Precise joint torque control method for two-inertia system with backlash using load-side encoder

Abstract

Force/torque control is attracting considerable attention for the realization of compliant motion in mechatronic systems such as industrial robots and human-support robots. They have transmission mechanisms such as gear reducers, which introduce resonance in the low frequency range and nonlinearity by backlash. To achieve high precision even with transmission mechanisms, the reduced cost of high-resolution encoders has increased the number of devices with load-side (gear-output-side) encoders in industry. Therefore, this study proposes a precise joint torque control method with backlash compensation by using load-side encoder information. The effective use of the load-side encoder information enables the proposed method to compensate the fast backlash effect in a feed forward manner. Moreover, based on the experimental analyses, the novel backlash compensation model is proposed to solve the problems caused by the conventional backlash compensation model. Simulation and experimental results demonstrate the advantages of the proposed method.