Enhanced Pressure Control Using a Disturbance Observer for Active Pneumatic Vibration Isolator (PVI)

Active pneumatic vibration isolators (PVI) are crucial in precision manufacturing, effectively suppressing unwanted vibrations. Although a pressure control is used to improve the dynamics of the pneumatic actuator, model uncertainties may degrade the vibration isolation performance. This paper presents enhanced pressure control with a disturbance observer (DOB) for active PVI. The dynamics of the pneumatic actuator is identified through measuring the frequency responses. The DOB-based robust pressure control system is constructed combining the DOB and the pressure PI (proportional-integral) feedback controller. The DOB is used to compensate for intrinsic resonance and uncertainties of the pneumatic actuator. The pressure feedback controller is designed based on the nominal model of the pneumatic actuator, and its performance is verified through experiment. Additionally, the pressure control system is integrated into a two-DOF vibration controller consisting of table acceleration feedback and floor vibration feedforward controllers. The performance of the active PVI is evaluated by measuring vibration transmissibility and response against an impact load. The vibration transmissibility is reduced by 16 dB at the 5.5 Hz and 26 dB at 10 Hz. Moreover, the settling time against impact load is decreased by 42.6%.