Pole-Zero Cancellation Speed Control With Variable Current Cut-Off Frequency for Servo Motors

This article presents a novel system parameter-independent double-loop solution to the speed control problem of servo motors incorporating the variable current cut-off frequency into the current-loop. The active damping terms for both the inner and outer loops make it possible to assign the pole-zero cancellation nature to the closed-loop system by cooperating the structured proportional-integral gains. The proposed analytic variable cut-off frequency mechanism automatically boosts the transient current-cut off frequency and decreases it to its initial value in the steady-state operation to secure the improved relative stability and reduced current ripple level, maintaining the rapid speed tracking behavior (feasibility of the high-speed cut-off frequency). The QUBE-servo2 kit experimentally verifies the practical benefits of the proposed solution.