Study on structural optimization design and cascade PID control of maglev actuator for active vibration isolation system

In view of the nonlinear output characteristics of actuators, and due to necessary large strokes for low-frequency vibration isolation platforms in microgravity environment, a method for structural optimization design and cascade PID control of maglev actuators was put forward based on the principle of Lorentz force. Furthermore, the method was utilized to design a magnetic circuit in accordance with the self-demagnetization effect and to multi-objectively optimize the structure parameters of a coil. A mathematical model was established of the remarkably nonlinear output force, due to the nonuniform magnetic fields to optimize its output force and current, so that the time-varying output requirements of controllers may be satisfied. System identification was performed to obtain the mathematical model of its control channel and design cascade PID controllers. This method was applied to lower the phase lag and equivalent time constant of a closed secondary circuit system so that not only the system stability and response rate may be improved, but also the growth of the gain of the controller may lead to growth of the damped natural frequency of the cascade control system; thus, the system settling time may fall and the system control quality may be improved. Simulation was also carried out to the cascade PID control corresponding to the mathematical model so that the cascade PID controller may have a relatively good control effect on disturbing acceleration signals. Experiments were carried out to cascade PID control of maglev actuators to further verify vibration control performances. Comparisons of the measured and simulated acceleration transmissibility data are basically consistent within the band 1-25Hz. Measured and simulated results indicate that application of the cascade PID control method may attenuate the control object in the range -22.522 to -2.189dB within the band 1-25Hz and perform effective vibration control.