| Permanent magnet synchronous motor drive system is widely used in industrial control,aerospace,transportation and other fields because of its small size,high power density,large starting torque and excellent performance.The electrical part of the drive system has a multi-variable strong coupling relationship with the transmission part,and when the transmission part fails,it will adversely affect the performance of the electrical part and even the entire system.Therefore,this thesis analyzes the mechanism of some faults in the drive system of permanent magnet synchronous motor in the transmission process,and adopts corresponding fault diagnosis methods and fault-tolerant control strategies to improve the reliability and stability of the system.Firstly,in order to realize the high-precision fault-tolerant control of permanent magnet synchronous motor drive,this thesis decouples and reduces the order of permanent magnet synchronous motor according to the coordinate transformation theory,establishes a mathematical model of permanent magnet synchronous motor,adopts vector control strategy,takes the unbalanced fault in the drive of permanent magnet synchronous motor as the research object,analyzes the fault mechanism,obtains the mathematical model of unbalanced fault through dynamic modeling,and finally establishes a mechatronics coupling model according to the connection between torques.Secondly,in order to extract the characteristics of the system under fault conditions more accurately,the vibration signal of the shaft of the drive system is collected by the sensor,the characteristic frequency of the unbalanced fault manifested in the system and the relationship between it and the motor speed are analyzed,and the load observer containing fault information is designed according to the information obtained by the sensor combined with the theory.On this basis,combined with the self-disturbance rejection control,fault diagnosis method and fault tolerance technology,the composite fault-tolerant control,stability analysis and simulation experiment verification of the whole system are carried out.In addition,the cascade active disturbance rejection composite fault tolerance controller and the non-string active disturbance rejection composite fault tolerance controller are designed respectively.For the nonlinearity of the system,the new smooth nonlinear function is used to replace the nonlinear fal function,and the superiority of compensating the controller’s immunity based on the new function and load observer model is verified by simulation and experiments.Under the non-cascade single-loop automatic disturbance rejection control structure,the problem of state constraint and control quantity saturation is considered,and the tracking differentiator is used to solve the problem between overshoot and rapidity in PID controller,and the drive system with unbalanced fault is better fault tolerance control effect through feedback and load observation feed-forward.Finally,aiming at the periodic sinusoidal disturbance problem when the system has unbalanced faults,considering that the frequency will change with the change of motor speed,a frequency adaptation mechanism is designed to estimate the harmonic frequency of the system in real time.On the one hand,considering the harmonic suppression problem from the controller,the LQR optimal harmonic controller based on frequency weighting is designed,and the effectiveness of the designed controller against harmonic suppression is proved by combining simulation and experimental results.On the other hand,from the perspective of the observer,the harmonic suppression expansion state observer is designed to observe and compensate for the time-varying sinusoidal disturbance and harmonic suppression,and the suppression principle of this method is analyzed from the perspective of frequency domain,and the final simulation and experimental results verify the effectiveness and superiority of this method,and can improve the stability and adaptability of the system to faults. |
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