Motor starting state detection method and controller based on single resistor current sampling

Abstract

The present invention discloses a motor starting state detection method and controller based on single-resistance current sampling. The motor starting state detection method includes: turning on the lower bridge of the three-phase U, V, and W motor, alternately applying a voltage signal with a preset duty cycle to any two phases of the three-phase motor, and detecting the phase current of the two phases respectively; judging whether the motor is in a stationary or forward / reverse rotation state based on the phase current amplitude of the two phases; if the motor is in a forward / reverse rotation state, recording the current zero-crossing moment of the two phases respectively based on the phase current waveform of the two phases; judging whether the motor is in a forward rotation state or a reverse rotation state based on the current zero-crossing moment of the two phases. The present invention judges whether the motor is in a stationary, forward rotation state, or reverse rotation state by comparing the amplitude and current zero-crossing moment of the two-phase phase current detected when the three-phase lower bridge of the motor is turned on, and using the time interval between specific current zero-crossing moments in different rotation directions.

Description

Technical Field

[0001] The present invention relates to the technical field of motor starting, and in particular to a motor starting state detection method and controller based on single-resistor current sampling. Background Art

[0002] Sensorless permanent magnet synchronous motor control systems are widely used in various scenarios. Detecting motor speed and position information before starting the motor plays a crucial role in ensuring reliable startup and is a key technology in sensorless motor control systems. Conventional technology uses hardware circuits to collect the motor's back-EMF and determine motor speed and position based on the relationship between the back-EMFs. This is known as the hardware back-EMF method.

[0003] However, hardware circuits will increase costs and increase the complexity of board layout. Determining the initial state of the motor before starting is a must before the motor starts, which can improve the success rate of starting. Adjusting the starting method according to the initial state of the motor can make the transition of the motor during the starting process smoother. In particular, the motor drive system using single-resistor current sampling cannot obtain the phase current during the three-axle braking using conventional methods, making the detection of the motor's starting state more difficult. Currently, there is an urgent need to solve the problem of obtaining the initial state of the motor before starting without hardware back-EMF circuits and single-resistor current sampling. Summary of the Invention

[0004] The main purpose of the present invention is to provide a motor starting state detection method and controller based on single resistor current sampling, aiming to obtain the initial state of the motor before starting.

[0005] To achieve the above objectives, the present invention proposes a motor starting state detection method based on single resistor current sampling, the motor state detection method comprising:

[0006] Turn on the lower bridges of the three-phase U, V, and W of the motor, alternately apply voltage signals with a preset duty cycle to any two phases of the three-phase motor, and detect the phase currents of the two phases respectively;

[0007] According to the phase current amplitudes of the two phases, it is determined whether the motor is in a stationary state or a forward or reverse rotation state;

[0008] If the motor is in the forward and reverse rotation state, the current zero-crossing moments of the two phases are recorded respectively according to the phase current waveforms of the two phases;

[0009] According to the zero-crossing moment of the current of the two phases, it is determined whether the motor is in the forward rotation state or the reverse rotation state.

[0010] Optionally, the alternately applying a voltage signal with a preset duty cycle to any two phases of the three-phase motor includes:

[0011] Applying a voltage signal with a preset duty cycle to the U phase, applying a voltage signal with a preset duty cycle to the V phase after a preset first sampling interval, and applying a voltage signal with a preset duty cycle to the U phase after a preset second sampling interval, and repeating the alternating process;

[0012] The detecting the phase currents of the two phases respectively includes:

[0013] The U-phase current is collected when a voltage signal with a preset duty cycle is applied to the U-phase, and the V-phase current is collected when a voltage signal with a preset duty cycle is applied to the V-phase.

[0014] Optionally, judging whether the motor is in a stationary state or a forward / reverse rotation state according to the amplitudes of the two-phase currents includes:

[0015] The maximum value of the phase current amplitude of the two phases within the preset first time is recorded as the first current value, and the first current value is compared with the preset static current threshold. If the first current value is less than the preset static current threshold, it is determined that the motor is in a static state; otherwise, it is determined that the motor is in a forward or reverse rotation state.

[0016] Optionally, recording the current zero-crossing moments of the two phases respectively according to the phase current waveforms of the two phases includes:

[0017] When the U-phase current value at the previous moment is negative and the U-phase current value at the current moment is positive, the current moment is recorded as the first U-phase current zero-crossing moment;

[0018] When the V-phase current value at the previous moment is negative and the V-phase current value at the current moment is positive, the current moment is recorded as the first V-phase current zero-crossing moment;

[0019] When the U-phase current changes from a positive value to a negative value, the moment when it changes from a negative value to a positive value again is recorded as the second U-phase current zero-crossing moment.

[0020] Optionally, judging whether the motor is in a forward rotation state or a reverse rotation state according to the zero-crossing moment of the two-phase current includes:

[0021] Obtaining a first zero-crossing time interval according to the first V-phase current zero-crossing time and the first U-phase current zero-crossing time;

[0022] Obtaining a second zero-crossing time interval according to the second U-phase current zero-crossing time and the first V-phase current zero-crossing time;

[0023] According to the comparison result of the first zero-crossing time interval and the second zero-crossing time interval, it is determined whether the motor is in the forward rotation state or the reverse rotation state.

[0024] Optionally, judging whether the motor is in the forward rotation state or the reverse rotation state according to a comparison result of the first zero-crossing time interval and the second zero-crossing time interval includes:

[0025] If the first zero-crossing time interval is greater than the second zero-crossing time interval, determining that the motor is in a reverse state;

[0026] If the first zero-crossing time interval is smaller than the second zero-crossing time interval, it is determined that the motor is in the forward rotation state.

[0027] Optionally, the motor state detection method further includes:

[0028] The rotational speed of the motor rotor is calculated according to the first zero-crossing time interval and the second zero-crossing time interval.

[0029] Optionally, the step of determining whether the motor is in a forward rotation state or a reverse rotation state further includes:

[0030] According to the forward rotation state or reverse rotation state of the motor, the motor position is determined at the next U-phase current zero-crossing moment.

[0031] Optionally, if the motor is in the forward rotation state, the electrical angle corresponding to the next U-phase current zero-crossing moment is set as the preset first electrical angle;

[0032] If the motor is in a reverse state, the electrical angle corresponding to the next U-phase current zero-crossing moment is set as the preset second electrical angle.

[0033] The present invention also proposes a controller, which includes: a processor and a storage medium, wherein the storage medium stores a motor starting state detection program based on single-resistor current sampling; after the motor starting state detection program based on single-resistor current sampling is executed by the processor, the corresponding steps of the motor starting state detection method based on single-resistor current sampling are implemented.

[0034] The present invention discloses a motor starting state detection method and controller based on single-resistance current sampling. The motor starting state detection method includes: turning on the lower bridge of the three-phase U, V, and W of the motor, alternately applying a voltage signal with a preset duty cycle to any two phases of the three-phase motor, and detecting the phase currents of the two phases respectively; judging whether the motor is in a stationary or forward / reverse rotation state based on the phase current amplitudes of the two phases; if the motor is in a forward / reverse rotation state, recording the current zero-crossing moments of the two phases respectively based on the phase current waveforms of the two phases; judging whether the motor is in a forward rotation state or a reverse rotation state based on the current zero-crossing moments of the two phases. The present invention judges whether the motor is in a forward rotation state or a reverse rotation state by comparing the time relationship between the specific current zero-crossing moments of different rotation directions based on the current zero-crossing moments of the two phases when the lower bridge of the three phases of the motor is turned on. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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.

[0036] Figure 1 This is a schematic diagram of the steps of a first embodiment of a method for detecting a motor starting state based on single-resistor current sampling according to the present invention;

[0037] Figure 2 Schematic diagram of UVW rotating phase currents according to the first embodiment of the motor starting state detection method based on single resistor current sampling of the present invention;

[0038] Figure 3 A schematic diagram of the WVU rotating phase current of the first embodiment of the motor starting state detection method based on single resistor current sampling of the present invention;

[0039] Figure 4 This is a phase current detection schematic diagram of a second embodiment of a motor starting state detection method based on single resistor current sampling according to the present invention;

[0040] Figure 5 This is a schematic diagram of the first step of a third embodiment of a method for detecting a motor starting state based on single-resistor current sampling according to the present invention;

[0041] Figure 6 This is a schematic diagram of the second step of the third embodiment of the motor starting state detection method based on single-resistor current sampling of the present invention.

[0042] 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

[0043] 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.

[0044] 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.

[0045] 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 be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0046] 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.

[0047] In order to solve the problem of how to obtain the initial state of the motor in the absence of hardware back electromotive force circuit and single resistor current sampling, the present invention proposes a motor starting state detection method and controller based on single resistor current sampling. In the first embodiment of the present invention, referring to Figure 1 , the motor state detection method includes:

[0048] Step S10: Turn on the lower bridges of the three-phase U, V, and W motors, alternately apply voltage signals with a preset duty cycle to any two phases of the three-phase motor, and detect the phase currents of the two phases respectively;

[0049] Step S20: Determine whether the motor is in a stationary state or in a forward or reverse rotation state based on the two-phase current amplitudes.

[0050] Step S30: If the motor is in the forward and reverse rotation states, record the current zero-crossing moments of the two phases according to the two-phase current waveforms;

[0051] Step S40: Determine whether the motor is in a forward rotation state or a reverse rotation state according to the zero-crossing moment of the two-phase current.

[0052] It should be noted that the motor's rotor may have one of three states: forward rotation, reverse rotation, and stationary. The present invention uses two phases of a three-phase motor to detect the current in both phases. It is easy to understand that in the initial state, when the motor is not started, the motor rotor rotates forward or reverse under the action of an external force. Furthermore, it should be noted that when the motor rotor rotates, a back electromotive force is generated. If the controller turns on the three lower bridges, this back electromotive force will generate a corresponding current. In the structure of a three-phase motor, the three phases are spaced at 120° phase angle intervals. Adjacent phases in a three-phase motor have different lead phases during forward and reverse rotation. For example, assuming that the motor rotor rotates in the UVW direction during forward rotation, when detecting the U-phase current and the V-phase current, the U-phase current will lead the V-phase current by 120°. Similarly, when detecting the U-phase current and the W-phase current, the U-phase current will lead the W-phase current by 240°. When detecting the V-phase current and the W-phase current, the V-phase current will lead the W-phase current by 120°. It is easy to understand that since the motor rotor rotates 360 degrees in one revolution, that is, one cycle is 360 degrees, 240 degrees ahead can also be regarded as 120 degrees behind.

[0053] It should be noted that the present invention detects the phase currents of any two phases in a three-phase motor. In specific applications, there are two methods: one is to fixedly detect the currents of two phases of the three phases of the motor, such as the U-phase current and the V-phase current; and make a judgment based on the detected U-phase current and the V-phase current. The second method is to store the judgment logic of the following three combinations in a database: U-phase and V-phase, U-phase and W-phase, and V-phase and W-phase. After selecting two phases of the three phases of the motor, the corresponding judgment logic is selected based on the selected two phases.

[0054] It is easy to understand that since the present invention uses two-phase currents in a three-phase motor to determine whether the motor is in forward or reverse rotation. Regardless of which combination is used, the phase difference between the two-phase currents changes as the forward and reverse rotation directions of the motor change. For example: if U-phase current and V-phase current are used, assuming that when the motor is in the forward rotation state, the U-phase current leads the V-phase current by 120°, correspondingly, when the motor is in the reverse state, the rotation direction of the motor rotor changes, and the V-phase current leads the U-phase current by 120°. The present invention determines the phase sequence relationship of the two-phase currents based on the zero-crossing moment of the two-phase currents, thereby determining whether the motor is in the forward rotation state or the reverse rotation state.

[0055] The motor may be in forward rotation, reverse rotation, or stationary state. When the motor is stationary, determining whether the motor is in forward rotation or reverse rotation based on the zero-crossing moments of the two-phase currents may be erroneous. Furthermore, obtaining and calculating the zero-crossing moments of the currents when the motor is stationary wastes computing resources.

[0056] It's crucial to determine whether the motor is stationary before starting. When a voltage signal with a preset duty cycle is applied to the motor's U and V phases, if the motor is stationary, the current in its windings will be affected by the motor's inherent characteristics (such as resistance and inductance) and the applied voltage, resulting in a relatively low current. By comparing the maximum absolute value of the U and V phase currents detected within a preset first time interval with a preset stationary current threshold, if the maximum value is less than the threshold, the motor is determined to be stationary. Conversely, if the maximum value is greater than the threshold, the motor is rotating in forward or reverse directions. This determination provides a foundation for subsequent control strategies. Only by accurately determining the motor's initial state can the stability and reliability of the motor startup process be ensured. The preset first time interval and the preset stationary current threshold can be determined by R&D personnel.

[0057] Reference Figure 2 , Figure 2 The three-phase current diagram is shown when the motor rotor rotates in the UVW direction and the three lower bridge brakes are opened. Figure 2 In the example, the U-phase current leads the V-phase current by 120°, and the V-phase current leads the W-phase current by 120°. The U-phase current zero-crossing times are recorded as U1, U2, and U3, respectively. The V-phase current zero-crossing times are recorded as V1 and V2, respectively. The W-phase current zero-crossing times are recorded as W1 and W2, respectively.

[0058] If we select the U and V phases of the motor, as shown in the figure, the time difference between U1 and V1 is smaller than the time difference between U3 and V1. Specifically, because the U-phase current leads the V-phase current by 120°, the time difference between U1 and V1 corresponds to a phase angle of 120°; the time difference between U3 and V1 corresponds to a phase angle of 240°. It is easy to see that the time difference between U1 and V1 is smaller than the time difference between U3 and V1. This conclusion indicates that the motor rotor rotates in the UVW direction, meaning that the motor is in forward or reverse rotation. Alternatively, the time difference between U1 and V2, and the time difference between U3 and V2, can be used to determine whether the motor is in forward or reverse rotation. Since U1 and U3 represent the start and end times of the U-phase current within a cycle, the motor rotor speed can be determined based on the time difference between U3 and U1.

[0059] It is easy to understand that the judgment logic for selecting the U phase and the W phase, or the V phase and the W phase in the three phases of the motor is the same as above, and will not be introduced here one by one. Figure 2 Using the U-phase current as the reference, plot the phase difference between the V-phase and W-phase currents relative to the U-phase. For ease of observation, select the phase where the two phase current zero crossings are recorded as the reference. When another two-phase combination is selected, reselect the reference and plot accordingly.

[0060] Reference Figure 3 , Figure 3 The diagram below shows the three-phase current when the motor rotor rotates in the direction of WVU and the three lower bridge brakes are opened. Figure 3 In the example, the W-phase current leads the V-phase current by 120°, and the V-phase current leads the U-phase current by 120°.

[0061] If we select the U and V phases of the motor's three phases, as shown in the figure, the time difference between U1 and V2 is greater than the time difference between U3 and V2. Specifically, since the V-phase current leads the U-phase current by 120°, or correspondingly, the U-phase current leads the V-phase current by 240°, the time difference between U1 and V2 is the duration corresponding to a phase angle of 240°; the time difference between U3 and V2 is the duration corresponding to a phase angle of 120°. It is easy to see that the time difference between U1 and V2 is greater than the time difference between U3 and V2. When this conclusion is reached, it can be concluded that the motor rotor rotates in the WVU direction, that is, the motor is in the reverse direction.

[0062] Since U1 and U3 are the start and end times of the U-phase current in one cycle, the speed of the motor rotor can be obtained based on the time difference between U3 and U1.

[0063] It is easy to understand that the judgment logic for selecting the U phase and the W phase among the three phases of the motor, or the V phase and the W phase among the three phases of the motor is the same as above, and will not be introduced one by one here. Figure 3 Using the U-phase current as the reference, plot the phase difference between the V-phase and W-phase currents relative to the U-phase. For ease of observation, select the phase where the two phase current zero crossings are recorded as the reference. When another two-phase combination is selected, reselect the reference and plot accordingly.

[0064] In order to achieve effective detection of the starting state of the motor, the present invention turns on the lower bridges of the three phases U, V, and W of the motor, and alternately applies a voltage signal with a preset duty cycle to any two phases of the three-phase motor. After the lower bridges of the three phases U, V, and W are turned on, if the motor is in a rotating state, the back electromotive force generated by the rotation acts on the winding to generate current. If the motor is in a stationary state, the current is zero. Since the three-phase composite current is always equal to zero, no current flows through the sampling resistor of the bus branch, and the controller cannot obtain the phase current information. At this time, a voltage signal with a preset duty cycle is alternately applied to any two phases of the three-phase motor, and the corresponding phase current flows through the bus sampling resistor. The controller sets a suitable sampling point to obtain the corresponding phase current information. It should be noted that, if Figure 4 As shown, while applying a voltage signal with a preset duty cycle, the phase current of the phase is detected. The preset duty cycle is determined by the R&D personnel; the high level application time corresponding to the preset duty cycle shall not be less than the minimum sampling window T min The minimum sampling window is generally set to the sum of the dead time, the phase current voltage drop establishment time on the sampling resistor and the ADC sampling time.

[0065] The present invention discloses a motor starting state detection method based on single-resistance current sampling, the motor starting state detection method comprising: turning on the motor U, V, and W three-phase lower bridge, alternately applying a voltage signal with a preset duty cycle to any two phases of the three-phase motor, and detecting the phase currents of the two phases respectively; judging whether the motor is in a stationary or forward / reverse rotation state according to the phase current amplitudes of the two phases; if the motor is in a forward / reverse rotation state, recording the current zero-crossing moments of the two phases respectively according to the phase current waveforms of the two phases; judging whether the motor is in a forward rotation state or a reverse rotation state according to the current zero-crossing moments of the two phases. The present invention judges whether the motor is in a forward rotation state or a reverse rotation state by comparing the time relationship between the specific current zero-crossing moments of different rotation directions and the current zero-crossing moments of the two phases when the motor three-phase lower bridge is turned on.

[0066] In a second embodiment of the present invention, a voltage is applied to the U-phase and the V-phase of the three-phase motor and a phase current is detected. The alternate application of a voltage signal with a preset duty cycle to any two phases of the three-phase motor comprises:

[0067] Apply a voltage signal with a preset duty cycle to the U phase, and after a preset first sampling interval, apply a voltage signal with a preset duty cycle to the V phase, and after a preset second sampling interval, apply a voltage signal with a preset duty cycle to the U phase, and repeat the alternation. Figure 4 , alternately applying a voltage signal with a preset duty cycle to the U phase and the V phase, the preset first sampling interval time T i1The time interval between the adjacent U-phase and V-phase voltage application, wherein the time when the U-phase voltage is applied is earlier than the time when the V-phase voltage is applied. The preset second sampling interval time T i2 is the time interval between the adjacent V-phase and U-phase voltage application, wherein the time when the V-phase voltage is applied is earlier than the time when the U-phase voltage is applied. i1 +T i2 The sampling of the U and V phase currents is completed once within the time, that is, the current sampling frequency is fi=1 / ( T i1 +T i2 ). According to Shannon's sampling theorem, the sampling frequency is required to be no less than twice the phase current frequency. In practical applications, the frequency of the phase current is related to the maximum speed of the motor in the forward and reverse states. It is recommended that the current sampling frequency be more than 6 times the maximum speed before the motor starts, converted into electrical frequency. At the same time, the bus voltage may increase during current sampling and decrease when the three lower bridges are fully open. If the sampling frequency is too high, the bus voltage may rise too high, triggering overvoltage protection. Therefore, it is necessary to select a suitable T in practical applications. i1 With T i2 value.

[0068] The detecting the phase currents of the two phases respectively includes:

[0069] The U-phase current is collected when a voltage signal with a preset duty cycle is applied to the U-phase, and the V-phase current is collected when a voltage signal with a preset duty cycle is applied to the V-phase.

[0070] Reference Figure 4 The present invention detects the U-phase current when a voltage signal is applied to the U-phase; and detects the V-phase current when a voltage signal is applied to the V-phase. It is easy to understand that only by applying voltage and allowing the corresponding phase current to pass through the sampling resistor of the busbar branch can the operating status of the motor be analyzed by detecting the current, providing valuable information for motor startup control. When no voltage is applied, the current passing through the busbar branch sampling resistor is always zero, and the phase current cannot be detected.

[0071] As can be seen from the first embodiment of the present invention, the current zero-crossing moment of any two phases in a three-phase motor can be used to determine whether the motor is in the forward rotation state or the reverse rotation state. The third embodiment of the present invention uses the U phase and the V phase as an example to specifically determine whether the motor is in the forward rotation state or the reverse rotation state based on the U phase and the V phase.

[0072] Reference Figure 5 In a third embodiment of the present invention, recording the current zero-crossing moments of the two phases according to the phase current waveforms of the two phases includes:

[0073] Step S310: When the U-phase current value at the previous moment is negative and the U-phase current value at the current moment is positive, record the current moment as the first U-phase current zero-crossing moment;

[0074] Step S320: When the V-phase current value at the previous moment is negative and the V-phase current value at the current moment is positive, record the current moment as the first V-phase current zero-crossing moment;

[0075] Step S330: After the U-phase current changes from a positive value to a negative value, the moment when the U-phase current changes from a negative value to a positive value again is recorded as the second U-phase current zero-crossing moment.

[0076] Reference Figure 2 and Figure 3 , Figure 2 and Figure 3 The zero-crossing moment of the U phase and the zero-crossing moment of the V phase in a cycle are shown in FIG. This embodiment selects the zero-crossing moment when the current changes from a negative value to a positive value. Specifically, the zero-crossing moment of the first U phase current is at U1, and the zero-crossing moment of the second U phase current is at U3. The zero-crossing moment of the first U phase current is at the beginning of a cycle, and the zero-crossing moment of the second U phase current is at the end of a cycle. The zero-crossing moment of the first V phase current is Figure 2 V1 and Figure 3 It is easy to understand that the speed of the motor rotor can be calculated based on the first U-phase current zero-crossing moment and the second U-phase current zero-crossing moment.

[0077] When the motor rotor is in UVW direction, such as Figure 2 As shown, the time between the first U-phase current zero-crossing moment and the first V-phase current zero-crossing moment corresponds to a phase difference of 120°. The time between the first V-phase current zero-crossing moment and the second U-phase current zero-crossing moment corresponds to a phase difference of 240°.

[0078] When the motor rotor is in WVU rotation direction, such as Figure 3 As shown, the time between the first U-phase current zero-crossing moment and the first V-phase current zero-crossing moment corresponds to a phase difference of 240°. The time between the first V-phase current zero-crossing moment and the second U-phase current zero-crossing moment corresponds to a phase difference of 120°.

[0079] Reference Figure 6 , judging whether the motor is in a forward rotation state or a reverse rotation state according to the zero-crossing moment of the two-phase current, includes:

[0080] Step S410: Obtain a first zero-crossing time interval according to the first V-phase current zero-crossing time and the first U-phase current zero-crossing time;

[0081] Step S420: Obtain a second zero-crossing time interval according to the second U-phase current zero-crossing time and the first V-phase current zero-crossing time;

[0082] Step S430: Determine whether the motor is in a forward rotation state or a reverse rotation state based on a comparison result of the first zero-crossing time interval and the second zero-crossing time interval.

[0083] It should be noted that the first zero-crossing time interval is the time between the first V-phase current zero-crossing time and the first U-phase current zero-crossing time, and the calculation formula is: T1=T v1 –T u1 Wherein, T1 is the first zero-crossing time interval, T v1 is the zero-crossing moment of the first V-phase current, T u1 is the time when the first U-phase current crosses zero. Similarly, the second zero-crossing time interval is the time between the second U-phase current zero-crossing time and the first V-phase current zero-crossing time, and the calculation formula is: T2=T u2 –T v1 ; Wherein, T2 is the second zero-crossing time interval, T u2 is the zero-crossing moment of the second U-phase current.

[0084] According to the comparison result of the first zero-crossing time interval and the second zero-crossing time interval, it is easy to understand that Figure 2 As shown, if the motor rotor rotates according to UVW, the first zero-crossing time interval is smaller than the second zero-crossing time interval. Figure 3 As shown, if the motor rotor rotates according to WVU, the first zero-crossing time interval is greater than the second zero-crossing time interval.

[0085] Therefore, the rotation direction of the motor rotor can be obtained according to the comparison result of the first zero-crossing time interval and the second zero-crossing time interval.

[0086] In one example, it is defined that the motor rotor rotates according to UVW as forward rotation, and the motor rotor rotates according to WVU as reverse rotation.

[0087] The step of determining whether the motor is in a forward rotation state or a reverse rotation state according to a comparison result of the first zero-crossing time interval and the second zero-crossing time interval includes:

[0088] If the first zero-crossing time interval is greater than the second zero-crossing time interval, it is determined that the motor is in a forward rotation state;

[0089] If the first zero-crossing time interval is smaller than the second zero-crossing time interval, it is determined that the motor is in a reverse state.

[0090] The motor state detection method further includes:

[0091] The rotational speed of the motor rotor is calculated according to the first zero-crossing time interval and the second zero-crossing time interval.

[0092] It should be noted that the length of a cycle can be obtained by adding the first zero-crossing time interval and the second zero-crossing time interval. That is, T=T1+T2. Where T is the length of a cycle. The formula for calculating the speed of the motor rotor is: , where n is the motor rotor speed in rpm, and p is the number of motor pole pairs.

[0093] It should be noted that within one cycle, the U-phase current has two current zero-crossing moments, and the current changes from positive to negative and from negative to positive, respectively. The method of determining whether the motor is in a forward rotation state or a reverse rotation state then includes: determining the motor position at the next U-phase current zero-crossing moment according to the forward rotation state or reverse rotation state of the motor. After obtaining the rotation direction of the motor rotor and based on the next U-phase current zero-crossing moment, determine the rotor position corresponding to the next U-phase current zero-crossing moment. Specifically, based on the next U-phase current zero-crossing moment, the U-phase current changes from positive to negative or from negative to positive to determine the position of the motor rotor. After obtaining the motor rotor position and the motor rotor rotation direction, a reference can be provided for motor control.

[0094] In addition, it should be pointed out that different motor parameters may cause the motor rotor to be in different positions and corresponding to different electrical angles when the U-phase current passes through zero. Taking into account that the rotor position corresponding to the U-phase current zero-crossing point changes when the motor rotor rotates forward and reverse. In order to facilitate the subsequent motor control, it is necessary to obtain the electrical angle corresponding to the U-phase current zero-crossing point. The present invention proposes a preset acquisition method. Specifically, if the motor is in a forward rotation state, the electrical angle corresponding to the next U-phase current zero-crossing point is set to a preset first electrical angle; if the motor is in a reverse rotation state, the electrical angle corresponding to the next U-phase current zero-crossing point is set to a preset second electrical angle. Research and development personnel can select appropriate preset first electrical angles and preset second electrical angles through experiments.

[0095] In addition, if the preset first electrical angle and the preset second electrical angle are determined by R&D personnel, the electrical angle of the motor can be divided according to the preset first electrical angle and the preset second electrical angle. It is easy to understand that there is an angle difference of 120° between each two phases of the U phase, V phase, and W phase of the three-phase motor; after obtaining the electrical angle corresponding to the motor rotor at the zero crossing point of the U phase, the electrical angles of other positions of the motor can be obtained.

[0096] The present invention further provides a controller comprising: a processor and a storage medium, wherein the storage medium stores a motor startup status detection program based on single-resistor current sampling; when executed by the processor, the motor startup status detection program based on single-resistor current sampling implements the steps corresponding to the motor startup status detection method based on single-resistor current sampling. Specifically, the controller may be a motor controller.

[0097] The specific steps of the motor starting state detection method based on single-resistor current sampling refer to the above embodiments. Since the controller 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 is only an optional embodiment of the present invention and does 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 direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A motor starting state detection method based on single resistor current sampling, characterized in that: The motor starting state detection method comprises: Turn on the lower bridges of the three-phase U, V, and W of the motor, alternately apply voltage signals with a preset duty cycle to any two phases of the three-phase motor, and detect the phase currents of the two phases respectively; According to the phase current amplitudes of the two phases, it is determined whether the motor is in a stationary state or a forward or reverse rotation state; If the motor is in the forward and reverse rotation state, the current zero-crossing moments of the two phases are recorded respectively according to the phase current waveforms of the two phases; According to the zero-crossing moment of the current of the two phases, it is determined whether the motor is in a forward rotation state or a reverse rotation state; The step of recording the current zero-crossing moments of the two phases according to the phase current waveforms of the two phases comprises: When the U-phase current value at the previous moment is negative and the U-phase current value at the current moment is positive, the current moment is recorded as the first U-phase current zero-crossing moment; When the V-phase current value at the previous moment is negative and the V-phase current value at the current moment is positive, the current moment is recorded as the first V-phase current zero-crossing moment; When the U-phase current changes from positive to negative, the moment when it changes from negative to positive again is recorded as the second U-phase current zero-crossing moment; The step of determining whether the motor is in a forward rotation state or a reverse rotation state according to the zero-crossing moment of the two-phase current includes: Obtaining a first zero-crossing time interval according to the first V-phase current zero-crossing time and the first U-phase current zero-crossing time; Obtaining a second zero-crossing time interval according to the second U-phase current zero-crossing time and the first V-phase current zero-crossing time; According to the comparison result of the first zero-crossing time interval and the second zero-crossing time interval, it is determined whether the motor is in the forward rotation state or the reverse rotation state.

2. The motor starting state detection method based on single resistor current sampling according to claim 1, characterized in that: The step of alternately applying a voltage signal with a preset duty cycle to any two phases of the three-phase motor includes: Applying a voltage signal with a preset duty cycle to the U phase, applying a voltage signal with a preset duty cycle to the V phase after a preset first sampling interval, and applying a voltage signal with a preset duty cycle to the U phase after a preset second sampling interval, and repeating the alternating process; The detecting the phase currents of the two phases respectively includes: The U-phase current is collected when a voltage signal with a preset duty cycle is applied to the U-phase, and the V-phase current is collected when a voltage signal with a preset duty cycle is applied to the V-phase.

3. The motor starting state detection method based on single resistor current sampling according to claim 1, characterized in that: The step of determining whether the motor is in a stationary state or in a forward or reverse rotation state based on the amplitudes of the two-phase currents includes: The maximum value of the phase current amplitude of the two phases within the preset first time is recorded as the first current value, and the first current value is compared with the preset static current threshold. If the first current value is less than the preset static current threshold, it is determined that the motor is in a static state; otherwise, it is determined that the motor is in a forward or reverse rotation state.

4. The motor starting state detection method based on single resistor current sampling according to claim 1, characterized in that: The step of determining whether the motor is in a forward rotation state or a reverse rotation state according to a comparison result of the first zero-crossing time interval and the second zero-crossing time interval includes: If the first zero-crossing time interval is greater than the second zero-crossing time interval, determining that the motor is in a reverse state; If the first zero-crossing time interval is smaller than the second zero-crossing time interval, it is determined that the motor is in the forward rotation state.

5. The motor starting state detection method based on single resistor current sampling according to claim 1, characterized in that: The motor starting state detection method further includes: The rotational speed of the motor rotor is calculated according to the first zero-crossing time interval and the second zero-crossing time interval.

6. The motor starting state detection method based on single resistor current sampling according to claim 1, characterized in that: The step of determining whether the motor is in a forward rotation state or a reverse rotation state comprises: According to the forward rotation state or reverse rotation state of the motor, the motor position is determined at the next U-phase current zero-crossing moment.

7. The motor starting state detection method based on single resistor current sampling according to claim 6, characterized in that: If the motor is in the forward rotation state, the electrical angle corresponding to the next U-phase current zero-crossing moment is set as the preset first electrical angle; If the motor is in a reverse state, the electrical angle corresponding to the next U-phase current zero-crossing moment is set as the preset second electrical angle.

8. A controller, characterized in that: The controller includes: a processor and a storage medium, wherein the storage medium stores a motor starting state detection program based on single-resistor current sampling; after being executed by the processor, the motor starting state detection program based on single-resistor current sampling implements the steps corresponding to the motor starting state detection method based on single-resistor current sampling as described in any one of claims 1 to 7.

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