Improvement of dual chamber pneumatic vibration isolators by using input-output linearization and Time Delay Control

Existing controls for the dual chamber pneumatic vibration isolator (DC-PVI) have the following problems: (1) unable to suppress both seismic vibration and direct disturbance (or payload disturbance) simultaneously; (2) complex and of high-order. In this paper, we have applied input-output linearization to the DC-PVI to derive a reduced-order model that enables the followings: (i) a reduced-order control design; (ii) simultaneous suppression with an accelerometer only. We have employed Time Delay Control (TDC), well-known for its simplicity and robustness to uncertainties and disturbance. Based on the reduced-order model and its corresponding TDC design, an active control scheme has been derived that requires only an accelerometer for its sensor. This scheme was experimented with a DC-PVI, which successfully suppresses seismic vibration and direct disturbance both separately and simultaneously. Faced with seismic vibration, the transmissibility of the DC-PVI with TDC has virtually no resonance peak at low frequency; under direct disturbance, the DC-PVI with TDC achieves a 65 percent reduction in settling time of that without TDC.