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.