Control mechanism based on differential electromagnet actuator for a room-sized optical instrument vibration isolation foundation

In order to improve further vibration isolation performance, a new active vibration control mechanism based on differential electromagnet actuator is presented for room-sized vibration isolation foundation. By using the differential scheme, the output force of the actuator is linear with control current. Because absolute velocity feedback method and Skyhook method have the similar performance in the weak damping conditions and the former method is more easier to realize, the absolute velocity feedback method is selected as the control strategy. The control strategy can efficiently improve the performance in resonance area without losing the performance of high frequency area. Experiment results show that by using the proposed mechanism, the mean square roots of velocity or angle velocity at the three degree-of-freedom z, θ_x and θ_y fall to 3.8 μm/s, 1.76 × 10^-6 rad/s and 1.49 × 10^-6 rad/s from 10.06 μm/s, 4.16 × 10^-6 rad/s and 4.65 × 10^-6 rad/s in time domain, and the vibration isolation performance in resonance area improves 10 dB in frequency domain.