High Speed Vibration Suppression Control for Pneumatic Isolation Table Using On-Off Input and Input Time-Delay Compensation

The main focus of the research reported herein is the improvement of the transient vibration suppression performance for large displacements using the active control. A response speed is not sufficient if conventional linear control methods are used to control large displacements because linear input used those methods prevent valves from switching between maximum input and minimum input instantly. So, a solenoid valve is employed, which can switch between maximum input and minimum input instantly. Consequently, the plant includes an on-off action and an input time-delay as the control input. It is known that the stabilization of this kind of system is difficult using conventional linear feedback controls such as the optimal regulator. Herein, FBM (feedback modulator) which compensates on-off action and state feedback control considering time-delay is used as a controller. However, the response may be oscillatory if conventional FBM is directly applied because integral characteristic included in FBM. Hence, in order to avoid such oscillatory inputs, dead-band function is added to the controller in the improvement method 1. If thus configured, response is expected to be stable. Moreover, in order to reduce steady state error, a dead-band compensator is added to the controller in the improvement method 2. As a result, settling time can be shortened to one-fourth of without controlled cases. The effectiveness of the proposed methods is verified by numerical simulations and experiments.