Motor starting direction judgment method, storage medium and motor control system

Abstract

The present invention provides a method for determining the starting direction of a motor, a storage medium, and a motor control system. The method for determining the starting direction of a motor is applied to a motor control system, the motor control system comprising: a control module, a power supply, a voltage sampling module, an inverter, and a motor. The method for determining the starting direction of a motor comprises: when the motor speed reaches a preset speed, suspending the first and second phases of the inverter; detecting the voltage of the first phase to obtain a first phase voltage value; obtaining a time window on both sides of a first duration based on the first phase voltage, and determining whether the motor is in a forward rotation state or a reverse rotation state based on the cumulative value of the first phase voltage within the time window. The present invention obtains the first and second phase voltages of the inverter and determines the operating state of the motor by detecting the cumulative value of the voltage in the time window on both sides within the duration, thereby solving the problem of obtaining the rotation direction of the motor rotor without a position sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of single-phase motors, and in particular to a method for determining a motor starting direction, a storage medium, and a motor control system. Background Art

[0002] Single-phase brushless DC motors are widely used in low-power wind turbines due to their low cost. In actual products, additional Hall effect sensors are often required to detect the motor's rotor position. This information is used to apply appropriate current to the motor for efficient control. For cost reasons, Hall effect sensors increase hardware costs.

[0003] The starting direction of a motor directly affects the performance of its connected load. Determining the motor's rotational direction is a prerequisite for using the motor to power the load. Determining the rotational direction of a single-phase motor without a position sensor is an urgent problem. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for determining the starting direction of a motor, which aims to obtain the rotation direction of the motor without a position sensor.

[0005] To achieve the above-mentioned object, the present invention proposes a method for determining the motor starting direction, which is applied to a motor control system. The motor control system includes: a control module, a power supply, a voltage sampling module, an inverter, and a motor; the motor starting direction determination method includes:

[0006] When the motor speed reaches the preset speed, the first and second phases of the inverter are suspended;

[0007] detecting the voltage of the first phase to obtain a first phase voltage value;

[0008] A time window on both sides of the first duration is obtained according to the first phase voltage, and it is determined whether the motor is in a forward rotation state or a reverse rotation state according to the accumulated value of the first phase voltage in the time window.

[0009] Optionally, acquiring time windows on both sides of the first duration according to the first phase voltage includes:

[0010] Based on the first phase voltage, a first duration is obtained; during the first duration, the first phase voltage value is greater than a preset voltage value;

[0011] Time windows on both sides of the first duration are acquired according to the first duration.

[0012] Optionally, the durations of the time windows on both sides of the first duration are equal, and the duration is a set multiple of a carrier period of the control signal received by the inverter.

[0013] Optionally, the distance between the midpoint of the time window on the left side of the first duration and the midpoint of the duration is the first interval duration; the distance between the midpoint of the time window on the right side of the first duration and the midpoint of the duration is the second interval duration;

[0014] The absolute value of the first interval duration is equal to the absolute value of the second interval duration.

[0015] Optionally, judging whether the motor is in a forward rotation state or a reverse rotation state according to the accumulated value of the first phase voltage in the time window includes:

[0016] If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is greater than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, the motor is in the forward rotation state;

[0017] If the accumulated value of the first phase voltage values ​​in the time window on the right side of the first duration is less than the accumulated value of the first phase voltage values ​​in the time window on the left side of the first duration, the motor is in a reverse state.

[0018] Optionally, when the motor speed reaches a first preset speed value, suspending the first phase and the second phase of the inverter, then includes:

[0019] detecting the voltage of the first phase to obtain a first phase voltage value, and detecting the voltage of the second phase to obtain a second phase voltage value;

[0020] Based on the first phase voltage and the second phase voltage, a first duration and a second duration are obtained; during the first duration, the first phase voltage value is greater than a preset voltage value; during the second duration, the second phase voltage value is greater than the preset voltage value;

[0021] Based on the comparison relationship between the cumulative values ​​of the first phase voltage values ​​in the time windows on both sides of the first duration and the comparison relationship between the cumulative values ​​of the second phase voltage values ​​in the time windows on both sides of the second duration, it is determined whether the motor is in the forward rotation state or the reverse rotation state.

[0022] Optionally, judging whether the motor is in the forward rotation state or the reverse rotation state based on a comparison relationship between cumulative values ​​of the first phase voltage values ​​in time windows on both sides of the first duration and a comparison relationship between cumulative values ​​of the second phase voltage values ​​in time windows on both sides of the second duration includes:

[0023] If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is greater than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, and the cumulative value of the second phase voltage value in the time window on the right side of the second duration is greater than the cumulative value of the second phase voltage value in the time window on the left side of the second duration, the motor is in the forward rotation state;

[0024] If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is less than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, and the cumulative value of the second phase voltage value in the time window on the right side of the second duration is less than the cumulative value of the second phase voltage value in the time window on the left side of the second duration, the motor is in a reverse state.

[0025] The present invention further provides a storage medium storing a motor starting direction determination program. When the motor starting direction determination program is executed by a processor, the steps of the motor starting direction determination method are implemented.

[0026] The present invention further provides a motor control system, comprising:

[0027] Inverter, power supply, control module, voltage sampling module and motor;

[0028] The first phase and the second phase of the inverter are connected to the first end and the second end of the motor respectively; the power supply supplies power to the inverter and the control module; the first sampling end of the voltage sampling module is connected to the first phase of the inverter, the second sampling end is connected to the second phase of the inverter, and the output end is connected to the control module; the control module is connected to the controlled end of the inverter;

[0029] The voltage sampling module is used to sample the voltage value of the first phase of the inverter and the voltage value of the second phase of the inverter, and output them to the control module;

[0030] The control module is used to determine whether the motor is in a forward rotation state or a reverse rotation state according to the voltage value of the first phase of the inverter and / or the voltage value of the second phase of the inverter.

[0031] Optionally, the control module is further configured to obtain the motor rotor speed based on the voltage of the first phase of the inverter and the voltage of the second phase of the inverter;

[0032] The control module is further configured to control the first phase and the second phase of the inverter to be suspended when the motor speed reaches a preset speed.

[0033] The present invention provides a method for determining the starting direction of a motor, a storage medium, and a motor control system. The method is applied to a motor control system comprising a control module, a power supply, a voltage sampling module, an inverter, and a motor. The method comprises: when the motor speed reaches a preset speed, suspending the first and second phases of the inverter; detecting the voltage of the first phase to obtain a first-phase voltage value; obtaining time windows on both sides of a first duration based on the first-phase voltage; and determining whether the motor is in a forward or reverse rotation state based on the accumulated value of the first-phase voltage within the time windows. The present invention obtains the voltages of the first and second phases of the inverter and determines the motor's operating state by detecting the accumulated voltage values ​​in the time windows on both sides within the duration, thereby solving the problem of determining the rotation direction of the motor rotor without a position sensor. Based on the comparison of the accumulated voltage values ​​in the time windows (e.g., the difference between the integrated values ​​of the two windows shows a specific pattern for forward rotation, while the pattern is opposite for reverse rotation), the direction of rotation can be quickly determined directly based on the numerical value relationship. This design eliminates the need for complex algorithms, reduces computational complexity, and makes the control strategy more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0035] Figure 1 This is a schematic diagram of the steps of an embodiment of a method for determining the starting direction of a motor according to the present invention;

[0036] Figure 2 This is a schematic diagram of the steps of the first embodiment of the method for determining the motor starting direction of the present invention;

[0037] Figure 3 This is a schematic diagram of the connection between the inverter and the motor in an embodiment of the method for determining the starting direction of the motor of the present invention;

[0038] Figure 4 This is a waveform diagram of the first back electromotive force of the inverter when the motor rotor is in forward and reverse directions according to an embodiment of the method for determining the starting direction of a motor of the present invention;

[0039] Figure 5 Schematic diagram of the waveform of the first phase voltage of the inverter within a single duration of an embodiment of the method for determining the starting direction of a motor of the present invention;

[0040] Figure 6 This is a schematic diagram of the waveforms of the first phase voltage and the second phase voltage of the inverter in the detection mode of an embodiment of the method for determining the starting direction of a motor of the present invention;

[0041] Figure 7 This is a schematic diagram of the waveforms of the motor phase current, the inverter first phase voltage and the second phase voltage when the motor starts according to an embodiment of the method for determining the starting direction of the motor of the present invention;

[0042] Figure 8 FIG. 1 is a topological diagram of an embodiment of a motor control system of the present invention.

[0043] Description of Figure Numbers:

[0044] A first switching device, Q1;

[0045] a second switching device, Q2;

[0046] A third switching device, Q3;

[0047] a fourth switching device, Q4;

[0048] Control module, 1;

[0049] Voltage sampling module, 2;

[0050] Inverter, 3.

[0051] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0054] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0055] In addition, in the present invention, descriptions such as "first" and "second" are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0056] In order to determine the rotation direction of a single-phase motor when it is started. The present invention proposes a method for determining the direction of motor starting, which is applied to a motor control system, the motor control system comprising: a control module, a power supply, a voltage sampling module, an inverter and a motor; Figure 1 As shown, the motor starting direction determination method includes:

[0057] Step S10: When the motor speed reaches a preset speed, the first phase and the second phase of the inverter are suspended;

[0058] Step S20: Detecting the voltage of the first phase to obtain a first phase voltage value;

[0059] Step S30: obtaining time windows on both sides of the first duration according to the first phase voltage, and determining whether the motor is in a forward rotation state or a reverse rotation state according to the accumulated value of the first phase voltage in the time window.

[0060] It should be explained that the first and second phases of the inverter are suspended, and the voltage values ​​of the first and second phases at this time are detected. The motor rotor rotates under the action of inertia, generating a back electromotive force; the back electromotive force of the first phase and the back electromotive force of the second phase are collected. It is easy to understand that the back electromotive force of the motor is positively correlated with the speed of the motor rotor; when the motor speed reaches the preset speed, the first and second phases of the inverter are suspended to ensure that the value of the back electromotive force is greater than the preset voltage value, thereby ensuring the success rate of subsequent identification. Specifically, if the value of the back electromotive force is too small, it will cause the difference between the cumulative values ​​of the voltages in the time windows on both sides of the duration to be too small. Under the action of the error, the comparison relationship of the voltages in the corresponding time windows on both sides under different motor operating states is changed. For example: if the motor is in the forward rotation state, the cumulative value of the voltage in the time window on the left side of the duration is less than the cumulative value of the voltage in the time window on the right side of the duration. However, since the cumulative value of the voltage in the time windows on both sides of the duration is small, the error may cause the cumulative value of the voltage in the left time window to become larger. At this time, the comparison relationship of the voltage in the time windows on both sides will be changed, and the cumulative value of the voltage in the time window on the left side of the duration will be greater than the cumulative value of the voltage in the time window on the right side of the duration; correspondingly, this comparison relationship is the comparison relationship when the motor is in the reverse state; therefore, if the motor speed is too low, the motor back electromotive force will be smaller, which will cause the determined motor operation state to be wrong.

[0061] It should be noted that the preset speed and the preset voltage are positively correlated and can be determined experimentally by researchers. The preset speed should be sufficiently high to ensure the validity of the back-EMF signal. Typically, it can be set to the minimum speed required to accurately determine the motor's direction of operation.

[0062] Reference Figure 3 , Figure 3 This diagram illustrates the connection between an inverter and a single-phase motor. The two ends of the single-phase motor are connected to the first and second phases of the inverter, respectively. Detecting the voltage of the first or second phase of the inverter is equivalent to detecting the voltage across the windings of the single-phase motor.

[0063] The present invention determines the rotation state of the motor based on the cumulative value of the voltage in the time window on both sides of the duration. It should be noted that the back electromotive force waveforms of most single-phase motors are asymmetric. When the first and second phases of the inverter are suspended, the rotation state of the motor is determined based on the asymmetry of the first or second phase voltage. Since the stator of a single-phase motor can only generate magnetic fields in two directions, an uneven air gap is designed during motor design so that the initial position of the rotor deviates from the armature axis, thereby generating starting torque, solving the starting problem, and generating asymmetric back electromotive force.

[0064] like Figure 4 As shown, the back electromotive force waveform of the single-phase motor is asymmetric, and the back electromotive force waveforms corresponding to the positive and negative rotations of the single-phase motor are different. The operating state of the single-phase motor rotor can be determined based on the back electromotive force waveform of the single-phase motor. Specifically, the operating state of the single-phase motor rotor is determined based on the comparison relationship between the cumulative values ​​of the voltage values ​​in the time windows on both sides of the duration. Since the back electromotive force waveform of the single-phase motor is asymmetric, there must be a time window on one side where the cumulative value of the voltage is greater than the time window on the other side. Therefore, the waveform of the back electromotive force can be determined based on the comparison relationship between the cumulative values ​​of the voltage values ​​in the time windows on both sides of the duration, and then the operating state of the single-phase motor rotor can be determined. The time windows on both sides of the first duration are obtained based on the first phase voltage. Specifically, the first phase voltage value is obtained by detecting the voltage of the first phase, and the first phase voltage curve is further obtained. It should be noted that the motor in the present invention refers to a single-phase motor, and the two ports of the single-phase motor are respectively connected to the first phase and the second phase of the inverter; the first duration is the duration that the first phase voltage waveform occupies on the time axis at one time during the stage when the first phase voltage value is greater than the preset voltage value, as shown in FIG. Figures 4 to 6 The period in which the first and second phases of the inverter are suspended can be referred to as the detection mode of the motor.

[0065] In addition, it should be noted that the present invention does not limit the specific terminal at which the single-phase motor is connected to the first phase of the inverter. Assuming that the single-phase motor has a first terminal and a second terminal, connected to the first and second phases of the inverter, respectively, the first terminal may be connected to the first phase and the second terminal to the second phase, or the first terminal may be connected to the second phase and the second terminal to the first phase. In actual judgment, the first phase voltage should not be simply regarded as the voltage value of the motor terminal corresponding to the specific, identified so-called "first phase of the inverter." It should be recognized that since the terminals of the single-phase motor connected to the two phases of the inverter are not fixed, the voltage of the first phase is detected to obtain the first phase voltage value; based on the first phase voltage, a time window on both sides of the first duration is obtained, and the accumulated value of the first phase voltage within the time window is used to determine whether the motor is in the forward or reverse rotation state. Alternatively, the voltage value of any phase of the inverter can be detected, and based on the acquired inverter phase voltage (phase voltage waveform or phase voltage value), a time window on both sides of the first duration is obtained, and the accumulated value of the phase voltage within the time window is used to determine whether the motor is in the forward or reverse rotation state.

[0066] It should be noted that the waveform of the back electromotive force is related to the operating state of the motor rotor. In one example, when the single-phase motor rotor rotates forward, the waveform of the back electromotive force is low at first and then increases. Figure 4 shown.

[0067] It should be clarified that the relationship between the back EMF waveform and the operating state of the motor rotor is determined by researchers based on the structure of the single-phase motor or experimental results. Accordingly, the back EMF waveform affects the comparative relationship between the cumulative voltage values ​​within the time windows on both sides of the duration. Therefore, the relationship between the comparative relationship between the cumulative voltage values ​​within the time windows on both sides of the duration and the operating state of the motor rotor can also be determined by researchers based on the structure of the single-phase motor or experimental results.

[0068] The present invention provides a method for determining the starting direction of a motor. The method is applied to a motor control system comprising a control module, a power supply, a voltage sampling module, an inverter, and a motor. The method comprises: when the motor speed reaches a preset speed, suspending the first and second phases of the inverter; detecting the voltage of the first phase to obtain a first-phase voltage value; obtaining time windows on both sides of a first duration based on the first-phase voltage; and determining whether the motor is in a forward or reverse rotation state based on the accumulated value of the first-phase voltage within the time windows. The present invention obtains the voltages of the first and second phases of the inverter and determines the motor's operating state by detecting the accumulated voltage values ​​in the time windows on both sides of the duration, thereby solving the problem of determining the rotation direction of the motor rotor without a position sensor. By comparing the accumulated voltage values ​​in the time windows (e.g., the difference between the accumulated values ​​in the two windows shows a specific pattern for forward rotation, while the pattern is opposite for reverse rotation), the direction of rotation can be quickly determined directly based on the numerical value relationship. This design eliminates the need for complex algorithms, reduces computational complexity, and makes the control strategy more efficient.

[0069] The forward rotation direction of the motor can be selected manually. The present invention does not limit the relationship between the comparison relationship of the cumulative value of the voltage in the time window on both sides of the duration and the rotation direction of the motor rotor, which is determined by the R&D personnel based on the structure of the single-phase motor or the experimental results. In the first embodiment of the present invention, the forward rotation of the motor is associated with the cumulative value of the voltage in the time window on the right side of the duration being greater than the cumulative value of the voltage in the time window on the left side of the duration. The determination of whether the motor is in the forward or reverse rotation state based on the cumulative value of the voltage in the time window on both sides of the duration specifically includes:

[0070] If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is greater than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, the motor is in the forward rotation state;

[0071] If the accumulated value of the first phase voltage values ​​in the time window on the right side of the first duration is less than the accumulated value of the first phase voltage values ​​in the time window on the left side of the first duration, the motor is in a reverse state.

[0072] It should be noted that the voltage waveform within the first duration represents the change trend of the voltage value of the first phase or the second phase over time. The right time window is later than the left time window in time. Figure 5 As shown, Figure 5 In an example, the voltage waveform of the inverter's first phase voltage when the motor rotor rotates forward is shown in Figure 2. It is explained that there are two time windows within a duration. The left time window refers to the time window to the left of the midpoint of the duration; the right time window refers to the time window to the right of the midpoint of the duration. Figure 5 and Figure 6 As shown, within the first duration, the first time window is the left time window of the first duration, and the second time window is the right time window of the first duration. Within the second duration, the third time window is the left time window of the second duration, and the fourth time window is the right time window of the second duration.

[0073] It should be explained that when the first and second phases of the inverter are suspended, assuming that the motor speed does not change suddenly, the waveforms of the voltage value of the first phase and the voltage value of the second phase of the inverter are similar, but there are differences in phase, such as Figure 2 In order to further reduce the detection error and avoid the single-phase voltage detection error causing the wrong motor rotor state, in a second embodiment of the present invention, when the motor speed reaches a first preset speed value, the first phase and the second phase of the inverter are suspended, and then the following steps are included:

[0074] Step S40: Detecting the voltage of the first phase to obtain a first phase voltage value, and detecting the voltage of the second phase to obtain a second phase voltage value;

[0075] Step S50: obtaining a first duration and a second duration based on the first phase voltage and the second phase voltage; during the first duration, the first phase voltage value is greater than a preset voltage value; during the second duration, the second phase voltage value is greater than the preset voltage value;

[0076] Step S60: Determine whether the motor is in the forward rotation state or the reverse rotation state based on the comparison relationship between the cumulative values ​​of the first phase voltage values ​​in the time windows on both sides of the first duration and the comparison relationship between the cumulative values ​​of the second phase voltage values ​​in the time windows on both sides of the second duration.

[0077] In the second embodiment, the voltage values ​​of the first and second phases of the inverter are detected, and the voltage waveforms of the first and second phases are used to determine whether the first and second phase voltage waveforms conform to the voltage waveforms corresponding to forward or reverse rotation of the motor rotor. In conjunction with the above, it is readily understood that the voltage waveforms corresponding to forward and reverse rotation of the motor rotor are determined by research and development personnel.

[0078] It should be noted that if Figure 6 As shown, in the detection mode of the motor, the operating state of the motor is obtained according to the first phase voltage and the second phase voltage respectively, and repeatability verification is performed to ensure that the obtained motor operating state is correct. First, the first duration and the second duration are obtained according to the first phase voltage and the second phase voltage. Specifically, within the first duration, the first phase voltage is greater than the preset voltage value; within the second duration, the second phase voltage is greater than the preset voltage value. It is worth noting that when the phase voltage is suspended and the motor rotates freely, there may be external forces that cause the motor to accelerate or decelerate, causing interference with the back electromotive force signal. Generally, the motor and its load have a certain degree of inertia, so when the external force is within a certain range, the present invention can be applied. The specific applicability needs to be determined by the user based on the experimental results according to the degree of asymmetry of the back electromotive force and the degree of change in the rotational speed.

[0079] The motor operating state corresponding to the first phase voltage waveform is determined based on a comparison of the cumulative values ​​of the first phase voltage values ​​within the time windows on both sides of the first duration. The motor operating state corresponding to the second phase voltage waveform is determined based on a comparison of the cumulative values ​​of the second phase voltage values ​​within the time windows on both sides of the second duration. When the motor operating states corresponding to the first and second phase voltage waveforms are the same, the motor is determined to be in the specified motor operating state. When the motor operating states corresponding to the first and second phase voltage waveforms are different, the motor operating state determination is deemed invalid.

[0080] In one example, determining whether the motor is in the forward rotation state or the reverse rotation state based on a comparison relationship between cumulative values ​​of first phase voltage values ​​in time windows on both sides of the first duration and a comparison relationship between cumulative values ​​of second phase voltage values ​​in time windows on both sides of the second duration includes:

[0081] If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is greater than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, and the cumulative value of the second phase voltage value in the time window on the right side of the second duration is greater than the cumulative value of the second phase voltage value in the time window on the left side of the second duration, the motor is in the forward rotation state;

[0082] If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is less than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, and the cumulative value of the second phase voltage value in the time window on the right side of the second duration is less than the cumulative value of the second phase voltage value in the time window on the left side of the second duration, the motor is in a reverse state.

[0083] In addition, it should be noted that when the motor speed reaches a preset speed, the first phase and the second phase of the inverter are suspended, which includes:

[0084] A voltage signal with a preset duty cycle is alternately applied to the first phase and the second phase of the inverter.

[0085] It is easy to understand that the motor starting direction needs to be determined after the motor is successfully driven. Figure 7 To increase the motor speed from zero to a preset speed, voltage signals with a preset duty cycle are alternately applied to the first and second phases of the inverter to increase the motor speed. In detection mode, the first and second phases of the inverter are left floating, and the voltage values ​​of the first and second phases of the inverter are measured.

[0086] The present invention determines the operating state of the motor by accumulating the voltage values ​​within the time windows on both sides of the duration. It will be readily understood that the accumulating voltage values ​​within the time windows are related to the duration of the time windows. In a third embodiment of the present invention, the durations of the time windows on both sides of the duration are equal, and the durations are set as multiples of the carrier period of the control signal received by the inverter.

[0087] It should be noted that the equal duration of the time windows on both sides of the duration can prevent the duration of the time window from becoming a factor affecting the cumulative value of the voltage within the time window. The carrier period is the basic time unit of the inverter PWM control signal. The window duration is a multiple of the carrier period, which can ensure that the position of each sampling window in the signal period is fixed. For example, no matter how the motor speed changes, the sampling is always aligned with the stable phase of the carrier signal, avoiding signal acquisition deviations caused by timing misalignment and ensuring the consistency of back electromotive force waveform detection. The set multiple can be determined by R&D personnel.

[0088] like Figure 5 As shown, Figure 5 In an example, the waveform of the inverter's first-phase voltage changes over a sustained period is shown. It's easy to understand that the waveform of the first-phase voltage has the following two conditions depending on the direction of rotation of the motor rotor:

[0089] First, the first phase voltage first rises steeply, then rises slowly, and then drops steeply. The midpoint of the slow rising phase is the midpoint of the duration.

[0090] Second, the first phase voltage first rises steeply, then slowly falls, and then falls steeply again. The midpoint of the slowly falling phase is the midpoint of the duration.

[0091] Whether the voltage waveform can be accurately identified as having a slow rise phase or a slow fall phase is the key to judging the motor's operating state. The time windows on both sides of the duration need to fall within the slow rise phase or the slow fall phase. The absolute value of the first duration is equal to the absolute value of the second duration, indicating that the time window on the left side of the duration is symmetrical with the time window on the right side of the duration. It has the following core advantages:

[0092] First, it can accurately capture back-EMF characteristics; the back-EMF waveform exhibits asymmetric characteristics during forward and reverse rotation (for example, "low first, then high" during forward rotation, and "high first, then low" during reverse rotation). The symmetrical window design covers key phases of the waveform, fully capturing the core area of ​​back-EMF variation. For example, during forward rotation, the symmetrical window can simultaneously capture the characteristics of the waveform's initial low-amplitude segment and subsequent high-amplitude segment, providing a more comprehensive basis for steering decisions.

[0093] Second, it suppresses interference and improves reliability. In actual operation, back EMF may be affected by non-ideal factors such as harmonics and noise. Symmetrical windows evenly distribute sampling points across the waveform. By comparing the integration results of the two windows, some of the effects of random interference can be offset. If one window is contaminated by transient noise, symmetrical sampling in the other window can balance the error, ensuring stable and reliable detection results.

[0094] like Figure 5 As shown, the voltage waveform in the slow rising stage or the slow falling stage should be taken as much as possible; wherein, the time length from the midpoint of the time window on the left side of the first duration to the midpoint of the duration is the first interval time length; the time length from the midpoint of the time window on the right side of the first duration to the midpoint of the duration is the second interval time length;

[0095] The absolute value of the first interval duration is equal to the absolute value of the second interval duration.

[0096] The value of the first interval duration can be adjusted by R&D personnel according to actual needs to ensure that the time window is in the slow rising phase or the slow falling phase. In one example, the absolute value of the first interval duration is 1 / 8 to 3 / 8 of the duration.

[0097] The present invention also provides a storage medium, wherein the storage medium stores a motor starting direction determination program, and when the motor starting direction determination program is executed by a processor, the motor starting direction determination method is implemented. The storage medium may be RAM, ROM, EPROM, or EEPROM.

[0098] Reference Figure 8 The present invention further proposes a motor control system, the motor control system comprising:

[0099] Inverter 3, control module 1, motor, power supply and voltage sampling module 2;

[0100] The first phase and the second phase of the inverter 3 are connected to the first end and the second end of the motor respectively; the power supply supplies power to the inverter and the control module; the first sampling end of the voltage sampling module 2 is connected to the first phase of the inverter 3, the second sampling end is connected to the second phase of the inverter 3, and the output end is connected to the control module 1; the control module 1 is connected to the controlled end of the inverter 3;

[0101] The voltage sampling module 2 is used to sample the voltage value of the first phase of the inverter 3 and / or the voltage value of the second phase of the inverter 3, and output it to the control module 1;

[0102] The control module 1 is used to determine whether the motor is in a forward rotation state or a reverse rotation state according to the voltage value of the first phase of the inverter 3 and the voltage value of the second phase of the inverter 3.

[0103] The control module 1 may include a controller such as an MCU, an FPGA, an SOC, a PLC, a CPU or a DSP, etc. The voltage sampling module 2 may perform voltage sampling using a resistor divider circuit.

[0104] The inverter 3 may include first to fourth switching devices. The first end of the first switching device Q1 and the first end of the third switching device Q3 are connected to a power source. The second end of the first switching device Q1 is connected to the first end of the single-phase motor and the first end of the second switching device Q2. The second end of the third switching device Q3 is connected to the second end of the single-phase motor and the first end of the fourth switching device Q4. The first to fourth switching devices may be MOS transistors. The controlled ends of the first to fourth switching devices are connected to the control module 1; the control module 1 controls the conduction or shutdown of the first to fourth switching devices.

[0105] In addition, since the motor control system lacks a position sensor, the rotor speed cannot be obtained through the position sensor. The control module 1 is also used to obtain the motor rotor speed based on the voltage of the first phase of the inverter 3 and the voltage of the second phase of the inverter 3. Specifically, the voltage cycle is determined by obtaining the commutation time of the first phase voltage and the second phase voltage, and then the motor rotor speed is obtained.

[0106] The control module 1 is further configured to control the first and second phases of the inverter 3 to be suspended when the motor speed reaches a preset speed. Specifically, the control module 1 outputs a control signal to the controlled terminals of the first to fourth switching devices in the inverter 3 to control the first to fourth switching devices to be turned off, thereby achieving the suspension of the first and second phases of the inverter 3.

[0107] The specific steps of the motor starting direction determination method refer to the above embodiments. Since the motor control system adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described in detail here. The above are only optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly or indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for determining the starting direction of a motor, characterized in that: The motor starting direction determination method is applied to a motor control system, which includes: a control module, a power supply, a voltage sampling module, an inverter, and a motor; the motor starting direction determination method includes: When the motor speed reaches the preset speed, the first and second phases of the inverter are suspended; detecting the voltage of the first phase to obtain a first phase voltage value; Obtaining time windows on both sides of the first duration according to the first phase voltage, and determining whether the motor is in a forward rotation state or a reverse rotation state according to an accumulated value of the first phase voltage within the time window; The time windows on both sides of the first duration are equal in duration, and the duration is a set multiple of a carrier period of the control signal received by the inverter; The time length from the midpoint of the time window on the left side of the first duration to the midpoint of the duration is the first interval duration; the time length from the midpoint of the time window on the right side of the first duration to the midpoint of the duration is the second interval duration; The absolute value of the first interval duration is equal to the absolute value of the second interval duration.

2. The method for determining the motor starting direction according to claim 1, wherein: The step of obtaining time windows on both sides of the first duration according to the first phase voltage includes: Based on the first phase voltage, a first duration is obtained; during the first duration, the first phase voltage value is greater than a preset voltage value; Time windows on both sides of the first duration are acquired according to the first duration.

3. The method for determining the motor starting direction according to claim 1, wherein: The step of determining whether the motor is in a forward rotation state or a reverse rotation state according to the accumulated value of the first phase voltage within the time window includes: If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is greater than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, the motor is in the forward rotation state; If the accumulated value of the first phase voltage values ​​in the time window on the right side of the first duration is less than the accumulated value of the first phase voltage values ​​in the time window on the left side of the first duration, the motor is in a reverse state.

4. The method for determining the motor starting direction according to claim 1, wherein: When the motor speed reaches a first preset speed value, the first phase and the second phase of the inverter are suspended, and then the following steps are included: detecting the voltage of the first phase to obtain a first phase voltage value, and detecting the voltage of the second phase to obtain a second phase voltage value; Based on the first phase voltage and the second phase voltage, a first duration and a second duration are obtained; during the first duration, the first phase voltage value is greater than a preset voltage value; during the second duration, the second phase voltage value is greater than the preset voltage value; Based on the comparison relationship between the cumulative values ​​of the first phase voltage values ​​in the time windows on both sides of the first duration and the comparison relationship between the cumulative values ​​of the second phase voltage values ​​in the time windows on both sides of the second duration, it is determined whether the motor is in the forward rotation state or the reverse rotation state.

5. The method for determining the motor starting direction according to claim 4, wherein: The determining whether the motor is in the forward rotation state or the reverse rotation state based on a comparison relationship between cumulative values ​​of the first phase voltage values ​​in time windows on both sides of the first duration and a comparison relationship between cumulative values ​​of the second phase voltage values ​​in time windows on both sides of the second duration includes: If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is greater than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, and the cumulative value of the second phase voltage value in the time window on the right side of the second duration is greater than the cumulative value of the second phase voltage value in the time window on the left side of the second duration, the motor is in the forward rotation state; If the cumulative value of the first phase voltage value in the time window on the right side of the first duration is less than the cumulative value of the first phase voltage value in the time window on the left side of the first duration, and the cumulative value of the second phase voltage value in the time window on the right side of the second duration is less than the cumulative value of the second phase voltage value in the time window on the left side of the second duration, the motor is in a reverse state.

6. A storage medium, characterized in that The storage medium stores a motor starting direction determination program, and when the motor starting direction determination program is executed by the processor, the steps of the motor starting direction determination method according to any one of claims 1 to 5 are implemented.

7. A motor control system, characterized in that: The motor control system includes: Inverter, power supply, control module, voltage sampling module and motor; The first phase and the second phase of the inverter are connected to the first end and the second end of the motor respectively; the power supply supplies power to the inverter and the control module; the first sampling end of the voltage sampling module is connected to the first phase of the inverter, the second sampling end is connected to the second phase of the inverter, and the output end is connected to the control module; the control module is connected to the controlled end of the inverter; The voltage sampling module is used to sample the voltage value of the first phase of the inverter and the voltage value of the second phase of the inverter, and output them to the control module; The control module is used to determine whether the motor is in a forward rotation state or a reverse rotation state according to the voltage value of the first phase of the inverter and / or the voltage value of the second phase of the inverter.

8. The motor control system according to claim 7, wherein: The control module is further configured to obtain the motor rotor speed based on the voltage of the first phase of the inverter and the voltage of the second phase of the inverter; The control module is further configured to control the first phase and the second phase of the inverter to be suspended when the motor speed reaches a preset speed.

Images