JP4254014B2 - Magnet type marker detection system and magnet type marker detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnet marker detection systems and magnet marker detection equipment capable of detecting a magnet type markers arranged in the road.
[0002]
[Prior art]
Conventionally, for example, as a technique for detecting a vehicle position, a method of detecting a vehicle position by laying a magnetic marker (lane marker) on a road and detecting a pole (magnetic pole) of the magnetic marker row by the vehicle is known. Are known.
[0003]
[Problems to be solved by the invention]
However, since there are structures that naturally magnetize and generate a magnetic field, such as a steel pier, on the road, in the case of the technique of arranging the magnetic markers using the magnetic poles described above, a natural magnetic field is used. There was a problem that the detection accuracy of the magnetic marker was inferior due to the influence of the above.
[0004]
The present invention has been made to solve the above problems, and an object thereof is to provide a detection accurate magnet marker detection systems and magnet marker detection equipment of magnet type marker.
[0005]
[Means for Solving the Problems and Effects of the Invention]
(1) According to the first aspect of the present invention, a magnetic marker detection is performed in which a magnetic marker is laid in the vehicle traveling direction on the road and the pole (magnetic pole) of the magnetic marker is attached to the vehicle. It is about the system.
[0006]
In the present invention, the magnetic marker poles are arranged according to a specific arrangement rule in which the next pole can be predicted from the already detected magnetic marker pole data.
For example, in the case of a repetitive arrangement of S poles and N poles, it can be seen that the next of the S poles is the N pole and the next of the N poles is the S pole. If it is arranged according to the rule, that is, the next pole from the previous pole arrangement (for example, M-sequence arrangement), the next pole is naturally understood, so such an arrangement is adopted. To do.
[0007]
In the magnetic marker detection device, since the arrangement rule of the magnetic marker is stored in the storage means, the storage means is based on the arrangement of the poles of the magnetic marker detected using the signal detection means so far. It is possible to predict (know) the pole of the next magnetic marker by the arrangement rule stored in (1).
[0008]
Therefore, when the pole of the next magnetic marker is predicted, the changing means determines the output signal of the signal detection means according to the predicted pole (so that the pole can be detected more suitably). Change processing.
That is, as will be described in detail later in claim 3, the output signal (sensor output signal) of the signal detection means (for example, the lane marker sensor) is used for the S pole and the N pole as illustrated in FIG. Since it is different, process the output signal when detecting the next pole so that the pole of the magnetic marker can be detected under the same conditions as much as possible (for example, align the order of peak and valley of the signal as before) ) Change.
[0009]
Thereby, the detection accuracy of the poles of the magnetic marker can be improved by eliminating the difference in the waveforms of the output signals of the S and N poles.
(2) In the invention of claim 2, the arrangement rule of the magnetic marker is an arrangement rule based on an M-sequence pseudo-random code.
[0010]
A kind of M-sequence code of a pseudo-random code, that is, an M-sequence spread code, is a sequence that is mathematically guaranteed not to have the same code in one period.
This M sequence is generated by performing feedback of mod2 addition from an n-stage shift register, and its code length (L) is 2 ⁿ -1.
[0011]
In the M sequence having a code length of 2 ⁿ −1, an arrangement of n codes (for example, [0001]) is important, and the characteristics of the arrangement of the M sequence are arbitrary consecutive n bits (for example, n = 4). Always has a different value from the other n bits.
In the present invention, the “part of continuous codes of the encoded magnetic marker array (that is, part of the continuous codes of the pseudo-random code)” that is the arrangement of the n codes is referred to as “partial code”. ".
[0012]
Therefore, if n-bit data can be recognized, it is possible to recognize the position of the n-bit data in the M series, and it is also possible to recognize the next n-bit data. That is, it can be predicted whether the next pole is the S pole or the N pole.
For example, if the partial code A shown in FIG. 5 can be recognized, it can be seen that the next partial code is B, and therefore the pole of each magnetic marker in the B partial code is also known. Can also be predicted.
[0013]
Here, the pseudo-random code (PN code) is a spreading code sequence used for spread spectrum communication, CDMA, etc., and an M-sequence pseudo-random code having a code length of 2 ⁿ -1 is within one period. All consecutive n or more codes have different properties.
(3) In the invention of claim 3, the changing means inverts the output signal of the signal detecting means (for example, lane marker sensor) according to the predicted pole of the magnetic marker.
[0014]
For example, as shown in FIG. 6A, since the output signal (sensor output signal) of the signal detection means is different between the S pole and the N pole, that is, the output voltage peaks and troughs are reversed between the S pole and the N pole. Therefore, if the determination level (threshold level) is used as it is, the determination timing is shifted between the S pole and the N pole (even if the S pole and the N pole appear in the same timing). As a result, the detection accuracy may deteriorate.
[0015]
Therefore, when the predicted next pole is different from the current pole, the output signal generated by the next pole is inverted as illustrated in FIG. 6B. Thereby, the order of the peaks and valleys of the electrical signal becomes the same, and the determination timing can be made uniform, so that the detection accuracy can be improved.
[0016]
(4) The invention of claim 4 shows a magnetic marker detection device used in the magnetic marker detection system according to any one of claims 1 to 3, and the magnetic marker detection device There exists an effect similar to Claim 1.
(5) In the invention of claim 5, the changing means inverts the output signal of the signal detecting means according to the predicted pole of the magnetic marker.
[0017]
Magnet marker detection apparatus of the present invention, that Sosu the same effects as claim 3.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the magnet marker detection system and a preferred embodiment of the magnet-type marker detection equipment of the present invention will be described in detail with reference to the drawings by way of example (Example).
Example 1
a) First, the configuration of the magnetic marker detection system of this embodiment will be described.
[0027]
As shown in FIG. 1, in this embodiment, magnetic markers (lane markers) 1 are laid at specific intervals (for example, at equal intervals of 1 m) along the road traveling direction. In the magnet type marker 1, one of the magnet poles (S pole or N pole) is directed to the ground.
[0028]
As shown in FIG. 2, the magnetic marker 1 is laid on the road according to a pseudo-random code arrangement with a 0 code of a pseudo random code (here, for example, an M-sequence code) having an N pole and a 1 code as an S pole.
On the other hand, as shown in FIG. 3, the vehicle includes a lane marker sensor 3 that detects the pole of the magnetic marker 1 that has passed, a storage device 5 that stores a database of the arrangement of the magnetic marker 1, and the like. A magnetic marker detection device including a vehicle speed sensor 7 for detecting a speed (vehicle speed) and an arithmetic device 9 for performing detection processing of the pole of the next magnetic marker 1 from the information is mounted.
[0029]
Hereinafter, each structure of a magnet type marker detection apparatus is demonstrated.
The lane marker sensor 3 is mainly composed of an electromagnet, detects a change in voltage generated by crossing the magnetic field of the magnetic marker 1, and sends the information to the arithmetic unit 9.
[0030]
The storage device 5 is various storage devices such as an EEPROM, a ROM, a CD-ROM, and a DVD, for example, and stores database information indicating the arrangement of the magnetic markers 1 laid on the road.
The vehicle speed sensor 7 is a known vehicle speed sensor, and detects the vehicle speed from, for example, the number of rotations of the crankshaft.
[0031]
The arithmetic unit 9 is mainly composed of a microcomputer, and is based on information such as the arrangement of the poles detected by the lane marker sensor 3, the arrangement of the magnetic markers 1 stored in the database, the vehicle speed obtained from the vehicle speed sensor 7, and the like. Thus, the pole of the magnetic marker 1 is detected.
[0032]
Among these, as shown in FIG. 4, the database stored in the storage device 5 includes a partial code string obtained from an M-sequence code string (see FIG. 2) laid on the road, and the respective parts. It holds information (data) on the positional relationship of the code string.
That is, in an M sequence having a code length of 2 ⁿ −1, a relationship between a partial code composed of n pieces of data (for example, 4 pieces in this case) and a distance from a starting point (reference partial code) indicated by the partial code. Is remembered.
[0033]
b) Next, the detection principle of the magnetic marker 1 by the magnetic marker detection system of the present embodiment will be described.
・ (Pole prediction)
First, for example, as in the M sequence (n = 4) shown in FIG. 5, the first partial code [0001] (= A), the next partial code [0010] (= B), and the next partial code [0100]. Considering the case of arrangement as in (= C), if the partial code [0001] (= A) is recognized, then the partial code [0010] (= B ).
[0034]
Therefore, if the M-sequence code is stored in advance, the next pole of the partial code [0001] (= A) is “0”, that is, the N pole.
・ (Signal inversion)
Further, as shown in FIG. 6A, the waveform of the voltage output from the lane marker sensor 3 differs depending on whether the pole of the magnetic marker 1 is the S pole or the N pole. Specifically, the order of peaks and valleys of the voltage waveform differs between the S pole and the N pole.
[0035]
Therefore, if the determination level (threshold level) is applied to the voltage waveform as it is, the detection timing of the peak of the waveform is different between the S pole and the N pole even at the same vehicle speed (and at equal intervals). It will be.
Therefore, in this embodiment, for example, when the next of the S pole is the N pole, the waveform of the next N pole is inverted around the reference voltage as shown in FIG. 6B. As a result, the same peak / valley waveform is obtained for both the S pole and the N pole, so that the detection timing of the peak of the waveform is aligned, thereby improving the detection accuracy.
[0036]
c) Next, the procedure of the magnetic marker detection method implemented by the magnetic marker detection system of the present embodiment will be described based on the flowchart of FIG.
First, in step 100 of FIG. 7, a signal from the lane marker sensor 3 is input to the arithmetic device 9 while the vehicle is traveling.
[0037]
In the first stage, the output signal obtained from the lane marker sensor 3 has a slight peak shift between the S pole and the N pole as shown in FIG. 6A, but the output signal is used as it is. Then, the pole of the magnetic marker 1 is detected.
In the subsequent step 110, the arrangement of the poles is recognized from the detected information of at least n (here, for example, four) poles. That is, a 4-digit partial code in a binary number such as [0001] is recognized from the detected array.
[0038]
In the following step 120, the recognized 4-digit partial code is referred to as data in the database, and the position of the read partial code in the M-sequence arrangement indicating the arrangement of the magnetic markers 1 arranged on the road is located. Recognize
For example, when [0100] is read, the partial code [0100] is the third partial code [0100] (= C) based on the information in the database shown in FIG. 4 (or FIG. 5). recognize.
[0039]
In the following step 130, the recognized partial code [0100] is referred to the database of FIG. 5 to grasp the next pole.
That is, in the arrangement shown in FIG. 5, the next code after the recognized partial code [0100] is “1”, and since “1” indicates the S pole, the next detected pole is the S pole. You can know this in advance.
[0040]
In subsequent step 140, it is determined whether or not the latest recognized pole matches the next detected pole. If an affirmative determination is made here, the process proceeds to step 160, while if a negative determination is made, the process proceeds to step 150.
In step 150, for example, assuming that the output signal of the S pole has been used as it is (without being inverted) until now, the next pole is the N pole opposite to the S pole, so that the output signal is inverted. .
[0041]
Specifically, a signal (voltage) output from the lane marker sensor 3 is input to the arithmetic device 9 via a known AD converter (not shown). The arithmetic device 9 monitors the input signal. When the sensor output is a reference voltage for a certain time and the next pole detected by the host vehicle is the N pole, as shown in FIG. Inverts around the reference voltage.
[0042]
In step 160, the output signal inverted in step 150 (or the output signal as it is if not inverted) is monitored at a certain threshold level as shown in FIG. Timings t ₁ , t ₂ , t ₃ , t _4, etc. that exceed the threshold level (or fall from the threshold level) are obtained.
[0043]
In the subsequent step 170, the timing at which the vehicle has passed the magnetic marker 1 is determined from the timings t _{1 to} t _{4 and the} like, and this processing is temporarily terminated.
For example, transit time = (t _n + t _{n + 1} ) / 2. (However, n is an odd number)
c) In the present embodiment, the following effects can be obtained by the above-described configuration.
[0044]
In the present embodiment, on a certain road, the magnetic marker 1 is embedded so as to be an M-sequence array having a code length of 2 ⁿ −1. The number of partial codes (for example, four) is read, and the pole of the magnetic marker 1 next to the partial code is predicted (ascertained).
[0045]
If the predicted pole of the next magnetic marker 1 is different from the current pole (the latest one of the poles detected so far), the output voltage of the lane marker sensor 3 when the next pole is detected is Invert.
Thereby, since the voltage waveforms of the S pole and the N pole are aligned, the timing at which the vehicle has passed through the magnetic marker 1 can always be known accurately, and thus the detection accuracy of the magnetic marker 1 is improved.
(Example 2)
Next, the second embodiment will be described, but the description of the same parts as the first embodiment will be omitted.
[0046]
In this embodiment, the determination level of the output signal of the lane marker sensor 3 is changed according to the vehicle speed.
a) First, the detection principle of the magnetic marker 1 of this embodiment will be described.
As shown in FIG. 8, the peak of the output signal (voltage) of the lane marker sensor 3 differs between when the vehicle speed is high and when the vehicle speed is low.
[0047]
That is, the amount of change in magnetic flux density per unit time immediately below the lane marker sensor 3 changes according to the vehicle speed, and the peak of the output signal increases as the vehicle speed increases.
Therefore, the higher the vehicle speed, the higher the determination level, so that the influence of noise can be effectively removed, and the detection accuracy is improved.
[0048]
b) Next, the control processing in the present embodiment will be described based on the flowchart of FIG.
First, in step 200 of FIG. 9, the signal from the vehicle speed sensor 7 is input (to the arithmetic unit 9) via an AD converter (not shown), and the vehicle speed is detected.
[0049]
In subsequent step 210, the output signal generated by the lane marker sensor 3 is input (to the arithmetic unit 9) via the AD converter.
In the subsequent step 220, a determination level (threshold level) corresponding to the vehicle speed is obtained from the map or the like stored in the storage device 5. Specifically, the threshold level is increased as the vehicle speed increases.
[0050]
In subsequent step 230, the output signal input in step 210 is monitored at the constant threshold level obtained in step 220, and timings t ₁ , t exceeding the threshold level (rising and falling) are exceeded. ₂ , t ₃ , t _4, etc. are obtained.
[0051]
In step 240, from the timing t ₁ ~t ₄ etc., the vehicle by determining a timing which has passed through the magnet marker 1, and this processing ends.
For example, transit time = (t _n + t _{n + 1} ) / 2. (However, n is an odd number)
Thus, in the present embodiment, the detection accuracy can be further improved by changing the threshold level according to the vehicle speed.
(Example 3)
Next, although Example 3 will be described, description of the same parts as those in Example 1 will be omitted.
[0052]
In this embodiment, the cutoff frequency of the output signal of the lane marker sensor 3 is changed according to the vehicle speed.
a) First, the detection principle of the magnetic marker 1 of this embodiment will be described.
The frequency of the output signal (voltage) of the lane marker sensor 3 differs between when the vehicle speed is high and when the vehicle speed is low.
[0053]
That is, the amount of change in magnetic flux density per unit time immediately below the lane marker sensor 3 changes according to the vehicle speed, and the frequency of the output signal increases as the vehicle speed increases.
Therefore, in this embodiment, a filter function (so-called digital filter) capable of changing the cutoff frequency according to the vehicle speed is mounted. And as the vehicle speed increases, for example, by increasing the cutoff frequency of the bandpass filter, the influence of noise can be effectively removed, so that the detection accuracy is improved.
[0054]
b) Next, the control processing in the present embodiment will be described based on the flowchart of FIG.
First, in step 300 of FIG. 10, the signal from the vehicle speed sensor 7 is input via the AD converter (to the arithmetic unit 9), and the vehicle speed is detected.
[0055]
In the subsequent step 310, the output signal generated by the lane marker sensor 3 is input (to the arithmetic unit 9) via the AD converter.
In the subsequent step 320, the center frequency f ₀ according to the vehicle speed, the lower limit f _{c of} the cut-off frequency, and the upper limit f of the cut-off frequency are calculated from the arithmetic expressions of the following formulas (1) to (3) stored in the storage device 5. _{Find n} .
[0056]
f _c = v / l (1)
f ₀ = 2f _c (2)
f _n = 3f _c (3)
However, f ₀ : Center frequency, v: Vehicle speed, l: Magnet marker laying pitch f _c : Lower limit of cut-off frequency, f _n : Upper limit of cut-off frequency, that is, the cut-off frequency is the vehicle speed and magnet marker laying pitch It can ask for.
[0057]
For example, as the vehicle speed increases, the frequency component of the output signal that passes through the filter (bandpass filter) is changed so as to cut the low frequency band.
In subsequent step 330, the output signal input in step 310 is cut at the cut-off frequencies f _c and f _n obtained in step 320.
[0058]
In the following step 340, the cut output signal is monitored at a predetermined constant threshold level, and a timing exceeding the threshold level (rising and falling) is obtained.
In the subsequent step 350, the timing at which the vehicle passes the magnetic marker 1 is determined from the timing and the like, and the present process is temporarily terminated.
[0059]
For example, passing time = (rise time + fall time) / 2.
As described above, in this embodiment, the detection accuracy can be further improved by changing the cutoff frequencies f _c and f _n according to the vehicle speed.
Needless to say, the present invention is not limited to the above-described embodiments and can be carried out in various modes without departing from the technical scope of the present invention.
[0061]
For example, in the third embodiment, the band-pass filter is taken as an example, but a low-pass filter or a high-pass filter may be used, for example.
[0062]
Further, instead of a digital filter, a filter (switching according to speed) may be configured by a hardware configuration.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a state of a magnetic marker embedded in a road.
FIG. 2 is an explanatory diagram showing a state of arrangement of magnetic markers arranged on a road.
FIG. 3 is an explanatory diagram illustrating a magnet type marker detection device according to a first embodiment.
FIG. 4 is an explanatory diagram illustrating a database according to the first embodiment.
FIG. 5 is an explanatory diagram illustrating an M sequence of n = 4 according to the first embodiment.
6A and 6B show output signals of the lane marker sensor of Example 1, where FIG. 6A is a graph showing output signals when not inverted, and FIG. 6B is a graph showing output signals when inverted.
FIG. 7 is a flowchart illustrating control processing according to the first exemplary embodiment.
8 is a graph showing an output signal of a lane marker sensor of Example 2. FIG.
FIG. 9 is a flowchart illustrating control processing according to the second embodiment.
FIG. 10 is a flowchart illustrating control processing according to the third embodiment.
[Explanation of symbols]
1 ... Magnetic marker (lane marker)
3 ... Lane marker sensor 5 ... Storage device 7 ... Vehicle speed sensor 9 ... Arithmetic unit

Claims (5)

In a magnetic marker detection system in which a magnetic marker is laid in the vehicle traveling direction on the road and the magnetic marker pole is detected by a magnetic marker detection device attached to the vehicle,
In accordance with a specific arrangement rule in which the next pole can be predicted from the magnetic marker pole data that has already been detected, a system for arranging the poles of the magnetic marker is configured.
The magnet type marker detection device,
Storage means for storing an arrangement rule of poles of the magnetic marker;
Signal detection means for detecting an electrical signal generated by crossing the magnetic field of the pole of the magnetic marker;
When the pole of the magnetic marker is detected using the signal detection means, a prediction means for predicting the pole of the next magnetic marker according to the arrangement rule stored in the storage means;
When predicting the pole of the next magnetic marker by the predicting means, changing means for changing the processing of the output signal of the signal detecting means according to the predicted pole;
A magnet type marker detection system comprising:  The magnet marker detection system according to claim 1, wherein the magnet ruler pole arrangement rule is an arrangement rule based on an M-sequence pseudo-random code.  3. The magnetic marker detection system according to claim 1, wherein the changing unit inverts an output signal of the signal detection unit according to the predicted pole of the magnetic marker. A magnetic marker detection device used in the magnetic marker detection system according to any one of claims 1 to 3,
Storage means for storing an arrangement rule of poles of the magnetic marker;
Signal detection means for detecting an electrical signal generated by crossing the magnetic field of the pole of the magnetic marker;
When the pole of the magnetic marker is detected using the signal detection means, a prediction means for predicting the pole of the next magnetic marker according to the arrangement rule stored in the storage means;
When predicting the pole of the next magnetic marker by the predicting means, changing means for changing the processing of the output signal of the signal detecting means according to the predicted pole;
A magnet type marker detection device comprising:  5. The magnetic marker detection apparatus according to claim 4, wherein the changing unit inverts the output signal of the signal detection unit according to the predicted pole of the magnetic marker.

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