Abstract

The modeling and analysis of a vibration isolated table system is investigated as a preliminary study for the design of an active feedback control system. The system consists of a table, a moving load traversing on the top surface of the table, and four identical pneumatic isolators supporting the table at four corners. For each isolator, there is a spool valve and a needle valve. A mathematical model of the system is developed, which includes the governing differential equations of the rigid table and pneumatic isolators, the nonlinear saturating characteristics of the spool valve, and the flow restriction of the needle valve. The isolation table is commercially available. Using MATRIXX/SystemBuild, the time response of the table is simulated for a few representative cases. The results indicate that the table will descend and not return to the original position, for any speed of the moving load, until the load stops. The higher the speed of the load, the quicker and farther down the table will descend. The larger the opening of the needle valve is, the table oscillates more because of less damping. The table response is relatively well damped even when the needle valve is fully open. The speed of the response, which is measured by the settling time, is fastest when the needle valve is open at about 25%.

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