A high-precision positioning rescue system for commercial vehicles based on Beidou PPP-B2b and short message

Abstract

The application discloses a kind of high-precision positioning rescue systems of commercial vehicle based on Beidou PPP-B2b and short message, it is related to satellite navigation positioning technical field, the application is introduced by PPP-B2b satellite-based augmentation, make high-precision positioning completely get rid of ground communication base station constraint, cover China and surrounding no network area, fill the service blank of traditional RTK / PPP scheme in communication blind area;Through the deep coupling of PPP-B2b absolute coordinate reference and adaptive NHC motion constraint, the filter is kept smooth transition in the switching process of GNSS signal from yes to no, from no to yes, significantly inhibit the long time drift of inertial navigation;And through the cooperation of structured differential encoding and cascaded error correction dynamic encoding, reliable transmission of high-density rescue information is completed in the limited Beidou short message bandwidth, and the error correction strength can be dynamically adjusted according to the channel quality, and the transmission efficiency and reliability are considered.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation and positioning technology, and in particular to a high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message service. Background Technology

[0002] With the development of intelligent connected vehicle technology, the demand for continuous, reliable, and high-precision vehicle positioning in complex environments is becoming increasingly urgent. Existing vehicle positioning solutions mainly suffer from the following technical bottlenecks: 1. High-precision positioning services are highly dependent on terrestrial communication infrastructure.

[0003] Differential positioning schemes based on CORS / RTK and PPP (Precise Point Positioning) services that rely on internet transmission cannot function in areas with 4G / 5G signal coverage blind spots, such as deserts, mountains, oceans, and uninhabited areas. Although the BeiDou-3 system broadcasts PPP-B2b precise point positioning signals free of charge via GEO satellites, theoretically enabling decimeter-to-centimeter positioning without a network, existing vehicle-mounted terminals generally do not integrate this signal reception and processing capabilities. This forces users to still rely on low-precision standard point positioning (SPP) in areas without a network, making it difficult to meet the accuracy requirements of emergency rescue scenarios.

[0004] 2. Lane-level positioning solutions rely on expensive sensors.

[0005] Current high-precision positioning often relies on LiDAR (Light Detection and Range) and high-resolution visual cameras, which have high hardware costs and significantly reduced positioning performance and poor robustness in severe weather conditions such as heavy rain, sandstorms, and dense fog.

[0006] 3. Rapid divergence of inertial navigation errors in satellite signal rejection environments.

[0007] In scenarios such as urban canyons and long tunnels, satellite signals are lost for extended periods, causing pure inertial navigation system errors to accumulate cubically over time. Existing technologies commonly employ nonholonomic constraints (NHC) and zero-velocity updates (ZUPT), where fixed constraint assumptions fail when vehicles experience non-nominal motions such as sideslip or drift, easily leading to filter divergence. Existing solutions also exhibit lag or misjudgment in constraint switching strategies, lacking a fine-grained perception and adaptive adjustment mechanism for the vehicle's transient dynamic state.

[0008] 4. The contradiction between the capacity of the BeiDou short message channel and the transmission of multi-dimensional rescue information.

[0009] The capacity of a single BeiDou-3 regional short message is approximately 14,000 bits (1,750 bytes), which is a significant improvement over BeiDou-2. However, when faced with complete rescue information including high-precision coordinates, multi-dimensional vehicle status, identification, and accident characteristics, the data volume remains insufficient. Existing solutions using natural language descriptions are prone to exceeding the limit and causing information truncation; while using general compression algorithms to process structured numerical data often results in unsatisfactory compression rates due to weak correlations between numerical values ​​and low dictionary hit rates for short data blocks.

[0010] 5. Reliability challenges of satellite-to-ground links under low signal-to-noise ratio.

[0011] In dense forests, under terrain obstruction, or in adverse weather conditions, the error rate of BeiDou short message communication links increases. Existing solutions generally lack adaptive cascaded error correction mechanisms for ultra-narrowband satellite channels, affecting the success rate of data transmission. Summary of the Invention

[0012] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract and title of the invention. Such simplifications or omissions shall not be used to limit the scope of the present invention.

[0013] In view of the aforementioned existing problems, the present invention is proposed.

[0014] To address the technical problems mentioned above, this invention provides the following technical solution: a high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message service, characterized by comprising: an on-board terminal for collecting satellite observation data, inertial measurement data, wheel speed data, and heading information; a BeiDou positioning module for receiving BeiDou PPP-B2b precise correction signals, performing PPP-B2b precise single-point positioning calculations, and outputting positioning results based on signal convergence status and GNSS availability; a short message communication module for transmitting rescue data via BeiDou short messages when there is no terrestrial communication network coverage; a data processing module for performing adaptive motion equation constraint processing on the positioning results, differential coding and cascaded error correction dynamic coding on the rescue data, and confidence evaluation on signal quality and motion state; and an auxiliary navigation interface module for outputting standardized positioning and attitude information to upper-layer applications and providing path deviation warnings and rescue path recommendation services.

[0015] In a preferred embodiment of the present invention, the vehicle-mounted terminal includes a BeiDou receiver, a GNSS receiver, an inertial measurement unit, a vehicle speed sensor, and a direction angle sensor; the BeiDou receiver supports B1I, B3I, and B2b tri-frequency reception, wherein the B2b frequency is used to receive PPP-B2b precision correction data; and the sampling rate of the inertial measurement unit is not lower than a first sampling rate threshold.

[0016] As a preferred embodiment of the present invention, the BeiDou positioning module has a built-in hierarchical positioning strategy: when PPP-B2b has not converged, the first positioning mode is adopted; when PPP-B2b convergence is completed, the second positioning mode is switched; and when the GNSS signal is completely lost, the third positioning mode is switched. The BeiDou positioning module also supports a preheating working mode, which starts PPP-B2b calculation in advance before the vehicle enters the blind spot of the ground communication network coverage.

[0017] As a preferred embodiment of the present invention, the adaptive motion equation constraint processing in the data processing module determines the vehicle motion state by real-time monitoring the lateral acceleration and yaw rate output by the inertial measurement unit and the left and right wheel speed difference collected by the vehicle terminal; when none of the three indicators exceed their respective preset thresholds, it is determined to be a first motion state and a first constraint strategy is adopted; when at least two indicators exceed their respective preset thresholds, it is determined to be a second motion state and a second constraint strategy is switched.

[0018] In a preferred embodiment of the present invention, the first constraint strategy includes standard nonholonomic constraints and zero-speed updates; the second constraint strategy includes relaxed nonholonomic constraints and auxiliary observation constraints based on wheel speed sensors; and the adaptive motion equation constraint processing completes constraint switching within a first preset delay time when the vehicle's motion state changes.

[0019] As a preferred embodiment of the present invention, the differential encoding in the data processing module adopts layered differential encoding, and differential compression encoding is performed on at least the longitude, latitude, altitude, heading angle, pitch angle, roll angle, timestamp and speed data, and the total data volume after encoding is the first preset data volume.

[0020] As a preferred embodiment of the present invention, the short message communication module divides the rescue data after differential encoding into multiple data packets according to priority and sends them sequentially. If the data packet fails to be sent, it is retransmitted according to a preset retransmission sequence, and the maximum number of retransmissions is a preset number.

[0021] In a preferred embodiment of the present invention, the cascaded error correction dynamic coding in the data processing module adopts a coding structure of cascaded external and internal codes; the short message communication module dynamically adjusts the coding strategy according to the real-time channel quality index: when the channel quality index is better than a first preset quality threshold, only the external code is enabled; when the channel quality index is worse than a second preset quality threshold, both the external code and the internal code are enabled; when the channel quality index is between the first preset quality threshold and the second preset quality threshold, the short message communication module dynamically selects to enable the external code or enable both the external code and the internal code simultaneously according to the real-time changes in the channel quality index.

[0022] As a preferred embodiment of the present invention, the confidence evaluation module in the data processing module calculates the positioning confidence based on the carrier-to-noise ratio, horizontal accuracy factor and the number of visible satellites, and calculates the motion state confidence based on the variance and velocity consistency error of the inertial measurement data. Data with a confidence level lower than the first confidence threshold is marked as invalid and not included in the fusion calculation.

[0023] As a preferred embodiment of the present invention, the data format output by the auxiliary navigation interface module conforms to the ISO19091 standard and includes at least longitude, latitude, altitude, heading angle, pitch angle, roll angle, velocity vector, horizontal accuracy factor, vertical accuracy factor, timestamp, and confidence assessment results in the WGS-84 coordinate system.

[0024] The beneficial effects of this invention are as follows: By introducing PPP-B2b satellite-based augmentation, this invention completely eliminates the constraints of ground communication base stations for high-precision positioning, covering China and surrounding areas without network coverage, filling the service gap in communication blind spots of traditional RTK / PPP solutions. Through deep coupling of the PPP-B2b absolute coordinate reference and adaptive NHC motion constraints, the filter maintains a smooth transition during the switching process from GNSS signal presence to absence and vice versa, significantly suppressing long-term inertial navigation drift. In a typical tunnel scenario, the position error after 120 seconds of GNSS loss is approximately on the order of 5 meters, an improvement of an order of magnitude compared to fixed-constraint schemes (error > 30 meters). Furthermore, this invention does not require expensive sensors such as lidar, achieving decimeter-level positioning solely through satellites and low-cost IMU / wheel speed, reducing the mass production cost of rescue terminals and facilitating large-scale deployment.

[0025] Furthermore, by combining structured differential coding (core data compression ratio of approximately 2.25:1) with cascaded error correction dynamic coding, reliable transmission of high-density rescue information was achieved within the limited bandwidth of BeiDou short message service. The error correction intensity can be dynamically adjusted according to channel quality, balancing transmission efficiency and reliability. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a structural diagram of a high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message, as shown in this invention. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of this invention.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0030] According to an embodiment of the present invention, in combination Figure 1 The diagram shown illustrates a high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message service, comprising: Example 1

[0031] This embodiment uses a typical application scenario of a commercial vehicle driving in a desert / mountainous environment, encountering an accident, and triggering a rescue as an example to explain in detail the specific implementation of the present invention.

[0032] I. Hardware Configuration In this embodiment, the hardware selection for the vehicle terminal is as follows: Beidou receiver: A UC6226NIS Beidou multi-frequency receiver from Hexin Xingtong is used, supporting B1I, B3I, and B2b tri-frequency reception. The B2b frequency is used to receive PPP-B2b precision correction data broadcast by the Beidou GEO satellite. This receiver also integrates RDSS (Radio Determination Satellite Service) short message communication functionality. GNSS receiver: A U-blox NEO-M9N GNSS receiver with a 10Hz update rate is used for auxiliary positioning and redundancy backup. Inertial Measurement Unit (IMU): An STMicroelectronics LSM6DSO six-axis inertial measurement unit is used, with a preferred first sampling rate threshold of 100Hz, for real-time measurement of the vehicle's three-axis acceleration and three-axis angular velocity. Vehicle speed sensor: Integrated into the vehicle's ABS system, it collects the rotational speed signals of the four wheels in real time. Heading angle sensor: A MEMS gyroscope is used for auxiliary heading estimation.

[0033] The aforementioned hardware together constitute the data acquisition front end of the vehicle terminal, providing raw data input for subsequent positioning calculations and data processing.

[0034] Workflow (I) Warm-up Phase -- Early Initiation of PPP-B2b Solution The vehicle left the last town with 4G / 5G network coverage at 15:00 that day and was about to enter a desert / mountainous section of road without terrestrial communication network coverage.

[0035] In the last section of the road where there is still network coverage, the system detects that it is about to enter a network-free area (which can be predicted by electronic map road network data or triggered manually by the driver) and automatically starts the preheating mode: The PPP-B2b precise point positioning calculation unit in the BeiDou positioning module starts receiving the PPP-B2b signal broadcast by BeiDou GEO satellites (priority C01, C02, C03, backup C04) in advance, decodes the precise orbit correction and precise clock error correction, and starts the non-differential non-combined precise point positioning calculation.

[0036] The PPP-B2b solution unit establishes the following observation equations for solution: The pseudorange observation is:

[0037] The carrier phase observation is as follows:

[0038] Where i represents the frequency of the observation; r represents the receiver; and s represents the satellite; This represents the pseudorange observation value at frequency point i; Indicates the geometric distance from the satellite to the receiver; Represents the speed of light in a vacuum; Indicates receiver clock bias; Indicates satellite clock bias; Indicates tropospheric delay; This represents the ionospheric delay at frequency i, and the code deviation at frequency i at the receiver. This indicates the code deviation at satellite frequency i; The observation noise at pseudorange i-frequency point; Represents the carrier phase observation value at frequency point i; The carrier wavelength represents frequency point i; Indicates the integer ambiguity of frequency point i; This represents the phase deviation at frequency i at the receiver. This indicates the phase deviation at satellite frequency point i; This represents the observation noise at carrier phase frequency point i.

[0039] During the warm-up phase, since the vehicle is still in a networked area, the positioning results are mainly output in RTK differential positioning mode, while PPP-B2b solution continues to run in the background to accumulate observation data during this period to accelerate subsequent convergence.

[0040] (II) PPP-B2b convergence complete -- enter high-precision mode At 15:25 that day, the PPP-B2b precise single-point positioning solution converged after 25 minutes.

[0041] The confidence assessment module makes a judgment based on the real-time positioning accuracy index: the horizontal positioning accuracy reaches 0.08m (RMS) and the vertical positioning accuracy reaches 0.15m (RMS), which meets the conditions for switching to high-precision mode.

[0042] The automatic switching logic of the Beidou positioning module's working mode is shown in Table 1: Table 1 Logic Table for Automatic Switching of Working Modes

[0043] Since PPP-B2b has converged at this time, the system automatically switches from the SPP (Standard Point Positioning) + INS (Inertial Navigation System) fusion mode to the PPP-B2b high-precision mode, and the positioning output horizontal accuracy is better than 0.1m.

[0044] The system continues to monitor the 4G / 5G network status. At this time, the network is still available, and the positioning output is based on PPP-B2b high-precision positioning results, with RTK results used as auxiliary verification.

[0045] (iii) Network signal loss -- PPP-B2b mode is unaffected At 15:30 that day, the vehicle drove into the depths of the desert, and the 4G / 5G signal was completely lost.

[0046] The short message communication module monitors the communication network status in real time. When the 4G / 5G signal strength is detected to be below -110dBm for more than 30 seconds, the system determines that the ground communication network is unavailable and automatically activates the BeiDou short message communication mode as a backup communication channel.

[0047] During this process, the PPP-B2b high-precision positioning mode is unaffected by the loss of 4G / 5G networks and continues to provide positioning services with an accuracy better than 0.1m, ensuring the vehicle's continuous high-precision positioning capability in areas without network coverage.

[0048] (iv) Adaptive Motion Equation Constraints - Real-time Response to Sideslip Events When driving on sandy roads, the vehicle skidded due to the soft road surface.

[0049] The adaptive motion equation constraint unit in the data processing module monitors three dynamic indicators in real time: IMU lateral acceleration: =-0.6g (preset threshold range is 0.25g~0.35g, typical value is 0.30g); Left and right wheel speed difference: Δdiff=12% (preset threshold range is 3%~8%, typical value is 5%); Yaw rate: =25° / s (the preset threshold range is 10° / s~20° / s, and the typical value is 15° / s).

[0050] The motion state classifier makes judgments based on the comparison results of three indicators with their respective preset thresholds, as shown in Table 2: Table 2 Constraint Strategy Judgment Table

[0051] At this point, all three indicators exceeded their respective preset thresholds. =-0.6g exceeds 0.30g, Δdiff=12% exceeds 5%, =25° / s exceeds 15° / s), which is judged as a serious abnormal motion state (sideslip).

[0052] A preferred approach is to use the following overall timing sequence for constraint switching in the adaptive equation of motion constraint unit: first, a hysteresis confirmation mechanism determines the motion state as sideslip (with a 200ms~500ms threshold exceeding the determination window), and then the constraint parameter execution switching is completed within 50ms (including the NHC variance being reduced from 0.01 (m / s)). 2 Relaxed to 0.5 (m / s)2 Operations include introducing wheel speed-assisted observation equations and updating their variance. In this embodiment, the state determination window is 200ms, so the total time from the first detection of the index exceeding the threshold to the completion of constraint switching does not exceed 250ms (i.e., 200ms determination window + 50ms switching execution).

[0053] Before switching (standard constraint mode): Nonholonomic constraint NHC is enabled, and the NHC constraint variance is set to the first variance value of 0.01 (m / s). 2 Enable Zero-Speed ​​Update (ZUPT) to force the three-axis speed to zero when the vehicle is stationary.

[0054] After switching (relaxed constraint mode): The NHC constraint variance is relaxed to the second variance value of 0.5 (m / s). 2 We introduce an auxiliary observation equation based on wheel speed sensors.

[0055] The wheel speed-assisted observation model is as follows: Let the wheel speeds of the left front, right front, left rear, and right rear be respectively... , , , If the effective rolling radius of the wheel is R, then the longitudinal speed of the vehicle is... satisfy:

[0056] When turning, the difference in speed between the left and right wheels and the yaw rate satisfy the following:

[0057] in, The wheelbase is the distance between the wheels. This indicates the difference in wheel speed between the left and right wheels.

[0058] The variance of the wheel speed auxiliary constraint is set to a third-party difference of 0.2 (m / s). 2 When severe wheel slippage occurs, the wheel speed auxiliary constraint variance is automatically widened to a fourth variance value of 1.0 (m / s). 2 .

[0059] Through the aforementioned adaptive constraint switching, the system maintains a smooth transition of the filter by using constraint switching while the GNSS signal is still available (PPP-B2b continuous positioning), thus preparing for the possible loss of GNSS signal in the future.

[0060] Furthermore, to prevent frequent switching near the threshold boundary, the system sets up a delayed confirmation mechanism: each indicator must continuously exceed the threshold for 200ms~500ms (200ms in this embodiment) for a state judgment window T1 before a motion state switch can be determined; the state can be determined to have recovered only after the indicator falls back to within the threshold and maintains the same duration. T1 and the constraint switching execution time T2 (the time for parameter update after judgment, 50ms in this embodiment) are two independent timing parameters. T1 prevents misjudgment, and T2 reflects real-time performance. The sum of the two is the complete state switching time sequence.

[0061] Similarly, only after all indicators have recovered to within the threshold and maintained for that duration will the system switch back to normal driving constraint mode.

[0062] (v) Accident Triggering and Data Collection When a vehicle rolls over, the onboard terminal detects the following accident characteristics by using the IMU's roll angle, pitch angle, and motion status. The specific judgment rules are as follows: Specifically, to determine if a rollover accident has occurred, the following conditions must be met simultaneously: absolute value of roll angle Roll rate And this state lasts for at least 0.5 seconds; after the rollover if or If the rollover continues for at least 3 seconds, it is confirmed that a rollover accident has occurred.

[0063] in, Indicates the roll angle. Indicates roll rate. Indicates the pitch angle.

[0064] Furthermore, the accident level is determined based on a combination of the rollover angle and lateral acceleration as follows: Mild: and ; Moderate: or ; Severe: , Multi-axis flipping occurs or a safety alarm is triggered.

[0065] in, Represents gravitational acceleration. represents lateral acceleration, and |·| indicates the absolute value sign.

[0066] After triggering the rollover detection, the system further determines whether the vehicle remains stationary. The determination criteria include: Synthesis speed Attitude angular velocity less than Furthermore, the above conditions must be met simultaneously for at least 5 seconds.

[0067] At this moment, the data processing module immediately collects and generates complete rescue data, including: high-precision positioning information (from PPP-B2b high-precision mode): longitude: 95.3456°E; latitude: 40.1234°N; altitude: 1250.5m; attitude information: heading angle, pitch angle, roll angle; velocity vector (currently 0); timestamp; accident signature code; vehicle identification number (VIN); driver information (including name and phone number); and vehicle status details.

[0068] in, Indicates the synthesis speed, synthesis speed = ,in, These are the eastward, northward, and skyward velocity components output by the INS, respectively, and the attitude angular velocity is taken as the maximum value of the three-axis angular velocity of the gyroscope.

[0069] (vi) Layered differential coding-structured compression The differential encoding unit in the data processing module performs hierarchical differential encoding on the above rescue data.

[0070] Specifically, the encoding scheme is shown in Table 3: Table 3 Encoding Scheme Table

[0071] It should be noted that the velocity field is encoded using the velocity change from the previous sampling epoch. After encoding, the core positioning data, namely position + attitude + velocity + timestamp + feature code + CRC (Cyclic Redundancy Check), is compressed from approximately 424 bits in the original floating-point representation to 188 bits, with a compression ratio of approximately 2.25:1.

[0072] The complete rescue data packet (including VIN, driver information, etc.) is approximately 1500 bits in its original form, and is significantly compressed after structured encoding.

[0073] (vii) Cascaded error correction dynamic coding - channel adaptation After encoding is completed, the cascaded error correction dynamic coding unit in the data processing module encodes and protects the data according to the current channel conditions.

[0074] This embodiment uses a concatenated structure of outer code RS code and inner code convolutional code, as shown in Table 4: Table 4. Encoding Structure Diagram

[0075] The short message communication module estimates the channel signal-to-noise ratio (SNR) in real time and dynamically adjusts the coding strategy, as shown in Table 5. Table 5. Schematic diagram of encoding strategy adjustment

[0076] In this embodiment, the preferred value of the first preset quality threshold is 10dB, the preferred value of the second preset quality threshold is 5dB, and the preferred value of the third preset quality threshold is 0dB, classifying the channel conditions into four levels: good, good, poor, and deteriorated. When the real-time channel quality index (such as signal-to-noise ratio SNR) is better than the first preset quality threshold (>10dB), the channel conditions are good, and transmission reliability can be guaranteed by simply using the outer code (RS(255,223)). When the SNR is between the first and second preset quality thresholds (5dB≤SNR≤10dB), the outer code and a convolutional code with a puncture rate of 3 / 4 are used. When the SNR is between the second and third preset quality thresholds (0dB≤SNR<5dB), the outer code and a convolutional code with a puncture rate of 2 / 3 are used. When the SNR is worse than the third preset quality threshold (<0dB), the channel conditions are deteriorated, and both the outer code and a convolutional code with a full code rate of 1 / 2 are used to ensure correct data reception. The above four-level switching is achieved in the cascaded error correction dynamic coding unit through a pre-coding parameter table (each level corresponds to a pre-calculated punch template and RS check byte group), and the switching delay does not exceed one coding block processing cycle.

[0077] In this embodiment, the accident site is located in a valley area, and the real-time channel estimation SNR is -2dB, falling into the degradation category (SNR<0dB). The concatenated error correction dynamic coding unit automatically selects the complete concatenated coding scheme (RS(255,223) + 1 / 2 rate convolutional code) according to the precoding parameter table, ensuring that the theoretical bit error rate is reduced from 10dB to -2dB in the low signal-to-noise ratio BeiDou channel (SNR≥-3dB). -3 The magnitude dropped to 10 -6 the following.

[0078] (viii) Short message packet transmission and retransmission The short message communication module divides the encoded rescue data into three packets according to priority and sends them sequentially, as shown in Table 6: Table 6 Rescue Data Transmission Table

[0079] The total data volume after encoding of the three packages accounts for less than 60% of the single-line capacity (14000 bits) of Beidou RDSS, leaving sufficient redundancy space for channel adaptive error correction.

[0080] The actual transmission process is as follows: First packet: Transmission successful, the ground receiver returns an ACK (Acknowledgment) message, and the vehicle terminal receives the acknowledgment and proceeds to send the next packet; Second packet: Transmission successful, the ground receiver returns an acknowledgment message; Third packet: First transmission failed (SNR=-2dB, caused by channel quality fluctuations).

[0081] Furthermore, the short message communication module initiates a retransmission mechanism, which specifically includes: waiting 2 seconds before performing the first retransmission, at which point the channel conditions improve (SNR=1dB), and the retransmission is successful; after the ground receiver receives the third packet, it sends an acknowledgment message.

[0082] All three packets were transmitted in approximately 10 seconds (including retransmission waiting time).

[0083] If a packet fails to transmit after three retransmissions (waiting 2 seconds, 5 seconds, and 5 seconds respectively), the packet data is cached in local storage, marked as pending transmission, and automatically retransmitted after the channel conditions improve, ensuring that no data is lost.

[0084] (ix) Confidence assessment – ​​ensuring data validity Throughout the positioning and communication process, the confidence assessment module runs continuously to evaluate the reliability and timeliness of various types of information.

[0085] Positioning reliability is calculated based on carrier-to-noise ratio (C / N0), horizontal accuracy factor (HDOP), and the number of visible satellites. :

[0086] in, Will Linearly normalize from 25~50dB-Hz to [0,1]; Linearly normalize HDOP from 1 to 10 to [0,1]; The number of satellites was linearly normalized from 4 to 18 to [0,1]. ; ; .

[0087] in, It is a single symbol representing the carrier-to-noise ratio, and C represents the confidence level. This represents the location reliability. f represents the linear piecewise normalization, and its specific expression is as follows:

[0088] in, This is the lower bound for the normalization of the indicator. This is the upper bound of the indicator normalization. These are sampled values.

[0089] Furthermore, based on the IMU acceleration variance and speed consistency error Calculate the confidence score of the motion state:

[0090] Among them, the weighting coefficient , f represents the normalization function, as above.

[0091] in, and The calculation process is as follows: The IMU's sampling rate is set to 100Hz by default, and it takes all data within 1 second before the current time t: { }, k=1,2,...,N. Where, =( )ᵀ represents the acceleration component vectors of the IMU at time k in the three directions (X, Y, Z) of the carrier coordinate system:

[0092]

[0093]

[0094]

[0095] in, This represents the velocity vector calculated from GNSS observations. This represents the velocity vector derived from the IMU mechanics programming, and || represents the modulo operation. This represents the number of data points within 1 second prior to time t.

[0096] Based on the following table, the confidence levels are graded and processed, as shown in Table 7: Table 7. Confidence Level Grading Table

[0097] When the difference between the data timestamp and the current system time is greater than a set value (such as 10 seconds), the data is marked as expired and will not participate in subsequent fusion calculations.

[0098] Throughout the entire accident rescue process in this embodiment, due to the good PPP-B2b signal (C / N0 approximately 45 dB-Hz), HDOP approximately 1.2, and 12 visible satellites, the positioning reliability was [high / low]. The value is approximately 0.81 (≥0.7), indicating that the location data is marked as high confidence and can normally participate in fusion calculations and rescue information output.

[0099] (x) Auxiliary navigation interface and rescue route recommendation The auxiliary navigation interface module converts positioning and data processing results into a standardized format, providing a standardized position / attitude data interface to upper-layer applications. The interface data format conforms to the ISO 19091 (ETSI TS 103301) standard. Specific outputs include: longitude, latitude, and altitude in the WGS84 coordinate system; heading, pitch, and roll angles; velocity vectors (longitudinal / lateral / vertical); positioning accuracy indicators (HDOP, VDOP (Vertical Dilution of Precision)); timestamps; and confidence assessment results. After receiving and reassembling the three data packets, the ground receiver obtains complete rescue information. Accident location: Longitude 95.3456°E, Latitude 40.1234°N, Altitude 1250.5m; Accident type: Rollover, severe; VIN; Driver information (name + phone number).

[0100] The auxiliary navigation interface module plans a route based on the current location and the nearest rescue station (longitude 95.2000°E, latitude 40.0500°N, straight-line distance approximately 18 kilometers), and recommends the optimal rescue route: drive southwest along Provincial Highway S312, with an estimated travel time of 25 minutes.

[0101] Meanwhile, the path deviation warning function continuously monitors the vehicle's position. When the vehicle deviates from the predetermined path by more than a set value (such as 5 meters), an warning is triggered to notify the driver or the rescue center.

[0102] As can be seen, this embodiment fully verifies all the core functions of the present invention in a desert / mountainous area with no terrestrial communication coverage, as shown in Table 8: Table 8. Detailed Implementation Process and Results

[0103] It should be noted that the 50ms in Table 8 is the time to complete the constraint switching, and the preceding 200ms is the time to start the constraint switching process after the threshold is exceeded. That is, the constraint switching is completed after a 200ms judgment window + 50ms switching execution (a total of 250ms).

[0104] This embodiment fully demonstrates that the present invention can achieve continuous high-precision positioning in areas without relying on terrestrial communication networks or high-cost environmental sensing sensors, and reliably transmit complete rescue information back via BeiDou short messages, providing complete technical support for emergency rescue.

[0105] Example 2

[0106] This embodiment uses a commercial vehicle entering a long tunnel (approximately 2 kilometers long, with an estimated passage time of approximately 120 seconds) as a scenario to focus on verifying the positioning continuity and adaptive constraint effect of the present invention in the case of complete loss of GNSS signal.

[0107] In this embodiment, the vehicle enters the tunnel at a speed of approximately 60 km / h. Before entering the tunnel, PPP-B2b has completed convergence, and the system is in PPP-B2b high-precision mode. After entering the tunnel, GNSS signals (including B1I, B3I, and B2b frequencies) are completely lost.

[0108] The BeiDou positioning module's automatic mode switching logic detects the loss of GNSS signal and automatically switches to pure inertial navigation + adaptive constraint mode.

[0109] The adaptive motion equation constraint unit monitors three dynamic parameters in real time. Since the road surface inside the tunnel is smooth and the vehicle is driving normally, none of the three parameters exceed the thresholds. The system determines this as a normal driving state and adopts the standard constraint mode: enabling nonholonomic constraints (NHC) and zero-speed update (ZUPT), with the NHC constraint variance set to the first variance value of 0.01 (m / s). 2 .

[0110] Under the above constraints, the position error of the inertial navigation system during the 120-second GNSS loss period is on the order of 5 meters, which is about 6 times (close to an order of magnitude) lower than the fixed constraint scheme (error > 30 meters).

[0111] When the vehicle exits the tunnel and the GNSS signal is restored, the confidence assessment module detects the location confidence. When the value is restored to ≥0.7, the Beidou positioning module automatically and smoothly switches from the pure inertial navigation + adaptive constraint mode back to the PPP-B2b high-precision mode. The filter maintains a smooth transition without jumps or oscillations.

[0112] This embodiment fully demonstrates the positioning continuity and filter stability of the present invention in scenarios where GNSS signals are lost for a long time.

[0113] Example 3

[0114] This embodiment uses the scenario of a commercial vehicle driving in heavy rain to verify the robustness of the invention without relying on visual / LiDAR sensors.

[0115] In heavy rain, the performance of existing lane-level positioning solutions based on lidar and high-resolution visual cameras degrades significantly (the field of view is obscured by rain and point cloud noise increases). This invention does not rely on the above-mentioned sensors, but relies solely on the BeiDou PPP-B2b satellite-based augmentation signal and IMU / wheel speed for tight-coupled positioning.

[0116] The BeiDou PPP-B2b signal operates in the B1I / B3I / B2b frequency band and has strong resistance to rain attenuation. In this embodiment, PPP-B2b can still be received and processed normally under heavy rain conditions, and the horizontal positioning accuracy remains within 0.1m.

[0117] Meanwhile, slippery road surfaces may cause minor skidding of vehicles. The adaptive motion equation constraint unit monitors three dynamic indicators in real time and dynamically adjusts the constraint strategy according to whether the indicators exceed the threshold to ensure that the filter does not diverge.

[0118] In terms of short message communication, the signal-to-noise ratio of the BeiDou short message channel may drop to a moderate level (0dB≤SNR≤10dB) during heavy rain. The cascaded error correction dynamic coding unit automatically selects the appropriate coding scheme (dynamic selection) based on real-time channel estimation to ensure the reliability of rescue data transmission.

[0119] This embodiment fully demonstrates the technical advantages and robustness of the present invention in not relying on high-cost environmental sensing sensors under harsh weather conditions.

[0120] Example 4

[0121] This embodiment uses a commercial vehicle driving in an urban canyon area (dense high-rise buildings, severe GNSS signal obstruction) as a scenario to verify the hierarchical positioning and mode switching capabilities of the present invention under conditions of frequent satellite signal obstruction.

[0122] In urban canyon areas, the number of visible GNSS satellites fluctuates drastically (4-12), the HDOP value fluctuates significantly (1.5-5.0), and the PPP-B2b signal may experience intermittent interruptions.

[0123] The confidence assessment module calculates location confidence in real time. : when When ≥0.7, the system adopts PPP-B2b high-precision mode; when 0.4≤ When <0.7, the system reduces the weight of PPP-B2b results in the fusion process and increases the contribution of INS; when When the value is less than 0.4, the system automatically switches to SPP+INS fusion mode to ensure uninterrupted positioning output.

[0124] When the vehicle leaves the urban canyon area, the PPP-B2b signal is restored, and the confidence assessment module determines... After recovering to ≥0.7, the system automatically switches back to PPP-B2b high-precision mode.

[0125] Throughout the process, the confidence assessment module ensures that data with a timestamp greater than 10 seconds from the current system time is marked as expired and not included in the fusion calculation, thus preventing outdated data from contaminating the filter.

[0126] Regarding short message communication, in urban canyon areas, if 4G / 5G signals are available (such as when there is still network coverage in urban areas), the system will prioritize using 4G / 5G networks to transmit rescue data; the BeiDou short message communication mode will only be automatically activated when the 4G / 5G signal strength is below -110dBm and lasts for more than 30 seconds.

[0127] This embodiment fully demonstrates the effectiveness of the hierarchical positioning strategy and confidence assessment mechanism of the present invention in complex electromagnetic environments.

[0128] The hardware selections in the above embodiments, such as the UC6226NIS from ChipStar, U-blox NEO-M9N, and STMicroelectronics LSM6DSO, and the threshold parameters, such as the three-index thresholds of 0.30g, 5%, and 15° / s, the state determination window of 200ms (preferred range 200~500ms), the constraint switching execution time of 50ms, and the constraint variance switching values ​​of 0.01 / 0.5 / 0.2 / 1.0 (m / s), are as follows: 2 The three retransmissions and the 2-second / 5-second waiting time are specific examples and do not constitute a limitation on the present invention.

[0129] In practice, the above thresholds can be calibrated according to vehicle load, tire model and chassis dynamics characteristics, and hardware selection can be adjusted according to performance requirements and cost budget, all of which fall within the protection scope of this invention.

[0130] The working mode switching conditions (4G / 5G signal strength below -110dBm and duration exceeding 30 seconds), confidence assessment weight coefficients, and confidence grading thresholds (0.4, 0.7, and 10 seconds) in each embodiment are also preferred examples, and those skilled in the art can adjust them according to actual application scenarios.

[0131] The system also includes one or more processors and memory.

[0132] The memory is used to store operable instructions that, when executed by the one or more processors, cause the one or more processors to perform operations, including the process of a high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message service as described in the foregoing embodiments, especially... Figure 1 The flowchart of the method is shown.

[0133] Other aspects disclosed in the embodiments of the present invention also propose a computer-readable medium for storing software including instructions executable by one or more computers, which, through execution, cause the one or more computers to perform operations, including the process of a high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message service as described in the foregoing embodiments, particularly... Figure 1 The flowchart of the method is shown.

[0134] It should be recognized that embodiments of the present invention may be implemented or carried out by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable storage medium.

[0135] The method can be implemented using standard programming techniques, including a non-transitory computer-readable storage medium configured with a computer program in the computer program, wherein the storage medium is configured such that the computer operates in a specific and predefined manner.

[0136] Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system; however, if required, the program can be implemented in assembly or machine language.

[0137] In any case, the language can be either compiled or interpreted.

[0138] Furthermore, for this purpose, the program can run on programmed application-specific integrated circuits.

[0139] The processes described herein (or variations and / or combinations thereof) can be executed under the control of one or more computer systems configured with executable instructions, and can be implemented by hardware or a combination thereof as code (e.g., executable instructions, one or more computer programs, or one or more applications) that commonly executes on one or more processors. The computer program includes a plurality of instructions executable by one or more processors.

[0140] Furthermore, the method can be implemented in any suitable computing platform, including but not limited to personal computers, minicomputers, mainframes, workstations, networked or distributed computing environments, standalone or integrated computer platforms, or in communication with charged particle tools or other imaging devices.

[0141] Various aspects of the present invention can be implemented in machine-readable code stored on a non-transitory storage medium or device, whether portable or integrated into a computing platform, such as a hard disk, optical read and / or write storage medium, RAM, ROM, etc., such that it can be read by a programmable computer, and when the storage medium or device is read by the computer, it can be used to configure and operate the computer to perform the processes described herein.

[0142] Furthermore, machine-readable code, or parts thereof, can be transmitted via wired or wireless networks.

[0143] When such media includes instructions or programs that combine with a microprocessor or other data processor to implement the steps described above, the invention described herein includes these and other different types of non-transitory computer-readable storage media.

[0144] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message service, characterized in that: include: The vehicle-mounted terminal is used to collect satellite observation data, inertial measurement data, wheel speed data, and heading information; The BeiDou positioning module is used to receive BeiDou PPP-B2b precise correction signals, perform PPP-B2b precise single-point positioning calculations, and output positioning results based on signal convergence status and GNSS availability. The short message communication module is used to transmit rescue data via BeiDou short messages when there is no terrestrial communication network coverage. The data processing module is used to perform adaptive motion equation constraint processing on the positioning results, perform differential coding and cascaded error correction dynamic coding on the rescue data, and evaluate the confidence of signal quality and motion status. The auxiliary navigation interface module is used to output standardized positioning and attitude information to upper-layer applications, and to provide path deviation warning and rescue path recommendation services.

2. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 1, characterized in that: The vehicle-mounted terminal includes a Beidou receiver, a GNSS receiver, an inertial measurement unit, a vehicle speed sensor, and a direction angle sensor; The Beidou receiver supports B1I, B3I, and B2b tri-frequency reception, with the B2b frequency used to receive PPP-B2b precision correction data; the sampling rate of the inertial measurement unit is not lower than the first sampling rate threshold.

3. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 1, characterized in that: The BeiDou positioning module has a built-in hierarchical positioning strategy: The first positioning mode is used when PPP-B2b fails to converge; the second positioning mode is switched after PPP-B2b convergence is completed; and the third positioning mode is switched when the GNSS signal is completely lost. The Beidou positioning module also supports a preheating mode, which initiates PPP-B2b calculation in advance before the vehicle enters a blind spot of the ground communication network coverage.

4. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 2, characterized in that: The adaptive motion equation constraint processing in the data processing module determines the vehicle's motion state by real-time monitoring of the lateral acceleration and yaw rate output by the inertial measurement unit and the speed difference between the left and right wheels collected by the vehicle terminal. When none of the three indicators exceed their respective preset thresholds, it is determined to be the first motion state and the first constraint strategy is adopted. When at least two indicators exceed their respective preset thresholds, it is determined to be the second motion state and the second constraint strategy is switched.

5. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 4, characterized in that: The first constraint strategy includes standard nonholonomic constraints and zero-rate updates; The second constraint strategy includes relaxing nonholonomic constraints and auxiliary observation constraints based on wheel speed sensors; The adaptive motion equation constraint processing completes the constraint switching within a first preset delay time when the vehicle's motion state changes.

6. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 1, characterized in that: The differential encoding in the data processing module adopts layered differential encoding, and differential compression encoding is performed on at least the longitude, latitude, altitude, heading angle, pitch angle, roll angle, timestamp and speed data. The total data volume after encoding is the first preset data volume.

7. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 6, characterized in that: The short message communication module divides the rescue data after differential encoding into multiple data packets according to priority and sends them sequentially. If a data packet fails to be sent, it will be retransmitted according to a preset retransmission sequence, with a maximum number of retransmissions.

8. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 1, characterized in that: The cascaded error correction dynamic coding in the data processing module adopts a coding structure that concatenates the outer code and the inner code; The short message communication module dynamically adjusts the coding strategy based on real-time channel quality indicators. When the channel quality index is better than the first preset quality threshold, only the outer code is enabled; when the channel quality index is worse than the second preset quality threshold, both the outer code and the inner code are enabled. When the channel quality index is between the first preset quality threshold and the second preset quality threshold, the short message communication module dynamically selects to enable the external code or enable both the external code and the internal code simultaneously based on the real-time changes of the channel quality index.

9. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 1, characterized in that: The confidence assessment module in the data processing module calculates the positioning confidence based on the carrier-to-noise ratio, horizontal accuracy factor and the number of visible satellites, and calculates the motion state confidence based on the variance of the inertial measurement data and the velocity consistency error. Data with a confidence level lower than the first confidence threshold is marked as invalid and is not included in the fusion calculation.

10. The high-precision positioning and rescue system for commercial vehicles based on BeiDou PPP-B2b and short message as described in claim 1, characterized in that: The data format output by the auxiliary navigation interface module conforms to the ISO19091 standard and includes at least longitude, latitude, altitude, heading angle, pitch angle, roll angle, velocity vector, horizontal accuracy factor, vertical accuracy factor, timestamp, and confidence assessment results in the WGS-84 coordinate system.

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