Model free robust impedance control of robot manipulators using fourier series expansion

Abstract

Impedance control is the most favorite control of robot manipulators in contact with environment. The dynamic behavior of robotic system in response to environment is prescribed by an impedance model. This model is certain and linear while the robot manipulator is uncertain and nonlinear. So the major challenge is overcoming uncertainty and nonlinearity to dominate the desired impedance model. This paper presents a robust impedance control strategy based on Variable Structure Model Reaching Control (VSMRC) and Function Approximation Techniques (FAT). FAT is based on Fourier series approximation. In contrast to other existing methods, the proposed approach includes two important properties. Firstly, it is robust against fast changes in uncertainty due to increased speed of convergence in Fourier series approximation. Secondly, it does not require uncertainties bound to be known. This scheme is simulated on an industrial selective compliance assembly robot arm (SCARA). Simulation results verify the theory and confirm the effectiveness of presented technique.