Modeling of Robot Joints with Friction,Backlash and Hysteresis

In order to improve the accuracy of robot joints model,a modeling approach is proposed,in which the friction, backlash and hysteresis characteristics are included in an integrated model.The proposed model is built upon dividing a robot joint into high-speed and low-speed axes respectively.The friction model of high-/low-speed axes are set up based on the GMS(generalized Maxwell-slip) model.Preisach model is utilized to describe the linear behaviors of the high-/low-speed axes of the hysteresis model,and the polynomial method is used to describe nonlinear stiffness in the hysteresis behavior to meet the actual conditions of the reducers' nonlinearity.A simple and effective method is developed to model the backlash behavior in which the speed difference of input and output axes is regarded as the state variable.Finally,an integrated robot joint model is established and simulated in the environment of Matlab/Simulink.Simulation results show that the proposed approach reflects the nonlinear features of robot joints effectively,and thereby can be used in robot joints modeling for describing characteristics and improving accuracy.