Travel Distance Estimation System

Abstract

Provided is a travel distance estimation system for appropriately estimating the travel distance of a vehicle using a communication method for which there are restrictions on communication frequency and wireless transmission data capacity. The system includes a communication terminal device and a server. The server sequentially receives a plurality of pieces of position information that have been wirelessly transmitted all at once from the communication terminal device and records the position information at a storage unit in the order in which the position information was received. The server extracts a prescribed number of candidate routes on the basis of the position information recorded at the storage unit for two consecutive points and estimates the average distance of the extracted candidate routes to be the distance between the two points.

Description

Technical Field

[0001] The present invention relates to a technique for estimating the traveling distance of a moving body, and particularly to a system for appropriately estimating the traveling distance of a moving body using a communication method with restrictions on the number of communications and the transmission data capacity.

Background Art

[0002] In recent years, various wireless communication standards have been put into practical use. In particular, LPWA (Low Power Wide Area) communication, which covers a wide area at low cost and low power consumption, has attracted attention.

[0003] While LPWA communication has the above-mentioned advantages, there are restrictions such as a limit on the number of communications that can be wirelessly transmitted, or a small capacity of data that can be wirelessly transmitted at one time. For example, "Sigfox (registered trademark)", which is one of LPWA communications, has a maximum transmission limit of 140 times per day and a maximum data capacity of 12 bytes that can be wirelessly transmitted at one time.

[0004] Therefore, generally, LPWA communication is adopted for systems that only need to wirelessly transmit information several times a day, for example, systems that detect the presence or absence of abnormalities in devices and wirelessly transmit the presence or absence of abnormalities to a server. (See Patent Document 1)

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the low cost of LPWA communication is a great attraction, and there is an increasing demand to apply LPWA communication to management systems that have been performed using the communication network of mobile phones.

[0007] For example, in a car-sharing service that manages the operation of many vehicles, there is a desire to collect the mileage of leased vehicles on a server and utilize it for vehicle maintenance. Until now, vehicle maintenance has been carried out at the timing when a certain period has elapsed. However, depending on the operating conditions of the vehicle, there are vehicles that do not require maintenance even after a certain period has elapsed, and there are also vehicles that require maintenance before a certain period has elapsed. The information that serves as a criterion for whether vehicle maintenance is necessary is the mileage.

[0008] The mileage of a vehicle is estimated by the vehicle itself measuring the number of wheel rotations, but there are variations due to tire conditions, tire size, etc. It is also possible to obtain mileage information from the vehicle, but the effort required to connect to the ECU (Electronic Control Unit) that manages the vehicle's mileage also increases.

[0009] Therefore, a mechanism can be considered in which the in-vehicle device sequentially acquires the position information of the vehicle using GNSS (Global Navigation Satellite System) without taking such effort, and wirelessly transmits the acquired position information to the server, and the server calculates the mileage of the vehicle.

[0010] However, when using LPWA communication with a transmission count limit, it is not possible to wirelessly transmit the vehicle's position information frequently, so it is necessary to estimate a distance close to the actual mileage of the vehicle from a limited number of position information.

[0011] An object of the present invention is to enable the use of a mileage estimation system, a communication terminal device, an uplink message transmission method, and a program for appropriately estimating the mileage of a moving object such as a vehicle using a communication method with limitations on the number of communications and the transmission data capacity.

Means for Solving the Problems

[0012] (1) To solve the above problems, a travel distance estimation system according to an aspect of the present invention includes a communication terminal device mounted on a moving body and a server that receives the position information of the moving body from the communication terminal device. The communication terminal device includes a position information acquisition unit and a communication unit. The position information acquisition unit sequentially acquires position information. The communication unit wirelessly transmits a plurality of pieces of position information to the server collectively. The server includes a server communication unit, a control unit, a route information storage unit, and a distance estimation unit. The server communication unit sequentially receives the plurality of pieces of position information wirelessly transmitted by the communication unit. The control unit records the position information in the storage unit in the order of sequential reception. The route information storage unit stores, in association with each other, route information regarding routes and intersections through which the moving body can pass and weight information indicating a cost. The distance estimation unit extracts a predetermined number of candidate routes that are candidates for a route with a low cost from the route information storage unit based on the continuous two-point position information recorded in the storage unit, and sets the average distance of the extracted candidate routes as the estimated distance between the two points.

[0013] (2) In the travel distance estimation system of (1) described above, the route information storage unit may further store, in association with each other, the route information, route position information indicating the position of the route, and intersection position information indicating the position of the intersection. The server may further include a second distance estimation unit. The second distance estimation unit extracts route information including route position information close to the positions of the two points from the route information storage unit based on the two-point position information recorded in the storage unit, and identifies an intersection indicated by the intersection position information that is close to the positions of the two points among the intersection position information stored in association with the extracted route information, and sets the distance passing through the two points and the identified intersection as the second estimated distance between the two points. The control unit may select either the estimated distance or the second estimated distance.

[0014] (3) In the travel distance estimation system of (1) described above, the route information storage unit may further store the route information in association with frequency information indicating the usage frequency of the route. The server may further include a third distance estimation unit. The third distance estimation unit identifies the route information with the highest usage frequency based on the position information of two points recorded in the storage unit, and sets the distance of the route indicated by the identified route information as the third estimated distance between the two points. The control unit may select either the estimated distance or the third estimated distance.

[0015] (4) In the travel distance estimation system of (2) described above, the route information storage unit may further store the route information in association with frequency information indicating the usage frequency of the route. The server may further include a third distance estimation unit. The third distance estimation unit identifies the route information with the highest usage frequency based on the position information of two points recorded in the storage unit, and sets the distance of the route indicated by the identified route information as the third estimated distance between the two points. The control unit may select any one of the estimated distance, the second estimated distance, and the third estimated distance.

[0016] (5) In the travel distance estimation system according to any one of (1) to (4) described above, the communication terminal device may further include a terminal control unit. The terminal control unit calculates difference information indicating the difference between the position information of two points recorded in the storage unit, and may not wirelessly transmit the position information to the server when the calculated difference information is 0 or smaller than a predetermined value.

[0017] (6) In the travel distance estimation system according to any one of (1) to (5) described above, the communication terminal device may further include a detection unit. The detection unit detects the start and end of the movement of the moving body. When the detection unit detects the start of the movement of the moving body, the communication unit wirelessly transmits to the server on-time content including the position information acquired by the position information acquisition unit and movement start information indicating the start of the movement of the moving body. Each time a predetermined time elapses since the start of the movement of the moving body, the communication unit wirelessly transmits to the server periodic content including a plurality of pieces of position information acquired by the position information acquisition unit. When the detection unit detects the end of the movement of the moving body, the communication unit wirelessly transmits to the server off-time content including the position information acquired by the position information acquisition unit and movement end information indicating the end of the movement of the moving body. The server communication unit receives the on-time content, periodic content, and off-time content wirelessly transmitted by the communication unit, and the distance estimation unit may estimate the distance between two points based on the position information included in the on-time content, periodic content, and off-time content.

[0018] (7) To solve the above problems, a travel distance estimation system according to an aspect of the present invention includes a communication terminal device mounted on a moving body and a server that communicates with the communication terminal device. The communication terminal device includes a detection unit, a position information acquisition unit, a terminal control unit, and a communication unit. The detection unit detects on / off of the power supply of the moving body. The position information acquisition unit sequentially acquires position information indicating the position where the moving body exists. The terminal control unit generates an upstream message including a sequence number indicating the transmission order, behavior information indicating the behavior of the moving body based on the on / off of the power supply detected by the detection unit, and a position information group specifying a plurality of positions based on the position information. The communication unit wirelessly transmits the upstream message to the server. When the detection unit detects power off, the terminal control unit generates an upstream message including behavior information indicating the end of movement of the moving body as behavior. When the detection unit detects power on, the terminal control unit generates an upstream message including behavior information indicating the start of movement of the moving body as behavior, and generates the upstream message without using the position information sequentially acquired by the position information acquisition unit between when power off is detected and when power on is detected. The server includes a server communication unit and a distance estimation unit. The server communication unit receives the upstream message wirelessly transmitted from the communication unit. The distance estimation unit estimates the travel distance of the moving body based on the position information group included in the upstream message received by the server communication unit.

[0019] (8) According to an aspect of the present invention, in the travel distance estimation system described in (7) above, the terminal control unit may further calculate difference information indicating the difference between the first position and the second position based on a plurality of pieces of position information sequentially acquired by the position information acquisition unit, and the position information group may include information indicating the first position and the difference information.

[0020] (9) According to an aspect of the present invention, in the travel distance estimation system described in (8) above, when the difference calculated by the terminal control unit is 0 or smaller than a predetermined value, the position information group may not include the difference information.

[0021] (10)One aspect of the present invention is in the travel distance estimation system described in any one of (7) to (9) above, wherein the position information acquisition unit acquires position information expressed in longitude and latitude, and the terminal control unit converts the position information sequentially acquired by the position information acquisition unit into information expressed in xy coordinates with a predetermined position as a reference position to generate an upstream message.

[0022] (11)To achieve the above object, a communication terminal device according to one aspect of the present invention is a communication terminal device mounted on a moving body, and includes a detection unit, a position information acquisition unit, a terminal control unit, and a communication unit. The detection unit detects on / off of the power supply of the moving body. The position information acquisition unit sequentially acquires position information indicating the position where the moving body exists. The terminal control unit generates an upstream message including a sequence number indicating the transmission order, behavior information indicating the behavior of the moving body based on on / off of the power supply detected by the detection unit, and a position information group specifying a plurality of positions based on the position information. The communication unit wirelessly transmits the upstream message to the server. When the detection unit detects that the power supply is off, the terminal control unit generates an upstream message including behavior information indicating the end of movement of the moving body. When the detection unit detects that the power supply is on, the terminal control unit generates an upstream message including behavior information indicating the start of movement of the moving body, and generates an upstream message without using the position information sequentially acquired by the position information acquisition unit between detecting that the power supply is off and detecting that the power supply is on.

[0023] (12)To achieve the above object, a transmission control method according to one aspect of the present invention is a method for controlling the transmission of an upstream message used in a communication terminal device mounted on a moving body and including a CPU (Central Processing Unit) and a memory, the method including: when detecting that the power supply of the moving body is off, wirelessly transmitting an upstream message including behavior information indicating the end of movement of the moving body; when detecting that the power supply is on, wirelessly transmitting an upstream message including behavior information indicating the start of movement of the moving body; and wirelessly transmitting an upstream message without using the position information sequentially acquired between detecting that the power supply is off and detecting that the power supply is on.

[0024] (13) To achieve the above object, a program according to an aspect of the present invention causes a communication terminal device mounted on a moving body and including a CPU and a memory to function as a position information acquisition unit that sequentially acquires position information indicating the position where the moving body exists, a detection unit that detects on / off of the power supply of the moving body, and a communication unit that wirelessly transmits an upstream message including a position information group that specifies a plurality of positions based on the position information to a server, and is a program that causes the communication terminal device to execute transmission control processing of the upstream message. The transmission control processing includes a step of wirelessly transmitting an upstream message including behavior information indicating the end of movement of the moving body when the detection unit detects that the power supply is off, a step of wirelessly transmitting an upstream message including behavior information indicating the start of movement of the moving body when the detection unit detects that the power supply is on, and a step of wirelessly transmitting an upstream message without using the position information sequentially acquired by the position information acquisition unit between the detection of the power supply off and the detection of the power supply on.

Effect of the Invention

[0025] Even when using a communication method with limitations on the number of communications and the transmission data capacity, the present invention can appropriately estimate the travel distance of the moving body.

Brief Description of the Drawings

[0026]

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Mode for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a travel distance estimation system according to this embodiment. This system is composed of a communication terminal device 11 mounted on a moving body 1, a base station group 2, a server 3, and a GNSS satellite group 4.

[0028] The mobile object 1 is a mobile object capable of traveling on roadways. The mobile object 1 includes not only four-wheeled automobiles, but also two-wheeled automobiles, bicycles, etc. Also included are mobile objects 1 with no passengers on board. The communication terminal device 11 mounted on the mobile object 1 has a location information acquisition function using GNSS and a Sigfox communication function, as will be described in detail later. The base station group 2 is a plurality of base stations capable of receiving radio waves based on the Sigfox communication method. The server 3 receives and collects information (data) identified from the radio waves received by the base station group 2. The GNSS satellite group 4 is a group of GNSS satellites, and each satellite transmits its location information and transmitted time information at any time.

[0029] Although not shown in the figure, it is assumed that there are multiple mobile objects 1 and communication terminal devices 11 mounted thereon in this system. The base station group 2 is arranged so that the reception areas covered by each base station overlap. A technical feature adopted by Sigfox communication is space diversity. This means that instead of only one base station receiving radio waves compatible with Sigfox communication, all base stations capable of receiving the radio waves receive the radio waves compatible with Sigfox communication, and the server 3 manages the data received by each base station as one piece of data.

[0030] The server 3 includes at least the functional units of a server communication unit 31, a control unit 32, a storage unit 33, a route information storage unit 34, and a distance estimation unit 35. Although not shown in the figure, the server 3 is a computer group constructed of multiple computers for the purpose of distributing the processing load.

[0031] The server communication unit 31 is composed of a communication module and the like. It has a function of sequentially receiving location information sequentially transmitted from the communication terminal device 11 via the base station group 2. The control unit 32 is composed of a CPU as hardware. The control unit 32 has a function of sorting the location information sequentially received by the server communication unit 31 and recording the location information in the storage unit 33 in the order of reception and in consecutive order.

[0032] The storage unit 33 is composed of a large-capacity storage medium such as a hard disk drive as hardware. The storage unit 33 stores the position information received sequentially under the control of the control unit 32. The storage unit 33 stores a program for estimating the travel distance of the moving body 1.

[0033] The route information storage unit 34 is composed of a large-capacity storage medium such as a hard disk drive as hardware. The route information storage unit 34 stores so-called map data. The map data includes route information regarding routes (also referred to as links) and intersections (also referred to as nodes). The route information includes type information indicating the type of the route (for example, national highway, prefectural road, highway, general road, etc.), name information indicating the name of the route, as well as road width, cost, and position information of the route and intersections.

[0034] The cost is a value obtained by quantifying the "difficulty of passing" of the route and is an evaluation value used in route search. There are various methods for determining the cost, and generally, different evaluation costs are used according to the search purpose. For example, if you want to search for the shortest-distance route, the length of the route becomes a major evaluation factor for determining the cost, but if it is a route search for reaching the destination in the shortest time, not only the distance but also the road width, traffic jam frequency, etc. are included as evaluation factors.

[0035] The distance estimation unit 35 is a functional unit virtually realized by the CPU executing a program. The distance estimation unit 35 has a function of estimating a value as close as possible to the actual travel distance between two points using the position information of two consecutive points recorded in the storage unit 33 and the route information stored in the route information storage unit 34. There are multiple methods for estimating the travel distance according to the present invention. The specific operations of each distance estimation process will be described later.

[0036] FIG. 2 is a diagram showing an example of the functional blocks of the communication terminal device 11. The communication terminal device 11 includes at least a position information acquisition unit 111, a communication unit 112, a memory 113, a behavior detection unit 114, a terminal control unit 115, a detection unit 116, and an auxiliary battery 117.

[0037] The position information acquisition unit 111 has a function of receiving a plurality of pieces of position information of each satellite transmitted from the GNSS satellite group 4 at any time and the time information of transmission. If the radio waves from the satellites can be received, that is, if the number of satellites that can be captured is 4 or more, the position information acquisition unit 111 can calculate and acquire the position information indicating the position of its own device using the information from these satellites. The position information acquisition unit 111 sequentially acquires the position information in units of seconds, and the terminal control unit 115 controls the acquired position information to be stored in the memory 113 in the order of acquisition.

[0038] FIG. 3 is a diagram showing an example of the position information sequentially stored in the memory 113. As shown in the figure, the terminal control unit 115 stores the latitude and longitude information calculated and acquired by the position information acquisition unit 111 in the memory 113 in the order of acquisition.

[0039] The communication unit 112 has a function of creating transmission data including position information in accordance with the Sigfox communication method. Since Sigfox has a limit on the number of communications per day (maximum 140 times), the communication unit 112 sets a cycle (interval) in accordance with the application and the number limit and transmits the position information. The transmission cycle of the position information can be changed when an event is detected or according to an instruction from the server 3.

[0040] In the present embodiment, a transmission cycle in units of minutes such as 4 minutes or 10 minutes is set in the communication unit 112. For example, when a transmission cycle of 4-minute intervals is set, the communication unit 112 can transmit the position information to the server 3 15 times per hour and continuously for about 9 hours. On the other hand, when transmitting at 10-minute intervals, the position information can be transmitted to the server 3 6 times per hour and continuously for approximately 24 hours. The transmission cycle may be changed according to the running state of the moving body 1.

[0041] The moving body 1 on which the communication terminal device 11 is mounted moves in the range of an average speed of 30 km / h to 60 km / h, depending on the road conditions during movement. In this case, the distance that the moving body 1 moves in one minute is 500 m to 1 km. Therefore, if one position information is sent every four minutes, the distance between the positions indicated by each consecutive position information will be 2 km to 4 km. When the area where the moving body 1 moves is an urban area, there are many intersections, and within the range of 2 km to 4 km, it is conceivable that the moving body 1 turns at intersections multiple times in four minutes.

[0042] If the number of position information that the server 3 can obtain is small, it is impossible to specify at which intersection the moving body 1 turned. And when the moving body 1 turns at intersections multiple times, the distance between the positions indicated by the position information becomes longer than the distance connected by a straight line between them. Thus, in order to estimate a moving distance close to the actual measurement, it is desirable that the communication terminal device 11 sends as many position information as possible to the server 3.

[0043] However, the data capacity that can be wirelessly transmitted at one time in Sigfox communication is as small as 12 bytes. The position information expressed in latitude and longitude has a data size of 8 bytes. In the case of 8 bytes, in Sigfox communication, only one position information can be wirelessly transmitted in one transmission. As described above, when position information is wirelessly transmitted at four-minute intervals, since the distance between the positions that the server 3 can obtain is 2 km to 4 km, depending on the area where the vehicle travels, there is a high possibility that the estimated distance will deviate significantly from the actual moving distance even when the distance is estimated.

[0044] Here, although the accuracy of the location information decreases, the data size of the location information can be reduced to 6 bytes. Since the Sigfox communication has a wireless transmission of 12 bytes per time, if the data size is 6 bytes, two pieces of location information can be wirelessly transmitted in one wireless transmission. Also, by taking the difference between two pieces of location information, the data capacity of the location information can be compressed. In this case, for the transmission capacity of 12 bytes per time, one normal location information (6 bytes) and the difference information of two pieces of location information (3 bytes × 2) can be wirelessly transmitted. Note that although the accuracy of the location information will deteriorate, further compression is also possible.

[0045] By wirelessly transmitting two or three pieces of location information together at 4-minute intervals, the distance interval between each piece of location information used for distance estimation at the server 3 can be reduced. As a result, in the distance estimation process described later, it becomes possible to estimate a number closer to the actually measured distance.

[0046] The communication unit 112 has a function of wirelessly transmitting a plurality of pieces of location information stored in the memory 113 to the server 3 together.

[0047] Note that there are multiple ways to select a plurality of pieces of location information to be transmitted together. Since the location information acquisition unit 111 sequentially acquires location information in seconds, when the transmission interval of the location information is 4 minutes, ideally 240 pieces of location information are acquired in 4 minutes. However, depending on the satellite capture situation, there may be cases where the location information cannot be acquired correctly. When selecting three pieces of location information and wirelessly transmitting them, it is desirable that the distances of each piece of location information are appropriately separated, or that the location information at the time of an event is appropriately selected. When the behavior detection unit 114 described later detects the behavior of the moving body 1, a method of selecting the location information acquired at the timing when the behavior is detected is also conceivable.

[0048] Furthermore, as a result of calculating the difference between one reference position information and the next acquired position information, it is conceivable that the difference information becomes zero or a value close to zero. For example, when the moving body 1 is stuck in traffic and cannot move at all, or when it is parked and taking a break. In such cases, since there is no change in distance and there is also a limit on the number of communications, it is also possible to implement control such that the position information is not wirelessly transmitted in this cycle, but is wirelessly transmitted the next time there is a change in the position information.

[0049] When the communication unit 112 wirelessly transmits the position information to the server 3, it attaches identification information for identifying that the communication terminal device 11 has wirelessly transmitted, and a sequence number indicating the acquisition order of the position information. With the identification information, the server 3 can identify from which communication terminal device the wirelessly transmitted position information is. Also, by attaching a sequence number, when retransmitting the position information, the server 3 can specify which order of position information it is.

[0050] The behavior detection unit 114 is composed of an acceleration sensor or a gyro sensor as hardware, and has a function of detecting the behavior of the moving body 1 on which the communication terminal device 11 is mounted. Among the behaviors of the moving body 1 that can be detected are acceleration, a change in the moving direction of the moving body 1, sudden stop, sudden start, collision, right turn or left turn at an intersection, driving on a gradient road, etc. When the behavior detection unit 114 detects these behaviors, the terminal control unit 115 stores the detected behavior information together with the position information acquired at the timing of the detection in the memory 13.

[0051] The terminal control unit 115 is composed of a CPU as hardware and controls the overall operations of each functional unit included in the communication terminal device 11. The detection unit 116 has a function of performing power management of the communication terminal device 11. The communication terminal device 11 receives power supply from the ACC (Accessary) power supply of the mobile body 1 and has a function of detecting when the ACC power supply of the mobile body 1 becomes ON or OFF. The detection unit 116 distributes power to the auxiliary battery 117. When the ACC power supply of the mobile body 1 becomes OFF, the detection unit 116 receives power supply from the auxiliary battery 117. The auxiliary battery 117 is a rechargeable battery. The auxiliary battery 117 stores power that can drive the communication terminal device 11 for a predetermined time even when the ACC power supply of the mobile body 1 is OFF by receiving power distribution from the detection unit 116.

[0052] The operation of the server 3 will be described. FIG. 4 is a diagram showing an example of the position information with sequence numbers stored in the storage unit 33. The server 3 performs a process of estimating the moving distance of the mobile body 1 using the position information stored in the storage unit 33 at regular intervals or when there is a request. Note that there are multiple optimal travel distance estimation processing methods in the present invention. Among them, two travel distance estimation processing methods that can particularly expect remarkable effects will be described below with reference to the drawings.

[0053] FIG. 5 is a diagram showing an example of the operation flow of the first travel distance estimation process. Note that the symbol "S" used in the description of the operation flow means step. When there is a request for the travel distance estimation process for the mobile body 1, the distance estimation unit 35 of the server 3 extracts two pieces of position information with consecutive sequence numbers and attached with identification information indicating the communication terminal device 11 mounted on the mobile body 1, and performs a route search between the two points (S1).

[0054] The route search method itself uses a known technique. For example, it is a shortest path search method that selects a combination of paths with the minimum added value of the cost assigned to the path. There are also several known algorithms for the shortest path search method. For example, there are the Dijkstra method, the Bellman - Ford method, the A* method, etc.

[0055] FIG. 6 is a diagram for explaining an example of a route candidate specified by the shortest path search method. In known route search, when a route search is performed by determining a start point and an end point, a plurality of candidate routes through which the moving body 1 can pass as the shortest route are listed and the user can select them. In the moving distance estimation process of the present invention, a predetermined number (for example, three) of candidate routes are extracted, and a process of adding the distances of the three extracted candidate routes and calculating an average value is performed. Note that the server 3 may or may not display the route candidates shown in FIG. 6.

[0056] The merits of the above distance estimation process will be described with reference to FIG. 6. When estimating the distance between points A and B shown in FIG. 6, if the straight-line distance between the two points is simply calculated, it is 3.3 km. On the other hand, when three route candidates between points A and B specified by the shortest path search method are specified, candidate 1 is 3.8 km, candidate 2 is 3.8 km, and candidate 3 is 4.1 km. The actual route traveled by the moving body 1 remains unknown from the position information. However, it is highly likely that one of the three routes listed as candidates is used, or that the routes as fragments included in each candidate route are connected and the moving body is moving.

[0057] The distance estimation unit 35 calculates 3.9 km, which is the value obtained by adding the distances of the three candidate routes and taking the average (average distance), as the estimated distance (S2). By using the first travel distance estimation process, even if the actual travel route is unknown, a plurality of routes with a high probability of travel are selected, and by taking the average value (average distance) of these, a large deviation can be reduced.

[0058] FIG. 7 is a diagram showing an example of the operation flow of the second travel distance estimation process. The distance estimation unit 35 of the server 3 functions as a second distance estimation unit. When there is a request for travel distance estimation processing for the moving body 1, two consecutive position information (A, B) with identification information indicating the communication terminal device 11 mounted on the moving body 1 is extracted, and from the route information stored in the route information storage unit 34, a route close to the positions of these two points is extracted, and among the intersections connected to the route, the intersection X close to the positions of A and B is specified (S11).

[0059] Here, with reference to FIGS. 8 and 9, the method for specifying the intersection X will be described. In the schematic diagram of FIG. 8, the solid line route connecting the points A, intersection X1, intersection X3, intersection X5, and point B is the actual travel route of the moving body 1. The travel distance of the moving body 1 is 0.6 km between A and X1, 1 km between X1 and X3, 1.4 km between X3 and X5, and 1 km between X5 and B, so the total is 4 km. On the other hand, the distance connecting point A and point B with a straight line is about 2.8 km. That is, it can be seen that simply connecting the acquired position information with a straight line is very different from the actual distance.

[0060] FIG. 9 is a schematic diagram for explaining distance estimation using the intersection specified by the second travel distance estimation process according to the present embodiment. The distance estimation unit 35 extracts Y1 and Y2 as the routes close to A, and extracts Y5 and Y6 as the routes close to B. Each of the routes Y1, Y2, Y5, Y6 includes route position information. The distance estimation unit 35 extracts the routes existing near points A and B from the comparison between the route position information of each of the routes Y1, Y2, Y5, Y6 and the position information of points A and B.

[0061] Next, the distance estimation unit 35 extracts the intersections connected to the routes Y1, Y2, Y5, Y6. Intersection X1 is connected to route Y1. Intersection X2 is connected to route Y2. Intersection X5 is connected to route Y5. Intersection X6 is connected to route Y6.

[0062] The route information storage unit 34 stores intersection position information as the route information of intersections X1, X2, X5, and X6. By comparing the position information of points A and B with the intersection position information of each intersection, the intersections with intersection position information close to points A and B can be identified. In the example of FIG. 9, intersections X1 and X6 are identified as the intersections close to points A and B. As a result, the distance estimation unit 35 calculates a total of 3.4 km as the estimated distance because, as the route including the identified intersections X1 and X6, the distance between A and X1 is 0.6 km, the distance between X1 and X6 is 2.1 km, and the distance between X6 and B is 0.7 km (S12).

[0063] The advantages of the second travel distance estimation process will be described. In the first travel distance estimation process, a plurality of candidate routes were identified using the route search function. However, when the distance between two points is short and there are many road intersections such as in urban areas, there is a possibility of extracting a route that would not normally be traveled as a candidate. This problem is also considered to be caused by errors in the acquired position information. As a method of solving such a problem, it is desirable to use another distance estimation method without using the first travel distance estimation process. By properly using the first travel distance estimation process and the second travel distance estimation process according to the area where the moving body 1 travels and the length of the acquired position information, the deviation from the actual travel distance can be reduced.

[0064] Also, as a third travel distance estimation process, it is conceivable to identify a frequently used route as the route between two points of the acquired position information and estimate the distance of the identified route as the distance between the two points. When the distance estimation unit 35 functions as the third distance estimation unit, the route information storage unit 34 may further store the route information in association with frequency information indicating the frequency of use of the route. The distance estimation unit 35 extracts the route information associated with the highest frequency information from the route information storage unit 34 based on the position information of the two points stored in the storage unit 33, and estimates the distance between the two points as the route information.

[0065] By combining the third travel distance estimation process with the first travel distance estimation process and the second travel distance estimation process and selectively using them according to conditions, the deviation from the actual travel distance can be reduced. That is, the control unit 32 may select any one of the estimated distance estimated by the distance estimation unit 35 using the first travel distance estimation process, the second estimated distance estimated by the second travel distance estimation process as the second distance estimation unit, and the third estimated distance estimated as the third distance estimation unit, and use it as the distance between two points.

[0066] A modification of the operation of the communication terminal device 11 according to the present invention will be described with reference to FIG. 10. FIG. 10 is a diagram showing an example of the position information transmission operation flow of the communication terminal device 11. The detection unit 116 of the communication terminal device 11 detects that the ACC power supply of the moving body 1 has been turned on (S21: Yes), and the terminal control unit 115 stores, in association with the position information acquired at the time of detection, movement start information indicating movement start as the behavior information of the moving body 1 in the memory 113. The communication unit 112 wirelessly transmits the position information including the movement start information as the behavior information as "on-time content" (S22). When the detection unit 116 detects that the ACC power supply of the moving body 1 has been turned off (S23: Yes), the terminal control unit 115 stores, in association with the position information acquired at the time of detection, movement end information indicating movement end as the behavior information of the moving body 1 in the memory 113. The communication unit 112 wirelessly transmits the position information including the movement end information as the behavior information as "off-time content" (S26).

[0067] When a predetermined time has elapsed and it is time for periodic timing (S24: Yes), the communication unit 112 selects a plurality of pieces of position information stored in the memory 113, generates "periodic content", and wirelessly transmits it to the server 3 (S25). The server 3 can calculate the estimated distance by determining that the position information from the position information including the movement start information to the position information including the movement end information is one travel route of the moving body 1.

[0068] The terminal control unit 115 may convert the position information expressed in longitude and latitude sequentially acquired by the position information acquisition unit 111 into information expressed in xy coordinates with a predetermined position as a reference position, and transmit it to the server 3. As described above, the data size of the position information expressed in longitude and latitude is 8 bytes. By converting the position information expressed in longitude and latitude into information expressed in plane rectangular coordinates, the data size can be compressed to 4 bytes.

[0069] As a method for converting the position information expressed in longitude and latitude into xy coordinates in a plane rectangular coordinate system, there are various known methods. In this modification example, as an example, the following formula

[0070] [Number] (1) [Number] (2) is used to convert the longitude λ to x and the latitude φ to y. z is 12. The values of the plane rectangular coordinates obtained by the above formulas (1) and (2) are further converted into offset coordinates with a certain area including the Japanese mainland shown in FIG. 11 as the range of the plane rectangular coordinate system.

[0071] The offset values in the certain area shown in FIG. 11 are 894000 for x and 371160 for y.

[0072] The position information of acquisition order 1 shown in FIG. 12 is information expressed in longitude and latitude, which is (34°40'50.5"N 135°10'35.7"E). When this position information is converted into plane rectangular coordinates using formulas (1) and (2), a value of (918018, 416472) is obtained. By subtracting the obtained plane rectangular coordinates by the offset values, offset coordinates of (24018, 45312) are obtained.

[0073] The maximum values of the x - coordinate and y - coordinate of the offset coordinates are 65535. That is, the x - coordinate and y - coordinate of the offset coordinates can be represented by 2 bytes (16 bits = 0 to 65535) respectively. That is, by converting the position information expressed in longitude and latitude into offset coordinates, the data length can be compressed to 4 bytes. Furthermore, when the offset coordinates are expressed as the differences from the coordinates of the starting position, the x - coordinate and y - coordinate of the offset coordinates can be represented by 1 byte (1 bit for + / -, 7 bits = 0 to 127) respectively. That is, they can be represented by a total of 2 bytes.

[0074] The position information in acquisition order 2 shown in FIG. 12 is (34°41'06.2"N 135°10'4 9.7"E). The offset coordinates obtained by converting the position information in acquisition order 2 using equations (1), (2) and the offset value are (24030, 45296). Taking the position in acquisition order 1 as starting position 1, and expressing the positions in acquisition orders 2, 3, and 4 acquired subsequently to acquisition order 1 as the differences from the offset coordinates of starting position 1, the position in acquisition order 2 is (12, - 16), the position in acquisition order 3 is (54, - 41), and the position in acquisition order 4 is (52, - 45).

[0075] Note that the position in acquisition order 3 may also be expressed as the difference from the position in acquisition order 2.

[0076] As shown in FIG. 13, the terminal control unit 115 generates sensor data (position information group) including a sequence number indicating the transmission order, behavior information, starting position information, and differences 1 to 3 as the payload of the upstream message. The sequence number is information indicating the transmission order, and the terminal control unit 115 assigns numbers from 0 to 64 to the sequence number in order, incrementing by 1 each time. When the terminal control unit 115 assigns 64 to the sequence number, it assigns 0 as the next sequence number.

[0077] As an example of the payload of the upstream message, as shown in FIG. 13, the terminal control unit 115 generates data in which sequence number 39 and behavior information indicating that the moving body 1 is in motion are added to the position information groups in the above acquisition order 1 to 4.

[0078] As shown in FIG. 14, the data structure of the upstream message is a 10-byte header, a maximum 12-byte payload, and a 4-byte footer. The payload is composed of sensor data which is a position information group including 2-byte data containing a sequence number and behavior information, 4-byte offset coordinates of the starting position which is the first position information, and three 2-byte differences between the first position and the second position, that is, the differences between the starting position and each subsequent position. The 10-byte header contains the identification information (4 bytes) of the communication terminal device 11. Further, the 4-byte footer contains HMAC (Hash-based Message Authentication Code) which is an authentication code and CRC (Cyclic Redundancy Check) which is an error detection code.

[0079] The terminal control unit 115 stores the position information sequentially acquired by the position information acquisition unit 111 in the memory 113 from when the detection unit 116 detects that the ACC power supply of the moving body 1 is turned on until it detects that the ACC power supply is turned off. However, when the difference information which is the difference from the reference position is 0 or smaller than a predetermined value, or when the differences are the same value, since the moving body 1 is staying at substantially the same position, duplicate position information will be transmitted to the server 3. Regarding such position information, the terminal control unit 115 does not include it in the position information group of the upstream message to be generated.

[0080] The communication terminal device 11 performs transmission control processing of the upstream message according to the operation flow shown in FIG. 15. The processes of S32 and S33 in the operation flow shown in FIG. 15 correspond to the process of S22 in the operation flow shown in FIG. 10, and the processes of S35 and S36 in the operation flow shown in FIG. 15 correspond to the process of S26 in the operation flow shown in FIG. 10.

[0081] When the detection unit 116 of the communication terminal device 11 detects that the ACC power supply of the mobile body 1 has been turned on (S31: Yes), the terminal control unit 115 causes the memory 113 to store the position information sequentially acquired by the position information acquisition unit 111 (S32).

[0082] Subsequently, the terminal control unit 115 generates an uplink message including a sequence number indicating the transmission order, movement start information indicating movement start as the behavior information of the mobile body 1 since the ACC power supply of the mobile body 1 is on, and a position information group specifying a plurality of positions based on the acquired position information, and stores the uplink message in the memory 113. The communication unit 112 wirelessly transmits the generated uplink message as "on-time content" (S33). Note that the uplink message including the movement start information may be transmitted immediately at the timing when the movement start is detected, or may be transmitted at the timing when the uplink message including the position information group is generated.

[0083] Following the process of S33, when the detection unit 116 detects that the ACC power supply of the mobile body 1 has been turned off (S34: Yes), the terminal control unit 115 stops the memory 113 from storing the position information sequentially acquired by the position information acquisition unit 111 (S35). Subsequently, the terminal control unit 115 generates an uplink message including a sequence number indicating the transmission order, movement end information indicating movement end as the behavior information of the mobile body 1 since the ACC power supply of the mobile body 1 is off, and a position information group specifying a plurality of positions based on the acquired position information, and stores the uplink message in the memory 113. The communication unit 112 wirelessly transmits the generated uplink message as "off-time content" (S36). After performing the process of S36, the terminal control unit 115 ends the operation.

[0084] In S34, when the detection unit 116 does not detect the turning-off of the ACC power supply (S34: No), and when it is time for the periodic timing of wirelessly transmitting the upstream message (S37: Yes), the terminal control unit 115 wirelessly transmits the upstream message generated based on the position information stored in the memory 113 to the server 3 (S38). After the process of S38, the terminal control unit 115 returns to the process of S34. In S37, when it is not the periodic timing (S37: No), the terminal control unit 115 returns to the process of S34.

[0085] The terminal control unit 115 of this modification example does not store in the memory 113 the position information sequentially acquired by the position information acquisition unit 111 during the period from detecting the turning-off of the ACC power supply of the moving body 1 to detecting the turning-on of the ACC power supply.

[0086] That is, since the position information acquired during the period from when the moving body 1 finishes moving to when it starts moving is not included in the upstream message transmitted to the server 3, the communication terminal device 11 can reduce the transmission of duplicate position information that is unnecessary for estimating the travel distance and occurs when the moving body 1 is in a stopped state.

[0087] The distance estimation unit 35 estimates the moving distance of the moving body 1 based on the upstream message received from the communication terminal device 11. The xy coordinates included in the upstream message can be converted into position information expressed in the original longitude and latitude. The distance estimation unit 35 estimates the distance between each position based on the converted position information.

[0088] As described above, the embodiments of the present invention have been described. However, the functional configurations and processes of the communication terminal device 11 and the server 3 described above are not limited to the above-described embodiments only.

[0089] For example, in the above-described embodiment, several events can be considered. For example, when the change in the position information sequentially acquired is small or 0, it is assumed that the moving body 1 is stopped. In this case, it is also possible to stop the wireless transmission of the position information and resume the wireless transmission when the difference information of the position information sequentially acquired becomes 0 or more.

[0090] The present invention can be embodied by modifying components without departing from the gist thereof in the implementation stage. Also, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments.

[0091] The present invention may, for example, appropriately combine all the components shown in the embodiments, or appropriately combine the additional components, or may be a communication terminal device constituting a travel distance estimation system, or may be an uplink message transmission method used for the communication terminal device, or a program for causing a computer to execute uplink message transmission processing.

[0092] Needless to say, various modifications and applications are possible within the scope not departing from the gist of the invention.

Industrial Applicability

[0093] The present invention can be applied to an information processing system that estimates a distance based on position information transmitted from a communication terminal device.

Explanation of Signs

[0094] 1 Mobile body 2 Base station group 3 Server 4 GNSS satellite group 11 Communication terminal device 31 Server communication unit 32 Control unit 33 Storage unit 34 Route information storage unit 35 Distance estimation unit 111 Position information acquisition unit 112 Communication unit 113 Memory 114 Behavior detection unit 115 Terminal control unit 116 Detection unit 117 Auxiliary battery

Claims

1. A travel distance estimation system including a communication terminal device mounted on a moving body and a server that receives position information of the moving body from the communication terminal device, The communication terminal device includes: A position information acquisition unit that sequentially acquires the position information; A communication unit that wirelessly transmits a plurality of the position information to the server in a lump. The server includes: A server communication unit that sequentially receives a plurality of the position information wirelessly transmitted by the communication unit; A control unit that records the position information in a storage unit in the order of sequential reception; A route information storage unit that stores, in association with each other, route information regarding a route and an intersection through which the moving body can pass, route position information indicating a position of the route, and intersection position information indicating a position of the intersection; Based on the position information of two consecutive points recorded in the storage unit, extracts, from the route information storage unit, the route information including the route position information close to the positions of the two points, and among the intersection position information stored in association with the extracted route information, identifies the intersection indicated by the intersection position information at a position close to the positions of the two points, and a distance estimation unit that sets a distance passing through the two points and the identified intersection as an estimated distance between the two points. A travel distance estimation system characterized by the above.

2. The route information storage unit further stores, in association with each other, the route information and weight information indicating a cost. The server further includes: Based on the position information of the two points, extracts a predetermined number of candidate routes that are candidates for the route with a lower cost from the route information storage unit, and a second distance estimation unit that sets an average distance of the extracted candidate routes as an estimated distance between the two points. The control unit selects either the estimated distance or the second estimated distance. The travel distance estimation system according to claim 1, characterized by the above.

3. The route information storage unit further stores the route information in association with frequency information indicating the usage frequency of the route. The server further is provided with a third distance estimation unit that specifies the route information with the highest usage frequency based on the position information of the two points, and sets the distance of the route indicated by the specified route information as a third estimated distance between the two points. The control unit selects either the estimated distance or the third estimated distance. The running distance estimation system according to claim 1, characterized in that.

4. The route information storage unit further stores the route information in association with frequency information indicating the usage frequency of the route. The server further is provided with a third distance estimation unit that specifies the route information with the highest usage frequency based on the position information of the two points recorded in the storage unit, and sets the distance of the route indicated by the specified route information as a third estimated distance between the two points. The control unit selects any one of the estimated distance, the second estimated distance, and the third estimated distance. The running distance estimation system according to claim 2, characterized in that.

5. The communication terminal device further includes a terminal control unit. The terminal control unit calculates difference information indicating the difference between the position information of the two points recorded in the storage unit, and does not wirelessly transmit the position information to the server when the calculated difference information is 0 or smaller than a predetermined value. The running distance estimation system according to any one of claims 1 to 4, characterized in that.

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