Rotor initial position detection method, program product and brushless direct current motor system

Abstract

The invention relates to a method for detecting the initial position of a rotor of a brushless direct current motor, and the method at least comprises the following steps: S1, injecting at least two first pulse voltages into different conduction phases of a stator winding, respectively and correspondingly detecting the terminal voltage of a suspended phase, and obtaining the size relation of the inductance of the stator winding of each phase according to the terminal voltage, the angular position of the rotor is preliminarily judged according to the magnitude relationship of the inductance; s2, two phases of stator windings with relatively small inductance are selected according to the magnitude relation of the inductance, second pulse voltages with opposite directions are injected into the two phases of stator windings, response current is detected, and the pulse width and / or the pulse amplitude of the second pulse voltages are / is larger than the first pulse voltage; and S3, determining the orientation of the magnetic pole according to the response current to determine the initial position of the rotor. The invention also relates to a computer program product and a brushless direct current motor system. The duration for the initial positioning of the rotor is significantly reduced and the current shock and noise during the initial positioning are greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of electromechanics, and in particular to a method for detecting the initial position of a rotor of a brushless DC motor. The present invention also relates to a corresponding computer program product and a corresponding brushless DC motor system. Background Art

[0002] A brushless DC motor has a rotor made of permanent magnetic material and a stator with a winding, and an electronic commutator replaces mechanical brushes. Therefore, the brushless DC motor has the advantages of simple structure, good linear mechanical characteristics, wide speed regulation range and high operating efficiency, and is widely used in different fields, such as vehicles or power tools.

[0003] During the operation of a brushless DC motor, it is necessary to obtain the rotor position to realize operation control. In existing brushless DC motors, Hall sensors are usually used to obtain the rotor position. However, Hall sensors increase the cost and volume of brushless DC motors and reduce reliability. Therefore, brushless DC motors without position sensors and control methods thereof have attracted widespread attention.

[0004] At present, many position detection methods have been proposed for brushless DC motors without position sensors, such as back-EMF zero-crossing detection valve, model reference adaptive method, state observer method, etc., but these methods cannot obtain the initial position of the rotor when the motor is in a stationary state. In order to locate the initial position of the motor rotor, six pulse voltages are generally injected into the stator windings of each phase, and the initial position of the rotor is determined by detecting the current response. Among them, since each pulse voltage needs to make the corresponding stator winding current reach saturation, the initial position of the rotor can be accurately determined, which makes the pulse width or pulse amplitude of each pulse voltage higher, resulting in a correspondingly large response current and causing current shock and noise that are difficult to ignore, seriously affecting the user experience. Summary of the invention

[0005] Therefore, the purpose of the present invention is to propose an improved method for detecting the initial position of the rotor of a brushless DC motor. The detection method can significantly reduce the duration of the initial positioning of the rotor and greatly reduce the current impact and noise during the initial positioning, thereby significantly improving the user experience.

[0006] According to a first aspect of the present invention, a method for detecting an initial position of a rotor of a brushless DC motor is provided, wherein the detection method comprises at least the following steps:

[0007] S1: injecting at least two first pulse voltages into different conduction phases of the stator winding of the brushless DC motor respectively, and detecting the terminal voltage of the suspended phase respectively, obtaining the magnitude relationship of the inductance of the stator winding of each phase according to the terminal voltage, and preliminarily determining the angular position of the rotor according to the magnitude relationship of the inductance;

[0008] S2: selecting a two-phase stator winding with a relatively small inductance according to the magnitude relationship of the inductance, injecting two second pulse voltages in opposite directions into the two-phase stator windings, and detecting the response currents respectively, wherein the pulse width and / or pulse amplitude of the second pulse voltage is greater than the first pulse voltage;

[0009] S3: Determine the magnetic pole orientation of the rotor according to the response current, and determine the initial position of the rotor in combination with the magnetic pole orientation and the angular position.

[0010] Compared with the prior art, in the detection method for the initial position of the rotor of the brushless DC motor according to the present invention, it is only necessary to inject at least two relatively small first pulse voltages and two relatively large second pulse voltages into the stator winding, and the angular position of the rotor is determined by obtaining the magnitude relationship of the inductance of the stator winding of each phase, and the magnetic pole orientation of the rotor is determined by detecting the response current, and the initial position of the rotor can be determined by combining the angular position and the magnetic pole orientation. In this way, the number of pulse voltages injected for detecting the initial position of the rotor and the time for initial positioning can be significantly reduced, and the pulse width and / or pulse amplitude of the injected pulse voltage can be partially reduced, which can effectively reduce the current impact and noise caused by the injected pulse voltage during initial positioning, thereby improving the user experience.

[0011] Exemplarily, step S1 may include the following sub-steps:

[0012] S11: firstly inject the first pulse voltage into the A-phase stator winding and the B-phase stator winding, and obtain the magnitude relationship of the inductance of the A-phase stator winding and the B-phase stator winding according to the terminal voltage of the C-phase stator winding;

[0013] S12: Then injecting the first pulse voltage into the stator winding with larger inductance among the A-phase stator winding and the B-phase stator winding and the C-phase stator winding, and obtaining the magnitude relationship between the inductance of the stator winding with larger inductance and the C-phase stator winding according to the terminal voltage of the stator winding with smaller inductance among the A-phase stator winding and the B-phase stator winding;

[0014] S13: Determine the stator winding with the largest inductance among the three-phase stator windings according to the results of S11 and S12, and determine the two sectors with an angle of about 60° where the rotor is located in combination with the curve graph of the stator winding inductance and the rotor angle position.

[0015] Exemplarily, step S1 may also include the following sub-steps:

[0016] S11': respectively injecting the three first pulse voltages into the A-phase stator winding and the B-phase stator winding, the A-phase stator winding and the C-phase stator winding, and the B-phase stator winding and the C-phase stator winding, and detecting the terminal voltage of the suspended phase accordingly;

[0017] S12': determining the magnitude relationship of the inductance of each stator winding in the three-phase stator winding according to each terminal voltage;

[0018] S13': according to the result of step S12' and the curve diagram of the stator winding inductance and the rotor angle position, determine the two sectors with an angle of about 30 degrees where the rotor is located.

[0019] Exemplarily, in step S1, the terminal voltage of the suspended phase corresponds to the divided voltage of a stator winding in the conductive phase, the divided voltage is proportional to the inductance of the stator winding, and the magnitude relationship of the inductance of the two-phase stator winding of the conductive phase is obtained according to the ratio of the divided voltage and the first pulse voltage, wherein the stator winding in the conductive phase corresponding to the suspended phase is determined according to the application state of the first pulse voltage.

[0020] Exemplarily, the pulse width and / or pulse amplitude of the second pulse voltage is at least three times greater than that of the first pulse voltage; and / or the pulse width of the second pulse voltage is greater than or equal to 50 μs; and / or the pulse width of the first pulse voltage is less than or equal to 15 μs.

[0021] Exemplarily, in step S3, the N pole of the rotor is in a sector corresponding to a conduction state having a larger response current.

[0022] Exemplarily, the first pulse voltage and the second pulse voltage are implemented so as to be spaced apart from each other.

[0023] Exemplarily, the interval time between each first pulse voltage is less than the interval time between two second pulse voltages; and / or, the interval time between each first pulse voltage is greater than or equal to twice the pulse width of the first pulse voltage; and / or, the interval time between two second pulse voltages is greater than or equal to twice the pulse width of the second pulse voltage.

[0024] According to a second aspect of the present invention, a computer program product is provided, comprising a computer program, wherein when the computer program is executed by one or more processors, the processors are capable of performing the detection method according to the present invention.

[0025] According to a third aspect of the present invention, there is provided a brushless DC motor system, wherein the brushless DC motor system at least comprises:

[0026] - Brushless DC motor;

[0027] - a converter, the converter comprising six switching power devices arranged in the form of a three-phase six-arm full bridge, wherein the converter is configured to be suitable for injecting a pulse voltage into the stator winding of the brushless DC motor;

[0028] - a voltage detection module, the voltage detection module being configured to detect a terminal voltage of a suspended phase of the stator winding;

[0029] - a current detection module, the current detection module being configured and adapted to detect a response current of the stator winding;

[0030] a control module, which is communicatively connected to the converter, the voltage detection module and the current detection module respectively and is configured to execute the detection method according to the present invention by using the computer program product according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be described in more detail below with reference to the accompanying drawings, so that the principles, features and advantages of the present invention can be better understood. The accompanying drawings include:

[0032] Figure 1 A schematic block diagram of a brushless DC motor system according to an exemplary embodiment of the present invention is shown;

[0033] Figure 2 A three-phase winding conduction state diagram of a brushless DC motor system according to an exemplary embodiment of the present invention is shown;

[0034] Figure 3 A schematic diagram showing the relationship between the rotor position and the inductance of the stator winding of a brushless DC motor according to an exemplary embodiment of the present invention is shown;

[0035] Figure 4 A schematic flow chart of a method for detecting an initial position of a rotor of a brushless DC motor according to an exemplary embodiment of the present invention is shown;

[0036] Figure 5a and Figure 5bThe equivalent circuit diagrams of the stator windings of the brushless DC motor according to an exemplary embodiment of the present invention are respectively shown;

[0037] Figure 6a and Figure 6b Schematic flow charts of sub-steps of step S1 of the detection method according to different exemplary embodiments of the present invention are respectively shown;

[0038] Figure 7 A schematic diagram of pulse voltage injection of a detection method according to an exemplary embodiment of the present invention is shown. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial technical effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention. Here, for the sake of brevity, elements with the same reference numerals are only marked once in the drawings.

[0040] It should be understood that, in this document, the expressions "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance, nor should they be understood as implicitly indicating the number of technical features indicated. Features defined as "first" or "second" may explicitly or implicitly indicate that at least one of the features is included.

[0041] Figure 1 FIG. 1 is a schematic block diagram of a brushless DC motor system 100 according to an exemplary embodiment of the present invention.

[0042] like Figure 1 As shown, the brushless DC motor system 100 includes a brushless DC motor 10, which has a rotor made of permanent magnetic material and a stator with a stator winding, wherein the stator winding is composed of a coil wound in a slot of the stator. When current passes through the stator winding, a magnetic field is generated by the stator winding, and the rotor rotates under the action of the magnetic field. The stator winding has three phases, ABC, and the phases have an angle interval of 120° relative to each other. A bidirectional current can flow through the stator winding of each phase. The generated magnetic field can be adjusted by changing the conduction phase and current direction of the stator winding, thereby realizing continuous rotation of the rotor and achieving the desired rotation direction and rotation speed. Here, the rotor is constructed, for example, in the form of an outer rotor rotating around the stator on the outside or in the form of an inner rotor arranged in the central cavity of the stator. For the sake of overview, the specific structure of the rotor and stator of the brushless DC motor 10 is not shown.

[0043] like Figure 1As shown, the brushless DC motor system 100 includes a converter 20, which has six switching power devices 21, which are configured as power transistors and are arranged in the form of a three-phase six-arm full bridge, so that a switching power device 21 is arranged at each of the two line ends of the stator winding of each phase. Exemplarily, a first switching power device T1 is arranged at the upper bridge arm of the A-phase stator winding, a second switching power device T2 is arranged at the lower bridge arm of the A-phase stator winding, a third switching power device T3 is arranged at the upper bridge arm of the B-phase stator winding, a fourth switching power device T4 is arranged at the lower bridge arm of the B-phase stator winding, a fifth switching power device T5 is arranged at the upper bridge arm of the C-phase stator winding, and a sixth switching power device T6 is arranged at the lower bridge arm of the C-phase stator winding (for the sake of simplicity, only the corresponding symbols are shown below). When connected to a power supply, a pulse voltage can be injected into the stator winding of the brushless DC motor 10 by controlling the on and off states of each switching power device 21 of the converter 20.

[0044] like Figure 1 As shown, the brushless DC motor system 100 includes a voltage detection module 30, which is respectively connected to the end of each phase stator winding and is configured to detect the terminal voltage of the suspended phase relative to the ground when a pulse voltage is injected into the stator winding of the conducting phase. Figure 6a and Figure 6b .

[0045] In the framework of the present invention, the "conduction phase" should be understood as the power switch devices arranged at the upper bridge arm of the first phase stator winding and the lower bridge arm of the second phase stator winding being closed, so that the two phase stator windings are connected to the power supply, so that when the voltage is applied by the power supply, the voltage is injected into the two phase stator windings and a response current is generated in the two phase stator windings; and the "suspended phase" should be understood as the third phase of the three-phase stator winding except the conduction phase, and the power switch devices corresponding to the third phase are all in the off state, so that no response current is generated in the stator winding of the third phase. Here, the suspended phase can also be called a non-injected phase.

[0046] like Figure 1 As shown, the brushless DC motor system 100 includes a current detection module 40, which is configured to detect the response current of the brushless DC motor 10. When a pulse voltage is injected into the brushless DC motor 10 through the inverter 20, the response current of the stator winding can be obtained by the current detection module 40.

[0047] like Figure 1As shown, the brushless DC motor system 100 includes a controller 50, which is respectively communicated with the converter 20, the voltage detection module 30 and the current detection module 40, wherein the controller 50 can inject the desired pulse voltage into the stator winding of each phase of the brushless DC motor 10 by controlling the switching state of each switching power device 21 in the converter 20.

[0048] Figure 2 FIG. 1 shows a three-phase winding conduction state diagram of a brushless DC motor system 100 according to an exemplary embodiment of the present invention.

[0049] like Figure 2 As shown, each switching power device 21 of the converter 20 has six conduction states within the electrical angle range of 360°, namely T1T6, T3T6, T3T2, T5T2, T5T4, and T1T4. These six conduction states divide the electrical angle range of 360° into six 60° sectors, namely sectors 1 to 6, wherein the symbol in each conduction state represents that the corresponding switching power device 21 is in a closed state, wherein A+ corresponds to the upper bridge arm of the A-phase stator winding, A- corresponds to the lower bridge arm of the A-phase stator winding, and so on. In a determined conduction state, the switching power device located in the upper bridge arm of the corresponding first phase and the switching power device located in the lower bridge arm of the corresponding second phase are closed to realize the circuit conduction of the stator winding of the brushless DC motor 10, and these two phases are the conduction phases, and the other third phase is the suspended phase. For example, when in the on state T1T6, the switching power device 21 located in the upper bridge arm of phase A and the switching power device 21 located in the lower bridge arm of phase C are closed, phase A and phase C are the on phases, and the voltage applied by the power supply can be injected into the stator windings of phase A and phase C, while the stator winding of phase B is a suspended phase or a non-injected phase.

[0050] Figure 3 A schematic relationship diagram between the rotor position and the inductance of the stator winding of a brushless DC motor 10 according to an exemplary embodiment of the present invention is shown, wherein the abscissa θ is the angle of the N pole of the rotor relative to the stator winding, and the ordinate L is the inductance of the stator winding.

[0051] Here, when the stator winding is energized, the permanent magnetic flux of the rotor and the additional magnetic flux generated by the stator winding current work together to affect the saturation of the stator core. When the permanent magnetic flux and the additional magnetic flux are in the same direction, a magnetizing effect is generated, the saturation of the stator core increases, and the inductance of the stator winding decreases; and when the permanent magnetic flux and the additional magnetic flux are in opposite directions, a demagnetizing effect is generated, the saturation of the stator core decreases, and the inductance of the stator winding increases.

[0052] like Figure 3As shown, when the angle of the rotor's N pole relative to a stator winding is 0°, the inductance of the stator winding is the smallest. As the rotor rotates, the inductance of the stator winding gradually increases, and reaches a maximum level when the angle of the rotor's N pole relative to the stator winding is 90°. In the process of the angle of the rotor's N pole relative to the stator winding from 90° to 180°, the inductance of the stator winding gradually decreases. Here, due to the combined effect of the rotor's permanent magnet flux and the additional flux generated by the stator winding current, the inductance of the stator winding when the angle of the rotor's N pole relative to the stator winding is 0° is less than the inductance when the angle of the rotor's N pole relative to the stator winding is 180°.

[0053] like Figure 3 As shown, since the stator windings of the three phases have an angular interval of 120° relative to each other, the change curves of the inductance of the stator windings of phases A, B and C with respect to the rotor position are staggered by 120° relative to each other, and the inductance curves of the stator windings of each phase have the same direction, wherein the inductance curve of the stator winding of phase A is represented by a solid line, the inductance curve of the stator winding of phase B is represented by a dotted line, and the inductance curve of the stator winding of phase C is represented by a dotted line. For example, the inductance of the stator winding of phase A at 0° is equal to the inductance of the stator winding of phase B at 120° and equal to the inductance of the stator winding of phase C at 240°. The angular position of the rotor can be determined by comparing the magnitude relationship of the inductance of the stator windings of each phase.

[0054] Figure 4 A schematic flow chart of a method for detecting an initial position of a rotor of a brushless DC motor 10 according to an exemplary embodiment of the present invention is shown. Figure 5a and Figure 5b The equivalent circuit diagrams of the stator windings of the brushless DC motor according to an exemplary embodiment of the present invention are respectively shown.

[0055] Figure 6a and Figure 6b Schematic flow charts of sub-steps of step S1 of the detection method according to different exemplary embodiments of the present invention are respectively shown.

[0056] like Figure 4 As shown, the method for detecting the initial position of the rotor of the brushless DC motor 10 according to the present invention comprises at least the following steps:

[0057] S1: injecting at least two first pulse voltages U1 into different conducting phases of the stator winding of the brushless DC motor 10, respectively, and detecting the terminal voltage of the suspended phase respectively, obtaining the magnitude relationship of the inductance of the stator winding of each phase according to the terminal voltage, and preliminarily determining the angular position of the rotor according to the magnitude relationship of the inductance;

[0058] S2: Select two-phase stator windings with relatively small inductance according to the magnitude relationship of the inductances, inject two second pulse voltages U2 in opposite directions into the two-phase stator windings, and detect the response current I respectively, wherein the pulse width and / or pulse amplitude of the second pulse voltage U2 is greater than the first pulse voltage U1;

[0059] S3: judging the magnetic pole orientation of the rotor according to the response current I detected in step S2, and determining the initial position of the rotor in combination with the magnetic pole orientation and the angular position.

[0060] Here, in step S1, the terminal voltage of the suspended phase corresponds to the divided voltage of one stator winding in the conducting phase. For example, the first pulse voltage U1 is injected into the A-phase stator winding and the B-phase stator winding, and the first pulse voltage U1 is applied to the inductance L of the A-phase stator winding. A and the inductance L of the B-phase stator winding B and accordingly detects the terminal voltage of the suspended phase C-phase stator winding, which is applied to the inductance L of the C-phase stator winding. C and ground, wherein the terminal voltage corresponds to the divided voltage of one of the stator windings in the conducting phases A and B, and the stator winding in the conducting phase corresponding to the suspended phase can be determined according to the application state of the first pulse voltage U1. For example, when the conducting state of the converter 20 is T1T4, the application state of the first pulse voltage is the upper bridge arm A+ of the A phase to the A phase stator winding and the B phase stator winding to the lower bridge arm B- of the B phase. In this case, the terminal voltage of the suspended phase C corresponds to the divided voltage U of the B phase stator winding. B ,like Figure 5a As shown; when the conduction state of the converter 20 is T3T2, the application state of the first pulse voltage is the upper bridge arm B+ of the B phase to the B phase stator winding and the A phase stator winding to the lower bridge arm A- of the A phase. At this time, the terminal voltage of the suspended phase C phase corresponds to the divided voltage U of the A phase stator winding. A ,like Figure 5b As shown.

[0061] Here, in step S1, the voltage division of a stator winding in the conducting phase is proportional to the inductance of the stator winding. The larger the voltage division, the larger the inductance of the stator winding. Therefore, the magnitude relationship of the inductance of the two-phase stator winding in the conducting phase can be obtained according to the ratio of the voltage division and the first pulse voltage U1. Figure 6a For example, when the terminal voltage of the suspended phase C, that is, the ratio of the voltage division of the B-phase stator winding to the first pulse voltage U1 is greater than 0.5, it indicates that the voltage division of the B-phase stator winding is greater than the voltage division of the A-phase stator winding, then the inductance of the B-phase stator winding is also greater than the inductance of the A-phase stator winding, and vice versa.

[0062] For example, Figure 6aAs shown, step S1 includes the following sub-steps:

[0063] S11: First, inject the first pulse voltage U1 into the A-phase stator winding and the B-phase stator winding, and correspondingly detect the terminal voltage of the suspended C-phase stator winding, and obtain the magnitude relationship of the inductance of the A-phase stator winding and the B-phase stator winding according to the terminal voltage of the C-phase stator winding;

[0064] S12: Then inject the first pulse voltage U1 into the stator winding with larger inductance among the A-phase stator winding and the B-phase stator winding and the C-phase stator winding. At this time, the stator winding with smaller inductance among the A-phase stator winding and the B-phase stator winding is a suspended phase, and the terminal voltage of the suspended phase is detected. According to the terminal voltage, the magnitude relationship of the inductance of the stator winding with larger inductance among the A-phase stator winding and the B-phase stator winding and the C-phase stator winding can be obtained;

[0065] S13: Determine the stator winding with the largest inductance among the three-phase stator windings according to the results of S11 and S12, and Figure 3 It can be seen from the graph of stator winding inductance and rotor angular position shown in that the state in which the inductance of a stator winding is the largest corresponds to two angular segments of approximately 60°, which are spaced 180° apart from each other, from which it can be determined that the rotor is in two sectors of approximately 60°. For example, taking the maximum inductance of the A-phase stator winding as an example, it can be seen that the rotor should be in a sector of 60° to 120° or a sector of 240° to 300°. Here, the angle size of the sector depends specifically on the motor parameters.

[0066] In this case, in step S1, only two first pulse voltages U1 need to be injected into the brushless DC motor 10. This can significantly reduce the duration for initial positioning of the rotor and greatly reduce the current surge and noise during initial positioning.

[0067] But it is also possible to consider that Figure 6b As shown, step S1 includes the following sub-steps:

[0068] S11': injecting three first pulse voltages U1 into the A-phase stator winding and the B-phase stator winding, the A-phase stator winding and the C-phase stator winding, and the B-phase stator winding and the C-phase stator winding respectively, and detecting the terminal voltage of the suspended phase accordingly;

[0069] S12': determining the magnitude relationship of the inductance of each stator winding in the three-phase stator winding according to each terminal voltage;

[0070] S13': Combine according to the result of step S12' Figure 3The graph of stator winding inductance and rotor angular position shown in FIG. 1 can determine the two sectors of about 30° in angle that the rotor is in. For example, when the detection result is that the inductance of the A-phase stator winding is greater than the inductance of the B-phase stator winding and the inductance of the B-phase stator winding is greater than the inductance of the C-phase stator winding, it can be seen that the rotor should be in the sector of 60° to 90° or the sector of 240° to 270°.

[0071] In this case, three first pulse voltages U1 need to be injected into the brushless DC motor 10 in step S1. Figure 6a The illustrated embodiment requires the injection of an additional first pulse voltage, but compared to the prior art it can still reduce the duration for initial positioning of the rotor and significantly reduce the current impact and noise during initial positioning, while also significantly improving the detection accuracy of the initial position of the rotor.

[0072] Exemplarily, in step S3, the N pole of the rotor is in a sector corresponding to a conduction state with a larger response current. When the N pole of the rotor is close to the stator winding, the inductance of the stator winding decreases due to the combined effect of the permanent magnetic flux of the rotor and the additional magnetic flux generated by the stator winding current. Here, the inductance of the stator winding affects the rate of change of the current in the stator winding, wherein the smaller the inductance of the stator winding, the greater the rate of change of the current of the stator winding, and the greater the response current of the stator winding when the pulse voltage is applied, so the larger response current indicates that the N pole of the rotor is in the sector corresponding to the conduction state. For example, when it is determined in step S1 that the inductance of the A-phase stator winding is the largest and the rotor should be in the sector of 60° to 120° or the sector of 240° to 300°, in step S2, the B-phase and C-phase stator windings with relatively small inductance are selected as the conduction phases, and two second pulse voltages U2 in opposite directions are injected into the stator windings of these two phases. The conduction states of the converter 20 are T3T6 and T5T4, respectively, and the response currents are detected respectively. When the response current of the conduction state T3T6 is greater than the response current of the conduction state T5T4, it indicates that the N pole of the rotor is in the 60° sector corresponding to the conduction state T3T6.

[0073] Figure 7 A schematic diagram of pulse voltage injection of a detection method according to an exemplary embodiment of the present invention is shown, wherein the horizontal axis t is time, the vertical axis U is the amplitude of the pulse voltage, and the dot-dashed line represents the response current I detected by the current detection module 40.

[0074] like Figure 7As shown, at least two, for example, three first pulse voltages U1 are injected in step S1, and two second pulse voltages U2 in opposite directions are injected in step S2, wherein the pulse width of the second pulse voltage U2 is greater than the pulse width of the first pulse voltage U1. Here, the response current I generated under the action of the first pulse voltage U1 is significantly smaller than the response current I generated under the action of the second pulse voltage U2, which can effectively reduce the current impact and noise during initial positioning as a whole. However, it can also be considered that the pulse amplitude of the second pulse voltage U2 is greater than the pulse amplitude of the first pulse voltage U1, which can also specifically increase the response current under the action of the second pulse voltage U2 to achieve accurate judgment of the magnetic pole orientation of the rotor.

[0075] Exemplarily, the pulse width and / or pulse amplitude of the second pulse voltage U2 is at least three times greater than that of the first pulse voltage U1. In particular, the pulse width of the second pulse voltage U2 is greater than or equal to 50 μs, while the pulse width of the first pulse voltage U1 is less than or equal to 15 μs. Of course, other values ​​of the pulse widths of the first pulse voltage U1 and the second pulse voltage U2 that are considered meaningful by those skilled in the art may also be considered.

[0076] Exemplarily, each first pulse voltage U1 and each second pulse voltage U2 are implemented at intervals from each other, which can avoid the adverse effect of inductor freewheeling on the response current.

[0077] For example, Figure 7 As shown, the interval time between each first pulse voltage U1 is less than the interval time between two second pulse voltages U2. In particular, the interval time between each first pulse voltage U1 is greater than or equal to twice the pulse width of the first pulse voltage U1, and the interval time between two second pulse voltages U2 is greater than or equal to twice the pulse width of the second pulse voltage U2. This prevents the inductor freewheeling from adversely affecting the detection of the response current I as much as possible. Of course, other time values ​​that are considered meaningful by those skilled in the art can also be considered.

[0078] Here, the controller 50 of the brushless DC motor system 100 can use a computer program product according to the present invention to execute a detection method for the initial position of the rotor of the brushless DC motor 10 according to the present invention, wherein the computer program product includes a computer program, wherein when the computer program is executed by one or more processors, the processor is capable of executing the detection method according to the present invention.

[0079] The above explanation of the embodiments only describes the invention within the framework of the examples. Of course, the individual features of the embodiments can be freely combined with one another as long as it makes technical sense, without departing from the framework of the invention.

[0080] Other advantages and alternative embodiments of the present invention are obvious to those skilled in the art. Therefore, the present invention in its broader sense is not limited to the specific details, representative structures and exemplary embodiments shown and described. On the contrary, those skilled in the art can make various modifications and substitutions without departing from the basic spirit and scope of the present invention.

Claims

1. A method for detecting the initial position of a rotor of a brushless DC motor (10), characterized in that: The detection method at least comprises the following steps: S1: injecting at least two first pulse voltages (U1) into different conducting phases of the stator winding of the brushless DC motor (10), respectively, and detecting the terminal voltage of the suspended phase respectively and correspondingly, obtaining the magnitude relationship of the inductance of the stator winding of each phase according to the terminal voltage, and preliminarily determining the angular position of the rotor according to the magnitude relationship of the inductance; S2: selecting a two-phase stator winding with a relatively small inductance according to the magnitude relationship of the inductance, injecting two second pulse voltages (U2) in opposite directions into the two-phase stator winding, and detecting the response current (I) respectively, wherein the pulse width and / or pulse amplitude of the second pulse voltage (U2) is greater than that of the first pulse voltage (U1); S3: Determine the magnetic pole orientation of the rotor according to the response current (I), and determine the initial position of the rotor in combination with the magnetic pole orientation and the angular position.

2. The detection method according to claim 1, characterized in that: Step S1 includes the following sub-steps: S11: First, inject the first pulse voltage (U1) into the A-phase stator winding and the B-phase stator winding, and obtain the magnitude relationship of the inductance of the A-phase stator winding and the B-phase stator winding according to the terminal voltage of the C-phase stator winding; S12: Then the first pulse voltage (U1) is injected into the stator winding with larger inductance among the A-phase stator winding and the B-phase stator winding and the C-phase stator winding, and the magnitude relationship between the inductance of the stator winding with larger inductance and the C-phase stator winding is obtained according to the terminal voltage of the stator winding with smaller inductance among the A-phase stator winding and the B-phase stator winding; S13: Determine the stator winding with the largest inductance among the three-phase stator windings according to the results of S11 and S12, and determine the two sectors with an angle of about 60° where the rotor is located in combination with the curve graph of the stator winding inductance and the rotor angle position.

3. The detection method according to claim 1, characterized in that: Step S1 includes the following sub-steps: S11': respectively injecting the three first pulse voltages (U1) into the A-phase stator winding and the B-phase stator winding, the A-phase stator winding and the C-phase stator winding, and the B-phase stator winding and the C-phase stator winding, and detecting the terminal voltage of the suspended phase accordingly; S12': determining the magnitude relationship of the inductance of each stator winding in the three-phase stator winding according to each terminal voltage respectively; S13': according to the result of step S12' and the curve diagram of the stator winding inductance and the rotor angle position, determine the two sectors with an angle of about 30 degrees where the rotor is located.

4. The detection method according to any one of claims 1 to 3, characterized in that: In step S1, the terminal voltage of the suspended phase corresponds to the divided voltage of a stator winding in the conductive phase, and the divided voltage is proportional to the inductance of the stator winding. The magnitude relationship of the inductance of the two-phase stator winding of the conductive phase is obtained according to the ratio of the divided voltage and the first pulse voltage, wherein the stator winding in the conductive phase corresponding to the suspended phase is determined according to the application state of the first pulse voltage (U1).

5. The detection method according to any one of the preceding claims, characterized in that The pulse width and / or pulse amplitude of the second pulse voltage (U2) is at least three times greater than that of the first pulse voltage (U1); and / or The pulse width of the second pulse voltage (U2) is greater than or equal to 50 μs; and / or The pulse width of the first pulse voltage (U1) is less than or equal to 15 μs.

6. The detection method according to any one of the preceding claims, characterized in that In step S3, the N pole of the rotor is in a sector corresponding to a conducting state with a larger response current.

7. The detection method according to any one of the preceding claims, characterized in that The first pulse voltage (U1) and the second pulse voltage (U2) are implemented at a distance from each other.

8. The detection method according to claim 7, characterized in that: The interval time between each first pulse voltage (U1) is shorter than the interval time between two second pulse voltages (U2); and / or The interval time between each first pulse voltage (U1) is greater than or equal to twice the pulse width of the first pulse voltage (U1); and / or The interval time between two second pulse voltages (U2) is greater than or equal to twice the pulse width of the second pulse voltage (U2).

9. A computer program product comprising a computer program, wherein: When the computer program is executed by one or more processors, the processors are capable of performing the detection method according to any one of claims 1-8.

10. A brushless DC motor system (100), characterized in that: The brushless DC motor system (100) comprises at least: - a brushless DC motor (10); - a converter (20), the converter comprising six switching power devices (21), the switching power devices being arranged in the form of a three-phase six-arm full bridge, wherein the converter is configured to be suitable for injecting a pulse voltage into the stator winding of the brushless DC motor (10); - a voltage detection module (30), which is configured to detect the terminal voltage of the suspended phase of the stator winding; - a current detection module (40) configured and adapted to detect a response current of the stator winding; - a control module (50), which is communicatively connected to the converter (20), the voltage detection module (30) and the current detection module (40) respectively and is configured to execute the detection method according to any one of claims 1 to 8 using the computer program product according to claim 9.

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