CN112019125A

CN112019125A - Low-speed control method of switched reluctance motor

Info

Publication number: CN112019125A
Application number: CN202010723856.7A
Authority: CN
Inventors: 杜杉杉
Original assignee: Ningbo Fotile Kitchen Ware Co Ltd
Current assignee: Ningbo Fotile Kitchen Ware Co Ltd
Priority date: 2020-07-24
Filing date: 2020-07-24
Publication date: 2020-12-01
Anticipated expiration: 2040-07-24
Also published as: CN112019125B

Abstract

A low-speed control method of a switched reluctance motor is characterized by comprising the following steps: firstly, starting a program, and detecting whether a motor is normally started; secondly, initializing and setting; third, timer t_CClearing and timing; fourthly, whether external interruption exists or not; fifthly, calculating V_rtAnd D_rt(ii) a Sixthly, solving T_C(ii) a Seven, T_CWhether or not greater than T_limit(ii) a Eight, T_D＝T_fix－T_CTurning to the tenth step; nine, T_D＝T_limitTurning to the tenth step; ten motor delay T_DTime reversing; eleven, t_CWhether or not greater than T_max(ii) a And twelfth, the duty cycle is increased. The invention has the advantages that: limiting delay tradeTo time T_DThe size of the motor is limited, the efficiency of the motor is improved, the rotating speed of the motor is stable, and the motor is suitable for the low-speed operation of the food processor.

Description

Low-speed control method of switched reluctance motor

Technical Field

The invention relates to the technical field of switched reluctance motors, in particular to a low-speed control method of a switched reluctance motor.

Background

The Switched Reluctance Motor (SRM) is a novel speed regulating motor with simple and firm structure, wide speed regulating range and high system reliability. The switch reluctance motor is mainly composed of a motor entity, a power converter, a controller, a position detector and the like, wherein the controller comprises the power converter and a control circuit, and the rotor position detector is installed at one end of the motor.

At present, a switched reluctance motor has been successfully applied to various fields such as electric vehicle driving, general industry, household appliances and textile machinery, and particularly in food processor products (such as high-speed wall breaking machines), the switched reluctance motor often needs to reach a high rotation speed of about 10000rpm (rpm is revolutions per minute), and is required to be capable of realizing quick start, which cannot be realized by adopting a traditional motor at all; the rotor structure of the switched reluctance motor has small limit on the rotating speed, and can be made into a high-rotating-speed motor, the rotor of the switched reluctance motor has small moment of inertia, and the magnitude and the direction of the phase turn torque can be changed when the current is subjected to phase change every time, so that the system has good dynamic response, and the switched reluctance motor is particularly suitable for food processor products due to the characteristics of the switched reluctance motor. However, the food processor product is usually required to be operated in a low-speed operation state (such as low-speed dough kneading) in addition to a high-speed operation state, but during the low-speed dough kneading process, because the blade is continuously contacted with the dough, a torque sudden change is easily caused, so that the output torque pulsation of the motor is large, the rotating speed of the product during the low-speed operation is unstable (the rotating speed during the low-speed dough kneading is usually required to be stable at 100rpm), and noise and vibration generated during the operation are also large.

In the prior art, as in the prior invention patent application 201310152752.5 "low-speed control algorithm of a switched reluctance motor", a low-speed control algorithm of a switched reluctance motor is disclosed, which is characterized in that: the method realizes the sectional control of the low rotating speed area of the switched reluctance motor, and comprises the following specific steps: the switched reluctance motor is initially started and is controlled by open-loop stepping at the stage of extremely low speed less than 200RPM, so that the switched reluctance motor is started smoothly and the extremely low speed operation is maintained; in the low-speed stage of the motor with the speed more than 200RPM and less than the minimum continuous pulse width rotating speed, closed-loop control of six-beat conduction with single-beat and double-beat alternate conduction is adopted; when the load is high, the fixed PWM frequency is automatically adopted for control; when the load is low, the on-time of a power converter switching device is fixed, and the off-time is dynamically changed, so that the switched reluctance motor can stably regulate the speed at a low-speed stage.

Although the above patent relates to a low-speed control method of a switched reluctance motor, the low-speed control method in the patent needs to determine the load change at the low-speed stage to adopt a proper control mode, and its essence is to solve the problem that how to realize the continuous operation of the switched reluctance motor at the low speed and realize the stable speed regulation at the low-speed operation, and the regulation mode is relatively complex, and the patent cannot well solve the problems of unstable rotating speed and large torque pulse of the food processor product in the prior art at the low speed and in the dough kneading operation state. In view of the foregoing, further improvements and improvements to low speed control methods for switched reluctance motors are currently desired.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a low-speed control method of a switched reluctance motor, which is high in motor efficiency and enables the motor rotation speed to be stable, for the current state of the prior art, and the low-speed control method enables the anti-disturbance performance of the motor when the torque suddenly changes to be improved, and is suitable for the characteristics of a food processor when the food processor operates at a low speed.

The technical scheme adopted by the invention for solving the technical problems is as follows: a low-speed control method of a switched reluctance motor is characterized by comprising the following steps:

step one, starting a program, detecting whether a motor is normally started, and if so, continuing to execute the next step; if not, prompting the motor to start the fault, and circulating the step;

step two, according to the preset target rotating speed V when the motor operates at low speed_setCalculating the fixed commutation time T of the motor_fixSetting window length limit time T_limitInitializing setting of real-time commutation time T_CAnd delay commutation time T_D；

Wherein the commutation time T is fixed_fixTo be at a preset target rotating speed V_setTheoretical time difference of next two adjacent external interrupts; window length limiting time T_limitIs a preset constant; real-time commutationTime T_CThe actual time required to receive the external interrupt again after the motor is switched; delay commutation time T_DTime to induce negative torque;

step three, timer t_CResetting and restarting timing;

step four, judging whether external interruption exists, if so, continuing the next step; if not, jumping to the step ten;

step five, detecting and obtaining the actual time difference T of two adjacent external interrupts in real time_extiAnd calculating to obtain the current real-time rotating speed V of the motor_rtAnd real-time output duty ratio D_rt；

Step six, outputting the duty ratio D according to real time_rtTo obtain the real-time commutation time T_C；

Step seven, judging the real-time reversing time T obtained in the step six_CWhether it is greater than the set window length limit time T_limitIf yes, continuing the next step; if not, jumping to the ninth step;

step eight, setting the delay reversing time T_D＝T_fix－T_CJumping to the step ten;

step nine, setting the delay reversing time T_D＝T_limitJumping to the step ten;

step ten, obtaining the current position of the rotor and the motor delay T_DReversing after time, and reversing time T in real time_CClearing;

step eleven, judging a timer t_CWhether the accumulated time length of the time interval is larger than the set maximum commutation time T or not_maxIf yes, continuing the next step; if not, returning to the third step;

step twelve, outputting the duty ratio D in real time_rtIncreasing n% every t milliseconds, and returning to the third step; wherein t and n are both preset constant values.

In order to limit the magnitude of the introduced negative torque and improve the efficiency of the motor, the window length is preferably limited by the time T_limitThe value ranges are preferably: 1/2T_fix≤T_limit≤4/5T_fix，T_limitThe larger the value, the higher the motor efficiency, T_limitThe small value, the better the ability to resist load disturbance, actually to select T_limit＝1/2T_fixIs a better value.

In order to prevent the influence of interference signals, avoid frequent switching of duty ratio caused by signal fluctuation and ensure the stability of the motor operation, the maximum commutation time T is preferably_maxThe value range is as follows: 1.2T_fix≤T_max≤1.5T_fix。

Preferably, the value range of t in the step twelve is as follows: t is more than or equal to 0.5 and less than or equal to 5; the value range of n in the step twelve is as follows: n is more than or equal to 0.05 and less than or equal to 0.2. The normal continuous rotation of the motor under the condition of large load resistance can be ensured by gradually increasing the duty ratio, and the energy waste caused by overlarge duty ratio can be avoided.

The calculation method for obtaining the real-time duty ratio in the fifth step can be realized by various algorithms in the prior art, and preferably, a traditional PID adjustment algorithm or a neuron adaptive algorithm or a fuzzy control algorithm can be adopted.

Preferably, the method for detecting whether the motor is normally started in the first step includes the following steps:

(1.1) starting a timer T1, detecting the current position of the rotor by a position sensor, and setting a conducting winding;

(1.2) judging whether the accumulated time length of the timer T1 is greater than the set maximum accumulated time T_totalIf yes, continuing to execute the next step; if not, jumping to the step (1.4);

(1.3) Start Duty ratio D_startN% increase every t milliseconds; wherein t and n are both preset constants;

(1.4) judging whether external interruption exists or not, and if so, executing the next step; if not, returning to the step (1.2);

(1.5) detecting the current position of the rotor by a position sensor, and conducting winding commutation;

and (1.6) clearing the timer T1, and starting the motor normally.

Preferably, the start dutyRatio D_startMay be set to 0.01.

Preferably, the value range of t in the step (1.3) is as follows: t is more than or equal to 0.5 and less than or equal to 5.

Preferably, the value range of n in the step (1.3) is as follows: n is more than or equal to 0.05 and less than or equal to 0.2.

Preferably, the maximum cumulative time T_totalThe value range is as follows: 1.2T_fix≤T_total≤1.5T_fix。

The switched reluctance motor of the embodiment is a four-phase 8/6-level switched reluctance motor, and for the motor structure of the four-phase 8/6-level switched reluctance motor, correspondingly, the current position of the motor rotor is detected by a position sensor arranged on the motor, and the position sensor comprises a transmission-type sensor and a shutter disk; the transmission-type sensor is provided with two adjacent a + salient poles and d-salient poles which are respectively arranged on the stator, the shading disc is a disc arranged on the rotor shaft, and the shading disc comprises a tooth groove structure matched with the salient poles and the grooves of the rotor in quantity and shape. If the switched reluctance motor with other structures is adopted, the arrangement mode of the position sensor needs to be changed correspondingly.

Compared with the prior art, the invention has the advantages that: redefining the concept of commutation time by detecting the real-time speed V_rtCalculating a real-time commutation time T_CAnd delay commutation time T_DAnd further controlling the motor to delay T each time_DReversing after the time, and setting the preset window length limit time T_limitTo limit the delay commutation time T_DThe size of the motor enables the introduced negative torque to be limited, and the efficiency of the motor to be improved; in addition, when the motor runs at a low speed, a mode similar to step control is adopted, so that the rotating speed of the motor is stable, the anti-disturbance performance is improved when the torque suddenly changes, and the method is suitable for the characteristic of low-speed running of the food processor.

Drawings

Fig. 1 is a schematic diagram of an arrangement structure of a position sensor of a four-phase 8/6-level switched reluctance motor according to an embodiment of the present invention.

Fig. 2 is a torque characteristic diagram of a four-phase 8/6-level switched reluctance motor according to an embodiment of the present invention.

Fig. 3 is a diagram illustrating a four-phase winding null stabilizing characteristic of a four-phase 8/6-level switched reluctance motor according to an embodiment of the present invention.

Fig. 4 is a diagram of position signal and conducting winding characteristics (start-up phase) of a four-phase 8/6-level switched reluctance motor according to an embodiment of the present invention.

Fig. 5 is a diagram of position signal and conducting winding characteristics of a four-phase 8/6-level switched reluctance motor according to an embodiment of the present invention (low speed operation stage).

Fig. 6 is a general flowchart of a low-speed control method of a motor according to an embodiment of the present invention.

Fig. 7 is a sub-flowchart of a motor start control method according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

In the embodiment, a four-phase 8/6-level switched reluctance motor is adopted, wherein 8 is a stator level, 6 is a rotor level, and the step angle is 15 degrees.

As shown in fig. 1, the motor of the present embodiment includes a stator 1 and a rotor 2, the position of the rotor 2 is detected by a photosensitive rotor position sensor, the photosensitive rotor position sensor generally includes a transmission-type photoelectric sensor (including a photoelectric switch of an infrared transmitting tube and an infrared receiving tube) and a light shielding disc, and the structures of the transmission-type photoelectric sensor and the light shielding disc are both in the prior art;

the transmission type photoelectric sensor comprises two sensors S and two sensors P, wherein the two sensors are respectively arranged on two adjacent stator 1 salient poles (an + salient pole and a d-salient pole), the centers of the sensor S and the a + salient pole of the stator 1 are aligned, the centers of the sensor P and the d-salient pole of the stator 1 are aligned, and the included angle formed by the sensor S and the sensor P after connection with the center of the motor is 45 degrees; a groove is formed between the infrared transmitting tube and the infrared receiving tube of each sensor, the shading disc is a disc arranged on the rotor shaft and can rotate synchronously with the rotor 2, shading sheets 3 matched with the cross section shapes of the convex teeth are arranged on the shading disc along the circumference at the positions corresponding to the convex teeth of the rotor, the shading sheets 3 are arranged perpendicular to the disc surface of the shading disc (namely 6 shading sheets 3 are included on the shading disc and are uniformly distributed along the circumference), and the hatching of the shading sheets arranged vertically is shown in figure 1;

when the convex teeth of the rotor 2 rotate to the position where the sensor S, P is arranged, the shading sheet 3 just passes through the groove of the sensor, the light of the infrared emission tube is shaded to cut off the photosensitive transistor, and the output state is 0; when the groove of the rotor is rotated to the position of the sensor S, P, no shading sheet passes through the groove of the sensor at this time, the light of the infrared emission tube is not shaded, the phototransistor is switched on, the output state is 1, and in one rotor angular period (namely 60 degrees), the sensor S and the sensor P can generate two square wave signals with the phase difference of 15 degrees and the duty ratio of 50 percent, and the two square wave signals are combined into four different states which respectively correspond to different reference positions of the four-phase winding.

If the motor rotates clockwise, the middle point of the lowest inductance of the winding of the phase a is taken as 0 °, as shown in fig. 2, that is, the torque characteristics of the windings of the motor when the motor rotates clockwise are shown.

Two sensors S, P are used to detect the external interrupt signal, when the sensor S, P detects a sudden change (i.e., a jump) in the signal, the motor enters the external interrupt, and the switched reluctance motor performs the commutation operation. For example, under the condition of 50rpm, the time difference between two external interruptions is 50ms, and the rotating speed of the motor can be continuously changed along with the disturbance of the torque in the actual use process, so the time difference between the two external interruptions in the actual operation of the motor is always changed.

As shown in fig. 3, a stable zero position for the A, B, C, D four-phase winding is shown. According to the minimum principle of the magnetic resistance of the switched reluctance motor, if a certain phase winding is excited by stable current, finally, the rotor is fixed at a stable zero position. If the two phase windings are energized with a steady current at the same time, the rotor will eventually also be held in the same steady position as in fig. 3.

For theFor a four-phase 8/6-level switched reluctance motor, when equal currents are excited to windings, a set of torque vectors with equal magnitude and different directions are generated

Wherein at the torque vector

The A-phase winding generates a stable zero (fixed in this position) at the torque vector

The B-phase winding generates a stable null (fixed in this position) which is spatially at a geometrical angle of 15 °, i.e. at a step angle. If the windings are energized in the order of a → B → C → D, the rotor of the switched reluctance motor will rotate step by step at a step angle of 15 °.

Considering that the torque of the switched reluctance motor is greatly changed when the switched reluctance motor is applied to the food processor, the torque is not known during starting, and two-phase starting is generally adopted in practice. In the starting process of the switched reluctance motor, in a rotor angle period of 0-60 degrees of rotor position, the electric sequence of each phase is AB → DA → CD → BC, which is similar to the double four-beat starting operation mode of a stepping motor. As shown in fig. 4, which is a characteristic diagram of the position signal and the conducting winding of the motor at the time of starting, the logical relationship between the position signal and the conducting phase (starting phase) of the motor is shown in table 1:

TABLE 1 Start-Up phase commutation logic

Table 1 above illustrates the conducting windings corresponding to different position signals of the motor, for example, when the position signal P11 is detected, the conducting windings are in a phase a and a phase B; when the position signal P00 is detected, the conductive winding is in the C-phase and the D-phase.

In view of the characteristics of the switched reluctance motor and the above problems when the switched reluctance motor operates at a low speed, in order to improve the disturbance resistance of the motor when the torque suddenly changes so that the motor can continuously and smoothly operate when the motor operates at the low speed, the present embodiment proposes a low-speed control method of the switched reluctance motor, as shown in fig. 6, which includes the following steps:

Wherein the commutation time T is fixed_fixTo be at a preset target rotating speed V_setTheoretical time difference of next two adjacent external interrupts; window length limiting time T_limitThe window length is limited by a preset constant value to limit the magnitude of the introduced negative torque so as to improve the efficiency of the motor_limitThe value ranges are preferably: 1/2T_fix≤T_limit≤4/5T_fix，T_limitThe larger the value, the higher the motor efficiency, T_limitThe smaller the value, the better the ability to resist load disturbance, and the practical embodiment is to select T_limit＝1/2T_fixIs a better value; real-time commutation time T_CThe actual time required to receive the external interrupt again after the motor is switched; delay commutation time T_DTime to induce negative torque;

step three, timer t_CResetting and restarting timing;

step five, detecting and obtaining the actual time difference T of two adjacent external interrupts in real time_extiAnd calculating to obtain the current real-time rotating speed V of the motor_rtAnd real-time output duty ratio D_rt(ii) a The calculation method for obtaining the real-time duty ratio can adopt the prior artPreferably, a traditional PID regulation algorithm or a neuron adaptive algorithm or a fuzzy control algorithm can be adopted;

step eleven, judging a timer t_CWhether the accumulated time length of the time interval is larger than the set maximum commutation time T or not_maxIf yes, continuing the next step; if not, returning to the third step; in order to prevent the influence of interference signals and ensure the stability of the operation of the motor, the maximum commutation time T_maxThe value range is as follows: 1.2T_fix≤T_max≤1.5T_fix；

Step twelve, outputting the duty ratio D in real time_rtIncreasing n% every t milliseconds, and returning to the third step; wherein t and n are both preset constant values; the value range of t is as follows: t is more than or equal to 0.5 and less than or equal to 5, and the value range of n is as follows: n is more than or equal to 0.05 and less than or equal to 0.2.

In addition, the detection of whether the motor is normally started in the first step may be implemented by various methods in the prior art, and as shown in fig. 7, the following conventional control method is preferably adopted in this embodiment, and specifically includes the following steps:

(1.1) the timer T1 is started, and the duty ratio D is started_startThe initial value of (2) is 0.01, the position sensor detects the current position of the rotor 2, and a conduction winding is set;

(1.2) judging timer T1 whether the accumulated time length is larger than the set maximum accumulated time T_totalIf yes, continuing to execute the next step; if not, jumping to the step (1.4); wherein the duty ratio is frequently changed to avoid the influence of interference, and the maximum accumulated time T_totalThe value ranges are preferably: 1.2T_fix≤T_total≤1.5T_fix；

(1.3) Start Duty ratio D_startN% increase every t milliseconds; wherein t and n are both preset constants; the value range of t is as follows: t is more than or equal to 0.5 and less than or equal to 5, and the value range of n is as follows: n is more than or equal to 0.05 and less than or equal to 0.2;

(1.5) detecting the current position of the rotor 2 by a position sensor, and conducting winding commutation;

and (1.6) clearing the timer T1, and starting the motor normally.

The low-speed control method is applicable to various types of switched reluctance motors, and the embodiment takes a four-phase 8/6-level switched reluctance motor as an example, and specifically describes a calculation method of each parameter involved in the control method.

Firstly, the real-time rotating speed V of the motor_rt

For the four-phase 8/6-level switched reluctance motor adopted in the embodiment, the actual time difference between two adjacent external interrupts is set as T_extiThen the motor real-time rotating speed V of the motor_rtSatisfies the following formula

The specific derivation process is as follows: assuming that the motor rotates at a constant speed, the sensor S, P will output 24 external interrupt signals when the motor rotates one turn, the sum of the time differences of the consecutive 24 external interrupts is the time required by the motor to rotate one turn, and the time difference between two adjacent external interrupts is T_extiThe time of one rotation of the motor is 24T_exti(in seconds) the rpm is defined as revolutions per minute and 60s per minute, whereby electricity is obtainedThe rotational speed of the machine is

The above derivation is applicable only to the switched reluctance motor in the current four-phase 8/6 stage configuration, and the position sensor mounting position is as shown in fig. 1.

② low speed reversing point (the low speed of the embodiment is the rotating speed between 40-300 rpm)

In the practical use scene of the motor running at low speed, the situation of sudden change of torque (for example, stirring food) often exists, and the embodiment adopts a mode of introducing negative torque to smooth the rotating speed.

Defining: fixed commutation time of T_fixI.e. at a preset target speed V_setTheoretical time difference of next two adjacent external interrupts; the preset target rotating speed is known as V_setThen, the motor speed calculation formula can be obtained

For example, when the set target rotation speed is 50rpm, T_fixAt 50ms, the switched reluctance motor is driven in a stepping motor-like manner, thereby achieving stabilization of the rotational speed.

③ delay commutation time T_D

Delay commutation time T_DFor custom parameters, representing the time to introduce negative torque, at initialization, T _D0; wherein, T_DThe larger the torque, the more negative torque introduced, the lower the motor efficiency; t is_DThe smaller the torque is, the less negative torque is introduced, the motor torque pulsation is large, and the T needs to be reasonably set_DThe torque pulse is effectively reduced on the premise of ensuring the efficiency of the motor, and the motor is ensured to operate at a stable rotating speed.

Fourthly, real-time reversing time T_C

Real-time commutation time T_CThe motor is represented to be a self-defined parameter again after reversingTime required to receive an external interrupt, on initialization, T_C＝T_fix；T_CThe larger the torque, the more positive torque, the higher the motor efficiency; t is_CThe smaller the positive torque, the less the motor efficiency.

Fifthly, limiting the time T by the window length_limit

Window length limiting time T_limitFor self-defining parameters, the value is a preset constant value, and the value range is preferably as follows: 1/2T_fix≤T_limit≤4/5T_fix，T_limitThe larger the value, the higher the motor efficiency, T_limitThe small value is better in capability of resisting load disturbance, and the embodiment is directed to a four-phase 8/6-level switched reluctance motor and is actually used for selecting T_limit＝1/2T_fixIs a better value, i.e.

Thus, the present embodiment delays the motor commutation time by T by introducing a negative torque_DTime, as shown in fig. 5, is a characteristic diagram of the position signal and the conducting winding of the motor in the low-speed operation state, and accordingly, the logical relationship between the position signal and the conducting phase (low-speed stage) of the motor is shown in table 2:

TABLE 2 Low speed run phase commutation logic

This embodiment is implemented by introducing a delayed commutation time T_DThe commutation time of the motor is artificially controlled and the commutation time T is delayed_DThe size of the motor is limited, so that the introduced negative torque is limited, and the motor efficiency is improved; adopt similar step control's mode during low-speed control for motor speed is stable, and the anti-disturbance performance when the torque sudden change improves, is applicable to the characteristic of cooking machine low-speed operation.

Claims

1. A low-speed control method of a switched reluctance motor is characterized by comprising the following steps:

Wherein the commutation time T is fixed_fixTo be at a preset target rotating speed V_setTheoretical time difference of next two adjacent external interrupts; window length limiting time T_limitIs a preset constant; real-time commutation time T_CThe actual time required to receive the external interrupt again after the motor is switched; delay commutation time T_DTime to induce negative torque;

step three, timer t_CResetting and restarting timing;

2. The low-speed control method of the switched reluctance motor according to claim 1, wherein: the window length limits the time T_limitThe value range is as follows: 1/2T_fix≤T_limit≤4/5T_fix。

3. The low-speed control method of the switched reluctance motor according to claim 1, wherein: the maximum commutation time T_maxThe value range is as follows: 1.2T_fix≤T_max≤1.5T_fix。

4. The low-speed control method of the switched reluctance motor according to claim 1, wherein: the value range of t in the step twelve is as follows: t is more than or equal to 0.5 and less than or equal to 5.

5. The low-speed control method of the switched reluctance motor according to claim 1, wherein: the value range of n in the step twelve is as follows: n is more than or equal to 0.05 and less than or equal to 0.2.

6. The low-speed control method of the switched reluctance motor according to claim 1, wherein: and the calculation method for obtaining the real-time duty ratio in the fifth step is a traditional PID (proportion integration differentiation) regulation algorithm or a neuron self-adaptive algorithm or a fuzzy control algorithm.

7. The low-speed control method of the switched reluctance motor according to claim 1, wherein: the method for detecting whether the motor is normally started in the first step comprises the following steps:

and (1.6) clearing the timer T1, and starting the motor normally.

8. The low-speed control method of the switched reluctance motor according to claim 7, wherein: the start-up duty cycle D_startIs 0.01.

9. The low-speed control method of the switched reluctance motor according to claim 7, wherein: the value range of t in the step (1.3) is as follows: t is more than or equal to 0.5 and less than or equal to 5.

10. The low-speed control method of the switched reluctance motor according to claim 7, wherein: the value range of n in the step (1.3) is as follows: n is more than or equal to 0.05 and less than or equal to 0.2.

11. The low-speed control method of the switched reluctance motor according to claim 7, wherein: the maximum accumulated time T_totalThe value range is as follows: 1.2T_fix≤T_total≤1.5T_fix。

12. The low-speed control method of the switched reluctance motor according to claim 1, wherein: the switched reluctance motor is a four-phase 8/6-level switched reluctance motor.

13. The low-speed control method of the switched reluctance motor according to claim 12, wherein: the current position of the motor rotor is detected and obtained by a position sensor arranged on the motor, and the position sensor comprises a transmission type sensor and a shading disc; the transmission-type sensor is provided with two adjacent a + salient poles and d-salient poles which are respectively arranged on the stator, the shading disc is a disc arranged on the rotor shaft, the shading disc comprises a shading sheet structure matched with the salient poles of the rotor in number and section shape, and the shading sheet is perpendicular to the shading disc.