Fuzzy-Based Adaptive Control for Isothermal Pneumatic Vibration Isolation with Full State Constraints and Voltage Saturation

Pneumatic vibration isolators are becoming increasingly critical in the field of ship and ocean engineering. However, air springs exhibit significant nonlinear characteristics, and the internal gas state is typically assumed to undergo adiabatic changes. This assumption neglects the effects of temperature variations during vibration isolation, leading to discrepancies between the dynamics model and actual behavior, affecting the control accuracy and generating excess heat into the thermostatic plant. In addition, the existence of a variety of constraints on the system in the actual working process also needs to be fully considered. To address these issues, this study proposes an isothermal air spring design using high-density copper wire to create a quasi-isothermal environment within the air chamber, which improves the model accuracy and enhance the system damping. On this basis, an adaptive fuzzy output feedback control strategy is introduced to mitigate the impact of nonlinear factors on the pneumatic vibration isolators, while limiting its displacement, velocity, and acceleration within the predefined range respectively. The control strategy utilizes displacement as the feedback signal, with velocity and acceleration states estimated via an observer. An isothermal air spring prototype was fabricated and experimentally verified that the proposed air spring and control strategy can improve the vibration isolation effect while avoiding the excess heat into the thermostatic environment.