Vibration Control of a Flexible Rotor Suspended by Active Electromagnetic Bearing. 5th Report. Feedforward Control with Variable Gains to Cancel out Unbalances.

Abstract

To reduce unbalance response of a flexible rotor suspended by electromagnetic bearings, two methods have mainly been investigated. One is the method to increase damping of the mechanical system ; the other is the method to cancel out unbalances. For the former method, PID control is generally used. Although PID control is very effective for reducing resonance vibration, in other ranges of rotational speed it yields little effect. On the other hand, with the latter method of feedforward control, it is expected that unbalance response is greatly attenuated in all ranges of rotational speed. In this paper, we used both PID control and feedforward control with variable gains against rotational speed. PID control needs to stabilize the rotor system and feedforward control is used to reduce unbalance response. From calculated and experimental results, we find that the above method has greater capability of suppressing vibration of a flexible rotor than does ordinary PID control.