Sensor block for magnetic measurement

Abstract

A magnetism measurement device according to the present invention includes: a first magnetic sensor (An) that detects magnetism acting along a first direction, the first direction being chosen arbitrarily; a second magnetic sensor (Bn) that detects magnetism acting along a second direction, the second direction crossing the first direction along which the first magnetic sensor detects magnetism; and a magnetic-field generating part (Cn) that generates a magnetic field in response to a flow of current. The magnetic-field generating part (Cn) is incorporated such that magnetism act along the first direction and the second direction in response to a flow of current in a state where the positions thereof facing the first magnetic sensor (An) and the second magnetic sensor (Bn) are fixed.

Description

Technical Field

[0001] The present invention relates to a magnetic measurement device including a magnetic sensor for measuring magnetism.

Background Art

[0002] Conventionally, a method has been proposed for detecting magnetic markers arranged on a road using a plurality of magnetic sensors attached to a vehicle (see, for example, Patent Document 1 below). In this method, the influence of external magnetic fields is suppressed by obtaining the difference between the magnetic measurement values of two or more of the plurality of magnetic sensors, and an attempt is made to improve the detection accuracy of magnetic markers. When obtaining the difference between the magnetic measurement values of two or more magnetic sensors, an error in the magnetic measurement value due to variations in the characteristics of the magnetic sensors can be amplified by the difference operation and become a large error.

[0003] Therefore, a magnetic measurement device incorporating a calibration function for magnetic sensors has been proposed (see, for example, Patent Document 2 below). The magnetic sensor included in this magnetic measurement device is a MI (Magneto Impedance) sensor in which a detection coil is externally inserted with respect to an amorphous wire forming a magnetosensitive body. In this magnetic field measurement device, a magnetic field generating coil is arranged in series with respect to the detection coil. By using the magnetic field generating coil, it becomes possible to calibrate the magnetic sensor at any time even during the operation of the magnetic field measurement device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional magnetic measuring devices described above have the following problems. Specifically, in the case of a magnetic measuring device that requires multiple directions for detecting magnetism, it becomes necessary to provide a magnetic field generating coil for each detection direction, which leads to increased costs. Furthermore, if multiple magnetic field generating coils are provided, variations in the magnetic output characteristics of the magnetic field generating coils can become a problem.

[0006] This invention has been made in view of the aforementioned conventional problems, and aims to provide a magnetic measuring device having multiple magnetic detection directions, which is easy to calibrate and cost-effective. [Means for solving the problem]

[0007] The present invention provides a first magnetic sensor for detecting a magnetism acting along any first direction, A second magnetic sensor detects a magnetism acting along a second direction intersecting the first direction in which the first magnetic sensor detects magnetism, It has a magnetic field generating unit that generates a magnetic field in response to the application of electricity, The magnetic field generating unit is located in a magnetic measuring device that is fixed in position relative to the first magnetic sensor and the second magnetic sensor, and is configured to apply magnetism along the first and second directions in response to the application of current. [Effects of the Invention]

[0008] The magnetic measuring device of the present invention comprises a magnetic field generating unit in addition to first and second magnetic sensors whose magnetic detection directions intersect with each other. This magnetic field generating unit can apply magnetism in both directions, corresponding to the direction in which the first magnetic sensor detects magnetism and the direction in which the second magnetic sensor detects magnetism, depending on the application of current. This magnetic field generating unit can be used for calibration of the first and second magnetic sensors.

[0009] According to the magnetic measuring device of the present invention, the first magnetic sensor and the second magnetic sensor can be calibrated by sharing a magnetic field generating unit. This magnetic measuring device is cost-effective because it does not require a separate magnetic field generating unit for calibration for the first and second magnetic sensors. Furthermore, in the magnetic measuring device of the present invention, since the magnetic field generating unit is shared between the first magnetic sensor and the second magnetic sensor, problems caused by variations in the magnetic output characteristics of the magnetic field generating unit for calibrating the first magnetic sensor and the magnetic field generating unit for calibrating the second magnetic sensor do not occur. [Brief explanation of the drawing]

[0010] [Figure 1] Front view of the vehicle with the sensor array attached in Example 1. [Figure 2] An overhead view showing a vehicle on a lane equipped with a magnetic marker in Example 1. [Figure 3] A block diagram showing the configuration of the sensor array in Example 1. [Figure 4] A block diagram showing the configuration of the magnetic sensor and calibration circuit in Example 1. [Figure 5] A diagram illustrating the positional relationship between the magnetic sensor and the magnetic field generating coil in Example 1. [Figure 6] A diagram illustrating the apparatus for performing the processing under maintenance mode in Example 1. [Figure 7] A flowchart showing the process for detecting a magnetic marker in Example 1. [Figure 8] A graph showing the temporal change in the magnetic measurement value (sum) of magnetic sensor An as it passes through the magnetic marker in Example 1. [Figure 9] A graph showing the change in the magnetic measurement value of magnetic sensor Bn when the sensor array is positioned directly above the magnetic marker in Example 1. [Figure 10] A flowchart showing the processing flow under maintenance mode in Example 1. [Figure 11] A flowchart showing the processing flow under normal mode in Example 1. [Figure 12] Explanatory drawing of the calibration process of the magnetic sensor in Example 1 (sensor output characteristics of the magnetic sensor before calibration). [Figure 13] Explanatory drawing of the calibration process of the magnetic sensor in Example 1 (sensor output characteristics of the magnetic sensor after calibration). [Figure 14] Explanatory drawing of another positional relationship between the magnetic sensor and the magnetic field generating coil in Example 2. [Figure 15] Explanatory drawing of another positional relationship between the magnetic sensor and the magnetic field generating coil in Example 2. [Figure 16] Explanatory drawing of another positional relationship between the magnetic sensor and the magnetic field generating coil in Example 2. [Figure 17] Explanatory drawing of another positional relationship between the magnetic sensor and the magnetic field generating coil in Example 3. [Figure 18] Explanatory drawing of another positional relationship between the magnetic sensor and the magnetic field generating coil in Example 3.

Mode for Carrying Out the Invention

[0011] The embodiments of the present invention will be specifically described using the following examples. (Example 1) This example relates to a marker detection device 1 for detecting a magnetic marker 10 disposed on a road. This content will be described using FIGS. 1 to 13.

[0012] The marker detection device 1 is an in-vehicle device incorporated in a vehicle 5 for detecting a magnetic marker 10 disposed on a road, as shown in FIGS. 1 and 2, and constitutes an example of a magnetic measurement device. The magnetic marker 10 is disposed on the road surface 100S, for example, along the center of the lane 100 on which the vehicle 5 travels. The magnetic marker 10 has, for example, a cylindrical shape with a diameter of 20 mm and a height of 28 mm, and is accommodated and embedded in a housing hole 100H drilled in the road surface 100S.

[0013] (1) Configuration of the marker detection device As shown in Figures 1 and 2, the marker detection device 1 is a device that combines a sensor array 11 in which multiple magnetic sensors are arranged, and a detection unit 12 that incorporates a CPU (central processing unit) and the like (not shown).

[0014] The sensor array 11 is a rod-shaped unit in which multiple magnetic sensors are arranged in a straight line. The sensor array 11 is mounted on the vehicle floor 50, which is the bottom surface of the vehicle 5. In the case of the vehicle 5 in this example, the mounting height is approximately 200 mm relative to the road surface 100S. The sensor array 11 incorporates a magnetic sensor that detects magnetism in the direction of travel and a magnetic sensor that detects magnetism in the vehicle width direction.

[0015] The detection unit 12 is a unit that processes the sensor signals output by the sensor array 11 to detect the magnetic marker 10. The detection result from the detection unit 12 is input to, for example, an ECU (not shown) on the vehicle 5 side and used for various controls such as automatic steering control and lane departure warning to keep the vehicle 5 in the lane 100. The configurations of the detection unit 12 and the sensor array 11 will be described in order below.

[0016] (1.1) Configuration of the detection unit The detection unit 12 (Figure 3) is a unit that includes a CPU for performing various calculations, as well as an electronic circuit board (not shown) on which memory elements such as ROM and RAM are mounted. The detection unit 12 includes a marker detection circuit for detecting the magnetic marker 10, and a lateral displacement measurement circuit for measuring the amount of lateral displacement of the vehicle 5 relative to the detected magnetic marker 10. (1.2) Sensor array configuration In the sensor array 11, as shown in Figure 3, sensor blocks Sn (where n is an integer from 1 to 15), each incorporating a magnetic sensor An·Bn, are arranged in a straight line. The sensor array 11 is mounted along the width of the vehicle, with sensor block S1 located on the left side of the vehicle 5 (passenger side in a right-hand drive vehicle) and arranged in numerical order towards the right. The spacing between sensor blocks Sn in the sensor array 11 is set to 10 cm. The sensor array 11 consists of 15 sensor blocks Sn, as well as a calibration circuit 110. Each sensor block Sn is an electronic component that incorporates a pair of magnetic sensors An·Bn and a magnetic field generating coil Cn into a single chip. Each sensor block Sn can also be considered as a magnetic sensor with the magnetic sensors An·Bn incorporated into it. In this case, the magnetic sensors An·Bn can also be considered as sensor elements.

[0017] The sensor array 11 is equipped with 15 output ports so that the sensor signals of each sensor block Sn can be output simultaneously. The sensor signals represent the magnetic measurement values ​​of magnetic sensor An and magnetic measurement values ​​of magnetic sensor Bn. The sensor array 11 performs magnetic measurement in response to the control signal from the detection unit 12 and inputs the sensor signals to the detection unit 12. As will be described in more detail later, the detection unit 12 inputs a control signal to the sensor array 11 each time it acquires a pulse signal output from the vehicle 5 side in accordance with the rotation of the wheels. The pulse signal is output each time the wheel rotates by an angle corresponding to a distance of, for example, 30 mm.

[0018] In the sensor array 11, 15 sensor blocks Sn are arranged in a straight line, thereby realizing a configuration in which 15 magnetic sensors An and Bn are arranged in a straight line. Furthermore, by employing sensor blocks Sn with a magnetic field generating coil Cn incorporated into them, a configuration in which a magnetic field generating coil Cn is individually attached to each magnetic sensor An and Bn is realized. Each sensor block Sn incorporates electronic circuits such as a pulse circuit 22 and a signal processing circuit 24, which will be described later. Two systems of electronic circuits such as the pulse circuit 22 and the signal processing circuit 24 are provided to correspond to magnetic sensors An and Bn. Alternatively, one system of electronic circuits may be provided, while the electronic circuits are shared between magnetic sensors An and Bn using time-division multiplexing.

[0019] One of the two magnetic sensors An·Bn (Figure 3) is an example of a first magnetic sensor that detects magnetism acting in either of the first directions, and the other is an example of a second magnetic sensor that detects magnetism acting in a second direction intersecting the first direction in which the first magnetic sensor detects magnetism. The magnetic sensors An·Bn in this example are capable of measuring magnetic components acting in mutually orthogonal directions. Each sensor block Sn is incorporated into the sensor array 11 such that, when the sensor array 11 is mounted on a vehicle, magnetic sensor An measures the magnetic component acting in the direction of travel, and magnetic sensor Bn measures the magnetic component acting in the vehicle width direction. The direction of travel and the vehicle width direction are examples of the first or second direction described above.

[0020] Each sensor block Sn's magnetic sensor An·Bn is a magnetic sensor constructed using an MI (Magneto-Impedance) element, as shown in Figure 4, which includes an amorphous wire (magnetic wire) 20 made of a CoFeSiB alloy with nearly zero magnetostriction, and a pickup coil (coil) 21 wound around this amorphous wire 20.

[0021] The An·Bn magnetic sensor is a highly sensitive sensor with a magnetic flux density measurement range of ±0.6 millitesla and a magnetic flux resolution of 0.02 microtesla within the measurement range. This high sensitivity is achieved by the MI effect, in which the impedance of the amorphous wire 20 changes sensitively in response to the external magnetic field.

[0022] The MI element detects the magnetism acting on the amorphous wire 20 by measuring the voltage generated in the pickup coil 21 when a pulsed current is passed through the amorphous wire 20. This MI element has detection sensitivity in the axial direction (longitudinal direction) of the amorphous wire 20, which is the magnetosensitive material.

[0023] In the sensor array 11 of this example, the axial direction of the amorphous wire 20 in magnetic sensor An and the axial direction of the amorphous wire 20 in magnetic sensor Bn are orthogonal to each other. Furthermore, the sensor array 11 of this example is mounted on the vehicle 5 such that the amorphous wire 20 of each magnetic sensor An is aligned with the direction of travel, and the amorphous wire 20 of each magnetic sensor Bn is aligned with the vehicle width direction.

[0024] The pulse circuit 22 (Figure 4) incorporated into the sensor block Sn is a circuit that generates a pulse signal which is the source of the pulse current that flows through the amorphous wire 20. The signal processing circuit 24 (Figure 4) is a circuit that uses a detector (synchronous detector) 241 that opens and closes in conjunction with the pulse signal to extract the induced voltage of the pickup coil 21, and an amplifier 242 amplifies that induced voltage. The signal processing circuit 24 uses the amplified induced voltage as the magnetic measurement value of the magnetic sensor. The amplification factor of the amplifier 242 can be adjusted by control of the calibration circuit 110.

[0025] The magnetic field generating coil Cn (Figure 3) is a cylindrical coil around which electric wires are wound to generate a magnetic field in response to current, and is an example of a magnetic field generating unit. The magnetic field generating coils Cn incorporated into each sensor block Sn are connected to each other in electrical series. The magnetic field generating coil Cn generates a magnetic field in response to current supplied by the calibration circuit 110, and applies magnetism to the magnetic sensors An and Bn. This magnetic field generating coil Cn is used for calibrating the magnetic sensors An and Bn. The magnetic field generating coil Cn, being a coil around which electric wires are wound, has the characteristic of high linearity of the magnetic quantity with respect to the magnitude of the current, making it suitable for calibrating the magnetic sensors An and Bn.

[0026] As shown in Figure 5, the magnetic field generating coil Cn is incorporated in a fixed position relative to the magnetic sensors An and Bn. In the same figure, the magnetic sensors An and Bn are represented by line segments schematically representing the magnetosensitive elements, and the magnetic field generating coil Cn is represented by a line segment representing the central axis. The detection directions of the magnetic sensors An and Bn are in the direction of the corresponding line segments. The detection axes of the magnetic sensors An and Bn coincide with the corresponding line segments. The cylindrical direction of the magnetic field generating coil Cn, in which the wire is wound to form a cylindrical shape, is in the direction of the line segment representing the central axis.

[0027] As shown in Figure 5, the cylindrical magnetic field generating coil Cn is incorporated so that its cylindrical direction intersects the vehicle width direction and the direction of travel at a 45-degree angle. Here, the cylindrical direction of the magnetic field generating coil Cn refers to the direction of the central axis of the cylindrical coil. Hereafter, the axis along the cylindrical direction of the magnetic field generating coil Cn will be referred to as the central axis of the magnetic field generating coil Cn. With the magnetic field generating coil Cn intersecting the vehicle width direction and the direction of travel at a 45-degree angle in this way, a magnetic field can be applied to both magnetic sensors An and Bn in response to current. Furthermore, in this example configuration, the positional relationship of the magnetic field generating coil Cn relative to magnetic sensor An is almost the same as the positional relationship of the magnetic field generating coil Cn relative to magnetic sensor Bn. Therefore, the magnetic field generating coil Cn can apply a magnetic field nearly equally to magnetic sensors An and Bn.

[0028] The magnetic field generating coils Cn of each sensor block Sn share common design specifications, as well as common embedding specifications, which are the relative positional relationships with the magnetic sensors An and Bn. Furthermore, as described above, each magnetic field generating coil Cn is arranged so as to apply magnetism evenly to the corresponding magnetic sensors An and Bn. In addition, since the magnetic field generating coils Cn of each sensor block Sn are connected in series as described above, the current supplied from the calibration circuit 110 is supplied equally to each magnetic field generating coil Cn.

[0029] Therefore, in terms of design, the magnetic field generating coil Cn of each sensor block Sn can generate magnetism equally, and furthermore, it can act equally on the corresponding magnetic sensors An and Bn. However, variations in the magnetic output characteristics of each magnetic field generating coil Cn are unavoidable, as are variations in the positional relationship between the magnetic field generating coil Cn and magnetic sensors An and Bn due to assembly errors in each sensor block Sn. Consequently, variations in the amount of magnetism acted by each magnetic field generating coil Cn on the corresponding magnetic sensors An and Bn are unavoidable.

[0030] The calibration circuit 110 (Figure 4) described above includes a coil drive circuit 114 that performs operations such as energizing the magnetic field generating coil Cn, and a calibration circuit 112 that performs calibration processing of the magnetic sensors An and Bn of each sensor block Sn. The calibration circuit 112, which is an example of a calibration unit, includes a CPU, ROM (read-only memory), RAM (random access memory), flash ROM, I / O, etc.

[0031] The calibration circuit 112 includes functions such as a storage unit that stores characteristic information (magnetic output characteristics) of each magnetic field generating coil Cn, and an estimation unit that calculates estimated measured values, which are estimated values ​​of the magnetic measurement values ​​of magnetic sensors An and Bn. The characteristic information of each magnetic field generating coil Cn stored in the storage unit is used by the estimation unit when calculating estimated measured values.

[0032] The coil drive circuit 114 includes a constant current circuit 114A that supplies current to the magnetic field generating coil Cn, and a current measurement circuit 114B that measures the current value of the supplied current. The constant current circuit 114A supplies current to the magnetic field generating coil Cn according to the control of the calibration circuit 110. The current measurement circuit 114B inputs the measured current value of the magnetic field generating coil Cn to the calibration circuit 112.

[0033] The calibration circuit 112 can execute at least two operating modes by having the CPU process a program read from ROM. These operating modes include a normal mode that is executed during the vehicle 5's service life, and a maintenance mode for factory shipment and maintenance work. Switching to maintenance mode is performed, for example, by the control of an externally connected maintenance device 61 (Figure 6).

[0034] The normal mode is the operating mode for calibrating the magnetic sensors An and Bn of each sensor block Sn during the vehicle 5's service life. The maintenance mode is the operating mode for identifying the magnetic output characteristics (characteristic information) of each magnetic field generating coil Cn using the reference magnetism of the Helmholtz coil 60 (see Figure 6). The characteristic information (described later) of each magnetic field generating coil Cn identified by this maintenance mode is stored in the memory unit of the calibration circuit 110 (calibration circuit 112) and used for calibrating the magnetic sensors An and Bn. The details of each operating mode will be explained later with reference to the flowcharts in Figures 10 and 11.

[0035] Here, the configuration of the device for performing processing under maintenance mode will be explained with reference to Figure 6. The device for performing processing under maintenance mode includes a dedicated maintenance device 61 that performs power supply and switching of operating modes, a magnetic field generator 6 that generates a uniform magnetic field, and the like. The magnetic field generator 6 is a magnetic device equipped with, for example, a Helmholtz coil 60.

[0036] The Helmholtz coil 60 is a coil system that includes two circular coils of common specifications, spaced apart on the same axis, with the distance between the two circular coils equal to the radius of the coils. The Helmholtz coil 60 can generate a highly uniform magnetic field by passing the same current in the same direction through the two circular coils. The magnetism generated by the Helmholtz coil 60 can be used as a reference magnetic field, which is a standard magnetic quantity. Alternatively, a Maxwell coil can be used, which further enhances the uniformity of the magnetic field by concentrically arranging a larger diameter coil on the outer circumference of the Helmholtz coil 60.

[0037] The maintenance device 61 controls both the sensor array 11 and the magnetic field generator 6 when performing processing under maintenance mode. The maintenance device 61 can supply operating power to the sensor array 11 and can also mediate the transmission and reception of status information indicating the operating status between the sensor array 11 and the magnetic field generator 6. Status information may include, for example, information indicating that the magnetic field generator 6 is in a standby state and ready to supply power to the Helmholtz coil 60.

[0038] (2) Operation of the marker detection device Next, we will outline the operation of the marker detection device 1, specifically (2.1) the detection operation of the magnetic marker 10, and then explain the contents of (2.2) the calibration operation of the sensor block Sn. As mentioned above, the calibration operation of the sensor block Sn consists of (2.2.1) processing under maintenance mode and (2.2.2) processing under normal mode.

[0039] (2.1) Magnetic marker detection operation As shown in Figure 7, the detection unit 12 outputs a control signal triggered by a pulse signal output from the vehicle 5 side every 30 mm, for example, to cause the sensor array 11 to perform magnetic measurement (S101). As described above, when the sensor array 11 performs magnetic measurement, it inputs sensor signals containing the magnetic measurement values ​​of magnetic sensor An and magnetic measurement values ​​of magnetic sensor Bn for each channel (15 channels, n=1 to 15) to the detection unit 12.

[0040] The detection unit 12 stores the sensor signals of each sensor block Sn in a memory buffer (not shown) as needed. The sensor signals of each sensor block Sn are stored in chronological order, starting with the oldest signals, over a predetermined period of time. As described above, the sensor signals of each sensor block Sn represent the magnetic measurement values ​​of magnetic sensor An and magnetic sensor Bn. Time-series data of the magnetic measurement values ​​of magnetic sensors An and Bn is generated in the memory buffer.

[0041] The detection unit (marker detection circuit) 12 uses the time-series data of the magnetic measurement value of the magnetic sensor An, which is the measured value of the magnetic component in the direction of travel, to perform marker detection processing (S102). For example, when the magnetic sensor An moves along the direction of travel of the vehicle 5 and passes directly over the magnetic marker 10, the magnetic measurement value in the direction of travel changes so that its positive and negative values ​​are reversed before and after the magnetic marker 10, as shown in Figure 8, and it crosses zero at the position directly above the magnetic marker 10.

[0042] While vehicle 5 is in motion, when a zero-crossing Zc occurs in which the sign of the sum of the magnetic measurement values ​​in the direction of travel detected by each magnetic sensor An in sensor block Sn reverses, it can be determined that the sensor array 11 is directly above the magnetic marker 10. When the sensor array 11 is directly above the magnetic marker 10 and a zero-crossing Zc occurs in the magnetic measurement values ​​in the direction of travel, the detection unit 12 determines that the magnetic marker 10 has been detected.

[0043] When the detection unit 12 determines that it has detected the magnetic marker 10 (S103:YES), it performs a measurement process for the amount of lateral displacement of the vehicle 5 relative to the magnetic marker 10 (S104). The detection unit (lateral displacement measurement circuit) 12 reads the magnetic measurement value of the magnetic sensor Bn of each sensor block Sn at the time when the sensor array 11 is positioned directly above the magnetic marker 10, that is, at the zero-crossing Zc point in Figure 9, and performs the lateral displacement measurement process. As described above, the magnetic measurement value of the magnetic sensor Bn is the measurement value of the magnetic component acting in the vehicle width direction. The magnetic measurement value of the magnetic sensor Bn of each sensor block Sn forms a data sequence that represents the distribution of the magnetic measurement value in the vehicle width direction in the vehicle width direction.

[0044] Here, for example, consider a magnetic sensor with the same specifications as magnetic sensor Bn, which measures the magnetic component along the vehicle width direction, and assume it moves along a virtual line in the vehicle width direction that passes directly above the magnetic marker 10. In this case, the magnetic measurement value in the vehicle width direction by this magnetic sensor will reverse in sign on both sides of the magnetic marker 10, and will change to cross zero at the position directly above the magnetic marker 10. Therefore, in a sensor array 11 in which 15 sensor blocks Sn are arranged in the vehicle width direction, the sign of the magnetic measurement value in the vehicle width direction detected by magnetic sensor Bn will differ depending on which side it is on via the magnetic marker 10.

[0045] In the change curve in Figure 9, which illustrates the data sequence of magnetic measurement values ​​(magnetic measurement values ​​in the vehicle width direction) from the magnetic sensor Bn of each sensor block Sn, a zero-crossing Zc occurs where the sign of the magnetic measurement value in the vehicle width direction reverses, corresponding to the position of the magnetic marker 10. The position of the zero-crossing Zc in the figure coincides with the position of the magnetic marker 10 in the vehicle width direction. The position of the magnetic marker 10 in the vehicle width direction can be identified as the position corresponding to the zero-crossing Zc.

[0046] The detection unit (lateral displacement measurement circuit) 12 measures the deviation of the vehicle 5 in the vehicle width direction relative to the magnetic marker 10 as the lateral displacement. In this example, the position of the central sensor block S8 of the sensor array 11, that is, the center of the vehicle 5 in the vehicle width direction, is set as the representative point. For example, in Figure 9, the position of the zero cross Zc corresponding to the magnetic marker 10 is at a position corresponding to S9.5, which is roughly midway between S9 and S10. As described above, the distance between sensor blocks S9 and S10 is 10 cm, so the lateral displacement of the representative point of the vehicle 5 (sensor block S8) relative to the magnetic marker 10 is (9.5 - 8) × 10 = 15 cm.

[0047] (2.2) Calibration operation of the sensor block As described above, the calibration circuit 110 (Figure 3) performs the following processes to calibrate the magnetic sensors An·Bn of each sensor block Sn of the sensor array 11: (2.2.1) processing under maintenance mode during factory shipment and maintenance work, and (2.2.2) processing under normal mode, which is the operating mode performed during the vehicle's service life.

[0048] As described above, the magnetic field generating coil Cn in each sensor block Sn of the sensor array 11 in this example is designed to generate a magnetic field that includes the magnetic component in the detection direction (direction of travel) of magnetic sensor An and the magnetic component in the detection direction (vehicle width direction) of magnetic sensor Bn. In the sensor array 11, magnetic sensors An and Bn can be calibrated using the magnetic field generating coil Cn of each sensor block Sn. The following procedures under maintenance mode and under normal mode are common to magnetic sensors An and Bn. Therefore, in the following explanation, the calibration method will be explained using magnetic sensor An as an example. Magnetic sensor Bn can also be calibrated for its magnetic characteristics using the same procedures under maintenance mode and under normal mode.

[0049] (2.2.1) Processing under maintenance mode The processing under maintenance mode is a process to identify the magnetic output characteristics (characteristic information) of the magnetic field generating coil Cn (Figures 3 and 4) using the reference magnetism of the Helmholtz coil 60 (Figure 6). Because the magnetic field generating coil Cn (Figures 3 and 4) exhibits high linearity between current value and magnetic quantity, knowing its magnetic output characteristics allows for quantitative control or estimation of the magnetic quantity acting on the magnetic sensor An. For example, if it is known that a magnetic quantity H acts on the magnetic sensor when a current of a certain value I is applied to the magnetic field generating coil Cn, then applying a current of 0.5I to the magnetic field generating coil Cn will apply a magnetic quantity of 0.5H to that magnetic sensor.

[0050] The maintenance mode process is performed using a magnetic field generator 6 and a maintenance device 61 that generate a uniform magnetic field (see Figure 6). The maintenance mode process is performed with the sensor array 11 held in a space where the magnetic field generator 6 uniformly forms a magnetic field (as illustrated in Figure 6). At this time, it is preferable that the sensor array 11 is held so that the direction of magnetic detection of the magnetic sensor An to be calibrated aligns with the uniform magnetic field. When the maintenance device 61 obtains status information indicating that the system is in a standby state and ready to be energized from the magnetic field generator 6 to the Helmholtz coil 60, it transfers this status information to the sensor array 11.

[0051] When the magnetic field generator 6 receives status information indicating that it is in standby mode, the calibration circuit 110 of the sensor array 11 causes each magnetic sensor An to perform magnetic measurement and obtains the sensor output value R1n when the magnetic field from the Helmholtz coil 60 is not acting (Figure 10, S201). The calibration circuit 110 stores the sensor output value R1n as the sensor output of each magnetic sensor An when the Helmholtz coil 60 and the magnetic field generating coil Cn are not energized. This sensor output value R1n is often not zero due to external magnetic fields in nature, offsets in the sensor output value, etc.

[0052] When the magnetic field generator 6 receives status information from the sensor array 11 indicating that magnetic measurement is complete, it starts energizing the Helmholtz coil 60 (S202). The magnetic field generator 6 controls the current supplied to the Helmholtz coil 60 so that a reference magnetic field Hk, which is a reference magnetic quantity, acts on each magnetic sensor An of the sensor array 11.

[0053] The magnetic field generated by the Helmholtz coil 60 acts on each magnetic sensor An as a bias magnetic field superimposed on the external magnetic field. Therefore, when the reference magnetic field Hk of the Helmholtz coil 60 is applied to each magnetic sensor An, the amount of magnetic field acting on the magnetic sensor An changes by the amount of the reference magnetic field Hk. That is, the reference magnetic difference value ΔHs, which is the amount of change in the magnetic field acting on each magnetic sensor An when the Helmholtz coil 60 is energized, is ΔHs = Hk. After the magnetic field generator 6 is in a state where the reference magnetic field Hk is applied to each magnetic sensor An, it transmits status information indicating that it is energized to the calibration circuit 110 via the maintenance device 61.

[0054] When the calibration circuit 110 receives status information from the magnetic field generator 6 indicating that power is being supplied, it causes each magnetic sensor An to perform magnetic measurement to obtain the sensor output value R2n (S203). Furthermore, the maintenance device 61 calculates a reference output difference value ΔRsn (=R2n-R1n), which is the amount of change in the sensor output of each magnetic sensor An when power is supplied to the Helmholtz coil 60, for each magnetic sensor An (S204, sensor characteristic acquisition step).

[0055] The calibration circuit 110 stores a numerical combination (ΔHs⇔ΔRsn) of the reference magnetic difference value ΔHs (common to each magnetic sensor An) stored in step S202 above and the reference output difference value ΔRsn calculated in step S204, as the sensor output characteristic, which is characteristic information for each magnetic sensor An (S205, sensor characteristic acquisition step). This combination represents the sensor output characteristic that the output difference value of magnetic sensor An when the amount of magnetic field acting on magnetic sensor An changes by ΔHs is ΔRsn.

[0056] When the magnetic field generator 6 (Figure 6) receives status information from the sensor array 11 indicating that it has finished storing the sensor output characteristics (characteristic information) of all magnetic sensors An, it stops supplying power to the Helmholtz coil 60 (Figure 6) (S206). When the sensor array 11 receives status information indicating that power to the Helmholtz coil 60 has been stopped, it starts supplying power to the magnetic field generating coil Cn (S207).

[0057] The current value I1 supplied to the magnetic field generating coil Cn should be set to a value that allows a magnetic field amount close to the reference magnetic field Hk (Hk) generated by the Helmholtz coil 60 to act on the magnetic sensor An, based on the design specifications of the magnetic field generating coil Cn, such as the number of turns and coil diameter. When the current supplied to the magnetic field generating coil Cn is switched from zero to current value I1, the current difference value, which is the change in the current supplied to the magnetic field generating coil Cn, becomes ΔIa = I1. Since the magnetic field generating coils Cn are connected in series, the current difference value ΔIa is common to all magnetic field generating coils Cn. On the other hand, since there is variation in the magnetic output characteristics of each magnetic field generating coil Cn, the amount of magnetic field that acts on the magnetic sensor An from each magnetic field generating coil Cn is not constant, and variation occurs.

[0058] The calibration circuit 110 performs magnetic measurements using each magnetic sensor An while current I1 is supplied to each magnetic field generating coil Cn, and acquires the sensor output value R3n for each magnetic sensor An (S208, magnetic measurement step). The calibration circuit 110 then performs a calculation for each magnetic sensor An by subtracting the sensor output value R1n (the sensor output value in S201 above) when the magnetic field generating coil Cn and the Helmholtz coil 60 are not acting from the sensor output value R3n when the magnetic field generating coil Cn is acting. As a result, the output difference value ΔRcn (=R3n-R1n), which is the change in the sensor output of the magnetic sensor An corresponding to the change in the current supplied to the magnetic field generating coil Cn, is acquired for each magnetic sensor An (S209, magnetic measurement step).

[0059] The calibration circuit 110 first refers to the sensor output characteristics (ΔHs⇔ΔRsn) of the magnetic sensor An stored in step S205 above in order to estimate the magnetic difference value ΔHan corresponding to the output difference value ΔRcn of each magnetic sensor An (S210, magnetic output characteristic acquisition step). Then, based on the sensor output characteristics of the magnetic sensor An, where the output difference value ΔRsn is generated due to the magnetic difference value ΔHs, the calibration circuit 110 calculates the magnetic difference value ΔHan (=(ΔRcn / ΔRsn)×ΔHs) corresponding to the output difference value ΔRcn of each magnetic sensor An (S209 above) (S211, magnetic output characteristic acquisition step). The calibration circuit 110 then stores the numerical combination of the magnetic difference value ΔHan and the current difference value ΔIa in association with each other as the magnetic output characteristics of the magnetic field generating coil Cn (S212, magnetic output characteristic acquisition step).

[0060] By performing the above procedure under maintenance mode, the sensor output characteristics of each magnetic sensor An can be determined by having the magnetic sensor An measure the reference magnetic field Hk of the Helmholtz coil 60 (sensor characteristic acquisition step). Furthermore, by measuring the magnetism acting on the magnetic field generating coil Cn using each magnetic sensor An whose sensor output characteristics have been determined (magnetic measurement step), the magnetic output characteristics of the magnetic field generating coil Cn can be determined (magnetic output characteristic acquisition step).

[0061] Generally, a magnetic field generating coil Cn around which an electric wire is wound exhibits high linearity in the magnitude of its magnetic field with respect to the magnitude of the current flowing through it, and the amount of magnetic field changes approximately proportionally to the value of the current. Therefore, using a magnetic field generating coil Cn with known magnetic output characteristics allows for quantitative control of the amount of magnetic field acting on the corresponding magnetic sensor An, which is useful for calibrating the magnetic sensor An.

[0062] (2.2.2) Processing under normal mode Similar to the process under maintenance mode described above, we will explain the process under normal mode using magnetic sensor An as an example. The same process under normal mode is possible for magnetic sensor Bn.

[0063] During the service life of vehicle 5, various magnetic fields act on each magnetic sensor An from both inside and outside the vehicle 5. In particular, vehicle 5 is equipped with various electronic components that can act as magnetic sources, and the magnetic fields from these electronic components act on the magnetic sensors An, sometimes exceeding the magnetic field from the magnetic markers 10. Furthermore, RC structures such as tunnels and bridges that make up the road can be large magnetic sources, so the magnitude of the external magnetic field acting on vehicle 5 from the outside also fluctuates depending on the driving environment.

[0064] Generally, the sensitivity of a magnetic sensor, that is, the ratio of the change in the sensor output value ΔR when the amount of magnetic field acting on it changes ΔH, can be treated as constant if ΔH is small. On the other hand, if the absolute value of the magnetic field being measured changes, that is, if the range of variation of the magnetic field changes, the sensitivity of the magnetic sensor An may change significantly. Furthermore, the degree of such sensitivity variation will differ for each magnetic sensor An due to individual differences. Therefore, if the range of variation of the magnetic field acting on each magnetic sensor An shifts during the usage period of the vehicle 5, there is a high possibility that variations will occur in the sensitivity of each magnetic sensor An.

[0065] The processing performed by the calibration circuit 110 in normal mode is carried out to improve the uniformity of the sensitivity of each magnetic sensor An during the service life of the vehicle 5. This processing in normal mode is preferable when a nearly uniform magnetic field is acting on each magnetic sensor An of the sensor array 11 from the outside.

[0066] The processing in normal mode can be performed even when the sensor array 11 is being acted upon by magnetism originating from relatively small magnetic sources such as magnetic markers 10 or manholes, or from the ends of large magnetic sources such as RC bridges, that is, when the magnetism acting on the sensor array 11 changes in accordance with the movement of the vehicle. As described above, the processing in normal mode is a process that utilizes the output difference value ΔRcn of the magnetic sensor An in response to the change in current supplied to the magnetic field generating coil Cn. For example, when applying a change in current to the magnetic sensor An, if the energization / de-energy is switched at short intervals, the change in the magnetism acting on the sensor array 11 in accordance with the movement of the vehicle is minor, and the accuracy of the output difference value ΔRcn is not significantly impaired. Therefore, the processing in normal mode can be performed with high accuracy even when the sensor array 11 is being acted upon by magnetism from magnetic markers 10, etc.

[0067] As shown in Figure 11, the calibration circuit 110 first measures a magnetic field acting nearly uniformly from the outside on each magnetic sensor An while the magnetic field generating coil Cn is de-energized, and sequentially stores the sensor output value R4n of each magnetic sensor An (S301). Next, the calibration circuit 110 starts energizing the magnetic field generating coil Cn (S302). The current value I2 at this time may be the same current value I1 as in step S207 under maintenance mode, or it may be a different current value. In this example, the same current value I2 as current value I1 is supplied to each magnetic field generating coil Cn. Therefore, the current difference value ΔIb = I2 = I1 is the amount of change in the current supplied to each magnetic field generating coil Cn.

[0068] The calibration circuit 110 causes each magnetic sensor An to perform magnetic measurement while current is supplied to each magnetic field generating coil Cn, and obtains the sensor output value R5n (S303). Then, it calculates the output difference value ΔRcn (=R5n-R4n) of each magnetic sensor An corresponding to the current change by the current difference value ΔIb at the start of current supply to the magnetic field generating coil Cn (S304).

[0069] The calibration circuit 110 performs threshold processing to determine whether the output difference value ΔRcn obtained in S304 falls within the range of a preset sensitivity correction threshold (S305). If the output difference value ΔRcn is greater than the lower limit of the sensitivity correction threshold and less than the upper limit of the sensitivity correction threshold, and falls within the range of the above sensitivity correction threshold (S305: YES), the calibration circuit 110 determines that there is no need to perform the calibration process for each magnetic sensor An, and bypasses this process.

[0070] On the other hand, if the output difference value ΔRcn is below the lower limit of the sensitivity correction threshold, or above the upper limit of the sensitivity correction threshold, and is outside the range of the above sensitivity correction threshold (S305:NO), the calibration circuit 110 further performs threshold processing to determine whether the output difference value ΔRcn falls within the range of a preset abnormality determination threshold (S306). If the output difference value ΔRcn is below the lower limit of the abnormality determination threshold, or if the output difference value ΔRcn is above the upper limit of the abnormality determination threshold, and is outside the range of the above abnormality determination threshold (S306:NO), the calibration circuit 110 does not perform processing to calibrate each magnetic sensor An, but notifies the detection unit 12 of the abnormality (S317).

[0071] If the output difference value ΔRcn is greater than the lower limit of the abnormality detection threshold and less than the upper limit of the abnormality detection threshold, and falls within the range of the above abnormality detection threshold (S306: YES), the calibration circuit 110 executes the processes of steps S307 to S310 for calibrating each magnetic sensor An. In order to calibrate each magnetic sensor An, the calibration circuit 110 first refers to the magnetic output characteristics (ΔHan⇔ΔIa) of the magnetic field generating coil Cn stored in step S212 under maintenance mode (S307). Then, using these magnetic output characteristics, the calibration circuit 110 estimates the magnetic difference value ΔHbn, which is the change in the amount of magnetism acting on each magnetic sensor An, based on the current difference value ΔIb when the current value I2 is applied to the magnetic field generating coil Cn in step S302 (S308, magnetic estimation step).

[0072] This method for estimating the magnetic difference value ΔHbn assumes that the magnetic difference value changes almost linearly with respect to the current difference value, and that the proportional relationship between ΔHan and ΔIa in the magnetic output characteristics (ΔHan⇔ΔIa) referenced in step S307 is maintained even when the external environment fluctuates. The magnetic difference value ΔHbn when the current difference value ΔIb acts on the magnetic field generating coil Cn can be estimated using the calculation formula ΔHbn=(ΔIb / ΔIa)×ΔHan. In this example, since the current difference value ΔIa=ΔIb, the magnetic difference value ΔHbn is equal to ΔHan.

[0073] The calibration circuit 110 determines the amplification factor of the output difference value ΔRcn such that the ratio of the output difference value ΔRcn of the magnetic sensor An related to step S304 to the magnetic difference value ΔHbn estimated in step S308 becomes a predetermined value (S309, calibration step). Then, the calibration circuit 110 calibrates each magnetic sensor An by setting the amplification factor of each magnetic sensor An determined by calculation to the corresponding amplifier 242 (S310, calibration step).

[0074] Here, the predetermined value in step S309 above represents the sensitivity of the magnetic sensor An to the magnetic difference value ΔHbn. Therefore, by performing step S309 above for each magnetic sensor An, the sensitivity of all magnetic sensors An can be made more uniform. This will be explained with reference to Figures 12 and 13, which illustrate the sensor output characteristics of any two magnetic sensors Aα and Aβ (α and β are different natural numbers between 1 and 15) among the magnetic sensors An. In these figures, the horizontal axis represents the magnetic quantity H acting on the magnetic sensor, and the vertical axis represents the sensor output value R of the magnetic sensor.

[0075] For example, when the amount of magnetic field acting changes by ΔH (i.e., when the magnetic difference value is ΔH), if there is a difference in sensitivity between any two magnetic sensors Aα and Aβ, a difference will occur in the output difference values ​​ΔRα and ΔRβ, which are the changes in the output values, as shown in Figure 12. By performing steps S309 and S310 above, which individually set the amplification factor for each magnetic sensor Aα and Aβ, the change amounts ΔRα' and ΔRβ' corresponding to each magnetic sensor Aα and Aβ can be made equal, as shown in Figure 13.

[0076] Furthermore, the calibration circuit 110 repeatedly performs the above-described normal mode processing when the range of variation of the magnetic quantity acting on the magnetic sensor An shifts due to fluctuations in the magnitude of the external magnetic field, or when the periodic calibration time arrives, and performs calibration of the magnetic sensor An as needed. According to the above operation method of the marker detection device 1, which includes the process of calibrating the magnetic sensor An, even if changes in the magnetic environment, changes over time, or environmental changes such as temperature and humidity occur, errors in the time difference value of each magnetic sensor An can be avoided, and detection accuracy can be maintained at a high level. In addition, since it is not necessary to bring the vehicle to a repair shop or the like each time for maintenance including calibration of the magnetic sensor An, the effort and expense on the part of the vehicle user can be reduced. It is also good to set thresholds for the high and low ranges of variation of the magnetic quantity.

[0077] The calibration method for magnetic sensor An has been described above, but magnetic sensor Bn can also be calibrated using the same method. Thus, the marker detection device 1 (an example of a magnetic measurement device) in this example is a device equipped with a calibration function for magnetic sensors An and Bn. Each magnetic sensor block Sn of the sensor array 11 in this example incorporates a magnetic field generating coil Cn that can apply magnetism to magnetic sensors An and Bn. By utilizing this magnetic field generating coil Cn, calibration of magnetic sensors An and Bn is possible under the normal operating conditions (normal mode) of the sensor array 11. Therefore, the sensor array 11 in this example can maintain good sensor characteristics of magnetic sensors An and Bn over the long period of use of the vehicle. With a sensor array 11 that has good sensor characteristics for magnetic sensors An and Bn, magnetic markers 10 can be detected with high reliability while suppressing false detections.

[0078] In this example, a magnetic field generating coil Cn is used as an example of a magnetic field generating unit, but the magnetic field generating unit can be anything that generates a magnetic field in response to current, and may even be a simple wire. Also, in this example, a configuration in which the sensor array 11 and the detection unit 12 are separate is shown, but the detection unit 12 may be incorporated into the sensor array 11 and integrated into one unit.

[0079] Furthermore, in this example, the magnetic field generating coil Cn is positioned so that its central axis is aligned radially within the 90-degree angle where the detection direction of magnetic sensor An and the detection direction of magnetic sensor Bn are orthogonal. Alternatively, the magnetic field generating coil Cn may be positioned outside the above 90-degree angle range so that its central axis is aligned radially.

[0080] In this example, the magnetic field generating coils Cn are connected electrically in series. When the magnetic field generating coils Cn are connected in series, an equal current can be supplied to each coil Cn simultaneously, allowing for efficient calibration of each magnetic sensor An·Bn.

[0081] In this example, the magnetic field generating coil Cn is positioned such that its central axis lies within the plane defined by the detection axis of magnetic sensor An (the central axis of the magnetic sensor, the axis along the detection direction) and the detection axis of magnetic sensor Bn (see Figure 5). It is not a mandatory requirement that the central axis of the magnetic field generating coil Cn lie within this plane. The magnetic field generating coil Cn may also be positioned so that its central axis is parallel to this plane. In other words, the central axis of the magnetic field generating coil Cn may intersect the detection axes of magnetic sensor An and magnetic sensor Bn in a twisted position. It is sufficient that the cylindrical direction of the magnetic field generating coil Cn intersects the detection direction of magnetic sensor An and magnetic sensor Bn. Furthermore, the central axis of the magnetic field generating coil Cn may be inclined with respect to the plane defined by the detection axes of magnetic sensor An and magnetic sensor Bn, that is, its central axis may be oblique to the plane.

[0082] For example, the expression "the detection direction of magnetic sensor An intersects the cylindrical direction that forms the axial direction of the central axis of the magnetic field generating coil Cn" includes the case where the central axis of the magnetosensitive element corresponding to the detection direction of magnetic sensor An and the central axis of the magnetic field generating coil Cn intersect in a twisted position. Also, for example, the expression "the detection direction of magnetic sensor An intersects the cylindrical direction that forms the axial direction of the central axis of the magnetic field generating coil Cn at a right angle" includes the case where the central axis of the magnetosensitive element corresponding to the detection direction of magnetic sensor An and the central axis of the magnetic field generating coil Cn intersect at a right angle in a twisted position.

[0083] In this example, the magnetic field generating coil Cn is positioned such that its central axis evenly divides the right angle (which may be a skewed positional relationship) formed by the detection axis of magnetic sensor An and the detection axis of magnetic field generating coil Bn. It is not a mandatory requirement that the central axis of the magnetic field generating coil Cn evenly divide the right angle where the detection axes of magnetic sensors An and Bn intersect; for example, it may be 30 degrees and 60 degrees, or other non-equal divisions. Furthermore, this example illustrates magnetic sensors An and Bn with orthogonal detection axes. The angle at which the detection axes of magnetic sensor An and magnetic sensor Bn intersect is not limited to a right angle. In addition, it is not a mandatory requirement that the detection axes of magnetic sensor An and magnetic sensor Bn lie in the same plane; they may be in a skewed positional relationship. It is also not a mandatory requirement that the magnetism of the magnetic field generating coil Cn acts evenly on magnetic sensors An and Bn.

[0084] In the maintenance mode, it is also possible to perform a calibration process to equalize the sensitivity of each magnetic sensor by utilizing the reference magnetic field Hk that the Helmholtz coil 60 acts on each magnetic sensor. In this calibration process, the amplification factor of each amplifier 242 should be set so that the output difference value, which is the amount of change in the sensor output output of the magnetic sensor, becomes uniform with respect to the magnetic difference value ΔHs that the Helmholtz coil 60 acts on each magnetic sensor. In this case, in step S205 in Figure 10, it is good practice to store the sensor output characteristics after performing this calibration process.

[0085] The characteristic information representing the sensor output characteristics of a magnetic sensor is exemplified by the combination of the magnetic difference value acting on the magnetic sensor and the output difference value, which is the change in the sensor output output by the magnetic sensor. The characteristic information of a magnetic sensor may also be a combination of the amount of magnetic field acting on the magnetic sensor and the sensor output value output by the magnetic sensor, or it may be the ratio of the sensor output value to the amount of magnetic field acting on it. The characteristic information only needs to represent the relationship between the magnetic field acting on the magnetic sensor and the sensor output by the magnetic sensor.

[0086] In this example, magnetic sensor An and magnetic sensor Bn are given as examples of the first and second magnetic sensors, and a magnetic measuring device (marker detection device 1) equipped with multiple combinations of the first and second magnetic sensors is also provided as an example. The magnetic measuring device may be equipped with only one combination of the first and second magnetic sensors.

[0087] (Example 2) This example shows a modified arrangement of the magnetic field generating coil Cn relative to the magnetic sensor An·Bn, based on the sensor block Sn of Example 1. The arrangement of the magnetic field generating coil Cn will be explained with reference to Figures 14 to 16. In Figures 14 to 16, similar to Figure 5 in Example 1, the magnetic sensor An·Bn is represented by line segments schematically representing the magnetosensitive element, and the magnetic field generating coil Cn is represented by line segments representing the central axis. The central axis is the axis along the cylindrical direction of the cylindrical magnetic field generating coil Cn.

[0088] Figure 14 shows an example in which a magnetic field generating coil Cn is positioned outside the region sandwiched between the detection axes (central axes of the magnetic sensors) of magnetic sensors An and Bn. Furthermore, the magnetic field generating coil Cn in the figure may be shifted in the direction of its cylinder. It is sufficient for the magnetic field generating coil Cn to generate magnetic components along the detection direction of magnetic sensor An and magnetic components along the detection direction of magnetic sensor Bn.

[0089] Figure 15 shows an example in which a magnetic field generating coil Cn is positioned along the detection direction of the magnetic sensor Bn. The magnetic field generating coil Cn has a cylindrical direction perpendicular to the detection direction of the magnetic sensor An, and its center in the cylindrical direction is offset in the cylindrical direction relative to the magnetic sensor An (relative to the axis of the detection axis of the magnetic sensor An). As illustrated in the figure, the magnetic field lines representing the magnetic field of the magnetic field generating coil Cn are nearly parallel to the cylindrical direction in the middle part of the magnetic field generating coil Cn, while at the ends of the magnetic field generating coil Cn, the magnetic field lines become oblique as if curving around. The oblique magnetic field lines contain a magnetic component perpendicular to the cylindrical direction of the magnetic field generating coil Cn. In the configuration shown in the figure, the magnetic component perpendicular to the cylindrical direction of the magnetic field generating coil Cn acts on the magnetic sensor An.

[0090] Figure 16 is a diagram illustrating the arrangement of the magnetic field generating coil Cn, which is not included in the technical concept of the present invention. In Figure 16, the cylindrical direction of the magnetic field generating coil Cn is perpendicular to the detection direction of the magnetic sensor An, and the center of the magnetic field generating coil Cn in the cylindrical direction is located on the axis of the detection axis of the magnetic sensor An. When the center of the magnetic field generating coil Cn in the cylindrical direction is located on the axis of the detection axis of the magnetic sensor An in this way, the magnetic component perpendicular to the cylindrical direction of the magnetic field generating coil Cn does not act on the magnetic sensor An. Therefore, the arrangement shown in Figure 16 is not included in the technical concept of the present invention.

[0091] On the other hand, arrangements in which the magnetic field generating coil Cn is shifted in the cylindrical direction relative to the arrangement in Figure 16, or arrangements in which the cylindrical direction of the magnetic field generating coil Cn is rotated so as not to be perpendicular to the detection direction of the magnetic sensor An, are also included in the technical concept of the present invention. The other components and effects are the same as in Example 1.

[0092] (Example 3) This example shows a modified configuration of the magnetic sensor based on the sensor block Sn of Example 1. This will be explained with reference to Figures 17 and 18. In these figures, the detection direction of each magnetic sensor is represented by the x, y, and z axes, and the central axis of the magnetic field generating coil Cn is represented by a line segment.

[0093] In the sensor block Sn of this example, as shown in Figure 17, three magnetic sensors are incorporated such that their detection directions align with three mutually orthogonal directions (the x, y, and z axes). The magnetic field generating coil Cn is positioned at a 45-degree angle to all three magnetic sensors. With the magnetic field generating coil Cn shown in the figure, a magnetic field can be applied simultaneously to the three mutually orthogonal magnetic sensors.

[0094] In Figure 18, the arrangement of the magnetic field generating coil Cn has been modified based on the configuration in Figure 17. In the configuration of Figure 18, the magnetic field generating coil Cn is parallel to the x-axis along the detection direction of one of the magnetic sensors. However, the cylindrical center of the magnetic field generating coil Cn is offset in the cylindrical direction with respect to the y-axis and z-axis along the detection directions of the other two magnetic sensors. The other components and effects are the same as in Example 1 or Example 2.

[0095] Although specific examples of the present invention have been described in detail as shown in the examples above, these examples only disclose an example of the technology covered by the claims. Needless to say, the claims should not be interpreted restrictively based on the configuration or numerical values ​​of the specific examples. The claims encompass technologies obtained by various modifications, changes, or combinations of the above examples using prior art or the knowledge of those skilled in the art. [Explanation of Symbols]

[0096] 1. Marker detection device (magnetic measuring device) 10 Magnetic Markers 11 Sensor Array 110 Calibration Circuit 112 Calibration circuit (storage unit, estimation unit, calibration unit) 12 detection units 125 Filtering circuit 127 Detection Processing Circuit 2 Sensor Blocks 20 Amorphous wire (magnetic wire) 21 Pickup coil (coil) Sn Sensor Block An, Bn magnetic sensor Cn magnetic field generating coil (magnetic field generating section, coil) 5 vehicles 6. Magnetic field generator 60 Helmholtz coil

Claims

1. A first magnetic sensor that detects a magnetism acting along one of the first directions, A second magnetic sensor detects a magnetism acting along a second direction intersecting the first direction in which the first magnetic sensor detects a magnetism, It has a magnetic field generating unit that generates a magnetic field in response to the application of electricity, The magnetic field generating unit is incorporated so as to be an integral part of the first magnetic sensor and the second magnetic sensor, with its position and angle relative to the first magnetic sensor and the second magnetic sensor fixed. The magnetic field generating unit is a cylindrical coil around which electric wires are wound, and is configured to apply magnetism along the first and second directions in response to current, The magnetic field generating unit is, The cylindrical coil is positioned such that its cylindrical direction intersects the first direction, its cylindrical direction is parallel to the first direction, or its cylindrical direction is perpendicular to the first direction and the center of its cylindrical direction is offset in the cylindrical direction relative to the first magnetic sensor, and The cylindrical direction is positioned such that it intersects with the second direction, the cylindrical direction is parallel to the second direction, or the cylindrical direction is perpendicular to the second direction and the center of the cylindrical direction is offset in the cylindrical direction relative to the second magnetic sensor. The cylindrical coil is a sensor block for magnetic measurement in which the cylindrical direction is perpendicular to at least one of the first and second directions, and the center of the cylindrical direction is offset in the direction of the cylinder with respect to a magnetic sensor that detects magnetism along that direction.

2. A sensor block for magnetic measurement according to claim 1, wherein the cylindrical coil has a cylindrical direction perpendicular to both the first direction and the second direction, and the center of the cylindrical direction is offset in the cylindrical direction relative to both the first magnetic sensor and the second magnetic sensor.

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