Effects and Compensations of Time Delay on the Dynamic Stiffness and Damping Coefficients of Active Magnetic Bearings

Aiming at the problem of small time delay in the control system of an active magnetic bearing (AMB), the direct approach is applied to study the effects and compensation of time delay on the dynamic stiffness and damping coefficients of active magnetic bearings. Second-derivative feedback is used to compensate time delay effects, and performance of the controller has been verified. The results indicate that the time delay mainly affects the dynamic performance of AMB system in the upper frequency band, and results in the increasing of bearing dynamic stiffness coefficient and the decreasing of bearing dynamic damping coefficient with the high-speed AMB, respectively. The relationship between second-derivative and bearing performance is investigated, and it is shown that the time delay effects on the bearing properties may be effectively compensated by using the second-derivative feedback.