Motor rotor position detection system and method using high-frequency signal injection into search coil

Abstract

A motor rotor position detection system using a high-frequency signal injection search coil includes a DC power supply that provides power to a brushless DC motor via an inverter, a motor controller connected to the inverter for controlling the operation of the inverter, and a search coil provided on the brushless DC motor for obtaining the brushless DC motor rotor position and expressing it through an inductance signal. The lead end of the search coil is connected to a signal gating circuit that obtains a high-frequency sinusoidal signal generated by a high-frequency sinusoidal signal generating circuit connected to the signal gating circuit. The lead end of the search coil also transmits the effective value of the high-frequency voltage component of each phase winding to the motor controller via an effective value detection circuit for the motor controller to control the output of the inverter. The motor controller is also connected to the signal gating circuit for controlling the gating of different output signals of the signal gating circuit. The present invention enables rotor position detection during low-speed operation of the motor and achieves electrical isolation between the armature winding and the strong and weak currents of the low-voltage, high-frequency signal circuit.

Description

Technical Field

[0001] The present invention relates to a method for detecting the position of a motor rotor, and more particularly to a system and method for detecting the position of a motor rotor by injecting a high-frequency signal into a search coil. Background Art

[0002] Brushless DC motors (BLDCs) are widely used in aerospace, rail transportation, medical devices, and household appliances due to their simple structure, reliable operation, and high efficiency. However, proper operation of BLDCs requires rotor position information. Position sensors struggle to guarantee reliable operation in harsh operating conditions such as high temperature, humidity, contamination, and high interference. Position sensors also increase the size of the motor, and their installation accuracy directly impacts reliable operation. Therefore, achieving sensorless control of BLDC motors is essential and has become a research hotspot.

[0003] When a motor runs at high speeds, rotor position is detected by measuring the back EMF in the armature winding, leveraging the positional relationship between the back EMF and the motor rotor. This method is relatively mature and widely used. However, the magnitude of the back EMF is affected by the motor's speed. When the motor runs at low speeds, the back EMF amplitude is small, making detection more difficult and resulting in large errors. Therefore, the back EMF method is not applicable when the motor is running at low speeds.

[0004] Affected by the motor's salient pole effect, the change characteristics of the motor winding's inductance are closely related to the rotor position, and its inductance value is not affected by the motor's speed. Therefore, detecting the rotor position through the inductance method is suitable for low-speed operation of the motor. The existing inductance method requires injecting a pulse voltage vector into the motor winding and comparing the difference in inductance value based on the magnitude of the response current. However, this response current is large and will generate unnecessary electromagnetic torque, which will cause significant interference to the normal operation of the motor. Although generating a low-voltage high-frequency signal through an independent high-frequency signal source and directly coupling it into the armature winding can reduce unnecessary electromagnetic torque while detecting inductance differences, when the inverter is working, the high-frequency signal will flow through the inverter and be short-circuited by the inverter's front-side capacitor or power supply, making it difficult to couple and inject it into the armature winding. This method is relatively difficult to implement. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a motor rotor position detection system and method that can achieve electrical isolation between the armature winding and the strong and weak electricity of the low-voltage high-frequency signal circuit, and realize the high-frequency signal injection search coil of the brushless DC motor without position sensor control.

[0006] The technical solution adopted by the present invention is a motor rotor position detection system using a high-frequency signal injection search coil. The system includes a brushless DC motor, a DC power supply that provides power to the brushless DC motor via an inverter, and a motor controller connected to the inverter for controlling the operation of the inverter. The brushless DC motor is provided with a search coil for detecting the rotor position of the brushless DC motor and expressing it through an inductance signal. The lead end of the search coil is connected to a signal gating circuit, which receives a high-frequency sinusoidal signal generated by a high-frequency sinusoidal signal generating circuit connected to the signal gating circuit through the signal gating circuit. The lead end of the search coil is also connected to an effective value detection circuit for transmitting a signal obtained by coupling the inductance signal with the high-frequency sinusoidal signal to the effective value detection circuit. The output end of the effective value detection circuit is connected to a motor controller for transmitting the detected effective value of the high-frequency voltage component of each phase winding of the search coil to the motor controller. The motor controller controls the output of the inverter based on the effective value of the high-frequency voltage component of each phase winding of the search coil. The motor controller is also connected to the signal gating circuit for controlling the gating of different output signals of the signal gating circuit.

[0007] The search coil includes three-phase coils: phase A, phase B, and phase C. Each phase coil is embedded in the internal structure of the brushless DC motor in a layout manner in which it is wound around a tooth of the corresponding phase of the motor stator. The three-phase coils are connected in a star configuration. The lead-out terminal of each phase and the neutral point lead-out terminal of the search coil are all led to the outside of the motor. The search coil is insulated from the motor armature winding and has no direct electrical connection.

[0008] A detection method for a motor rotor position detection system using a high-frequency signal injected into a search coil comprises the following steps:

[0009] 1) applying a set voltage vector to the armature winding of the brushless DC motor to initially pre-position the brushless DC motor so that the north pole of the motor rotor is in the electrical angle range of 0° to 180°, or in the electrical angle range of 180° to 360°;

[0010] 2) The motor controller controls the operation of the gating circuit. The high-frequency sinusoidal signal flows through the signal gating circuit and is injected into the ab phase, bc phase, and ca phase of the search coil in sequence.

[0011] 3) When high-frequency sinusoidal signals are injected into the search coil's a and b phases, the effective value detection circuit converts the obtained high-frequency sinusoidal voltages of phases a and b into effective values ​​U a_rms and U b_rms Since the larger the inductance value, the larger the high-frequency voltage is, the larger the effective value of the conversion is. Therefore, the motor controller compares the effective value output by the sampling effective value detection circuit to obtain the a-phase inductance L. a and b-phase inductance L bSimilarly, when high-frequency sinusoidal signals are injected into the b and c phases of the search coil, the effective value detection circuit converts the high-frequency sinusoidal voltages of phases b and c into effective values ​​U b_rms and U c_rms , by detecting U b_rms and U c_rms Compare the b-phase inductance L b and c-phase inductance L c Similarly, when high-frequency sinusoidal signals are injected into the search coil's two phases ca, the effective value detection circuit converts the obtained high-frequency sinusoidal voltages of phase c and phase a into effective values ​​U c_rms and U a_rms , by detecting U c_rms and U a_rms Compare the c-phase inductance L c and phase a inductance L a The size of the search coil is finally obtained. a 、L b and L c The size relationship between the three;

[0012] 4) According to the three-phase inductance L of the search coil a 、L b and L c The relationship between the three and the initial pre-positioning interval in step 1) are used to determine the precise electrical angle interval where the motor rotor's N pole is located;

[0013] 5) The motor controller applies corresponding switching signals to the inverter to drive the brushless DC motor according to the precise electrical angle interval of the motor rotor's N pole;

[0014] 6) Return to step 2) and continue the cycle to achieve continuous operation of the brushless DC motor under position sensorless control.

[0015] Step 4) includes:

[0016] In L a> L c≥ L b When the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle intervals of 0° to 30° or 180° to 210°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 0° to 30°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 180° to 210°;

[0017] In L c≥ L a> L bWhen the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is in the small electrical angle range of 30° to 60°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is in the small electrical angle range of 210° to 240°.

[0018] In L c> L b≥ L a When the initial pre-positioning of the N pole of the motor rotor is in the large electrical angle interval of 0° to 180°, it is judged that the N pole of the motor rotor is in the small electrical angle interval of 60° to 90°; when the initial pre-positioning of the N pole of the motor rotor is in the large electrical angle interval of 180° to 360°, it is judged that the N pole of the motor rotor is in the small electrical angle interval of 240° to 270°.

[0019] In L b≥ L c> L a When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle ranges of 90° to 120° or 270° to 300°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 90° to 120°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 270° to 300°;

[0020] In L b> L a≥ L c When the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle intervals of 120° to 150° or 300° to 330°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 120° to 150°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 300° to 330°;

[0021] When L a≥ L b> L cWhen the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle ranges of 150° to 180° or 330° to 360°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 150° to 180°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 330° to 360°.

[0022] The present invention's motor rotor position detection system and method using a high-frequency signal injection search coil enables rotor position detection when the motor is running at low speed, solving the problem of high-frequency signal injection when the motor is operating without a position sensor, and achieving electrical isolation between the armature winding and the high and low voltage high-frequency signal circuits. The present invention has the following beneficial effects:

[0023] 1. The present invention solves the problem of position detection failure caused by the small back EMF amplitude when the motor is stationary or running at low speed. The rotor position can still be detected when the motor is stationary or running at low speed.

[0024] 2. The present invention injects a high-frequency sinusoidal signal into the search coil, obtains the voltage of each phase winding of the search coil through the effective value detection circuit, and thus compares the inductance relationship between each phase winding, and detects the electrical angle range of the rotor in real time, which facilitates the commutation control of the brushless DC motor.

[0025] 3. The search coil of the present invention is insulated from the motor armature winding and has no direct electrical connection, which avoids the influence of the strong current in the armature winding on the low-voltage high-frequency signal circuit. It solves the problem that when the motor is running, the high-frequency signal will be short-circuited by the capacitor on the front side of the inverter or the DC power supply, making it difficult to inject the high-frequency sinusoidal signal.

[0026] 4. The present invention realizes the electrical isolation between the armature winding circuit and the low-voltage and high-frequency signal circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the change between the inductance value of the search coil and the rotor position in the present invention;

[0028] Figure 2 It is a schematic diagram of the motor rotor position detection system of the present invention that injects a high-frequency signal into the search coil;

[0029] Figure 3 This is a schematic diagram of the arrangement of phases a, b, and c of the search coil in the motor;

[0030] Figure 4a This is a schematic diagram of the equivalent circuit for high-frequency signal injection into the search coil ab phase and detection of the effective value of the high-frequency voltage component;

[0031] Figure 4b This is a schematic diagram of the equivalent circuit for high-frequency signal injection into the search coil bc phase and detection of the effective value of the high-frequency voltage component;

[0032] Figure 4c It is a schematic diagram of the equivalent circuit of high-frequency signal injection into the search coil ca phase and high-frequency voltage component effective value detection.

[0033] In the picture

[0034] 1: DC power supply 2: Inverter

[0035] 3: Brushless DC motor 4: Search coil

[0036] 5: High-frequency sinusoidal signal generating circuit 6: Signal gating circuit

[0037] 7: Effective value detection circuit 8: Motor controller DETAILED DESCRIPTION

[0038] The motor rotor position detection system and method using a high-frequency signal injection search coil according to the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0039] like Figure 2 As shown, the motor rotor position detection system of the present invention using a high-frequency signal injection search coil includes a brushless DC motor 3, a DC power supply 1 for providing power to the brushless DC motor 3 through an inverter 2, and a motor controller 8 connected to the inverter 2 for controlling the operation of the inverter 2. The brushless DC motor 3 is provided with a search coil 4 for obtaining the rotor position of the brushless DC motor 3 and reflecting it through an inductance signal. The lead end of the search coil 4 is connected to a signal gating circuit 6, and the signal gating circuit 6 obtains a high-frequency sinusoidal signal generated by a high-frequency sinusoidal signal generating circuit 5 connected to the signal gating circuit 6. The lead end of the search coil 4 is also connected to an effective value detection circuit 7 for sending the signal after coupling the inductance signal and the high-frequency sinusoidal signal to the effective value detection circuit 7. The output end of the effective value detection circuit 7 is connected to a motor controller 8 for sending the detected effective value of the high-frequency voltage component of each phase winding of the search coil 4 to the motor controller 8. The motor controller 8 controls the output of the inverter 2 according to the effective value of the high-frequency voltage component of each phase winding of the search coil 4. The motor controller 8 is also connected to the signal selection circuit 6 for controlling the selection of different output signals of the signal selection circuit 6.

[0040] The inductance of the search coil 4 is affected by the salient pole effect of the motor rotor and presents a periodic sinusoidal change. The change law between the magnitude of the inductance and the rotor position is as follows: Figure 1The variation characteristics of the inductance values ​​of the three-phase windings of the search coil 4 have similar variation patterns to the variation characteristics of the inductance values ​​of the armature windings A, B and C phases.

[0041] The search coil 4 can be embedded in the internal structure of the brushless DC motor in various forms and layouts. The search coil can be wound on the stator teeth of the motor. The three-phase search coil adopts a star connection and is sequentially combined into phase a, phase b and phase c coils.

[0042] like Figure 3 As shown, the search coil 4 comprises three phase coils: phases A, B, and C. Each phase coil is embedded within the brushless DC motor, wound around a tooth of the corresponding phase of the motor stator. The three-phase coils are connected in a star configuration, with each phase lead and the search coil neutral point lead leading to the outside of the motor. The search coil 4 is insulated from the motor armature winding, eliminating a direct electrical connection between them. This ensures electrical isolation between the high-voltage and low-voltage signal loops and the armature windings. This prevents the high-voltage current in the armature winding from affecting the low-voltage, high-frequency signal loop, resolving the issue of high-frequency signals being shorted by the inverter front-side capacitor or the DC power supply during motor operation, making it difficult to inject high-frequency sinusoidal signals.

[0043] In an embodiment of the present invention:

[0044] The motor controller 8 is based on TI's TMS320F28335 main control chip, which has ADC sampling function. The pulse signal sent by the ePWM module is used to control the inverter switch tube. Its rich GPIO port outputs high and low level signals that can be used to control external circuits.

[0045] The high-frequency signal generated by the high-frequency sinusoidal signal generating circuit 5 is sent out by the signal source chip ICL8038, and the frequency and amplitude of the signal sent out can be flexibly adjusted.

[0046] The signal selection circuit 6 uses an analog switch circuit chip 74HC4053. The input signals of the S1, S2, and S3 pins of the 74HC4053 are controlled by the GPIO output signal of the motor controller 8. The GPIO port outputs corresponding high and low levels to control the 74HC4053 to selectively pass the high-frequency signal. The high-frequency signal is sequentially injected into the ab phase, bc phase, and ca phase of the search coil through the 74HC4053 to realize signal injection of different phases.

[0047] The effective value detection circuit 7 is mainly composed of an effective value detection chip AD637 and a bandpass filter with a bandwidth center frequency consistent with the frequency of the high-frequency signal. The filter filters out the low-frequency noise induced in the search coil when the motor is running, extracts the high-frequency signal and inputs it into the AD637 chip. The AD637 chip outputs the effective value of the high-frequency signal, which is transmitted to the ADC sampling port of the motor controller 8. The motor controller 8 processes the effective value of the high-frequency signal obtained by sampling the a-phase, b-phase, and c-phase windings of the search coil.

[0048] The detection method of the motor rotor position detection system using a high-frequency signal injection search coil described in the present invention injects a low-voltage, high-frequency sinusoidal signal generated by a high-frequency signal source into the ab, bc, and ca phases of the brushless DC motor search coil 4 through a signal gating circuit 6. An effective value detection circuit 7 extracts the effective value of the high-frequency voltage obtained by each phase winding and transmits it to a motor controller 8. The inductance of each phase winding is compared and the electrical angle range of the motor rotor is determined based on the change in the inductance of the search coil 4 with the rotor position, thereby achieving sensorless position control of the brushless DC motor. Specifically, the method includes the following steps:

[0049] 1) applying a set voltage vector to the armature winding of the brushless DC motor 3 to perform initial pre-positioning on the brushless DC motor 3 so that the north pole of the motor rotor is in the electrical angle range of 0° to 180°, or in the electrical angle range of 180° to 360°;

[0050] 2) The motor controller 8 controls the operation of the signal gating circuit 6, and the high-frequency sinusoidal signal flows through the signal gating circuit 6 and is sequentially injected into the ab phase, bc phase, and ca phase of the search coil 4;

[0051] 3) When high-frequency sinusoidal signals are injected into the search coil 4, the effective value detection circuit 7 converts the obtained high-frequency sinusoidal voltages of phases a and b into effective values ​​(DC values) U a_rms and U b_rms , the equivalent circuit is as follows Figure 4a As shown; Since the larger the inductance value, the larger the high-frequency voltage is, the larger the effective value of the conversion is, so the motor controller 8 compares the effective value output by sampling the effective value detection circuit 7 to obtain the a-phase inductance L a and b-phase inductance L b Similarly, when the high-frequency sinusoidal signal is injected into the bc phase of the search coil 4, the effective value detection circuit 7 converts the obtained high-frequency sinusoidal voltage of the b phase and the c phase into the effective value U b_rms and U c_rms , by detecting U b_rms and U c_rms Compare the b-phase inductance L b and c-phase inductance L c The size of the equivalent circuit is as follows Figure 4b Similarly, when the high-frequency sinusoidal signal is injected into the two phases ca of the search coil 4, the effective value detection circuit 7 converts the obtained high-frequency sinusoidal voltage of phase c and phase a into effective value U c_rms and U a_rms , by detecting U c_rms and U a_rms Compare the c-phase inductance L c and phase a inductance L a The size of the equivalent circuit is as follows Figure 4c As shown; Finally, the three-phase inductance L of the search coil 4 is obtained a 、L b and L c The size relationship between the three;

[0052] 4) According to the three-phase inductance L of the search coil 4 a 、L b and L c The size relationship between the three, combined Figure 1 The inductance distribution characteristics shown in FIG. 1 and step 1) determining the precise electrical angle interval of the motor rotor N pole include:

[0053] In L a> L c≥ L b When the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle intervals of 0° to 30° or 180° to 210°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 0° to 30°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 180° to 210°;

[0054] In L c≥ L a> L b When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is in the small electrical angle range of 30° to 60°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is in the small electrical angle range of 210° to 240°.

[0055] In L c> L b≥ L aWhen the initial pre-positioning of the N pole of the motor rotor is in the large electrical angle interval of 0° to 180°, it is judged that the N pole of the motor rotor is in the small electrical angle interval of 60° to 90°; when the initial pre-positioning of the N pole of the motor rotor is in the large electrical angle interval of 180° to 360°, it is judged that the N pole of the motor rotor is in the small electrical angle interval of 240° to 270°.

[0056] In L b≥ L c> L a When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle ranges of 90° to 120° or 270° to 300°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 90° to 120°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 270° to 300°;

[0057] In L b> L a≥ L c When the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle intervals of 120° to 150° or 300° to 330°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 120° to 150°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 300° to 330°;

[0058] When L a≥ L b> L c When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle ranges of 150° to 180° or 330° to 360°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 150° to 180°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle range of 330° to 360°.

[0059] 5) The motor controller 8 applies a corresponding switching signal to the inverter 2 to drive the brushless DC motor 3 according to the precise electrical angle interval of the motor rotor's N pole;

[0060] 6) Return to step 2) and continue the cycle to achieve continuous operation of the brushless DC motor under position sensorless control.

[0061] The corresponding relationship between the three-phase inductance of the search coil 4 and the electrical angle interval of the motor rotor N pole is shown in Table 1.

[0062] Table 1 Comparison of the three-phase inductance of the search coil and the N-pole electrical angle range of the motor rotor

[0063]

Claims

1. A motor rotor position detection system with a high-frequency signal injected into a search coil, comprising a brushless DC motor (3), a DC power supply (1) for supplying power to the brushless DC motor (3) via an inverter (2), and a motor controller (8) connected to the inverter (2) for controlling the operation of the inverter (2), characterized in that: The brushless DC motor (3) is provided with a search coil (4) for obtaining the rotor position of the brushless DC motor (3) and expressing it through an inductance signal. The lead end of the search coil (4) is connected to a signal gating circuit (6), and the high-frequency sinusoidal signal generated by the high-frequency sinusoidal signal generating circuit (5) connected to the signal gating circuit (6) is obtained through the signal gating circuit (6). The lead end of the search coil (4) is also connected to an effective value detection circuit (7) for sending the signal after the inductance signal and the high-frequency sinusoidal signal are coupled to the effective value detection circuit (7). The output end of the effective value detection circuit (7) is connected to a motor controller (8) for sending the detected effective value of the high-frequency voltage component of each phase winding of the search coil (4) to the motor controller (8). The motor controller (8) controls the output of the inverter (2) according to the effective value of the high-frequency voltage component of each phase winding of the search coil (4). The motor controller (8) is also connected to the signal gating circuit (6) for controlling the gating of different output signals of the signal gating circuit (6); The search coil (4) includes three-phase coils of phase A, phase B and phase C. Each phase coil is embedded in the internal structure of the brushless DC motor in a layout manner of being wound around a tooth of the corresponding phase of the motor stator. The three-phase coils are connected in a star configuration. The lead-out terminal of each phase and the lead-out terminal of the search coil neutral point are all led out to the outside of the motor. The search coil (4) is insulated from the motor armature winding and has no direct electrical connection.

2. A detection method for a motor rotor position detection system using a high-frequency signal injection search coil according to claim 1, characterized in that: The steps include: 1) applying a set voltage vector to the armature winding of the brushless DC motor (3) to initially pre-position the brushless DC motor (3) so that the N pole of the motor rotor is in the electrical angle range of 0° to 180°, or in the electrical angle range of 180° to 360°; 2) The motor controller (8) controls the operation of the signal selection circuit (6), and the high-frequency sinusoidal signal flows through the signal selection circuit (6) and is sequentially injected into the ab phase, bc phase, and ca phase of the search coil (4); 3) When high-frequency sinusoidal signals are injected into the search coil (4) at phases a and b, the effective value detection circuit (7) converts the obtained high-frequency sinusoidal voltages of phases a and b into effective values ​​U a_rms and U b_rms Since the larger the inductance value, the larger the high-frequency voltage is, the larger the effective value of the conversion is, so the motor controller (8) compares the effective value output by the sampling effective value detection circuit (7) to obtain the a-phase inductance L a and b-phase inductance L b Similarly, when a high-frequency sinusoidal signal is injected into the b and c phases of the search coil (4), the effective value detection circuit (7) converts the obtained high-frequency sinusoidal voltages of the b and c phases into effective values ​​U b_rms and U c_rms , by detecting U b_rms and U c_rms Compare the b-phase inductance L b and c-phase inductance L c Similarly, when a high-frequency sinusoidal signal is injected into the two phases ca of the search coil (4), the effective value detection circuit (7) converts the obtained high-frequency sinusoidal voltages of phase c and phase a into effective values ​​U c_rms and U a_rms , by detecting U c_rms and U a_rms Compare the c-phase inductance L c and phase a inductance L a Finally, the three-phase inductance L of the search coil (4) is obtained. a 、L b and L c The size relationship between the three; 4) According to the three-phase inductance L of the search coil (4) a 、L b and L c The relationship between the three and the initial pre-positioning interval in step 1) determine the precise electrical angle interval where the motor rotor's N pole is located; include: In L a> L c≥ L b When the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the two electrical angle intervals of 0° to 30° or 180° to 210°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 0° to 30°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle interval of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is located in the small electrical angle interval of 180° to 210°; In L c≥ L a> L b When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily judged that the N pole of the motor rotor is in the small electrical angle range of 30° to 60°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily judged that the N pole of the motor rotor is in the small electrical angle range of 210° to 240°. In L c> L b≥ L a When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily determined that the N pole of the motor rotor is located in the electrical angle range of 60° to 90° or 240° to 270°. When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily determined that the N pole of the motor rotor is located in the small electrical angle range of 60° to 90°. When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily determined that the N pole of the motor rotor is located in the small electrical angle range of 240° to 270°. In L b≥ L c> L a When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily determined that the N pole of the motor rotor is located in the electrical angle range of 90° to 120° or 270° to 300°. When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily determined that the N pole of the motor rotor is located in the small electrical angle range of 90° to 120°. When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily determined that the N pole of the motor rotor is located in the small electrical angle range of 270° to 300°. In L b> L a≥ L c When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily determined that the N pole of the motor rotor is located in the electrical angle range of 120° to 150° or 300° to 330°. When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, it is preliminarily determined that the N pole of the motor rotor is located in the small electrical angle range of 120° to 150°. When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, it is preliminarily determined that the N pole of the motor rotor is located in the small electrical angle range of 300° to 330°. When L a≥ L b> L c When the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 0° to 180°, the N pole of the motor rotor is preliminarily judged to be in the small electrical angle range of 150° to 180°; when the N pole of the motor rotor is initially pre-positioned in the large electrical angle range of 180° to 360°, the N pole of the motor rotor is preliminarily judged to be in the small electrical angle range of 330° to 360°. 5) The motor controller (8) applies a corresponding switching signal to the inverter (2) to drive the brushless DC motor (3) according to the precise electrical angle interval of the motor rotor's N pole; 6) Return to step 2) and continue the cycle to achieve continuous operation of the brushless DC motor under position sensorless control.

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