JP6631385B2 - Magnetic marker polarity determination method and polarity determination device - Google Patents

Description

  The present invention relates to a polarity determination method and a polarity determination device for determining the polarity of a magnetic marker laid on a traveling path of a vehicle.

  2. Description of the Related Art Conventionally, a marker system for a vehicle for using a magnetic marker laid on a road for driving assistance has been known (for example, see Patent Document 1). According to the marker system, for example, various types of driving support such as automatic steering control, lane departure warning, and automatic driving can be realized by detecting a magnetic marker laid along the lane of the road on the vehicle side. Further, among such marker systems, there is a system that can provide information to a vehicle using the magnetic polarity of magnetic markers arranged along the road direction (for example, see Patent Document 2).

JP 2005-202478 A JP 2003-109182 A

  However, the conventional marker system has the following problems. That is, there is a problem that the accuracy of determining the polarity of the magnetic marker may be impaired due to disturbance magnetism acting on the magnetic sensor. For example, in RC bridges and tunnels that form roads, iron reinforcing plates, reinforcing bars, and the like for securing structural strength are stretched inside, and such RC structures are very much used. It can be a large magnetic source. While the remanent magnetization of ferrous materials such as rebar is extremely small compared to magnets, magnets that exceed geomagnetism are generated due to the huge volume of bridges and tunnels. And a relatively large magnetic field may be generated. For example, the magnetic fields of various magnetic sources existing on roads, such as bridges and tunnels, are one of the factors that reduce the reliability of the polarity determination of the magnetic marker.

  The present invention has been made in view of the above-described conventional problems, and has as its object to provide a polarity determination method and a polarity determination device capable of determining the polarity of a magnetic marker with high certainty.

One aspect of the present invention is a polarity determination method for determining the polarity of a magnetic marker laid on a traveling path using at least two or more magnetic sensors attached to a vehicle,
A first which can be calculated by one or two or more difference calculations on magnetic measurement values obtained by two or more magnetic sensors of the plurality of magnetic sensors having different mounting positions at the same measurement timing. A gradient generating step of generating a magnetic gradient of
A process of determining the polarity of the magnetic marker using at least one of a second magnetic gradient that is a difference between the first magnetic gradients having different measurement timings and a first magnetic gradient. And a method for determining the polarity of the magnetic marker.

One aspect of the present invention is a polarity determination device mounted on a vehicle to detect a magnetic marker laid on a road,
At least two or more magnetic sensors;
And a polarity determining means for determining the polarity of the magnetic marker,
The polarity judging means is provided in a magnetic marker polarity judging device which is means for executing the above-described magnetic marker polarity judging method.

  The polarity determination method of the magnetic marker according to the present invention was conceived by paying attention to the fact that the distribution of the magnetic gradient generated around the magnetic source varies depending on the size of the magnetic source. This magnetic marker detection method removes a magnetic component of a magnetic source having a size larger than that of the magnetic marker by utilizing the difference in distribution of the magnetic gradient as described above, thereby increasing the detection reliability of the magnetic marker. How to improve.

  The gradient generation step in the magnetic marker detection method according to the present invention is a step of acquiring the first magnetic gradient that can be calculated by a difference operation on magnetic measurement values of the two or more magnetic sensors. According to this gradient generation step, by taking the difference between the magnetic measurement values of the two or more magnetic sensors, magnetic noise acting uniformly on the two or more magnetic sensors can be removed, and the magnetic gradient can be extracted with high certainty. it can.

  As described above, the magnetic marker polarity determination method according to the present invention performs the gradient generation step of removing magnetic noise that acts uniformly due to the difference between the magnetic measurement values of the two or more magnetic sensors. And a method of determining the polarity of the magnetic marker after removing the magnetic disturbance.

  The polarity determination method according to the present invention is an excellent method capable of improving the reliability of determination of the polarity of a magnetic marker by suppressing a magnetic component acting from a magnetic source having a size larger than that of the magnetic marker. The magnetic marker polarity determination device that employs this polarity determination method has high reliability and excellent characteristics that can determine the polarity of the magnetic marker.

FIG. 2 is a front view of the vehicle with the sensor array attached thereto according to the first embodiment. FIG. 2 is an overhead view illustrating a lane on which a magnetic marker is laid in the first embodiment. FIG. 2 is a block diagram illustrating a functional configuration of the magnetic marker detection device according to the first embodiment. FIG. 2 is a block diagram showing the remaining part of the functional configuration of the magnetic marker detection device according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration of a magnetic sensor according to the first embodiment. FIG. 4 is a flowchart illustrating a flow of a marker detection process according to the first embodiment. FIG. 5 is an explanatory diagram illustrating a change in magnetic distribution in the vehicle width direction when passing through a magnetic marker having an N pole in the first embodiment. FIG. 4 is an explanatory diagram illustrating a change in a magnetic distribution in a vehicle width direction when the vehicle passes an S-pole magnetic marker in the first embodiment. FIG. 4 is an explanatory diagram illustrating a change in a magnetic gradient distribution in a vehicle width direction when the vehicle passes an N-pole magnetic marker in the first embodiment. FIG. 4 is an explanatory diagram illustrating a change in a magnetic gradient distribution in a vehicle width direction when the vehicle passes an S-pole magnetic marker in the first embodiment. FIG. 4 is an explanatory diagram of a filtering process according to the first embodiment. FIG. 9 is a block diagram illustrating a functional configuration of a magnetic marker detection device according to a second embodiment. FIG. 9 is a block diagram illustrating a remaining part of the functional configuration of the magnetic marker detection device according to the second embodiment. FIG. 11 is a flowchart illustrating a flow of a marker detection process according to the second embodiment. 9 is a graph showing a temporal change of a magnetic gradient in a vehicle width direction and a magnetic gradient in a traveling direction in the second embodiment. FIG. 11 is an explanatory diagram of a filtering process in the second embodiment. FIG. 13 is a block diagram illustrating a functional configuration of a magnetic marker detection device according to a third embodiment.

  The combination of two or more magnetic sensors for which the difference between the magnetic measurement values is calculated in the gradient generation step according to the present invention may be a combination including two adjacent magnetic sensors, and may be one or two. A combination including two adjacent magnetic sensors via another magnetic sensor may be used.

  For the first magnetic gradient that can be calculated by the difference operation on the magnetic measurement values of two or more magnetic sensors, it is not an essential requirement that the first magnetic gradient is actually calculated by the difference operation. The first magnetic gradient may be a value that can be calculated by the difference calculation. For example, the concept of the present invention may be applied to a first magnetic gradient whose difference is obtained by using a differential circuit based on an analog circuit, as long as the first magnetic gradient can be calculated by a difference calculation. Included.

  The first magnetic gradient that can be calculated by one or two or more difference calculations on the magnetic measurement values of two or more magnetic sensors is, for example, arranged in a two-dimensional vertical and horizontal array. Regarding the magnetic sensors, a first difference that is a difference between the magnetic measurement values of the two magnetic sensors in the vertical direction, a second difference that is a difference between the magnetic measurement values of the two magnetic sensors in the horizontal direction, and two magnetisms in the oblique direction. A third difference that is a difference between the magnetic measurement values of the sensor, a fourth difference that is a difference between the first differences at two positions in the horizontal direction, and a difference between the second differences at two positions in the vertical direction. Each of a certain fifth difference, a sixth difference which is a difference between the first differences at two positions in the vertical direction, and the like is one time or two times for magnetic measurement values of two or more magnetic sensors. Magnetic gradient that can be calculated by multiple difference calculations There, both of which correspond to the first magnetic gradient.

  The magnetic measurement values obtained by two or more magnetic sensors at the same measurement timing do not need to be exactly the same at the measurement timing. For example, if the measurement process is repeatedly performed, the measurement is performed during the same orbit. Means that the measured values are magnetic. For example, if it is difficult to acquire the magnetic measurement values of each magnetic sensor at exactly the same time and it is necessary to acquire them sequentially, the magnetic measurement values acquired during one cycle of the order will be acquired at the same measurement timing. It can be said that the measured magnetic value.

  On the other hand, the second magnetic gradient according to the present invention is a difference between the first magnetic gradients at different measurement timings at which the target magnetic measurement values are obtained. The difference in the measurement timing at which the magnetic measurement value is acquired means that, for example, when the measurement process is repeatedly performed, the magnetic measurement value is a magnetic measurement value measured in different rounds during the repetition. Since the position of the traveling vehicle advances in the traveling direction as time passes, the second magnetic gradient can be grasped as a difference between the first magnetic gradient at two positions in the traveling direction.

  In the polarity determination step in the polarity determination method according to the present invention, a filter output value is generated by performing a filter process for suppressing or cutting off at least a low frequency component with respect to a change in the traveling direction of the vehicle of any one of the magnetic gradients. The polarity of the magnetic marker may be determined using the output value of the filter.

  According to the filtering process, a low frequency component in the change in the traveling direction of the magnetic gradient can be suppressed. Assuming magnetic sources of different sizes, the change in magnetic gradient in the direction of penetrating the magnetic field is more gradual for large magnetic sources and steeper for small magnetic sources. According to the filter processing for suppressing a low frequency component as described above, a magnetic component derived from a magnetic source having a size larger than that of the magnetic marker can be effectively removed.

  The filter processing may be processing using an analog filter or processing using a digital filter. As the digital filter, an infinite impulse response (IIR) filter such as a Kalman filter, a finite impulse response (FIR) filter, or the like can be employed. As the analog filter, a CR filter combining a capacitor and a resistor, an LC filter combining a coil and a capacitor, and the like can be employed.

The plurality of magnetic sensors are arranged at least in a vehicle width direction of the vehicle, and in the gradient generation step, at least a difference calculation process of magnetic measurement values of the two magnetic sensors arranged in the vehicle width direction is performed. good.
It is also possible to employ a sensor array in which a plurality of magnetic sensors are arranged along the vehicle width direction. If such a sensor array is mounted on a vehicle, the magnetic properties of the magnetic marker can be measured with high reliability, for example, as traced by a line scanner. The above-described difference calculation process includes not only a process of actually performing subtraction to calculate a difference, but also a process of calculating a difference using an electric circuit.

The plurality of magnetic sensors are arranged at least in the traveling direction, and in the gradient generation step, it is preferable to execute at least a difference calculation process of magnetic measurement values of two magnetic sensors arranged in the traveling direction.
If a plurality of magnetic sensors are arranged in the traveling direction, the magnetic gradient in the traveling direction can be calculated with high accuracy by, for example, calculating the difference between the magnetic measurement values of the two magnetic sensors that have performed measurement at the same time.

The frequency characteristic of the filter applied to the filter processing may be switched according to whether the traveling road on which the vehicle is traveling is a motorway or a general road.
Among the roads forming a part of the travel road, when comparing a motorway and a general road, for example, the scale of a structure such as a bridge or a tunnel, the presence or absence of a signboard of a roadside store, and the like are different. Therefore, by switching the frequency characteristics of the filter according to the type of road, the detection reliability of the magnetic marker can be further improved.

Embodiments of the present invention will be specifically described using the following examples.
(Example 1)
This example relates to a magnetic marker detection device 1 having a function as a polarity determination device that determines the polarity of a magnetic marker 10 laid on a road that is an example of a traveling road. This content will be described with reference to FIGS.

As shown in FIGS. 1 and 2, the magnetic marker detection system 1S includes a combination of a magnetic marker 10 laid on a road and a magnetic marker detection device 1 on the vehicle 5 side.
The magnetic marker 10 has a flat shape with a diameter of 100 mm and a thickness of 1.5 mm, one of the front and back forms an N pole, and the other forms an S pole. The magnetic marker 10 can be adhesively bonded to the road surface 100S, and is laid along the center of the lane 100 on which the vehicle 5 runs. The magnetic marker 10 is laid with the N pole on the upper side so that the N pole is detected on the vehicle side in the lane of the one lane road on one side, and the S pole is on the upper side in the overtaking lane of the road having two or more lanes on one side. The lane is laid so that the N pole is on the upper surface. On the vehicle 5 side, the type of the lane can be determined by determining the polarity of the installed magnetic marker 1.

  As shown in FIGS. 3 and 4, the magnetic marker detection device 1 includes a sensor array 11 in which 15 magnetic sensors C1 to 15 (hereinafter, referred to as Cn, where n is a natural number of 1 to 15) are arranged in a straight line. And a detection unit 12 incorporating a CPU and the like (not shown). The sensor array 11 is a sensor unit attached to a vehicle body floor 50 that corresponds to a bottom surface of the vehicle 5. In the case of the vehicle 5 of this example, the mounting height of the sensor array 11 based on the road surface 100S is 200 mm.

  The detection unit 12 is an arithmetic unit that executes various arithmetic processes for detecting the magnetic marker 10 and determining the polarity. The detection unit 12 performs an arithmetic process using a sensor signal output from the sensor array 11. The detection result and the like by the detection unit 12 are input to, for example, an ECU (not shown) on the vehicle 5 side, and are used for various controls such as automatic steering control for maintaining a lane, lane departure warning, and automatic driving. Note that, instead of this example, the function of the detection unit 12 may be integrated into the sensor array 11 to be integrated.

Hereinafter, the configurations of the sensor array 11 and the detection unit 12 will be described, and then the operation of the magnetic marker detection device 1 will be described.
The sensor array 11 shown in FIG. 3 includes difference circuits G1 to G14 for calculating a difference between magnetic measurement values of two adjacent magnetic sensors in addition to the 15 magnetic sensors Cn (Gm is described as Gm, where m is 1 to 14). Natural number). The sensor array 11 is mounted along the vehicle width direction such that the magnetic sensors C1 are located on the left side of the vehicle (passenger seat side of a right-hand drive vehicle) and are arranged in numerical order toward the right side.

  As for the interval between the magnetic sensors Cn in the sensor array 11, it is necessary to set an interval such that the magnetism of the magnetic marker 10 can be detected by at least two magnetic sensors Cn. If such an interval is set, the magnetic gradient can be calculated by the difference calculation by the difference circuit Gm. Therefore, in this example, the interval between the magnetic sensors Cn in the sensor array 11 is set to 70 mm.

  The sensor array 11 outputs, as a sensor signal, a magnetic gradient in the vehicle width direction, which is a difference operation value obtained by the difference circuit Gm. The sensor array 11 has an output port of 14 channels (not shown) so that the difference operation value of the difference circuit Gm can be output simultaneously. The detailed configuration of the magnetic sensor Cn will be described later.

  The detection unit 12 in FIGS. 3 and 4 is an electronic board on which a memory element such as a ROM (read only memory) or a RAM (random access memory) is mounted in addition to a CPU (central processing unit) for executing various operations. (Not shown). The detection unit 12 constitutes a detection unit that executes the magnetic marker detection method of the present example together with the difference circuit Gm of the sensor array 11. The detection unit 12 corresponds to simultaneous capture of sensor signals of 14 channels output from the sensor array 11.

  The detection unit 12 has, as a functional circuit configuration, a filter processing circuit 125 (FIG. 3) that performs a filtering process on the series data output from the sensor array 11 as a sensor signal, and a detection processing circuit 127 (FIG. 3) that performs a marker detection process. ), And a polarity determination circuit 129 (FIG. 4) as an example of a polarity determination means for determining the polarity of the magnetic marker 10. The polarity determination circuit 129 is provided electrically in parallel with the filter processing circuit 125 and the detection processing circuit 127. Furthermore, in the detection unit 12, data areas M1 to M14 (denoted as Mm as appropriate) for storing data (magnetic gradient in the vehicle width direction) output from the sensor array 11, and data areas H1 to H1 for storing filter output values of filter processing. H14 (appropriately described as Hm) is provided.

The data area Mm in FIGS. 3 and 4 is a storage area for sequentially storing data represented by 14-channel sensor signals output from the sensor array 11 at a 3 kHz cycle as described above, and storing the data as sequence data for each channel. .
The filter processing circuit 125 is a circuit that performs a filtering process on the sequence data of 14 channels stored in the data area Mm for each channel. The filter applied to this filtering is a high-pass filter that suppresses or blocks low-frequency components and passes high-frequency components. In this example, an IIR filter is employed as a filter.
The polarity determination circuit 129 is a circuit that determines the polarity of the magnetic marker 10 by using the 14-channel sequence data stored in the data area Mm as input data. As described above, the polarity determination circuit 129 is provided electrically in parallel with the filter processing circuit 125.

  Here, the magnetic sensor Cn will be described in detail. The magnetic sensor Cn forming the sensor array 11 is a one-chip MI sensor in which the MI element 21 and the drive circuit are integrated as shown in FIG. The MI element 21 is an element including an amorphous wire 211 made of a CoFeSiB-based alloy and having almost zero magnetostriction, and a pickup coil 213 wound around the amorphous wire 211. The magnetic sensor Cn detects magnetism acting on the amorphous wire 211 by measuring a voltage generated in the pickup coil 213 when a pulse current is applied to the amorphous wire 211. The MI element 21 has a detection sensitivity in the axial direction of the amorphous wire 211 that is a magnetic sensitive body. In each magnetic sensor Cn of the sensor array 11, an amorphous wire 211 is provided along the vehicle width direction.

  The drive circuit is an electronic circuit that includes a pulse circuit 23 that supplies a pulse current to the amorphous wire 211 and a signal processing circuit 25 that samples and outputs a voltage generated by the pickup coil 213 at a predetermined timing. The pulse circuit 23 is a circuit including a pulse generator 231 that generates a pulse signal that is a source of a pulse current. The signal processing circuit 25 is a circuit that extracts an induced voltage of the pickup coil 213 through a synchronous detection 251 that is opened and closed in conjunction with a pulse signal, and amplifies the induced voltage at a predetermined amplification rate by an amplifier 253. The signal amplified by the signal processing circuit 25 is output to the outside as a sensor signal.

  The magnetic sensor Cn is a high-sensitivity sensor having a measurement range of magnetic flux density of ± 0.6 mT and a magnetic flux resolution within the measurement range of 0.02 μT. Such high sensitivity is realized by the MI element 21 utilizing the MI effect that the impedance of the amorphous wire 211 changes sensitively according to an external magnetic field. Further, the magnetic sensor Cn can perform high-speed sampling at a cycle of 3 kHz, and also supports high-speed running of the vehicle. In this example, the cycle of the magnetic measurement by the sensor array 11 is set to 3 kHz, and the sensor array 11 inputs a sensor signal to the detection unit 12 every time the magnetic measurement is performed.

  Next, the contents of the magnetic marker detection method and the polarity determination method executed by the magnetic marker detection device 1 configured as described above will be described with reference to the flowchart of FIG. The process of FIG. 7 is executed in synchronization with the measurement by each magnetic sensor Cn of the sensor array 11.

(FIG. 6, Step S101) Magnetic Measurement The sensor array 11 executes magnetic measurement by each magnetic sensor Cn at a cycle of 3 kHz. As described above, in each of the magnetic sensors Cn, the amorphous wire 211 (see FIG. 5), which is a magnetic sensor, is disposed along the vehicle width direction. Since the magnetism acting on the magnetic marker 10 in the vehicle width direction is directed to both sides of the magnetic marker 10, the direction of the magnetism acting on each magnetic sensor Cn in the vehicle width direction is opposite depending on the left or right side of the magnetic marker 10. At the same time, the direction is reversed depending on whether the magnetic marker 10 is the N pole or the S pole.

  In this example, the magnetic sensor Cn located on the left side of the N-pole magnetic marker 10 outputs a negative sensor signal, and the magnetic sensor Cn located on the right side outputs a positive sensor signal. A drive circuit is configured. In the magnetic sensor Cn having such a driving circuit, the sensor signal of the magnetic sensor Cn located on the left side of the magnetic marker 10 of the S pole is theoretically a positive value, and the sensor of the magnetic sensor Cn located on the right side is theoretically provided. The signal has a negative value. However, in actual magnetic measurement affected by disturbance magnetism, it is difficult to accurately determine the polarity of the magnetic marker 10 based only on the sign of the sensor signal.

  7 and 8 illustrate the distribution of magnetism in the vehicle width direction acting on each magnetic sensor Cn included in the sensor array 11. FIG. 7 corresponds to the magnetic marker 10 of the north pole, and FIG. 8 corresponds to the magnetic marker 10 of the south pole. In these figures, the traveling direction (time direction, longitudinal direction of the road) of the vehicle 5 is defined from the upper left position p1 to the lower right position p7, and the sensor array 11 is located directly above the N-pole magnetic marker 10. The moment of the position is the position p4. The position p1 → p4 is a section approaching the magnetic marker 10, and the position p4 → p7 is a section away from the magnetic marker 10.

  The distribution waveform of the magnetic gradient in the vehicle width direction at each position in FIGS. 7 and 8 has a difference in the amplitude of the waveform, but in each case, a zero cross occurs in accordance with the position of the magnetic marker 10 in the vehicle width direction. Alternating lid waveforms with opposite signs on both sides of the zero cross. When the vehicle 5 to which the sensor array 11 is attached passes the magnetic marker 10, the amplitude of the distribution waveform of the lid gradually increases as the vehicle 5 approaches the magnetic marker 10, and directly above the magnetic marker 10 (at a position p 4). ) Gives the maximum amplitude. Thereafter, as the vehicle 5 moves away from the magnetic marker 10, the amplitude of the distribution waveform of the lids gradually decreases. In the magnetic marker 10 of the north pole and the magnetic marker 10 of the south pole, the order of the positive and negative waveforms of the two peaks is reversed.

(FIG. 6, Step S102) Difference Calculation The magnetic measurement value of each magnetic sensor Cn is input to a difference circuit Gm (FIG. 3) constituting the sensor array 11. For example, the difference circuit G1 receives the magnetic measurement values of the magnetic sensors C1 and C2, and executes a difference calculation process of subtracting the magnetic measurement value of C1 from the magnetic measurement value of C2 (gradient generation step). As described above, the difference circuit Gm executes a difference operation of subtracting the magnetic measurement value of the magnetic sensor Cm (m is a natural number of 1 to 14) from the magnetic measurement value of the magnetic sensor C (m + 1).

  The difference calculation value of the difference circuit Gm is a difference between the magnetic measurement values of two adjacent magnetic sensors Cn in the sensor array 11, and indicates a magnetic gradient in the vehicle width direction which is an example of the first magnetic gradient. The distribution waveform of the magnetic gradient in the vehicle width direction is a waveform in which small peaks in opposite directions are adjacent to both sides of a high peak as illustrated in the graphs of positions p1 to p7 in FIGS. FIG. 9 corresponds to the magnetic marker 10 having the N pole, and FIG. 10 corresponds to the magnetic marker 10 having the S pole.

  The difference calculation (gradient generation step, step S102 in FIG. 6) for calculating the magnetic gradient in the vehicle width direction as described above is effective in removing common magnetic noise that uniformly acts on each magnetic sensor Cn. . Common magnetic noise is likely to be generated not only from geomagnetism but also from a large-sized magnetic source such as an iron bridge or another vehicle. In the case of a large magnetic source, the magnetic field loop from the north pole to the south pole becomes very large, so that the magnetic field approaches uniformly at a position intermediate between the two poles, and the magnetism acting on each magnetic sensor Cn is nearly uniform. Has become.

  The sensor array 11 simultaneously outputs sensor signals of 14 channels, each of which includes a difference operation value of the difference circuit Gm. The detection unit 12 stores the series data for each channel based on the sensor signal in the data area Mm (FIGS. 3 and 4). When a new sensor signal is acquired, the detection unit 12 deletes the oldest data in the data area Mm and sequentially sends each data in the data area Mm to provide an empty area, and converts the data represented by the newly acquired sensor signal. Store in the free area.

  The sequence data in the time direction of the data area Mm has a distribution of one mountain whose amplitude increases as the vehicle 5 approaches the magnetic marker 10, reaches a maximum amplitude at the position p4, and decreases as the vehicle 5 moves away from the magnetic marker 10. For example, the diagonal graphs on the right side of FIGS. 9 and 10 illustrate changes in the series data corresponding to positions in the vehicle width direction passing directly above the magnetic marker 10. In this graph, the advancing direction (time direction) is defined on an axis diagonally downward and to the right in the figure, and the magnetic gradient in the vehicle width direction is defined on an orthogonal axis.

(FIG. 6, Step S103) Filter Processing The detection unit 12 inputs each series data stored in the data area Mm to the filter processing circuit 125 for each channel, and performs a filter processing for cutting off low frequency components and passing high frequency components. Execute (filter processing step). Specifically, a filter output value is calculated by convolution of the IIR filter with respect to the series data in the data area Mm, and stored in the data area Hm (FIG. 3).

(FIG. 6, Step S104) Marker Detection Process The detection unit 12 executes a marker detection process for detecting the magnetic marker 10 using the filter output value stored in the data area Hm. The detection unit 12 detects the presence or absence of the magnetic marker 10, and when the detection is successful, calculates the position of the magnetic marker 10 in the vehicle width direction relative to the sensor array 11.

  For example, in the case of a large magnetic source such as a bridge or a tunnel, the difference calculation in S102 of FIG. 6 exhibits a certain effect. However, even in the case of a large magnetic source, a magnetic gradient is generated around a magnetic pole end due to a magnetic field. If a magnetic gradient has occurred, it is difficult to remove it only by the difference calculation in S102.

  The rate of change of the magnetic gradient differs between the large magnetic source and the small magnetic source due to the difference in the distance between the magnetic poles. That is, in a large magnetic source having a long distance between the magnetic poles, the distance until the magnetic gradient of one magnetic pole transitions to the magnetic gradient of the other magnetic pole is long, and the magnetic gradient changes slowly. On the other hand, when the distance between the magnetic poles becomes short, the change of the magnetic gradient becomes sharp and the change rate becomes large. According to the filter processing for cutting off low-frequency components, it is possible to remove a magnetic gradient having a gradual change and a small change rate.

  When passing through the N-pole magnetic marker 10, the peak value of the magnetic gradient in the vehicle width direction obtained by the difference calculation in S102 in FIG. 6 becomes a positive value, and changes as shown in the oblique graph on the right side in FIG. When the vehicle 5 travels along the lane 100, theoretically, a positive peak occurs each time the vehicle 5 passes the magnetic marker 10. However, in the actual road environment, due to the presence of a magnetic source such as a bridge or a tunnel, a theoretical change in which a peak periodically appears every time the magnetic marker 10 is passed cannot be obtained. As shown in FIG. 11A, it may be difficult to determine the peak due to the influence of disturbance magnetism. By intercepting the low-frequency component with respect to such a temporal change in the magnetic gradient in the vehicle width direction, it is possible to approach the theoretical change in which the peak periodically appears as shown in FIG. The marker 10 can be easily detected. When passing through the magnetic marker 10 of the S pole, the peak value of the magnetic gradient in the same vehicle width direction becomes a negative value as shown in FIG. 10, and the sign is reversed from that of the case of the N pole in FIG.

  In contrast to FIG. 11B exemplifying the filter output value in the case of the N pole, in the case of the magnetic marker 10 of the S pole, the sign is reversed. Therefore, in performing the detection processing of the magnetic marker 10, when the absolute value processing is performed on the filter output value stored in the data area Hm, the threshold processing is performed to detect the peak, and thus the magnetic marker 10 is detected. good. If the absolute value processing is performed, a peak value on the positive side appears regardless of whether it is the N pole or the S pole. Therefore, the peak can be detected relatively easily by threshold processing for detecting a positive value equal to or more than a predetermined value.

(FIG. 6, Step S105) Polarity Determination Processing The magnetic marker detection device 1 having a function as a polarity determination device determines the polarity of the detected magnetic marker 10 (polarity determination step). The magnetic marker detection device 1 is provided with the polarity determination circuit 129 of FIG. 4 in parallel with the configuration after the filter processing circuit 125 in FIG. When the magnetic marker 10 is detected (at the position p4), the polarity determination circuit 129 executes a polarity determination process for determining whether the peak value is positive or negative with reference to the magnetic gradient of the data area Mm in the vehicle width direction. Then, if the peak value is a positive value as shown in FIG. 9, it is determined to be the N pole, and if the peak value is a negative value as shown in FIG. 10, it is determined to be the S pole. If the magnetic marker 10 detected in the marker detection processing (S104 in FIG. 6) is the S pole, the type of the traveling lane can be determined to be the overtaking lane. It can be distinguished from other lanes.

  The magnetic marker detection method as described above is based on a combination of a gradient generation step of obtaining a difference between magnetic measurement values of two magnetic sensors and a filter processing step of performing a filtering process using a high-pass filter for a change in a traveling direction of a magnetic gradient. This is a detection method for removing magnetism that causes disturbance. Disturbance magnetism acting uniformly can be effectively removed by the difference between the magnetic measurement values of the two magnetic sensors. On the other hand, the disturbance magnetism from the peripheral magnetic field at the end, which is the magnetic pole of a large magnetic source such as a bridge or a tunnel, can be effectively removed by filtering with a high-pass filter.

  Further, in the polarity determination method of the present example, the polarity of the magnetic marker 10 is determined by using the sign of the peak value of the magnetic gradient in the vehicle width direction, which is the difference between the magnetic measurement values of two magnetic sensors Cn adjacent to each other in the sensor array 11. Is determined. By using the magnetic gradient in the vehicle width direction in which the disturbance magnetism acting uniformly as described above is effectively removed, the polarity of the magnetic marker 10 can be determined with high certainty.

  As described above, the polarity determination method of the magnetic marker 10 according to the present embodiment is an excellent determination method that can determine the polarity of the magnetic marker 10 with high reliability by calculating the magnetic gradient and removing the magnetism that causes disturbance. The magnetic marker detection device 1 having a function as a polarity determination device that executes this polarity determination method is a device having excellent characteristics capable of determining the polarity of the detected magnetic marker 10 with high certainty.

  In this example, in the detection processing of the magnetic marker 10, the magnetic marker 10 is detected by threshold processing after applying the absolute value processing to the filter value of the data area Hm (FIG. 3). The absolute value processing of the filter output value stored in the data area Hm may be omitted. In this case, the filter output value stored in the data area Hm is subjected to threshold processing using two positive and negative thresholds for detecting a positive peak and a negative peak, and positive and negative peaks are detected. May be used to detect the magnetic marker 10. In this case, if a positive peak can be detected, it can be determined that the N-pole magnetic marker 10 has been detected, and if a negative peak can be detected, it can be determined that the S-pole magnetic marker 10 has been detected. As described above, the polarity of the magnetic marker 10 can be determined using the filter value of the data area Hm.

  In this example, the magnetic sensor Cn having sensitivity in the vehicle width direction is employed, but a magnetic sensor having sensitivity in the traveling direction or a magnetic sensor having sensitivity in the vertical direction may be used. Further, for example, a magnetic sensor having sensitivity in two axial directions of the vehicle width direction and the traveling direction or in two axial directions of the traveling direction and the vertical direction may be employed. For example, three magnetic axes in the vehicle width direction, the traveling direction and the vertical direction may be used. A magnetic sensor having sensitivity in the direction may be employed. If a magnetic sensor having sensitivity in a plurality of axial directions is used, the magnitude of magnetism and the direction of action of magnetism can be measured, and a magnetic vector can be generated. It is also possible to distinguish between the magnetism of the magnetic marker 10 and the disturbance magnetism using the difference between the magnetic vectors and the rate of change of the difference in the traveling direction.

  Although the one-dimensional filter processing in the traveling direction (time direction) of the vehicle has been illustrated, the spatial filter processing is performed on a magnetic change in a two-dimensional space defined by the traveling direction (time direction) of the vehicle and the vehicle width direction. To remove disturbance magnetism. A spatial filter may be applied to a magnetic change in a two-dimensional space defined by the vehicle width direction and the vertical direction. Further, with respect to a magnetic change in a spatio-temporal region obtained by combining the traveling direction (time direction) of the vehicle with the two-dimensional space, a spatio-temporal filter may be applied to remove disturbance magnetism.

The width of the lane 100 is different between a motorway such as an expressway and a general road, and there is a difference such as the presence or absence of a signboard or a telephone pole at a store. Therefore, it is also possible to switch the frequency characteristics of the filter applied to the filter processing according to whether it is a motorway or a general road. For example, if the lane 100 is an automobile-only road that is relatively wide and has few signboards at stores, the cutoff frequency for cutting off low frequencies may be reduced, or the cutoff characteristics of the filter may be set gently. If the cutoff characteristic is moderate, the degree of freedom in designing the filter increases, and the calculation load required for the filter processing may be reduced. On the other hand, on a general road in which the number of magnetic sources causing disturbance is relatively large, the cutoff frequency may be switched to a higher value. Further, the interval between the magnetic markers 10 laid on the road may be detected, and the frequency characteristics of the filter may be switched according to the interval.
Further, instead of the high-pass filter, a band-pass filter that allows a specific frequency region to pass can be adopted.

  In the present embodiment, the magnetic gradient in the vehicle width direction is generated by the difference calculation for the magnetic sensors Cn arranged in the vehicle width direction, but instead or additionally, the magnetic sensors Cn are arranged in the traveling direction of the vehicle. For the two magnetic sensors arranged in the traveling direction, a magnetic gradient in the traveling direction may be obtained by a difference calculation, and this may be treated as a first magnetic gradient.

  In this example, the information of the type of the traveling lane is provided to the vehicle using the polarity of the magnetic marker 10. The code of the combination of the N pole and the S pole may be provided to the vehicle using the polarity of the magnetic marker 10. The information represented by the code includes various kinds of information such as position information, traffic information, and warning information.

(Example 2)
The present example is an example in which preprocessing for filter processing is added based on the magnetic marker detection method of the first embodiment. This content will be described with reference to FIGS.
In the detection unit 12 of FIGS. 12 and 13, based on the detection unit 12 of the first embodiment, between the data area Mm and the filter processing circuit 125, difference circuits T1 to T14 (denoted as Tm as appropriate), a difference circuit Data areas N1 to N14 for storing the difference operation value of Tm (appropriately described as Nm) are added. Further, as shown in FIG. 13, a polarity determination circuit 129 is provided in parallel downstream of the data area Nm.

The difference circuit Tm sets a magnetic gradient in the vehicle width direction represented by the sensor signal of the sensor array 11 as a first magnetic gradient, and calculates a difference between the first magnetic gradients at two positions separated by a predetermined distance in the traveling direction of the vehicle, This is a circuit that calculates a magnetic gradient in the traveling direction, which is an example of a second magnetic gradient.
The data area Nm is a storage area in which the second magnetic gradient, which is the difference operation value of the difference circuit Tm, is stored as needed, and is stored as series data in the traveling direction. The series data in the data area Nm is to be filtered.

  Next, the contents of the magnetic marker detection method of this example will be described with reference to the flowchart of FIG. In the processing of FIG. 7, the step S101 for measuring the magnetic field by each magnetic sensor Cn of the sensor array 11 and the step S102 for calculating the magnetic gradient in the vehicle width direction (gradient generation step) are the processes having the same specifications as in the first embodiment. It is. The sensor array 11 that has generated the magnetic gradient in the vehicle width direction, which is the first magnetic gradient, by the difference calculation in step S102, outputs the sensor signals of 14 channels all at once.

  When the detection unit 12 acquires the sensor signal of the sensor array 11, the magnetic gradient in the vehicle width direction represented by the sensor signal is sequentially stored in the data area Mm to generate sequence data. As described above with reference to FIG. 9, the change in the magnetic gradient in the vehicle width direction formed by the series data is, for example, in the case of the N pole, as shown in the graph of FIG. 15A in the traveling direction of the vehicle.

  The detection unit 12 uses the magnetic gradient in the vehicle width direction as the first magnetic gradient, and calculates the difference between the first magnetic gradients at the two positions in the traveling direction, so that the magnetic field in the traveling direction as the second magnetic gradient is calculated. A gradient is generated (S112, gradient generation step). Specifically, as shown in the graph of FIG. 15A (example of the case of the N pole), data at two positions separated by a predetermined distance and in the traveling direction from the series data of the magnetic gradient in the vehicle width direction that changes, By selecting the magnetic gradient in the vehicle width direction and calculating the difference, a magnetic gradient in the traveling direction, which is the second magnetic gradient, is generated. The detection unit 12 sequentially generates the magnetic gradient in the traveling direction, which is the second magnetic gradient, while shifting the “predetermined distance” in the traveling direction in FIG. Then, by sequentially storing the generated magnetic gradients in the traveling direction in the data area Nm, the series data in the traveling direction of the second magnetic gradient is generated. The distribution of the magnetic gradient in the traveling direction formed by the series data is as shown in a graph illustrated in FIG. The graph for the S pole is not shown, but the sign of the graph of FIG. 15 for the N pole is reversed.

  The detection unit 12 inputs the series data of the magnetic gradient in the traveling direction of the 14 channels stored in the data area Nm to the filter processing circuit 125, and executes a filter process of cutting off low-frequency components and passing high-frequency components (S103). ). Thereafter, the detection processing circuit 127 of the detection unit 12 executes a marker detection process for detecting the magnetic marker 10 using the data stored in the data area Hm (S104).

  The magnetic gradient in the traveling direction of the vehicle 5 while traveling along the lane 100 theoretically changes such that the waveform including the zero cross in FIG. However, for example, when a vehicle approaches a magnetic source structure such as a bridge or a tunnel, a magnetic field around the magnetic pole located at the end of the magnetic source structure such as a bridge acts and the traveling direction is increased. May be changed as shown in FIG. On the other hand, the filter processing in step S103 is very effective. By applying a filter process for blocking the low-frequency component with respect to the change in FIG. 16A, it is possible to approach the theoretical change in which the zero cross periodically appears as shown in FIG. By detecting this zero cross, the magnetic marker 10 can be detected.

  In the polarity determination process (FIG. 14, S105), the zero cross of the magnetic gradient (second magnetic gradient) in the data area Nm when the magnetic marker 10 is detected is as shown in FIGS. 15B and 16B. If it is a zero crossing from positive to negative, it can be determined as an N pole, and if it is a zero crossing from negative to positive, it can be determined as an S pole.

  The predetermined distance for generating the magnetic gradient in the traveling direction, which is the second magnetic gradient, may be set to a distance of, for example, 30 to 150 mm in consideration of the size of the magnetic marker 10 to be detected. Further, for example, if the magnetic marker detecting device 1 has a function of estimating the size of the magnetic marker 10 and the above-described predetermined distance is changed according to the estimated size, the magnetic marker 10 having various specifications can be detected with high reliability. become able to.

  In this example, the difference between the magnetic measurement values of the magnetic sensors Cn adjacent in the vehicle width direction is defined as a first magnetic gradient, and the difference between the first magnetic gradient at two positions in the traveling direction is defined as a second magnetic gradient. The filter processing is applied to the change in the traveling direction of the second magnetic gradient. Here, the filtering process is applied to the change in the magnetic gradient after the difference is applied twice, but the number of times of the difference can be increased to 3, 4,. Increasing the number of differences is particularly effective in removing magnetic noise that acts uniformly on each magnetic sensor, while increasing the number of differences decreases the effective signal level and reduces the S / N ratio. Tends to decrease. In selecting the number of times of the difference, it is good to consider the balance between the effect of removing magnetic noise and the adverse effect due to the decrease in the S / N ratio.

In this example, the polarity of the magnetic marker 10 is determined using the magnetic gradient of the data area Nm, but the polarity can be determined using the filter output value of the data area Hm, as in the first embodiment. It is. The polarity can be determined based on whether positive → negative zero cross or negative → positive zero cross.
The other configuration and operation and effect are the same as those of the first embodiment.

(Example 3)
This embodiment is an example in which the configuration of the sensor array 11 is changed based on the magnetic marker detection device 1 of the first embodiment. This content will be described with reference to FIG.
In the sensor array 11 of this example, the magnetic sensors are arranged in a two-dimensional array of two rows in the traveling direction and 15 columns in the vehicle width direction. The interval between the magnetic sensors Cn in the vehicle width direction in the sensor array 11 is 70 mm as in the first embodiment, while the interval between the magnetic sensors Cn in the traveling direction is 30 mm. In the detection unit 12, a polarity determination circuit is provided in parallel downstream of the data area Mm as in FIG. 4 referred to in the first embodiment.

  In each magnetic sensor constituting the sensor array 11, an amorphous wire, which is a magnetic sensitive body, is disposed along the traveling direction of the vehicle, and the magnetic sensitivity is set in the traveling direction. In the following description, the 15 magnetic sensors on the front side in the traveling direction are C1A to C15A (hereinafter, referred to as CnA, where n is a natural number of 1 to 15), and the 15 magnetic sensors on the rear side in the traveling direction are C1B to C15B. (Hereinafter, described as CnB, n is a natural number of 1 to 15.)

  The sensor array 11 of this example includes two types of differential circuits K1 to K15 (hereinafter, described as Kn) and differential circuits S1 to S14 (hereinafter, described as Sm, where m is a natural number of 1 to 14). . The difference circuit Kn is a circuit that calculates a difference between a magnetic measurement value of the magnetic sensor CnA and a magnetic measurement value of the magnetic sensor CnB to obtain a first magnetic gradient. The difference circuit Sm calculates a difference between the first magnetic gradient by the difference circuit Km + 1 and the first magnetic gradient by the difference circuit Km, and thereby calculates a new magnetic gradient different from the first magnetic gradient by the difference circuit Kn. 1 is a circuit for obtaining a magnetic gradient of 1.

  The sensor array 11 simultaneously outputs the first magnetic gradient, which is the difference operation value of the difference circuit Kn, via a 14-channel output port (not shown). The detection unit 12 includes data areas M1 to M14 as in the first embodiment. The detection unit 12 stores the first magnetic gradient of the 14 channels output from the sensor array 11 all at once in the data areas M1 to M14, and generates series data for each channel.

  As with the first embodiment, the detection unit 12 applies filter processing using a high-pass filter to the series data for each channel, and stores filter output values, which are outputs of the filter processing, in the data areas H1 to H14. Then, the detection unit 12 performs a marker detection process using the filter output values stored in the data areas H1 to H14 as input values, and detects the presence or absence of a magnetic marker. Further, similarly to the first embodiment, the polarity determination processing can be executed using the magnetic gradient of the data area Mm as an input value.

  In calculating the difference between the magnetic measurement values of the two magnetic sensors (the first magnetic gradient by the above-described difference circuit Kn), two magnetic sensors having a small interval of about 10 mm to 50 mm may be targeted. However, if magnetic sensors are arranged in the vehicle width direction at a narrow interval of 30 mm in this example to realize a sensor array 11 having a width of about 1 m, for example, each row in the vehicle width direction (1 m ÷ 30 mm) = approximately 33 magnetic sensors are required, and the entire sensor array 11 requires about 66 magnetic sensors, which is twice as large. On the other hand, if the interval between the magnetic sensors in the traveling direction is set to 30 mm and the interval in the vehicle width direction is set to 70 mm as in this example, the number of magnetic sensors required for the sensor array 11 can be reduced, and (1 m The sensor array 11 can be composed of about 28 magnetic sensors, which is twice as large as (÷ 70 mm) = about 14.

In this example, the polarity of the magnetic marker 10 is determined using the magnetic gradient of the data area Mm, but the polarity can be determined using the filter output value of the data area Hm, as in the first embodiment. It is. The polarity can be determined based on whether positive → negative zero cross or negative → positive zero cross.
The other configuration and operation and effect are the same as those of the first embodiment.

  As described above, specific examples of the present invention have been described in detail as in the embodiments, but these specific examples only disclose examples of the technology included in the claims. Needless to say, the scope of the claims should not be interpreted in a limited manner by the configuration, numerical values, and the like of the specific examples. The scope of the claims encompasses techniques in which the above-described specific examples are variously modified, changed, or appropriately combined using known techniques or knowledge of those skilled in the art.

1 Magnetic marker detection device (polarity determination device)
1S Magnetic marker detection system 10 Magnetic marker 100 Lane 11 Sensor array 12 Detection unit 125 Filter processing circuit 127 Detection processing circuit 129 Polarity determination circuit (polarity determination means)
5 vehicles

Claims (6)

A polarity determination method for determining the polarity of a magnetic marker laid on a traveling path using at least two or more magnetic sensors attached to a vehicle,
A first which can be calculated by one or two or more difference calculations on magnetic measurement values obtained by two or more magnetic sensors of the plurality of magnetic sensors having different mounting positions at the same measurement timing. A gradient generating step of generating a magnetic gradient of
A process of determining the polarity of the magnetic marker using at least one of a second magnetic gradient that is a difference between the first magnetic gradients having different measurement timings and a first magnetic gradient. And a polarity determining method for performing a magnetic marker.   2. The method according to claim 1, wherein in the polarity determining step, a filter output value is generated by performing a filter process for suppressing or cutting off at least a low frequency component with respect to a change in the traveling direction of the vehicle with any of the magnetic gradients. A method of determining the polarity of a magnetic marker using a filter output value to determine the polarity of the magnetic marker.   3. The magnetic sensor according to claim 1, wherein the plurality of magnetic sensors are arranged at least in a vehicle width direction, and in the gradient generation step, at least two magnetic sensors arranged in the vehicle width direction. 3. Of determining the polarity of the magnetic marker that executes the difference calculation processing of (1).   The magnetic sensor according to any one of claims 1 to 3, wherein the plurality of magnetic sensors are arranged at least in the traveling direction, and in the gradient generation step, at least two magnetic sensors arranged in the traveling direction. A method of determining the polarity of a magnetic marker that executes a difference calculation process of a measured value.   The magnetic marker according to any one of claims 1 to 4, wherein a frequency characteristic of a filter applied to the filter processing is switched according to whether a traveling road on which the vehicle is traveling is an automobile exclusive road or a general road. Polarity determination method. A polarity determination device mounted on a vehicle to detect a magnetic marker laid on a traveling path,
At least two or more magnetic sensors;
And a polarity determining means for determining the polarity of the magnetic marker,
A polarity determination device for a magnetic marker, wherein the polarity determination unit is configured to execute the polarity determination method according to claim 1.

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