An energy-saving digital key system for vehicle and operation method thereof

Abstract

The application belongs to the field of automobile electronics, and relates to an energy-saving automobile digital key system and a running method.The main structure of the system comprises a digital key, the digital key and an automobile end communicate through UWB signals and Bluetooth or ZigBee;the automobile end comprises a vehicle-mounted UWB unit;the vehicle-mounted UWB unit comprises a vehicle-mounted UWB module and a vehicle-mounted radio frequency module;the vehicle-mounted radio frequency module is Bluetooth or ZigBee;the antenna of the vehicle-mounted UWB module is an array antenna;the vehicle-mounted UWB unit carries out position calculation of the digital key through the incidence angle of the digital key to each antenna of the vehicle-mounted UWB module.Compared with the digital key based on TOF and AOA algorithms, the digital key positioning algorithm of the application is simple and efficient, and can complete positioning by sending UWB signals only once, does not need TOF ranging, can effectively reduce power consumption, and increases the endurance of the digital key.

Description

Technical fields:

[0001] This invention belongs to the field of automotive electronics technology and relates to an energy-saving automotive digital key system and its operating method. The positioning algorithm of this digital key is simple and efficient, and positioning can be completed by sending a UWB signal only once, which can effectively reduce power consumption and increase the battery life of the digital key. Background technology:

[0002] Compared to Bluetooth communication technology, UWB communication technology offers higher security and positioning accuracy, making it suitable for applications in automotive digital keys. For example, Chinese patent application CN202210178502.8 describes a car key based on BLE and UWB, comprising a motion detection module, a Bluetooth communication module, an ultra-wideband communication module, and a processing module. The processing module activates the Bluetooth communication module to communicate with the vehicle when it receives motion status information from the car key. Then, when the Bluetooth connection strength reaches a preset value, it activates the ultra-wideband communication module to obtain the actual location information of the car key. Finally, it sends a corresponding unlock / lock signal or vehicle start permission signal to the vehicle based on the actual location information of the car key. If no motion status information from the car key is received within a preset time, the Bluetooth communication module and the ultra-wideband communication module are deactivated. However, the working method and principle of BLE and UWB positioning are not described. Chinese patent application CN202210270631.X discloses a control system and method for triggering a welcome mode based on UWB. This system senses the position signal of a portable device with UWB functionality and triggers a corresponding welcome mode based on changes in that position signal. When the distance to the vehicle is 5 to 10 meters, the DLP headlights turn on, displaying a welcome pattern; the ground lights illuminate, displaying the car brand logo; the exterior fish-scale lights turn on, providing a warm glow. When the distance to the vehicle is within 5 meters, the doors automatically open, the driver's seat moves back 30 cm, and rotates 30° outwards, achieving a seat-to-side courtesy function. When the occupant sensor detects that a user is in the driver's seat, the doors automatically close, the driver's seat rotates back to its original position, moves forward to the preset optimal driving position, and the vehicle's infotainment screen displays a welcome interface and announces welcome. However, this patent does not describe the positioning method used by the UWB system.

[0003] Chinese patent application CN202010725760.4 discloses a car door handle module and its implementation method based on UWB technology. The implementation method includes: Step 1, when the door handle module receives an unlocking trigger signal, performing Time-of-Flight (ToF) ranging on the door handle module and the UWB smart device based on UWB technology, and calculating the ToF distance. TOF UWB smart devices include smart keys and smartphones with UWB modules; Step 2: Measure the angle of arrival (AoA) of the door handle module and the UWB smart device based on UWB technology; Step 3: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] TOFThe AoA data from step 2 is used to calculate the three-dimensional coordinates of the UWB smart device. Step 4 involves determining whether the UWB smart device is within a legal area based on the preset vehicle calibration range inside and outside the vehicle. If it is, the door unlocking function is executed. However, the TOF positioning method requires multiple communications to obtain distance information before the UWB digital key location can be determined based on the AoA information. Because UWB chips consume a lot of power, multiple UWB signal transmissions and receptions increase the power consumption of the digital key, reducing battery life.

[0004] It is necessary to develop a low-power automotive digital key system and method based on UWB signal transmission and reception. Summary of the Invention:

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an energy-saving car digital key system and operating method. The digital key only needs to send a UWB signal to the car once to complete positioning, effectively reducing power consumption and increasing the digital key's battery life.

[0006] To achieve the above objectives, this invention provides an energy-saving automotive digital key system. Its main structure includes a digital key, which communicates with the vehicle via UWB signals and Bluetooth or ZigBee. The vehicle includes an onboard UWB unit; the onboard UWB unit includes an onboard UWB module and an onboard radio frequency module; the onboard radio frequency module uses Bluetooth or ZigBee; the onboard UWB module's antenna is an array antenna; the onboard UWB unit calculates the digital key's position based on the incident angle of the digital key to each antenna of the onboard UWB module.

[0007] The present invention comprises five vehicle-mounted UWB modules, of which four are located at the four corners of the vehicle body and one is located in the middle of the vehicle interior.

[0008] The digital key of this invention includes a second microcontroller, a UWB module, a first radio frequency module, a second radio frequency module, and a power supply. The second microcontroller is used to calculate the distance between the digital key and the vehicle and to activate the UWB module. The UWB module is used to send UWB signals to the vehicle's UWB module. The first radio frequency module is used to assist communication between the digital key and the vehicle; the first radio frequency module is either Bluetooth Low Energy or ZigBee. The second radio frequency module is used to assist in opening the vehicle door; the second radio frequency module is NFC. The UWB module, the first radio frequency module, and the second radio frequency module are all electrically connected to the second microcontroller. The power supply is electrically connected to the second microcontroller.

[0009] The digital key of the present invention also includes an inertial detection unit, which is connected to the second microcontroller via electrical signals to detect whether the digital key is in use, thereby further assisting in reducing power consumption.

[0010] This invention also provides a method for operating an energy-saving car digital key. The digital key communicates with the car via UWB signals and Bluetooth or ZigBee. The digital key first communicates with the car via Bluetooth or ZigBee. When the digital key and the car reach a set distance, the digital key communicates with the car via UWB signals. The car calculates the position of the digital key by measuring the incident angle of each antenna of the onboard UWB module from the digital key. When the calculated distance between the digital key and the car is within the unlocking position, the car door is unlocked.

[0011] The antenna of the vehicle-mounted UWB module described in this invention is an array antenna.

[0012] The digital key location calculation method described in this invention is as follows: Let the incident angle between the digital key and the two antennas of a certain vehicle-mounted UWB module be... and Set the system measurement error to n i The antenna coordinates of the vehicle-mounted UWB module are (x, i = 1, 2). i y i (i = 1, 2), let the coordinates of the digital key be (x, y), then the angle of incidence can be expressed as:

[0013]

[0014] In the formula, φ i for If the true value is obtained, then the relationship between the measured angle of incidence and the digital key and the vehicle-mounted UWB unit is:

[0015]

[0016] Furthermore, we can obtain that

[0017] xsin(φ i +n i )-ycos(φ i +n i )=x i sin(φ i +n i )-y i cos(φ i +n i (3)

[0018] When the system measurement error n i When it is small enough, sinn i ≈n i cosn i ≈1. Therefore, equation (3) can be simplified to obtain,

[0019] xsinφ i -ycosφii =x i sinφ ii -y i cosφ i +n i [(x i -x)cosφ+(y i -y)sinφ] (4)

[0020] Represented in matrix form as follows:

[0021] Hx=K+δ (5)

[0022] In the formula, H represents K indicates x represents the position coordinate.

[0023] The solution was obtained using the least squares method.

[0024] x=(H T H) -1 H T K (6)

[0025] This will allow you to obtain the location of the digital key to the vehicle's UWB module;

[0026] Similarly, the location of the digital key to all in-vehicle UWB modules is calculated, and thus the location of the digital key is obtained.

[0027] Compared with existing technologies and digital keys using TOF and AOA algorithms, the positioning algorithm of the digital key designed in this invention is simple and efficient. It only needs to send a UWB signal once to complete the positioning, without the need for TOF ranging (TOF ranging requires two transmissions and one reception to complete the positioning). This can effectively reduce power consumption and increase the battery life of the digital key. Combining it with low-power Bluetooth / ZigBee technology can further reduce the power consumption of the digital key and increase its battery life. Attached image description:

[0028] Figure 1 This is a schematic diagram illustrating the overall structural principle of the energy-saving car digital key system involved in this invention.

[0029] Figure 2 This is a schematic diagram illustrating the distribution principle of the vehicle-mounted UWB module involved in this invention on a car.

[0030] Figure 3 This is a schematic diagram of the AOA positioning principle of the energy-saving car digital key system involved in this invention.

[0031] Figure 4 This is a schematic diagram of the working process of the energy-saving car digital key system involved in this invention. Detailed implementation method:

[0032] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings.

[0033] Example 1:

[0034] This embodiment relates to an energy-saving car digital key system, the main structure of which includes an on-board UWB unit 1 and a digital key 2. The on-board UWB unit 1 is used to receive and process signals from the digital key 2; the digital key 2 is a UWB signal transmitter; the on-board UWB unit 1 and the digital key 2 communicate with each other via UWB signals and Bluetooth or ZigBee.

[0035] The vehicle-mounted UWB unit 1 includes a first microcontroller 11, a vehicle-mounted UWB module 12, a vehicle-mounted radio frequency module 13, and a vehicle central driving controller 14. The first microcontroller 11 is used to process various signals and determine the position between the digital key 2 and the vehicle. The vehicle-mounted UWB module 12 is used to receive UWB data packets sent by the digital key 2. The vehicle-mounted radio frequency module 13 is Bluetooth Low Energy or ZigBee, used to assist communication between the digital key 2 and the vehicle central driving controller. The vehicle-mounted UWB module 12 and the vehicle-mounted radio frequency module 13 are electrically connected to the first microcontroller 11; the first microcontroller 11 is also communicatively connected to the central driving controller 14.

[0036] There are 5 vehicle-mounted UWB modules 12, with 4 vehicle-mounted UWB modules distributed at the four corners of the vehicle body and 1 vehicle-mounted UWB module located in the middle of the vehicle interior.

[0037] The digital key 2 includes a second microcontroller 21, a UWB module 22, a first radio frequency module 23, a second radio frequency module 24, and a power supply 25. The second microcontroller 21 is used to process information from the various parts connected to it. The UWB module 22 is used to send UWB signals to the vehicle-mounted UWB module 12. The first radio frequency module 23 is used to assist the communication between the digital key 2 and the vehicle, and to determine the distance between the digital key and the vehicle. The first radio frequency module is either Bluetooth Low Energy or ZigBee. The second radio frequency module is used to assist in opening the car door and can be NFC. The UWB module, the first radio frequency module, and the second radio frequency module are all electrically connected to the second microcontroller. The power supply is electrically connected to the second microcontroller.

[0038] The digital key also includes an inertial detection unit 26, which is electrically connected to the second microcontroller 21 to detect whether the digital key is in use, thereby further helping to reduce power consumption.

[0039] The inertial detection unit 26 is an accelerometer or gyroscope, etc.

[0040] Each module of the vehicle-mounted UWB module has an array antenna, and the antenna shape can be customized according to requirements. The relative distance between two antennas is less than λ / 2, where λ is the wavelength of the UWB signal, and the vehicle-mounted UWB chip used can provide the incident angle or related measurement values.

[0041] In this embodiment, the Bluetooth / Zigbee module typically operates at a current of less than 10 milliamps, while the UWB module draws tens of milliamps or even higher. To reduce power consumption, the workflow of the low-power automotive digital key system described in this embodiment is as follows:

[0042] (1) The inertial detection module of the digital key is used to detect whether the digital key is moving. The inertial detection unit detects whether the digital key is in use. When the digital key is detected to be in use, its first radio frequency module receives the signal from the vehicle radio frequency module and transmits it to the second microcontroller.

[0043] (2) According to the RSSI (Received Signal Strength Indication) formula P = A - 10nlog(d), the second microcontroller of the digital key calculates the distance between the digital key and the car;

[0044] In the formula, P represents the RSSI value of the receiver when the distance of the digital key from the transmitter (car) is d, A is the RSSI value at a reference distance of 1m, and n is the path loss factor.

[0045] (3) When the second microcontroller calculates that the digital key and the car have not reached the set distance, the digital key continues to receive the signal from the vehicle radio frequency module and calculate the distance.

[0046] (4) When the second microcontroller calculates that the digital key and the car have reached the set distance, the second microcontroller sends a start signal to the UWB module of the digital key, the UWB module starts working and sends a UWB signal;

[0047] (5) The vehicle-mounted UWB module of the vehicle-mounted UWB unit receives the UWB signal from the digital key and transmits the measured incident angle value of each antenna to the first microcontroller to perform position calculation; the specific calculation process is as follows:

[0048] Taking one of the vehicle-mounted UWB modules as an example, let the angle of incidence of the UWB signal from the digital key to this module be... and Set the system measurement error to n i The antenna coordinates of the vehicle-mounted UWB module are (x, i = 1, 2). i y i (i = 1, 2), let the coordinates of the digital key be (x, y), then the angle of incidence can be expressed as:

[0049]

[0050] In the formula, φ i for If the true value is obtained, then the relationship between the measured angle of incidence and the digital key and the vehicle-mounted UWB unit is:

[0051]

[0052] Furthermore, we can obtain that

[0053] xsin(φ i +n i )-ycos(φ i +n i )=x i sin(φ i +n i )-y i cos(φ i +n i (3)

[0054] When the system measurement error n i When it is small enough, sinn i ≈n i cosn i ≈1. Therefore, equation (3) can be simplified to obtain,

[0055] xsinφ i -ycosφ ii =x i sinφ ii -y i cosφ i +n i [(x i -x)cosφ+(y i -y)sinφ] (4)

[0056] Represented in matrix form as follows:

[0057] Hx=K+δ (5)

[0058] In the formula, H represents K indicates x represents the position coordinate.

[0059] The solution was obtained using the least squares method.

[0060] x=(H T H) -1 H T K (6)

[0061] This will allow you to obtain the location of the digital key to the vehicle's UWB module;

[0062] Similarly, the location of the digital key to the other four vehicle UWB modules is calculated, and thus the location of the digital key is obtained.

[0063] (6) When the first microcontroller of the vehicle-mounted UWB unit calculates that the distance between the digital key and the car is within the unlock position, the first microcontroller sends an unlock signal data packet to the central driving controller of the car, and the car door is unlocked.

[0064] (7) When the digital key is out of power, place the digital key against the NFC card reader on the car and use the second radio frequency module of the digital key to unlock the car.

[0065] Furthermore, to ensure security, when the digital key communicates with the car, the car will first determine whether the digital key is the car key for that vehicle.

[0066] Compared to existing technologies, this embodiment reduces the number of communication operations based on UWB, which can further reduce the power consumption of the digital key and extend its battery life.

Claims

1. A method for operating an energy-saving car digital key, characterized in that, The digital key communicates with the car via UWB signals and Bluetooth or ZigBee. The digital key first communicates with the car via Bluetooth or ZigBee. When the digital key and the car reach a set distance, the digital key communicates with the car via UWB signals. The car calculates the position of the digital key by measuring the angle of incidence of each antenna of the digital key to the onboard UWB module. When the calculated distance between the digital key and the car is within the unlock position, the car door is unlocked. The method for calculating the location of a digital key is as follows: Let the angle of incidence between the digital key and the two antennas of a certain vehicle-mounted UWB module be . and Set the system measurement error to be The antenna coordinates of the vehicle-mounted UWB module are i=1,2. Set the digital key coordinates as Then the angle of incidence is expressed as: (1) In the formula, for If the true value is obtained, then the relationship between the measured angle of incidence and the digital key and the vehicle-mounted UWB unit is: (2) Further, (3) When system measurement error Enough hours ; Therefore, equation (3) can be simplified to obtain, (4) Represented in matrix form as follows: (5) In the formula, H represents K represents x represents the position coordinates , The solution was obtained using the least squares method. (6) This will allow you to obtain the location of the digital key to the vehicle's UWB module; Similarly, the location of the digital key to all in-vehicle UWB modules is calculated, and thus the location of the digital key is obtained.

2. The operating method of the energy-saving car digital key according to claim 1, characterized in that, The antenna of the vehicle-mounted UWB module is an array antenna.

3. An energy-saving car digital key system, characterized in that, The main structure includes a digital key, which communicates with the vehicle via UWB signals and Bluetooth or ZigBee. The vehicle includes an onboard UWB unit, which comprises an onboard UWB module and an onboard radio frequency module. The onboard radio frequency module uses Bluetooth or ZigBee. The antenna of the onboard UWB module is an array antenna. The onboard UWB unit calculates the position of the digital key by measuring the angle of incidence from the digital key to each antenna of the onboard UWB module. The method for calculating the location of a digital key is as follows: Let the angle of incidence between the digital key and the two antennas of a certain vehicle-mounted UWB module be . and Set the system measurement error to be The antenna coordinates of the vehicle-mounted UWB module are i=1,2. Set the digital key coordinates as Then the angle of incidence is expressed as: (1) In the formula, for If the true value is obtained, then the relationship between the measured angle of incidence and the digital key and the vehicle-mounted UWB unit is: (2) Further, (3) When system measurement error Enough hours ; Therefore, equation (3) can be simplified to obtain, (4) Represented in matrix form as follows: (5) In the formula, H represents K represents x represents the position coordinates , The solution was obtained using the least squares method. (6) This will allow you to obtain the location of the digital key to the vehicle's UWB module; Similarly, the location of the digital key to all in-vehicle UWB modules is calculated, and thus the location of the digital key is obtained.

4. The energy-saving automotive digital key system according to claim 3, characterized in that, There are 5 vehicle-mounted UWB modules, with 4 of them located at the four corners of the vehicle body and 1 located in the middle of the vehicle interior.

5. The energy-saving automotive digital key system according to claim 3, characterized in that, The digital key includes a second microcontroller, a UWB module, a first radio frequency module, a second radio frequency module, and a power supply. The second microcontroller is used to calculate the distance between the digital key and the vehicle and to activate the UWB module. The UWB module is used to send UWB signals to the vehicle's UWB module. The first radio frequency module is used to assist communication between the digital key and the vehicle; the first radio frequency module is either Bluetooth or ZigBee. The second radio frequency module is used to assist in unlocking the car door; the second radio frequency module is NFC. The UWB module, the first radio frequency module, and the second radio frequency module are all electrically connected to the second microcontroller. The power supply is electrically connected to the second microcontroller.

6. The energy-saving automotive digital key system according to claim 3, characterized in that, The digital key also includes an inertial detection unit, which is connected to the second microcontroller via electrical signals to detect whether the digital key is in use, thereby further helping to reduce power consumption.

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