Research On Optimal Torque Control Strategy Of Fault Tolerant Permanent Magnet Machine

Using electric actuators is one of the most important characters of all electric aircraft. If electric actuators are being used instead of hydraulic pressure for the plane, the system of hydraulic pressure could be cancelled or reduced. Then the reliability and maintain would be increased and the weight of the plane would be decreased significantly. Nowadays, redundancy technology is widely used in electric actuation system.Compared with dual redundancy BLDCM, Fault Tolerant Permanent Magnet Machine (FTPMM) has the advantages of good winding utilization, small volume and light weight. Furthermore, it has the capabilities of fault tolerant and fault isolation but doesn't require current balance, which makes it a strong competitor of implementing motor of electric actuator.At the beginning of this thesis, FTPMM's fault tolerance and isolation characteristics are analyzed and a mathematical model of the motor is deduced. This thesis proposes an optimal torque control system of FTPMM, then the principle of optimal torque control strategy is analyzed and two methods of fault diagnosis with open-circuit and end short-circuit of winding. The outer loop of control system is speed loop, using PI controller. The inner current loop is used a digital current hysteresis modulating method by optimizing the duty cycle. In addition, the control system is modeled and simulated by MATLAB / Simulink.This paper has successfully designed a set of full digital optimal torque control system of six-phase FTPMM. The hardware platform mainly consists of the following three parts: a digital signal processor TMS320LF2407 for the control core, CPLD-M4A5 128/64 for the failure integrating unit, intelligent power module (IPM) for the power unit. Software design use assembly language to achieve the fault diagnosis processing, optimal torque control algorithms, and digital current hysteresis procedures and so on. Based on the hardware and software, the whole system has been debugged.Through testing, the control system has achieved the following properties: when given speed is 2000r/min and load torque is 1N·m, the output torque and speed performance after open circuit or the end short-circuit fault of one-phase occurrence is as good as normal, which show that the optimal torque control strategy is feasible and effective.