Vehicle Systems

Abstract

A vehicular system (1) that includes: a measurement unit (2) that is installed on a vehicle (5) to detect magnetic markers (10) that are provided along a route; a database (36) that stores position information for the magnetic markers (10); and a control unit (32) that references a storage area of the database (36) and acquires the position information for the magnetic markers (10). The database (36) stores position information for each magnetic marker (10) in association with the distance to the magnetic marker (10) from a reference point on the route, and after the vehicle (5) has passed the reference point, the distances traveled until detection of the magnetic markers (10) are used to reference the database (36) and thereby acquire position information for newly detected magnetic markers (10).

Description

[Technical Field]

[0001] The present invention relates to a system for a vehicle for utilizing magnetic markers. [Background technology]

[0002] Conventionally, systems have been known that use magnetic markers placed along the road to assist driving to keep the vehicle in its lane (see, for example, Patent Documents 1 and 2 listed below). In these driving assistance systems, the amount of lateral deviation of the vehicle from the magnetic markers arranged along the center of the lane is measured, and the results are used for lane departure warning and lateral control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-141594 [Patent Document 2] Japanese Patent Application Publication No. 2018-169301 Summary of the Invention [Problem to be solved by the invention]

[0004] Using magnetic markers arranged in the center of the lane as a reference makes it possible to grasp the widthwise bias of the vehicle's position within the lane. However, there is a problem in that it is difficult to uniquely identify the magnetic markers detected by the vehicle, and it is difficult to obtain attribute information of the magnetic markers, such as their location.

[0005] The present invention has been made in consideration of the above-mentioned problems of the conventional art, and aims to provide a vehicle system that can uniquely identify magnetic markers and acquire attribute information with high reliability. [Means for solving the problem]

[0006] The present invention provides a vehicle system for acquiring attribute information of magnetic markers arranged along a road while the vehicle is traveling, the system comprising: a magnetic sensor attached to the vehicle for detecting the magnetic marker; a distance determination unit for determining a distance traveled by the vehicle; a database that stores attribute information of the magnetic markers; an information acquisition unit that refers to a storage area of ​​the database and acquires attribute information of the magnetic marker detected by the vehicle, The database stores attribute information of each magnetic marker, linked to information that can identify the distance from a reference point on the track to each magnetic marker, The information acquisition unit is in a vehicle system that acquires attribute information of the magnetic marker detected by the vehicle by referring to the database using the distance traveled by the vehicle after passing the reference point until the magnetic marker is detected.

[0007] The vehicle system of the present invention includes a distance determination unit for determining the distance traveled in addition to a magnetic sensor used to detect the magnetic markers. The database constituting this vehicle system stores attribute information for each magnetic marker, linked to information that can determine the distance from a reference point on the road to each magnetic marker.

[0008] In the vehicle system of the present invention, by referring to a database using the distance traveled by the vehicle after passing a reference point, the magnetic marker detected by the vehicle can be identified and attribute information of that magnetic marker can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a configuration diagram of a vehicle system according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a magnetic marker to which an RFID tag is attached in the first embodiment. [Figure 3] FIG. 2 is a front view of the RFID tag according to the first embodiment. [Figure 4] FIG. 2 is a block diagram showing the electrical configuration of the vehicle system according to the first embodiment. [Figure 5]FIG. 10 is an explanatory diagram of a data map for each reference magnetic marker in the first embodiment. [Figure 6] 3 is a flowchart showing the flow of operations of the vehicle system in the first embodiment. [Figure 7] FIG. 10 is an explanatory diagram of a vehicle path in the second embodiment. [Figure 8] FIG. 10 is an explanatory diagram of a data map for each reference magnetic marker in the second embodiment. [Figure 9] 10 is a flowchart showing the flow of operations of the vehicle system in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiments of the present invention will be specifically described using the following examples. Example 1 This example relates to a vehicle system 1 that can provide attribute information of a magnetic marker 10 to a vehicle 5 that detects the magnetic marker 10. The details of this will be described with reference to FIGS.

[0011] The vehicle system 1 (FIG. 1) is a system that acquires attribute information of magnetic markers 10 arranged along a road, which is an example of a roadway, while the vehicle 5 is traveling. In the configuration of this example, the magnetic markers 10 are arranged along the center of a lane 100 divided by left and right lane marks 101.

[0012] The magnetic markers 10 arranged along the lane 100 include a reference magnetic marker. In FIG. 1, the reference magnetic marker is denoted by the symbol 10T to distinguish it from non-reference magnetic markers. The reference magnetic marker 10T holds an RFID (Radio Frequency IDentification) tag 15. The vehicle 5 identifies the newly detected magnetic marker 10 by using the distance traveled after passing the reference magnetic marker 10T, and acquires attribute information of the magnetic marker 10. The attribute information of the magnetic marker 10 includes location information indicating the placement position of the magnetic marker 10, information indicating the type of road, lane, etc.

[0013] The vehicle system 1 of this example can be combined with, for example, a navigation system 6 provided in the vehicle 5. The navigation system 6 includes a navigation ECU 61 that realizes a navigation function and a map database (map DB) 65 that stores detailed three-dimensional map data (3D map data). Although a detailed description will be omitted, the navigation ECU 61 uses the vehicle position identified by the vehicle system 1 to display a map of the surrounding area and provide route guidance by screen display, audio output, etc.

[0014] As shown in Figure 2, the magnetic marker 10 is a cylindrical magnet with a diameter of 20 mm and a height of 28 mm. The magnetic marker 10 is installed, for example, housed in a hole drilled in the road surface 100S. In this example, the magnetic markers 10 are installed at intervals of, for example, 5 m along the lane 100. The magnet serving as the magnetic marker 10 is an isotropic ferrite plastic magnet in which iron oxide magnetic powder, a magnetic material, is dispersed in a polymeric base material.

[0015] As shown in Figures 1 and 2, some of the magnetic markers 10, known as reference magnetic markers 10T, hold RFID tags 15 that wirelessly output information. The RFID tags 15 are sheet-like electronic components that are placed on the end faces of the magnets that make up the magnetic markers 10T. The RFID tags 15 are passive tags that operate via external wireless power supply and output tag information including a tag ID, which is identification information. The tag ID is identification information for the RFID tag 15 and can be used to identify the corresponding reference magnetic marker 10T.

[0016] The reference magnetic marker 10T is laid on the roadway so that the RFID tag 15 is positioned above it. Of the magnetic markers 10 arranged at intervals along the lane 100, the reference magnetic markers 10T may be placed at appropriate intervals, or may be placed at characteristic locations such as branching points, merging points, and stop points.

[0017] As shown in Fig. 3, the RFID tag 15 is an electronic component in which an IC chip 157 is mounted on the surface of a tag sheet 150 cut out from, for example, a PET (Polyethylene Terephthalate) film. A printed pattern of a loop coil 151 and an antenna 153 is provided on the surface of the tag sheet 150. The loop coil 151 is a receiving coil that generates an excitation current by external electromagnetic induction. The antenna 153 is a transmitting antenna for wirelessly transmitting tag information. A UHF band wireless tag is preferably used as the RFID tag 15.

[0018] The vehicle system 1 of this example is an on-board system mounted on a vehicle 5. The vehicle 5 includes, as components of the vehicle system 1, a wheel speed sensor 39 that detects wheel rotation, a tag reader 34 that acquires tag information from an RFID tag 15, a measurement unit 2 that detects magnetic markers 10, a control unit 32 that controls the tag reader 34 and the measurement unit 2, a database 36 that stores attribute information of the magnetic markers 10, and the like.

[0019] 1 and 4, the tag reader 34 is a communication unit equipped with a wireless antenna 340. The tag reader 34 is disposed in the front of the vehicle 5, for example, inside the front bumper of the vehicle 5. The tag reader 34 performs wireless communication with the RFID tag 15 attached to the reference magnetic marker 10T. The tag reader 34 operates the RFID tag 15 by wireless power supply and acquires tag information wirelessly transmitted (output) by the RFID tag 15. The tag reader 34 inputs the acquired tag information to the control unit 32 as needed.

[0020] As shown in Figures 1 and 4, the measurement unit 2 is a unit that integrates a sensor array 21 including magnetic sensors Cn and an IMU (Inertial Measurement Unit) 22 that enables positioning by inertial navigation. The measurement unit 2 is a long, thin, rod-shaped unit. The measurement unit 2 is attached, for example, to the inside of the front bumper of the vehicle 5, along the vehicle width direction. The measurement unit 2 is attached facing parallel to the road surface 100S. In this example, the installation height of the measurement unit 2 relative to the road surface 100S is 200 mm.

[0021] The sensor array 21 (FIG. 4) includes 15 magnetic sensors Cn (n is an integer between 1 and 15) and a detection processing circuit 212 incorporating a CPU (Central Processing Unit) (not shown). The magnetic sensors Cn are arranged in a straight line along the longitudinal direction of the measurement unit 2. The magnetic sensors Cn are spaced at equal intervals of 10 cm. The sensor array 21 is attached to the vehicle 5 so that the central magnetic sensor C8 is positioned at the center in the vehicle width direction. The magnetic sensors Cn may be, for example, MI sensors that detect magnetism by utilizing the well-known MI effect (Magnet Impedance Effect), in which the impedance of a magnetically sensitive material such as amorphous wire changes sensitively in response to an external magnetic field.

[0022] The detection processing circuit 212 (FIG. 4) provided in the sensor array 21 is an arithmetic circuit that executes marker detection processing and the like to detect the magnetic marker 10. Although not shown, this detection processing circuit 212 is configured using a CPU that executes various calculations, as well as memory elements such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0023] The detection processing circuit 212 acquires the sensor signals output by each magnetic sensor Cn at a frequency of 3 kHz and executes the marker detection process. In the marker detection process, in addition to detecting the magnetic marker 10, the lateral deviation of the vehicle 5 relative to the magnetic marker 10 is measured. After executing the marker detection process, the detection processing circuit 212 inputs the result to the control unit 32.

[0024] The IMU 22 (FIG. 4) incorporated in the measurement unit 2 is an inertial navigation unit for estimating the relative position of the vehicle 5 by inertial navigation. The IMU 22 acquires measurement values ​​necessary for estimating the relative position of the vehicle 5 by inertial navigation. The IMU 22 includes a two-axis magnetic sensor 221, which is an electronic compass that measures orientation, a two-axis acceleration sensor 222 that measures acceleration, and a two-axis gyro sensor 223 that measures angular velocity. In particular, based on the measurement signal of the IMU 22, it is possible to identify the angular displacement amount and displacement speed (yaw rate) of the vehicle orientation. The IMU 22 is an example of an orientation estimation unit that estimates the absolute orientation of the vehicle or a relative orientation that indicates a change in the orientation of the vehicle.

[0025] 4, the control unit 32 is a unit that controls the tag reader 34 and the measurement unit 2, and also acquires attribute information of the magnetic marker 10. The control unit 32 includes a CPU that performs various calculations, as well as an electronic board (not shown) on which memory elements such as ROM and RAM are mounted.

[0026] The control unit 32 is connected to the wheel speed sensor 39 and a storage device (not shown) such as a hard disk drive. The database 36, which stores the attribute information of each magnetic marker 10, is constructed using the storage area of ​​this storage device. The wheel speed sensor 39 is a sensor that outputs a pulse signal once every time the wheel rotates a predetermined amount. The distance traveled by the vehicle 5 can be calculated by multiplying the number of times the wheel speed sensor 39 outputs a pulse signal by the distance equivalent to the predetermined amount of rotation, or by adding and integrating the distance equivalent to the predetermined amount of rotation each time a pulse signal is output. The control unit 32, in combination with the wheel speed sensor 39, constitutes a distance determination unit that determines the distance traveled by the vehicle 5.

[0027] The database 36 is a database that stores attribute information of each magnetic marker 10 and also stores the tag ID of the RFID tag 15 attached to the reference magnetic marker 10T. The database 36 is configured to include a data map, for example, as shown in FIG. 5, that is prepared for each reference magnetic marker 10T. Each data map is linked to the tag ID associated with the reference magnetic marker 10T. By referring to the database 36 using the tag ID, it is possible to identify the map data of the reference magnetic marker 10T associated with that tag ID.

[0028] The data map (FIG. 5) is a data map in which attribute information of each magnetic marker 10 arranged along a route from a reference magnetic marker 10T as a starting point to the first reference magnetic marker 10T downstream is recorded. The attribute information of each magnetic marker 10, including the reference magnetic marker 10T as the starting point, includes, for example, latitude and longitude position information and road type information.

[0029] In the data map (Figure 5), distance information and a count number (Count No.) are linked to the attribute information of each magnetic marker 10. The distance information is an example of information that can identify the distance from the reference magnetic marker 10T that serves as the starting point to the corresponding magnetic marker 10. The count number is an example of information that can identify the ordinal number of the corresponding magnetic marker 10, starting from the reference magnetic marker 10T.

[0030] In addition to the distance information and count number, a tag ID is linked to the attribute information of the reference magnetic marker 10T. On the data map, the reference magnetic marker 10T can be immediately identified by the presence of the linked tag ID. As the tag ID linked to the data map, the tag ID linked to the attribute information of the reference magnetic marker 10T may be used, or tag ID linking data for the data map may be set separately.

[0031] The control unit 32 functions as an information acquisition unit that refers to a storage area of ​​a database 36 that includes the data map of Fig. 5, for example, and acquires attribute information of a newly detected magnetic marker 10. The control unit 32 as an information acquisition unit selects a corresponding data map (e.g., Fig. 5) using the tag ID of a reference magnetic marker 10T. Then, when a new magnetic marker 10 is detected, it identifies one of the magnetic markers 10 in the selected data map using the travel distance of the vehicle 5 after passing the reference magnetic marker 10T or the number of times the magnetic marker 10 has been detected, and reads the attribute information of that magnetic marker 10.

[0032] Next, the operation of the vehicle system 1, centered on the control unit 32, will be described with reference to the flow diagram of Fig. 6. While the vehicle 5 is traveling, the control unit 32 accumulates the travel distance of the vehicle 5 (S102) every time it acquires a pulse signal from the wheel speed sensor 39 (S101: YES). When the magnetic marker 10 is detected (S103: YES), the control unit 32 increments the number of times the magnetic marker 10 has been detected by one, and determines whether or not the tag ID of the RFID tag 15 has been acquired (S104).

[0033] If the control unit 32 acquires the tag ID (S104: YES), i.e., if the detected magnetic marker 10 is the reference magnetic marker 10T, it uses the tag ID to refer to the database 36 and selects the data map (e.g., FIG. 5) linked to that tag ID (S105). Then, the control unit 32 identifies the reference magnetic marker 10T in the data map and acquires its attribute information (S106), and resets the accumulated travel distance to zero (S107). When resetting the travel distance, it is advisable to also reset the number of times the magnetic marker 10 has been detected.

[0034] On the other hand, if the magnetic marker 10 is detected but the tag ID is not acquired (S103: YES → S104: NO), the control unit 32 determines that the detected magnetic marker 10 is a non-reference magnetic marker 10. Then, the control unit 32 refers to the data map selected in step S105 above (S115). Note that the processing following S104: NO when the tag ID is not acquired should be performed after the detection of the reference magnetic marker 10T. This is because the data map to be referenced is not yet selected before the detection of the reference magnetic marker 10T.

[0035] The control unit 32 finds a magnetic marker 10 in the data map (e.g., FIG. 5) whose (linked) distance and count number match the accumulated travel distance and detection count, and identifies it as the magnetic marker 10 detected in step S103 (S116). Then, the control unit 32 acquires attribute information of the magnetic marker 10 identified in this way (S117). For example, by using the installation position of the magnetic marker 10 as a reference, it is possible to identify the vehicle position when the magnetic marker 10 was detected.

[0036] If a magnetic marker 10 goes undetected, the following problem occurs when referring to the data map (e.g., FIG. 5) in step S115. That is, a magnetic marker whose associated distance matches the accumulated travel distance in the data map is different from a magnetic marker whose associated count number matches the number of times it is detected. In this case, the control unit 32 identifies the magnetic marker whose accumulated travel distance matches as the detected magnetic marker 10. This is because, if a magnetic marker 10 goes undetected, the number of times it is detected will be less than the number of times it actually passes the magnetic marker 10, whereas the travel distance is accumulated with high reliability according to the travel of the vehicle 5.

[0037] During the execution of the processing loop of Figure 6, the control unit 32 determines the angular displacement of the vehicle heading (vehicle orientation) based on the measurement signal of the IMU 22. If the displacement of the vehicle heading exceeds a predetermined threshold, the control unit 32 determines that the vehicle 5 has left the lane in which the magnetic markers 10 are arranged by making a right or left turn, etc. When the control unit 32 determines that the vehicle 5 has left the lane in which the magnetic markers 10 are arranged, it is preferable to interrupt the execution of the processing loop of Figure 6, erase the stored data of the reference magnetic marker 10T, the accumulated travel distance, and the number of times the magnetic marker 10 has been detected, and wait for the detection of a new reference magnetic marker 10T. It is preferable to determine the threshold value above taking into account geometric specifications such as the curvature of the road.

[0038] In the vehicle system 1 of this example configured as described above, the vehicle 5 has a wheel speed sensor 39, which makes it possible to identify the distance traveled. In the database 36 constituting the vehicle system 1, attribute information such as the position information of each magnetic marker 10 is stored, linked to information that can identify the distance from a reference magnetic marker 10T, which is a reference point on the road, to each magnetic marker 10.

[0039] When the vehicle system 1 passes a reference magnetic marker 10T, it refers to the database 36 and selects a corresponding data map (e.g., FIG. 5). Then, after passing the reference magnetic marker 10T, it identifies a newly detected magnetic marker 10 by referring to the data map using the travel distance of the vehicle 5, etc., and obtains attribute information of that magnetic marker. When identifying a magnetic marker 10 using the travel distance, even if a magnetic marker 10 goes undetected after passing the reference magnetic marker 10T, it is possible to identify the newly detected magnetic marker 10 with high reliability.

[0040] In this example, a cylindrical ferrite plastic magnet is used as the magnet that makes up the magnetic marker 10, but a sheet-shaped ferrite rubber magnet may also be used. Bonded magnets, which are formed by kneading magnetic powder into a binder made of a polymeric material such as rubber or plastic, have the characteristic of high electrical internal resistance. Using a bonded magnet can suppress eddy currents that can occur inside the magnet when transmitting the power required to operate the RFID tag 15, improving power transmission efficiency. The shape of the magnet that makes up the magnetic marker 10 may be any shape other than cylindrical or sheet-shaped.

[0041] In this example, the RFID tag 15 is stacked on one end face (front face) of the magnet that constitutes the magnetic marker 10T. Alternatively, the RFID tag 15 may be disposed on the outer peripheral surface (back face or side face) of the magnet other than the front face, or the RFID tag 15 may be partially or entirely embedded inside the magnet.

[0042] Furthermore, if a sheet-like magnetic marker such as the one described above is used instead of the cylindrical magnetic marker 10, it can be attached to the road surface 100S without drilling holes in the road surface 100S. When attaching an RFID tag to a sheet-like magnetic marker, the RFID tag 15 may be stacked on the surface. Furthermore, a magnetic marker made of two magnetic sheets bonded together may be used. In this case, the RFID tag may be placed between the layers of the two magnetic sheets.

[0043] The magnetic sensor Cn may be, for example, a magnetic sensor that is sensitive in the longitudinal direction and the width direction of the vehicle 5. Alternatively, the magnetic sensor Cn may be sensitive in one or two of the longitudinal direction, the vertical direction, and the width direction. Alternatively, the magnetic sensor Cn may be sensitive in three mutually perpendicular directions. Instead of the magnetic sensor Cn, an electronic compass may be used to detect the magnetic marker. With an electronic compass, for example, when the vehicle passes the magnetic marker, the magnetic marker can be detected by sensing a change in the direction of the magnetism acting from the magnetic marker. An electronic compass provided in the IMU 22 may also be used.

[0044] In this example, the measurement unit 2 is illustrated as being integrated with the sensor array 21 and the IMU 22, but the two may be configured separately. In this example, the configuration of the vehicle system 1 is described as being applied to a vehicle 5 traveling on a road, but the vehicle system 1 may also be applied to a work vehicle used in a factory, a residence, etc.

[0045] In this example, a reference magnetic marker 10T is used as the reference point. Instead of a magnetic marker, a characteristic point on the track that can be identified by the structure of the track or a landmark on the track may be set as the reference point.

[0046] Examples of road structures include branches, junctions, and intersections. These road structures can be recognized by, for example, processing a forward image captured by an imaging camera with an image processing device (an example of a processing circuit). It is also possible to use a LIDAR unit that can measure the distance to a reflective object ahead using laser light or the like. The LIDAR unit can detect lane markings 101 with retroreflective properties, understand their shapes, and recognize road structures such as branches.

[0047] Landmarks on the road include, for example, traffic signs, road signs, road markings such as pedestrian crossings, commercial signs, traffic information signs, and structures such as buildings, tunnels, and bridges. These road markers can be recognized by processing forward images captured by an imaging camera with an image processing device (an example of a processing circuit). Signs and structures can be recognized by grasping their three-dimensional structure with a lidar unit or a processing device for three-dimensional data from millimeter-wave radar.

[0048] If the magnetic sensors are operating properly and the magnetic markers are installed properly, all magnetic markers 10 on the route traveled by the vehicle 5 should be detected without omission. In such a case, for example, when a magnetic marker is detected after passing a reference magnetic marker 10T, the attribute information of the magnetic marker (see FIG. 5 ) associated with distance information corresponding to the distance traveled by the vehicle 5 after passing the reference magnetic marker 10T should be associated with information (count number (Count No.)) corresponding to the actual number of times the magnetic marker was detected after the detection of the reference magnetic marker 10T until the detection of the magnetic marker. In other words, if the magnetic sensors and magnetic markers are in good condition, when a magnetic marker 10 is detected after the detection of the reference magnetic marker 10T, the attribute information associated with the distance information corresponding to the distance traveled by the vehicle and the attribute information associated with the count number corresponding to the actual number of times the magnetic marker was detected should match.

[0049] By determining whether the attribute information linked to the distance information corresponding to the travel distance of the vehicle matches or does not match the attribute information linked to the count number corresponding to the actual number of detections, the operating state of the magnetic sensor can be determined based on the determination result. A sensor diagnostic unit that determines the operating state of the magnetic sensor in this way may be provided in, for example, the control unit 32.

[0050] For example, the operating state of the magnetic sensor provided in the measurement unit 2 may be estimated based on the degree of mismatch between the attribute information corresponding to the vehicle's travel distance and the attribute information corresponding to the actual number of detections. The degree of mismatch may be, for example, the magnitude of the difference between the count number associated with the attribute information associated with the distance information corresponding to the travel distance and the actual number of detections. Another example of the degree of mismatch may be the number of times a mismatch is determined. Another example of the frequency of a mismatch may be the percentage of mismatches among the number of times a match or mismatch is determined. For example, threshold processing may be applied to the magnitude of the difference in the case of a mismatch, the number of mismatches, or the frequency of mismatches. If the threshold is exceeded, it may be determined that the magnetic sensor is likely or likely to be malfunctioning. When such a determination is made, it is possible to display a malfunction message or suspend driving control using the magnetic markers.

[0051] The data map in this example (FIG. 5) is a data map that records attribute information for each magnetic marker 10 along a path from the reference magnetic marker 10T as the starting point to the first downstream reference magnetic marker 10T. Alternatively, a data map may be used that records attribute information for each magnetic marker along a path to the second or third downstream reference magnetic marker 10T, or along a path covering a predetermined distance, such as 100 meters downstream. When such a data map is employed, even if magnetic detection of the reference magnetic marker 10T is missed or tag ID reading fails, subsequent magnetic markers 10 can be identified by using the travel distance. In this case, it is advisable to switch the data map to be referenced when a new reference magnetic marker 10T is detected.

[0052] Example 2 This example is an example in which the configuration of the data map is changed based on the vehicle system of the first embodiment so as to be able to handle a route including an intersection 108, which is an example of a branch point where the vehicle 5 can select a route. The contents of this example will be described with reference to Figs. 4 and 7 to 9.

[0053] The vehicle system of this example is capable of handling a route including an intersection 108, for example, as shown in FIG. 7. Note that the numbers attached to each magnetic marker 10 in FIG. 7 indicate the ordinal number of the magnetic marker 10, starting from the reference magnetic marker 10T. In the example shown in FIG. 7, a vehicle that has passed the reference magnetic marker 10T passes through four non-reference magnetic markers 10 and arrives at the intersection 108. This intersection 108 is a four-way intersection where roads intersect at a cross. A vehicle 5 that has arrived at the intersection 108 via the reference magnetic marker 10T can alternatively select one of three routes: a route that goes straight through the intersection 108, a route that turns right and branches off at the intersection 108, or a route that turns left and branches off at the intersection 108.

[0054] If a route that goes straight through the intersection 108 is selected, the vehicle passing through the intersection 108 will sequentially detect magnetic markers 10 arranged horizontally from number 5 onwards in the same figure. If a route that branches off by turning right at the intersection 108 is selected, the vehicle passing through the intersection 108 will sequentially detect magnetic markers 10 arranged vertically downward from number 5 onwards in the same figure. If a route that branches off by turning left at the intersection 108 is selected, the vehicle passing through the intersection 108 will sequentially detect magnetic markers 10 arranged vertically upward from number 5 onwards in the same figure.

[0055] The database 36 of the vehicle system 1 of this example stores the data map shown in Fig. 8 so as to be able to accommodate the above-mentioned three types of routes after passing through the intersection 108. In the data map in Fig. 8, the data map is divided into data maps for the upstream side and downstream side of the intersection 108. Furthermore, for the downstream side, three types of data maps are prepared for each route, corresponding individually to a straight route, a route for turning right, and a route for turning left.

[0056] The route-specific data maps (Fig. 8) include a data map for going straight, a data map for turning left, and a data map for turning right. Each downstream data map records attribute information for each magnetic marker 10 on the route from the intersection 108 to the new reference magnetic marker 10T.

[0057] In the data map of Figure 8, in addition to information on the distance to each magnetic marker 10 and a count number, a lane direction difference, which is an example of direction information, is set as information linked to the attribute information of each magnetic marker 10. The lane direction difference is the angular difference between the lane direction (road direction) at the installation position of the reference magnetic marker 10T and the lane direction at the installation position of each magnetic marker 10. This angular difference is an example of the relative direction of the road direction at the installation position of the magnetic marker 10 with respect to the road direction at the installation position (reference point) of the reference magnetic marker 10T.

[0058] The vehicle system 1 of this example operates according to the flow diagram of Fig. 9. Among the step numbers in Fig. 9, processing steps in the 100s, such as S101 and S102, are the same as the processing steps of Fig. 6 referred to in the first embodiment. When the magnetic marker 10 is detected (S103: YES), the control unit 32 of the vehicle system 1 of this example calculates the yaw angle yaw, which represents the vehicle orientation (vehicle direction), using a measurement signal from the IMU 22, which is an example of an orientation estimation unit (S203). The yaw angle yaw in this example is an absolute orientation, but it may also be a relative orientation.

[0059] If the detected magnetic marker 10 is the reference magnetic marker 10T and the tag ID has been acquired (S104: YES), the control unit 32 executes the processes of steps S105 to S107. In particular, in step S105, the control unit 32 identifies the reference magnetic marker 10T associated with the tag ID, and selects the data map (FIG. 8) associated with the tag ID from the data maps stored in the database 36.

[0060] The control unit 32 executes steps S105 to S107 followed by step S208. In step S208, the control unit 32 stores the yaw angle yaw calculated in step S203 as yawSTD, which is the reference yaw angle (S208).

[0061] When the control unit 32 detects a non-reference magnetic marker 10 after the reference magnetic marker 10T has passed (S103: YES → S203 → S104: NO), it subtracts the yaw angle yaw calculated in step S203 from the reference yaw angle yawSTD to calculate the yaw angle difference Δyaw (S214). This yaw angle difference Δyaw is an example of a relative heading that represents a change in the orientation of the vehicle 5 when a new magnetic marker 10 is detected, relative to the yaw angle yawSTD that represents the vehicle heading when the reference magnetic marker 10T, which is an example of a reference point, has passed. Then, the control unit 32 refers to the data map selected in step S105 above using the accumulated travel distance and yaw angle difference Δyaw (S215). Note that the processing following S104: NO when a tag ID has not been acquired is preferably performed after the reference magnetic marker 10T is detected. This is because, before the reference magnetic marker 10T is detected, the data map to be referred to is in an unselected state.

[0062] The control unit 32 identifies, among the magnetic markers 10 in the data map, a magnetic marker whose distance associated with its attribute information matches the accumulated travel distance and whose associated road direction difference matches the yaw angle difference Δyaw calculated in step S214 as the newly detected magnetic marker 10 (S116).Then, the control unit 32 reads and acquires the attribute information of the identified magnetic marker 10 from the data map (S117).

[0063] In step S116, the fact that the road heading difference, which is an example of direction information, matches the yaw angle difference Δyaw means that the road heading difference can be considered to match the yaw angle difference Δyaw by threshold processing, in which a threshold based on the road heading difference is applied to the yaw angle difference Δyaw. For example, the threshold can be set to approximately ±3 degrees based on the road heading difference. For example, if the yaw angle difference Δyaw falls within the range from (road heading difference -3 degrees) to (road heading difference +3 degrees), it is recommended to determine that the road heading difference matches the yaw angle difference Δyaw.

[0064] For example, assume that the yaw angle difference Δyaw is, for example, 1 degree when a new magnetic marker 10 is detected after passing the magnetic marker 10 with count number 4 in Fig. 7. In this case, the yaw angle difference Δyaw is within a range of ±3 degrees with respect to the road direction difference of 3 degrees for the magnetic marker 10 with count number 5 in the data map for straight travel, and therefore the control unit 32 determines that the vehicle 5 traveled without branching off from the straight-travel path at the intersection 108. In this case, the control unit 32, which is an example of a branch detection unit, selects the straight-travel data map from the three types of data maps (Fig. 8) downstream of the intersection 108, and acquires attribute information of the newly detected magnetic marker 10 (magnetic marker with count number 5).

[0065] Also, for example, assume that the yaw angle difference Δyaw is, for example, 93 degrees (−86 degrees) when a new magnetic marker 10 is detected after passing the magnetic marker 10 with count number 4 in Fig. 7. In this case, since the yaw angle difference Δyaw is outside the range of ±3 degrees with respect to the road direction difference of 3 degrees for the magnetic marker 10 with count number 5 in the straight-ahead data map, the control unit 32, which is an example of a branch detection unit, determines that the vehicle 5 has branched off from the straight-ahead path at the intersection 108.

[0066] In this case, the control unit 32 refers to the lane heading difference associated with the magnetic marker 10 with count number 5 in the right-turn and left-turn data maps (see FIG. 8). When the yaw angle difference Δyaw is 93 degrees (−86 degrees) as described above, the yaw angle difference Δyaw is within a range of ±3 degrees with respect to the lane heading difference of 95 degrees (−85 degrees) associated with the magnetic marker 10 with count number 5 in the right-turn (left-turn) data map, and therefore the control unit 32 can determine that the vehicle 5 has made a right turn (left turn) at the intersection 108. The control unit 32 acquires attribute information of the newly detected magnetic marker 10 (magnetic marker with count number 5) from the right-turn (left-turn) data map among the three types of data maps (FIG. 8) downstream of the intersection 108.

[0067] In this way, the vehicle system 1 of this example is a system that can handle a route that includes, for example, the intersection 108 in Fig. 7. This vehicle system 1 can handle vehicles that go straight at the intersection 108 as well as vehicles that turn right or left.

[0068] It is also possible to identify a branch from the lane in which the magnetic markers 10 are arranged by using the lane direction difference in Figure 8. This configuration will be explained using an example in which the magnetic marker 10 with count number 3 in the figure is detected. The lane direction difference linked to the attribute information of the magnetic marker 10 with count number 3 is 5 degrees.

[0069] Therefore, it is also possible to set a threshold value of, for example, ±3 degrees (2 degrees and 8 degrees) based on 5 degrees, which is the difference in road direction related to the magnetic marker 10 No. 3, and apply threshold processing to the yaw angle difference Δyaw when the magnetic marker 10 No. 3 is detected. For example, if the yaw angle difference Δyaw when the magnetic marker 10 No. 3 is detected is less than (or less than) 2 degrees or more than (or more than) 8 degrees, it is possible to determine that the vehicle 5 has diverged from the route on which the magnetic markers 10 are arranged.

[0070] In this way, in the configuration of this example, a branch is determined using the road direction difference, which is the angular difference (an example of a relative direction) between the lane direction (road direction) at the location of the reference magnetic marker 10T and the lane direction at the location of each magnetic marker 10. The yaw angle difference Δyaw, which is compared with this road direction difference, is not affected by missed detection of a magnetic marker 10. By comparing the road direction difference with the yaw angle difference Δyaw, a branch can be determined with high reliability even if a magnetic marker 10 is missed from detection.

[0071] It is also possible to determine whether a vehicle has branched off by using the difference in the road direction difference between two adjacent magnetic markers 10. For example, in FIG. 8, the road direction difference between the magnetic marker 10 with count number 2 is 3 degrees, and the road direction difference between the magnetic marker 10 with count number 3 is 5 degrees, resulting in a difference of 2 degrees. For example, the difference between the yaw angle yaw representing the vehicle direction when the magnetic marker 10 with count number 2 is detected and the yaw angle yaw representing the vehicle direction when the magnetic marker 10 with count number 3 is detected can be compared with the difference in road direction difference of 2 degrees. When the difference in vehicle direction does not match the difference in road direction difference, it can be determined that the vehicle has branched off. It is advisable to set an appropriate threshold value to determine whether the roads match.

[0072] In this example, a method of using a measurement signal from the IMU 22, which is an example of an orientation estimation unit, is exemplified as a method of calculating the yaw angle yaw, which indicates the vehicle orientation. The yaw angle yaw may also be calculated using the measurement value (yaw rate) of a yaw rate sensor. For example, the amount of fluctuation in the yaw angle yaw can be calculated by integrating the measurement value of the yaw rate sensor over time. The displacement of the vehicle orientation (relative orientation) relative to the vehicle direction when passing the reference point can be calculated by integrating the measurement value of the yaw rate sensor over time after passing the reference point.

[0073] In this example, the relative direction with respect to the road direction at the location of the reference magnetic marker 10T is used as the direction information of the road direction at the location of the magnetic marker 10. Alternatively, an absolute direction may be used. Furthermore, in this example, a relative direction representing a change in the direction of the vehicle 5 is used to determine whether to go straight, turn right, or turn left at an intersection 108, or to determine whether to branch off from a route, but an absolute direction of the direction of the vehicle 5 may also be used.

[0074] In this example, an intersection 108 is illustrated as a branch point where the vehicle 5 can select a route. Examples of branch points include a point where a main highway branches off onto a side road, a three-way intersection, and a junction of roads that turn off from a road where a magnetic marker 10 is installed. The other configurations and effects are the same as those of the first embodiment.

[0075] Although specific examples of the present invention have been described in detail as examples, these examples merely disclose examples of the technology encompassed by the claims. Needless to say, the scope of the claims should not be interpreted as being limited by the configurations, numerical values, etc. of the specific examples. The claims encompass technologies that are obtained by variously modifying, changing, or appropriately combining the above specific examples by utilizing publicly known technology and the knowledge of those skilled in the art. [Explanation of symbols]

[0076] 1 Vehicle Systems 10 Magnetic Markers 10T reference magnetic marker 100 lanes 100S road surface 15 RFID tags (wireless tags) 2. Measurement Unit 21 Sensor Array 212 detection processing circuit 22 IMU (Direction estimation unit) Cn magnetic sensor 32 Control unit (distance determination unit, information acquisition unit, branch detection unit) 34 Tag Reader 36 databases 39 Wheel speed sensor (distance determination section) 5 vehicles

Claims

1. A vehicle system for acquiring attribute information of magnetic markers arranged along a road while the vehicle is traveling, comprising: a magnetic sensor attached to the vehicle for detecting the magnetic marker; a distance determination unit for determining a distance traveled by the vehicle; a database that stores attribute information of the magnetic markers; an information acquisition unit that refers to the database and acquires attribute information of the magnetic marker detected by the vehicle, The database stores attribute information of each magnetic marker in association with information that can identify the distance from a reference point on the track to each magnetic marker, the information acquisition unit refers to the database using the distance specified by the distance specification unit after the vehicle has passed the reference point until the magnetic marker is detected; The information acquisition unit is a vehicle system that acquires, from the attribute information of the magnetic marker stored in the database, attribute information that is linked to information that can identify a distance that matches the distance identified by the distance identification unit after the vehicle passes the reference point until the magnetic marker is detected, as attribute information of the magnetic marker detected by the vehicle.

2. 2. The method according to claim 1, wherein the magnetic markers include a reference magnetic marker and a non-reference magnetic marker; a circuit for determining whether the magnetic marker detected by the magnetic sensor is the reference magnetic marker or the non-reference magnetic marker; A system for a vehicle, wherein the reference point is a point where the reference magnetic marker is disposed.

3. 3. The method according to claim 2, wherein a wireless tag that outputs identification information is attached to the reference magnetic marker, A vehicle system including a tag reader mounted on the vehicle for receiving the identification information from the wireless tag.

4. According to claim 1, the reference points are set at characteristic points on the course that can be identified by the structure of the course or by landmarks on the course, A vehicle system including a processing circuit mounted on the vehicle for recognizing the structure of the track or landmarks on the track.

5. 5. The vehicle system according to claim 1, wherein the attribute information of the magnetic marker includes at least location information indicating the installation location of the magnetic marker.

6. According to any one of claims 1 to 4, the database is configured to include a data map for each reference point, to which identification information of the reference point is linked and in which at least attribute information of magnetic markers arranged on a route from the reference point to another reference point downstream of the track is recorded; When a magnetic marker is detected after the vehicle passes a reference point, the information acquisition unit refers to a data map corresponding to the reference point and acquires attribute information of the magnetic marker from the attribute information recorded in the data map.

7. According to claim 6, when a branch point where a vehicle can select a route is present on the route, the data map is configured to include a data map on an upstream side of the branch point and a data map for each route on a downstream side of the branch point, A vehicle system in which one of the route-specific data maps is selected depending on the route of the vehicle at the branch point.

8. According to any one of claims 1 to 4, the attribute information of the magnetic marker is linked to orientation information that indicates an absolute orientation or a relative orientation of the running direction at the installation position of the magnetic marker, a direction estimation unit that estimates an absolute direction of the vehicle's orientation or a relative direction that indicates a change in the vehicle's orientation; a branch detection unit that detects a branch of the vehicle by comparing the direction indicated by the direction information linked to the attribute information of the magnetic marker with the direction estimated by the direction estimation unit.

9. 9. The method according to claim 8, wherein the direction information is a relative direction of the running direction at the position where the magnetic marker is disposed with respect to the running direction at the reference point, A vehicle system in which the estimated orientation by the orientation estimation unit is a relative orientation, which is the change in the orientation of the vehicle when the magnetic marker is detected, based on the orientation of the vehicle when it passed the reference point.

10. 9. The vehicle system according to claim 8, wherein the branch detection unit detects a branch for a vehicle by threshold processing in which a threshold set based on the direction indicated by the direction information linked to the attribute information of the magnetic marker is applied to the direction estimated by the direction estimation unit.

11. 5. The method according to claim 1, further comprising: a sensor diagnostic unit for diagnosing an operating state of the magnetic sensor; The database stores attribute information of the magnetic markers by linking information that can specify the distance from a reference point on the track to each magnetic marker, as well as information that can specify the ordinal number of each magnetic marker from the reference point on the track, The vehicle system is configured such that, when any magnetic marker is detected after the vehicle has passed the reference point, the sensor diagnostic unit determines whether attribute information linked to information corresponding to the distance traveled by the vehicle before detecting the magnetic marker matches or does not match attribute information linked to information corresponding to the number of times the magnetic marker was detected before detecting the magnetic marker, and diagnoses the operating state of the magnetic sensor based on the determination result.

12. 12. The vehicle system according to claim 11, wherein the sensor diagnostic unit is configured to diagnose the operating state of the magnetic sensor depending on the number or frequency of the mismatch.

13. According to claim 3, when the circuit for making the determination receives the identification information from a wireless tag attached to a magnetic marker detected by the magnetic sensor, the circuit for making the determination determines that the detected magnetic marker is the reference magnetic marker, A vehicle system that determines that a detected magnetic marker is a non-standard magnetic marker when the identification information cannot be received from a wireless tag attached to the magnetic marker detected by the magnetic sensor.

14. 7. The vehicle according to claim 6, further comprising a circuit for identifying the reference point while the vehicle is running. The data map for each reference point records attribute information of magnetic markers placed along a route from a reference point corresponding to the associated identification information as a starting point, passing another adjacent reference point on the downstream side of the track, to a second or subsequent reference point further downstream, The information acquisition unit changes the data map it references each time a new reference point is identified by the reference point identification circuit.

15. According to claim 7, the attribute information of the magnetic marker is linked to orientation information that indicates the absolute orientation or relative orientation of the running direction at the position where the magnetic marker is installed, a direction estimation unit that estimates an absolute direction of the vehicle's orientation or a relative direction that indicates a change in the vehicle's orientation; A vehicle system in which one of the route-specific data maps is selected based on a result of comparing the direction indicated by the direction information linked to the attribute information of the magnetic marker with the direction estimated by the direction estimation unit.

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