Vehicle sensor

Abstract

To provide a vehicle detector for enabling an effective use of a reflection wave even when a vehicle is not detected.SOLUTION: A vehicle detector 1 includes: an ultrasonic head part 10 which is installed over a road R, so as to transmit an ultrasonic wave toward a road surface R of an opposite road and also to receive a reflection wave of the ultrasonic wave; and a vehicle detection unit 21 where information based on a distance from the ultrasonic head part 10 to the road surface R is set and which acquires a reflection arrival time and detects a vehicle V traveling on the road surface R on the basis of the acquired reflection arrival time. The vehicle detection unit 21 determines that the vehicle V is detected when the reflection arrival time is less than a threshold th1, and determines that a change of a road surface state of the road surface R is detected when the reflection arrival time is equal to or more than the threshold th1 and also less than a threshold th2. When it is determined that the vehicle is detected, the vehicle detection unit 21 does not use the reflection arrival time for movement average calculation, and then, does not use the time for detection of the change of the road surface state of the road.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a vehicle sensor that senses a vehicle traveling on a road.

Background Art

[0002] Conventionally, in order to examine traffic volume on a road or the like, a vehicle sensor that detects the presence or absence of a vehicle using ultrasonic waves is known. Such a vehicle sensor, for example, attaches a head for transmitting and receiving ultrasonic waves so as to face the road surface from above the road, transmits ultrasonic waves in a substantially vertical direction from the head toward the road surface, and senses a vehicle based on the time until the reflected wave is received (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The vehicle sensor of Patent Document 1 is intended to sense a vehicle. On the other hand, when a vehicle is not sensed, a reflected wave reflected by a road surface or the like is detected. However, currently, the reflected wave reflected by a road surface or the like is not particularly utilized. That is, currently, during the period when a vehicle is detected, the received reflected wave is effectively utilized, but it cannot be said that it is effectively utilized during the period when a vehicle is not detected.

[0005] Therefore, an object of the present invention is to provide a vehicle sensor that can effectively utilize a reflected wave even when a vehicle is not sensed.

Means for Solving the Problems

[0006] The invention made to solve the above problems is provided above a road, transmits ultrasonic waves toward the facing road, and receives a reflected wave of the ultrasonic waves. It includes an ultrasonic head unit, an acquisition unit that acquires information regarding the time from when the ultrasonic head unit transmits the ultrasonic waves until it receives the reflected wave, and a detection unit that detects a vehicle traveling on the road based on the information regarding the time acquired by the acquisition unit. The detection unit has distance information from the ultrasonic head unit to the road set, and when the information regarding the time is less than a first threshold value which is a value regarding the time serving as a criterion for determining that the vehicle has been detected, it determines that the vehicle has been detected. When the information regarding the time is equal to or greater than the first threshold value and less than the time from when the ultrasonic head unit transmits the ultrasonic waves until it receives the reflected wave reflected by the road calculated based on the distance information, it determines that a change in the road surface condition has been detected. When it determines that the vehicle has been detected, it does not use the information regarding the time for detecting the change in the road surface condition of the road. This is a vehicle detector characterized by this.

[0007] Further, the detection unit has a second threshold value set which is a value less than the time from when the ultrasonic head unit transmits the ultrasonic waves until it receives the reflected wave reflected by the road calculated based on the distance information and equal to or greater than the first threshold value. When the information regarding the time is equal to or greater than the first threshold value and less than the second threshold value, it can be characterized in that it determines that a change in the road surface condition of the road has been detected.

[0008] Further, it can be characterized in that it further includes a temperature detection unit that detects the ambient temperature around the ultrasonic head unit, and the detection unit corrects the first threshold value and the second threshold value based on the ambient temperature detected by the temperature detection unit.

[0009] Further, it can be characterized in that when the detection unit determines that a change in the road surface condition of the road has been detected, it outputs warning information.

[0010] Further, it includes a storage unit that stores information regarding the presence or absence of output of the warning information when the power supply is turned off. When the power supply is turned on again after being turned off, the sensing unit refers to the information regarding the presence or absence of output of the warning information. If the information indicates that the warning information is to be output, the warning information can be output regardless of the current determination result.

[0011] Also, it is installed above the road, includes an ultrasonic head unit that transmits ultrasonic waves toward the facing road and receives the reflected waves of the ultrasonic waves, and an acquisition unit that acquires information regarding the distance to the object that reflected the ultrasonic waves based on the time from when the ultrasonic head unit transmits the ultrasonic waves until it receives the reflected waves. Further, it includes a sensing unit that senses a vehicle traveling on the road based on the information regarding the distance acquired by the acquisition unit. The sensing unit has the distance information from the ultrasonic head unit to the road set. When the information regarding the distance is less than a first threshold value which is a value regarding the distance serving as a criterion for determining that the vehicle has been sensed, it determines that the vehicle has been sensed. When the information regarding the distance is equal to or greater than the first threshold value and less than the distance based on the distance information, it determines that a change in the road surface condition has been detected. When it determines that the vehicle has been sensed, the information regarding the distance is not used for detecting a change in the road surface condition of the road. It can be a vehicle sensor characterized by this.

Advantages of the Invention

[0012] According to the present invention, it is possible to detect changes in the road surface condition such as waterlogging and snow accumulation. Further, when it is determined that a vehicle has been sensed, since the information regarding the time is not used for detecting a change in the road surface condition of the road, there is no possibility that the state of the change in the road surface condition is erroneously detected due to the information when the vehicle is sensed. Therefore, the reflected waves when the vehicle is not sensed can also be effectively utilized.

Brief Description of the Drawings

[0013]

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Figure 10

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] FIG. 1 is a diagram showing an installation example of the vehicle detector 1 according to the present embodiment. As shown in this figure, the vehicle detector 1 includes a controller 20 attached to a pole 151 erected beside the road surface R of the road on which the vehicle travels, and a ultrasonic head unit 10 attached to an arm 152 extending from the pole 151 above the road.

[0015] As is well known, the ultrasonic head unit 10 includes a transmitter that transmits ultrasonic waves of a predetermined frequency toward the road surface R, and a receiver that receives the reflected wave of the ultrasonic waves and converts it into an electrical signal.

[0016] As shown in FIG. 2, the controller 20 includes a vehicle detection unit 21, a communication processing unit 22, and a temperature sensor 23.

[0017] The vehicle detection unit 21 outputs a transmission signal transmitted as ultrasonic waves from the transmitter of the ultrasonic head unit 10 at a constant period. Also, the vehicle detection unit 21 receives an electrical signal indicating the reflected wave received by the receiver of the ultrasonic head unit 10, and measures the time (reflection arrival time) from the output of the transmission signal to the reception of the electrical signal of the reflected wave. That is, the vehicle detection unit 21 functions as an acquisition unit that acquires information regarding the time from when the ultrasonic head unit 10 transmits ultrasonic waves until the reflected wave is received.

[0018] Also, the vehicle detection unit 21 detects a vehicle based on the measured reflection arrival time and a predetermined threshold value for vehicle detection (first threshold value), and outputs vehicle detection information. Further, when no vehicle is detected, the vehicle detection unit 21 detects a change in the road surface condition based on the measured time and a predetermined threshold value for detecting a change in the road surface condition (second threshold value), and outputs an alarm (warning information) when a change in the road surface condition is detected.

[0019] Here, the road surface condition in the present embodiment refers to a state that affects the running of the vehicle V due to waterlogging, snow accumulation, or deposits on the road surface R such as sediment.

[0020] Furthermore, distance information from the road surface R to the ultrasonic head unit 10, that is, the height H0 of the ultrasonic head unit 10 is set in the vehicle detection unit 21 (see FIG. 3).

[0021] The communication processing unit 22 transmits the vehicle detection information detected by the vehicle detection unit 21 to the track server 30. The vehicle detection information may include not only information indicating that a vehicle has been detected, but also the number of vehicles detected (passing number, count number) within a predetermined time, the duration of detection, and the like.

[0022] The temperature sensor 23 detects the air temperature in the vicinity of the installation position of the vehicle detector 1 on the road surface R. The temperature sensor 23 may be installed inside or near the ultrasonic head unit 10 instead of the control unit 20. That is, it is sufficient if the air temperature in the atmosphere through which the ultrasonic waves transmitted by the ultrasonic head unit 10 propagate can be detected or estimated. That is, the temperature sensor 23 functions as a temperature detection unit that detects the ambient temperature of the ultrasonic head unit 10.

[0023] The tracking server 30 is a server device installed, for example, in the office of a road administrator or the like. The tracking server 30 collects vehicle detection information transmitted from the control unit 20. The collected information is used for traffic volume surveys, signal control, and the like.

[0024] The automatic notification device 40 is a notification device installed, for example, beside a road or the like, and notifies of road flooding or the like. The automatic notification device 40 makes a notification of flooding or the like based on an alarm transmitted from the control unit 20.

[0025] Next, the operation of the control unit 20 having the above-described configuration will be described with reference to FIGS. 3 to 6. FIG. 3 is a diagram showing, in the upper part, the case where a vehicle is not detected, that is, the relationship between the ultrasonic head unit 10 and the road surface R, and in the lower part, an example of the waveform of the ultrasonic wave transmitted from the ultrasonic head unit 10 and the waveform of the reflected wave reflected by the road surface of the road R.

[0026] As shown in the upper part of FIG. 3, the ultrasonic wave transmitted from the ultrasonic head unit 10 is reflected by the road surface R, and the reflected wave is received by the ultrasonic head unit 10. At this time, as shown in the lower part of FIG. 3, the signal waveform transmitted from the ultrasonic head unit 10 is received as a reflected waveform reflected by the road surface R. Here, let the reflection arrival time in the case of FIG. 3 be t0. That is, t0 is the reflection arrival time when reflected by the road surface R. In the lower part of FIG. 3, the difference between the transmitted waveform and the reflected wave waveform is taken into account for attenuation and the like.

[0027] Next, the case where the vehicle V is detected is shown in FIG. 4. FIG. 4 is a diagram showing, in the upper part, the case where the vehicle V is detected, and in the lower part, an example of the waveform of the ultrasonic wave transmitted from the ultrasonic head unit 10 and the waveform of the reflected wave reflected by the vehicle V.

[0028] As shown in the upper part of FIG. 4, the ultrasonic wave transmitted from the ultrasonic head unit 10 is reflected by the vehicle V, and the reflected wave is received by the ultrasonic head unit 10. At this time, as shown in the lower part of FIG. 4, the signal waveform transmitted from the ultrasonic head unit 10 is received as a reflected waveform reflected by the vehicle V. Here, let the reflection arrival time in the case of FIG. 4 be t1. That is, t1 is the reflection arrival time when reflected by the vehicle V. Since the reflecting surface in the vehicle V is at a position higher than the road surface R (a position closer to the ultrasonic head unit 10), the distance that the ultrasonic wave propagates becomes shorter, and the reflection arrival time t1 becomes shorter than the reflection arrival time t0.

[0029] In the present embodiment, in order to detect the vehicle V, a threshold value th1 is set for the reflection arrival time. This threshold value th1 is set to the time when reflected at a height at which the vehicle V can be detected. As an example of the threshold value th1, it can be set to the time when reflected at a height of 50 cm from the road surface R.

[0030] Also, it is known that the speed of sound changes depending on the temperature. Therefore, in the present embodiment, the threshold value th1 is corrected by the air temperature detected by the temperature sensor 23 (see FIG. 5). The speed of sound C is known to be calculated by the following formula (1) when the temperature (air temperature) is te. C = 331.5 + 0.6te [m / s] ··· (1)

[0031] For example, when the air temperature is 15°C and 30°C, the speed of sound is 340.5 m / s and 349.5 m / s respectively from formula (1). Also, the distance H from the ultrasonic head unit 10 to the reflecting surface is known to be calculated by the following formula (2) when the reflection arrival time is t. H = (C × t) / 2 [m] ··· (2)

[0032] For example, when the ultrasonic head unit 10 is installed at a height of 5 m (H0 = 5 m) from the road surface R and vehicle detection is set at a height of 50 cm (0.5 m) from the road surface R. At this time, from formula (2), the threshold value th1 is about 26.4 ms when the air temperature is 15°C, and about 25.8 ms when the air temperature is 30°C.

[0033] This temperature correction may be performed by presetting a calculation formula or the like in the vehicle detection unit 21, or by presetting a table showing the relationship between the height of the ultrasonic head unit 10, the height for vehicle detection, the air temperature, and the threshold value th1 in the vehicle detection unit 21.

[0034] Next, the detection of changes in road surface conditions such as waterlogging and snow accumulation will be described with reference to FIG. 6. FIG. 6 is a diagram in which the upper part shows the case where the road surface (road) R is waterlogged, and the lower part shows an example of the waveform of the ultrasonic wave transmitted from the ultrasonic head unit 10 and the waveform of the reflected wave reflected on the water surface.

[0035] As shown in the upper part of FIG. 6, the ultrasonic wave transmitted from the ultrasonic head unit 10 is reflected by the water surface W, and the reflected wave is received by the ultrasonic head unit 10. In FIG. 6, since there is waterlogging, the water surface W is at a position higher than the road surface R. Therefore, the height H1 from the water surface W to the ultrasonic head unit 10 is smaller than the height H0 from the road surface R to the ultrasonic head unit 10. When in the state as shown in the upper part of FIG. 6, as shown in the lower part of FIG. 6, the signal waveform transmitted from the ultrasonic head unit 10 becomes a reflected waveform and is received. Here, since the water surface W is at a position higher than the road surface R, the distance that the ultrasonic wave propagates becomes shorter, and the reflection arrival time becomes shorter than the time t0 shown in FIG. 3.

[0036] Therefore, in the present embodiment, for the reflection arrival time, in addition to the threshold value th1, a threshold value th2, which is a value larger than the threshold value th1, that is, the time when the reflection occurs at a height lower than the height at which the vehicle V can be detected, is set.

[0037] This threshold value th2 is preferably set to be a time corresponding to a height at which there is an obstacle to driving on the road due to waterlogging, snow accumulation, etc., and an alarm needs to be issued. For example, if the threshold value th1 corresponds to the time at a position 50 cm from the road surface R, the threshold value th2 can be set to the time corresponding to a position about 20 cm from the road surface R. Note that this threshold value th2 is also corrected according to the temperature (air temperature). Since this threshold value th2 is for detecting waterlogging, snow accumulation, etc. as described above, it goes without saying that it is set to the time corresponding to a position higher than the road surface R.

[0038] When the vehicle V is detected, a value less than the normal direct threshold th1 is usually detected. On the other hand, in the case of flooding or snow accumulation, since the water surface or the like gradually rises, the reflected arrival time is such that a value equal to or greater than the threshold th1 is detected once. Therefore, when a value of the reflected arrival time equal to or greater than the threshold th1 is detected, it is possible to determine whether or not there is flooding by comparing it with the threshold th2.

[0039] Next, the operations of detecting the vehicle V and flooding or the like in the vehicle detector 1 described above will be described with reference to the flowchart of FIG. 7. The flowchart shown in FIG. 7 mainly operates in the vehicle detection unit 21.

[0040] First, the height H0 of the ultrasonic head unit 10 is set in the vehicle detection unit 21 (step S11). Next, the reflected arrival time is measured (step S12). That is, the time from when the vehicle detection unit 21 outputs a transmission signal until it receives the electrical signal of the reflected wave is measured.

[0041] Next, the threshold th1 and the threshold th2 are corrected based on the air temperature detected by the temperature sensor 23 (step S13). Note that step S13 may be performed as appropriate according to the detected air temperature, not after step S12. That is, the vehicle detection unit 21 corrects the threshold th1 (first threshold) and the threshold th2 (second threshold) based on the air temperature (ambient temperature) detected by the temperature sensor 23 (temperature detection unit).

[0042] Next, it is determined whether or not the reflected arrival time measured in step S12 is less than the threshold th1 (step S14). If it is less than the threshold th1 (step S14: Yes), vehicle detection information is output as vehicle detection (step S15). When including the number of vehicle detections and the duration of detection within a predetermined time as the vehicle detection information, the count of the number of detections is incremented or the like for each determination in step S14. That is, the vehicle detection unit 21 determines that the vehicle has been detected when the reflected arrival time (information related to time) is less than the threshold th1 (first threshold, which is a value related to the time serving as a reference for determining that the vehicle has been detected).

[0043] Next, it is determined whether or not the sensing operation has ended (step S16). If not (step S16: No), the process returns to step S12. If it has ended (step S16: Yes), the flowchart ends.

[0044] On the other hand, as a result of the determination in step S14, if it is equal to or greater than the threshold value th1 (step S14: No), it is determined that the vehicle is not sensed. Therefore, in order to determine whether there is a change in the road surface condition such as waterlogging, the moving average of the reflected arrival time is calculated (step S17). In the present embodiment, the change in the road surface condition is detected not by one reflected arrival time but by the moving average of a plurality of reflected arrival times. This is because waterlogging and the like do not change rapidly compared to the vehicle, and to reduce the influence of waves generated when the vehicle passes through.

[0045] The number of terms when calculating the moving average of the reflected arrival time may be determined as appropriate. However, when calculating the moving average in step S17, the reflected arrival time determined to sense the vehicle in step S14 is not used. That is, the reflected arrival time determined to sense the vehicle is not incorporated as a term for calculating the moving average. For example, when it is determined in step S14 that the vehicle is sensed, instead of the reflected arrival time, the reflected arrival time measured one time before (determined not to sense the vehicle) is included to calculate the moving average.

[0046] An example is shown in FIG. 8. For easier explanation, FIG. 8 explains not the reflected arrival time but the water level from the road surface. As the actual detection result, the water level is 5 cm at time t1, the vehicle (height from the road is several tens of cm) at time t2, and the water level is 5 cm at time t3. In this case, when calculating the moving average, the value of the water level of 5 cm at the previous time t1 is used as the value at time t2. This continues during the period when the value at time t2 is included in the moving average.

[0047] Also, not limited to using the previous value, the moving average may be calculated without including the reflected arrival time when it is determined in step S14 that the vehicle is sensed. In the example of FIG. 8, the moving average may be calculated based on the values of t1 and t3 excluding t2.

[0048] Next, it is determined whether it is less than a threshold value th2 based on the moving average value calculated in step S17 (step S18). If it is less than the threshold value th2 (step S18: Yes), an alarm is output as the detection of a change in the road surface condition such as waterlogging (step S19). If it is greater than or equal to the threshold value th2 (step S18: No), it is considered that there is no change in the road surface condition to the extent of outputting road surface detection or an alarm, and the process proceeds to step S16 without doing anything. That is, the vehicle detection unit 21 determines that a change in the road surface condition has been detected when the reflection arrival time (information regarding time) is greater than or equal to a threshold value th1 (first threshold value) and less than a threshold value th2 (second threshold value) that is greater than or equal to the threshold value th1 (first threshold value) and less than the time based on the height H0 (distance information).

[0049] Also, in the present embodiment, when the power supply of the vehicle detector 1 turns off during the output of an alarm (warning information) and then the power supply resumes, the control unit 20 outputs an alarm regardless of the value of the measured reflection arrival time, at least immediately after the resumption. This is in consideration of the possibility that the waterlogging state continues when the power supply turns off due to the influence of waterlogging or the like and then resumes. Note that the period during which an alarm is output regardless of the value of the reflection arrival time measured after the power supply resumes may be determined as appropriate. After the elapse of the said period, the operation returns to the operation according to the flowchart of FIG. 7.

[0050] In order to output an alarm regardless of the value of the reflection arrival time measured after the power supply resumes as described above, the control unit 20 may, for example, store information on the presence or absence of the current alarm output (information regarding the presence or absence of the output of warning information at the time of power cut) in a storage unit such as an internal memory (non-volatile memory), and determine whether to output an alarm by referring to the storage unit after the power supply resumes.

[0051] According to this embodiment, the vehicle sensor 1 is installed above the road surface, transmits ultrasonic waves toward the road surface R of the facing road, and receives the reflected waves of the ultrasonic waves. The vehicle sensor 1 includes an ultrasonic head unit 10 and a vehicle sensing unit 21. The vehicle sensing unit 21 acquires the reflection arrival time and senses a vehicle V traveling on the road surface R based on the acquired reflection arrival time. The distance information from the ultrasonic head unit 10 to the road surface R is set in the vehicle sensing unit 21. When the reflection arrival time is less than the threshold value th1, it is determined that the vehicle V has been sensed. When the reflection arrival time is equal to or greater than the threshold value th1 and less than the threshold value th2, it is determined that a change in the road surface state of the road surface R has been detected. When the vehicle sensing unit 21 determines that the vehicle has been sensed, the reflection arrival time is not used for calculating the moving average and is not used for detecting a change in the road surface state of the road.

[0052] With the vehicle sensor 1 configured as described above, it is possible to detect changes in the road surface state of the road surface R such as waterlogging and snow accumulation. Furthermore, when it is determined that the vehicle has been sensed, the reflection arrival time is not used for detecting a change in the road surface state of the road. Therefore, there is no possibility that the state of the change in the road surface state is erroneously detected due to the information when the vehicle is sensed. Therefore, the reflected waves when the vehicle V is not sensed can also be effectively used. In addition, since the vehicle sensor 1 alone can detect changes in the road surface state such as waterlogging, there is no need to separately provide a device or the like for detecting waterlogging or the like. Also, by setting the threshold value th2, it is possible to determine a change in the road surface state without misjudging it as the road surface R even if the calculation accuracy of the reflection arrival time is low.

[0053] In addition, the vehicle sensor 1 further includes a temperature sensor 23 that detects the ambient temperature around the ultrasonic head unit 10, and the vehicle sensing unit 21 corrects the threshold values th1 and th2 based on the ambient temperature detected by the temperature sensor 23. By doing so, it is possible to use threshold values that correct the speed of sound that changes with temperature. Therefore, it is possible to accurately determine changes in the vehicle and the road surface state.

[0054] In addition, when the vehicle detection unit 21 determines that it has detected a change in the road surface condition, it outputs an alarm. Therefore, when the state becomes unsuitable for passage, measures such as blocking the passage can be taken.

[0055] Further, it includes a storage unit that stores information regarding the presence or absence of alarm output when the power of the vehicle detector 1 is cut off. When the power is restored after being cut off, the detection unit 20 refers to the information regarding the presence or absence of alarm output. If the information indicates that an alarm has been output, an alarm is output regardless of the current determination result. By doing so, for example, even when the flooded state continues before and after the power is cut off, the alarm can be continuously output.

[0056] In the above-described embodiment, only one second threshold value is set, but a plurality of second threshold values may be set. By setting a plurality of second threshold values, the degree of urgency can be determined step by step. In that case, for the alarm, for example, when the second threshold values are set at three heights corresponding to 20 cm, 30 cm, and 40 cm from the road surface R, information for identifying which threshold value has been exceeded may also be included. Also, an alarm may be output if the first threshold value is not set and the time is less than the time when the ultrasonic wave is reflected by the road surface R and is above the first threshold value. That is, when the reflection arrival time (information regarding time) is equal to or greater than the threshold value th1 (the first threshold value) and less than the time from when the ultrasonic head unit 10 calculates based on the height H0 (distance information) and transmits the ultrasonic wave until the reflected wave reflected by the road is received, it may be determined that a change in the road surface condition of the road has been detected.

[0057] In the above-described embodiment, the threshold value is set in terms of time for the reflection arrival time, but the reflection arrival time may be converted into distance and the threshold value may be set in terms of distance.

[0058] (Second Embodiment) Next, a warning system according to a second embodiment of the present invention will be described with reference to FIGS. 9 to 10. The same parts as those in the above-described first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0059] This embodiment is an alarm system 100 equipped with the vehicle sensor 1 described in the first embodiment. As shown in FIG. 9, the alarm system 100 includes a vehicle sensor 1, a monitoring device 30A, and a road information control device 50.

[0060] In addition to the vehicle sensing information described in the first embodiment, in this embodiment, the vehicle sensor 1 also transmits an alarm (alarm information) to the monitoring device 30A. It should be noted that it is preferable to provide a plurality of vehicle sensors 1 as shown in FIG. 9. The plurality of vehicle sensors 1 shown in FIG. 9 are, of course, installed at different roads and locations.

[0061] In addition to the functions of the tracking server 30 described in the first embodiment, the monitoring device 30A collects the received alarm information and transmits the collected alarm information to the road information control device 50. That is, the monitoring device 30A functions as a collecting device that collects alarm information (warning information) transmitted from a plurality of vehicle sensors 1.

[0062] In this embodiment, the vehicle sensor 1 and the monitoring device 30A are connected by a communication line such as a dedicated line N1 or a public line N2. Both the dedicated line N1 and the public line N2 may be wireless communication or wired communication.

[0063] Note that the monitoring device 30A has the functions of the tracking server 30 and collects alarm information using an existing communication line as in the first embodiment, but the monitoring device 30A may be prepared separately from the tracking server 30. In that case, the above-mentioned dedicated line N1 or public line N2 may be used as a new communication line.

[0064] The road information control device 50 provides information to the information board 60, the disaster prevention radio 70, etc. based on the alarm information transmitted from the monitoring device 30A. That is, the road information control device 50 functions as a providing device that provides information based on the alarm information (warning information) collected by the monitoring device 30A (collecting device).

[0065] Specifically, the road information control device 50 acquires a hazard map in advance, predicts the roads that will become impassable based on the hazard map and the alarm information, and transmits the prediction results to the information board 60, the disaster prevention radio 70, etc. For example, regarding the installation position of the vehicle sensor 1 that outputs the alarm information, referring to the flooding hazard map, for the roads where equivalent flooding is predicted at positions around the said position, or for the information board 60 installed on the route leading to the road that has received the alarm information or the road where flooding has been predicted, and the disaster prevention radio 70 of the area to which the said road belongs, information indicating impassability or caution is transmitted.

[0066] Also, the alarm information may include the reflection arrival time and the value obtained by converting the reflection arrival time into distance. By doing so, it becomes possible to obtain the actual depth of flooding together with the alarm information. For example, it is also possible to make a determination such that it is impassable when the depth is deep and caution is required when the depth is shallow.

[0067] Moreover, by accumulating the alarm information in the road information control device 50, it is also possible to detect the locations where flooding is likely to occur outside the locations indicated as underpasses in the hazard map, etc.

[0068] The information board 60 is a display board installed for the purpose of providing information such as traffic jams, traffic accidents, and weather on the road, and is also called a road information board, a road information bulletin board, or a road information display device. The road information control device 50 and the information board 60 are connected by a predetermined communication line.

[0069] The disaster prevention radio 70 is composed of a master station provided in an administrative agency, slave stations equipped with loudspeakers provided at predetermined locations in the area under the jurisdiction of the administrative agency, and household receivers provided in facilities such as residences. It is a well-known wireless system in which the slave loudspeaker stations and the household receivers receive information from the master station according to the area, such as disaster warning information and emergency information such as alarms, and output it as voice information or character information.

[0070] Note that the monitoring device 30A and the road information control device 50 may be installed in the same facility. Also, the road information control device 50 may provide information not only to the information board 60 and the disaster prevention radio 70, but also to the traffic control center (police), the road administrator, or to the vehicle (driver) through VICS (registered trademark).

[0071] FIG. 10 shows another embodiment of the alarm system. In FIG. 10, the vehicle sensor 1 transmits alarm information and the like to the management device 30B.

[0072] The management device 30B is installed, for example, at the office of the road administrator or the like. The management device 30B collects alarm information and the like from the vehicle sensor 1 and presents it to the road administrator and the like. The road administrator changes the display of the information board 60 and makes notifications to relevant organizations based on the alarm information collected by the management device 30B. That is, in the example of FIG. 10, the collection device and the providing device are integrated.

[0073] Note that in FIG. 10, only one management device 30B is shown, but there may be a plurality. That is, the vehicle sensor 1 may transmit alarm information to a plurality of management devices 30B. In this case, the plurality of management devices 30B may be, for example, one is a national agency and the other is a local government or the like.

[0074] Also, the management device 30B may have the function of the tracking server 30, or may be a device for collecting alarm information. Therefore, the connection between the management device 30B and the vehicle sensor 1 may be an existing line or a new line.

[0075] According to this embodiment, the warning system 100 includes a vehicle sensor 1 installed on a road and capable of outputting alarm information regarding changes in the road surface, a monitoring device 30A that collects the alarm information transmitted from the plurality of vehicle sensors 1, and a road information control device 50 that provides information based on the alarm information collected by the monitoring device 30A. By doing so, not only can the alarm information be directly notified, but it can also be provided as wide-area information in combination with other information such as a hazard map. Therefore, it is possible to provide information based on the warning information that indicates changes in the road surface conditions of the road, such as waterlogging and snow accumulation.

[0076] Further, the road information control device 50 may provide information based on the alarm information to the information board 60 or the disaster prevention radio 70. By doing so, it is possible to surely provide information to institutions such as the drivers of vehicles traveling on the road, the local governments and residents to which the road belongs, etc., for which the provision is necessary.

[0077] Note that the present invention is not limited to the above embodiment. That is, those skilled in the art can variously modify and implement it in accordance with conventionally known knowledge without departing from the gist of the present invention. As long as the configuration of the vehicle sensor and the warning system of the present invention is still included even by such modifications, of course, it is included in the scope of the present invention.

Explanation of Reference Numerals

[0078] 1 Vehicle sensor 10 Ultrasonic head unit 20 Control unit 21 Vehicle sensing unit (road information setting unit, acquisition unit, sensing unit) 23 Temperature sensor (temperature detection unit) 30A Monitoring device (collection device) 30B Management device (collection device, providing device) 50 Road information control device (providing device) 60 Information board (predetermined device) 70 Disaster prevention radio (predetermined device) 100 Warning system

Claims

1. An ultrasonic head unit that is installed above a road, transmits ultrasonic waves toward the facing road, and receives the reflected waves of the ultrasonic waves; An acquisition unit that acquires information regarding the time from when the ultrasonic head unit transmits the ultrasonic waves until it receives the reflected waves; A sensing unit that senses a vehicle traveling on the road and detects a change in the road surface condition of the road based on the information regarding the time acquired by the acquisition unit; A storage unit that stores information regarding the presence or absence of output of alarm information when the power is turned off, comprising: The sensing unit: Distance information from the ultrasonic head unit to the road is set, When the information regarding the time is less than a first threshold value which is a value regarding the time serving as a criterion for determining that the vehicle has been sensed, it is determined that the vehicle has been sensed, When the moving average of the information regarding the time is equal to or greater than the first threshold value and less than the time from when the ultrasonic head unit transmits the ultrasonic waves until it receives the reflected waves reflected by the road calculated based on the distance information, it is determined that a change in the road surface condition of the road has been detected, The information regarding the time when it is determined that the vehicle has been sensed is not used for calculating the moving average when detecting a change in the road surface condition of the road, When it is determined that a change in the road surface condition of the road has been detected, the alarm information is output, When the power is turned on again after being turned off, referring to the information regarding the presence or absence of output of the alarm information, if the information indicates that the alarm information has been output, the alarm information is output regardless of the current determination result. A vehicle sensor characterized by the above.

2. The sensing unit is set with a second threshold value which is a value equal to or greater than the first threshold value and less than the time from when the ultrasonic head unit transmits the ultrasonic waves until it receives the reflected waves reflected by the road calculated based on the distance information, When the information regarding the time is equal to or greater than the first threshold value and less than the second threshold value, it is determined that a change in the road surface condition of the road has been detected. The vehicle sensor according to claim 1, characterized by the above.

3. Further comprising a temperature detection unit that detects the ambient temperature around the ultrasonic head unit, The sensing unit corrects the first threshold value and the second threshold value based on the ambient temperature detected by the temperature detection unit. The vehicle sensor according to claim 2, characterized by the above.

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