Position sensorless DC brushless motor and starting method thereof

Abstract

The invention relates to a position sensorless direct current brushless motor and a starting method thereof. The motor comprises a motor housing, a front end cover, a rear end cover, a rotor, a stator, a two-phase armature winding, a power tube integrated board, an encoder, an encoder accessory, a rear cover, a zero-crossing detection module, a motor control module and a three-phase drive module. The rear cover is connected to the rear end cover, the encoder is arranged in the rear cover and connected to the rear end of the rotor, the power tube integrated board comprises a stator power tube and a rotor power tube, the power tube integrated board is communicated with the encoder, one end of the zero-crossing detection module is connected to the encoder, and the other end is connected to the motor control module, one end of the three-phase drive module is connected to the motor control module, and the other end is communicated with the two-phase armature winding, the encoder accessory is connected to the encoder, and the position sensorless direct current brushless motor has high operating efficiency and accuracy, low loss, strong anti-interference ability and small size.

Description

Technical Field

[0001] The invention relates to a position sensor-free direct current brushless motor and a starting method thereof. Background Art

[0002] It is difficult to correctly detect the back electromotive force when the existing brushless DC motor is stationary or running at low speed. There are two problems when the motor starts: one is the problem of stationary starting, and the other is the problem of synchronous switching. To solve the above problems, there are many starting methods in the prior art, but some of them require the addition of peripheral circuits, and some are closely related to the motor characteristics.

[0003] There are many methods for measuring the position of a position sensorless brushless DC motor, such as the terminal voltage method, the current method, and the state observation method, but the back-EMF method is still the most commonly used. This method determines the position of the rotor pole by detecting the zero-crossing point of the back-EMF, thereby determining the switching time of the power device in the inverter. Although this method is simple and practical, since the back-EMF is superimposed with the pulse width modulation waveform output by the inverter and the spike interference generated by the switching process of the power device, the problem of how to filter out the strong interference pulses mixed in the back-EMF becomes a difficulty in detecting the zero-crossing point of the back-EMF. There are many methods for filtering out interference, but they often cause the back-EMF to produce a phase shift, and this phase shift varies greatly due to different operating frequencies, and it is difficult to correct it through compensation methods. Since the zero-crossing point of the back-EMF cannot be accurately measured, it will inevitably affect the accuracy of the switching time of the power device, thereby affecting the operating efficiency of the motor. Summary of the invention

[0004] The purpose of the present invention is to provide a position sensorless DC brushless motor with high operating efficiency and accuracy, low loss, strong anti-interference ability and small size in view of the defects of the prior art.

[0005] The present invention is achieved through the following technical solutions:

[0006] A position sensorless DC brushless motor comprises a motor housing, a front end cover, a rear end cover, a rotor, a stator, and a two-phase armature winding, wherein the front end cover and the rear end cover are respectively connected to the two ends of the motor housing, the rotor is arranged in the motor housing, the front end and the rear end of the rotor are respectively connected to the front end cover and the rear end cover through bearings, the stator is sleeved outside the rotor, and the two-phase armature winding is arranged on the stator.

[0007] In order to achieve more accurate starting of the motor, reduce losses and improve motor efficiency, the position sensorless DC brushless motor adopts pure software starting, and also includes a power tube integrated board, an encoder, encoder accessories, a rear cover, a zero-crossing detection module, a motor control module and a three-phase drive module. The rear cover is connected to the rear end cover, the encoder is arranged in the rear cover and connected to the rear end of the rotor, the power tube integrated board includes a stator power tube and a rotor power tube, the power tube integrated board is communicated with the encoder, one end of the zero-crossing detection module is connected to the encoder, and the other end is connected to the motor control module, one end of the three-phase drive module is connected to the motor control module, and the other end is communicated with the two-phase armature winding, and the encoder accessories are connected to the encoder.

[0008] In order to achieve accurate measurement of the rotor speed, the encoder and encoder accessories include an operational amplifier, a first MOS tube, a second MOS tube, a first zener diode, a second zener diode, a first triode, a second triode, a first resistor, a second resistor, a third resistor, a fourth resistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor and a second capacitor. The base of the first triode is connected to the base of the second triode, the emitter of the first triode is connected to the collector of the second triode, the emitter of the second triode is grounded, one end of the first resistor is connected to the base of the first triode, the second resistor is connected between the base of the first triode and the emitter of the second triode, the source of the first MOS tube is connected to the drain of the second MOS tube, and the control electrode of the first MOS tube is connected to the emitter of the first triode and the collector of the second triode. The first MOS tube is connected to the control electrode of the second MOS tube, the first resistor is connected to the source electrode of the second MOS tube, the second MOS tube is connected to the ground after being connected in series with the first resistor, the first zener diode is connected between the drain and the source electrode of the first MOS tube, the second zener diode is connected between the drain and the source electrode of the second MOS tube, the negative input terminal of the operational amplifier is connected in series with the second resistor and then grounded, the positive input terminal of the operational amplifier is connected in series with the third resistor and then connected between the source electrode of the second MOS tube and the first resistor, the negative power supply terminal of the operational amplifier is grounded, the positive power supply terminal of the operational amplifier is connected in series with the second capacitor and then grounded, one end of the first capacitor is connected between the third resistor and the positive input terminal of the operational amplifier, and the other end is grounded, the fourth resistor is connected between the negative input terminal of the operational amplifier and the output terminal of the operational amplifier, and one end of the fifth resistor is connected to the output terminal of the operational amplifier.

[0009] In order to improve the stability, safety and ease of use of the motor connector, the position sensorless DC brushless motor also includes a first aviation socket and a second aviation socket, the first aviation socket is connected to the two-phase armature winding, and the second aviation socket is connected to the encoder.

[0010] In order to improve the reliability of the motor control module and reduce the volume of the motor control module, the motor control module includes an IR2130 integrated block.

[0011] The present invention also includes a method for starting a position sensorless brushless DC motor. During starting, the system adopts a three-stage method and uses pure software to implement starting. The starting process of the motor is divided into three stages: pre-positioning, acceleration, and synchronous switching. The method mainly includes the following steps:

[0012] 1) When the motor is stationary, the initial position of the rotor is unknown. First, a short current is passed through the two-phase armature winding to stabilize the rotor poles on the axis of the synthetic magnetic field of the two-phase windings to achieve pre-positioning, which is used as the initial position of the rotor poles;

[0013] 2) Then, the corresponding stator power tube and rotor power tube are turned on according to the correct spatial phase relationship between the stator and rotor magnetic poles, and the mode is switched at a fixed time. At this time, zero-crossing detection is not performed;

[0014] 3) As the motor speed gradually increases, the back electromotive force also gradually increases. When it increases to a certain value, the terminal voltage is detected to determine the position of the rotor, and the result is fed back to the motor control module;

[0015] 4) Subsequently, the motor control module controls the zero-crossing detection module to start, and uses a combination of instantaneous state detection and state prediction to determine whether the rotor crosses the zero point. Specifically, the state of the three-phase drive module is detected at the moment when the switching noise of the high-power device stator power tube and rotor power tube in the power tube integrated board is extinguished, and the arrival time of the rotor zero crossing is determined by detecting the waveform generated by the periodic switching noise of the high-power device stator power tube and rotor power tube. At the same time, the circuit composed of the encoder and the encoder accessories is used to obtain the rotor speed according to the zero-crossing period, and the phase change frequency of the next cycle is estimated. The above state prediction method is used for correction, and the conduction time of the three-phase power device in the three-phase drive module is calculated, and then the accurate time of the next round of zero crossing is calibrated. This cycle is repeated. When the zero crossing is correctly detected for 5 consecutive times, the operation is switched from the external synchronous operation stage to the self-synchronous operation stage.

[0016] The beneficial effects of the present invention are:

[0017] 1. This sensorless brushless DC motor adopts multi-stage starting, combines instantaneous state detection and state prediction, does not require a filter when extracting back electromotive force, and avoids the generation of phase shift;

[0018] 2. Add AC / DC application pulse mode to achieve two voltage operation states for the same motor;

[0019] 3. Use the moment when the switching noise of the high-power device is extinguished to detect the state of the three-phase drive module, so as to determine the arrival time of the rotor zero crossing point, and use the state prediction method to make corrections and calculate the conduction time of the three-phase power device;

[0020] 4. The patterned position detection method is used to effectively detect the zero-crossing point, making the switching time more accurate, thereby improving the efficiency of the motor and enabling the motor to run more smoothly and accurately;

[0021] 5. The motor control module has strong control function, perfect protection function and stable working performance;

[0022] 6. The peripheral circuits required for the composed system are simple and have strong anti-interference ability, which is particularly suitable for occasions with high requirements on controller size and price-performance ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a position sensorless brushless DC motor of the present invention;

[0024] Figure 2 A circuit diagram of an encoder and encoder accessories of a position sensorless brushless DC motor of the present invention;

[0025] Figure 3 The figure is a schematic diagram of the speed calculation principle of the position sensorless brushless DC motor of the present invention. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the protection scope of the present invention. The directional terms mentioned in the present invention, such as "up", "down", "front", "back", "left", "right", "top", "bottom", etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and understand the present invention, rather than to limit the present invention.

[0027] like Figure 1 As shown, a position sensorless DC brushless motor includes a motor housing 1, a front end cover 2, a rear end cover 3, a rotor 4, a stator 5, and a two-phase armature winding 6. The front end cover 2 and the rear end cover 3 are respectively connected to the two ends of the motor housing 1, and the rotor 4 is arranged in the motor housing 1. The front end and the rear end of the rotor 4 are respectively connected to the front end cover 2 and the rear end cover 3 through bearings 7. The stator 5 is sleeved outside the rotor 4, and the two-phase armature winding 6 is arranged on the stator 5.

[0028] It also includes a power tube integrated board 8, an encoder 9, an encoder accessory 10, a rear cover 11, a zero-crossing detection module 12, a motor control module 13, a three-phase drive module 16, a first aviation socket 14 and a second aviation socket 15, wherein the motor control module 13 includes an IR2130 integrated block 131, the rear cover 11 is connected to the rear end cover 3, the encoder 9 is arranged in the rear cover 11 and connected to the rear end of the rotor 4, the power tube integrated board 8 includes a stator power tube 81 and a rotor power tube 82, the power tube integrated board 8 is connected to the encoder 9, one end of the zero-crossing detection module 12 is connected to the encoder 9, and the other end is connected to the motor control module 13, one end of the three-phase drive module 16 is connected to the motor control module 13, and the other end is connected to the two-phase armature winding 6, the encoder accessory 10 is connected to the encoder 9, the first aviation socket 14 is connected to the two-phase armature winding 6, and the second aviation socket 15 is connected to the encoder 9.

[0029] When the motor starts, the system will use a three-stage, pure software to start the motor, dividing the motor starting process into three stages: pre-positioning, acceleration, and synchronous switching. It mainly includes the following steps:

[0030] 1) When the motor is stationary, the initial position of the rotor 4 is unknown. First, a short current is passed through the two-phase armature winding 6 to stabilize the magnetic poles of the rotor 4 on the axis of the synthetic magnetic field of the two-phase armature winding 6, so as to achieve pre-positioning, which is used as the initial position of the magnetic poles of the rotor 4;

[0031] 2) Then, according to the correct spatial phase relationship between the magnetic poles of the stator 5 and the rotor 4, the corresponding stator power tube 81 and the rotor power tube are turned on 82, and the mode is switched at a fixed time, and zero-crossing detection is not performed at this time;

[0032] 3) As the motor speed gradually increases, the back electromotive force also gradually increases. When it increases to a certain value, the terminal voltage is detected to determine the position of the rotor 4, and the result is fed back to the motor control module 13;

[0033] 4) Subsequently, the motor control module 13 controls the zero-crossing detection module 12 to start, and uses a combination of instantaneous state detection and state prediction to determine whether the rotor crosses the zero point. Specifically, the state of the three-phase drive module 16 is detected at the moment when the switching noise of the high-power device stator power tube 81 and the rotor power tube 82 in the power tube integrated board 8 is extinguished, and the arrival time of the zero-crossing point of the rotor 4 is determined by detecting the waveform generated by the periodic switching noise of the high-power device stator power tube 81 and the rotor power tube 82. At the same time, the circuit composed of the encoder 9 and the encoder accessory 10 is used to obtain the speed of the rotor 4 according to the zero-crossing period, and the phase change frequency of the next cycle is estimated. The above state prediction method is used for correction, and the conduction time of the three-phase power device in the three-phase drive module 16 is calculated, and then the accurate time of the next round of zero-crossing is checked. This cycle is repeated. When the zero-crossing point is correctly detected for 5 consecutive times, it is switched from the external synchronous operation stage to the self-synchronous operation stage.

[0034] like Figure 2As shown, the encoder 9 and the encoder accessory 10 are used for measuring the rotation speed of the rotor 4 in the above step 4), and include an operational amplifier IC1, a first MOS tube M1, a second MOS tube M2, a first voltage stabilizing diode D1, a second voltage stabilizing diode D2, a first transistor Q1, a second transistor Q2, a first resistor R11, a second resistor R12, a third resistor R13, a fourth resistor R14, a first resistor R21, a second resistor R22, a third resistor R23, a fourth resistor R24, a fifth resistor R25, and a first capacitor C1. and the second capacitor C2, the base of the first triode Q1 is connected to the base of the second triode Q2, the emitter of the first triode Q1 is connected to the collector of the second triode Q2, the emitter of the second triode Q2 is grounded, one end of the first resistor R11 is connected to the base of the first triode Q1, the second resistor R12 is connected between the base of the first triode Q1 and the emitter of the second triode Q2, the source of the first MOS tube M1 is connected to the drain of the second MOS tube M2, the control electrode of the first MOS tube M1 is connected to the emitter of the first triode Q1 The emitter and the collector of the second triode Q2 are connected, the control electrode of the second MOS tube M2 is connected in series with the fourth resistor R14 and then grounded, one end of the third resistor R13 is connected to the control electrode of the second MOS tube M2, the source electrode of the second MOS tube M2 is connected in series with the first resistor R21 and then grounded, the drain and source of the first MOS tube M1 are connected with the first voltage zener diode D1, the drain and source of the second MOS tube M2 are connected with the second voltage zener diode D2, the negative input terminal of the operational amplifier IC1 is connected in series with the second resistor R22 and then grounded, and the operational amplifier The positive input terminal of IC1 is connected in series with the third resistor R23 and then connected between the source of the second MOS tube M2 and the first resistor R21. The negative power supply terminal of the operational amplifier IC1 is grounded. The positive power supply terminal of the operational amplifier IC1 is connected in series with the second capacitor C2 and then grounded. One end of the first capacitor C1 is connected between the third resistor R23 and the positive input terminal of the operational amplifier IC1, and the other end is grounded. The fourth resistor R24 ​​is connected between the negative input terminal and the output terminal of the operational amplifier IC1. One end of the fifth resistor R25 is connected to the output terminal of the operational amplifier IC1.

[0035] When the motor rotates, the encoder 9 generates two orthogonal pulse signals, which are sent to the integrated encoder 9 and encoder accessory 10 through the DEP1 and DEP2 ports of the DSP. Figure 2 The orthogonal coding processing circuit shown performs 4 times frequency phase detection processing.

[0036] When the speed loop sampling time arrives, DSP first obtains the 4-fold frequency count value of the pulse feedback from encoder 9 within the sampling period time interval, from which the time required for the motor to rotate one circle can be calculated. The speed is calculated by simple division and implemented using DSP. The principle is as follows Figure 3 shown.

[0037] The above-mentioned embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A position sensorless DC brushless motor, comprising a motor housing (1), a front end cover (2), a rear end cover (3), a rotor (4), a stator (5), and a two-phase armature winding (6), wherein the front end cover (2) and the rear end cover (3) are respectively connected to two ends of the motor housing (1), the rotor (4) is arranged in the motor housing (1), the front end and the rear end of the rotor (4) are respectively connected to the front end cover (2) and the rear end cover (3) through bearings (7), the stator (5) is sleeved outside the rotor (4), and the two-phase armature winding (6) is arranged on the stator (5), characterized in that: The invention also comprises a power tube integrated board (8), an encoder (9), an encoder accessory (10), a rear cover (11), a zero-crossing detection module (12), a motor control module (13) and a three-phase drive module (16). The rear cover (11) is connected to the rear end cover (3). The encoder (9) is arranged in the rear cover (11) and connected to the rear end of the rotor (4). The power tube integrated board (8) comprises a stator power tube (81) and a rotor power tube (82). The power tube integrated board (8) is in communication with the encoder (9). One end of the zero-crossing detection module (12) is connected to the encoder (9) and the other end is connected to the motor control module (13). One end of the three-phase drive module (16) is connected to the motor control module (13) and the other end is in communication with the two-phase armature winding (6). The encoder accessory (10) is connected to the encoder (9). The encoder (9) and the encoder accessory (10) include an operational amplifier (IC1), a first MOS tube (M1), a second MOS tube (M2), a first voltage-stabilizing diode (D1), a second voltage-stabilizing diode (D2), a first transistor (Q1), a second transistor (Q2), a first resistor (R11), a second resistor (R12), a third resistor (R13), a fourth resistor (R14), a first resistor (R21), a second resistor (R22), a third resistor (R23), a fourth resistor (R24), a fifth resistor (R25), a first capacitor (C1) and a second capacitor (C2 ), the base of the first triode (Q1) is connected to the base of the second triode (Q2), the emitter of the first triode (Q1) is connected to the collector of the second triode (Q2), the emitter of the second triode (Q2) is grounded, one end of the first resistor (R11) is connected to the base of the first triode (Q1), the second resistor (R12) is connected between the base of the first triode (Q1) and the emitter of the second triode (Q2), the source of the first MOS tube (M1) is connected to the drain of the second MOS tube (M2), the control electrode of the first MOS tube (M1) is connected to the emitter of the first triode (Q1) and The collector of the second triode (Q2), the control electrode of the second MOS tube (M2) is connected in series with the fourth resistor (R14) and then grounded, one end of the third resistor (R13) is connected to the control electrode of the second MOS tube (M2), the source electrode of the second MOS tube (M2) is connected in series with the first resistor (R21) and then grounded, a first voltage stabilizing diode (D1) is connected between the drain and source of the first MOS tube (M1), a second voltage stabilizing diode (D2) is connected between the drain and source of the second MOS tube (M2), the negative input terminal of the operational amplifier (IC1) is connected in series with the second resistor (R22) and then grounded, and the operational amplifier (IC1) 1), the positive input terminal of the operational amplifier (IC1) is connected in series with a third resistor (R23) and then connected between the source of the second MOS tube (M2) and the first resistor (R21), the negative power supply terminal of the operational amplifier (IC1) is grounded, the positive power supply terminal of the operational amplifier (IC1) is connected in series with a second capacitor (C2) and then grounded, one end of the first capacitor (C1) is connected between the third resistor (R23) and the positive input terminal of the operational amplifier (IC1), and the other end is grounded, the fourth resistor (R24) is connected between the negative input terminal and the output terminal of the operational amplifier (IC1), and one end of the fifth resistor (R25) is connected to the output terminal of the operational amplifier (IC1), It also includes a first aviation socket (14) and a second aviation socket (15), wherein the first aviation socket (14) is connected to the two-phase armature winding (6), and the second aviation socket (15) is connected to the encoder (9).

2. The position sensorless brushless DC motor according to claim 1, characterized in that: The motor control module (13) comprises an IR2130 integrated block (131).

3. A method for starting a position sensorless brushless DC motor, using the position sensorless brushless DC motor as claimed in any one of claims 1 to 2, characterized in that: Using pure software startup, including the following steps: 1) passing a short current through a set two-phase armature winding (6) to stabilize the magnetic poles of the rotor (4) on the axis of the synthetic magnetic field of the two-phase armature winding (6), and taking this as the initial position of the magnetic poles of the rotor (4); 2) according to the correct spatial phase relationship between the magnetic poles of the stator (5) and the rotor (4), the corresponding stator power tube (81) and the rotor power tube (82) are turned on, and the mode is switched at a fixed time; 3) detecting the terminal voltage, determining the position of the rotor (4), and feeding the result back to the motor control module (13); 4) The motor control module (13) controls the zero-crossing detection module (12) to start, and uses a combination of instantaneous state detection and state prediction to determine whether the rotor has passed through the zero point. Specifically, the state of the three-phase drive module (16) is detected at the moment when the switching noise of the high-power device stator power tube (81) and the rotor power tube (82) in the power tube integrated board (8) is extinguished, and the arrival time of the zero-crossing point of the rotor (4) is determined by detecting the waveform generated by the periodic switching noise of the high-power device stator power tube (81) and the rotor power tube (82). At the same time, a circuit composed of an encoder (9) and an encoder accessory (10) is used to obtain the speed of the rotor (4) according to the zero-crossing period, and the phase change frequency of the next cycle is estimated. The above state prediction method is used for correction, and the conduction time of the three-phase power device in the three-phase drive module (16) is calculated, and then the accurate time of the next round of zero-crossing is checked. This cycle is repeated. When the zero-crossing point is correctly detected for 5 consecutive times, the operation is switched from the external synchronous operation stage to the self-synchronous operation stage.

Images