limbs is bi-directional, i.e. whether arm movements can affect the lumbosacral locomotor circuitry. Here we tested the effects of voluntary rhythmic arm movements on the lower limbs. Participants lay horizontally on their side with each leg suspended in an unloading exoskeleton. They moved their arms on an overhead treadmill as if they walked on their hands. Hand-walking in the antero-posterior direction resulted in significant locomotor-like movements of the legs in 58% of the participants. We further investigated quantitatively the responses in a subset of the responsive subjects. We found that the electromyographic (EMG) activity of proximal leg muscles was modulated over each cycle with a timing similar to that of normal locomotion. The frequency of kinematic and EMG oscillations in the legs typically differed from that of arm oscillations. The effect of hand-walking was direction specific since medio-lateral arm movements did not evoke appreciably leg air-stepping. Using externally imposed trunk movements and biomechanical modelling, we ruled out that the leg movements associated with hand-walking were mainly due to the mechanical transmission of trunk oscillations. EMG activity in hamstring muscles associated with hand-walking often continued when the leg movements were transiently blocked by the experimenter or following the termination of arm movements. The present results reinforce the idea that there exists a functional neural coupling between arm and legs

Design and Control of a Knee Exoskeleton for Assistance and Power Augmentation

Thanks to the technological advancements, assistive lower limb exoskeletons are moving from laboratory settings to daily life scenarios. This dissertation makes a contribution toward the development of assistive/power augmentation knee exoskeletons with an improved wearability, ergonomics and intuitive use. In particular, the design and the control of a novel knee exoskeleton system, the iT-Knee Bipedal System, is presented. It is composed by: a novel mechanism to transmit the assistance generated by the exoskeleton to the knee joint in a more ergonomic manner; a novel method that requires limited information to estimate online the torques experienced by the ankles, knees and hips of a person wearing the exoskeleton; a novel sensor system for shoes able to track the feet orientation and monitor their full contact wrench with the ground. In particular, the iT-Knee exoskeleton, the main component of the aforementioned system, is introduced. It is a novel six degree of freedom knee exoskeleton module with under-actuated kinematics, able to assist the flexion/extension motion of the knee while all the other joint\u2019s movements are accommodated. Thanks to its mechanism, the system: solves the problem of the alignment between the joint of the user and the exoskeleton; it automatically adjusts to different users\u2019 size; reduces the undesired forces and torques exchanged between the attachment points of its structure and the user\u2019s skin. From a control point of view, a novel approach to address difficulties arising in real life scenarios (i.e. noncyclic locomotion activity, unexpected terrain or unpredicted interactions with the surroundings) is presented. It is based on a method that estimates online the torques experienced by a person at his ankles, knees and hips with the major advantage that does not rely on any information of the user\u2019s upper body (i.e. pose, weight and center of mass location) or on any interaction of the user\u2019s upper body with the environment (i.e. payload handling or pushing and pulling task). This is achieved v by monitoring the full contact wrench of the subject with the ground and applying an inverse dynamic approach to the lower body segments. To track the full contact wrench between the subject\u2019s feet and the ground, a novel add on system for shoes has been developed. The iT-Shoe is adjustable to different user\u2019s size and accommodates the plantar flexion of the foot. It tracks the interactions and the orientation of the foot thanks to two 6axis Force/Torque sensors, developed in-house, with dedicated embedded MEMS IMUs placed at the toe and heel area. Different tasks and ground conditions were tested to validate and highlight the potentiality of the proposed knee exoskeleton system. The experimental results obtained and the feedback collected confirm the validity of the research conducted toward the design of more ergonomic and intuitive to use exoskeletons

Active Versus Passive Control of Arm Swing: Implication of the Restriction of Pelvis Rotation during Human Locomotion

To date, it remains unclear how passive dynamics and active neural control contribute to arm swing during human locomotion. The passive hypothesis attributes arm swing to the passive transfer of energy from the legs to the arms via biomechanical linkages, while the active hypothesis states that arm swing is actively driven by muscles via neural mechanisms. The present study aims to investigate this phenomenon further by disrupting the biomechanical linkages, thereby directly challenging the passive hypothesis. Ten healthy individuals walked on a treadmill with and without an apparatus that constrained pelvis rotation at 3 different speeds (2 mph, 3 mph, and 4 mph). Spatial (upper and lower limb movement amplitudes) and temporal (movement frequencies and phase relationships between segment trajectories) aspects of limb movement were analyzed. The pelvis rotation was reduced by an average of 60.6% while constrained. As the treadmill speed increased, the movement amplitude of the upper and lower limbs increased. While the pelvis was constrained, arm swing amplitude decreased and the muscle activity of the upper limbs and lower limbs was similar to walking in the unconstrained condition. The movement frequency patterns and phase relations between segment trajectories were also conserved irrespective of speed and pelvis constraint conditions. These results provide evidence that passive elements are a significant factor in arm swing amplitude. However, the conserved EMG patterns and movement frequencies are suggestive of an underlying neural drive that contributes to the maintenance of the temporal aspects of gait. These observations are most likely due to passive dynamics in addition to neural mechanisms that maintain the rhythmic locomotor pattern via upper and lower limb central pattern generators (CPGs)

Üner Tan Syndrome: Review and Emergence of Human Quadrupedalism in Self-Organization,\ud Attractors and Evolutionary Perspectives\ud

The first man reported in the world literature exhibiting habitual quadrupedal locomotion was discovered by a British traveler and writer on the famous Baghdat road near Havsa/Samsun on the middle Black-Sea coast of Turkey (Childs, 1917). Interestingly, no single case with human quadrupedalism was reported in the scientific literature after Child's first description in 1917 until the first report on the Uner Tan syndrome (UTS: quadrupedalism, mental retardation, and impaired speech or no speech)in 2005 (Tan, 2005, 2006). Between 2005 and 2010, 10 families exhibiting the syndrome were discovered in Turkey with 33 cases: 14 women (42.4%) and 19 men (57.6%). Including a few cases from other countries, there were 25 men (64.1%)and 14 women (35.9%). The number of men significantly exceeded the number of women (p < .05). Genetics alone did not seem to be informative for the origins of many syndromes, including the Uner Tan syndrome. From the viewpoint of dynamical systems theory, there may not be a single factor including the neural and/or genetic codes that predetermines the emergence of the human quadrupedalism.Rather, it may involve a self-organization process, consisting of many decentralized and local interactions among neuronal, genetic, and environmental subsystems. The most remarkable characteristic of the UTS, the diagonal-sequence quadrupedalism is well developed in primates. The evolutionarily advantage of this gait is not known. However, there seems to be an evolutionarily advantage of this type of locomotion for primate evolution, with regard to the emergence of complex neural circuits with related highly complex structures. Namely, only primates with diagonal-sequence quadrupedal locomotion followed an evolution favoring larger brains, highly developed cognitive abilities with hand skills, and language, with erect posture and bipedal locomotion, creating the unity of human being. It was suggested that UTS may be considered a further example for Darwinian diseases, which may be associated with an evolutionary understanding of the disorders using evolutionary principles, such as the natural selection. On the other hand, the human quadrupedalism was proposed to be a phenotypic example of evolution of reverse, i.e., the reacquisition by derived populations of the same character states as those of ancestor populations. It was also suggested that the emergence of the human quadrupedalism may be related to self-organizing processes occurring in complex systems, which select or attract one preferred behavioral state or locomotor trait out of many possible attractor states. Concerning the locomotor patterns, the dynamical systems in brain and body of the developing child may prefer some kind of locomotion, according to interactions of the internal components and the environmental conditions, without a direct role of any causative factor(s), such as genetic or neural codes, consistent with the concept of self-organization, suggesting no single element may have a causal priority

Respiratory, postural and spatio-kinetic motor stabilization, internal models, top-down timed motor coordination and expanded cerebello-cerebral circuitry: a review

Human dexterity, bipedality, and song/speech vocalization in Homo are reviewed within a motor evolution perspective in regard to &#xd;&#xa;&#xd;&#xa;(i) brain expansion in cerebello-cerebral circuitry, &#xd;&#xa;(ii) enhanced predictive internal modeling of body kinematics, body kinetics and action organization, &#xd;&#xa;(iii) motor mastery due to prolonged practice, &#xd;&#xa;(iv) task-determined top-down, and accurately timed feedforward motor adjustment of multiple-body/artifact elements, and &#xd;&#xa;(v) reduction in automatic preflex/spinal reflex mechanisms that would otherwise restrict such top-down processes. &#xd;&#xa;&#xd;&#xa;Dual-task interference and developmental neuroimaging research argues that such internal modeling based motor capabilities are concomitant with the evolution of &#xd;&#xa;(vi) enhanced attentional, executive function and other high-level cognitive processes, and that &#xd;&#xa;(vii) these provide dexterity, bipedality and vocalization with effector nonspecific neural resources. &#xd;&#xa;&#xd;&#xa;The possibility is also raised that such neural resources could &#xd;&#xa;(viii) underlie human internal model based nonmotor cognitions. &#xd;&#xa

Mechanical engineering challenges in humanoid robotics

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 36-39).Humanoid robots are artificial constructs designed to emulate the human body in form and function. They are a unique class of robots whose anthropomorphic nature renders them particularly well-suited to interact with humans in a world designed for humans. The present work examines a subset of the plethora of engineering challenges that face modem developers of humanoid robots, with a focus on challenges that fall within the domain of mechanical engineering. The challenge of emulating human bipedal locomotion on a robotic platform is reviewed in the context of the evolutionary origins of human bipedalism and the biomechanics of walking and running. Precise joint angle control bipedal robots and passive-dynamic walkers, the two most prominent classes of modem bipedal robots, are found to have their own strengths and shortcomings. An integration of the strengths from both classes is likely to characterize the next generation of humanoid robots. The challenge of replicating human arm and hand dexterity with a robotic system is reviewed in the context of the evolutionary origins and kinematic structure of human forelimbs. Form-focused design and function-focused design, two distinct approaches to the design of modem robotic arms and hands, are found to have their own strengths and shortcomings. An integration of the strengths from both approaches is likely to characterize the next generation of humanoid robots.by Peter Guang Yi Lu.S.B

Reversible silencing of spinal neurons unmasks a left-right coordination continuum.

This dissertation is focused on dissecting the functional role of two anatomically-defined pathways in the adult rat spinal cord. A TetOn dual virus system was used to selectively and reversibly induce enhanced tetanus neurotoxin expression in L2 neurons that project to L5 (L2-L5) or C6 (long ascending propriospinal neurons, LAPNs). Results focus on the changes observed during overground locomotion. The dissertation is divided into four chapters. Chapter One is a focused introduction to locomotion, including its broad description, the central mechanisms of its expression, how genetic-based approaches defined these mechanisms, and the limitations in these approaches. It concludes with details of the silencing paradigm used here and a summary of the main findings. Chapter Two describes the functional consequences of silencing L2-L5 interneurons. The focus is on selective disruption of hindlimb coordination during overground locomotion, revealing a continuum from walk to hop. These changes are independent of speed, step frequency, and other spatiotemporal features of gait. Left-right alternation was restored during swimming and stereotypic exploration, suggesting a task-specific role. Silencing L2-L5 interneurons partially uncoupled the hindlimbs, allowing spontaneous shifts in coordination on a step-by-step basis. It is proposed this pathway distributes temporal information for left-right hindlimb alternation, securing effective coordination in a context-dependent manner. Chapter Three focuses on the consequences of silencing LAPNs.Three patterns of interlimb coupling are disrupted: left-right forelimb, left-right hindlimb, and contralateral hindlimb-forelimb coordination. Observed again was a context-dependent continuum from walk-to-hop, irrespective of step frequency, speed, and the salient features that define locomotion. However, instead of spontaneous shifts in coordination as observed from L2-L5 interneuron silencing, the breadth of coupling patterns expressed were maintained on a step-by-step basis. It is proposed that this ascending, inter-enlargement pathway distributes temporal information required for left-right alternation at the shoulder and pelvic girdles in a context-dependent manner. Collectively, these data suggest that L2-L5 interneurons and LAPNs are key pathways that distribute left-right patterning information throughout the neuraxis. The functional role(s) of these pathways are exquisitely gated to the context at hand, suggesting that the locomotor circuitry undergoes functional reorganization thereby endowing or masking the silencing-induced disruptions to interlimb coordination

Coordination between arm and leg movements during locomotion

To evaluate the contrasting dynamical and biomechanical interpretations of the 2:1 frequency coordination between arm and leg movements that occurs at low walking velocities and the 1:1 frequency coordination that occurs at higher walking velocities, the authors conducted an experiment in which they quantified the effect of walking velocity on the stability of the frequency and phase coordination between the individual limb movements. Spectral analyses revealed the presence of 2:1 frequency coordination as a consistent feature of the data in only 3 out of 8 participants at walking velocities ranging from 1.0 to 2.0 km/h, in spite of the fact that the eigenfrequencies of the arms were rather similar across participants. The degree of interlimb coupling, as indexed by weighted coherence and variability of relative phase, was lower for the arm movements and for ipsilateral and diagonal combinations of arm and leg movements than for the leg movements. Furthermore, the coupling between all pairs of limb movements was found to increase with walking velocity, whereas no clear signs were observed that the switches from 2:1 to 1:1 frequency coordination and vice versa were preceded by loss of stability. Therefore, neither a purely biomechanical nor a purely dynamical model is optimally suited to explain these results. Instead, an integrative model involving elements of both approaches seems to be required