JP2005122256A - Vehicle position detection device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize high-accuracy and high-reliability vehicle position detection device at low cost. <P>SOLUTION: About output signals of n number of magnetic sensors 12 of a magnetic sensor array 10 to a magnet 30 laid in a travel lane 20, the output signals of the adjacent magnetic sensors are interpolated to generate a magnetic flux density distribution 40 having higher resolution. A section of a threshold level of 50 or above is cut out from the magnetic flux density distribution 40, and a horizontal position of the gravity center a signal area of the section is found. A difference between the horizontal position of the gravity center and the center of the magnetic sensor array 10 is found, and the difference is detected as a horizontal position of a vehicle (displacement of the vehicle from a center part of the travel lane 20). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a vehicle position detection device that detects the position of a vehicle that travels automatically, and more particularly to a vehicle position detection device that is suitable for detecting the position of a vehicle relative to the center of a travel lane using a magnetic sensor array.

In recent years, attention has been focused on autonomous traveling systems. One such autonomous traveling system is an unmanned driving system. Various methods have been proposed as a vehicle driving lane automatic guidance method in an unmanned driving system, and representative examples include an optical method, a magnetic method, and an image processing method. Among these systems, the magnetic system is promising because it is not affected by the environment such as weather and dust and the system configuration can be simplified.

As a vehicle position detection device using such a magnetic system, a magnetic sensor array embedded in the center of a running lane is detected by a magnetic sensor array arranged in the lateral direction (vehicle width direction) below the vehicle, and the magnetic sensor There is known a configuration in which the position of the vehicle in the lateral direction with respect to the central portion of the traveling lane is detected based on the output of the array. The magnetic sensor array is a magnetic detection device in which a plurality of magnetic sensors are arranged in an array at equal intervals.

Conventionally, as such a vehicle position detecting device, magnetic sensors using an amorphous magnetic material that detects an external magnetic field with high sensitivity by changing a magnetization vector by a current pulse sent from a built-in oscillator are arranged at equal intervals. Some magnetic sensor arrays are used. In this vehicle position detection device, the magnetic sensor array detects the magnetic strength (magnetic force) of the magnetic marker embedded in the center of the travel path (travel lane) by the magnetic sensor array, and the magnetic distribution calculation device based on the detection result. The magnetic distribution of the mountain shape (the distribution of the entire magnetic force detected by each magnetic sensor of the magnetic sensor array) is calculated. Then, the central point calculation device calculates the central point (position of the magnetic marker) of the magnetic distribution. The center point calculation device cuts the magnetic distribution (magnetic flux density distribution) with a predetermined intensity, and calculates the coordinates of the center of the cut points at both ends by addition averaging. Then, this calculated value is determined as the position of the magnetic marker. In addition, since the magnetic distribution by the magnetic marker has a characteristic that the change is large at the central peripheral part and is slow at both ends, the density of the magnetic sensor of the magnetic sensor array is not equal at the central part and its peripheral part. Devise it so that it is higher and the density is lower at both ends. Thus, by configuring the magnetic sensor array of the magnetic sensor array to correspond to the magnetic distribution characteristics, the magnetic distribution of the magnetic marker can be obtained more efficiently and with higher accuracy. As a result, the position of the magnetic marker Can be obtained with higher accuracy. In this vehicle position detection device, consecutive numbers (sensor position numbers) from 1 are assigned in order from the leftmost magnetic sensor, and the sensor position numbers are acquired as position information. For example, when the number of magnetic sensors installed is (2n-1), the center position X0 of the magnetic sensor array is n. Therefore, the lateral displacement amount of the vehicle position, that is, the position of the vehicle in the lateral direction with respect to the center of the travel lane is the difference between the center position X0 and the position number XM calculated by the center point calculation device (= XM-X0).
(See Patent Document 1).

In addition, a vehicle position detection device that detects the position of a magnet laid in a traveling lane by the method shown in FIG. 6 is also known.
In FIG. 6A, the magnetic sensor array 1110 includes n magnetic switches 1112 arranged at a pitch of 5 mm (the pitch is the distance between the centers of adjacent magnetic sensors 1112). Each magnetic switch 1112 is turned on by a magnetic force equal to or higher than a predetermined threshold level (threshold value) 1150, and is turned off when the magnetic switch is less than that. A magnet 1130 is embedded in the center of the traveling lane 1120. The magnet 1130 is embedded so that the top and bottom become magnetic poles. The magnet 1130 is a disk-shaped magnet 1130a as shown in FIG. 5B or a bar-shaped magnet 1130b as shown in FIG.
A plurality are embedded at a predetermined interval in the center of 120.

The magnetic flux density distribution 1140 in the vertical direction when the magnetic sensor array 1110 and the magnet 1130 are in the positional relationship as shown in FIG. 6A is a curve as shown in FIG. In this case, the number of magnetic switches 1112 to be turned on (magnetic switches 1112 that have detected a magnetic force of the threshold level 1150 or higher) is the third to eighth from the left, and the center of the third and eighth magnetic switches 1112, that is, 5 It is determined that the magnet 1112 is embedded in the center of the sixth and sixth magnetic switches.

At this time, the determination position of the magnet 1130 is 22.5 mm from the left when the center of the first magnetic switch 1112 is the origin. Thus, in the case of the magnetic sensor array 1110 in which the magnetic switches 1112 are arranged at a pitch of 5 mm, the position of the magnet 1130 can be detected with an accuracy (2.5 mm) that is ½ of the pitch of the magnetic switches 1112.
JP 2002-169614 A

In the case of the former vehicle position detection device, magnetic sensors at both ends that detect a magnetic force equal to or higher than the threshold level are obtained, and the position of the magnetic marker is calculated from the arithmetic average of the position numbers of the magnetic sensors at both ends. When noise is superimposed on the magnetic force detected by the sensor, an error in the detection position of the magnetic marker increases. This is because the magnetic sensor whose output is lower than the threshold level is detected as the magnetic sensor at both ends when there is no noise. For this reason, the position in the lateral direction of the vehicle (vehicle position) with respect to the center of the traveling lane cannot be detected with high reliability.

In the case of the latter vehicle position detection device, the position detection accuracy of the magnet 1130 is the magnetic sensor 11.
It is determined at a pitch of 12. For this reason, the detection accuracy is limited by the size of the magnetic sensor 1112. At present, the limit of the pitch of the magnetic sensor 1112 is 5 mm.
The position detection accuracy is limited to 2.5 mm. Therefore, when this vehicle position detection device is mounted on a vehicle, the detection accuracy of the vehicle position is limited to 2.5 mm.

Further, since the position detection accuracy of the magnet 1130 is proportional to the pitch of the magnetic sensors 1112 disposed in the magnetic sensor array 1110, even if the pitch of the magnetic sensors 1112 can be made narrower in the future, the position detection of the magnet 1130 is detected. In order to increase the accuracy, it is necessary to increase the number of elements of the magnetic sensor 1112 to be arranged, so that the manufacturing cost of the magnetic sensor array 1110 increases. For this reason, when it was going to implement | achieve the high precision of a vehicle position detection apparatus, there existed a fault that the manufacturing cost of a vehicle position detection apparatus had to be made high.

An object of the present invention is to provide a vehicle position detection device that can detect a vehicle position with high accuracy and high reliability and that is low in manufacturing cost.

The invention according to claim 1 (the vehicle position detection device according to the first aspect of the present invention) detects the magnetic field of the magnetic marker laid in the traveling direction at the central portion of the traveling lane, thereby detecting the central portion of the traveling lane. On the premise of a vehicle position detection device that detects the position of the vehicle in the lateral direction, a magnetic sensor array, calculation means, and detection means are provided. ,
The magnetic sensor array has a plurality of magnetic sensors arranged in the lateral direction. This magnetic sensor array is installed at, for example, the lower part or the side part of the vehicle.

The calculation means extracts a section having a predetermined threshold level or higher from the first magnetic flux density distribution obtained from the output signal of each magnetic sensor of the magnetic sensor array, and calculates the horizontal center of gravity of the first magnetic flux density distribution in the section. Find the direction position.
The detecting means detects the lateral position of the vehicle based on the lateral position of the center of gravity obtained by the calculating means and the central position of the magnetic sensor array.

The vehicle position detection device of the first aspect configured as described above is based on the output signals of all magnetic sensors that are equal to or higher than a predetermined threshold level in the first magnetic flux density distribution, and the threshold in the first magnetic flux density distribution. The horizontal position of the center of gravity of the signal area in the section above the level is obtained. When obtaining the lateral position of the center of gravity, a plurality of output signals (for example, all output signals) in the section are used. Then, the lateral position of the vehicle is calculated based on the lateral position of the center of gravity and the central position of the magnetic sensor array. This lateral position is, for example, the difference (distance) between the lateral position of the center of gravity and the center of the magnetic sensor array. The lateral position of the center of gravity can be regarded as the position of the magnetic marker laid at the center of the traveling lane. Further, if the magnetic sensor array is installed in the vehicle such that the center in the lateral direction coincides with the center in the lateral direction of the vehicle, the center of the magnetic sensor array becomes equal to the center of the vehicle. Therefore, in this case, the difference is a lateral distance between the center of the vehicle and the center of the traveling lane, that is, a lateral displacement (amount of lateral displacement) from the center of the traveling lane at the center of the vehicle. Accordingly, by calculating the difference, it is possible to detect a lateral shift from the center of the traveling lane of the vehicle.

Thus, according to the vehicle position detection device of the first aspect, among the output signals of all the magnetic sensors of the magnetic sensor array, a plurality of output signals (for example, all output signals) having a predetermined threshold level or higher. Since the position of the magnet laid in the traveling lane is detected based on the extracted output signal, even if noise is superimposed on the extracted part of the output signal, the noise is The influence on the position detection can be suppressed, and the lateral position of the center of gravity, that is, the position of the magnet can be detected with high accuracy and high reliability. For this reason, it becomes possible to detect the position (vehicle position) in the lateral direction of the vehicle with respect to the central portion of the traveling lane with higher accuracy and higher reliability.

The invention according to claim 2 (the vehicle position detection apparatus according to the second aspect of the present invention) further includes a creation means in addition to each means included in the vehicle position detection apparatus according to the first aspect.
The creating means interpolates between the outputs of the adjacent magnetic sensors of the magnetic sensor array based on the first magnetic flux density distribution to generate a second magnetic flux having a larger number of signals than the first magnetic flux density distribution. Create a density distribution.

Then, the calculating means extracts a section having a predetermined threshold level or more from the second magnetic flux density distribution created by the creating means, and determines the lateral position of the center of gravity of the second magnetic flux density distribution in the section. The detecting means is based on the lateral position of the center of gravity of the second magnetic flux density distribution obtained by the calculating means and the center position of the magnetic sensor array.
The lateral position of the vehicle is calculated.

The vehicle position detection device of the second aspect of the present invention having the above-described configuration interpolates between adjacent output signals of discrete first magnetic flux density distributions obtained by the magnetic sensor array, and the first magnetic flux density distribution. 2nd magnetic flux density distribution with many signals is produced. Then, a section having a predetermined threshold level or more is extracted from the high-resolution second magnetic flux density distribution, and the center of gravity in the signal area of the extracted section is extracted from a plurality of signals (for example, all signals) in the section. And the lateral position of the center of gravity (the position of the magnet laid on the traveling lane) is detected. Then, for example, the difference between the lateral position of the center of gravity and the central position of the magnetic sensor array is obtained, and the difference is detected as the lateral position of the vehicle with respect to the center of the traveling lane.

Thus, according to the vehicle position detection device of the second aspect, not only the output signal of the magnetic sensor in the section of the first magnetic flux density distribution but also the signal obtained by interpolation between the magnetic sensor output signals. The lateral position of the center of gravity is detected based on the signal. For this reason, the position of the magnet can be detected with high accuracy without reducing the magnetic sensor pitch of the magnetic sensor array and increasing the number of elements of the magnetic sensor. Further, the detection accuracy of the magnet position is higher than that of the vehicle position detection device of the first aspect. As in the first vehicle position detection device, even if noise is superimposed on the output signals of some magnetic sensors used for calculating the position of the center of gravity in the lateral direction, the noise is detected in the lateral position of the center of gravity. Therefore, the position of the magnet can be detected with high accuracy and high reliability. For this reason, the position in the lateral direction of the vehicle can be detected with high accuracy and high reliability.

In the vehicle position detection apparatus according to the first and second aspects, the creation unit, the calculation unit, and the detection unit can be realized by, for example, software processing by executing a program of an MPU (microprocessor). For example, as described in claim 3, the calculating means obtains a sum of moments of all signals in the section of the first or second magnetic flux density distribution around the midpoint position of the section, The horizontal position of the center of gravity is obtained by searching for a position where the sum of the moments becomes zero. Moreover, the calculation means is, for example,
According to a fourth aspect of the present invention, a signal area in the section of the first or second magnetic flux density distribution is obtained, and a lateral position of the center of gravity is obtained from the signal area.

The program according to claim 5 of the present invention (the program according to the first aspect) detects the magnetic field of the magnetic marker laid in the traveling direction in the central portion of the traveling lane, so that the side of the vehicle with respect to the central portion of the traveling lane is detected. It is premised on a program that causes a computer to execute processing for detecting a position in a direction. Then, a section having a predetermined threshold level or more is extracted from the first magnetic flux density distribution obtained from the output signal of each magnetic sensor of the magnetic sensor array having the plurality of magnetic sensors arranged in the lateral direction, A calculating step for obtaining a lateral position of the center of gravity of the first magnetic flux density distribution, and a detecting step for detecting a lateral position of the vehicle based on the lateral position of the center of gravity obtained by the calculating step. And causing the computer to execute a process comprising:

The program according to claim 6 of the present invention (the program according to the second aspect) includes the calculation step and the detection step included in the program according to the first aspect, and further, based on the first magnetic flux density distribution, the magnetic field. A creation step of creating a second magnetic flux density distribution having more signals than the first magnetic flux density distribution by interpolating between the outputs of adjacent magnetic sensors of the sensor array.

Then, the calculating step extracts a section having a predetermined threshold level or more from the second magnetic flux density distribution created by the creating step, and determines a lateral position of the center of gravity of the second magnetic flux density distribution in the section. The detecting and calculating step calculates the lateral position of the vehicle based on the lateral position of the center of gravity of the second magnetic flux density distribution determined by the calculating step. In the calculation step of the program, the sum of moments of all signals in the section of the first or second magnetic flux density distribution centering on the midpoint position of the section is calculated, for example, as in claim 7. The horizontal position of the center of gravity is determined by searching for a position where the sum of the moments is zero. Further, the calculation step of the program according to the first and second aspects obtains a signal area in the section of the first or second magnetic flux density distribution, for example, as in claim 8, and calculates the signal area from the signal area. The lateral position of the center of gravity is obtained.

Also in the program of the 1st and 2nd aspect of this invention, the effect similar to the 1st and 2nd vehicle position detection apparatus of this invention is acquired.

According to the present invention, a section of a predetermined threshold level or higher is extracted from the first magnetic flux density distribution obtained by the magnetic sensor array, and the section of the first magnetic flux density distribution is higher than the predetermined threshold level in the section. Based on all magnetic sensor outputs, the lateral position of the center of gravity of the section area of the first magnetic flux density distribution is calculated, and the calculated position is detected as the position of the magnet. Thus, since the lateral position of the center of gravity is obtained based on all the outputs in the section, the lateral position of the center of gravity is obtained even if noise is superimposed on some magnetic sensor outputs in the section. Since the calculation result is a value in which the influence of the noise is suppressed, the position of the magnet can be detected with higher accuracy and higher reliability than before. Therefore, it is possible to realize vehicle position detection that can detect the vehicle position with higher accuracy and higher reliability than in the past.

Further, the first discrete magnetic flux density distribution obtained by the magnetic sensor array is interpolated to create a second magnetic flux density distribution with higher resolution, and a predetermined threshold is obtained from the second magnetic flux density distribution with high resolution. The section above the level is extracted, the position in the horizontal direction of the center of gravity of the magnetic flux density distribution in the extracted section is calculated, and the calculated position is detected as the position of the magnet. Even without increasing, it is possible to detect the position of the magnet with higher accuracy than in the past. For this reason, the vehicle position detection apparatus which can detect a vehicle position with high precision and high reliability is realizable at low cost.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram for explaining the principle of the vehicle position detection device of the present invention.
In the figure, the magnetic sensor array 10 has the same configuration as the magnetic sensor array 1110 in FIG. 6, and n magnetic sensors 12 are arranged at a pitch of 5 mm in the horizontal direction (X direction). The magnetic sensor 12 outputs an analog signal corresponding to the detected magnetic strength (magnetic force). The magnets 30 are arranged, for example, at equal intervals in the center of the traveling lane 20, and the magnetization direction is a direction perpendicular to the road surface of the traveling lane 20. The magnetic sensor array 10 is installed in the lower part of a vehicle (not shown) that travels on the travel lane 20. In the present invention, the magnetic sensor array 1
The installation position of 0 is not limited to the lower part of the vehicle. For example, like the side part of the vehicle,
Any position can be used as long as it can detect the magnetism of the magnet arranged in the traveling lane.

In the case of FIG. 1, the magnet 30 is the fifth magnetic sensor 12 (12-5) of the magnetic sensor array 10.
) And the sixth magnetic sensor 12 (12-6) is located vertically below the intermediate position. The output 60 of each magnetic sensor 12 of the magnetic sensor array 10 in the positional relationship between the magnetic sensor array 10 and the magnet 30 is represented by a vertical bar graph (histogram) in FIG. In the bar graph, the vertical axis is the output value of each magnetic sensor 12 of the magnetic sensor array 10, and the horizontal axis is the horizontal direction (X) where the center of the leftmost (first) magnetic sensor 12 of the magnetic sensor array 10 is the origin. Direction).

Since the pitch of the magnetic sensor 12 in the magnetic sensor array 10 is 5 mm, the magnetic detection output of the magnet 30 by the magnetic sensor array 10 is a discrete magnetic flux density distribution (
Magnetic distribution). In this embodiment, interpolation is made between the outputs 60 of the adjacent magnetic sensors 12 and FIG.
Is obtained (the magnetic flux density distribution 40 is also a discrete distribution curve, but the resolution is higher than the magnetic flux density distribution obtained by the magnetic sensor array 10). For this interpolation, for example, interpolation of function approximation is used. Interpolation for function approximation includes spline interpolation,
Interpolation using a polynomial (such as Lagrangian interpolation), iterative interpolation (such as Newton interpolation), and orthogonal polynomial interpolation (such as Chebyshev Czech interpolation) are used.

Then, data having a threshold level (threshold value) of 50 or more is extracted from the values obtained by the interpolation and the outputs 60 of all the magnetic sensors 12 of the magnetic sensor array 10, and the magnetic flux density distribution is extracted based on these extracted data. Magnetic sensor 12 having a threshold level 50 or higher within 40
The X coordinate of the center of gravity of the section area having the output is obtained. Then, the X coordinate of the center of gravity is represented by the magnet 30.
Detect as the position of. The threshold level 50 is set by a disturbance level signal (a detection signal of an external magnetic field such as magnetization or geomagnetism of a vehicle in which the magnetic sensor array 10 is installed).
It is for cutting. The value of the threshold level 50 is set to a value appropriate for the cut.

In the case of the example shown in FIG. 1, a section A having an X coordinate of Xs to Xt is cut out as a section of the magnetic flux density distribution 40 having a threshold level 50 or higher. Then, the center of gravity of the region 70 of the magnetic flux density distribution 40 in this section A is obtained. In this case, the X coordinate of the center of gravity is 21 mm (a position 1 mm to the right of the center of the fifth magnetic sensor 12), and the value of the X coordinate of the center of gravity (= 21 mm) is detected as the position of the magnet 30. In this way, the position of the magnet 30 can be determined with higher accuracy (accurate accuracy of 1.5 mm) than the above-described conventional vehicle position detection device of FIG.
The lateral position of 21 mm is obtained by an algorithm shown in the flowcharts of FIGS. 3 and 4 described later. The lateral position (vehicle position) with respect to the center of the traveling lane 20 of a vehicle (not shown) on which the magnetic sensor array 102 is mounted is the center of the magnetic sensor array 10 and the detection position of the magnet 30 (the center of the traveling lane 20). It is calculated as the difference (distance).

In the system shown in FIG. 1, the first magnetic flux density distribution obtained by the magnetic sensor array 10 is interpolated, and the position of the magnet 30 is detected based on the second magnetic flux density distribution 40 obtained by the interpolation. However, in the present invention, the interpolation process is not necessarily required, and the position of the magnet 30 may be detected from the first magnetic flux density distribution obtained by the magnetic sensor array 10. In the case of this method, a threshold level of 5 is determined from the first magnetic flux density distribution.
A section of zero or more is cut out, the lateral position of the center of gravity in the section of the first magnetic flux density distribution is calculated, and the calculated position is detected as the position of the magnet 30. Then, the difference between the detection position of the magnet 30 and the center of the magnetic sensor array 10 is detected as the lateral position of the vehicle on which the magnetic sensor array 10 is mounted.

FIG. 2 is a block diagram showing a hardware configuration of the vehicle position detection apparatus according to the embodiment of the present invention based on the principle of FIG.
In the figure, a vehicle position detection apparatus 100 includes a magnetic sensor array 102 including n magnetic sensors 101, n magnetic sensor preamplifiers 103, m multiplexers 105,
m sample hold circuits 107, m A / D converters (analog / digital converters)
109 and an MPU (micro processor) 111.

The magnetic sensor array 102 has the same configuration as the magnetic sensor array 10 shown in FIG. The magnetic sensor 101 is a sensor that detects the magnetic field of the magnet 30 in FIG. 1 and outputs an analog signal corresponding to the magnetic strength (magnetic force) to the magnetic sensor preamplifier 103. The magnetic sensor preamplifier 103 amplifies the analog signal input from the magnetic sensor 101 and outputs the amplified analog signal to the multiplexer 105. The magnetic sensor 101 and the magnetic sensor preamplifier 103 are provided in a one-to-one correspondence.

The multiplexer 105 selectively outputs the p analog signals input from the p magnetic sensor preamplifiers 103 one by one in a time-division order one by one. The sample hold circuit 107 includes an analog switch 107a and an integrator 107b. When the analog switch 107a is closed, the output (analog signal) of the multiplexer 105 is read (sampled), and the analog signal is input to the integrator 1.
Hold at 07b (hold). The A / D converter 109 converts the analog signal held by the sample hold circuit 107 into a digital signal. Analog switch 107
a is opened and closed by a control signal (not shown) output from the MPU 111.

The MPU 111 sequentially reads digital signals output from the m A / D converters 109 (digital values of analog signals output from the magnetic sensor 101), and temporarily stores them in a memory (not shown). . And the position (X coordinate) of the said magnet is detected based on those m digital signals. Details of this detection process will be described later.

As described above, the magnetic sensor 101 and the magnetic sensor preamplifier 103 are respectively
n are provided. In addition, the multiplexer 105, the sample hold circuit 107, and the A / D
M converters 109 are provided. Here, since one multiplexer 105 is provided for each of the p magnetic sensor preamplifiers 103, m = n / p. In this embodiment, n is set to a value divisible by p.

Next, a vehicle position detection process performed when the MPU 111 executes a program stored in a memory (not shown) will be described with reference to FIGS. 3 and 4
These are flowcharts explaining operation | movement of the vehicle position detection apparatus of a structure of FIG. FIG. 5 is a diagram showing a specific example of the center-of-gravity calculation process shown in the flowchart of FIG.

First, FIG. 3 will be described. FIG. 3 is a flowchart for explaining the overall operation of the vehicle position detection apparatus of FIG. 2. The vehicle position detection process shown in this flowchart is executed by the MPU 111. The MPU 111 executes the vehicle position detection process by executing a program stored in a memory (not shown).

The MPU 111 first converts the outputs of the 1st to n-th magnetic sensors 101 of the magnetic sensor array 102 converted from analog signals into digital signals by the A / D converter 109, into the array D [
n]. The array D [n] is a one-dimensional array having n array elements D [1] to D [n], and is mounted in the memory. The outputs of the 1st to nth magnetic sensors 101 are stored in D [1] to D [n], respectively (step S1).

Next, the MPU 111 performs the following expression (1) for each element D [i] (i = 1 to n) of the array D [n],
DA [i] = Ki · DA [i] (1)
Ki: The sensitivity correction coefficient array DA [n] of the i-th magnetic sensor 101 is created (step S2).

The sensitivity correction coefficient Ki (i = 1 to n) in the equation (1) is a coefficient for correcting the sensitivity variation for each magnetic sensor 101, is obtained at the manufacturing stage of each magnetic sensor 101, and is stored in advance in the memory. Store it in.
Subsequently, DA [1] to DA [2], DA [2] to DA [3], ..., DA [n-1] to DA [n]
The value of the intermediate point of each section is obtained by interpolation, and array DB [X] is created (step S3).

The array DB [X] is a one-dimensional array composed of X elements DB [1] to DB [X]. When the number of interpolation points in each section is q, X = q (n-1) + n.
Thus, the resolution is higher than the first magnetic flux density distribution from the discrete magnetic flux density distribution (first magnetic flux density distribution) configured from the output data of the n magnetic sensors 101 of the magnetic sensor array 102. A discrete magnetic flux density distribution (second magnetic flux density distribution) composed of X pieces (X> n) of magnetic data is obtained.

Next, a threshold level (from the X elements DB [1] to DB [X] of the array DB [X] is selected.
Lth) or more elements DB [Xs] to DB [Xt] are extracted. At this time, the position data Xs
, Xt are stored in the memory (step S4). Then, based on DB [Xs] to DB [Xt], the center of gravity calculation process for obtaining the center of gravity position Xc and the like in the region of the section Xs to Xt of the second magnetic flux density distribution is performed (step S5), and step S1 is performed again. Return to.

In the center-of-gravity calculation process, as described later, in addition to the center-of-gravity position Xc, the position of the magnet 30 and the amount of lateral deviation (difference between the magnet 30 and the center of the magnetic sensor array 102) are calculated and output.
In this manner, the position of the magnet 30 laid on the traveling lane 20 and the amount of lateral deviation are detected and output while repeating steps S1 to S5.

FIG. 4 is a flowchart illustrating in detail the gravity center calculation process in step S5 of FIG.
In the following description, for the sake of convenience, the center of gravity of the section of the second magnetic flux density distribution that is equal to or higher than the threshold level Lth is expressed as “center of gravity”.
First, an intermediate point Xc between the position Xs and the position Xt acquired in step S4 in FIG. 3 is obtained (step S11). Next, the moments of DB [Xs] to DB [Xt] around Xc are calculated, and the sum of those moments is calculated (step S12). In this moment calculation, the clockwise direction is the positive direction of the moment. In addition, a formula for calculating the sum of moments (Mo) is defined as the following formula (2). Hereinafter, for the sake of convenience, the sum of moments (Mo) is expressed as “moment”.

The value of the moment becomes 0 when Xc is equal to the X coordinate of the center of gravity. If Xc is on the left side of the X coordinate of the center of gravity, the moment value is positive, and if Xc is on the right side of the X coordinate of the center of gravity, it is negative. As the absolute value of this positive / negative value is larger, Xc is farther from the X coordinate of the center of gravity (the distance between Xc and the X coordinate of the center of gravity is larger).

Next, it is determined whether the previous step S12 is the first calculation of moment (step S1).
3) If it is the first calculation, go to step S14, otherwise go to step S13.
In step S13, it is determined whether the polarity of the moment calculated in step S14 of the previous process (previous moment) and the moment calculated in step S14 of the current process (current moment) have changed, and the polarity must have changed. If the polarity has changed, the process proceeds to step S18.

In step S15, the value of the moment is determined. If the value is negative, step S16 is performed.
If positive, the process proceeds to step S17, and if 0, the process proceeds to step S18.
In step S16, the value of Xc is decreased by 1, and the process returns to step S12. Step S17
Then, the value of Xc is incremented by 1, and the process returns to step S12.

In the process of steps S12 to S17, the moment calculation is 1 in step S13.
It is determined whether or not it is the first time, and the process branches to step S14 or step S15. Immediately after the first moment calculation is performed, the previous moment does not exist yet, so the process proceeds to step S14. This is because the polarity of the moment cannot be compared.

Further, the intermediate point Xc obtained in step S11 is the center of gravity (moment is 0), right of the center of gravity (
The moment is negative) or left of the center of gravity (moment is positive). In order to obtain the X coordinate of the center of gravity, a search for bringing the value of Xc closer to the X coordinate of the center of gravity is necessary. In this embodiment, in steps S16 and S17, the value of Xc is made closer to the X coordinate of the center of gravity little by little while increasing (in the case of the left of the center of gravity) and decreasing (in the case of the right of the center of gravity) of Xc. Go. In this case, Xc (X coordinate of the center of gravity) where the moment value is 0 in the best case
Is obtained. In other cases, Xc jumps over the X coordinate of the center of gravity, and to the right of the center of gravity (
When the first Xc is to the left of the center of gravity) or to the left of the center of gravity (when the first Xc is to the right of the center of gravity). Thus, when Xc jumps over the center of gravity, the polarity of the moment changes before and after that. It is step S14 that two types of cases where Xc as described above jumps over the center of gravity are determined. If a change in the polarity of the moment is detected in step S14, the process proceeds to step S18 and proceeds to a process for adjusting the value of Xc. On the other hand, in step S14,
If no change in the polarity of the moment is detected, the process proceeds to step S15.

In step S15, it is determined whether Xc is one of the above three, and the moment value is 0.
If Xc coincides with the X coordinate of the center of gravity, the process immediately proceeds to step 22. If the moment is negative (Xc is to the right of the center of gravity), go to step S16 to move Xc to the left.
If the moment is positive (Xc is to the left of the center of gravity), step S1 is used to move Xc to the right.
Proceed to 7.

In step S18, the absolute value of the previous moment is compared with the absolute value of the current moment. If the absolute value of the previous moment is equal to or greater than the absolute value of the current moment, the process immediately proceeds to step S22, and if vice versa, the process proceeds to step S19.
In step S19, the value (polarity) of the current moment is checked. If the value (polarity) is negative, the process proceeds to step S20, and if positive, the process proceeds to step S21. In step S20, Xc
1 is decreased by 1 and the process proceeds to step S22. In step S21, the value of Xc is incremented by 1, and the process proceeds to step S22.

In step S18, it is determined which of the previous and current Xc is closer to the X coordinate of the center of gravity. Since the moment value becomes smaller as Xc is closer to the X coordinate of the center of gravity, step S18 is performed.
If the current moment is smaller than the previous moment, that is, if Xc obtained this time is closer to the X coordinate of the center of gravity than Xc obtained last time, the process proceeds to step S22. On the other hand, the X I asked for this time
If c is farther from the X coordinate of the center of gravity than Xc obtained last time, the process proceeds to step S19. In step S19, the value (polarity) of the moment is checked. If the value (polarity) is negative, the value of Xc is decreased by 1 and Xc is moved to the left so that it approaches the X coordinate of the center of gravity. move on.
On the other hand, if the moment value (polarity) is positive this time, the value of Xc is increased by 1 and Xc
Is moved to the right to approach the X coordinate of the center of gravity, and the process proceeds to step S22.

In step S22, the X-coordinate Xc of the gravity center position finally obtained is expressed by the following equations (3) and (4
) To a distance Lc from the center of the first magnetic sensor 101 of the magnetic sensor array 102. Further, the lateral deviation amount (distance from the center of the magnetic sensor array 102 of the detection position of the magnet 30), that is, the vehicle position L is calculated by the following equations (3) and (5).

d = p / (q + 1) (3)
Lc = d × (Xc−1) (4)
L = Lc−d × {(X−1) / 2 + 1} (5)
d: Interpolation pitch (mm)
p: pitch of the magnetic sensor 101 (mm)
q: Number of Interpolation Points Next, the center of gravity calculation process shown in the flowchart of FIG. 4 will be described in more detail with reference to a specific example of FIG. FIG. 5 shows the procedure 4 for detecting the X coordinate Xc of the center of gravity in the center of gravity position calculation process.
Types of cases are shown as Examples 1 to 4. In the figure, Xj represents the correct X coordinate of the center of gravity (the X coordinate of the position where the moment becomes 0).

In Example 1 shown in FIG. 5A, the value of moment (first moment) is 5 (positive) in Xc (= Xa) obtained first. Therefore, in step S15 in FIG. 4, it is determined that the moment value is positive, and in step S17, the value of Xc is set to “Xa + 1”.
In step S12, the second moment is calculated as Xc = Xa + 1, and the value becomes -7 (negative). As a result, it is determined in step S14 that the polarity of the moment has changed. Next, in step S18, it is determined that the absolute value of the previous moment is smaller than the absolute value of the current moment. Subsequently, in step S20, the value of Xc is 1. Subtraction is performed and the value of Xc becomes Xa. This Xa is detected as the X coordinate (= Xc) of the center of gravity.

In this example 1, Xc obtained first is away from the X coordinate (= Xj) of the center of gravity to the left side, and then Xc is brought closer to the X coordinate of the center of gravity while increasing the value of Xc one by one. This is an example of the case (first case) where the polarity of the moment sometimes changes and the value of the moment when the polarity changes is equal to or greater than the previously obtained moment value. In such a case, since the Xc obtained at the end is farther from the X coordinate of the center of gravity than the Xc obtained before that,
The X coordinate value of the center of gravity is calculated from the value obtained by subtracting 1 from the Xc value obtained last, that is, the Xc value obtained before that, and the calculated position is detected as the position of the magnet 30.

In Example 2 shown in FIG. 5B, the value of moment (first moment) is −5 (negative) in Xc (= Xa) obtained first. Therefore, in step S15 in FIG. 4, it is determined that the moment value is negative, and in step S16, the value of Xc is set to “Xa−1”. In step S12, the second moment is calculated as Xc = Xa-1,
The value is 4 (positive). Thereby, it is determined in step S14 that the polarity of the moment has changed, and then in step S18, it is determined that the absolute value of the previous moment is greater than or equal to the absolute value of the current moment. This “Xa-1” is detected as the X coordinate (= Xc) of the center of gravity.

In this example 2, Xc obtained first is far to the right from the X coordinate (= xj) of the center of gravity, and then Xc is made closer to the X coordinate of the center of gravity while decreasing the value of Xc one by one. This is an example of a case (second case) in which the moment polarity sometimes changes and the moment value when the polarity changes is smaller than the moment value obtained last time. In such a case, since the Xc obtained at the end is closer to the X coordinate of the center of gravity than the Xc obtained before, the X coordinate value of the center of gravity is calculated from the finally obtained Xc, and the calculated position is determined as the magnet. Detect as 30 position.

Although not illustrated in FIG. 5, when Xc obtained first is on the left side of the X coordinate of the center of gravity, and then Xc is brought closer to the X coordinate of the center of gravity while increasing the value of Xc one by one. In the case where the polarity of the moment changes and the Xc when the moment polarity changes is closer to the X coordinate of the center of gravity than the previously obtained Xc (third case), the processing of the second case is performed. Is changed to execute the process of step S17 instead of step S16 in the determination of step S15, and the X coordinate value of the center of gravity is calculated from the value of Xc obtained last,
The calculated position can be detected as the position of the magnet 30.

In Example 3 shown in FIG. 5C, the value of moment (first moment) is −4 (negative) in Xc (= Xa) obtained first. Therefore, in step S15 in FIG. 4, it is determined that the moment value is negative, and in step S16, the value of Xc is “Xa−1”. In step S12, the second moment is calculated as Xc = Xa-1, and the value becomes 5 (positive). Accordingly, it is determined in step S14 that the polarity of the moment has changed, and then in step S18, it is determined that the absolute value of the previous moment is less than the absolute value of the current moment, and in step S19, the current moment is positive. Step S
In 21, the value of Xc is set to Xa. This Xa is detected as the X coordinate (= Xc) of the center of gravity.

In this example 3, Xc obtained first is away to the right from the X coordinate of the center of gravity, and then
The moment polarity changes when Xc is brought closer to the X coordinate of the center of gravity while decreasing the value of Xc one by one, and Xc when the moment polarity changes is the previously obtained Xc
This is an example of a case (fourth case) farther from the X coordinate of the center of gravity. In such a case, the Xc value obtained last is increased by 1, the X coordinate of the center of gravity is calculated from the increased Xc, and the calculated position is detected as the position of the magnet 30.

In Example 4 shown in FIG. 5D, the value of moment (first moment) is 0 in Xc (= Xa) obtained first. Therefore, in step S15 in FIG. 4, it is determined that the value of the moment is 0, and Xa is detected as the X coordinate (= Xc) of the center of gravity. Thus, in Example 4, since Xc (= Xa) obtained first matches the X coordinate (= Xj) of the center of gravity, the position of the X coordinate of the center of gravity is calculated from the Xc, and the calculated position is set as the magnet 30. Detect as the position of.

This example 4 is an example of a case (fifth case) in which Xc obtained first or finally coincides with the X coordinate (= Xj) of the center of gravity. That is, in the fifth case, Xc obtained first is away from the X coordinate of the center of gravity (on the right side or the left side), and then Xc is decreased (increase or decrease the value of Xc one by one). This includes the case where Xc becomes the X coordinate of the center of gravity when approaching the coordinates.

Thus, according to the embodiment of the present invention, the discrete value (magnetic sensor 101) of the discrete magnetic flux density distribution (first magnetic flux density distribution) obtained by the magnetic sensor 101 of the magnetic sensor array 102 is obtained.
) To create a higher-resolution magnetic flux density distribution (second magnetic flux density distribution) 40. Then, from the high-resolution second magnetic flux density distribution 40, the threshold level Lth.
The above section (Xs to Xt) is extracted, the center of gravity of the magnetic flux density distribution in the extracted section is obtained,
The X coordinate (lateral position) Xc of the center of gravity is detected as the position of the magnet. For this reason, even if the magnetic sensor pitch of the magnetic sensor array is the same as the conventional one, the position of the magnet can be detected with higher accuracy than the conventional vehicle position detecting device. Moreover, since the outputs of all the magnetic sensors 101 in the section are used when determining the center of gravity, even if noise is superimposed on some magnetic sensor outputs in the section, the influence of the noise can be suppressed, and high The position of the magnet can be detected with reliability.

In the above embodiment, the first magnetic flux density distribution obtained by the magnetic sensor array 102 is interpolated, and the position of the magnet 30 is detected with high accuracy based on the second magnetic flux density distribution 40 obtained by the interpolation. However, based on the first magnetic flux density distribution, the position of the magnet 30 may be detected by the same method as in the above embodiment. In this method, after the array DA [n] is created in step S2 of the flowchart of FIG. 2, the processing in step S3 is skipped, and the processing after step S4 is performed instead of the array DB [X]. It can be realized by executing using

In the above embodiment, the center of gravity is obtained by the moment. However, the area of a region having a signal equal to or higher than the threshold level of the magnetic flux density distribution may be obtained, and the center of gravity may be obtained from the area. As this method, for example, a signal having a threshold level of 50 or more is extracted from the second magnetic flux density distribution 40, the sum of the extracted signals is obtained, and a vertical straight line (with the X coordinate axis on the X coordinate axis) is obtained. A method of obtaining the X coordinate of a vertical straight line) and detecting the X coordinate as the X coordinate of the center of gravity can be considered. Also, X between all the extracted signals and adjacent signals
You may make it obtain | require the sum total of the multiplication of the distance of a direction (distance between the output signals of the magnetic sensor 12, or interpolation pitch) as said area. In the case of this method, for example, the vertical cutting line that bisects the area from the section is obtained, and the X coordinate of the cutting line is detected as the X coordinate of the center of gravity.

Moreover, in the said Example, although the magnet 30 is used as a magnetic marker laid in the traveling lane 20, this invention is not applied only to the traveling lane in which the magnet was laid, and magnetic markers other than a magnet are used. It can also be applied to laid lanes.

The vehicle position can be detected with high accuracy, high reliability and low cost by the magnetic marker laid on the driving lane, so that the vehicle position detection of autonomous driving systems such as unmanned vehicles and robots and safety vehicles for automatic driving in the near future Applicable to sensor applications.

It is a figure explaining the principle of the vehicle position detection apparatus of this invention. It is a block diagram which shows the hardware constitutions of the vehicle position detection apparatus of the Example of this invention. It is a flowchart explaining the whole operation | movement of the Example. It is a flowchart explaining the gravity center calculation process in the Example in detail. It is a figure which shows the specific example of the detection procedure of the X coordinate of the gravity center in the same gravity center calculation process. It is a figure explaining the structure and operation | movement principle of the conventional vehicle position detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic sensor array 12 Magnetic sensor 100 Vehicle position detection apparatus 101 Magnetic sensor 102 Magnetic sensor array 103 Magnetic sensor preamplifier 105 Multiplexer 107 Sample hold circuit 107a Analog switch 107b Integration circuit 109 A / D converter 111 MPU

Claims (8)

A vehicle position detection device that detects a position in a lateral direction of a vehicle with respect to a central portion of the traveling lane by detecting a magnetic field of a magnetic marker laid in the traveling direction at a central portion of the traveling lane,
A magnetic sensor array having a plurality of magnetic sensors arranged in the lateral direction;
A section having a predetermined threshold level or higher is extracted from the first magnetic flux density distribution obtained from the output signal of each magnetic sensor of the magnetic sensor array, and the lateral position of the center of gravity of the first magnetic flux density distribution in the section is extracted. A calculating means to obtain;
A vehicle position detection apparatus comprising: detection means for detecting a lateral position of the vehicle based on the position of the center of gravity obtained by the calculation means and the center position of the magnetic sensor array. further,
Based on the first magnetic flux density distribution, interpolation is performed between the outputs of adjacent magnetic sensors in the magnetic sensor array to create a second magnetic flux density distribution having a larger number of signals than the first magnetic flux density distribution. With creation means to
The calculating means extracts a section having a predetermined threshold level or more from the second magnetic flux density distribution created by the creating means, and obtains the lateral position of the center of gravity of the second magnetic flux density distribution in the section.
The detecting means calculates a lateral position of the vehicle based on a lateral position of a center of gravity of the second magnetic flux density distribution obtained by the calculating means and a central position of the magnetic sensor array;
The vehicle position detecting device according to claim 1. The calculation means obtains a sum of moments of all signals in the section of the first or second magnetic flux density distribution around the midpoint position of the section, and determines a position where the sum of the moments is zero. Obtaining a lateral position of the center of gravity by searching;
The vehicle position detection device according to claim 1 or 2, characterized in that. The calculation means obtains a signal area in the section of the first or second magnetic flux density distribution,
Obtaining a lateral position of the center of gravity from the signal area;
The vehicle position detection device according to claim 1 or 2, characterized in that. A program for causing a computer to execute a process of detecting a position in a lateral direction of a vehicle with respect to a central portion of the traveling lane by detecting a magnetic field of a magnetic marker laid in a traveling direction at a central portion of the traveling lane,
A section having a predetermined threshold level or more is extracted from a first magnetic flux density distribution obtained from an output signal of each magnetic sensor of the magnetic sensor array having a plurality of magnetic sensors arranged in the lateral direction, and the first section in the section is extracted. A calculation step for obtaining a lateral position of the center of gravity of the magnetic flux density distribution of 1;
A detecting step of detecting a lateral position of the vehicle based on a lateral position of the center of gravity obtained by the calculating step and a central position of the magnetic sensor array;
A program for causing a computer to execute a process comprising: further,
Based on the first magnetic flux density distribution, interpolation is performed between the outputs of adjacent magnetic sensors in the magnetic sensor array to create a second magnetic flux density distribution having a larger number of signals than the first magnetic flux density distribution. With a creation step to
The calculating step extracts a section having a predetermined threshold level or more from the second magnetic flux density distribution created by the creating step, and obtains a lateral position of the center of gravity of the second magnetic flux density distribution in the section.
The detecting step calculates a lateral position of the vehicle based on a lateral position of a center of gravity of the second magnetic flux density distribution obtained in the calculating step and a central position of the magnetic sensor array;
The program according to claim 5. The calculating step obtains a sum of moments of all signals in the section of the first or second magnetic flux density distribution around the midpoint position of the section, and determines a position where the sum of the moments becomes zero. Obtaining a lateral position of the center of gravity by searching;
The program according to claim 5 or 6. The calculating step calculates a signal area in the section of the first or second magnetic flux density distribution, and determines a lateral position of the center of gravity from the signal area;
The program according to claim 5 or 6.

Images