Improved Sliding Mode-Active Disturbance Rejection Control of Electromagnetic Linear Actuator for Direct-Drive System

Abstract

The electromagnetic linear actuator is used as the core drive unit to achieve high precision and high response in the direct-drive actuation system. In order to improve the response performance and control accuracy of the linear drive unit, an improved sliding mode-active disturbance rejection control (ISM-ADRC) method was proposed. A motor model was established based on improved LuGre dynamic friction. The position loop adopts the improved integral traditional sliding mode control based on an extended state observer, and the current loop adopts PI control. The stability of the system is verified based on the Lyapunov theory. A nonlinear dilated state observer is used to effectively observe the electromagnetic linear actuator position and velocity information while estimating and compensating the internal and external uncertainty perturbations. At the same time, the saturation function sat(s) is used to replace the sign(s) and introduce the power function of the displacement error variable. The improved integral sliding mode control law further improves the response speed and control accuracy of the controller while reducing the jitter inherent in the conventional sliding mode. Simulation and experimental data show that the proposed improved sliding mode-active disturbance rejection control reduces the 8-mm step response time of the electromagnetic linear actuator by 21.9% and the steady-state error by less than 0.01 mm compared with the conventional sliding-mode control, while the system has 49.4% less adjustment time for abrupt load changes and is more robust to different loads and noise.

Keywords

• electromagnetic linear actuator
• direct drive
• traditional sliding mode control
• active disturbance rejection control
• position control