Driving assist system

Abstract

To provide a driving assist system that, when travel through autonomous driving assist cannot be taken over to manual driving by a user's driving maneuver, enables the takeover without imposing a load on the user.SOLUTION: When a vehicle is traveling through autonomous driving assist, a takeover point where travel through autonomous driving assist is taken over to travel through manual driving is designated. If travel through autonomous driving assist cannot be taken over to travel through manual driving at the takeover point, a halt position around the takeover point where the vehicle can be tentatively halted is searched. A loop route along which the vehicle returns to the takeover point with the takeover point as a start point is also searched. Either moving to the halt position or traveling along the loop route is selected as a future movement of the vehicle. Travel through autonomous driving assist is continued according to the selected movement of the vehicle.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a driving assistance device that assists a vehicle in traveling by automatic driving assistance. [Background technology]

[0002] In recent years, in addition to manual driving, in which a vehicle is driven based on a user's driving operation, new automated driving assistance systems have been proposed that assist a user in driving a vehicle by having the vehicle perform some or all of the user's driving operations.The automated driving assistance system, for example, constantly detects the current position of the vehicle, the lane in which the vehicle is traveling, and the positions of other vehicles in the vicinity, and automatically controls the vehicle, including steering, drive sources, and braking, so that the vehicle travels along a predetermined route.

[0003] While autonomous driving assistance has the advantage of reducing the burden on the user, situations may arise in which the user needs to drive manually. For example, when the destination is a location on a road where the vehicle cannot be parked and it is determined that the vehicle has arrived at the destination, or when the vehicle enters a road where autonomous driving assistance is difficult, such as a narrow street. In such situations, it is necessary to switch from autonomous driving assistance to manual driving as quickly as possible. However, this may not be possible due to reasons such as the user not being ready to drive. For example, Japanese Patent Application Laid-Open No. 2008-290680 proposes a technology that sets a handover point where autonomous driving assistance will be switched to manual driving, and guides the vehicle to an evacuation area if the handover from autonomous driving assistance to manual driving cannot be completed at the handover point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-290680 A (paragraphs 0024-0038) Summary of the Invention [Problem to be solved by the invention]

[0005] Here, the technology described in Patent Document 1 moves the vehicle to an evacuation area if it is not possible to hand over to manual driving, but such an evacuation area is not necessarily nearby, and moving to the evacuation area could result in the vehicle moving far away from its original destination or planned route.

[0006] The present invention has been made to solve the above-mentioned problems in the past, and aims to provide a driving assistance device that, when it is not possible to switch from driving with automatic driving assistance to manual driving under user driving operation, makes it possible to select either moving to a stopping location or driving on a loop route as the next action, and enables subsequent handover without placing a burden on the user. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the driving assistance device of the present invention has a handover point setting means for setting a handover point where handover from automatic driving assistance to manual driving occurs while the vehicle is traveling with automatic driving assistance; a handover determination means for determining whether handover from automatic driving assistance to manual driving can be performed at the handover point; a stopping position search means for searching for a stopping position around the handover point where the vehicle can be temporarily stopped if it is determined by the handover determination means that handover cannot be performed; a loop route search means for searching for a loop route that is a route starting from the handover point and returning to the handover point if it is determined by the handover determination means that handover cannot be performed; an action selection means for selecting whether the vehicle's future action will be to move to the stopping position or to travel along the loop route; and a driving control means for continuing driving with automatic driving assistance in accordance with the vehicle's action selected by the action selection means. [Effects of the Invention]

[0008] According to the driving assistance device of the present invention having the above configuration, when it is not possible to switch over from driving with automated driving assistance to manual driving by the user, it becomes possible to select a future action from either moving to a stopping location or driving along a loop route. As a result, it is possible to select a future action that is more appropriate for the vehicle's situation, and it is also possible to allow the user to take over the driving control thereafter without placing a burden on the user. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing the configuration of a navigation device according to an embodiment of the present invention. [Figure 2] 4 is a flowchart of an autonomous driving assistance program according to the present embodiment. [Figure 3] FIG. 10 is a diagram illustrating a method for calculating a first cost. [Figure 4] FIG. 10 is a diagram illustrating a method for calculating a second cost. [Figure 5] FIG. 10 is a diagram illustrating a method for searching for a loop route. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment in which a driving assistance device according to the present invention is embodied in a navigation device 1 will be described in detail with reference to the drawings. First, a schematic configuration of the navigation device 1 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the navigation device 1 according to this embodiment.

[0011] As shown in FIG. 1 , the navigation device 1 according to this embodiment includes a current position detection unit 11 that detects the current position of the vehicle in which the navigation device 1 is installed, a data recording unit 12 that records various data, a navigation ECU 13 that performs various calculations based on input information, an operation unit 14 that accepts user operations, a liquid crystal display 15 that displays to the user a map of the area around the vehicle and information about the guide route (the planned route of the vehicle) set in the navigation device 1, a speaker 16 that outputs audio guidance regarding the route guide, a DVD drive 17 that reads a DVD as a storage medium, and a communication module 18 that communicates with an information center such as a probe center or a VICS (Vehicle Information and Communication System) center. The navigation device 1 is also connected to an external camera 19 and various sensors installed in the vehicle in which the navigation device 1 is installed via an in-vehicle network such as a CAN. The navigation device 1 is also connected to a vehicle control ECU 20 that performs various controls for the vehicle in which the navigation device 1 is installed, allowing bidirectional communication. Various operation buttons 21 installed in the vehicle, such as an automatic driving start button, are also connected.

[0012] Here, a vehicle equipped with the navigation device 1 is a vehicle capable of manual driving, in which the vehicle travels based on the user's driving operations, as well as assisted driving using automatic driving assistance, in which the vehicle travels automatically along a pre-set route or road without the user's driving operations.

[0013] Furthermore, autonomous driving assistance may be provided for all road sections, or may be configured to be provided only while the vehicle is traveling on a specific road section (for example, a highway with a gate (manned or unmanned, toll or free) at the boundary). In the following explanation, the autonomous driving section in which autonomous driving assistance is provided is assumed to be a general road or highway excluding narrow streets. Parking lots are also included in the autonomous driving section, and the explanation will be given assuming that autonomous driving assistance is basically provided within the autonomous driving section from the time the vehicle starts traveling until the time it ends traveling (until the vehicle is parked). However, autonomous driving assistance is not always provided when the vehicle is traveling on an autonomous driving section, but is only provided when the user selects to provide autonomous driving assistance (for example, by turning on the autonomous driving start button) and it is determined that autonomous driving assistance is possible.

[0014] In vehicle control in automated driving assistance, for example, the current position of the vehicle, the lane the vehicle is traveling on, and the positions of surrounding obstacles are detected at any time, and vehicle control such as steering, drive source, and braking is automatically performed so that the vehicle travels at a speed according to a speed plan generated along the travel trajectory or planned travel route (guidance route) generated by the navigation device 1. Note that in assisted travel using automated driving assistance in this embodiment, lane changes, right and left turns, and parking operations are also performed automatically by the automated driving assistance, but special travel such as lane changes, right and left turns, and parking operations may be performed by manual driving without using automated driving assistance.

[0015] Each of the components of the navigation device 1 will be explained below in order. The current position detection unit 11 is composed of a GPS 22, a vehicle speed sensor 23, a steering sensor 24, a gyro sensor 25, etc., and is capable of detecting the current vehicle position, direction, vehicle traveling speed, current time, etc. Here, the vehicle speed sensor 23 in particular is a sensor for detecting the vehicle's travel distance and speed, and generates pulses in response to the rotation of the vehicle's drive wheels and outputs the pulse signals to the navigation ECU 13. The navigation ECU 13 then calculates the rotation speed of the drive wheels and travel distance by counting the generated pulses. Note that the navigation device 1 does not need to be equipped with all four types of sensors described above, and the navigation device 1 may be configured to be equipped with only one or more of these types of sensors.

[0016] The data recording unit 12 also includes a hard disk (not shown) as an external storage device and recording medium, and a recording head (not shown) which is a driver for reading the map information DB 31 and predetermined programs recorded on the hard disk and for writing predetermined data to the hard disk. Note that the data recording unit 12 may be configured with a memory card or an optical disk such as a CD or DVD instead of a hard disk. The map information DB 31 may also be stored in an external server and acquired by the navigation device 1 through communication.

[0017] Here, the map information DB 31 is a storage means that stores, for example, link data 33 relating to roads (links), node data 34 relating to node points, search data 35 used for processing related to route search and change, facility data 36 relating to facilities, map display data for displaying maps, intersection data relating to each intersection, search data for searching for points, etc.

[0018] The link data 33 also includes data representing the width, gradient, cant, bank, road surface condition, merging section, road structure, presence or absence of shoulder space, number of lanes on the road, points where the number of lanes decreases, points where the road width narrows, and railroad crossings for each link that makes up the road; data representing the radius of curvature, intersections, T-junctions, corner entrances and exits for corners; data representing downhill roads, uphill roads, and the like for road attributes; and data representing toll roads such as national highways, prefectural roads, and narrow streets for road types, as well as toll roads such as national expressways, urban expressways, motorways, general toll roads, and toll bridges for road types. In particular, in this embodiment, the information necessary for assisted driving using autonomous driving assistance is stored, and in addition to the number of lanes on the road, information identifying the traffic divisions in the direction of travel for each lane and the connections between roads (specifically, the correspondence between the lanes on the road before passing through the intersection and the lanes on the road after passing through the intersection), the speed limit set on the road, and information regarding dividing lines painted on the road (center lines, lane boundaries, outer lines of the road, guide lines, guidance strips, etc.) is also stored.

[0019] The node data 34 also includes data such as the coordinates (positions) of actual road branching points (including intersections, T-junctions, etc.) and node points set at predetermined distances on each road depending on the radius of curvature, node attributes indicating whether the node corresponds to an intersection, a connecting link number list which is a list of link numbers of links connecting to the node, an adjacent node number list which is a list of node numbers of nodes adjacent to the node via links, and the height (altitude) of each node point.

[0020] Furthermore, various data used in route search processing for searching for a route from a starting point (for example, the current position of the vehicle) to a set destination are recorded as the search data 35. Specifically, cost calculation data used to calculate search costs, such as a cost that quantifies the suitability of an intersection as a route (hereinafter referred to as intersection cost) and a cost that quantifies the suitability of a link that constitutes a road as a route (hereinafter referred to as link cost), are stored.

[0021] Additionally, various data related to facilities (locations) across the country, such as the facility genre, name, and location information, is stored as facility data 36. In particular, for parking lots, data necessary for parking using automated driving assistance is stored, including, for example, information about the entrance to the parking lot, layout information for the aisles and parking spaces in the parking lot, information about the dividing lines that separate the parking spaces, and connection information indicating the connection relationship between the entrance to the parking lot and the lanes (which lanes can be used to enter the parking lot), etc.

[0022] Meanwhile, the navigation ECU (electronic control unit) 13 is an electronic control unit that controls the entire navigation device 1. It includes a CPU 41 as a calculation device and control device, a RAM 42 that serves as a working memory for the CPU 41 to perform various calculation processes and stores route data and the like when a route is searched, a ROM 43 that stores control programs as well as the automated driving assistance program (see FIG. 2 ) described below, and a flash memory 44 that stores programs read from the ROM 43. The navigation ECU 13 also includes various processing algorithms. For example, the handover point setting means sets a handover point where the vehicle is driven with automated driving assistance to manually driven while the vehicle is driving with automated driving assistance. The handover determination means determines whether the handover from the automated driving assistance to the manual driving was successful at the handover point. The stop position search means searches for a stop position around the handover point where the vehicle can be temporarily stopped if the handover determination means determines that the handover was not successful. The loop route search means searches for a loop route that starts from the handover point and returns to the handover point when the handover determination means determines that the handover could not be performed. The action selection means selects whether the vehicle will move to a stop position or travel along the loop route as a future vehicle action. The driving control means continues driving with automated driving assistance in accordance with the vehicle action selected by the action selection means.

[0023] The operation unit 14 is operated when inputting a departure point as a starting point of a trip and a destination point as a destination of a trip, and has a plurality of operation switches (not shown) such as various keys and buttons. The navigation ECU 13 controls the execution of various corresponding operations based on switch signals output by pressing each switch. The operation unit 14 may have a touch panel provided on the front surface of the liquid crystal display 15. It may also have a microphone and a voice recognition device.

[0024] The liquid crystal display 15 also displays map images including roads, traffic information, operation guidance, operation menus, key guidance, guidance information along the guided route (planned driving route), news, weather forecasts, time, emails, television programs, etc. Note that a HUD or HMD may be used instead of the liquid crystal display 15.

[0025] Furthermore, the speaker 16 outputs audio guidance for guiding the vehicle along a guide route (planned travel route) based on instructions from the navigation ECU 13, and traffic information guidance.

[0026] The DVD drive 17 is a drive that can read data recorded on a recording medium such as a DVD or CD. Based on the read data, music and video are played, and the map information DB 31 is updated. Instead of the DVD drive 17, a card slot for reading and writing data to a memory card may be provided.

[0027] The communication module 18 is a communication device for receiving traffic information, probe information, weather information, etc. transmitted from a traffic information center, such as a VICS center or a probe center, and corresponds to, for example, a mobile phone or DCM. It also includes a vehicle-to-vehicle communication device for communicating between vehicles and a road-to-vehicle communication device for communicating with roadside devices.

[0028] The exterior camera 19 is composed of a camera using a solid-state image sensor such as a CCD, and is mounted above the front bumper of the vehicle with its optical axis oriented downward at a predetermined angle from the horizontal. The exterior camera 19 captures an image of the area ahead of the vehicle when the vehicle is traveling in an autonomous driving zone. The vehicle control ECU 20 processes the captured image to detect lane markings on the road on which the vehicle is traveling and other vehicles in the vicinity, and controls the autonomous driving of the vehicle based on the detection results. The exterior camera 19 may be positioned behind or to the side of the vehicle, in addition to the front. Instead of a camera, a sensor such as a millimeter-wave radar, vehicle-to-vehicle communication, or road-to-vehicle communication may be used to detect other vehicles.

[0029] The vehicle control ECU 20 is an electronic control unit that controls the vehicle equipped with the navigation device 1. The vehicle control ECU 20 is also connected to each drive unit of the vehicle, such as the steering, brakes, and accelerator, and in this embodiment, after automatic driving assistance has started in the vehicle, the vehicle control ECU 20 controls each drive unit to implement automatic driving assistance for the vehicle. If an override is performed by the user during automatic driving assistance, the ECU 20 detects that an override has been performed.

[0030] Here, the navigation ECU 13 transmits various types of assistance information related to autonomous driving assistance generated by the navigation device 1 to the vehicle control ECU 20 via the CAN when the planned driving route (guidance route) of the vehicle is determined or after the vehicle starts driving. The vehicle control ECU 20 then uses the received various types of assistance information to provide autonomous driving assistance after the vehicle starts driving. Examples of assistance information include a recommended driving path for the vehicle, a speed plan indicating the vehicle speed during driving, etc. Note that it is also possible to transmit information specifying the planned driving route (guidance route) that specifies the route the vehicle will travel, without transmitting the specific driving path.

[0031] Next, an automatic driving assistance program executed by the CPU 41 in the navigation device 1 according to this embodiment having the above configuration will be described with reference to Fig. 2. Fig. 2 is a flowchart of the automatic driving assistance program according to this embodiment. The automatic driving assistance program is executed when the vehicle is traveling with automatic driving assistance, and is a program that switches over from automatic driving assistance to manual driving as necessary. The program shown in the flowchart in Fig. 2 below is stored in the RAM 42 and ROM 43 provided in the navigation device 1, and is executed by the CPU 41.

[0032] First, in step (hereinafter abbreviated as S) 1 of the automatic driving assistance program, the CPU 41 determines whether or not a situation exists in which it is necessary to switch from automatic driving assistance to manual driving. Here, a situation in which it is necessary to switch to manual driving is, for example, when the destination is set to a location on a road where the vehicle cannot be parked, and it is determined that the destination has been reached or will soon be reached. In such a situation, the vehicle cannot determine whether the user should continue driving or park, and if so, where to park, so it is necessary to switch to manual driving.

[0033] The second reason is when it is expected that the vehicle will enter a non-autonomous driving zone, such as a narrow street. In this embodiment, the autonomous driving zone where the vehicle will be assisted in autonomous driving is set in advance, but narrow streets where the area in which the vehicle will be traveling is unclear and difficult to navigate are excluded from the autonomous driving zone. Therefore, if the planned driving route includes a narrow street, it is necessary to switch to manual driving before entering the narrow street.

[0034] If it is determined that the situation requires a transition from automated driving assistance to manual driving (S1: YES), the process proceeds to S2. On the other hand, if the situation does not require a transition from automated driving assistance to manual driving (S1: NO), the automated driving assistance continues.

[0035] In S2, the CPU 41 sets a handover point where the automatic driving assistance will be handed over to manual driving. The handover point is set on the planned driving route, in the direction of travel from the vehicle's current position. For example, a section 300 m ahead from the vehicle's current position along the planned driving route is set as the handover point, and together with setting the handover point, a voice guidance is output from the speaker 16 saying, "Automatic driving assistance will be terminated, so please continue driving manually," to prompt the user to hand over to manual driving.

[0036] However, if there is a transfer-exclusion section ahead in the vehicle's direction of travel where it is undesirable to transfer control to manual driving, the transfer point is set excluding the transfer-exclusion section. Examples of transfer-exclusion sections include intersections and merging points. If there is such a transfer-exclusion section, the transfer point is set after the vehicle has passed through the transfer-exclusion section, and after the setting, audio guidance is output to prompt the user to transfer control to manual driving.

[0037] Thereafter, in S3, the CPU 41 determines whether or not the automatic driving assistance driving has been handed over to the manual driving driving at the handover point set in S2. Specifically, when it is determined that the user has performed a vehicle operation (override) such as steering, braking, or accelerator operation based on a signal from the vehicle control ECU 20, the CPU 41 determines that the automatic driving assistance driving has been handed over to the manual driving driving.

[0038] If it is determined that the transition from automated driving assistance to manual driving was successful at the transfer point set in S2 (S3: YES), the process proceeds to S4. On the other hand, if it is determined that the transition from automated driving assistance to manual driving was not successful at the transfer point set in S2, that is, if the transfer point was passed without any vehicle operation by the user, such as steering, braking, or accelerating (S3: NO), the process proceeds to S5.

[0039] In S4, the CPU 41 switches over from automatic driving assistance to manual driving. That is, it sends an automatic driving assistance stop signal to the vehicle control ECU 20, and thereafter, vehicle control related to automatic driving assistance is not performed. Note that, regarding vehicle control related to automatic driving assistance, when the vehicle is performing assisted driving with automatic driving assistance, in which the vehicle automatically travels along a predetermined route or road, all control of accelerator operation, brake operation, and steering operation for vehicle driving is not performed, but automatic braking in an emergency, for example, continues to function as needed even after switching to manual driving.

[0040] Meanwhile, in S5, the CPU 41 searches for a parking location within the vicinity of the vehicle (for example, within 500 m) where the vehicle can be temporarily stopped. Potential parking locations include roadside spaces and parking lots large enough to park the vehicle. Parking lots include, for example, public parking lots, private paid parking lots such as coin parking lots, and parking lots attached to facilities. However, with regard to parking lots attached to facilities, it is desirable to limit the parking lots to those attached to facilities that the user has visited in the past or facilities of a type that the user is likely to visit based on the user's travel history.

[0041] Thereafter, the processes of S6 to S9 are performed for each stop position (hereinafter referred to as stop position candidate) found in S5, and after the processes have been performed for all stop position candidates found in S5, the process proceeds to S10.

[0042] First, in S6, the CPU 41 searches for a travel route from the current vehicle position (which also corresponds to the takeover point set in S2 where the takeover was not possible) to a candidate stopping position. The travel route is searched for, for example, using map information and the well-known Dijkstra algorithm. The travel route may also be searched for by an external server device having map information, rather than by the navigation device 1. For example, information specifying the current vehicle position and destination may be transmitted to the external server device as a route search request, and the navigation device 1 may receive the route searched by the server based on the route search request.

[0043] Next, in S7, the CPU 41 calculates the time required for the vehicle to travel along the route found in S6 and stop at the candidate stopping location. Note that the calculation of the time in S7 takes into consideration the speed limit set for the road, road congestion information, and if the stopping location is a parking lot, the congestion level in the parking lot.

[0044] Next, in S8, the CPU 41 acquires the type of location where the stop position candidate exists. In this embodiment, the locations where the stop position candidate exists include the shoulder of a road, a public parking lot, a paid parking lot, and a parking lot attached to a facility, and in S8, it is acquired which of these locations the stop position candidate to be processed is located.

[0045] Next, in S9, the CPU 41 calculates a cost (hereinafter referred to as the first cost) indicating the burden on the user for traveling to the candidate stop location based on the time required to stop at the candidate stop location calculated in S7 and the type of location where the candidate stop location is located obtained in S8.

[0046] The method for calculating the first cost in S9 will be described below with reference to FIG. As shown in FIG. 3, the first cost is calculated by multiplying the time required to stop at a candidate stopping location by a coefficient. The coefficient is determined as shown in FIG. 3 based on the type of location where the candidate stopping location is located, taking into account the burden (labor and financial burden) on the user required to stop. Specifically, the coefficient is "×1.0" for a road shoulder, "×1.5" for a public parking lot, "×4.0" for a paid parking lot, and "×2.0" for a facility parking lot (limited to facilities that the user has visited in the past or that are likely to be visited based on the user's travel history). For example, in the example shown in FIG. 3, if the time required to stop at a candidate stopping location is the same, the first cost is calculated to be the smallest when stopping at a road shoulder, and the first cost is calculated to be the largest when stopping at a paid parking lot.

[0047] After the first costs have been calculated for all the stop position candidates found in S5, the process proceeds to S10.

[0048] In S10, the CPU 41 determines whether a grace period has been set by the user. The grace period is the time required by the user to take over when the user is unable to take over due to reasons such as the user not being ready to drive. For example, the grace period is input by the user by operating the operation unit 14 after the voice guidance for the user to take over to manual driving is output in S2. However, the user does not necessarily have to set the grace period, and may not be set even if the user does not take over. In addition to manually setting the grace period, the device may automatically predict and set the grace period by detecting the user's current situation using an in-vehicle camera or the like.

[0049] If it is determined that the user has set a grace period (S10: YES), the process proceeds to S14. On the other hand, if it is determined that the user has not set a grace period (S10: NO), the process proceeds to S11.

[0050] In S11, the CPU 41 searches for a loop route that starts from the vehicle's current position (which also corresponds to the takeover point set in S2 where the takeover was not possible) and returns to the same takeover point. Specifically, the search is for a route that uses the takeover point as both the start point and the destination, and in S11, the search is for the shortest loop route that will minimize the overall length of the loop route. The loop route search is performed, for example, using map information and the well-known Dijkstra algorithm. The loop route search may also be performed by an external server device that has map information, rather than the navigation device 1. For example, information specifying the vehicle's current position and destination may be sent to the external server device as a route search request, and the navigation device 1 may receive the route searched by the server based on the route search request.

[0051] Thereafter, in S12, the CPU 41 calculates the loop time required for the vehicle to complete the loop and return to the handover point if the vehicle travels along the loop route found in S11. The calculation of the loop time in S12 takes into consideration the speed limit set for the road, traffic congestion information on the road, etc.

[0052] Next, in S13, the CPU 41 calculates a cost (hereinafter referred to as a second cost) indicating the burden on the user of traveling the loop route found in S11, based on the round trip time calculated in S12.

[0053] The method for calculating the second cost in S13 will be described below with reference to FIG. As shown in Figure 4, if no grace period is set, the second cost is calculated by multiplying the travel time of the loop route found in S11 by a coefficient. The coefficient is a fixed value, for example, "x 3.0." Therefore, the longer the time required to travel around the loop route, the larger the calculated second cost will be. Then, the process proceeds to S17.

[0054] On the other hand, in S14, which is executed when a grace period has been set, the CPU 41 searches for a loop route, which is a route that starts from the vehicle's current position (which also corresponds to the transfer point set in S2 where transfer was not possible) and returns to the same transfer point, as in S11. However, in the loop route search in S14, a loop route is searched for in which the time required to travel the loop route and return to the transfer point is longer than the grace period set by the user, and the difference is as small as possible. Note that the loop route search is performed, for example, using map information and the well-known Dijkstra algorithm. Furthermore, the loop route search may be performed not by the navigation device 1 but by an external server device having map information. For example, information specifying the vehicle's current position and destination may be transmitted to the external server device as a route search request, and the navigation device 1 may receive the route searched by the server based on the route search request.

[0055] Furthermore, the condition in S14 that the time required to travel the loop route and return to the handover point is longer than the grace time set by the user and the difference is as small as possible does not necessarily require traveling around the loop route only once; it can be satisfied by traveling around the same loop route multiple times. For example, as shown in Figure 5, if the grace time is set to 10 minutes and there are two loop routes, a first loop route with a 3-minute loop time and a second loop route with a 15-minute loop time, the first loop route will have a shorter loop time than the grace time if it is traveled only once, but if it is traveled four times, the grace time will be longer than the loop time, and the difference will be 2 minutes. For the second loop route with a 15-minute loop time, the difference from the grace time will be 5 minutes, so the route that travels around the first loop route four times will be selected preferentially in S14.

[0056] However, the loop route may be assumed to be a single circuit, in which case the second loop route will be selected preferentially in S14.

[0057] Thereafter, in S15, the CPU 41 calculates the loop time required for the vehicle to complete the loop and return to the handover point if the vehicle travels along the loop route found in S14. If a route that requires multiple loops is found, the CPU 41 calculates the loop time required for the multiple loops. Note that the calculation of the loop time in S15 takes into consideration the speed limit set for the road, road congestion information, etc.

[0058] Next, in S16, the CPU 41 calculates a cost (second cost) indicating the burden on the user of traveling the loop route found in S14, based on the difference between the circumnavigation time and the grace time calculated in S15.

[0059] The method for calculating the second cost in S16 will be described below with reference to FIG. As shown in Figure 4, when a grace period is set, the second cost is calculated by multiplying the difference between the loop route travel time and the grace period found in S14 by a coefficient. The coefficient is a fixed value, for example, "x 3.0." Therefore, the larger the difference between the time required to travel around the loop route and the grace period, the larger the calculated second cost will be. Then, the process proceeds to S17.

[0060] In S17, the CPU 41 compares the first cost calculated in S9 (there may be multiple first costs) with the second cost calculated in S13 or S16, and selects the route with the lowest cost as the future vehicle behavior. That is, if the first cost is small, the future vehicle behavior is selected to move to the stop position (if there are multiple stop position candidates, the stop position candidate with the lowest cost), and if the second cost is small, the future vehicle behavior is selected to travel the loop route.

[0061] Thereafter, in S18, the CPU 41 transmits an instruction signal to the vehicle control ECU 20 to instruct the vehicle control ECU 20 to continue driving with the automatic driving assistance in accordance with the vehicle behavior selected in S17. Specifically, the CPU 41 transmits the driving route (a route to the stopping position or a loop route) indicating the future vehicle behavior selected in S17 to the vehicle control ECU 20 via the CAN. As a result, the vehicle control ECU 20 performs automatic driving control in accordance with the information received from the navigation device 1.

[0062] Furthermore, when continuing autonomous driving assistance, if the vehicle moves to a stop position, it will move in a direction different from the destination, so it is desirable to output voice guidance such as, "Moving to stop position XX (name of stop position) to perform handover." Furthermore, when traveling on a loop route, it is desirable to output voice guidance such as, "The vehicle will circle around until handover is possible."

[0063] As described above in detail, the navigation device 1 and the computer program executed by the navigation device 1 according to this embodiment set a handover point (S2) at which a transition from automated driving assistance to manual driving is performed while the vehicle is traveling with automated driving assistance. However, if the transition from automated driving assistance to manual driving cannot be performed at the handover point, a parking location where the vehicle can be temporarily stopped around the handover point is searched for (S5). A loop route that starts from the handover point and returns to the handover point is also searched for (S11, S14). The system selects whether the vehicle will move to the parking location or travel the loop route as its future vehicle action (S17). The system continues the automated driving assistance according to the selected vehicle action (S18). Therefore, if the transition from automated driving assistance to manual driving by the user cannot be performed, the system allows the user to select either moving to the parking location or traveling the loop route as the future action. As a result, the system can select a future action that is more appropriate for the vehicle's situation, and the system can perform the subsequent transition without burdening the user. In addition, a travel route from the vehicle's current position to the stopping position is searched for, and the cost for the travel route is calculated as a first cost taking into account the distance of the travel route or the time required for travel (S9), and the cost for the loop route is calculated as a second cost taking into account the distance of the loop route or the time required for the circuit (S13, S16).The first cost and the second cost are compared, and if the first cost is smaller, the vehicle's future action is selected to move to the stopping position, and if the second cost is smaller, the vehicle's future action is selected to travel along the loop route (S17).By comparing the costs, it is possible to select an action that is more suitable for the user. Furthermore, since the first cost is corrected depending on the type of location where the stop position is located, it becomes possible to select a stop position that places less of a burden on the user. In addition, the system sets the grace period required by the user to switch from driving with automated driving assistance to driving with manual driving, and searches for a loop route that minimizes the difference between the time required to drive the loop route and return to the handover point and the grace period, so it is possible to prevent the time until handover to manual driving from becoming longer than necessary.

[0064] The present invention is not limited to the above-described embodiment, and it goes without saying that various improvements and modifications are possible within the scope of the present invention. For example, in this embodiment, when calculating the first cost in S9, the cost is calculated taking into account the time required to travel from the current position of the vehicle to the candidate stop position, but the cost may also be calculated taking into account the travel distance from the current position of the vehicle to the candidate stop position.Similarly, when calculating the second cost in S13 and S16, the cost is calculated taking into account the circumnavigation time required to travel the loop route, but the cost may also be calculated taking into account the distance of the loop route.

[0065] Furthermore, in this embodiment, S3 determines whether or not the transfer from automatic driving assistance to manual driving has been successful at the transfer point set in S2. However, rather than determining whether or not the transfer has been successful, it may be determined whether or not the transfer is possible, i.e., whether or not the transfer point has not yet been passed but whether or not it is expected that the transfer will be possible.

[0066] In this embodiment, the automatic driving control for automatically driving the vehicle without the user's driving operation has been described as the vehicle control ECU 20 controlling all of the accelerator operation, brake operation, and steering operation, which are operations related to the vehicle's behavior, among the vehicle operations. However, the automatic driving control may also be defined as the vehicle control ECU 20 controlling at least one of the accelerator operation, brake operation, and steering operation, which are operations related to the vehicle's behavior, among the vehicle operations. On the other hand, manual driving by the user's driving operation will be described as the user performing all of the accelerator operation, brake operation, and steering operation, which are operations related to the vehicle's behavior, among the vehicle operations.

[0067] In this embodiment, the autonomous driving assistance program (FIG. 2) is executed by the navigation device 1, but it may be executed by the vehicle control ECU 20 or another in-vehicle device. In that case, the vehicle control ECU 20 is configured to obtain the current position of the vehicle, map information, traffic information, etc. from the navigation device 1.

[0068] Furthermore, the present invention can be applied to devices other than navigation devices that have a route search function. For example, the present invention can be applied to mobile phones, smartphones, tablet devices, personal computers, etc. (hereinafter referred to as mobile devices, etc.). The present invention can also be applied to systems consisting of a server and a mobile device, etc. In such cases, each step of the above-described autonomous driving assistance program (FIG. 2) may be implemented by either the server or the mobile device, etc. However, when the present invention is applied to a mobile device, etc., a vehicle capable of executing autonomous driving control and the mobile device, etc. must be connected so as to be able to communicate (either wired or wireless). [Explanation of symbols]

[0069] 1... navigation device (driving assistance device), 13... navigation ECU, 20... vehicle control ECU, 31... map information DB, 41... CPU, 42... RAM, 43... ROM

Claims

1. a handover point setting means for setting a handover point at which a transition is made from autonomous driving assistance to manual driving while the vehicle is traveling with autonomous driving assistance; a handover determination means for determining whether or not handover from autonomous driving assistance to manual driving has been successfully performed at the handover point; a stop position search means for searching for a stop position around the handover point where the vehicle can be temporarily stopped when the handover determination means determines that the handover cannot be performed; a loop route searching means for searching for a loop route that is a route starting from the handover point and returning to the handover point when the handover determining means determines that the handover could not be performed; action selection means for selecting whether to move to the stop position or to travel along the loop route as a future action of the vehicle; and a driving control means for continuing driving with automatic driving assistance in accordance with the vehicle behavior selected by the behavior selection means.

2. The action selection means searching for a travel route from the current position of the vehicle to the stop position, and calculating a cost for the travel route as a first cost in consideration of the distance of the travel route or the time required for travel; calculating a cost for the loop route as a second cost, taking into account the distance of the loop route or the time required for completing the loop route; 2. The driving assistance device according to claim 1, wherein the first cost is compared with the second cost, and if the first cost is smaller, the device selects moving to the stop position as the future vehicle action, and if the second cost is smaller, the device selects traveling along the loop route as the future vehicle action.

3. The driving assistance device according to claim 2 , wherein the action selection means corrects the first cost depending on a type of location where the stopping position is present.

4. a grace time setting means for setting a grace time required by a user to switch from driving with automatic driving assistance to driving with manual driving, 4. The driving assistance device according to claim 1, wherein the loop route search means searches for a loop route that minimizes the difference between the time required to travel the loop route and return to the handover point and the grace time.

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