Hall Fault Diagnosis And Fault Tolerant Control Of Brushless DC Motor

Permanent magnet brushless DC motors are widely used in our daily work and life due to their good drive control performance,wide adjustable speed range,stable output torque and other advantages.BLDCM driven by square wave requires 6 Hall commutation positions in one electrical cycle,in another word,the rotor position information at 6 specific points;PMSM driven by sine waves requires high-precision real-time rotor position in one cycle information.Therefore,for a permanent magnet brushless DC motor drive system with a position sensor,the performance of the commonly used Hall position sensor is critical to the performance of the entire system.When the sensor function fails in some special environments,the online diagnosis of the faulty sensor and the corresponding compensation means are of great significance in actual engineering.Aiming at the single and double hall fault types,This dissertation analyzed the output signal characteristics of the sensors under fault,then proposed two fault diagnosis methods based on Hall jump edge and Hall state sequence.The first method relies on detecting whether the difference between the Hall output values of the other two phases at the two edges of the non fault sensor is ‘1’.The second method is to show the hall states of three sensors when all 18 single and double hall faults are listed as the diagnosis sequence to judge the fault.However,there is a large amount of calculation and loss of steering information under double hall fault.Established the mathematical model of Brushless DC motor and summarized the advantages of existing fault-tolerant control algorithms.Based on the classical extrapolation algorithm,an improved scheme for the first-order Taylor expansion method is proposed,which added Smooth correction link and simplified the calculation of the algorithm by calculating the angle increment in the PWM cycle.Developed the hardware system of Brushless DC motor drive,Based on TMS320F2812 as the main control chip,a fault-tolerant control experimental platform is built.Programmed the software for the improved extrapolation algorithm.Set up three groups of experiments: low-speed no-load,constant load variable speed and constant speed variable load to verify the response speed of fault diagnosis strategy and the reliability of fault-tolerant algorithm while simulating the single and double hall faults.Analyzed the experimental data such as phase current and rotor position prediction,and finally,it is concluded that the diagnosis scheme has high efficiency and accuracy,the fault-tolerant algorithm has stable and good performance,and can meet the fault-tolerant control requirements under different conditions.