Robust Motion Control of the Frictionless Positioning Device Suspended by Cone-Shaped Active Magnetic Bearings

A time delay controller with state feedback is proposed for the frictionless positioning device which is subject to the variations of inertia and the presence of measurement noise. The time delay controller, which is combined with a low-pass filter to attenuate the effect of measurement noise, ensures the asymptotic stability of the closed loop system. It isfound that the low-pass filter tends to increase the robustness in the design of time delay controller as well as the gain and phase margins of the closed loop system. Simulation results support that the proposed controller guarantees a good tracking performance irrespective of the variation o..finertia and the presence of measurement noise.