Magnetic marker, magnetic marker laying method, and azimuth estimation method

Abstract

A magnetic markers (1) laid on a travel path (10) so as to be usable for travel control of a vehicle (2), such as automatic steering control, lane departure warning, or autonomous driving, is composed of a pair of rod-shaped magnets provided with combination of a N-pole and an S-pole facing each other. The direction in which the N-pole and the S-pole positioned at both ends face each other is along a road surface (10S), and the magnetic marker (1) is embedded sideways to coincide with the direction of a travel path (1). Using a magnetic marker (1) embedded in this way makes it possible to reduce the embedding depth and suppress construction costs.

Description

Magnetic marker, magnetic marker installation method, and direction estimation method

[0001] The present invention relates to a magnetic marker that is laid on a vehicle track.

[0002] Conventionally, magnetic markers that are laid on roads so as to be detectable by vehicles have been known (see, for example, Patent Document 1). If a vehicle is capable of detecting magnetic markers, the relative position of the vehicle can be estimated using the detected magnetic marker as a reference. For example, by using magnetic markers laid along a lane as a reference, the lateral deviation of a vehicle within the lane can be measured. By utilizing the lateral deviation of a vehicle within the lane, various driving assistance systems such as automatic steering control, lane departure warning, and autonomous driving can be realized.

[0003] The following Patent Document 1 describes a columnar magnetic marker and a sheet-like magnetic marker. The columnar magnetic marker is generally embedded in a receiving hole drilled in the road surface. On the other hand, the sheet-like magnetic marker can be attached to the road surface and laid down.

[0004] Japanese Patent Application Laid-Open No. 2005-202478

[0005] However, the conventional magnetic markers have the following problems: Increasing the surface area of ​​a sheet-shaped magnetic marker to increase its magnetic force may impair the accuracy of measuring the relative position based on the magnetic marker. Furthermore, in the case of a columnar magnetic marker, increasing the magnetic force while minimizing the increase in cross-sectional area requires an increase in the axial dimension, which necessitates a deeper hole for installation, potentially increasing construction costs.

[0006] The present invention has been made in consideration of the above-mentioned conventional problems, and aims to provide a magnetic marker, a method for installing a magnetic marker, and a direction estimation method that can achieve both low construction costs and high positioning accuracy.

[0007] One aspect of the present invention is a magnetic marker that is laid on a roadway so that it can be used to control vehicle travel, and is composed of a pair of magnets with opposing north and south poles, and is laid on the roadway so that the direction in which the north and south poles face each other is along the road surface.

[0008] One aspect of the present invention is a method for laying magnetic markers on a roadway so that they can be used to control vehicle travel, wherein the magnetic markers consist of a pair of magnets with opposing north and south poles, and the magnetic markers are laid so that the direction in which the north and south poles face each other is along the road surface.

[0009] One aspect of the present invention is a method for estimating the direction of travel of a vehicle using a magnetic marker laid on a roadway, wherein the magnetic marker is made of a magnet having a pair of opposing north and south poles, and is laid on the roadway with the opposing north and south poles aligned along the road surface, the vehicle is provided with a magnetic detection circuit that detects magnetism acting from the magnetic marker, and the direction of travel of the vehicle is estimated using the results of magnetic detection by the magnetic detection circuit to measure the lateral deviation of the vehicle relative to the magnetic marker, and based on changes in the lateral deviation when the vehicle passes the magnetic marker, estimates the deviation of the vehicle's direction of travel from the opposing direction of the north and south poles of the magnetic marker.

[0010] The magnetic marker of the present invention is composed of a pair of magnets with opposing north and south poles, and is installed on a road with the opposing north and south poles aligned along the road surface. Because this magnetic marker is installed horizontally, there is no need to drill deep holes, which reduces installation costs.

[0011] According to the magnetic marker of the present invention, the traveling direction of a vehicle can be estimated using only one magnetic marker, without using the lateral deviation relative to other magnetic markers. When a vehicle passes this magnetic marker, the lateral deviation of the vehicle changes. Based on the change in lateral deviation when the vehicle passes the magnetic marker, it is possible to estimate the deviation of the traveling direction of the vehicle relative to the direction in which the north and south poles face each other.

[0012] 1 is a perspective view of a magnetic marker; a perspective view of a receiving hole drilled in a road surface; an explanatory diagram showing the cross-sectional structure of a road; an explanatory diagram of a vehicle traveling on a road; a structural diagram of a sensor unit; a graph illustrating an example of a change in magnetic measurement value Gv (sum) when passing a magnetic marker; a graph illustrating an example of a change in magnetic measurement value Gt (sum) when passing a magnetic marker; a graph illustrating an example of an approximation curve of the distribution of magnetic measurement values ​​Gt by each magnetic sensor when the sensor unit is located at the midpoint of the magnetic marker; a graph illustrating an example of an approximation curve of the distribution of magnetic measurement values ​​Gv by each magnetic sensor when the sensor unit is located at the north pole of the magnetic marker; a graph illustrating an example of an approximation curve of the distribution of magnetic measurement values ​​Gv by each magnetic sensor when the sensor unit is located at the south pole of the magnetic marker; an explanatory diagram of a method for estimating the angular deviation of a vehicle's traveling direction from the direction of the road.

[0013] The embodiments of the present invention will be specifically described using the following examples. (Example 1) This example relates to a magnetic marker 1. The contents of this example will be described using Figs. 1 to 11.

[0014] 1 and 2, the magnetic marker 1 is a rod-shaped magnetic marker made up of a pair of magnets with a north pole and a south pole facing each other. The magnetic marker 1 is embedded in a receiving hole 100 drilled in the road surface 10S (the surface of the track 10). The magnetic markers 1 are placed along the track 10, for example, at intervals of 5 m.

[0015] The magnet that makes up the magnetic marker 1 is a round bar magnet with a diameter of 20 mm and a length of 500 mm. The magnetic marker 1 may be the magnet itself, a magnet with a coating material applied to its outer surface, or a magnet housed in a resin case, for example. The round bar magnet has opposite magnetic poles at both ends, with the north and south poles facing each other longitudinally. The magnet is a ferrite plastic magnet in which iron oxide magnetic powder, a magnetic material, is dispersed in a polymeric base material, and has a maximum energy product (BHmax) of 6.4 kJ / cubic meter.

[0016] The storage hole 100 (Fig. 2) that stores the magnetic marker 1 is a long hole that runs along the direction of the track 10. The bottom of the storage hole 100 has a fixed depth of 100 mm. The magnetic marker 1 is placed horizontally on the bottom of the storage hole 100 so that the direction from the north pole to the south pole coincides with the direction of the track 10. Note that in each figure, including Fig. 2, that shows the magnetic marker 1 together with the vehicle 2 or the track 10, the size of the magnetic marker 1 is illustrated larger than it actually is.

[0017] Here, the cross-sectional structure of the road forming the track 10 will be explained. As shown in Figure 3, the cross-sectional structure of a road paved with a paving material such as asphalt has a three-layer structure consisting of a roadbed 10C made of compacted soil, a road base 10B made of granular material such as crushed stone or crushed run, and a surface layer 10A made of a heated asphalt mixture. The surface layer 10A is approximately 50 mm thick, and the road base 10B is approximately 100 mm thick. The surface layer 10A is layered on top of the lower layer, the road base 10B.

[0018] As mentioned above, the storage hole 100 for the magnetic marker 1 is 100 mm deep. The diameter of the magnetic marker 1 is 20 mm. The buried magnetic marker 1 is located in a range of 80 to 100 mm deep. This depth of 80 to 100 mm is the depth of the roadbed 10B beyond the surface layer 10A, which is approximately 50 mm thick.

[0019] Next, the vehicle 2 (FIG. 4) using the magnetic marker 1 is, for example, a typical passenger car, with a width of 1.8 m and a length of 4.5 m. The vehicle 2 has operating mechanisms such as a steering wheel, accelerator, and brake. The vehicle 2 is equipped with a plurality of actuators (not shown) that drive these operating mechanisms, and a control unit 20 that controls these actuators. The vehicle 2 can be manually driven by a driver, and can also be automatically driven under the control of the control unit 20. The vehicle 2 can automatically drive using the magnetic marker 1 laid along the road 10. The vehicle 2 is controlled by the control unit 20 to steer so as to suppress lateral deviation from the magnetic marker 1.

[0020] The vehicle 2 is equipped with a sensor unit 3 (Figure 5) for detecting the magnetic marker 1. The sensor unit 3 is a rod-shaped unit in which 15 magnetic sensors C1 to C15 are arranged in a straight line. The 15 magnetic sensors C1 to C15 are spaced at equal intervals of 10 cm. The sensor unit 3 is attached, for example, to the inside of the front bumper of the vehicle 2, with its longitudinal direction aligned with the vehicle width direction. In the case of the vehicle 2 in this example, the attachment height of the sensor unit 3 relative to the road surface 10S is 200 mm. The magnetic sensor C1 is located on the left side of the vehicle 2, and the magnetic sensor C15 is located on the right side of the vehicle 2.

[0021] The sensor unit 3 includes a combination of 15 magnetic sensors Cn (n is an integer between 1 and 15) and a signal processing circuit 30 incorporating a CPU (not shown). The sensor unit 3 is an example of a magnetic detection circuit. The magnetic sensors Cn are sensors that detect magnetism using the well-known MI (Magneto-Impedance) effect. The MI effect is a magnetic effect in which the impedance of a magnetically sensitive material such as amorphous wire changes sensitively in response to an external magnetic field. Each magnetic sensor Cn incorporates two amorphous wires that are perpendicular to each other. The magnetic sensors Cn detect magnetic components acting along the longitudinal direction of each amorphous wire and output a sensor signal representing the magnitude of the magnetic component (magnetic measurement value).

[0022] In the sensor unit 3, the axial direction (longitudinal direction) of the two amorphous wires is the same for all 15 magnetic sensors Cn. The sensor unit 3 is attached to the vehicle 2 so that the two amorphous wires of each magnetic sensor Cn are aligned along the traveling direction and the vertical direction. The vertical direction is an example of a direction perpendicular to the traveling direction.

[0023] The signal processing circuit 30 (FIG. 5) is a circuit that executes various processes such as marker detection processing for detecting the magnetic marker 1. The signal processing circuit 30 executes various processes by processing the sensor signals of the magnetic sensors Cn. The sensor signals processed by the signal processing circuit 30 are signals that represent a magnetic measurement value Gv that indicates the magnitude of the magnetic component acting along the vertical direction, and a magnetic measurement value Gt that indicates the magnitude of the magnetic component acting along the traveling direction.

[0024] The signal processing circuit 30 is configured to store the magnetic measurement values ​​Gv, Gt obtained by the magnetic sensor Cn over a predetermined time period in the past, and executes various processes using the magnetic measurement values ​​Gv, Gt obtained over the predetermined time period in the past.

[0025] In addition to the marker detection process, the signal processing circuit 30 also performs a process of measuring the lateral deviation with respect to the magnetic marker 1 and a process of measuring the traveling direction of the vehicle 2. The signal processing circuit 30 inputs the results of these processes to the control unit 20. The control unit 20 uses the processing results of the signal processing circuit 30 to perform vehicle control such as automatic steering control for lane keeping, lane departure warning, and automatic driving.

[0026] Next, a method for installing the magnetic marker 1 and a method for using the magnetic marker 1 by the vehicle 2 will be described. (Magnetic Marker Installation Method) When installing the magnetic marker 1, first, a storage hole 100 (FIG. 2) is drilled in the road surface 10S. The storage hole 100 is a hole for storing the magnetic marker 1. The storage hole 100 containing the magnetic marker 1 is backfilled with granular material such as crushed stone or crushed run to a depth of 50 mm from the road surface 10S. The area 50 mm deep from the road surface 10S is backfilled with a heated asphalt mixture. This allows a layered structure of the roadbed 10B and the surface layer 10A to be formed inside the storage hole 100. In addition, the surface of the storage hole 100 is finished in the same manner as the surrounding road surface 10S.

[0027] Here, we will explain road repair. When a road is operated for a long period of time, defects such as potholes can occur on the road surface 10S. A pothole is a hole that occurs when part of the surface layer 10A (Figure 3) made of a heated asphalt mixture peels off from the road surface. Potholes can be repaired, for example, by repaving the road surface 10S. Repaving is a repair process that involves removing the deteriorated surface layer 10A to expose the roadbed 10B and laying a new surface layer 10A made of paving material such as asphalt. By laying a new surface layer 10A through repaving, a defect-free road surface 10S can be restored. As described above, the magnetic marker 1 in this example is embedded in the roadbed 10B. Therefore, the magnetic marker 1 in this example is not dug up during repaving and does not need to be reapplied every time repaving is performed. The magnetic marker 1 can be used for a long period of time.

[0028] (Method of Using Magnetic Markers by Vehicles) The vehicle 2 detects the magnetic marker 1 while traveling. Then, it measures the lateral deviation from the detected magnetic marker 1, estimates the traveling direction of the vehicle 2, etc. Below, the contents of (1) the marker detection process, (2) the process of measuring the lateral deviation from the magnetic marker, and (3) the process of estimating the traveling direction of the vehicle will be described.

[0029] (1) Marker Detection Process While the vehicle 2 is traveling, it repeatedly executes the marker detection process at a frequency of, for example, 3 kHz. For example, when passing a magnetic marker 1, the sum of the magnetic measurement values ​​Gv (magnetic measurement values ​​in the vertical direction) obtained by the 15 magnetic sensors Cn changes as shown in Figure 6. In this figure, the magnetic field acting from the north pole is considered positive, and the magnetic field acting from the south pole is considered negative.

[0030] As described above, the round rod-shaped magnetic marker 1 in this example is installed horizontally so that the direction from the north pole to the south pole coincides with the direction of the track 10. When the vehicle 2 approaches the magnetic marker 1 (FIG. 6), the magnetism of the north pole first acts on the sensor unit 3. The sum of the magnetic measurement values ​​Gv (vertical magnetic measurement values) of the 15 magnetic sensors Cn gradually increases in the positive direction as the sensor unit 3 approaches the north pole of the magnetic marker 1, reaching a positive peak at the position of the north pole. After that, when the sensor unit 3 reaches the midpoint 1M of the magnetic marker 1 in the longitudinal direction, the magnetic measurement value Gv (sum) becomes zero. After passing the midpoint 1M, as the sensor unit 3 approaches the south pole, the magnetic measurement value Gv (sum) gradually increases in the negative direction, reaching a negative peak at the position of the south pole. After that, as the sensor unit 3 passes the south pole, the magnetic measurement value Gv (sum) gradually decreases to zero. In this way, a zero cross occurs at the midpoint 1M of the magnetic marker 1 in the change in the magnetic measurement value Gv (sum) in the direction of travel.

[0031] Furthermore, when the vehicle 2 passes the magnetic marker 1, the sum of the magnetic measurement values ​​Gt (magnetic measurement values ​​in the direction of travel) obtained by the 15 magnetic sensors Cn changes as shown in Figure 7. In this figure, the magnetic field directed from the north pole to the south pole is considered positive, and the magnetic field directed from the south pole to the north pole is considered negative. The distribution of the magnetic measurement values ​​Gt (sum) in the direction of travel peaks at the midpoint 1M of the magnetic marker 1 and forms a mountain-shaped distribution in which the values ​​decrease toward the north pole or south pole at either end.

[0032] The magnetic marker 1 can be detected by focusing on the above-described changes in the magnetic measurement value Gv ( FIG. 6 ) and the magnetic measurement value Gt ( FIG. 7 ) when the sensor unit 3 passes the magnetic marker 1. For example, the detection condition for the magnetic marker 1 can be set such that the magnetic measurement value Gv (sum) crosses zero and the magnetic measurement value Gt (sum) reaches a peak.

[0033] (2) Process for Measuring Lateral Deviation from Magnetic Marker According to the above detection conditions, when the sensor unit 3 is positioned at the midpoint 1M of the magnetic marker 1, the magnetic marker 1 can be detected. At this time, the magnetic measurement values ​​Gt of the magnetic sensors C1 to C15 are distributed in the vehicle width direction as shown in Figure 8. In this figure, the distribution of the magnetic measurement values ​​Gt by each magnetic sensor Cn is shown by an approximate curve. In this figure, the left side corresponds to the left side of the vehicle 2, and the right side corresponds to the right side of the vehicle 2.

[0034] The position of the peak in the vehicle width direction in the distribution of the magnetic measurement value Gt in Figure 8 indicates the position of the magnetic marker 1. For example, if the vehicle 2 deviates to the right relative to the magnetic marker 1, the position of the peak in the vehicle width direction will be shifted to the left in the figure. For example, if the vehicle 2 deviates to the left relative to the magnetic marker 1, the position of the peak in the vehicle width direction will be shifted to the right in the figure. In this way, by identifying the position of the peak in the vehicle width direction, it is possible to measure the lateral deviation of the vehicle 2 relative to the magnetic marker 1.

[0035] (3) Estimation of vehicle traveling direction The magnetic marker 1 of this example can be used to estimate the traveling direction of the vehicle 2. Below, we will explain how to estimate the angular deviation of the traveling direction of the vehicle 2 from the direction of the road 10. In the configuration of this example, the magnetic marker 1 in the form of a round rod is laid along the direction of the road 10. The angular deviation of the traveling direction of the vehicle 2 from the longitudinal direction of the magnetic marker 1 matches the angular deviation of the traveling direction of the vehicle 2 from the direction of the road 10.

[0036] As described above with reference to Figure 6, when the sensor unit 3 is located at the north pole of the magnetic marker 1, the magnetic measurement value Gv (sum) reaches a positive peak. By detecting a positive peak of the magnetic measurement value Gv (sum), the first point in time at which the sensor unit 3 is located at the north pole of the magnetic marker 1 can be identified. Furthermore, when the sensor unit 3 is located at the south pole of the magnetic marker 1, the magnetic measurement value Gv (sum) reaches a negative peak. By detecting a negative peak of the magnetic measurement value Gv (sum), the second point in time at which the sensor unit 3 is located at the south pole of the magnetic marker 1 can be identified.

[0037] The distribution of the magnetic measurement values ​​Gv of each magnetic sensor Cn at the first time point is as shown in Figure 9. The distribution of the magnetic measurement values ​​Gv of each magnetic sensor Cn at the second time point is as shown in Figure 10. Based on Figures 9 and 10, the lateral deviation Of1 of the vehicle 2 relative to the north pole of the magnetic marker 1 (an example of a first lateral deviation; see Figure 11) and the lateral deviation Of2 of the vehicle 2 relative to the south pole (an example of a second lateral deviation; see Figure 11) can be measured using a method similar to that described with reference to Figure 8.

[0038] From the lateral deviations Of1 and Of2 relative to the north and south poles at different positions in the direction of the road 10, the angular deviation R of the traveling direction Dir of the vehicle 2 relative to the direction Mx of the road 10 can be estimated, as shown in Figure 11. The angular deviation R can be calculated using the amount of change Ofd in the lateral deviation relative to the magnetic marker 1 while passing through the magnetic marker 1. The amount of change Ofd in the lateral deviation can be calculated as the difference between the lateral deviations Of1 and Of2, as shown in Equation 1. Ofd = Of1 - Of2 (Equation 1)

[0039] The angular deviation R of the traveling direction of the vehicle 2 relative to the longitudinal direction of the magnetic marker 1 can be calculated using Equation 2, which includes the ratio (Ofd / S) of the change (difference) in lateral deviation Ofd to the length S of the magnetic marker (500 mm in this example). R = arctan(Ofd / S) (Equation 2)

[0040] As described above, the magnetic marker 1 of this example is a magnetic marker that has a pair of opposing north and south poles. The magnetic marker 1 is laid on the track 10 with the opposing direction of the north and south poles (magnetization direction) aligned with the road surface 10S. Because this magnetic marker 1 is laid horizontally, there is no need to drill deep holes, which reduces construction costs. For example, even if the axial dimension of the magnetic marker 1 is increased to strengthen the magnetic force, there is no need to deepen the storage hole 100.

[0041] When a rod-shaped magnetic marker 1 is buried vertically, the occupying range in the depth direction becomes longer. For example, if the magnetic marker 1 is to be buried deeper than the surface layer 10A that will be renewed by repaving, it is necessary to drill a deeper storage hole. Furthermore, when a rod-shaped magnetic marker 1 is buried vertically, depending on the length of the magnetic marker 1, there is a risk that it will not fit into the layer of the roadbed 10B and may end up reaching the roadbed 10C. In contrast, if the magnetic marker 1 is laid horizontally along the road surface 10S, such construction inconveniences can be avoided.

[0042] According to the magnetic marker 1 of this example, it is possible to estimate the traveling direction of the vehicle 2 using only one magnetic marker 1, without using the lateral deviation relative to other magnetic markers. When the vehicle 2 passes by the magnetic marker 1 of this example, the lateral deviation may change. For example, based on the temporal change in the lateral deviation, such as a change from the lateral deviation relative to the north pole to the lateral deviation relative to the south pole, it is possible to estimate the deviation of the traveling direction of the vehicle 2 based on the opposing direction of the north pole and the south pole.

[0043] In this example, a magnetic marker 1 having a length of 500 mm is illustrated. The length of the magnetic marker 1 may be in the range of 100 to 500 mm, including the 500 mm length in this example. If the length of the magnetic marker 1 is less than 100 mm, the magnetic field loop formed between the north and south poles at both ends becomes small. A smaller magnetic field loop reduces the magnetic field acting at higher positions, potentially making detection by a magnetic sensor attached to the underside of the vehicle difficult. On the other hand, if the length of the magnetic marker 1 exceeds 500 mm, the magnetic field loop formed between the north and south poles at both ends becomes excessively large, resulting in a decrease in magnetic flux density at a low position near the center of the magnetic marker (around the midpoint between the north and south poles). If the magnetic sensor is attached at a relatively low position, it may become difficult to detect characteristic magnetic changes, such as the change in the magnetic measurement value Gv illustrated in FIG. 6 or the change in the magnetic measurement value Gt illustrated in FIG. 7. The magnetic marker 1 has north and south poles at both ends. Therefore, the length of the magnetic marker 1 is the distance between the north pole and the south pole of the magnetic source.

[0044] In this example, the magnetic marker 1 is buried to a depth of 100 mm. The magnetic marker 1 may be buried to a depth of 0 to 500 mm. If the burial depth exceeds 500 mm, the magnetic flux density on the surface side of the road may become small, making detection by a magnetic sensor difficult.

[0045] In this example, the magnetic marker 1 has a circular cross section, but the cross section may be polygonal. Instead of the magnetic marker 1 made of a rod-shaped magnet, a magnetic marker made of a strip-shaped (tape-shaped) magnet may be used. The strip-shaped magnet may have a north pole and a south pole at both ends.

[0046] The sensor unit 3 of this example can detect both a magnetic component acting along the direction of travel and a magnetic component acting along the vertical direction. The sensor unit may also be capable of detecting magnetic components including a magnetic component acting along the direction of travel and a magnetic component acting in the vertical direction. A magnetic sensor equipped with a magnetic sensor that is oblique to both the direction of travel and the vertical direction can detect a composite component of the magnetic component acting along the direction of travel and the magnetic component acting in the vertical direction. If the orientation of the magnetic sensor is known, the magnetic component acting along the direction of travel and the magnetic component acting in the vertical direction can be identified based on this composite component. Preferably, the angle of obliqueness relative to the direction of travel and the angle of obliqueness relative to the vertical direction are set to be approximately the same.

[0047] Furthermore, instead of a combination of the traveling direction and the vertical direction, the sensor unit may be capable of detecting a magnetic component acting along the traveling direction and a magnetic component acting along the vehicle width direction (lateral direction).The sensor unit may be capable of detecting a magnetic component acting along the traveling direction, a magnetic component acting along the vertical direction, and a magnetic component acting along the vehicle width direction.

[0048] In this example, the deviation of the traveling direction of the vehicle 2 from the direction of the road 10 (angular deviation R in FIG. 11 ) is estimated. Alternatively, it is also possible to repeatedly measure the lateral deviation while the sensor unit 3 passes the magnetic marker 1. For example, at the midpoint 1M of the magnetic marker 1, the magnetic measurement value Gv becomes a small value (zero crossing), but the magnetic measurement value Gt becomes a peak. Also, at the north pole or south pole of the magnetic marker 1, the magnetic measurement value Gt becomes a small value, but the magnetic measurement value Gv becomes a positive or negative peak.

[0049] Therefore, it is also possible to calculate the sum of squares of the magnetic measurement values ​​Gv and Gt for each magnetic sensor Cn. The distribution of this sum of squares in the vehicle width direction (the distribution of the sum of squares for each magnetic sensor Cn) has a large peak directly above the magnetic marker 1 at each position throughout the longitudinal direction, regardless of the position in the longitudinal direction (the direction in which the north and south poles face each other; the magnetization direction) of the round bar-shaped magnetic marker 1. By identifying the position in the vehicle width direction of the peak of the sum of squares of the magnetic measurement values ​​Gv and Gt, it is also possible to measure the lateral deviation at each position throughout the longitudinal direction, regardless of the longitudinal position of the magnetic marker 1. It is also possible to calculate the degree of change in lateral deviation according to the movement distance when the sensor unit 3 passes the magnetic marker 1, i.e., the change in positional lateral deviation, as the deviation of the traveling direction of the vehicle 2 relative to the direction of the road 10. The value of the change in positional lateral deviation may be multiplied by a control gain to control the steering angle of the vehicle 2.

[0050] 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.

[0051] REFERENCE SIGNS LIST 1 Magnetic marker 10 Track 100 Storage hole 10A Surface layer 10B Roadbed 10C Roadbed 10S Road surface 2 Vehicle 20 Control unit 3 Sensor unit (magnetic detection circuit) 30 Signal processing circuit

Claims

1. A magnetic marker that is laid on a roadway so that it can be used to control vehicle travel, and is composed of a pair of magnets with opposing north and south poles, and is laid on the roadway so that the direction in which the north and south poles face each other is along the road surface.

2. In claim 1, the track is a track in which the direction of vehicle travel is determined, and the magnetic marker is installed so that the direction in which the north and south poles face each other is along the direction of the track.

3. A magnetic marker according to claim 1 or 2, wherein the magnet is a rod-shaped or strip-shaped magnet with a north pole end and a south pole end at both ends.

4. A magnetic marker according to claim 3, wherein the distance between the north pole and the south pole is 100 mm to 500 mm.

5. A method for laying magnetic markers on roads so that they can be used to control vehicle travel, wherein the magnetic markers are made of a pair of magnets with opposing north and south poles, and the magnetic markers are laid so that the direction in which the north and south poles face each other is along the road surface.

6. A method according to claim 5, wherein the track is a track in which the direction of vehicle travel is determined, and the magnetic markers are installed so that the direction in which the north and south poles face each other is along the direction of the track.

7. A method of laying magnetic markers as set forth in claim 5 or 6, wherein the track is a paved road, with a surface layer made of paving material forming the road surface laminated on a lower layer, and the magnetic markers are disposed beyond the surface layer and on the lower layer.

8. A method for estimating the direction of travel of a vehicle using a magnetic marker laid on a roadway, wherein the magnetic marker is composed of a magnet with a pair of opposing north and south poles, and is laid on the roadway with the opposing north and south poles aligned with the road surface, the vehicle is equipped with a magnetic detection circuit that detects the magnetic field acting from the magnetic marker, the method comprising: measuring the lateral deviation of the vehicle relative to the magnetic marker using the magnetic detection results from the magnetic detection circuit; and estimating the deviation of the vehicle's direction of travel relative to the opposing direction of the north and south poles of the magnetic marker based on changes in the lateral deviation as the vehicle passes the magnetic marker.

9. A direction estimation method according to claim 8, wherein the one magnetic marker is installed so that the direction in which the north pole and south pole face each other coincides with the direction of the track.

10. A direction estimation method as claimed in claim 9, wherein the magnetic detection circuit is capable of acquiring a magnetic measurement value Gv acting in the vertical direction and a magnetic measurement value Gt acting in the direction of travel of the vehicle, and the one magnetic marker is detected when the positive and negative signs of the magnetic measurement value Gv are reversed and the magnetic measurement value Gt reaches a positive or negative peak.

11. A direction estimation method as claimed in claim 9, wherein the magnetic detection circuit is capable of acquiring magnetic measurement values ​​Gv acting in the vertical direction and magnetic measurement values ​​Gt acting in the direction of travel of the vehicle at multiple locations in the vehicle width direction, and the process of measuring the lateral deviation measures the lateral deviation of the vehicle relative to the one magnetic marker by identifying the maximum value in the distribution of the square sums of the magnetic measurement values ​​Gv and Gt in the vehicle width direction.

12. A heading estimation method according to claim 11, wherein the lateral deviation of the vehicle relative to said one magnetic marker is measured at each position over the entire range in the direction in which said north pole and south pole face each other.

13. A direction estimation method according to claim 8, wherein the magnet is a rod-shaped or strip-shaped magnet with a north pole end and a south pole end at both ends, and the distance between the north pole and the south pole is 100 mm to 500 mm.

14. A heading estimation method as set forth in any one of claims 8 to 13, wherein the lateral deviation measuring process measures a first lateral deviation from the north pole of the one magnetic marker and a second lateral deviation from the south pole of the one magnetic marker, and the estimation process estimates the deviation in the vehicle's direction of travel based on the ratio of the difference between the first lateral deviation and the second lateral deviation to the length of the one magnetic marker.

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