Control method of switched reluctance motor, food processor using the control method, and food processor control method

Abstract

A control method for a switched reluctance motor, characterized in that it includes the following steps: step one, program starts, initialization settings; step two, the motor starts, and rotates in the set rotation direction; step three, the motor runs in a normal working mode; step four, determine whether the motor is blocked, if so, execute step five; if not, return to step three; step five, the motor rotates in the opposite direction according to a preset mode, and returns to step four. The present invention also discloses a food processor using the above control method and a control method for the food processor. The advantages of the present invention are: the preset torque increase upper limit allows the motor to slowly increase force when encountering resistance during food cooking (cooking), simulating the action of flipping food left and right during actual cooking, and can maintain the integrity of the food, and is suitable for the cooking mode of the food processor.

Description

Technical Field

[0001] The present invention relates to a switched reluctance motor, and more particularly to a control method for a switched reluctance motor under low-speed operation (such as a cooking mode) and a food processor using the switched reluctance motor control method, and also to an operating mode of a food processor using the switched reluctance motor 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, 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. At present, the switched reluctance motor is mostly used as the driving component in food processors. The switched reluctance motor has a wide speed regulation range, high system reliability, and the advantages of fast starting and braking. The switched reluctance motor in the prior art is mostly used in high-speed occasions, such as high-speed wall breaking machines, which often need to reach a high speed of about 10,000 rpm. The rotor moment of inertia of the switched reluctance motor is small, and the magnitude and direction of the phase torque can be changed every time the current changes phase, so the system has a good dynamic response; there are many designs and improvement schemes for the switched reluctance motor under high-speed operation in the prior art, but there are relatively few studies on the dynamic performance of the switched reluctance motor under ultra-low speed operation such as cooking (speed range of 40-200 rpm). If the traditional motor is used in the food processor, it cannot intelligently sense the food. It is easy to crush the food when cooking at ultra-low speed, and the integrity of the food cannot be guaranteed, which affects the taste of the cooking.

[0004] Existing Chinese invention patent applications such as application number ZL201810472338.5, "A New Type of Ultra-Low Speed ​​High Torque Switched Reluctance Motor", provide a new type of ultra-low speed high torque switched reluctance motor. The patent mainly improves the design of the stator assembly and the rotor assembly from the mechanical structure. The use of the above motor can form a magnetic circuit with a shorter distance, achieving the purpose of increasing torque and reducing speed. However, the patent does not involve how to implement the control method of the switched reluctance motor in the low-speed operation mode. When the switched reluctance motor is running in the cooking mode, once it encounters resistance, the motor is easy to find stuck or continue to rotate, causing the food to be crushed, and it is impossible to adjust the torque in time and realize intelligent automatic stir-frying. Therefore, in view of the above-mentioned problems, how to improve the intelligence of the food processor in the ultra-low speed operation mode (such as cooking) is a problem that needs to be solved urgently, and further improvements need to be made to the existing switched reluctance motor. Summary of the invention

[0005] The first technical problem to be solved by the present invention is to provide a control method for a switched reluctance motor that can effectively avoid motor stalling or food crushing in view of the above-mentioned prior art status.

[0006] The second technical problem to be solved by the present invention is to provide a food processor that adopts the above-mentioned switched reluctance motor control method.

[0007] The third technical problem to be solved by the present invention is to provide a control method for a food processor adopting the above-mentioned switched reluctance motor control method.

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

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

[0010] Step 2: The motor starts and rotates in the set direction;

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

[0012] Step 4: Determine whether the motor is stalled. If yes, proceed to step 5; if no, return to step 3;

[0013] Step 5: The motor rotates in the reverse direction according to the preset mode and returns to step 4.

[0014] When the motor is blocked, it can be prevented from getting stuck by reversing. Preferably, the preset mode in step 5 can be: the motor first realizes reverse rotation according to the set reversal angle or the set reversal time, and then the motor resumes the set rotation direction in step 2. That is, the motor resumes the preset rotation direction after reversing a certain angle or a certain time.

[0015] Preferably, the set reversal angle is 15° to 90°, preferably 30°; the set reversal time is 20ms to 100ms, preferably 50ms.

[0016] As another preferred embodiment, the preset mode in step 5 may also be: the motor realizes reverse rotation in a direction opposite to the current rotation direction and maintains the reverse rotation direction. That is, once the motor is stalled, it realizes reverse rotation until the next stall occurs, the motor reverses again, and so on, and the motor does not resume the preset rotation direction after reversing.

[0017] In order to avoid frequent reverse rotation of the motor, as a further preferred embodiment, if the motor is blocked, the following steps are further provided between step 4 and step 5: step 4-1, the motor increases the motor torque to determine whether the preset condition is met, if so, execute step 5; if not, return to step 4. That is, after the motor is blocked, it does not immediately reverse, but first increases the torque to continue to maintain the original rotation direction. If the motor still cannot be driven to continue rotating, reverse control is then implemented, thereby effectively avoiding the blocking caused by interference, making the motor run more smoothly, and at the same time reducing the noise caused by frequent reverse rotation switching.

[0018] The increase of the motor torque can be achieved by various methods in the prior art. Preferably, the increase of the motor torque can be achieved by the following methods: increasing the motor torque by increasing the duty cycle; or increasing the motor torque by increasing the current value; or increasing the motor torque by increasing the phase voltage of the winding. The increase of the duty cycle, current, and phase voltage of the winding can indirectly increase the motor torque, and are various optional solutions for increasing the motor torque.

[0019] The preset condition for stopping the increase of the motor torque can be implemented by various existing technical methods, and judged by presetting various thresholds. Preferably, the preset condition in step 4-1 can be: the total amount of increase of the motor torque reaches the set maximum increment value; or the total time of the increase of the motor torque reaches the set maximum cumulative duration; or the current of the motor reaches the set maximum current value; or the number of cycles in the process of increasing the motor torque reaches the set cumulative number of cycles. The increase of the motor torque does not increase indefinitely. After reaching the preset condition, if the motor is still blocked, it is necessary to implement reverse control.

[0020] In order to cook and stir-fry different foods in a targeted manner, as a further preferred embodiment, the following steps may be set between step 4 and step 4-1: step 4-0, selecting a preset threshold value of the maximum increase in motor torque according to the type of food to be processed. When the motor is started, the type of food may be selected, and for foods with different soft and hard textures, an appropriate maximum torque increment may be used to avoid the food from being crushed and improve the taste of the cooked food.

[0021] There are many ways to increase the motor torque, which can be achieved by using various force-adding modes in the prior art. Preferably, the increase in the motor torque can be achieved by gradually increasing the torque monotonically over time. Preferably, the slow force-adding of the torque can be achieved by using a linear function, a square function, or an exponential function.

[0022] As another preferred embodiment, the increase in the motor torque may also be in the form of a step-by-step increase in the torque over time, such as the torque directly increasing in steps from the current value to the preset value within a unit time.

[0023] As another preferred embodiment, in step 5, between the motor performing reverse rotation according to a preset mode and returning to step 4, the following steps are also included: step 5-1, the motor increases the motor torque according to a set condition. That is, the increase in the motor torque can also be performed after the motor is reversed. The set condition is that the total amount of increase in the motor torque reaches a set maximum incremental value; or the total time of the increase in the motor torque reaches a set maximum cumulative duration; or the current of the motor reaches a set maximum current value.

[0024] Preferably, the increase in the motor torque is achieved by: increasing the motor torque by increasing the duty cycle; or increasing the motor torque by increasing the current value; or increasing the motor torque by increasing the phase voltage of the winding.

[0025] Preferably, the increase of the motor torque in step 5-1 occurs when the motor is reversed or after the motor is fully reversed. The increase of the motor torque can be performed simultaneously with the reverse rotation, or the force can be added after the motor is fully reversed.

[0026] Preferably, the setting condition in step 5-1 is that the motor increases the torque according to a set torque increase amount within a preset reversal angle or reversal time.

[0027] Preferably, the initialization setting in step 1 includes setting the starting duty cycle D of the motor. start and rotation direction, and set the motor's operating speed V.

[0028] As a preference, the startup duty cycle D start The initial value range can be set to 0.01~0.05. The duty cycle does not need to be very large at the beginning, as long as it can ensure that the motor can rotate.

[0029] Preferably, the motor in step 2 is started in an ultra-low speed working mode, and the motor working speed V in the ultra-low speed working mode is usually set in the range of 40rpm-200rpm. The ultra-low speed range is mainly for the cooking mode of the food processor.

[0030] The method for determining whether the motor is stalled can be implemented in various ways in the prior art. Preferably, the determination of whether the motor is stalled in step four is preferably implemented by the following method: setting a current threshold, torque threshold, speed threshold, or position signal threshold when the motor is stalled. Once the current, torque, speed, or position signal of the motor reaches or exceeds the set threshold, it is determined that the motor is stalled.

[0031] As a further preferred embodiment, judging whether the motor is stalled in step 4 can be implemented by the following steps:

[0032] Step 4a, the timer counts the external interruption and sets the timing time to T1, the position sensor detects the current position of the rotor and sets the conducting winding;

[0033] Step 4b: Determine whether the timer time T1 is greater than the set maximum cumulative time T set If yes, the motor is determined to be blocked and the program is exited; if no, the next step 4c is executed; wherein the maximum accumulated time T set The length of the window for waiting for external interrupts to arrive;

[0034] Step 4c, determine whether an external interrupt has arrived, if so, the set conduction winding is commutated and return to step 4a; if not, return to step 4b.

[0035] When the external interruption does not occur for a long time, it is necessary to slowly increase the power of the motor (ie, increase the torque). As a preferred embodiment, the maximum cumulative time T set The maximum cumulative time T is the length of the set window for waiting for the external interrupt to arrive. set The value range of can be 60ms to 100ms, and 70ms is preferably the best value.

[0036] As a further preferred embodiment, in step 4b, if it is determined that the motor is stalled, the following steps are continued to be performed to achieve slow increase of the motor torque:

[0037] Step 4d: real-time output duty cycle D rt Increase by n% every t milliseconds; where t and n are preset constants;

[0038] Step 4e: Determine whether the timer time T1 is greater than T set +T inc If yes, the motor rotates in the direction opposite to the set rotation direction, and the conducting winding is switched according to the conduction sequence after the motor is reversed. At the same time, the timing time T1 of the timer is reset, and the process returns to step 4a; if no, the process executes step 4c;

[0039] Among them, the Indicates the maximum increase time of the duty cycle from D1 to D2; D1 indicates the duty cycle corresponding to the current motor torque M obtained by detection, and D2 indicates the duty cycle corresponding to the motor torque M+△M; △M is the maximum increase in torque within the preset position signal angle range, and △D is the increase in the preset duty cycle per millisecond. By increasing the set duty cycle per unit time, the motor torque can be slowly increased, which is simple and convenient to operate and easy to implement.

[0040] Preferably, the preset duty cycle increment ΔD per millisecond has a value range of 0.05% to 0.2%. The duty cycle increment ΔD per millisecond determines the smoothness of speed regulation. If ΔD is too small, the motor will stop, and if ΔD is too large, there will be a speed overshoot problem. Therefore, it is necessary to set a suitable value range to ensure the smooth rotation and continuity of the motor.

[0041] When the motor is running at ultra-low speed, in order to prevent the food from being crushed, the increased torque cannot be too large, and at the same time, a certain rotational torque must be guaranteed. Preferably, the maximum torque increase △M is in the range of 0.01Nm to 0.05Nm. The maximum torque increase △M is the maximum torque increment within a single step angle (15° in this embodiment). If it is too small, the motor will not be able to pass through when encountering food stuck, and if it is too large, the food will be crushed.

[0042] Preferably, the value range of t in step 4d is: 0.5≤t≤5.

[0043] Preferably, the value range of n in step 4d is: 0.05≤n≤0.2.

[0044] As a further preferred embodiment, in order to facilitate operation and control and ensure the smooth rotation and uniform force application of the motor, in step 4c, the set conduction winding commutation is achieved through the following steps:

[0045] Step 4c-1, determine whether the current rotation direction of the motor is consistent with the set rotation direction, if yes, execute the next step 4c-2; if no, jump to step 4c-4;

[0046] Step 4c-2: Real-time detection to obtain the actual time difference T between two adjacent external interruptions exti , and calculate the current real-time speed V of the motor rt , adjust the duty cycle to achieve the preset working speed V of the motor;

[0047] Step 4c-3, the conducting winding is switched according to the conducting sequence of the current motor rotation direction, the timing time T1 of the timer is reset, and the process returns to step 4a;

[0048] Step 4c-4, the motor rotates in the direction opposite to the set rotation direction, and the conduction winding is switched according to the conduction sequence after the motor is reversed, that is, the motor does not need to be restored to the preset rotation direction after reversal. At the same time, the timing time T1 of the timer is reset and returns to step 4a.

[0049] Preferably, the value angle of the preset position signal angle interval can be set to the motor step angle. For the switched reluctance motor, which is a four-phase 8 / 6-level switched reluctance motor, the motor step angle is 15°. If it is a 6 / 4-level switched reluctance motor, the step angle is 30°, and the value angle of the preset position signal angle interval can be 30°.

[0050] The switched reluctance motor of this embodiment is a four-phase 8 / 6-level switched reluctance motor. For the motor structure of the four-phase 8 / 6-level switched reluctance motor, the current position of the motor rotor is detected by a position sensor arranged on the motor. The position sensor includes a transmission sensor and a shading disk. There are two transmission sensors, which are respectively arranged on adjacent a+ salient poles and d- salient poles on the stator. The shading disk is a disk arranged on the rotor shaft. The shading disk includes a shading plate structure that matches the number and cross-sectional shape of the salient poles of the rotor, and the shading plate is arranged perpendicular to the shading disk. If a switched reluctance motor of other structures is used, the setting method of the position sensor needs to be changed accordingly.

[0051] The technical solution adopted by the present invention to solve the second technical problem is: a food processor, including a switched reluctance motor, characterized in that: the switched reluctance motor works using the control method described above.

[0052] The technical solution adopted by the present invention to solve the third technical problem is: a control method for a food processor, the food processor comprising a stirring device and a switched reluctance motor capable of driving the stirring device to work, characterized in that the working mode of the food processor comprises an anti-crushing mode, and the control method of the food processor comprises: in the anti-crushing mode, the food processor adopts the control method as described above to control the rotation of the switched reluctance motor, and the switched reluctance motor drives the stirring device to stir the food in the food processor.

[0053] Compared with the prior art, the advantages of the present invention are: through the characteristics of the switched reluctance motor that can rotate forward and reverse and has a fast commutation speed, the motor can be controlled to run in the opposite direction when encountering resistance during cooking food (frying), imitating the action of flipping food left and right during actual cooking, and effectively avoiding motor jamming or food jamming; further, by pre-setting an upper limit of torque increase (i.e., the maximum torque increase △M) or limiting the time of force addition, slow force addition can be achieved in the case of motor jam. Once the torque increase upper limit is exceeded or the motor still cannot rotate normally for a specified period of time, the motor is controlled to reverse. This control method is not easy to crush food in the application of the motor's ultra-slow speed working mode, can maintain the integrity of the food, and is suitable for the cooking mode of the food processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1The figure is a schematic diagram of the arrangement structure of the position sensor of the four-phase 8 / 6-pole switched reluctance motor according to an embodiment of the present invention.

[0055] Figure 2 4 is a torque characteristic diagram of a four-phase 8 / 6-pole switched reluctance motor according to an embodiment of the present invention.

[0056] Figure 3 This is a stable zero-position characteristic diagram of the four-phase winding of the four-phase 8 / 6-level switched reluctance motor according to an embodiment of the present invention.

[0057] Figure 4 1 is a characteristic diagram of the position signal and the conducting winding of the four-phase 8 / 6-pole switched reluctance motor according to an embodiment of the present invention (starting stage).

[0058] Figure 5 This is one of the step block diagrams of the motor control method according to an embodiment of the present invention.

[0059] Figure 6 This is the second step block diagram of the motor control method according to an embodiment of the present invention.

[0060] Figure 7 This is a specific implementation flow chart of the motor control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below with reference to the accompanying drawings.

[0062] This embodiment adopts a four-phase 8 / 6-pole switched reluctance motor, where 8 is the number of stator poles and 6 is the number of rotor poles, and the step angle of the motor is 15°.

[0063] like Figure 1 As shown, the motor of this 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 is generally composed of a transmissive photoelectric sensor (including a photoelectric switch of 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 arts.

[0064] There are two transmissive photoelectric sensors, namely, sensor S and sensor P. The two sensors are respectively arranged on two adjacent salient poles of the stator 1 (a+ salient pole and d- salient pole), wherein the sensor S is aligned with the center of the a+ salient pole of the stator 1, and the sensor P is aligned with the center of the d- salient pole of the stator 1. The angle between the sensor S and the sensor P relative to the motor center line is 45°; wherein a groove is formed between the infrared transmitting 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, and the shading disk is provided with a shading sheet 3 matching the cross-sectional shape of the convex tooth at the position of each convex tooth of the rotor along the circumference, and the shading sheet 3 is arranged perpendicular to the disk surface of the shading disk (that is, the shading disk includes 6 shading sheets 3 and is evenly distributed along the circumference). Figure 1 The section line shown in is the section line of the vertically arranged shading sheet;

[0065] When the convex teeth of the rotor 2 rotate to the position where sensors S and P are set, the shading plate 3 just passes through the groove of the sensor, the light of the infrared emitting tube is blocked, and its phototransistor is cut off, and the output state is 0; when the groove of the rotor rotates to the position of sensors S and P, no shading plate passes through the groove of the sensor, the light of the infrared emitting tube is not blocked, the phototransistor is turned on, and the output state is 1. Then, within one rotor angle period (i.e. 60°), sensor S and sensor P will generate two square wave signals with a phase difference of 15° and a duty cycle of 50%, and they are combined into four different states, corresponding to different reference positions of the four-phase windings.

[0066] If the motor rotates clockwise, the midpoint of the lowest inductance of phase A winding is taken as 0°. Figure 2 As shown, the torque characteristics of each winding of the motor when rotating clockwise are displayed.

[0067] The two sensors S and P are used to detect external interrupt signals. When the sensors S and P detect a sudden change in the signal (i.e., a jump occurs), the motor enters an external interrupt and the switched reluctance motor performs a commutation operation. For example, at 50rpm, the time difference between the two external interrupts is 50ms. However, in actual use, the motor speed will continue to change with the torque disturbance. Therefore, the time difference between the two external interrupts of the motor in actual operation is constantly changing.

[0068] like Figure 3 As shown in the figure, the stable zero position of the four-phase windings A, B, C, and D is given. According to the principle of minimum magnetic resistance of the switched reluctance motor, if a stable current is excited to a certain phase winding, the rotor will eventually be fixed at the stable zero position. If a stable current is excited to two phase windings at the same time, the rotor will eventually be fixed at and Figure 3 The same stable position.

[0069] For a four-phase 8 / 6-pole switched reluctance motor, when the current of equal magnitude is excited to each winding, a set of torque vectors of equal magnitude and different directions will be generated. Among them, in the torque vector Under the excitation of the A-phase winding, a stable zero position is generated (fixed at this position). Under the excitation of , the B-phase winding produces a stable zero position (fixed at this position), and the two stable zero positions are at a geometric angle of 15° in space, that is, the angle of 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°.

[0070] Considering the application of switched reluctance motor in food processor, its torque varies greatly and the torque at startup is unknown, so two-phase startup is usually adopted in practice. During the startup process of the switched reluctance motor, in a rotor angle cycle of 0° to 60°, the power-on sequence of each phase is AB→DA→CD→BC, which is similar to the double four-beat startup operation mode of the stepping motor. Figure 4 As shown in FIG. 1 , the characteristic diagram of the motor position signal and the conduction winding at startup is shown. The logical relationship between the motor position signal and the conduction phase (starting stage) is shown in Table 1:

[0071]

[0072] Table 1. Phase switching logic during startup

[0073] 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 phases A and B; when the position signal P00 is detected, the conducting windings are phases C and D.

[0074] In cooking applications, the speed requirement is very low, so there is a certain nonlinearity in the output torque and duty cycle. Traditional motor control methods will continue to increase the torque when the motor encounters resistance until the motor overcomes the resistance and continues to rotate, or directly alarm the motor is stuck. This control method is difficult to ensure the integrity of food in cooking mode, and cannot simulate the action of manually frying food. When used in a food processor, the final cooking effect is relatively poor, and the food produced not only looks bad, but also affects the taste.

[0075] In order to solve the above problems, Figure 5 As shown, this embodiment provides a control method for a switched reluctance motor, and the control method includes the following steps:

[0076] Step 1: Start the program and initialize the settings;

[0077] Step 2: The motor starts and rotates in the set direction;

[0078] Step 3: The motor runs in normal working mode;

[0079] Step 4: Determine whether the motor is stalled. If yes, proceed to step 5; if no, return to step 3;

[0080] Step 5: The motor rotates in the reverse direction according to the preset mode and returns to step 4.

[0081] The above control method is to reverse the motor immediately when the motor is stalled to simulate the frying action and avoid food getting stuck. However, in order to prevent the motor from frequently switching back and forth to rotate in the opposite direction, when the motor is stalled, a certain force can be applied to the motor first, and the torque can be slowly increased. If it is still stalled, the motor can be reversed again, thereby preventing the food from being crushed. Therefore, the above control method can add step 4-1 when the motor is stalled to achieve a gradual force increase process.

[0082] Furthermore, in order to better meet the requirements of different food materials and to control the force applied to different foods in a targeted manner, the present embodiment may further add a step of selecting the maximum torque increment before step 4-1. Specifically, the control method of the switched reluctance motor of the present embodiment may include the following steps:

[0083] Step 1: Start the program and initialize the settings. The initialization settings may include setting the motor's starting duty cycle D. start and the direction of rotation, and set the motor's operating speed V; among them, the starting duty cycle D start The initial value range of can be 0.01~0.05; the motor operating speed V is set according to different working scenarios of the motor. The motor of this embodiment is started in an ultra-low speed working mode, and the motor operating speed V in the ultra-low speed working mode has a value range of 40rpm-200rpm.

[0084] Step 2: The motor starts and rotates in the set direction.

[0085] Step 3: The motor runs in normal working mode.

[0086] Step 4, determine whether the motor is stuck, if so, execute step 4-0; if not, return to step 3; here, determining whether the motor is stuck is achieved through various methods in the prior art, preferably it can be achieved through the following method: set a current threshold or torque threshold or speed threshold or position signal threshold when the motor is stuck, once the motor's current or torque or speed or position signal reaches or exceeds the set threshold, it is determined that the motor is stuck.

[0087] Step 4-0: Select a preset threshold value for the maximum increase in motor torque according to the type of food to be processed.

[0088] Step 4-1: The motor increases the motor torque to determine whether the preset conditions are met. If yes, execute step five; if not, return to step four.

[0089] The preset conditions in step 4-1 can be implemented in various ways in the prior art, and preferably can be: the increase in the motor torque reaches a set maximum incremental value; or the total time of the motor torque increase reaches a set maximum cumulative duration; or the motor current reaches a set maximum current value; or the number of cycles in the motor torque increase process reaches a set cumulative number of cycles.

[0090] The increase of motor torque can be achieved by the following methods in the prior art: increasing the motor torque by increasing the duty cycle; increasing the motor torque by increasing the current value; or increasing the motor torque by increasing the phase voltage of the winding. The increase of duty cycle, current, and winding phase voltage can indirectly increase the motor torque. The motor torque can be slowly increased by increasing the preset duty cycle, current, and winding phase voltage value in unit time.

[0091] In addition, the increase of the motor torque is not achieved in one step. The amplitude of each increase can be set, and the torque can be gradually increased by slowly adding force. The gradual increase in torque can be achieved by various force adding modes in the prior art. Preferably, each increase in the motor torque can be gradually increased by monotonically increasing the torque over time, such as increasing the torque as a linear function over time, or increasing the torque as a square function over time, or increasing the torque as an exponential function over time, thereby achieving a gradual increase in the torque.

[0092] As another preferred embodiment, the increase in the motor torque may also be achieved by increasing the torque in steps over time, that is, the torque increases directly from the current value to the preset value in steps each time.

[0093] The various functions in the above torque increasing mode are all existing technologies, and other functions besides the above functions can also be used to realize the torque increasing.

[0094] Step five, the motor rotates in the reverse direction according to the preset mode, and returns to step four. Among them, the preset mode in step five can be: the motor first realizes reverse rotation according to the set reversal angle or the set reversal time, and then the motor restores the set rotation direction in step two, that is, the motor first reverses, and then restores the preset rotation direction, wherein the set reversal angle is 15°~90°, preferably 30°; the set reversal time is 20ms~100ms, preferably 50ms; the preset mode in step five can also be: the motor realizes reverse rotation in the direction opposite to the current rotation direction, and maintains the reverse rotation direction, that is, the motor maintains the rotation direction after reversing until the next stall occurs. The above two preset modes can simulate the action of manual frying, and effectively avoid the situation where food is stuck in the food processor during processing.

[0095] As another preferred embodiment, Figure 6 As shown, in step five, between the motor performing reverse rotation according to a preset mode and returning to step four, the following steps are also included: step 5-1, the motor increases the motor torque according to the set conditions. That is, the increase in the motor torque can also be performed after the motor is reversed. The set conditions are that the total amount of increase in the motor torque reaches the set maximum incremental value; or the total time of the increase in the motor torque reaches the set maximum cumulative duration; or the current of the motor reaches the set maximum current value. The increase in the motor torque is achieved by: increasing the motor torque by increasing the duty cycle; or increasing the motor torque by increasing the current value; or increasing the motor torque by increasing the phase voltage of the winding.

[0096] Preferably, the increase of the motor torque in step 5-1 occurs when the motor is reversed or after the motor is fully reversed. The increase of the motor torque can be performed simultaneously with the reverse rotation, or the force can be added after the reverse rotation is fully reversed; the condition set in step 5-1 is that the motor increases the torque according to the set torque increase amount within the preset reverse angle or reverse time.

[0097] like Figure 7 As shown, for the above Figure 5 The step block diagram of the control method shown in the figure is a more specific and detailed control flow chart, in which the duty cycle is mainly used as the adjustment parameter, and the waiting time of the external interrupt is collected by the timer timing method. The operation is simple and convenient, and there is no need to change or increase the existing structure of the motor equipment. It is easy to implement and has low control cost. Specifically, the control method includes the following steps:

[0098] Step 400: The program starts and the starting duty cycle D of the motor is set. start , operating speed V and rotation direction; starting duty cycle D startThe initial value range can be set to 0.01-0.05, and the rotation direction can be clockwise or counterclockwise. This embodiment is mainly for the cooking mode of the food processor, so the motor works in the ultra-low speed working mode, and the working speed V of the motor is usually set to a range of 40rpm-200rpm.

[0099] Step 401: The motor is started in an ultra-low speed working mode.

[0100] Step 4a, the timer counts the external interruption and sets the timing time to T1, the position sensor detects the current position of the rotor and sets the conducting winding;

[0101] Step 4b: Determine whether the timer time T1 is greater than the set maximum cumulative time T set If yes, it is determined that the motor is stalled, and the process jumps to step 4d; if no, the process goes to step 4c;

[0102] When the external interruption does not come for a long time, it means that the motor is blocked (such as the blade is stuck by food), and the motor needs to be slowly powered (i.e., the torque is increased). The maximum cumulative time T set The maximum cumulative time T is the length of the window for waiting for an external interrupt to arrive. set The value range is 60ms to 100ms, and 70ms is preferably the best.

[0103] Step 4c, determine whether an external interrupt has arrived, if yes, execute step 4c-1; if no, return to step 4b.

[0104] Step 4d: real-time output duty cycle D rt Increase by n% every t milliseconds; wherein t and n are preset constants, the value range of t is: 0.5≤t≤5, and the value range of n is: 0.05≤n≤0.2.

[0105] Step 4e: Determine whether the timer time T1 is greater than T set +T inc If yes, execute step 4c-4; if no, execute step 4c;

[0106] Among them, the It represents the maximum increase time of the duty cycle from D1 to D2; D1 represents the duty cycle corresponding to the current torque M of the motor obtained by detection, and the corresponding function relationship is D1=h(M); D2 represents the duty cycle corresponding to the motor torque M+△M, and the corresponding function relationship is D2=h(M+△M). The corresponding relationship between torque and duty cycle belongs to the prior art. If one of the parameter values ​​of torque or duty cycle is known, the other parameter value can be reversely deduced; △M is the maximum increase of torque within the preset position signal angle range, and △D is the preset increase of duty cycle per millisecond.

[0107] The switched reluctance motor of this embodiment is a four-phase 8 / 6-level switched reluctance motor, and the minimum value angle of the preset position signal angle interval can be selected as the motor step angle, that is, the value is 15°. If it is a 6 / 4-level switched reluctance motor, the step angle is 30°, and the minimum value angle of the preset position signal angle interval can be 30°;

[0108] The maximum torque increase △M of this embodiment is the maximum torque increment within a single step angle (i.e., 15°). When the motor is running at ultra-low speed, in order to prevent the food from being crushed, the increased torque cannot be too large. If the value of the maximum torque increment is too small, the motor will not be able to pass when the food is stuck. During the experiment, we selected the following representative foods as examples, and the △M value corresponding to each food is shown in Table 2:

[0109] Food Types △M(Nm) Ribs 0.05 Pot-fried pork 0.03 Vegetarian Chicken 0.02 Pickled Fish 0.01

[0110] Table 2. Maximum increase in torque corresponding to different foods

[0111] It can be seen that for the currently common cooking ingredients, the value range of the maximum torque increase △M is preferably 0.01Nm~0.05Nm, preferably 0.02Nm; this value range can basically take into account the stir-frying of harder foods (such as bones) and softer foods (such as fish), and avoid the food being crushed during the stir-frying process.

[0112] In addition, the preset duty cycle increment △D per millisecond has a value range of 0.05% to 0.2%, preferably 0.1%. The duty cycle increment △D per millisecond determines the smoothness of the speed regulation. If △D is too small, the motor will stop, and if △D is too large, there will be a speed overshoot problem. Therefore, it is necessary to set a suitable value range to ensure the smooth rotation and continuity of the motor.

[0113] Step 4c-1, determine whether the current rotation direction of the motor is consistent with the set rotation direction, if yes, execute the next step 4c-2; if no, jump to step 4c-4;

[0114] Step 4c-2: Real-time detection to obtain the actual time difference T between two adjacent external interruptions exti , and calculate the current real-time speed V of the motor rt , adjust the duty cycle to achieve the preset operating speed V of the motor; the duty cycle adjustment can be achieved using the known PI adjustment algorithm.

[0115] Step 4c-3, the conducting winding is switched according to the conducting sequence of the current motor rotation direction, the timing time T1 of the timer is reset, and the process returns to step 4a;

[0116] Step 4c-4, the motor rotates in the direction opposite to the set rotation direction, and the conduction winding is switched according to the conduction sequence after the motor is reversed. At the same time, the timing time T1 of the timer is reset, and the process returns to step 4a.

[0117] The control method of this embodiment includes a motor soft start process. The control method is simple and easy to implement. In the ultra-low speed working mode of the motor (cooking mode), by slowly adding force and effectively controlling the timing of motor commutation and reversal, it can prevent food from being crushed, realize the action of simulating manual stir-frying of food, and improve the intelligent operation level and cooking effect of the food processor.

[0118] In addition, the present embodiment also discloses a food processor and a control method thereof, wherein the food processor includes a stirring device and a switched reluctance motor, wherein the food processor can select different working modes according to different ingredients or cooking methods when working, and the working modes include an anti-crushing mode. When the anti-crushing mode is selected, the switched reluctance motor of the food processor rotates and works using the control method described above. At the same time, the switched reluctance motor drives the stirring device to stir the ingredients. The anti-crushing mode can effectively prevent food from getting stuck during the working process of the food processor, and can also simulate the effect of manual stir-frying to avoid food being crushed, thereby achieving a better cooking effect.

Claims

1. A control method for a switched reluctance motor, characterized in that: The control method comprises the following steps: Step 1: Start the program and initialize the settings; Step 2: The motor starts and rotates in the set direction; Step 3: The motor runs in normal working mode; Step 4: Determine whether the motor is stalled. If yes, proceed to step 5; if no, return to step 3; Step 5: The motor rotates in the reverse direction according to the preset mode, and returns to step 4; The preset mode in step 5 is: the motor first realizes reverse rotation according to the set reverse angle or the set reverse time, and then the motor restores the set rotation direction in step 2; or the preset mode in step 5 is: the motor realizes reverse rotation in the direction opposite to the current rotation direction and maintains the reverse rotation direction; If the motor is stalled, the following steps are provided between step 4 and step 5: Step 4-1, the motor increases the motor torque to determine whether the preset condition is met, if yes, execute step five; if not, return to step four; The preset conditions in step 4-1 are: the total amount of increase in the motor torque reaches the set maximum incremental value; or the total time of the motor torque increase reaches the set maximum cumulative duration; or the motor current reaches the set maximum current value; or the number of cycles in the process of increasing the motor torque reaches the set cumulative number of cycles; In step 4, determining whether the motor is stalled is specifically implemented by the following steps: Step 4a, the timer counts the external interruption and sets the timing time to T1, the position sensor detects the current position of the rotor and sets the conducting winding; Step 4b: Determine whether the timer time T1 is greater than the set maximum cumulative time T set If yes, the motor is determined to be blocked and the program is exited; if no, the next step 4c is executed; wherein the maximum accumulated time T set The length of the window for waiting for external interrupts to arrive; Step 4c, determine whether an external interrupt has arrived, if so, the set conduction winding is commutated, and return to step 4a; if not, return to step 4b; In step 4b, if it is determined that the motor is stalled, the following steps are continued to be performed to achieve slow increase of the motor torque: Step 4d: real-time output duty cycle D rt Increase by n% every t milliseconds; where t and n are preset constants; Step 4e: Determine whether the timer time T1 is greater than T set +T inc If yes, the motor rotates in the direction opposite to the set rotation direction, and the conducting winding is switched according to the conduction sequence after the motor is reversed. At the same time, the timing time T1 of the timer is reset, and the process returns to step 4a; if no, the process executes step 4c; Among them, the Indicates the maximum increase time of the duty cycle from D1 to D2; D1 indicates the duty cycle corresponding to the current torque M of the motor obtained by detection, and D2 indicates the duty cycle corresponding to the motor torque M+ΔM; ΔM is the maximum increase in torque within the preset position signal angle interval, and ΔD is the preset increase in duty cycle per millisecond; In step 4c, the set conduction winding commutation is achieved by the following steps: Step 4c-1, determine whether the current rotation direction of the motor is consistent with the set rotation direction, if yes, execute the next step 4c-2; if no, jump to step 4c-4; Step 4c-2: Real-time detection to obtain the actual time difference T between two adjacent external interruptions exti , and calculate the current real-time speed V of the motor rt , adjust the duty cycle to achieve the preset working speed V of the motor; Step 4c-3, the conducting winding is switched according to the conducting sequence of the current motor rotation direction, the timing time T1 of the timer is reset, and the process returns to step 4a; Step 4c-4, the motor rotates in the direction opposite to the set rotation direction, and the conduction winding is switched according to the conduction sequence after the motor is reversed. At the same time, the timing time T1 of the timer is reset, and the process returns to step 4a.

2. The control method of the switched reluctance motor according to claim 1, characterized in that: The set reversal angle is 15° to 90°.

3. The control method of the switched reluctance motor according to claim 1, characterized in that: The set reversal time is 20ms to 100ms.

4. The control method of the switched reluctance motor according to claim 1, characterized in that: The increase of the motor torque is achieved by: increasing the duty cycle to increase the motor torque; or increasing the current value to increase the motor torque; or increasing the phase voltage of the winding to increase the motor torque.

5. The control method of the switched reluctance motor according to claim 1, characterized in that: The increase in the motor torque is gradually increased in a manner that the torque increases monotonically over time.

6. The control method of the switched reluctance motor according to claim 5, characterized in that: The monotonically increasing manner includes a linear function manner, a square function manner, or an exponential function manner.

7. The control method of the switched reluctance motor according to claim 1, characterized in that: The increase in the motor torque is in the form of a step-by-step increase in torque over time.

8. The control method of the switched reluctance motor according to claim 1, characterized in that: The following steps are also arranged between step 4 and step 4-1: Step 4-0: Select a preset threshold value for the maximum increase in motor torque according to the type of food to be processed.

9. The control method of the switched reluctance motor according to claim 1, characterized in that: In step 5, the motor rotates in the reverse direction according to the preset mode and returns to step 4, and the following steps are also included: Step 5-1: The motor increases the motor torque according to the set conditions.

10. The control method of the switched reluctance motor according to claim 9, characterized in that: The increase of the motor torque in step 5-1 occurs when the motor is reversed or after the reverse rotation is completed.

11. The control method of the switched reluctance motor according to claim 9, characterized in that: The setting condition in step 5-1 is that the motor increases the torque according to the set torque increase amount within a preset reversal angle or reversal time.

12. The control method of the switched reluctance motor according to claim 9, characterized in that: The set conditions are that the total amount of increase in the motor torque reaches a set maximum incremental value; or the total time of the motor torque increase reaches a set maximum cumulative duration; or the motor current reaches a set maximum current value.

13. The control method of the switched reluctance motor according to claim 9, characterized in that: The increase of the motor torque is achieved by: increasing the duty cycle to increase the motor torque; or increasing the current value to increase the motor torque; or increasing the phase voltage of the winding to increase the motor torque.

14. The control method of the switched reluctance motor according to claim 1, characterized in that: The initialization setting in step 1 includes setting the starting duty cycle D of the motor. start and rotation direction, and set the motor's operating speed V.

15. The control method of the switched reluctance motor according to claim 14, characterized in that: The startup duty cycle D start The initial value ranges from 0.01 to 0.

05.

16. The control method of the switched reluctance motor according to claim 1, characterized in that: The motor in step 2 is started in an ultra-low speed working mode, and the motor working speed V in the ultra-low speed working mode has a value range of 40rpm-200rpm.

17. The control method of the switched reluctance motor according to claim 1, characterized in that: In the step 4, determining whether the motor is stalled is achieved by the following method: setting a current threshold, torque threshold, speed threshold, or position signal threshold when the motor is stalled; once the current, torque, speed, or position signal of the motor reaches or exceeds the set threshold, it is determined that the motor is stalled.

18. The control method of the switched reluctance motor according to claim 1, characterized in that: The maximum cumulative time T set The value range is 60ms to 100ms.

19. The control method of the switched reluctance motor according to claim 1, characterized in that: The preset duty cycle increase amount ΔD per millisecond has a value range of 0.05% to 0.2%.

20. The control method of the switched reluctance motor according to claim 1, characterized in that: The maximum torque increase ΔM has a value range of 0.01 Nm to 0.05 Nm.

21. The control method of the switched reluctance motor according to claim 1, characterized in that: The value range of t in step 4d is: 0.5≤t≤5.

22. The control method of the switched reluctance motor according to claim 1, characterized in that: The value range of n in step 4d is: 0.05≤n≤0.

2.

23. The control method of the switched reluctance motor according to claim 1, characterized in that: The value angle of the preset position signal angle interval is the motor step angle.

24. 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, and the motor step angle is 15°.

25. A food processor, comprising a switched reluctance motor, characterized in that: The switched reluctance motor operates using the control method described in any one of claims 1 to 24.

26. A method for controlling a food processor, the food processor comprising a stirring device and a switched reluctance motor capable of driving the stirring device, characterized in that: The working mode of the food processor includes an anti-crushing mode, and the control method of the food processor includes: In the anti-crushing mode, the food processor uses the control method according to any one of claims 1 to 24 to control the rotation of the switched reluctance motor, and the switched reluctance motor drives the stirring device to stir the food in the food processor.

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