Study on Vibration Control in Magnetic Bearings

1989 Fiscal Year Final Research Report Summary

• Project/Area Number: 63850052
• Research Category: Grant-in-Aid for Developmental Scientific Research
• Allocation Type: Single-year Grants
• Research Field: 機械力学・制御工学
• Research Institution: Kyushu University
• Principal Investigator: FUKATA Satoru Kyushu University, Faculty of Engineering, Professor., 工学部, 教授 (40110837)
• Co-Investigator(Kenkyū-buntansha): OKABE Tadashi Kyushu University, Faculty of Engineering, Research Associate., 工学部, 助手 (00185464) ; AYABE Takashi Kyushu University, Faculty of Engineering, Research Associate., 工学部, 助手 (50127958) ; SUEOKA Atsuo Kyushu University, Faculty of Engineering, Professor., 工学部, 教授 (80038083)
• Project Period (FY): 1988 – 1989
• Keywords: Magnetic bearing / Active magnetic bearing / Vibration control / Critical speed / Bending vibration / Observer / PID control

Research Abstract

This study dealt with the restriction of the resonance caused by bending vibrations, to run beyond the critical speeds elastic rotors supported by active magnetic radial-bearings. A full-order observer was applied to the control systems. This control system is applicable if the controlled system is controllable and observable, and is robust for the noise problem. A PID control is also applied to compare the control performances. In the bearing system considered, the two radial bearings are the same in form and in characteristics, the elastic rotor is symmetric, and the electromagnets and the displacement sensor are in collocation. By neglecting the gyroscopic effects, the dynamics of rotor is decoupled into the two systems: the translatory motion with the first-order vibration mode and the conical notion with the second-order vibration mode. The compensators are realized by analog circuits.
The experimental results are summarized as follows. 1. The feedback compensation based on a full-order observer is useful to restrict the resonance caused by the first-order bending vibration. The whirling in the critical speed (about 9,000rpm) was restricted with the amplitude of about 10/mum. 2. A PID control system gave a better performance; the observer-based control gave a similar one, which shows the effectiveness of the application of observers. 3. The two compensators could not restrict the second-order vibration mode, because the electromagnets and the displacement sensor are located near the node of the vibration mode. 4. The gyroscopic effects does not act on the first critical speed, which seems due to the symmetricity of the rotor, but increased the second critical speed about 20%.