Active Vibration Isolation Using an Electrical Damper or an Electrical Dynamic Absorber

This paper describes a theoretical and experimental study to show how an electrical damper or an electrical dynamic absorber, implemented using an electromagnetic actuator and an accelerometer, can control vibration transmission through a vibration isolator. The electrical damper is realized by feeding back the equipment velocity to the actuator with constant gain. The electrical dynamic absorber is realized by feeding back the equipment acceleration through a second-order low-pass filter. Because it is found that the plant on a flexible base is asymptotically similar to that on a rigid base, the optimal parameters of the control filter are determined analytically, independent of the base dynamics. Experimental results show that the electrical dynamic absorber has a similar performance to the electrical damper. The maximum reduction in transmitted vibration achieved was about 38 dB for both methods. It is also shown that the electrical dynamic absorber is more robust to undesirable dynamics outside the control bandwidth. Another advantage of the electrical dynamic absorber is that it does not require an integrator to transform acceleration into velocity.