JP6490557B2 - Target detection apparatus, target detection method, and target detection program - Google Patents

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 that detects a target based on a signal detection result from a sensor that detects a signal exceeding a threshold value by observing the target such as a radar device or a sonar device, the target is detected reliably. In addition, a target detection process (see Non-Patent Document 1) by SPRT (Sequential Probability Ratio Test) is used. 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 case where the determination is performed by determining the number of observations corresponding to the sample size in advance, this determination method uses “target detection” or “target non-detection” at two specified points that define the model of the false target and the true target. The average number of observations required for determination can be reduced. However, there is a problem that the average number of observations required for the determination of “target detection” is further reduced.

  The present embodiment has been made in view of the above problems, and an object thereof is to provide a target detection device, a target detection method, and a target detection program that can reduce the average number of observations required for determination of “target detection”.

  In order to solve the above problem, the target detection apparatus according to the present embodiment includes an evaluation value calculation unit and a determination unit. The evaluation value calculation unit inputs a signal detection result from a sensor that observes the target and detects a signal that is equal to or greater than a threshold value. If the signal detection result is signal detection, the detected signal amplitude and the false target signal amplitude An evaluation value is calculated based on a probability density function and a probability density function of a true target signal amplitude, and when the signal detection result is a signal non-detection, based on a false target signal non-detection probability and a true target signal non-detection probability To calculate an evaluation value. The determination unit determines the evaluation value calculated by the evaluation value calculation unit based on the upper threshold value and the lower threshold value of the evaluation value. As a result of the determination, “target detection”, “target non-detection”, Select one of “Pending judgment”.

The block diagram which shows the structure of the target detection apparatus which concerns on embodiment. The flowchart which shows the specific example of the flow of a process of the target detection apparatus which concerns on 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 value. Based on the signal detection result, the likelihood ratio ST (k) for the k-th observation is calculated. The determination unit 23, the upper threshold value from the threshold value calculation unit 21 T _U and the lower threshold T _L, based on the likelihood ratio ST (k) from the likelihood ratio calculation unit 22, determined by the following formula (1) And select one of “target detection”, “target non-detection”, and “determination pending” 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.

The threshold calculation unit 21, based on the type I error rate α and type II error rates beta, calculates the upper threshold T _U and the lower threshold T _L for the likelihood ratio (step S201). Upper threshold _{T U} and the lower threshold _{T L} is calculated by the following equation (2).

The likelihood ratio calculation unit 22 performs the observation k-th time 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 number of signal detections m. Likelihood ratio ST (k) is calculated (step S202). The likelihood ratio ST (k) for the k-th observation is calculated by the following equation (3).

The determination unit 23 compares the upper threshold _{T U} from observation k-th likelihood ratio ST (k) and the threshold value calculation unit 21 from the likelihood ratio calculation unit 22 (step S203), the likelihood ratio ST ( k) is the determination result to the case of more than the upper threshold _{T U} will be referred to as a "target detection" (step S204). Further, when the likelihood ratio ST (k) is smaller than the upper threshold _{T U} compares the lower threshold _{T L} from the threshold calculator 21 and the likelihood ratio ST (k) (step S205), likelihood When the degree ratio ST (k) is equal to or lower than the lower threshold value _TL , the determination result is “target non-detection” (step S206). Otherwise (likelihood ratio ST (k) is greater than the lower threshold T _L, is smaller than the upper threshold T _U), the determination result is "indeterminant" (step S207). And the determination result of said step S204, S206, S207 is output (step S208), and the process of observation k-th is completed. When the determination unit 23 determines “determination pending”, the process from step S201 is repeated based on the observation (k + 1) th signal detection result (step S209).

Here, in the target detection device having the above configuration, based on the signal detection result from the sensor that observes the target and detects a signal equal to or higher than the threshold, the false target signal detection probability P _F , and the true target signal detection probability P _D. The k-th likelihood ratio ST (k) has been calculated, and a signal amplitude that has a larger amount of information and is equal to or greater than a threshold value is not used to calculate the likelihood ratio ST (k).

Therefore, in the embodiment described below, when a signal detection result from a sensor (not shown, for example, a radar device, a sonar device, etc.) is input and the signal detection result is signal detection, the detected signal amplitude a, false target The probability ratio ST (k) for the k-th observation is calculated as an evaluation value based on the probability density function f (a | a ₀ ) of the signal amplitude and the probability density function g (a | a ₁ ) of the true target signal amplitude. If the signal detection result is signal non-detection, the likelihood of observation k times as an evaluation value based on the false target signal non-detection probability (1-P _F ) and the true target signal non-detection probability (1-P _D ). The degree ratio ST (k) is calculated. Then, a determination about the likelihood ratio ST (k) based on the upper threshold T _U and the lower threshold T _L of likelihood ratio ST (k), the determination result as "target detection", "target not detected" By selecting either “determination pending”, the average number of observations required for the determination of “target detection” is reduced.

  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. This target detection apparatus includes a threshold value calculation unit 11, a likelihood ratio calculation unit 12, and a determination unit 13.

The threshold value calculating section 11 calculates the upper threshold T _U and the lower threshold T _L of an evaluation value likelihood ratio.

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 first calculation unit 121 detects the detected signal amplitude a and the probability density function f (a | a of the false target signal amplitude. ₀ ), the likelihood ratio ST (k) for the k-th observation is calculated as an evaluation value based on the probability density function g (a | a ₁ ) of the true target signal amplitude. Further, when the signal detection result from the sensor is signal non-detection, the second calculation unit 122 has a false target signal non-detection probability (1-P _F ) and a true target signal non-detection probability (1-P _D ). The likelihood ratio ST (k) for the k-th observation is calculated as an evaluation value based on the above.

The determination unit 13, the upper threshold value from the threshold value calculation unit 11 _{T U} and the lower threshold _{T L,} based on the likelihood ratio ST (k) from the likelihood ratio calculation unit 12, the following equation (4) (( 1) (same as equation 1), and select “target detection”, “target non-detection”, or “determination pending” as the determination result.

  FIG. 2 is a flowchart showing a specific example of the processing flow of the target detection apparatus according to the present embodiment. A processing flow of the target detection apparatus according to the present embodiment will be described with reference to FIG.

The threshold calculation unit 11, based on the type I error rate α and type II error rates beta, calculates the upper threshold T _U and the lower threshold T _L for the likelihood ratio (step S101). Approximate value of the upper threshold T _U and the lower threshold T _L is calculated by the following equation (5).

The likelihood ratio calculation unit 12 determines whether the signal detection result is signal detection or signal non-detection (step S102). When the signal detection result is signal detection, the detected signal amplitude a, the false target The probability ratio ST (k) for the k-th observation is calculated as an evaluation value based on the probability density function f (a | a ₀ ) of the signal amplitude and the probability density function g (a | a ₁ ) of the true target signal amplitude. If the signal detection result is signal non-detection (step S103), observation is made as an evaluation value based on the false target signal non-detection probability (1-P _F ) and the true target signal non-detection probability (1-P _D ). The kth likelihood ratio ST (k) is calculated (step S104). The likelihood ratio ST (k) for the k-th observation is calculated by the following equation (6).

Here, a 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 a ₁ represents a probability density function g (•) of the true target signal amplitude. Represents a parameter group consisting of a plurality of parameters. 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 | a) 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 a ₁ ).

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

The determination unit 13 compares the upper threshold _{T U} from likelihood ratio ST (k) and the threshold value calculation unit 11 from the likelihood ratio calculation unit 12 (step S105), the likelihood ratio ST (k) is the upper the determination results in the case of more than the threshold _{T U} will be referred to as a "target detection" (step S106). When the likelihood ratio ST (k) is smaller than the upper threshold _{T U} compares the lower threshold _{T L} from the threshold calculator 11 and the likelihood ratio ST (k) (step S107), the likelihood ratio When ST (k) is equal to or lower than the lower threshold value _TL , the determination result is “target not detected” (step S108). Otherwise (likelihood ratio ST (k) is greater than the lower threshold T _L, is smaller than the upper threshold T _U), the determination result is "indeterminant" (step S109). And the determination result of said step S106, S108, S109 is output (step S110), and the process of observation k time is completed. When the determination unit 13 determines “determination pending”, the processing from step S101 is repeated based on the signal detection result of the observation (k + 1) th (step S111).

In the above description, when the signal detection result is signal detection, the detected signal amplitude a, the probability density function f (a | a ₀ ) of the false target signal amplitude, and the probability density function g (a of the true target signal amplitude Although an example in which the likelihood ratio ST (k) is calculated as an evaluation value based on | a ₁ ) has been shown, the detected signal amplitude a, the likelihood function L ₀ (a) of the false target signal amplitude, the true target The likelihood ratio ST (k) can be calculated as an evaluation value based on the likelihood function L ₁ (a) of the 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 Likelihood ratio ST (k) can be calculated as an evaluation value based on (a) / L ₀ (a)).

In the above, an example in which the likelihood ratio is used as the evaluation value is shown. However, as shown in the basic configuration of the target detection apparatus, the likelihood ratio obtained by logarithmically converting each value (more precisely, the log likelihood ratio). ) To perform processing. In this case, an approximate value of the upper threshold T _U and the lower threshold T _L is calculated by the following equation (7).

Corresponding k-th likelihood ratio ST (k) is calculated by the following equation (8).

  Furthermore, instead of inputting the signal detection result from the sensor, the signal detection result processed by the correlation means and the temporary target registration update means described in Patent Document 1 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 amplitude Based on the probability density function f (a | a ₀ ) and the probability density function g (a | a ₁ ) of the true target signal amplitude, the kth likelihood ratio ST (k) is calculated as an evaluation value, and signal detection is performed. When the result is signal non-detection, the observation k-th likelihood ratio ST () as an evaluation value based on the false target signal non-detection probability (1-P _F ) and the true target signal non-detection probability (1-P _D ) k) is calculated. Then, a determination about the likelihood ratio ST (k) based on the upper threshold T _U and the lower threshold T _L of likelihood ratio ST (k), the determination result as "target detection", "target not detected" By selecting one of “determination pending”, it is possible to reduce the average number of observations required for the determination of “target detection”.

  Note that the target detection processing according to the above embodiment can be configured as a program that causes a computer to realize the functions of the threshold value calculation unit 11, the likelihood ratio calculation unit 12, and the determination unit 13.

  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 Threshold calculation unit,
12 ... Likelihood ratio calculation unit, 121 ... First calculation unit, 122 ... Second calculation unit,
13: Determination unit.

Claims (6)

Input a signal detection result from a sensor that observes the target and detects a signal that is equal to or greater than the threshold value. If the signal detection result is signal detection, the detected signal amplitude, the probability density function of the false target signal amplitude, the true target An evaluation value is calculated based on the probability density function of the signal amplitude of the signal, and 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. An evaluation value calculation unit;
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” A target detection apparatus comprising: a determination unit that selects any of the above. When the signal detection result is signal detection, the evaluation value calculation unit calculates a likelihood ratio of observation k (k is an arbitrary natural number) times as the evaluation value based on a probability density function, and the signal detection result In the case of signal non-detection, the likelihood ratio of the k-th observation is calculated as the evaluation value based on the signal non-detection probability,
The target detection apparatus according to claim 1, wherein the determination unit determines the likelihood ratio calculated by the evaluation value calculation unit.   The target detection apparatus according to claim 1, wherein the evaluation value calculation unit and the determination unit collectively process a plurality of signal detection results. The evaluation value calculation unit calculates a likelihood ratio as the evaluation value using a plurality of signal detection results,
The target detection apparatus according to claim 1, wherein the determination unit determines the likelihood ratio calculated by the evaluation value calculation unit. Input a signal detection result from a sensor that observes the target and detects a signal that is equal to or greater than the threshold value. If the signal detection result is signal detection, the detected signal amplitude, the probability density function of the false target signal amplitude, the true target The evaluation value is calculated based on the probability density function of the signal amplitude of the signal, and when the signal detection result is a 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. ,
Target detection for determining the evaluation value based on the upper threshold value and the lower threshold value of the evaluation value, and selecting any one of “target detection”, “target non-detection”, and “determination pending” as a result of the determination Method. A target detection program for causing a computer to execute processing for detecting a target,
Input a signal detection result from a sensor that observes the target and detects a signal that is equal to or greater than the threshold value. If the signal detection result is signal detection, the detected signal amplitude, the probability density function of the false target signal amplitude, the true target An evaluation value is calculated based on the probability density function of the signal amplitude of the signal, and 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. An evaluation value calculating step;
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” A target detection program comprising: a determination step for selecting any of the above.

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