| Active magnetic bearings (AMB), which use the controllable attractive force of electromagnets to maintain a rotating ferromagnetic body contact-free in its nominal position, have seriously developed in the rotating machinery; provide numerous advantages compared with the conventional bearings, such as: no contact, no wear, no lubrication, long life and controllable dynamic characteristics etc.AMB is a typical mechatronic system, which includes electric subsystem (including sensors, controller and power amplifier) and mechanical system (including rotor, stator and coil). The performance of the AMB system is mainly determined by the electric control system. This paper is focuses on the controller and power amplifier of the AMB.First the structure and theory of the AMB system are introduced, the model of a single degree-of-freedom AMB is built, and its performance is simulated through MATLAB Simulink. Then the circuit topology, control method and modulation technique of the power amplifier are discussed. Two PWM based current control switching power amplifiers with two and three level are designed and tested. The digital controller of AMB and several control stratagems are proposed and discussed, the PID control arithmetic is chosen to realize the control function. At last, the whole ABM system is debugged, and the suspension of 4 degree-of-freedom is realized in the experiment. |
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