Dynamic Modelling and Adaptive Control of An Upper-Limb Robotic Exoskeleton

Abstract

This paper presents the modelling and control of a novel upper-limb exoskeleton with a serial structure. The dynamic modelling is performed by using the Newton-Euler method, followed by linear transformations to obtain a minimal parameter set containing unknown dynamic parameters. By considering uncertain factors such as inertial forces and transmission losses within motor internal reducers, a periodic trajectory is designed for the purpose of parameter identification. The weighted least squares method was employed for this purpose, estimated values for the dynamic parameters are calculated and compared with actual values by employing the root mean square error and mean absolute error. Additionally, a zero-force control based on an outer-loop PID strategy has been devised, and the viability of the dynamic model and the controller has been demonstrated through experimentation. The results demonstrate that the proposed upper-limb exoskeleton can be employed to enhance the efficacy of robot-assisted rehabilitation.