JP2017194353A - Polarity measurement method and polarity measuring device of magnetic marker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarity measurement method and a polarity measuring device capable of determining polarity of a magnetic marker with high reliability.SOLUTION: A polarity determination method for determining polarity of a magnetic marker laid on a driving road uses a plurality of at least two magnetic sensors mounted to a vehicle to execute a slope generation step of generating a first magnetic slope that can be calculated by a differential operation targeted for a magnetic measurement value that at least two magnetic sensors from among a plurality of magnetic sensors having different mount positions measure at the same measurement timing, and a polarity determination step of executing processing for determining polarity of a magnetic marker with a second magnetic slope as a difference of the first magnetic slope having different measurement timing as an input value.SELECTED DRAWING: Figure 6

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 vehicle marker system for using a magnetic marker laid on a road for driving assistance is known (see, for example, Patent Document 1). According to the marker system, for example, various driving assistances such as automatic steering control, lane departure warning, and automatic driving can be realized by detecting a magnetic marker laid along a road lane on the vehicle side. Furthermore, among such marker systems, there is a system that can provide information to the vehicle side by using the magnetic polarity of magnetic markers arranged along the road direction (see, for example, 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 determination accuracy of 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, steel reinforcing plates and reinforcing bars are installed inside to ensure structural strength. It can be a large source of magnetism. While the remanent magnetization of iron materials such as reinforcing bars is negligible compared to magnets, magnetism exceeding the geomagnetism occurs due to the huge volume of bridges and tunnels, etc. May generate a relatively large magnetic field. For example, the magnetic fields of various magnetic sources that exist on the road, such as structures such as bridges and tunnels, are one of the factors that reduce the polarity determination accuracy of the magnetic marker.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a polarity determination method and a polarity determination device that can determine 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 travel path using at least two or more magnetic sensors attached to a vehicle.
A first that can be calculated by one or two or more times of difference calculation for magnetic measurement values acquired 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 for generating a magnetic gradient of
Processing for determining the polarity of the magnetic marker by using at least one of the second magnetic gradient, which is the difference between the first magnetic gradients having different measurement timings, and the first magnetic gradient. And a polarity determination step for executing magnetic markers, and a polarity determination method for magnetic markers for executing.

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

  The magnetic marker polarity determination method 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. In this magnetic marker detection method, the magnetic component of the magnetic source having a size larger than that of the magnetic marker is removed using the difference in distribution of the magnetic gradient as described above, thereby improving the detection certainty of the magnetic marker. It is a way 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 calculation for the magnetic measurement values of the two or more magnetic sensors. According to this gradient generation step, magnetic noise acting uniformly on the two or more magnetic sensors can be removed by taking the difference between the magnetic measurement values of the two or more magnetic sensors, and the magnetic gradient can be extracted with high reliability. it can.

  As described above, the polarity determination method of the magnetic marker 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. In this method, the polarity of the magnetic marker is determined after removing the magnetic field that causes disturbance.

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

FIG. 3 is a front view of a vehicle with a sensor array attached thereto according to the first embodiment. The bird's-eye view which shows the lane in which the magnetic marker was laid in Example 1. FIG. FIG. 3 is a block diagram illustrating a functional configuration of the magnetic marker detection device according to the first embodiment. FIG. 3 is a block diagram illustrating a remaining part of the functional configuration of the magnetic marker detection device according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration of a magnetic sensor in the first embodiment. FIG. 3 is a flowchart showing the flow of marker detection processing in the first embodiment. FIG. 3 is an explanatory diagram illustrating a change in magnetic distribution in the vehicle width direction when passing through an N-pole magnetic marker in the first embodiment. FIG. 3 is an explanatory diagram illustrating the change in the magnetic distribution in the vehicle width direction when passing through the south pole magnetic marker in the first embodiment. FIG. 3 is an explanatory diagram illustrating a change in the magnetic gradient distribution in the vehicle width direction when passing through an N-pole magnetic marker in the first embodiment. FIG. 3 is an explanatory diagram illustrating the change in the magnetic gradient distribution in the vehicle width direction when passing through the S-pole magnetic marker in the first embodiment. FIG. 3 is an explanatory diagram of filter processing in the first embodiment. The block diagram which shows the functional structure of the magnetic marker detection apparatus in Example 2. FIG. FIG. 10 is a block diagram showing the remaining part of the functional configuration of the magnetic marker detection device in Embodiment 2. FIG. 9 is a flowchart showing the flow of marker detection processing in the second embodiment. The graph which shows the time change of the magnetic gradient of the vehicle width direction in Example 2, and the magnetic gradient of the advancing direction. Explanatory drawing of the filter process in Example 2. FIG. FIG. 9 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 calculating the difference between the magnetic measurement values in the gradient generation step according to the present invention may be a combination including two adjacent magnetic sensors, or one or two, etc. A combination including two magnetic sensors adjacent to each other with another magnetic sensor interposed therebetween may be used.

  Regarding the first magnetic gradient that can be calculated by the difference calculation for the magnetic measurement values of two or more magnetic sensors, it is not essential to actually calculate the first magnetic gradient by the difference calculation. The said 1st magnetic gradient should just be a value which can be calculated by difference calculation. For example, even if it is the 1st magnetic gradient which calculated | required the difference using the differential circuit by an analog circuit, as long as this 1st magnetic gradient can be calculated also by difference calculation, the concept of this invention is used. Is included.

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

  It is not necessary for the magnetic measurement values acquired by the two or more magnetic sensors at the same measurement timing to be the same as the measurement timing. For example, if the measurement process is repeated, it is measured repeatedly in the same round. It means that it is a magnetic measurement value. For example, if it is difficult to acquire the magnetic measurement values of each magnetic sensor at the same time and it is necessary to acquire them in order, the magnetic measurement values acquired during one round of the order are acquired at the same measurement timing. It can be said that the measured magnetic value.

  On the other hand, the 2nd magnetic gradient which concerns on this invention is a difference of the said 1st magnetic gradient from which the measurement timing from which the target magnetic measurement value was acquired differs. When the measurement timing at which the magnetic measurement value is acquired is different, for example, when the measurement process is repeated, it means that the measurement value is measured at different laps during the repetition. Since the position of the traveling vehicle advances in accordance with the passage of time, the second magnetic gradient can be grasped as the difference between the first magnetic gradients at the two positions in the traveling direction.

  In the polarity determination step of the polarity determination method according to the present invention, a filter process for suppressing or blocking at least a low frequency component is performed on the change in the traveling direction of the vehicle of any one of the magnetic gradients to generate a filter output value. The polarity of the magnetic marker may be determined using the filter output value.

  According to the filtering process, it is possible to suppress a low frequency component of the change in the traveling direction of the magnetic gradient. Assuming magnetic sources with different sizes, the change in the magnetic gradient in the direction penetrating the magnetic field is more gradual for large magnetic sources and sharper for small magnetic sources. According to the filtering process that suppresses 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 process may be an analog filter process or a digital filter process. As the digital filter, an infinite impulse response (IIR) filter such as a Kalman filter or a finite impulse response (FIR) filter can be employed. As an analog filter, a CR filter combining a capacitor and a resistor, an LC filter combining a coil and a capacitor, or the like can be used.

The plurality of magnetic sensors are arranged at least in the 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 executed. 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 attached to a vehicle, the magnetism of the magnetic marker can be measured with high certainty, for example, as traced by a line scanner. Note that the difference calculation process includes not only a process of actually subtracting and calculating a difference, but also a process of calculating a difference using an electrical circuit.

The plurality of magnetic sensors may be arranged at least in the traveling direction, and in the gradient generation step, at least a difference calculation process between magnetic measurement values of two magnetic sensors arranged in the traveling direction may be executed.
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 two magnetic sensors that have simultaneously performed measurement.

The frequency characteristics of the filter applied to the filter processing may be switched depending on whether the travel path in which the vehicle is traveling is an automobile-only road or a general road.
When roads that are part of the road are compared with roads dedicated to automobiles and ordinary roads, for example, the size of structures such as bridges and tunnels, the presence or absence of signs on roadside shops, and the like are different. Therefore, if the frequency characteristics of the filter are switched depending on the type of road, the detection certainty of the magnetic marker can be further improved.

The embodiment of the present invention will be specifically described with reference to the following examples.
Example 1
This example is an example relating to the magnetic marker detection device 1 having a function as a polarity determination device that determines the polarity of the magnetic marker 10 laid on a road that is an example of a traveling road. The contents will be described with reference to FIGS.

As shown in FIGS. 1 and 2, the magnetic marker detection system 1 </ b> S 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 surfaces has an N pole, and the other has an S pole. The magnetic marker 10 can be bonded to the road surface 100S, and is laid along the center of the lane 100 on which the vehicle 5 travels. The magnetic marker 10 is laid on the N pole as the upper surface so that the N pole is detected on the vehicle side in the road lane on one lane on one side, the S pole is on the upper surface in the overtaking lane on a road with two or more lanes on one side In this lane, the N pole is laid on the top surface. On the vehicle 5 side, the type of lane can be determined by determining the polarity of the magnetic marker 1 laid.

  As shown in FIGS. 3 and 4, the magnetic marker detection device 1 includes a sensor array 11 in which 15 magnetic sensors C <b> 1 to 15 (hereinafter referred to as Cn; n is a natural number of 1 to 15) are arranged in a straight line; A detection unit 12 having a built-in CPU or the like (not shown) is combined. The sensor array 11 is a sensor unit that is attached to the vehicle body floor 50 that contacts the bottom surface of the vehicle 5. In the case of the vehicle 5 of this example, the mounting height of the sensor array 11 with reference to 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 arithmetic processing using the sensor signal output from the sensor array 11. The detection result by the detection unit 12 is input to, for example, an ECU (not shown) on the vehicle 5 side, and is used for various controls such as automatic steering control for maintaining the lane, lane departure warning, and automatic driving. Instead of this example, the sensor array 11 may be integrated by incorporating the function of the detection unit 12.

Hereinafter, the configuration 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, in addition to the 15 magnetic sensors Cn, difference circuits G1 to G14 (referred to as Gm as appropriate. M is 1 to 14) that performs a difference calculation of magnetic measurement values of two adjacent magnetic sensors. Natural number.). The sensor array 11 is attached along the vehicle width direction so that the magnetic sensor C1 is positioned on the left side of the vehicle (passenger seat side of the right-hand drive vehicle) and is arranged in numerical order toward the right side.

  About the space | interval of the magnetic sensor Cn in the sensor array 11, it is necessary to set the space | interval which can detect the magnetism of the magnetic marker 10 with the at least 2 magnetic sensor 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 a magnetic gradient in the vehicle width direction, which is a difference calculation value by the difference circuit Gm, as a sensor signal. The sensor array 11 includes a 14-channel output port (not shown) so that the difference calculation value of the difference circuit Gm can be output simultaneously. The detailed configuration of the magnetic sensor Cn will be described later.

  3 and 4 is an electronic board on which a memory element such as a ROM (read only memory) and a RAM (random access memory) is mounted in addition to a CPU (central processing unit) that executes various operations. (Not shown). The detection unit 12 constitutes detection means for executing the magnetic marker detection method of this example together with the difference circuit Gm of the sensor array 11. This detection unit 12 corresponds to simultaneous capture of 14-channel sensor signals 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 filter processing on the series data that the sensor array 11 outputs as a sensor signal, and a detection processing circuit 127 (FIG. 3) that executes marker detection processing. ), And a polarity determination circuit 129 (FIG. 4) which is an example of a polarity determination means for determining the polarity of the magnetic marker 10. The polarity determination circuit 129 is provided in parallel with the filter processing circuit 125 and the detection processing circuit 127. Further, 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 the filter processing. H14 (denoted as Hm as appropriate) is provided.

The data area Mm in FIGS. 3 and 4 is a storage area for sequentially storing the data represented by the 14-channel sensor signals output by the sensor array 11 at a cycle of 3 kHz as described above, and storing the data as series data for each channel. .
The filter processing circuit 125 is a circuit that performs filter processing for each channel on the 14-channel series data stored in the data area Mm. The filter applied to this filter processing 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 the filter.
The polarity determination circuit 129 is a circuit that determines the polarity of the magnetic marker 10 using the 14-channel series data stored in the data area Mm as input data. As described above, the polarity determination circuit 129 is provided in parallel with the filter processing circuit 125.

  Here, the magnetic sensor Cn will be described in detail. As shown in FIG. 5, the magnetic sensor Cn constituting the sensor array 11 is a one-chip MI sensor in which the MI element 21 and the drive circuit are integrated. The MI element 21 is an element including an amorphous wire 211 made of a CoFeSiB alloy and having substantially 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 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 disposed along the vehicle width direction.

  The drive circuit is an electronic circuit including 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 in 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 takes out 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 it with a predetermined amplification factor 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 highly sensitive sensor having a magnetic flux density measurement range of ± 0.6 millitesla and a magnetic flux resolution within the measurement range of 0.02 microtesla. 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 the external magnetic field. Further, the magnetic sensor Cn can perform high-speed sampling at a cycle of 3 kHz, and is compatible with high-speed driving of the vehicle. In this example, the period of 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 apparatus 1 configured as described above will be described with reference to the flowchart of FIG. The process of FIG. 6 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 performs the magnetic measurement by each magnetic sensor Cn with a period of 3 kHz. As described above, in each magnetic sensor Cn, the amorphous wire 211 (see FIG. 5), which is a magnetic sensitive body, is disposed along the vehicle width direction. Since the magnetism that the magnetic marker 10 acts in the vehicle width direction is directed to both sides of the magnetic marker 10, the direction of the magnetism that each magnetic sensor Cn acts in the vehicle width direction is opposite on the left side or the right side of the magnetic marker 10. At the same time, the direction is reversed depending on whether the magnetic marker 10 is N-pole or S-pole.

  In this example, the magnetic sensor Cn positioned on the left side of the N-pole magnetic marker 10 outputs a negative sensor signal, and the magnetic sensor Cn positioned on the right side outputs a positive sensor signal. A drive circuit is configured. In the magnetic sensor Cn in which the drive circuit is configured in this way, theoretically, the sensor signal of the magnetic sensor Cn located on the left side of the magnetic marker 10 of the S pole has a positive value, and the sensor of the magnetic sensor Cn located on the right side. The signal is negative. 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 positive / negative of the sensor signal.

  Each graph in FIG. 7 and FIG. 8 illustrates the distribution of magnetism in the vehicle width direction acting on each magnetic sensor Cn constituting the sensor array 11. 7 corresponds to the N-pole magnetic marker 10, and FIG. 8 corresponds to the S-pole magnetic marker 10. In these drawings, the traveling direction of the vehicle 5 (time direction, longitudinal direction of the road) 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 positioning is the position p4. The position p1 → p4 is a section approaching the magnetic marker 10, and the position p4 → p7 is a section moving 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 both cases, a zero cross occurs corresponding to the position of the magnetic marker 10 in the vehicle width direction. On both sides of the zero cross, the waveform is a staggered two peaks with opposite signs. When the vehicle 5 to which the sensor array 11 is attached passes through the magnetic marker 10, the amplitude of the distribution waveform of the top mountain gradually increases as the vehicle 5 approaches the magnetic marker 10, and directly above the magnetic marker 10 (position p4). ) At maximum amplitude. Thereafter, as the vehicle 5 moves away from the magnetic marker 10, the amplitude of the distribution waveform of the top mountain gradually decreases. It should be noted that the N-pole magnetic marker 10 and the S-pole magnetic marker 10 are reversed in the order of the top and bottom waveform.

(FIG. 6, Step S102) Difference Calculation The magnetic measurement value of each magnetic sensor Cn is input to the 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 for subtracting the C1 magnetic measurement value from the C2 magnetic measurement value (gradient generation step). As described above, the difference circuit Gm performs a difference calculation by 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 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 a first magnetic gradient. As illustrated in the graphs at positions p1 to p7 in FIGS. 9 and 10, the distribution waveform of the magnetic gradient in the vehicle width direction is a waveform in which small peaks in the positive and negative directions are adjacent to both sides of the high mountain. 9 corresponds to the N-pole magnetic marker 10, and FIG. 10 corresponds to the S-pole magnetic marker 10.

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

  The sensor array 11 simultaneously outputs 14-channel sensor signals composed of the difference calculation values of the difference circuit Gm. The detection unit 12 stores the series data for each channel based on this sensor signal in the data area Mm (FIGS. 3 and 4). When the detection unit 12 acquires a new sensor signal, the detection unit 12 deletes the oldest data in the data area Mm and sequentially forwards each data in the data area Mm to provide an empty area, and the data represented by the newly acquired sensor signal. Store in that free space.

  The time-series data in the data area Mm has a distribution in which the amplitude increases as the vehicle 5 approaches the magnetic marker 10, reaches the maximum amplitude at the position p <b> 4, and decreases as the distance from the magnetic marker 10 decreases. For example, the diagonal graphs on the right side of FIGS. 9 and 10 illustrate changes in the series data corresponding to the position in the vehicle width direction passing directly above the magnetic marker 10. In this graph, an advancing direction (time direction) is defined on an axis directed diagonally downward to the right in the figure, and a 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 filter processing that blocks low frequency components and allows high frequency components to pass. Execute (filtering step). Specifically, the filter output value is calculated by convolution calculation 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 S <b> 104) Marker Detection Processing The detection unit 12 executes marker detection processing 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, if it can be detected, obtains the position in the vehicle width direction of the magnetic marker 10 facing the sensor array 11 by calculation.

  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 generation source, a magnetic gradient is generated around the end portion serving as a magnetic pole due to the wraparound of the magnetic field. If there is a magnetic gradient, it will be difficult to remove only by the difference calculation in S102.

  The change rate 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 with 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 change in the magnetic gradient is gradual. On the other hand, when the distance between the magnetic poles is shortened, the change in the magnetic gradient is abrupt and the rate of change is increased. According to the filter processing that cuts off the low-frequency component, it is possible to remove the magnetic gradient that changes slowly and has 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 by the difference calculation in S102 of FIG. 6 becomes a positive value, and changes as shown in the diagonal graph on the right side of FIG. When the vehicle 5 travels along the lane 100, theoretically, a positive peak occurs every time it passes through the magnetic marker 10. However, in the actual road environment, for example, 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 illustrating the above, it may be difficult to distinguish the peak due to the influence of disturbance magnetism. If the low-frequency component is cut off with respect to the temporal change of the magnetic gradient in the vehicle width direction, the above peak can be brought close to a theoretical change periodically 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 positive / negative is reversed from the case of the N pole in FIG.

  In the case of the magnetic marker 10 having the S pole, the positive / negative is reversed with respect to FIG. 11B illustrating the filter output value in the case of the N pole. Therefore, in performing the detection process of the magnetic marker 10, when the absolute value process is performed on the filter output value stored in the data area Hm, the threshold process is performed to detect the peak, thereby detecting the magnetic marker 10. good. If the absolute value processing is performed, the peak value on the positive side appears regardless of whether it is N pole or S pole. Therefore, the peak can be detected relatively easily by threshold processing that detects a positive value greater 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). In the magnetic marker detection device 1, the polarity determination circuit 129 of FIG. 4 is provided in parallel with the configuration after the filter processing circuit 125 in FIG. When the magnetic marker 10 is detected (position p4), the polarity determination circuit 129 executes polarity determination processing for determining whether the peak value is positive or negative with reference to the magnetic gradient in the vehicle width direction of the data area Mm. If it is a positive peak value as shown in FIG. 9, it is determined as the N pole, and if it is a negative peak as shown in FIG. 10, it is determined as the S pole. If the magnetic marker 10 detected in the above marker detection process (FIG. 6, S104) is the S pole, the type of lane being traveled can be determined as an overtaking lane, and if it is the N pole, an overtaking lane such as a driving 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 for obtaining a difference between magnetic measurement values of two magnetic sensors, and a filter processing step for performing a filtering process using a high-pass filter for a change in the traveling direction of the magnetic gradient. This is a detection method for removing the magnetic field that causes disturbance. The disturbance magnetism that acts 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 tunnel, can be effectively removed by filtering with a high-pass filter.

  Further, in the polarity determination method of this example, the polarity of the magnetic marker 10 is obtained by using the positive / negative of the peak value of the magnetic gradient in the vehicle width direction, which is the difference between the magnetic measurement values of two adjacent magnetic sensors Cn in the sensor array 11. Determine. The polarity of the magnetic marker 10 can be determined with high reliability by using the magnetic gradient in the vehicle width direction in which the disturbance magnetic force acting uniformly as described above is effectively removed.

  Thus, the polarity determination method of the magnetic marker 10 of this example is an excellent determination method that can determine the polarity of the magnetic marker 10 with high certainty by calculating the magnetic gradient and removing the magnetic field that is a 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 that can determine the polarity of the detected magnetic marker 10 with high certainty.

  In this example, the magnetic marker 10 is detected by threshold processing after the absolute value processing is applied to the filter value of the data area Hm (FIG. 3) in the detection processing of the magnetic marker 10. 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 to detect positive and negative peaks. Thus, the magnetic marker 10 may be detected. 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. Thus, it is possible to determine the polarity of the magnetic marker 10 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. However, 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 the two-axis direction of the vehicle width direction and the traveling direction or in the two-axis direction of the traveling direction and the vertical direction may be adopted. A magnetic sensor having sensitivity in the direction may be adopted. If a magnetic sensor having sensitivity in a plurality of axial directions is used, the magnetic action direction can be measured together with the magnitude of the magnetism, 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 of the magnetic vectors and the rate of change in the traveling direction of the difference.

  Although the one-dimensional filtering process in the traveling direction (time direction) of the vehicle is illustrated, the spatial filtering process is performed for a magnetic change in a two-dimensional space defined by the traveling direction (time direction) of the vehicle and the vehicle width direction. It is also possible to remove the 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. Furthermore, a disturbance magnetic field may be removed by applying a spatiotemporal filter to a magnetic change in a spatiotemporal region in which the traveling direction (time direction) of the vehicle is combined with the two-dimensional space.

There is a difference in the width of the lane 100 between the road for exclusive use of automobiles such as an expressway and a general road, and the presence or absence of a signboard or a telephone pole of a store. Therefore, it is also possible to switch the frequency characteristics of the filter applied to the filter processing depending on whether the road is an automobile road or a general road. For example, in the case of an automobile-only road with a relatively wide lane 100 and few signboards for stores, the cut-off frequency for blocking low frequencies may be lowered, or the cut-off characteristics of the filter may be set gently. If the cutoff characteristic is gentle, 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, the cut-off frequency may be switched to a higher level on a general road where the number of magnetic generation sources that cause disturbance is relatively large. Furthermore, it is also possible to detect the interval between the magnetic markers 10 laid on the road and switch the frequency characteristics of the filter according to this interval.
Further, instead of the high pass filter, a band pass filter that passes a specific frequency region may be employed.

  In this example, for the magnetic sensor Cn arranged in the vehicle width direction, a magnetic gradient in the vehicle width direction is generated by the difference calculation. Instead of or in addition to this, the magnetic sensor Cn is 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 difference calculation, and this may be handled as the first magnetic gradient.

  Note that in this example, the polarity of the magnetic marker 10 is used to provide information on the type of lane being traveled to the vehicle side. It is also possible to use the polarity of the magnetic marker 10 and provide the vehicle with a code based on a combination of the N pole and the S pole. Information represented by the code includes various information such as position information, traffic information, and alarm information.

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

The difference circuit Tm uses 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. It is a circuit which calculates as a magnetic gradient of the advancing direction which is an example of a 2nd magnetic gradient.
The data area Nm is a storage area that stores the second magnetic gradient, which is the difference calculation value of the difference circuit Tm, as needed, and stores it as series data in the traveling direction. The series data in the data area Nm is the target of the filtering process.

  Next, the contents of the magnetic marker detection method of this example will be described with reference to the flowchart of FIG. Of the processes in the figure, step S101 for magnetic measurement by each magnetic sensor Cn of the sensor array 11 and step S102 (gradient generation step) for calculating the magnetic gradient in the vehicle width direction have the same specifications as in the first embodiment. It is. The sensor array 11 which 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 14-channel sensor signals 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 series data. As described above with reference to FIG. 9, the change in the magnetic gradient in the vehicle width direction formed by this series data is as shown in the graph of FIG.

  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, thereby calculating the magnetic field in the traveling direction as the second magnetic gradient. A gradient is generated (S112, gradient generation step). Specifically, data at two positions separated by a predetermined distance in the traveling direction from the series data of the magnetic gradient in the vehicle width direction that changes as shown in the graph of FIG. 15A (example of N pole). The magnetic gradient in the vehicle width direction) is selected and the difference is calculated to generate the magnetic gradient in the traveling direction, which is the second magnetic gradient. The detection unit 12 sequentially generates a magnetic gradient in the traveling direction, which is the second magnetic gradient, while shifting the “predetermined distance” in the traveling direction in FIG. Then, the magnetic gradient in the traveling direction generated in this way is sequentially stored in the data area Nm, thereby generating series data in the traveling direction of the second magnetic gradient. The distribution of the magnetic gradient in the traveling direction formed by the series data is as shown in the graph illustrated in FIG. In addition, although illustration is abbreviate | omitted about the graph in the case of S pole, it becomes a thing in which positive / negative was reversed with respect to the graph of FIG. 15 in the case of N pole.

  The detection unit 12 inputs the 14-channel magnetic gradient series data stored in the data area Nm to the filter processing circuit 125, and executes a filtering process that blocks low-frequency components and allows high-frequency components to pass (S103). ). Thereafter, the detection processing circuit 127 of the detection unit 12 executes marker detection processing for detecting the magnetic marker 10 using the data stored in the data area Hm (S104).

  The magnetic gradient in the traveling direction while the vehicle 5 is traveling along the lane 100 theoretically changes so that the waveform including the zero cross in FIG. However, for example, when a vehicle approaches a magnetic source such as a bridge or tunnel, a magnetic field around the magnetic pole located at the end of the magnetic source such as a bridge acts on the traveling direction. May change as shown in FIG. 16 (a). On the other hand, the filtering process in step S103 is very effective. With respect to the change in FIG. 16 (a), by applying a filter process that cuts off low frequency components, it is possible to approach the theoretical change in which the above-mentioned zero cross appears periodically as shown in FIG. 16 (b). The magnetic marker 10 can be detected by detecting this zero cross.

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

  In addition, as said predetermined distance for producing | generating the magnetic gradient of the advancing direction which is a 2nd magnetic gradient, it is good to set distances, such as 30-150 mm, in view of the size of the magnetic marker 10 of a detection target. Further, for example, if the magnetic marker detection device 1 has a function of estimating the size of the magnetic marker 10 and the predetermined distance is changed according to the estimated size, the magnetic marker 10 of 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 the first magnetic gradient, and the difference between the first magnetic gradients at the two positions in the traveling direction is the second magnetic gradient. A filtering process 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 differences can be increased to three times, four times, and so on. 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. Tend to decrease. In selecting the number of differences, it is preferable to consider a balance between the effect of removing magnetic noise and the like and the adverse effect of a 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. However, as in the first embodiment, the polarity can also be determined using the filter output value of the data area Hm. It is. The polarity can be determined by positive → negative zero cross or negative → positive zero cross.
Other configurations and operational effects are the same as those in the first embodiment.

(Example 3)
In this example, the configuration of the sensor array 11 is changed based on the magnetic marker detection device 1 of the first embodiment. The contents will be described with reference to FIG.
In the sensor array 11 of this example, magnetic sensors are arranged in a two-dimensional array with two rows in the traveling direction and 15 columns in the vehicle width direction. The distance 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 distance 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 on the downstream side 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 that 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. 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 referred to as CnB. N is a natural number of 1 to 15).

  The sensor array 11 of this example includes two types of difference circuits K1 to K15 (hereinafter referred to as Kn) and difference circuits S1 to S14 (hereinafter referred to as Sm. M is a natural number of 1 to 14). . The difference circuit Kn is a circuit that calculates the difference between the magnetic measurement value of the magnetic sensor CnA and the magnetic measurement value of the magnetic sensor CnB to obtain the first magnetic gradient. The difference circuit Sm calculates a difference between the first magnetic gradient generated by the difference circuit Km + 1 and the first magnetic gradient generated by the difference circuit Km, thereby making a new first difference different from the first magnetic gradient generated 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 calculation 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 14-channel first magnetic gradient output from the sensor array 11 all at once in the data areas M1 to M14, and generates series data for each channel.

  About the series data for every channel, the detection unit 12 applies the filter process by a high pass filter similarly to Example 1, and stores the filter output value which is the output of a filter process in the data areas H1-H14. And the detection unit 12 performs the marker detection process which used the filter output value stored in the data areas H1-H14 as an input value, and detects the presence or absence of a magnetic marker. Similarly to the first embodiment, the polarity determination process 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 difference circuit Kn), two magnetic sensors having a narrow 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 achieve a sensor array 11 having a width of about 1 m, for example, (1 m ÷ 30 mm) = about in each row in the vehicle width direction. 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 distance between the magnetic sensors in the traveling direction is set to 30 mm as in the present example, and the distance in the vehicle width direction is set to 70 mm, the number of magnetic sensors required for the sensor array 11 can be reduced (1 m ÷ 70 mm) = The sensor array 11 can be configured by about 28 magnetic sensors, which is twice the number of 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 also be determined using the filter output value of the data area Hm as in the first embodiment. It is. The polarity can be determined by positive → negative zero cross or negative → positive zero cross.
Other configurations and operational effects are the same as those in the first embodiment.

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

1 Magnetic marker detector (polarity detector)
DESCRIPTION OF SYMBOLS 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 Vehicle

Claims (6)

A polarity determination method for determining the polarity of a magnetic marker laid on a travel path using at least two or more magnetic sensors attached to a vehicle,
A first that can be calculated by one or two or more times of difference calculation for magnetic measurement values acquired 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 for generating a magnetic gradient of
Processing for determining the polarity of the magnetic marker by using at least one of the second magnetic gradient, which is the difference between the first magnetic gradients having different measurement timings, and the first magnetic gradient. And a polarity determination step of performing magnetic marker polarity determination.   In claim 1, in the polarity determination step, a filter process for suppressing or blocking at least a low frequency component is performed on the change in the traveling direction of the vehicle of any one of the magnetic gradients to generate a filter output value, A magnetic marker polarity determination method for determining the polarity of the magnetic marker using a filter output value.   3. The magnetic sensor according to claim 1, wherein 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 magnetic measurement values of the two magnetic sensors arranged in the vehicle width direction. Magnetic marker polarity determination method for executing the difference calculation process.   4. The magnetic sensor according to claim 1, 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 are magnetized. A method for determining the polarity of a magnetic marker that executes a difference calculation process of measured values.   The magnetic marker according to any one of claims 1 to 4, wherein the frequency characteristic of the filter applied to the filter processing is switched according to whether a travel path on which the vehicle is traveling is an automobile-only road or a general road. Polarity judgment method. A polarity determination device mounted on a vehicle to detect a magnetic marker laid on a travel path,
At least two or more magnetic sensors;
Polarity determination means for determining the polarity of the magnetic marker,
The polarity determination unit of a magnetic marker, which is a unit configured to execute the polarity determination method according to any one of claims 1 to 5.

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