Research On A Six-phase Fault-tolerant Permanent-magnet Machine Used For Aviation Servo System

The development of advanced equipments,such as hypersonic vehicles,have placed stringent performance requirements on aviation servo systems.Compared with the traditional redundant fault-tolerant servo system,the multiphase fault-tolerant electic servo system has the characteristics of smaller size,higher power density and stronger fault tolerance,and it has been widely concerned by scholars.When a fault occurs in the motor winding or inverter switching tube s of the multiphase fault-tolerant servo system.There is no need to change system hardware.By adopting appropriate fault-tolerant control strategies,the full torque output under the fault state can be achieved to meet the application requirements of aviation servo system.The electromagnetic design,open circuit and short circuit fault-tolerance control of six compatible permanent magnet motors are studied in this paper,based on the application background of aviation servo.And the major work can be summarized as follows:Firstly,the electromagnetic scheme design and majorization of a six-phase fault-tolerant permanent magnet motor are researched.The selection principle of the pole-slot matching scheme for six-phase fault-tolerance permanent magnet motors is given,and the electromagnetic scheme and fixed rotor structure form of the six-phase fault-tolerance permanent magnet motors are determined in combination with technical indicators.The use of Halbach permanent magnet array for the motor rotor is discussed in order to reduce the permanent magnet loss and the motor torque ripple.Rotor adopts Halbach permanent magnet structure instead of surface mount permanent magnet in order to reduce the permanent magnet eddy current loss and reduce the motor torque ripple.The influence of Halbach permanent magnet array and the key parameters of the motor rotor on the performance of the motor is analyzed,the key structural parameters of the motor are determined.The calculation method of the stator slot leakage inductance of the motor is further studied,and the method of suppressing the short circuit current of the motor winding is given.Secondly,the fault-tolerant control strategy of six-phase fault-tolerant permanent magnet motors under open circuit faults including one-phase and two-phase windings is studied.The torque output characteristics of the motor in normal operation and different open-circuit fault conditions are analyzed,and the mechanism of the torque ripple of the motor under fault conditions is clarified.With the minimum copper loss as the goal,the open-circuit fault-tolerant control strategy based on constant magnetomotive force principle and the instantaneous power balance principle is studied.The finite element method is used to verify the correctness of the control methods,and the control effects of these two fault-tolerant control strategies are further synthesized.Finally,the winding short-circuit fault characteristics and fault-tolerant control method of six-phase fault-tolerant permanent-magnet motors are analyzed.The short circuit current is calculated by analytical method,and the variation characteristics of the short circuit current of the winding and its influence on the torque characteristics of the motor are analyzed.The fault-tolerant control strategies of short-circuit fault based on the instantaneous power balance principle is studied to achieve the full torque output of the motor in the state of short-circuit fault,while reducing the torque ripple of the motor at the same time.