Informatics and Engineering Systems Faculty Publications

Document Type

Conference Proceeding

Publication Date

10-27-2025

Abstract

We present a robust PID control for a 2 DoF exoskeleton actuated by permanent-magnet direct current (PMDC) motors. The control design exploits the architecture of the exoskeleton’s dynamical model, which is regarded as the interconnection of a mechanical and an electrical subsystems. The inner loop control for the mechanical subsystem uses robust PID control while the outer control loop uses a model-based control for the electrical subsystem. Lyapunov’s second method is used to show asymptotic stability of the position and velocity tracking error equilibrium point. Asymptotic stability in Lyapunov sense is proved in a twofold procedure. First, it is shown that both mechanical and electrical subsystems of the closed loop system are input to state stable with respect to conveniently selected inputs. Second, asymptotic stability of the interconnected mechanical and electrical subsystems is shown via Lyapunov’s stability direct method. Finally, the performance of the closed-loop system, composed of the exoskeleton model and the proposed control algorithm, is tested via numerical simulations in SIMULINK™ of MATLAB™. The simulation results show good performance and satisfactory angular position and velocity tracking as well as electric current tracking. Further research is under development to relax some assumption imposed here related to parameter uncertainty and to improve the results presented here.

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DOI

10.1115/DETC2025-168604

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