A time-difference threshold-based target positioning tracking method and time-difference positioning system

Abstract

The application provides a target positioning tracking method based on a time difference threshold and a time difference positioning system, which comprises the following steps: firstly, obtaining a determined target at a current time, and preliminarily predicting the position of the target at the next time through the position and speed information of the target at the current time; discarding observation points with a large distance difference, and collecting observation points meeting the distance requirement; accurately predicting the position of the target according to the position and speed of the target, inversely calculating the measured time difference according to the accurately predicted position information; and calculating the measured time difference of the observation points; calculating the error variance between the measured time difference of the observation points and the observed time difference of the predicted points; only the observation points with the measured time difference error variance lower than a certain time difference threshold are considered as new observation information of the target to be tracked, and can be associated with the target to be tracked and the position of the target to be tracked is updated; then, the cycle iteration is performed at the next observation time, and the continuous tracking of the target is maintained.

Description

Technical Field

[0001] This invention relates to the field of time difference positioning system technology, and more specifically, to a target positioning and tracking method and a time difference positioning system based on a time difference threshold. Background Technology

[0002] Time difference positioning systems have the advantages of relatively simple system design and high positioning accuracy, and are widely used in the location and tracking of interference sources. By continuously observing the interference source target, its trajectory can be formed.

[0003] Existing target tracking methods in time difference positioning systems mainly involve associating observation points with known targets through a tracking gate. The tracking gate is a geographical region centered on the predicted location, and the shape of the region can be circular, truncated fan-shaped, elliptical, rectangular, etc. The targets within the tracking gate are then associated and fused. The association methods are also based on nearest neighbor algorithms centered on the predicted location, joint probabilistic data association methods, etc. These methods were first applied in the field of radar detection, and they all start from the position and velocity of the newly observed target to associate and track the target. Therefore, they are widely used in single-station direction finding and positioning, multi-station time difference positioning and other systems.

[0004] Existing target tracking technologies all use the current position of the observation point as a reference, treating the target's positioning error as a uniform positional distribution, lacking targeted analysis and processing of the positioning error. In multi-station time difference positioning scenarios, due to changes in target position and observation station distribution, the target position positioning error is large and the positioning distribution is uneven. Using traditional tracking methods such as distance gates will cause target tracking errors and failure to correlate. Summary of the Invention

[0005] This invention aims to at least address one of the technical problems in the prior art: the lack of targeted analysis and processing of positioning errors; the large positioning error and uneven positioning distribution caused by changes in target location and observation station distribution in multi-station time difference positioning scenarios; and the fact that traditional tracking methods such as distance gates can cause target tracking errors and failure to correlate.

[0006] Therefore, the first aspect of the present invention provides a target localization and tracking method based on time difference threshold.

[0007] A second aspect of the present invention provides a time difference positioning system.

[0008] This invention provides a target localization and tracking method based on time difference threshold, comprising the following steps:

[0009] S1. Obtain the current trajectory information of the target to be tracked, and predict the position information of the target to be tracked at the next moment based on the existing trajectory information of the target to be tracked.

[0010] S2. Establish a positioning equation that includes the position coordinates of the target to be tracked and the measurement time difference based on the position coordinates of the observation station;

[0011] S3. Substitute the predicted position coordinates of the target to be tracked in S1 into the positioning equation established in S2, and calculate the measurement time difference corresponding to the predicted position coordinates.

[0012] S4. Use the coordinate information of all observation points that may be the next position of the target to be tracked as observed by the time difference positioning system as the position coordinate information of the target to be tracked, and input them into the positioning equation established in S2 to calculate the measurement time difference corresponding to the observation point.

[0013] S5. Compare the measurement time difference calculated in S4 with the measurement time difference calculated in S3 to determine whether the measurement time difference of the observation point meets the time difference threshold requirement; if it does not meet the threshold, the observation point will not be associated with the target to be tracked; if it does meet the threshold, the observation point will be associated with the target to be tracked.

[0014] S6. Calculate the position information of the target at the next moment based on the measurement time difference corresponding to all observation points associated with the target. After completing the position update, repeat S1~S5 to maintain the tracking of the target.

[0015] According to the above-described target localization and tracking method based on time difference threshold of the present invention, it may further have the following additional technical features:

[0016] In the above technical solution, S1 includes the following steps:

[0017] S11. Based on the current position and velocity information of the target to be tracked, use the dynamic equations to make a preliminary prediction of the target's position information at the next moment;

[0018] S12. Obtain the location information of all observation points, and determine whether the observation points exceed the distance threshold compared with the preliminary predicted location information in S11. Discard the observation points that exceed the distance threshold and retain the observation points that meet the distance threshold.

[0019] S13. Based on the current position and velocity information of the target to be tracked, use the Kalman filter method to accurately predict the position information of the target to be tracked at the next moment.

[0020] In the above technical solution, S2 establishes a positioning equation based on the intersection of the time difference measurement surface and the Earth's sphere:

[0021]

[0022]

[0023] in,( x, y, z) represents the position coordinates of the target to be tracked. X i ，Y i ，Z i ( ) represents the location coordinates of the observation station. e The eccentricity of the Earth ellipsoid model. C At the speed of light, T 1 and T 2 is for measuring time difference. a It is the radius of the Earth's major axis.

[0024] In the above technical solution, the method for determining whether the measurement time difference of the observation point meets the time difference threshold requirement in S5 is as follows:

[0025]

[0026] Where K is the threshold constant for time difference, ρ The standard deviation of the residuals. T 1i and T 2i This represents the measurement time difference corresponding to the observation points in S4. T 1p and T 2p This represents the measurement time difference corresponding to the predicted position coordinate information in S3.

[0027] In the above technical solution, the standard deviation of the residual is calculated as follows:

[0028]

[0029] in, ρ d This is due to time difference measurement error. ρ p This is the time difference deviation converted from the location prediction error.

[0030] In the above technical solution, in S6, the average or weighted average of the measurement time differences corresponding to all observation points associated with the target to be tracked is calculated to obtain the measurement time difference of the target to be tracked. The measurement time difference of the target to be tracked is then substituted into the positioning equation established in S2, and the calculation result is used as the position information of the target to be tracked at the next moment.

[0031] The present invention also provides a time difference positioning system, which is applied to a target positioning and tracking method based on a time difference threshold as described in any of the above technical solutions. The time difference positioning system is used for positioning a single target or simultaneously positioning multiple targets.

[0032] According to the time difference positioning system of the present invention, the following additional technical features may also be provided:

[0033] In the above technical solution, the time difference positioning system obtains observation points that may be the next position of the target to be tracked based on the time difference positioning method.

[0034] In summary, due to the adoption of the above-mentioned technical features, the beneficial effects of the present invention are:

[0035] Compared to the traditional method of tracking targets using a range gate, this invention can maintain a relatively stable measurement error of time difference even when the configuration and position of the observation station are constantly changing, and can still continuously track the target to form a very good continuous track.

[0036] Tracking targets from the perspective of time difference measurement can eliminate the impact of target position changes caused by differences in target position and observation station configuration, simplify the target tracking process, and improve the accuracy of target tracking and positioning.

[0037] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0039] Figure 1 This is a flowchart of a target localization and tracking method based on a time difference threshold according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram showing the distribution of measurement values ​​at different locations relative to the observation station;

[0041] Figure 3 This is a basic diagram of target tracking principles;

[0042] Figure 4 This is a schematic diagram illustrating the target tracking effect using a traditional distance gate.

[0043] Figure 5 This is a schematic diagram illustrating the target tracking effect of a time difference positioning system according to an embodiment of the present invention;

[0044] Figure 6 This is a comparison diagram of the tracking performance of a time difference positioning system according to an embodiment of the present invention and a positioning system using a traditional distance gate for tracking two targets moving in parallel.

[0045] Figure 7 This is a comparison diagram of the tracking performance of a time difference positioning system according to an embodiment of the present invention and a positioning system using a traditional distance gate for dual targets with intersecting flight paths. Detailed Implementation

[0046] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0048] The following reference Figures 1 to 7 This invention describes a target localization and tracking method and a time difference localization system based on a time difference threshold, provided by some embodiments of the present invention.

[0049] Some embodiments of this application provide a target localization and tracking method based on time difference threshold.

[0050] like Figures 1 to 7 As shown, the first embodiment of the present invention proposes a target localization and tracking method based on time difference threshold, including the following steps:

[0051] S1. Obtain the current trajectory information of the target to be tracked, which includes the coordinate position and velocity information of the target to be tracked at the current moment; predict the position information of the target to be tracked at the next moment based on the existing trajectory information of the target to be tracked.

[0052] Specifically, S1 includes the following steps:

[0053] S11. Based on the current position and velocity information of the target to be tracked, use the dynamic equations to make a preliminary prediction of the target's position information at the next moment;

[0054] Based on the dynamic equations, given the direction of motion, velocity, and time interval of the target to be tracked, the position information of the target at the next moment can be preliminarily predicted, thus completing a coarse prediction of the target's position.

[0055] S12. Obtain the location information of all observation points, and determine whether the observation points exceed the distance threshold compared with the preliminary predicted location information in S11. Discard the observation points that exceed the distance threshold and retain the observation points that meet the distance threshold.

[0056] Under the same time difference measurement error, the positioning accuracy will vary depending on the relative position of the distance observation station. Furthermore, the distribution of observations at multiple observation locations for the same target will also differ. Figure 2 The figure shows the distribution of measured values ​​at different locations relative to the observation station under simulation conditions:

[0057] The observation points are all points observed by the observation station that could be the next position of the target to be tracked. The position information of the observation points can be obtained based on the measurement time difference measured by the observation station. When the coordinate position of the observation point differs too much from the preliminary predicted coordinate position of the target to be tracked, it is determined that the observation point exceeds the specified distance threshold. The distance threshold can be set according to the time interval and the target speed. There is no need to associate the observation points that exceed the distance threshold, so it is sufficient to retain the observation points that meet the distance threshold requirements.

[0058] S13. Based on the current position and velocity information of the target to be tracked, use the Kalman filter method to accurately predict the position information of the target to be tracked at the next moment.

[0059] Among them, the use of Kalman filtering to accurately predict the position information of the target to be tracked at the next moment is a technique used in traditional target positioning and tracking methods. Compared with the coarse prediction position in S11, it can further obtain more accurate prediction results.

[0060] S2. Establish a positioning equation that includes the position coordinates of the target to be tracked and the measurement time difference based on the position coordinates of the observation station;

[0061] In S2, taking a typical three-station time difference positioning system as an example, the target is located by intersecting two time difference surfaces with the Earth's sphere, and the positioning equation is established as follows:

[0062]

[0063]

[0064] in,( x, y, z ) represents the position coordinates of the target to be tracked. X i ，Y i ，Z i ( ) represents the location coordinates of the observation station. e The eccentricity of the Earth ellipsoid model. C At the speed of light, T 1 and T 2 is for measuring time difference. a It is the radius of the Earth's major axis.

[0065] S3. Substitute the predicted position coordinates of the target to be tracked from S1 into the positioning equation established in S2, and calculate the measurement time difference corresponding to the predicted position coordinates. T 1p and T 2p ;

[0066] S4. Substitute the coordinates of all observation points observed by the time difference positioning system that could be the next position of the target to be tracked into the positioning equation established in S2 to calculate the measurement time difference corresponding to the observation points. T 1i and T 2i ;

[0067] S5. Compare the measurement time difference calculated in S4 with the measurement time difference calculated in S3 to determine whether the measurement time difference of the observation point meets the time difference threshold requirement; if it does not meet the threshold, the observation point will not be associated with the target to be tracked; if it does meet the threshold, the observation point will be associated with the target to be tracked.

[0068] When performing multi-target tracking, observation points that exceed the distance threshold discarded in S12 and observation points that do not meet the time difference threshold requirements in S5 can be used as observation points associated with other targets, and it is also necessary to determine the distance threshold and time difference threshold.

[0069] The method in S5 for determining whether the measurement time difference of the observation point meets the time difference threshold requirement is as follows:

[0070]

[0071] Where K is the threshold constant for time difference (which can be set to 1 by default and can be adjusted according to the actual tracking effect). ρ The standard deviation of the residuals. T 1i and T 2i This represents the measurement time difference corresponding to the observation points in S4. T 1p and T 2p This represents the measurement time difference corresponding to the predicted position coordinate information in S3.

[0072] The standard deviation of the residuals is calculated as follows:

[0073]

[0074] in, ρ d For time difference measurement error (e.g., with a base length of 100km and a required positioning accuracy of 1km, the system's time difference measurement error is approximately 50ns). ρ p The time difference deviation (usually around 10ns) is converted from the position prediction error.

[0075] The basic principles of target tracking are as follows Figure 3 As shown, assume the target's current predicted position is Z. pThe measurement time difference of the prediction result can be calculated using the positioning equation in S2. T 1p and T 2p Similarly, we can calculate the value of each observation point. Z i Corresponding time difference T 1i and T 2i Substituting the calculation results into the formula in S5 for determining whether the measurement time difference of the observation point meets the time difference threshold requirement, we can determine whether the observation point is associated with the target to be tracked. That is, only observation points with time difference errors below a certain threshold are considered as new observation information of the target to be tracked.

[0076] S6. Calculate the position information of the target at the next moment based on the measurement time difference corresponding to all observation points associated with the target. After completing the position update, repeat S1~S5 to maintain the tracking of the target.

[0077] In S6, the average or weighted average of the measurement time differences corresponding to all observation points associated with the target to be tracked is calculated to obtain the measurement time difference of the target to be tracked. T 1t and T 2t The measurement time difference of the target to be tracked T 1t and T 2t Substituting the positioning equation established by S2, the position coordinates of the target to be tracked are calculated in reverse, and the calculation result is used as the position information of the target to be tracked at the next moment.

[0078] The second embodiment of the present invention proposes a target localization and tracking method based on a time difference threshold, and, based on the first embodiment, as follows: Figures 1 to 7 As shown, the process includes the following:

[0079] First, the target at the current moment is identified. Using the target's current position and velocity information, a preliminary prediction of the target's position at the next moment is made. Then, the position information of observation points is obtained through all measurement time differences measured by the measurement stations. Observation points with significantly different distances are discarded, and those meeting the distance requirements are collected. Based on the target's position and velocity, a precise position prediction is made, and the measurement time difference is calculated from the precise predicted position information. The measurement time difference of each observation point is then calculated. The variance of the error between the measurement time difference of an observation point and the observation time difference of the predicted point is calculated. Only observation points with a measurement time difference error variance below a certain time difference threshold are considered new observation information for the target to be tracked. These observations can then be correlated with the target and their positions updated. The process then proceeds to the next observation moment for iterative tracking, maintaining continuous target tracking. The flowchart is as follows: Figure 1 As shown.

[0080] The third embodiment of the present invention proposes a time difference positioning system, in which the target positioning and tracking method based on time difference threshold as described in any of the above embodiments is applied;

[0081] like Figure 4 The diagram shows the effect of tracking a known ship target using a traditional distance gate based on actual observation data. All positioning points in the diagram represent the observed position values ​​of a single ship target. The lines represent targets from the same batch generated by the automatic tracking algorithm. Individual points are new batches created due to tracking loss. For the same target, the more individual points processed, the more batches are involved, and the worse the tracking effect.

[0082] As can be seen from the figure, the elliptical area is the region with larger positioning errors due to changes in the configuration of the observation station. If a traditional range gate is used in this area, it will cause severe batching and poor target tracking performance.

[0083] Therefore, when using the traditional range gate method to track targets, regardless of how the range gate is set, changes in the observation station configuration or the relative position between the observation station and the target will cause the target to fail to be tracked, resulting in additional batches or even tracking errors.

[0084] like Figure 5 The figure shows the effect of using the time-difference positioning system of this embodiment to track and locate the target. As can be seen from the figure, even when the system's positioning accuracy deteriorates (within the elliptical area), it can still track the target without causing erroneous batching. A relatively ideal target tracking effect is achieved.

[0085] This embodiment still achieves relatively good tracking performance even in situations where confusion easily occurs in multi-target tracking, such as... Figure 6In a tracking scenario where two targets are 50km apart, the traditional range gate method suffers from target confusion when positioning accuracy deteriorates. Figure 6 (Left), while the time difference positioning system in this embodiment, after adopting the target positioning and tracking method based on the time difference threshold, can effectively distinguish between two targets ( Figure 6 right).

[0086] like Figure 7 This is a comparison chart showing the performance when two target tracks intersect. Traditional range-gate tracking suffers from confusion. Figure 7 (Left), and the time difference positioning system in this embodiment can effectively distinguish between two targets and achieve a good tracking effect after adopting the target positioning and tracking method based on the time difference threshold.

[0087] Therefore, the time difference positioning system used in this embodiment is significantly better than the traditional method for multi-target positioning and tracking.

[0088] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A target localization and tracking method based on time difference threshold, characterized in that, Includes the following steps: S1. Obtain the current trajectory information of the target to be tracked, and predict the position information of the target to be tracked at the next moment based on the existing trajectory information of the target to be tracked. S2. Establish a positioning equation that includes the position coordinates of the target to be tracked and the measurement time difference based on the position coordinates of the observation station; S3. Substitute the predicted position coordinates of the target to be tracked in S1 into the positioning equation established in S2, and calculate the measurement time difference corresponding to the predicted position coordinates. S4. Use the coordinate information of all observation points that may be the next position of the target to be tracked as observed by the time difference positioning system as the position coordinate information of the target to be tracked, and input them into the positioning equation established in S2 to calculate the measurement time difference corresponding to the observation point. S5. Compare the measurement time difference calculated in S4 with the measurement time difference calculated in S3 to determine whether the measurement time difference of the observation point meets the time difference threshold requirement; if it does not meet the threshold, the observation point will not be associated with the target to be tracked; if it does meet the threshold, the observation point will be associated with the target to be tracked. S6. Calculate the position information of the target to be tracked at the next moment based on the measurement time difference corresponding to all observation points associated with the target to be tracked. After completing the position update, repeat S1~S5 to maintain the tracking of the target. In S2, a positioning equation is established based on the intersection of the time difference measurement surface and the Earth's sphere: in,( x, y, z ) represents the position coordinates of the target to be tracked. X i ，Y i ，Z i ( ) represents the location coordinates of the observation station. e The eccentricity of the Earth ellipsoid model. C At the speed of light, T 1 and T 2 is for measuring time difference. a The radius of the Earth's major axis; The method in S5 for determining whether the measurement time difference of the observation point meets the time difference threshold requirement is as follows: Where K is the threshold constant for time difference, ρ The standard deviation of the residuals. T 1i and T 2i This represents the measurement time difference corresponding to the observation points in S4. T 1p and T 2p The measurement time difference corresponding to the predicted position coordinate information in S3; The standard deviation of the residuals is calculated as follows: in, ρ d This is due to time difference measurement error. ρ p This is the time difference deviation converted from the location prediction error.

2. The target localization and tracking method based on time difference threshold according to claim 1, characterized in that, S1 includes the following steps: S11. Based on the current position and velocity information of the target to be tracked, use the dynamic equations to make a preliminary prediction of the target's position information at the next moment; S12. Obtain the location information of all observation points, and determine whether the observation points exceed the distance threshold compared with the preliminary predicted location information in S11. Discard the observation points that exceed the distance threshold and retain the observation points that meet the distance threshold. S13. Based on the current position and velocity information of the target to be tracked, use the Kalman filter method to accurately predict the position information of the target to be tracked at the next moment.

3. The target localization and tracking method based on time difference threshold according to claim 1, characterized in that, In S6, the average or weighted average of the measurement time differences corresponding to all observation points associated with the target to be tracked is calculated to obtain the measurement time difference of the target to be tracked. The measurement time difference of the target to be tracked is then substituted into the positioning equation established in S2, and the calculation result is used as the position information of the target to be tracked at the next moment.

4. A time-difference positioning system, characterized in that, The target localization and tracking method based on time difference threshold is applied to any one of claims 1 to 3, wherein the time difference positioning system is used for the localization of a single target or the simultaneous localization of multiple targets.

5. A time difference positioning system according to claim 4, characterized in that, The time difference positioning system obtains observation points that may be the next position of the target to be tracked based on the time difference positioning method.

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