Research On Design And Control Of Active-passive Hybrid Vibration Isolation Platform Based On Air Spring And Electromagnetic Actuator

Vibration isolation is a key technology to inhabit vibration which transmits from power machinery of naval ships to the hull. Air spring has excellent characteristics such as large carrying capacity, high standing wave frequency and superior vibration isolation performance in high frequency. It has good application prospects in naval ships' vibration isolation. However, air spring can't overcome the drawbacks of passive vibration, such as limited controllable frequency range and unchangeable shapes of transmissibility. On the contrary, electromagnetic actuator has more advantages, such as fast response, wide frequency response and easy control. A hybrid vibration isolation system consisting of air spring and electromagnetic actuator can maximize their potentials and fulfill broadband vibration isolation for navy ships. Thus it has important research significance.Firstly, the bearing characteristics and stiffness characteristics of an air spring are analyzed by theoretical computation and experimental tests. Results show that, with a certain nonlinear characteristics, air spring's bearing capacity and stiffness increase with the growth of inflation pressure. The theoretical mechanical model of electromagnetic actuator is established. Then the frequency response characteristics of an electromagnetic actuator and its supporting power amplifier are tested.Secondly, based on the principle of minimum force transmissibility, the basis for the selection of vibration isolation units in active-passive hybrid vibration isolation system is proposed. An active-passive hybrid vibration isolation platform using air springs and electromagnetic actuators is built, including the design of main structure of the platform. The modal analysis of the vibration isolation platform is carried out using Finite Element Method.Thirdly, in order to address the physical modeling difficulties of the electromagnetic actuating system and air spring, the method of system identification is used to establish the transfer function model of the hybrid vibration isolation system. By introducing the genetic algorithm, a simple and reliable PID controller is designed. It overcomes the defects of conventional PID controller which has difficulty in setting parameters and exploiting the potential. According to different input signals, the PID controller based on genetic algorithm is designed and the active control simulations are carried out. It is found that PID control method based on genetic algorithm has strong adaptability to different interference inputs. Compared with passive control system, the PID active control system obtains a better effect, and the vibration isolation performance is remarkable near the natural frequency of vibration isolation system.Lastly, the PID active control experiment is conducted on the built active-passive hybrid vibration isolation platform. The experimental results show that the PID control system obtains a good performance in broadband vibration isolation of 10Hz~50Hz, especially near the natural frequency of the system, the acceleration RMS reduces about 50%, which are found to be in agreement with the simulated results.