Opportunity signal positioning error compensation method based on iridium IRA

Abstract

The invention discloses an opportunity signal positioning error compensation method based on iridium IRA, and relates to the field of opportunity signal positioning. The problem that in the prior art, an accurate initial solution is difficult to obtain in the environment that no positioning reference information exists in a low-orbit satellite opportunity signal positioning method is solved. The method comprises the following steps: connecting receiver hardware for receiving an iridium downlink signal; the iridium satellite downlink signal is analyzed; demodulating to obtain iridium downlink information; acquiring the projection latitude and longitude of the iridium relative to the earth surface, and calculating the average projection position of multiple times of data; calculating a rough position solution based on a global particle swarm algorithm; acquiring propagation delay; calculating the satellite position and speed by adopting propagation delay; the Doppler frequency shift of the center frequency of the IRA 11 frequency band signal in the iridium downlink signal is confirmed by using a maximum paraphrasing estimation method; the initial position, the position and speed of the iridium downlink signal satellite and Doppler frequency shift are substituted into a Doppler positioning equation, and a position solution is solved through least square. The method is suitable for the research field of satellite orbit correction algorithms.

Description

Technical Field

[0001] The invention relates to the technical field of opportunity signal positioning, and in particular to an Iridium-based opportunity signal positioning error compensation method. Background Art

[0002] Low Earth Orbit (LEO) opportunity signal positioning is an emerging positioning technology. Due to its advantages such as global coverage, high signal strength, fast update frequency and low latency, it is widely used in navigation, timing, monitoring and rescue. Faced with challenges such as complex and changing environments, traditional satellite signal obstruction and interference, a single positioning system is limited by the limited signal source and reliability, and it is difficult to meet the needs of high-precision positioning. At the same time, the collaborative positioning system composed of opportunity signals emitted by multiple low-orbit satellites has stronger robustness, higher positioning accuracy and wider coverage, and plays an increasingly important role in unmanned driving, the Internet of Things, precision agriculture and other fields.

[0003] Low-orbit satellite opportunity signal positioning is a navigation positioning problem, which is often coupled with Doppler positioning. At present, domestic and foreign scholars have conducted little research on this type of problem, and its content can be divided into three aspects: signal Doppler solution optimization, satellite orbit estimation optimization, and positioning solution algorithm optimization. The satellite orbit correction algorithm is an error elimination algorithm based on delay propagation. At present, in the field of low-orbit satellite opportunity signal positioning, there has been no progress in the research on satellite orbit correction algorithms. Traditional low-orbit satellite opportunity signal positioning algorithms focus on optimizing the Doppler accuracy of the receiver, while ignoring the error of propagation delay on satellite orbit estimation. For the positioning system, in the process of positioning convergence, the acquisition of initial positioning is crucial for estimating the propagation delay and achieving high-precision positioning results. Summary of the invention

[0004] The present invention aims to solve the problem that the positioning method based on low-orbit satellite opportunity signal positioning in the prior art shows that it is difficult to obtain an accurate initial solution in an environment without positioning reference information, which leads to large positioning errors and even failure to converge to a correct solution.

[0005] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] Solution 1: The present invention proposes a method for compensating positioning errors of opportunity signals based on Iridium satellites, the method comprising the following steps:

[0007] S1. Connect the receiver hardware to receive Iridium downlink signals;

[0008] S2, analyzing the received Iridium downlink signal;

[0009] S3, demodulating the received Iridium downlink signal to obtain Iridium downlink information IRA;

[0010] S4. Obtain the projection longitude and latitude of the Iridium satellite relative to the earth's surface based on the Iridium satellite downlink information IRA Calculate the average projection position of multiple data

[0011] S5. Based on the calculated average projection position And the visible range of Iridium satellites, the rough position solution is calculated based on the global particle swarm algorithm

[0012] S6. Solve based on rough position Get the propagation delay τ;

[0013] S7. Use TLE file and SGP4 file to determine the satellite position, and use propagation delay τ to calculate the satellite position and speed

[0014] S8. Use the maximum likelihood estimation method to determine the Doppler shift of the IRA 11 band signal center frequency in the Iridium downlink signal

[0015] S9, the initial position Satellite location and speed Doppler shift The Doppler positioning equation is substituted into the position solution through least square method, and the satellite position is corrected by the opportunity signal positioning error compensation method based on Iridium IRA.

[0016] Furthermore, a preferred implementation manner is provided, in which the received Iridium downlink signal analyzed in S2 is obtained by analyzing it through a Butterworth filter.

[0017] Further, a preferred implementation is provided, wherein S3 specifically includes:

[0018] S3.1, filtering the received Iridium downlink signal and performing a windowing operation on it;

[0019] S3.2, set the windowed signal strength threshold, cyclically judge the entire frequency domain signal, and capture the pilot information of the windowed signal;

[0020] S3.3, set the period to 90ms and capture the next windowed signal;

[0021] S3.4, demodulate the next captured windowed signal using BPSK to obtain a binary code;

[0022] S3.5. Decode the windowed signal according to the Iridium IRA binary coding rule. The Iridium IRA parses the windowed signal to include the projection longitude and latitude LAT and LON of the satellite position on the earth, and the satellite number of the Iridium downlink signal, thereby completing the acquisition of the Iridium downlink information IRA.

[0023] Further, a preferred implementation is provided, in S5, a global particle swarm algorithm is designed to solve the rough position solution The method is:

[0024] S5.1, initialize the variables of the particle swarm;

[0025] S5.2. Based on the calculated average projection position And the particle boundary is obtained from the radiation range of the Iridium downlink signal:

[0026]

[0027] S5.3. Calculate the PSO optimization objective function according to the Doppler frequency shift formula:

[0028]

[0029] Where p = [φ, λ] is the target latitude and longitude of the receiver, and [x, y, z] can be obtained by the following formula:

[0030]

[0031] in e is the radius of the Earth;

[0032] S5.4. Use PSO algorithm to traverse and obtain the optimal solution

[0033] Further, a preferred embodiment is provided, in S6, based on the rough position solution The method to obtain the propagation delay τ is:

[0034] S6.1. Based on the calculated propagation delay

[0035] S6.2. Satellite position based on propagation delay Make compensation

[0036]

[0037] Among them, h i = kk-sign(f d (k))τ,a i ,b i c i d i A i Bi C i D i are the cubic interpolation coefficients, which are obtained by the cubic interpolation formula.

[0038] Further, a preferred implementation is provided, in S7, the propagation delay τ is used to calculate and optimize the satellite position estimation to solve the satellite position and speed The method is:

[0039] S7.1. Obtain the satellite orbit plane inclination and ascending node right ascension information for the day;

[0040] S7.2, establish the SGP4 model based on satellite TLES information;

[0041] S7.3. Obtain the satellite position velocity sequence output by the SGP4 model and

[0042] Further, a preferred embodiment is provided, in S8, the Doppler shift of the center frequency of the IRA 11 frequency band signal in the Iridium downlink signal is determined by using the maximum likelihood estimation method. The method is:

[0043] S8.1. Determine the rough Doppler estimate using fast Fourier transform for the window where the pilot is located

[0044] S8.2. Window the frequency domain and use the maximum relief estimate to estimate the fine Doppler of the frequency domain signal within the window.

[0045] S8.3, according to the windowed time and Doppler curve diagram, and compared with the ID of the Iridium downlink signal satellite analyzed in step 2, the Doppler frequency shift of the IRA 11 frequency band signal center frequency in the Iridium downlink signal is completed. confirmation.

[0046] Further, a preferred embodiment is provided, wherein the initial position in 9 Calculated by PSODC algorithm.

[0047] Solution 2: A computer device includes a memory and a processor, wherein the memory stores a computer program. When the processor runs the computer program stored in the memory, the processor executes any one of the methods described in Solution 1.

[0048] Solution three: a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the method described in any one of claim 1.

[0049] The present invention is beneficial in that:

[0050] The present invention combines the analysis of Iridium downlink broadcast signals with opportunity signal positioning, solves the initial position through the PSO algorithm, solves the problem of inaccurate initial position of Doppler positioning by least squares solution, and can improve the accuracy of final positioning convergence and increase computing efficiency.

[0051] The present invention extracts the initial positioning from the Iridium downlink broadcast signal, calculates the propagation delay through the initial positioning, and applies the propagation delay to compensate for the satellite orbit estimation error, thereby increasing the estimation accuracy of the satellite position and speed. Compared with the traditional algorithm without compensation, the present algorithm is superior to the traditional algorithm in positioning accuracy.

[0052] It is also applicable to the research field of satellite orbit correction algorithms. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flow chart of the Iridium opportunity signal positioning error compensation method in the Iridium opportunity signal positioning error compensation method described in Implementation Method 1.

[0054] Figure 2 This is a simulation diagram of the Iridium-based opportunity signal positioning error compensation method described in Implementation Example 11.

[0055] Figure 3 The PSO optimization method described in the eleventh embodiment Schematic diagram.

[0056] Figure 4 This is a schematic diagram of the measured Doppler time curve described in the eleventh embodiment.

[0057] Figure 5 This is a schematic diagram of the actual measurement results of the eleventh embodiment. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the implementation methods of the present application clearer, the technical solutions in the implementation methods of the present application will be clearly and completely described below in conjunction with the drawings in the implementation methods of the present application. Obviously, the described implementation methods are only part of the implementation methods of the present application, not all of the implementation methods.

[0059] Embodiment 1: This embodiment provides a method for compensating positioning errors of opportunity signals based on Iridium satellites, and the method comprises the following steps:

[0060] S1. Connect the receiver hardware to receive Iridium downlink signals;

[0061] S2, analyzing the received Iridium downlink signal;

[0062] S3, demodulating the received Iridium downlink signal to obtain Iridium downlink information IRA;

[0063] S4. Obtain the projection longitude and latitude of the Iridium satellite relative to the earth's surface based on the Iridium satellite downlink information IRA Calculate the average projection position of multiple data

[0064] S5. Based on the calculated average projection position And the visible range of Iridium satellites, the rough position solution is calculated based on the global particle swarm algorithm

[0065] S6. Solve based on rough position Get the propagation delay τ;

[0066] S7. Use the TLE file and SGP4 file to determine the position of the Iridium downlink signal satellite, and use the propagation delay τ to calculate the satellite position and speed

[0067] S8. Use the maximum likelihood estimation method to determine the Doppler shift of the IRA 11 band signal center frequency in the Iridium downlink signal

[0068] S9, the initial position Iridium downlink signal satellite position and speed Doppler shift Substitute it into the Doppler positioning equation and solve the position solution through least squares.

[0069] Implementation method 2: This implementation method further limits the Iridium-based opportunity signal positioning error compensation method described in implementation method 1. The received Iridium downlink signal analyzed in S2 is obtained by using a Butterworth filter.

[0070] Implementation method 3: This implementation method further limits the Iridium-based opportunity signal positioning error compensation method described in implementation method 1, and S3 specifically includes:

[0071] S3.1, filtering the received Iridium downlink signal and performing a windowing operation on it;

[0072] S3.2, set the windowed signal strength threshold, cyclically judge the entire frequency domain signal, and capture the pilot information of the windowed signal;

[0073] S3.3, set the period to 90ms and capture the next windowed signal;

[0074] S3.4, demodulate the next captured windowed signal using BPSK to obtain a binary code;

[0075] S3.5. Decode the windowed signal according to the Iridium IRA binary coding rule. The Iridium IRA parses the windowed signal to include the projection longitude and latitude LAT and LON of the satellite position on the earth, and the satellite number of the Iridium downlink signal, thereby completing the acquisition of the Iridium downlink information IRA.

[0076] Implementation method 4: This implementation method further limits the Iridium-based opportunity signal positioning error compensation method described in implementation method 3. In S5, a global particle swarm algorithm is designed to solve the rough position solution. The method is:

[0077] S5.1, initialize the variables of the particle swarm;

[0078] S5.2. Based on the calculated average projection position And the particle boundary is obtained from the radiation range of the Iridium downlink signal:

[0079]

[0080] S5.3. Calculate the PSO optimization objective function according to the Doppler frequency shift formula:

[0081]

[0082] Where p = [φ, λ] is the target latitude and longitude of the receiver, and [x, y, z] can be obtained by the following formula:

[0083]

[0084] in e is the radius of the Earth;

[0085] S5.4. Use PSO algorithm to traverse and obtain the optimal solution

[0086] Implementation mode 5: This implementation mode further limits the Iridium-based opportunity signal positioning error compensation method described in Implementation mode 1. In S6, the positioning error compensation method is based on the rough position solution. The method to obtain the propagation delay τ is:

[0087] S6.1. Based on the calculated propagation delay

[0088] S6.2. Satellite position based on propagation delay Make compensation

[0089]

[0090] Among them, hi = kk-sign(f d (k))τ,a i ,b i c i d i A i B i C i D i are the cubic interpolation coefficients, which are obtained by the cubic interpolation formula.

[0091] Implementation 6: This implementation is a further limitation of the Iridium-based opportunity signal positioning error compensation method described in Implementation 1. In S7, the propagation delay τ is used to calculate and optimize the satellite position estimation to solve the satellite position. and speed The method is:

[0092] S7.1. Obtain the satellite orbit plane inclination and ascending node right ascension information for the day;

[0093] S7.2, establish the SGP4 model based on satellite TLES information;

[0094] S7.3. Obtain the satellite position velocity sequence output by the SGP4 model and

[0095] Implementation VII: This implementation is a further limitation of the Iridium-based opportunity signal positioning error compensation method described in Implementation 1. In S8, the maximum likelihood estimation method is used to confirm the Doppler frequency shift of the center frequency of the IRA11 frequency band signal in the Iridium downlink signal. The method is:

[0096] S8.1. Determine the rough Doppler estimate using fast Fourier transform for the window where the pilot is located

[0097] S8.2. Window the frequency domain and use the maximum relief estimate to estimate the fine Doppler of the frequency domain signal within the window.

[0098] S8.3, according to the windowed time and Doppler curve diagram, and compared with the ID of the Iridium downlink signal satellite analyzed in step 2, the Doppler frequency shift of the IRA 11 frequency band signal center frequency in the Iridium downlink signal is completed. confirmation.

[0099] Implementation 8: This implementation further defines the Iridium-based opportunity signal positioning error compensation method described in Implementation 1. In S9, the initial position Calculated by PSODC algorithm.

[0100] Embodiment 9: This embodiment proposes a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes the method described in any one of embodiments 1 to 8.

[0101] Embodiment 9: This embodiment proposes a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the method described in any one of embodiments 1 to 8 are implemented.

[0102] Implementation eleven: This implementation provides an example, which is used to explain the above implementations one to ten. The specific example is as follows:

[0103] See also Figures 1 to 5 This embodiment describes an Iridium downlink signal error compensation positioning method, which includes the following steps:

[0104] Step 1: Connect the hardware to receive the signal. Figure 2 The parameters are shown in Table 1;

[0105] Step 1.1, set clock synchronization Use high-precision clock for synchronization and set receiver parameters as shown in Table 1;

[0106] Step 1.2, use C++ to write the gnuradio receiver code, including the usrp source, bandpass filter, and file writing;

[0107] Step 2: parse the received signal, use a Butterworth filter to perform a windowing operation on the signal, set a window power threshold, and traverse the signal to determine the signal pilot;

[0108] Step 2.1, after locking the pilot, use the pilot to demodulate the signal in the window using BPSK to obtain a digital signal;

[0109] Step 2.2, the bit stream is decoded by using the Viterbi algorithm;

[0110] Step 2.3, find the starting point of the frame in the continuous bit stream according to the synchronization sequence;

[0111] Step 2.4: Remove the bit stuffing bits according to the protocol specification and assemble into data packets according to the protocol;

[0112] Step 3: After obtaining the pilot signal, obtain the Doppler frequency shift through the pilot signal;

[0113] Step 3.1: Use fast Fourier transform to determine the rough Doppler estimate for the window where the pilot is located

[0114] Step 3.2: Add a window in the frequency domain and use the maximum relief estimation to estimate the fine Doppler of the frequency domain signal in the window.

[0115]

[0116] Step 3.3: Generate a time-Doppler curve based on the windowing and compare it with the satellite ID of the signal analyzed in step 2 to determine the signal Doppler source.

[0117] Step 4: Match the satellite Doppler with the satellite ID, and determine the position and speed of the satellite with the corresponding ID according to the satellite ID.

[0118] Step 4.1, search for the corresponding two-line element set file (Two-Line Element Sets TLES) according to the satellite ID, and obtain the satellite orbit plane inclination, ascending node right ascension and other information on that day;

[0119] Step 4.2: Establish the SGP4 model based on the satellite TLES information, and set the sampling rate to 60ms for the windowing time.

[0120] Step 4.3: Obtain the satellite position velocity sequence output by the SGP4 model and

[0121] Step 5: Correct the satellite position using the Iridium IRA-based opportunity signal positioning error compensation method

[0122] Step 5.1, initialize the variables of the particle swarm;

[0123] Step 5.2: According to the required projection longitude and latitude And the particle boundary is obtained from the radiation range of the Iridium downlink signal:

[0124]

[0125] Step 5.3: According to the Doppler frequency shift formula, the PSO optimization objective function is as follows:

[0126]

[0127] Where p = [φ, λ] is the target latitude and longitude of the receiver, and [x, y, z] can be obtained by the following formula:

[0128]

[0129] in e is the radius of the Earth.

[0130] Step 5.4: Use the PSO algorithm to traverse and obtain the optimal solution

[0131] Step 5.5: Estimate the propagation delay based on the calculation

[0132] Step 5.6: Satellite position based on propagation delay Make compensation

[0133]

[0134] where h i = kk-sign(f d (k))τ,a i ,b i c i d i A i B i C i D i are the cubic interpolation coefficients, which are obtained by the cubic interpolation formula.

[0135] Step 6: Substitute all the acquired Doppler and satellite position velocity initial positions into the Doppler positioning formula to solve.

[0136] Step 6.1, simplify the Doppler formula according to the position relationship between the receiver and the transmitter;

[0137] Step 6.1.1, the basic Doppler frequency shift formula is as follows, where f d is the measured Doppler shift, is the rate at which the distance between the satellite and the receiver changes, c is the speed of light, and f c is the carrier frequency

[0138]

[0139] Step 6.1.2: In the Earth-Centered, Earth-Fixed ECEF coordinate system, It can be expressed as follows, where P SA (k) and P R are the corrected satellite position at the kth sampling moment and the receiver position, V SA (k) and V R are the corrected satellite velocity at the kth sampling moment and the received motion velocity respectively;

[0140]

[0141] Step 6.1.3: When the receiver is moving slowly or is stationary, the speed can be ignored relative to the transmitter speed. Then simplify the formula as follows:

[0142]

[0143] Step 6.1.4: When the receiver receives multiple satellite signals, multiple satellite positions and corresponding Doppler shifts are solved and the formula is modified as follows, where δ r The Doppler error caused by the common clock difference between the satellite and the receiver can be solved and eliminated in subsequent iterations:

[0144]

[0145] Step 6.2: Linearize the above formula using the Levenberg–Marquardt algorithm and solve it iteratively;

[0146] Step 6.2.1: After linearizing the formula, its differential expression is:

[0147] Fd=J·Δx+ξ

[0148] in J is the linearized Jacobian matrix

[0149] Step 6.2.2, solve its Jacobian matrix J, the Jacobian matrix expression is:

[0150]

[0151] Step 6.2.3: Use the Levenberg–Marquardt algorithm to bring in the initial position and iterate the equation, which is expressed as:

[0152] Δx=(J T WJ+λI) -1 J T WΔF d

[0153] where Δx is the differential form of the receiver position vector, J is the Jacobian matrix, W is the weight matrix (usually the identity matrix), λ is the damping parameter, I is the identity matrix, and ΔF d is the differential form of the observation vector of the Doppler shift.

[0154] Step 6.2.2: Iterate and update the receiver position P using the above formula R , until the residual converges.

[0155] Table 1 Receiver parameters

[0156] Parameter name Numeric Sampling rate 2MHz Center frequency 1626.25MHz bandwidth 1MHz Sampling time 10mins

[0157] The present implementation mode is further described below in conjunction with specific embodiments;

[0158] Example:

[0159] Build a receiving device, which consists of USRP, host computer and receiving antenna. Set the center frequency to 1626.25, the bandwidth to 1MHZ, and the sampling rate to 2MHz.

[0160] The traditional Doppler positioning algorithm and the opportunity signal positioning error compensation algorithm based on Iridium IRA are used to simulate and compare under the same environment. The parameters are shown in Table 2. The results are shown in Figure 2 As shown in the figure, the signal error cannot be well simulated in the simulation. The same set of data collected in the same environment is compared using the traditional Doppler positioning algorithm and the method adopted by the present invention. Partial sampling is used for repeated positioning, full sampling is used for positioning, and the opportunity signal positioning error compensation algorithm based on Iridium IRA is used for comparison. The useful information parsed from the downlink signal is shown in Table 3. PSO is used for The optimization result is shown in the figure Figure 3 As shown, its time Doppler diagram is as follows Figure 4 As shown, the results are Figure 5 As shown in Table 7, the positioning result errors of the two algorithms for the same data are shown.

[0161] Table 2 Simulation parameters

[0162]

[0163] Table 3 Measured analysis data of some Iridium downlink signals

[0164]

[0165]

[0166] Table 4. The actual positioning results of the traditional algorithm and the algorithm proposed in this paper

[0167]

[0168] Combining the above data and Figure 5 It can be seen that the positioning accuracy obtained by the traditional Doppler positioning algorithm is 126.6618m and 48.431m, and the root mean square error is 126.662m. The positioning accuracy obtained by the algorithm proposed in this patent is -100.767m and 31.554m, and the root mean square error is 105.592m. Compared with the traditional Doppler positioning algorithm, the root mean square error of the positioning accuracy obtained by this algorithm is reduced by 24.56m. Therefore, the improved algorithm has higher positioning accuracy.

[0169] In summary, the algorithm proposed in the present invention realizes Iridium opportunity signal positioning. Moreover, while realizing Doppler positioning, the algorithm can estimate the initial position through the PSODC algorithm to correct the satellite position and speed, reduce the estimation error of the satellite position and speed, and improve the accuracy of low-orbit satellite opportunity signal positioning.

[0170] Figure 1 Any process or method description in the flowchart described in or otherwise described herein can be understood as representing a module, fragment or portion of a code including one or N executable instructions for implementing the steps of a custom logic function or process, and the scope of the preferred embodiment of the present invention includes other implementations, in which the functions may be performed in a substantially simultaneous manner or in a reverse order according to the functions involved, which should be understood by a person skilled in the art of the technical field to which the embodiments of the present invention belong. The logic and / or steps represented in the flowchart or otherwise described herein illustrate the possible implementation architecture, functions and operations of the apparatus and methods according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of a code contains one or more executable instructions for implementing the specified logic function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in reverse order, depending on the functions involved. It is also noted that each block in the block diagram or flowchart, and combinations of blocks in the block diagram or flowchart, may be implemented by a dedicated hardware-based system that performs the specified functions or operations, or may be implemented by a combination of dedicated hardware and computer instructions. For example, what may be considered as an ordered list of executable instructions for implementing a logical function may be embodied in any computer-readable medium for use by an instruction execution system, apparatus or device, such as a computer-based system, a system including a processor, or other system that can fetch instructions from and execute instructions from an instruction execution system, apparatus or device, or used in conjunction with such instruction execution systems, apparatuses or devices.

[0171] Those skilled in the art will appreciate that the above are only preferred embodiments of the present invention, and the various embodiments of the present disclosure and / or the features described in the claims may be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. It is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments, or perform equivalent substitutions on some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

[0172] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for compensating positioning errors of opportunity signals based on Iridium IRA, characterized in that: The method comprises the following steps: S1. Connect the receiver hardware to receive Iridium downlink signals; S2, analyzing the received Iridium downlink signal; S3, demodulating the received Iridium downlink signal to obtain Iridium downlink information IRA; S4. Obtain the projection longitude and latitude of the Iridium satellite relative to the earth's surface based on the Iridium satellite downlink information IRA Calculate the average projection position of multiple data S5. Based on the calculated average projection position And the visible range of Iridium satellites, the rough position solution is calculated based on the global particle swarm algorithm S6. Solve based on rough position Get the propagation delay τ; S7. Use TLE file and SGP4 file to determine the satellite position, and use propagation delay τ to calculate the satellite position and speed S8. Use the maximum likelihood estimation method to determine the Doppler shift of the IRA11 band signal center frequency in the Iridium downlink signal S9, the initial position Satellite Position and speed Doppler shift The Doppler positioning equation is substituted into the position solution through least square method, and the satellite position is corrected by the opportunity signal positioning error compensation method based on Iridium IRA.

2. The method for compensating positioning error of opportunity signal based on Iridium IRA according to claim 1, characterized in that: The Iridium downlink signal received by S2 is obtained by analyzing it through a Butterworth filter.

3. The method for compensating positioning error of opportunity signal based on Iridium IRA according to claim 1, characterized in that: S3 specifically includes: S3.1, filtering the received Iridium downlink signal and performing a windowing operation on it; S3.2, set the windowed signal strength threshold, cyclically judge the entire frequency domain signal, and capture the pilot information of the windowed signal; S3.3, set the period to 90ms and capture the next windowed signal; S3.4, demodulate the next captured windowed signal using BPSK to obtain a binary code; S3.

5. Decode the windowed signal according to the Iridium IRA binary coding rule. The Iridium IRA parses the windowed signal to include the projection longitude and latitude LAT and LON of the satellite position on the earth, and the satellite number of the Iridium downlink signal, thereby completing the acquisition of the Iridium downlink information IRA.

4. The method for compensating positioning error of opportunity signal based on Iridium IRA according to claim 3, characterized in that: Design a global particle swarm algorithm in S5 to solve the rough position solution The method is: S5.1, initialize the variables of the particle swarm; S5.

2. Based on the calculated average projection position And the particle boundary is obtained from the radiation range of the Iridium downlink signal: S5.

3. Calculate the PSO optimization objective function according to the Doppler frequency shift formula: Where p = [φ, λ] is the target latitude and longitude of the receiver, and [x, y, z] can be obtained as follows: in e is the radius of the Earth; S5.

4. Use PSO algorithm to traverse and obtain the optimal solution 5. The method for compensating positioning error of opportunity signal based on Iridium IRA according to claim 1, characterized in that: S6 solves the problem based on the rough position The method to obtain the propagation delay τ is: S6.

1. Based on the calculated propagation delay S6.

2. Satellite position based on propagation delay Make compensation Among them, h i = kk-sign(f d (k))τ,a i ,b i c i d i A i B i C i D i are the cubic interpolation coefficients, which are obtained by the cubic interpolation formula.

6. The method for compensating positioning error of opportunity signal based on Iridium IRA according to claim 1, characterized in that: In S7, propagation delay τ is used to calculate and optimize satellite position estimation to solve satellite position and speed The method is: S7.

1. Obtain the satellite orbit plane inclination and ascending node right ascension information; S7.2, establish the SGP4 model based on satellite TLES information; S7.

3. Obtain the satellite position velocity sequence output by the SGP4 model and 7. The method for compensating positioning error of opportunity signal based on Iridium IRA according to claim 1, characterized in that: In S8, the maximum likelihood estimation method was used to determine the Doppler shift of the center frequency of the IRA11 band signal in the Iridium downlink signal. The method is: S8.

1. Determine the rough Doppler estimate using fast Fourier transform for the window where the pilot is located S8.

2. Add a window in the frequency domain and use the maximum likelihood estimation method to determine the fine Doppler signal in the frequency domain. S8.3, according to the windowed time and Doppler curve diagram, and compared with the ID of the Iridium downlink signal satellite analyzed in step 2, the Doppler frequency shift of the IRA 11 frequency band signal center frequency in the Iridium downlink signal is completed. confirmation.

8. The method for compensating positioning error of opportunity signal based on Iridium IRA according to claim 1, characterized in that: Initial position in S9 Calculated by PSODC algorithm.

9. A computer device comprising a memory and a processor, characterized in that A computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the method according to any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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