An Active Disturbance Rejection controller design of a vertical direct-driven servo system

The plant studied in this paper has significant nonlinearity and unbalanced gravitational torque, which have adverse effects on the control performance. To reduce thus effects, modeling the nonlinearity and unbalanced torque was generally considered to be essential in the controller design. Unfortunately, the accurate model is always unable to be reached. For this reason, the idea of Active Disturbance Rejection Control (ADRC) is introduced. The ESO is applied to estimate the total disturbance including nonlinearity and gravitational torque. After then, the estimated disturbance is cancelled out in the control. Furthermore, the feedforward control is combined with ADRC to obtain faster response. In the end, the real test is conducted in comparison with traditional PID control, under the reference of step and sinusoid signal. The results show the better performance of ADRC.