JP5004177B2 - Magnetic moving body speed detector - Google Patents

Description

  The present invention relates to a magnetic moving body speed detecting device for detecting the speed of a moving body made of a magnetic material.

  As an apparatus for detecting a moving body such as a vehicle, an ultrasonic type or microwave type moving body detecting apparatus shown in Patent Document 1, an image processing type moving body detecting apparatus shown in Patent Document 2, and a loop shown in Patent Document 3 In addition to the coil-type moving body detection device and the magnetic moving body detection device disclosed in Patent Documents 4 and 5, an air tube type moving body detection device and the like have been proposed.

In addition, when detecting the moving speed of the moving body, a moving body speed detecting device that radiates ultrasonic waves or microwaves and detects the speed of the moving body based on the phase shift of the reflected wave using the Doppler effect. Other than the above, the mobile body detection devices as described above are arranged at two locations along the traveling direction of the mobile body, and based on the detection time difference between the two locations and the interval between the two locations, A moving body speed detecting device for calculating the speed can be considered. In such a moving body speed detection device, the device becomes large and expensive, or requires complicated installation work such as accurately installing at least two sensors at a predetermined distance.
JP 2000-149183 A JP 2005-173787 A JP-A-10-288673 JP 2000-11292 A Japanese Patent Laid-Open No. 10-172093

On the other hand, similarly to the one shown in Patent Document 5 , one magnetic sensor having x and y axes that are mutually orthogonal sensitivity axes is installed horizontally beside the road, and is detected for each sensitivity axis. There has been proposed an apparatus for calculating a direction θ of a detected magnetic field generated from a vehicle from a biaxial magnetic field and determining a moving direction of the vehicle based on a change in the direction θ of the detected magnetic field. According to this, it is possible to detect the vehicle and the moving direction of the vehicle only by providing the magnetic sensor in one place. However, the change in the direction θ of the detected magnetic field has a drawback in that it cannot accurately detect the moving speed of the vehicle.

  The present invention has been made in the background of the above circumstances, and an object of the present invention is to provide a magnetic moving body speed detection device that is easy to install and can obtain high measurement accuracy.

  As a result of various investigations on the background of the above circumstances, the present inventor has determined the strength of the magnetic field in each of the two directions of the X-axis direction and the Y-axis direction perpendicular to each other by a pair of magnetic sensors at predetermined intervals. Using each detected value obtained by detection, an expression that satisfies the Stokes theorem in the magnetic field is expressed, and when the expression is modified, the speed of the moving object can be obtained from the above detected values and obtained in this way. From the measured values, we found that the measurement accuracy is comparable to the measured values of other speed measuring devices. The present invention has been made based on such findings.

  The gist of the invention according to claim 1 for achieving the above object is as follows: (a) a magnetic moving body speed detecting device for detecting the speed of a moving body made of a magnetic body relatively moving in the X-axis direction; And (b) detecting the intensity of the magnetic field in the X-axis direction and the intensity of the magnetic field in the Y-axis direction, which are arranged at a certain distance in the Y-axis direction orthogonal to the X-axis direction, respectively. 1 magnetic sensor and 2nd magnetic sensor, (c) The average value of the magnetic field strength of the Y-axis direction detected at the 1st time by the 1st magnetic sensor and the 2nd magnetic sensor, respectively, the 1st magnetic sensor and the 2nd magnetic sensor Y-axis direction magnetic field temporal change amount calculating means for calculating a Y-axis direction magnetic field temporal change amount dHy that is a difference from an average value of the Y-axis direction magnetic field strengths respectively detected at the second time by the two magnetic sensors; (d) First time by the first magnetic sensor. And the difference between the average value of the X-axis direction magnetic field strength detected at the second time and the average value of the X-axis direction magnetic field strength detected at the first time and the second time by the second magnetic sensor, respectively. X-axis direction magnetic field spatial difference value calculating means for calculating the X-axis direction magnetic field spatial difference value ΔHx, and (e) calculated by the Y-axis direction magnetic field temporal change amount calculating means from a previously stored relationship. Based on the ratio value of the Y axis direction magnetic field temporal variation dHy and the X axis direction magnetic field spatial difference value ΔHx calculated by the X axis direction magnetic field spatial difference value calculation means, the velocity v of the moving body is calculated. Speed calculation means for calculating.

  Further, in the invention according to claim 2, in the invention according to claim 1, when the time difference between the first time and the second time is dt and the constant distance is 2a, the previously stored relationship is v = (2a / dt) (dHy / ΔHx).

  According to a third aspect of the present invention, in the first or second aspect of the invention, the relationship is from the relative position of the first magnetic sensor at the first time to the relative position of the second magnetic sensor at the first time, The circular integral value of the strength of the magnetic field is zero in the circular path passing through the relative position of the second magnetic sensor at the second time and the relative position of the first magnetic sensor at the second time in order. It is set in advance based on Stokes' theorem.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein: (a) the moving body is a vehicle that passes along a traveling lane set in advance on a traveling road surface; (b) The first magnetic sensor and the second magnetic sensor are provided at fixed positions at a certain distance in a direction perpendicular to the traveling lane at a location adjacent to the traveling lane on the traveling road surface. It is characterized by that.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the first magnetic sensor and the second magnetic sensor are a pair of amorphous elements arranged along the X-axis direction and the Y-axis direction. A magnetic metal wire and a pickup coil wound around the amorphous magnetic metal wire to detect the impedance of the amorphous magnetic metal wire when a pulse current is passed through the amorphous magnetic metal wire. It is characterized by being.

  According to the magnetic moving body speed detecting device of the invention of claim 1, the speed calculating means calculates the Y-axis direction magnetic field temporally calculated by the Y-axis direction magnetic field temporal change calculating means from the relationship stored in advance. Since the velocity v of the moving body is calculated based on the ratio value between the change amount dHy and the X-axis direction magnetic field spatial difference value ΔHx calculated by the X-axis direction magnetic field spatial difference value calculation means, the X-axis The first magnetic sensor and the second magnetic sensor that respectively detect the magnetic field strength in the direction and the magnetic field strength in the Y-axis direction are separated by a certain distance in the Y-axis direction at one location along the moving direction of the moving body. Since the velocity v of the moving body is measured by arranging, a magnetic moving body speed detecting device that is easy to install and can obtain high measurement accuracy can be obtained.

  According to the magnetic mobile body speed detection device of the invention of claim 2, when the time difference between the first time and the second time is dt and the constant distance is 2a, the previously stored relationship is , V = (2a / dt) (dHy / ΔHx), the relationship between the actual Y-axis direction magnetic field temporal variation dHy and the X-axis direction magnetic field spatial difference value ΔHx (dHy / ΔHx) ), The speed v of the moving body can be easily obtained.

  Further, according to the magnetic mobile body speed detection device of the invention of claim 3, the relationship is from the relative position of the first magnetic sensor at the first time to the relative position of the second magnetic sensor at the first time. In the circular path that returns to the relative position of the first magnetic sensor at the original first time through the relative position of the second magnetic sensor at the second time and the relative position of the first magnetic sensor at the second time in order. Because it is preset based on Stokes' theorem that the round-trip integral value of the magnetic field strength is zero, it is affected by changes in offset values due to geomagnetic fluctuations, sensor noise, and random noise. It is difficult to obtain the reliability of the measured velocity v of the moving body.

  Further, according to the magnetic mobile body speed detection device of the invention according to claim 4, the mobile body is a vehicle that passes along a traveling lane preset on a traveling road surface, and the first magnetic sensor and Since the second magnetic sensor is provided at a fixed position in the direction perpendicular to the traveling lane at a certain distance in a location adjacent to the traveling lane on the traveling road surface, the second magnetic sensor travels on the traveling road surface. The speed of the vehicle is obtained.

According to the magnetic moving body speed detection device of the invention according to claim 5, the first magnetic sensor and the second magnetic sensor are a pair of amorphous magnetic metal wires arranged along the X-axis direction and the Y-axis direction. And a pickup coil wound around the amorphous magnetic metal wire in order to detect the impedance of the amorphous magnetic metal wire when a pulse current is applied to the amorphous magnetic metal wire. Since the magnetic field detection resolution has a high measurement sensitivity of about 10 ⁻⁶ , higher measurement accuracy can be obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to conceptual drawings. In addition, since each figure is a conceptual diagram, the mechanical structure of a detail, the dimensional ratio of each part, etc. are not necessarily drawn correctly.

  FIG. 1 is a diagram illustrating a vehicle speed detection apparatus 10 that detects the speed of a vehicle 12 that is a mobile body, that is, a vehicle speed v, as an example of a magnetic mobile body speed detection apparatus. As shown in FIG. 1, the traveling direction of the vehicle 12 traveling along the traveling lane on the traveling path 14 is set as the X-axis direction, and the direction orthogonal to the moving direction is set as the Y-axis direction.

  The vehicle speed detection device 10 includes a first magnetic sensor 20 and a second magnetic sensor 22 which are disposed at a constant distance 2a in the Y-axis direction orthogonal to the X-axis direction on the shoulder 16 adjacent to the traveling road 14, and An arithmetic control device 24 that calculates the speed v of the vehicle 12 by performing arithmetic processing on the signals output from the first magnetic sensor 20 and the second magnetic sensor 22 according to a program stored in advance, and the arithmetic control device 24 calculates it. And a display output device 26 for displaying and outputting the speed v of the vehicle 12 and the like. In FIG. 1, a first magnetic sensor 20 ′ and a second magnetic sensor 22 ′ indicated by broken lines indicate relative positions of the first magnetic sensor 20 and the second magnetic sensor 22 with respect to the vehicle 12 after a predetermined time dt.

The first magnetic sensor 20 detects the magnetic field strength H _{X1 in the X-} axis direction and the magnetic field strength H _Y1 in the Y-axis direction, respectively. The second magnetic sensor 22 also detects the magnetic field strength H _{X2 in the X-} axis direction and the magnetic field strength H _Y2 in the Y-axis direction, respectively. The arithmetic and control unit 24 is a so-called microcomputer including an A / D converter 28, a CPU 30, a ROM 32, a RAM 34, and a display output control circuit 36. The CPU 30 is stored in advance in the ROM 32 using the temporary storage function of the RAM 34. By calculating the input signal according to the program, the speed v of the vehicle 12 is calculated and the speed v of the vehicle 12 is displayed on the display output device 26, or a signal representing the speed v of the vehicle 12 is displayed. Output to other devices.

Since the first magnetic sensor 20 and the second magnetic sensor 22 are configured similarly, the first magnetic sensor 20 will be representatively described with reference to FIG. In FIG. 2, the first magnetic sensor 20 detects the impedance of the amorphous magnetic metal wire 40a disposed in the X-axis direction and the impedance of the amorphous magnetic metal wire 40a when a pulse current is passed through the amorphous magnetic metal wire 40a. In addition, a pulse current is passed through the X-axis direction detecting element 40 having a pickup coil 40b wound around the amorphous magnetic metal wire 40a, the amorphous magnetic metal wire 42a arranged in the Y-axis direction, and the amorphous magnetic metal wire 42a. In order to detect the impedance of the amorphous magnetic metal wire 42a at the time, the Y-axis direction detecting element 42 including a pickup coil 42b wound around the amorphous magnetic metal wire 42a, and a clock signal output from the oscillator 44 Based on the above amorphous magnetic metal wire 40a And a timing control circuit 46 for alternately outputting a pulse current to the amorphous magnetic metal wire 42a, and a pickup coil wound around the amorphous magnetic metal wire 40a and the amorphous magnetic metal wire 42a when the pulse current is applied to them. 40b and a sample hold circuit 48 for holding voltage signals induced in the pickup coil 42b, one or the other of the voltage signals alternately output from the sample hold circuit 48 according to the output switching signal, and the reference voltage generator 50 A differential amplifier 52 that alternately compares the reference voltage and outputs a signal indicating the detected magnetic field strength H _X1 in the X-axis direction and a signal indicating the detected magnetic field strength H _Y1 in the Y-axis direction alternately. And. The amorphous magnetic metal wires 40a and 42a are made of, for example, FeCoSiB amorphous metal wires annealed at 520 ° C. for 2 seconds.

The first magnetic sensor 20 has a magnetic impedance effect (MI effect: Magneto-Impedance Effect), which is a phenomenon in which impedance when a pulse current is passed through the amorphous magnetic metal wires 40a and 42a is greatly changed according to an external magnetic field, The pickup coils 40b and 42b wound around the amorphous magnetic metal wires 40a and 42a utilize the phenomenon that an induced voltage proportional to the strength of the external magnetic field is generated, and have a high frequency of about 10 kHz or 100 kHz. And a relatively high magnetic field detection resolution of about 10 ⁻⁶ G (Gauss). The main raw material of the vehicle 12 is a magnetic material such as a steel plate, a steel pipe, a forged material, or cast iron, and the vehicle 12 has a magnetic charge. Such traffic of the vehicle 12 causes a change in the magnetic field (magnetic field) HX in the _X direction and a change in the magnetic field HY in the _Y direction, for example, as shown in FIG. The first magnetic sensor 20 and the second magnetic sensor 22 detect such changes in the magnetic fields H _X and H _Y.

FIG. 4 is a functional block diagram for explaining a main part of the control function of the arithmetic and control unit 24. In FIG. 4, the vehicle recognizing means 60 uses, for example, the magnetic field vector H ^V = √ (from the magnetic field strength H _X1 in the X-axis direction detected by the first magnetic sensor 20 and the magnetic field strength H _{Y1 in} the Y-axis direction. _{H X1} ² + H _Y1 ²⁾ calculates, based on the fact that lies between the vehicle judgment value that the magnetic field vector ^{H V} is set in advance that is, the measurement start determination value ^H _{V 1} and the measurement end determination value ^H _{V 2} vehicle 12 is determined and recognized as passing. Figure 5 is a diagram showing the temporal change of the magnetic field vector H ^V, for example, the measurement start determination value H ^V ₁ is about 15% of the maximum value H ^V _max temporal change of the magnetic field vector H ^V The measurement end determination value H ^V ₂ is set to a value about 50% of the maximum value H ^V _max of the temporal change of the magnetic field vector H ^V.

The storage means 62 stores the magnetic field strength H _X1 in the X-axis direction and the magnetic field strength in the Y-axis direction detected by the first magnetic sensor 20 while the vehicle recognition means 60 recognizes that the vehicle is passing. H _Y1 , the first magnetic field strength H _X2 detected by the second magnetic sensor 22 and the first magnetic field strength H _{Y2 in} the Y-axis direction are separated by a predetermined sampling period. At least two sampling values at time t and second time t + dt are sequentially stored. The storage means 62 also stores the number of recognized vehicles recognized by the vehicle recognition means 60, that is, the number of vehicles.

The X-axis direction magnetic field spatial difference value calculation means 64 is a line in the integration interval vdt from the relative position of the second magnetic sensor 22 at the first time t to the relative position of the second magnetic sensor 22 ′ at the second time t + dt. An integral value vdt [H _X2 ] is calculated. This line integral value vdt [H _X2 ] is the magnetic field strength H _X2 (t) at the first time stored in the storage means 62 and the magnetic field strength H at the second time in the X axis direction. _{Using X2} (t + dt), the magnetic field strength H _X2 (t) in the X-axis direction at the first time t and the magnetic field strength H _X2 (t + dt) in the X-axis direction at the second time t + dt By multiplying the average value of (H _X2 (t + dt) + H _X2 (t)) / 2 by the integration interval vdt, it is possible to easily calculate using a small amount of sampling data. Similarly, the X-axis direction magnetic field spatial difference value calculation means 64 calculates the line integral value vdt [H in the integration interval vdt from the relative position of the first magnetic sensor 20 ′ to the relative position of the first magnetic sensor 20. _X1 ] is calculated. The line integral value vdt [H _X1 ] is the intensity of the magnetic field H _X1 (t + dt) in the X-axis direction at the second time and the magnetic field in the X-axis direction at the first time t stored in the storage means 62. with strength H _{X1 (t),} the intensity of the magnetic field of their X-axis direction of the first time _t H _{X1 (t)} and a second time t + intensity in the X-axis direction of the magnetic field dt H _{X1 (t} + dt ) By multiplying the average value (H _X1 (t + dt) + H _X1 (t)) / 2 by the integration interval vdt, it can be easily calculated using a small amount of sampling data. Then, X-axis direction magnetic field spatial differential value calculating means 64, which line integration value vdt _{[H X2]} and vdt X direction magnetic field spatial differential value which is the difference between _{[H X1] ΔHX (= vdt} [H X1] - vdt [H _X2 ]) is calculated.

The Y-axis direction magnetic field temporal variation calculation means 66 calculates the line integral value in the integration interval 2a from the position of the first magnetic sensor 20 at the first time t to the position of the second magnetic sensor 22 at the first time t. 2aH _Y (t) is calculated. This line integral value 2aH _Y (t) is calculated using the first magnetic field strengths H _Y1 (t) and H _Y2 (t) in the Y-axis direction at the first time t stored in the storage means 62. By multiplying the average value (H _Y1 (t) + H _Y2 (t)) / 2 of the magnetic field strengths H _Y1 (t) and H _Y2 (t) in the Y-axis direction at time t by the integration interval 2a It can be easily calculated using sampling data. Similarly, the Y-axis direction magnetic field temporal variation calculation means 66 performs line integration in the integration interval 2a from the position of the second magnetic sensor 22 ′ to the position of the first magnetic sensor 20 ′ at the second time t + dt. The value 2aH _Y (t + dt) is calculated. The line integral value 2aH _Y (t + dt) is obtained by calculating the magnetic field strengths H _Y1 (t + dt) and H _Y2 (t + dt) in the Y-axis direction at the second time t + dt stored in the storage means 62. And the average value of the magnetic field strengths H _Y1 (t + dt) and H _Y2 (t + dt) at the second time t + dt (H _Y1 (t + dt) + H _Y2 (t + dt) ) / 2 can be easily calculated using a small amount of sampling data by multiplying the integration interval 2a. Then, the Y-axis direction magnetic field temporal change calculation means 66 calculates the temporal change of the Y-axis direction magnetic field per unit time dt, which is the difference between the line integral values 2aH _Y (t) and 2aH _Y (t + dt). The quantity dH _Y (= H _Y (t) −H _Y (t + dt)) is calculated.

The speed calculation means 68 calculates the Y-axis direction magnetic field temporal change amount dHy calculated by the Y-axis direction magnetic field temporal change amount calculation means 66 from the relational expression (1) stored in advance, and the X-axis direction magnetic field spatial difference. Based on the ratio value (dH _y / ΔH _X ) of the X-axis direction magnetic field spatial difference value ΔH _X calculated by the value calculation means 64, the speed v (km / h) of the vehicle 12 is calculated. Then, the display output control means 70 causes the display output device 26 to display an image of the speed v of the vehicle 12 calculated by the speed calculation means 68, the number of recognized vehicles, that is, the number of vehicles stored in the storage means 62, or Signals representing the speed v of the vehicles 12 and the number of vehicles are output.

v = (2a / dt) (dH _Y / ΔH _X ) (1)

This equation (1) is derived by using the so-called Stokes theorem that the revolving component value in the magnetic field becomes zero regardless of the revolving direction. That is, in FIG. 1, the relative position A of the first magnetic sensor 20 at the first time t, the relative position B of the second magnetic sensor 22 at the first time t, and the relative position C of the second magnetic sensor 22 at the second time t + dt. Considering the circular integration of the magnetic field returning to the relative position D of the first magnetic sensor 20 at the second time and the relative position A of the first magnetic sensor 20 at the original first time t, the line integral of the magnetic field in the section AB. The value is 2aH _Y (t), the line integral value of the magnetic field in the section BC is v · dt [H _X1 ], the line component value of the magnetic field in the section CD is −2aH _Y (t + dt), and the section D−. The line integral value of the magnetic field at A is −vdt [H _X2 ]. Since the sum of them is zero according to the Stokes theorem, Equation (2) is obtained. When this is transformed into a formula representing the vehicle speed v, (3) is obtained. Then, if ΔH _X = [H _X2 −H _X1 ] and dH _Y = H _Y (t) −H _Y (t + dt), then Equation (1) is obtained. In equation (1), 2a is the distance (m) between the first magnetic sensor 20 and the second magnetic sensor 22, and dt is the sampling time (sec), both of which are known constants. When the axial magnetic field temporal variation dHy and the X-axis magnetic field spatial difference value ΔH _X are calculated, and the ratio value (dHy / ΔH _X ) is calculated, the vehicle speed v is calculated based on the calculated value.

2aH _Y (t) + vdt [H _X1 ] −2 aH _Y (t + dt) −vdt [H _X2 ] = 0
(2)
v = (2a / dt) [ H Y (t) -H Y (t + dt)] / (H X2 -H X1)
(3)

FIG. 6 is a flowchart for explaining a main part of the control operation of the arithmetic control device 24. In FIG. 6, steps corresponding to the vehicle recognition means 60 (hereinafter, steps are omitted) In S1, for example, the magnetic field strength H _X1 in the X-axis direction detected by the first magnetic sensor 20 and the magnetic field in the Y-axis direction are detected. from strength _{H Y1} Metropolitan magnetic field vector ^{_{H V = √ (H X1 2}} + H Y1 2) is calculated, the magnetic field vector ^{H V} is preset and the measurement start determination value ^H _{V 1} and the measurement end determination value ^H _{V 2} Whether or not the vehicle 12 is passing is determined based on what is between the two.

If the determination in S1 is negative, this routine is terminated. If the determination is affirmative, in S2, the first magnetic sensor 20 and the second magnetic sensor 22 detect the magnetic field in the X-axis direction at the first time t. The strengths H _X1 (t) and H _X2 (t) are detected, and in S3, the first magnetic sensor 20 and the second magnetic sensor 22 use the magnetic field strength H _Y1 (Y Y direction at the first time t). t) and H _Y2 (t) are measured. Then, in S4 corresponding to the storage means 62, the magnetic field strengths H _X1 (t) and H _X2 (t) in the X-axis direction at the first time t and the magnetic field strength in the Y-axis direction at the first time t. H _Y1 (t) and H _Y2 (t) are stored.

Next, in S5, it is determined whether or not the sampling at the second time t + dt after the sampling period dt set in advance from the sampling at the first time t is completed. Since this determination is initially denied, S2 to S4 are executed again at the second time t + dt. That is, in S2, the first magnetic sensor 20 and the second magnetic sensor 22 detect the magnetic field strengths H _X1 (t + dt) and H _X2 (t + dt) in the X-axis direction at the second time t + dt. In S3, the first magnetic sensor 20 and the second magnetic sensor 22 measure the magnetic field strengths H _Y1 (t + dt) and H _Y2 (t + dt) in the Y-axis direction at the second time t + dt. In S4 corresponding to the storage means 62, the magnetic field strengths H _X1 (t + dt) and H _X2 (t + dt) in the X-axis direction at the second time t + dt and the Y-axis direction at the second time t + dt The magnetic field strengths H _Y1 (t + dt) and H _Y2 (t + dt) are stored.

Next, in S6 corresponding to the X-axis direction magnetic field spatial difference value calculation means 64, from the relative position of the second magnetic sensor 22 at the first time t to the relative position of the second magnetic sensor 22 ′ at the second time t + dt. The line integral value vdt [H _X2 ] in the integration interval vdt is the stored magnetic field strength H _X2 (t) in the X-axis direction at the first time and the magnetic field strength in the X-axis direction at the second time. H _X2 with _(t + dt), the intensity of the magnetic field of their X-axis direction of the first time _t H _{X2 (t)} and a second time t + intensity in the X-axis direction of the magnetic field dt H _{X2 (t} + dt ) Average value [H _X2 ] _av = (H _X2 (t + dt) + H _X2 (t)) / 2 is multiplied by the integration interval vdt. Further, the line integral value vdt [H _X1 ] in the integration interval vdt from the relative position of the first magnetic sensor 20 ′ to the relative position of the first magnetic sensor 20 is stored in the X-axis direction at the stored second time. Using the magnetic field strength H _X1 (t + dt) and the magnetic field strength H _X1 (t) in the X-axis direction at the first time t, the magnetic field strength H _{X1 in} the X-axis direction at the first time t. (t) and the average value [H _X1 ] _av = (H _X1 (t + dt) + H _X1 (t)) / 2 of the magnetic field strength H _X1 (t + dt) in the X-axis direction at the second time t + dt It can be calculated by multiplying the integration interval vdt. Then, by obtaining the difference between the line integral values vdt [H _X2 ] and vdt [H _X1 ], the X-direction magnetic field spatial difference value ΔH _X (= vdt [H _X1 ] −vdt [H _X2 ]) is calculated. Is done.

In S7 corresponding to the subsequent Y-axis direction magnetic field temporal variation calculation means 66, the integration interval from the position of the first magnetic sensor 20 at the first time t to the position of the second magnetic sensor 22 at the first time t. The line integral value 2aH _Y (t) at 2a is obtained using the stored magnetic field strengths H _Y1 (t) and H _Y2 (t) in the Y-axis direction at the first time t stored at the first time t. It is calculated by multiplying the average value (H _Y1 (t) + H _Y2 (t)) / 2 of the magnetic field strengths H _Y1 (t) and H _Y2 (t) in the Y-axis direction by the integration interval 2a. . Similarly, the line integration value 2aH _Y (t + dt) in the integration section 2a between the position of the second magnetic sensor 22 ′ and the position of the first magnetic sensor 20 ′ at the second time t + dt is stored as described above. Using the magnetic field strengths H _Y1 (t + dt) and H _Y2 (t + dt) at the second time t + dt, the magnetic field strength H _Y1 ( t + dt) and the average value of H _Y2 (t + dt) (H _Y1 (t + dt) + H _Y2 (t + dt)) / 2 are multiplied by the integration interval 2a. Then, by obtaining the difference between these line integral values 2aH _Y (t) and 2aH _Y (t + dt), the temporal change amount dH _Y (= H _Y (t) of the Y-axis direction magnetic field per unit time dt is obtained. -H _Y (t + dt)) is calculated.

Next, in S8 corresponding to the velocity calculating means 68, the Y-axis direction magnetic field temporal variation dHy calculated in S7 and the X-axis direction magnetic field spatial difference calculated in S6 from the relational expression (1) stored in advance. Based on the value ΔH _X , specifically, based on the ratio value (dHy / ΔH _X ) between the Y-axis direction magnetic field temporal variation dHy and the X-axis direction magnetic field spatial difference value ΔH _X , the vehicle 12 The speed v (km / h) is calculated. In S9 corresponding to the display output control means 70, the speed v of the vehicle 12 calculated in S8, the number of recognized vehicles, that is, the number of vehicles stored in the storage means 62, are displayed on the display output device 26, or A signal representing the speed v of the vehicles 12 and the number of vehicles is output.

Next, the result of the simulation performed by the present inventors under the following conditions will be described. In this simulation, as shown in FIG. 7, the vehicle is set as a flat plate having a length 2L of 4 m and a width L of 2 m, a magnetization parallel model CP having a positive magnetization in the first half of the vehicle and a negative magnetization in the second half, A magnetic vertical model CV having positive magnetization on the sensor-side half of the vehicle and negative magnetization on the opposite side is set, the traveling direction of the vehicle is set in the X-axis direction, and the width direction is set in the Y-direction. 2 is set to 0.3 m, and the magnetic sensor 3 is set such that the distance J in the X-axis direction is 0.6 m from the magnetic sensor 1, and the distance from the vehicle to the middle between the magnetic sensor and the magnetic sensor is set. The distance was set to 1.8 m, the detection magnetic field of the magnetic sensor m (m = 1, 2, 3) was set to Hm, and the vehicle speed v was set to 40 km / h. Further, in this simulation, the size H ^V1 sensing magnetic field vector of the vehicle in the magnetic sensor 1 is set to 6 mg.

FIG. 8 is a diagram for explaining equations (4) and (5) used for calculating the magnetic field change related to the magnetization parallel model CP in the simulation. Assuming a uniform magnetic pole in the X-axis direction, assuming that the magnetic pole density is σ and the distance to the magnetic pole is d, the magnetic field H _Y (x) in the Y-axis direction is as follows. The magnetic field H _X (x) in the X-axis direction is as follows.

H _Y (x) = (σ / 2πμ ₀ ) [tan ⁻¹ (x ₂ −x) / d−tan ⁻¹ (x ₁ −x) / d]
H _X (x) = (− σ / 2πμ ₀ ) ln (| √d ² + (xx ₂ ) ² || (√d ² + (xx ₂ ) ² |
/ | D ² |

Here, according to the cosine theorem, the angles θ ₁ and θ ₂ in FIG. From these equations and the above equation, the magnetic field H _X (x) in the _X- axis direction and the magnetic field H _Y (x) in the Y-axis direction by the magnetization parallel model CP are expressed by the following equations (4) and (5).
θ ₁ = cos ⁻¹ (r ₀ ² + r ₁ ² + L ² ) / 2r ₀ r ₁
θ ₂ = cos ⁻¹ (r ₀ ² + r ₂ ² + L ² ) / 2r ₀ r ₂

FIG. 9 is a diagram for explaining the equations (6) and (7) used for calculating the magnetic field change related to the magnetization perpendicular model CV in the simulation. The width of the magnetization distribution is L, which is half that of the magnetization parallel model CP, the magnetic pole density σ ′ is twice that of σ, and a uniform magnetic pole is assumed in the Y-axis direction. the magnetic field H determined the _{Y (x)} and the X-axis direction of the magnetic field H _{X (x),} further from the respective angle theta _{1 'and} theta _2' is shown in FIG. 9 by the cosine theorem equation, the magnetic field in the X-axis direction H _X (x) is expressed by the following equation (4), and the magnetic field H _Y (x) in the Y-axis direction is expressed by the following equation (5).

H _X = (− σ / 2πμ ₀ ) ln (| r ₁ || r ₂ | / | r ₀ | ² ) (4)
H _Y = (σ / 2πμ ₀ ) [θ ₂ −θ ₁ ] (5)
H _X = (σ ′ / 2πμ ₀ ) [θ ₂ '−θ ₁ '] (6)
H _Y = (− σ ′ / 2πμ ₀ ) ln (| r ₁ ′ || r ₂ ′ | / | r ₀ ′ | ² ) (7)

  FIG. 10 shows the result of calculating the detected magnetic field of the magnetic sensor 1 using the equations (4) and (5) of the magnetization parallel model CP, and FIG. 11 shows the actual road using the actual first magnetic sensor 20. The detected magnetic field when the vehicle passes is shown. Comparing the two, it can be considered that the waveforms are almost the same, so the validity of this simulation model is confirmed.

In general, with respect to the strength of the magnetic field detected by the first magnetic sensor 20 or the second magnetic sensor 22, the offset value varies by about 0.4 mG due to variations in geomagnetism. For this reason, the influence on the speed calculation when a deviation occurs between the initial offset value and the actual offset value was examined. The offset value is a deviation value from the zero value of the base line of the detected waveform. That is, the change of the speed calculation value when the current offset value of the magnetic sensor 1 fluctuates in the range of −0.4 to 0.4 mG as compared with the initial setting value of the offset value is simulated using the equation (1). At the same time, the magnetization parallel model CP and the magnetization perpendicular model CV were examined in comparison with the simulation results of the velocity calculation values obtained using the phase difference method. In this phase difference method, as shown in FIG. 7, waveforms indicating changes in the magnetic fields detected by the magnetic sensor 1 and the magnetic sensor 3 arranged at a predetermined distance A (for example, 0.6 m) apart in the X-axis direction. The vehicle speed v (= A / D) is calculated based on the phase difference D (msec) between the two and the predetermined distance. FIG. 12 shows the phase difference D _X between the magnetic field strength H _X1 in the X-axis direction detected by the magnetic sensor 1 and the magnetic field strength H _X3 in the X-axis direction detected by the magnetic sensor 3. Figure 13 shows the phase difference D _Y between the magnetic field intensity H _Y3 of the detected Y-axis direction by the magnetic field intensity H _Y1 and the magnetic sensor 3 of the detected Y-axis direction by the magnetic sensor 1.

FIG. 14 shows the speed calculation value when the offset value fluctuates in the range of −0.4 to 0.4 mG. ◇ indicates the vehicle speed value obtained from Equation (1) derived from Stokes' theorem, while □ indicates the vehicle speed value obtained from Equations (4) and (5) for the magnetization parallel model CP. And Δ are vehicle speed values obtained from the equations (6) and (7) for the perpendicular magnetization model CV. As is clear from FIG. 14, the vehicle speed value obtained using the equation (1) derived from the Stokes theorem is not affected by the fluctuation of the offset value due to the fluctuation of geomagnetism. The vehicle speed value v obtained from the equation (1) derived from the Stokes theorem indicated by ◇ is the Y generated between the output difference ΔH _{X in} the X-axis direction of the magnetic sensor 1 and the magnetic sensor 2 and the minute time dt. Since it is calculated from the ratio value (dH _Y / ΔH _X ) with the axial output difference dH _Y , the vehicle is being recognized even if there is a deviation from the initial set value due to offset fluctuation over a long period of time. If there is no offset fluctuation, it is considered that the speed calculation is not affected.

  Next, the influence of noise at the measurement location will be considered. In general, positive and negative sensor noises of about 0.15 mG are generated even when no vehicle passes. As this noise, a sine wave noise having an amplitude of 0.2 mG is given to the X-axis direction and the Y-axis direction of the magnetic sensor 1, and the speed according to each method when the frequency of the sine wave noise is changed from 10 to 100 Hz. The error of the value was simulated. FIG. 15 shows the result. The symbol ◇ indicating the vehicle speed value obtained from the equation (1) derived from Stokes' theorem is hardly influenced regardless of the change in the frequency of the sine wave noise. However, for the magnetization parallel model CP, □ indicating the vehicle speed value obtained from the equations (4) and (5), and for the magnetization perpendicular model CV, Δ representing the vehicle speed value obtained from the equations (6) and (7). The mark is greatly influenced by a change in the frequency of the sine wave noise. The square mark is affected by about 10%, and the triangle mark is influenced by a maximum of about 25%.

  Furthermore, the influence of random noise is considered. In general magnetic field measurement, in order to maintain measurement accuracy, it is necessary to have performance that is hardly affected by random noise. Therefore, virtually different types of random noise as shown in FIG. 16, for example, are given in the X-axis direction and Y-axis direction of all magnetic sensors, pseudo-random numbers are changed, and simulation is performed 200 times. The error rate (%) of the vehicle speed value calculated by each method was compared. FIG. 17 shows a distribution of error rates of vehicle speed values calculated by the above methods. In FIG. 17, the ◇ mark indicating the error rate distribution of the vehicle speed value obtained from the equation (1) derived from Stokes's theorem is a normal distribution within an error rate range of about ± 5% centered on the zero value. It has become. On the other hand, the □ mark indicating the error rate distribution of the vehicle speed value obtained from the equations (4) and (5) for the magnetization parallel model CP is not a normal distribution but within an error rate range of about ± 10%. In addition, the Δ mark indicating the error rate distribution of the vehicle speed value obtained from the equations (6) and (7) for the perpendicular magnetization model CV is not a normal distribution but within an error rate range of about ± 20%. Distribution.

The phase difference method is a differential calculation method that uses one point of the offset value to obtain a time difference, and is easily affected by noise. In addition, compared with the magnetization parallel model CP, the magnetization perpendicular model CV has a smaller change rate of the magnetic field in the vicinity of the offset value, and thus the influence of noise is considered to be larger. On the other hand, in the vehicle speed value obtained from the equation (1) derived from Stokes' theorem, noise is generated in dH _Y and ΔH _X when calculating the speed, but a spatial difference is taken. It is considered that the noise component of ΔH _X is canceled out.

Furthermore, this inventor performed the measurement using the vehicle speed detection apparatus 10 of a present Example, and the measurement using a speed gun using the motor vehicle of the same vehicle type. In this experiment, the first magnetic sensor 20 and the second magnetic sensor 22 having a mutual interval of 0.3 m in the Y-axis direction are installed at a height of 1.1 m, and 1.4 per sampling period of about 1/4 second. The speed of the automobile was changed in a range of ˜2.6 m, and data of 50 km / h or more was measured with a sampling period ½. FIG. 18 shows the result. According to this, calculation speed obtained a high accuracy of error rate of about 3% variation in waveforms were those R ² value is as small as 99%.

  As described above, according to the vehicle speed detection device 10 of the present embodiment, the speed calculation unit 68 calculates, for example, the Y axis direction magnetic field temporal change amount calculation unit 66 from the previously stored relationship shown in the equation (1). Vehicle (moving body) 12 based on the ratio value of the Y axis direction magnetic field temporal variation dHy and the X axis direction magnetic field spatial difference value calculation means 64 calculated by the X axis direction magnetic field spatial difference value ΔHx. Therefore, the first magnetic sensor 20 and the second magnetic sensor 22 that detect the strength of the magnetic field in the X-axis direction and the strength of the magnetic field in the Y-axis direction, respectively, are used as the traveling direction of the vehicle 12. Since the speed v of the vehicle 12 is measured by disposing a certain distance 2a in the Y-axis direction at one location along the line, installation is easy and high measurement accuracy is obtained.

  Further, according to the vehicle speed detection device 10 of the present embodiment, when the time difference between the first time t and the second time t + dt is dt and the certain distance is 2a, the previously stored relationship is v = (2a / Dt) (dHy / ΔHx), the vehicle based on the relationship between the actual Y-axis direction magnetic field temporal variation dHy and the X-axis direction magnetic field spatial difference value ΔHx (dHy / ΔHx). A speed of 12 can be easily obtained.

  Further, according to the vehicle speed detection device 10 of the present embodiment, the relationship represented by the above formula (1) is that the second magnetic sensor 22 at the first time t is from the relative position of the first magnetic sensor 20 at the first time t. The rotation returns to the relative position of the first magnetic sensor 20 at the first time t through the relative position, the relative position of the second magnetic sensor 22 at the second time t + dt, and the relative position of the first magnetic sensor 20 at the second time t + dt. Since it is set in advance based on Stokes' theorem that the circulation integral value of the magnetic field strength is zero in the path or the reverse circuit path, the change in the offset value due to the geomagnetism fluctuation, the sensor noise, Insensitive to random noise, the reliability of the measured velocity v of the moving body can be obtained.

  Further, according to the vehicle speed detection device 10 of the present embodiment, the vehicle 12 that passes along the traveling lane set in advance on the road surface of the traveling road 14 is used as the moving body, and the first magnetic sensor 20 and Since the second magnetic sensor 22 is provided at a fixed position at a certain distance 2a in a direction perpendicular to the traveling lane on the shoulder 16 of the traveling road 14 adjacent to the traveling lane, The speed of the vehicle 12 traveling on the 14 road surfaces is measured.

Further, according to the vehicle speed detection device 10 of the present embodiment, the first magnetic sensor 20 and the second magnetic sensor 22 include a pair of amorphous magnetic metal wires 40a and 42a disposed along the X-axis direction and the Y-axis direction. In order to detect the impedance of the amorphous magnetic metal wires 40a and 42a when a pulse current is applied to the amorphous magnetic metal wires 40a and 42a, respectively, a pickup coil 40b wound around the amorphous magnetic metal wires 40a and 42a and 42b, respectively, and therefore has high measurement sensitivity with a magnetic field detection resolution of about 10 ^−6, so that higher measurement accuracy can be obtained.

  As mentioned above, although one Example of this invention was described in detail with reference to drawings, this invention is implemented also in another aspect.

  For example, the first magnetic sensor 20 and the second magnetic sensor 22 described above are magneto-impedance effect (MI) type sensors, but are flux gate (FG) sensors, Hall element sensors, ferromagnetic magnetoresistances. MR (Magneto-Resistance effect) type sensor, Giant Magneto-Resistance effect (GMR) sensor, Tunnel Magneto-Resistance effect (TMR) sensor, optical fiber magnetic sensor, etc. It may be a magnetic sensor. In short, it is only necessary to be able to detect the magnetic field strength in the X-axis direction and the magnetic field strength in the Y-axis direction, respectively.

  Moreover, although the above-mentioned 1st magnetic sensor 20 and the 2nd magnetic sensor 22 were comprised as shown in FIG. 2, you may be comprised from the circuit different from it.

  Further, in the vehicle speed detection device 10 of the above-described embodiment, the speed v of the vehicle 12 is detected. However, a moving body other than the vehicle 12, for example, a ship moving on the water, a moving object such as a transported object on a conveyor, etc. It may be used for speed detection.

In the above-described embodiment, the magnetic field strength H _X1 in the X-axis direction and the magnetic field strength H _{Y1 in} the Y-axis direction detected by the first magnetic sensor 20 and the X magnetic field detected by the second magnetic sensor 22 are used. The sampling cycle for sampling the magnetic field strength H _{X2 in the} axial direction and the magnetic field strength H _{Y2 in} the Y-axis direction does not necessarily match the storage cycle for storing them in the storage means 62. It is better to match the power consumption.

  In addition, what was mentioned above is an illustration to the last and can be suitably changed as needed. In addition, although not illustrated one by one, the present invention can be variously modified without departing from the spirit of the present invention.

It is a conceptual diagram explaining the structure and arrangement | positioning of the vehicle speed detection apparatus of one Example of this invention. It is a circuit diagram explaining the structure of the 1st magnetic sensor of FIG. It is a figure which shows the waveform showing the magnetic field intensity detected by the 1st magnetic sensor of FIG. It is a functional block diagram explaining the principal part of the control function of the arithmetic and control unit of FIG. It is a figure which shows the waveform showing the magnetic field vector used in the vehicle recognition means of FIG. 4, and the determination value for vehicle recognition. It is a flowchart explaining the principal part of the control action of the arithmetic and control unit of FIG. It is a figure explaining the precondition of the simulation of the action | operation of the arithmetic and control apparatus of FIG. It is a figure explaining the calculation formula used to calculate the detection magnetic field with respect to the magnetization parallel model CP used in the simulation of FIG. It is a figure explaining the calculation formula which calculates the detection magnetic field with respect to the perpendicular | vertical magnetization model CV used in the simulation of FIG. It is a figure which shows the change of the magnetic field detected in relation to a movement to the vehicle calculated in the simulation of FIG. It is a figure which shows the change of the magnetic field actually detected in the vehicle speed detection apparatus of FIG. In the simulation of FIG. 7, the magnetic field strength H _X1 in the X-axis direction detected by the magnetic sensor 1 and the magnetic field strength H _X3 in the X-axis direction detected by the magnetic sensor 3, which are obtained to measure the vehicle speed by the phase difference method. It illustrates a phase difference D _X between. In the simulation of FIG. 7, the magnetic field intensity H _Y1 in the Y-axis direction detected by the magnetic sensor ₁ and the magnetic field intensity H _Y3 in the Y-axis direction detected by the magnetic sensor 3, which are obtained for measuring the vehicle speed by the phase difference method. It illustrates a phase difference D _Y with. In order to show the error of the calculated speed with respect to the fluctuation of the offset value, the vehicle speed value obtained from the equation (1) derived from the Stokes theorem ((mark) and the magnetization parallel model CP are obtained by the simulation of FIG. FIG. 6 is a diagram showing a vehicle speed value (marked by □) and a vehicle speed value (marked by Δ) obtained for a magnetization perpendicular model CV. In order to show the error rate with respect to the noise frequency, the vehicle speed value obtained from the equation (1) derived from the Stokes theorem (に よ り mark) and the vehicle speed value obtained for the magnetized parallel model CP ( It is a figure which shows the vehicle speed value ((triangle | delta) mark) calculated | required about the magnetization perpendicular | vertical model CV. It is a figure which shows the random noise used in order to investigate distribution of an error rate in the simulation of FIG. In order to show the distribution of the error rate when the random noise shown in FIG. 16 is given, the vehicle speed value (◇ mark) obtained from the equation (1) derived from the Stokes theorem by the simulation of FIG. It is a figure which shows the vehicle speed value (□ mark) calculated | required about the magnetization parallel model CP, and the vehicle speed value (△ mark) calculated | required about the magnetization perpendicular | vertical model CV. It is a figure which shows the relationship between the measured value of the vehicle speed detection apparatus of the Example of FIG. 1, and the measured value of a speed gun.

Explanation of symbols

10: Vehicle speed detection device (magnetic moving body speed detection device)
12: Vehicle (moving body)
20: first magnetic sensor 22: second magnetic sensor 40: X-axis direction detection element 40a: amorphous magnetic metal wire 40b: pickup coil 42: Y-axis direction detection element 42a: amorphous magnetic metal wire 42b: pickup coil 64: X-axis Direction magnetic field spatial difference value calculating means 66: Y-axis direction magnetic field temporal variation calculating means 68: Speed calculating means

Claims (5)

A magnetic moving body speed detecting device for detecting the speed of a moving body made of a magnetic body that moves relatively in the X-axis direction,
A first magnetic sensor and a second magnetism, which are arranged at a certain distance in the Y-axis direction perpendicular to the X-axis direction and detect the strength of the magnetic field in the X-axis direction and the strength of the magnetic field in the Y-axis direction, respectively. A sensor,
The average value of the magnetic field strength in the Y-axis direction detected at the first time by the first magnetic sensor and the second magnetic sensor, and Y detected at the second time by the first magnetic sensor and the second magnetic sensor, respectively. Y-axis direction magnetic field temporal change amount calculating means for calculating a Y-axis direction magnetic field temporal change amount dHy which is a difference from an average value of the axial magnetic field strength;
The average value of the magnetic field strength in the X-axis direction detected at the first time and the second time by the first magnetic sensor, and the X-axis direction detected at the first time and the second time by the second magnetic sensor, respectively. X-axis direction magnetic field spatial difference value calculating means for calculating an X-axis direction magnetic field spatial difference value ΔHx which is a difference from the average value of the magnetic field strength;
From the relationship stored in advance, the Y-axis direction magnetic field temporal change amount dHy calculated by the Y-axis direction magnetic field temporal change amount calculation means and the X-axis direction calculated by the X-axis direction magnetic field spatial difference value calculation means And a speed calculating means for calculating a speed v of the moving body based on a ratio value of the magnetic field spatial difference value ΔHx. When the time difference between the first time and the second time is dt and the constant distance is 2a,
2. The magnetic moving body speed detecting apparatus according to claim 1, wherein the relationship stored in advance is v = (2a / dt) (dHy / ΔHx). The relationship from the relative position of the first magnetic sensor at the first time to the relative position of the second magnetic sensor at the first time, the relative position of the second magnetic sensor at the second time, and the relative position of the first magnetic sensor at the second time. 3. The Stokes theorem that the circular integral of the magnetic field strength is zero in a circular path that sequentially passes through the relative position and returns to the relative position of the first magnetic sensor is set in advance. Magnetic moving body speed detection device. The moving body is a vehicle that passes along a traveling lane set in advance on a traveling road surface,
2. The first magnetic sensor and the second magnetic sensor are provided to be fixed at a predetermined distance in a direction perpendicular to the travel lane at a location adjacent to the travel lane on the travel road surface. Any one of the magnetic type | mold mobile body speed detection apparatus of thru | or 3. The first magnetic sensor and the second magnetic sensor include a pair of amorphous magnetic metal wires arranged along the X-axis direction and the Y-axis direction, and the amorphous magnetic metal wires when a pulse current is passed through the amorphous magnetic metal wires. 5. The magnetic moving body speed detection device according to claim 1, further comprising a pickup coil wound around the amorphous magnetic metal wire in order to detect the impedance of the magnetic magnetic body.

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