Robust Controller Design for Ball Screw Drives with Varying Resonant Mode via $\mu$-synthesis

This paper presents a robust control strategy for ball screw drives with the varying axial resonant mode. Since the varying resonant mode can significantly deteriorate the performance of control systems, a structured uncertainty is introduced to cover the variation range of the resonant mode and build an uncertain model. With this uncertain model, the μ-synthesis technique is adopted to design the robust controller for overcoming the performance deterioration. The standard control configuration of μ-synthesis is improved by introducing a reference model, which improves the solution convergence and specifies the closed-loop performance. The capability of the proposed control strategy for suppressing the resonant mode is validated through the analyses in both frequency and time domains, in comparison to a standard μ-synthesis controller and a conventional PID controller. Furthermore, the comparison is conducted in a series of experiments. The results show that the proposed control strategy can improve the performance in trajectory tracking and disturbance rejection for ball screw drives in the presence of the varying resonant mode.