Design of the most popular modular hybrid control

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Design of a switched reluctance motor analog-to-digital hybrid control system Abstract: This paper introduces a design scheme of switched reluctance motor analog-to-digital hybrid control system. The mathematical model and working principle of switched reluctance motor are analyzed, and a speed single closed-loop control scheme based on fixed angle voltage chopping mode is proposed. The control loop adopts analog mode to realize PI speed regulation, and the feedback loop adopts a single-chip microcomputer system with 80C51 as the core to convert the position signal and feedback speed. At the same time, the corresponding hardware structure is given

key words: switched reluctance motor, analog control, digital control

1 Introduction

switched reluctance motor has been more and more widely used in industry because of its simple structure, low manufacturing cost, good controllability, reliable operation, high efficiency and superior comprehensive performance. At present, the United States, Canada, Yugoslavia and other countries have successively carried out research work, and made progress in the integrated design of the system, the electromagnetic analysis of motors, the application of microcomputers, the application of new power electronic devices, and the development of new structural forms (such as single-phase motors, sensorless motors, etc.). A number of universities, research institutes and factories in China have invested in the development and manufacture of switched reluctance motor systems every year. Based on the fixed angle voltage chopping control strategy, a simple and practical control system of small power switched reluctance motor is designed by using the speed single closed loop and the mode of analog-to-digital mixing

2. Basic structure and principle of switched reluctance motor control system

2.1 linear mathematical model of switched reluctance motor [1]

switched reluctance motor belongs to double salient variable reluctance motor, and the salient poles of its stator and rotor are made of ordinary silicon steel sheets. The rotor has neither windings nor permanent magnets, and the stator pole is wound with a concentrated winding. In the existing conventional design, the magnetic saturation of the iron core is generally ignored, and the magnetic flux leakage is not considered, that is, the magnetic flux is all transferred in and out of the air gap. C. packing list. In this case, the air gap magnetic conductivity is only determined by the pole arc angle of the coincidence part of the stator and rotor, that is, the air gap magnetic conductivity is only a function of the rotor angle. The curve of inductance changing with angle is shown in Figure 1:

analysis shows that in the rising section of the inductance curve, the incoming winding current generates a positive electromagnetic torque, and in the falling section of the inductance curve, the incoming winding current generates a reverse electromagnetic torque. Therefore, the torque direction can be changed by changing the time when the winding is energized. The same as TNP series spring change fatigue testing machine is applicable to various springs (high strength, high stress, anisotropic parts, special materials), dynamic experiments of elastic components, normal temperature cycle life experiments and other fatigue performance tests and research. When adjusting the pulse width, the winding current is controlled, so as to achieve the purpose of adjusting the speed

2.2 system principle block diagram [1][2]

the structural block diagram of analog-to-digital hybrid control system is shown in Figure 2:

after the deviation between the given speed and the feedback speed is output by the speed regulator, it is used as the input control signal of PWM circuit to control and adjust the pulse width of a certain frequency, the square wave pulse acts on the power circuit, and through the switching action of IGBT, The DC power supply voltage applied to the phase winding of SR motor is chopped into square wave voltage with corresponding frequency and duty cycle, so as to change the effective value of the voltage at both ends of the phase winding and realize the speed control of SR motor

logic electric the spring cylinder coil spring fatigue testing machine developed by Shandong Sida high-tech adopts a mechanical structure, integrates the angular displacement signal and control mode, and outputs a multi-channel signal that conforms to the motor phase number and realizes speed regulation control; After the position detection signal passes through the digital frequency doubling and frequency voltage conversion circuit, the feedback speed is output

3. Design of power converter [2]

in the main circuit of common power converters of SRM, commonly used are motor double wound type, capacitor split phase type, H-bridge type, and asymmetric half bridge type. This paper adopts the design scheme as shown in Figure 3, and achieves good results in the experiment. Designed for 8/6 pole switched reluctance motor, in the above circuit, we apply three-phase AC rectification to both ends of the motor winding. Taking phase a as an example, each phase has only one controllable device T1 and one freewheeling diode DL1, which can be carried out in single-phase or two-phase mode. This paper uses single-phase to verify that when the controllable device T1 is turned on, the rectified current passes through winding a, driving it to generate electric torque; When it is turned off, the winding freewheeling through diode DL1, in which R2 and C3 play the role of protecting controllable devices. In order to avoid current shock during startup, a high-power resistor R1 is connected in series in circuit C1. After the system enters the stable operation state, disconnect it

4. Design of switched reluctance motor digital analog hybrid system

4.1 rotor angular displacement detection [1][2]

there are many types of angular displacement sensors suitable for switched reluctance motor speed regulation system, among which the most commonly used is photoelectric type. Its advantage is that it has simple structure and high position accuracy, but it is afraid of dust, so it needs a well sealed dust cover. In this paper, a four-phase 8/6 pole structure is adopted, and half of the detection scheme is adopted for position detection. The step angle is 15 degrees, the pole distance angle of the rotor is 60 degrees, the number of teeth and slots of the rotary table is the same as the number of salient poles and grooves of the rotor, which are evenly distributed, and the angle occupied is 30 degrees. The rotary table is installed on the rotor shaft and rotates synchronously, and the two photoelectric pulse generators S1 and S2 with an included angle of 75 degrees are fixed at 75/2 degrees on the left and right sides of the stator centerline respectively

when the convex teeth in the disc turn to the positions of slotted photoelectric pulse generators S1 and S2, the output state is 0 because the light of the light-emitting tube is blocked. When it is not blocked, the output state is 1. Then within a rotor angle period of 60 degrees, S1 and S2 generate two square wave signals with a phase difference of 15 degrees and a duty cycle of 50%. It is combined into four different states, representing different reference positions of the four phase winding of the motor

the position pulse signal output by the photoelectric pulse generator shown in Figure 5 has certain rising and falling edges, so as to reduce the waste of resources and other phenomena. For this reason, after the photoelectric triode outputs the voltage, we use a comparator with a hysteresis loop for shaping to eliminate the "burr" of the output position signal and its rising and falling edges

4.2 θ off、 θ Determination and starting mode of on [2]

analysis of the inductance curve in Figure 1 above shows that it changes θ On changes the current in the rising section of the inductance, thus changing the motor torque, changing θ Off generally does not affect the current peak value, but affects the width of the current waveform and its relative position with the inductance curve. This paper adopts the control mode of fixed angle chopping, θ Off and θ On should take into account the middle value of high and low speed operation, and its applicable speed regulation range is generally not too large, such as the ratio of 1:20

when starting the motor, it is required that the rotor can start at the maximum torque at any position, so at this time, the winding current should be naturally on and off. The four phase 8/6 pole motor in this paper is taken as θ on =0。 , θ off =30。 , But when the speed increases gradually, it should be θ off

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