JP7497284B2 - Navigation device, navigation method, and computer program - Google Patents

Description

The present invention relates to a navigation device, a navigation method, and a computer program.

In recent years, navigation technologies have been developed for autonomously moving robots and self-driving vehicles traveling outdoors. For example, Patent Document 1 describes a navigation data generation system that acquires navigation data based on the navigation route and the node types of intermediate nodes (operations to be performed by the vehicle at the nodes) when automatically transporting an object.

JP 2019-537730 A

When remotely monitoring a robot or an autonomous vehicle moving autonomously outdoors via wireless communication, it is preferable for the robot to travel along a route that does not result in a disconnection of wireless communication. However, the conventional navigation technology described above is unable to perform route search that avoids disconnection of wireless communication. It is also preferable to perform an appropriate route search for cases where wireless communication does not disconnect or is disconnected.

The present invention was made in consideration of these circumstances, and its purpose is to achieve stable wireless communication when remotely monitoring a moving object via wireless communication, and to perform appropriate route search in cases where wireless communication is not interrupted or is interrupted.

(1) One aspect of the present invention is a navigation device that provides route information indicating a route from a departure point to a destination for a mobile body that is remotely monitored via a wireless communication line, and includes: a position wireless quality information storage unit that stores position wireless quality information in which a position is associated with a wireless communication quality at the position and recorded; a wireless disconnection probability calculation unit that calculates a wireless disconnection probability, which is the probability that wireless communication will be disconnected, for each position based on the position wireless quality information stored in the position wireless quality information storage unit; and a route search unit that calculates a total link cost for each of the route candidates so that the higher the wireless disconnection probability , the higher the ratio of the travel cost associated with reaching the destination that occurs when wireless communication is disconnected compared to the travel cost associated with reaching the destination when wireless communication is not disconnected, and searches for the route from among the route candidates based on the calculated total link cost.
(2) One aspect of the present invention is a navigation device as described above in (1), in which the route search unit reflects in the overall link cost an expected increase in travel time that would occur if wireless communication was interrupted, with respect to the travel time required to reach the destination.
(3) In one aspect of the present invention, the total link cost of a candidate route to be calculated is calculated by the following formula: Total link cost = "Probability of wireless communication not being disconnected on the candidate route to be calculated" x "Travel cost unrelated to wireless communication quality of the candidate route to be calculated" + "Probability of wireless communication disconnection on the candidate route to be calculated" x "(Travel cost of alternative candidate route) + (Travel cost incurred to return the moving body to the starting point of the candidate route to be calculated if wireless communication is disconnected while the moving body is moving on the candidate route to be calculated )", in a navigation device of either (1) or (2) above.
(4) One aspect of the present invention is a navigation device according to any one of (1) to (3) above, wherein the wireless disconnection probability calculation unit changes the wireless disconnection probability depending on the wireless frequency band used by the mobile body for wireless communication and the date and time when the mobile body moves.
(5) One aspect of the present invention is the navigation device of (4) above, wherein the wireless disconnection probability calculation unit changes the wireless disconnection probability according to the probability that the moving object will pass through each candidate route in each time period.
(6) One aspect of the present invention is a navigation device according to any of (1) to (5) above, wherein the location wireless quality information storage unit stores location wireless quality base station information in which base station identification information identifying a base station providing a wireless communication connection at each location is associated with the location wireless quality information and recorded, and the wireless disconnection probability calculation unit treats the wireless disconnection probability as a dependent event within the same base station area, but treats it as an independent event between different base station areas.
(7) One aspect of the present invention is the navigation device of any of (1) to (6) above, wherein the mobile object is a mobile object that performs delivery, and the route is a route along which the mobile object makes delivery.

(8) One aspect of the present invention is a navigation method for providing route information indicating a route from a departure point to a destination to a mobile object that is remotely monitored via a wireless communication line, the navigation method including: a position wireless quality information storing step of storing, in a position wireless quality information storage unit, position wireless quality information that is recorded in association with a position and a wireless communication quality at the position; a wireless disconnection probability calculating step of calculating, for each position, a wireless disconnection probability that is the probability that wireless communication will be disconnected, based on the position wireless quality information stored in the position wireless quality information storage unit; and a route searching step of calculating a total link cost for each of the route candidates so that the higher the wireless disconnection probability, the higher the ratio of the travel cost related to reaching the destination that occurs when wireless communication is disconnected compared to the travel cost related to reaching the destination in a case where wireless communication is not disconnected, and searching for the route from among the route candidates based on the calculated total link cost.

(9) One aspect of the present invention is a computer program for causing a computer of a navigation device that provides route information indicating a route from a departure point to a destination for a mobile object that is remotely monitored via a wireless communication line to execute the following steps: a position wireless quality information storage step of storing, in a position wireless quality information storage unit, position wireless quality information that is recorded in association with a position and a wireless communication quality at the position; a wireless disconnection probability calculation step of calculating, for each position, a wireless disconnection probability that is the probability that wireless communication will be disconnected, based on the position wireless quality information stored in the position wireless quality information storage unit; and a route search step of calculating a total link cost for each of the route candidates so that the higher the wireless disconnection probability , the higher the ratio of the travel cost related to reaching the destination that occurs when wireless communication is disconnected compared to the travel cost related to reaching the destination in a case where wireless communication is not disconnected, and searching for the route from among the route candidates based on the calculated total link cost.

The present invention provides the advantage of being able to realize stable wireless communication when remotely monitoring a moving object via wireless communication, as well as being able to perform appropriate route search when the wireless communication is not interrupted or is interrupted.

1 is a block diagram showing an example of the configuration of a navigation system according to an embodiment; 10 is a diagram illustrating an example of the configuration of a location/wireless quality/base station ID storage unit according to an embodiment; FIG. 11 is an explanatory diagram for explaining an example of a route search method. FIG. 2 is an explanatory diagram for explaining a route search method according to an embodiment; FIG. 1 is an explanatory diagram for explaining an example of a route search according to an embodiment; FIG. 1 is an explanatory diagram for explaining an example of a route search according to an embodiment; FIG. 1 is an explanatory diagram for explaining an example of a route search according to an embodiment; 10 is a flowchart showing a procedure for calculating a total link cost according to an embodiment; 1 is a flowchart showing an example of a procedure of a route search method according to an embodiment.

The following describes an embodiment of the present invention with reference to the drawings. In this embodiment, a navigation system in a delivery service system that uses autonomously moving robots (hereinafter referred to as mobile robots) to make deliveries is used as an example.

Fig. 1 is a block diagram showing an example of the configuration of a navigation system 10 according to an embodiment. In Fig. 1, a mobile robot 2 communicates with a navigation device 4 via a wireless communication line. The mobile robot 2 is an example of a moving body. The navigation device 4 provides the mobile robot 2 with route information indicating a route from a starting point to a destination.

The navigation device 4 according to this embodiment has a remote monitoring function in addition to a navigation function. Note that the remote monitoring function may be provided by a device other than the navigation device 4 that is external to the mobile robot 2.

The navigation device 4 uses a remote monitoring function to remotely monitor the mobile robot 2 via wireless communication. For example, the navigation device 4 receives images captured by the mobile robot 2 and sounds picked up by the mobile robot 2 via a wireless communication line, and displays or plays the received images and sounds. A monitor watches the images and sounds, thereby monitoring the movement status of the mobile robot 2 in real time. For this reason, the delivery service system according to this embodiment requires the mobile robot 2 to achieve stable wireless communication. Therefore, in this embodiment, the navigation device 4 provides route information for achieving stable wireless communication in the mobile robot 2.

In the unlikely event that wireless communication in the mobile robot 2 becomes unstable and communication with the navigation device 4 is cut off, the mobile robot 2 is designed to autonomously return to a location where communication with the navigation device 4 is restored. For this reason, the route taken by the mobile robot 2 to reach the destination may differ depending on whether wireless communication is not cut off or not. Therefore, in this embodiment, the navigation device 4 is designed to perform an appropriate route search for cases in which wireless communication in the mobile robot 2 is not cut off or is cut off.

The configuration of the navigation system 10 according to this embodiment will be described below with reference to FIG. 1.

[User terminal]
The user terminal 1 is a terminal used by a user of the delivery service system according to this embodiment (hereinafter referred to as a delivery service user). The delivery service user requests delivery by specifying a destination to which a package is to be delivered. The user terminal 1 may be a mobile communication terminal device such as a smartphone or a tablet computer (tablet PC), or may be a stationary communication terminal device (e.g., a stationary personal computer).

The user terminal 1 includes a product ordering unit 101 and a destination information input unit 102. The product ordering unit 101 selects a product and places an order for the selected product in response to operations performed by the delivery service user.

The product ordering unit 101 may manage the remaining quantity of goods owned by the delivery service user in real time, and automatically order replenishment goods when the remaining quantity of goods falls below a preset threshold.

The destination information input unit 102 inputs destination information indicating the destination, such as an address, when the product ordering unit 101 orders a product. The destination information may be specified by the delivery service user each time, or the destination information input unit 102 may record destination information previously specified by the delivery service user and automatically reuse the recorded destination information.

The destination information input unit 102 may use a positioning function of the GPS (Global Positioning System) provided in the user terminal 1 to set the current location acquired by the GPS as the destination. The destination information input unit 102 may also add an image of the scenery around the user terminal 1 captured by a camera of the user terminal 1 to the destination information as reference information for the destination.

[Mobile robot]
The mobile robot 2 is a robot capable of autonomous travel. The mobile robot 2 travels, for example, within a city and delivers packages to destinations designated by delivery service users.

The mobile robot 2 includes a current position acquisition unit 201, a wireless quality acquisition unit 202, a base station identification information (base station ID) acquisition unit 203, a status acquisition unit 204, a wireless communication unit 205, a route information storage unit 206, an imaging unit 207, an operation determination unit 208, and an operation control unit 209.

The current position acquisition unit 201 acquires the current position (position information) using a positioning system such as GPS. The wireless quality acquisition unit 202 acquires the wireless communication quality (wireless communication quality information) when the wireless communication unit 205 performs wireless communication with the navigation device 4 for each wireless communication method and wireless frequency band supported by the wireless communication unit 205.

The base station ID acquisition unit 203 acquires the base station ID of each base station with which the mobile robot 2 (wireless communication unit 205) can establish a wireless communication connection. The base station ID is identification information that individually identifies each base station. An example of a base station ID is what is called a CID (Cell ID). Note that by combining the MCC (Mobile Country Code), MNC (Mobile Network Code), LAC (Location Area Code), and CID (Cell ID), it is possible to uniquely identify the base station of each country and each telecommunications carrier.

The status acquisition unit 204 acquires status data (status information) such as the remaining battery level, temperature, and movement speed from various sensors equipped on the mobile robot 2.

The wireless communication unit 205 performs wireless communication with the navigation device 4. The wireless communication unit 205 supports wireless communication methods such as LTE (Long Term Evolution) and 5G (fifth generation mobile communication system), and performs wireless communication via a base station of the wireless communication method that it supports. The wireless communication unit 205 may also support an unlicensed wireless communication method such as Wi-Fi (registered trademark), and perform wireless communication using the unlicensed wireless communication method.

The wireless communication unit 205 transmits information obtained by the current position acquisition unit 201, wireless quality acquisition unit 202, base station ID acquisition unit 203, and status acquisition unit 204 to the operation monitoring unit 401 of the navigation device 4. The wireless communication unit 205 also receives route information transmitted from the route distribution unit 411 of the navigation device 4 and stores it in the route information storage unit 206. The route information stored in the route information storage unit 206 is used to determine the operation of the mobile robot 2.

The imaging unit 207 captures an image of the traveling direction of the mobile robot 2. The operation determination unit 208 determines the next operation of the mobile robot 2. When moving along a route indicated by the route information stored in the route information storage unit 206, the operation determination unit 208 determines an operation suited to the surrounding environment of the mobile robot 2 using the current position acquired by the current position acquisition unit 201, the captured image captured by the imaging unit 207, etc.

The motion control unit 209 causes the mobile robot 2 to execute the motion determined by the motion determination unit 208. The motion control unit 209 controls the type and speed of travel of the mobile robot 2, such as moving forward, backward, or turning right or left, as well as types of motion other than travel, such as changing the imaging direction of the imaging unit 207.

[Mobile devices]
The mobile terminal 3 is a mobile communication terminal device such as a smartphone or a tablet PC. The mobile terminal 3 may be used as the user terminal 1, or may be separate from the user terminal 1. For example, the mobile terminal 3 may be the mobile terminals of all subscribers who have subscribed to a specific wireless communication carrier and have agreed to obtain location information with the wireless communication carrier.

The mobile terminal 3 periodically reports to the navigation device 4 its current location (location information) and the wireless communication quality (wireless communication quality information) at the current location for each wireless communication method and wireless frequency band that it supports.

[Navigation device]
The navigation device 4 navigates one or more mobile robots 2 from a starting point to a destination. The navigation device 4 also monitors the operation of one or more mobile robots 2.

The navigation device 4 includes an operation monitoring unit 401, an operation information storage unit 402, a position/wireless quality/base station ID storage unit 403, a map information storage unit 404, a mobile terminal position information storage unit 405, an outdoor population density estimation unit 406, a wireless disconnection probability calculation unit 407, an order information storage unit 408, a destination acquisition unit 409, a route search unit 410, and a route distribution unit 411.

The functions of the navigation device 4 are realized by the navigation device 4 being equipped with computer hardware such as a CPU (Central Processing Unit) and memory, and the CPU executing a computer program stored in the memory. The navigation device 4 may be configured using a general-purpose computer device, or may be configured as a dedicated hardware device. For example, the navigation device 4 may be configured using a server computer connected to a communication network such as the Internet. The functions of the navigation device 4 may be realized by cloud computing. The navigation device 4 may be realized by a single computer, or may be realized by distributing the functions of the navigation device 4 among multiple computers. The navigation device 4 may also be configured to set up a website using, for example, a WWW system.

The operation monitoring unit 401 performs operation monitoring of one or more mobile robots 2. The operation monitoring unit 401 performs operation monitoring by associating position information, wireless communication quality information, and status information received in real time from the mobile robot 2 with information identifying the individual mobile robot 2 (mobile robot ID). The operation monitoring unit 401 performs operation monitoring based on information (position information, wireless communication quality information, and status information) that is updated periodically, for example, at one-second intervals. The operation monitoring unit 401 analyzes the position information, wireless communication quality information, and status information received from the mobile robot 2, and when a fault in the mobile robot 2 is detected, for example, an alarm is issued to a supervisor. The operation information storage unit 402 stores the information (position information, wireless communication quality information, and status information) received by the operation monitoring unit 401 from the mobile robot 2 in order to investigate the cause of the fault and to consider future countermeasures.

The location/wireless quality/base station ID storage unit 403 stores location/wireless quality/base station information in which location information, wireless communication quality information, and base station ID are associated and recorded for each wireless communication method and wireless frequency band.

The position information, wireless communication quality information, and base station ID recorded in the position wireless quality base station information are information transmitted from the mobile robot 2 or the portable terminal 3 to the navigation device 4. Note that position information, wireless communication quality information, and base station ID measured by a device other than the mobile robot 2 or the portable terminal 3 may also be recorded in the position wireless quality base station information.

The location information is, for example, GPS coordinates. For indoor facilities where GPS coordinates cannot be obtained, absolute location information obtained by indoor positioning technology such as IMES (Indoor MEssaging System) may be used as the location information. The wireless communication quality information is, for example, RSRP (Reference Signal Received Power) indicating the received power of LTE.

The location wireless quality base station information may be provided for each date, day of the week, time period, or event. For example, location wireless quality base station information for weekdays (Monday to Friday) and location wireless quality base station information for holidays (Saturday, Sunday, and public holidays) may be provided. For example, location wireless quality base station information for daytime hours and location wireless quality base station information for nighttime hours may be provided. For example, location wireless quality base station information for New Year's Day, Golden Week, and Obon may be provided.

Fig. 2 is a diagram showing an example of the configuration of the position/wireless quality/base station ID storage unit 403 according to this embodiment. In the example of Fig. 2, the position/wireless quality/base station ID storage unit 403 stores, for the wireless communication method "LTE", position/wireless quality/base station information 4031 of wireless frequency band _LTE_a and position/wireless quality/base station information 4032 of wireless frequency band _LTE_b. In addition, for the wireless communication method "5G", the position/wireless quality/base station ID storage unit 403 stores, for the wireless communication method "5G", position/wireless quality/base station information 4033 of wireless frequency band _5G_a and position/wireless quality/base station information 4034 of wireless frequency band _5G_b.

For example, LTE uses radio frequency bands such as Band 1 (2.1 GHz) and Band 18 (800 MHz). For 5G, the 28 GHz band is used.

For example, the position wireless quality base station information 4031 is information in which the wireless communication quality and the base station ID at each position _a, position _b, ... of the wireless frequency band _LTE_a of the wireless communication method "LTE" are associated and recorded. For example, the position wireless quality base station information 4033 is information in which the wireless communication quality and the base station ID at each position _a, position _b, ... of the wireless frequency band _5G_a of the wireless communication method "5G" are associated and recorded.

The position wireless quality base station information 4032 is information in which the wireless communication quality and the base station ID at each of positions _a, _b, ... in the wireless frequency band _LTE_b of the wireless communication system "LTE" are associated and recorded. Note that in the position wireless quality base station information 4032, the same base station ID _LTE_b_ab is associated and recorded with positions _a and _b. This is because, in the wireless frequency band _LTE_b of the wireless communication system "LTE", at the time when the wireless communication quality at positions _a and _b was measured, the base station with base station ID _LTE_b_ab was providing the wireless communication connection at positions _a and _b.

In the position wireless quality base station information, the base station ID is information that identifies the base station that provides a wireless communication connection at the position associated with the base station ID. Furthermore, in the position wireless quality base station information, the base station ID is information that identifies the base station that provided a wireless communication connection at the position associated with the base station ID at the time of measuring the wireless communication quality at that position.

In addition, in the position wireless quality base station information, the wireless communication quality and base station ID recorded in association with the position may be the base station ID of the base station from which the best wireless communication quality was obtained at the position. Furthermore, in the position wireless quality base station information, the wireless communication quality and base station ID recorded in association with the position may be the base station IDs of all base stations from which wireless communication quality was obtained at the position and their wireless communication qualities.

In this embodiment, the position/wireless quality/base station ID storage unit 403 stores position/wireless quality/base station information of an area including at least the service target area of this delivery service system. The service target area of this delivery service system is an area (target area) for which the navigation device 4 provides route information. The position/wireless quality/base station ID storage unit 403 according to this embodiment stores position/wireless quality/base station information in which a position included in the target area is associated with the wireless communication quality and base station ID at that position and recorded for each wireless communication method (LTE, 5G, etc.) and wireless frequency band (wireless frequency band LTE_a, wireless frequency band LTE_b, wireless frequency band 5G_a, wireless frequency band 5G_b, etc.) for which wireless communication services are provided in the target area for which the navigation device 4 provides route information.

The map information storage unit 404 stores nationwide road map data and associated facility data such as various facilities and shops. The road map data is provided as link data in which roads on a map are divided into multiple parts with intersections and the like as nodes, and the parts between each node are defined as links. This link data includes data such as a link-specific identifier (link ID), link length, position information (longitude, latitude) of the start and end points (nodes) of the link, angle (direction) data, road width, and road type. The road map data may also include lane information indicating lanes that the mobile robot 2 can travel. The map information storage unit 404 may also store indoor map data.

The mobile terminal location information storage unit 405 stores the history of location information for each mobile terminal 3. For example, it stores the GPS coordinates of each mobile terminal 3 in association with the time.

The outdoor population density estimation unit 406 determines whether each mobile terminal 3 was indoors or outdoors based on the history of location information stored in the mobile terminal location information storage unit 405, and estimates the outdoor population density for each pre-set area based on this determination result. The outdoor population density is the number of people per unit area outdoors. Information such as the outdoor population density calculated by the outdoor population density estimation unit 406 is stored in the map information storage unit 404 in association with the corresponding link data in the road map data of the map information storage unit 404.

For example, the outdoor population density estimation unit 406 determines that a mobile terminal 3 was indoors if the change in location information is less than a certain amount and is judged to have changed very little, and determines that the mobile terminal 3 was outdoors if the change in the location information is greater than a certain amount and is judged to have changed to some extent.

The outdoor population density estimation unit 406 may also perform map matching by comparing the location information of each mobile terminal 3 with road map data stored in the map information storage unit 404, and estimate that the mobile terminal 3 was using a road. Map matching is a process in which location information obtained by GPS, which may contain errors, is corrected using map information to place the location on a road. Map matching is used, for example, in car navigation systems.

The outdoor population density estimation unit 406 may also determine whether the means of transportation of the mobile terminal 3 is walking or a vehicle based on the movement speed of the mobile terminal 3.

The outdoor population density estimation unit 406 may estimate the outdoor population density for each month, day of the week, and time period. This is because the outdoor population density may vary significantly depending on the month, day of the week, time period, etc., even in the same area.

The outdoor population density estimation unit 406 may also estimate the outdoor population density using a method other than the method using the location information of the mobile terminal 3. For example, the outdoor population density estimation unit 406 may use video captured by the mobile robot 2 and estimate the outdoor population density based on the results of image recognition of people in the captured video.

The wireless disconnection probability calculation unit 407 calculates the wireless disconnection probability on each road. The wireless disconnection probability is the probability that wireless communication will be disconnected. The wireless disconnection probability calculation unit 407 calculates the wireless disconnection probability for each location based on the location wireless quality information stored in the location/wireless quality/base station ID storage unit 403. The location wireless quality information is information recorded from the location wireless quality base station information in which a location is associated with the wireless communication quality at that location.

The wireless disconnection probability calculation unit 407 may change the wireless disconnection probability according to the wireless frequency band used by the mobile robot 2 for wireless communication and the date and time when the mobile robot 2 moves. Specifically, the wireless disconnection probability calculation unit 407 changes the wireless disconnection probability based on the position wireless quality information of each wireless frequency band stored in the position/wireless quality/base station ID storage unit 403 and the outdoor population density for each month, day of the week, and time period estimated by the outdoor population density estimation unit 406.

For example, in a high frequency band with strong linearity such as the 28 GHz band used in the wireless communication system "5G", the vehicle congestion situation may have a large effect on radio wave propagation. On the other hand, in a low frequency band such as the 800 MHz band used in the wireless communication system "LTE", the vehicle congestion situation is considered to have little effect on radio wave propagation. Therefore, when the mobile robot 2 uses a high frequency band for wireless communication, the wireless disconnection probability calculation unit 407 changes the wireless disconnection probability based on the vehicle congestion situation for each month, day of the week, and time period determined from the outdoor population density for each month, day of the week, and time period. For example, when the vehicle congestion situation is at a certain level or higher, the wireless disconnection probability calculation unit 407 increases the wireless disconnection probability by a certain amount. On the other hand, when the mobile robot 2 uses a low frequency band for wireless communication, the wireless disconnection probability calculation unit 407 does not reflect the vehicle congestion situation in the wireless disconnection probability.

The wireless disconnection probability calculation unit 407 may also change the wireless disconnection probability according to the probability that the mobile robot 2 passes each road in each time period. The time period when the mobile robot 2 passes each road can be predicted by estimating the travel time from the route search results by the route search unit 410 described later. However, the time period when the mobile robot 2 actually passes each road may shift forward or backward, and depending on this shift, for example, it may change whether the time period when the mobile robot 2 passes a certain road is a time period when it is congested with vehicles. For this reason, the wireless disconnection probability calculation unit 407 calculates the probability that the mobile robot 2 passes each road in each time period from the record of the mobile robot 2's past movement results, changes the vehicular congestion state on each road in accordance with this probability, and changes the wireless disconnection probability according to the vehicular congestion state after this change.

The order information storage unit 408 receives order information for ordering products from the user terminal 1 and stores the received order information. The order information storage unit 408 works in conjunction with a purchasing system (not shown) to carry out purchasing processing and formulate a product delivery plan. The order information storage unit 408 stores scheduled delivery information such as the departure point, destination, and time period for the mobile robot 2 to deliver the products according to the formulated product delivery plan. The destination acquisition unit 409 acquires destination information from the order information or scheduled delivery information stored in the order information storage unit 408.

The route search unit 410 searches for a route from the starting point of the mobile robot 2 to the destination as the planned route along which the mobile robot 2 is to travel. The destination of the mobile robot 2 is a location indicated by the destination information acquired by the destination acquisition unit 409. The starting point of the mobile robot 2 is set in advance. For example, a product distribution base (e.g., a logistics warehouse where the products are stored or a distribution store nearest to the destination) is set in advance as the starting point of the mobile robot 2. In addition, when the mobile robot 2 is transported to the vicinity of the destination by a vehicle, the location of the transport destination of the mobile robot 2 is set in advance as the starting point of the mobile robot 2.

The route search unit 410 calculates a total link cost for each candidate route based on the wireless disconnection probability calculated by the wireless disconnection probability calculation unit 407, the travel cost for reaching the destination when wireless communication is not disconnected, and the travel cost for reaching the destination that occurs when wireless communication is disconnected. The route search unit 410 searches for a route from among the candidate routes based on the calculated total link cost.

The route search unit 410 sequentially calculates (accumulates) the cost of the roads (links) from the starting point to the destination to the next reachable intersection (node), and selects the route from the starting point to the destination with the smallest cost. Therefore, if a small total link cost value is set for a road, that road is more likely to be selected as a route. The route search unit 410 can use, for example, Dijkstra's algorithm, A* algorithm, genetic algorithm, etc. as a route search method.

The route distribution unit 411 transmits route information indicating the route searched by the route search unit 410 to the mobile robot 2.

(Calculation method for total link cost)
A method of calculating the total link cost by the route search unit 410 will be described. If wireless communication is cut off while the mobile robot 2 is moving, remote monitoring becomes impossible, so the mobile robot 2 returns to a point where wireless communication is restored and movement can be resumed, searches for an alternative route where wireless communication can be continued, and moves along the discovered alternative route. Therefore, when wireless communication is cut off, there is a possibility that the travel time required to reach the destination will increase due to the return of the route and movement to the destination via the alternative route. Therefore, in this embodiment, the route search unit 410 reflects in the total link cost the expected amount of increase in travel time (expected amount of increase in travel time) that occurs when wireless communication is cut off, with respect to the travel time required to reach the destination. In this way, an efficient route that takes into account the reduction in the total travel time is searched for.

The route search unit 410 calculates the total link cost for each road (link) of the route candidate, for example, using the following formula (1).

Total link cost of the link being calculated = "Probability of wireless communication not being disconnected on the link being calculated" x "Movement cost not related to wireless communication quality on the link being calculated" + "Probability of wireless communication being disconnected on the link being calculated" x "(Movement cost of alternative link) + (Movement cost related to moving to the alternative link)" ... (1)

In the above formula (1), the "probability that wireless communication will not be disconnected on the calculation target link" and the "probability of wireless communication disconnection on the calculation target link" are values that sum to 1 (100%). The "travel cost unrelated to the wireless communication quality of the calculation target link" is the travel cost unrelated to the wireless communication quality, such as the distance required for the calculation target link or the time required for travel. The "travel cost of the alternative link" is the travel cost when using a link (alternative link) that is used to reach the destination instead of the calculation target link when wireless communication is disconnected. The "travel cost related to travel to the alternative link" is the travel cost incurred to return to the starting point of the calculation target link when wireless communication is disconnected.

Next, an example of a route search according to this embodiment will be described.
FIG. 3 is an explanatory diagram for explaining an example of a route search method. FIG. 4 is an explanatory diagram for explaining a route search method according to this embodiment. In FIG. 3 and FIG. 4, circles indicate nodes, and lines connecting nodes indicate links. The starting node is S, and the destination node is G. Numbers written on links indicate link costs. FIG. 3 shows link costs when wireless communication quality is not taken into consideration. On the other hand, FIG. 4 shows total link costs according to this embodiment when wireless communication quality is taken into consideration. Here, it is assumed that the link between node b and node d has poor wireless communication quality and is highly likely to be disconnected from wireless communication.

In the case of the link costs in FIG. 3, as a result of the route search, "S → b → d → G" is selected as the route from the starting point "node S" to the destination "node G", as this is the route with the smallest total link cost. Since the link costs in FIG. 3 do not take into account the quality of wireless communication, the link "b → d", which has a high possibility of wireless communication being disconnected, is selected as the route. As a result, if wireless communication between the mobile robot 2 and the navigation device 4 is disconnected on the selected route, there is a possibility that the mobile robot 2 will not be able to be remotely monitored.

On the other hand, in FIG. 4, the wireless disconnection probability calculation unit 407 calculates a wireless disconnection probability of 0.80 (80%) for the link "b → d". The total link cost of the link "b → d" is calculated as follows using the above formula (1):

Total link cost of link "b → d" = "Probability of wireless communication not being disconnected on link "b → d" (1 - 0.80)" x "Movement cost not related to wireless communication quality on link "b → d" (4)" + "Probability of wireless communication being disconnected on link "b → d" (0.80)" x "(Movement cost of alternative link (10)) + (Movement cost related to moving to alternative link (5))" = 12.8

In calculating the total link cost of this link "b → d", the "alternative link travel cost" is "10", which is the travel cost of "b → c → d" from node b via the alternative route to arrive at node d in the shortest time. In addition, the "travel cost related to travel to the alternative link" is set to "5", which is the expected average travel time required to return to the starting point of node b if wireless communication is interrupted while traveling on link "b → d".

According to the total link cost in FIG. 4, link "b → d" which has a high possibility of wireless communication being disconnected is not selected as a route. Then, in the case of the total link cost in FIG. 4, as a result of the route search, "S → a → G" is selected as the route from the starting point "node S" to the destination "node G", which is the route with the smallest total link cost. This selected route "S → a → G" makes it possible to realize stable wireless communication in the mobile robot 2. This allows the mobile robot 2 to be stably monitored remotely via wireless communication.

In the above Figure 4, the wireless disconnection probability is set only for link "b → d", but in reality, the wireless disconnection probability can be set for multiple links. Below, Figures 5, 6, and 7 are given as examples of route search when the wireless disconnection probability is set for multiple links.

In Figures 5, 6, and 7, the wireless disconnection probability calculation unit 407 calculates a wireless disconnection probability of "0.8 (80%)" for the link "b → d", and the wireless disconnection probability calculation unit 407 calculates a wireless disconnection probability of "0.65 (65%)" for the link "c → d".

When the mobile robot 2 moves to the destination, there is a possibility that it will hand over to multiple base stations installed in different locations. Here, since the installation locations of each base station are different, it is considered that the wireless disconnection probability of a certain link affects the wireless disconnection probability of other links within the same base station area, but does not affect links within another base station area. For this reason, it is preferable to treat the wireless disconnection probability as a dependent event within the same base station area, but as an independent event between different base station areas. In this embodiment, the wireless disconnection probability calculation unit 407 treats the wireless disconnection probability as a dependent event within the same base station area, but as an independent event between different base station areas.

In Figure 5, the base station ID corresponding to link "b → d" is "aaa", and the base station ID corresponding to link "c → d" is "bbb", and each is a separate base station area, and the probability of wireless disconnection is treated as an independent event. Then, the total link cost of link "b → d" is calculated as follows using formula (1) above.

Total link cost of link "b → d" = "Probability of wireless communication not being disconnected on link "b → d" (1 - 0.80)" x "Movement cost not related to wireless communication quality on link "b → d" (4)" + "Probability of wireless communication being disconnected on link "b → d" (0.80)" x "(Movement cost of alternative link (11 x 0.65 + 10 x 0.35))) + (Movement cost related to moving to alternative link (5))" = 13.32

In Figure 4 above, the travel cost of the alternative link was the travel cost of "b → c → d" which was "10". On the other hand, in Figure 5, the travel cost of "b → a → G" which is "11" occurs with a probability of "0.65" and the travel cost of "10" which is "b → c → d" occurs with a probability of "0.35 (1-0.65)", so the travel cost of the alternative link is "11 x 0.65 + 10 x 0.35". This is because when wireless communication is cut off at link "b → d", if wireless communication is also cut off at link "c → d", the alternative route "b → c → d (travel cost "10")" cannot be used, and the alternative route "b → a → G (travel cost "11")" is used. Also, the wireless disconnection probability of link "b → d" which is "0.80" and the wireless disconnection probability of link "c → d" which is "0.65" are treated as independent events.

In Figure 5, since the goal point (G) is included in the alternative route for link "b → d", the travel cost for "b → a → G" is used instead of the travel cost for "b → a → G → d".

The total link cost of link "c → d" is calculated as follows using formula (1) above:

Total link cost of link "c → d" = "Probability of wireless communication not being disconnected on link "c → d" (1 - 0.65)" x "Movement cost not related to wireless communication quality on link "c → d" (7)" + "Probability of wireless communication being disconnected on link "c → d" (0.65)" x "(Movement cost of alternative link (14 x 0.8 + 7 x 0.2))) + (Movement cost related to moving to alternative link (8))" = 15.84

Next, in Figure 6, the base station IDs corresponding to link "b→d" and link "c→d" are both "aaa", and both are in the same base station area, so the probability of wireless disconnection is treated as a dependent event. Then, the total link cost of link "b→d" is calculated as follows using formula (1) above.

Total link cost of link "b → d" = "Probability of wireless communication not being disconnected on link "b → d" (1-0.80)" x "Movement cost not related to wireless communication quality on link "b → d" (4)" + "Probability of wireless communication being disconnected on link "b → d" (0.80)" x "(Movement cost of alternative link (11 x (1-(0.8-0.65))) + 10 x (0.8-0.65))) + (Movement cost related to moving to alternative link (5))" = 13.48

In calculating the total link cost of link "b → d", the probability of wireless disconnection of link "b → d" being "0.8" and the probability of wireless disconnection of link "c → d" being "0.65" are considered to be dependent events, and if wireless communication is disconnected on link "b → d" with a wireless disconnection probability of "0.8", then wireless communication will be disconnected on link "c → d" with a probability of "0.85 = 1 - (0.8 - 0.65)".

The total link cost of link "c → d" is calculated using formula (1) above as follows:

Total link cost of link "c → d" = "Probability of wireless communication not being disconnected on link "c → d" (1 - 0.65)" x "Movement cost not related to wireless communication quality on link "c → d" (7)" + "Probability of wireless communication being disconnected on link "c → d" (0.65)" x "(Movement cost of alternative link (14) + (Movement cost related to moving to alternative link (8))" = 16.75

In the calculation of the total link cost of link "c → d", if wireless communication is disconnected on link "c → d", there is a 100% probability that wireless communication will be disconnected on link "b → d", which has a higher probability of wireless communication being disconnected than link "c → d". If the probability of wireless communication being disconnected within the same base station area is treated as a dependent event in this way, when searching for an alternative route, other routes within the same base station area will have a higher probability of wireless communication being disconnected than in the case of independent events, making it more difficult for these other routes to be selected as alternative routes.

Next, in FIG. 7, the base station ID corresponding to link "b→d" is "aaa", the base station IDs corresponding to link "c→d" are "aaa" and "bbb", and link "c→d" is within the connection range of multiple base stations. In this case, in link "c→d", even if wireless communication with base station "aaa" is cut off, the mobile robot 2 can continue wireless communication by performing a handover to base station "bbb". Therefore, in FIG. 7, as in FIG. 5, the probability of wireless communication being cut off is treated as an independent event for link "b→d" and link "c→d". As a result, the total link costs of link "b→d" and link "c→d" are the same as those in FIG. 5.

Next, the procedure for calculating the total link cost will be described with reference to FIG. 8. FIG. 8 is a flowchart showing the procedure for calculating the total link cost according to this embodiment. Here, natural numbers starting from 1 are set as identifiers (link IDs) for each link.

(Step S101) The route search unit 410 sets a travel cost that is not related to wireless communication quality for each link. The travel cost that is not related to wireless communication quality is, for example, the required distance of the link or the time required for travel.

(Step S102) The route search unit 410 executes the following loop process for all link IDs in sequence, starting with the initial link ID value "1".

(Step S103) The route search unit 410 determines whether the wireless disconnection probability of the link of the calculation target link ID is other than 0. If the wireless disconnection probability is other than 0, the process proceeds to step S104. On the other hand, if the wireless disconnection probability is 0, the process proceeds to step S105.

(Step S104) The route search unit 410 calculates the total link cost of the link with the calculation target link ID using the above formula (1).

If the wireless disconnection probability is 0, step S104 is not executed, and the total link cost of the link with the link ID to be calculated is the travel cost set in step S101, which is not related to the wireless communication quality.

(Step S105) The route search unit 410 increments the calculation target link ID by 1.

(Step S106) When the route search unit 410 has completed loop processing for all link IDs, it ends the processing in FIG. 8.

Next, the route search method according to this embodiment will be described with reference to FIG. 9. FIG. 9 is a flowchart showing an example of the procedure of the route search method according to this embodiment.

(Step S1) The route search unit 410 acquires the starting point from which the mobile robot 2 starts traveling and the destination to which the mobile robot 2 will travel.

(Step S2) The route search unit 410 acquires the type of mobile robot 2 and the details of the delivery. The type of mobile robot 2 is classified according to the size, structure, etc. of the mobile robot 2. The type of mobile robot 2 is also classified according to the wireless communication method and wireless frequency band that the mobile robot 2 can use. The details of the delivery by the mobile robot 2 are, for example, the type of cargo delivered by the mobile robot 2 and the expected load amount.

The size and structure of the mobile robot 2, and the type and expected load of the cargo delivered by the mobile robot 2 are used for the travel cost unrelated to the wireless communication quality. For example, a small mobile robot 2 can travel safely on a link of a road with a width less than a threshold, so the travel cost unrelated to the wireless communication quality is not increased, but the travel cost is increased for a large mobile robot 2. Also, depending on the structure of the mobile robot 2, it may be difficult to overcome steps in the road, so for the relevant type of mobile robot 2, the travel cost is increased for links of roads with steps. Also, if the type of cargo delivered by the mobile robot 2 is fragile, it is preferable for the robot 2 to travel on roads with few bumps, so the travel cost for links of roads with few bumps is reduced, while the travel cost for links of roads with many bumps is increased.

(Step S3) The route search unit 410 recognizes the wireless communication method and wireless frequency band that can be used by the mobile robot 2 from the type of the mobile robot 2 acquired in step S2. The correspondence between the type of the mobile robot 2 and the available wireless communication method and wireless frequency band is set in advance in the navigation device 4.

(Step S4) The route search unit 410 acquires the wireless disconnection probability of each link of each road included in the search range including the starting point and destination of the mobile robot 2 acquired in step S1 from the wireless disconnection probability calculation unit 407. Next, the route search unit 410 calculates the total link cost for each link of each road included in the search range.

In addition, when there are multiple wireless communication methods and wireless frequency bands available for the mobile robot 2, the route search unit 410 may calculate the overall link cost for each link of each road for the wireless communication method and wireless frequency band that provides the best wireless communication quality.

(Step S5) The route search unit 410 searches for a route from the starting point to the destination of the mobile robot 2 acquired in step S1 based on the total link cost calculated in step S4. In this route search, a route is searched for that minimizes the sum of the total link costs of each link traversed from the starting point to the destination.

(Step S6) The route distribution unit 411 transmits route information indicating the route searched for in step S5 to the mobile robot 2.

According to the above-described embodiment, it is possible to provide route information for realizing stable wireless communication in the mobile robot 2. In addition, it is possible to perform appropriate route search for cases in which wireless communication in the mobile robot 2 is not disconnected or is disconnected. In addition, by reflecting the expected increase in travel time in the total link cost, it is possible to search for an efficient route that takes into account the reduction of the total travel time.

The above describes an embodiment of the present invention in detail with reference to the drawings, but the specific configuration is not limited to this embodiment and includes design modifications within the scope of the present invention.

In the above-described embodiment, the navigation system is applied to a delivery service system, but it may also be applied to systems other than delivery service systems. For example, the navigation system according to the above-described embodiment may be applied to a road inspection service system that inspects roads using a mobile robot.

In the above-described embodiment, a mobile robot is given as an example of a mobile body, but the present invention is not limited to this. A vehicle that performs automatic driving (automatic driving vehicle), an air vehicle that flies autonomously, etc. may also be used as a mobile body.

In addition, a computer program for implementing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the term "computer system" may include hardware such as an OS and peripheral devices.
In addition, the term "computer-readable recording medium" refers to a storage device such as a flexible disk, a magneto-optical disk, a ROM, a writable non-volatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disc), or a hard disk built into a computer system.

Furthermore, the term "computer-readable recording medium" includes devices that retain a program for a certain period of time, such as volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that serves as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line.
The program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by a transmission wave in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be a program for implementing some of the above-mentioned functions, or may be a so-called differential file (differential program) that can implement the above-mentioned functions in combination with a program already recorded in the computer system.

1...user terminal, 2...mobile robot, 3...portable terminal, 4...navigation device, 10...navigation system, 401...operation monitoring unit, 402...operation information storage unit, 403...position/wireless quality/base station ID storage unit, 404...map information storage unit, 405...portable terminal position information storage unit, 406...outdoor population density estimation unit, 407...wireless disconnection probability calculation unit, 408...order information storage unit, 409...destination acquisition unit, 410...route search unit, 411...route distribution unit

Claims (9)

A navigation device that provides route information indicating a route from a departure point to a destination to a mobile object that is remotely monitored via a wireless communication line,
a position/wireless quality information storage unit that stores position/wireless quality information in which a position and a wireless communication quality at the position are associated with each other and recorded;
a wireless disconnection probability calculation unit that calculates a wireless disconnection probability, which is a probability that wireless communication will be disconnected, for each position based on the position wireless quality information stored in the position wireless quality information storage unit;
a route search unit that calculates a total link cost for each of the route candidates and searches for the route from among the route candidates based on the calculated total link cost so that the higher the probability of wireless disconnection, the higher the ratio of a travel cost to reach the destination that occurs when wireless communication is disconnected compared to a travel cost to reach the destination when wireless communication is not disconnected;
A navigation device comprising: The route search unit reflects an expected increase in travel time that occurs when wireless communication is disconnected, with respect to the travel time required to reach the destination, in the overall link cost.
2. The navigation device of claim 1. The total link cost of the route candidate is calculated by the following formula:
Total link cost = "Probability of wireless communication not being disconnected on the calculation target route candidate" x "Travel cost not related to wireless communication quality of the calculation target route candidate" + "Wireless disconnection probability of the calculation target route candidate" x "(Travel cost of alternative route candidate) + (Travel cost incurred when the mobile body returns to the starting point of the calculation target route candidate when wireless communication is disconnected while the mobile body is moving on the calculation target route candidate )"
3. A navigation device according to claim 1 or 2. the wireless disconnection probability calculation unit changes the wireless disconnection probability depending on a wireless frequency band used by the mobile object for wireless communication and a date and time when the mobile object moves;
A navigation device according to any one of claims 1 to 3. the wireless disconnection probability calculation unit changes the wireless disconnection probability in accordance with a probability that the moving object passes through each route candidate in each time period;
5. A navigation device according to claim 4. the position/wireless quality information storage unit stores position/wireless quality base station information in which base station identification information for identifying a base station providing a wireless communication connection at each position is recorded in association with the position/wireless quality information;
the wireless disconnection probability calculation unit treats the wireless disconnection probability as a dependent event within the same base station area, and treats it as an independent event between different base station areas;
A navigation device according to any one of claims 1 to 5. The mobile object is a mobile object that performs delivery,
The route is a route along which the mobile unit delivers the information.
A navigation device according to any one of claims 1 to 6. A navigation method for providing route information indicating a route from a departure point to a destination to a mobile object, the route information indicating a route from a departure point to a destination, the method comprising:
a position/wireless quality information storage step of storing, in a position/wireless quality information storage unit, position/wireless quality information in which a position and a wireless communication quality at the position are associated with each other and recorded;
a wireless disconnection probability calculation step of calculating a wireless disconnection probability, which is a probability that wireless communication will be disconnected, for each position based on the position wireless quality information stored in the position wireless quality information storage unit;
a route searching step of calculating a total link cost for each of the route candidates, and searching for the route from among the route candidates based on the calculated total link cost, so that the higher the probability of wireless disconnection, the higher the ratio of the travel cost to reach the destination that occurs when wireless communication is disconnected to the travel cost to reach the destination when wireless communication is not disconnected becomes;
A navigation method including: A computer of a navigation device that provides route information indicating a route from a departure point to a destination to a mobile object that is remotely monitored via a wireless communication line,
a position/wireless quality information storage step of storing, in a position/wireless quality information storage unit, position/wireless quality information in which a position and a wireless communication quality at the position are associated with each other and recorded;
a wireless disconnection probability calculation step of calculating a wireless disconnection probability, which is a probability that wireless communication will be disconnected, for each position based on the position wireless quality information stored in the position wireless quality information storage unit;
a route search step of calculating a total link cost for each of the route candidates, and searching for the route from among the route candidates based on the calculated total link cost, so that the higher the probability of wireless disconnection, the higher the ratio of the travel cost to reach the destination that occurs when wireless communication is disconnected compared to the travel cost to reach the destination when wireless communication is not disconnected;
A computer program for executing the above.

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