Flight path constraint-based robust ranging method for aviation search and rescue equipment

Abstract

According to the flight path constraint-based robust ranging method for the aviation search and rescue equipment, the variation of the position of a search and rescue aircraft restrains the variation of the distance under the condition that the position of a search and rescue target is fixed or slightly changed, so that if the variation of the position of the search and rescue aircraft is slightly changed, the search and rescue target can be found out. However, the measured distance value suddenly changes greatly, it is indicated that the distance data at the moment is abnormal, and the abnormal distance variation is further corrected by means of the position variation. According to the method, the outliers in the distance measurement data are accurately detected based on the constraint information of the flight path of the search and rescue aircraft, and the variation of the distance between the search and rescue aircraft and the search and rescue target at the current moment is estimated according to the displacement of the search and rescue aircraft at the historical moment, so that the outliers in the distance measurement data are corrected, and a relatively accurate distance measurement result is obtained.

Description

Technical Field

[0001] The invention relates to the field of aviation search and rescue, and in particular to an aviation search and rescue equipment anti-differential ranging method based on track constraints. Background Art

[0002] The aviation search and rescue system can locate parachuting pilots or crashed aircraft and carry out rescue activities. It is an important means to increase the survival rate of victims. When the satellite navigation equipment carried by the search and rescue target is damaged or the positioning is invalid, the distance measurement and direction finding method can be used to determine the location of the search and rescue target. The currently widely used distance measurement 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 the search and rescue equipment and the search and rescue target. This method has the advantages of simple implementation and high measurement accuracy. However, since radio signals are easily interfered during transmission, there will be significant outliers in the distance measurement data, which will affect the search and rescue effect.

[0003] The existing solution is mainly to smooth or filter the ranging data. Although it can weaken the influence of outliers to a certain extent, the smoothing or filtering process requires subjective setting of judgment thresholds to distinguish whether the data is abnormal, which mostly relies on personnel experience and cannot accurately distinguish whether the data is abnormal. In addition, data smoothing or filtering will also process normal data, and the correction effect on significant outliers is not ideal, which is not conducive to quickly and accurately determining the location of the search and rescue target. The Chinese patent application with publication number CN113326878A discloses "A method, device and computer equipment for eliminating wild values ​​in track measurement data", which uses the Kalman filter innovation chi-square test method to identify wild values ​​in track measurement data. This method has high implementation complexity and low reliability, and does not use the key information of track constraints. Summary of the invention

[0004] In order to solve the problem of wild values ​​in the distance measurement data of aviation search and rescue equipment, the present invention proposes a robust distance measurement method for aviation search and rescue equipment based on track constraints. The method can accurately detect wild values ​​in the distance measurement data based on the constraint information of the flight track of the search and rescue aircraft, and can estimate the change in the distance between the search and rescue aircraft and the search and rescue target at the current moment according to the displacement of the search and rescue aircraft at the historical moment, thereby correcting the wild values ​​in the distance measurement data and obtaining a more accurate distance measurement 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 distance measuring device, that is, when the position of the search and rescue target is fixed or changes slightly, the change in the position of the search and rescue aircraft constrains the change in the distance. In this case, if the change in the position of the search and rescue aircraft does not change much, but the measured distance value suddenly changes significantly, it means that the distance data at this time is abnormal. Furthermore, the position change can also be used to correct the abnormal distance change.

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

[0007] A method for robust ranging of aviation search and rescue equipment based on track constraints comprises the following steps:

[0008] 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

[0009] 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

[0010] 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:

[0011] 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;

[0012] 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 at time k+1.

[0013] Furthermore, in step 1, the displacement ΔP of the search and rescue aircraft between time k and time k+1 is k+1,k 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 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;

[0016] The distance change obtained by radio ranging between time k and time k+1 Defined as:

[0017]

[0018] R k =cΔt k +ε k

[0019] 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.

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

[0021] Δr k+1,k =H k ΔP k+1,k

[0022]

[0023] Where (x, y, z) T Represents 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.

[0024] Furthermore, in step 2, the maximum value of the actual distance change between time k and time k+1 is for

[0025]

[0026] Furthermore, in step 4, considering that the direction of the search and rescue aircraft changes very little between adjacent moments, we get

[0027] H k ≈H k-1

[0028] 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:

[0029]

[0030] 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 :

[0031]

[0032] Get the corrected measured distance at the k+1th moment for:

[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 abnormal values ​​in the distance measurement data, the present invention can accurately detect the abnormal values ​​based on the constraint information of the track.

[0037] 2) The present invention can estimate the distance change at the current moment according to the distance change and the track data at the previous moment, thereby correcting the abnormal distance measurement data and obtaining a more accurate distance measurement result.

[0038] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through 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 easily understood from the description of the embodiments in conjunction with the following drawings, in which:

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

[0041] Figure 2 : Flowchart of the present invention.

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

[0043] Figure 4 : The distance changes based on radio ranging and track before correction.

[0044] Figure 5 : The distance changes obtained based on radio ranging and track after correction. DETAILED DESCRIPTION

[0045] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting 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 constraints. Figure 1 The application scenario of the present invention is shown. In the figure, after the search and rescue aircraft has determined the direction 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 equipment in the search and rescue aircraft transmits a radio signal using BPSK (Binary Phase Shift Keying) modulation and starts timing. After the search and rescue target receives the signal, it immediately replies with a radio signal using the same modulation. After the search and rescue aircraft receives the reply BPSK signal, it stops timing. The ranging system subtracts the signal receiving and sending processing time from the one-way transmission time of the radio ranging signal, and then multiplies it by the speed of light to obtain the transmission distance of the signal, and then 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 with, resulting in significantly larger abnormal values ​​in the ranging data. The present invention can detect these abnormal values ​​in the ranging data and correct them.

[0047] The process of this embodiment is as follows Figure 2As shown, the specific steps include:

[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 (time k and time k+1) through the position data of the 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 time k and time k+1

[0049] The displacement of the rescue aircraft between two moments ΔP k+1,k Defined as:

[0050]

[0051] 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 respectively 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.

[0052] The distance change obtained by radio ranging between time k and time k+1 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 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.

[0056] Step 2: According to the displacement ΔP of the search and rescue aircraft between time k and time k+1 k+1,k and the actual distance change Δr k+1,k The relationship between 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

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

[0058]

[0059] Where (x, y, z) T Represents the position vector of the search and rescue target, and assumes that the position of the search and rescue target is fixed.

[0060] The position of the search and rescue aircraft at time k+1 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) So,

[0062]

[0063] Substituting equation (6) at (x, y, z) T Taylor expansion is performed at , and the higher-order terms are omitted, and we can get

[0064]

[0065] Assume Δr k+1,k =r k+1 -r k , then the position change ΔP k+1,k and the actual distance change Δr k+1,k The relationship expression 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 the 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, the ranging device also takes time to receive and process the signal. In addition, since the amplitude, frequency, and phase of the ranging signal will change during the signal transmission process, the reception and processing time of the ranging signal is not fixed, and this time will be converted into the ranging error ε k The ranging error is defined as:

[0075]

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

[0077] By measuring the transmission and reception processing time of the ranging signal, ε can be obtained signal The approximate value and The maximum value of signal It is a fixed value (corresponding to the minimum signal receiving and sending processing time), which can be subtracted when calculating the distance to eliminate its influence on the ranging result. Therefore, It is the main factor affecting the ranging error. The maximum value of max , for two consecutive moments, the change in ranging error caused by signal processing time is:

[0078] Δε=ε k+1 -ε k (14)

[0079] because so

[0080] |Δε|≤ε max (15)

[0081] Step 3: Determine the distance value. Here we set 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, judging the distance measurement value R at the k+1th moment k+1 Is it normal?

[0082] Will The change in distance between the measured 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 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. The specific judgment method is:

[0083]

[0084] 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 The outliers in the odometry data are then corrected.

[0085] Because the direction of the search and rescue aircraft changes little in a short time (within 1 second),

[0086] H k ≈H k-1 (17)

[0087] 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 can be estimated for:

[0088]

[0089] Since the previous distance measurement value is normal, the distance change between the measured time k-1 and time k is used The actual distance change Δr between the approximate k-1 moment and the k moment k,k-1 :

[0090]

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

[0092]

[0093] The effect of the present invention is described below by taking a distance measurement process of aviation search and rescue equipment as an example:

[0094] Figure 3 The distances obtained based on radio ranging and track are shown in Figure 2. Figure 3It can be seen that the distance values ​​obtained based on radio ranging and based on track are consistent most of the time, and the curves of the two are almost overlapping. However, at 227 seconds, 364 seconds, and 373 seconds, the distance values ​​obtained based on radio ranging are significantly larger, indicating that the radio ranging data at this time may be abnormal.

[0095] Further, use Figure 3 The data in can be used to calculate the distance change between the previous and next moments. The result is as follows Figure 4 (a) is shown. This figure also proves that the distance value obtained based on radio ranging does have a large fluctuation. Subtracting the distance changes based on radio ranging and based on track can get the difference between the two, and the result is shown in Figure 4 (b) shows the difference between the two distance changes. The values ​​at 226 seconds, 363 seconds, and 372 seconds are 1.116 km, 0.178 km, and 1.235 km, respectively. The difference of 1 second between these three times and the time in Figure (3) is because the data of the two moments before and after are subtracted.

[0096] Setting error ε max = 0.1 km. According to formula (16), the distance measurement results at the 226th second, 363rd second and 372nd second are abnormal and need to be corrected. Therefore, the result obtained after correction using formula (20) is as follows: Figure 5 As shown. Figure 5 In (a), the distance change obtained based on radio ranging will no longer increase significantly, but Figure 5 In (b), the difference between the two distance measurement methods is less than ε at all times. max , indicating that the ranging result at this time is normal.

[0097] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent 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 at time k+1.

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 5. The method for robust ranging of aviation search and rescue equipment based on track constraints according to claim 1, characterized in that: In step 4, considering that the direction of the search and rescue aircraft changes very little between adjacent moments, we get H k ≈H k-1 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:

Images