Research On Fault Diagnosis And Fault-tolerant Control Of Brushless DC Motor System

Brushless DC Motor has been widely used in the fields of electric vehicles, instrument, automation and aviation due to its qualities such as small volume, high efficiency, long life expectancy, wide speed calibration and convenient maintenance. In the brushless dc motor control system, the system failure caused by the vulnerability of power electronic device which is yet to be solved, this limits the improvement of the performance of the brushless dc motor control and hinders its application in occasions that demand precision and reliability. Therefore, increasing attention has been drawn to brushless dc motor fault diagnosis technology research. This paper mainly focuses on the brushless dc motor control system of inverter power tube failure, position sensor fault diagnosis and fault-tolerant control.Firstly, the basic structure and working principle of brushless dc motor is introduced, the operation characteristics of system under the four types of inverter open-circuit fault and position sensor fault is analyzed, and a fault diagnosis based on three phase current selected as the output characteristics is included. Based on Daubechines series wavelet's sensitivity of singular signal, db5 wavelet is chosen to analyze the three phase current Using traditional wavelet decomposition of the layers of detail signals to observe the effects is susceptible to noise and other factors and easy to cause the diagnostic mistakes or unable to diagnose, therefore the product of three or more layers of wavelet transform detail signals as new secondary decomposition to determine the fault time is presented, which can locate the fault point precisely. According to the change of the energy and the phase current to determine the fault types.Secondly, the Luenberger observer is established based on the mathematical model of brushless dc motor, for estimating the rotor position information, and then the rotational speed. Analysis of the working state of brushless dc motor fault reconstruction by the widely used four switch inverter fault tolerant topology, in order to compensate for the decrease of the output performance of the brushless dc motor by using the four switch inverter fault tolerant topology, a new kind of fault-tolerant inverter topology is presented. When the system is running normally, the emergency bridge of the fault-tolerant doesn't work, once found the inverter fault, the system will quickly electrically isolate fault component, and its driving signal will still be transferred to the corresponding emergency bridge power tube leaving the control algorithm unchanged, so that the reconstruction system can still run normally.Finally, some simulation and experiments were done based on MATLAB and TMS320F28055 platform, the results show that the proposed fault diagnosis method is feasible in the brushless dc motor, and the fault-tolerant inverter can respond immediately after identifying failure, then drive emergency bridge conduction so as to maintain the system output performance.