Unmanned aerial vehicle servo control system hardware circuit

Abstract

The utility model discloses a hardware circuit of a servo control system of an unmanned aerial vehicle, which belongs to the field of steering engine control and comprises a control module and a driving module which are stacked in a double-layer manner, and the control module comprises a main control chip, a wide-voltage power conversion circuit, a communication circuit and an interface circuit; the main control chip is respectively connected with the wide-voltage power conversion circuit, the communication circuit and the interface circuit; the driving module comprises a pre-driving chip, a three-phase inverter bridge and a current sampling circuit; the pre-drive chip is respectively connected with the three-phase inverter bridge and the current sampling circuit; the control module and the driving module are interconnected through a board-to-board connector; and the current sampling circuit is connected with the main control chip. The circuit is compact in overall size, high in integration level, high in interference immunity and wide in voltage adaptability, and suitable for precise control over the steering engine of the unmanned aerial vehicle.

Description

Technical Field

[0001] This utility model relates to the field of servo motor control, and in particular to a hardware circuit for a servo control system for unmanned aerial vehicles (UAVs). Background Technology

[0002] Servo servos are the core actuators of UAV flight control systems, and their performance directly affects the aircraft's maneuverability, stability, and safety. Traditional servo systems mainly include three types: pneumatic, hydraulic, and electromechanical, all of which have significant drawbacks: pneumatic servos are driven by compressed air, resulting in low response speed, large positioning errors, and limited output torque; hydraulic servos, while providing high torque, are complex systems (containing components such as oil pumps and servo valves, contributing significantly to the overall weight), and require preheating in low-temperature environments, leading to high maintenance costs; electromechanical servos, as a third-generation technology, while offering high power density advantages, still face three major bottlenecks in practical applications:

[0003] 1. Large hardware size: The separate design of the control board and the driver board results in low space utilization, making it difficult to meet the lightweight requirements of drones;

[0004] 2. Weak anti-interference capability: The high-frequency noise generated by MOSFET switching distorts the current sampling. The traditional STM32 controller's built-in ADC solution cannot effectively suppress the interference, resulting in a large steady-state error in the position loop.

[0005] 3. Insufficient system reliability: Narrow power input range, no reverse connection protection circuit, and single communication interface (such as only CAN or RS485), making the system prone to shutdown due to bus failure.

[0006] Therefore, there is an urgent need for an innovative hardware architecture that combines high-density integration, strong anti-interference capabilities, and wide voltage adaptability to break through the technical bottleneck of UAV servo control systems. Utility Model Content

[0007] The purpose of this invention is to overcome the problems existing in the prior art and to provide a hardware circuit for a drone servo control system.

[0008] The objective of this utility model is achieved through the following technical solution:

[0009] A hardware circuit for a drone servo control system is provided, comprising a double-layer stacked structure:

[0010] The control module includes a main control chip, a wide-voltage power conversion circuit, a communication circuit, and an interface circuit; the main control chip is connected to the wide-voltage power conversion circuit, the communication circuit, and the interface circuit respectively.

[0011] The drive module includes a pre-drive chip, a three-phase inverter bridge, and a current sampling circuit; the pre-drive chip is connected to the three-phase inverter bridge and the current sampling circuit respectively.

[0012] The control module and the drive module are interconnected via a board-to-board connector; the current sampling circuit is connected to the main control chip.

[0013] In some embodiments, the wide-voltage power conversion circuit includes an input stage anti-reverse insertion circuit, a first-stage buck circuit, and a second-stage buck circuit.

[0014] In some embodiments, the communication circuit includes dual RS485 circuits and dual CAN circuits.

[0015] In some embodiments, the interface circuit includes a first interface circuit and a second interface circuit. The first interface circuit is connected to the pre-driver chip via a wire-to-wire connector, and the second interface circuit is connected to a peripheral device via an aviation plug.

[0016] In some embodiments, the control module further includes a storage circuit, which includes an AT24C02 chip, and the AT24C02 chip is connected to the main control chip via an IIC bus interface.

[0017] In some embodiments, the current sampling circuit is a low-side three-resistance sampling circuit, including an INA240A1 current amplifier, which is connected to the main control chip.

[0018] In some embodiments, the three-phase inverter bridge includes a multiplexing circuit, the switching circuit including a MOSFET switch, a gate resistor connected in series with the gate of the MOSFET switch, and a fast recovery diode connected in parallel with the gate resistor.

[0019] In some embodiments, the main control chip is an STM32G474RBT6 and the pre-driver chip is an FD6288T.

[0020] In some embodiments, the first-stage buck circuit includes an LMR38020SDDAR chip, and the second-stage buck circuit includes a TLV1117 chip.

[0021] In some embodiments, the control module and the drive module are a 4-layer PCB stacked structure.

[0022] It should be further noted that the technical features corresponding to the above embodiments can be combined or substituted with each other to form new technical solutions without conflict.

[0023] Compared with the prior art, the beneficial effects of this utility model are:

[0024] 1. The control board and driver board adopt a two-layer stacked hardware architecture, which includes a control module (upper level) and a driver module (lower level), and are interconnected through board-to-board connectors, which significantly reduces the size compared to discrete solutions.

[0025] 2. The current sampling adopts the INA240A1 external amplifier with a low-side three-resistor topology, which solves the problem of insufficient noise immunity of the microcontroller's built-in ADC.

[0026] 3. A fast recovery diode is connected in parallel to the MOSFET gate to accelerate turn-off and reduce crosstalk.

[0027] 4. It adopts a wide voltage output, reverse connection protection circuit and multi-stage filtering design to adapt to the fluctuation of drone battery and enhance power supply robustness.

[0028] 5. In terms of communication, it adopts dual RS485 and dual CAN interfaces, and supports multi-protocol hot backup.

[0029] Specifically, the control module is based on the STM32G474, integrating a wide-voltage power supply (24-60V input) and dual RS485 / dual CAN communication; the drive module drives a three-phase inverter bridge through an FD6288T pre-driver chip and adopts an anti-interference current sampling scheme with low-side three resistors and an INA240A1 amplifier. With an ultra-compact overall size of approximately 69mm × 45mm × 29mm, it combines high integration, strong anti-interference capabilities, and wide voltage adaptability, making it suitable for precision control of UAV servos. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the hardware circuit architecture of a drone servo control system according to the present invention.

[0031] Figure 2 This is the circuit schematic diagram of the STM32G474RBT6 core board of this utility model;

[0032] Figure 3 This is a schematic diagram of the circuit surrounding the main control chip of this utility model;

[0033] Figure 4 This is a schematic diagram of the input stage anti-reverse insertion circuit of this utility model;

[0034] Figure 5 This is a circuit diagram for the bus voltage acquisition of this utility model;

[0035] Figure 6 This is the circuit diagram for the VDC to 5V converter of this utility model;

[0036] Figure 7 This is the circuit diagram for the 5V to 3.3V converter of this utility model;

[0037] Figure 8This is the schematic diagram of the RS485 circuit of this utility model;

[0038] Figure 9 This is the schematic diagram of the CAN circuit of this utility model;

[0039] Figure 10 This is a schematic diagram of the storage circuit of this utility model;

[0040] Figure 11 This is a schematic diagram of the Hall effect current processing circuit of this utility model;

[0041] Figure 12 This is a schematic diagram of the interface circuit of the control board of this utility model;

[0042] Figure 13 This is the circuit schematic of the pre-driver chip of this utility model;

[0043] Figure 14 This is the schematic diagram of the three-phase inverter bridge circuit of this utility model;

[0044] Figure 15 This is a diagram of the three-phase current sampling circuit of this utility model;

[0045] Figure 16 This is the circuit diagram for the VDC to 12V converter of this utility model;

[0046] Figure 17 This is the circuit diagram for the 12V to 3.3V converter of this utility model.

[0047] Figure 18 This is a schematic diagram of the interface circuit of the driver board of this utility model. Detailed Implementation

[0048] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0049] In the description of this utility model, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0050] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0051] like Figure 1 This invention provides a hardware circuit for a drone servo control system, comprising a double-layer stacked structure:

[0052] The control module includes a main control chip, a wide-voltage power conversion circuit, a communication circuit, and an interface circuit; the main control chip is connected to the wide-voltage power conversion circuit, the communication circuit, and the interface circuit respectively.

[0053] The drive module includes a pre-drive chip, a three-phase inverter bridge, and a current sampling circuit; the pre-drive chip is connected to the three-phase inverter bridge and the current sampling circuit respectively.

[0054] The control module and the drive module are interconnected via a board-to-board connector; the current sampling circuit is connected to the main control chip.

[0055] Specifically, a dual-layer stacked hardware architecture is adopted, including a control module (upper level) and a drive module (lower level), interconnected via board-to-board connectors. The overall size is optimized to 69mm×45mm×29mm, and the weight is ≤57g. During operation, the interface of the control module (control board) receives flight control commands, and the interface of the drive module (drive board) outputs PWM to the servo motors. The control board and the drive board transmit PWM / current / position signals through a 10-pin board-to-board connector.

[0056] For example, such as Figure 2-3 As shown, the core control module consists of the STM32G474RBT6 main control chip and its surrounding circuitry. The STM32G474RBT6 main control chip is primarily responsible for receiving and parsing data packets sent from the host computer. It receives the output signal from the three-phase current sampling circuit, reconstructs the three-phase currents Ia, Ib, and Ic, executes the FOC sensing algorithm and SVPWM modulation, outputs six complementary PWM waves through a timer, and communicates with the servo controller. The surrounding circuitry mainly consists of an MCU power supply circuit, a 24MHz crystal oscillator circuit, a reset circuit, and a debugging circuit.

[0057] For example, the main control module's power supply module is designed with a wide voltage input range of 24V~60V. To prevent the control board from burning out due to reverse power insertion during use, an input-level anti-reverse insertion circuit based on CJA C70P06 is designed at the power connection point, utilizing the unidirectional conductivity of diodes. Figure 4 As shown. The bus voltage acquisition circuit uses the LMV321DBVR chip, such as... Figure 5 As shown. The first-stage step-down circuit uses the LMR38020SDDAR chip to step down 24-60V to 5V, as... Figure 6 As shown, the two-stage step-down circuit uses the TLV1117LV33DCYT power supply chip to convert 5V to 3.3V. Figure 7 As shown.

[0058] For example, the main control module's communication circuit includes an RS485 circuit and a CAN circuit. RS485 uses differential transmission to ensure the accuracy of transmitted information, with a maximum transmission distance of thousands of meters and the ability to connect multiple devices, thus it is widely used in industrial applications. The RS485 circuit uses the SIT3485ESA chip from Coretech, such as... Figure 8 As shown, this chip features a 3.3V power supply and a maximum communication rate of 12Mbps. The CAN bus uses differential transmission, offering strong anti-interference capabilities, and compared to the RS485 bus, it supports multi-master architectures. The CAN circuit uses the SIT65HVD230DR chip from Coretech, such as... Figure 9 As shown, the chip features a 3.3V power supply and simple peripheral circuitry.

[0059] For example, the main control module's storage circuit uses the AT24C02 chip, such as Figure 10 As shown, the AT24C02 is a 2K-bit serial CMOS E2PROM containing 256 8-bit bytes. Utilizing advanced CMOS technology, it significantly reduces power consumption. The AT24C02 has an 8-byte page write buffer, operates via an IIC bus interface, and features dedicated write protection. It has an erase cycle life of up to 10,000 times and a data storage time exceeding 100 years.

[0060] For example, the Hall processing module of the main control module uses a 10nF capacitor to filter the Hall signal and connects it to a 4.7kΩ pull-up resistor, such as... Figure 11 As shown.

[0061] For example, the main control module interface circuit has two interfaces. Interface 1 uses a WAFER-SH1.0-10PWB wire-to-wire connector to communicate with the driver board, and interface 2 uses a J30J-25TJW-J aviation connector to communicate with peripherals. Figure 12 As shown.

[0062] For example, the drive module mainly includes a pre-drive chip, a three-phase inverter circuit, a three-phase current sampling circuit, and a power supply circuit. First, the three-phase sampling circuit collects the three-phase current and performs coordinate transformation, converting it from a three-phase rotating coordinate system to a two-phase stationary coordinate system. The encoder analyzes the current motor rotor mechanical angle, and then, based on the motor data in the message, converts it into electrical angles, which are fed back to the closed loop. In the position closed loop, the position loop obtains the current speed value through a position PID controller based on the deviation between the target position and the actual position. This value serves as the input to the speed closed loop PI controller; the deviation from the actual speed is used to derive the current iq and id values ​​through speed PI control. The obtained iq and id values ​​serve as the input to the current loop, and through a current PI controller, uq and ud are obtained. uq and ud are used as inputs to the SVPWM algorithm to calculate the PWM duty cycle, and are output to the three-phase full-bridge circuit through the corresponding GPIO, thereby controlling the bridge arm switching time. The speed closed loop and current closed loop follow the same principle.

[0063] For driving small to medium power brushless DC motors, MOSFETs with high withstand voltage and high rated current are generally used. However, even after level conversion by the isolation circuit, the six complementary PWM waves output by the MCU still cannot meet the requirements of fast-switching MOSFETs. Furthermore, in order to further isolate the control loop from the main power loop, and to improve switching speed, reduce switching losses, and suppress switching noise.

[0064] For example, the pre-driver chip is FD6288T, such as Figure 13 As shown. To overcome the shortcomings of insufficient instantaneous power supply due to the long power transmission line and to improve power filtering, a 2.2uF energy storage capacitor and a 100nF filter capacitor are provided at the power supply terminal of the FD6288T. To ensure that the high-side MOSFET of the half-bridge remains continuously on when needed, rather than experiencing cyclical unstable states such as on / off states, a 100nF bootstrap capacitor is connected between the VB and VS pins of the FD6288T. This ensures that the Vgs of the high-side MOSFET in the half-bridge circuit remains stable at around 10V when it is on, thus keeping the MOSFET on. Furthermore, to prevent current backflow into the 12V power supply, a low on-state voltage drop switching diode is connected in series between the 12V power supply and the VB pin.

[0065] Brushless DC motors require a sinusoidal voltage with a 120° phase difference between the three phases to drive them, thus necessitating an inverter circuit to convert DC to AC. For three-phase voltage source inverters driven by PMSMs, Space Voltage Pulse Width Modulation (SVPWM) is typically employed. SVPWM abandons the original SPWM algorithm, using the switching of the inverter's space voltage vector to obtain a quasi-circular rotating magnetic field, thereby attracting the rotor to rotate in a quasi-circular manner, resulting in less torque ripple and a more circular motion trajectory for the PMSM. SVPWM is actually implemented through a special combination of switching trigger sequence and pulse width, which generates a sinusoidal current with a 120° phase difference and low distortion in the electronic coils.

[0066] The pre-drive circuit outputs a PWM wave to drive the three-phase bridge arms. To ensure no oscillation occurs during MOSFET switching, for example, a 33Ω gate resistor is connected in series with the gates of the six MOSFETs in the three-phase inverter bridge. Furthermore, to ensure rapid MOSFET turn-off, a fast recovery diode with a forward voltage drop of 0.1V is connected in parallel across the series gate resistors, providing a path for rapid current release. Figure 14 As shown. This achieves a faster turn-off than turn-on, avoiding the short circuit phenomenon that occurs when the upper and lower MOSFETs in the same half-bridge are turned on simultaneously.

[0067] During motor operation, a large amount of high-frequency interference is generated. To prevent this high-frequency interference from causing electromagnetic interference to the digital and analog parts through the DC-DC circuit, a 1uF capacitor is connected in parallel at the large capacitor of the three-phase inverter circuit for filtering.

[0068] Three-phase brushless DC motors are driven by sensing, and the required rotation speed or angle information must be obtained by sampling the three-phase currents Ia, Ib, and Ic. Therefore, sampling the three-phase current is very important for the control and drive system of BLDC motors, and the accuracy of the three-phase current sampling determines the correctness of the closed loop of the entire control system.

[0069] Three-phase current sampling generally involves two sampling locations and three sampling schemes. If the sampling resistor is placed between the upper and lower bridge arm connection points of each half-bridge circuit and the motor phase, it is called high-side sampling; if the sampling resistor is placed between the source (s) of the lower bridge arm MOSFET of each half-bridge circuit and ground (GND), it is called low-side sampling. High-side sampling is more advantageous for sampling accuracy, but it has greater common-mode interference. Low-side sampling, on the other hand, has no common-mode interference and its sampling accuracy meets control requirements. Based on the number of sampling resistors, sampling schemes are divided into single-resistor sampling, dual-resistor sampling, and three-resistor sampling. Single-resistor sampling has the lowest cost but is more complex to implement; while three-resistor sampling has the highest cost but the best accuracy. Therefore, this invention adopts the low-side three-resistor sampling scheme.

[0070] Because the rapid switching of MOSFETs in a three-phase inverter circuit generates high-frequency pulse interference, which can affect the accuracy of current sampling and even lead to sampling failure, in order to suppress the influence of high-frequency spike interference, for example, the current sampling circuit uses TI's INA240A1 as a current amplifier with a gain of 20V / V. Figure 15 As shown.

[0071] For example, the power module circuit of the driver board requires both 12V and 3.3V voltages, except for the power circuit. The VDC voltage to 12V conversion uses the LMR38020SDDAR power chip, such as... Figure 16 As shown. The 12V to 3.3V conversion uses the TLV1117IMPX-3.3 / NOPB power supply chip, such as... Figure 17 As shown.

[0072] For example, the driver board interface module has two interfaces. Interface 1 uses a WAFER-SH1.0-10PWB wire-to-wire connector to communicate with the control board, and interface 2 uses a J30J-9TJW-J aviation connector to communicate with peripherals. Figure 18 As shown.

[0073] This invention features a 4-layer PCB stacked design for the control and driver boards, significantly reducing their size compared to discrete solutions. Current sampling utilizes an INA240A1 external amplifier with a low-side three-resistor topology, resolving the issue of insufficient noise immunity in the microcontroller's built-in ADC. Fast recovery diodes are connected in parallel to the MOSFET gates to accelerate turn-off and reduce crosstalk. A wide-voltage output, reverse connection protection circuitry, and multi-stage filtering design adapt to fluctuations in drone battery power, enhancing power supply robustness. For communication, dual RS485 and dual CAN interfaces are used, supporting multi-protocol hot backup.

[0074] Based on the above circuit design, the workflow of this utility model is as follows:

[0075] The power input is 24V to 60V, which is then stepped down to 5V and 3.3V by the anti-reverse circuit to supply the control board. After the STM32G474 parses the instructions, it executes the FOC algorithm to generate SVPWM. The driver board outputs three-phase voltage to drive the servo motor. The current sampling signal is amplified by the INA240A1 and then converted by the STM32G474 using Clarke and Park conversions, and the closed-loop correction is output.

[0076] The above detailed embodiments are a detailed description of the present utility model. It should not be considered that the specific embodiments of the present utility model are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present utility model, and all of these should be considered to fall within the protection scope of the present utility model.

Claims

1. A hardware circuit for a UAV servo control system, characterized in that, Including double-layer stacked: The control module includes a main control chip, a wide-voltage power conversion circuit, a communication circuit, and an interface circuit; the main control chip is connected to the wide-voltage power conversion circuit, the communication circuit, and the interface circuit respectively. The drive module includes a pre-drive chip, a three-phase inverter bridge, and a current sampling circuit; the pre-drive chip is connected to the three-phase inverter bridge and the current sampling circuit respectively. The control module and the drive module are interconnected via a board-to-board connector; the current sampling circuit is connected to the main control chip.

2. The hardware circuit of the UAV servo control system according to claim 1, characterized in that, The wide voltage power conversion circuit includes an input stage anti-reverse insertion circuit, a first-stage step-down circuit, and a second-stage step-down circuit.

3. The hardware circuit of the UAV servo control system according to claim 1, characterized in that, The communication circuit includes dual RS485 circuits and dual CAN circuits.

4. The hardware circuit of a UAV servo control system according to claim 1, characterized in that, The interface circuit includes a first interface circuit and a second interface circuit. The first interface circuit is connected to the pre-driver chip via a wire-to-wire connector, and the second interface circuit is connected to the peripheral device via an aviation plug.

5. The hardware circuit of a UAV servo control system according to claim 1, characterized in that, The control module also includes a storage circuit, which includes an AT24C02 chip. The AT24C02 chip is connected to the main control chip via an IIC bus interface.

6. The hardware circuit of a UAV servo control system according to claim 1, characterized in that, The current sampling circuit is a low-side three-resistance sampling circuit, including an INA240A1 current amplifier, which is connected to the main control chip.

7. The hardware circuit of a UAV servo control system according to claim 1, characterized in that, The three-phase inverter bridge includes a multi-channel switching circuit, which includes a MOSFET switch. A gate resistor is connected in series with the gate of the MOSFET switch, and a fast recovery diode is connected in parallel with the gate resistor.

8. The hardware circuit of a UAV servo control system according to claim 1, characterized in that, The main control chip is model STM32G474RBT6, and the pre-driver chip is model FD6288T.

9. The hardware circuit of a UAV servo control system according to claim 2, characterized in that, The first-stage buck circuit includes an LMR38020SDDAR chip, and the second-stage buck circuit includes a TLV1117 chip.

10. The hardware circuit of a UAV servo control system according to claim 1, characterized in that, The control module and drive module are a 4-layer PCB stacked structure.

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