Study on nonlinear friction compensation for bi-axis servo system based-on ADRC

In view of the friction nonlinearity and uncertain external disturbance in the bi-axis servo system, on the basis of analyzing the contour error of the system, combined with the cross-coupling control idea, an improved second-order Active Disturbance Rejection Controller (ADRC) was proposed. The inner disturbance and outside disturbance of the system, as well as the friction could be observed and compensated by the high-gain extended state observer (ESO) of ADRC, which has strong robustness. Due to proposing a new nonlinear function to overcome the rough of conventional nonlinear function in the nonlinear state error feedback of conventional ADRC, so the system is un-sensitive to the friction. The simulation and comparison analysis indicate that the system based on improved ADRC can well compensate the nonlinear friction, and has better robustness, so the contour error can be also reduced.