Design of active orthosis is a challenging problem from both the dynamicsimulation and control points of view. The redundancy problem of thesimultaneous human-orthosis actuation is an interesting exercise to solveconcerning the analytical and computational cost effectiveness. Thephysiological static optimization approach tries to solve the actuation sharingproblem. Its objective is to quantify the contributions of muscles and activeorthosis to the net joint torques in order to select the proper actuator forthe joint. Depending on the disability of each patient, different controllerscan be designed. As a matter of fact, the duration of the gait cycle for eachpatient should be different. In this paper, a PI controller is designed whoseparameters are tuned by optimizing a cost function which takes into account thepatients 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 squarederrors. The performance of the method is shown by designing the controller forthree types of patients, ordered from low to high disability. The objective ofthis work is to use optimal control techniques based on physiological staticoptimization approach to the design of active orthosis and its control.
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