Hierarchical neural control of human postural balance and bipedal walking in sagittal plane

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 177-192).The cerebrocerebellar system has been known to be a central part in human motion control and execution. However, engineering descriptions of the system, especially in relation to lower body motion, have been very limited. This thesis proposes an integrated hierarchical neural model of sagittal planar human postural balance and biped walking to 1) investigate an explicit mechanism of the cerebrocerebellar and other related neural systems, 2) explain the principles of human postural balancing and biped walking control in terms of the central nervous systems, and 3) provide a biologically inspired framework for the design of humanoid or other biomorphic robot locomotion. The modeling was designed to confirm neurophysiological plausibility and achieve practical simplicity as well. The combination of scheduled long-loop proprioceptive and force feedback represents the cerebrocerebellar system to implement postural balance strategies despite the presence of signal transmission delays and phase lags. The model demonstrates that the postural control can be substantially linear within regions of the kinematic state-space with switching driven by sensed variables.(cont.) A improved and simplified version of the cerebrocerebellar system is combined with the spinal pattern generation to account for human nominal walking and various robustness tasks. The synergy organization of the spinal pattern generation simplifies control of joint actuation. The substantial decoupling of the various neural circuits facilitates generation of modulated behaviors. This thesis suggests that kinematic control with no explicit internal model of body dynamics may be sufficient for those lower body motion tasks and play a common role in postural balance and walking. All simulated performances are evaluated with respect to actual observations of kinematics, electromyogram, etc.by Sungho JoPh.D

Design and implementation of balance control in a humanoid robot

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaf 28).A proportional derivative control strategy was developed for the purpose of achieving balance in a humanoid robot. An artificial muscle model was adapted which modified physiological parameters for the purpose of controlling a lightweight robot skeleton. Gains were modified as a function of joint angles to permit low gain near the equilibrium point, and consequently to promote a human-like swaying behavior that is energy-efficient. The control strategy was testing by placing a non-zero initial condition on the ankle joint angle and observing the robot, both physically and in simulation, attempt to achieve a stable swaying pattern. This was achieved successfully in a simulation of the robot's mass and inertial parameters, but further efforts must be made to obtain the same behavior in the robot. The ability of a robot to successfully balance using a human-like sway pattern adds another successful biomimetic feature to humanoid robot control and in addition should improve the efficiency of such systems.by Brendan J. Englot.S.B

ADVANCES IN BALANCE AND BIOFEEDBACK MEASUREMENT: THE CASE FOR HEALTH-BASED, POSTURAL SERIOUS GAMES

Health games are increasingly seen as a means to address issues from therapy and rehabilitation. Yet, as a transformative technology, rarely have such games been explored or exploited to assist research into pathologies. Serious games for research (SGR) to uncover pathologies would allow clinicians to develop new differential diagnostics while providing a positive experience for the subject. This paper is not about game design; nevertheless it presents an outlook to considerations that could be taken forward when developing health-based SGRs for pathomechanics, etiopathogenesis and biofeedback. This work relates to preliminary studies on balance challenges manifested in pathologies of the central nervous system. As technology advancements seek to augment human sensory contact between virtual and real worlds this may impact on how virtual environments are used and designed in future. As a consequence heightened sensory (or lack of thereof) may result in falls, for example users with vestibular disorder – because postural stability is a key aspect of motor ability that allows individuals to sustain and maintain the desired physical position of their body Here, our investigation is specific to functional correspondence of the incidental properties in human body sway between healthy subjects and subjects with dyslexia. Our early results suggest postural sway between healthy subjects and those with mild disorders can be distinguished

Stability and Stabilization of Systems with Time Delay: Limitations and Opportunities

Time-delays are important components of many dynamical systems that describe coupling or interconnection between dynamics, propagation, or transport phenomena in shared environments, in heredity, and in competition in population dynamics. This monograph addresses the problem of stability analysis and the stabilisation of dynamical systems subjected to time-delays. It presents a wide and self-contained panorama of analytical methods and computational algorithms using a unified eigenvalue-based approach illustrated by examples and applications in electrical and mechanical engineering, biology, and complex network analysis

Modeling cerebrocerebellar control in horizontal planar arm movements of humans and the monkey

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.Includes bibliographical references (leaves 215-236).In daily life, animals including humans make a wide repertoire of limb movements effortlessly without consciously thinking about joint trajectories or muscle contractions. These movements are the outcome of a series of processes and computations carried out by multiple subsystems within the central nervous system. In particular, the cerebrocerebellar system is central to motor control and has been modeled by many investigators. The bulk of cerebrocerebellar control involves both forward command and sensory feedback information inextricably combined. However, it is not yet clear how these types of signals are reflected in spiking activity in cerebellar cells in vivo. Segmentation of apparently continuous movements was first observed more than a century ago. Since then, submovements, which have been identified by non-smooth speed profiles, have been described in many types of movements. However, physiological origins of submovement have not been well understood. This thesis demonstrates that a currently proposed recurrent integrator PID (RIPID) cerebellar limb control model (Massaquoi 2006a) is consistent with average neural activity recorded in a monkey by developing the Recurrent Integrator-based Cerebellar Simple Spike (RICSS) model.(cont.) The RICSS formulation is consistent with known or plausible cerebrocerebellar and spinocerebellar neurocircuitry, including hypothetical classification of mossy fiber signals. The RICSS model accounts well for variety of cerebellar simple spike activity recorded from the monkey and outperforms any other existing models. The RIPID model is extended to include a simplified cortico-basal ganglionic loop to capture statistical characterization of intermittency observed in individual trials of the monkey. In order to extend the capability of the RIPID model to a larger workspace and faster movements, the model needs to be gainscheduled based on the local state information. A linear parameter varying (LPV) formulation, which shares a similar structure to that suggested by the RICSS model, is performed and its applicability was tested on human subjects performing double step tasks which requires rapid change in movement directions.by Kazutaka Takahashi.Ph.D

Robotic compensation of cerebellar ataxia

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 115-117).The cerebellum is believed to play a role in dynamic compensation in the human motor control system. When it is damaged, subjects make clumsy movements with reduced acceleration, increased overshoot, and swerving in multi-joint movements. These errors, which are referred to clinically as ataxia, are consistent with failing to compensate for the dynamics of the body, especially its inertia during high speed movements. We have developed a robotic system that is capable of dynamically canceling some of the inertial effects in order to reduce the severity of ataxia. This compensator is designed by modeling the closed loop behavior of a subject coupled to a robotic manipulandum. The model is used to solve for the controller needed to produce dynamics in which the inertia of the subject's limb is effectively reduced. The performance of the inertial compensator was tested on both real subjects and a mechanical model designed to reproduce the primary features the subjects' dynamics. The mechanical model provides known and consistent dynamics which facilitates analysis of the compensator performance. The mechanical model confirmed the functionality of the inertial compensator by demonstrating an increase in both the natural frequency and damping ratio of the mechanical model's mass-spring-damper like dynamics. The effect of the inertial compensator on subjects with cerebellar ataxia was measured by their performance on a timed tracing task. The subject with pure ataxia showed a significant improvement in tracing accuracy under inertial compensation, when compared with uncompensated motions.(cont.) This thesis demonstrates that, in at least some situations, it is possible to mechatronically compensate for the errors associated with cerebellar ataxia by correcting for the dynamics of the limb. This demonstration lends support to the theory that the cerebellum plays a role in dynamics compensation, and it also lays the groundwork for future robotic correction of cerebellar ataxia, a disorder for which there is currently no treatment.by Eric D. Smith.S.M

Life Sciences Program Tasks and Bibliography

This document includes information on all peer reviewed projects funded by the Office of Life and Microgravity Sciences and Applications, Life Sciences Division during fiscal year 1995. Additionally, this inaugural edition of the Task Book includes information for FY 1994 programs. This document will be published annually and made available to scientists in the space life sciences field both as a hard copy and as an interactive Internet web pag

Life Sciences Program Tasks and Bibliography for FY 1996

This document includes information on all peer reviewed projects funded by the Office of Life and Microgravity Sciences and Applications, Life Sciences Division during fiscal year 1996. This document will be published annually and made available to scientists in the space life sciences field both as a hard copy and as an interactive Internet web page