Vehicle detection device, vehicle detection method, and determination device

Abstract

To provide a vehicle detection device capable of suppressing an erroneous detection.SOLUTION: A vehicle detection device 1 comprises: a light-projecting unit 2 that projects pulse light; a light-receiving unit 3 arranged to face the light-projecting unit and receiving the pulsed light from the light-projecting unit to generate a light reception signal; a comparison unit that compares a signal voltage of the light reception signal with a reference voltage; a measurement unit that measures a time during which the signal voltage of the light reception signal is higher than the reference voltage; and a determination unit that determines presence or absence of an object between the light-projecting unit and the light-receiving unit based on a length of the time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle detection device, a vehicle detection method, and a determination device. [Background technology]

[0002] Patent Document 1 discloses a vehicle detection device that includes light-projecting units arranged on one side of the lane in the width direction and arranged in multiple rows in the height direction, and light-receiving units arranged in multiple rows in the height direction, facing the light-projecting units in the width direction across the lane and paired with each light-projecting unit, and that detects whether or not a vehicle is present in the lane based on a light-receiving signal that indicates whether or not the optical axis connecting the detection light projected by the light-projecting units and the light-receiving units that receive the detection light is blocked. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-185436 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the vehicle detection device as described above, in rainy weather or the like, the light projected from the light-projecting unit may be reflected by the road surface and enter the light-receiving unit, which may result in erroneous detection.

[0005] The present invention has been made in consideration of the above-mentioned problems, and a main object of the present invention is to provide a vehicle detection device, a vehicle detection method, and a determination device that are capable of suppressing erroneous detection. [Means for solving the problem]

[0006] In order to solve the above problems, a vehicle detection device of one embodiment of the present invention comprises a light-projecting unit that projects a pulsed light, a light-receiving unit arranged opposite the light-projecting unit that receives the pulsed light from the light-projecting unit and generates a received light signal, a comparison unit that compares a signal voltage of the received light signal with a reference voltage, a measurement unit that measures the time during which the signal voltage of the received light signal is greater than the reference voltage, and a determination unit that determines the presence or absence of an object between the light-projecting unit and the light-receiving unit based on the length of time.

[0007] In another aspect of the vehicle detection method of the present invention, a light-projecting unit projects a pulsed light, a light-receiving unit arranged opposite the light-projecting unit receives the pulsed light from the light-projecting unit to generate a light-receiving signal, compares the signal voltage of the light-receiving signal with a reference voltage, measures the time during which the signal voltage of the light-receiving signal is greater than the reference voltage, and determines the presence or absence of an object between the light-projecting unit and the light-receiving unit based on the length of time.

[0008] In addition, a determination device of another aspect of the present invention includes a receiving unit that receives an output signal from a comparison unit that compares a signal voltage of a received light signal generated by a light receiving unit that receives pulsed light from a light projecting unit with a reference voltage, a measurement unit that measures the time during which the signal voltage of the received light signal is greater than the reference voltage based on the output signal, and a determination unit that determines the presence or absence of an object between the light projecting unit and the light receiving unit based on the length of time. Effect of the Invention

[0009] According to the present invention, it is possible to suppress erroneous detection. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a vehicle detection device according to an embodiment. [Diagram 2] 1A and 1B are diagrams illustrating an example of object detection by a vehicle detection device. [Diagram 3] 4 is a circuit diagram showing an example of a light receiving section and a comparison section. FIG. [Figure 4] FIG. 1 is a block diagram illustrating an example of a determination device. [Diagram 5] FIG. 11 is a diagram illustrating an example of a determination made by a determining unit. [Figure 6] FIG. 13 illustrates an example of time measurement. [Figure 7] FIG. 1 is a diagram illustrating an example of object detection. [Figure 8] FIG. 13 is a diagram illustrating an example of detection time. [Figure 9] FIG. 13 is a diagram illustrating an example of detection time. [Figure 10] FIG. 13 is a diagram illustrating an example of detection time. [Figure 11] FIG. 13 is a diagram illustrating an example of detection time. [Figure 12] FIG. 11 is a circuit diagram showing a reference example. [Figure 13] FIG. 13 is a diagram showing a modified example of the determination device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] 1 and 2 are diagrams illustrating an example of a vehicle detection device 1 according to an embodiment. The vehicle detection device 1 includes a light projecting unit 2 and a light receiving unit 3, and the light projected from the light projecting unit 2 is received by the light receiving unit 3. The light is, for example, infrared light.

[0013] In this embodiment, the vehicle detection device 1 is a transmission type multi-optical axis photoelectric sensor, and the light-projecting unit 2 and the light-receiving unit 3 form multiple optical axes arranged in the vertical direction. The light-projecting unit 2 includes multiple light-emitting elements 21 arranged in the vertical direction, and the light-receiving unit 3 includes multiple light-receiving elements 31 arranged in the vertical direction.

[0014] The light-projecting unit 2 and the light-receiving unit 3 are disposed opposite each other across a road RD on which a vehicle VH travels. When light from the light-projecting unit 2 to the light-receiving unit 3 is blocked by an object such as a vehicle VH, the object is detected.

[0015] 2, at the bottom of the vehicle detection device 1, a part of the light projected from the light projecting unit 2 may be reflected by the road surface and enter the light receiving unit 3. In that case, even if an object B exists between the light projecting unit 2 and the light receiving unit 3, the object B may not be detected.

[0016] Furthermore, since the detection resolution of the vehicle detection device 1 depends on the number of pairs of light-emitting elements 21 and light-receiving elements 31, if it is attempted to detect even small objects relative to the vehicle VH, such as a tow bar, it is necessary to arrange a large number of light-emitting elements 21 and light-receiving elements 31 with a narrow pitch.

[0017] Therefore, in this embodiment, as described below, these problems are solved by measuring the length of time during which the signal voltage of the received light signal is greater than the reference voltage, and using the measured length of time for judgment.

[0018] 3 is a circuit diagram showing an example of the light receiving section 3 and the comparison section 4. The diagram also shows an example of the signal waveform of each element. The configuration shown in the diagram is provided for each of the multiple light receiving elements 31 included in the light receiving section 3.

[0019] In this embodiment, the light projecting unit 2 projects pulsed light having a predetermined time width. The light receiving element 31 receives the pulsed light projected from the light projecting unit 2 and generates a light receiving signal. The light receiving signal is a rectangular wave corresponding to the pulsed light.

[0020] The received light signal is input to a comparison section (for example, a comparison circuit) 4 through a differentiation circuit 32 and an amplification / filtering circuit 33. The amplification / filtering circuit 33 includes a plurality of amplifiers, and amplifies the received light signal and extracts components in a predetermined frequency band.

[0021] The comparator 4 compares the signal voltage of the light receiving signal with a reference voltage RF. The comparator 4 outputs a high-level voltage when the signal voltage of the light receiving signal is greater than the reference voltage RF, and outputs a low-level voltage when the signal voltage of the light receiving signal is less than the reference voltage RF.

[0022] The time during which the signal voltage of the received light signal is greater than the reference voltage RF (hereafter referred to as the detection time tdet The length of the detection time t corresponds to the intensity of the pulsed light. det The lower the intensity of the pulsed light, the longer the detection time t det becomes shorter.

[0023] Therefore, when the pulsed light is directly incident on the light receiving element 31, the detection time t det On the other hand, when the pulsed light does not directly enter the light receiving element 31 and only the light reflected by the road surface enters the light receiving element 31, the detection time t det becomes relatively short.

[0024] 4 is a block diagram showing an example of a functional configuration of the determination device 5. The determination device 5 is, for example, a field programmable gate array (FPGA). However, the determination device 5 is not limited to this and may be another programmable logic device (PLD) or a computer including a CPU or the like.

[0025] The determination device 5 includes, as functional units, a receiving unit 51, a measuring unit 52, and a determining unit 53. The receiving unit 51 receives the output signal of the comparing unit 4. The measuring unit 52 determines, based on the output signal of the comparing unit 4, the time during which the signal voltage of the received light signal is greater than the reference voltage RF (detection time t det ) measure the length.

[0026] The determination unit 53 detects the detection time t det Based on the length of the detection time t det Based on the length of the light, the quality of the installation or maintenance of the light projecting unit 2 and the light receiving unit 3 is further judged.

[0027] 5 is a diagram showing an example of a determination made by the determination unit 53. The thresholds t1, t2, and t3 have a relationship of t1>t2>t3. The determination unit 53 determines the detection time t det If the length of the light-projecting portion 2 is equal to or less than a threshold value t3 (an example of a first threshold value), it is determined that an object B is present between the light-projecting portion 2 and the light-receiving portion 3.

[0028] In addition, the determination unit 53 determines the detection time t det If the length of the light-transmitting portion 2 exceeds the threshold value t1 (an example of the second threshold value), it is determined that there is no object B between the light-transmitting portion 2 and the light-receiving portion 3, and that the installation or maintenance of the light-transmitting portion 2 and the light-receiving portion 3 is good (i.e., there is no defect).

[0029] In addition, the determination unit 53 determines the detection time t det When the length of the detection time t exceeds the threshold value t3 and is equal to or less than the threshold value t1, the determination unit 53 determines that the installation or maintenance of the light projecting unit 2 and the light receiving unit 3 is defective. det If the length of the detection time t exceeds the threshold t3 and is equal to or less than the threshold t2, it is determined that the maintenance is defective. det If the length of the contact exceeds the threshold value t2 and is equal to or less than the threshold value t1, the contact is determined to be improperly installed.

[0030] Poor installation occurs when insufficient light enters due to, for example, misalignment of the optical axes of the light-projecting unit 2 and the light-receiving unit 3 during installation. Poor maintenance occurs when insufficient light enters due, for example, to dirt on the lenses of the light-projecting unit 2 and the light-receiving unit 3 caused by long-term use.

[0031] In this way, the detection time t det By making a judgment based on the length of the pulsed light, it is possible to distinguish between a state in which the pulsed light directly enters the light receiving element 31 and a state in which the pulsed light does not directly enter the light receiving element 31 and only the reflected light reflected by the road surface enters the light receiving element 31, thereby making it possible to suppress erroneous detection. In addition to the presence or absence of an object, it is also possible to judge the quality of installation or maintenance.

[0032] As shown in FIG. 2, the light reflected by the road surface enters only a portion of the light receiving elements 31 located on the lower side of the plurality of light receiving elements 31 provided in the light receiving unit 3. Therefore, for these light receiving elements 31, the detection time t det The presence or absence of an object may be determined based on the length of the light receiving element 31, and the presence or absence of an object may be determined based on the presence or absence of light reception for the remaining light receiving elements 31 in a conventional manner.

[0033] Figure 6 shows the detection time t detMeasurement window for measuring t WIN The measurement unit 52 detects the detection time t det That is, the measurement unit 52 may measure the light intensity in a predetermined measurement window t WIN During this period, the detection time t det This makes it possible to reduce the influence of disturbances, etc.

[0034] 7 is a diagram showing an example in which the vehicle detection device 1 detects an object smaller than a vehicle, such as a tow bar P. According to this embodiment, as described below, even if the number of light-emitting elements 21 and light-receiving elements 31 is reduced and the pitch is increased compared to conventional methods, it is possible to maintain the detection resolution.

[0035] As shown in the figure, since the light emitted from the light-emitting element 21 has a certain spread, for example, light L2 emitted from the second light-emitting element 21b is received not only by the second light-receiving element 31b that is paired with it, but also by the light-receiving elements 31a and 31c above and below it. Similarly, light L3 emitted from the third light-emitting element 21c is received not only by the third light-receiving element 31c that is paired with it, but also by the light-receiving elements 31b and 31d above and below it.

[0036] Now, when considering a state in which a tow bar P is positioned between the light projecting unit 2 and the light receiving unit 3, the shadow created by the light L2 being blocked by the tow bar P is positioned between the second and third light receiving elements 31b and 31c, so the amount of light received by the light receiving elements 31b and 31c for the light L2 does not change. On the other hand, the shadow created by the light L3 being blocked by the tow bar P is positioned on the second light receiving element 31b, so the amount of light received by the light receiving element 31b for the light L3 changes.

[0037] As described above, according to this embodiment, the detection time t det In the example shown in the figure, the tow bar P can be detected by the change in the amount of light received by the second light receiving element 31b. In this way, even if the number of light emitting elements 21 and light receiving elements 31 is reduced and the pitch is widened, the detection time tdet By determining the intensity of the received light based on the length of the sensor, it is possible to maintain the detection resolution.

[0038] Figure 8 shows the detection time t det 7 is a diagram for explaining an example of performing object detection by comparing a plurality of detection times t det The presence or absence of an object between the light projector 2 and the light receiver 3 may be determined based on the difference in length.

[0039] The figure shows the detection times t det1 ~t det3 When there is no object between the light projector 2 and the light receiver 3, the detection time is t det1 ~t det3 The lengths of the detection times t det1 ~t det3 Some of the lengths will be shorter than others.

[0040] For example, as shown in the figure, the determination unit 53 determines the longest detection time t det3 The detection time t when the difference between det1 ,t det2 When there are two or more, it is determined that an object is present between the light projecting unit 2 and the light receiving unit 3.

[0041] Also, as shown in FIG. 9, the detection time t det1 ,t det2 The detection time t det3 If the distance is short, it can be estimated that an object is present between the light-emitting element 21b and the light-receiving element 31c.

[0042] 10 and 11 show the detection time t det FIG. 11 is a diagram illustrating another example of object detection based on the variation of the detection time t det and the previously measured detection time t detThe presence or absence of an object between the light projecting unit 2 and the light receiving unit 3 may be determined based on the difference in length between the light projecting unit 2 and the light receiving unit 3.

[0043] FIG. 10 shows the detection time t det(n-1) and the detection time t measured when an object is between the light projector 2 and the light receiver 3. det(n) The detection time t det(n) is the detection time t det(n-1) will be shorter than

[0044] For example, the determination unit 53 determines whether the detected time t det(n) and the detection time t det(n) The detection time t measured before the length of det(n-1) When the difference between the lengths of the light projecting unit 2 and the light receiving unit 3 becomes equal to or greater than a threshold value, it is determined that an object is present between the light projecting unit 2 and the light receiving unit 3.

[0045] In the above embodiment, the determination device 5 is configured with an FPGA or the like or a computer, which has the following advantages.

[0046] In the conventional method, the signal voltage of the received light signal is below the threshold V th It is judged whether the value is equal to or larger than the threshold V th is a fixed value. In this case, the threshold value V is set according to the condition where the distance between the light-emitting part and the light-receiving part is the longest. th However, if the distance between the light-emitting part and the light-receiving part is shorter than that, the threshold value V th is not an optimal threshold.

[0047] In contrast, in the present embodiment, since an FPGA or a computer is used, the detection time t det The threshold t applied to th For example, the detection time t det Set the initial value t det0 Let the initial value t det0 The threshold value t th In this way, an appropriate threshold value can be set.

[0048] In addition, in the conventional method, the signal voltage of all received light signals is below the threshold V th The light-emitting unit and the light-receiving unit are installed while checking that the above is the case, but in that case, the installation is not necessarily optimal. Alternatively, the light-emitting unit and the light-receiving unit are installed while checking with an oscilloscope that the waveform of the received light signal is maximized, but in that case, the installation is time-consuming because an oscilloscope is required.

[0049] In contrast, in this embodiment, the detection time t det In order to measure the length of det It is easy to adjust the installation to maximize the detection time t det Since the length of the wire can be checked, it is easier to check than when using an oscilloscope.

[0050] 12 is a circuit diagram showing a reference example. As shown in the figure, a plurality of comparators 41-43 having different reference voltages RF1-RF3 may be provided to determine the strength of the signal voltage of the received light signal. The reference voltages RF1-RF3 in the figure have a relationship of RF1>RF2>RF3.

[0051] For example, similar to the judgment example shown in Figure 5 above, when all of the comparison units 41 to 43 output high-level voltages, the judgment unit 53 judges that there is no object B between the light-projecting unit 2 and the light-receiving unit 3, and that the installation or maintenance of the light-projecting unit 2 and the light-receiving unit 3 is good.

[0052] Furthermore, when the comparison unit 41 outputs a low level voltage and the comparison units 42 and 43 output a high level voltage, the determination unit 53 determines that there is a maintenance defect. When the comparison units 41 and 42 output a low level voltage and the comparison unit 43 outputs a high level voltage, the determination unit 53 determines that there is an installation defect.

[0053] Furthermore, when all of the comparison units 41 to 43 output a low level voltage, the determination unit 53 determines that an object B is present between the light projecting unit 2 and the light receiving unit 3. By measuring the strength of the signal voltage of the light receiving signal in this manner using the multiple comparison units 41 to 43, it is also possible to suppress erroneous detection and determine whether the installation or maintenance is satisfactory.

[0054] [Variations] The determination device 5 according to the modified example described below is configured with a computer including a CPU and the like, and determines the detection time t det The type of vehicle VH passing between the light projecting unit 2 and the light receiving unit 3 is identified from the time series data of the length of the light.

[0055] 13 is a block diagram showing an example of a functional configuration of a determination device 5 according to a modified example. The determination device 5 according to the modified example further includes a normalization unit 54, a vehicle type identification unit 55, and a model storage unit 56 in addition to a receiving unit 51, a measurement unit 52, and a determination unit 53.

[0056] The receiving unit 51, the measuring unit 52, the determining unit 53, the normalizing unit 54, and the vehicle type identifying unit 55 are realized by the CPU of the determining device 5 executing information processing according to a program. The model holding unit 56 is constructed in the memory of the determining device 5.

[0057] The normalization unit 54 is connected to a vehicle speed detection unit 6 that detects the speed of the vehicle VH, and acquires vehicle speed data from the vehicle speed detection unit 6. The vehicle speed detection unit 6 is provided near the light projecting unit 2 and the light receiving unit 3, and detects the speed of the vehicle VH traveling on the road RD.

[0058] The measurement unit 52 measures a plurality of detection times t det The time series data having a length of t is provided to the normalization unit 54 and the vehicle type identification unit 55. The time series data is a detection time t det Represents the change over time.

[0059] The normalization unit 54 normalizes the time series data acquired from the measurement unit 52 in accordance with the vehicle speed data acquired from the vehicle speed detection unit 6. Specifically, the normalization unit 54 divides the time axis of the time series data by the vehicle speed.

[0060] The vehicle type identification unit 55 uses the learned model stored in the model holding unit 56 to identify the vehicle type of the vehicle VH passing between the light projector 2 and the light receiver 3 from the normalized time series data acquired from the normalization unit 54. The vehicle type may be, for example, a light vehicle, a regular vehicle, a medium-sized vehicle, etc.

[0061] The trained model stored in the model holding unit 56 is generated in advance by machine learning, for example, using time-series data for learning as input data and vehicle models as teacher data.

[0062] The time series data for learning is the detection time t det The time series data is measured and normalized in the same way as the time series data of length

[0063] The vehicle type as the teacher data is determined based on, for example, the tire width calculated from the detection data of the tread embedded in the road. The determined vehicle type is associated with the learning time-series data to create a learning dataset.

[0064] The trained model is, for example, a convolutional neural network that includes a convolutional layer, a pooling layer, a fully connected layer, and an output layer. In particular, a deep neural network in which neurons are combined in multiple stages is preferable.

[0065] Learning is realized by inputting learning time-series data as input data into the model, performing calculations, outputting the vehicle model as output data, calculating the difference between the vehicle model as the output data and the vehicle model as the training data, and adjusting the model parameters so that the difference is reduced. In addition, between learning rounds, the validity of the model is evaluated using a test data set.

[0066] According to the above-described modified example, even if a step board is not provided on the road RD, the detection time t det From the time-series data of the length, it is possible to identify the type of vehicle VH passing between the light projecting unit 2 and the light receiving unit 3.

[0067] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made by those skilled in the art. [Explanation of symbols]

[0068] 1 vehicle detection device, 2 light projection unit, 21 light emitting element, 3 light receiving unit, 31 light receiving element, 32 differentiation circuit, 33 amplification and filtering circuit, 4 comparison unit, 5 judgment device, 51 reception unit, 52 measurement unit, 53 judgment unit, 54 normalization unit, 55 vehicle type identification unit, 56 model storage unit

Claims

1. a light projection unit that projects pulsed light; a light receiving section disposed opposite to the light projecting section, receiving the pulsed light from the light projecting section and generating a light receiving signal; a comparison unit that compares a signal voltage of the light receiving signal with a reference voltage; a measurement unit that measures a time during which a signal voltage of the light reception signal generated by receiving the pulsed light once is greater than the reference voltage; a determination unit that determines whether or not an object is present between the light projecting unit and the light receiving unit based on the length of time; A vehicle detection device comprising:

2. The determination unit further determines whether installation or maintenance of the vehicle detection device is good or bad based on the length of time. The vehicle detection device of claim 1 .

3. The determination unit is If the length of time is equal to or less than a first threshold value, it is determined that an object is present between the light projecting unit and the light receiving unit; If the length of time exceeds the first threshold and is equal to or less than the second threshold, it is determined that there is no object between the light projecting unit and the light receiving unit, but the installation or maintenance of the vehicle detection device is defective; If the length of time exceeds the second threshold, it is determined that there is no object between the light projecting unit and the light receiving unit, and that the installation or maintenance of the vehicle detection device is good. The vehicle detection device of claim 2.

4. the measurement unit measures the length of time in a measurement window that is set based on the timing at which the light projector projects the pulsed light.

4. A vehicle detection device according to claim 1.

5. The light projecting unit includes a plurality of light emitting elements arranged in a vertical direction, The light receiving unit includes a plurality of light receiving elements arranged in a vertical direction, The comparison unit is provided for each of the plurality of light receiving elements.

5. A vehicle detection device according to claim 1.

6. the determination unit determines that there is an object between the light projecting unit and the light receiving unit when a predetermined number or more of the lengths of time are measured for the plurality of light receiving elements and the difference between the length of time and the longest length of time is equal to or greater than a threshold value, or when a part of the lengths of time are shorter than the remaining lengths of time.

6. The vehicle detection device of claim 5.

7. the determination unit determines the presence or absence of an object between the light projecting unit and the light receiving unit based on the length of time measured for a portion of the light receiving elements located on a lower side among the plurality of light receiving elements.

7. A vehicle detection device according to claim 5 or 6.

8. the determination unit determines that an object is present between the light projecting unit and the light receiving unit when a difference between the length of the time and a length of the time measured before the length of the time is measured becomes equal to or greater than a threshold value. A vehicle detection device according to any one of claims 1 to 7.

9. The present invention further includes an identification unit that identifies a type of vehicle passing between the light projecting unit and the light receiving unit from time series data of the lengths of the times measured for the plurality of light receiving elements by using a trained model.

6. The vehicle detection device of claim 5.

10. A detection unit for detecting a speed of the vehicle is further provided. The identification unit identifies the type of the vehicle from the time-series data normalized according to the speed of the vehicle.

10. The vehicle detection device of claim 9.

11. The light-emitting unit emits pulsed light, a light receiving unit disposed opposite to the light projecting unit receives the pulsed light from the light projecting unit and generates a light receiving signal; Comparing a signal voltage of the received light signal with a reference voltage; measuring a time during which a signal voltage of the light reception signal generated by receiving the pulsed light once is greater than the reference voltage; determining whether or not an object is present between the light projecting unit and the light receiving unit based on the length of time; Vehicle detection methods.

12. a receiving section for receiving an output signal from a comparing section for comparing a signal voltage of a light receiving signal generated by a light receiving section for receiving a pulsed light from a light projecting section with a reference voltage; a measurement unit that measures, based on the output signal, a length of time during which a signal voltage of the light reception signal generated by receiving the pulsed light once is greater than the reference voltage; a determination unit that determines whether or not an object is present between the light projecting unit and the light receiving unit based on the length of time; A determination device comprising:

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