Modeling and simulating the nonlinear characters of robot joints

This paper presents a new approach to establish a dynamic model of robot joints. The model is constructed by ideally dividing a robot joint into high-speed block and low-speed block and described with nonlinear characteristics such as friction, backlash and hysteresis. The friction behavior of two blocks is captured by the Generalized Maxwell-Slip model. The Preisach model is used to describe the hysteresis character of joints. Because the “congruency” assumption of hysteresis, which is needed in the Preisach model, is not strictly tenable in complex joints, so there construct the hysteresis model through Preisach model plus a nonlinear stiffness. A simple and effective method is developed to model the backlash behavior in joints. The integrated joint model of an industry robot built by our laboratory is established and simulation model is constructed in Simulink of Matlab. The validity of this model is demonstrated and a new avenue opened in this way.