Full Closed Loop Algorithm of Position and Torque Double Loop Control Based on Linear Active Disturbance Rejection

The full-closed-loop feed servo system of a computer numerical control (CNC) machine tool uses a linear encoder on the load side for position control, requiring high accuracy, fast response, and good robustness. Traditional full-closed loop feed servos employ a tri-loop control scheme consisting of position, velocity, and torque loops, but they struggle to achieve high position loop bandwidth due to factors such as speed detection and system delay. In this paper, a full-closed loop control method based on linear active disturbance rejection control (LADRC) is proposed, which utilizes the idea of active-disturbance rejection to design a position and torque dual-loop control. A state observer is designed to observe the total disturbance and output of the system, and a proportional-derivative (PD) controller is designed based on the bandwidth, simplifying the parameter tuning process. Compared to traditional tri-loop proportion integration (PI) control theory, the proposed method achieves higher bandwidth and smaller position tracking error.