LIN-based vehicle-mounted BDS positioning system and working method thereof

Abstract

The application relates to a LIN-based vehicle-mounted BDS positioning system and a working method thereof, and belongs to the technical field of vehicle-mounted positioning. The system comprises a vehicle-mounted BDS positioning receiving module, a LIN bus controller module and a vehicle terminal module which are sequentially connected. The vehicle-mounted BDS positioning receiving module is used for capturing BDS satellites and transmitting navigation messages. The LIN bus controller module is used for transmitting the navigation messages from the vehicle-mounted BDS positioning receiving module to the vehicle terminal module. The vehicle terminal module uses the received navigation message data to perform ionospheric model calculation and obtains vehicle positioning. Compared with the existing positioning system, the application has the characteristics of low cost, low complexity, low power consumption, high reliability, super-long transmission distance, high flexibility, small ionospheric error and good compatibility with original vehicle-mounted equipment.

Description

Technical Field

[0001] This invention relates to a LIN-based vehicle BDS positioning system and its working method, belonging to the field of vehicle positioning technology. Background Technology

[0002] A Global Navigation Satellite System (GNSS) is a space-based radio navigation and positioning system that provides users with all-weather 3D coordinates, velocity, and time information at any location on the Earth's surface or in near-Earth space. Since the development of global satellite navigation systems, represented by the US Global Positioning System (GPS), Russia, the European Union, and China have established their own modern navigation systems: GLONASS, Galileo, and BeiDou, respectively, providing global users with services in navigation, positioning, surveying, agriculture, rescue, surveillance and management, and military applications.

[0003] On June 23, 2020, the final satellite of China's BeiDou-3 Navigation Satellite System (BDS-3) was successfully launched. Through the construction of this third-generation satellite and its signal, the BeiDou system ushered in an era where its navigation capabilities expanded from regional to global coverage. Compared to BDS-2, BDS-3 satellites utilize rubidium-hydrogen atomic clocks and improve the accuracy of space signals. Compared to other navigation systems, the BeiDou system also features interconnectivity between its satellites. Among the four global navigation satellite systems, BDS is the only one that combines geostationary orbit (GEO), inclined geosynchronous orbit (IGSO), and medium Earth orbit (MEO) satellites. It provides global positioning, navigation, and timing (RNSS), global short message communication (GSMC), and international search and rescue (SAR) services; and in China and surrounding regions, it provides satellite-based augmentation (SBAS), ground-based augmentation (GAS), precise point positioning (PPP), and regional short message communication (RSMC) services.

[0004] In recent years, my country's vehicle navigation and positioning system has experienced tremendous development. Statistics show that the global total number of cars has reached 1.2 billion, while my country's total is around 140 million. This vast market provides a broad prospect and enormous potential for vehicle navigation and positioning. As the BeiDou system matures, its application in automobiles is becoming increasingly widespread. A vehicle navigation and positioning system consists of an in-vehicle navigation receiver, an in-vehicle data transmission carrier, and a vehicle terminal. Data transmission methods within the vehicle include wired transmission such as CAN (Controller Area Network), CAN FD (CAN with Flexible Data-Rate), LIN, FlexRay, MOST (Media Oriented Systems Transport), and Ethernet, as well as wireless transmission such as WiFi and Bluetooth. Given a fixed receiver model, the choice of different data transmission carriers is crucial, directly affecting the reliability, power consumption, flexibility, and cost of the navigation and positioning system. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a LIN-based vehicle-mounted BDS positioning system. Compared to existing positioning systems, it features low cost, low complexity, low power consumption, high reliability, ultra-long transmission distance, high flexibility, small ionospheric error, and excellent compatibility with existing vehicle-mounted equipment.

[0006] The present invention also provides a method for operating the above-mentioned LIN-based vehicle BDS positioning system.

[0007] Terminology Explanation:

[0008] LIN: LIN (Local Interconnect Network) is a type of local area network (LAN) proposed by Festo in Germany in 2000. It is currently widely used in automotive electronic control systems and is a simple, low-cost network. The LIN bus is a simple, low-cost automotive LAN primarily used to drive low-speed sensors and actuators in vehicles, such as lighting control and door lock control.

[0009] BDS: BeiDou Navigation Satellite System is a global satellite navigation system developed by China. It mainly consists of three parts: a satellite navigation and positioning system, a data transmission system, and an application service system. This system provides users with various application services, such as positioning, navigation, ranging, and velocity measurement.

[0010] CODE: CODE is the European Orbit Determination Centre, which provides tropospheric delay values ​​for GNSS observation stations every 7200 seconds.

[0011] VTEC: Vertical Total Electron Content (VTEC) is a quantitative indicator of the total number of electrons in the Earth's ionosphere. It is determined by the vertical distribution of electrons in the ionosphere and typically corresponds to the thickness of the ionosphere. VTEC is measured by the GPS satellite positioning system and can be used to estimate ionospheric thickness and analyze ionospheric structure and motion characteristics.

[0012] FF: Flip-flop, triggered by the clock edge, can store 1 bit of data, and is the basic storage unit of reg.

[0013] LUT: Lookup Table. It is typically used to measure the resources used.

[0014] I / O: Interface with the outside world, mainly related to requirements.

[0015] The technical solution of the present invention is as follows:

[0016] A LIN-based vehicle-mounted BDS positioning system includes a vehicle-mounted BDS positioning receiver module, a LIN bus controller module, and a vehicle terminal module connected in sequence.

[0017] The vehicle-mounted BDS positioning receiver module is used to capture BDS satellites and transmit navigation messages;

[0018] The LIN bus controller module is used to transmit navigation messages from the vehicle-mounted BDS positioning receiver module to the vehicle terminal module.

[0019] The vehicle terminal module uses the received navigation message data to perform ionospheric model calculations to obtain the vehicle's location.

[0020] The working method of the above-mentioned LIN-based vehicle BDS positioning system includes the following steps:

[0021] (1) The vehicle-mounted BDS positioning receiver module captures BDS satellites and transmits navigation messages in K9 format;

[0022] (2) The LIN bus controller module receives navigation messages from the vehicle BDS positioning receiver module and then transmits the navigation messages to the vehicle terminal module.

[0023] (3) The vehicle terminal module uses the received navigation message data to perform ionospheric model calculations to obtain the vehicle's location.

[0024] According to a preferred embodiment of the present invention, the calculation process in step (3) is as follows:

[0025] ① Puncture point calculation

[0026]

[0027] In the formula, H represents the ionospheric height (generally 300–450 km), and R... E The average radius of the Earth is 6371 km. (E1, Az) represent the altitude and azimuth angles of the satellite relative to the observation station, respectively. z and z' represent the zenith angles of the observation station and the puncture point, respectively. λ represents the latitude and longitude of the observation station. PP Indicates the latitude and longitude of the puncture point; The latitude is the geomagnetic coordinate; α represents the puncture point; the calculation yields...

[0028] ②VTEC calculation

[0029]

[0030] In the formula, z represents the receiver zenith distance, and R E H represents the Earth's radius. ion The height of the thin layer is represented by f1 and f2, which represent the carrier frequencies of the two carriers L1 (1575.42MHz) and L2 (1227.60MHz), respectively. ρ2 and ρ1 represent the pseudorange observation values ​​of the two frequency bands, respectively.

[0031] ③ Calculation of spherical harmonic function model:

[0032] After VTEC is calculated, different VTEC values ​​are used as E v Value, puncture point Substituting λ into β and s respectively, the values ​​of other parameters n and m are obtained by calculating the ionospheric harmonic function below, thus obtaining the complete spherical harmonic function model, as follows:

[0033]

[0034] The spherical harmonic function model described above can be used to inversely deduce VTEC at any latitude and longitude. 伪距法 ;

[0035] ④ Holt-Winter' additive prediction model calculation:

[0036] Selecting periodic and seasonal time series data from time series analysis methods better reflects the changing trends of the ionosphere and improves the accuracy of the Holt-Winter additive prediction model.

[0037] The initial value calculation formula for the Holt-Winter additive model is as follows:

[0038]

[0039] I t =X t -S t

[0040] bt =0 (t=1,2,...,L)

[0041] The Holt-Winter additive model is represented as follows:

[0042]

[0043] In the formula, S t X is the stable component at time t. t VTEC represents the observation value at time t. 预测 I t b represents the seasonal component at time t. i F represents the trend component at time t. t+m Let m represent the trend component at time m, m represent the number of predicted times, L represent the season length, and α, β, and γ represent the smoothing parameters.

[0044] ⑤ Preliminary fitting of the corrected model

[0045] VTEC = a * VTEC 伪距法 +b*VTEC 预测

[0046] The above formula is used to fit the spherical harmonics to the prediction model, and the coefficients a and b are determined by the least squares method.

[0047] ⑥ Preliminary fitting for ionospheric anomaly assessment:

[0048]

[0049]

[0050] Determine if the calculated value meets the abnormal threshold condition:

[0051]

[0052] Indicates the upper bound for determination. This indicates the lower bound for determination, with the subscript i representing time, VTEC median VTEC represents the median of the predicted values. (Projection) VTEC represents the additive prediction model. 计算值 The calculated values ​​are the results after the initial fitting correction in step ⑤;

[0053] ⑦ Delete the portion that exceeds the abnormal threshold condition to obtain the final VTEC value;

[0054] ⑧ Substitute the received navigation message and the calculated VTEC into the carrier phase smoothing pseudorange to calculate the positioning coordinates.

[0055] According to a preferred embodiment of the present invention, in step ⑧, the calculation process is as follows:

[0056] I. The dual-frequency pseudorange observation equations and carrier phase observation equations for the GNSS system are as follows:

[0057]

[0058]

[0059] In the formula, j represents the satellite number, k represents the frequency number, ρ represents the pseudorange observation value from the satellite to the receiver at the observation station, L represents the carrier phase observation value, c represents the speed of light, dt1 represents the receiver clock error, dt2 represents the satellite clock error, T and I represent the tropospheric and ionospheric delay errors of the signal propagation path, respectively, br and bs represent the hardware delay errors between the receiver and the satellite, respectively; ε represents the pseudorange code observation noise, λ represents the wavelength, and N represents the carrier phase integer ambiguity. Indicates pseudorange observations;

[0060] II. Substitute the VTEC into the calculation as I ρ Substitute pseudorange observations ρ, as part of the navigation message, is incorporated into the ephemeris file O. ρ With T ρ Values, as well as the speed of light c and noise ε ρ γ was then calculated to be:

[0061] ρ=γ+O ρ +c(σt u -σt s )+I ρ +T ρ +ε ρ

[0062] III. Calculate the current vehicle coordinates x using the satellite coordinates X / Y / Z from the ephemeris file. u / y u / z u :

[0063]

[0064] The beneficial effects of this invention are as follows:

[0065] This invention provides a LIN-based vehicle-mounted BDS positioning system, which, compared with existing positioning systems, features low cost, low complexity, low power consumption, high reliability, ultra-long transmission distance, and high flexibility. Furthermore, it adopts a novel ionospheric model with small ionospheric error and has excellent compatibility with existing vehicle-mounted equipment. Attached Figure Description

[0066] Figure 1This is a schematic diagram of the overall structure of the present invention;

[0067] Figure 2 This is a simulation diagram of the master frame header and slave navigation data received by the LIN bus controller module of this invention.

[0068] Figure 3 This is a simulation diagram of the slave receiving frame header and sending navigation data in the LIN bus controller module of the present invention;

[0069] Figure 4 This is a comparison diagram of the ionospheric model of this invention and the traditional VTEC model;

[0070] Figure 5 This is a comparison chart of the positioning results processed by the receiving terminal and the RTK calibration results of the present invention. Detailed Implementation

[0071] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0072] Example 1:

[0073] like Figure 1 As shown, this embodiment provides a LIN-based vehicle BDS positioning system, including a vehicle BDS positioning receiver module, a LIN bus controller module, and a vehicle terminal module connected in sequence.

[0074] The vehicle-mounted BDS positioning receiver module is used to capture BDS satellites and transmit navigation messages;

[0075] The LIN bus controller module is used to transmit navigation messages from the vehicle-mounted BDS positioning receiver module to the vehicle terminal module.

[0076] The vehicle terminal module uses the received navigation message data to perform ionospheric model calculations to obtain the vehicle's location.

[0077] The working method of the above-mentioned LIN-based vehicle BDS positioning system includes the following steps:

[0078] (1) The vehicle-mounted BDS positioning receiver module captures BDS satellites and transmits navigation messages in K9 format;

[0079] (2) The LIN bus controller module receives navigation messages from the vehicle BDS positioning receiver module and then transmits the navigation messages to the vehicle terminal module.

[0080] (3) The vehicle terminal module uses the received navigation message data to perform ionospheric model calculations to obtain the vehicle's location.

[0081] The calculation process in step (3) is as follows:

[0082] ① Puncture point calculation

[0083]

[0084] In the formula, H represents the ionospheric height (generally 300–450 km), and R... E The average radius of the Earth is 6371 km. (E1, Az) represent the altitude and azimuth angles of the satellite relative to the observation station, respectively. z and z' represent the zenith angles of the observation station and the puncture point, respectively. λ represents the latitude and longitude of the observation station. PP Indicates the latitude and longitude of the puncture point; The latitude is the geomagnetic coordinate; α represents the puncture point; the calculation yields...

[0085] ②VTEC calculation

[0086]

[0087] In the formula, z represents the receiver zenith distance, and R E H represents the Earth's radius. ion The height of the thin layer is represented by f1 and f2, which represent the carrier frequencies of the two carriers L1 (1575.42MHz) and L2 (1227.60MHz), respectively. ρ2 and ρ1 represent the pseudorange observation values ​​of the two frequency bands, respectively.

[0088] ③ Calculation of spherical harmonic function model:

[0089] After VTEC is calculated, different VTEC values ​​are used as E v Value, puncture point Substituting λ into β and s respectively, the values ​​of other parameters n and m are obtained by calculating the ionospheric harmonic function below, thus obtaining the complete spherical harmonic function model, as follows:

[0090]

[0091] The spherical harmonic function model described above can be used to inversely deduce VTEC at any latitude and longitude. 伪距法 ;

[0092] ④ Holt-Winter' additive prediction model calculation:

[0093] Selecting periodic and seasonal time series data from time series analysis methods better reflects the changing trends of the ionosphere and improves the accuracy of the Holt-Winter additive prediction model.

[0094] The initial value calculation formula for the Holt-Winter additive model is as follows:

[0095]

[0096] I t=X t -S t

[0097] b t =0 (t=1,2,...,L)

[0098] The Holt-Winter additive model is represented as follows:

[0099]

[0100] In the formula, S t X is the stable component at time t. t VTEC represents the observation value at time t. 预测 I t b represents the seasonal component at time t. i F represents the trend component at time t. t+m Let m represent the trend component at time m, m represent the number of predicted times, L represent the season length, and α, β, and γ represent the smoothing parameters.

[0101] ⑤ Preliminary fitting of the corrected model

[0102] VTEC = a * VTEC 伪距法 +b*VTEC 预测

[0103] The above formula is used to fit the spherical harmonics to the prediction model, and the coefficients a and b are determined by the least squares method.

[0104] ⑥ Preliminary fitting for ionospheric anomaly assessment:

[0105]

[0106]

[0107] Determine if the calculated value meets the abnormal threshold condition:

[0108]

[0109] Indicates the upper bound for determination. This indicates the lower bound for determination, with the subscript i representing time, VTEC median VTEC represents the median of the predicted values. (Projection) VTEC represents the additive prediction model. 计算值 The calculated values ​​are the results after the initial fitting correction in step ⑤;

[0110] ⑦ Delete the portion that exceeds the abnormal threshold condition to obtain the final VTEC value;

[0111] ⑧ Substitute the received navigation message and the calculated VTEC into the carrier phase smoothing pseudorange to calculate the positioning coordinates.

[0112] In step ⑧, the calculation process is as follows:

[0113] I. The dual-frequency pseudorange observation equations and carrier phase observation equations for the GNSS system are as follows:

[0114]

[0115]

[0116] In the formula, j represents the satellite number, k represents the frequency number, ρ represents the pseudorange observation value from the satellite to the receiver at the observation station, L represents the carrier phase observation value, c represents the speed of light, dt1 represents the receiver clock error, dt2 represents the satellite clock error, T and I represent the tropospheric and ionospheric delay errors of the signal propagation path, respectively, br and bs represent the hardware delay errors between the receiver and the satellite, respectively; ε represents the pseudorange code observation noise, λ represents the wavelength, and N represents the carrier phase integer ambiguity. Indicates pseudorange observations;

[0117] II. Substitute the VTEC into the calculation as I ρ Substitute pseudorange observations ρ, as part of the navigation message, is incorporated into the ephemeris file O. ρ With T ρ Values, as well as the speed of light c and noise ε ρ γ was then calculated to be:

[0118] ρ=γ+O ρ +c(σt u -σt s )+I ρ +T ρ +ε ρ

[0119] III. Calculate the current vehicle coordinates x using the satellite coordinates X / Y / Z from the ephemeris file. u / y u / z u :

[0120]

[0121] Depend on Figure 2 and Figure 3 The simulation results show that the LIN bus controller module of the present invention can fully realize the data transmission navigation message function;

[0122] The resource usage of the LIN bus controller module of this invention is shown in the table below. The LIN bus controller module consumes few resources.

[0123]

[0124] Figure 4 This demonstrates that the ionospheric model proposed in this invention is superior to traditional models in terms of accuracy, and can effectively correct outliers.

[0125] Figure 5 The comparison with the RTK value shows that the system of the present invention can effectively complete the designed function and achieve good results.

[0126] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A working method for a LIN-based vehicle-mounted BDS positioning system, characterized in that, The steps are as follows: (1) The vehicle-mounted BDS positioning receiver module captures BDS satellites and transmits navigation messages in K9 format; (2) The LIN bus controller module receives the navigation message from the vehicle BDS positioning receiver module and then transmits the navigation message to the vehicle terminal module; (3) The vehicle terminal module uses the received navigation message data to perform ionospheric model calculations to obtain the vehicle's location; The calculation process is as follows: ① Puncture point calculation ； In the formula, H represents the height of the ionosphere. This represents the Earth's average radius, which is 6371 km. These represent the elevation and azimuth angles of the satellite relative to the observation station, respectively, while z and z' represent the zenith angles of the observation station and the puncture point, respectively. Indicates the latitude and longitude of the observation station. Indicates the latitude and longitude of the puncture point; This refers to geomagnetic latitude. Indicates the puncture point; calculated as follows ; ②VTEC calculation ； In the formula, ZA represents the receiver zenith distance. Represents the Earth's radius. Indicates the thickness of the thin layer. and These represent the carrier frequencies of carriers L1 and L2, respectively. , These represent pseudorange observations for the two frequency bands, respectively. ③ Calculation of spherical harmonic function model: After VTEC calculation is completed, different VTEC values ​​are used as... Value, puncture point , Substitute them separately The values ​​of other parameters n and m are obtained from the ionospheric harmonic function calculation, and then the complete spherical harmonic function model is obtained, as follows: ； The spherical harmonic function model described above can be used to inversely deduce any latitude and longitude. ; ④ Holt-Winter' additive prediction model calculation: The initial value calculation formula for the Holt-Winter additive model is as follows: ； The Holt-Winter additive model is represented as follows: ； In the formula, For the stable component at time t, The observed value at time t is... , Indicates the seasonal component at time t. This represents the trend component at time t. This represents the trend component at time m, where m represents the number of predicted times and L represents the season length. , , Indicates the smoothing parameter; ⑤ Preliminary fitting of the corrected model ； The above formula is used to fit the spherical harmonics to the prediction model, and the coefficients a and b are determined by the least squares method. ⑥ Preliminary fitting for ionospheric anomaly assessment: ； ； Determine if the calculated value meets the abnormal threshold condition: ； Indicates the upper bound for determination. This indicates the lower bound for judgment, where the subscript i represents time. This represents the median of the predicted values. VTEC represents the additive prediction model. The calculated values ​​are the results after the initial fitting correction in step ⑤; ⑦ Delete the portion that exceeds the abnormal threshold condition to obtain the final VTEC value; ⑧ Substitute the received navigation message and the calculated VTEC into the carrier phase smoothing pseudorange to calculate the positioning coordinates.

2. The working method of the LIN-based vehicle BDS positioning system as described in claim 1, characterized in that, In step ⑧, the calculation process is as follows: I. The dual-frequency pseudorange observation equations and carrier phase observation equations for the GNSS system are as follows: ； ； In the formula, j represents the satellite number, and k represents the frequency number. The pseudorange observation value from the satellite to the receiver at the observation station represents the carrier phase observation value, and c represents the speed of light. Indicates receiver clock bias. T represents the satellite clock bias. These represent the tropospheric and ionospheric delay errors in the signal propagation path, respectively. and These represent the hardware delay errors of the receiver and the satellite, respectively. This indicates pseudorange code observation noise. Indicates wavelength. Indicates carrier phase integer ambiguity. Represents pseudorange observations; II. Substitute the VTEC into the calculation as Substitute pseudorange observations As navigation messages Import ephemeris file and Values, as well as the speed of light c and noise. The result was obtained after calculation. : ； III. Calculate the current vehicle coordinates by combining the satellite coordinates (X / Y / Z) from the ephemeris file. / / : 。

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