A Robust Ranging Method for Aerial Search and Rescue Equipment Based on Track Constraints

Abstract

The present invention proposes a robust ranging method for aviation search and rescue equipment based on track constraints. Since when the position of the search and rescue target is fixed or changes little, the change amount of the position of the search and rescue aircraft restricts the change amount of the distance. Therefore, if the change amount of the position of the search and rescue aircraft changes little, but the measured distance value suddenly changes greatly, it indicates that the distance data at this time is abnormal, and further uses the change amount of the position to correct the abnormal change amount of the distance. This method accurately detects the outliers in the ranging data based on the constraint information of the flight track of the search and rescue aircraft, and estimates the change amount of the distance between the search and rescue aircraft and the search and rescue target at the current moment according to the displacement amount of the search and rescue aircraft at the historical moment, so as to correct the outliers in the ranging data and obtain a more accurate ranging result.

Description

Technical Field

[0001] The present invention relates to the field of aviation search and rescue, and specifically to a robust ranging method for aviation search and rescue equipment based on track constraint. Background Art

[0002] An aviation search and rescue system can locate a parachuting pilot or a crashed aircraft and carry out rescue activities, which is an important means to improve the survival probability of the victims. In the case where the satellite navigation equipment carried by the search and rescue target is damaged or the positioning is invalid, the method of ranging plus direction finding can be used to determine the position of the search and rescue target. The currently widely used ranging method is to measure the distance between the search and rescue equipment and the search and rescue target by measuring the transmission time of the radio signal between them. This method has the advantages of simple implementation and high measurement accuracy. However, since the radio signal is easily interfered during the transmission process, there will be a situation where significant outliers exist in the ranging data, which affects the search and rescue effect.

[0003] The existing solutions mainly perform smoothing or filtering processing on the ranging data. Although it can weaken the influence of outliers to a certain extent, the smoothing or filtering processing requires subjective setting of judgment thresholds by humans to distinguish whether the data is abnormal, which mostly depends on personnel experience and cannot accurately distinguish whether the data is abnormal. In addition, data smoothing or filtering also processes normal data, and the correction effect on significant outliers is not ideal, which is not conducive to quickly and accurately determining the position of the search and rescue target. Chinese patent application with publication number CN113326878A discloses "A method, device and computer equipment for removing outliers in track measurement data", which uses the Kalman filter innovation chi-square test method to identify outliers in track measurement data. This method has high implementation complexity and low reliability, and does not utilize the key information of track constraint. Summary of the Invention

[0004] In order to solve the problem of outliers existing in the ranging data of aviation search and rescue equipment, the present invention proposes a robust ranging method for aviation search and rescue equipment based on track constraint. This method can accurately detect outliers in the ranging data based on the constraint information of the flight trajectory of the search and rescue aircraft, and can estimate the change amount of the distance between the search and rescue aircraft and the search and rescue target at the current moment according to the displacement amount of the search and rescue aircraft at the historical moment, so as to correct the outliers in the ranging data and obtain a more accurate ranging result.

[0005] The basic principle of the present invention is that there is a constraint relationship between the change in the position of the search and rescue aircraft and the change in the distance output by the ranging device, that is, when the position of the search and rescue target remains fixed or changes little, the change in the position of the search and rescue aircraft restricts the change in the distance. In this case, if the change in the position of the search and rescue aircraft changes little, but the measured distance value suddenly changes greatly, it indicates that the distance data at this time is abnormal. Further, the abnormal change in the distance can be corrected using the change in the position.

[0006] The technical solution of the present invention is as follows:

[0007] An anti - robust ranging method for aviation search and rescue equipment based on track constraint, comprising the following steps:

[0008] Step 1: The search and rescue aircraft uses the on - board navigation and positioning system to obtain its own position information P, and calculates the displacement ΔP of the search and rescue aircraft between the k - th moment and the (k + 1)-th moment through the position data at the k - th moment and the (k + 1)-th moment k+1,k ; At the same time, the search and rescue aircraft measures the distance R between the search and rescue aircraft and the search and rescue target through radio ranging, and calculates the change in the distance between the k - th moment and the (k + 1)-th moment

[0009] Step 2: According to the relationship between the displacement of the search and rescue aircraft and the change in the distance between the k - th moment and the (k + 1)-th moment, use ΔP k+1,k to estimate the maximum value of the actual change in the distance between the search and rescue aircraft and the search and rescue target between the k - th moment and the (k + 1)-th moment

[0010] Step 3: Consider the distance R between the search and rescue aircraft and the search and rescue target measured at the k - th moment k as a normal value, and judge whether the distance measurement value R k+1 at the (k + 1)-th moment is normal through the following process:

[0011] Add the maximum value ε of the radio ranging error max , and then compare the sum of the two with the measured change in the distance between the k - th moment and the (k + 1)-th moment . If the former is less than the latter, it indicates that the ranging data R k+1 is an abnormal value and needs to be processed by anti - robustness, and enter Step 4; otherwise, the ranging data is normal, return to Step 1 to continue judging the data of the next moment;

[0012] Step 4: According to the actual change in the distance Δr k,k-1 between the (k - 1)-th moment and the k - th moment and the displacement ΔP k+1,k of the search and rescue aircraft between the k - th moment and the (k + 1)-th moment estimate the actual change in the distance between the k - th moment and the (k + 1)-th moment, and use and R k Correct the distance measurement value at the (k + 1)-th moment.

[0013] Furthermore, in step 1, the displacement ΔP of the search and rescue aircraft between the k-th moment and the (k + 1)-th moment k+1,k is defined as:

[0014] ΔP k+1,k =(Δx k+1,k , Δy k+1,k , Δz k+1,k ) T =P k+1 -P k

[0015] where P k =(x k , y k , z k ) T represents the position vector of the search and rescue aircraft at the k-th moment, and Δx k+1,k , Δy k+1,k and Δz k+1,k respectively represent the position change amounts of the search and rescue aircraft in the x-axis, y-axis, and z-axis directions from the k-th moment to the (k + 1)-th moment;

[0016] The distance change amount obtained by radio ranging between the k-th moment and the (k + 1)-th moment is defined as:

[0017]

[0018] R k =cΔt k +ε k

[0019] where R k represents the distance between the search and rescue aircraft and the search and rescue target measured based on radio ranging technology at the k-th moment; c represents the speed of light; Δt k represents the transmission time of the radio signal from the search and rescue aircraft to the search and rescue target, and ε k represents the ranging error at the k-th moment.

[0020] Furthermore, in step 2, the relationship expression between the displacement ΔP k+1,k and the actual distance change amount Δr k+1,k is:

[0021] Δr k+1,k =H k ΔP k+1,k

[0022]

[0023] In the formula, (x, y, z) T represents the position of the search and rescue target, and r k represents the actual distance between the search and rescue aircraft and the search and rescue target at the k-th moment.

[0024] Furthermore, in step 2, the maximum value of the change in the actual distance between the k-th moment and the (k + 1)-th moment is

[0025]

[0026] Furthermore, in step 4, considering that the direction change of the search and rescue aircraft is very small between adjacent moments, we obtain

[0027] H k ≈H k-1

[0028] Using the change in the actual distance Δr between the (k - 1)-th moment and the k-th moment k,k-1 and the displacement ΔP of the search and rescue aircraft between the k-th moment and the (k + 1)-th moment k+1,k , the change in the actual distance between the k-th moment and the (k + 1)-th moment is estimated to be :

[0029]

[0030] where the change in the measured distance between the (k - 1)-th moment and the k-th moment is used to approximate the change in the actual distance Δr between the (k - 1)-th moment and the k-th moment k,k-1 :

[0031]

[0032] The corrected measured distance at the (k + 1)-th moment is obtained as:

[0033]

[0034] Beneficial effects

[0035] The robust ranging method for aviation search and rescue equipment based on track constraints proposed by the present invention has the following advantages:

[0036] 1) When there are outliers in the ranging data, the present invention can accurately detect the outliers based on the constraint information of the track.

[0037] 2) The present invention can estimate the change in the distance at the current moment according to the change in the distance and the data at the previous moment of the track, so as to correct the abnormal ranging data and obtain a more accurate ranging result.

[0038] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Brief Description of the Drawings

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0040] Figure 1 : Schematic diagram of the application scenario of the present invention.

[0041] Figure 2 : Flow chart of the present invention.

[0042] Figure 3 : Schematic diagrams of distances obtained based on radio ranging and track respectively.

[0043] Figure 4 : Amounts of change in distances obtained based on radio ranging and track respectively before calibration.

[0044] Figure 5 : Amounts of change in distances obtained based on radio ranging and track respectively after calibration. Detailed Description of the Embodiments

[0045] Embodiments of the present invention will be described in detail below. The embodiments are exemplary and are intended to explain the present invention, and should not be construed as a limitation of the present invention.

[0046] Aiming at the problem of outliers in the ranging data of aviation search and rescue equipment, the present invention proposes a robust ranging method for aviation search and rescue equipment based on track constraint. Figure 1 shows the application scenario of the present invention. In this figure, after the search and rescue aircraft determines the azimuth of the search and rescue target, it flies towards the search and rescue target and obtains its own position information at different times through the Beidou satellite navigation system. At the same time, the ranging device in the search and rescue aircraft emits a radio signal modulated by BPSK (Binary Phase Shift Keying) and starts timing. After the search and rescue target receives the signal, it immediately replies with a radio signal modulated by the same modulation method. The search and rescue aircraft stops timing after receiving the replied BPSK signal. The ranging system subtracts the signal transceiver processing time from the one-way transmission time of the radio ranging signal, and then multiplies by the speed of light to obtain the transmission distance of the signal, and further obtains the distance between the search and rescue aircraft and the search and rescue target. During the flight of the search and rescue aircraft, the radio ranging signal may be interfered, resulting in obvious abnormally large values in the ranging data. The present invention can detect these outliers in the ranging data and correct them.

[0047] The process of this embodiment is as shown in Figure 2As shown in the figure, it specifically includes the following steps:

[0048] Step 1: The search and rescue aircraft uses the Beidou satellite navigation system to obtain its own position information P, and calculates the displacement ΔP of the search and rescue aircraft between two consecutive moments (moment k and moment k + 1) through the position data of these two moments k+1,k ; At the same time, the search and rescue aircraft measures the distance R between the search and rescue aircraft and the search and rescue target through radio ranging technology, and calculates the change in distance between moment k and moment k + 1

[0049] The displacement ΔP of the search and rescue aircraft between two moments k+1,k is defined as:

[0050]

[0051] In the formula, P k =(x k , y k , z k ) T represents the position vector of the search and rescue aircraft at the k-th moment, and Δx k+1,k , Δy k+1,k and Δz k+1,k respectively represent the position changes of the search and rescue aircraft in the x-axis, y-axis, and z-axis directions from the k-th moment to the k + 1-th moment.

[0052] The change in distance obtained by radio ranging between the k-th moment and the k + 1-th moment is defined as:

[0053]

[0054] R k =cΔt k +ε k (3)

[0055] In the formula, R k represents the distance between the search and rescue aircraft and the search and rescue target measured based on radio ranging technology at the k-th moment; c represents the speed of light; Δt k represents the transmission time of the radio signal from the search and rescue aircraft to the search and rescue target, and ε k represents the ranging error at the k-th moment.

[0056] Step 2: According to the relationship between the displacement ΔP of the search and rescue aircraft between the k-th moment and the k + 1-th moment k+1,k and the actual change in distance Δr k+1,k , use ΔP k+1,k to estimate the maximum value of the actual change in distance between the search and rescue aircraft and the search and rescue target between the k-th moment and the k + 1-th moment

[0057] At the k-th moment, the actual distance r between the search and rescue aircraft and the search and rescue target k can be expressed as

[0058]

[0059] where (x, y, z) T represents the position vector of the search and rescue target, and it is assumed that the position of the search and rescue target is fixed and unchanged.

[0060] The position of the search and rescue aircraft at the (k + 1)-th moment is

[0061] (x k+1 , y k+1 , z k+1 ) T =(x k +Δx k+1,k , y k +Δy k+1,k , z k +Δz k+1,k ) T (5) Then

[0062]

[0063] Expand Equation (6) at (x, y, z) T and omit the high-order terms, we can obtain

[0064]

[0065] Let Δr k+1,k =r k+1 -r k , then the relationship expression between the position change ΔP k+1,k and the actual distance change Δr k+1,k is:[[]]

[0066] Δr k+1,k =H k ΔP k+1,k (8)

[0067]

[0068] Because

[0069] ‖Δr k+1,k ‖ = ‖H k ΔP k+1,k ‖ ≤ ‖H k ‖·‖ΔP k+1,k ‖ = ‖ΔP k+1,k ‖ (10)

[0070]

[0071] In the formula, ‖·‖ represents the modulus of a vector.

[0072] Therefore, the maximum value of the actual distance change obtained based on the track is:

[0073]

[0074] Although theoretically However, when using radio ranging technology, in addition to the signal transmission time, it also takes time for the ranging device to receive and process the signal. In addition, since parameters such as the amplitude, frequency, and phase of the ranging signal will change during the signal transmission process, the time for receiving and processing the ranging signal is not fixed, and this time will be converted into a ranging error ε k . Define the ranging error as:

[0075]

[0076] In the formula, ε signal and respectively represent the fixed error term and the random error term of ε k .

[0077] By measuring the time for receiving and transmitting the ranging signal, an approximate value of ε signal and the maximum value of can be obtained. Since ε signal is a fixed value (corresponding to the minimum time for receiving and transmitting the signal), it can be subtracted when calculating the distance to eliminate its influence on the ranging result. Therefore, is the main factor affecting the size of the ranging error. Denote the maximum value of as ε max . For two consecutive moments, the change in the ranging error caused by the signal processing time is:

[0078] Δε = ε k+1 -ε k (14)

[0079] Because So

[0080] |Δε| ≤ ε max (15)

[0081] Step 3: Judge the ranging value. Here, we set the distance R k measured at the k-th moment between the search and rescue aircraft and the search and rescue target as a normal value, and judge whether the distance measurement value R k+1 at the (k + 1)-th moment is normal.

[0082] Take The distance change amount between the measured k-th moment and the (k + 1)-th moment is compared. If the former is less than the latter, it indicates that the ranging data R k+1 is an outlier and needs to be robustly processed, then go to step 4; otherwise, the ranging data is normal, return to step 1 to continue judging the data of the next moment. The specific judgment method is as follows:

[0083]

[0084] Step 4: According to the actual distance change amount Δr between the (k - 1)-th moment and the k-th moment k,k-1 and the displacement amount ΔP of the search and rescue aircraft between the k-th moment and the (k + 1)-th moment k+1,k estimate the actual distance change amount between the k-th moment and the (k + 1)-th moment Then correct the outlier in the ranging data.

[0085] Because the direction change of the search and rescue aircraft is small within a short time (within 1 second), so

[0086] H k ≈H k-1 (17)

[0087] Using the actual distance change amount Δr between the (k - 1)-th moment and the k-th moment k,k-1 and the displacement amount ΔP of the search and rescue aircraft between the k-th moment and the (k + 1)-th moment k+1,k , the actual distance change amount between the k-th moment and the (k + 1)-th moment can be estimated as:

[0088]

[0089] Among them, since the previous distance measurement value is normal, the measured distance change amount between the (k - 1)-th moment and the k-th moment is used to approximate the actual distance change amount Δr between the (k - 1)-th moment and the k-th moment k,k-1 :

[0090]

[0091] Therefore, the measured distance at the (k + 1)-th moment after correction is:

[0092]

[0093] The following takes the ranging process of an aviation search and rescue device as an example to illustrate the effect of the present invention:

[0094] Figure 3 are the distance schematic diagrams respectively based on radio ranging and based on the flight track. From Figure 3It can be seen that the distance values obtained based on radio ranging and those obtained based on the track are consistent most of the time, and the curves of the two almost overlap. However, at the 227th second, 364th second, and 373rd second, the distance values obtained based on radio ranging are significantly larger, indicating that the radio ranging data may be abnormal at this time.

[0095] Furthermore, using Figure 3 the data in Figure 4 (a), the distance change amounts between two consecutive moments can be calculated, and the results are as shown in Figure 4 (a). This figure also proves that the distance values obtained based on radio ranging do show significant fluctuations. Subtracting the distance change amounts obtained based on radio ranging and those based on the track respectively gives the difference between the two, and the results are shown in Figure 4 (b), which reflects the difference between the two distance change amounts. The values at the 226th second, 363rd second, and 372nd second are 1.116 km, 0.178 km, and 1.235 km respectively. The difference of 1 second between these three times and the times in Figure (3) is due to taking the difference between the data of two consecutive moments.

[0096] Set the error amount ε max = 0.1 km. According to Equation (16), it can be seen that the ranging results at the 226th second, 363rd second, and 372nd second are abnormal and need to be corrected. Thus, the results obtained after correction using Equation (20) are as shown in Figure 5 . In Figure 5 (a), the distance change amount obtained based on radio ranging will no longer increase significantly, and in Figure 5 (b), the difference between the two ranging methods is less than ε max throughout all times, indicating that the ranging results are normal at this time.

[0097] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A robust ranging method for aviation search and rescue equipment based on track constraints, characterized in that: The following steps are involved: Step 1: The search and rescue aircraft uses the onboard navigation and positioning system to obtain its own position information P, and calculates the displacement ΔP of the search and rescue aircraft between time k and time k+1 through the position data at time k and time k+1 k+1,k At the same time, the search and rescue aircraft measures the distance R between the search and rescue aircraft and the search and rescue target through radio ranging, and calculates the distance change between time k and time k+1 Step 2: Based on the relationship between the displacement and distance change of the search and rescue aircraft between time k and time k+1, use ΔP k+1,k Estimate the maximum value of the actual distance change between the search and rescue aircraft and the search and rescue target between time k and time k+1 Step 3: Consider the distance R between the search and rescue aircraft and the search and rescue target measured at the kth moment k is a normal value. The distance measurement value R at the k+1th moment is determined by the following process. k+1 Normal: Will Add the maximum value of the radio ranging error ε max , and then add the sum of the two to the measured distance change between time k and time k+1 Compare, if the former is smaller than the latter, it means that the distance data R k+1 If it is an abnormal value, it needs to be processed for error resistance and go to step 4; otherwise, the ranging data is normal and go back to step 1 to continue to judge the data at the next moment; Step 4: According to the actual distance change Δr between time k-1 and time k k,k-1 And the displacement ΔP of the search and rescue aircraft between time k and time k+1 k+1,k Estimate the actual distance change between time k and time k+1 use and R k Correct the distance measurement value at the k+1th moment; the specific process is: Considering that the direction of the search and rescue aircraft changes very little between adjacent moments, we get H k ≈H k-1 Then use the actual distance change Δr between time k-1 and time k k,k-1 And the displacement ΔP of the search and rescue aircraft between time k and time k+1 k+1,k , the actual distance change between time k and time k+1 is estimated for: The measured distance change between the k-1 moment and the k moment is used The actual distance change Δr between the approximate k-1 moment and the k moment k,k-1 : Get the corrected measured distance at the k+1th moment for:

2. The robust ranging method for aviation search and rescue equipment based on track constraints according to claim 1, characterized in that: In step 1, the displacement of the rescue aircraft between time k and time k+1 is ΔP k+1,k Defined as: ΔP k+1,k =(Δx k+1,k ,Δy k+1,k ,Δz k+1,k ) T =P k+1 -P k Where P k =(x k ,y k ,z k ) T represents the position vector of the search and rescue aircraft at the kth moment, Δx k+1,k , Δy k+1,k and Δz k+1,k They represent the position changes of the search and rescue aircraft from the kth moment to the k+1th moment in the x-axis, y-axis and z-axis directions respectively; The distance change obtained by radio ranging between time k and time k+1 Defined as: R k =cΔt k +e k In the formula, R k represents the distance between the search and rescue aircraft and the search and rescue target measured based on the radio ranging technology at the kth moment; c represents the speed of light; Δt k represents the transmission time of the radio signal from the search and rescue aircraft to the search and rescue target, ε k represents the ranging error at the kth moment.

3. The method for robust ranging of aviation search and rescue equipment based on track constraints according to claim 2, characterized in that: In step 2, the displacement ΔP k+1,k and the actual distance change Δr k+1,k The relationship expression is: Δr k+1,k =H k ΔP k+1,k Where (x, y, z) T Indicates the location of the search and rescue target, r k Represents the actual distance between the search and rescue aircraft and the search and rescue target at the kth moment.

4. The robust ranging method for aviation search and rescue equipment based on track constraints according to claim 3 is characterized by: In step 2, the maximum value of the actual distance change between time k and time k+1 for

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