WO2013105328A1 - 移動距離計測装置 - Google Patents
移動距離計測装置 Download PDFInfo
- Publication number
- WO2013105328A1 WO2013105328A1 PCT/JP2012/078352 JP2012078352W WO2013105328A1 WO 2013105328 A1 WO2013105328 A1 WO 2013105328A1 JP 2012078352 W JP2012078352 W JP 2012078352W WO 2013105328 A1 WO2013105328 A1 WO 2013105328A1
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- WIPO (PCT)
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- vehicle
- distance
- measuring device
- signal
- moving distance
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Classifications
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- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/123—Traffic control systems for road vehicles indicating the position of vehicles, e.g. scheduled vehicles; Managing passenger vehicles circulating according to a fixed timetable, e.g. buses, trains, trams
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S13/60—Velocity or trajectory determination systems; Sense-of-movement determination systems wherein the transmitter and receiver are mounted on the moving object, e.g. for determining ground speed, drift angle, ground track
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C22/00—Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
- G01C22/02—Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers by conversion into electric waveforms and subsequent integration, e.g. using tachometer generator
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/86—Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
Definitions
- This invention relates to a moving distance measuring device for measuring the moving distance of a vehicle.
- Patent Document 1 As a moving distance measuring device that is attached to a vehicle (train) and measures the moving distance of the vehicle using radio waves, for example, there is a device using a Doppler frequency as shown in Patent Document 1.
- a transmission signal is irradiated on the ground (rail track surface) as a radio wave, and a reflected signal that is a reflected wave is mixed with the transmission signal to obtain a Doppler signal component.
- the travel distance of the vehicle is obtained by analyzing the Doppler frequency and calculating and integrating the travel speed of the vehicle.
- the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a moving distance measuring device that can accurately measure the moving distance of a vehicle even when the vehicle is traveling on a curve. It is said.
- a moving distance measuring apparatus is provided in a vehicle and receives a radio wave that is provided in the vicinity of the transmission means that irradiates the ground with a transmission signal as a radio wave, and that is radiated by the transmission means and reflected by the ground.
- FIG. 1 is a diagram showing a train to which a moving distance measuring device 1 according to Embodiment 1 is attached.
- a rail 2 is laid on a track on which the vehicle travels, and sleepers 3 that support the rail 2 are laid at predetermined intervals below the rail 2. Further, gravel stones (ballasts) 4 are spread between the sleepers 3.
- a carriage 7 is connected to the front and rear of the bottom surface of the vehicle body 5 via a connecting shaft 6 (6a, 6b), and wheels 8 are attached to the carriage 7.
- the moving distance measuring device 1 is attached to a substantially center of the bottom surface of the vehicle body 5 (a midpoint position between the connecting shaft 6 a and the connecting shaft 6 b) via a fitting 9.
- the distance between the bottom surface of the moving distance measuring device 1 and the top surface of the rail 2 is about 20 to 60 cm.
- the movement distance measuring device 1 measures the movement distance of the vehicle.
- the moving distance measuring apparatus 1 includes an oscillator 101, a transmission antenna (transmission means) 102a, a reception antenna (reception means) 102b, an amplifier 103, an IQ demodulator 104, a phase conversion integrator 105, and a gyro sensor.
- the oscillator 101 generates a high frequency signal.
- the oscillator 101 outputs a stable high-frequency signal by synchronizing a PLL (phase lock loop) with a reference signal source having excellent temperature characteristics such as a crystal oscillator.
- the high frequency signal generated by the oscillator 101 is output as a transmission signal to the transmission antenna 102a and the IQ demodulator 104.
- the transmitting antenna 102a irradiates the ground (an oblique direction below the traveling direction of the vehicle) with a transmission signal from the oscillator 101 as a radio wave.
- the reception antenna 102b is installed in the vicinity of the transmission antenna 102a, and receives a radio wave irradiated by the transmission antenna 102a and reflected by the ground to acquire a reflected signal.
- the reflected signal acquired by the receiving antenna 102 b is output to the amplifier 103.
- the transmitting antenna 102a and the receiving antenna 102b can be formed on the same substrate if they are configured with patch antennas.
- the components can be handled as one antenna 102, and the functions can include the transmitting antenna 102a and the receiving antenna 102b.
- the polarization directions of the transmission antenna 102a and the reception antenna 102b are assumed to be horizontal polarization. That is, it is parallel to the longitudinal direction of the sleepers 3 and is orthogonal to the longitudinal direction of the rails 2.
- the amplifier 103 amplifies the reflected signal from the receiving antenna 102b to a predetermined amplitude level.
- the reflected signal amplified by the amplifier 103 is output to the IQ demodulator 104.
- the IQ demodulator 104 performs quadrature detection on the reflected signal from the amplifier 103 using the transmission signal from the oscillator 101 as a reference signal.
- the signal quadrature detected by the IQ demodulator 104 is output to the phase conversion integrator 105.
- the phase conversion integrator 105 calculates the moving distance of the vehicle by calculating and integrating the phase based on the signal from the IQ demodulator 104.
- the phase conversion integrator 105 returns the movement distance to zero when a reset signal is input from the outside via the input terminal 108.
- a signal indicating the movement distance calculated by the phase conversion integrator 105 is output to the correction calculator 107.
- the IQ demodulator 104 and the phase conversion integrator 105 constitute distance calculation means.
- the gyro sensor 106 measures the rotational angular velocity of the vehicle.
- a signal indicating the rotational angular velocity measured by the gyro sensor 106 is output to the correction calculator 107.
- the correction calculator 107 corrects the movement distance calculated by the phase conversion integrator 105 based on the rotational angular velocity measured by the gyro sensor 106.
- a signal indicating the movement distance corrected by the correction calculator 107 is output to the outside via the output terminal 109.
- FIG. 3A is a schematic view of the moving distance measuring device 1 as viewed from the bottom side
- FIG. 3B is a schematic view of the moving distance measuring device 1 as viewed from the side surface.
- a broken line 201 is a line that bisects the left and right of the movement distance measuring apparatus 1 symmetrically, and coincides with the traveling direction axis of the vehicle.
- the broken line 202 is a perpendicular which bisects the moving distance measuring device 1 symmetrically back and forth.
- a broken line 203 is a line inclined by an angle ⁇ from the vertical line 202 in a diagonal direction below the traveling direction of the vehicle.
- the angle ⁇ is 45 degrees.
- the antenna 102 is arranged so that the center thereof is located on the broken line 201 and the radiation direction of the radio wave coincides with the broken line 203.
- the gyro sensor 106 is arranged so as to be positioned on the vertical line 202 (center of the moving distance measuring device 1).
- the oscillator 101 generates a high frequency signal (transmission signal) (step ST1).
- transmission signal transmission signal
- the oscillator 101 in order to change the phase of the reflected wave when the vehicle body 5 moves, it is necessary to select a frequency such that the rail track surface is not a smooth surface but a rough surface with respect to the transmitted wave.
- the Rayleigh standard is known as this standard, and can be treated as a rough surface if the wavelength is shorter than 1/8 of the unevenness of the object.
- the rail track surface is rough with respect to the radio waves.
- a rail track surface is a horizontal surface with the sleepers 3 and the gravel stones 4.
- the curve has an inclination called a cant, but a plane parallel to the upper surface of the sleepers 3 is called a rail track surface.
- the transmitting antenna 102a applies the transmission signal from the oscillator 101 as a radio wave and irradiates the ground (an oblique direction below the traveling direction of the vehicle) (step ST2).
- the transmission wave radiated from the transmission antenna 102a is applied to an area centered at a point where the broken line 203 intersects the rail track surface, and the sleepers 3 and gravel stones 4 in the irradiated area are irradiated. reflect.
- the transmission wave is irradiated in an oblique direction, the reflection at the slightly near side (the point where the solid line 204 and the rail track surface intersect) is the strongest at the point where the broken line 203 intersects with the rail track surface.
- the distance between the antenna 102 and the rail track surface is shorter in the foreground, and the amount of deviation depends on the directivity sharpness of the transmitting antenna 102a. That is, the direction in which the reflection intensity is strongest approaches the broken line 203 as the directivity is sharper (the amount of deviation decreases), and moves away from the broken line 203 as the directivity increases (the amount of deviation increases).
- the direction of the maximum directivity gain is the same, and the angle ⁇ is 45 degrees, 42 Reflection in the degree direction is the strongest.
- the receiving antenna 102b receives the radio wave irradiated by the transmitting antenna 102a and reflected from the ground to acquire a reflected signal, and the amplifier 103 amplifies the reflected signal to a predetermined amplitude level (step ST3).
- the IQ demodulator 104 performs quadrature detection on the reflected signal from the amplifier 103 using the transmission signal from the oscillator 101 as a reference signal, and the phase conversion integrator 105 calculates and integrates the phase from the quadrature detection result.
- the moving distance of the vehicle is calculated (step ST4).
- the directivity pattern 205 is the same between the transmitting antenna 102a and the receiving antenna 102b.
- a function representing the directivity pattern 205 is F ( ⁇ ).
- ⁇ is an angle based on the direction of the broken line 203.
- H ( ⁇ ) of the reflected wave is expressed by the following equation (1).
- h is the height from the rail track surface to the midpoint between the transmitting antenna 102a and the receiving antenna 102b. If the angle ⁇ at which H ( ⁇ ) is maximized is obtained, the direction becomes the direction of the solid line 204.
- the directivity patterns 205 of the transmission antenna 102a and the reception antenna 102b are measured in advance.
- the direction (angle ⁇ ) of the solid line 204 can be determined from the directivity pattern 205 (F ( ⁇ )) of the antenna 102, the height h of the antenna 102, and the mounting angle ⁇ of the antenna 102. Can be sought. Then, the moving distance of the vehicle is calculated using the reflected wave from the direction of the solid line 204.
- gravel stone 4 (or sleeper 3 or the like) exists at a point where the solid line 204 and the rail track surface intersect, and the vector ⁇ y has a direction and magnitude that the gravel stone 4 apparently advances per minute unit time. Show. Of course, actually, the gravel stone 4 does not move, but the vehicle (movement distance measuring device 1) moves, but here, the movement distance measuring device 1 is considered as a reference.
- the minute unit time is a time interval at which the distance traveled by the vehicle at the maximum speed is a value (1/10 or less) sufficiently smaller than the wavelength of the transmission wave.
- the amount of change ⁇ r in the distance of the gravel stone 4 with respect to the antenna 102 is expressed by the following equation (2).
- ⁇ r ⁇ y ⁇ sin ( ⁇ ) (2)
- the phase ⁇ of the reflected wave changes by the following equation (3) in a minute unit time.
- ⁇ 2 (2 ⁇ / ⁇ ) ⁇ ⁇ r (3)
- This phase change ⁇ appears as a change in the output of the IQ demodulator 104.
- the IQ demodulator 104 outputs an IQ signal having two components, an I component and a Q component, by orthogonal detection of the reflected signal and the transmission signal.
- the phase conversion integrator 105 obtains a phase from atan (Q / I).
- the phase is obtained from the output of the IQ demodulator 104, the differential phase is obtained therefrom, and the movement distance is calculated by further integration.
- the plurality of processes are not necessary, and the moving distance of the vehicle can be calculated directly from the output of the IQ demodulator 104. This point will be described with reference to FIG.
- FIG. 6 is a diagram showing the relationship between the I component (X axis) and Q component (Y axis) of the IQ demodulator 104 output and the moving distance (Z axis) of the vehicle.
- Reference numeral 206 in this figure denotes a spiral that shows the phase rotating on the XY plane extended to the Z axis. Note that the phase rotates clockwise, and the clockwise rotation of the phase is positive.
- the integrated phase is obtained from the output of the IQ demodulator 104, the integrated phase becomes one point on the spiral 206. If the integrated phase is ⁇ , the moving distance Y is expressed by the following equation (4).
- Y ⁇ / (sin ( ⁇ ) ⁇ 4 ⁇ / ⁇ ) (4)
- a point 207 on the spiral 206 is a point where the phase changes from 2 ⁇ to 0.
- the phase is calculated not to rotate on the spiral 206 and return from 2 ⁇ to 0, but to rotate the next rotation from 2 ⁇ to 4 ⁇ .
- Stacking these phase discontinuities so as to be continuous is known as phase unwrapping, and this method is used here. That is, the phase is integrated over 2 ⁇ or more, and the moving distance is obtained from the integrated phase.
- processing speed is important. That is, even when the vehicle is traveling at the maximum speed assumed, a processing speed at which sufficient sample points can be obtained for the phase to make one round is required. Therefore, it is necessary to perform processing at a time interval equal to or less than the minute unit time described above.
- the phase conversion integrator 105 can calculate the moving distance directly from the output of the IQ demodulator 104 by obtaining the integrated phase obtained by integrating the rotation of the phase over 2 ⁇ or more.
- amplitude information is not used when calculating the moving distance of the vehicle. This amplitude information is very unstable, and the amplitude changes greatly when the reflection state of the radio wave on the rail track changes due to rainfall or snowfall. In addition, the amplitude changes like a spike when passing over a metal object such as an iron bridge or a point.
- the frequency component of this spike-like waveform is very wide, and the conventional method of calculating the moving distance of the vehicle by analyzing the Doppler frequency greatly changes the Doppler spectrum as a whole, and obtains an accurate Doppler frequency. The problem that it becomes impossible to occur.
- the moving distance measuring apparatus 1 of the present invention can calculate the moving distance of the vehicle without using the amplitude information, the moving distance can be accurately calculated even if the reflection state of the radio wave on the rail track fluctuates. it can.
- the phase conversion integrator 105 returns the movement distance to zero when a reset signal is input from the outside via the input terminal 108.
- the gyro sensor 106 measures the rotational angular velocity of the vehicle, and the correction computing unit 107 performs the phase conversion integrator 105 based on this rotational angular velocity.
- the calculated movement distance is corrected (step ST5).
- the error during the curve travel of the phase conversion integrator 105 output and the correction method by the gyro sensor 106 and the correction calculator 107 will be described with reference to FIG.
- the broken line 208 is a line indicating the center of the rail 2
- the center point 209 is a point indicating the center of the curve radius of the vehicle
- the line segment 210 is the center point 209 and the center point of the moving distance measuring device 1.
- the intersecting point 211 is a point where the broken line 210 and the perpendicular line dropped from the connecting shaft 6a to the broken line 210 side (the center point of the moving distance measuring device 1).
- the intersecting point 212 intersects the broken line 208 and the broken line 210. Is a point.
- the length (curve radius) from the center point 209 to the connecting shaft 6a is R
- the length from the moving distance measuring device 1 (intersection 211) to the connecting shaft 6a is m
- the length between the connecting shafts 6a and 6b is L
- the distance e between the intersection 211 and the intersection 212 is expressed by the following equation (5).
- This distance e is an amount that the traveling distance measuring device 1 enters inside the broken line 208 that is the center of the rail by curve traveling, and becomes larger as the curve radius R is shorter. That is, as the curve radius R is shorter, the moving distance measuring device 1 passes through the inside of the curve.
- the movement amount l of the vehicle that has advanced in minute unit time is expressed by the following equation (6).
- the movement amount l ′ of the movement distance measuring apparatus 1 advanced in a minute unit time is expressed by the following equation (7).
- the difference ⁇ l between the movement amount l and the movement amount l ′ is expressed by the following equation (8). Therefore, the decrease rate k is expressed by the following equation (9).
- the movement distance measured by the non-contact type device that measures the speed and movement distance by observing the ground is actually measured on the right curve and the left curve every time the vehicle travels the curve.
- the rate of decrease k Observed by the rate of decrease k from the actual speed.
- the curve radius R is 160 m
- the length L between the connecting shafts 6a and 6b is 14.176 m
- a non-contact device that measures the speed and moving distance by observing the ground is connected to the connecting shaft 6a.
- the reduction rate k is about 0.1%.
- the first embodiment uses the gyro sensor 106 that independently measures the rotational angular velocity of the vehicle.
- the gyro sensor 106 is a sensor that measures the rotation angle of the yaw angle with respect to the traveling direction of the vehicle body 5 per unit time. And the yaw angle per minute unit time coincides with the rotation angle ⁇ .
- This equation (1) is obtained by calculating the distance l ′ measured by the moving distance measuring device 1, the rotation angle ⁇ per minute unit time measured by the gyro sensor 106, and from the moving distance measuring device 1 (intersection 211) to the connecting shaft 6a. This indicates that the moving distance l of the vehicle can be calculated from the length m and the length L between the connecting shafts 6a and 6b.
- the moving distance before a minute unit time is stored, and the difference l ′ from the current moving distance Y that is the output of the phase conversion integrator 105 is calculated. Then, the distance l traveled by the vehicle is calculated from the difference l ′ using the equation (10). Then, an error amount (l ⁇ l ′) during curve traveling is calculated and integrated. Then, a value obtained by adding the accumulated error amount G to the movement distance Y is output as the final movement distance.
- the measurement result is prevented from being shorter than actual due to an error caused by the movement distance measuring device 1 passing inside the curve. Therefore, since the rotational angular velocity is measured by the gyro sensor 106 and the measurement result is corrected, the moving distance can be accurately measured even when the vehicle is traveling in a curve.
- the vehicle travel distance is measured using the phase of the reflected wave without using amplitude information, the reflected state of the radio wave on the rail track changes when there is a metal object in front of the device. Even so, the travel distance of the vehicle can be accurately measured. Further, since the reflected wave from the direction where the reflection intensity is maximum is used, the measurement accuracy can be improved.
- Embodiment 2 shows a case where an angle measuring device 110 that measures an angle with respect to the ground (rail track surface) of the vehicle is used.
- FIG. 8 is a view showing a vehicle to which a moving distance measuring apparatus 1 according to Embodiment 2 of the present invention is attached.
- the moving distance measuring device 1 according to the second embodiment shown in FIG. 8 changes the gyro sensor 106 of the moving distance measuring device 1 according to the first embodiment shown in FIG. 1 to an angle measuring device (curve parameter measuring means) 110.
- Other configurations are the same, and the same reference numerals are given and description thereof is omitted.
- the angle measuring device 110 is attached to the connecting shaft 6 of the vehicle and measures the angle of the vehicle with respect to the ground by measuring the angle of the carriage 7 with respect to the vehicle body 5.
- an encoder or the like can be applied as the angle measuring device 110.
- a signal indicating the angle measured by the angle measuring device 110 is output to the correction computing unit 107.
- the correction calculator 107 corrects the moving distance calculated by the phase conversion integrator 105 based on the angle measured by the angle measuring device 110 instead of the rotational angular velocity measured by the gyro sensor 106.
- a movement distance before a minute unit time is stored, and a difference l 'from the current movement distance Y that is an output of the phase conversion integrator 105 is calculated. Then, using the angle measured by the angle measuring device 110, the distance l traveled by the vehicle is calculated from the difference l 'using the equation (12). Then, an error amount (l ⁇ l ′) during curve traveling is calculated and integrated. Then, a value obtained by adding the accumulated error amount G to the movement distance Y is output as the final movement distance.
- the second embodiment even if it is configured to measure the angle of the vehicle with respect to the ground and correct the measurement error of the movement distance during the curve running, the same as in the first embodiment.
- the effect of can be obtained.
- the gyro sensor 106 a highly sensitive sensor is required to measure a minute curve.
- the encoder it is only necessary to measure the angle of the carriage 7 with respect to the vehicle, and the measurement can be performed with low cost and high accuracy.
- Embodiment 3 shows a case where the distance calculation means calculates the moving distance of the vehicle using the phase.
- Embodiment 3 shows a case where the distance calculation means calculates the moving distance of the vehicle using the Doppler frequency.
- FIG. 9 is a diagram for explaining the internal function of the movement distance measuring apparatus 1 according to the third embodiment.
- the moving distance measuring apparatus 1 according to the third embodiment shown in FIG. 9 includes an IQ demodulator 104 and a phase conversion integrator 105 of the moving distance measuring apparatus 1 according to the first embodiment shown in FIG.
- the detector 112 and the speed integrator 113 are changed.
- Other configurations are the same, and the same reference numerals are given and description thereof is omitted.
- the multiplier 111 multiplies the reflected signal from the amplifier 103 by using the high frequency signal from the oscillator 101 as a reference signal.
- the signal multiplied by the multiplier 111 is output to the Doppler detector 112.
- the Doppler detector 112 detects a Doppler signal based on the signal from the multiplier 111.
- the Doppler signal detected by the Doppler detector 112 is output to the speed integrator 113.
- the speed integrator 113 calculates the travel distance of the vehicle based on the Doppler signal from the Doppler detector 112. The speed integrator 113 returns the movement distance to zero when a reset signal is input from the outside via the input terminal 108. A signal indicating the movement distance calculated by the speed integrator 113 is output to the correction calculator 107.
- the multiplier 111, the Doppler detector 112, and the speed integrator 113 constitute distance calculating means.
- correction computing unit 107 corrects the movement distance calculated by the speed integrator 113 based on the rotational angular velocity measured by the gyro sensor 106.
- the Doppler detector 112 extracts the Doppler signal. That is, the Doppler detector 112 first passes the signal from the multiplier 111 through a low-pass filter to remove high frequency components and extracts a Doppler signal. Then, the Doppler signal is subjected to Fourier transform to calculate a Doppler spectrum, and a frequency F at which the Doppler spectrum becomes maximum is extracted. The frequency F at which the Doppler spectrum becomes maximum substantially matches the Doppler frequency Fd.
- the speed integrator 113 calculates the moving speed V of the vehicle using Expression (15). If the period for calculating the moving speed V is ⁇ T, the distance ⁇ L moved during this time can be calculated as V ⁇ ⁇ T. Therefore, the distance traveled by the vehicle can be calculated by integrating the distance ⁇ L. The speed integrator 113 returns the movement distance to zero when a reset signal is input from the outside via the input terminal 26. Other operations are the same as those in the first embodiment, and a description thereof will be omitted.
- a function for correcting a measurement error at the time of curve traveling is additionally mounted on the basis of an apparatus for obtaining a moving distance of a vehicle by an existing Doppler method.
- the measurement accuracy of the movement distance can be greatly improved compared to the conventional apparatus.
- it is configured to use the reflected wave from the direction in which the reflection intensity is maximum, so that measurement accuracy can be improved.
- the present invention is not limited to this, and the angle measuring device 110 shown in the second embodiment is used. May be used.
- the travel distance measuring device can be used for a travel distance measuring device that can accurately measure the travel distance of a vehicle even when the vehicle is traveling in a curve and measures the travel distance of a vehicle such as a train. Suitable for
- 1 travel distance measuring device 1 travel distance measuring device, 2 rails, 3 sleepers, 4 gravel stones, 5 body, 6, 6a, 6b connecting shaft, 7 bogies, 8 wheels, 9 fittings, 101 oscillator, 102 antenna, 102a transmitting antenna (transmitting means) , 102b, receiving antenna (receiving means), 103 amplifier, 104 IQ demodulator, 105 phase conversion integrator, 106 gyro sensor (curve parameter measuring means), 107 correction calculator (correction calculating means), 108 input terminal, 109 output terminal 110, angle measuring device (curve parameter measuring means), 111 multiplier, 112 Doppler detector, 113 speed integrator.
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Abstract
Description
実施の形態1.
図1は実施の形態1に係る移動距離計測装置1が取り付けられた列車を示す図である。
図1に示すように、車両が走行する軌道には、レール2が敷かれ、その下にレール2を支える枕木3が所定の間隔で敷かれている。また、枕木3の間には砂利石(バラスト)4が敷き詰められている。一方、列車の車体5の底面の前後には、接続軸6(6a,6b)を介して台車7が接続されており、この台車7には車輪8が取り付けられている。
また、車体5の底面の略中央(接続軸6aと接続軸6bとの中点位置)には、艤装金具9を介して移動距離計測装置1が取り付けられている。なお、移動距離計測装置1の底面とレール2の上面との間隔は、20~60cm程度となるようにする。
移動距離計測装置1は、車両の移動距離を計測するものである。この移動距離計測装置1は、図2に示すように、発振器101、送信アンテナ(送信手段)102a、受信アンテナ(受信手段)102b、増幅器103、IQ復調器104、位相変換積分器105、ジャイロセンサ(カーブパラメータ計測手段)106、補正演算器(補正演算手段)107、入力端子108および出力端子109から構成されている。
受信アンテナ102bは、送信アンテナ102aの近傍に設置され、送信アンテナ102aにより照射され地面で反射した電波を受信して反射信号を取得するものである。この受信アンテナ102bにより取得された反射信号は増幅器103に出力される。
なお、IQ復調器104および位相変換積分器105は距離演算手段を構成する。
補正演算器107は、ジャイロセンサ106により計測された回転角速度に基づいて、位相変換積分器105により算出された移動距離を補正するものである。この補正演算器107により補正された移動距離を示す信号は出力端子109を介して外部に出力される。
図3(a)において、破線201は、移動距離計測装置1の左右を対称に二等分する線であり、車両の進行方向軸と一致する。また、図3(b)において、破線202は、移動距離計測装置1を前後に対称に二等分する垂線である。また、破線203は、車両の進行方向下斜め方向に垂線202から角度θだけ傾いた線である。なお、角度θは45度である。
この図3に示すように、アンテナ102は、その中心が破線201上に位置し、電波の放射方向が破線203に一致するように配置されている。また、ジャイロセンサ106は、垂線202上(移動距離計測装置1の中心)に位置するように配置されている。
移動距離計測装置1の動作では、図4に示すように、まず、発振器101は、高周波信号(送信信号)を発生する(ステップST1)。ここで、車体5が移動した場合に反射波の位相を変化させるため、送信波に対してレール軌道面が滑らかな面ではなく、粗い面となるような周波数を選ぶ必要がある。この基準としてレイリー基準が知られており、物体の凹凸の間隔の1/8より波長が短ければ粗い面として扱うことができる。枕木3や砂利石4などの地面形状の凹凸の間隔は約10cm程度であり、波長が10cm÷8=1.25cm以下の電波、すなわち3×10^8÷0.0125m=24GHz以上の周波数の電波を用いることで、その電波に対してレール軌道面は粗い面となる。なお、レール軌道面とは、枕木3や砂利石4がある水平面のことである。もちろん、カーブではカントと呼ばれる傾斜がついているが、枕木3の上面と平行な面をレール軌道面と呼ぶ。
以下では、図5を用いて、車両の移動に伴って生じる位相変換積分器105出力の変化について説明する。
図5において、指向性パターン205は、送信アンテナ102aと受信アンテナ102bとで同一であるとする。また、指向性パターン205を表す関数をF(η)とする。なお、ηは、破線203方向を基準にした角度である。そして、地面反射率やアンテナ102の絶対利得を無視すると、反射波の強度H(η)は次式(1)で表される。
ここで、hはレール軌道面から送信アンテナ102aと受信アンテナ102bの中点までの高さである。このH(η)が最大となる角度ηを求めれば、その方向が実線204の方向となる。なお、送信アンテナ102aと受信アンテナ102bの指向性パターン205は予め計測しておく。この式(1)を用いることで、アンテナ102の指向性パターン205(F(η))、アンテナ102の高さh、および、アンテナ102の取り付け角度θから、実線204の方向(角度η)を求めることができる。そして、この実線204の方向からの反射波を用いて車両の移動距離の算出を行う。
Δr=Δy×sin(θ-η) (2)
また、送信波の波長をλとすると、微小単位時間で反射波の位相θは次式(3)だけ変化する。
Δθ=2(2π/λ)×Δr (3)
この位相の変化ΔθがIQ復調器104出力の変化として現れる。この際、IQ復調器104は、反射信号と送信信号との直交検波により、I成分とQ成分の2つの成分を有するIQ信号を出力する。そして、位相変換積分器105は、atan(Q/I)から位相を得る。なお、atanは逆正接である。そして、微小単位時間前との差分位相がΔθとなるため、微小単位時間当たりの移動距離Δyを算出することができる。よって、この差分位相Δθを積分することで、その積分時間で車両が移動した距離を求めることができる。
IQ復調器104出力から積算位相を求めると、当該積算位相は螺旋206上の1点となる。その積算位相をψとすると移動距離Yは次式(4)で表される。
Y=ψ/(sin(θ-η)×4π/λ) (4)
このフェーズアンラップがうまく機能するためには、処理速度が重要である。すなわち、車両が想定する最高速度で走行中であっても、位相が1周まわるのに十分なサンプル点が得られる処理速度が求められる。よって、先に説明した微小単位時間以下の時間間隔で処理を行う必要がある。
ここで、本発明の移動距離計測装置1では、車両の移動距離を算出する際に振幅情報は用いない。この振幅情報は非常に不安定であり、レール軌道の電波の反射状態が降雨や降雪などで変化することで振幅が大きく変わる。また、鉄橋やポイントなど金属物体の上を通過すると振幅がスパイク状に変化する。このスパイク状波形の周波数成分は非常に広帯域であり、ドップラ周波数を解析することで車両の移動距離を算出する従来の方法では、ドップラスペクトルが全体的に大きく変動し、正確なドップラ周波数を得ることができなくなるという課題が生じる。それに対して、本発明の移動距離計測装置1では、振幅情報を用いずに車両の移動距離を算出できるため、レール軌道の電波の反射状態が変動しても正確に移動距離を算出することができる。
なお、位相変換積分器105は、入力端子108を介して外部からリセット信号が入力された場合には、移動距離をゼロに戻す。
以下では、位相変換積分器105出力のカーブ走行時での誤差と、ジャイロセンサ106および補正演算器107による補正方法について、図7を参照しながら説明する。
この距離eは、カーブ走行によって移動距離計測装置1がレール中央である破線208より内側に入った量であり、カーブ半径Rが短いほど大きくなる。すなわち、カーブ半径Rが短いほど、移動距離計測装置1はカーブの内側を通る。この事実は、移動距離計測装置1のように、地面を観測して速度や移動距離を測定する非接触式の装置に対して重大な問題を引き起すが、これまで問題視されてこなかった。
一方、微小単位時間で進んだ移動距離計測装置1の移動量l’は次式(7)で表される。
そして、移動量lと移動量l’との差Δlは次式(8)となる。
したがって、減少率kは次式(9)で表される。
例えば、カーブ半径Rが160mであり、接続軸6a,6b間の長さLが14.176mであり、地面を観測して速度や移動距離を測定する非接触式の装置が接続軸6aと接続軸6bとの中点に設置されている場合、減少率kは約0.1%となる。
この式(1)は、移動距離計測装置1により計測された距離l’、ジャイロセンサ106により計測された微小単位時間当りの回転角度φ、移動距離計測装置1(交点211)から接続軸6aまでの長さm、および、接続軸6a,6b間の長さLから、車両の移動距離lが算出できることを示している。
また、振幅情報を使わずに反射波の位相によって車両の移動距離を計測するように構成したので、金属物体が装置の正面に存在する場合など、レール軌道の電波の反射状態が変化する状況下であっても正確に車両の移動距離を計測することができる。さらに、反射強度が最大となる方向からの反射波を用いるように構成したので、計測精度を向上することができる。
実施の形態1では、車両のカーブ走行に関する所定のパラメータを計測するカーブパラメータ計測手段として、車両の回転角速度を計測するジャイロセンサ106を用いた場合について示した。それに対して、実施の形態2では、車両の地面(レール軌道面)に対する角度を計測する角度計測装置110を用いた場合について示す。
図8はこの発明の実施の形態2に係る移動距離計測装置1が取り付けられた車両を示す図である。図8に示す実施の形態2に係る移動距離計測装置1は、図1に示す実施の形態1に係る移動距離計測装置1のジャイロセンサ106を角度計測装置(カーブパラメータ計測手段)110に変更したものである。その他の構成は同様であり、同一の符号を付してその説明を省略する。
なお、補正演算器107は、ジャイロセンサ106により計測された回転角速度に代えて、角度計測装置110により計測された角度に基づいて、位相変換積分器105により算出された移動距離を補正する。
この式(11)を式(6)に代入して式(5),(7)を用いて整理すると、次式(12)が得られる。
実施の形態1,2では、距離演算手段が、位相を用いて車両の移動距離を算出する場合について示した。それに対して、実施の形態3では、距離演算手段が、ドップラ周波数を用いて車両の移動距離を算出する場合について示す。
図9は実施の形態3に係る移動距離計測装置1の内部機能を説明する図である。図9に示す実施の形態3に係る移動距離計測装置1は、図2に示す実施の形態1に係る移動距離計測装置1のIQ復調器104および位相変換積分器105を、乗算器111、ドップラ検出器112および速度積算器113に変更したものである。その他の構成は同様であり、同一の符号を付してその説明を省略する。
なお、乗算器111、ドップラ検出器112および速度積算器113は距離演算手段を構成する。
V’=V×sin(θ-η)(13)
また、送信信号の波長をλとすると、ドップラ周波数Fdは次式(14)で表される。
Fd=2×V’/λ (14)
よって、式(13),(14)から、車両の移動速度Vは次式(15)で表される。
V=F×λ/(2×sin(θ-η)) (15)
ここで、Fはドップラ検出器112出力である。
その他の動作については実施の形態1と同じであり、その説明を省略する。
Claims (6)
- 車両に設けられ、送信信号を電波として地面に照射する送信手段と、
前記送信手段の近傍に設けられ、当該送信手段により放射されて前記地面で反射した電波を受信して反射信号を取得する受信手段と、
前記受信手段により取得された反射信号に基づいて前記車両の移動距離を算出する距離演算手段と、
前記車両のカーブ走行に関する所定のパラメータを計測するカーブパラメータ計測手段と、
前記カーブパラメータ計測手段により計測されたパラメータに基づいて、前記距離演算手段により算出された移動距離を補正する補正演算手段と
を備えた移動距離計測装置。 - 前記車両は鉄道車両であって、移動距離計測装置は台車間の車両床下に艤装された
ことを特徴とする請求項1記載の移動距離計測装置。 - 前記補正演算手段は、前記カーブパラメータ計測手段により計測されたパラメータ、台車間の距離、および、前記移動距離計測装置と台車間の距離に基づいて、前記距離演算手段により算出された移動距離を補正する
ことを特徴とする請求項1または請求項2項記載の移動距離計測装置。 - 前記カーブパラメータ計測手段は、前記車両の回転角速度を計測するジャイロセンサである
ことを特徴とする請求項1から請求項3のうちのいずれか1項記載の移動距離計測装置。 - 前記距離演算手段は、前記反射信号を前記送信信号で直交検波して位相を算出し、当該位相を2π以上にわたって積算することで、移動距離を算出する
ことを特徴とする請求項1から請求項4のうちのいずれか1項記載の移動距離計測装置。 - 前記距離演算手段は、
前記反射信号を前記送信信号と乗算する乗算器と、
前記乗算手段により乗算された信号からドップラ信号を検出するドップラ検出器と、
前記ドップラ検出器により検出されたドップラ信号から前記車両の速度を算出し、当該速度を積算することで、移動距離を算出する速度積算器とを有する
ことを特徴とする請求項1から請求項5のうちのいずれか1項記載の移動距離計測装置。
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