On-board terminal device and vehicle collision prevention method

An on-board terminal device includes a location measuring section that measures a location of an own vehicle, a wireless communication section that transmits own vehicle information including location information of the own vehicle to other vehicles and receives other vehicle information including location information of the other vehicles from the other vehicles by execution of wireless communication with the other vehicles, and a monitoring section that estimates the location of the other vehicles and calculates a relative distance between the own vehicle and the other vehicles when the wireless communication has been interrupted, and executes an alarm process for preventing collision of the own vehicle and the other vehicles when the relative distance is less than a predetermined threshold.

TECHNICAL FIELD

The present invention relates to an on-board terminal device and a vehicle collision prevention method.

BACKGROUND ART

Generally, in mines, construction sites and the like, haulage vehicles such as a dump truck are used. With respect to these haulage vehicles, when a traffic collision occurs between vehicles, in addition to the direct damage by the accident, a severe interference occurs in execution of the operation also because the mining operation in the mine and the construction work in the construction site are interrupted. Therefore, it becomes important to surely prevent the traffic collision.

However, in these haulage vehicles, the blind spot for an operator operating the vehicle is wider compared with ordinary automobiles. Therefore, there is a problem that, even in a case where there exists another vehicle which may collide with the own vehicle, the operator cannot recognize the other vehicle and the traffic collision is liable to occur.

With respect to the problem described above, a system has been proposed which supplements the field of view of the operator to prevent the traffic collision. For example, a system is known which prevents collision by detecting a forward obstacle using a sensor such as a laser radar and issues an alarm. Also, in Patent Literature 1, there is described a device which acquires location information of other vehicles by wireless communication, issues an alarm in detecting proximity to the own vehicle, and thereby prevents collision.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the haulage vehicles used in mines, construction sites, and the like, a region of poor condition for wireless communication is possibly found in the periphery of the own vehicle because of the radio wave shielding effect of the own vehicle body. For example, when an antenna for wireless communication is installed at the front part of the vehicle body, the radio wave is shielded by the vehicle body in the short distance region in the rear, and there is a case where wireless communication with other vehicles existing in the region is impossible. However, according to the technology described in Patent Literature 1, existence of such region has not been considered. Therefore, when another vehicle enters this region, in spite that the other vehicle exists at a short distance from the own vehicle and there is a high risk of collision with the own vehicle, an alarm cannot be issued. Accordingly, sufficient collision prevention could not be achieved.

The present invention has been achieved in view of the problems in prior arts as described above. The object of the present invention is to surely prevent collision of the own vehicle and other vehicles even when a region where wireless communication is not available exists in the periphery of the own vehicle.

Solution to Problem

An on-board terminal device according to the present invention includes a GPS that measures a location of an own vehicle or a location measuring sensor that obtains the location of the own vehicle based on the result of measurement of the relative distance to a reference point arranged within a mine; a transmitter that transmits own vehicle information including location information of the own vehicle to other vehicles and a receiver that receives other vehicle information including location information of the other vehicles transmitted from the other vehicles by execution of wireless communication with the other vehicles; and a computer, wherein the computer is configured to estimate the location of the other vehicles, calculate relative distances between the own vehicle and the other vehicles when the wireless communication has been interrupted, execute an alarm process for preventing collision of the own vehicle and the other vehicles when the relative distance is less than a predetermined threshold, and notify an operator of the own vehicle with a notification about the other vehicle, or output a control signal for executing travel control of the own vehicle to the own vehicle, wherein when the computer outputs alarm information including information on a region where the wireless communication is not available in the periphery of the own vehicle in the alarm process, the computer notifies the operator of the own vehicle of the region where the wireless communication is not available based on the alarm information, or outputs the control signal of a case where the other vehicles exist in the region where the wireless communication is not available based on the alarm information, and wherein the computer calculates a reception rate of the wireless communication with respect to a plurality of divided regions set beforehand in the periphery of the own vehicle respectively based on a reception log of the other vehicle information of the past, and determines divided regions where the reception rate of the wireless communication is less than a predetermined reference value out of the plurality of divided regions to be a region where the wireless communication is not available.

According to the vehicle collision prevention method by the present invention, vehicle collision is prevented by measuring a location of an own vehicle; transmitting own vehicle information including location information of the own vehicle to other vehicles and receiving other vehicle information including location information of the other vehicles from the other vehicles by executing wireless communication with the other vehicles; estimating locations of the other vehicles and calculating a relative distance between the own vehicle and the other vehicles when the wireless communication has been interrupted; and executing an alarm process for preventing collision of the own vehicle and the other vehicles by a computer when the relative distance is less than a predetermined threshold to thereby prevent collision of the own vehicle and the other vehicles, wherein alarm information including information on a region where the wireless communication is not available in the periphery of the own vehicle is outputted from the computer in the alarm process, and an operator of the own vehicle is notified of the region where the wireless communication is not available or, when there exists the other vehicle in the region where the wireless communication is not available, a control signal for executing travel control of the own vehicle is outputted to the own vehicle based on the alarm information.

Advantageous Effects of Invention

According to the present invention, even when a region where wireless communication is not available exists in the periphery of the own vehicle, collision of own vehicle and other vehicles can be surely prevented.

DESCRIPTION OF EMBODIMENT

Below, embodiments of the present invention will be explained in detail referring to the drawings.

First Embodiment

FIG. 1is a drawing showing a configuration of a safety driving assistance system including a safety driving assistance device that is an application example of an on-board terminal device related to the first embodiment of the present invention. The safety driving assistance system shown inFIG. 1is configured of vehicles101,102,103and safety driving assistance devices110mounted respectively on these vehicles.

The vehicles101,102,103are used in mine sites and the like. They include heavy work vehicle such as a dump truck, wheel loader, and a grader for example, and an excavator, a light vehicle and the like which do not fall under the category of the heavy work vehicle. Further, inFIG. 1, although there is shown an example of the safety driving assistance system where the safety driving assistance devices110are mounted respectively on three vehicles101,102,103, the safety driving assistance system according to the present embodiment may be configured by mounting the safety driving assistance devices110respectively on vehicles fewer or greater in number than that mentioned above.

Each of the safety driving assistance devices110executes wireless communication with each other, and transmits and receives wireless communication information301. By acquisition of the wireless communication information301from other safety driving assistance devices110, each safety driving assistance device110acquires information of other vehicles, and prevents the risk of collision with other vehicles when there is such risk. Also, it is preferable that the wireless communication information301from each safety driving assistance device110is periodically transmitted to a range to which the radio wave can reach by broadcasting irrespective of existence of other vehicles in the periphery.

InFIG. 1, a configuration of the safety driving assistance device110boarded on the vehicle101is illustrated as a representative example. Below, the configuration of this safety driving assistance device110will be explained. Further, although the safety driving assistance devices110boarded on the vehicles102,103also have similar configurations respectively, explanation thereof will be omitted. Also, in the explanation below, the vehicle101will be referred to as “own vehicle”, and the vehicles102,103will be referred to as “other vehicles”.

The safety driving assistance device110includes a dynamic information acquiring section121, a location measuring section122, a wireless communication section123, an own vehicle/other vehicle information managing section124, a collision risk determining section125, a radio wave state monitoring section126, and an operator notification section127.

The dynamic information acquiring section121acquires various information dynamically changing according to the state of the own vehicle as dynamic information on the own vehicle. This dynamic information includes operation information of the brake pedal, operation information of the steering, loading status information of the own vehicle, motion status information of the own vehicle, and so on for example. The dynamic information acquiring section121can acquire the dynamic information through an on-board network such as CAN (Controller Area Network) from an electronic control device (not illustrated) boarded on the own vehicle for example. Further, the dynamic information may be acquired by detecting the motion status of the own vehicle using a sensor such as an acceleration sensor and a yaw rate sensor. The dynamic information acquiring section121outputs the acquired dynamic information to the own vehicle/other vehicle information managing section124.

The location measuring section122measures a location of the own vehicle, and outputs the location information showing the measurement result to the own vehicle/other vehicle information managing section124. The location measuring section122can measure the absolute location of the own vehicle using GPS (Global Positioning System) for example. Also, the location measuring section122may obtain the location of the own vehicle based on the result of measurement of the relative distance to a reference point arranged within the mine by a sensor.

The wireless communication section123has a function of executing wireless communication with other vehicles. By this wireless communication, the wireless communication section123transmits the wireless communication information301on the own vehicle to the other vehicles, and receives the wireless communication information301on the other vehicles from the other vehicles.

The own vehicle/other vehicle information managing section124generates information on the state and location of the own vehicle (will be hereinafter referred to as “own vehicle information”) based on the dynamic information from the dynamic information acquiring section121and the location information from the location measuring section122. The own vehicle/other vehicle information managing section124has a vehicle information DB130, stores the generated own vehicle information in this vehicle information DB130, and manages the generated own vehicle information. The own vehicle information stored in the vehicle information DB130is outputted from the own vehicle/other vehicle information managing section124to the wireless communication section123, and is transmitted from the wireless communication section123to the other vehicles as the wireless communication information301on the own vehicle. Meanwhile, information on the other vehicles (will be hereinafter referred to as “other vehicle information”) received as the wireless communication information301by the wireless communication section123is outputted from the wireless communication section123to the own vehicle/other vehicle information managing section124. The own vehicle/other vehicle information managing section124stores this other vehicle information in the vehicle information DB130, and manages this other vehicle information. Also, the own vehicle information and the other vehicle information stored in the vehicle information DB130are outputted from the own vehicle/other vehicle information managing section124to the collision risk determining section125and radio wave state monitoring section126according to the necessity.

The collision risk determining section125determines the risk of collision of the own vehicle and other vehicles based on the own vehicle information and other vehicle information outputted from the own vehicle/other vehicle information managing section124. For example, when the relative distance of the other vehicle with respect to the own vehicle becomes equal to or less than a constant distance, the collision risk determining section125determines that there is a collision risk. At this time, the determination method may be changed by the collision risk determining section125according to the combination of the vehicle type of the own vehicle and the other vehicle, and so on. As a result, when it is determined that there is a collision risk, the collision risk determining section125notifies the operator notification section127of the determination result.

The radio wave state monitoring section126monitors the radio wave state of wireless communication by the wireless communication section123in the periphery of the own vehicle based on the other vehicle information outputted from the own vehicle/other vehicle information managing section124. The radio wave state monitoring section126has a reception log DB.150, and monitors the radio wave state by storing a reception log of the other vehicle information in this reception log DB.150and managing the reception log of the other vehicle information. At this time, when such a state continues that the other vehicle information cannot be received from a certain other vehicle, the radio wave state monitoring section126determines that wireless communication has been interrupted between the other vehicle in question, and stores information showing the determination result in the reception log DB.150. Also, the radio wave state monitoring section126estimates the relative location of the other vehicle in question with respect to the own vehicle based on the other vehicle information having been received from the other vehicle in question in the past, and alarm information on the other vehicle in question is outputted to the operator notification section127according to the necessity. This alarm information includes information showing that the other vehicle in question has entered the region where wireless communication is not available in the periphery of the own vehicle, information on the region, and so on. Also, concrete contents of the process executed by the radio wave state monitoring section126in monitoring the radio wave state will be explained below in detail.

Also, the region where wireless communication becomes hard in the periphery of the own vehicle changes according to the vehicle type, height, direction, traveling location in the mine and the like of the other vehicle. Therefore, it is preferable that the radio wave state monitoring section126manages such information in the reception log DB.150, and identifies the region where wireless communication is not available using such information.

The operator notification section127executes notification on other vehicles having a risk of collision with the own vehicle to the operator of the own vehicle based on the determination result of the collision risk notified from the collision risk determining section125and the alarm information outputted from the radio wave state monitoring section126. The operator notification section127can execute notification on the other vehicles by ringing a buzzer, lighting a lamp, and displaying an alarm screen for example.

Also, with respect to the safety driving assistance device110, the dynamic information acquiring section121, the own vehicle/other vehicle information managing section124, the collision risk determining section125, and the radio wave state monitoring section126described above can be achieved respectively using the process of computers configured of CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and the like. Also, the vehicle information DB130and reception log DB.150can be achieved by using storage devices such as HDD (Hard Disk Drive) and a flash memory.

FIG. 2is a drawing showing an example of the notification screen to an operator displayed on the operator notification section127. InFIG. 2, (a) shows an example of a notification screen201in the normal time when an alarm has not been issued. (b) shows a notification screen202of alarming time when other vehicle has entered the region where wireless communication is not available. (c) shows a notification screen203of other alarming time when other vehicle has entered the region where wireless communication is not available.

When there is no alarm in particular, the operator notification section127displays the location of the own vehicle101and the location of the other vehicles102,103existing in the periphery of the own vehicle101on the notification screen201as shown inFIG. 2 (a). Meanwhile, when the other vehicle information from the other vehicle102has become non-receivable, the radio wave state monitoring section126determines that the other vehicle102has entered the region where wireless communication is not available, and outputs alarm information to the operator notification section127. When this alarm information is received, the operator notification section127displays the notification screen202of the alarming time as shown inFIG. 2 (b)for example, and notifies the operator of the fact that the other vehicle102has entered the region where wireless communication is not available. Apart from the above, the notification screen203of the alarming time as shown inFIG. 2(c) for example may be displayed on the operator notification section127. On this notification screen203, the region where wireless communication is not available estimated by the radio wave state monitoring section126is displayed as shown by the oblique line part in the drawing, and the vehicle102is displayed within the region. Thus, it is possible to display such screen that the operator can easily understand the location relation between the own vehicle101and the other vehicle102.

FIG. 3is a drawing showing a data format example of the wireless communication information301transmitted and received by the wireless communication section123of the safety driving assistance device110. As shown inFIG. 3, the wireless communication information301is configured of a vehicle identifier311, a vehicle type312, a degree of latitude313, a degree of longitude314, a vehicle speed315, a traveling direction316, a vehicle direction317, a vehicle height317, and a vehicle status319.

The vehicle identifier311is an identifier for uniquely identifying the vehicle of the transmission source. With respect to each vehicle used in the mine site, a value of the identifier not duplicating with each other is set beforehand in order to identify each vehicle uniquely. With respect to the vehicle identifier311, a value of the identifier of a vehicle on which the safety driving assistance device110having transmitted the wireless communication information301is boarded is set.

The vehicle type312is an identifier for identifying the type of the vehicle of the transmission source. With respect to the vehicle type312, a value is set which corresponds to the type of each vehicle such as a dump truck, wheel loader, grader, dozer, excavator, and light vehicle for example.

The degree of latitude313and the degree of longitude314are information showing the location of the vehicle of the transmission source. With respect to the degree of latitude313and the degree of longitude314, a degree of latitude and a degree of longitude corresponding to the location of the vehicle in question in the mine measured by the location measuring section122are set respectively. Further, although the location of the vehicle of the transmission source is expressed by the degree of latitude313and the degree of longitude314in the example ofFIG. 3, the location of the vehicle may be expressed using values other than the above. For example, it is also possible to arrange a reference point of the location within the mine and to express the location of the vehicle of the transmission source using values of an exclusive coordinate system which express the relative location with respect to the reference point, and so on.

The vehicle speed315is information showing the speed of the vehicle of the transmission source. The speed of the vehicle of the transmission source can be obtained based on the change amount of the location measured by the location measuring section122and the dynamic information acquired by the dynamic information acquiring section121for example.

The traveling direction316is information showing the traveling direction of the vehicle of the transmission source. The traveling direction of the vehicle of the transmission source can be obtained based on the direction of change of the location measured by the location measuring section122and the dynamic information acquired by the dynamic information acquiring section121for example.

The vehicle direction317is information showing the direction of the vehicle of the transmission source. For example, when the vehicle is traveling straight, the traveling direction316and the vehicle direction317become a same value. Meanwhile, when the vehicle is retracting, the difference of the value of the traveling direction316and the value of the vehicle direction317becomes 180 degrees, and the directions opposite to each other are shown.

The vehicle height317is information showing the height of the vehicle of the transmission source.

The vehicle status319is information showing the status of the vehicle of the transmission source. The content of the vehicle status expressed by this vehicle status319is set beforehand for each type of the vehicle shown by the vehicle type312. For example, when the vehicle of the transmission source is a dump truck, a value corresponding to the loading status of the vehicle is set for the vehicle status319. Also, when the vehicle of the transmission source is a light vehicle, a constant initial value is set for the vehicle status319irrespective of the vehicle status.

FIG. 4is a drawing showing a configuration example of the vehicle information DB130. As shown inFIG. 4, in the vehicle information DB130, each data of a vehicle identifier132, a vehicle type133, a vehicle height134, a degree of latitude135, a degree of longitude136, a vehicle speed137, a traveling direction138, a vehicle direction139, a vehicle status142, a reception time140, and a managing status141are stored in each line corresponding to each vehicle. InFIG. 4, the data of the first line show the own vehicle information, and the data of the second and succeeding lines show the other vehicle information.

The vehicle identifier132is an identifier for uniquely identifying each vehicle data-managed in the vehicle information DB130. As described above, with respect to each vehicle used in the mine site, a value of the identifier not duplicating with each other is set beforehand in order to identify each vehicle uniquely. In the case of the own vehicle information, as the identifier of the own vehicle, a value set beforehand is stored in the vehicle identifier132. In the case of the other vehicle information, values set in the vehicle identifier311ofFIG. 3in the wireless communication information301received by the wireless communication section123are stored in the vehicle identifier132.

The vehicle type133is an identifier for identifying the type of each vehicle data-managed in the vehicle information DB130.

The vehicle height134is a datum showing the height of each vehicle data-managed in the vehicle information DB130.

The degree of latitude135and the degree of longitude136are data showing the location of each vehicle data-managed in the vehicle information DB130. In the case of the own vehicle information, values corresponding to the location of the own vehicle measured by the location measuring section122are stored in the degree of latitude135and the degree of longitude136respectively.

The vehicle speed137is a datum showing the speed of each vehicle data-managed in the vehicle information DB130. In the case of the own vehicle information, the speed of the own vehicle is obtained based on the change amount of the location measured by the location measuring section122and the dynamic information acquired by the dynamic information acquiring section121, and the value of the speed of the own vehicle is stored in the vehicle speed137.

The traveling direction138is a datum showing the traveling direction of each vehicle data-managed in the vehicle information DB130. Also, in the example ofFIG. 4, the true north direction is taken as the reference direction, and the traveling direction of each vehicle is expressed by the angle from the reference direction with the clockwise direction being positive.

The vehicle direction139is a datum showing the direction of each vehicle data-managed in the vehicle information DB130. Also, in the example ofFIG. 4, similarly to the traveling direction138, the true north direction is taken as the reference direction, and the direction of each vehicle is expressed by the angle from the reference direction with the clockwise direction being positive.

The vehicle status142is a datum showing the status of each vehicle data-managed in the vehicle information DB130. Similarly to the vehicle status319ofFIG. 3, the content of the vehicle status expressed by this vehicle status142is set beforehand for each type of the vehicle shown by the vehicle type133. Also, in the example ofFIG. 4, when the vehicle type133is a dump truck, either of “0” showing “not yet loading” or “1” showing “with load” is stored in the vehicle status142. “With load” shows a status where ore or soil has been loaded onto the vessel of the dump truck as shown inFIG. 10. Meanwhile, when the vehicle type133is other than the dump truck, “0” is stored in the vehicle status142in all cases. In the case of the own vehicle information, when the own vehicle is a dump truck, whether or not the status is “during loading” is determined based on the live load calculated using a pressure sensor as shown in Japanese Patent No. 5160468 for example, and a value corresponding to the determination result is stored in the vehicle status142. Meanwhile, when the own vehicle is not a dump truck, a predetermined value is stored in the vehicle status142. In the case of the other vehicle information, a value set in the vehicle status319ofFIG. 3in the wireless communication information301received by the wireless communication section123is stored in the vehicle status142.

The reception time140is a datum showing the data generating time of each vehicle in the vehicle information DB130. In the case of the own vehicle information, the calculation time of the value stored in the degree of latitude135and the degree of the longitude136respectively is stored in the reception time140. In the case of the other vehicle information, the time when the wireless communication information301was received for the last time from the vehicle in question by the wireless communication section123is stored in the reception time140.

The managing status141is a datum showing the data managing status of each vehicle in the vehicle information DB130. In the example ofFIG. 4, a case where the value of the managing status141is “0” shows that respective data of the line in question are in unused status. Meanwhile, a case where the value of the managing status141is “1” shows that respective data of the line in question have been periodically updated. Also, a case where the value of the managing status141is “2” shows that respective data of the line in question have not been updated for some time. In concrete terms, in the case of the own vehicle information, when respective data described above are updated based on the location and dynamic information of the own vehicle, “1” is set to the value of the managing status141. Also, when a predetermined period of time or more elapses from the last updating, “2” is set to the value of the managing status141. In the case of the other vehicle information, when respective data described above are updated based on the wireless communication information301received by the wireless communication section123, “1” is set to the value of the managing status141. Also, when a predetermined period of time or more elapses from the last updating, if the relative distance of the other vehicle in question with respect to the own vehicle is equal to or less than a predetermined threshold, “2” is set to the value of the managing status141. In this case, it is estimated that the other vehicle in question exists in the region where wireless communication is not available in the periphery of the own vehicle. Meanwhile, when a predetermined period of time or more elapses from the last updating, if the relative distance of the other vehicle in question with respect to the own vehicle is equal to or greater than the threshold described above, “0” is set to the value of the managing status141. In this case, it is estimated that the other vehicle in question exists at a location sufficiently apart from the own vehicle and wireless communication cannot reach. When “0” is set to the value of the managing status141, all of the other vehicle information on the other vehicle in question is erased (reset) in the vehicle information DB130.

Also, in the example of the vehicle information DB130shown inFIG. 4, the value of the vehicle identifier132of the own vehicle information stored in the first line is “101”, and the value of the vehicle type133is “dump truck”. Further, the values of the vehicle identifier132of the other vehicle information stored respectively in the second line and the third line are “102” and “103”, and the values of the vehicle type133are “light vehicle” and “excavator”. This expresses that, as shown in the system configuration example ofFIG. 1, the other vehicle102that is a light vehicle and the other vehicle103that is an excavator exist in the periphery of the own vehicle101, and the vehicle information of them is managed in the vehicle information DB130. Also, all of the values of the managing status141of the vehicle information of them are “1”. This expresses that both of the own vehicle information on the own vehicle101and the other vehicle information on the other vehicles102,103have been updated periodically, and both of the other vehicles102,103exist at locations where wireless communication with the own vehicle101is possible.

FIG. 5is a drawing showing a configuration example of the reception log DB.150. As shown inFIG. 5, the reception log DB.150is configured so that respective elements of a vehicle height151, a vehicle type152, a relative distance153, an angle154, a relative direction155, a vehicle status159, number of times156, the number of successful reception157, and a reception rate158are set in each line. Among these constituent elements, the vehicle height151, vehicle type152, relative distance153, angle154, relative direction155, and vehicle status159are classification elements for classifying plural numbers of the other vehicles into plural groups according to respective features. To these classification elements, values that are predetermined so that combination becomes different for each line are set respectively. Meanwhile, the number of times156, the number of successful reception157, and reception rate158are log elements that express the reception log of the other vehicle information of each group classified by the classification elements described above. The values of these log elements are set respectively by processing of the radio wave state monitoring section126, and are updated at every predetermined period.

The vehicle height151is a classification element on the height of the vehicle. In the reception log DB.150, the height range of three kinds for example is set to the vehicle height151according to the height of the other vehicle to be classified. The radio wave state monitoring section126determines the height range shown in the vehicle height151into which each of the other vehicles falls based on the value of the vehicle height134in the other vehicle information ofFIG. 4, and classifies each of the other vehicles according to the determination result.

The vehicle type152is a classification element on the type of the vehicle. In the reception log DB.150, the vehicle type such as “light vehicle”, “excavator”, and “dump truck” for example is set to the vehicle type152according to the type of the other vehicle to be classified.

The relative distance153and the angle154are classification elements on the location of the vehicle. The radio wave state monitoring section126manages the region in the periphery of the own vehicle while dividing it into plural regions in order to identify the region where wireless communication is not available in the periphery of the own vehicle. In concrete terms, the region in the periphery of the own vehicle is divided into plural regions by dividing plural concentric circles centered on the own vehicle so as to be separated into a predetermined angle for example. In the reception log DB.150, the ranges of the distance and the angle are respectively set to the relative distance153and the angle154corresponding to each of these divided regions. In other words, each of the divided regions in the periphery of the own vehicle can be identified using the values of the relative distance153and the angle154. Also, when other region dividing method is employed, it is preferable to employ such value that can identify each of the regions divided by the method instead of the relative distance153and the angle154.

The relative direction155is a classification element on the direction of the vehicle. In the reception log DB.150, the angle range of four kinds for example is set to the relative direction155according to the direction of the other vehicle to be classified.

The vehicle status159is a classification element on the status of the vehicle. In the reception log DB.150, the value such as “0” and “1” for example is set to the vehicle status159according to the status of the other vehicle to be classified.

The number of times156expresses the total of the number of times each of the other vehicles of the group corresponding to the line in question has transmitted the other vehicle information. When the other vehicle information stored in the vehicle information DB130is updated because the wireless communication information301has been received from the other vehicle, or when the wireless communication information301from the other vehicle could not be received even when a predetermined period of time elapsed after reception of the last time, the radio wave state monitoring section126increases the value of the number of times156of the group corresponding to the other vehicle in question.

The number of successful reception157expresses the number of successful reception of the other vehicle information transmitted from each of the other vehicles of the group corresponding to the line in question. When the other vehicle information stored in the vehicle information DB130has been normally updated by the wireless communication information301having been received from the other vehicle, the radio wave state monitoring section126increases the value of the number of successful reception157of the group corresponding to the other vehicle in question.

The reception rate158expresses the probability with which the other vehicle information transmitted from each of the other vehicles of the group corresponding to the line in question could be received normally. When the values of the number of times156and the number of successful reception157described above have been updated respectively, the radio wave state monitoring section126obtains the reception rate based on these values after the update, and updates the value of the reception rate158of the group in question. In the example shown inFIG. 5, out of the group where the vehicle type152is “light vehicle”, in both of two groups where the angle range expressed by the angle154is “0-22.5” and “22.5-45”, the value of the reception rate158is “1.0”. Meanwhile, in two groups where the angle range expressed by the angle154is “125-147.5”, the value of the reception rate158is “0.0” and “0.1”. Thus, it is known that, when the other vehicle that is a light vehicle exists behind the own vehicle, the probability with which the own vehicle can normally receive the other vehicle information from the other vehicle is low. Also, when the vehicle type152is “dump truck”, in two groups where the distance range expressed by the relative distance153is “0-5” and the angle range expressed by the angle154is “0-22.5”, if the angle range expressed by the relative direction155differs, the value of the reception rate158changes from “1.0” to “0.7”. Thus, it is known that, when the other vehicle is a dump truck, even when a vehicle exists at a same location, if the direction is different, the probability with which the other vehicle information can be normally received changes.

By using such reception log DB.150as described above, the radio wave state monitoring section126can calculate the reception rate158of wireless communication on plural regions set beforehand in the periphery of the own vehicle respectively based on the values of the number of times156and the number of successful reception157expressing the reception log of the other vehicle information of the past. Also, based on the classification elements such as the vehicle height151, the vehicle type152, the relative direction155with the own vehicle, and the vehicle status159, plural other vehicles are classified into plural groups, and the reception rate158of the wireless communication can be calculated for each divided region identified by the values of the relative distance153and the angle154with respect to each of the groups. Also, the classification elements used in classifying other vehicles into groups are not limited to those cited in above explanation, and other classification elements may be used. Furthermore, it is not necessary to use all classification elements, and it is possible not to use optional classification elements.

FIG. 6is a drawing showing a distribution example of a region where wireless communication is not available.FIG. 6shows the location of the region where wireless communication is not available as seen from the own vehicle, the location being estimated by the radio wave state monitoring section126. As described above, the radio wave state monitoring section126divides the region in the periphery of the own vehicle into plural regions according to the values of the relative distance153and the angle154explained inFIG. 5. Using the value of the reception rate158in each of these divided regions, whether wireless communication with the other vehicle is possible or hard is managed.

FIG. 6 (a)shows an example of a region distribution drawing601of a case where the region in the periphery of the own vehicle is divided into a concentric circle shape. Divided regions shown by hatching in the region distribution drawing601show the regions where the value of the reception rate158is lower than a predetermined threshold. In other words, this case shows that there exists a region where wireless communication is not available in the vicinity of the rear of the own vehicle. Also, the region distribution drawing601can be generated from the values of the reception rate158of respective groups where the vehicle type152is “light vehicle” in the reception log DB.150exemplified inFIG. 5.

FIG. 6 (b)shows an example of a region distribution drawing602of a case where the region in the periphery of the own vehicle is divided into a rectangular shape. Divided regions shown by hatching in the region distribution drawing602show the regions where the value of the reception rate158is lower than a predetermined threshold. In other words, this case shows that there exists a region where wireless communication is not available in the vicinity of the right front of the own vehicle. Also, when the region distribution drawing602is used, each divided region identified by the values of the relative distance153and the angle154in the reception log DB.150exemplified inFIG. 5should be associated with each divided region of the region distribution drawing602.

FIG. 7is a process flow diagram of the radio wave state monitoring section126at the time of reception of wireless communication. The radio wave state monitoring section126can execute the process shown in the process flow ofFIG. 7by executing by a computer a predetermined program stored beforehand when the wireless communication section123has received the wireless communication information301.

When the wireless communication information301(other vehicle information) is received from the other vehicle, the wireless communication section123demodulates the wireless communication information301and outputs the demodulated wireless communication information301to the own vehicle/other vehicle information managing section124in such format as shown inFIG. 3. The own vehicle/other vehicle information managing section124updates the vehicle information DB130using the other vehicle information outputted from the wireless communication section123. At this time, when the value of the managing status141ofFIG. 4is “1” or “2” and there exists a line whose value of the vehicle identifier132agrees with the vehicle identifier311ofFIG. 3in the vehicle information DB130, the own vehicle/other vehicle information managing section124overwrites respective data of the line based on the content of the other vehicle information having been received, and sets the managing status141to “1”. Meanwhile, when there exists no line whose value of the vehicle identifier132agrees with the vehicle identifier311among the lines whose value of the managing status141is “1” or “2”, the own vehicle/other vehicle information managing section124sets respective data of the other vehicle information having been received to an appropriate line whose value of the managing status141is “0”, and sets the managing status141to “1”. When the vehicle information DB130has been updated, the own vehicle/other vehicle information managing section124notifies the radio wave state monitoring section126of the event.

When an update notification of the vehicle information DB130is received from the own vehicle/other vehicle information managing section124, the radio wave state monitoring section126starts the process ofFIG. 7(step700). The radio wave state monitoring section126acquires updated other vehicle information from the own vehicle/other vehicle information managing section124(step701). The radio wave state monitoring section126further acquires the own vehicle information from the own vehicle/other vehicle information managing section124(step702).

The radio wave state monitoring section126estimates the present location of the own vehicle based on the own vehicle information acquired in step702(step703). At this time, the radio wave state monitoring section126estimates the present location of the own vehicle based on various information included in the own vehicle information, namely the information such as the degree of latitude, degree of longitude, reception time, vehicle speed, and traveling direction for example. When the location of the own vehicle has been estimated thus, the radio wave state monitoring section126calculates the relative location of the other vehicle with respect to the own vehicle based on the location of the own vehicle estimated and the other vehicle information acquired in step701(step703). At this time, the radio wave state monitoring section126estimates the present location of the other vehicle based on various information included in the other vehicle information, namely the information such as the degree of latitude, degree of longitude, reception time, vehicle speed, and traveling direction for example. Also, the radio wave state monitoring section126calculates, based on the location of the own vehicle and the location of the other vehicle having been estimated, the relative distance between the own vehicle and the other vehicle, the direction along which the other vehicle exists when the traveling direction of the own vehicle is used as the reference, the traveling direction of the other vehicle when the traveling direction of the own vehicle is used as the reference, and so on. Thus, the radio wave state monitoring section126calculates the relative location of the other vehicle with respect to the own vehicle.

The radio wave state monitoring section126updates the reception log DB.150based on the relative location of the other vehicle calculated in step703(step704). At this time, the radio wave state monitoring section126identifies to which line the other vehicle in question corresponds in the reception log DB.150using the classification elements of the vehicle height151, vehicle type152, relative distance153, angle154, relative direction155, and vehicle status159ofFIG. 5based on the other vehicle information acquired in step701and the relative location of the other vehicle calculated in step703. Thus, the radio wave state monitoring section126classifies the other vehicle in question into an appropriate group. Also, the radio wave state monitoring section126updates the values of the number of times156and the number of successful reception157in the identified line (group), by adding 1 each to these values. Further, the radio wave state monitoring section126calculates the value of new reception rate158by dividing the value of the updated number of times156by the updated value of the number of successful reception157, and updates the value of reception rate158using the thus calculated value.

When the reception log DB.150is updated in step704, the radio wave state monitoring section126finishes the process flow ofFIG. 7(step705). Thereafter, the radio wave state monitoring section126waits until new wireless communication information301is received by the wireless communication section123.

FIG. 8is a periodic process flow diagram of the radio wave state monitoring section126.

The radio wave state monitoring section126starts execution of the process shown in thisFIG. 8for every constant processing period set beforehand (step800).

The radio wave state monitoring section126acquires a set of information of the own vehicle and the reception information from the other vehicles from the own vehicle/other vehicle information managing section124(step801). In concrete terms, the radio wave state monitoring section126acquires both of the own vehicle information stored in the first line in the vehicle information DB130ofFIG. 4and the other vehicle information whose value of the managing status141is “1” or “2” out of the other vehicle information stored in the second and succeeding lines from the own vehicle/other vehicle information managing section124.

When required information has been acquired in step801, the radio wave state monitoring section126executes a loop process in which processes from step811to step819explained below are executed for respective other vehicles (step810, step820). When execution of the loop process has been finished for all other vehicles that have acquired the other vehicle information, the radio wave state monitoring section126finishes the process flow ofFIG. 8(step821).

In the loop process, the radio wave state monitoring section126selects some other vehicle as a processing object, and confirms whether the value of the managing status141of the other vehicle information acquired in step801on the other vehicle in question is “2” (step811). As a result, when the value of the managing status141is “2”, the process proceeds to step812. If it is not the case, namely when the value of the managing status141is “1”, the process proceeds to step813.

When the process proceeds from step811to step812, the radio wave state monitoring section126determines whether or not the difference between the reception time of the other vehicle information from the other vehicle in question and the present time is less than a predetermined alarm determination time (step812). At this time, the radio wave state monitoring section126can identify the reception time of the other vehicle information from the value of the reception time140of the other vehicle information acquired in step801. As a result, when the difference between the reception time and the present time is less than the alarm determination time, the process proceeds to step819. If it is not the case, namely when the difference between the reception time and the present time is equal to or greater than the alarm determination time, the process proceeds to step814.

When the process proceeds from step812to step814, the radio wave state monitoring section126deletes the other vehicle information on the other vehicle in question from the vehicle information DB130(step814). At this time, the radio wave state monitoring section126sets the value of the managing status141to “0” for the line showing the other vehicle information of the other vehicle in question in the vehicle information DB130, and erases (resets) all values of other respective data. When step814has been executed, the radio wave state monitoring section126finishes the loop process for the other vehicle in question.

When the process proceeds from step811to step813, the radio wave state monitoring section126determines whether or not the difference between the reception time of the other vehicle information from the other vehicle in question and the present time is equal to or greater than a predetermined interruption determination time (step813). At this time, the radio wave state monitoring section126can identify the reception time of the other vehicle information from the value of the reception time140of the other vehicle information acquired in step801similarly to step812described above. As a result, when the difference between the reception time and the present time is equal to or less than the interruption determination time, the radio wave state monitoring section126determines that wireless communication has not yet been interrupted between the own vehicle and the other vehicle in question, and finishes the loop process for the other vehicle in question. Meanwhile, when the difference between the reception time and the present time is equal to or greater than the interruption determination time, the radio wave state monitoring section126determines that wireless communication has been interrupted between the own vehicle and the other vehicle in question, and proceeds the process to step815.

When the process proceeds from step813to step815, the radio wave state monitoring section126calculates the relative distance between the other vehicle in question and the own vehicle (step815). At this time, the radio wave state monitoring section126estimates the present location of the own vehicle and the other vehicle in question respectively from the values of the degree of latitude135, degree of longitude136, reception time140, vehicle speed137, and traveling direction138in each of the own vehicle information and the other vehicle information acquired in step801, and calculates the distance between the own vehicle and the other vehicle in question. Thus, the relative distance of the other vehicle in question with respect to the own vehicle can be calculated.

When the relative distance has been calculated in step815, the radio wave state monitoring section126determines whether or not the relative distance is equal to or less than a predetermined threshold (step816). As a result, when the relative distance is equal to or less than the threshold, the radio wave state monitoring section126determines that the other vehicle in question has entered a region where wireless communication is not available in the periphery of the own vehicle, and proceeds the process to step817. Meanwhile, when the relative distance is equal to or greater than the threshold, the radio wave state monitoring section126determines that wireless communication is impossible because the other vehicle in question exists at a location apart from the own vehicle, and proceeds the process to step818.

When the process proceeds from step816to step817, the radio wave state monitoring section126determines that reception of the other vehicle information on the other vehicle in question has failed, and updates the vehicle information DB130(step817). At this time, the radio wave state monitoring section126sets the value of the managing status141to “2” for the line showing the other vehicle information of the other vehicle in question in the vehicle information DB130. Also, the radio wave state monitoring section126calculates the relative distance, angle, and relative direction of the other vehicle in question with respect to the own vehicle from the present location of the own vehicle and the other vehicle in question calculated in step815, and, using the calculation result of them and the values of the vehicle type133, vehicle height134, and vehicle status142in the other vehicle information, and retrieves the line (group) corresponding to the other vehicle in question within the reception log DB.150. As a result, if the radio wave state monitoring section126can retrieve the corresponding line, and updates the value of the number of times156in the line by adding 1, and calculates the value of new reception rate158by dividing the value of the updated number of times156by the value of the number of successful reception157, and updates the value of the reception rate158using the thus calculated value. When step817has been executed, the radio wave state monitoring section126makes the process proceed to step819.

When the process proceeds from step812or step817to step819, the radio wave state monitoring section126executes an alarm process for preventing collision of the own vehicle and the other vehicle in question. Details of this alarm process will be explained below referring to the process flow ofFIG. 9. When the alarm process has been executed in step819, the radio wave state monitoring section126finishes the loop process for the other vehicle in question.

When the process proceeds from step816to step818, the radio wave state monitoring section126deletes the other vehicle information on the other vehicle in question from the vehicle information DB130(step818). At this time, similarly to step814described above, the radio wave state monitoring section126sets the value of the managing status141to “0” for the line showing the other vehicle information of the other vehicle in question in the vehicle information DB130, and erases (resets) all values of other respective data. When step818has been executed, the radio wave state monitoring section126finishes the loop process for the other vehicle in question.

By executing the process described above, when the difference between the reception time and the present time has been determined to be equal to or greater than the interruption determination time in step813and the relative distance has been determined to be equal to or less than the threshold in step816, the radio wave state monitoring section126can determine that wireless communication between the own vehicle and the other vehicle in question has been interrupted by entry of the other vehicle in question to the region where wireless communication is not available. In this case, until it is determined thereafter that the difference between the reception time and the present time is equal to or greater than the alarm determination time in step812, the radio wave state monitoring section126can continuously execute the alarm process of step819at every predetermined period. Also, the time when the alarm process is executed then (alarm time) is determined from the difference between the alarm determination time and the interruption determination time. When wireless communication with the other vehicle in question is restarted after a lapse of the alarm time or within the alarm time, the radio wave state monitoring section126determines that the difference between the reception time and the present time is equal to or greater than the alarm determination time in step812, or determines that the difference between the reception time and the present time is equal to or less than the interruption determination time in step813. As a result, execution of the alarm process of step819for the other vehicle in question is stopped.

FIG. 9is a process flow diagram showing a flow of the alarm process in the first embodiment of the present invention. The radio wave state monitoring section126starts execution of the process shown in thisFIG. 9in step819ofFIG. 8(step900).

The radio wave state monitoring section126extracts the data of each divided region in which all conditions of the vehicle height, vehicle type, relative direction, and vehicle status agree with those of the other vehicle having been selected as the processing object from the reception log DB.150(step901). In other words, in step901, the radio wave state monitoring section126extracts from the reception log DB.150the data of each line (group) where the values of the vehicle height151, vehicle type152, and vehicle status159correspond to the height, type, and status of the other vehicle in question obtained from the other vehicle information acquired in step801ofFIG. 8and where the relative direction155corresponds to the relative direction of the other vehicle calculated from the direction of the own vehicle and other vehicle information acquired in step801ofFIG. 8.

The radio wave state monitoring section126determines whether or not the value of the number of times156is equal to or greater than a predetermined threshold with respect to all lines where the data have been extracted in step901(step902). As a result, the radio wave state monitoring section126proceeds the process to step913when the value of the number of times156is equal to or greater than the threshold in all lines, and proceeds the process to step903when the value of the number of times156is less than the threshold in at least one line.

When the process proceeds from step902to step903, the radio wave state monitoring section126extracts from the reception log DB.150the data of each divided region where each condition of the vehicle height, vehicle type, and relative direction agree with those of the other vehicle selected as the processing object (step903). In other words, in step903, the radio wave state monitoring section126extracts from the reception log DB.150the data of each line (group) where the vehicle status differs from that of the other vehicle in question in addition to the data of each line (group) having been extracted in step901. In the data extracted then, the values of the vehicle height151and vehicle type152respectively correspond to the height and type of the other vehicle in question obtained from the other vehicle information acquired in step801ofFIG. 8, and the values of the relative direction155respectively correspond to the relative direction of the other vehicle in question obtained from the other vehicle information and the own vehicle information acquired in step801ofFIG. 8; however, the values of the vehicle status159include those that do not correspond to the status of the other vehicle in question.

When the data have been extracted in step903, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157for each divided region, and recalculates the value of the reception rate158(step904). In other words, in step904, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157included in each line (group) where the values of the vehicle height151, vehicle type152, and relative direction155respectively agree and where the values of the vehicle status159differ for each combination of the relative distance153and angle154respectively. Also, the radio wave state monitoring section126recalculates the value of the reception rate158after summing-up for each divided region by dividing each of the obtained total values of the number of successful reception157by each total value of the number of times156. Thus, the radio wave state monitoring section126merges groups where the values of the vehicle height151, vehicle type152, and relative direction155are equal to those of the other vehicle in question and the value of the vehicle status159differs from that of the other vehicle in question in the reception log DB.150, and recalculates the reception rate of each divided region.

The radio wave state monitoring section126determines whether or not all of the total values of the number of times156obtained in step904is equal to or greater than a predetermined threshold (step905). As a result, the radio wave state monitoring section126proceeds the process to step913when all of the values of the number of times156after summing-up is equal to or greater than the threshold, and proceeds the process to step906when at least one value of the number of times156after summing-up is less than the threshold.

When the process proceeds from step905to step906, the radio wave state monitoring section126extracts from the reception log DB.150the data of each divided region where each condition of the vehicle height and vehicle type agrees with that of the other vehicle selected as the processing object (step906). In other words, in step906, the radio wave state monitoring section126extracts from the reception log DB.150the data of each line (group) where the direction differs from that of the other vehicle in question in addition to the data of each line (group) extracted in step903. In the data extracted then, although the values of the vehicle height151and vehicle type152respectively correspond to the height and type of the other vehicle in question obtained from the other vehicle information acquired in step801ofFIG. 8, the values of the relative direction155and vehicle status159include those not corresponding to the direction and status of the other vehicle in question.

When the data have been extracted in step906, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157for each divided region, and recalculates the value of the reception rate158(step907). In other words, in step907, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157included in each line (group) where the values of the vehicle height151and vehicle type152respectively agree and the value of at least one of the relative direction155and vehicle status159differs for each combination of the relative distance153and angle154respectively. Also, the radio wave state monitoring section126recalculates the value of the reception rate158after summing-up for each divided region by dividing each of the obtained total values of the number of successful reception157by each total value of the number of times156. Thus, the radio wave state monitoring section126merges groups where the values of the vehicle height151and vehicle type152are equal to those of the other vehicle in question and where the value of at least one of the relative direction155and vehicle status159differs from that of the other vehicle in question in the reception log DB.150, and recalculates the reception rate of each divided region.

The radio wave state monitoring section126determines whether or not all of the total values of the number of times156obtained in step907is equal to or greater than a predetermined threshold (step908). As a result, the process proceeds to step913when all of the values of the number of times156after summing-up is equal to or greater than the threshold, and the process proceeds to step909when at least one value of the number of times156after summing-up is less than the threshold.

When the process proceeds from step908to step909, the radio wave state monitoring section126extracts from the reception log DB.150the data of each divided region where the condition of the vehicle height agrees with that of the other vehicle selected as the processing object (step909). In other words, in step906, the radio wave state monitoring section126extracts from the reception log DB.150the data of each line (group) where the vehicle type differs from that of the other vehicle in question in addition to the data of each line (group) extracted in step906. In the data extracted then, although the value of the vehicle height151corresponds to the height of the other vehicle in question obtained from the other vehicle information acquired in step801ofFIG. 8, the values of the vehicle type152, relative direction155, and vehicle status159include those not corresponding to the type, direction, and status of the other vehicle in question.

When the data have been extracted in step909, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157for each divided region, and recalculates the value of the reception rate158(step910). In other words, in step910, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157included in each line (group) where the values of the vehicle height151agree and the value of at least one of the vehicle type152, relative direction155, and vehicle status159differs for each combination of the relative distance153and angle154respectively. Also, the radio wave state monitoring section126recalculates the value of the reception rate158after summing-up for each divided region by dividing each of the obtained total values of the number of successful reception157by each total value of the number of times156. Thus, the radio wave state monitoring section126merges groups where the value of the vehicle height151is equal to that of the other vehicle in question and the value of at least one of the vehicle type152, relative direction155, and vehicle status159differs from that of the other vehicle in question in the reception log DB.150, and recalculates the reception rate of each divided region.

The radio wave state monitoring section126determines whether or not all of the total values of the number of times156obtained in step910is equal to or greater than a predetermined threshold (step911). As a result, the radio wave state monitoring section126proceeds the process to step913when all of the values of the number of times156after summing-up is equal to or greater than the threshold, and proceeds the process to step912when at least one value of the number of times156after summing-up is less than the threshold.

When the process proceeds from step911to step912, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157for each divided region with respect to all data within the reception log DB.150, and recalculates the value of the reception rate158(step912). In other words, in step912, the radio wave state monitoring section126sums up the values of the number of times156and the number of successful reception157included in each line (group) where the value of at least one of the vehicle height151, vehicle type152, relative direction155, and vehicle status159differs for each combination of the relative distance153and angle154respectively. Also, the radio wave state monitoring section126recalculates the value of the reception rate158after summing-up for each divided region by dividing each of the obtained total values of the number of successful reception157by each total value of the number of times156. Thus, the radio wave state monitoring section126merges groups where the value of at least one of the vehicle height151, vehicle type152, relative direction155, and vehicle status159differs in the reception log DB.150, and recalculates the reception rate of each divided region. When step912has been executed, the radio wave state monitoring section126proceeds the process to step913.

The radio wave state monitoring section126determines whether or not each of the value of the reception rate158in the data of each line extracted in step901described above or the value of the reception rate158after summing-up recalculated in any of steps904,907,910, and912is less than a predetermined reference value for each combination of the relative distance153and angle154, namely for each divided region. As a result, when there is a combination of the relative distance153and angle154where the reception rate is less than the reference value, the radio wave state monitoring section126determines the divided region identified by the combination is a region where wireless communication is not available in the periphery of the own vehicle and extracts it (step913).

When step913has been executed, the radio wave state monitoring section126outputs alarm information on the other vehicle in question to the operator notification section127(step914). At this time, the radio wave state monitoring section126generates the alarm information based on information showing the relative location of the other vehicle in question with respect to the own vehicle and so on and information showing the region where wireless communication is not available extracted in step913, and outputs the alarm information to the operator notification section127. Based on this alarm information, the operator notification section127executes alarming by notifying the operator of the own vehicle of the region where wireless communication is not available. When step914has been executed, the radio wave state monitoring section126finishes the alarm process ofFIG. 9(step915).

According to the first embodiment of the present invention explained above, actions and effects below are exerted.

(1) The safety driving assistance device110that is an on-board terminal device includes the location measuring section122that measures the location of the own vehicle, the wireless communication section123that transmits the own vehicle information including the location information of the own vehicle to the other vehicles and receives the other vehicle information including the location information of the other vehicles from the other vehicles by execution of wireless communication with the other vehicles, and the radio wave state monitoring section126. The radio wave state monitoring section126estimates the location of the other vehicles and calculates the relative distance between the own vehicle and the other vehicles (step815) when wireless communication with the other vehicles has been interrupted, and, when this relative distance is less than a predetermined threshold, executes an alarm process (step819) for preventing collision of the own vehicle and the other vehicles. With such configuration, even when there exists a region where wireless communication is not available in the periphery of the own vehicle, collision of the own vehicle and the other vehicles can be surely prevented.

(2) The safety driving assistance device110further includes the operator notification section127that executes notification on the other vehicles to the operator of the own vehicle. The radio wave state monitoring section126outputs the alarm information including the information on the region where wireless communication is not available in the periphery of the own vehicle to the operator notification section127in the alarm process (step914). Based on this alarm information, the operator notification section127notifies the operator of the own vehicle of the region where wireless communication is not available. With such configuration, when there exists a region where wireless communication is not available in the periphery of the own vehicle, the region can be surely notified to the operator of the own vehicle to draw attention.

(3) The radio wave state monitoring section126has the reception log DB.150, and calculates the reception rate of wireless communication respectively for plural divided regions set beforehand in the periphery of the own vehicle as shown inFIG. 6based on the values of the number of times156and the number of successful reception157expressing the reception log of the other vehicle information of the past accumulated in this reception log DB.150. Also, out of plural divided regions, the radio wave state monitoring section126determines the divided region where the reception rate of wireless communication is less than a predetermined reference value is a region where wireless communication is not available (step913). With such configuration, the region where wireless communication is not available existing in the periphery of the own vehicle can be surely and precisely identified.

(4) The wireless communication section123executes wireless communication with the plural other vehicles102,103respectively. The radio wave state monitoring section126classifies the plural other vehicles102,103into plural groups based on the predetermined classification elements, and calculates the reception rate158of wireless communication for each divided region expressed by a combination of the values of the relative distance153and angle154with respect to each of the groups. This classification element can include at least either one of the vehicle height151, vehicle type152, relative direction155with own vehicle, and vehicle status159. With such configuration, the reception rate of wireless communication can be precisely calculated for each divided region considering the feature of each vehicle.

(5) The radio wave state monitoring section126determines whether or not the total value of the reception number of times of the other vehicle information from respective other vehicles included in the same group of the other vehicle with which wireless communication has been interrupted is less than a predetermined threshold based on the value of the number of times156in each line of the reception log DB.150(steps902,905,908,911). As a result, when the total value of the reception number of times is less than the threshold, the radio wave state monitoring section126merges the group in question and other groups, and calculates the reception rate of wireless communication (steps904,907,910,912). With such configuration, even when the reception number of times of the other vehicle information is insufficient for calculating the reception rate, the reception rate can be calculated semi-precisely.

(6) When execution of the alarm process is started in step819after it is determined that wireless communication has been interrupted in step813, during the period of the alarm time from that time point until when it is determined that the difference between the reception time and the present time is equal to or less than a predetermined alarm determination time in step812, the radio wave state monitoring section126executes the alarm process continuously. Such an alarm time is determined from the difference between the alarm determination time used in determination of step812and the interruption determination time used in determination of step813. Meanwhile, when wireless communication is restarted after a lapse of the alarm time or within the alarm time, the radio wave state monitoring section126determines that the difference between the reception time and the present time is equal to or greater than the alarm determination time in step812, or determines that the difference between the reception time and the present time is equal to or less than the interruption determination time in step813. Thus, the radio wave state monitoring section126stops execution of the alarm process of step819. With such configuration, execution of the alarm process can be started and stopped at proper timing.

Second Embodiment

FIG. 11is a drawing showing a configuration of a safety driving assistance system including a safety driving assistance device that is an application example of an on-board terminal device related to the second embodiment of the present invention. Compared with the safety driving assistance system according to the first embodiment of the present invention shown inFIG. 1, the safety driving assistance system shown inFIG. 11is different in terms that the safety driving assistance device110includes a control signal output section128instead of the operator notification section127.

The control signal output section128outputs a control signal to the own vehicle, the control signal being for executing travel control of the own vehicle so as to avoid collision of the own vehicle and the other vehicles based on the determination result of the collision risk notified from the collision risk determining section125and the alarm information outputted from the radio wave state monitoring section126. The control signal output section128can output a control signal instructing braking to the own vehicle and a control signal instructing the direction for avoiding the other vehicle having a risk of collision with the own vehicle to the own vehicle for example as a control signal for executing travel control of the own vehicle.

In the present embodiment, although the radio wave state monitoring section126executes a process similar to that of the first embodiment explained inFIGS. 7, 8respectively, the radio wave state monitoring section126executes a process different from that of the first embodiment only in the alarm process executed in step819ofFIG. 8. Below, the alarm process executed in the present embodiment will be explained.

FIG. 12is a process flow diagram showing a flow of the alarm process in the second embodiment of the present invention. In step819ofFIG. 8, the radio wave state monitoring section126starts execution of the process shown in thisFIG. 12(step900).

In steps901-913, the radio wave state monitoring section126executes processes similar to those of the first embodiment explained inFIG. 9respectively.

When step913has been executed, the radio wave state monitoring section126outputs alarm information on the other vehicle in question to the control signal output section128(step914A). At this time, the radio wave state monitoring section126generates alarm information based on information showing the relative location of the other vehicle in question with respect to the own vehicle and so on and information showing the region where wireless communication is not available extracted in step913, and outputs the alarm information to the control signal output section128. Based on this alarm information, the control signal output section128outputs to the own vehicle a control signal of a case where the other vehicle exists in the region where wireless communication is not available. When step914A has been executed, the radio wave state monitoring section126finishes the alarm process ofFIG. 12(step915).

According to the second embodiment of the present invention explained above, actions and effects similar to those of (1), (3)-(6) explained in the first embodiment are exerted. Also, instead of the action and effect of (2), actions and effects of (7) described below are exerted.

(7) The safety driving assistance device110further includes the control signal output section128that outputs to the own vehicle a control signal for executing travel control of the own vehicle. The radio wave state monitoring section126outputs the alarm information including information on the region where wireless communication is not available in the periphery of the own vehicle to the control signal output section128in the alarm process (step914A). Based on this alarm information, the control signal output section128outputs a control signal of a case where the other vehicle exists in the region where wireless communication is not available. With such configuration, when the other vehicle exists in the region where wireless communication is not available, the control signal for surely avoiding collision with the other vehicle can be outputted to the own vehicle.

As explained above, according to the present invention, in safety driving assistance using wireless communication, when other vehicle enters a region where wireless communication is not available due to the radio wave shielding effect of the own vehicle and the other vehicle in the vicinity of the own vehicle, required notification to the operator and control signal outputting required for travel control of the own vehicle can be executed. In concrete terms, the fact that the vehicle in question has entered the region where wireless communication is not available and the estimated location of the region with respect to the own vehicle can be outputted as the notification to the operator or the control signal to the own vehicle. Therefore, it helps the operator and the travel control device of the own vehicle to grasp the present location of the other vehicles, and can contribute to prevention of collision.

Also, according to the present invention, even when the region where wireless communication is not available changes according to the status of the own vehicle and the other vehicles, flexible response becomes possible. In other words, in a dump truck and the like, the radio wave shielding effect changes according to the loading status also. However, according to the present invention, even in such case, the region where wireless communication is not available can be surely determined from the communication status during working, and therefore flexible response is possible.

Furthermore, each embodiment and various modifications explained above are only an example, and the present invention is not limited to the contents of them as far as the features of the invention are not spoiled. The present invention is not limited to the embodiments and the modifications described above, and various alterations are possible within a scope not deviating from the substance of the present invention.

The disclosed contents of the basic application for the right of priority described below are hereby incorporated by reference.

LIST OF REFERENCE SIGNS