PID Control to Maglev Train System

The advantage of linear PID control is easy tuning, but its obvious disadvantage is the conflict between the stiffness and the performance when this approach is applied to magnetic suspension system. In order to enhance the stiffness of the system, the usual way of linear PID control is to increase the proportion feedback, but this approach is likely to degrade the performance of the system and even make the system unstable. In order to tackle the problem between the stiffness and the system performance, an approach named nonlinear PID control method is introduced in the paper. This method combines the advantages of robust control and easy tuning. It can provide high stiffness and does not influence the dynamic performance of the system around the operating point, which reinforces the system ability of resisting outside force impact. The implementation of the nonlinear PID control approach is introduced. The resisting impact capability of the two approaches is compared through experiments and the superiority of nonlinear PID control over linear PID control is demonstrated via experiments also.