Control driver of brushless motor

Abstract

The invention relates to the technical field of motor control, in particular to a control driver of a brushless motor, which comprises a hardware system adopting a six-layer PCB (printed circuit board) electromagnetic isolation structure, an STM32G4 master controller, a DRV8302 driving chip and a DirectFET (field effect transistor) MOSFET (metal oxide semiconductor field effect transistor), and is provided with a Hall, an incremental encoder, an SPI (serial peripheral interface) and four types of sensor interfaces; the system further comprises a software system, three-closed-loop FOC control is achieved, and the three-closed-loop FOC control comprises current zero offset automatic calibration based on a DCCAL pin, bus voltage virtual amplification SVPWM modulation, temperature rise compensation dynamic current loop gain and an inductive or non-inductive dual-mode switching mechanism. According to the invention, on the premise that the hardware cost and the size are not increased, the torque and the speed of the small brushless motor can be controlled, and sensor compatibility and reasonable deployment of a high-order control algorithm are realized.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and more particularly to a control driver for a brushless motor. Background Technology

[0002] Motor control systems are mainly divided into three categories globally: brushed DC motors, brushless DC motors, and stepper motors. In application scenarios with clear requirements for high performance, ultra-small size, and high-precision control, brushless DC motors have become the most promising choice due to their high efficiency, long lifespan, and excellent dynamic response characteristics.

[0003] However, due to limitations in control system cost and technological complexity, current high-level control solutions for brushless motors are mostly concentrated in industrial-grade high-power equipment, such as robotic arms, electric vehicles, and wind power generation systems. The motors used in these applications are typically large in size and have high power. In contrast, in miniaturized equipment or precision micro-systems, due to the lack of suitable dedicated drive solutions for small brushless motors, the industry generally still relies on brushed motors or general-purpose electronic speed controllers to drive brushless motors.

[0004] Furthermore, brushless motors require a wide variety of position / speed sensors, including incremental encoders, absolute encoders, and Hall effect sensors. The requirements for the driver's peripheral hardware circuitry vary significantly depending on the sensor. Drivers for small brushless motors on the market generally lack multi-sensor compatibility, especially for sensorless small brushless motors. Key parameters such as phase resistance, inductance, and back EMF constant are not only difficult to obtain accurately, but also exhibit large parameter dispersion among products of the same model, further hindering the application of high-order control algorithms in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a control driver for a brushless motor to solve the technical problems of poor sensor compatibility and difficulty in deploying high-order control algorithms in existing small brushless motor drive control technologies.

[0006] This invention provides a control driver for a brushless motor, comprising a hardware system and a software control system. The hardware system includes at least an STM32G4 series main controller, a DRV8302 gate driver chip, an IRF7480 MOSFET power switch, multiple types of position sensor interfaces, a dual-resistor current sampling circuit, and a six-layer printed circuit board. The software control system operates on a three-closed-loop control architecture based on field-oriented control, including at least a position loop controller, a speed loop controller, and a current loop controller, and integrates a current zero-bias automatic calibration module, a dynamic gain compensation module, an SVPWM modulator, and a sensored or sensorless dual-mode switching module.

[0007] It should be noted that the hardware system and software control system of this invention work together to achieve high-performance FOC control for small brushless motors. The software control system runs a three-closed-loop control architecture based on FOC and integrates an algorithm optimization module for the electrical and thermal characteristics of small brushless motors.

[0008] In some embodiments, the six-layer printed circuit board is arranged from top to bottom as follows: Top Layer, GND Layer signal ground layer, Power Layer motor power trace layer, PGND Layer power ground layer, VDD Layer logic power layer, and Bottom Layer; wherein... The Power Layer motor power routing layer is provided with three-phase output routing, bus positive and negative terminals and MOSFET source and drain connection lines. Logic signal lines are arranged on the Top Layer and the Bottom Layer. The GND Layer signal ground layer and the PGND Layer power ground layer are connected at a single point through a ferrite bead or a 0Ω resistor. In some embodiments, the IRF7480 MOSFET power switch is based on a DirectFET package, with its bottom metal pads directly soldered to the PCB heat dissipation copper foil; the DRV8302 gate driver chip integrates a three-way half-bridge gate driver, a bootstrap boost circuit, a high-side bootstrap capacitor charging circuit, and a dual-channel current sensing operational amplifier, and the DRV8302 gate driver chip is connected to a dual-resistor current sampling circuit.

[0009] In some embodiments, the multi-type position sensor interface includes at least a Hall sensor interface, an incremental encoder interface, an SPI bus interface, and... The bus interface includes the Hall sensor interface, the incremental encoder interface, the SPI bus interface, and the... The bus interface shares the same set of GPIO pins and implements interface multiplexing based on software configuration.

[0010] In some embodiments, when the system is powered on, the automatic current zero-bias calibration module decrements the DC_CAL calibration pin of the DRV8302 gate driver chip for 10ms, causing the internal current sensing operational amplifier to enter calibration mode. It then continuously acquires the raw values ​​from the dual-resistor current sampling circuit via an analog-to-digital converter, discards the maximum and minimum 5% of data, and averages the results to obtain the zero-bias voltage V. offset1 With V offset2 .

[0011] In some embodiments, the current loop controller introduces a dynamic gain coefficient: K comp =Kbase ×(1+α×ΔT) Among them, K base α is the reference gain; α is the temperature compensation coefficient; ΔT is the difference between the junction temperature measured by the temperature sensor built into the STM32G4 series main controller and the nominal temperature of 25℃.

[0012] In some embodiments, the SVPWM modulator uses a virtual bus voltage V_bus_virtual=V_bus_meas×β in sector determination and action time calculation, where V_bus_meas is the bus voltage acquired in real time; β is a preset scaling factor, and its value ranges from 1.1 to 1.3.

[0013] In some embodiments, the sensing or non-sensing dual-mode switching module enters sensing mode when it detects a valid signal from an external sensor interface, utilizing the Hall sensor interface, the incremental encoder interface, the SPI bus interface, or the... The rotor electrical angle is obtained via the bus interface; When no valid external sensor signal is detected, the system switches to a sensorless mode and constructs a state equation based on an extended Kalman filter, where the state variables include at least the rotor electrical angle θ. e Electric angular velocity ω e It also controls the periodic update of the state estimate to output the rotor electrical angle θ. e .

[0014] In some embodiments, the state equations of the extended Kalman filter are constructed based on the motor terminal voltage and phase current, and the parameters of the state equations of the extended Kalman filter are adjusted based on the nominal parameters of the motor.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The control driver of this invention can be adapted to drive various small brushless motors with voltage levels ranging from 8V to 48V, and achieves a speed control error of no more than ±0.5% within the speed range of 0rpm-30000rpm; a torque fluctuation peak-to-peak value of less than 5% within the load range of 0.1N·m to 1.5N·m; a forward / reverse switching response time of less than 10ms; and an efficiency improvement of 12% to 18% compared to traditional drivers. 2. Through highly integrated hardware platform design and deep optimization of software control algorithms, including current zero bias automatic calibration method, SVPWM modulation strategy, dynamic current loop gain, and sensorless dual-mode FOC architecture, high-order vector control has been successfully implemented in the field of small brushless motor drive for the first time. 3. This invention resolves the technical contradiction between existing ESCs or general-purpose drivers and multi-sensor compatibility and high energy efficiency, providing a mass-producible and low-cost control solution for small brushless motors in fields such as micro-robots and precision instruments. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic block diagram of the control driver of the present invention; Figure 2 This is a flowchart illustrating the three-closed-loop control structure and transformation module of the FOC control algorithm of the present invention. Figure 3 This is a schematic diagram of the hardware system connection of the present invention; Figure 4 This is a physical structural diagram of the present invention; Figure 5 This is a schematic diagram of the circuit connection of the sensor interface of the present invention. Detailed Implementation

[0018] The following will be based on embodiments of the present invention. Figures 1-5 The technical solutions in the embodiments of the present invention will be clearly and completely described together. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] Partial interpretation: 1. ADC: Analog-to-Digital Converter, an electronic device that converts continuously changing analog signals (such as voltage, temperature, sound) into discrete digital signals (0 and 1) that can be processed by a computer.

[0020] Example This embodiment provides a control driver for a brushless motor, including a hardware system and a software control system. The hardware system includes at least an STM32G4 series main controller, a DRV8302 gate driver chip, an IRF7480 MOSFET power switch, multiple types of position sensor interfaces, a dual-resistor current sampling circuit, and a six-layer printed circuit board. The software control system runs a three-closed-loop control architecture based on field-oriented control, including at least a position loop controller, a speed loop controller, and a current loop controller, and integrates a current zero-bias automatic calibration module, a dynamic gain compensation module, an SVPWM modulator, and a sensory or sensorless dual-mode switching module.

[0021] To better understand this invention, the details are as follows: first, The main controller is an STMicroelectronics STM32G4 series microcontroller, featuring a 170MHz clock frequency and a single-precision floating-point unit (FPU) for executing Clark transformation, Park transformation, inverse Park transformation, a three-loop PID controller (position loop, speed loop, current loop), and sensorless observer algorithms. The DRV8302 gate driver chip integrates a three-way half-bridge driver, a bootstrap boost circuit, and dual-channel current-sensing operational amplifiers, directly driving IRF7480 MOSFET power switches to form a three-phase inverter bridge.

[0022] The IRF7480 uses a DirectFET package with an on-resistance as low as 4.5mΩ. The bottom metal pads are directly soldered to the PCB's copper heat dissipation foil, effectively reducing high-frequency switching losses and improving heat conduction efficiency. The entire board employs a six-layer stack-up structure: the top layer houses logic signal lines, such as PWM, encoder input, or... The bus. Furthermore, the first inner layer is the signal ground layer GND, the second inner layer is dedicated to motor power routing: it only contains three-phase output, bus positive and negative terminals and MOSFET connection lines, the third inner layer is the power ground layer PGND, the fourth inner layer is the logic power layer VDD, and the bottom layer reuses some logic signal lines.

[0023] The motor power trace layer is completely shielded by a plane on both the top and bottom. The logic ground GND and the power ground PGND are connected at a single point through a ferrite bead to avoid ground loop interference. All vias are filled with conductive resin and immersion gold is used to ensure the integrity of high-frequency signals.

[0024] then, In terms of sensor compatibility, the Hall sensor interface provides three digital input channels to receive U / V / W Hall signals; the incremental encoder interface receives A / B / Z three-phase signals, which are decoded by the STM32G4's internal QEP module; and the SPI bus interface supports a maximum clock rate of 10MHz for connecting absolute magnetic encoders. The bus interface address is configurable, making it compatible with low-speed absolute position sensors.

[0025] The present invention includes a Hall sensor interface, an incremental encoder interface, and an SPI bus interface. The four types of bus interfaces share the same set of GPIO pins. Through software configuration of the multiplexing mode, a single board can be adapted to multiple types of motors.

[0026] Immediately afterwards, The software control system operates on a three-closed-loop FOC architecture. After the system powers on, it executes the initialization calibration procedure as follows: Lowering the DC_CAL calibration pin of DRV8302 for 10ms will put the internal current sensing op-amp into calibration mode. At this time, the three-phase bridge arm is in a high-impedance state and no current flows through the dual-resistor current sampling circuit. The zero bias voltage V is obtained by continuously acquiring the raw values ​​of the dual sampling channels 1000 times using an ADC, removing the maximum and minimum 5% of data, and then averaging the results. offset1 With V offset2 ; Store the bias value in non-volatile memory; During motor operation, the corresponding bias value is subtracted in real time, and the third-phase current is calculated using Kirchhoff's law Ic=-(Ia + Ib) to construct a complete three-phase current vector.

[0027] Understandably, the aforementioned calibration process can eliminate the impact of op-amp offset, PCB temperature drift, and ADC quantization error on current sampling, ensuring the accuracy of current calculation in FOC control.

[0028] Then, The current loop controller introduces a dynamic gain coefficient K. comp =K base ×(1+α×ΔT), where ΔT is the difference between the junction temperature measured by the STM32G4's built-in temperature sensor and the nominal temperature of 25℃, and α is the preset compensation coefficient. This mechanism compensates for the current response lag caused by the increase in winding resistance of the small motor with temperature rise, and maintains the stability of the current loop bandwidth. The speed loop controller and position loop controller adopt a standard discrete PI structure, and the integral term is set with anti-saturation limit to prevent overshoot caused by sudden change in setting.

[0029] When the external sensor is active, the system enters sensing mode: the Hall signal is digitally filtered and then interpolated by 60° electrical angle to generate a continuous θ. e The incremental encoder completes the initial positioning by combining QEP decoding with the Z-phase. The encoder directly reads the absolute electrical angle.

[0030] When there is no effective sensor signal, it automatically switches to sensorless mode: the extended Kalman filter state equation is constructed based on the terminal voltage and phase current, and the state variables include the rotor electrical angle θ. e Electric angular velocity ω e It also controls the periodic update of the state estimate and outputs θ. e The position information required for FOC coordinate transformation is adapted to the discreteness of different small motor parameters.

[0031] Then, The SVPWM modulator receives the α-β axis voltage commands output from the inverse Park transform module and combines them with the bus voltage to generate six PWM signals to drive the three-phase inverter bridge. To improve the control linearity under low voltage conditions, the following virtual voltage compensation strategy is implemented: Real-time acquisition of bus voltage V_bus_meas; Calculate the virtual bus voltage V_bus_virtual = V_bus_meas × β, where β is taken as 1.1~1.3; In SVPWM sector determination and activation time calculation, V_bus_virtual is used to replace the actual value.

[0032] The aforementioned strategy can improve low-speed torque stability. At the same time, since the actual voltage applied to the motor is limited by the SVPWM duty cycle, it will not exceed the motor's rated voltage, thus not increasing additional power consumption.

[0033] To better illustrate the present invention, the following example is provided: Taking the driving of a small 12V / 0.5A brushless motor as an example, after the system is powered on, it completes the current zero bias calibration, detects that the SPI interface is connected to the AS5048 magnetic encoder, and enters the sensor FOC mode.

[0034] The user sets the target speed to 10,000 rpm. The position loop controller outputs the speed command to the speed loop controller, which then outputs the q-axis current command Iq_ref to the current loop controller via PI regulation. The current loop calculates Id and Iq based on the calibrated Ia and Ib, and outputs Vd and Vq via PI regulation after dynamic gain compensation. These are then converted into PWM signals through inverse Park transform and SVPWM modulation to drive the IRF7480 MOSFET3 to turn on and off, thus synthesizing a sinusoidal current to drive the motor.

[0035] Actual measurements show: The steady-state speed error is ±0.3%, the peak-to-peak torque fluctuation is 4.2%, the forward / reverse switching time is 8ms, and the efficiency is 82%, which is 15% higher than the traditional method. In sensorless mode, when driving a Hall-less motor of the same specification, the EKF observer successfully estimated the rotor position, achieving smooth start-up and operation from 0rpm to 20000rpm, verifying the effectiveness of dual-mode control.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0037] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A control driver for a brushless motor, comprising a hardware system and a software control system, characterized in that, The hardware system includes at least an STM32G4 series main controller, a DRV8302 gate driver chip, an IRF7480 MOSFET power switch, multiple types of position sensor interfaces, a dual-resistor current sampling circuit, and a six-layer printed circuit board. The software control system operates on a three-closed-loop control architecture based on field-oriented control, including at least a position loop controller, a speed loop controller, and a current loop controller, and integrates a current zero-bias automatic calibration module, a dynamic gain compensation module, an SVPWM modulator, and a sensory or sensorless dual-mode switching module.

2. The control driver according to claim 1, characterized in that, The six-layer printed circuit board is arranged from top to bottom as follows: Top Layer, GND Layer (signal ground layer), Power Layer (motor power trace layer), PGND Layer (power ground layer), VDD Layer (logic power layer), and Bottom Layer (bottom layer); among which... The Power Layer motor power routing layer is provided with three-phase output routing, bus positive and negative terminals and MOSFET source and drain connection lines. Logic signal lines are arranged on the Top Layer and the Bottom Layer. The GND Layer signal ground and the PGND Layer power ground are connected at a single point through a ferrite bead or a 0Ω resistor.

3. The control driver according to claim 2, characterized in that, The IRF7480 MOSFET power switch is based on a DirectFET package, with its bottom metal pads directly soldered to the PCB heat dissipation copper foil. The DRV8302 gate driver chip integrates a three-way half-bridge gate driver, a bootstrap boost circuit, a high-side bootstrap capacitor charging circuit, and a dual-channel current sensing operational amplifier. The DRV8302 gate driver chip is connected to a dual-resistor current sampling circuit.

4. The control driver according to claim 1, characterized in that, The multi-type position sensor interfaces include at least a Hall sensor interface, an incremental encoder interface, an SPI bus interface, and... The bus interface includes the Hall sensor interface, the incremental encoder interface, the SPI bus interface, and the... The bus interface shares the same set of GPIO pins and implements interface multiplexing based on software configuration.

5. The control driver according to claim 3, characterized in that, When the system powers on, the automatic current zero-bias calibration module decrements the DC_CAL calibration pin of the DRV8302 gate driver chip for 10ms, causing the internal current sensing operational amplifier to enter calibration mode. It then continuously acquires the raw values ​​from the dual-resistor current sampling circuit via an analog-to-digital converter, discards the maximum and minimum 5% data points, and averages the results to obtain the zero-bias voltage V. offset1 With V offset2 .

6. The control driver according to claim 5, characterized in that, The current loop controller introduces a dynamic gain coefficient: K comp =K base ×(1+α×ΔT) Among them, K base α is the reference gain; α is the temperature compensation coefficient; ΔT is the difference between the junction temperature measured by the temperature sensor built into the STM32G4 series main controller and the nominal temperature of 25℃.

7. The control driver according to claim 1, characterized in that, The SVPWM modulator uses a virtual bus voltage V_bus_virtual=V_bus_meas×β in sector determination and action time calculation, where V_bus_meas is the real-time acquired bus voltage; β is a preset scaling factor with a value range of 1.1 to 1.

3.

8. The control driver according to claim 4, characterized in that, The sensing or non-sensing dual-mode switching module enters sensing mode when it detects a valid signal from an external sensor interface, utilizing the Hall sensor interface, the incremental encoder interface, the SPI bus interface, or the... The rotor electrical angle is obtained via the bus interface; When no valid external sensor signal is detected, the system switches to a sensorless mode and constructs a state equation based on an extended Kalman filter, where the state variables include at least the rotor electrical angle θ. e Electric angular velocity ω e It also controls the periodic update of the state estimate to output the rotor electrical angle θ. e .

9. The control driver according to claim 8, characterized in that, The state equation of the extended Kalman filter is constructed based on the motor terminal voltage and phase current, and the parameters of the state equation of the extended Kalman filter are adjusted based on the nominal parameters of the motor.

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