On Electric Control System For Active Magnetic Bearing

Active magnetic bearing (AMB) is a high performance, novel type bearing which suspends the rotor by controlled magtronics force in a contact-free manner. The AMB has many advantages such as contact-free, no need of lubrication, no wear, low noise, high rotation speed, etc. The maximum speed is only limited by the material intensity of the rotor. So the AMB fits some execrably environments, such as high speed, vacuum super clean, etc.AMB is a typical mechtronical system, which includes electronic system (sensors, controller and power amplifier) and mechanical system (rotor, AMB stator and motor). The performance of the AMB is determined mainly by the electric control system. This thesis focuses on the electric control system of the AMB.First, the structure of the AMB is introduced. The magnetic field coupling between neighbors electromagnetic is analyzed with LEMM software and then solved. A high-speed rotor model is put forward. Second, the position sensor system is designed which fit the AMB structure and some other needing contact-free measure environment. The position sensor is electric eddy type and has differential structure. Thirdly, a digital control system based DSP is designed, which can control 5 degree of freedom of the AMB. Decentralized PID control algorithm is used in the digital control system. Forthly, a PWM power amplifier and synchronous PWM power amplifier is designed and tested. To acquire a small current harmonious, a three-level PWM power amplifier is designed.Interferer of the AMB electronic control system is discussed. A so called "interfere avoid" method is used in digital control system and has resolved the interfering from the PWM power amplifier.Stable suspension and high-speed rotation 40000r/min without load are realized on an AMB grinding spindle. The high-speed rotation 23000r/min with all the loads is realized on a high-speed centrifugal spraying drier.