Research on Direct Position Servo Control of Voice Coil Motor with LCL Filter Based on Active Disturbance Rejection Control

Because of its advantages of small size, high positioning accuracy, simple control, voice coil motor (VCM) is widely used in high-precision positioning systems such as disk drive, medical equipment, precision electronic tubes, etc. Digital control is the most commonly used control method for VCM positioning system, since the digital control method has less loss than the analog control method. However, the problem of large current ripple caused by PWM chopping occurs in digitally controlled system. To deal with this issue, LCL filter is combined with VCM in this paper. The VCM position servo control system with LCL filter turns to a 5th order system. Moreover, LCL filter resonance is a problem that must be considered. In this paper, traditional three-loop structure with PID regulator is first designed for the system, and the parameters tuning and LCL filter resonance suppression are studied. An additional capacitive current sensor is needed in this method to achieve LCL filter resonance suppression. In order to eliminate the additional capacitive current sensor, and further improve the position response speed, this paper proposes a direct position servo control method based on active disturbance rejection control (ADRC). ADRC method can estimate and compensate the disturbances in real time, so the system has better robustness. In addition, LCL filter resonance is suppressed by ADRC active damping, so there is no need for an additional capacitor current sensor.