A control method for a switched reluctance motor and a food processor using the same

Abstract

A control method for a switched reluctance motor is characterized by comprising the following steps: 1. program start and initialization settings; 2. energizing each winding of the motor according to the excitation mode of the half-step drive of the stepper motor; 3. the motor operates in the normal working mode; 4. whether the motor enters the overshoot mode, if so, executing step 5; if not, returning to step 3; 5. continuously energizing the current conducting phase winding within a limited time, so that the rotor oscillates at the stable zero position of the current conducting phase winding; 6. adjusting the motor torque, and returning to step 4. The present invention also relates to a food processor using the above control method. The advantages of the present invention are: energizing each winding according to the half-step drive mode of the stepper motor to achieve ultra-low speed operation of the switched reluctance motor, continuously energizing the current winding when receiving an external interrupt, so that the motor can achieve oscillation at the stable zero position (i.e., generating the effect of blade shaking) after each phase change, thereby preventing food from being stuck.

Description

Technical Field

[0001] The present invention relates to a switched reluctance motor, and in particular to a control method for the switched reluctance motor and a food processor using the control method. Background Art

[0002] In recent years, with the continuous improvement of people's living standards, various food processors have entered people's daily lives. The working principle of a food processor is that the blades at the bottom of the mixing cup rotate at high speed and repeatedly crush the food under the action of water flow. In addition to the function of crushing food, today's high-end food processors also have the functions of cooking and baking.

[0003] The motor is the core component that determines the performance and quality of food processors. Currently, switched reluctance motors are mostly used as driving components in food processors. The switched reluctance motor is a new type of speed-regulating motor. Its speed-regulating system combines the advantages of both DC and AC speed-regulating systems and is a new generation of stepless speed-regulating system. In the existing technology, there are many designs and improvement schemes for switched reluctance motors under high-speed operation. However, there are relatively few studies on the dynamic performance of switched reluctance motors in application scenarios such as cooking at ultra-low speeds (such as a speed range of 5-50rpm). If traditional motors are used in food processors, they cannot intelligently sense food. When cooking at ultra-low speeds, the food is easily crushed and the integrity of the food cannot be guaranteed, which in turn affects the taste of the food.

[0004] Existing Chinese invention patent applications, such as application number ZL201810472338.5, titled "A New Ultra-Low-Speed, High-Torque Switched Reluctance Motor," provide a new ultra-low-speed, high-torque switched reluctance motor. This patent primarily improves the mechanical design of the stator and rotor assemblies. The motor can form a shorter magnetic circuit, achieving both increased torque and reduced speed. However, the patent does not address how to implement low-speed control of the switched reluctance motor. When the switched reluctance motor is operating in stir-fry mode and encounters resistance, the motor can easily become stuck or, if continued rotation occurs, crush the food, preventing timely torque adjustment and intelligent automatic stir-frying.

[0005] Therefore, in response to the above-mentioned problems, how to improve the intelligence level of food processors in ultra-low speed operation mode (such as cooking) is an issue that needs to be solved urgently, and further improvements are needed to the existing switched reluctance motors. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a control method for a switched reluctance motor in response to the above-mentioned existing technical status, which can ensure stable operation of the motor and effectively prevent food from getting stuck.

[0007] The second technical problem to be solved by the present invention is to provide a food processor adopting the control method of the above-mentioned switched reluctance motor in response to the above-mentioned existing technical status.

[0008] The technical solution adopted by the present invention to solve the first technical problem is: a control method for a switched reluctance motor, characterized in that the control method includes the following steps:

[0009] Step 1: Start the program and initialize the settings;

[0010] Step 2: Start the motor and energize each winding of the motor according to the set excitation mode;

[0011] Step 3: The motor runs in normal working mode;

[0012] Step 4: Determine whether the motor enters the overshoot mode (i.e., the motor speed exceeds the speed in the normal operating mode). If so, proceed to step 5; if not, return to step 3.

[0013] Step 5: within a limited time, continuously energize the current conducting phase winding (single-phase conducting winding or double-phase conducting winding);

[0014] Step 6: Set the corresponding torque adjustment amount according to the different oscillation states of the motor rotor, reduce the torque of the motor according to the corresponding torque adjustment amount, and return to step 4.

[0015] As another preferred embodiment, step 6 reduces the motor torque by the following method: In step 6, a torque adjustment value is set according to the oscillation state of the motor rotor, and the motor torque is reduced according to the torque adjustment value until the motor torque is reduced to a set torque value or a timer reaches a set window time, and then the process returns to step 3. Specifically, the total amount of motor torque reduction is set by empirical value, and the reduction stops when the preset value or the preset timer time is reached, thereby exiting the overshoot loop and returning to normal operating mode.

[0016] For the convenience of operation and detection, preferably, the oscillation state of the motor rotor in step six can be determined according to the oscillation number, oscillation frequency or oscillation period of the motor rotor within the limited time in step five.

[0017] As a further preferred embodiment, the oscillation state of the motor rotor in step 6 includes the following three situations:

[0018] A. No oscillation, set the first torque adjustment amount;

[0019] B. The oscillation is moderate and the torque adjustment is zero;

[0020] C. Excessive oscillation, set the second torque adjustment amount;

[0021] The first torque adjustment amount and the second torque adjustment amount are both positive numbers greater than zero, and the first torque adjustment amount is greater than the second torque adjustment amount.

[0022] Preferably, the motor rotor oscillation state is detected by the following method:

[0023] A. If it is detected that the number of times the motor rotor passes through the dead point from the commutation point is less than or equal to 1 within the limited time described in step 5, there is no oscillation, and the motor torque is reduced according to the set first torque adjustment amount;

[0024] B. If the number of times the motor rotor passes through the dead point from the commutation point is detected to be less than or equal to the preset number of oscillations within the limited time described in step 5, the oscillation is moderate, the motor torque remains unchanged, and the motor produces a shaking effect;

[0025] C. If it is detected that the number of times the motor rotor passes through the dead point from the commutation point is greater than the preset number of oscillations within the limited time described in step 5, the oscillation is excessive, and the motor torque is reduced according to the set second torque adjustment amount;

[0026] The preset number of oscillations is a positive integer greater than or equal to 2.

[0027] In order to ensure the reliable starting and operation of the motor, as a further preferred embodiment, the following steps are also included between step 2 and step 3: step 2a, detecting whether the motor starts normally, if so, executing step 3; if not, prompting a motor starting failure, waiting for the fault to be eliminated and looping this step.

[0028] As an example, the initialization settings in step 1 may include setting the motor speed V and the direction of rotation, and setting the motor output torque to Tor, the external interrupt count to N, and the timer time to t. j .

[0029] Preferably, the range of the set speed V of the motor is: 5 rpm≤V≤50 rpm. This ultra-low speed range is mainly for the cooking application mode of the food processor.

[0030] As a further preferred embodiment, the step 4 of determining whether the motor is overshooting can be implemented by the following method:

[0031] Step 4a: The external interrupt count N is cleared and the timer count time t j Reset to zero and restart the timing;

[0032] Step 4b: Detect whether an external interrupt is received. If so, execute step 4c; if not, after the external interrupt waiting time reaches the maximum set threshold, a fault alarm is prompted;

[0033] Step 4c: Timer time tj Is it greater than or equal to the theoretical commutation time T set If yes, the external interrupt instruction is executed and the process returns to step 4a; if no, the process goes to step 5. If the external interrupt arrives early, it can be determined that the motor has overshot, and the process enters the overshot mode.

[0034] As an example, the time limit in step 5 is the window time Δt, where Δt=T set -t j , T set This window allows the motor to oscillate before the next interruption, preventing overshoot caused by premature interruption and ensuring smooth motor operation.

[0035] As a further preferred embodiment, with respect to the three oscillation states set in step 6 above, the adjustment of the motor torque can be achieved by the following steps:

[0036] Step 6a, detecting whether the motor rotor oscillates at the stable zero position of the current conducting phase. If yes, proceed to step 6b; if no, proceed to step 6c;

[0037] Step 6b: Determine whether the current oscillation number exceeds the preset oscillation number N. set If yes, proceed to step 6d; if no, return to step 4c;

[0038] Step 6c: Determine whether the current motor output torque Tor is greater than the set first torque adjustment value ΔTor1. If so, Tor = Tor - ΔTor1, and return to step 4c; if not, Tor = 0, and return to step 4c;

[0039] Step 6d: Determine whether the current motor output torque Tor is greater than the set second torque adjustment value ΔTor2. If so, Tor = Tor - ΔTor2, and return to step 4c; if not, Tor = 0, and return to step 4c.

[0040] As a further preferred embodiment, in step 4b, if no external interrupt is received, a fault alarm is prompted after the external interrupt waiting time reaches the maximum set threshold, which is specifically implemented by the following steps:

[0041] Step 4b-1, the timer counts time t j Is it greater than or equal to the theoretical commutation time T set If yes, proceed to step 4b-2; if no, return to step 4b;

[0042] Step 4b-2: Determine the timer's timing time t j Is it greater than or equal to the set maximum timing time T maxIf yes, the motor fault alarm is prompted and the program ends; if no, the motor torque Tor increases by △T every t time, and then returns to step 4b, where the maximum set threshold in step 4b is the set maximum timing time T max , t and △T are preset constants.

[0043] In order to avoid interference and prevent the motor from reporting frequent errors, as a further preferred embodiment, executing the external interrupt instruction in step 4c and returning to step 4a includes the following steps:

[0044] Step 4c-1: Determine the timer's timing time t j Is it equal to the theoretical commutation time T set If yes, the conducting winding is commutated according to the conduction sequence of the current motor rotation direction and returns to step 4a; if no, the timer timing time t j Greater than the theoretical commutation time T set , the external interrupt delay indicates that the motor torque may not be large enough and needs to be appropriately increased. The motor torque Tor is increased by △T every t time, and the conduction winding is commutated according to the conduction sequence of the current motor rotation direction, and then returns to step 4a, where t and △T are both preset constants.

[0045] In order to avoid excessive oscillation, preferably, the preset oscillation number N in step 6b is set The value range is: 3≤N set ≤6. If the oscillation is too little, the shaking effect to prevent sticking will not be achieved. If the oscillation is too much, the motor torque will be too large and the food will be easily crushed. Therefore, it is necessary to control the number of motor oscillations and thus control the motor torque to work within a reasonable range.

[0046] When the motor is running at ultra-low speed, in order to avoid speed overshoot (for example, when food is stuck and suddenly bounces off, the load suddenly decreases), preferably, the first torque adjustment value ΔTor1 in step 6c satisfies the following formula:

[0047]

[0048] in, is the proportional coefficient, A is a constant and 1.5≤A≤2; △T d is the preset basic torque adjustment amount, △T d The value range is 1.0×10 -3 Nm≤△T d ≤5.0×10 -3Nm. The first torque adjustment value △Tor1 takes into account the ratio between the current interruption time and the theoretical interruption time, and selects the adjustment range of the motor torque according to the degree of load mutation: for example, when cooking, if the food is suddenly bounced away, the motor load will suddenly become much smaller, and the interruption will come early. The ratio is large, in order to prevent the motor speed from overshooting, the motor torque should be reduced by a larger margin; if the actual interruption time is close to the theoretical interruption time, at this moment When the ratio is small, the actual torque of the motor is only slightly too large. In this case, the reduction in motor torque can be smaller.

[0049] Preferably, the value range of the second torque adjustment value ΔTor2 in step 6d is: 5.0×10 -4 Nm≤△T≤1.0×10 -3 Nm. When there is too much oscillation, in order to avoid excessive motor torque, it is necessary to fine-tune the motor torque in the oscillation state to gradually reduce the torque and ensure stable operation of the motor.

[0050] Preferably, the value range of t is: 0.5 milliseconds ≤ t ≤ 2 milliseconds, with t = 1 millisecond being the best.

[0051] When the motor is running at ultra-low speed, in order to avoid the food from being crushed, the increased torque cannot be too large. At the same time, a certain rotational torque must be guaranteed to complete the motor phase change. As a preferred method, the ΔT value range is: 1.0×10 -4 Nm≤△T≤5.0×10 -4 Nm.

[0052] In order to ensure the reliable operation of the motor, it is preferred that the maximum timing time T set in step 4b-2 is max The value range is: 3s≤T max ≤5s. When the interrupt waiting time exceeds the maximum timing time T max If the interrupt still does not arrive at this time, it is considered that the motor has failed and a warning is required.

[0053] Preferably, the switched reluctance motor of the present application is a four-phase 8 / 6-level switched reluctance motor.

[0054] In order to simplify the structure and facilitate installation and detection, as a further preferred embodiment, the current position of the motor rotor is detected by a position sensor arranged on the motor, and the position sensor includes a transmission sensor and a shading disk; wherein, the transmission sensor includes a first sensor and a second sensor respectively fixed on two adjacent stator salient poles, and the angle between the first sensor and the second sensor and the center line of the switched reluctance motor is 45°; the transmission sensor also includes a third sensor and a fourth sensor respectively arranged on the two adjacent stator salient poles, and the angle between the third sensor and the fourth sensor and the center line of the switched reluctance motor is 45°, the angle between the third sensor and the first sensor and the center line of the switched reluctance motor is 7.5°, and the angle between the fourth sensor and the second sensor and the center line of the switched reluctance motor is 7.5°; the shading disk is a disk arranged on the rotor shaft, and the shading disk includes a shading plate structure that matches the salient poles of the rotor in number and cross-sectional shape, and the shading plate is arranged perpendicular to the shading disk. The arrangement of the above four sensors can detect in real time whether the switched reluctance motor has oscillation at a stable zero position (single-phase winding conducting or bidirectional windings conducting at the same time) without changing the motor structure.

[0055] The technical solution adopted by the present invention to solve the above-mentioned second technical problem is: a food processor, including a switched reluctance motor, characterized in that: the switched reluctance motor adopts the control method described above to achieve operation.

[0056] Compared with the prior art, the advantages of the present invention are:

[0057] 1. By energizing each winding of the switched reluctance motor with the excitation method of the half-step drive of the stepping motor, a low-speed control method of the switched reluctance motor can be realized, so that the motor can run stably in the ultra-low speed mode of 5-50rpm;

[0058] 2. When motor overshoot occurs, the current winding is continuously energized, allowing the switched reluctance motor to achieve stable zero-position oscillation after each phase change (i.e., creating a blade shaking effect). This can reduce motor torque and avoid speed overshoot, and prevent food from getting stuck. This effectively solves the problem of food getting stuck in the blades and causing food breakage during ultra-low-speed cooking, making it more conducive to Chinese cooking (such as stir-frying spare ribs and other vegetables).

[0059] 3. According to different application scenarios, the reduction of motor torque can be reasonably controlled to effectively avoid motor speed overshoot, which can ensure the smooth operation of the motor and improve the reliability and safety of the equipment;

[0060] 4. Based on the rotor position detection structure of the existing switched reluctance motor, without changing other motor structures, an additional pair of position sensors is set up to detect the number of oscillations of each phase winding at a stable zero position in the half-step drive mode. The structure is simple and easy to implement, with low manufacturing cost and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a schematic diagram of the structure of a four-phase 8 / 6-pole switched reluctance motor in the prior art;

[0062] Figure 2 This is a schematic structural diagram of a four-phase 8 / 6-pole switched reluctance motor according to an embodiment of the present invention;

[0063] Figure 3 Schematic diagram of the stable zero position relationship between the four sensors S1-S4 and the bridge arm according to an embodiment of the present invention;

[0064] Figure 4 Schematic diagram of continuous oscillation of a phase at a stable zero position according to an embodiment of the present invention;

[0065] Figure 5 This is a block diagram of the overall steps of the switched reluctance motor control method according to an embodiment of the present invention.

[0066] Figure 6 This is a flow chart of a specific embodiment of a switched reluctance motor control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0067] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0068] like Figure 1 Figure 1 shows a switched reluctance motor in the prior art, which uses a four-phase 8 / 6-pole switched reluctance motor, where 8 represents the number of stator poles and 6 represents the number of rotor poles. The step angle of the motor is 15°. The reluctance motor 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 consists of a transmissive photoelectric sensor (a photoelectric switch including an infrared transmitting tube and an infrared receiving tube) and a shielding disk. The structures of the transmissive photoelectric sensor and the shielding disk are both prior art.

[0069] There are two transmissive photoelectric sensors, namely the first sensor S1 and the second sensor S2. The two sensors are respectively arranged on two adjacent salient poles of the stator 1 (the a+ salient pole and the d- salient pole). The first sensor S1 is aligned with the center of the a+ salient pole of the stator 1, and the second sensor S2 is aligned with the center of the d- salient pole of the stator 1. The angle between the first sensor S1 and the second sensor S2 and the motor center is 45°. A groove is formed between the infrared emitting tube and the infrared receiving tube of each sensor. The shading disk is a disk arranged on the rotor shaft and can rotate synchronously with the rotor 2. The shading disk is provided with a shading plate 3 matching the cross-sectional shape of each convex tooth along the circumference at the position corresponding to each convex tooth of the rotor. The shading plate 3 is arranged perpendicular to the disk surface of the shading disk (that is, the shading disk includes 6 shading plates 3 and is evenly distributed along the circumference). Figure 1 The section line shown in is the section line of the vertically arranged light shielding sheet;

[0070] When the protruding teeth of the rotor 2 rotate to the position where the first sensors S1 and S2 are set, the shielding plate 3 just passes through the groove of the sensor, the light of the infrared emitting tube is blocked, and the photosensitive transistor is turned off, and the output state is 0; when the groove of the rotor rotates to the position of the first sensors S1 and S2, there is no shielding plate passing through the groove of the sensor, the light of the infrared emitting tube is not blocked, the photosensitive transistor is turned on, and the output state is 1, then in one rotor angle cycle (i.e. Figure 1 Within the 60° shown in FIG. 1 , the first sensor S1 and the second sensor S2 generate two square wave signals with a phase difference of 15° and a duty cycle of 50%, which are combined into four different states corresponding to different reference positions of the four-phase windings.

[0071] The first and second sensors S1 and S2 are also used to detect external interrupt signals. When the first and second sensors S1 and S2 detect a sudden change in the signal (i.e., a jump), the motor enters an external interrupt state, and the switched reluctance motor performs commutation. For example, at a speed of 50 rpm, the time difference between two external interrupts is 50 ms. However, in actual operation, the motor speed will continuously change with torque disturbances. Therefore, the time difference between the two external interrupts in actual operation of the motor will constantly change.

[0072] like Figure 2 As shown in FIG. 1 , the structure diagram of the switched reluctance motor of this embodiment is shown. The motor of this embodiment also adopts a four-phase 8 / 6-level switched reluctance motor. Figure 1), this embodiment adds two other sensors, that is, a third sensor S3 and a fourth sensor S4 are further provided on two adjacent stator salient poles (a+ salient pole and d- salient pole), and the angle between the third sensor S3 and the fourth sensor S4 and the center line of the switched reluctance motor is also 45°, the angle between the third sensor S3 and the first sensor S1 and the center line of the switched reluctance motor is 7.5°, and the angle between the fourth sensor S4 and the second sensor S2 and the center line of the switched reluctance motor is 7.5°.

[0073] According to the principle of minimum magnetic resistance of the switched reluctance motor, if a stable current is excited to a certain phase winding or to two phase windings at the same time, the rotor will eventually be fixed at the stable zero position of the corresponding phase winding.

[0074] like Figure 3 As shown in the figure, it is a schematic diagram of the stable zero position relationship between the four sensors and the bridge arm of this embodiment. When the A phase is continuously energized, the stable zero position of the A phase is at the intersection of 10 / 00 of the second sensor S2 and the first sensor S1 signal; similarly, when the AD phase is continuously energized, the stable zero position of the AD phase is at 10 / 00 of the fourth sensor S4 and the third sensor S3 signal.

[0075] In view of the inherent characteristics of the switched reluctance motor, for the application scenarios of the food processor in ultra-low speed operation mode (such as cooking), the motor control of this embodiment draws on the half-step drive excitation method of the stepper motor, that is, when single-phase excitation is performed, the motor shaft stops at the full-step position. After the driver receives the next pulse, it excites the other phase and keeps the original phase in the excitation state. The motor shaft will move half a step angle and stop in the middle of two adjacent full-step positions.

[0076] For example, using a stepper motor in half-step drive mode, with clockwise rotation as an example, if the current conducting phase is C, then the next conducting phase is BC. The motor will conduct in the order C → BC → B → AB → A → AD → D → CD → C →…; similarly, if the motor rotates counterclockwise, the motor will conduct in the order CD → D → AD → A → AB → B → BC → C → CD…. Compared to existing single-phase winding conduction commutation modes, the half-step drive excitation method allows the motor to operate at a lower speed range. The motor of this embodiment can achieve ultra-low speed operation, with a speed range of 5-50rpm.

[0077] When the motor is turned on and commutated in the above-mentioned clockwise or counterclockwise order, if a continuous conduction current is given during each phase change, the motor rotor will vibrate near the stable zero position of the currently turned-on phase winding, that is, the rotor oscillates back and forth near the stable zero position, thereby allowing the food processor to produce a shaking blade effect during operation, preventing food from getting stuck in the blade.

[0078] like Figure 4 As shown in the figure, using the principle of stable zero position, when one or two phases of a switched reluctance motor are continuously conducting, the motor will be fixed at the stable zero position of that phase. Due to the inertia of the switched reluctance motor, it will continue to oscillate around this stable zero position until it finally stabilizes. If the motor drive phase changes from phase C to phase BC, and phase C is continuously conducting, the motor will continue to oscillate near the stable zero position of phase C. Each time it passes through the stable zero position, the oscillation count is calculated, and the motor will eventually stabilize at the stable zero position of phase C.

[0079] In a food processor application, this oscillation can produce a shaking effect on the blade, that is, shaking back and forth at a stable zero position, thereby preventing food ingredients from getting stuck in the blade.

[0080] In this embodiment, the motor speed is mainly used to prevent the motor from overshooting (the motor speed exceeds the set normal value), that is, to prevent the food from being suddenly ejected (such as when frying ribs, bones are stuck and ejected by the blades) and causing the motor to rotate too fast or run unsteadily, thereby crushing the food. At the same time, it also prevents the food from being stuck and causing the motor to jam or not operate normally. Figure 2 The position sensor setting shown in the figure achieves stable operation of the motor in overshoot mode through the following control method.

[0081] Specifically, if Figure 5 FIG. 1 is a flowchart of a method for controlling a switched reluctance according to an embodiment of the present invention, comprising the following steps:

[0082] Step 1: Start the program and initialize the settings;

[0083] Step 2: Start the motor and energize the windings of the motor according to the set excitation method; in this embodiment, the half-step drive excitation method of the stepper motor is preferably used;

[0084] Step 3: The motor runs in normal working mode;

[0085] Step 4: Determine whether the motor has entered the overshoot mode. If so, proceed to step 5; if not, return to step 3.

[0086] Step 5: Within a limited time, continuously energize the currently conducting phase winding so that the motor rotor generates an oscillation effect at the stable zero position of the currently conducting phase winding; in the half-step drive excitation mode, the currently conducting phase winding may be a single-phase winding or a dual-phase conducting winding;

[0087] Step 6. Set the corresponding torque adjustment amount according to the motor rotor oscillation state (or oscillation intensity or oscillation level). Different oscillation states have different corresponding torque adjustment amounts. According to the application scenarios under different oscillation states, reduce the motor torque through the preset torque adjustment amount and return to step 4.

[0088] As another preferred embodiment, the step 6 may also use the following method to achieve the reduction of the motor torque:

[0089] Step 6: Set the torque adjustment amount according to the different states of the motor rotor oscillation. The motor reduces torque according to the torque adjustment amount until the motor torque decreases to the set torque value or the timer reaches the set window time, and then returns to step 3. In other words, the total amount of motor torque reduction is set by experience. When it reaches the preset value or the preset timer time, the reduction stops, exiting the overshoot cycle and returning to normal operation mode.

[0090] The oscillation state (or oscillation intensity or oscillation level) of the motor rotor in this embodiment includes the following three situations:

[0091] A. No oscillation, set the first torque adjustment amount;

[0092] B. The oscillation is moderate and the torque adjustment is zero;

[0093] C. Excessive oscillation, set the second torque adjustment amount;

[0094] The first torque adjustment amount and the second torque adjustment amount are both positive numbers greater than zero, and the first torque adjustment amount is greater than the second torque adjustment amount.

[0095] The motor rotor oscillation state in the above step six can be determined according to the number of oscillations, the oscillation frequency, or the oscillation period within the limited time in step five.

[0096] The oscillation state is determined by the number of oscillations using the following method:

[0097] A. If it is detected that the number of times the motor rotor passes through the dead point (i.e., the oscillation dead point) from the commutation point within the limited time described in step 5 is less than or equal to 1, there is no oscillation, and the motor torque is reduced according to the set first torque adjustment amount;

[0098] B. If the number of times the motor rotor passes through the dead point from the commutation point is detected to be less than or equal to the preset number of oscillations within the limited time described in step 5, the oscillation is moderate and the oscillation state is maintained, the motor torque remains unchanged, and the motor produces a shaking effect;

[0099] C. If it is detected that the number of times the motor rotor passes through the dead point from the commutation point is greater than the preset number of oscillations within the limited time described in step 5, the oscillation is excessive, and the motor torque is reduced according to the set second torque adjustment amount;

[0100] The preset number of oscillations is a positive integer greater than or equal to 2.

[0101] In addition, the oscillation state can also be judged by the oscillation frequency and oscillation period. Excessive oscillation may occur if the oscillation frequency is too high or the oscillation period is too short. Only within the appropriate frequency and period range can the oscillation be moderate. If the oscillation frequency is not detected, it means that no oscillation occurs.

[0102] In this embodiment, determining whether the motor has entered the overshoot mode can be implemented using various methods in the prior art. Simply, it can be determined by directly detecting the speed, or by detecting the duration of an external interruption. If the external interruption occurs early, it means that the torque is too large, the speed is too fast, and the motor has entered the overshoot mode.

[0103] The control method of this embodiment is aimed at the motor overshoot stage, especially when the motor is in the ultra-low speed operation mode in the food processor application. When the motor changes phases, the speed is too fast (overshoot). By continuously energizing the current winding, the switched reluctance motor can achieve oscillation at a stable zero position after each phase change (that is, producing the effect of blade shaking). This can not only reduce the motor torque and avoid speed overshoot, but also avoid food getting stuck in the overshoot stage, effectively solving the problem of food getting stuck in the blade and causing food to break when cooking at ultra-low speed, ensuring the smooth operation of the motor, and reducing noise at the same time, which is more conducive to Chinese cooking (such as stir-frying spare ribs, cooking, etc.).

[0104] like Figure 6 As shown in FIG, this is a specific flow chart of this embodiment further refined based on the above step block diagram:

[0105] Step 1: Start the program, initialize the settings, and set the motor speed V and rotation direction. The switched reluctance motor of this embodiment is used in cooking scenarios and can run in the ultra-low speed range. The set motor speed V range is 5rpm≤V≤50rpm, and the rotation direction can be clockwise or counterclockwise.

[0106] At the same time, set the motor output torque to Tor, the external interrupt count to N, and the timer timing to t j , and calculate the theoretical commutation time T when the motor runs at a constant speed according to the set speed V set ;

[0107] Assuming that the motor rotates at a constant speed, when the motor rotates one circle, the output signals of the first sensor S1, the second sensor S2, the third sensor S3 and the fourth sensor S4 in this embodiment will output 48 external interrupts. The sum of the time differences of these 48 consecutive external interrupts is the time required for the motor to rotate one circle. Let the time difference between two adjacent external interrupts be T set(ie theoretical commutation time), the time it takes for the motor to make one revolution is 48T set , the unit is seconds, the speed (rpm) is defined as "revolutions per minute (60s)", so the motor speed Therefore, given the preset motor speed V, the theoretical commutation time can be calculated.

[0108] Step 2: Energize each winding of the motor according to the excitation method of the half-step drive of the stepper motor; taking clockwise rotation as an example, if the current conductive phase is C, then the next conductive phase is BC, and the motor will be turned on in the order of C→BC→B→AB→A→AD→D→CD→C→…; similarly, if the motor rotates counterclockwise, the motor will be turned on in the order of CD→D→AD→A→AB→B→BC→C→CD…

[0109] Step 2a: Check whether the motor starts normally. If yes, proceed to step 3; if not, prompt the motor to start failure, wait for the failure to be eliminated and loop this step. Check whether the motor starts normally can be achieved by various methods in the prior art, which will not be described in detail here.

[0110] Step 3: The motor runs in normal working mode.

[0111] Step 4a: The external interrupt count N is cleared and the timer count time t j Reset to zero and restart the timing.

[0112] Step 4b: Check whether an external interrupt is received. If yes, execute step 4c; if not, execute step 4b-1.

[0113] Step 4c: Timer time t j Is it greater than or equal to the theoretical commutation time T set If yes, go to step 4c-1; if no, go to step 5. j It is the actual commutation time of the motor. Since the motor speed will continue to change with the torque disturbance, the commutation time of the motor in actual operation is always changing.

[0114] Step 4b-1, the timer counts time t j Is it greater than or equal to the theoretical commutation time T set , if so, t j ≥T set This means that the interrupt comes slowly, indicating that the load is large, the motor torque is insufficient, the motor commutation time is delayed, and the torque needs to be increased appropriately, then continue with step 4b-2; if not, return to step 4b and continue to wait for the arrival of the external interrupt.

[0115] Step 4b-2: Determine the timer's timing time tj Is it greater than or equal to the set maximum timing time T max If yes, the motor fault alarm is prompted and the program ends; if no, the motor torque Tor increases by △T every t time, and then returns to step 4b, where t and △T are both preset constants, and the value range of △T is: 1.0×10 -4 Nm≤△T≤5.0×10 -4 The value range of Nm, t is 0.5 milliseconds ≤ t ≤ 2 milliseconds. In this embodiment, t = 1 millisecond is optimal.

[0116] Step 4c-1: Determine the timer's timing time t j Is it equal to the theoretical commutation time T set If yes, the conducting winding is commutated according to the conduction sequence of the current motor rotation direction and returns to step 4a; if no, the timer timing time t j Greater than the theoretical commutation time T set , the motor torque Tor increases by △T every time t, the conduction winding is commutated according to the conduction sequence of the current motor rotation direction, and then returns to step 4a;

[0117] Wherein, t and ΔT are both preset constants, and the value range of t is 0.5ms≤t≤2ms. In this embodiment, t=1, ms is the best (ms represents milliseconds). Here, the maximum timing time T max The value range is: 3s≤T max ≤5s. If there is no phase change for a long time (i.e., no interruption), the motor is considered to have a fault. △T is the torque increment of the motor within the set time. It is used to adjust the motor torque in application scenarios with interrupt delay. For example, if there is a lot of food in the food processor, the motor rotation is hindered and there may be phase change jams. In this case, it is necessary to slowly increase the force to increase the motor torque to achieve smooth and continuous rotation of the motor.

[0118] Step 5: Within the window time △t, the current conducting phase winding is continuously energized so that the motor rotor produces an oscillation effect at the stable zero position of the current conducting phase winding; according to the winding conduction sequence when the motor rotates clockwise or counterclockwise in the half-step drive mode, the current conducting phase winding may be a single-phase conducting winding or a two-phase conducting winding. The continuous energization time of the current winding is the window time △t = T set -t j , which is the limited time mentioned.

[0119] Step 6a, detecting whether the motor rotor oscillates at the stable zero position of the current conducting phase. If yes, proceed to step 6b; if no, proceed to step 6c;

[0120] Step 6b: Determine whether the current oscillation number exceeds the preset oscillation number N. set (Nset is an integer greater than 1), if yes, proceed to step 6d; if no, return to step 4c; the preset number of oscillations N set The value range of is preferably: 3≤N set ≤6. According to the working principle of the reluctance motor, when the current phase winding is continuously energized, the motor will oscillate at a stable zero position. However, the number of oscillations should not be too many. If the number of oscillations is too many, it means that the motor torque is too large. The motor torque needs to be appropriately reduced to reduce the oscillation, thereby ensuring the smooth operation of the motor.

[0121] Step 6c: Determine whether the current motor output torque Tor is greater than the set first torque adjustment value ΔTor1. If so, Tor = Tor - ΔTor1, and return to step 4c; if not, Tor = 0, and return to step 4c;

[0122] The first torque adjustment value △Tor1 satisfies the following formula:

[0123]

[0124] in, is the proportional coefficient, A is a constant and 1.5≤A≤2; △T d is the preset basic torque adjustment amount, △T d is the preset experience value, and its value range is 1.0×10 -3 Nm≤△T d ≤5.0×10 -3 The first torque adjustment value △Tor1 is used to adjust the motor torque in application scenarios where the motor speed is too high. For example, when frying spareribs, the food is bounced away and the motor load suddenly changes from large to small. At this time, the torque needs to be quickly reduced, and the amount of torque reduction should be slightly larger.

[0125] Step 6d: Determine whether the current motor output torque Tor is greater than the set second torque adjustment value ΔTor2. If so, Tor = Tor - ΔTor2, and return to step 4c; if not, Tor = 0, and return to step 4c; the value range of the second torque adjustment value ΔTor2 is: 5.0×10 -4 Nm≤△T≤1.0×10 -3 Nm.

[0126] The second torque adjustment value △Tor2 is used to adjust the motor torque in the application scenario of food getting stuck. For example, when cooking, food gets stuck in the blade. The blade can be shaken by oscillating at a stable zero position to shake out the food and prevent it from getting stuck. However, when the oscillation is too much, the torque needs to be reduced, but the amount of torque reduction needs to be smaller.

[0127] In the above specific control flow chart, there are four different adjustment values for adjusting the motor output torque Tor, namely ΔTor1, ΔTor2, ΔT and 0. In this embodiment, according to different motor application scenarios, the order of the four adjustment values is set as follows: ΔTor1>ΔTor2>ΔT>0;

[0128] When the motor load suddenly changes from large to small, the motor torque is too large, resulting in an excessively fast speed. In this case, the torque needs to be reduced quickly. In this case, the torque reduction adjustment amount is △Tor1.

[0129] When the motor oscillates excessively, the torque needs to be reduced. In this case, the torque reduction does not need to be too much, and the adjustment amount of the torque reduction can be △Tor2.

[0130] When the motor fails to achieve phase change within the theoretical calculation time, the motor's torque is too small and it is necessary to slowly increase the force to achieve smooth rotation of the motor. The adjustment amount of each torque increase is △T to avoid speed overshoot.

[0131] There is another special case, that is, during the cooking process, if the ribs are stuck, when the motor increases the torque, the ribs will suddenly pop out, and then the motor speed will surge. Although the motor load also suddenly changes from large to small, when the motor torque is too small, that is, less than the torque adjustment amount itself, at this time, the motor output torque Tor is directly set to 0, that is, Tor = 0, so that the tool stops for a while, and the motor can achieve buffer deceleration.

[0132] This embodiment adopts a half-step drive mode borrowed from a stepper motor, which can realize the operation of the motor in ultra-low speed mode. By setting four sensors, the number of oscillations of the motor winding when it is stable at zero position can be detected. This control method is applied to the motor overshoot mode and can make the blade produce a shaking effect when food is stuck, thereby effectively reducing or preventing the occurrence of sticking. At the same time, according to different application scenarios in the motor overshoot mode, the motor torque is differentiated and adjusted to achieve smooth operation of the motor, effectively solving the problem of food getting stuck in the blade and causing food to break when cooking at ultra-low speed. There is no overshoot in the speed, ensuring the safety and reliability of the equipment operation. The control method of this embodiment is simple to implement, highly operational and practical, and has a good prospect for promotion and application.

Claims

1. A control method for a switched reluctance motor, characterized in that: The control method includes the following steps: Step 1: Start the program and initialize the settings; Step 2: Start the motor and energize each winding of the motor according to the set excitation mode; Step 3: The motor runs in normal working mode; Step 4: Determine whether the motor has entered the overshoot mode. If so, proceed to step 5; if not, return to step 3. Step 5: within a limited time, continuously energize the currently conducting phase winding; Step 6: Set the corresponding torque adjustment amount according to the different oscillation states of the motor rotor, and reduce the torque of the motor according to the corresponding torque adjustment amount, and return to step 4; The fourth step of determining whether the motor is overshooting is implemented by the following method: Step 4a: The external interrupt count N is cleared and the timer count time t j Reset to zero and restart the timing; Step 4b: Detect whether an external interrupt is received. If so, execute step 4c; if not, after the external interrupt waiting time reaches the maximum set threshold, a fault alarm is prompted; Step 4c: Timer time t j Is it greater than or equal to the theoretical commutation time T set If yes, execute the external interrupt instruction and return to step 4a; if no, go to step 5; The electronic rotor oscillation state in step 6 includes the following three situations: A. No oscillation, set the first torque adjustment amount; B. The oscillation is moderate and the torque adjustment is zero; C. Excessive oscillation, set the second torque adjustment amount; Wherein, the first torque adjustment amount and the second torque adjustment amount are both positive numbers greater than zero, and the first torque adjustment amount is greater than the second torque adjustment amount; The adjustment of the motor torque in step 6 is achieved by the following steps: Step 6a, detecting whether the motor rotor oscillates at the stable zero position of the current conducting phase. If yes, proceed to step 6b; if no, proceed to step 6c; Step 6b: Determine whether the current oscillation number exceeds the preset oscillation number N. set If yes, proceed to step 6d; if no, return to step 4c; Step 6c: Determine whether the current motor output torque Tor is greater than the set first torque adjustment value ΔTor1. If so, Tor = Tor - ΔTor1, and return to step 4c; if not, Tor = 0, and return to step 4c; Step 6d: Determine whether the current motor output torque Tor is greater than the set second torque adjustment value ΔTor2. If so, Tor=Tor-ΔTor2, and return to step 4c; if not, Tor=0, and return to step 4c.

2. The control method of the switched reluctance motor according to claim 1, characterized in that: The step 6 uses the following method to reduce the motor torque: Step 6: Set the corresponding torque adjustment amount according to the different oscillation states. The motor reduces the torque according to the corresponding torque adjustment amount until the motor torque is reduced to the set torque value or the timer time reaches the set window time, and then return to step 3.

3. The control method of the switched reluctance motor according to claim 1, wherein: The excitation mode set in the step 2 is a half-step drive excitation mode of a stepping motor.

4. The control method of the switched reluctance motor according to claim 1, wherein: The continuously energizing the currently conducting phase winding in step 5 is continuously energizing the single-phase winding or continuously energizing the two-phase winding.

5. The control method of the switched reluctance motor according to claim 1, wherein: The oscillation state of the electronic rotor is detected by the following method: A. If it is detected that the number of times the motor rotor passes through the dead point from the commutation point is less than or equal to 1 within the limited time described in step 5, there is no oscillation, and the motor torque is reduced according to the set first torque adjustment amount; B. If the number of times the motor rotor passes through the dead point from the commutation point is detected to be less than or equal to the preset number of oscillations within the limited time described in step 5, the oscillation is moderate, the motor torque remains unchanged, and the motor produces a shaking effect; C. If it is detected that the number of times the motor rotor passes through the dead point from the commutation point is greater than the preset number of oscillations within the limited time described in step 5, the oscillation is excessive, and the motor torque is reduced according to the set second torque adjustment amount; The preset number of oscillations is a positive integer greater than or equal to 2.

6. The control method of the switched reluctance motor according to claim 1, characterized in that: The following steps are included between step 2 and step 3: Step 2a: Check whether the motor starts normally. If yes, proceed to step 3; if not, it will prompt that the motor starts up faulty. Wait until the fault is eliminated and then loop this step.

7. The control method of the switched reluctance motor according to claim 1, characterized in that: The initialization settings in step 1 include setting the motor speed V and rotation direction, and setting the motor output torque to Tor, the external interrupt count to N, and the timer timing to t j .

8. The control method of the switched reluctance motor according to claim 7, characterized in that: The value range of the set speed V of the motor is: 5rpm≤V≤50rpm.

9. The control method of the switched reluctance motor according to claim 1, characterized in that: The limited time in step 5 is the window time Δt, and the window time Δt=T set -t j , T set is the theoretical commutation time of the motor.

10. The control method of the switched reluctance motor according to claim 1, characterized in that: In step 4b, if no external interrupt is received, a fault alarm is prompted after the external interrupt waiting time reaches the maximum set threshold, which is specifically implemented by the following steps: Step 4b-1, the timer counts time t j Is it greater than or equal to the theoretical commutation time T set If yes, proceed to step 4b-2; if no, return to step 4b; Step 4b-2: Determine the timer's timing time t j Is it greater than or equal to the set maximum timing time T max If yes, the motor fault alarm is prompted and the program ends; if no, the motor torque Tor increases by ΔT every t time, and then returns to step 4b, where the maximum set threshold in step 4b is the set maximum timing time T max , t and ΔT are preset constants.

11. The control method of the switched reluctance motor according to claim 1, characterized in that: In step 4c, executing the external interrupt instruction and returning to step 4a specifically includes the following steps: Step 4c-1: Determine the timer's timing time t j Is it equal to the theoretical commutation time T set If so, the conduction winding is commutated according to the conduction sequence of the current motor rotation direction, and the process returns to step 4a. If not, the motor torque Tor is increased by ΔT every t time interval, the conduction winding is commutated according to the conduction sequence of the current motor rotation direction, and the process returns to step 4a. Wherein, t and ΔT are both preset constants.

12. The control method of the switched reluctance motor according to claim 1, characterized in that: The preset oscillation number N in step 6b is set The value range is: 3≤N set ≤6.

13. The control method of the switched reluctance motor according to claim 1, wherein: The first torque adjustment value ΔTor1 in step 6c satisfies the following formula: in, is the proportional coefficient, A is a constant and 1.5≤A≤2; ΔT d is the preset basic torque adjustment, ΔT d The value range is 1.0×10 -3 Nm≤ΔT d ≤5.0×10 -3 Nm.

14. The control method of the switched reluctance motor according to claim 1, characterized in that: The value range of the second torque adjustment amount ΔTor2 in step 6d is: 5.0×10 -4 Nm≤ΔT≤1.0×10 -3 Nm.

15. The control method of the switched reluctance motor according to claim 10 or 11, characterized in that: The value range of t is: 0.5ms≤t≤2ms.

16. The control method of the switched reluctance motor according to claim 10 or 11, characterized in that: The ΔT value range is: 1.0×10 -4 Nm≤ΔT≤5.0×10 -4 Nm.

17. The control method of the switched reluctance motor according to claim 10, characterized in that: The maximum timing time T set in step 4b-2 max The value range is: 3s≤T max ≤5s.

18. The control method of the switched reluctance motor according to claim 1, characterized in that: The switched reluctance motor is a four-phase 8 / 6-pole switched reluctance motor.

19. The control method of the switched reluctance motor according to claim 1, characterized in that: The current position of the motor rotor is detected by a position sensor provided on the motor, wherein the position sensor includes a transmission sensor and a shielding disk; The transmissive sensor includes a first sensor and a second sensor respectively fixedly disposed on two adjacent stator salient poles, and the angle between the first sensor and the second sensor and the center line of the switched reluctance motor is 45°. The transmissive sensor also includes a third sensor and a fourth sensor respectively disposed on the two adjacent stator salient poles, and the angle between the third sensor and the fourth sensor and the center line of the switched reluctance motor is 45°, the angle between the third sensor and the first sensor and the center line of the switched reluctance motor is 7.5°, and the angle between the fourth sensor and the second sensor and the center line of the switched reluctance motor is 7.5°. The shading disc is a disc arranged on the rotor shaft. The shading disc includes a shading disc structure that matches the number and cross-sectional shape of the rotor's salient poles, and the shading disc is arranged perpendicular to the shading disc.

20. A food processor comprising a switched reluctance motor, characterized in that: The switched reluctance motor operates by adopting the control method described in any one of claims 1 to 19.

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