Current Controller Design of Precision Servo Drive

This paper presents a design of a modified digital current controller of an electric machine, which is controlled with the pulse-width modulated power converter. The proposed solution includes the method of a modified current feedback oversampling, which improves the robustness against the noise, and a modified current controller, which increases the bandwidth of closed control loop compared to the state-of-the-art controller. The proposed solution is focused on the digital signal processor implementation without significant increasing of the computational load. The controller parameter setting procedure enabling to achieve both high control bandwidth and the robustness against the parameter changes is presented. Analytical and experimental studies were carried out for a planar precision servo drive with a control frequency of 20 kHz. The achieved current closed loop bandwidth is 5.5 kHz estimated using -3 dB criterion and 3 kHz estimated using -90 degree criterion.