Balancing Control and Backlash Compensation of Leg Exoskeleton using Hybrid Jacobian-Fuzzy Control

N. Aphiratsakun and M. Parnichkun (Thailand)


ALEX-I, Fuzzy Logic Control, GCP, Jacobian Compensation Control, Leg Exoskeleton, ZMP.


This paper proposes a technique for balance and control of Asian Institute of Technology Leg EXoskeleton-I (ALEX-I) known as Hybrid Jacobian-Fuzzy Control which is based on the concept of Zero Moment Point (ZMP). ALEX-I has been designed and developed to assist patients suffering from immobility due to the loss of power on lower limbs. The balanced posture of joint trajectories (set points) under ZMP criterion are generated offline using Jacobian analysis. Jacobian Compensation Control (JCC) converts the compensated set point data into Joint space. Force plate which is formed by placing 4 loadcells on each foot is used to obtain Ground Contact Point (GCP) data. Fuzzy Logic Control (FLC) is used to compensate joints with backlash problem which occurs in ALEX-I. Uncontrollable movement of the upper part of wearer, uncertainties of the model parameters, noises, backlash, and joints gap are considered as disturbance. The 12 outputs from JCC act as the compensated angles for the 12 joints in the roll, pitch and yaw axes that retain the actual ZMP in the convex hull region of the supporting area. The 4 outputs from FLC are the compensated angles for joints with backlash problem (ankle) in the system.

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