Robust Impedance Control for Rehabilitation Robot

Abstract

Original Research Paper Received 31 May 2015 Accepted 19 June 2015 Available Online 13 July 2015 In this study, novel robust impedance control for lower-limb rehabilitation robotic system using voltage control strategy is used. Most existing control approaches are based on control torque strategy, which requires knowledge of robot dynamics as well as dynamics of patients. This obliges the controller to overcome complex problems such as uncertainty and nonlinearity involved in the dynamics of the system, robot and patients. Conversely, the voltage-based control approaches are free from the system dynamics. In addition, it considers the actuator dynamics. The performance of voltage-based approaches is demonstrated by experimental result in robotic applications. Compared with torque control scheme, it is simpler, less computational and more efficient. Nevertheless, uncertainty of actuator dynamics results in challenges for the voltage control strategy applications. The present paper presents novel robust impedance control based on the voltage control strategy. To overcome uncertainties, the adaptive fuzzy estimator is designed based on the voltage-based strategy. The proposed control is verified by stability analysis. To illustrate the effectiveness of the control approach, 1-DOF lower-limb rehabilitation robot is designed. Both torque-based impedance control and the voltage-based impedance control are compared through therapeutic exercise. It is shown that the voltage-based impedance control performs better than the traditional torque-based impedance control. Simulation and experimental results both show that the proposed voltage-based robust impedance control is superior to voltage-based impedance control in presence of uncertainties.