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

Abstract

The invention provides a motor starting direction judgment method, a storage medium and a motor control system, the motor starting direction judgment method is applied to the motor control system, and the motor control system comprises a control module, a power supply, a voltage sampling module, an inverter and a motor; the motor starting direction judgment method comprises the steps that when the rotating speed of a motor reaches a preset rotating speed, a first phase and a second phase of an inverter are suspended; detecting the voltage of the first phase to obtain a first phase voltage value; and acquiring time windows on two sides of the first duration according to the first phase voltage, and judging whether the motor is in a forward rotation state or a reverse rotation state according to an accumulated value of the first phase voltage in the time windows. According to the method, the first phase voltage and the second phase voltage of the inverter are obtained, the operation state of the motor is judged by detecting the voltage accumulated value of the time windows on the two sides within the duration, and therefore the purpose of obtaining the rotation direction of the motor rotor under the condition that no position sensor exists is achieved.

Description

Technical Field

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

[0002] Single-phase brushless DC motors are widely used in the field of small-power fans due to their low cost advantage. In actual products, additional Hall sensors are often required to detect the rotor position of the motor, and appropriate current is applied to the motor in combination with the rotor position information to complete the efficient control of the single-phase motor. Considering the cost, the Hall sensor will increase the hardware cost.

[0003] The starting direction of the motor is directly related to the execution effect of the load connected to the motor. Judging the rotation direction of the motor is a prerequisite for applying the motor to provide power for the load. In the case of no position sensor, it is an urgent problem to obtain the rotation direction of the single-phase motor. Summary of the Invention

[0004] The main object of the present invention is to provide a method for judging the starting direction of a motor, aiming to obtain the rotation direction of the motor under the condition of no position sensor.

[0005] To achieve the above object, the method for judging the starting direction of a motor proposed by the present invention is applied to a motor control system, and the motor control system includes: a control module, a power supply, a voltage sampling module, an inverter, and a motor; the method for judging the starting direction of a motor includes: When the motor speed reaches the preset speed, the first phase and the second phase of the inverter are suspended; Detect the voltage of the first phase to obtain the first-phase voltage value; According to the first-phase voltage, obtain the time windows on both sides of the first duration, and judge whether the motor is in the forward rotation state or the reverse rotation state according to the cumulative value of the first-phase voltage within the time windows.

[0006] Optionally, the obtaining of the time windows on both sides of the first duration according to the first-phase voltage includes: Based on the first-phase voltage, obtain the first duration; within the first duration, the first-phase voltage value is greater than the preset voltage value; Obtain the time windows on both sides of the first duration according to the first duration.

[0007] Optionally, the time windows on both sides of the first duration are of equal duration, and the duration is a set multiple of the carrier period of the control signal received by the inverter.

[0008] Optionally, the duration 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 duration 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.

[0009] Optionally, the judging whether the motor is in the forward rotation state or the reverse rotation state according to the cumulative value of the first-phase voltage within the time window includes: If the cumulative value of the first-phase voltage values within the time window on the right side of the first duration is greater than the cumulative value of the first-phase voltage values within the time window on the left side of the first duration, the motor is in the forward rotation state; If the cumulative value of the first-phase voltage values within the time window on the right side of the first duration is less than the cumulative value of the first-phase voltage values within the time window on the left side of the first duration, the motor is in the reverse rotation state.

[0010] Optionally, after the first phase and the second phase of the inverter are suspended when the motor speed reaches the first preset speed value, the following steps are included: Detect the voltage of the first phase to obtain the first-phase voltage value, and detect the voltage of the second phase to obtain the second-phase voltage value; Based on the first-phase voltage and the second-phase voltage, obtain the first duration and the second duration; within the first duration, the first-phase voltage value is greater than the preset voltage value; within the second duration, the second-phase voltage value is greater than the preset voltage value; Judge whether the motor is in the forward rotation state or the reverse rotation state according to the comparison relationship of the cumulative values of the first-phase voltage values within the time windows on both sides of the first duration and the comparison relationship of the cumulative values of the second-phase voltage values within the time windows on both sides of the second duration.

[0011] Optionally, the judging whether the motor is in the forward rotation state or the reverse rotation state according to the comparison relationship of the cumulative values of the first-phase voltage values within the time windows on both sides of the first duration and the comparison relationship of the cumulative values of the second-phase voltage values within the time windows on both sides of the second duration includes: If the cumulative value of the first-phase voltage values within the time window on the right side of the first duration is greater than the cumulative value of the first-phase voltage values within the time window on the left side of the first duration, and the cumulative value of the second-phase voltage values within the time window on the right side of the second duration is greater than the cumulative value of the second-phase voltage values within 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 values within the right time window of the first duration is less than the cumulative value of the first-phase voltage values within the left time window of the first duration, and the cumulative value of the second-phase voltage values within the right time window of the second duration is less than the cumulative value of the second-phase voltage values within the left time window of the second duration, then the motor is in the reverse state.

[0012] The present invention also provides a storage medium storing a motor starting direction determination program, which, when run by a processor, implements the steps of the motor starting direction determination method described above.

[0013] The present invention also provides a motor control system, which includes: an inverter, a power supply, a control module, a voltage sampling module, and a motor; The first phase and the second phase of the inverter are respectively connected to the first end and the second end of the motor; 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 configured 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 configured to determine whether the motor is in the forward rotation state or the 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.

[0014] Optionally, the control module is further configured to obtain the motor rotor speed according to 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 floating when the motor speed reaches a preset speed.

[0015] The present invention provides a method for judging the starting direction of a motor, a storage medium, and a motor control system. The method for judging the starting direction of the motor is applied to the motor control system, and the motor control system includes: a control module, a power supply, a voltage sampling module, an inverter, and a motor. The method for judging the starting direction of the motor includes: when the motor speed reaches a preset speed, leaving the first phase and the second phase of the inverter open; detecting the voltage of the first phase to obtain a first-phase voltage value; obtaining time windows on both sides of a first duration according to the first-phase voltage, and judging whether the motor is in a forward rotation state or a reverse rotation state according to the cumulative value of the first-phase voltage within the time windows. The present invention solves the problem of obtaining the rotation direction of the motor rotor without a position sensor by obtaining the voltages of the first phase and the second phase of the inverter and judging the operating state of the motor according to the cumulative voltage values within the time windows on both sides of the detected duration. Based on the comparison of the voltage cumulative values of the time windows (for example, when rotating forward, the difference in the integral values of the two windows shows a specific pattern, and when rotating backward, the pattern is opposite), the rotation direction can be quickly determined directly through the magnitude relationship of the numerical values. This design does not require a complex algorithm, reduces the calculation amount, and makes the control strategy more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on the structures shown in these drawings without creative efforts.

[0017] Figure 1 It is a schematic diagram of the steps of an embodiment of the method for judging the starting direction of the motor of the present invention; Figure 2 It is a schematic diagram of the steps of the first embodiment of the method for judging the starting direction of the motor of the present invention; Figure 3 It is a schematic diagram of the connection between the inverter and the motor in an embodiment of the method for judging the starting direction of the motor of the present invention; Figure 4 It is a waveform diagram of the back electromotive force of the first phase of the inverter in the case of forward and reverse rotation of the motor rotor in an embodiment of the method for judging the starting direction of the motor of the present invention; Figure 5 It is a waveform schematic diagram of the voltage of the first phase of the inverter within a single duration in an embodiment of the method for judging the starting direction of the motor of the present invention; Figure 6 It is a waveform schematic diagram of the voltage of the first phase and the second phase of the inverter in the detection mode in an embodiment of the method for judging the starting direction of the motor of the present invention; Figure 7Schematic diagram of the motor phase current, the first-phase voltage, and the second-phase voltage waveforms of the motor during startup in an embodiment of the motor startup direction determination method of the present invention; Figure 8 Topological structure diagram of an embodiment of the motor control system of the present invention.

[0018] Explanation of the reference numerals in the drawings: The first switching device, Q1; The second switching device, Q2; The third switching device, Q3; The fourth switching device, Q4; The control module, 1; The voltage sampling module, 2; The inverter, 3.

[0019] The implementation, functional features, and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0021] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0022] In the present invention, unless otherwise clearly defined and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. 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.

[0023] In addition, in the present invention, descriptions such as "first" and "second" are for descriptive purposes only, and should not be construed as indicating or implying their 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 addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] In order to determine the rotation direction when a single-phase motor starts. The present invention proposes a method for judging the starting direction of a motor, and the method for judging the starting direction of the motor is applied to a motor control system, and the motor control system includes: a control module, a power supply, a voltage sampling module, an inverter, and a motor; as Figure 1 shown, the method for judging the starting direction of the motor includes: Step S10, when the motor speed reaches a preset speed, suspend the first phase and the second phase of the inverter; Step S20, detect the voltage of the first phase to obtain a first-phase voltage value; Step S30, obtain time windows on both sides of a first duration according to the first-phase voltage, and judge whether the motor is in a forward rotation state or a reverse rotation state according to the cumulative value of the first-phase voltage within the time window.

[0025] It should be explained that the first phase and the second phase of the inverter are left floating, and the voltage values of the first phase and the second phase are detected at this time. The motor rotor rotates under the action of inertia, generating 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 rotational speed of the motor rotor; when the motor speed reaches the preset speed, the first phase and the second phase of the inverter are left floating 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 within the time windows on both sides of the duration to be too small. Under the action of errors, the comparison relationship of the voltages within the corresponding time windows on both sides under different motor operating states will change. For example: when the motor is rotating forward, the cumulative voltage value within the left time window of the duration is less than the cumulative voltage value within the right time window of the duration. However, due to the small cumulative voltage values within the time windows on both sides of the duration, errors may cause the cumulative voltage value within the left time window to increase, and at this time, the comparison relationship of the voltages within the time windows on both sides will change to that the cumulative voltage value within the left time window of the duration is greater than the cumulative voltage value within the right time window of the duration; correspondingly, this comparison relationship is the comparison relationship when the motor is in the reverse rotation state; therefore, too small a motor speed will result in too small a back electromotive force of the motor, thereby causing an error in the determined motor operating state.

[0026] It should be noted that the preset speed is positively correlated with the preset voltage value, and the R & D personnel can determine the value of the preset speed and the preset voltage value through experiments. The preset speed needs to be set large enough to ensure the effectiveness of the back electromotive force signal. Usually, it can be set to the minimum speed that can accurately judge the running direction of the motor.

[0027] Refer to Figure 3 , Figure 3 shows the connection relationship between the inverter and the single-phase motor. The two ends of the single-phase motor are respectively connected to the first phase and the second phase of the inverter. Detecting the voltage value of the first phase or the second phase of the inverter is to detect the voltage value at both ends of the single-phase motor winding.

[0028] The present invention judges the rotation state of the motor according to the cumulative values of the voltages within the time windows on both sides of the duration. It should be noted that the back electromotive force waveforms of most single-phase motors are asymmetric. In the case where the first phase and the second phase of the inverter are left floating, the rotation state of the motor is determined according to the asymmetry of the voltage of the first phase or the second phase. Since the stator of a single-phase motor can only generate magnetic fields in two directions, during the design of the motor, by designing an uneven air gap, the initial position of the rotor is deviated from the armature axis, thereby generating a starting torque to solve the starting problem, and at the same time generating an asymmetric back electromotive force.

[0029] Such asFigure 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 rotor of the single-phase motor can be determined according to the back electromotive force waveform of the single-phase motor. Specifically, the operating state of the rotor of the single-phase motor is determined according to the comparison relationship of the cumulative values of the voltage values within 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 situation where the cumulative voltage value of one time window is greater than that of the other time window. Therefore, the waveform of the back electromotive force can be determined according to the comparison relationship of the cumulative values of the voltage values within the time windows on both sides of the duration, and then the operating state of the rotor of the single-phase motor can be determined. The time windows on both sides of the first duration are obtained according to the first-phase voltage. Specifically, the first-phase voltage value is obtained by detecting the voltage of the first phase, and further the first-phase voltage curve is 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 occupied by the single first-phase voltage waveform on the time axis during the stage when the first-phase voltage value is greater than the preset voltage value, as Figures 4 to 6 As shown. The period when the first phase and the second phase of the inverter are left floating can be referred to as the detection mode of the motor.

[0030] In addition, it should be particularly pointed out that in the present invention, the specific connection end of the single-phase motor to the first phase of the inverter is not limited; assuming that the single-phase motor has a first end and a second end, which are respectively connected to the first phase and the second phase of the inverter; it can be that the first end is connected to the first phase and the second end is connected to the second phase, or it can be that the first end is connected to the second phase and the second end is connected to the first phase. In actual judgment, the first-phase voltage should not be simply regarded as the voltage value corresponding to the so-called "first phase of the inverter" with a specific and identified motor end. 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; the time windows on both sides of the first duration are obtained according to the first-phase voltage, and according to the cumulative value of the first-phase voltage within the time window, it is judged whether the motor is in the forward rotation state or the reverse rotation state; it can also be to detect the voltage value of any phase of the inverter, obtain the time windows on both sides of the first duration according to the obtained phase voltage (phase voltage waveform or phase voltage value) of the inverter, and judge whether the motor is in the forward rotation state or the reverse rotation state according to the cumulative value of the phase voltage within the time window.

[0031] It should be noted that the waveform of the back electromotive force is associated with the operating state of the motor rotor. In one example, when the rotor of the single-phase motor rotates forward, the waveform of the back electromotive force is first lower and then increases, as Figure 4 shown.

[0032] It should be clear that the relationship between the waveform of the back electromotive force and the operating state of the motor rotor is determined by the R & D personnel based on the structure of the single-phase motor or the experimental results. Correspondingly, the waveform of the back electromotive force affects the comparison relationship of the cumulative values of the voltage within the time windows on both sides of the duration. Therefore, the relationship between the comparison relationship of the cumulative values of the voltage within the time windows on both sides of the duration and the operating state of the motor rotor can also be determined by the R & D personnel based on the structure of the single-phase motor or the experimental results.

[0033] The present invention provides a method for judging the starting direction of a motor. The method for judging the starting direction of the motor 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 method for judging the starting direction of the motor includes: when the motor speed reaches a preset speed, suspending the first phase and the second phase 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 according to the first-phase voltage, and judging whether the motor is in a forward rotation state or a reverse rotation state according to the cumulative value of the first-phase voltage within the time windows. The present invention solves the problem of obtaining the rotation direction of the motor rotor without a position sensor by obtaining the voltages of the first phase and the second phase of the inverter and judging the operating state of the motor by detecting the cumulative values of the voltage within the time windows on both sides of the duration. Based on the comparison of the cumulative values of the voltage within the time windows (for example, when rotating forward, the difference between the cumulative values of the two windows shows a specific pattern, and when rotating in reverse, the pattern is opposite), the rotation direction can be quickly determined directly by the magnitude relationship of the numerical values. This design does not require a complex algorithm, reduces the calculation amount, and makes the control strategy more efficient.

[0034] The forward rotation direction of the motor can be selected artificially. The present invention does not limit the relationship between the comparison relationship of the cumulative values of the voltage within the time windows 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 within the time window on the right side of the duration being greater than the cumulative value of the voltage within the time window on the left side of the duration. The judging whether the motor is in a forward rotation or a reverse rotation state according to the cumulative values of the voltage within the time windows on both sides of the duration specifically includes: If the cumulative value of the first-phase voltage values within the time window on the right side of the first duration is greater than the cumulative value of the first-phase voltage values within the time window on the left side of the first duration, the motor is in a forward rotation state; If the cumulative value of the first-phase voltage values within the time window on the right side of the first duration is less than the cumulative value of the first-phase voltage values within the time window on the left side of the first duration, the motor is in a reverse rotation state.

[0035] It should be noted that the voltage waveform within the first duration represents the variation trend of the voltage value of the first phase or the second phase over time. The right time window is later in time than the left time window. As Figure 5 shown, Figure 5 In an example, it is a voltage waveform diagram of the first phase voltage of the inverter when the motor rotor rotates forward. Here, it should be noted that within a duration, there are two time windows. The left time window refers to the time window to the left of the midpoint of the duration with the midpoint of the duration as the demarcation line; the right time window refers to the time window to the right of the midpoint of the duration with the midpoint of the duration as the demarcation line. As Figure 5 and Figure 6 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.

[0036] It should be explained that when the first phase and the second phase of the inverter are floating, assuming that the motor speed does not change suddenly, the waveforms of the voltage values of the first phase and the second phase of the inverter are similar, and there are differences in phase, as Figure 2 shown. To further reduce the detection error and avoid obtaining an incorrect motor rotor state due to the single-phase voltage detection error. In the second embodiment of the present invention, when the motor speed reaches the first preset speed value, the first phase and the second phase of the inverter are made floating, and then it includes: Step S40: Detect the voltage of the first phase to obtain the first-phase voltage value, and detect the voltage of the second phase to obtain the second-phase voltage value; Step S50: Based on the first-phase voltage and the second-phase voltage, obtain the first duration and the second duration; within the first duration, the first-phase voltage value is greater than the preset voltage value; within the second duration, the second-phase voltage value is greater than the preset voltage value; Step S60: According to the comparison relationship of the cumulative values of the first-phase voltage values within the two time windows of the first duration, and the comparison relationship of the cumulative values of the second-phase voltage values within the two time windows of the second duration, determine whether the motor is in the forward rotation state or the reverse rotation state.

[0037] In the second embodiment, the voltage values of the first phase and the second phase of the inverter are detected, and whether the first-phase voltage waveform and the second-phase voltage waveform conform to the voltage waveforms corresponding to the forward rotation or reverse rotation of the motor rotor is determined through the first-phase voltage waveform and the second-phase voltage waveform. Combining the above description, it is easy to understand that the voltage waveforms corresponding to the forward rotation and reverse rotation of the motor rotor are determined by the R & D personnel.

[0038] It should be noted that asFigure 6 As shown, in the detection mode of the motor, by obtaining the operating state of the motor according to the first-phase voltage and the second-phase voltage respectively, repetitive verification is carried out to ensure that the obtained operating state of the motor is correct. First, according to the first-phase voltage and the second-phase voltage, a first duration and a second duration are obtained. Specifically, within the first duration, the first-phase voltage is greater than a preset voltage value; within the second duration, the second-phase voltage is greater than the preset voltage value. It should be noted that when the phase voltage is floating and the motor rotates freely, there may be external forces that cause the motor to accelerate or decelerate, interfering with the back electromotive force signal. Generally, the motor and its load have a certain degree of inertia. Therefore, when the external force is within a certain range, the present invention is applicable. The specific applicability needs to be determined by the user according to the experimental results based on the degree of back electromotive force asymmetry and the degree of change in rotational speed.

[0039] According to the comparison relationship of the cumulative values of the first-phase voltage values within the two time windows on both sides of the first duration, the operating state of the motor corresponding to the first-phase voltage waveform is obtained; according to the comparison relationship of the cumulative values of the second-phase voltage values within the two time windows on both sides of the second duration, the operating state of the motor corresponding to the second-phase voltage waveform is obtained. When the operating states of the motor corresponding to the first-phase voltage waveform and the second-phase voltage waveform are the same, it is determined that the motor is in the operating state. When the operating states of the motor corresponding to the first-phase voltage waveform and the second-phase voltage waveform are different, it is determined that the judgment of the operating state of the motor this time is invalid.

[0040] In an example, the judging whether the motor is in the forward rotation state or the reverse rotation state according to the comparison relationship of the cumulative values of the first-phase voltage values within the two time windows on both sides of the first duration and the comparison relationship of the cumulative values of the second-phase voltage values within the two time windows on both sides of the second duration includes: If the cumulative value of the first-phase voltage values within the right time window of the first duration is greater than the cumulative value of the first-phase voltage values within the left time window of the first duration, and the cumulative value of the second-phase voltage values within the right time window of the second duration is greater than the cumulative value of the second-phase voltage values within the left time window of the second duration, then the motor is in the forward rotation state; If the cumulative value of the first-phase voltage values within the right time window of the first duration is less than the cumulative value of the first-phase voltage values within the left time window of the first duration, and the cumulative value of the second-phase voltage values within the right time window of the second duration is less than the cumulative value of the second-phase voltage values within the left time window of the second duration, then the motor is in the reverse rotation state.

[0041] In addition, it should be noted that before floating the first phase and the second phase of the inverter when the motor speed reaches the preset speed, it includes: Apply voltage signals with a preset duty cycle to the first phase and the second phase of the inverter alternately.

[0042] It is easy to understand that to determine the starting direction of the motor, it is necessary to make the determination after the motor has been successfully driven. Refer to Figure 7 , to increase the speed of the motor from zero to a preset speed, it is necessary to alternately apply voltage signals with a preset duty cycle to the first phase and the second phase of the inverter to increase the speed of the motor. In the detection mode, the first phase and the second phase of the inverter are left floating, and the voltage values of the first phase and the second phase of the inverter are detected.

[0043] The present invention determines the operating state of the motor based on the cumulative values of the voltage values within the time windows on both sides of the duration. It is easy to understand that the cumulative value of the voltage values within the time window is related to the duration of the time window. In the third embodiment of the present invention, the durations of the time windows on both sides of the duration are equal, and the duration is a set multiple of the carrier period of the control signal received by the inverter.

[0044] It should be noted that the equal durations 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, and the window duration is in a multiple relationship with the carrier period, which can ensure that the position of each sampling window in the signal period is fixed. For example, regardless of how the motor speed changes, the sampling is always aligned with the stable stage of the carrier signal, avoiding signal acquisition deviation caused by timing misalignment and ensuring the consistency of the back electromotive force waveform detection. The set multiple can be determined by the R & D personnel.

[0045] As Figure 5 shown, Figure 5 shows the waveform change of the voltage of the first phase of the inverter within a duration in an example. It is easy to understand that the waveform of the first-phase voltage has the following two situations according to the different rotation directions of the motor rotor: First, the voltage of the first phase rises steeply first, then rises slowly, and then drops steeply. The midpoint of the slow-rising stage is the midpoint of this duration.

[0046] Second, the voltage of the first phase rises steeply first, then drops slowly, and then drops steeply. The midpoint of the slow-dropping stage is the midpoint of this duration.

[0047] Whether it is possible to accurately identify that the voltage waveform has a slow-rising stage or a slow-dropping stage is the key to determining the operating state of the motor. It is necessary for the time windows on both sides of the duration to fall within the slow-rising stage or the slow-dropping stage. 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 symmetric with the time window on the right side of the duration. It has the following core advantages: First, it can accurately capture the back electromotive force characteristics; the back electromotive force waveform shows asymmetric characteristics during forward and reverse rotations (for example, "first low then high" during forward rotation and "first high then low" during reverse rotation). The symmetric window design can respectively cover the key stages of the waveform and completely collect the core area of the back electromotive force change. For example, during forward rotation, the characteristics of the initial low-amplitude segment and the subsequent high-amplitude segment of the waveform can be obtained simultaneously through the symmetric window, providing a more comprehensive basis for steering judgment.

[0048] Second, it suppresses interference and improves reliability; during actual operation, the back electromotive force may be interfered by non-ideal factors such as harmonics and noise. The symmetric window makes the sampling points evenly distributed on the waveform. By comparing the integration results of the two windows, the influence of some random interference can be offset. When a certain window is contaminated by instantaneous noise, the symmetric sampling of the other window can balance the error and ensure the stability and reliability of the detection result.

[0049] As Figure 5 shown, the voltage waveform in the slow-rising stage or the slow-falling stage should be preferably taken; wherein, the duration from the midpoint of the left time window of the first duration to the midpoint of the duration is the first interval duration; the duration from the midpoint of the right time window 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.

[0050] 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 stage or the slow-falling stage. In one example, the absolute value of the first interval duration is 1 / 8 to 3 / 8 of the duration.

[0051] The present invention also proposes a storage medium, which stores a motor starting direction judgment program. When the motor starting direction judgment program is run by a processor, the motor starting direction judgment method is implemented. The storage medium can be RAM, ROM, EPROM or EEPROM, etc.

[0052] Referring to Figure 8 , the present invention also proposes a motor control system, which includes: Inverter 3, control module 1, motor, power supply and voltage sampling module 2; The first phase and the second phase of the inverter 3 are respectively connected to the first end and the second end of the motor; 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; The voltage sampling module 2 is configured 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 the same to the control module 1; The control module 1 is configured to determine whether the motor is in the forward rotation state or the 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.

[0053] Wherein, the control module 1 may include controllers such as MCU, FPGA, SOC, PLC, CPU or DSP. The voltage sampling module 2 may perform voltage sampling by using a resistor voltage division circuit.

[0054] 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 the power supply, and 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 cutoff of the first to fourth switching devices.

[0055] In addition, since there is no position sensor in the motor control system, the rotor speed cannot be obtained through the position sensor. The control module 1 is further configured to obtain the motor rotor speed according to the voltage of the first phase of the inverter 3 and the voltage of the second phase of the inverter 3; specifically, by obtaining the commutation moments of the first-phase voltage and the second-phase voltage, determining the voltage period, and further obtaining the motor rotor speed.

[0056] The control module 1 is further configured to control the first phase and the second phase of the inverter 3 to be floating when the motor speed reaches a preset speed. Specifically, by outputting a control signal to the controlled ends of the first to fourth switching devices in the inverter 3, the first to fourth switching devices are controlled to turn off, so as to achieve the floating of the first phase and the second phase of the inverter 3.

[0057] For the specific steps of the motor starting direction judgment method, refer to the above embodiments. Since the present 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 elaborated here one by one. The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields are all 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 a preset speed, the first phase and the second phase of the inverter are suspended; Detecting the voltage of the first phase to obtain a first phase voltage value; 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.

2. The method for determining the motor starting direction according to claim 1, characterized in that: The step of acquiring 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; The 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 2, characterized in that: 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.

4. The method for determining the motor starting direction according to claim 2, characterized in that: 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; The absolute value of the first interval duration is equal to the absolute value of the second interval duration.

5. The method for determining the motor starting direction according to claim 1, characterized in that: The step of 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: If the accumulated value of the first phase voltage value in the time window on the right side of the first duration is greater than the accumulated value of the first phase voltage value in the time window on the left side of the first duration, the motor is in a forward rotation state; If the accumulated value of the first phase voltage value in the time window on the right side of the first duration is less than the accumulated value of the first phase voltage value in the time window on the left side of the first duration, the motor is in a reverse state.

6. The method for determining the motor starting direction according to claim 1, characterized in that: 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 a preset voltage value; Based on the comparison relationship between the accumulated values ​​of the first phase voltage values ​​in the time windows on both sides of the first duration and the comparison relationship between the accumulated 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.

7. The method for determining the motor starting direction according to claim 6, characterized in that: The step of judging whether the motor is in a forward rotation state or a reverse rotation state according to a 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 cumulative values ​​of the second phase voltage values ​​in the 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.

8. 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 7 are implemented.

9. A motor control system, characterized in that: The motor control system comprises: 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.

10. The motor control system according to claim 9, characterized in that: The control module is further used to obtain the motor rotor speed according to the voltage of the first phase of the inverter and the voltage of the second phase of the inverter; The control module is further used to control the first phase and the second phase of the inverter to be suspended when the motor speed reaches a preset speed.

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