Modeling and composite nonlinear feedback control of voice coil motor in high precision positioning system

In this paper, a composite nonlinear feedback (CNF) control method is adopted for servo positioning table which is driven by voice coil motor (VCM), it consists of a linear feedback part for achieving fast response and a nonlinear feedback part for suppressing the overshoot. Meanwhile, the disturbance observer (DOB) is designed to compensate the original CNF control so as to eliminate the time-varying disturbance and improve the positioning accurate. In addition, to make the DOB be able to observe the disturbances accurately, the mathematical model of VCM is established accurately, which takes the air damping, eddy current damping and elastic stiffness into consideration. The experimental and simulation results show that the parameters of VCM are identified precisely, and the improved CNF control method can improve transient performance, steady-state accuracy, it has more robustness to suppress the external disturbance and uncertainty in servo positioning system.