Time delay control with state feedback for azimuth motion of the frictionless positioning device

A time delay controller with state feedback is proposed for azimuth motion control of the frictionless positioning device which is subject to the variations of inertia in 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 is found that the low-pass filter tends to increase the robustness in the design of the time delay controller, as well as the gain and phase margins of the closed-loop system. Numerical and experimental results support that the proposed controller guarantees a good tracking performance, irrespective of the variation of inertia and the presence of measurement noise.