Brushless direct current motor control system and brushless direct current motor controller adopting same

Abstract

The invention discloses a brushless direct-current motor control system and a brushless direct-current motor controller adopting the same, which realize a current loop and generate a motor driving signal through hardware circuit design, cancel a rotating speed loop and a corresponding motor rotating speed measurement module, and only reserve a position loop in embedded software. The resource overhead of the embedded processor is greatly reduced, so that embedded software can bear more other work tasks, the hardware design is simplified, the product cost is reduced, and the volume and the weight of a product are favorably compressed. Moreover, according to a current loop control strategy, an existing PWM control mode is improved into current direct control, the system complexity is further reduced, the design is simplified, EMI electromagnetic interference noise in the device can be reduced, smoother rotating motion can be provided, the tiny jitter defect of a PWM driving mode at the zero-current intersection position is avoided, and the reliability of the device is improved. And a hardware circuit control mode also has the advantages of simplicity, high efficiency and quick response.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular, to a brushless DC motor control system. Additionally, it also relates to a brushless DC motor controller employing the above control system. Background Art

[0002] Since the birth of the permanent magnet brushless DC motor in the 1960s, it has been widely used in various fields such as aerospace, industrial control, and household appliances due to its advantages of simple structure, reliable operation, convenient maintenance, high operating efficiency, and good speed regulation performance. When the brushless DC motor is used as an actuator to achieve the required deflection angle position of the product, such as the opening of the liquid / gas valve on the engine, the rudder surface deflection angle of the electric rudder, the attitude control of the multi-degree-of-freedom azimuth control pan-tilt, etc., the brushless DC motor control system needs to detect signals such as the actual deflection angle, the actual speed of the motor, the position of the motor rotor, and the phase current of the motor, and control the steering and speed of the brushless DC motor in real time, so as to meet the requirements of the product for steady-state and dynamic performance indicators such as angle position accuracy, response time, and overshoot.

[0003] The typical architecture of the existing brushless DC motor control system is as Figure 1 shown. The required deflection angle position of the product is the system input. The motor control system includes three closed-loop circuits: a position loop, a speed loop, and a current loop. The power part is a three-phase inverter full bridge. The PWM drive signal generation module determines the PWM duty cycle of the power switch drive signal according to the set motor phase voltage, and determines the commutation logic according to the motor rotor position measured by the Hall device, and outputs six-way power switch drive signals to the three-phase inverter full bridge. The inverter outputs a three-phase AC square wave signal to the stator armature winding of the brushless DC motor to control the steering and speed of the motor. The motor output shaft is mechanically connected to a gear reducer to reduce the rotational speed, driving the output shaft of the reducer to rotate to the required angle position, and the actual deflection angle of the output shaft is measured by an angle sensor. The current sensor can be a milliohm resistor connected in series in the power circuit, or a Hall current sensor can be selected to achieve non-contact measurement. The angle sensor can measure the actual deflection angle position of the product actuator through a rotary potentiometer. The Hall device (3 Hall switch-type position sensors, arranged at intervals of 120° on the motor) can also be replaced by an optical encoder or an electromagnetic sensor to monitor the motor rotor position in real time to implement the motor commutation logic.

[0004] However, the typical architecture has the following disadvantages: The three control loops need to be implemented by programming in the embedded software, and the PWM drive signal generation module for implementing the commutation logic is currently allocated to be implemented in the software, which will consume a large amount of computing resources and time resources of the embedded processor. Moreover, due to the need for three closed-loop controls, the process of tuning the internal control parameters is difficult and time-consuming. In addition, this architecture also requires designing a dedicated motor speed measurement module and speed measurement method, and the support of corresponding sensors. When the embedded software of the product control system needs to undertake more tasks, such as in addition to controlling the brushless DC motor, it needs to complete tasks such as multi-signal acquisition control, signal processing algorithms, control of other actuators, and multi-channel communication, this typical architecture is not an optimal technical solution. In addition, when the application fields and usage scenarios of the product require developers to further simplify the design of the motor control system, improve reliability, reduce hardware costs, and compress the volume and weight of the product, this typical architecture is also difficult to meet the requirements. Summary of the Invention

[0005] The present invention provides a brushless DC motor control system and a brushless DC motor controller using the same, which greatly reduces the resource overhead of the embedded processor, enables the embedded software to undertake more other tasks, simplifies the hardware design, reduces the product cost, is beneficial to compressing the volume and weight of the product, and reduces the system complexity and simplifies the design.

[0006] According to one aspect of the present invention, there is provided a brushless DC motor control system, comprising:

[0007] An angle sensor for measuring the deflection angle of the output shaft of the reducer;

[0008] Embedded software, carried in the embedded hardware, for inputting the desired deflection angle and the sampled and measured deflection angle, and calculating the set motor current according to the difference between the desired deflection angle and the measured deflection angle;

[0009] A current sensor for measuring the motor current;

[0010] A motor current control circuit for outputting a motor forward and reverse switch signal according to the signal polarity of the set motor current, and controlling the on or off of the DC power supply of the three-phase inverter full bridge according to the signal magnitude of the set motor current and the magnitude of the measured motor current, so as to realize the closed-loop control of the motor current;

[0011] Three Hall devices for measuring the position of the motor rotor;

[0012] A motor drive signal generation circuit for controlling the rotation direction of the motor according to the motor forward and reverse switch signal, controlling the commutation logic of the motor according to the position of the motor rotor, and outputting six drive signals to the three-phase inverter full bridge;

[0013] A three-phase inverter full bridge is used to invert the direct current output by a direct current power supply into a three-phase alternating current square wave signal according to six drive signals and then output it to a motor.

[0014] Further, the motor current control circuit includes an inverting proportional amplifier circuit, a logarithmic amplifier circuit, a non-inverting proportional amplifier circuit, a comparison circuit, and a direct current power supply circuit. The inverting proportional amplifier circuit is used to perform inverting proportional amplification on the set motor current signal. The logarithmic amplifier circuit outputs a motor forward and reverse switch signal to the motor drive signal generation circuit according to the signal polarity of the set motor current after inversion, and logarithmically amplifies its magnitude after removing the signal polarity of the set motor current after inversion, and outputs a positive voltage signal related to the magnitude of the set motor current signal to the comparison circuit. The non-inverting proportional amplifier circuit performs non-inverting proportional amplification on the measured motor current signal and then outputs it to the comparison circuit. The comparison circuit compares the amplified measured motor current signal with the positive voltage signal output by the logarithmic amplifier circuit, and outputs a switch drive signal of the direct current power supply to the direct current power supply circuit according to the comparison result. The direct current power supply circuit is used to provide a direct current power supply for the three-phase inverter full bridge, and the output end of the direct current power supply circuit is fed back to the comparison circuit. When the measured motor current is greater than the first threshold, the comparison circuit controls the output of the direct current power supply circuit to be turned off. When the measured motor current is less than the second threshold, the comparison circuit controls the output of the direct current power supply circuit to be turned on, where the first threshold is greater than the second threshold.

[0015] Further, the logarithmic amplifier circuit includes a resistor R3, a resistor R4, a resistor R5, a capacitor C1, an operational amplifier N2, a zener diode V1, a diode V2, a diode V3, a resistor R6, a resistor R7, an operational amplifier N3, a resistor R8, a zener diode V4, a resistor R20, and an NPN transistor N5. The first end of the resistor R3 is connected to the output end of the inverting proportional amplification circuit, and the second end is respectively connected to the input end of the operational amplifier N2, the first end of the capacitor C1, the first end of the resistor R4, and the first end of the resistor R5. The output end of the operational amplifier N2 is respectively connected to the second end of the capacitor C1, the first end of the resistor R20, and the input end of the zener diode V1. The second end of the resistor R20 is connected to the base of the NPN transistor N5. The collector of the NPN transistor N5 is connected to the motor drive signal generation circuit, and the emitter is grounded. The output end of the zener diode V1 is respectively connected to the cathode of the diode V2 and the anode of the diode V3. The anode of the diode V2 is respectively connected to the second end of the resistor R4 and the first end of the resistor R6. The cathode of the diode V3 is respectively connected to the second end of the resistor R5 and the input end of the operational amplifier N3. The second end of the resistor R6 and the first end of the resistor R7 are both connected to the other input end of the operational amplifier N3. The second end of the resistor R7 and the first end of the resistor R8 are both connected to the output end of the operational amplifier N3. The second end of the resistor R8 is respectively connected to the output end of the zener diode V4 and the comparison circuit. The input end of the zener diode V4 is grounded.

[0016] Further, when the polarity of the motor current signal is set to positive, the output motor forward / reverse switch signal is low level, and the motor rotates in reverse; when the polarity of the motor current signal is set to negative, the output motor forward / reverse switch signal is high level, and the motor rotates forward.

[0017] Further, the comparison circuit includes a resistor R12, a resistor R13, a resistor R14, a resistor R15, a capacitor C3, and an operational amplifier N5. The first end of the resistor R12 is connected to the output end of the non-inverting proportional amplification circuit. The second end of the resistor R12 is respectively connected to the first end of the resistor R13, the first end of the resistor R14, the first end of the capacitor C3, and the input end of the operational amplifier N5. The other input end of the operational amplifier N5 is connected to the output end of the logarithmic amplifier circuit. The second end of the resistor R13 is grounded. The second end of the capacitor C3 is connected to the first end of the resistor R15. The second end of the resistor R15 is connected to the output end of the operational amplifier N5. The second end of the resistor R14 is connected to the output end of the DC power supply circuit. The output end of the operational amplifier N5 is connected to the DC power supply circuit.

[0018] Further, the DC power supply circuit includes a resistor R16, a resistor R17, an NPN transistor V6, a resistor R18, a resistor R19, a PNP transistor V7, and a DC power supply. The first end of the resistor R16 is connected to the output end of the comparison circuit, the second end of the resistor R16 is connected to the base of the NPN transistor V6, the emitter of the NPN transistor V6 is connected to the first end of the resistor R17, the second end of the resistor R17 is grounded, the collector of the NPN transistor V6 is connected to the first end of the resistor R18, the second end of the resistor R18 is connected to the first end of the resistor R19 and the base of the PNP transistor V7, the second ends of the resistor R19 and the emitter of the PNP transistor V7 are both connected to the positive pole of the DC power supply, the negative pole of the DC power supply is grounded, and the collector of the PNP transistor V7 is respectively connected to the resistor R14 and the three-phase inverter full bridge.

[0019] Further, when the measured motor current is greater than the first threshold, the output of the operational amplifier N5 is ground, both the NPN transistor V6 and the PNP transistor V7 are cut off, and the DC power supply stops supplying power to the three-phase inverter full bridge; when the measured motor current is less than the second threshold, the output of the operational amplifier N5 is high level, both the NPN transistor V6 and the PNP transistor V7 are turned on, and the DC power supply starts to supply power to the three-phase inverter full bridge.

[0020] Further, the motor current control circuit further includes a low-pass filter circuit before the in-phase proportional amplification circuit, which is used to perform low-pass filtering processing on the measured motor current signal.

[0021] Further, the motor drive signal generation circuit includes a control chip and three drive chips. The control chip is respectively connected to the motor current control circuit, three Hall devices, and three drive chips, and is used to output six drive signals according to the input motor forward and reverse switch signal and the motor rotor position signal. The six drive signals are power-amplified by the three drive chips and then output to the three-phase inverter full bridge to drive the three-phase inverter full bridge to invert the direct current into a three-phase alternating current square wave signal.

[0022] In addition, the present invention also provides a brushless DC motor controller, which adopts the brushless DC motor control system as described above.

[0023] The present invention has the following beneficial effects:

[0024] The brushless DC motor control system of the present invention realizes the current loop circuit and generates the motor drive signal through the hardware circuit design, cancels the speed loop and the corresponding motor speed measurement module, and only retains the position loop circuit in the embedded software, greatly reducing the resource overhead of the embedded processor, enabling the embedded software to undertake more other tasks, simplifying the hardware design, reducing the product cost, and being beneficial to reducing the volume and weight of the product. Moreover, the current loop control strategy improves the existing PWM control method to direct current control, further reducing the system complexity, simplifying the design, and also helping to reduce the EMI electromagnetic interference noise inside the device, providing a smoother rotational motion, avoiding the small jitter defect at the zero current crossover of the PWM drive method, and the hardware circuit control method also has the advantages of simplicity, high efficiency, and rapid response. In addition, there are only two analog signals, namely measuring the deflection angle and setting the motor current, that need to be interacted between the embedded hardware and other hardware parts, which is beneficial to the miniaturization and modular design of other hardware parts. After being placed and installed near the brushless motor and encapsulated into a black box, it is beneficial to further reduce the volume and weight of the product.

[0025] In addition, the brushless DC motor controller of the present invention also has the above advantages.

[0026] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the drawings for a further detailed description of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0028] Figure 1 is a schematic diagram of the typical architecture of the existing brushless DC motor control system;

[0029] Figure 2 is a schematic diagram of the architecture of the brushless DC motor control system according to the preferred embodiment of the present application;

[0030] Figure 3 is a schematic diagram of the embedded system according to the preferred embodiment of the present application;

[0031] Figure 4 is a schematic diagram of the circuit structure of the motor current control circuit according to the preferred embodiment of the present application;

[0032] Figure 5 is a schematic diagram of the motor drive signal generation circuit, three-phase inverter full bridge, and motor according to the preferred embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0034] Referring to Figure 2 , a preferred embodiment of the present application provides a brushless DC motor control system, including:

[0035] An angle sensor for measuring the deflection angle of the output shaft of the reducer;

[0036] Embedded software, carried in the embedded hardware, for inputting the desired deflection angle and the sampled and measured deflection angle, and calculating the set motor current according to the difference between the desired deflection angle and the measured deflection angle;

[0037] A current sensor for measuring the motor current;

[0038] A motor current control circuit for outputting a motor forward and reverse switch signal according to the signal polarity of the set motor current, and controlling the on or off of the DC power supply of the three-phase inverter full bridge according to the signal magnitude of the set motor current and the magnitude of the measured motor current, so as to realize the closed-loop control of the motor current;

[0039] Three Hall devices for measuring the position of the motor rotor;

[0040] A motor drive signal generation circuit for controlling the rotation direction of the motor according to the motor forward and reverse switch signal, controlling the commutation logic of the motor according to the position of the motor rotor, and outputting six drive signals to the three-phase inverter full bridge;

[0041] A three-phase inverter full bridge for inverting the direct current output by the DC power supply into a three-phase AC square wave signal according to the six drive signals and then outputting it to the motor.

[0042] It can be understood that in this embodiment, the working process of the brushless DC motor control system is as follows: Only the position control loop is retained in the embedded software. The desired deflection angle (i.e., the deflection angle position required by the product) comes from an external input of the product or the output of other functional modules within the product. The embedded software samples the output signal of the angle sensor through an ADC chip to obtain the measured deflection angle, and inputs the difference between the expected value and the measured value of the deflection angle into the PI control algorithm to calculate the set motor current value. The current sensor measures the motor current in real time and transmits the measured motor current to the motor current control circuit. The motor current control circuit is responsible for implementing the current control loop. It outputs the motor forward and reverse switch signals according to the signal polarity of the set motor current to control the rotation direction of the motor, and converts the signal value of the set motor current into the upper and lower threshold values of the motor current through the hardware circuit. The measured motor current is compared with the upper and lower threshold values to control the on or off of the DC power supply of the three-phase inverter full bridge, thereby realizing the closed-loop control of the motor current. Moreover, the motor rotor position is measured by three Hall devices. When the motor forward and reverse switch signals and the switch signals of the three Hall devices reflecting the motor rotor position are input into the motor drive signal generation circuit, the motor drive signal generation circuit controls the rotation direction of the motor according to the motor forward and reverse switch signals, controls the commutation logic of the motor according to the motor rotor position, and outputs six drive signals to the three-phase inverter full bridge to control the three-phase inverter full bridge to invert the direct current output by the DC power supply into a three-phase AC square wave signal and output it to the motor to drive the motor to rotate. Among them, the angle sensor is preferably a rotary potentiometer, which is installed on the output shaft of the speed reducer. After the motor output shaft reduces the speed through the gear speed reducer, it drives the output shaft of the speed reducer to rotate to the desired deflection angle position. During this process, the deflection angle of the output shaft of the speed reducer can be detected in real time through the rotary potentiometer. In addition, the current sensor is preferably a sampling resistor arranged in the grounding loop of the three-phase inverter full bridge, and the three Hall devices are installed on the motor at intervals of 120°. In addition, the motor is preferably a general permanent magnet brushless DC motor with power and torque meeting the requirements.

[0043] It can be understood that the brushless DC motor control system of this embodiment realizes the current loop circuit and generates the motor drive signal through the hardware circuit design, cancels the speed loop and the corresponding motor speed measurement module, and only retains the position loop circuit in the embedded software, greatly reducing the resource overhead of the embedded processor, enabling the embedded software to undertake more other tasks, simplifying the hardware design, reducing the product cost, and being conducive to compressing the product volume and weight. Moreover, the current loop control strategy improves the existing PWM control method to direct current control, further reducing the system complexity, simplifying the design, and also helping to reduce the EMI electromagnetic interference noise inside the device, providing a smoother rotational motion, avoiding the small jitter defect at the zero current crossover of the PWM drive method, and the hardware circuit control method also has the advantages of simplicity, high efficiency, and rapid response. In addition, there are only two analog signals, namely measuring the deflection angle and setting the motor current, that need to be interacted between the embedded hardware and other hardware parts, which is conducive to miniaturizing and modularizing other hardware parts, and encapsulating them as a black box after being placed and installed near the brushless motor, which is conducive to further compressing the product volume and weight.

[0044] Among them, the embedded software is carried on an embedded hardware platform such as a DSP processor, an MCU controller, or an ARM single-chip microcomputer. The brushless DC motor control system of the present invention only assigns the position loop circuit to the embedded software, with extremely small overhead on the computing resources and time resources of the embedded processor. The appropriate type and model of the embedded processor can be selected according to other system requirements assigned to the software by the product. The corresponding embedded system block diagram is as Figure 3 shown. The embedded software runs periodically, reads the measured deflection angle value after analog-to-digital conversion by the ADC chip, calculates the difference with the expected deflection angle value, calculates and outputs the motor current signal that needs to be set using the PI algorithm, and outputs it after digital-to-analog conversion by the DAC chip, which can meet the real-time control requirements and the control quality requirements of the product for the deflection angle position. Among them, the PI coefficients in the PI algorithm can quickly determine the optimal value through parameter tuning, meet the steady-state and dynamic performance requirements of the product deflection angle position, are simple in design, can be quickly implemented, and effectively shorten the project development time.

[0045] It can be understood that there are only two analog signals that need to be interacted between the embedded system of the present invention and other hardware parts of the brushless DC motor control system, namely measuring the deflection angle and setting the motor current. It is very easy to miniaturize and modularize other hardware parts of the brushless DC motor control system in the design, and encapsulate them as a black box after being placed and installed near the brushless motor. The black box and the embedded system only interact in terms of control through two analog signals, which is conducive to reducing the product volume and weight.

[0046] In addition, as Figure 4As shown, the motor current control circuit includes an inverting proportional amplifier circuit, a logarithmic amplifier circuit, a non-inverting proportional amplifier circuit, a comparison circuit, and a DC power supply circuit. The inverting proportional amplifier circuit is used to perform inverting proportional amplification on the set motor current signal. The logarithmic amplifier circuit outputs a motor forward / reverse switch signal to the motor drive signal generation circuit according to the signal polarity of the set motor current after inversion, and performs logarithmic amplification on its magnitude after removing the signal polarity of the set motor current after inversion, and outputs a positive voltage signal related to the magnitude of the set motor current signal to the comparison circuit. The non-inverting proportional amplifier circuit performs non-inverting proportional amplification on the measured motor current signal and then outputs it to the comparison circuit. The comparison circuit compares the amplified measured motor current signal with the positive voltage signal output by the logarithmic amplifier circuit, and outputs a switch drive signal for the DC power supply to the DC power supply circuit according to the comparison result. The DC power supply circuit is used to provide DC power to the three-phase inverter full bridge, and the output end of the DC power supply circuit is fed back to the comparison circuit. When the measured motor current is greater than the first threshold, the comparison circuit controls the output of the DC power supply circuit to be turned off. When the measured motor current is less than the second threshold, the comparison circuit controls the output of the DC power supply circuit to be turned on, where the first threshold is greater than the second threshold.

[0047] Among them, the inverting proportional amplifier circuit includes a resistor R1, a resistor R2, and an operational amplifier N1. The first end of the resistor R1 is connected to the embedded hardware, the second end of the resistor R1 and the first end of the resistor R2 are connected to the inverting input terminal of the operational amplifier N1, the non-inverting input terminal of the operational amplifier N1 is grounded, the second end of the resistor R2 is connected to the operational amplifier N1, and the output terminal of the operational amplifier N1 is also connected to the input terminal of the logarithmic amplifier circuit. Among them, the inverting proportional amplifier circuit belongs to an existing circuit, and its working principle will not be elaborated here.

[0048] In addition, the logarithmic amplifier circuit includes a resistor R3, a resistor R4, a resistor R5, a capacitor C1, an operational amplifier N2, a zener diode V1, a diode V2, a diode V3, a resistor R6, a resistor R7, an operational amplifier N3, a resistor R8, a zener diode V4, a resistor R20, and an NPN transistor N5. The first end of the resistor R3 is connected to the output end of the inverting proportional amplification circuit, that is, to the output end of the operational amplifier N1. The second end is respectively connected to the inverting input end of the operational amplifier N2, the first end of the capacitor C1, the first end of the resistor R4, and the first end of the resistor R5. The output end of the operational amplifier N2 is respectively connected to the second end of the capacitor C1, the first end of the resistor R20, and the input end of the zener diode V1. The non-inverting input end of the operational amplifier N2 is grounded. The second end of the resistor R20 is connected to the base of the NPN transistor N5. The collector of the NPN transistor N5 is connected to the motor drive signal generation circuit, and the emitter is grounded. The output end of the zener diode V1 is respectively connected to the negative electrode of the diode V2 and the positive electrode of the diode V3. The positive electrode of the diode V2 is respectively connected to the second end of the resistor R4 and the first end of the resistor R6. The negative electrode of the diode V3 is respectively connected to the second end of the resistor R5 and the non-inverting input end of the operational amplifier N3. The second end of the resistor R6 and the first end of the resistor R7 are both connected to the inverting input end of the operational amplifier N3. The second end of the resistor R7 and the first end of the resistor R8 are both connected to the output end of the operational amplifier N3. The second end of the resistor R8 is respectively connected to the output end of the zener diode V4 and the comparison circuit. The input end of the zener diode V4 is grounded. Among them, the zener diode V1 is a 3.3V zener diode, and the zener diode V4 is a 10V zener diode.

[0049] It can be understood that the output terminal of the operational amplifier N2 outputs a motor forward and reverse switch signal to the motor drive signal generation circuit via the resistor R20 and the NPN transistor V5. When the polarity of the set motor current signal is positive, it becomes negative after commutation by the inverting proportional amplification circuit and then amplified by the operational amplifier N2, causing the NPN transistor V5 to turn off, and the output motor forward and reverse switch signal is at a low level of 0V, and the motor rotates in reverse; when the polarity of the set motor current signal is negative, it becomes positive after commutation by the inverting proportional amplification circuit and then amplified by the operational amplifier N2, causing the NPN transistor V5 to turn on, and the output motor forward and reverse switch signal is at a high level of 5V, and the motor rotates forward. In addition, the resistor R3, resistor R4, resistor R5, capacitor C1, operational amplifier N2, zener diode V1, diode V2, diode V3, resistor R6, resistor R7, and operational amplifier N3 constitute a detection logarithmic amplifier, which can remove the polarity of the set motor current signal after inversion and logarithmically amplify the signal magnitude of the set motor current, and output a positive voltage related to the signal magnitude of the set motor current to the comparison circuit. Moreover, the detection logarithmic amplifier can also provide a wider input signal dynamic range, maintaining a high gain when the position error is small to improve the system response speed.

[0050] In addition, the non-inverting proportional amplification circuit includes a resistor R10, a resistor R11, and an operational amplifier N4. The non-inverting input terminal of the operational amplifier N4 is connected to the measured motor current signal, and the measured motor current signal comes from the voltage signal on the sampling resistor connected in series in the grounding loop of the three-phase full-bridge inverter. The first end of the resistor R10 is grounded, the second end is connected to the inverting input terminal of the operational amplifier N4, the first end of the resistor R11 is connected to the inverting input terminal of the operational amplifier N4, and the second end is connected to the output terminal of the operational amplifier N4. Among them, the non-inverting proportional amplification circuit is an existing circuit, and its working principle will not be elaborated here.

[0051] In addition, the comparison circuit includes a resistor R12, a resistor R13, a resistor R14, a resistor R15, a capacitor C3, and an operational amplifier N5. The first end of the resistor R12 is connected to the output terminal of the non-inverting proportional amplification circuit, and the second end of the resistor R12 is respectively connected to the first end of the resistor R13, the first end of the resistor R14, the first end of the capacitor C3, and the inverting input terminal of the operational amplifier N5. The non-inverting input terminal of the operational amplifier N5 is connected to the output terminal of the logarithmic amplifier circuit. The second end of the resistor R13 is grounded, the second end of the capacitor C3 is connected to the first end of the resistor R15, the second end of the resistor R15 is connected to the output terminal of the operational amplifier N5, the second end of the resistor R14 is connected to the output terminal of the DC power supply circuit, and the output terminal of the operational amplifier N5 is connected to the DC power supply circuit.

[0052] It can be understood that the operational amplifier N5 compares the amplified measured motor current signal with the positive voltage signal output by the operational amplifier N3, and controls the on / off of the power supply line of the three-phase inverter full bridge according to the comparison result.

[0053] In addition, the DC power supply circuit includes a resistor R16, a resistor R17, an NPN transistor V6, a resistor R18, a resistor R19, a PNP transistor V7 and a DC power supply. The first end of the resistor R16 is connected to the output end of the comparison circuit, the second end of the resistor R16 is connected to the base of the NPN transistor V6, the emitter of the NPN transistor V6 is connected to the first end of the resistor R17, the second end of the resistor R17 is grounded, the collector of the NPN transistor V6 is connected to the first end of the resistor R18, the second end of the resistor R18 is connected to the first end of the resistor R19 and the base of the PNP transistor V7, the second ends of the resistor R19 and the emitter of the PNP transistor V7 are both connected to the positive pole of the DC power supply, the negative pole of the DC power supply is grounded, and the collector of the PNP transistor V7 is connected to the resistor R14 and the three-phase inverter full bridge respectively. Among them, the DC power supply is 20V.

[0054] It can be understood that the DC power supply of the three-phase inverter full bridge is connected to the inverting input terminal of the operational amplifier N5 through the resistor R14, providing a feedback loop. After the motor current signal is passed through the logarithmic amplifier with the operational amplifiers N2 and N3 as the core, a positive voltage signal related to the absolute value of the set motor current signal is output to the non-inverting input terminal of the operational amplifier N5. The operational amplifier N5 is powered by a +15V DC power supply. When the measured motor current is greater than the first threshold Ithreshold1, the output of the operational amplifier N5 is grounded, causing the NPN transistor V6 to be cut off, no current passes through the resistor R19, the base voltage of the PNP transistor V7 is 20V, and the PNP transistor V7 is also cut off, and the DC power supply stops supplying power to the three-phase inverter full bridge; when the measured motor current is less than the second threshold Ithreshold2, the output of the operational amplifier N5 is the high level +15V, and after current limiting through the resistor R16, the NPN transistor V6 is turned on, the 20V DC power supply is grounded through the resistor R19, the resistor R18, and the resistor R17, the base voltage of the PNP transistor V7 is about 17V, the PNP transistor V7 is turned on, and the DC power supply starts to supply power to the three-phase inverter full bridge. Among them, Ithreshold1 > Ithreshold2.

[0055] Therefore, when the measured motor current is greater than the first threshold Ithreshold1, the current loop control strategy of the present invention automatically shuts off the DC power supply of the three-phase inverter full bridge. After the motor loses power supply, the motor current decreases. When the measured motor current is less than the second threshold Ithreshold2, the DC power supply of the three-phase inverter full bridge is reconnected. After the motor has power supply, it continues to rotate and the motor current increases. By adopting this BangBang control method, the motor current is controlled, forming a closed loop of the motor current. The present invention improves the current loop control strategy from the PWM control method to direct current control, further reducing the system complexity, simplifying the design, and also helping to reduce the EMI electromagnetic interference noise inside the device. It can provide a smoother rotational motion, avoiding the small jitter defect at the zero current crossing of the PWM drive method. The hardware circuit control method also has the advantages of simplicity, high efficiency, and rapid response. Moreover, when the measured motor current exceeds the first threshold Ithreshold1, the DC power supply of the three-phase inverter full bridge is automatically turned off, eliminating the need for a dedicated overcurrent protection circuit design, further simplifying the hardware design and reducing the product cost.

[0056] Optionally, the motor current control circuit further includes a low-pass filter circuit before the in-phase proportional amplifier circuit for performing low-pass filtering on the measured motor current signal. The low-pass filter circuit includes a resistor R9 and a capacitor C2. The first end of the resistor R9 is connected to the current sensor, the second end of the resistor R9 is respectively connected to the first end of the capacitor C2 and the non-inverting input terminal of the operational amplifier N4, and the second end of the capacitor C2 is grounded.

[0057] In addition, as Figure 5 shown, the motor drive signal generation circuit includes a control chip and three drive chips. The control chip is respectively connected to the motor current control circuit, three Hall devices, and three drive chips, and is used to output six drive signals according to the input motor forward and reverse switch signal and motor rotor position signal. The six drive signals are power amplified by the three drive chips and then output to the three-phase inverter full bridge to drive the three-phase inverter full bridge to invert direct current into three-phase alternating square wave signals.

[0058] Specifically, the control chip D1 selects the MC33035 chip of Motorola. The forward and reverse switch signal of the motor is input to pin 3. Pin 8 is shorted to pin 11, and pin 12 is shorted to pin 13, so that the motor drive signal is not adjusted by PWM. Pins 22 and 23 are shorted to ground, so that the 120° phase and the brake signal are not enabled. The drive chip selects the IR2101 device of IR company. The three-phase inverter full bridge is built by six MOSFET switches. The DC power supply of the three-phase inverter full bridge comes from the motor current control circuit, and the motor current control circuit turns on or off the DC power supply of the three-phase inverter full bridge according to the measured motor current signal. The output signals of three Hall switch devices installed on the brushless DC motor at intervals of 120° are connected to pins 4, 5, and 6 of the MC33035 chip. The MC33035 chip realizes the commutation logic control of the motor according to the change of the Hall device switch signal. A 0.15Ω sampling resistor R21 is selected and connected in series in the grounding circuit of the three-phase inverter full bridge to measure the motor current.

[0059] It can be understood that the motor drive signal generation circuit of the present invention is constructed around a dedicated brushless DC motor control chip (such as the MC33035 chip of Motorola or other motor control chips with similar functions). The forward and reverse switch signal of the motor is input to pin 3 of the MC33035 chip to control the rotation direction of the motor. The switch signals of three Hall devices reflecting the position of the motor rotor are input to the MC33035 chip to determine the commutation logic of the motor. The MC33035 chip outputs six drive signals, which are amplified by the IR2101 drive chip and then drive the conduction or cut-off of six MOSFET switches in the three-phase inverter full bridge. The inverter outputs three-phase AC square wave signals to the U, V, and W phase lines of the motor to drive the motor to rotate. The structure of the motor drive signal generation circuit is simple and the hardware cost is low.

[0060] In addition, another embodiment of the present invention also provides a brushless DC motor controller, preferably adopting the above-mentioned brushless DC motor control system.

[0061] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0062] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A brushless DC motor control system, characterized in that, Comprising: An angle sensor for measuring the deflection angle of the output shaft of the reducer; Embedded software, carried in the embedded hardware, for inputting the desired deflection angle and the sampled measured deflection angle, and calculating the set motor current based on the difference between the desired deflection angle and the measured deflection angle; A current sensor for measuring the motor current; A motor current control circuit for outputting a motor forward and reverse switch signal according to the signal polarity of the set motor current, and controlling the on or off of the DC power supply of the three-phase inverter full bridge according to the signal magnitude of the set motor current and the magnitude of the measured motor current, so as to realize the closed-loop control of the motor current; Three Hall devices for measuring the motor rotor position; A motor drive signal generation circuit for controlling the rotation direction of the motor according to the motor forward and reverse switch signal, controlling the commutation logic of the motor according to the motor rotor position, and outputting six drive signals to the three-phase inverter full bridge; A three-phase inverter full bridge for inverting the direct current output by the DC power supply into a three-phase alternating current square wave signal according to the six drive signals and then outputting it to the motor.

2. The brushless DC motor control system according to claim 1, wherein, The motor current control circuit includes an inverting proportional amplifier circuit, a logarithmic amplifier circuit, a non-inverting proportional amplifier circuit, a comparison circuit and a DC power supply circuit. The inverting proportional amplifier circuit is used for inverting proportional amplification of the set motor current signal. The logarithmic amplifier circuit outputs a motor forward and reverse switch signal to the motor drive signal generation circuit according to the signal polarity of the inverted set motor current, and logarithmically amplifies its magnitude after removing the signal polarity of the inverted set motor current, and outputs a positive voltage signal related to the signal magnitude of the set motor current signal to the comparison circuit. The non-inverting proportional amplifier circuit outputs the measured motor current signal after non-inverting proportional amplification to the comparison circuit. The comparison circuit compares the amplified measured motor current signal with the positive voltage signal output by the logarithmic amplifier circuit, and outputs a switch drive signal of the DC power supply to the DC power supply circuit according to the comparison result. The DC power supply circuit is used to provide DC power for the three-phase inverter full bridge, and the output end of the DC power supply circuit is fed back to the comparison circuit. When the measured motor current is greater than the first threshold, the comparison circuit controls the output of the DC power supply circuit to turn off. When the measured motor current is less than the second threshold, the comparison circuit controls the output of the DC power supply circuit to turn on, where the first threshold is greater than the second threshold.

3. The brushless DC motor control system according to claim 2, wherein The logarithmic amplifier circuit includes a resistor R3, a resistor R4, a resistor R5, a capacitor C1, an operational amplifier N2, a zener diode V1, a diode V2, a diode V3, a resistor R6, a resistor R7, an operational amplifier N3, a resistor R8, a zener diode V4, a resistor R20, and an NPN transistor N5. The first end of the resistor R3 is connected to the output end of the inverting proportional amplification circuit, and the second end is respectively connected to the input end of the operational amplifier N2, the first end of the capacitor C1, the first end of the resistor R4, and the first end of the resistor R5. The output end of the operational amplifier N2 is respectively connected to the second end of the capacitor C1, the first end of the resistor R20, and the input end of the zener diode V1. The second end of the resistor R20 is connected to the base of the NPN transistor N5. The collector of the NPN transistor N5 is connected to the motor drive signal generation circuit, and the emitter is grounded. The output end of the zener diode V1 is respectively connected to the cathode of the diode V2 and the anode of the diode V3. The anode of the diode V2 is respectively connected to the second end of the resistor R4 and the first end of the resistor R6. The cathode of the diode V3 is respectively connected to the second end of the resistor R5 and the input end of the operational amplifier N3. The second end of the resistor R6 and the first end of the resistor R7 are both connected to the other input end of the operational amplifier N3. The second end of the resistor R7 and the first end of the resistor R8 are both connected to the output end of the operational amplifier N3. The second end of the resistor R8 is respectively connected to the output end of the zener diode V4 and the comparison circuit. The input end of the zener diode V4 is grounded.

4. The brushless DC motor control system according to claim 3, wherein When the polarity of the motor current signal is set to positive, the output motor forward / reverse switch signal is at a low level, and the motor rotates in reverse; when the polarity of the motor current signal is set to negative, the output motor forward / reverse switch signal is at a high level, and the motor rotates forward.

5. The brushless DC motor control system according to claim 3, wherein The comparison circuit includes a resistor R12, a resistor R13, a resistor R14, a resistor R15, a capacitor C3, and an operational amplifier N5. The first end of the resistor R12 is connected to the output end of the non-inverting proportional amplification circuit. The second end of the resistor R12 is respectively connected to the first end of the resistor R13, the first end of the resistor R14, the first end of the capacitor C3, and the input end of the operational amplifier N5. The other input end of the operational amplifier N5 is connected to the output end of the logarithmic amplifier circuit. The second end of the resistor R13 is grounded. The second end of the capacitor C3 is connected to the first end of the resistor R15. The second end of the resistor R15 is connected to the output end of the operational amplifier N5. The second end of the resistor R14 is connected to the output end of the DC power supply circuit. The output end of the operational amplifier N5 is connected to the DC power supply circuit.

6. The brushless DC motor control system according to claim 5, characterized in that, The DC power supply circuit includes resistor R16, resistor R17, NPN transistor V6, resistor R18, resistor R19, PNP transistor V7 and a DC power supply. The first end of resistor R16 is connected to the output terminal of the comparison circuit, the second end of resistor R16 is connected to the base of NPN transistor V6, the emitter of NPN transistor V6 is connected to the first end of resistor R17, the second end of resistor R17 is grounded, the collector of NPN transistor V6 is connected to the first end of resistor R18, the second end of resistor R18 is connected to the first end of resistor R19 and the base of PNP transistor V7, the second ends of resistor R19 and the emitter of PNP transistor V7 are both connected to the positive pole of the DC power supply, the negative pole of the DC power supply is grounded, and the collector of PNP transistor V7 is respectively connected to resistor R14 and the three-phase inverter full bridge.

7. The brushless DC motor control system according to claim 6, wherein When the measured motor current is greater than the first threshold, the output of operational amplifier N5 is ground, both NPN transistor V6 and PNP transistor V7 are cut off, and the DC power supply stops supplying power to the three-phase inverter full bridge; when the measured motor current is less than the second threshold, the output of operational amplifier N5 is high level, both NPN transistor V6 and PNP transistor V7 are turned on, and the DC power supply starts to supply power to the three-phase inverter full bridge.

8. The brushless DC motor control system according to claim 2, wherein, The motor current control circuit further includes a low-pass filter circuit before the in-phase proportional amplification circuit, which is used to perform low-pass filtering on the measured motor current signal.

9. The brushless DC motor control system according to claim 1, wherein The motor drive signal generation circuit includes a control chip and three drive chips. The control chip is respectively connected to the motor current control circuit, three Hall devices and three drive chips, and is used to output six drive signals according to the input motor forward and reverse switch signal and motor rotor position signal. The six drive signals are power amplified by the three drive chips and then output to the three-phase inverter full bridge to drive the three-phase inverter full bridge to invert the direct current into a three-phase AC square wave signal.

10. A brushless DC motor controller, characterized in that, Adopt the brushless DC motor control system according to any one of claims 1 to 9.

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