A Threshold-Free Receiver Autonomous Integrity Monitoring Method

Abstract

The present invention discloses a method for autonomous integrity monitoring of a threshold-free receiver, comprising: step 1, solving a receiver initial position solution vector; step 2, calculating a post-positioning pseudo-range residual value of each GNSS satellite according to the receiver initial position solution vector; step 3, finding the maximum value #imgabs0# among the post-positioning pseudo-range residual values ​​and setting it as a parameter σ max Assignment, σ max Satisfies: #imgabs1#Step 4, set the parameter σ max Divide into k equal parts, where k≥2, and thereby obtain k sub-intervals; step five, set a counter with an initial value of zero for each GNSS satellite; step six, for each sub-interval, check whether the residual pseudo-range value after positioning of each GNSS satellite is within the sub-interval range, if so, add 1 to the count of the corresponding counter; step seven, construct a weight matrix, and use the weighted least squares algorithm to re-solve to obtain a new receiver position solution vector. The present invention can eliminate the problem that the RAIM algorithm needs to manually set the detection threshold, can be applied to different positioning scenarios, and improve positioning performance.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation and positioning, and in particular to a threshold-free receiver autonomous integrity monitoring method. Background Art

[0002] At present, satellite positioning has fully entered the era of multiple global navigation satellite systems (Global Navigation Satellite System, GNSS). The world's four core GNSS constellations (China's Beidou, the United States' GPS, Russia's GLONASS, and Europe's Galileo) provide a total of more than one hundred navigation satellites. Users around the world can receive signals from more than ten or even more than thirty GNSS satellites at any time. Therefore, the status quo of satellite navigation positioning has changed a lot. In many urban positioning scenarios, the main problem faced by users is no longer the inability to obtain a sufficient number of visible satellites, but to correctly detect and exclude those satellites that are severely affected by errors such as non-line of sight (NLOS) and multi-path interference to ensure a stable and reliable positioning result.

[0003] Therefore, the receiver autonomous integrity monitoring algorithm (RAIM) has become one of the standard features of modern receiver terminals, including many consumer-grade terminals. The concept of the RAIM algorithm was first created and developed in the field of civil aviation. The purpose is to autonomously monitor the health of navigation satellite signals and promptly warn users when abnormalities or failures occur. Its basic principle is to check the consistency of the measurement values, that is, the position solution produced by the measurement values ​​that are severely contaminated by NLOS and multipath is less consistent than that of the "pure" and line of sight (LOS) satellite measurements. In other words, the position solution obtained using the correct measurement values ​​is more consistent than the position solution obtained using the measurement values ​​affected by NLOS and multipath errors. Therefore, the measurement values ​​can be evaluated and screened accordingly. By eliminating the faulty measurement values, a more accurate and reliable position solution result can be obtained.

[0004] With the continuous efforts of researchers, some variants and improved RAIM algorithms have been proposed to better eliminate abnormal or gross measurement values ​​and ensure the reliability of positioning results. However, one of the key factors that determine its performance is how to determine the detection quantity and its threshold. Generally, the RAIM algorithm uses the pseudorange residual after satellite positioning as the detection quantity, and believes that when the detection quantity exceeds a given threshold δ, the corresponding satellite measurement value has a serious error and should be eliminated; otherwise, the measurement value is considered reliable and should be retained. Therefore, the most critical point of RAIM and its variant algorithms is to determine the detection threshold δ (which actually depends on the pseudorange measurement error σ), which directly determines the accuracy of the detection result. However, since it is difficult to estimate and determine the exact value of the pseudorange measurement error σ, it can generally only be given in advance by the user based on his own experience. In addition, σ also changes with the positioning environment (such as open or blocked) and the satellite constellation. Therefore, in actual positioning work, the user-defined measurement error σ and its detection threshold δ are generally difficult to match the actual situation well. Another embarrassing problem is that although RAIM can identify and eliminate measurements with serious errors, it may not necessarily obtain the best position solution. This is because the GNSS positioning accuracy depends not only on the pseudo-range measurement error, but also on the size of the satellite constellation geometric precision factor (Dilution of Precision, DOP). Therefore, the RAIM algorithm may cause the deterioration of the constellation DOP value due to the deletion of satellites in certain specific spatial directions, and thus may not necessarily obtain the best positioning result in the end. These situations seriously restrict the actual performance of the RAIM algorithm and its adaptability to different positioning scenarios. Summary of the invention

[0005] In view of this, an embodiment of the present invention proposes a threshold-free receiver autonomous integrity monitoring method, which is used to eliminate the RAIM algorithm's reliance on artificially setting a detection threshold, and can be applied to different positioning scenarios and improve the positioning performance of user receivers.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a threshold-free receiver autonomous integrity monitoring method, comprising:

[0007] Step 1: Use GNSS satellites and their pseudo-range measurements to obtain the receiver initial position solution vector Δx0;

[0008] Step 2: Calculate the residual pseudo-range value of each GNSS satellite after positioning based on the receiver initial position solution vector Δx0 Where n is the number of GNSS satellites;

[0009] Step 3: Find the residual value of the pseudorange after positioning The maximum value in and the parameter σ max Assignment, where the parameter σ max satisfy:

[0010] Step 4: Set the parameter σ max Divide into k equal parts, where k ≥ 2, and thus obtain k sub-intervals, the ranges are:

[0011] Step 5: Set a counter Q with an initial value of zero for each GNSS satellite. i (i=1,2,…,n);

[0012] Step 6: for each of the sub-intervals, check the residual pseudo-range values ​​of each GNSS satellite after positioning one by one. Is it within the range of the sub-interval? If so, the counter Q corresponding to the GNSS satellite is set to i The count of (i=1,2,…,n) is increased by 1, otherwise the count remains unchanged;

[0013] Step 7: Using the counter Q i (i=1,2,…,n) count values, construct a diagonal weight matrix W: W=diag(Q1,Q2,…,Q n ), and use the weighted least squares algorithm to re-solve and obtain the new receiver position solution vector Δx.

[0014] By using the threshold-free receiver autonomous integrity monitoring method provided by the present invention, the confidence of each GNSS satellite measurement value is statistically obtained by performing 0 / 1 discretization sampling processing on the post-positioning pseudo-range residual of the GNSS satellite, and a weight matrix is ​​constructed therefrom to adaptively suppress those measurements with low confidence (i.e., large measurement errors). Thus, it not only achieves better performance and effect than the traditional RAIM algorithm, but also eliminates the defect of the traditional RAIM algorithm that the detection threshold value needs to be set manually based on experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention provides a threshold-free receiver autonomous integrity monitoring method. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is described in detail below in conjunction with the drawings and specific implementation methods. The embodiments of the present disclosure are further described in detail below in conjunction with the drawings and specific implementation methods, but are not intended to limit the present disclosure.

[0017] The words "first", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different parts. The words "include" or "comprise" and similar words mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of including other elements. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0018] All terms (including technical terms or scientific terms) used in the present disclosure have the same meanings as those understood by ordinary technicians in the field to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries, such as general dictionaries, should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined herein.

[0019] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0020] In view of the above problems existing in the traditional RAIM algorithm, the inventor of the present invention provides a threshold-free receiver autonomous integrity monitoring method, comprising the following steps:

[0021] Step 1: Use GNSS satellites and their pseudo-range measurements to obtain the receiver initial position solution vector Δx0;

[0022] Step 2: Calculate the residual pseudo-range value of each GNSS satellite after positioning based on the receiver initial position solution vector Δx0 Where n is the number of GNSS satellites;

[0023] Step 3: Find the residual value of the pseudorange after positioning The maximum value in and the parameter σ max Assignment, where the parameter σ max satisfy:

[0024] Step 4: Set the parameter σ max Divide into k equal parts, where k ≥ 2, and thus obtain k sub-intervals, the ranges are:

[0025] Step 5: Set a counter Q with an initial value of zero for each GNSS satellite. i (i=1,2,…,n);

[0026] Step 6: for each of the sub-intervals, check the residual pseudo-range values ​​of each GNSS satellite after positioning one by one. Is it within the range of the sub-interval? If so, the counter Q corresponding to the GNSS satellite is set to i The count of (i=1,2,…,n) is increased by 1, otherwise the count remains unchanged;

[0027] Step 7: Using the counter Q i (i=1,2,…,n) count values, construct a diagonal weight matrix W: W=diag(Q1,Q2,…,Q n ), and use the weighted least squares algorithm to re-solve and obtain the new receiver position solution vector Δx.

[0028] Specifically, in the step 1, the receiver initial position solution vector Δx0 is obtained by using the least squares algorithm and utilizing the available GNSS satellites and their pseudo-range measurement values.

[0029] According to the basic principle of satellite navigation positioning, the GNSS observation equation group has a matrix form as shown in formula (1):

[0030] GΔx0=b (1)

[0031] Where: G is the satellite direction cosine matrix; Δx0 is the initial position solution vector composed of the three-dimensional coordinate position and clock error of the user receiver; b is the residual vector of the pseudo-range observation value before GNSS satellite positioning.

[0032] Using the least squares algorithm to solve equation (1), we have:

[0033] Δx0=(G T G) -1 G T b (2)

[0034] In the step 2, the residual pseudo-range value after positioning of each GNSS satellite is calculated based on the initial position solution vector Δx0 of the receiver. Where n is the number of GNSS satellites. Preferably, it is not necessary to solve the positioning equation (2) before calculating the post-positioning pseudorange residual Assuming that the change in the three-dimensional coordinate position and clock error of the user receiver is small, the satellite direction cosine matrix G before and after positioning can be considered equal. Therefore, the pseudo-range residual vector b before positioning can be quickly converted to the pseudo-range residual vector after positioning using equation (3).

[0035]

[0036] In step 3, find the residual value of pseudorange after each positioning (i.e. vector ) and the parameter σ max Assignment, where the parameter σ max satisfy: Preferably, in practical use, the parameter σ max The value of That's it.

[0037] In step 4, the parameter σ max Divide into k equal parts, where k ≥ 2, and thus obtain k sub-intervals, the ranges are: Preferably, in practical use, the parameter k can be 5≤k≤10.

[0038] In step 5, a counter Q with an initial value of zero is set for each GNSS satellite. i (i=1,2,…,n).

[0039] In step 6, for each of the sub-intervals in step 4, the post-positioning pseudo-range residual values ​​of each of the GNSS satellites are checked one by one. Is it within the range of the sub-interval? If so, the counter Q corresponding to the GNSS satellite is set to i The count of (i=1,2,…,n) is increased by 1, otherwise the count remains unchanged.

[0040] In step seven, the counter Q is used i (i=1,2,…,n) count values, construct a diagonal weight matrix W: W=diag(Q1,Q2,…,Q n ), and use the weighted least squares algorithm to re-solve and obtain the new receiver position solution vector Δx.

[0041] The positioning equation when solving with the weighted least squares algorithm is:

[0042] Δx=(G T CG) -1 G T Cb (4)

[0043] Where C = W T W.

[0044] By using the threshold-free receiver autonomous integrity monitoring method provided by the present invention, those measurements with low confidence (i.e., those whose measurement errors are considered to be large) can be adaptively suppressed. Thus, the performance and effect of the traditional RAIM algorithm can be obtained, and the defect of the traditional RAIM algorithm that the detection threshold value needs to be set manually based on experience is eliminated, and it can adapt to different positioning scenarios and improve the positioning performance of the user receiver.

[0045] A number of embodiments of the present invention have been described in detail above, but the present invention is not limited to these specific embodiments. Those skilled in the art can make various variations and modifications to the embodiments based on the concept of the present invention, and these variations and modifications should all fall within the scope of protection claimed by the present invention.

Claims

1. A threshold-free receiver autonomous integrity monitoring method, comprising: Step 1: Use GNSS satellites and their pseudo-range measurements to obtain the receiver initial position solution vector Δx0; Step 2: Calculate the residual pseudo-range value of each GNSS satellite after positioning based on the receiver initial position solution vector Δx0 Where n is the number of GNSS satellites; Step 3: Find the residual value of the pseudorange after positioning The maximum value in and the parameter σ max Assignment, where the parameter σ max satisfy: Step 4: Set the parameter σ max Divide into k equal parts, where k ≥ 2, and thus obtain k sub-intervals, the ranges are: Step 5, setting a counter Qi (i=1, 2, ..., n) with an initial value of zero for each of the GNSS satellites; Step 6: for each of the sub-intervals, check the residual pseudo-range values ​​of each GNSS satellite after positioning one by one. whether it is within the range of the subinterval, if so, adding 1 to the count of the counter Qi (i=1, 2, ..., n) corresponding to the GNSS satellite, otherwise the count remains unchanged; Step 7: Using the count value of the counter Qi (i=1, 2, ..., n), construct a diagonal weight matrix W: W=diag(Q1, Q2, ..., Q n ), and use the weighted least squares algorithm to re-solve and obtain the new receiver position solution vector Δx.

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