Two-phase brushless direct current motor having stable torque, and control method therefor

Abstract

Disclosed in the present invention are a two-phase brushless direct current motor having stable torque, and a control method therefor. The two-phase brushless direct current motor comprises a stator and a rotor; the stator comprises a stator iron core and 4*n stator windings wound around the stator iron core; the rotor comprises a rotor iron core and 6*n permanent-magnet poles surrounding the rotor iron core; n is a positive integer; and the polarities of adjacent permanent-magnet poles are opposite. In the present invention, the utilization efficiency of the stator windings is high, the weight of the brushless direct current motor is reduced, the torque ripple is small, and the present invention is suitable for application scenarios of continuous power output.

Description

A two-phase brushless DC motor with stable torque and its control method Technical Field

[0001] The present invention relates to the technical field of brushless DC motors, and in particular to a two-phase brushless DC motor with stable torque and a control method thereof. Background Art

[0002] Brushless DC motors are widely used in various industries, especially in multi-rotor drones, which generally use brushless DC motors as their power source. Commonly used brushless DC motors are mainly three-phase brushless DC motors.

[0003] Existing three-phase brushless DC motors consist of a basic unit consisting of a three-phase stator winding and two permanent magnet poles, with a stator winding and permanent magnet pole ratio of 3:2. During operation, an electronic speed regulator simulates the generation of three-phase alternating current and generates an alternating magnetic field through the stator winding, which produces a push-pull effect with the permanent magnet poles, thereby converting electrical energy into mechanical rotational energy. However, there are the following disadvantages: the magnetic field itself has only two poles, so at any given time, one of the three stator windings is always inoperative, and the winding utilization efficiency is no more than 67%. Since the weight of the brushless DC motor mainly comes from the stator core and the stator windings wound around the stator core, the stator winding utilization efficiency is low, significantly reducing the power-to-weight ratio of the motor.

[0004] There is also a technical solution for a two-phase brushless DC motor in which the number of stator windings matches the number of permanent magnet poles. Although the stator winding utilization efficiency is high, it has the following disadvantages: large torque pulsation. With each step angle, the torque reaches its maximum at the beginning of the step angle and approaches zero at the end of the step angle. This is not suitable for application scenarios such as multi-rotor drones that require continuous power output.

[0005] Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a two-phase brushless DC motor with stable torque and a control method thereof, which has high utilization efficiency of the stator winding, reduces the weight of the brushless DC motor, and has small torque pulsation.

[0007] In order to solve the above problems, the present invention adopts the following technical solutions:

[0008] A torque-stable two-phase brushless DC motor of the present invention includes a stator and a rotor, wherein the stator includes a stator core and 4*n stator windings wound around the stator core, and the rotor includes a rotor core and 6*n permanent magnet poles wound around the rotor core, where n is a positive integer and the polarities of adjacent permanent magnet poles are opposite.

[0009] In this solution, every four adjacent stator windings form a group, and the electronic speed regulator controls the current phase difference of adjacent stator windings in each group of stator windings to be 90°. Combined with the specific combination of the ratio of the number of stator windings to the number of permanent magnet poles being 4:6, when the torque generated by one stator winding decreases, the torque generated by the adjacent stator winding increases. The torques generated by any two adjacent stator windings are in a complementary working state, thereby generating stable torque output. This solves the technical problem of large torque pulsation in other two-phase brushless DC motors and is suitable for application scenarios of continuous power output.

[0010] In this solution, the ratio of the number of stator windings to the number of permanent magnet poles is 4:6. This reduces the number of stator windings compared to traditional three-phase brushless DC motors, ensuring that the stator windings are always in normal operation, improving stator winding efficiency. This solution uses only two-thirds the number of stator windings used in traditional three-phase brushless DC motors. While the number of permanent magnet poles has increased, the weight of the permanent magnet poles is much lighter than that of the stator windings, reducing the weight of the brushless DC motor and improving the power-to-weight ratio.

[0011] Preferably, the 4*n stator windings form a circle and are arranged at equal intervals along the circle, and the 6*n permanent magnet poles form a circle and are arranged at equal intervals along the circle.

[0012] Preferably, the rotor core is arranged on the inner side of the stator core, the permanent magnet poles are arranged on the outer side wall of the rotor core, and the stator winding is arranged on the inner side wall of the stator core; or, the stator core is arranged on the inner side of the rotor core, the stator winding is arranged on the outer side wall of the stator core, and the permanent magnet poles are arranged on the inner side wall of the rotor core.

[0013] The rotor on the outside of the stator constitutes an outer rotor brushless DC motor, and the rotor on the inside of the stator constitutes an inner rotor brushless DC motor.

[0014] Preferably, the 4*n stator windings are divided into n groups, each group of stator windings includes 4 adjacent stator windings, and the 4 adjacent stator windings are recorded in clockwise direction as stator winding A, stator winding B, stator winding C, and stator winding D. All A stator windings are connected in series in forward direction to form a first series circuit, all B stator windings are connected in series in forward direction to form a second series circuit, all C stator windings are connected in series in forward direction to form a third series circuit, and all D stator windings are connected in series in forward direction to form a fourth series circuit.

[0015] The stator winding has a coil start and a coil end. All stator windings A are numbered 1, 2, 3, ..., n in a clockwise direction, where 1 ≤ i ≤ n-1. The coil end of stator winding A numbered i is connected to the coil start of stator winding A numbered i+1, forming a first series circuit. Similarly, stator windings B, C, and D are connected to form second, third, and fourth series circuits.

[0016] Because the current phase difference between adjacent stator windings is 90°, the phase difference between two stator windings separated by one position (such as stator winding A and stator winding C, stator winding B and stator winding D) is 0° or 180°. There are multiple ways to combine the two stator windings separated by one position into a magnetic pole pair.

[0017] Preferably, the winding directions of all stator windings are consistent, the first series circuit and the third series circuit are connected in anti-parallel to form a first parallel circuit, and the second series circuit and the fourth series circuit are connected in anti-parallel to form a second parallel circuit.

[0018] Connect the starting end of the coil of stator winding A numbered 1 in the first series circuit to the ending end of the coil of stator winding C numbered n in the third series circuit, and connect the ending end of the coil of stator winding A numbered n in the first series circuit to the starting end of the coil of stator winding C numbered 1 in the third series circuit, to form a first parallel circuit. Connect the starting end of the coil of stator winding B numbered 1 in the second series circuit to the ending end of the coil of stator winding D numbered n in the fourth series circuit, and connect the ending end of the coil of stator winding B numbered n in the second series circuit to the starting end of the coil of stator winding D numbered 1 in the fourth series circuit, to form a second parallel circuit.

[0019] After the first series circuit and the third series circuit are connected in reverse parallel to form a first parallel circuit, they can share the same control circuit of the electronic speed controller. Since the current directions in stator winding A and stator winding C are opposite and the winding directions are consistent, the current phase difference between stator winding A and stator winding C is 180°, and the electromagnetic polarities are exactly opposite at the same time. After the second series circuit and the fourth series circuit are connected in reverse parallel to form a second parallel circuit, they can share the same control circuit of the electronic speed controller. Since the current directions in stator winding B and stator winding D are opposite and the winding directions are consistent, the current phase difference between stator winding B and stator winding D is 180°, and the electromagnetic polarities are exactly opposite at the same time.

[0020] Preferably, the torque-stable two-phase brushless DC motor also includes an electronic speed regulator, the two ends of the first parallel circuit are electrically connected to the first input end and the first output end of the electronic speed regulator, and the two ends of the second parallel circuit are electrically connected to the second input end and the second output end of the electronic speed regulator.

[0021] Preferably, the winding directions of the stator winding A and the stator winding B are consistent, the winding directions of the stator winding C and the stator winding D are consistent, the winding directions of the stator winding A and the stator winding C are opposite, the winding directions of the stator winding B and the stator winding D are opposite, the first series circuit and the third series circuit are connected in series in forward direction to form a fifth series circuit, and the second series circuit and the fourth series circuit are connected in series in forward direction to form a sixth series circuit.

[0022] After the first series circuit and the third series circuit are connected in series in the forward direction to form the fifth series circuit, they can share the same control circuit of the electronic speed regulator. Since the winding directions of stator winding A and stator winding C are opposite and the current directions are consistent, the electromagnetic polarities of stator winding A and stator winding C are exactly opposite at the same time. After the second series circuit and the fourth series circuit are connected in series in the forward direction to form the sixth series circuit, they can share the same control circuit of the electronic speed regulator. Since the winding directions of stator winding B and stator winding D are opposite and the current directions are consistent, the electromagnetic polarities of stator winding B and stator winding D are exactly opposite at the same time.

[0023] Preferably, the torque-stable two-phase brushless DC motor also includes an electronic speed regulator, the two ends of the fifth series circuit are electrically connected to the first input end and the first output end of the electronic speed regulator, respectively, and the two ends of the sixth series circuit are electrically connected to the second input end and the second output end of the electronic speed regulator, respectively.

[0024] Preferably, the stator core is provided with a detection component for detecting the position of the rotor, and the detection component includes two or more Hall sensors arranged along the circumferential direction.

[0025] A control method for a two-phase brushless DC motor with stable torque according to the present invention is used for the above-mentioned two-phase brushless DC motor with stable torque, comprising the following steps: using an electronic speed regulator to control the current input to stator winding A, stator winding B, stator winding C, and stator winding D, and controlling the current phase difference between adjacent stator windings in each group of stator windings to be 90°.

[0026] The electronic speed regulator controls the stator winding's control current to be a sine wave or a square wave.

[0027] The beneficial effects of the present invention are: high utilization efficiency of the stator winding, reduced weight of the brushless DC motor, improved power-to-weight ratio, small torque pulsation, and suitable for application scenarios of continuous power output. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic structural diagram of Example 1;

[0029] FIG2 is a current waveform diagram of each stator winding of Example 1;

[0030] FIG3 is a schematic structural diagram of Example 2;

[0031] FIG4 is a schematic diagram of an example structure of Example 2.

[0032] In the figure: 1. Stator core, 2. Stator winding, 3. Rotor core, 4. Permanent magnet pole. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0034] Example 1: A torque-stable two-phase brushless DC motor of this embodiment, as shown in Figure 1, includes a stator and a rotor, the stator includes a stator core 1 and 4*n stator windings 2 wrapped around the stator core 1, the 4*n stator windings 2 form a circle and are arranged at equal intervals along the circle, the rotor includes a rotor core 3 and 6*n permanent magnet poles 4 wrapped around the rotor core 3, n is a positive integer, the 6*n permanent magnet poles 4 form a circle and are arranged at equal intervals along the circle, and the polarities of adjacent permanent magnet poles 4 are opposite.

[0035] The rotor core 3 is arranged on the inner side of the stator core 1, the permanent magnet pole 4 is arranged on the outer side wall of the rotor core 3, and the stator winding 2 is arranged on the inner side wall of the stator core 1. The stator core 3 is provided with a detection component for detecting the rotor position, and the detection component includes two or more Hall sensors arranged along the circumferential direction.

[0036] In this solution, the rotor forms an inner rotor brushless DC motor on the inner side of the stator, and every four adjacent stator windings form a group. The electronic speed regulator controls the current phase difference of adjacent stator windings in each group of stator windings to be 90°. The ideal waveform of the control current is a sine wave. Considering the cost factor, a square wave (trapezoidal wave) can also be used. The permanent magnet poles are arranged in an NS polarity staggered, combined with a specific combination of the number of stator windings and the number of permanent magnet poles with a ratio of 4:6. When the torque generated by one of the stator windings decreases, the torque generated by the adjacent stator winding increases, and vice versa. The torques generated by any two adjacent stator windings are in a complementary working state, thereby generating stable torque output, solving the technical problem of large torque pulsation in other two-phase brushless DC motors, and being suitable for application scenarios of continuous power output.

[0037] Take a two-phase brushless DC motor consisting of four stator windings and six permanent magnet poles as an example, as shown in Figure 1. The four stator windings are recorded as stator winding A, stator winding B, stator winding C, and stator winding D in clockwise order. The winding directions of the four stator windings are consistent. Figure 1 is the state of the two-phase brushless DC motor at time t. The currents of the four stator windings are shown in Figure 2. The current phase difference between adjacent stator windings is 90°, the current phase difference between stator winding A and stator winding C is 180°, and the current phase difference between stator winding B and stator winding D is 180°. At time t, the currents of stator winding A and stator winding C reach their maximum values ​​and stator winding A and stator winding C are at their maximum values. The windings are located in the middle of the two permanent magnet poles and contribute the most to the torque. The current of stator winding B and stator winding D is exactly 0 and stator winding B and stator winding D face a permanent magnet pole respectively, so their contribution to the torque is zero. When the rotor continues to rotate, the contribution of stator winding A and stator winding C to the torque gradually decreases, and the contribution of stator winding B and stator winding D to the torque gradually increases. When the contribution of stator winding B and stator winding D to the torque reaches the maximum, the contribution of stator winding A and stator winding C to the torque is just reduced to zero. The torque generated by the two adjacent stator windings is in a complementary working state, which reduces the torque pulsation and thus produces a stable torque output.

[0038] In this solution, the ratio of the number of stator windings to the number of permanent magnet poles is 4:6. This reduces the number of stator windings compared to traditional three-phase brushless DC motors, ensuring that the stator windings are in normal operation at all times, improving stator winding efficiency by 50%. This solution uses only two-thirds the number of stator windings used in traditional three-phase brushless DC motors. While the number of permanent magnet poles has increased, the weight of the permanent magnet poles is much lighter than that of the stator windings, reducing the weight of the brushless DC motor and improving the power-to-weight ratio.

[0039] There are two ways to connect the stator winding:

[0040] Method (1):

[0041] The 4*n stator windings 2 are divided into n groups, each group of stator windings includes four adjacent stator windings. The four adjacent stator windings 2 are sequentially recorded as stator winding A, stator winding B, stator winding C, and stator winding D in a clockwise direction. All A stator windings are sequentially connected in series in a forward direction to form a first series circuit, all B stator windings are sequentially connected in series in a forward direction to form a second series circuit, all C stator windings are sequentially connected in series in a forward direction to form a third series circuit, and all D stator windings are sequentially connected in series in a forward direction to form a fourth series circuit. The winding directions of all stator windings are consistent. The first series circuit and the third series circuit are connected in anti-parallel to form a first parallel circuit, and the second series circuit and the fourth series circuit are connected in anti-parallel to form a second parallel circuit.

[0042] A two-phase brushless DC motor with stable torque also includes an electronic speed regulator, wherein two ends of a first parallel circuit are electrically connected to a first input end and a first output end of the electronic speed regulator, respectively, and two ends of a second parallel circuit are electrically connected to a second input end and a second output end of the electronic speed regulator, respectively.

[0043] The stator winding has a coil start and a coil end. All stator windings A are numbered 1, 2, 3, ..., n in a clockwise direction, where 1 ≤ i ≤ n-1. The coil end of stator winding A numbered i is connected to the coil start of stator winding A numbered i+1, forming a first series circuit. Similarly, stator windings B, C, and D are connected to form second, third, and fourth series circuits.

[0044] Connect the starting end of the coil of stator winding A numbered 1 in the first series circuit to the ending end of the coil of stator winding C numbered n in the third series circuit, and connect the ending end of the coil of stator winding A numbered n in the first series circuit to the starting end of the coil of stator winding C numbered 1 in the third series circuit, to form a first parallel circuit. Connect the starting end of the coil of stator winding B numbered 1 in the second series circuit to the ending end of the coil of stator winding D numbered n in the fourth series circuit, and connect the ending end of the coil of stator winding B numbered n in the second series circuit to the starting end of the coil of stator winding D numbered 1 in the fourth series circuit, to form a second parallel circuit.

[0045] After the first series circuit and the third series circuit are connected in reverse parallel to form a first parallel circuit, they can share the same control circuit of the electronic speed controller. Since the current directions in stator winding A and stator winding C are opposite and the winding directions are consistent, the current phase difference between stator winding A and stator winding C is 180°, and the electromagnetic polarities are exactly opposite at the same time. After the second series circuit and the fourth series circuit are connected in reverse parallel to form a second parallel circuit, they can share the same control circuit of the electronic speed controller. Since the current directions in stator winding B and stator winding D are opposite and the winding directions are consistent, the current phase difference between stator winding B and stator winding D is 180°, and the electromagnetic polarities are exactly opposite at the same time.

[0046] Method (2):

[0047] The 4*n stator windings 2 are divided into n groups, each group of stator windings includes four adjacent stator windings. The four adjacent stator windings 2 are sequentially recorded as stator winding A, stator winding B, stator winding C, and stator winding D in a clockwise direction. All A stator windings are sequentially connected in series in a forward direction to form a first series circuit, all B stator windings are sequentially connected in series in a forward direction to form a second series circuit, all C stator windings are sequentially connected in series in a forward direction to form a third series circuit, and all D stator windings are sequentially connected in series in a forward direction to form a fourth series circuit. The stator windings A and B have the same winding direction, the stator windings C and D have the same winding direction, the stator windings A and C have opposite winding directions, and the stator windings B and D have opposite winding directions. The first series circuit and the third series circuit are connected in series in a forward direction to form a fifth series circuit, and the second series circuit and the fourth series circuit are connected in series in a forward direction to form a sixth series circuit.

[0048] A two-phase brushless DC motor with stable torque also includes an electronic speed regulator, wherein the two ends of the fifth series circuit are electrically connected to the first input end and the first output end of the electronic speed regulator respectively, and the two ends of the sixth series circuit are electrically connected to the second input end and the second output end of the electronic speed regulator respectively.

[0049] The stator winding has a coil start and a coil end. All stator windings A are numbered 1, 2, 3, ..., n in a clockwise direction, where 1 ≤ i ≤ n-1. The coil end of stator winding A numbered i is connected to the coil start of stator winding A numbered i+1, forming a first series circuit. Similarly, stator windings B, C, and D are connected to form second, third, and fourth series circuits.

[0050] The coil terminating end of the stator winding A numbered n in the first series circuit is connected to the coil starting end of the stator winding C numbered 1 in the third series circuit to form a fifth series circuit, and the coil terminating end of the stator winding B numbered n in the second series circuit is connected to the coil starting end of the stator winding D numbered 1 in the fourth series circuit to form a sixth series circuit.

[0051] After the first series circuit and the third series circuit are connected in series in the forward direction to form the fifth series circuit, they can share the same control circuit of the electronic speed regulator. Since the winding directions of stator winding A and stator winding C are opposite and the current directions are consistent, the electromagnetic polarities of stator winding A and stator winding C are exactly opposite at the same time. After the second series circuit and the fourth series circuit are connected in series in the forward direction to form the sixth series circuit, they can share the same control circuit of the electronic speed regulator. Since the winding directions of stator winding B and stator winding D are opposite and the current directions are consistent, the electromagnetic polarities of stator winding B and stator winding D are exactly opposite at the same time.

[0052] A two-phase brushless DC motor consisting of four stator windings and six permanent magnet poles is only the most basic combination. In actual use, it can be expanded proportionally according to demand to evolve into a series of products with a ratio of 4:6 between the number of stator windings and the number of permanent magnet poles, such as 8:12, 12:18, 16:24, etc., to adapt to applications with different requirements.

[0053] A control method for a two-phase brushless DC motor with stable torque in this embodiment is used for the above-mentioned two-phase brushless DC motor with stable torque, comprising the following steps:

[0054] The electronic speed regulator controls the stator winding's control current to be a sine wave or a square wave;

[0055] When the two-phase brushless DC motor adopts the stator winding connection method of method (1), the control method is as follows: the electronic speed regulator controls the current phase difference between the first parallel circuit and the second parallel circuit to be 90°, that is, the current phase difference between stator winding A and stator winding B is 90°, the current phase difference between stator winding B and stator winding C is 90°, the current phase difference between stator winding C and stator winding D is 90°, the current phase difference between stator winding A and stator winding C is 180°, and the current phase difference between stator winding B and stator winding D is 180°;

[0056] When the two-phase brushless DC motor adopts the stator winding connection method of method (2), the control method is as follows: the electronic speed regulator controls the current phase difference between the fifth series circuit and the sixth series circuit to be 90°, that is, the current phase difference between stator winding A and stator winding B is 90°, the current phase difference between stator winding B and stator winding C is 90°, the current phase difference between stator winding C and stator winding D is 90°, the current phase difference between stator winding A and stator winding C is 0°, and the current phase difference between stator winding B and stator winding D is 0°.

[0057] Take a two-phase brushless DC motor consisting of four stator windings and six permanent magnet poles as an example, as shown in Figure 1. The four stator windings are sequentially recorded as stator winding A, stator winding B, stator winding C, and stator winding D in a clockwise direction. The winding directions of the four stator windings are consistent. The six permanent magnet poles are sequentially recorded as the first permanent magnet pole of N polarity, the second permanent magnet pole of S polarity, the third permanent magnet pole of N polarity, the fourth permanent magnet pole of S polarity, the fifth permanent magnet pole of N polarity, and the sixth permanent magnet pole of S polarity in a clockwise direction. Initially, the stator winding B faces the The second permanent magnet pole with S polarity, the D stator winding is facing the fifth permanent magnet pole with N polarity, half of the A stator winding is aligned with half of the first permanent magnet pole, the other half of the A stator winding is aligned with half of the sixth permanent magnet pole, half of the C stator winding is aligned with half of the third permanent magnet pole, and the other half of the C stator winding is aligned with half of the fourth permanent magnet pole. The electronic speed controller controls the current phase difference of adjacent stator windings in each group of stator windings to be 90°. Initially, the currents of the A stator winding and the C stator winding reach the maximum value and are in opposite directions, and the currents of the B stator winding and the D stator winding are 0.

[0058] Example 2: The structure of this example is basically the same as that of Example 1, except that, as shown in Figure 3, the stator core 1 is arranged on the inner side of the rotor core 3, the stator winding 2 is arranged on the outer wall of the stator core 3, and the permanent magnet pole 4 is arranged on the inner wall of the rotor core 3.

[0059] In this solution, the rotor is located outside the stator to form an outer rotor brushless DC motor.

[0060] Taking a two-phase brushless DC motor consisting of 28 stator windings and 42 permanent magnet poles as an example, the stator is shown in Figure 4. The 28 stator windings are divided into 7 groups, each group of stator windings includes 4 adjacent stator windings. The 4 adjacent stator windings are recorded as stator winding A, stator winding B, stator winding C, and stator winding D in a clockwise direction. The rotor composed of 42 permanent magnet poles can directly use the rotor of an existing three-phase brushless DC motor, saving development costs.

[0061] The control method of a two-phase brushless DC motor with stable torque in this embodiment is used for the above-mentioned two-phase brushless DC motor with stable torque, and is the same as that in embodiment 1.

Claims

1. A two-phase brushless DC motor with stable torque, comprising a stator and a rotor, characterized in that: The stator comprises a stator core (1) and 4*n stator windings (2) wound around the stator core (1); the rotor comprises a rotor core (3) and 6*n permanent magnetic poles (4) wound around the rotor core, n being a positive integer, and the polarities of adjacent permanent magnetic poles (4) are opposite.

2. A two-phase brushless DC motor with stable torque according to claim 1, characterized in that: The 4*n stator windings (2) form a circle and are arranged at equal intervals along the circle, and the 6*n permanent magnet poles (4) form a circle and are arranged at equal intervals along the circle.

3. A two-phase brushless DC motor with stable torque according to claim 1, characterized in that: The rotor core (3) is arranged on the inner side of the stator core (1), the permanent magnet poles (4) are arranged on the outer side wall of the rotor core (3), and the stator winding (2) is arranged on the inner side wall of the stator core (1); or, the stator core (1) is arranged on the inner side of the rotor core (3), the stator winding (2) is arranged on the outer side wall of the stator core (1), and the permanent magnet poles (4) are arranged on the inner side wall of the rotor core (3).

4. A two-phase brushless DC motor with stable torque according to claim 1, 2 or 3, characterized in that: The 4*n stator windings (2) are divided into n groups, each group of stator windings includes 4 adjacent stator windings, and the 4 adjacent stator windings are sequentially recorded as A stator winding, B stator winding, C stator winding, and D stator winding in a clockwise direction. All A stator windings are sequentially connected in series in a forward direction to form a first series circuit, all B stator windings are sequentially connected in series in a forward direction to form a second series circuit, all C stator windings are sequentially connected in series in a forward direction to form a third series circuit, and all D stator windings are sequentially connected in series in a forward direction to form a fourth series circuit.

5. A two-phase brushless DC motor with stable torque according to claim 4, characterized in that: The winding directions of all stator windings (2) are consistent; the first series circuit and the third series circuit are connected in reverse parallel to form a first parallel circuit; and the second series circuit and the fourth series circuit are connected in reverse parallel to form a second parallel circuit.

6. A two-phase brushless DC motor with stable torque according to claim 5, characterized in that: It also includes an electronic speed regulator, wherein the two ends of the first parallel circuit are electrically connected to the first input end and the first output end of the electronic speed regulator respectively, and the two ends of the second parallel circuit are electrically connected to the second input end and the second output end of the electronic speed regulator respectively.

7. A two-phase brushless DC motor with stable torque according to claim 4, characterized in that: The winding directions of the A stator winding and the B stator winding are consistent, the winding directions of the C stator winding and the D stator winding are consistent, the winding directions of the A stator winding and the C stator winding are opposite, the winding directions of the B stator winding and the D stator winding are opposite, the first series circuit and the third series circuit are connected in series in forward direction to form a fifth series circuit, and the second series circuit and the fourth series circuit are connected in series in forward direction to form a sixth series circuit.

8. The torque-stable two-phase brushless DC motor according to claim 7, characterized in that: It also includes an electronic speed regulator, wherein the two ends of the fifth series circuit are electrically connected to the first input end and the first output end of the electronic speed regulator respectively, and the two ends of the sixth series circuit are electrically connected to the second input end and the second output end of the electronic speed regulator respectively.

9. A torque-stable two-phase brushless DC motor according to claim 1, 2 or 3, characterized in that: The stator core (1) is provided with a detection component for detecting the position of the rotor, and the detection component comprises more than two Hall sensors arranged along the circumferential direction.

10. A control method for a two-phase brushless DC motor with stable torque, used for the two-phase brushless DC motor with stable torque as claimed in claim 4, characterized in that: The following steps are involved: An electronic speed regulator is used to control the input current of stator winding A, stator winding B, stator winding C, and stator winding D, and the current phase difference of adjacent stator windings in each group of stator windings is controlled to be 90°.

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