Back electromotive force sampling method and control system for sensorless square wave control

Abstract

The present invention discloses a back electromotive force sampling method and control system for non-inductive square wave control, which includes an ADC module with a multi-channel integrated trigger mechanism and relates to the field of motor control technology. The method comprises: within each PWM control cycle, triggering the analog-to-digital converter (ADC) module for the first time via a first ADC trigger source to sample the bus voltage and the floating phase terminal voltage of the motor to be sampled, obtaining a first voltage value of the bus voltage and a second voltage value of the floating phase terminal voltage, detecting the first zero crossing of the back electromotive force; if the first remaining time is greater than or equal to the sampling time of the ADC module, triggering the ADC module via a second ADC trigger source to repeatedly sample the floating phase terminal voltage at least once, detecting the second zero crossing of the back electromotive force, and continuing until the second remaining time of the valid signal after repeated sampling is less than the sampling time of the ADC module. The present invention shortens sampling time and improves the accuracy of back electromotive force zero crossing detection.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular, to a method and a control system for back electromotive force sampling with sensorless square wave control. Background Art

[0002] In the sensorless square wave control of a brushless direct current (BLDC) motor, the back electromotive force of the motor is usually collected as a key input for the zero-crossing commutation algorithm. The zero-crossing commutation algorithm is a control algorithm in BLDC control. By detecting the terminal voltages of the three phases of the BLDC motor and judging the zero-crossing point according to the magnitudes of the terminal voltages, the rotor position can be determined. Then, by controlling the current according to the rotor position, the rotational speed of the brushless motor can be adjusted. Detecting the three-phase terminal voltages of the BLDC and then judging the zero-crossing point of the back electromotive force means that each time the zero-crossing detection requires collecting 3 analog data of the three phases at the terminals, and the sampling time consumed is relatively long. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this purpose, an object of the present invention is to provide a method and a control system for back electromotive force sampling with sensorless square wave control to shorten the sampling time consumed.

[0004] According to a first aspect of an embodiment of the present invention, a method for back electromotive force sampling with sensorless square wave control is provided. The sampling method includes:

[0005] Within each PWM (Pulse-Width Modulation) control period of the motor to be sampled, the ADC first trigger source is used to trigger the analog-to-digital converter (ADC) module to sample the bus voltage and the floating phase terminal voltage of the motor to be sampled for the first time, obtaining a first voltage value of the bus voltage and a second voltage value of the floating phase terminal voltage;

[0006] Based on the first voltage value and the second voltage value, the first zero-crossing point of the back electromotive force is detected, and the first remaining time of the valid signal within this PWM control period is determined;

[0007] If the first remaining time is greater than or equal to the sampling time of the ADC module, the ADC second trigger source is used to trigger the ADC module to perform at least one repeated sampling on the floating phase terminal voltage, obtaining a third voltage value of the floating phase terminal voltage. Based on the first voltage value and the third voltage value, the second zero-crossing point of the back electromotive force is detected until the second remaining time of the valid signal after the repeated sampling is less than the sampling time of the ADC module.

[0008] Optionally, the ADC module is configured with a multi-channel integrated triggering mechanism, and the multi-channel integrated triggering mechanism includes at least two trigger sources, including the ADC first trigger source and the ADC second trigger source. The first trigger source is the update event trigger source of the PWM timing module; the second trigger source is the software trigger source.

[0009] Optionally, in the multi-channel integrated triggering mechanism, any one of the trigger sources is configured to enable one or more sampling channels of the ADC module.

[0010] Optionally, the triggering of the analog-to-digital converter (ADC) module to sample the bus voltage and the floating phase terminal voltage of the motor to be sampled includes:

[0011] In the case where the ADC first trigger source is configured to enable a plurality of target sampling channels, trigger the ADC module to sample the target sampling channels in sequence. The target sampling channels include the sampling channels corresponding to the bus voltage and the floating phase terminal voltage.

[0012] Optionally, the ADC first trigger source includes at least one of the following:

[0013] Timer, event output module.

[0014] Optionally, the ADC second trigger source is configured to have the following trigger condition:

[0015] Trigger when the preset controller program runs to the program target position.

[0016] Optionally, the detecting the first zero crossing of the back electromotive force based on the first voltage value and the second voltage value includes:

[0017] If the second voltage value is half of the first voltage value, the time point of collecting the second voltage value is the first zero crossing.

[0018] According to the second aspect of the embodiments of the present invention, a back electromotive force sampling control system for sensorless square wave control is provided. The control system includes: a three-phase half-bridge drive circuit, a microcontroller unit (MCU);

[0019] The MCU is configured to store a computer program, and the computer program is configured to perform the sensorless square wave control back electromotive force sampling method described in any one of the above, and determine the zero crossing of the back electromotive force;

[0020] The three-phase half-bridge drive circuit is configured to control the commutation operation of the motor to be sampled based on the determined zero crossing.

[0021] In the solution provided by the embodiments of the present invention, in this way, according to the solution provided by the embodiments of the present invention, within each PWM control period, only the bus voltage and the floating phase terminal voltage need to be collected. The obtained voltage values can be used for zero-crossing detection, and it is not necessary to collect all three-phase terminal voltages. At most, only two data need to be collected each time, and the first voltage value of the bus voltage only needs to be collected once, reducing the number of sampling channels of the required ADC module and shortening the sampling time consumption. Therefore, the zero-crossing can be detected faster, thereby improving the efficiency of subsequent motor control and the commutation detection accuracy of the sensorless square wave algorithm.

[0022] Moreover, by combining the use of the first ADC trigger source and the second ADC trigger source, it is possible to try to detect the zero-crossing as many times as possible within one PWM control period under the condition that the sampling time of the ADC permits, which can also improve the detection accuracy.

[0023] Some of the additional aspects and advantages of the present invention will be given in the following description, some will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic flow chart of a back electromotive force sampling method provided by an embodiment of the present invention;

[0025] Figure 2 is a level waveform diagram of a PWM control period provided by an embodiment of the present invention;

[0026] Figure 3 is a schematic structural diagram of the first BLDC provided by an embodiment of the present invention;

[0027] Figure 4 is a schematic structural diagram of the second BLDC provided by an embodiment of the present invention;

[0028] Figure 5 is a voltage waveform diagram of the first BLDC provided by an embodiment of the present invention;

[0029] Figure 6 is a voltage waveform diagram of the second BLDC provided by an embodiment of the present invention;

[0030] Figure 7 is a schematic structural diagram of a multi-channel integrated trigger mechanism of an ADC module provided by an embodiment of the present invention;

[0031] Figure 8 is a schematic structural diagram of a control system of sensorless square wave control provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0033] The back electromotive force sampling method and control system for sensorless square wave control according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0034] In one embodiment of the present invention, refer to Figure 1 , a back electromotive force sampling method for sensorless square wave control is provided, including the following method steps S101 - S103.

[0035] S101: In each PWM control cycle of the motor to be sampled, the analog - to - digital converter ADC module is first triggered by the ADC first trigger source to sample the bus voltage and the floating phase terminal voltage of the motor to be sampled, obtaining a first voltage value of the bus voltage and a second voltage value of the floating phase terminal voltage;

[0036] S102: Based on the first voltage value and the second voltage value, the first zero - crossing point of the back electromotive force is detected, and the first remaining time of the valid signal within this PWM control cycle is determined;

[0037] S103: If the first remaining time is greater than or equal to the sampling time of the ADC module, the ADC module is triggered by the ADC second trigger source to perform at least one repeated sampling of the floating phase terminal voltage, obtaining a third voltage value of the floating phase terminal voltage. The second zero - crossing point of the back electromotive force is detected based on the first voltage value and the third voltage value until the second remaining time of the valid signal after the repeated sampling is less than the sampling time of the ADC module.

[0038] PWM (Pulse - Width Modulation) refers to the pulse - width modulation technology, which is an equivalent signal output modulation means. Common parameters include carrier frequency, duty cycle, period, etc. Assuming a PWM carrier frequency of 10 kHz, the corresponding PWM control cycle is 100 μs. Within one PWM cycle, the power switch of the motor to be sampled realizes one switching cycle, thereby controlling the speed and torque of the motor.

[0039] The motor has a stator core and a rotor with a permanent magnet structure, etc. There are stator windings on the stator core. When a voltage is applied to the stator windings and a certain current is passed through the stator windings, a corresponding electromagnetic torque can be generated, thereby driving the rotor to rotate. For square wave control, there are usually 6 different angular voltage vectors. The correct voltage vector needs to be selected according to the rotor position to drive the rotor to rotate in the desired direction. Therefore, certain means are needed to obtain the rotor position information. Zero - crossing based commutation belongs to a sensorless square wave control algorithm.

[0040] A signal with a duty cycle within one PWM control period is the actual effective output. That is, in the switching cycle, on corresponds to a high level and off corresponds to a low level. The time of the effective signal is the high-level time, such as Figure 2 the time represented by PWM_ON in the figure. It can be seen from the figure that in one PWM control period, one switching operation is performed.

[0041] In the above embodiment, the motor to be sampled is a brushless DC motor BLDC. The BLDC drive circuit is a three-phase half-bridge drive circuit, as Figure 3 shown. Among them, components 1, 2, and 3 represent the upper-bridge MOS (MOSFET, metal-oxide semiconductor field-effect transistor) of the BLDC, and components 4, 5, and 6 represent the lower-bridge MOS of the BLDC.

[0042] Lines U, V, and W are connected to the three phases of the BLDC. By conducting the stator windings of two of the phases (one upper-bridge phase and one lower-bridge phase), a voltage vector is output to drive the rotor to rotate, and the unconducted phase is the floating phase.

[0043] For example, in Figure 3 , a MOS drive signal can be given to component 3 to conduct the positive power supply and the W phase of the motor, and a MOS drive signal can be given to component 5 to conduct the negative power supply and the V phase of the motor. The MOS transistor is a switching device that plays a role in connecting the winding and the power supply. The waveform of W+V- is formed as Figure 5 shown in sector 1. Sectors 1-6 represent the conduction conditions of different phases when the motor rotates one week, which are U+V-, U+W-, V+W-, V+U-, W+U- in sequence. The plus sign indicates the conduction of the positive pole, and the minus sign indicates the conduction of the negative pole. The three groups of waveform diagrams represent the voltage changes of the U, V, and W three phases.

[0044] In Figure 3 , a diode is also provided on the right side of the MOS transistor of each phase. The existence of the diode is to protect the circuit when the MOS transistor is suddenly turned off but there is still current in the motor winding. Since the motor winding is essentially an inductor and the current cannot change suddenly, the current needs to be released by the loop. Therefore, the existence of the diode can make the current in the motor decrease slowly.

[0045] In motor control, the motor stator voltage needs to be 90° out of phase with the rotor position to generate the maximum electromagnetic torque. Therefore, it is necessary to determine the rotor position of the motor to determine the output voltage vector.

[0046] By detecting the zero-crossing moment of the back electromotive force of the floating phase, the rotor position of the BLDC can be determined, thereby adjusting the rotation speed of the brushless motor.

[0047] 1. The positive busbar is connected above the components 1, 2, and 3, and the negative busbar is connected below the components 4, 5, and 6. Specifically, as shown in Figure 4 the first voltage value of the busbar voltage is U bus .

[0048] Figure 4 In ,

[0048] , and Figure 4 , the BLDC is also the motor to be sampled. The upper-bridge MOS of the W phase and the lower-bridge MOS of the V phase are turned on, and the U phase is the floating phase. For the turned-on MOS transistors, the voltage value generating the voltage is U mos .

[0049] The sampling process of the ADC (Analog-to-Digital Converter) module is as follows (1)-(5).

[0050] (1) Sampling: The ADC first samples the analog signal, that is, captures the signal of the busbar voltage at specific time points. According to the Nyquist sampling theorem, the sampling frequency must be at least twice the highest frequency of the signal to avoid aliasing.

[0051] (2) Holding: After sampling, the ADC temporarily holds this voltage signal for subsequent quantization processing. This stage is called "sample and hold".

[0052] (3) Quantization: In the quantization stage, the ADC converts the sampled and held voltage signal into discrete digital values.

[0053] (4) Encoding: The quantized discrete levels are converted into binary codes, which are the formats that can be understood and processed by digital systems. For example, a 3-bit ADC can quantize the discrete digital values into 8 levels and represent them with 3-bit binary numbers (from 000 to 111).

[0054] (5) Output: Finally, the ADC outputs this binary numerical value, which is the first voltage value.

[0055] The method of sampling the floating-phase terminal voltage is the same as that of sampling the busbar voltage. The only difference is whether it is sampling the busbar or the floating phase of the motor to be sampled. Details are not described here.

[0056] When the first voltage value and the second voltage value are obtained, the first zero-crossing point of the back electromotive force can be detected in the following way:

[0057] If the second voltage value is half of the first voltage value, the time point of collecting the second voltage value is the first zero-crossing point.

[0058] Taking Figure 4 as an example, the upper-bridge MOS of the W phase and the lower-bridge MOS of the V phase are turned on, and the U phase is the floating phase. As shown in Figure 4 the busbar voltage is U bus, the voltage drop of the MOS transistor is U mos , the actual voltage of the W phase of the motor relative to the negative pole should be U bus - U mos , the actual voltage of the V phase of the motor relative to the negative pole should be U mos , the reference voltage for the zero crossing of the U phase should be half of the sum of the W phase and the V phase: (U bus - U mos + U mo s) / 2, that is, U bus / 2. That is to say, the bus voltage can be directly used as the reference level for judging the zero crossing of the back electromotive force in the sensorless square wave control algorithm.

[0059] If the first zero crossing is detected, the specific control method is as follows:

[0060] Motor control divides the voltage output by the inverter circuit into 0 to 360°, with each 60° as a sector. Sensorless square wave control is to output a voltage vector in each sector to drive the motor rotor to rotate. After detecting the first zero crossing, wait for a period of time (theoretically the time for the motor to rotate 30 electrical degrees), and then switch the voltage vector. The square wave algorithm completes the work of switching sectors.

[0061] In the case of each 60° as a sector. However, when updating the voltage vector and entering a new sector, the motor will rotate 30° before reaching the position where the back electromotive force is 0. Therefore, after we detect the zero crossing, the motor has to rotate another 30° before we will switch the voltage vector and enter the next sector. That is to say, the moment when the back electromotive force is 0 generally appears in the middle of a sector, and the voltage vector is switched 6 times when the motor rotates one circle.

[0062] The detection method and motor control method of the second zero crossing are similar to those of the first zero crossing, and the only difference lies in the detection time and the trigger source.

[0063] After detecting the first zero crossing, as Figure 6 shown, the first trigger source of the ADC triggers the ADC module to sample the bus voltage and the floating phase terminal voltage, that is, Figure 6 after the first trigger in , if there is remaining time within the period, that is, the first remaining time, and the first remaining time is greater than or equal to the sampling time of the ADC module, so that it is sufficient to perform another sampling, then the second trigger source of the ADC is used to implement software-triggered ADC sampling to detect whether there is a second zero crossing, that is, the second trigger in the figure; each time software triggering is performed, a third voltage value is detected, and whether there is a second zero crossing is detected according to the first voltage value and the third voltage value sampled this time. After sampling, the second remaining time of the valid signal is updated. If the remaining time is still greater than or equal to the sampling time of the ADC module, that is, it is still possible to sample again, then repeated sampling is performed, that is, the second trigger source of the ADC is used again. Figure 6The situation of one hardware trigger and two software triggers within each PWM control period is shown. In the case where the remaining time of the valid signal is longer, there can also be three or four software trigger samplings. In this way, a commutation operation can be performed when a zero-crossing event occurs during any sampling in any period, including detecting the first zero-crossing point or the second zero-crossing point.

[0064] Within each period, if the second remaining time is insufficient, wait for the start of the first ADC trigger source in the next PWM period.

[0065] Both the first remaining time and the second remaining time refer to the time between the moment after the end of this sampling and the end moment of the valid signal.

[0066] In one embodiment, the first ADC trigger source includes at least one of the following: a timer, an event output module.

[0067] The second ADC trigger source is configured to have the following trigger condition: trigger when the preset controller program runs to the program target position.

[0068] The software trigger source enables the ADC module to start working by relying on code execution. The specific target position can be set to any position in the controller program. The hardware trigger source relies on some output signals of the module, such as the update of the timer, the comparison event signal output by the event output module, etc. The way and moment of hardware trigger are relatively fixed, and the moment of software trigger is relatively more flexible, so that the number of sampling times can be increased more flexibly according to the length of the remaining time.

[0069] Thus, by selecting the bus voltage as the reference level and the back electromotive force zero-crossing judgment basis, the ADC module only needs to sample the bus voltage and the floating phase terminal voltage to perform the back electromotive force zero-crossing judgment. And, since the PWM control period in the motor control system is relatively short, usually between 50 us and 100 us. The bus voltage fluctuates little during this process, and the first bus voltage value within one PWM control period can be regarded as a fixed value.

[0070] In this way, according to the solution provided by the embodiment of the present invention, only the bus voltage and the floating phase terminal voltage need to be collected within each PWM control period, and the obtained voltage values can be used for zero-crossing detection. It is not necessary to collect all three-phase terminal voltages. At most two data need to be collected each time, and the first bus voltage value only needs to be collected once, reducing the number of sampling channels of the required ADC module, shortening the sampling time consumption, and being able to detect the zero-crossing point faster, thereby improving the efficiency of subsequent motor control and the commutation detection accuracy of the sensorless square wave algorithm.

[0071] Moreover, by combining the use of the first ADC trigger source and the second ADC trigger source, it is possible to attempt to detect the zero crossing as many times as possible within one PWM control period under the condition allowed by the sampling time of the ADC, and the detection accuracy can also be improved.

[0072] In one embodiment, the ADC module is configured with a multi-channel integrated trigger mechanism. The multi-channel integrated trigger mechanism includes at least two trigger sources, including the first ADC trigger source and the second ADC trigger source. The first trigger source is the update event trigger source of the PWM timing module; the second trigger source is the software trigger source.

[0073] Among them, the update event can be updated once per PWM cycle, so that an ADC sampling triggered by a hardware trigger source is performed at the beginning of each cycle.

[0074] As Figure 7 shown, the multi-channel integrated trigger mechanism establishes a trigger mapping relationship between multiple sampling channels and multiple trigger sources.

[0075] ADC channels 1 to 3 are three sampling channels of the ADC module, and ADC trigger sources 1 to 3 are three independent trigger sources.

[0076] In the multi-channel integrated trigger mechanism, any trigger source is configured to enable one or more sampling channels of the ADC module. Specifically, in the multi-channel integrated trigger mechanism, the ADC module can have an independent trigger mechanism or an integrated trigger mechanism.

[0077] The independent trigger mechanism means that after each trigger source is enabled, it independently triggers the corresponding ADC channel. For example: after enabling trigger source 1, ADC channel 1 performs sampling conversion; after enabling trigger source 2, ADC channel 2 performs sampling conversion; after enabling trigger source 3, ADC channel 3 performs sampling conversion.

[0078] The integrated trigger mechanism means that the difference from the independent trigger mechanism is that after enabling ADC trigger source 1, the ADC module automatically performs conversions on a predetermined number of ADC channels in sequence. For example: if the predetermined number of ADC channels N is 3, after enabling ADC trigger source 1, the ADC module automatically performs conversions on ADC channel 1, ADC channel 2, and ADC channel 3 in sequence. And the working modes of other ADC trigger sources have no difference from the independent trigger mechanism: after enabling ADC trigger source 2, ADC channel 2 performs sampling conversion; after enabling ADC trigger source 3, ADC channel 3 performs sampling conversion.

[0079] Any ADC trigger source can be set as a hardware trigger source or a software trigger source. For example, set ADC trigger source 1 as a hardware trigger source and ADC trigger source 2 as a software trigger source; or set both ADC trigger sources 1 and 2 as software trigger sources.

[0080] In this case, the analog-to-digital converter (ADC) module is triggered to sample the bus voltage and the floating-phase terminal voltage of the motor to be sampled, including:

[0081] When the first ADC trigger source is configured to enable multiple target sampling channels, the ADC module is triggered to sample the target sampling channels in sequence. The target sampling channels include the sampling channels corresponding to the bus voltage and the floating-phase terminal voltage.

[0082] For example, using ADC trigger source 1 as the hardware trigger source, the target sampling channels include: ADC channel 1 for sampling the bus voltage; ADC channel 2 for sampling the floating-phase terminal voltage. In this way, a single trigger action of the trigger source can obtain the first voltage value and the second voltage value.

[0083] The software trigger source can be set to ADC trigger source 2 to trigger ADC channel 2 to sample the floating-phase terminal voltage. If the remaining time in the current period is insufficient, the process ends and waits for the hardware to automatically enable trigger source 1 at the start of the next PWM period.

[0084] Compared with the existing sensorless square-wave technology, in the PWM control period, the method of modifying the trigger mode of the ADC module after the first hardware trigger of the ADC module and then re-triggering the ADC module, according to the above comprehensive trigger mechanism to configure the mapping relationship between multiple trigger sources and sampling channels, can simply and conveniently achieve multiple samplings of the back electromotive force of the BLDC in a single PWM control period.

[0085] In an embodiment of the present invention, a back electromotive force zero-crossing sampling system is further provided. The system includes: a three-phase half-bridge drive circuit and a microcontroller unit (MCU).

[0086] The MCU is used to store a computer program, and the computer program is configured to execute the back electromotive force sampling method of sensorless square-wave control described in any of the above embodiments to determine the zero-crossing point of the back electromotive force.

[0087] The three-phase half-bridge drive circuit is used to control the commutation operation of the motor to be sampled based on the determined zero-crossing point.

[0088] Among them, the above zero-crossing point can be the detected first zero-crossing point or the second zero-crossing point.

[0089] Such as Figure 8As shown in the figure, in the sensorless square-wave control system of the present invention, the MCU provides six PWM signals to the three-phase half-bridge drive circuit, and drives the BLDC through the three-phase half-bridge drive circuit to achieve voltage control of the BLDC. At the same time, the ADC trigger source of the MCU is set to sample the bus voltage and the floating-phase voltage of the BLDC. Among them, the first ADC trigger source can sample the bus voltage and the floating-phase voltage, and the second ADC trigger source only samples the floating-phase voltage. Figure 8 The power supply in it is used to supply power to the MCU and the three-phase half-bridge drive.

[0090] It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits with logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits with appropriate combinational logic gate circuits, programmable gate arrays (PGA), field programmable gate arrays (FPGA), etc.

[0091] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0092] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0093] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0094] In the present invention, unless otherwise clearly stipulated and defined, terms such as "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0095] In the present invention, unless otherwise clearly stipulated and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0096] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A back electromotive force sampling method for non-inductive square wave control, characterized in that: The sampling method includes: In each PWM control cycle of the motor to be sampled, the analog-to-digital converter (ADC) module is first triggered by the first ADC trigger source to sample the bus voltage and the floating-phase terminal voltage of the motor to be sampled, obtaining a first voltage value of the bus voltage and a second voltage value of the floating-phase terminal voltage; Based on the first voltage value and the second voltage value, the first zero-crossing point of the back electromotive force is detected, and the first remaining time of the valid signal within this PWM control cycle is determined; If the first remaining time is greater than or equal to the sampling time of the ADC module, the ADC module is triggered by the second ADC trigger source to perform at least one repeated sampling of the floating-phase terminal voltage, obtaining a third voltage value of the floating-phase terminal voltage. Based on the first voltage value and the third voltage value, the second zero-crossing point of the back electromotive force is detected until the second remaining time of the valid signal after the repeated sampling is less than the sampling time of the ADC module; The ADC module is configured with a multi-channel integrated trigger mechanism, and the multi-channel integrated trigger mechanism includes at least two trigger sources, including the first ADC trigger source and the second ADC trigger source. The first trigger source is the update event trigger source of the PWM timing module; the second trigger source is a software trigger source; Among them, the update event is updated once in each PWM cycle, so that an ADC sampling triggered by a hardware trigger source is performed at the beginning of each cycle.

2. The back electromotive force sampling method of non-inductive square wave control according to claim 1 is characterized in that: In the multi-channel integrated trigger mechanism, any trigger source is configured to enable one or more sampling channels of the ADC module.

3. The back electromotive force sampling method of non-inductive square wave control according to claim 2 is characterized in that: The triggering of the ADC module to sample the bus voltage and the floating-phase terminal voltage of the motor to be sampled includes: When the first ADC trigger source is configured to enable multiple target sampling channels, the ADC module is triggered to sequentially sample the target sampling channels, and the target sampling channels include the sampling channels corresponding to the bus voltage and the floating-phase terminal voltage.

4. The back electromotive force sampling method of non-inductive square wave control according to claim 1 is characterized in that: The first ADC trigger source includes at least one of the following: Timer, event output module.

5. The back electromotive force sampling method of non-inductive square wave control according to claim 1 is characterized in that: The second ADC trigger source is configured to have the following trigger condition: Trigger when the preset controller program runs to the program target position.

6. The back electromotive force sampling method of non-inductive square wave control according to claim 1 is characterized in that: The detecting of the first zero-crossing point of the back electromotive force based on the first voltage value and the second voltage value includes: If the second voltage value is half of the first voltage value, the time point when the second voltage value is collected is the first zero-crossing point.

7. A non-inductive square wave controlled back electromotive force sampling control system, characterized in that: The control system includes: a three-phase half-bridge drive circuit, a microcontroller unit (MCU); The MCU is used to store a computer program, and the computer program is configured to execute the back electromotive force sampling method of sensorless square wave control according to any one of claims 1-6, and determine the zero-crossing point of the back electromotive force; The three-phase half-bridge drive circuit is used to control the commutation operation of the motor to be sampled based on the determined zero-crossing point.

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