  Design of active orthosis is a challenging problem from both the dynamic
simulation and control points of view. The redundancy problem of the
simultaneous human-orthosis actuation is an interesting exercise to solve
concerning the analytical and computational cost effectiveness. The
physiological static optimization approach tries to solve the actuation sharing
problem. Its objective is to quantify the contributions of muscles and active
orthosis to the net joint torques in order to select the proper actuator for
the joint. Depending on the disability of each patient, different controllers
can be designed. As a matter of fact, the duration of the gait cycle for each
patient should be different. In this paper, a PI controller is designed whose
parameters are tuned by optimizing a cost function which takes into account the
patients muscle power and the error of the knee angle with the reference value.
Moreover, the final time is obtained by minimizing the mean of integral squared
errors. The performance of the method is shown by designing the controller for
three types of patients, ordered from low to high disability. The objective of
this work is to use optimal control techniques based on physiological static
optimization approach to the design of active orthosis and its control.
