Identification and Control of Control Delay for Digital Control Magnetic Bearing System

The delay time of an active magnetic bearing (AMB) digital control system with a decentralized PID controller is measured. Numerical simulation results of time delay effects on the dynamic performance of a 2-axis controlled active magnetic bearing rotor system (AMBRS) are presented. An investigation of reducing time delay effects using a Smith predictor controller is also introduced. Experimental results show that the scale of delay time is from decades to hundreds microseconds. Furthemore, the simulation results indicate that time delay mainly affects journal center orbit, And results in the instability of the first natural mode of AMBRS. The simulation results also prove that Smith predictor is very effective in reducing time delay effects.