Quasi-zero pneumatic stiffness vibration isolator using disturbance observer based pressure control

초록

Precision instruments are highly susceptible to external disturbances such as ground vibrations, acoustic noise, and equipment-induced disturbances, necessitating advanced vibration isolation techniques to ensure stable operational environments. This paper presents a novel pressure measurement-based approach to realizing quasizero stiffness (QZS) behavior in pneumatic vibration isolators (PVIs) through a disturbance observer (DOB)-based pressure control. A dynamic model of the pneumatic actuator is formulated by incorporating volume-induced pressure variations, enabling accurate characterization of pneumatic stiffness behavior. The DOB-based control method combines real-time pressure measurement with model-based estimation to compensate for volumeinduced disturbances without structural modifications. Frequency-domain analyses, including the air spring dynamics, root-locus, and vibration transmissibility, are conducted to evaluate the effectiveness of the proposed control method. Experimental investigations, comprising static and dynamic characterization of the air spring, vibration isolation performance tests, and multi-degree-of-freedom implementation, are performed to validate the approach. The DOB-based pressure control reduces the system's natural frequency from 5.75 Hz to 2.75 Hz, and by combining with acceleration feedback control, further improves vibration isolation by 20.8 dB at 10 Hz. These results validate the effectiveness of the proposed pressure measurement-based control framework for shaping the dynamic stiffness of PVIs.

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