Study On Sliding Mode Observer For Sensorless Control Of A Salient-pole Pmsm Used In Renewable Energy Car

Position estimator for sensorless control of a Permanent Magnet Synchronous Motor(PMSM)is more suitable for renewable energy cars for its simple structure, easy maintenance, small size and low cost. Main features and suitable occasions of all kinds of position sensorless methods have been analyzed. Combining with the features of PMSM and the demand of project, Sliding Model Observer(SMO) is the best choice because of its robust performance to disturbances.Traditional vector control system of PMSM using mechanical position sensor has been established. And also the whole process of breakdown of mechanical position sensor has been analyzed The SMO has been added in the original control system which will increase the safety degree of the new energy vehicle. Two main research details have been identified by analyzing the principle of SMO, the first one is how to reduce the chattering of SMO, and the second is that how to compensate the delayed phase.Following, the chattering phenomenon of SMO has been analyzed, and three ways to reduce chattering of the observer have been proposed. The first one is using a variable ratio of control function instead of the fixed ratio. The second one is using a consecutive control function instead of the switching function. The third one is using the Phase Locked Loop(PLL) to track the phase of back electromotive force. These ways have been verified in simulation and experiments.Then, the phase delay phenomenon of SMO has been analyzed. The low frequency pass filter(LPF) is used to reduce high frequency disturbances. Reducing the phase delay increased by LPF by establishing forth-order sliding state equations. Compensation of the phase delay caused by above reasons by experiments has been done, which has been verified in experiments.At last, the software design using TMSDSP28335 has been completed, experiments on reducing the chattering shows that the variable ratio and consecutive function are useful. The PLL can reduce high frequency disturbances in back-EMF and track the phase well. Compensation will ensure its normal works. Experiments contain all conditions shows that the designed SMO position-sensorless control system is feasible, at the same time, this paper points out the applicable conditions and limitations.