A method for suppressing false alarm of FOD radar to pavement expansion joint

Abstract

The application discloses a kind of FOD radar false alarm suppression methods of pavement expansion joint, belong to radar data processing technical field.The method considers that the distribution of expansion joint on the airport pavement has clear rule, and then the detection threshold of echo power is set to preliminarily screen out the distance gate that may contain FOD target, and then the interval threshold value and frequency threshold value of distance gate are set, the characteristics that the echo power of airport pavement expansion joint satisfies are screened out, so that the false alarm that may be produced by expansion joint is eliminated in the FOD target detected by FOD radar.

Description

TECHNICAL FIELD

[0001] The application relates to a method for suppressing false alarms of a FOD radar on a pavement expansion joint, and belongs to the technical field of radar data processing. BACKGROUND

[0002] The safety of aircraft taking off and landing is of great concern in the aviation industry, and foreign object debris (FOD) on the airport runway can pose a serious safety threat to aircraft taking off and landing. Cases have shown that the engine of an aircraft can easily suck in foreign "intruders" on the runway, causing the engine to fail and resulting in a large amount of property damage and even casualties. At present, China still uses manual methods to search for FOD in the safety of aircraft taking off and landing at airports, which is low in efficiency, high in cost, and has a high rate of missed detection, and the runway needs to be closed during the inspection, which is difficult to meet the increasingly busy safety guarantee work of aircraft taking off and landing.

[0003] A FOD detection radar is a professional microwave device for detecting FOD, which can detect FOD at any time and in all weather, realize real-time monitoring of the airport runway, provide accurate positioning information for FOD removal and disposal, and avoid disasters. The FOD detection radar mainly uses radar detection technology, video image recognition technology, and a combination of the two to detect foreign objects on the aircraft runway. The radar detection technology has good detection effect on metal FOD, mainly uses millimeter wave radar to scan the runway, and determines the position of the FOD according to the reflected echo. However, since the distribution of the expansion joint of the airport runway has a clear rule, there is usually an expansion joint every few meters, that is, the expansion joints are equally spaced on the airport runway. The expansion joint has a certain width and depth, and also forms a strong reflected echo, which has similar echo spectrum characteristics to FOD, so it will cause more clutter false alarms.

[0004] In radar engineering, how to reduce the false alarm of the airport runway expansion joint clutter is a basic and crucial issue. Before the deployment and application of a radar, the clutter characteristics of the current runway need to be processed in a targeted manner to adapt the radar to the current environment and achieve the best use performance. However, it is difficult to filter the traditional method for the runway expansion joint clutter; it is difficult to automatically identify and filter the ground expansion joint from the background clutter, and the engineering demand is urgent. After investigating the public literature, no effective technology has been found to solve this problem. SUMMARY

[0005] In order to solve the problem of false alarm of the airport runway expansion joint clutter, the application provides a method for suppressing false alarms of a FOD radar on a pavement expansion joint, which comprises:

[0006] Setting a detection threshold In the echo spectrum, each distance gate is traversed i , the echo power is foundP [ i ]≥ the distance gate, and the array index is stored; i indicates the label of each distance gate;

[0007] determine whether there are adjacent distance gates in the array index, if there are, only one of the adjacent distance gates is retained to obtain an array index1;

[0008] calculate the interval values between each distance gate in the index1, store all the interval values in an array interval, and set an interval threshold value delete the interval values in the array interval that are less than from the array interval;

[0009] count the frequency of each element in the interval, and set a frequency threshold value delete the interval values in the interval that are less than from the interval, and assume that there are K elements left in the interval after the deletion;

[0010] for any frame of spectrum graph detected by the FOD radar, obtain the point tracks therein to form a point track set point; and use the elements in the interval to find and eliminate false alarm points in the point track set point.

[0011] Optionally, the detection threshold is determined according to the size of the expansion joint of the airport runway.

[0012] Optionally, the determination of whether there are adjacent distance gates in the array index, if there are, only one of the adjacent distance gates is retained to obtain an array index1, comprises:

[0013] the adjacent distance gates in the array index are a group of adjacent distance gates, and the array index contains m groups of adjacent distance gates, wherein the n group of adjacent distance gates contains N distance gates index n (j,j+1,…,j+N), 0≤ n ≤ m ;

[0014] the power corresponding to each distance gate in the n group of adjacent distance gates is [P j ,P j+1 ,…,P j+N ], and the distance gate with the largest power value is retained, and the other distance gates in the n group of adjacent distance gates are eliminatedN -1 distance gate;

[0015] Will m After performing the above elimination operation on the adjacent distance gates of the group, the array index1 is obtained.

[0016] Optionally, the interval threshold value Determined based on the distance between expansion joints in the airport pavement.

[0017] Optionally, the frequency threshold value Determined based on the set POD false negative rate.

[0018] Optionally, the remaining interval K Sort the elements from largest to smallest.

[0019] Optionally, the step of using elements in the interval to find and remove false alarm points from the point set includes:

[0020] Set false alarm rejection threshold ;

[0021] Determine all points (points) i ') Distance from the door Determine the distance to the door Does the power value at that location exceed If it exceeds, then the point( i The alert was determined to be a false alarm and deleted; among them, Indicates the first interval k Interval values, , K ≥ .

[0022] Optionally, the false alarm rejection threshold Determined based on the echo power of the expansion joints in the airport pavement.

[0023] This application also provides a FOD detection method, which uses the above-mentioned FOD radar suppression method for pavement expansion joints to suppress false alarms based on the detection results of FOD radar.

[0024] The beneficial effects of this invention are:

[0025] This application takes into account the clear pattern of the distribution of expansion joints on airport pavement, and then preliminarily screens out the range gates that may contain FOD targets by setting the detection threshold of echo power. Then, by setting the interval threshold and frequency threshold of the range gate, it screens out the characteristics that the echo power of airport pavement expansion joints meets, thereby eliminating false alarms that may be caused by expansion joints from the FOD targets detected by FOD radar. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of a method for suppressing false alarms of pavement expansion joints using FOD radar, provided by the present invention.

[0028] Figure 2 This is a simulation diagram of a one-dimensional range spectrum detected by FOD radar in one embodiment of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] Explanation of technical terms:

[0031] 1. Range Gate: Radar calculates distance by converting time to distance using the propagation speed of electromagnetic waves in space. Assuming the radar's distance from the target is R, the distance traveled from the radar's emitted electromagnetic wave to the target and back is 2R. Therefore, the flight time is t = 2R / c, and the flight distance is R = ct / 2.

[0032] In modern radar systems, echo signals are acquired by ADC chips (Analog-to-digital converters, chips used to convert analog signals into digital signals). During the conversion process, the sampling rate discretizes the echo signal. Therefore, for an ADC with a sampling rate of fs, the sampling time is Ts = 1 / fs. In radar systems, the distance the electromagnetic wave travels within Ts is called the range gate; that is, the range gate represents the range cell in the radar detection space corresponding to the discrete sampling point.

[0033] 2. Target information: refers to the target information detected by radar, which can be obtained from the echo spectrum.

[0034] Example 1:

[0035] This embodiment provides a method for suppressing false alarms at pavement expansion joints using FOD radar, the method comprising:

[0036] Set detection threshold In the echo spectrum, traverse each range gate i Find the echo power P [i ]≥ The distance gate is stored in the array index; i Indicates the label of each distance gate; detection threshold The threshold value is determined based on the size of the expansion joint at the airport. Generally, the larger the expansion joint, the larger the threshold value. The specific value can be determined by technicians based on the actual situation of the airport.

[0037] Determine if there are adjacent distance gates in the array index. If they exist, keep only one of the adjacent distance gates and obtain the array index1. Usually, if a target is too large, it will occupy multiple adjacent distance gates. Therefore, if this situation exists, keep only one of the multiple adjacent distance gates.

[0038] Calculate the interval values ​​between each pair of distance gates in index1, store all interval values ​​in the array interval, and set the interval threshold value. The interval values ​​in the array interval are less than Delete interval values; interval threshold values The setting is mainly based on the fact that there is a certain interval between expansion joints. Therefore, the threshold value is set according to the distance between expansion joints. Generally, the larger the distance between airport expansion joints, the larger the threshold value. By setting this threshold value, targets with intervals smaller than the expansion joint can be excluded, thereby filtering out false alarms that may belong to the expansion joint echo.

[0039] Count the frequency of each element in interval and set a frequency threshold. The interval with a frequency less than The interval value is deleted, assuming that after deletion, there are still values ​​remaining in interval. K One element; frequency threshold The setting is mainly based on the fact that there is more than one expansion joint. Usually, the specific value of this threshold is set with regard to the POD missed detection rate that the airport can accept. If the POD missed detection rate is to be low, then the threshold value is higher.

[0040] After the above steps, the virtual target points generated by the expansion joints can be filtered out. Then, for any frame of spectrum detected by the FOD radar, the points are obtained to form a point set. The points set is then searched for and removed using the elements in interval, thus suppressing the false alarms of the FOD radar against the pavement expansion joints.

[0041] Example 2

[0042] This embodiment provides a method for suppressing false alarms from pavement expansion joints using FOD radar. Please refer to [link / reference]. Figure 1 The method includes:

[0043] (1) Set detection threshold In the echo spectrum, traverse each range gate i Find the echo power P [ i ]≥ The distance gate is stored in the array index;

[0044] (2) Determine if there are adjacent distance gates in the index. If so, remove the distance gates. The removal method is as follows:

[0045] Suppose that the adjacent distance gates in the array index are called a set of adjacent distance gates, and the array index contains m Group of adjacent distance gates, where the first n Group adjacent distance gate contains N The distance to the gate index n (j,j+1,…,j+N), 0≤ n ≤ m ;No. n In the group of adjacent distance gates N The echo power corresponding to each distance gate is [P] j ,P j+1 ,…,P j+N First, find the range gate at the point where the echo power is maximum. Assume the range gate at the maximum point is... , then Delete other doors at the specified distances, leaving only the ones at the specified distances. .

[0046] other m The same rejection operation is performed on adjacent doors in group -1.

[0047] right m After all adjacent distance gates in a group have undergone the above elimination operation, the remaining distance gates in the array index form array index1.

[0048] The following section performs interval calculations on the distribution characteristics of the spectrogram.

[0049] (3) Calculate the interval between each element in index1, sort the interval values ​​from largest to smallest, and store them in the array interval. Set the interval threshold value. The interval value is less than Delete the value.

[0050] (4) Count the frequency of each element in interval, sort them in descending order, and store them in the array interval_freq. Each interval corresponds one-to-one with the elements in interval_freq. Set a frequency threshold. , find the elements in interval_freq whose frequency is less than , and delete the elements in the corresponding interval.

[0051] After the above steps are performed, the elements in the resulting interval are the virtual target points generated by all expansion joints. Subsequently, all target points detected by the FOD radar are removed from the virtual target points to complete the suppression of the false alarm of the FOD radar to the pavement expansion joint, specifically:

[0052] Given the point traces in a frame of the radar-detected spectrum graph, form a point trace set point; use the elements in the interval to find and remove false alarm points, and the specific method is as follows:

[0053] Set the false alarm removal threshold , given that the distance gate of the point trace point( i ') is . If the power value at the distance gate exceeds , the point trace point( i ') is determined to be a false alarm and is deleted. Among them, , , i ' and k all need to traverse all values in the array.

[0054] The point traces in the spectrum graph can be obtained according to the echo spectrum received by the radar.

[0055] To further introduce the method of the present application, the following describes setting the detection threshold , interval threshold value , frequency threshold value , false alarm removal threshold according to the specific expansion joint information of the airport:

[0056] (1) Set the detection threshold , in the echo spectrum, traverse each distance gate i , find the distance gate whose echo power P [ i ]≥ , and store it in the array index;

[0057] (2) Determine whether there are adjacent distance gates in index. After determination, there are adjacent distance gates, and distance gate removal is performed in index. The index array after removing the adjacent distance gates is denoted as index1.

[0058] Interval calculation is performed on the distribution characteristics of the spectrum graph

[0059] (3) Calculate the interval between each element in index1, sort the interval value from large to small, and store it in the array interval. Set the interval threshold value , remove the value in interval whose interval value is less than .

[0060] (4) Count the frequency of each element in interval, and sort it in descending order, and store it in the array interval_freq. Set the frequency threshold value , find the element in interval_freq whose frequency is less than , and delete the element in interval corresponding to the element.

[0061] Suppose that the point set point in a certain frame spectrum detected by the radar is known; set the false alarm removal threshold , and the distance gate of point ( i ') is known . If the power value at the distance gate is greater than , point ( i ') is determined as false alarm and is deleted. Wherein, , , i ' and k all need to traverse all values in the array.

[0062] After the above calculation, 4 peak points marked by Figure 2 are found in the spectrum, and the equal interval is 3319 distance gates, and the above algorithm can remove the 4 false alarm points.

[0063] According to the actual situation of the airport, it is judged that the false alarm generated by the expansion joint can be effectively removed by the method.

[0064] Some steps in the embodiment of the application can be realized by software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0065] The above only describes the preferred embodiments of the application, and does not limit the application, and any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A method for suppressing false alarms from pavement expansion joints using FOD radar, characterized in that, The method includes: Set detection threshold In the echo spectrum, traverse each range gate i Find the echo power P [ i ]≥ The distance gate is stored in the array index; i The label indicating the distance between the doors; Determine if there are adjacent distance gates in the array index. If they exist, keep only one of the adjacent distance gates and obtain the array index1. Calculate the interval values ​​between each pair of distance gates in index1, store all interval values ​​in the array interval, and set the interval threshold value. The interval values ​​in the array interval are less than Delete the interval value; Count the frequency of each element in interval and set a frequency threshold. The interval with a frequency less than The interval value is deleted, assuming that after deletion, there are still values ​​remaining in interval. K One element; For any frame of spectrum detected by the FOD radar, obtain the points within it to form a point set; use the elements in interval to find and remove false alarm points from the point set; The process of using elements in interval to find and remove false alarm points from the point set includes: Set false alarm rejection threshold ; Determine all points (points) i ') Distance from the door Determine the distance to the door Does the power value at that location exceed If it exceeds, then the point( i The alert was determined to be a false alarm and deleted; among them, Indicates the first interval k Interval values, , K ≥ .

2. The method according to claim 1, characterized in that, The detection threshold Determined based on the size of the expansion joints in the airport pavement.

3. The method according to claim 2, characterized in that, The step of determining whether there are adjacent distance gates in the array index is performed. If they exist, only one of the adjacent distance gates is retained to obtain the array index1, which includes: Let the adjacent distance gates in the array `index` be considered a group of adjacent distance gates. The array `index` contains... m Group of adjacent distance gates, where the first n Group adjacent distance gate contains N The distance to the gate index n (j,j+1,…,j+N), 0≤ n ≤ m ; No. n The power corresponding to each distance gate in a group of adjacent distance gates is [P] j ,P j+1 ,…,P j+N [The system retains the distance gate with the highest power value and removes the second gate.] n Other in the group of adjacent distance gates N -1 distance gate; Will m After performing the above elimination operation on the adjacent distance gates of the group, the array index1 is obtained.

4. The method according to claim 3, characterized in that, The interval threshold Determined based on the distance between expansion joints in the airport pavement.

5. The method according to claim 4, characterized in that, The frequency threshold Determined based on the set POD false negative rate.

6. The method according to claim 5, characterized in that, The remaining interval K Sort the elements from largest to smallest.

7. The method according to claim 6, characterized in that, The false alarm rejection threshold Determined based on the echo power of the expansion joints in the airport pavement.

8. A method for detecting FOD (Foreign Object Destruction), characterized in that, The method described herein uses the method described in any one of claims 1-7 to suppress false alarms based on the detection results of the FOD radar.

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