Design and simulation of an active vibration isolator based on pneumatic-electromagnetic hybrid driving

Large airborne optical systems require very high beam pointing control accuracy, which will put forward some new challenges for the design of an airborne isolation platform. We analyze the characteristics of aircraft structural vibration, and propose to develop a pneumatic and electromagnetic hybrid driving isolator. The isolator uses an adjustable pneumatic air spring with an external air container to suspend the payload, and a coaxial electromagnetic actuator is integrated with the output rod of the isolator, which provides a broadband active control force for the payload. The preliminarily determined carrying capacity is 150~190 kg and the isolation frequency range is from 1 Hz to 100 Hz. This paper firstly describes the principles of pneumatic/electromagnetic hybrid driving and presents a structural layout of the isolator. Then it simplifies the system, establishes the physical model, and derives the dynamic equations of the isolator. Finally, the Matlab/Simulink numerical simulations of the isolator are conducted to research respectively the feasibility and efficiency of PID control algorithm and LQR control algorithms. The simulation results and their analysis show preliminarily that: (1) the two active control algorithms are efficient, and the payload's vibration displacement amplitude can be reduced to ±10 μm level under a wide frequency band (1~100 Hz) random vertical disturbance; (2) this vibration reduced performance of the isolator can meet the installation requirements of large airborne optical equipment. The comparison between the PID and LQR control methods shows that the vibration reduced performance of the PID method is slightly better than that of the LQR method for a single isolator system; besides, the PID method is easy to implement.