Comparison of Several Active Disturbance Rejection Control Methods for Rigid-Flexible Coupling Motion Stage

The accuracy of traditional direct drive motion stage with mechanical bearing is difficult to be effectively improved due to the nonlinear friction disturbance. In this paper, a rigid-flexible coupling motion stage is invented, which uses the elastic deformation of flexure hinges to compensate the friction dead zone. Furthermore, the high-frequency disturbance of the friction is transformed into the low-frequency elastic deformation. Since the invented motion stage is composed of both rigid and elastic parts, the control for the stage remains challenging. The proportional-integral-derivative (PID) control and the active disturbance rejection control (ADRC) designed with eight different extended state observers (ESO) are rigorously compared. Firstly, for the rigid-flexible coupling motion stage, the tracking performance of the ADRC is obviously better than the PID control. Moreover, the convergence speed of the reduced order ESO (RESO) is not necessarily fast than the full-order ESO. Furthermore, among the different ESOs, the cascaded ESO design consisting of two full-order ESOs (ESO-ESO) has the fastest convergence speed.