Compensation of Stribeck-Type Nonlinear Friction in Positioning Control Using Equivalent-Input-Disturbance Approach

A method of compensating for Stribeck-type nonlinear friction torque for a two-mass mechatronic system has been devised based on the equivalent-inputdisturbance (EID) approach. The nonlinearity in the system is treated as an input-dependent disturbance, and an EID estimator is designed that estimates it. The incorporation of the estimate into the control input compensates for the nonlinearity. Simulation results demonstrate the validity of the method and show that the compensation accuracy is closely related to the time constant of the low-pass filter.