Perfomance enhancement of single/dual chamber pneumatic vibration isolation systems by input-output linearization and time delay control

Abstract

This thesis shows that the performance of both single chamber (SC-PVI) and dual chamber pneumatic vibration isolator (DC-PVI) are simply and effectively enhanced by using input-output linearization and time delay control (TDC). From applying input-output linearization to existing models, we have derived new models of both SC-PVI and DC-PVI. The new model of the SC-PVI system is called the new state space model; the DC-PVI’s the reduced-order model. Both two models, almost the same, are of second order and controllable canonical form with the air mass-flow as the control input. Accordingly, these models offer frameworks that enable simultaneous suppression with an accelerometer only. We have employed TDC, well-known for its simplicity and robustness to uncertainties and disturbance. Owing to the similarities between two models, the procedure and result of TDC design on two models are the same. Thanks to the new models, the TDC requires only an accelerometer for its sensor. The TDC was experimented with the SC-PVI as well as DC-PVI, which successfully suppresses seismic vibration and direct disturbance both separately and simultaneously. Faced with seismic vibration, the transmissibility curves of the TDC-enabled SC-PVI and DC-PVI show virtually no resonance peak at low frequency; under direct disturbance, both PVIs with TDC achieve over 60% reductions in settling time, comparing with not controlled PVI systems. The additional analysis of experimental results shows that TDC effectively estimates the modeling error along with other uncertainties and cancels them, while achieving desired closed-loop dynamics. Finally, based on comparative study, a guideline is proposed for selecting the appropriate PVIs.