UWB digital key positioning system fused with imu

Abstract

The utility model provides a kind of UWB digital key positioning system of fusion IMU, to solve the technical problems that existing system has high cost, installation is complex. The utility model includes digital key, first UWB anchor point and second UWB anchor point deployed in car;MCU control unit, IMU module and UWB module are equipped in the digital key, IMU module and UWB module are connected with MCU control unit, UWB module is connected with first UWB anchor point and second UWB anchor point communication respectively. The utility model reduces the quantity of UWB anchor point, the utility model effectively reduces the construction cost of UWB multi-anchor positioning system, reduces system overall power consumption, enhances scene adaptation flexibility, expands application range.

Description

Technical Field

[0001] This utility model relates to the field of automotive electronics technology, and in particular to a UWB digital key positioning system. Background Technology

[0002] In today's era of rapid technological development, the automotive industry is undergoing unprecedented changes, rapidly moving towards intelligence and electrification. Users are also placing new demands on the user experience, specifically in terms of the increasing need for convenience and safety in vehicles. Users hope that their interaction with vehicles can be simple and efficient, without cumbersome operating steps, while also ensuring safety.

[0003] Traditional keys, due to their limitations such as being easily lost, inconvenient to carry, and cumbersome to operate, can no longer meet modern users' demands for convenience when opening and starting vehicles. Furthermore, driven by users' security needs, digital keys have emerged, becoming a key element in enhancing the user experience by enabling precise and secure keyless entry and start functions.

[0004] The advent of digital keys has completely transformed the way users interact with their vehicles. Through wireless communication technology, users simply need to carry a device with digital key functionality, such as a smartphone or smartwatch, and the doors will automatically unlock when they approach the vehicle. Once inside, they can easily start the engine without needing to insert a key as in the traditional method. This convenient interaction not only saves users time and effort but also enhances the vehicle's technological sophistication and luxury.

[0005] Among the many technical solutions for implementing digital keys, Ultra Wideband (UWB) wireless communication technology has become a popular choice in the field due to its significant advantages, such as strong resistance to multipath interference, good penetration, and high security. Furthermore, UWB technology can achieve distance measurement and position calculation with centimeter-level or even higher precision, providing a solid technical foundation for accurate door unlocking and start authorization.

[0006] Current mainstream UWB digital key solutions typically require the deployment of multiple UWB anchor points on the vehicle. For example, the utility model patent with application number 202220735258.6. Although this multi-anchor point architecture helps ensure positioning accuracy, it also increases the hardware cost and installation complexity of the system. Utility Model Content

[0007] To address the technical problems of high cost and complex installation in existing systems, this invention proposes a UWB digital key positioning system that integrates an IMU, which reduces the cost and installation complexity of the UWB digital key positioning system while ensuring positioning accuracy.

[0008] To achieve the above objectives, the technical solution of this utility model is as follows: a UWB digital key positioning system integrating an IMU, comprising a digital key, a first UWB anchor point and a second UWB anchor point deployed inside a vehicle; the digital key is equipped with an MCU control unit, an IMU module and a UWB module, both of which are connected to the MCU control unit, and the UWB module is communicatively connected to the first UWB anchor point and the second UWB anchor point respectively.

[0009] Preferably, the first UWB anchor point is located at the front of the vehicle, and the second UWB anchor point is located at the rear of the vehicle; the first UWB anchor point or the second UWB anchor point is the main anchor point.

[0010] Preferably, the digital key includes a PCB board, on which the MCU control unit, UWB module and IMU module are all mounted; the PCB board also has a Bluetooth module, which is connected to the MCU control unit and wirelessly connected to the vehicle's control system.

[0011] Preferably, the Bluetooth module is connected to the MCU control unit via a UART asynchronous serial interface, the MCU control unit is connected to the UWB module via an SPI serial bus interface, and the IMU module is connected to the MCU control unit via an I2C bus interface.

[0012] Preferably, the UWB module includes a UWB chip, a bandpass filter, and a ceramic antenna. The UWB chip is connected to the bandpass filter and the MCU control unit, respectively, and the bandpass filter is connected to the ceramic antenna.

[0013] Preferably, the ceramic antenna is arranged in the middle area of ​​the lower front of the PCB board; the Bluetooth module adopts a serpentine antenna, which is arranged in the edge area of ​​one side of the reverse side of the PCB board.

[0014] Preferably, the MCU control unit uses an MCU chip, the RX and TX pins of the MCU chip are connected to the Bluetooth module, the SPI-NSS, SPI-SCK, SPI-MISO, and SPI-MOSI pins of the MCU chip are connected to the UWB chip of the UWB module, and the SCL and SDI pins of the MCU chip are connected to the IMU module. The NRST pin of the MCU chip is connected to the power supply VDD through a pull-up resistor R1. The NRST pin is connected to ground via a push-button switch S1 and a capacitor C1. The BTN pin of the MCU chip is grounded through a pull-down resistor R20 and connected to the power supply VDD via a switch S4. The BOOT0 pin of the MCU chip is connected to one end of resistor R2 and one end of switch S3. The other end of resistor R2 is grounded, and the other end of switch S3 is connected to the power supply VDD.

[0015] Preferably, the Bluetooth module uses a Bluetooth chip, and the RX and TX pins of the Bluetooth chip are connected to the RX and TX pins of the MCU chip, respectively; the feed point of the serpentine antenna is connected to inductor L3, and the other end of inductor L3 is connected to the ANT pin of the Bluetooth chip; the common node between inductor L3 and the ANT pin is grounded through capacitor C56. The RF-P pin of the UWB chip is connected in series with the second BP pin of the bandpass filter via capacitor C40, and the RF-N pin of the UWB chip is connected in series with the first BP pin of the bandpass filter via capacitor C42, thus completing DC blocking and impedance transformation; the IN pin of the ceramic antenna is connected to the UP pin of the bandpass filter.

[0016] Preferably, the IMU module is an IMU chip, which integrates a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer; the SCL / SCLK pin and SDA / SDI pin of the IMU chip are connected to the SCL pin and SDI pin of the MCU chip, respectively.

[0017] Preferably, the three power decoupling pins of the Bluetooth chip are grounded through a capacitor; the DCC pin of the Bluetooth chip is connected to inductor L1, and inductors L1 and L2 are connected in series and then connected to the DEC4 pin of the Bluetooth chip; the connection node between inductor L2 and the DEC4 pin is grounded through capacitor C49; the three VDD pins of the Bluetooth chip are all connected in parallel to a 3.3V DC power supply, and the three VDD pins are grounded through a capacitor. The XL1 pin of the Bluetooth chip is connected to one end of the two-pin crystal oscillator X1 and one end of capacitor C47. The other end of the two-pin crystal oscillator X1 is connected to one end of capacitor C48 and the XL2 pin of the Bluetooth chip. The other ends of capacitors C47 and C48 are both grounded. The XC1 pin of the Bluetooth chip is connected to one end of capacitor C53 and the third pin of an external four-pin crystal oscillator. The other end of capacitor C53 is connected to the second pin of the four-pin crystal oscillator and ground. The XC2 pin of the Bluetooth chip is connected to the first pin of an external four-pin crystal oscillator and one end of capacitor C52. The other end of capacitor C52 is connected to the fourth pin of the four-pin crystal oscillator and ground. The SPICSn, SPICLK, SPIMISO, and SPIMOSI pins of the UWB chip are respectively connected to the SPI-NSS, SPI-SCK, SPI-MISO, and SPI-MOSI pins of the MCU chip. The VDDDREG pin of the UWB chip is electrically connected to the VDDDIG pin. The VDDDREG pin is grounded through capacitor C39, and the VDDDIG pin is grounded through capacitor C16. The GPIO5 pin of the UWB chip is connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R10, the VDDIO pin of the UWB chip, and one end of capacitor C25. The other end of capacitor C25 is grounded. The other end of resistor R10 is connected to the GPIO6 pin of the UWB chip. The VSSIO pin of the UWB chip is grounded. The TESTMODE and FORCEON pins of the UWB chip are both grounded. The IRQ pin of the UWB chip is connected to both pin PB0 of the chip and one end of resistor R5. The other end of resistor R5 is grounded. The VDDIO pin of the UWB chip is connected to one end of capacitor C22, and the VSSIO pin is grounded together with the other end of capacitor C22. The XLAT1 and XLAT2 pins of the UWB chip, together with crystal oscillator X2 and capacitors C23 and C24, form a clock oscillation circuit. The VREF pin of the UWB chip is grounded through resistor R9; the VDDMS pin of the UWB chip is grounded through capacitor C26; the VDDIF pin of the UWB chip is grounded through capacitor C28; and the VDDSYN pin of the UWB chip is grounded through capacitor C32. The CLKTUNE pin of the UWB chip is connected to one end of resistor R11 and capacitor C30 respectively. The other end of resistor R11 is connected to one end of capacitor C34. The VDDCLK pin is connected to the other end of capacitor C34, the other end of capacitor C30 and one end of capacitor C38. The other end of capacitor C38 is grounded. The VDDVCO pin of the UWB chip is connected to one end of capacitors C31, C36 and C37. The other end of capacitor C31 is grounded, the other end of capacitor C36 is connected to one end of resistor R12, and the other ends of resistor R12 and capacitor C37 are both connected to the VCOTUNE pin. The first RESV pin of the IMU chip is connected to the power supply VDD; the SDA / SDI pin of the IMU chip is connected to the power supply VDD through resistor R13; the SCL / SCLK pin of the IMU chip is connected to the power supply VDD through resistor R15; the nCS pin of the IMU chip is connected to the power supply VDD through resistor R19. The IMU chip's ADO / SDO pin is grounded through resistor R16; the IMU chip's REFOUT pin is grounded through capacitor C44; the IMU chip's FSYNC pin is grounded through resistor R17; the IMU chip's second RESV pin is grounded; the IMU chip's GND pin is grounded; and the IMU chip's EXP pin is grounded. The VDD pin of the IMU chip is connected to the power supply VDD and one end of capacitor C43, while the other end of capacitor C43 is grounded.

[0018] The beneficial effects of this utility model are as follows: By reducing the number of UWB anchor points, this utility model effectively reduces the construction cost of the UWB multi-anchor point positioning system, reduces the overall power consumption of the system, enhances the flexibility of scene adaptation, expands the application scope, and has significant application advantages. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of this utility model.

[0021] Figure 2 This is a schematic diagram of the antenna structure layout in one embodiment of the present invention, wherein (a) is a schematic diagram of the layout of the ceramic antenna and (b) is a schematic diagram of the layout of the serpentine antenna.

[0022] Figure 3 This is a circuit diagram of the MCU control unit in one embodiment of the present invention.

[0023] Figure 4 This is a circuit diagram of the Bluetooth module in one embodiment of the present invention.

[0024] Figure 5 This is a circuit diagram of the UWB module in one embodiment of the present invention.

[0025] Figure 6 This is a circuit diagram of the IMU module in one embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] like Figure 1 As shown, a UWB digital key positioning system integrating an IMU includes a digital key, a first UWB anchor point and a second UWB anchor point deployed inside a vehicle; the first UWB anchor point is located at the front of the vehicle, and the second UWB anchor point is located at the rear of the vehicle, and the digital key is communicatively connected to the first UWB anchor point and the second UWB anchor point respectively.

[0028] The first UWB anchor point or the second UWB anchor point is used as the main anchor point. In this embodiment, anchor point A in the figure is the first UWB anchor point and serves as the main anchor point; anchor point B is the second UWB anchor point.

[0029] The digital key includes a PCB board, on which are provided an MCU control unit, a Bluetooth module, a UWB module, and an IMU module; the Bluetooth module, UWB module, and IMU module are all connected to the MCU control unit, and the Bluetooth module is connected to a first UWB anchor point and a second UWB anchor point respectively.

[0030] The Bluetooth module is used for vehicle authentication. After successful authentication, the Bluetooth module is activated to perform RSSI ranging and transmits the RSSI ranging data to the MCU control unit via the UART asynchronous serial interface. Based on the received RSSI ranging data, if the Bluetooth ranging value is less than a preset threshold, the MCU control unit transmits an enable command to the UWB module via the SPI serial bus interface. Upon receiving the enable command from the MCU control unit, the UWB module performs TOF ranging with the first and second UWB anchor points, and the main anchor point calculates the position coordinates based on the data. The IMU module calculates the yaw angle in real time based on the movement posture of the digital key and sends the yaw angle data to the MCU control unit via the I2C bus interface. The MCU control unit then transmits the yaw angle data to the main anchor point via the UWB module.

[0031] The main anchor point, based on its position coordinates and received yaw angle data, eliminates ambiguous coordinates during the positioning process. The specific process is as follows: The main anchor point and the second UWB anchor point, using Time-of-Flight (TOF) ranging technology, each draw circles with themselves as centers and the measured distance to the digital key as radii. The two circles intersect, creating two points: one corresponding to the digital key's true position, and the other a mirrored, ambiguous point. The MCU control unit built into the main anchor point analyzes the real-time yaw angle information transmitted by the digital key, identifies and eliminates ambiguous coordinates, thereby accurately calculating the digital key's position information.

[0032] The Bluetooth module is connected to a 2.4GHz onboard PCB serpentine antenna, which is located on the right edge of the reverse side of the PCB. The physical layout of the serpentine antenna A2 in this embodiment is as follows: Figure 2 As shown in (b), the serpentine antenna has advantages such as low production cost and compact layout.

[0033] The MCU control unit uses an STM32F103RCT6 MCU chip U6, such as Figure 3 As shown, the NRST pin of the MCU chip U6 is an asynchronous reset input that is active low. This pin is connected to the power supply VDD through a pull-up resistor R1 to ensure that it is high under normal conditions. At the same time, the push button switch S1 is connected to ground for manual reset triggering. A capacitor C1 is also connected to ground to filter out high-frequency noise interference.

[0034] The BTN pin (PA3 pin) of the MCU chip U6 is used for key press input detection. This pin is grounded through a pull-down resistor R20 to ensure that the pin remains stably low when the switch S4 is not triggered. The other end of the switch S4 is connected to the power supply VDD, and when pressed, it directly pulls the BTN pin high. The core function of the resistor R20 as a pull-down resistor is to provide a defined low-level reference while limiting the current when the switch is on.

[0035] The BOOT0 pin of MCU chip U6 is connected to one end of resistor R2 and one end of switch S3. The other end of resistor R2 is grounded, and the other end of switch S3 is connected to the power supply VDD. The BOOT0 pin is grounded through the pull-down resistor R2, enabling MCU chip U6 to boot from main memory. When switch S3 is pressed, the BOOT0 pin is pulled to the power supply voltage, and MCU chip U6 enters the system memory boot mode.

[0036] The Bluetooth module uses a Bluetooth chip U5 with model number NRF52832-QFAA-R, such as... Figure 4As shown, the RX pin (P0.07 pin) and TX pin (P0.08 pin) of Bluetooth chip U5 are connected to the RX pin (PC11 pin) and TX pin (PC10 pin) of MCU chip U6, respectively, thus constructing an asynchronous full-duplex communication link. The feed point of serpentine antenna A2 is connected to inductor L3, and the other end of inductor L3 is connected to the ANT pin of Bluetooth chip U5 to form the main transmission path of radio frequency signal; one end of capacitor C56 is connected to the common node of inductor L3 and ANT pin, and the other end is grounded. Capacitor C56 can filter out noise and form an impedance matching network with inductor L3 to reduce the reflection loss of radio frequency signal during transmission.

[0037] The DEC1, DEC2, and DEC3 pins of the Bluetooth chip U5 are all power decoupling pins, connected to one end of capacitors C45, C55, and C54 respectively, with the other end grounded. This is used to stabilize the power supply to the internal core circuit of the chip and suppress high-frequency interference. The DCC pin of the Bluetooth chip U5 is the output terminal of the internal DC / DC regulator. Its output voltage needs to provide input to the internal 1.3V LDO. Inductors L1 and L2 are connected in series. One end of inductor L1 is connected to the DCC pin, and the other end of L1 is connected to one end of inductor L2. The other end of inductor L2 is connected to the DEC4 pin (power decoupling pin) of the Bluetooth chip U5. The connection point between inductor L2 and the DEC4 pin is connected to one end of capacitor C49, with the other end of capacitor C49 grounded to optimize the purity of the DC / DC output power supply.

[0038] The XL1 pin of Bluetooth chip U5 is connected to one end of the two-pin crystal oscillator X1 and one end of capacitor C47. The other end of the two-pin crystal oscillator X1 is connected to one end of capacitor C48 and the XL2 pin of Bluetooth chip U5. The other ends of capacitors C47 and C48 are grounded. The XC1 pin of Bluetooth chip U5 is connected to one end of capacitor C53 and the third pin of the external four-pin crystal oscillator; the other end of capacitor C53 is connected to the second pin of the four-pin crystal oscillator and ground. The XC2 pin of Bluetooth chip U5 is connected to the first pin of the external four-pin crystal oscillator and one end of capacitor C52; the other end of capacitor C52 is connected to the fourth pin of the four-pin crystal oscillator and ground. Capacitors C47, C48, C52, and C53 are all load capacitors matching the external four-pin crystal oscillator to stabilize the oscillation frequency.

[0039] The VDD pins of the Bluetooth chip U5 include pins 14, 36, and 48. All three pins are connected in parallel to a 3.3V DC power supply. Pin 14 supplies power to the chip's underlying layers, pin 36 supplies power to the RF circuitry and high-speed clock module, and pin 48 supplies power to the core logic circuitry. Capacitors C51, C50, and C46 are connected in parallel next to pins 14, 36, and 48, respectively, to suppress power supply noise. The other ends of all three capacitors are grounded.

[0040] The circuit diagram of the UWB module is as follows: Figure 5 As shown, the UWB module includes a UWB chip U1 of model DW1000, a bandpass filter U3 of model HHM1595A1, and a ceramic antenna A1 of model ACS5200HFAUWB. The UWB chip is connected to the bandpass filter and the MCU chip, respectively, and the bandpass filter is connected to the ceramic antenna A1.

[0041] The ceramic antenna A1 is arranged in the middle area of ​​the lower front of the PCB board; in this embodiment, the physical layout of the ceramic antenna A1 is as follows: Figure 2 As shown in (a), deploying the ceramic antenna A1 and the serpentine antenna A2 on different planes of the PCB board can reduce interference and coupling between different antennas and effectively optimize the coexistence performance of multiple antennas.

[0042] Specifically, after receiving the enable command transmitted by the MCU control unit, the UWB module performs TOF ranging with the first and second UWB anchor points through the ceramic antenna A1.

[0043] The RF-P pin of UWB chip U1 is connected in series with capacitor C40 to the second BP pin of bandpass filter, and the RF-N pin of UWB chip U1 is connected in series with capacitor C42 to the first BP pin of bandpass filter U3, thus completing DC blocking and impedance transformation.

[0044] The SPICSn, SPICLK, SPIMISO, and SPIMOSI pins of the UWB chip U1 are connected to the SPI-NSS (PA4), SPI-SCK (PA5), SPI-MISO (PA6), and SPI-MOSI (PA7) pins of the MCU chip, respectively, to establish a synchronous full-duplex communication link, enabling precise wake-up of the UWB module and initiating the Bluetooth-UWB dual-mode cooperative positioning mechanism. This achieves centimeter-level precision spatial positioning switching while maintaining low power consumption.

[0045] The VDDDREG pin of the UWB chip U1 is the output terminal of the chip's internal digital voltage regulator, whose core function is to provide a precise, regulated voltage. The VDDDIG pin is the power input terminal of the chip's general-purpose digital circuitry, requiring a stable voltage to ensure the reliability of digital signal transmission and processing. The VDDDREG pin is electrically connected to the VDDDIG pin. The VDDDREG pin is connected to one end of capacitor C39, and the VDDDIG pin is connected to one end of capacitor C16. The other ends of capacitors C39 and C16 are grounded. The core functions of capacitors C39 and C16 are filtering, voltage regulation, and suppression of power supply noise.

[0046] The GPIO5 pin of the UWB chip U1 is connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R10, the VDDIO pin (pin 31) of the UWB chip U1, and one end of capacitor C25. The other end of resistor R10 is connected to the GPIO6 pin of the UWB chip U1. The other end of capacitor C25 is connected to ground and the VSSIO pin (pin 32) of the UWB chip U1. The connection of GPIO5 and GPIO6 pins to resistors R8 and R10, and capacitor C25 is primarily to provide a stable voltage level and noise suppression for the SPI mode hardware configuration during the chip initialization phase.

[0047] The TESTMODE and FORCEON pins of UWB chip U1 are both grounded. The IRQ pin of UWB chip U1 is simultaneously connected to pin PB0 of chip U6 and one end of resistor R5, with the other end of resistor R5 grounded. Resistor R5 can stably pull the IRQ pin low in the default state, avoiding false interruptions caused by the pin floating when no valid interrupt event occurs, thus ensuring system stability.

[0048] The VDDIO pin (pin 42) of the UWB chip U1 is connected to one end of capacitor C22, and the VSSIO pin (pin 43) and the other end of capacitor C22 are grounded together. Capacitor C22 mainly serves to decouple and filter, so as to ensure the stability and purity of the power supply to the VDDIO pin.

[0049] The XLAT1 pin of the UWB chip U1 is connected to both the third pin of the crystal oscillator X2 and one end of capacitor C24. The other end of capacitor C24 is connected to both the second pin of the crystal oscillator X2 and ground. The XLAT2 pin of the UWB chip U1 is connected to both the first pin of the crystal oscillator X2 and one end of capacitor C23. The other end of capacitor C23 is connected to both the fourth pin of X2 and ground. The XLAT1 and XLAT2 pins of the UWB chip U1, together with the crystal oscillator X2 and capacitors C23 and C24, form a complete clock oscillation circuit. The crystal oscillator X2 provides a stable clock reference signal for the UWB chip U1, and capacitors C23 and C24 stabilize the oscillation frequency and filter out high-frequency noise.

[0050] The VREF pin of the UWB chip U1 is the reference voltage pin, which provides a stable reference voltage for the analog or digital circuits inside the chip. The VREF pin is connected to resistor R9, and the other end of resistor R9 is grounded. Resistor R9 is used to adjust the level of the reference voltage.

[0051] The VDDMS pin of the UWB chip U1 provides power to specific modules inside the chip. The VDDMS pin is connected to capacitor C26, and the other end of capacitor C26 is grounded. Capacitor C26 serves as a decoupling capacitor, and its main function is to filter out high-frequency noise on the power line.

[0052] The VDDIF pin of the UWB chip U1 is used to provide power to the chip's interface circuit. The VDDIF pin is connected to capacitor C28, and the other end of capacitor C28 is grounded. Capacitor C28 can effectively suppress these noises and ensure the voltage of the VDDIF pin is stable.

[0053] The CLKTUNE pin of the UWB chip U1 is used to adjust parameters such as the frequency or phase of the chip's internal clock. The CLKTUNE pin is connected to one end of resistor R11 and capacitor C30, and the other end of resistor R11 is connected to one end of capacitor C34. This connection method forms an RC circuit, which can be used to adjust the electrical characteristics of the CLKTUNE pin. The VDDCLK pin provides power to the chip's clock-related circuits. The VDDCLK pin is connected to the other end of capacitor C34 and capacitor C30, as well as one end of capacitor C38. The other end of capacitor C38 is grounded. Capacitors C34, C30, and C38 together form a decoupling and filtering circuit. The combination of multiple capacitors can more effectively filter out power supply noise in different frequency bands.

[0054] The VDDSYN pin of the UWB chip U1 provides power to the frequency synthesizer and other related circuits inside the chip. The VDDSYN pin is connected to one end of capacitor C32, and the other end of capacitor C32 is grounded. Capacitor C32 can effectively filter out high-frequency noise and maintain the stability of the voltage on the VDDSYN pin.

[0055] The VDDVCO pin of the UWB chip U1 provides power to the internal voltage-controlled oscillator (VCO). The VDDVCO pin is also connected to one end of capacitors C31, C36, and C37. The other end of capacitor C31 is grounded, and the other end of capacitor C36 is connected to one end of resistor R12. The other ends of resistor R12 and capacitor C37 are both connected to the VCOTUNE pin. Capacitor C31 filters out power supply noise, ensuring the purity of the VCO's operating power supply. The voltage divider-filtering of capacitor C36 and resistor R12 provides a stable base control voltage for the VCOTUNE pin. Capacitor C37 further stabilizes the VCOTUNE pin voltage, ensuring the accuracy and stability of the VCO output frequency.

[0056] The IN pin of the ceramic antenna A1 is connected to the UP pin of the bandpass filter U3.

[0057] The IMU module uses a single-chip nine-DOF sensor, specifically the MPU9250 IMU chip U2. This single-chip nine-DOF sensor integrates a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer. The circuit diagram of the IMU module is shown below. Figure 6 As shown, the SCL / SCLK pin and SDA / SDI pin of IMU chip U2 are connected to the SCL pin (PB6 pin) and SDI pin (PB7 pin) of MCU chip U6, respectively, to establish a synchronous half-duplex communication link.

[0058] The first RESV pin of the IMU chip U2 is connected to the power supply VDD to ensure stable operation of the internal circuitry. The VDDIO pin of the IMU chip U2 provides power to the digital circuitry. The VDDIO pin is connected to the power supply VDD and one end of capacitor C41, while the other end of capacitor C41 is connected to ground. This reduces power supply noise interference with the digital signals.

[0059] The ADO / SDO pins of the IMU chip U2 are dual-function pins. In I2C mode, they implement the ADO function, and in SPI mode, they implement the SDO function. The function switches according to the chip's communication mode. Resistor R16 is a pull-down resistor. The ADO / SDO pins are connected to one end of resistor R16, and the other end of resistor R16 is grounded to avoid the pins being floating and to ensure the stability of the interface communication.

[0060] The REFOUT pin of the IMU chip U2 is the output pin of the internal regulator, which is connected to the output of the internal LDO (low dropout linear regulator) to provide a stable reference voltage for the internal analog circuit of the chip. Capacitor C44 is the LDO filter capacitor. The REFOUT pin is connected to one end of capacitor C44, and the other end of capacitor C44 is grounded to stabilize the working state of the LDO.

[0061] The FSYNC pin of the IMU chip U2 is the frame synchronization input pin, used for external synchronization sensor data acquisition. The FSYNC pin is connected to one end of resistor R17, and the other end of resistor R17 is grounded. This can fix the FSYNC pin level to low and prevent the internal synchronization circuit of the chip from being falsely triggered due to level fluctuation.

[0062] The SDA / SDI pin of IMU chip U2 is a dual-function pin. In I2C mode, it is serial data (SDA), and in SPI mode, it is serial data input (SDI). The SDA / SDI pin is connected to one end of resistor R13, and the other end of resistor R13 is connected to the power supply VDD. The SCL / SCLK pin of IMU chip U2 is also a dual-function pin. In I2C mode, it is serial clock (SCL), and in SPI mode, it is serial clock (SCLK). The SCL / SCLK pin is connected to one end of resistor R15, and the other end of resistor R15 is connected to the power supply. Resistors R13 and R15 are pull-up resistors, which can meet the open-drain output characteristics of the I2C bus.

[0063] The nCS pin of IMU chip U2 is the SPI chip select pin (active low). The nCS pin is connected to one end of resistor R19, and the other end of resistor R19 is connected to the power supply VDD. The nCS pin is fixed to a high level when idle to ensure that the chip is in an "unselected" state and to avoid level fluctuations caused by the nCS pin being left floating.

[0064] The VDD pin of the IMU chip U2 is the main power supply pin, which provides power to all internal circuits of the chip. The VDD pin is connected to the power supply VDD and one end of capacitor C43. The other end of capacitor C43 is grounded, which can filter out high-frequency noise and instantaneous current fluctuations of the VDD power supply.

[0065] The second RESV pin of the IMU chip U2 is grounded to prevent circuit malfunctions caused by floating. The GND pin is grounded to provide a current return path for all circuits of the chip. The EXP pin is grounded to achieve heat dissipation and EMC (electromagnetic compatibility) optimization.

[0066] The DMP (Digital Motion Processor) built into the IMU chip U2 can read raw data from the three-axis gyroscope, three-axis accelerometer and three-axis magnetometer in real time, and calculate the yaw angle directly inside the sensors, reducing the computational burden on the MCU chip U6.

[0067] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A UWB digital key positioning system integrating an IMU, characterized in that, It includes a digital key, a first UWB anchor point and a second UWB anchor point deployed inside the vehicle; the digital key is equipped with an MCU control unit, an IMU module and a UWB module, both of which are connected to the MCU control unit, and the UWB module is communicatively connected to the first UWB anchor point and the second UWB anchor point respectively.

2. The UWB digital key positioning system with integrated IMU according to claim 1, characterized in that, The first UWB anchor point is located at the front of the vehicle, and the second UWB anchor point is located at the rear of the vehicle; the first UWB anchor point or the second UWB anchor point is the main anchor point.

3. The UWB digital key positioning system with integrated IMU according to claim 1 or 2, characterized in that, The digital key includes a PCB board, on which an MCU control unit, a UWB module, and an IMU module are all mounted. The PCB board also has a Bluetooth module, which is connected to the MCU control unit and wirelessly connected to the vehicle's control system.

4. The UWB digital key positioning system with integrated IMU according to claim 3, characterized in that, The Bluetooth module is connected to the MCU control unit via a UART asynchronous serial interface, the MCU control unit is connected to the UWB module via an SPI serial bus interface, and the IMU module is connected to the MCU control unit via an I2C bus interface.

5. The UWB digital key positioning system with integrated IMU according to claim 3, characterized in that, The UWB module includes a UWB chip, a bandpass filter, and a ceramic antenna. The UWB chip is connected to the bandpass filter and the MCU control unit, respectively, and the bandpass filter is connected to the ceramic antenna.

6. The UWB digital key positioning system with integrated IMU according to claim 5, characterized in that, The ceramic antenna is located in the middle area at the bottom front of the PCB board; the Bluetooth module uses a serpentine antenna, which is located on the edge area of ​​the reverse side of the PCB board.

7. The UWB digital key positioning system with integrated IMU according to claim 5 or 6, characterized in that, The MCU control unit uses an MCU chip. The RX and TX pins of the MCU chip are connected to the Bluetooth module. The SPI-NSS, SPI-SCK, SPI-MISO, and SPI-MOSI pins of the MCU chip are connected to the UWB chip of the UWB module. The SCL and SDI pins of the MCU chip are connected to the IMU module. The NRST pin of the MCU chip is connected to the power supply VDD through a pull-up resistor R1. The NRST pin is connected to ground via a push-button switch S1 and a capacitor C1. The BTN pin of the MCU chip is grounded through a pull-down resistor R20 and connected to the power supply VDD via a switch S4. The BOOT0 pin of the MCU chip is connected to one end of resistor R2 and one end of switch S3. The other end of resistor R2 is grounded, and the other end of switch S3 is connected to the power supply VDD.

8. The UWB digital key positioning system with integrated IMU according to claim 7, characterized in that, The Bluetooth module uses a Bluetooth chip, whose RX and TX pins are connected to the RX and TX pins of the MCU chip, respectively; the feed point of the serpentine antenna is connected to inductor L3, and the other end of inductor L3 is connected to the ANT pin of the Bluetooth chip; the common node between inductor L3 and the ANT pin is grounded through capacitor C56. The RF-P pin of the UWB chip is connected in series with the second BP pin of the bandpass filter via capacitor C40, and the RF-N pin of the UWB chip is connected in series with the first BP pin of the bandpass filter via capacitor C42, thus completing DC blocking and impedance transformation; the IN pin of the ceramic antenna is connected to the UP pin of the bandpass filter.

9. The UWB digital key positioning system with integrated IMU according to claim 8, characterized in that, The IMU module is an IMU chip, which integrates a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer. The SCL / SCLK pin and SDA / SDI pin of the IMU chip are connected to the SCL pin and SDI pin of the MCU chip U6, respectively.

10. The UWB digital key positioning system with integrated IMU according to claim 9, characterized in that, The three power decoupling pins of the Bluetooth chip are grounded through a capacitor; the DCC pin of the Bluetooth chip is connected to inductor L1, and inductors L1 and L2 are connected in series and then connected to the DEC4 pin of the Bluetooth chip; the connection point between inductor L2 and the DEC4 pin is grounded through capacitor C49; the three VDD pins of the Bluetooth chip are all connected in parallel to a 3.3V DC power supply, and the three VDD pins are grounded through a capacitor. The XL1 pin of the Bluetooth chip is connected to one end of the two-pin crystal oscillator X1 and one end of capacitor C47. The other end of the two-pin crystal oscillator X1 is connected to one end of capacitor C48 and the XL2 pin of the Bluetooth chip. The other ends of capacitors C47 and C48 are both grounded. The XC1 pin of the Bluetooth chip is connected to one end of capacitor C53 and the third pin of an external four-pin crystal oscillator. The other end of capacitor C53 is connected to the second pin of the four-pin crystal oscillator and ground. The XC2 pin of the Bluetooth chip is connected to the first pin of an external four-pin crystal oscillator and one end of capacitor C52. The other end of capacitor C52 is connected to the fourth pin of the four-pin crystal oscillator and ground. The SPICSn, SPICLK, SPIMISO, and SPIMOSI pins of the UWB chip are respectively connected to the SPI-NSS, SPI-SCK, SPI-MISO, and SPI-MOSI pins of the MCU chip. The VDDDREG pin of the UWB chip is electrically connected to the VDDDIG pin. The VDDDREG pin is grounded through capacitor C39, and the VDDDIG pin is grounded through capacitor C16. The GPIO5 pin of the UWB chip is connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R10, the VDDIO pin of the UWB chip, and one end of capacitor C25. The other end of capacitor C25 is grounded. The other end of resistor R10 is connected to the GPIO6 pin of the UWB chip. The VSSIO pin of the UWB chip is grounded. The TESTMODE and FORCEON pins of the UWB chip are both grounded. The IRQ pin of the UWB chip is connected to both pin PB0 of the chip and one end of resistor R5. The other end of resistor R5 is grounded. The VDDIO pin of the UWB chip is connected to one end of capacitor C22, and the VSSIO pin is grounded together with the other end of capacitor C22. The XLAT1 and XLAT2 pins of the UWB chip, together with crystal oscillator X2 and capacitors C23 and C24, form a clock oscillation circuit. The VREF pin of the UWB chip is grounded through resistor R9; the VDDMS pin of the UWB chip is grounded through capacitor C26; the VDDIF pin of the UWB chip is grounded through capacitor C28; and the VDDSYN pin of the UWB chip is grounded through capacitor C32. The CLKTUNE pin of the UWB chip is connected to one end of resistor R11 and capacitor C30 respectively. The other end of resistor R11 is connected to one end of capacitor C34. The VDDCLK pin is connected to the other end of capacitor C34, the other end of capacitor C30 and one end of capacitor C38. The other end of capacitor C38 is grounded. The VDDVCO pin of the UWB chip is connected to one end of capacitors C31, C36 and C37. The other end of capacitor C31 is grounded, the other end of capacitor C36 is connected to one end of resistor R12, and the other ends of resistor R12 and capacitor C37 are both connected to the VCOTUNE pin. The first RESV pin of the IMU chip is connected to the power supply VDD; the SDA / SDI pin of the IMU chip is connected to the power supply VDD through resistor R13; the SCL / SCLK pin of the IMU chip is connected to the power supply VDD through resistor R15; the nCS pin of the IMU chip is connected to the power supply VDD through resistor R19. The IMU chip's ADO / SDO pin is grounded through resistor R16; the IMU chip's REFOUT pin is grounded through capacitor C44; the IMU chip's FSYNC pin is grounded through resistor R17; the IMU chip's second RESV pin is grounded; the IMU chip's GND pin is grounded; and the IMU chip's EXP pin is grounded. The VDD pin of the IMU chip is connected to the power supply VDD and one end of capacitor C43, while the other end of capacitor C43 is grounded.

Images