Single-loop output-feedback positioning technique for servo systems via second-order pole-zero cancellation approach

This article presents an advanced order-reduction technique for servo motor positioning applications by explicitly handling the model-plant mismatches caused by parameter and load uncertainties. The resultant output feedback system establishes an observer-based single-loop structure ensuring first-order position dynamics by the second-order pole-zero cancellation mechanism. Two contributions are provided: first, the plant parameter information-free angular velocity and acceleration observer leading to the first-order estimation dynamics by the proposed gain structure; second, the output-feedback positioning law constraining the closed-loop behavior into the first-order dynamics through the observer-based active damping injection causing the second-order pole-zero cancellation, requiring the only nominal plant parameter values. An experimental testbed using QUBE-servo2 confirms the practical effectiveness of the proposed control scheme.