On Speed Estimation And Control Of Servo Motors

Permanent magnet synchronous motors (PMSM) have been developed rapidly in recent years. The sensorless of PMSM has become one of hot issues in this field.Firstly, this thesis elaborates the relevant achievements both domestic and abroad. In addition, the excellence and imperfection of PMSM sensorless technology have been summarized. Secondly, it is pointed out that sliding mode control (SMC) is extensively applied in sensorless control systems, however, the chattering that happens at the observer using the signum function or the sigmoid function as a switching function results in fluctuation of motor motion since the switching function of conventional SMC is discontinuous. Finally, a novel switching function of SMC is presented in this thesis, and the chattering phenomenon of conventional SMC is effectively restrained.The sliding mode control systems generally use the signum function or the sigmoid function as its switching function, which will result in the the discontinuities in the sliding mode control process. This thesis analyses the causes of chattering phenomenon and argues that the existing discontinuity point in signum function or sigmoid function applied as a switching function will lead to the chattering problems in the SMC system. The use of sigmoid function in the whole range can not obtain the reference values and has high computational complexity. Therefore, this thesis proposes a sinusoidal function to be as a switching function in sliding mode observer, and the above-mentioned problems can be effectively solved. Theoretical analysis and Matlab/Simulink simulation results show that the sinusoidal function can effectively weaken the chattering phenomenon, and it is suitable for using in sliding mode control systems. The studies in this thesis have both theoretical value and practical significance.