Design of a Filter-Based Iterative Learning Control and Its Application to the Tension Force Tracking of a Lower-limb Orthosis

概要

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Based on two-dimensional (2-D) system theory, this study proposes a design method for a filter-based iterative learning control (FILC) scheme. The FILC scheme consists of a proportional feedback controller and a feedforward filter. The 2-D model for the FILC is established in the form of the so-called “Roessors model”. Moreover, stability for a 2-D separable model can be simplified, with only one criterion to be met. In order to utilize the criterion derived from the 2-D separable system, the overall FILC control system is constructed in the form of a 2-D separable system by assuming a new state for the 2-D model. Therefore, a sufficient and necessary condition for convergence of the overall control system can be reached. Moreover, to validate the design criteria, we establish design criteria for the feedforward filter and conduct a simulation. Finally, the proposed scheme is applied to the force tracking of a lower-limb orthosis with pneumatic muscle actuator (PMA). Excellent force-tracking performance is achieved through experimental verification.