Stiffness characteristics analysis and variable stiffness control for a permanent magnetic levitation system with variable magnetic circuit

Aiming at nonlinear varying feature of levitation force in a permanent magnet suspension system with variable magnetic circuit, the system's stiffness characteristics were analyzed, a variation stiffness control method was proposed to decrease the system's sensitivity to external disturbance. Firstly, effects of system structure and control parameters on suspension stiffness were analyzed based on the system mechanical model to propose a variable stiffness control method based on suspension object displacement. Then, change ranges of parameters were designed according to the presupposed load capacity and displacement variation to make the system stiffness vary according to the given control law. Finally, simulation and test analysis were conducted for the system's floating up stability and sensitivity to external disturbance. The results were compared with those using the PID control method. The results showed that the proposed variable stiffness control method can ensure the system to stably float up; it can reduce displacement variation of suspension object by 50% under external load; it can greatly reduce the system's sensitivity to external disturbance; compared with the traditional PID control method, its control characteristics are greatly improved. © 2020, Editorial Office of Journal of Vibration and Shock. All right reserved.