JP2017156146A - Target detector, target detection method, and target detection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the average number of times observation is made as needed for determination of target detection when detecting a target on the basis of a signal detection result from a sensor.SOLUTION: A target detector of the present embodiment calculates an evaluation value on the basis of a detected signal amplitude, the probability density function of signal amplitude of a false target, and the probability density function of signal amplitude of a true target when a signal detection result from a sensor that observes a target and detects a signal equal to or greater than a threshold is "signal detected," and calculates the evaluation value on the basis of the signal nondetection probability of the false target and the signal nondetection probability of the true target when the signal detection result is "signal undetected." Meanwhile, the target detector makes determination as to the evaluation value on the basis of an upper-side threshold and a lower-side threshold, determines the termination of determination as to an observation count in the signal detection result when an observation count threshold is reached and selects one of "determination terminated" and "determination pending," and selects and outputs one of "target detected," "target undetected," and "determination pending" on the basis of the result of determination as to the evaluation value and the result of determination as to the observation count.SELECTED DRAWING: Figure 1

Description

  The present embodiment relates to a target detection apparatus, a target detection method, and a target detection program that detect a target based on a signal detection result from a sensor that observes the target.

Conventionally, in a target detection device, a target is detected based on a signal detection result from a sensor that observes a target such as a radar device or a sonar device and detects a signal equal to or greater than a threshold value. At this time, a target detection process (see Non-Patent Document 1) by SPRT (Sequential Probability Ratio Test) is used as a method for reliably detecting the target. Target detecting process by the SPRT sets hypotheses H ₁ to the hypothesis H ₀ is "not a target is present,""there is a target," the hypothesis H ₁ to the "target is present" by the hypothesis test This is a method of determining “target detection” when it is adopted.

JP 2003-43132 A

Samuel S. Blackman, Multiple-Target Tracking with Radar Applications, Artech House, 1986.

  In the target detection apparatus using the conventional SPRT, an evaluation value is calculated every time a signal detection result is input without previously setting the number of observations corresponding to the sample size (same meaning as “sample size”), “Target detection” when the evaluation value is equal to or higher than the upper threshold, “No target detection” when the evaluation value is equal to or lower than the lower threshold, and “Decision pending” when the evaluation value is larger than the lower threshold and smaller than the upper threshold Is determined.

  Compared with the method of determining the number of observations corresponding to the sample size in advance, this target detection determination method has two target points that define the model of the false target and the true target. This contributes to the reduction of the average number of observations required for the determination of “target not detected”. However, in actual operation, there is a problem that further reduction of the average number of observations required for determination of “target detection” or “target non-detection” is required. In addition, there is a problem that a case where a very large number of observations are required for the determination of “target detection” or “target non-detection” occurs.

  The present embodiment has been made in view of the above problems, and can reduce the average number of observations required for determination of “target detection” or “target non-detection”, and can determine “target detection” or “target non-detection”. An object of the present invention is to provide a target detection apparatus, a target detection method, and a target detection program that can prevent the occurrence of a case that requires a very large number of observations.

  According to the embodiment, a target detection device that detects a target based on a signal detection result from a sensor that detects a signal that is equal to or greater than a threshold value by observing the target, an evaluation value calculation unit, an evaluation value determination unit, An observation number determination unit and a comprehensive determination unit are provided. When the signal detection result is “signal detection”, the evaluation value calculation unit evaluates based on the detected signal amplitude, the probability density function of the false target signal amplitude, and the probability density function of the true target signal amplitude. When the signal detection result is “signal non-detection”, the evaluation value is calculated based on the false target signal non-detection probability and the true target signal non-detection probability. The evaluation value determination unit determines the evaluation value calculated by the evaluation value calculation unit based on an upper threshold value and a lower threshold value of the evaluation value. As a result of the determination, “target detection”, “target failure” Select either “Detect” or “Decision pending”. The observation number determination unit determines the end of determination for the number of observations in the signal detection result when the number of observations reaches a threshold value, and the result of the determination is either “end of determination” or “determination pending” Select. The comprehensive determination unit makes a comprehensive determination based on the determination result by the evaluation value determination unit and the determination result by the observation number determination unit, and as a result of the determination, "target detection", "target non-detection" , “Determine pending” is selected.

The block diagram which shows the structure of the target detection apparatus which concerns on this embodiment. The flowchart which shows the first half of the flow of a process of the target detection apparatus which concerns on this embodiment. The flowchart which shows the second half of the process flow of the target detection apparatus which concerns on this embodiment. The block diagram which shows the basic composition of the target detection apparatus using SPRT. The flowchart which shows the specific example of the flow of a process of the target detection apparatus shown in FIG.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

  First, prior to describing this embodiment, a basic configuration of a target detection apparatus using SPRT will be described.

  FIG. 3 is a block diagram showing a basic configuration of a target detection apparatus using SPRT. The target detection apparatus shown in FIG. 3 includes a threshold value calculation unit 21, a likelihood ratio calculation unit 22, and a determination unit 23.

The threshold calculation unit 21 calculates the upper threshold T _U and the lower threshold T _L of likelihood ratio is an evaluation value. The likelihood ratio calculation unit 22 determines the signal detection count m at the observation count k as a signal detection result from a sensor (not shown, for example, a radar device, a sonar device, etc.) that observes the target and detects a signal that is equal to or greater than the threshold. Based on the signal detection result, the observation k-th likelihood ratio ST (k) (hereinafter referred to as “observation k-th likelihood ratio ST (k)” is used as the evaluation value. Is sometimes abbreviated as “)”. The determination unit 23 based on the upper threshold value from the threshold value calculation unit 21 T _U and the lower threshold T _L, likelihood ratio from the likelihood ratio calculation unit 22 ST (k), the target by the following expression (1) The detection is determined, and “target detection”, “target non-detection”, or “determination pending” is selected as the determination result.

  FIG. 4 is a flowchart showing a specific example of the processing flow of the target detection apparatus shown in FIG. The process flow of the target detection apparatus will be described with reference to FIG.

First, in the threshold calculating unit 21, errors ratio of Type α and on the basis of the type II error rates beta, calculates the upper threshold T _U and the lower threshold T _L of likelihood ratio ST (k) ( Step S201). Upper threshold _{T U} and the lower threshold _{T L} is calculated by the following equation (2).

Next, in the likelihood ratio calculation unit 22, based on the false target signal detection probability P _F , the true target signal detection probability P _D , the number of observations k as the signal detection result from the sensor, and the signal detection number m, A likelihood ratio ST (k) is calculated (step S202). The likelihood ratio ST (k) is calculated by the following equation (3).

Then, in the determination unit 23 compares the likelihood ratio from the likelihood ratio calculation unit 22 ST (k) and an upper threshold value _{T U} from the threshold value calculation unit 21 (step S203), the likelihood ratio ST (k ) is in the case of more than the upper threshold _{T U (ST (k) ≧} T U) and (YES), the determination result "target detection" (step S204). The lower threshold value from when the likelihood ratio ST (k) is smaller than the upper threshold _{T U (ST (k) <} T U) in (NO), the likelihood ratio ST (k) and the threshold value calculation unit 21 T _L is compared (step S205), and when the likelihood ratio ST (k) is equal to or lower than the lower threshold value T _L (ST (k) ≦ T _L ) (YES), the determination result is “target non-detection”. (Step S206). In cases other than the above (when the likelihood ratio ST (k) is larger than the lower threshold value T _{L and} smaller than the upper threshold value T _U (T _L <ST (k) <T _U )) (NO), determination The result is “determination pending” (step S207). Then, the above determination result is output (step S208). If the determination result of the determination unit 23 is “determination pending”, the processing from step S201 is performed based on the signal detection result of the observation (k + 1) th time. Run repeatedly.

Here, in the target detection device having the above-described configuration, the likelihood ratio calculation unit 22 observes the target and detects the number of observations k and the number of signal detections m, which are signal detection results from a sensor that detects a signal equal to or greater than the threshold, and the false target. The likelihood ratio ST (k) is calculated based on the signal detection probability P _F and the true target signal detection probability P _D. In this case, when attention is paid to the signal amplitude equal to or larger than the threshold value, the signal ratio is not used for calculating the likelihood ratio ST (k) despite having a larger amount of information. Further, in the target detection device having the above configuration, since the number of observations is not determined, the maximum value of the number of observations cannot be limited to a predetermined value.

Therefore, in the embodiment shown below, when the signal detection result from a sensor (not shown, for example, a radar device, a sonar device, etc.) is “signal detection”, the detected signal amplitude a, the false target signal amplitude The k-th likelihood ratio ST (k) is calculated as an evaluation value based on the probability density function f (a | θ ₀ ) and the probability density function g (a | θ ₁ ) of the true target signal amplitude. Further, when the signal detection result is “signal non-detection”, the evaluation value is calculated based on the false target signal non-detection probability (1-P _F ) and the true target signal non-detection probability (1-P _D ). The likelihood ratio ST (k) for the k-th observation is calculated. Then, with a determination of the upper threshold T _U and the lower threshold T _L observed k th likelihood ratio ST based on the (k), a determination is made about the number of observations k, based on these decision, overall Specifically, “target detection”, “target non-detection”, and “determination pending” are determined. In this way, in the determination of target detection, the average number of observations required for the determination of “target detection” or “target non-detection” is reduced, and the determination of “target detection” or “target non-detection” is very large. The occurrence of cases that require the number of observations is prevented.

(Embodiment)
Hereinafter, the present embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a block diagram showing the configuration of the target detection apparatus according to this embodiment. The target detection apparatus includes a likelihood ratio threshold calculation unit 11, a likelihood ratio calculation unit 12, a likelihood ratio determination unit 13, a frequency threshold selection unit 14, an observation frequency determination unit 15, and a comprehensive determination unit 16.

The likelihood ratio threshold value calculation unit 11 calculates the upper threshold T _U and the lower threshold T _L of likelihood ratio is an evaluation value of the present embodiment.

The likelihood ratio calculation unit 12 includes a first calculation unit 121 that calculates a likelihood ratio based on a probability density function, and a second calculation unit 122 that calculates a likelihood ratio based on a signal non-detection probability. Prepare. That is, when the signal detection result from the sensor is input and the signal detection result is “signal detection” (the signal amplitude is greater than or equal to the threshold value), the first calculation unit 121 detects the detected signal amplitude a, the false target Based on the probability density function f (a | θ ₀ ) of the signal amplitude and the probability density function g (a | θ ₁ ) of the true target signal amplitude, the likelihood ratio ST (k) for the k-th observation is calculated as an evaluation value. To do. In addition, when the signal detection result from the sensor is “signal non-detection” (the signal amplitude is less than the threshold value), the second calculation unit 122 determines the false target signal non-detection probability (1−P _F ), the true target. The likelihood ratio ST (k) for the k-th observation is calculated as an evaluation value based on the signal non-detection probability (1-P _D ).

The likelihood ratio determining unit 13, based on the upper threshold T _U and the lower threshold T _L from the likelihood ratio threshold calculating unit _11, the likelihood ratio from the likelihood ratio calculation unit 12 ST (k), below The target detection is determined by equation (4) (same as equation (1)), and “target detection”, “target non-detection”, and “determination” are determined as the result of determination by likelihood ratio (hereinafter, the likelihood ratio determination result). Select “Hold”.

The count threshold selecting unit 14 selects a number of observations threshold T _k. The observation frequency determination unit 15 performs a determination according to the following equation (5) based on the observation frequency k input as a signal detection result from the sensor and the observation frequency threshold T _k selected by the frequency threshold selection unit 14. As a result of determination based on the number of observations (hereinafter referred to as observation number determination result), either “end of determination” or “pending determination” is selected.

Based on the likelihood ratio determination result from the likelihood ratio determination unit 13 and the observation number determination result from the observation number determination unit 15, the comprehensive determination unit 16 performs a comprehensive determination result (hereinafter referred to as a comprehensive determination result). Select one of “target detection”, “target non-detection”, and “determination pending”. A specific example of comprehensive determination is shown in Table 1.

  In the specific example shown in Table 1, the likelihood ratio determination result from the likelihood ratio determination unit 13 is “determination pending”, and the observation number determination result from the observation number determination unit 15 is “determination completed”. Although the example in which the comprehensive determination result is “target detection” has been shown, it is configured that the comprehensive determination result is “target non-detection”, or the likelihood ratio ST (k) at the time of “end of determination” is determined. It may be configured to select either “target detection” or “target non-detection” based on the end threshold. It is also possible to set a correspondence other than the above.

  FIG. 2A and FIG. 2B are flowcharts showing the processing flow of the first half and second half of the target detection apparatus according to this embodiment, respectively. A processing flow of the target detection apparatus according to the present embodiment will be described with reference to FIG.

First, in the likelihood ratio threshold value calculation unit 11, errors ratio of Type α and on the basis of the type II error rates beta, calculates the upper threshold T _U and the lower threshold T _L (step S101). Approximate value of the upper threshold T _U and the lower threshold T _L is calculated by the following equation (6).

Next, the likelihood ratio calculation unit 12 determines whether or not the signal detection result is “signal detection” (whether or not the signal amplitude is greater than or equal to a threshold value) (step S102). In this determination, when the signal detection result is “signal detection” (YES), the detected signal amplitude a, the probability density function f (a | θ ₀ ) of the false target signal amplitude, the true target signal amplitude Based on the probability density function g (a | θ ₁ ), a likelihood ratio ST (k) is calculated as an evaluation value (step S103). Further, "non-signal detection" signal detection result in the case (less than the signal amplitude threshold "signal not detected") of (NO), the signal non-detection probability of false targets (1-P _F), the true target signals Based on the non-detection probability (1-P _D ), a likelihood ratio ST (k) is calculated as an evaluation value (step S104). The likelihood ratio ST (k) is calculated by the following equation (7).

Here, θ ₀ represents a parameter of the probability density function f (•) of the false target signal amplitude or a parameter group consisting of a plurality of parameters, and θ ₁ represents the probability density function g (•) of the true target signal amplitude. Or a parameter group composed of a plurality of parameters. Further, the false target signal non-detection probability (1-P _F ) corresponds to the probability that the false target signal amplitude is less than the threshold, and the probability density function f (x | θ) of the false target signal amplitude variable x. ₀ ) can be calculated as an integral value from 0 to a threshold value. Similarly, the true target signal non-detection probability (1-P _D ) corresponds to the probability that the true target signal amplitude is less than the threshold, and the probability density function g (x |) of the true target signal amplitude variable x. It can be calculated as an integral value from 0 to a threshold value of θ ₁ ).

When the probability distribution of the true target signal amplitude belongs to the same probability distribution as that of the false target signal amplitude, the probability density function of the true target signal amplitude can be expressed by f (a | θ ₁ ). it can.

Then, in the likelihood ratio determination unit 13 compares the likelihood ratio from the likelihood ratio calculation unit 12 ST (k) and an upper threshold value _{T U} from likelihood ratio threshold value calculation unit 11 (step S105). Result of the comparison, when the likelihood ratio ST (k) is not less than the upper threshold _{T U (ST (k) ≧} T U) and (YES), the likelihood ratio determination result "target detection" (step S106) . If the likelihood ratio ST (k) is smaller than the upper threshold _{T U (ST (k) <} T U) in (NO), the underside of the likelihood ratio ST (k) and likelihood ratio threshold value calculation unit 11 The threshold value _TL is compared (step S107). As a result of the comparison, if the likelihood ratio ST (k) is equal to or lower than the lower threshold value _TL (ST (k) ≦ _TL ) (YES), the likelihood ratio determination result is “target non-detection” (step S108). In cases other than the above (when the likelihood ratio ST (k) is larger than the lower threshold value T _{L and} smaller than the upper threshold value T _U (T _L <ST (k) <T _U )) (NO), the likelihood The degree ratio determination result is set to “determination pending” (step S109).

Then, in the number of threshold selection unit 14 selects a number of observations threshold _{T k} (step S110). Next, the observation frequency determination unit 15 compares the observation frequency k, which is a signal detection result from the sensor, with the selected observation frequency threshold value T _k (step S111). As a result of the comparison, if the number of observations k is equal to or greater than the observation number threshold value T _k (k ≧ T _k ) (YES), the observation number determination result is set to “end of determination” (step S112). In cases other than the above (when the number of observations _k is smaller than the observation number threshold value T _k (k <T _k )) (NO), the observation number determination result is set to “determination pending” (step S113).

  Next, in the comprehensive determination unit 16, based on the likelihood ratio determination result from the likelihood ratio determination unit 13 and the observation number determination result from the observation number determination unit 15, “target detection”, “target” Either “not detected” or “determination pending” is selected (step S114), and the selected comprehensive determination result is output (step S115). When the comprehensive determination result of the comprehensive determination unit 16 is “determination pending”, the processing from step S101 is repeatedly executed based on the observation (k + 1) th signal detection result.

In the above-described embodiment, when the signal detection result is “signal detection”, the detected signal amplitude a, the probability density function f (a | θ ₀ ) of the false target signal amplitude, and the probability of the true target signal amplitude Although an example of calculating the likelihood ratio ST (k) as an evaluation value based on the density function g (a | θ ₁ ) has been shown, the likelihood function L _{0 of the} detected signal amplitude a and the false target signal amplitude is shown. (A) The likelihood ratio ST (k) can be calculated as an evaluation value based on the likelihood function L ₁ (a) of the true target signal amplitude. Further, the detected signal amplitude a, the likelihood ratio LR of false target likelihood function of the signal amplitude of _L 0 (a) and the likelihood function _L 1 of the signal amplitude of the true target (a) (a) (= L 1 Based on (a) / L ₀ (a)), the likelihood ratio ST (k) can be calculated as an evaluation value.

In the above embodiment, an example is shown in which the likelihood ratio is used as the evaluation value. However, as shown in the basic configuration of the target detection device, the likelihood ratio obtained by logarithmically converting each value (more precisely, the logarithm) The processing can be performed using the likelihood ratio. In this case, an approximate value of the upper threshold T _U and the lower threshold T _L is calculated by the following equation (8).

The corresponding likelihood ratio ST (k) is calculated by the following equation (9).

  Furthermore, instead of inputting the signal detection result from the sensor, the signal detection result processed by the correlating means and the temporary target registration updating means described in Patent Document 1 (the motion data of the temporary target is used for the detection signal). The result of the determination by the correlation gate) can be input. Accordingly, it is possible to make a determination by inputting a signal detection result with few errors under a false alarm environment, a multi-target environment, or a complex environment thereof.

  In addition to the sequential processing that is performed each time a signal detection result is input, the above-described processing is signal detection multiple times (for example, three times from the observation kth to the observation (k + 2) th). It can comprise so that it may implement by the mini batch process which processes a result collectively. Further, the mini-batch processing can be configured to calculate a likelihood ratio as an evaluation value using a plurality of signal detection results, and to make a determination on the calculated likelihood ratio.

As described above, according to the target detection apparatus according to the present embodiment, when the signal detection result from the sensor is input and the signal detection result is “signal detection”, the detected signal amplitude a, the false target signal Based on the probability density function f (a | θ ₀ ) of the amplitude and the probability density function g (a | θ ₁ ) of the true target signal amplitude, the likelihood ratio ST (k) for the k-th observation is calculated as an evaluation value. . In addition, when the signal detection result is “signal non-detection”, the evaluation value is observed based on the false target signal non-detection probability (1-P _F ) and the true target signal non-detection probability (1-P _D ). The likelihood ratio ST (k) for the second time is calculated. Then, with a determination of the upper threshold T _U and the lower threshold T _L observed k th likelihood ratio ST based on the (k), a determination is made about the number of observations k, based on these decision, overall Specifically, “target detection”, “target non-detection”, and “determination pending” are determined. By doing in this way, the average number of observations required for the determination of “target detection” or “target non-detection” can be reduced.

  Instead of reducing the average number of observations required for the determination of “target detection” or “target non-detection”, the first type error rate α and the second type error rate β can be kept low.

  In addition, according to the target detection apparatus according to the present embodiment, in order to determine the number of observations, the maximum number of observations required for the determination of “target detection” or “target non-detection” is limited to a predetermined value. Can do. As a result, it is possible to prevent the occurrence of a case that requires a very large number of observations for the determination of “target detection” or “target non-detection”.

  Note that the target detection processing according to the above embodiment includes the likelihood ratio threshold calculation unit 11, the likelihood ratio calculation unit 12, the likelihood ratio determination unit 13, the frequency threshold selection unit 14, the observation frequency determination unit 15, and the comprehensive determination unit 16. It can be configured as a program for causing a computer to execute each processing function.

  All of the above embodiments can be applied to a target detection device that detects a target based on a signal detection result from a sensor such as a radar device or a sonar device.

  In addition, the present embodiment is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

11 ... Likelihood ratio threshold value calculation part,
12 ... Likelihood ratio calculation unit, 121 ... First calculation unit, 122 ... Second calculation unit,
13 ... Likelihood ratio determination unit,
14: Number of times threshold selection unit,
15 ... Observation frequency determination unit,
16: Comprehensive determination unit.

Claims (3)

A target detection device that detects a target based on a signal detection result from a sensor that observes the target and detects a signal that is equal to or greater than a threshold,
When the signal detection result is “signal detection”, an evaluation value is calculated based on the detected signal amplitude, the probability density function of the false target signal amplitude, the probability density function of the true target signal amplitude, and the signal When the detection result is “signal non-detection”, an evaluation value calculation unit that calculates an evaluation value based on a false target signal non-detection probability, a true target signal non-detection probability;
The evaluation value calculated by the evaluation value calculation unit is determined based on the upper threshold value and the lower threshold value of the evaluation value. As a result of the determination, “target detection”, “target not detected”, “determination pending” An evaluation value determination unit that selects any one of
Regarding the number of observations in the signal detection result, determination of the end of determination is performed when the number of observations reaches a threshold value, and an observation number determination unit that selects either “end of determination” or “determination pending” as a result of the determination When,
Comprehensive determination is made based on the determination result by the evaluation value determination unit and the determination result by the observation number determination unit, and as a result of the determination, “target detection”, “target non-detection”, “determination pending” A target detection apparatus comprising: a comprehensive determination unit that selects one of them. A target detection method for detecting a target based on a signal detection result from a sensor for observing a target and detecting a signal equal to or higher than a threshold,
When the signal detection result is “signal detection”, an evaluation value is calculated based on the detected signal amplitude, the probability density function of the false target signal amplitude, the probability density function of the true target signal amplitude, and the signal When the detection result is “signal non-detection”, the evaluation value is calculated based on the false target signal non-detection probability and the true target signal non-detection probability,
The evaluation value is determined based on the upper threshold value and the lower threshold value of the evaluation value, and as a result of the determination, one of “target detection”, “target non-detection”, and “determination pending” is selected,
For the number of observations in the signal detection result, determine the end of determination when the observation number threshold is reached, and select either `` end of determination '' or `` determination pending '' as the result of the determination,
Comprehensive determination is made based on the result of determination on the evaluation value and the result of determination on the number of observations. As a result of the determination, “target detection”, “target non-detection”, “determination pending” Target detection method to select one. A target detection program for causing a computer to execute a process of detecting a target based on a signal detection result from a sensor that detects a signal equal to or higher than a threshold value by observing the target,
When the signal detection result is “signal detection”, an evaluation value is calculated based on the detected signal amplitude, the probability density function of the false target signal amplitude, the probability density function of the true target signal amplitude, and the signal When the detection result is “signal non-detection”, an evaluation value calculation step for calculating an evaluation value based on the false target signal non-detection probability and the true target signal non-detection probability;
The evaluation value calculated in the evaluation value calculation step is determined based on the upper threshold value and the lower threshold value of the evaluation value. As a result of the determination, “target detection”, “target not detected”, “determination pending” An evaluation value determination step for selecting one of the following:
For the number of observations in the signal detection result, determine the end of determination at the time when the observation number threshold is reached, and the number of observations determination step for selecting either `` end of determination '' or `` determination pending '' as a result of the determination;
Comprehensive determination is performed based on the determination result in the evaluation value determination step and the determination result in the observation number determination step. As the determination result, “target detection”, “target non-detection”, “determination pending” A target detection program comprising: a comprehensive determination step for selecting one of them.

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