A method for controlling the speed of a brushless motor

Abstract

The present invention relates to the field of motor speed control, and in particular to a method for controlling the speed of a brushed motor, comprising a motor control unit, a motor speed signal detection unit, and an interface M+, an interface M‑, and an interface S; the motor control unit is connected to the interface M+ and the interface M‑, the motor speed signal detection unit is connected to the interface S, and the output end of the motor speed signal detection unit is connected to a MOTO_CH port; the specific steps include: in an initial stage, a constant voltage method is used to control the brushed motor, and after the brushed motor is quickly accelerated to approach a target speed value of the brushed motor, constant speed control is switched to, and a pulse time between the interface S and the interface M+ and the interface M‑ of the brushed motor is increased to obtain a speed at which the brush of the brushed motor rotates one circle, thereby accurately obtaining a speed value of the brushed motor, and accurately regulating the speed of the brushed motor through the motor control unit, thereby avoiding the problem of poor motor speed control accuracy caused by differences in internal resistance inside the motor.

Description

Technical Field

[0001] The invention relates to the field of motor speed control, and in particular to a brushed motor speed control method. Background Art

[0002] Brushed motor, also known as Brushed DC Motor, is a common type of motor. It contains a brush device, and its main function is to convert electrical energy into mechanical energy (motor) or mechanical energy into electrical energy (generator). Brushed motor is the basis of all motors and has a wide range of applications.

[0003] The main structure of a brushed motor includes a stator, a rotor, and brushes. The stator has magnetic poles (winding type or permanent magnet type) and the rotor has windings. When current passes through the stator windings, a rotating magnetic field is generated, which attracts the rotor coils and generates electromagnetic induction, thereby generating a rotational torque. In order to maintain continuous rotation, the direction of the current needs to be changed periodically, which is achieved through brushes and commutators. The brushes distribute the DC power from the power supply to each coil of the stator, while the commutator is responsible for switching the direction of the current at the appropriate time.

[0004] There are three common ways to control brushed motors, namely, direct on / off or setting a fixed duty cycle, constant voltage control, and constant speed control. The constant speed control currently on the market uses the motor's own reverse electromotive force to perform corresponding control. However, this method calculates the approximate internal resistance of the motor and performs algorithm control in a fixed manner with the motor's internal resistance. Due to the inconsistency of internal resistance between different motors, there will be a certain deviation in the center value of the speed, and the speed range value control accuracy is poor. Summary of the invention

[0005] The object of the present invention is to provide a method for controlling the speed of a brushed motor, aiming to improve the problem of deviation in the center value of the speed caused by inconsistent internal resistance between different motors in the conventional constant speed control method.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A brushless motor speed control method includes a motor control unit, a motor speed signal detection unit, and an interface M+, an interface M-, and an interface S;

[0008] The interface M+, the interface M- and the interface S are connected to the three brushes respectively; the motor control unit is connected to the interface M+ and the interface M-, the motor speed signal detection unit is connected to the interface S, and the output end of the motor speed signal detection unit is connected to the MOTO_CH port;

[0009] The specific steps include:

[0010] S1 is turned on, and the motor control unit performs constant voltage control on the brushed motor;

[0011] S2 obtains the voltage value at both ends of the brush motor. When the voltage value at both ends of the brush motor is greater than or equal to the constant voltage setting value of the brush motor, the motor control unit performs constant speed control on the brush motor.

[0012] S3 determines whether the MOTO_CH port is at a low level, if so, proceeds to step S4, otherwise proceeds to step S5;

[0013] S4 determines if Moto_CH_Work_Flag is 0 and lasts for 300us. If so, Moto_CH_Work_Flag is set to 1, otherwise, timer T4 is cleared;

[0014] S5 determines whether Moto_CH_Work_Flag is 1 when a rising edge interrupt occurs at the MOTO_CH port.

[0015] If yes, clear the MOTO_CH port pulse time value, assign the effective timer T4 count value between the last rising edge and the next rising edge to the MOTO_CH port pulse time, and clear the timer T4 value;

[0016] Otherwise, the rising edge interrupt is considered as an abnormal signal, and the pulse time value of the MOTO_CH port is output;

[0017] S6 obtains the brush motor speed through the pulse time value of the MOTO_CH port, and controls the motor control unit to adjust the brush motor speed;

[0018] Among them, Moto_CH_Work_Flag is the continuous low level flag of the MOTO_CH port.

[0019] Furthermore, the step S1 also includes

[0020] Step S1.1 obtains the voltage value across the brushed motor.

[0021] When Motor_Vol_Value<(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), adjust the duty cycle by 10-20 values.

[0022] When Motor_Vol_Value>(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), adjust the duty cycle by 1-5 values;

[0023] Among them, Motor_Vol_Value is the current voltage value across the brushed motor, Motor_Vol_Set_Value is the constant voltage setting value of the brushed motor, and Motor_Vol_Differ_Value is the difference between the constant voltage setting value of the brushed motor and the target voltage value.

[0024] Furthermore, the motor control unit includes a control module, a voltage detection module, a current sampling module and a filtering module;

[0025] The filter module is electrically connected between the interface M+ and the interface M-;

[0026] The input end of the control module is connected to the MOTO_PWM signal end to receive an external PWM signal; the first output end of the control module is electrically connected to the voltage detection module and the interface M+, and the output end of the voltage detection module outputs a V_M voltage signal; the second output end of the control module is electrically connected to the positive pole of the power supply; the first input end of the current sampling module is electrically connected to the interface M-, the second input end of the current sampling module is grounded, and the output end of the current sampling module outputs an I_M current signal.

[0027] Further, the control module includes a field effect transistor Q1, a transistor Q3, a resistor R1, a resistor R2, a resistor R5 and a resistor R9;

[0028] One end of the resistor R5 is connected to the MOTO_PWM signal end as an input end, the other end of the resistor R5 is electrically connected to one end of the resistor R9 and the base of the transistor Q3, the collector of the transistor Q3 is electrically connected to one end of the resistor R2, and the other end of the resistor R2 is electrically connected to the pin 4 of the field effect transistor Q1 and one end of the resistor R1; the pins 5, 6, 7 and 8 of the field effect transistor Q1 are all electrically connected to the input end of the voltage detection module and the interface M+;

[0029] The other end of the resistor R1 and pins 1 and 2 of the field effect transistor Q1 are electrically connected to the positive electrode of the power supply, and the emitter of the transistor Q3 and the other end of the resistor R9 are grounded.

[0030] Further, the voltage detection module includes a resistor R3, a resistor R6, a resistor R11 and a capacitor C3;

[0031] One end of the resistor R3 is electrically connected to the first output end of the control module, the other end of the resistor R3 is electrically connected to one end of the resistor R6 and one end of the resistor R11, the other end of the resistor R6 is electrically connected to one end of the capacitor C3, and serves as an output end to output a V_M voltage signal;

[0032] The other end of the resistor R11 and the other end of the capacitor C3 are both grounded.

[0033] Further, the current sampling module includes a resistor R12, a resistor R13, a resistor R14 and a capacitor C5;

[0034] One end of the resistor R12, one end of the resistor R13 and one end of the resistor R14 are all electrically connected to the interface M-, and the other end of the resistor R14 is electrically connected to one end of the capacitor C5 and serves as an output end to output an I_M current signal;

[0035] The other end of the capacitor C5, the other end of the resistor R12 and the other end of the resistor R13 are all grounded.

[0036] Furthermore, the filtering module includes a capacitor C1 and a diode D1, the capacitor C1 is electrically connected between the interface M+ and the interface M-, the anode of the diode D1 is electrically connected to the interface M-, and the cathode of the diode D1 is electrically connected to the interface M+.

[0037] Further, the motor speed signal detection unit includes a transistor Q2, a resistor R4, a resistor R7, a resistor R8, a resistor R10 and a capacitor C2, a capacitor C4;

[0038] One end of the resistor R7 is electrically connected to the interface S, the other end of the resistor R7 is electrically connected to one end of the resistor R8 and one end of the capacitor C4, the other end of the resistor R8 is electrically connected to one end of the resistor R10 and the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to one end of the resistor R4 and one end of the capacitor C2, and is connected to the MOTO_CH port as an output terminal;

[0039] The other end of the resistor R10 , the other end of the capacitor C4 , the other end of the capacitor C2 , and the emitter of the transistor Q2 are all grounded.

[0040] Furthermore, the following condition is satisfied:

[0041] A*τ1<1 / 4T;

[0042] 3 <A<8;

[0043] The τ1 is a filtering time constant of a filter formed by the resistor R7 and the capacitor C4, and the T is the time it takes for the rotor of the brushed motor to rotate 120°.

[0044] Furthermore, the following condition is satisfied:

[0045] τ2>B*f;

[0046] 5 <B<10;

[0047] The τ2 is a filtering time constant of a filter formed by the resistor R4 and the capacitor C2, and the f is a driving frequency of the brushed motor.

[0048] After adopting the above technical solution, the present invention has the following advantages compared with the background technology:

[0049] In the initial stage, a constant voltage method is used to control the brush motor. After the brush motor is quickly accelerated to approach the target speed value of the brush motor, it is switched to constant speed control. By increasing the pulse time between the interface S and the interface M+ and interface M- of the brush motor, the speed of the brush motor's brush rotation for one circle is obtained, thereby accurately obtaining the speed value of the brush motor. The speed of the brush motor is precisely regulated by the motor control unit, thereby avoiding the problem of poor motor speed control accuracy caused by differences in the internal resistance of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A block diagram of the brushless motor speed control method of the present invention;

[0051] Figure 2 A circuit diagram of a motor control unit and a motor speed signal detection unit of the brushed motor speed control method of the present invention;

[0052] Figure 3 This is a connection relationship diagram of interface M+, interface M- and interface S of the brush motor speed control method of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] In addition, it should be noted that the terms "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element of the present invention must have a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0055] When an element is referred to as being “fixed to” or “disposed on” or “provided on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0056] Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0057] Example

[0058] Please refer to Figure 1-3 As shown, this embodiment provides a method for controlling the speed of a brushed motor, including a motor control unit, a motor speed signal detection unit, and an interface M+, an interface M-, and an interface S. The interface M+, the interface M-, and the interface S are respectively connected to three brushes; the motor control unit is connected to the interface M+ and the interface M-, the motor speed signal detection unit is connected to the interface S, and the output end of the motor speed signal detection unit is connected to the MOTO_CH port.

[0059] Please refer to Figure 3 As shown, in this embodiment, during the 120° rotation of the rotor of the brushed motor, in the 0-30° stage, the interface S is connected to the interface M+, in the 30-90° stage, the interface S is suspended, and in the 90-120° stage, the interface S is connected to M-.

[0060] Please refer to Figure 1 As shown, the specific steps include:

[0061] S1 is turned on, and the motor control unit performs constant voltage control on the brushed motor;

[0062] S2 obtains the voltage value at both ends of the brush motor. When the voltage value at both ends of the brush motor is greater than or equal to the constant voltage setting value of the brush motor, the motor control unit performs constant speed control on the brush motor.

[0063] S3 determines whether the MOTO_CH port is at a low level, if so, proceeds to step S4, otherwise proceeds to step S5;

[0064] S4 determines whether Moto_CH_Work_Flag is 0 and lasts for 300us. If so, Moto_CH_Work_Flag is set to 1, otherwise the timer T4 is cleared. Since the high-voltage pulse generated when the rotor rotates between 30-90° will be affected by the actual load of the brushed motor, when the brushed motor is overloaded, the reverse voltage will be too large, causing the filtered voltage in this area to turn on the transistor, causing the MOTO_CH port signal to be pulled to half power or to a low level in a short time. Steps S3 and S4 are used to check the level of the MOTO_CH port to avoid mis-conduction that affects the accuracy of the brushed motor speed control. Similarly, the duration can also be 200us, 400us or other time intervals.

[0065] S5 determines whether Moto_CH_Work_Flag is 1 when a rising edge interrupt occurs at the MOTO_CH port.

[0066] If yes, clear the MOTO_CH port pulse time value, assign the effective timer T4 count value between the last rising edge and the next rising edge to the MOTO_CH port pulse time, and clear the timer T4 value;

[0067] Otherwise, the rising edge interrupt is considered as an abnormal signal, and the pulse time value of the MOTO_CH port is output;

[0068] S6 obtains the brush motor speed through the pulse time value of the MOTO_CH port and controls the motor control unit to adjust the brush motor speed.

[0069] Among them, Moto_CH_Work_Flag is the continuous low level flag of the MOTO_CH port.

[0070] The frequency F of the brushed motor for one revolution is equal to the frequency of the timer T4 divided by the frequency division ratio of 12 divided by the pulse time of the MOTO_CH port; combined with the speed formula n=60*F / p, where p is the number of rotating magnetic fields of the brushed motor, in this embodiment, p=3. It can be obtained that the target speed value of the brushed motor is equal to 60 multiplied by the frequency of the timer T4 divided by the frequency division ratio of 12 divided by the pulse time of the MOTO_CH port divided by 3.

[0071] In this embodiment, a constant voltage method is adopted in the initial stage to control the brush motor. After the brush motor is quickly accelerated to approach the target speed value of the brush motor, constant speed control is switched to the constant speed control. By increasing the pulse time between the interface S and the interface M+ and the interface M- of the brush motor, the speed of the brush of the brush motor rotating one circle is obtained, thereby accurately obtaining the speed value of the brush motor. The speed of the brush motor is precisely regulated by the motor control unit, thereby avoiding the problem of poor motor speed control accuracy caused by the difference in the internal resistance of the motor.

[0072] Furthermore, step S1 also includes

[0073] Step S1.1 obtains the voltage value across the brushed motor.

[0074] When Motor_Vol_Value<(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), the duty cycle is adjusted by 10-20 values; in this embodiment, when Motor_Vol_Value<(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), the duty cycle is adjusted by 15 values; similarly, when Motor_Vol_Value<(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), the duty cycle can also be adjusted by 10 values ​​or 20 values.

[0075] When Motor_Vol_Value>(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), the duty cycle is adjusted by 1-5 values; in this embodiment, when Motor_Vol_Value>(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), the duty cycle is adjusted by 3 values; similarly, when Motor_Vol_Value>(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), the duty cycle can also be adjusted by 1 value or 5 values.

[0076] Among them, Motor_Vol_Value is the current voltage value across the brushed motor, Motor_Vol_Set_Value is the constant voltage setting value of the brushed motor, and Motor_Vol_Differ_Value is the difference between the constant voltage setting value of the brushed motor and the target voltage value.

[0077] When the speed of the brushed motor is low, the duty cycle is adjusted greatly to increase the speed of the brushed motor and quickly approach the target speed. When the speed of the brushed motor is greater than the target speed, the duty cycle is adjusted slightly to avoid a rapid decrease in speed that affects the driving effect of the brushed motor.

[0078] Please refer to Figure 2As shown, specifically, the motor control unit includes a control module, a voltage detection module, a current sampling module and a filter module. The filter module is electrically connected between the interface M+ and the interface M-. The input end of the control module is connected to the MOTO_PWM signal end, receives the external PWM signal, and adjusts the speed of the brushed motor. The first output end of the control module is electrically connected to the voltage detection module and the interface M+, and the output end of the voltage detection module outputs a V_M voltage signal. The second output end of the control module is electrically connected to the positive pole of the power supply. The first input end of the current sampling module is electrically connected to the interface M-, the second input end of the current sampling module is grounded, and the output end of the current sampling module outputs an I_M current signal.

[0079] Specifically, the control module includes a field effect transistor Q1, a transistor Q3, a resistor R1, a resistor R2, a resistor R5 and a resistor R.

[0080] One end of the resistor R5 is connected to the MOTO_PWM signal end as an input end, the other end of the resistor R5 is electrically connected to one end of the resistor R9 and the base of the transistor Q3, the collector of the transistor Q3 is electrically connected to one end of the resistor R2, and the other end of the resistor R2 is electrically connected to the pin 4 of the field effect transistor Q1 and one end of the resistor R1. Pins 5, 6, 7 and 8 of the field effect transistor Q1 are all electrically connected to the input end of the voltage detection module and the interface M+.

[0081] The other end of the resistor R1 and the pins 1 and 2 of the field effect transistor Q1 are electrically connected to the positive electrode of the power supply, and the emitter of the transistor Q3 and the other end of the resistor R9 are grounded. In this embodiment, the model of the field effect transistor Q1 is NP4409SR-G, the interface CN1 is connected to the battery as a power source to supply power to the control module, and B+ is the positive electrode of the battery.

[0082] Specifically, the voltage detection module includes a resistor R3, a resistor R6, a resistor R11 and a capacitor C3.

[0083] One end of the resistor R3 is electrically connected to the first output end of the control module, that is, one end of the resistor R3 is electrically connected to pins 5, 6, 7, and 8 of the field effect transistor Q1. The other end of the resistor R3 is electrically connected to one end of the resistor R6 and one end of the resistor R11, and the other end of the resistor R6 is electrically connected to one end of the capacitor C3, and outputs the V_M voltage signal as an output end.

[0084] The other end of the resistor R11 and the other end of the capacitor C3 are both grounded.

[0085] Specifically, the current sampling module includes a resistor R12, a resistor R13, a resistor R14 and a capacitor C5.

[0086] One end of the resistor R12, one end of the resistor R13 and one end of the resistor R14 are all electrically connected to the interface M-, and the other end of the resistor R14 is electrically connected to one end of the capacitor C5 and serves as an output end to output the I_M current signal.

[0087] The other end of the capacitor C5, the other end of the resistor R12 and the other end of the resistor R13 are all grounded.

[0088] Specifically, the filter module includes a capacitor C1 and a diode D1, the capacitor C1 is electrically connected between the interface M+ and the interface M-, the anode of the diode D1 is electrically connected to the interface M-, and the cathode of the diode D1 is electrically connected to the interface M+.

[0089] Specifically, the motor speed signal detection unit includes a transistor Q2, a resistor R4, a resistor R7, a resistor R8, a resistor R10, a capacitor C2, and a capacitor C4.

[0090] One end of the resistor R7 is electrically connected to the interface S, the other end of the resistor R7 is electrically connected to one end of the resistor R8 and one end of the capacitor C4, the other end of the resistor R8 is electrically connected to one end of the resistor R10 and the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to one end of the resistor R4 and one end of the capacitor C2, and is connected to the MOTO_CH port as an output end.

[0091] The other end of the resistor R10, the other end of the capacitor C4, the other end of the capacitor C2 and the emitter of the transistor Q2 are all grounded.

[0092] The motor speed signal unit satisfies the following conditional formula:

[0093] A*τ1<1 / 4T;

[0094] 3 <A<8;

[0095] τ2>B*f;

[0096] 5 <B<10;

[0097] Wherein, τ1 is the filtering time constant of the filter composed of the resistor R7 and the capacitor C4, τ2 is the filtering time constant of the filter composed of the resistor R4 and the capacitor C2, T is the time for the rotor of the brushed motor to rotate 120°, and f is the driving frequency of the brushed motor. In this embodiment, A is equal to 5, and similarly, A can also be equal to 4 or 7; B is equal to 7, and similarly, B can also be equal to 6 or 9.

[0098] The filtering time constant of the filter composed of the resistor R7 and the capacitor C4 is controlled to avoid it being too large, resulting in the interface S being connected to the interface M- and being unable to be pulled to a low level after passing through the resistor R7 and the capacitor C4; at the same time, it is prevented from being too small, resulting in the inability to suppress the oscillation waveform generated by the reverse electromotive force of the brush motor itself during the floating stage of the interface S.

[0099] The resistors R8 and R10 perform voltage division, and the voltage division ratio of the resistors R8 and R10 requires filtering out the signal waveform of the first 90° of a cycle to prevent the transistor from being turned on.

[0100] The filtering time constant of the filter composed of resistor R4 and capacitor C2 is controlled to prevent the voltage of the oscillation waveform from exceeding the actual high-level voltage due to excessive load, resulting in false triggering of transistor Q2 and affecting the accuracy of receiving the pulse time value of the MOTO_CH port.

[0101] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for controlling the speed of a brushless motor, characterized in that: It includes a motor control unit, a motor speed signal detection unit and an interface M+, an interface M-, and an interface S; The interface M+, the interface M- and the interface S are connected to the three brushes respectively; the motor control unit is connected to the interface M+ and the interface M-, the motor speed signal detection unit is connected to the interface S, and the output end of the motor speed signal detection unit is connected to the MOTO_CH port; The specific steps include: S1 is turned on, and the motor control unit performs constant voltage control on the brushed motor; S2 obtains the voltage value at both ends of the brush motor. When the voltage value at both ends of the brush motor is greater than or equal to the constant voltage setting value of the brush motor, the motor control unit performs constant speed control on the brush motor. S3 determines whether the MOTO_CH port is at a low level, if so, proceeds to step S4, otherwise proceeds to step S5; S4 determines if Moto_CH_Work_Flag is 0 and lasts for 300us. If so, Moto_CH_Work_Flag is set to 1, otherwise, timer T4 is cleared; S5 determines whether Moto_CH_Work_Flag is 1 when a rising edge interrupt occurs at the MOTO_CH port. If yes, clear the MOTO_CH port pulse time value, assign the effective timer T4 count value between the last rising edge and the next rising edge to the MOTO_CH port pulse time, and clear the timer T4 value; Otherwise, the rising edge interrupt is considered as an abnormal signal, and the pulse time value of the MOTO_CH port is output; S6 obtains the brush motor speed through the pulse time value of the MOTO_CH port, and controls the motor control unit to adjust the brush motor speed; Among them, Moto_CH_Work_Flag is the continuous low level flag of the MOTO_CH port.

2. The method for controlling the speed of a brushless motor according to claim 1, characterized in that: The step S1 also includes Step S1.1 obtains the voltage value across the brushed motor. When Motor_Vol_Value<(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), adjust the duty cycle by 10-20 values. When Motor_Vol_Value>(Motor_Vol_Set_Value-Motor_Vol_Differ_Value), adjust the duty cycle by 1-5 values; Among them, Motor_Vol_Value is the current voltage value across the brushed motor, Motor_Vol_Set_Value is the constant voltage setting value of the brushed motor, and Motor_Vol_Differ_Value is the difference between the constant voltage setting value of the brushed motor and the target voltage value.

3. The method for controlling the speed of a brushless motor according to claim 1, wherein: The motor control unit includes a control module, a voltage detection module, a current sampling module and a filtering module; The filter module is electrically connected between the interface M+ and the interface M-; The input end of the control module is connected to the MOTO_PWM signal end to receive an external PWM signal; the first output end of the control module is electrically connected to the voltage detection module and the interface M+, and the output end of the voltage detection module outputs a V_M voltage signal; the second output end of the control module is electrically connected to the positive pole of the power supply; the first input end of the current sampling module is electrically connected to the interface M-, the second input end of the current sampling module is grounded, and the output end of the current sampling module outputs an I_M current signal.

4. The method for controlling the speed of a brushed motor according to claim 3, characterized in that: The control module includes a field effect transistor Q1, a transistor Q3, a resistor R1, a resistor R2, a resistor R5 and a resistor R9; One end of the resistor R5 is connected to the MOTO_PWM signal end as an input end, the other end of the resistor R5 is electrically connected to one end of the resistor R9 and the base of the transistor Q3, the collector of the transistor Q3 is electrically connected to one end of the resistor R2, and the other end of the resistor R2 is electrically connected to the pin 4 of the field effect transistor Q1 and one end of the resistor R1; the pins 5, 6, 7 and 8 of the field effect transistor Q1 are all electrically connected to the input end of the voltage detection module and the interface M+; The other end of the resistor R1 and pins 1 and 2 of the field effect transistor Q1 are electrically connected to the positive electrode of the power supply, and the emitter of the transistor Q3 and the other end of the resistor R9 are grounded.

5. The method for controlling the speed of a brushed motor according to claim 3, characterized in that: The voltage detection module includes a resistor R3, a resistor R6, a resistor R11 and a capacitor C3; One end of the resistor R3 is electrically connected to the first output end of the control module, the other end of the resistor R3 is electrically connected to one end of the resistor R6 and one end of the resistor R11, the other end of the resistor R6 is electrically connected to one end of the capacitor C3, and serves as an output end to output a V_M voltage signal; The other end of the resistor R11 and the other end of the capacitor C3 are both grounded.

6. The method for controlling the speed of a brushed motor according to claim 3, characterized in that: The current sampling module includes a resistor R12, a resistor R13, a resistor R14 and a capacitor C5; One end of the resistor R12, one end of the resistor R13 and one end of the resistor R14 are all electrically connected to the interface M-, and the other end of the resistor R14 is electrically connected to one end of the capacitor C5 and serves as an output end to output an I_M current signal; The other end of the capacitor C5, the other end of the resistor R12 and the other end of the resistor R13 are all grounded.

7. The method for controlling the speed of a brushed motor according to claim 3, characterized in that: The filtering module includes a capacitor C1 and a diode D1. The capacitor C1 is electrically connected between the interface M+ and the interface M-. The anode of the diode D1 is electrically connected to the interface M-. The cathode of the diode D1 is electrically connected to the interface M+.

8. The method for controlling the speed of a brushed motor according to claim 1, characterized in that: The motor speed signal detection unit includes a transistor Q2, a resistor R4, a resistor R7, a resistor R8, a resistor R10 and a capacitor C2, a capacitor C4; One end of the resistor R7 is electrically connected to the interface S, the other end of the resistor R7 is electrically connected to one end of the resistor R8 and one end of the capacitor C4, the other end of the resistor R8 is electrically connected to one end of the resistor R10 and the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to one end of the resistor R4 and one end of the capacitor C2, and is connected to the MOTO_CH port as an output terminal; The other end of the resistor R10 , the other end of the capacitor C4 , the other end of the capacitor C2 , and the emitter of the transistor Q2 are all grounded.

9. The method for controlling the speed of a brushed motor according to claim 8, characterized in that: Satisfy the following conditions: A*τ1<1 / 4T; 3<A<8； The τ1 is a filtering time constant of a filter formed by the resistor R7 and the capacitor C4, and the T is the time it takes for the rotor of the brushed motor to rotate 120°.

10. The method for controlling the speed of a brushed motor according to claim 8, characterized in that: Satisfy the following conditions: τ2>B*f; 5<B<10； The τ2 is a filtering time constant of a filter formed by the resistor R4 and the capacitor C2, and the f is a driving frequency of the brushed motor.

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