Vehicle-mounted GPS positioning and orientation attitude measurement system

Abstract

The invention discloses a vehicle-mounted GPS (Global Position System) positioning, orientation and attitude measurement system, which relates to the technical field of vehicle-mounted systems, and has the key points of the technical scheme that the system mainly realizes vehicle positioning, orientation and vehicle attitude measurement, accurately provides a vehicle running state, monitors the change of a vehicle in a transportation process and provides decision information for a driver and a management layer. According to the product, three GPS receiving terminal antennas are installed on the same base line, the shortest distance between two antennas is 14 cm, the longest distance between two antennas is 6 m, three GPS modules synchronously receive the carrier phase observed quantity of a satellite, the length of a base line vector of the center points of the two antennas is rapidly calculated through the least square method, and therefore the course, the roll and the pitch angle relative to the reference are obtained. Experimental results show that under a 6m base line, only one second is needed for positioning, the accuracy of the course, the roll and the pitch angle is superior to 0.5 mil, and the method can be widely applied to positioning, orientation and attitude measurement of large vehicles.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle-mounted systems, and more specifically, to a vehicle-mounted GPS positioning, orientation and attitude measurement system. Background Art

[0002] GPS, also known as the "Global Positioning System for Satellite Time Measurement and Navigation", consists of 24 artificial satellites at an altitude of about 20,000 kilometers. It is widely used for carrier positioning, and its positioning accuracy can reach the centimeter level. Domestic and foreign experts have proposed research based on the application of GPS in carrier orientation and attitude measurement. The orientation and attitude products developed have the disadvantages of single function, low accuracy, and narrow application range. Therefore, it is very necessary to develop a GPS positioning, orientation, and attitude measurement system based on large special vehicles. In response to this problem, the present invention proposes a least squares method to quickly determine the ambiguity range, search and optimal judgment, and calculate the optimal carrier position, heading, and attitude. Summary of the invention

[0003] The purpose of the present invention is to provide a vehicle-mounted GPS positioning, orientation and attitude measurement system, which proposes a least square method to quickly determine the ambiguity range, search and optimal judgment, and calculate the optimal carrier position, heading and attitude.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions: a vehicle-mounted GPS positioning, orientation and attitude measurement system, the system comprising a data receiving module, a data storage module, a data parsing module and a user terminal;

[0005] A data receiving module, which is composed of a receiving board and an antenna bracket. The data receiving module sends the received satellite observation data to the data storage module in real time;

[0006] A data storage module, wherein the data storage module realizes a function of storing data through a data storage device;

[0007] A data analysis module, which analyzes various satellite ephemeris data and observation data, calculates the real-time position coordinate data of each satellite based on the ephemeris data, prepares for solving the positioning coordinates, and calculates the satellite state matrix and the angle between the line vector of the two receiving antennas and the north direction based on the observation data;

[0008] The user terminal is a control computer, and the system outputs coordinate information, speed, azimuth and pitch angle to the user terminal every second.

[0009] The present invention is further configured as follows: the system includes three functions of positioning, orientation and navigation, wherein the positioning information part is processed by three GPS receiving antennas using fusion technology and the position information is output through the CAN port or RS232 serial port; the orientation part is mainly composed of three GPS receiving antennas installed on the carrier to form a baseline to measure the azimuth and pitch angle solutions.

[0010] The present invention also provides a vehicle-mounted GPS positioning, orientation and attitude measurement device, which comprises the vehicle-mounted GPS positioning, orientation and attitude measurement system.

[0011] The present invention is further configured as follows: the device comprises a computer, an antenna bracket and a receiving board, the antenna bracket is connected to three receiving boards, and each of the receiving boards is connected to a GPS receiving antenna.

[0012] The present invention is further configured as follows: the computer casing is reinforced with aluminum alloy, and the installation dimensions of the computer are as follows: 320 mm in length, 200 mm in width, and 138 mm in height.

[0013] The present invention is further configured as follows: the three receiving boards are receiving board 1, receiving board 2, and receiving board 3 from left to right, and the three receiving antennas are receiving antenna 1, receiving antenna 2, and receiving antenna 3 from left to right, and the horizontal distance between receiving antenna 1 and receiving antenna 3 is 6000±0.4mm, and the horizontal distance between receiving antenna 2 and receiving antenna 3 is 140±0.4mm.

[0014] In summary, the present invention has the following beneficial effects: The present invention proposes a least square method to quickly determine the ambiguity range, search and optimal judgment, and calculate the optimal carrier position, heading, and attitude. Under a 6m baseline, positioning only takes 1s, and the heading, roll and pitch angle accuracy is better than 0.5mil, which can be widely used in large vehicle positioning, orientation, and attitude measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the installation angle of the calibration system in the present invention;

[0016] Figure 2 It is a schematic diagram comparing the accuracy of GPS single point positioning and differential positioning in the present invention;

[0017] Figure 3 It is a schematic diagram comparing the GPS positioning and orientation system and the standard heading system in the present invention;

[0018] Figure 4 It is a schematic diagram of information exchange between the GPS orientation attitude measurement system and the vehicle in the present invention;

[0019] Figure 5 It is a hardware block diagram of the system in the present invention;

[0020] Figure 6 It is the principle diagram of the system mainboard in the present invention;

[0021] Figure 7 It is a schematic diagram of a GPS simple test receiving terminal in the present invention;

[0022] Figure 8 It is the appearance diagram of the satellite positioning attitude measuring instrument in the present invention;

[0023] Fig. 9 It is a schematic diagram of antenna installation in the present invention;

[0024] Fig.10 It is a schematic diagram of the system composition in the present invention;

[0025] Fig.11 The invention relates to a GPS satellite positioning attitude measuring instrument. DETAILED DESCRIPTION

[0026] The following is combined with Figure 1-11 The present invention is described in further detail.

[0027] Example 1: Installation error calibration

[0028] Before using the GPS orientation system, the installation error needs to be calibrated. Install the three GPS antennas on the 6m aluminum alloy baseline as required, and install the baseline on the central axis of the carriage. b axis, then the heading angle ψ is the moving coordinate system x b The projection of the axis in the geographic coordinate system and the shadow of the geographic coordinate system n The angle between the axes is the heading angle of the vehicle, with north to east deflection as positive; the pitch angle θ is the moving coordinate system (vehicle) x b The angle between the axis and the projection of the coordinate system is positive when it is upward. Since the center axis of the vehicle cannot be found theoretically during the installation process, there will inevitably be installation errors. Therefore, calibrating the installation error is the key to applying the vehicle-mounted GPS positioning, orientation and attitude measurement system.

[0029] There are two common methods for calibrating GPS baseline installation errors: the aiming pole measurement method and the auxiliary equipment measurement method. This paper adopts the auxiliary equipment measurement method, selects a high-precision reference heading system, the north-finding accuracy is less than 0.1 mil, and the odometer combined navigation accuracy is less than 1‰. Two standard points are selected to first calibrate the angle between the high-precision reference heading system and the vehicle's centerline.

[0030] Using the method of calibrating a high-precision reference attitude system: the standard points are as follows Figure 1 Point A (starting point) and point B (end point), point C is the calculated end point coordinate when the high-precision reference heading system reaches point B. The angle of ∠BAC is α1, the angle between the line connecting points A and B and the X-axis (east) is α3, and the angle between the line connecting points A and C and the X-axis (east) is α2. The installation angle between the high-precision reference heading system and the vehicle is:

[0031] α1=α3-α2 (1)

[0032] Calibrate the baseline installation error angle: Use the multiple north-seeking method, use the high-precision reference heading system and GPS positioning and orientation system to simultaneously seek north for at least 5 times without abnormality, and take the average value of the north-seeking results. The average north-seeking value of the high-precision strapdown inertial navigation system is ψ1, and the average north-seeking value of the GPS orientation system is ψ2. Then the GPS baseline installation error α is:

[0033] α=ψ2-(ψ1-α1) (2)

[0034] Therefore, the real-time heading value output by the GPS orientation positioning system to the vehicle is:

[0035] ψ=ψ-α (3)

[0036] Example 2: Positioning test

[0037] The GPS positioning accuracy test uses the standard points provided by the Surveying and Mapping Bureau as the benchmark, and the positioning accuracy is higher than 10cm. When there are 3 or more satellite signals, the CEP accuracy is higher than 10cm; the CEP accuracy of single-point positioning exceeds 10m. The test results are as follows Figure 2 .

[0038] Example 3: Directed Testing

[0039] 1. Directed static test

[0040] In order to accurately test the orientation accuracy, it is necessary to use a high-precision turntable to test the orientation repeatability and orthogonality in four quadrants. First, level the high-precision digital turntable and fix the 6m baseline of the vehicle-mounted GPS orientation instrument on the digital turntable, with the center point coinciding with the center point of the digital turntable. Find north five times in a row at the 0° position, then turn 90 degrees and test five times in a row in four quadrants. The test results of each quadrant are as shown in Table 1:

[0041] Table 1 System real-time test data Unit: mil

[0042]

[0043] 2. Directional dynamic testing

[0044] The heading accuracy test of the GPS positioning and orientation system first installs three GPS antennas on the same baseline. The baseline length is 6m, and the shortest distance between the two GPS antennas is 14cm. The baseline is installed on the central axis of the top of the vehicle so that the system can normally receive GPS signals. Secondly, the central axis of the baseline and the central axis of the vehicle cannot completely coincide. It is necessary to calibrate the installation error angle between the installation baseline and the central axis of the vehicle. The attitude accuracy is based on the high-precision reference attitude system, and the heading measurement accuracy exceeds 0.1mil. The positioning accuracy uses RTK high-precision real-time dynamic differential positioning equipment to measure standard points for calibration, and the positioning accuracy is better than 10cm. The results of multiple consecutive dynamic experiments are shown in Table 2:

[0045] Table 2 Real-time heading data Unit: mil

[0046]

[0047] From the experimental results in the table above, it can be seen that the relative error between the dynamic navigation accuracy of the vehicle-mounted GPS orientation system and the heading of the standard system is less than 0.2 mil, and the mean square error is less than 0.02.

[0048] The heading tracking is as follows Figure 3 As shown:

[0049] 3. GPS orientation and attitude measurement system, RFID and GPRS collaborative application

[0050] The GPS orientation and attitude measurement system is applied to large vehicles. How to monitor transportation in real time and send information to the monitoring center requires the help of logistics technology and wireless transmission technology. The items with RFID tags are read in real time through wireless high-frequency readers and writers. The body temperature and other detection indicators are transmitted to the data processing integrated machine through the temperature sensor. The video camera transmits the internal monitoring information of the vehicle to the driving control room through the network. In addition, there is also vehicle location information, heading, attitude, speed, mileage and other information. After receiving the information, the information processing integrated machine immediately starts the GPRS wireless transmission module and uses the public wireless network to transmit the data to the control center in real time. See below for details. Figure 4 .

[0051] Example 4: Hardware and structural design of vehicle-mounted GPS orientation and attitude measurement system

[0052] (I) Hardware platform construction

[0053] When the vehicle-mounted GPS satellite positioning, orientation and attitude measurement system is working, it first sends the satellite observation data received by the three GPS receiving boards to the data storage device in real time through the three RS-232 ports, and parses various satellite ephemeris data and observation data. Then, the real-time position coordinate data of each satellite is calculated based on the ephemeris data to prepare for solving the positioning coordinates. Then, the satellite state matrix and the angle between the line vector of the two receiving antennas and the north direction are calculated based on the observation data.

[0054] In the process of directional design, the overall performance needs to implement relevant national standards, industry standards, and enterprise standards to make the design standardized and standardized. Based on this, we adopted the following computer platform composition scheme. The data volume is large, the processing process is complex, the data is processed separately by type and level, and a large amount of intermediate data results need to be saved. Most of the data in the entire data processing process is floating-point operation. Therefore, the CPU is required to have not only extremely strong floating-point operation capabilities, but also strong external device interface control and management capabilities.

[0055] (II) Selection of CPU board for computing processing unit

[0056] The data analysis module needs to be equipped with a computing processing unit. The computing processing unit of the present invention adopts Intel's Pentium-class chip with a main frequency of more than 600MHz, a memory of 4G bytes, and an electronic disk of 512G bytes. The CPU is characterized by fast computing speed and high computing accuracy. It can realize 64-bit double-precision floating-point operations and fully meet the design requirements. At the same time, the CPU has 6 RS232 ports, 3 of which are used to receive data from 3 GPS receiving boards, and the other serial port communicates with the user.

[0057] The connection between the above boards is completed through the motherboard. The advantages of this solution are simple and convenient assembly, few connections, simplicity, and easy disassembly and maintenance.

[0058] (3) GPS satellite receiving board

[0059] Among the three GPS satellite receiving boards (OEM products), the GPS receiving board OEM with original observation output is selected. The receiving antenna is the domestic GG aviation antenna. Its main functions are: receiving GPS signals, and through a series of processing processes such as frequency conversion amplification and filtering, it can track, lock and measure GPS signals; and provide the data information required to calculate the position and direction.

[0060] (IV) Circuit Design

[0061] In terms of power selection, an external controlled switching power supply design with excellent performance is selected, which has the characteristics of stable output voltage, high conversion efficiency, wide input voltage range, and over-current and over-voltage protection. In the design and treatment of power heat dissipation, the thermal power supply is placed close to the casing, and then heat transfer paste is applied between the casing and the thermal power supply to achieve the purpose of heat dissipation. The designed power board is small in size and has strong electromagnetic interference suppression ability, which can fully meet the overall requirement of input voltage of 24±4V; the serial port level conversion chip uses MAX202EPE to complete the conversion between 3 GPS serial ports TTL level and RS232 level; the CAN output uses CSM100 serial to CAN chip, which has stable performance and wide temperature range; the motherboard design mainly completes the power supply of each board, serial port level conversion, CSM100 serial to CAN chip and other power and data receiving connections and installations, and each board is connected to Figure 5 , the design schematic diagram of the modified system motherboard is as follows Figure 6 shown.

[0062] (V) Software Design

[0063] The vehicle-mounted GPS satellite positioning, orientation and attitude measurement system includes three functions: positioning, orientation and navigation. The positioning information part is processed by 3 GPS receiving antennas using fusion technology, and the position information is output through the CAN port or RS232 serial port; the orientation part is mainly composed of three GPS receiving antennas installed on the carrier to form a baseline to measure the azimuth and pitch angle. The system outputs coordinate information, speed, azimuth and pitch angle to the user terminal every second, and the user terminal is a control computer. The key technology of the system is mainly to use the least squares method to determine the ambiguity range, the search of ambiguity and its rapidity, and the optimal determination of ambiguity, and the realization of the orientation function.

[0064] The vehicle-mounted GPS satellite positioning, orientation and attitude measurement system software is developed under the DOS 6.22 operating system. All programs are developed using Borland C++3.0 software and C language to improve the readability and maintainability of the software.

[0065] In order to meet the real-time requirements of the system, the interrupt method is used to read GPS telegram data from the serial port. Three global data variables are set in the program as three receiving antenna buffers. The array buffer is set as large as possible to receive and temporarily store data to avoid data overflow. When receiving data, the first-in-first-out data processing method is adopted. Each reception is pushed forward from the end of the array. When the program takes out the data, it searches for the qualified data header until the data header is found. Otherwise, the previous data is squeezed out and the data tail is found at the same time. The data checksum is calculated to be consistent with the checksum in the GPS data, and it is judged as useful data. This method solves the problem of receiving GPS data better. Some resources of the receiving program are as follows:

[0066] void interrupt receiver1(void) / / interrupt receiving data

[0067] { / / Receive data from GPS OEM board 1}

[0068] void interrupt receiver2(void) / / interrupt receiving data

[0069] { / / Receive data from GPS OEM board 2}

[0070] void interrupt receiver3(void) / / interrupt receiving data

[0071] { / / Receive data from GPS OEM board 3}

[0072] void interrupt receiver4(void) / / interrupt receiving data

[0073] { / / External data exchange}

[0074] void interrupt receiver5(void) / / interrupt receiving data

[0075] { / / Configure CAN module data exchange}

[0076] The data is sent in the form of query. To extract 5 different sets of data from the GPS OEM board, the data needs to be sent to the OEM board. In addition, the solved data is output through serial port 5.

[0077] void sendcom1(void) / / send data

[0078] { / / Send data from GPS OEM board 1

[0079] }

[0080] void sendcom2(void) / / send data

[0081] { / / Send data from GPS OEM board 2

[0082] }

[0083] void sendcom3(void) / / send data

[0084] { / / Send data from GPS OEM board 3

[0085] }

[0086] void sendcom4(void) / / send data

[0087] { / / Send data to the receiving end

[0088] }

[0089] void CAN_set(void) / / send data

[0090] { / / Send CAN100 configuration

[0091] }

[0092] void CAN_send(void) / / send data

[0093] { / / CAN sends data

[0094] }

[0095] Simple test receiving terminal Figure 7VC serial port programming uses the Serial.cpp and Serial.h serial port development files developed by Microsoft. By setting the serial port parameters, you can directly write a program to test the terminal. 1. Open the serial port function

[0096] BOOL CSeries::Init(int port,DWORD BaudRate,BYTE StopBits,BYTE Parity,BYTE ByteSize,int BuffCount);

[0097] Port: port number, BaudRate: baud rate, StopBits: stop bits, Parity: parity bits, ByteSize: data bits, BuffCount: buffer.

[0098] 2. Close the serial port function

[0099] BOOL CSeries::Close();

[0100] (VI) Structural design

[0101] The installation dimensions of the computer are: 320mm long, 200mm wide, and 138mm high. The vehicle-mounted GPS satellite positioning, orientation, and attitude measurement system adopts a black box solution. It is small, beautiful, and lightweight, with a compact internal structure, a reasonable layout, and convenient maintenance and assembly. It meets the requirements of durability, dustproof, waterproof, and vibration and impact resistance; the appearance structure and the installed shock absorber are tight and reliable and can be wall-mounted. The casing is reinforced with aluminum alloy, which has a good effect on electromagnetic shielding. The installation dimensions and appearance structure diagram of the computer are shown in Figure 8 .

[0102] The receiving antenna of the GPS satellite positioning attitude meter is an aviation antenna, which requires three antennas to be in a horizontal line, and the three antennas are arranged from left to right as antenna 1, antenna 2, and antenna 3. The horizontal distance between antenna 1 and antenna 3 is 6000±0.4mm, and the horizontal distance between antenna 2 and antenna 3 is 140±0.4mm.

[0103] Working principle:

[0104] 1. GPS positioning, orientation, and attitude measurement algorithms

[0105] (I) Theoretical basis of GPS positioning

[0106] 1. Theoretical basis of GPS absolute positioning

[0107] GPS positioning is divided into absolute positioning and relative positioning. In the absolute positioning equation, there is a clock difference in the pseudo-range measurement observation value of the receiving terminal, which adds an unknown quantity. It requires four satellite observation values ​​to solve the equation simultaneously. The observation equation is:

[0108]

[0109] Where ρ: pseudorange observation, R: distance from receiving antenna to satellite, r: receiving antenna clock difference, (X S , Y S , Z S ): instantaneous geocentric coordinates of the satellite; (X p , Y p , Z p ): The geocentric coordinates of the receiving terminal, which is the quantity to be determined. Differentiate ρ and substitute the initial value into the approximate coordinates (X p0 , Y p0 , Z p0 ), forming the basic equation of pseudorange positioning:

[0110] A i X i -L i =0 (1.2)

[0111] Find the unique solution to equation 1.2 and determine X p , Y p , Z p , the value of r. If precise measurement is required, it is necessary to receive signals from more than 8 satellites to ensure an accuracy of centimeters.

[0112] A i X i -L i =V i (1.3)

[0113] The principle of least squares method is used to calculate the position of the receiving antenna:

[0114] X i =(A T A) L A T L (1.4)

[0115] The GPS terminal receiving antenna and OEM chip both have the function of receiving RTCM SC-104 format differential GPS signals, and correct the pseudorange according to the time of obtaining the position information. Since the pseudorange correction number cannot receive data at every moment, it is obtained by using the time difference.

[0116]

[0117] 2. Theoretical basis of GPS relative positioning

[0118] The basic observation equation of GPS relative positioning is:

[0119]

[0120] φ: phase observation; R: distance from receiving antenna to satellite; r: receiving antenna clock error; δ: delay in troposphere and ionosphere.

[0121] Since φ in the observation equation is the phase decimal, N is the phase integer number, and τ is the delay correction of the signal passing through the troposphere and ionosphere; (X S , Y S , Z S ): the instantaneous coordinate of the satellite relative to the center of the earth; (X P , Y P , Z P ): receiving terminal to geocentric coordinates.

[0122] GPS relative positioning generally uses two terminal receiving antennas installed at two measuring points to observe the ephemeris data at the same time, receive GPS data and establish phase observations to obtain the basic single-difference observation equation:

[0123]

[0124] In equations (1.6) and (1.7), the superscript j is the number of the received satellite, and the subscripts 1 and 2 are the monitoring station numbers. Therefore, at the same time, the single-difference observation equation can be established based on the data received from two satellites, and then the double-difference observation equation can be solved jointly.

[0125]

[0126] The double-difference observation equation created by formula (1.8) is obtained by solving the difference between the length of the two terminal receiving antennas fixed on the same baseline and the obtained phase integer number N. The N value is generally not affected by external factors such as changes in time, space, and region.

[0127] 3. GPS single baseline attitude solution and error analysis

[0128] A single baseline is a baseline, that is, the GPS antennas are installed on a straight line, and the baseline is installed along the longitudinal axis of the carrier. In the present invention, a 6m baseline is taken as an example, and three GPS antennas are installed on the same aluminum alloy metal rod. The baseline is installed along the actual central axis of the carrier.

[0129] R b =[b 0 0] T (1.9)

[0130] Where b is the baseline length in meters.

[0131] The baseline vector should correspond to the geographic coordinate system E, and the coordinates are:

[0132] R n =[x n y n z n ] T (1.10)

[0133] According to the posture matrix The orthogonality of can get the estimated values ​​of heading angle ψ and pitch angle θ:

[0134] ψ=tan -1 (y n / x n ) (1.11)

[0135]

[0136] The value range of ψ is 0°~360°, and the value range of θ is -90°~90°. According to the solution results and the attitude matrix The true values ​​of the heading angle and pitch angle are obtained by judging the signs of each element.

[0137] In order to reduce the heading angle and pitch angle errors, it is necessary to find the error source and analyze the cause and impact of the error, so as to improve the initialization and navigation accuracy. The heading angle ψ is derived to obtain its deviation:

[0138]

[0139] Ignoring the product term of the coordinate value deviation, the deviation of the heading angle ψ is obtained:

[0140]

[0141] It can be concluded that:

[0142] σ ψ <max(XDOP, YDOP)σ / b cosθ (1.15)

[0143] Similarly, the pitch angle σ is derived θ variance:

[0144]

[0145] σ θ The value range of is:

[0146] σ θ <max(XDOP, YDOP, ZDOP)σ / b (1.17)

[0147] From equations (1.14) and (1.16), we can see that the heading angle ψ and the pitch angle σ θ The accuracy of the solution is inversely proportional to the length of the GPS installation baseline. The longer the baseline, the smaller the error. According to the application scope and characteristics of GPS orientation measurement on land vehicles, the baseline length is generally selected to be 3m, 6m, or 12m and fixed on the center axis of the vehicle to solve the heading angle ψ and pitch angle σ θ .

[0148] 4. GPS dual baseline attitude solution analysis

[0149] If you want to detect the heading angle, pitch angle, and roll angle of the carrier, you can use three or more GPS antennas and receiving antennas. The GPS receiving antenna is installed on two mutually perpendicular baselines. The longer baseline is 6m and is installed on the longitudinal center axis of the top of the vehicle. The other baseline is 3m long and perpendicular to the longer baseline and is also installed in the horizontal axis direction of the vehicle. The two mutually perpendicular baselines are in the same coordinate system. The GPS antenna needs to receive more than 4 satellites and solve the attitude angle of the baseline plane through simultaneous equations. Attitude matrix Solution:

[0150]

[0151] Use T ij Representing the elements in the attitude matrix, we can get:

[0152]

[0153] θ=-arcsin T 13 (1.20)

[0154]

[0155] In order to accurately measure the attitude angle of the vehicle, two mutually perpendicular baselines are installed on the vehicle body, of which the longer baseline is installed on the longitudinal center axis of the roof. b1 , R b2 is the coordinate of the mobile coordinate system, in R n1 , R n2 is the coordinate of the geographic coordinate system. By establishing three mutually orthogonal vectors in the moving coordinate system, we can get:

[0156]

[0157] It is also possible to create three mutually orthogonal vectors in the geographic coordinate system:

[0158]

[0159] We can get two 3x 3 matrices:

[0160] Mb =[V1 V2 V3]M n =[U1 U2 U3] (1.24)

[0161] From formula (1.24), we can get M b With M n Relationship:

[0162]

[0163] Since the two installed baseline vectors are not parallel but perpendicular to each other, the matrix is ​​full rank and reversible. The attitude matrix can be obtained by equation (1.25):

[0164]

[0165] The baseline length is a known condition, and you can use a ruler to measure multiple times to find the average value to avoid measurement errors. If you need to measure the roll angle, the GPS antenna needs to be installed vertically, and you need to use an angle ruler to ensure that the antenna installation error is minimized. In theory, the longer the GPS baseline, the higher the measurement accuracy, but it is impossible to achieve the ideal length in reality. Therefore, in order to meet higher accuracy, a 6m baseline is selected.

[0166] 2. Heading determination of vehicle-mounted GPS orientation and attitude measurement system

[0167] The heading determination of the vehicle-mounted GPS orientation and attitude measurement system is relatively complicated. The three GPS receiving antennas are installed on a baseline with a length of 6 meters through the single baseline installation method. The antennas should be installed on the same straight line as much as possible. Two GPS receiving antennas 14cm apart are used for coarse north finding; two antennas 6.00m apart are used for precise north finding. When the number of satellites exceeds 4, the receiving antennas connected to two GPS antennas with shorter distances can quickly find the north within 10 seconds with an accuracy better than 2mil; the receiving antennas connected to two antennas with longer distances can determine the precise north direction within 1 minute with an accuracy of more than 0.5mil. Precise north finding uses the determination of initial ambiguity, the determination of the search range, and the rapid search for a set of solutions within the threshold whose fitting residuals are less than a given value. Finally, the fitting residuals are determined, and the optimal solution is selected to determine the precise north direction.

[0168] (I) GPS ambiguity search range

[0169] The satellite spatial layout determines the search range, and the double difference equation can be written as:

[0170] Q i =H i1 X1+H i2 X2+H i3 X3+N i (2.1)

[0171] To find the range of N, we only need to find the range of H1X1, H2X2, and H3X3, because:

[0172]

[0173] According to the conditional value theory, we can get

[0174]

[0175] To solve and determine the ambiguity range, the ambiguity is regarded as the value to be calculated. The double difference equation in (2.1) can be rewritten as:

[0176]

[0177] The range of the ambiguity N can be obtained by finding the intersection of equations (2.1) and (2.4).

[0178] (II) GPS Ambiguity Search

[0179] The double difference model can be written as: θ = H x +N (2.5)

[0180] Taking the 3m baseline as an example (the present invention adopts the 6m baseline), the ambiguity search range of each satellite is:

[0181]

[0182] The maximum number of satellites can reach 12, so the number of ambiguity solution sets is: 60 11 = 36279705600 billion. For each ambiguity solution, 300 seconds of data are needed to calculate the coordinates and the residual sum of squares. The amount of calculation is very large. A new decision tree search algorithm is used to greatly reduce the amount of calculation and shorten the calculation time. Generally, a very small set of ambiguity true value solutions can be obtained within 1 second.

[0183] (III) Optimal determination of GPS ambiguity and carrier integer number

[0184] Ambiguity optimal judgment is a technical difficulty in GPS data acquisition. Due to the long transmission distance of satellite signals, the process is easily affected by external electromagnetic interference, or the circuit and noise signal of the receiving antenna itself, the received data may not be real data, and fuzzy judgment is required. Fuzzy judgment is more complicated. According to experiments and reasoning, the ratio of the suboptimal residual sum of squares to the optimal residual sum of squares is roughly χ 2 distributed.

[0185] Carrier cycle number: Phase measurement θ i , the smallest n i and X, calculated from the least squares fit X .

[0186] θ i =H i Xn i +ε i=1,2,3,……m (2.6)

[0187]

[0188] (IV) Fast Data Search Algorithm

[0189] The search algorithm is a traversal process that gradually searches for the target that meets the requirements based on the pre-set initial conditions and agreed judgment rules. According to the derivation process of the carrier integer number W of formula (2.7), the fast search algorithm is used to obtain W( x , n ).

[0190]

[0191] Let W 12 =(θ1-H i X +6) 2 +(θ2-H i X +5) 2

[0192] but

[0193] The least squares fit calculates X m

[0194]

[0195] The least squares fit calculates X i

[0196] W1=(θ1-H1X1+n1) 2

[0197]

[0198] (V) Quickly determine the heading angle

[0199] Rapid and high-precision determination of the heading angle is a key indicator for the orientation measurement system to adapt to complex environments and meet vehicle orientation requirements. Select coordinate point A as the base point, point B as another coordinate point, and point A to point B as the direction vector. The heading angle of the two points is determined through coordinate conversion.

[0200] 1. Find A = (X1, Y1, Z1) T Coordinate point longitude Latitude λ1.

[0201]

[0202] when hour,

[0203]

[0204]

[0205] e 2 =1-(1-f) 2 (2.20)

[0206] 2. Solve the heading angle, using the longitude of point A latitude Conversion matrix from geocentric coordinates to geographic coordinates:

[0207]

[0208] A L =T LE A (2.22)

[0209] B L =T LE B (2.23)

[0210] A L With B L To transform points A and B in the geocentric coordinate system to A in the geographic coordinate system with A as the origin L , B L Two points.

[0211]

[0212]

[0213] According to formulas (2.26) and (2.27), the heading angle ψ and pitch angle φ of the carrier are obtained.

[0214] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A vehicle-mounted GPS positioning, orientation and attitude measurement system, characterized by: The system includes a data receiving module, a data storage module, a data parsing module and a user terminal; A data receiving module, which is composed of a receiving board and an antenna bracket. The data receiving module sends the received satellite observation data to the data storage module in real time; A data storage module, wherein the data storage module realizes a function of storing data through a data storage device; A data analysis module, which analyzes various satellite ephemeris data and observation data, calculates the real-time position coordinate data of each satellite based on the ephemeris data, prepares for solving the positioning coordinates, and calculates the satellite state matrix and the angle between the line vector of the two receiving antennas and the north direction based on the observation data; The user terminal is a control computer. The system outputs coordinate information, speed, azimuth and pitch angle to the user terminal every second.

2. A vehicle-mounted GPS positioning, orientation and attitude measurement system according to claim 1, characterized in that: The system includes three functions: positioning, orientation and navigation. The positioning information part is processed by three GPS receiving antennas using fusion technology and the position information is output through the CAN port or RS232 serial port; the orientation part is mainly composed of three GPS receiving antennas on the installation carrier to form a baseline to measure the azimuth and pitch angle.

3. A vehicle-mounted GPS positioning, orientation and attitude measurement device, characterized in that: The device comprises the vehicle-mounted GPS positioning, orientation and attitude measurement system as described in any one of claims 1-2.

4. A vehicle-mounted GPS positioning, orientation and attitude measurement device according to claim 3, characterized in that: The device comprises a computer, an antenna bracket and a receiving board. The antenna bracket is connected to three receiving boards, and each receiving board is connected to a GPS receiving antenna.

5. A vehicle-mounted GPS positioning, orientation and attitude measurement device according to claim 4, characterized in that: The computer case is reinforced with aluminum alloy, and the installation dimensions of the computer are as follows: 320 mm in length, 200 mm in width, and 138 mm in height.

6. A vehicle-mounted GPS positioning, orientation and attitude measurement device according to claim 4, characterized in that: The three receiving boards are receiving board 1, receiving board 2, and receiving board 3 from left to right, and the three receiving antennas are receiving antenna 1, receiving antenna 2, and receiving antenna 3 from left to right. The horizontal distance between receiving antenna 1 and receiving antenna 3 is 6000±0.4mm, and the horizontal distance between receiving antenna 2 and receiving antenna 3 is 140±0.4mm.

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