Linear Active Disturbance Rejection Control for Hydraulic Position Servo System

The high-precision motion control of the hydraulic position servo system (HPSS) is facing enormous challenges, because of the problems of parametric uncertainties, flow nonlinearity of servo valve, and unknown external disturbances in a hydraulic system. To address these problems in the framework of linear active disturbance rejection control (LADRC), the traditional third-order model of HPSS is reconstructed into two parts: a single integrator and generalized disturbances. The rationality of the model is demonstrated by the time domain and frequency domain. Then a first-order LADRC can be applied successfully. Meanwhile, a model-auxiliary linear extended state observer (MLESO) is established when the load pressure is measurable. Simulation and calculation show that the MLESO works only under heavy load applications. Co-simulations are carried out to illustrate the effectiveness of the proposed method.