Optimal Control Parameterization for ActivelPassive EXoskeleton with Variable Impedance Actuator.

An ActivelPassive EXoskeleton (APEX) has been investigated to provide continuous assistance as a passive device, while having tunable dynamic properties through a variable impedance actuator. This paper introduces a novel computational method for APEX to search suitable dynamic properties to assist a given task. An optimal parameter selection problem is formulated based on a hybrid system model, and a gradient method is proposed to solve the nonlinear optimization problem. A simulation study is conducted, and the results indicate that the method can search the global optimum of the problem to provide users with suitable passive assistance.