Sensorless position control of active magnetic bearings based on high frequency signal injection with digital signal processing

The high frequency signal injection method in the sensorless position control of active magnetic bearings (AMB), has some merits such in that there is no steady-state error in the estimated position and can control the amplitude of the signals used for position estimation. In this paper, a method to inject a high frequency signal and to process the signal to obtain the position of the rotor has been proposed. In this method, all the signal processing is done in the digital domain, and in contrast to the analog method, there is no offset nor are there any continuous tuning problems. The proposed method does not need additional hardware for signal injection and signal processing. The PWM inverter, which is used to regulate coil current, generates the injection signal, and the DSP, which is used to control the system, performs signal processing in a normal sampling cycle. The experimental results show reasonable performance with regard to the 4-degree-of-freedom control of rotor position, while rotating at 30,000 [r/min].