Research On The Sensorless Control Technique Of Permanent Magnet Synchronous Motor

In the high performance permanent magnet synchronous motor (PMSM) drive system, it is necessary that there exists a closed-loop control system in order to control the speed and position of the motor precisely and dynamically. As such, mechanical sensors are needed and installed on the rotor shaft for measuring the speed and position of the rotor. However, these added mechanical sensors will increase the volume and weight of the whole system, which limits the use of the PMSM in some special situations. Therefore, controlling the PMSM precisely without sensors becomes a hot area in this field. So far, however, there is no control strategy that can be used to control the PMSM precisely among the whole speed without sensors. Hence, in this thesis, we present some control strategies of the PMSM without sensors under different speeds and try to operate the PMSM precisely and reliably among the whole speed. The main achievements are outlined as follows.1. A model reference adaptive system and an adaptive full-order observer are designed based on the hyperstability theory. The impacts on the performance of the PMSM without sensors are compared, when the model reference adaptive system and the adaptive full-order observer are adopted, respectively. Meanwhile, how to select the feedback gain matrix in the adaptive full-order observer is analyzed in details.2. A sliding mode observer for measuring the speed and position of the rotor and a sliding mode controller used in the forward channel of the vector control system are constructed, after the principles and the features of the sliding mode variable structure control are analyzed. However, the side effect of the sliding mode method causes chattering due to its mechanism, so we perform the following researches to eliminate and weaken it:(1) we combine the sliding mode observer with the phase-locked loop (PLL) and the model reference adaptive theory, respectively. By using them, the signals of the speed and position of the rotor are acquired and the infulences of the chattering of the sliding mode method on the signals can be eliminated;(2) The sliding mode controller based on the variable index reaching law is designed in order to weaken the chattering.3. For the problems that appear when the fundamental wave model control strategy works in the low speed and zero speed, the fluctuating high frequency signal injection method is used to build the synchronous shaft high-pass filter, which can extract the fundamental current component from stator current. However, in the high-frequency signal injection method, the polarity of the magnetic pole cannot be identified at the rotor initial position. Therefore, based on the saturation saliency effects, we apply the pulse voltage injection method to get the difference among the current responses and use it to identified the polarity of the magnetic pole.4. Some control algorithms for the PMSM without sensors that are established on the fundamental wave model and the high frequency excitation model are carried out on our simulation platform. Moreover, they are also run on our hardware platform and experiments show that they are effective. Further, we combine the control algorithms based on the fundamental wave model with those algorithms based on the high frequency excitation model to establish new algorithms, which can control the PMSM without sensors precisely among all speeds.