Study On Parameters Calculation Of Axial Field Disk Type Switched Reluctance Motor And Driving System

Axial field disk type switched reluctance motor integrates the advantages of switched reluctance motor and disk type motor, so this kind motor has high power density, large torque, compact structure, etc. This paper has studied the motor structure, calculation of magnetic circuit, optimization of control algorithm and design of control system.Magnetic circuit analysis is an important means for the electromagnetic design and performance analysis of all kinds of motor. At present, the magnetic circuit analysis method widely used in switched reluctance motor is based on analytical calculation of magnetization curve of several key rotor positions, and this method has not been applied to the study of axial field disk type switched reluctance motor, which made this kind of motor has not been widely used. For the axial field disk type switched reluctance motor, this paper has calculated the magnetization curve of the center alignment position of the stator tooth and the rotor tooth, the center alignment position of the stator tooth and the rotor groove and the critical position of the stator tooth and the rotor tooth. First of all, the key positions of the magnetic circuit structure had been determined according to the results of finite element calculation. Then, the winding coil’s flux, which had been produced by a given current, was analytical calculated. In the calculating process, the magnetic field lines were equivalent to circular arc or straight line, and the core magnetic resistance was ignored. So we could get the relationship between the flux and current, namely magnetization curve.First of all, the key position’s magnetization curve of the axial field disk type switched reluctance motor was modeled. Then, the design method of radial magnetic field switched reluctance motor was used to study the motor. Finally, a12/8single stator and single rotor axial field disk type switched reluctance motor has been manufactured, and the comparison of numerical calculation result, magnetic circuit analytical calculation result and testing result has proved the correctness and effectiveness of the analytical calculation.The axial field disk type switched reluctance motor has double convex pole structure, which is different from the radial magnetic field switched reluctance motor, and the differences will lead to different mathematical models of the two types of motor. It is difficult to establish more accurate mathematical model because of the nonlinear electromagnetic characteristics of switched reluctance motor, and it is not feasible using traditional control method to drive this motor. This paper has proposed the optimal axial field disk type switched reluctance motor control strategy based on neural network. First of all, through the discrete experiments on the prototype motor, it has been found that the switched reluctance motor’s turn-on and turn-off angle has important influence on the output torque, and the optimal switching angle of the motor has been defined. Secondly, the complicated nonlinear relationship between the inputs and outputs of switched reluctance motor was studied, and the neural network has been introduced to the motor driving. Then, current optimal switched reluctance motor nonlinear multivariable static three layer BP neural network controller model has been designed, which output variables were target current, turn-on angle and turn-off angle, the input variables were target torque and current speed of motor, and this neural network controller can be combinated with the traditional PID controller to constitute the speed feedback control system so that the system could have some dynamic characters. The methods of online training neural network have been designed, and variable step size fitting optimization method based on least squares has been designed in order to get online training data quickly. Finally, the prototype experiments have proved the correctness of the analysis and the validity of neural network control in switched reluctance motor. In the axial field disk type switched reluctance motor control system, this paper has studied the main circuit structure and MOSFET driving optimization etc. In the main circuit structure, this paper has proposed an H bridge structure based on synchronous rectification to control switched reluctance motor, in this main circuit structure, the plurality parallel power MOSFETs were used to instead the freewheeling diodes used in half bridge structure, and rational control method should be designed to realize the freewheeling function. Theoretical analysis and experiments have proved that the proposed control method could reduce the wheeling power significantly and improve the efficiency of power conversion.This paper has also proposed a MOSFET optimization method based on dynamic driving power, and the dynamic power assistant system designed in this paper has realized the power MOSFET ideal driving, which could reduce electromagnetic radiation and increase the reliability of the system. This driving method has two working stage:double power driving stage and single power driving stage. In the double power driving stage, appropriate driving parameters should be selected to make the driving circuit working in the opening delay stage, which can increase the driving current effectively and reduce opening delay time of MOSFET. In single power driving stage, the drive system works in the current rising stage of MOSFET, one part of the driving output current is charging the dynamic power, and the other part is driving the MOSFET, which can reduce the driving current and slow down rising rate of the drain current. Then, after the gate voltage increased to Miller voltage, MOSFET would get into voltage drop stage, the gate voltage of MOSFET will be fixed to Miller voltage value, and all output driving current is charged to gate capacitance of MOSFET, which will shorten the duration of the Miller effect and accelerate the MOSFET drain source voltage drop speed. Finally, the gate voltage will begin to increase after the Miller effect is finished, and all of the output driving current come back to the state of charging the dynamic power and MOSFET gate capacitors. Experiments have shown that the optimized driving method based on dynamic power could effectively optimize the opening process of MOSFET.