JPH0634647A - Measuring equipment for speed - Google Patents

Abstract

PURPOSE:To prevent occurrence of an error even when distance information varies and thereby to enable measurement of a correct ground speed by determining a difference signal between distance detectors on the basis of the information on distances to light application points in prescribed numbers on an object of measurement. CONSTITUTION:Three distance detectors A, B and C are provided at an interval (d) on the same axis being parallel to the direction of movement of a moving body. The detectors A, B and C project light at a right angle substantially onto the surface of an object of measurement and receive it therefrom and they output information on distances to the surface of the object of measurement, i.e., unevenness signals (a), (b) and (c). Differential computation units 51 and 52 execute differential computation and determine difference signals a-b and b-c respectively. A correlative speed computation unit 6 executes mutual correlation computations between the difference signals a-b and b-c, detects a delay time Z0 between the two signals and calculates a speed V of the moving body on the basis of this time. By determining the two difference signals between the distance detectors, in other words, noise of the same phase (noise of the same phase and the same amplitude superposed on unevenness information of an output signal of each detector) generated due to variation of the distance can be cleared.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a non-contact method for calculating the speed of a moving object by irradiating a measuring object having a rough surface with a light beam from the moving object and obtaining information on the surface roughness of the object. More specifically, the present invention relates to a device for measuring the ground speed of an automobile or the like.

[0002]

2. Description of the Related Art A laser Doppler system is one of non-contact velocity measuring systems. There is also a method of calculating the velocity based on the uneven brightness pattern on the surface of the non-measurement object. This technology is described in detail in "Japanese Patent Publication No. 55-44346" and "Vehicle speed measurement using correlation (August 1975, Transactions of the Society of Instrument and Control Engineers, Vol. 11, No. 4)". Further, as a method of calculating the velocity based on the unevenness information, there is a technique described in "Japanese Patent Laid-Open No. 4-47286".

FIG. 14 shows a block diagram of a conventional example of a speed measuring device of a system that estimates the moving speed of an object to be measured based on information on the surface roughness of the object to be measured. The unevenness information on the surface of the object to be measured is taken out from each of the two distance detectors arranged along the moving direction of the object to be measured, and the cross-correlation operation is performed to calculate the time shift amount of the two signals (delay time = Zo) is detected, and the velocity is calculated by v = d / Zo (d is the distance between the pair of distance detectors).

[0004]

The laser Doppler system has a high spatial resolution and is suitable for speed measurement in a micro region, but is not suitable for a ground speedometer of a vehicle or the like. On the other hand, the method of calculating the velocity based on the uneven pattern of light and dark is suitable for measuring the velocity of the macro area on the surface of the DUT, but in principle when the contrast of light and dark on the surface of the DUT is extremely low. In addition, when the object to be measured has a large undulation, there is a problem in that the accuracy and accuracy of the speed measurement decrease.

Further, the unevenness information in the conventional method of calculating the velocity based on the unevenness information is the distance information between the specified minute portion of the surface of the object to be measured and the distance detector. Therefore,
When the distance detector itself has a positional change and the distance information changes, the distance detector is also affected by the influence and changes.

For example, when the distance detector is used as a ground speed measuring device for an automobile, the object to be measured is generally a road. At this time, if there are fluctuations due to vehicle bounces or engine vibrations, the bounces and vibrations become the bounces and vibrations of the distance detector itself, causing fluctuations in the distance between the road surface and the distance detectors. In this output signal, noise having the same phase and the same amplitude (hereinafter referred to as “in-phase noise”) is superimposed on the road unevenness information. As a result, an error occurs in the measurement speed.

In view of the above problems, the present invention can accurately measure the ground speed without causing an error even when the distance detector itself fluctuates and the distance information to the object to be measured fluctuates. The purpose is to provide a device.

[0008]

In order to solve the above problems, the first object to be measured is irradiated by irradiating the object to be measured which moves in a predetermined direction with light and receiving the reflected light from the object to be measured. , Second, third distance detecting means for obtaining distance information to the second and third light irradiation points, respectively, distance information from the first distance detecting means, and distance information from the second distance detecting means. A first differential calculator that calculates a difference from the distance information, and a second differential calculator that calculates a difference between the distance information from the second distance detecting means and the distance information from the third distance detecting means. And the output of the first differential computing unit and the output of the second differential computing unit are calculated, and the output of the first differential computing unit and the output of the second differential computing unit are calculated. From the correlation calculator that calculates the delay time with and the speed calculator that calculates the speed of the DUT based on the delay time obtained by the correlation calculator Made is, first, second, third light irradiation point is on the axis parallel to the predetermined direction of movement of the object, the second light irradiation point, the first with respect to the predetermined direction
Is separated from the light irradiation point by a predetermined distance, and the third light irradiation point is separated from the second light irradiation point by the same distance as the above-described predetermined distance in the predetermined direction. It is characterized by

Further, the distance information to the light irradiation point of the object to be measured is obtained by irradiating the object to be measured with light and receiving the reflected light from the object to be measured, respectively. Fourth distance detecting means, a first differential calculator for calculating a difference between the distance information from the first distance detecting means and the distance information from the second distance detecting means, and a third distance detecting means A second differential calculator for performing a difference calculation between the distance information from the first distance calculator and the distance information from the fourth distance detector, and the output of the first differential calculator and the output of the second differential calculator. The cross-correlation calculation of
Correlation calculator for calculating the delay time between the output of the differential calculator and the output of the second differential calculator, and a speed for calculating the speed of the DUT based on the delay time obtained by the correlation calculator And a third light irradiation point on the axis which passes through the first light irradiation point and is parallel to the predetermined direction and which is first with respect to the predetermined direction.
The fourth light irradiation point is separated from the second light irradiation point by a predetermined distance, and the fourth light irradiation point passes through the second light irradiation point on an axis parallel to the predetermined direction and in the second direction with respect to the predetermined direction. It is characterized in that it is separated from the light irradiation point by the same distance as the above-mentioned predetermined distance. At this time, an axis passing through the first and third light irradiation points,
The axis passing through the second and fourth light irradiation points may be the same axis.

The distance detecting means described above includes a light projecting means for projecting a light beam onto the object to be measured, a light receiving lens for detecting the direction of light reflected from the object to be measured, and a light incident position detecting element. Means may be provided to output a distance information signal to the object to be measured based on the principle of triangulation.

[0011]

When the distance detector is used as a ground speed measuring device of an automobile, the in-phase noise is superimposed on the road unevenness information in the output signal of each distance detector as described above.
Since the in-phase noise is added to all the distance detectors at the same time regardless of the difference in the installation position (light irradiation position), the present invention eliminates the in-phase noise by taking the difference between the two distance detectors. be able to.

Further, one set of two distance detectors for performing the difference calculation is set. Both light irradiation by one distance detector of this one set (referred to as "first set A") and another distance detector of another set prepared separately (referred to as "second set A") Both distance detectors are arranged so that the points are on the same axis parallel to the moving direction. Further, the other distance detector (“first
Both of the light irradiation points by the other distance detector of another set (referred to as "B of the second set") and the other distance detector of another set (referred to as "B of the second set") exist on the same axis parallel to the moving direction. Both distance detectors are arranged in this manner.

By doing so, the distance detectors corresponding to each set (“first set of A” and “second set of A”,
Alternatively, the “first set of B” and the “second set of B”) detect the unevenness information at the same point on the surface of the DUT at different times. Furthermore, since the interval between the irradiation points according to the “first set and the second set of A” is the same as the interval between the irradiation points according to the “first set and the second set of B”, there is a time lag for detecting unevenness information at the same point. The amounts are the same (the amount of shift between "A of the first set" and "A of the second set" and the amount of shift between "B of the first set" and "B of the second set").

By using the two sets of distance detectors, the road unevenness information synthesized by the two distance detectors of the same set in which the in-phase noise has been eliminated and the road unevenness information synthesized and detected It is possible to obtain unevenness information in which the amplitudes and phases are substantially the same as the time is shifted.

[0015]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a speed measuring device according to this embodiment. Three distance detectors A, B, and C are installed at intervals d on the same axis parallel to the moving direction of the object to be measured (speed measuring device). At this time, the distance detectors A, B, and C project and receive light substantially at right angles to the surface of the object to be measured. Hereinafter, the output signals of the distance detectors A, B and C will be referred to as (a), (b) and (c), respectively.

The differential calculators 51 and 52 (a)-
Find (b) and (b)-(c). The correlation / velocity calculator 6 calculates the two difference signals (a)-(b) and (b).
-(C) is cross-correlated, first the delay time (Zo) of both signals is detected, and then the calculation formula v = d / Zo (d
Is the distance between the set of distance detectors) to calculate the velocity v.

The structure of the distance detector 1 used for this is shown in FIG. The projection beam emitted from the LED 2 is reflected by the surface of the DUT 4 via the projection lens 21.
The reflected light is condensed through the light receiving lens 31 and is incident on the light receiving surface of the light incident position detection element (PSD) 3.

Current output value I of the light incident position distance detecting element 3
_A, I _B corresponds to the center-of-gravity position of the spot light focused on the light receiving surface. Therefore, the distance information from the distance detector 1 to the surface of the DUT 4, more specifically, to the light irradiation point 41 by the LED 2 on the surface of the DUT 4 is based on the current output values I _A and I _B at this time. I _A / I _B or, (I _A -I _B)
It is obtained by calculating / (I _A + I _B ).

FIG. 3 shows a block diagram of an arithmetic processing system from distance detection to speed calculation. The unevenness signals (a), (b) and (c) up to the object to be measured are output from the distance detectors A, B and C, respectively. The differential calculator 51 outputs the difference signals (a)-(b), and the differential calculator 52 outputs the difference signals (b)-(c) to the correlation calculator 61. The correlation calculator 61 has two difference signals (a)-(b) and (b)-(c).
Perform cross-correlation calculation between (a)-(b) and (b)-
The delay time Zo, which is the amount of time that the waveform deviates from (c), is calculated. The speed calculator 62 calculates the speed v based on the delay time Zo.
To calculate.

FIG. 4 shows a schematic configuration of an embodiment of the speed measurement according to the present invention using the speed measurement device shown in FIG. 1, and a detailed description will be given in sequence until the speed calculation is compared with the conventional example.

The unevenness on the surface of the object to be measured is as shown in the figure, and the speed measuring device is arranged for the information. The distance detector is A from the front in the moving direction of the speed measuring device,
B and C are arranged in this order. The display positions of the distance detectors A, B, and C shown in the drawing each represent a spatial initial position relating to the moving direction at t = 0.

When the speed measuring device is moved at the speed v, each distance detector outputs distance information as shown in FIG. 5 when no noise is included and as shown in FIG. 8 when noise is included. actually,
This distance information is information indicating the relative distance between each distance detector and the object to be measured, that is, the amount of change in each distance. The waveforms in FIGS. 5, 6, 8 and 9 are obtained when the speed measuring device is moved at a constant speed v such that the distance 1 in FIG. Is.

Distance detectors A, B when there is no in-phase noise,
The output signal waveforms (a), (b), and (c) from C are made to coincide with each other at the initial positions in time, and are respectively shown in FIGS.
As shown in (c). In the conventional method, the outputs (a) and (b) from the distance detectors A and B are different from the outputs (a) and (b) in this embodiment.
Three pieces (b) and (c) are obtained.

From this figure, it is understood that the signals (a), (b) and (c) are repeated with a time lag due to the difference in the arrangement position, that is, with a delay time Zo, since no noise is included. You don't need to calculate the correlation to understand.

Further, the waveforms of the difference signals (a)-(b) and the difference signals (b)-(c) by the differential calculator of the speed measuring device according to the method of this embodiment are respectively shown in FIG. , (B)
Shown in. Also in this figure, as in FIG. 5, each difference signal is repeated with a time difference (delay time Zo) due to the difference in the arrangement position.

When there is no in-phase noise, that is, when the signals shown in FIGS. 5 and 6 are obtained, the results of the correlation calculation are as shown in FIGS. 7A and 7B, and the delay time Zo
The values of are both equal and correct. However, here, Z indicates the amount of change in the correlation calculation.

Next, when common-mode noise is added, consideration will be given by comparing this example with the conventional example.

The waveforms of outputs (a), (b) and (c) from the distance detectors A, B and C in the presence of in-phase noise are shown in FIGS. 8 (a), 8 (b) and 8 (c), respectively. Show. Further, the waveforms of the difference signals (a)-(b) and (b)-(c) by the differential calculator of the speed measuring device according to the method of this embodiment are shown in FIGS. 9 (a) and 9 (b), respectively. .

The delay time Zo cannot be found from FIG. 8 as in FIG. However, according to the present embodiment, even when in-phase noise is added, it is easily understood that each difference signal is repeated with a delay time Zo, as in FIG. 6 in the absence of noise.

At this time, the correlation result in the case of the conventional example is shown in FIG.
(A), and the maximum value of the correlation value is basically Z = Zo and Z
It appears at two points of = 0, and generally the delay time tends to be shorter than it actually is, and it becomes 0 or a value close to 0 depending on the situation.
On the other hand, according to the method of this embodiment, the difference signal (a) −
In (b) and (b)-(c), in-phase noise components are removed by subtraction. As a result, the correct delay time Z
This means that o is calculated (FIG. 10B).

According to the above-described embodiment, the distance detector has three
The number of units is sufficient, and the speed measuring device can be downsized. 11 to 13 show modified examples in which four distance detectors that project and receive light at a right angle to the surface to be measured are used.

Distance detectors are arranged in the order of ABCD on the same axis parallel to the moving direction, and the difference between the output of the distance detector A and the output of the distance detector B is calculated, and the output of the distance detector C and the distance are calculated. FIG. 11 shows a speed measuring device that calculates the difference from the output of the detector D.
Shown in (a). Here, it is necessary to make the distance between the light irradiation points by the distance detectors A and C equal to the distance between the light irradiation points by the distance detectors B and D. In other words, since the projected light and received light of each distance detector are set substantially at right angles to the surface to be measured, the distance between the distance detector AC and the distance between the distance detector BD is equal.

Further, if the distance between the light irradiation points, in this case, the distance between the distance detector AC and the distance between the distance detectors BD is kept equal, the order of the distance detectors in FIG. 11B may be arranged in this order. At this time, the difference calculation is performed between the output of the distance detector A and the output of the distance detector B, and between the output of the distance detector C and the output of the distance detector D.

FIG. 12 shows a modification in which the axis connecting the light irradiation points (here, the axis on which the distance detector is arranged) is not arranged on the same axis but on two axes parallel to the moving direction. Here, if the difference calculation between the output of the distance detector A and the output of the distance detector B and the difference calculation between the output of the distance detector C and the output of the distance detector D are performed, the distance detector A and the distance It is necessary that the detector C is on the same axis, and the distance detector B and the distance detector D are on the same axis.

Further, if the distance between the light irradiation points by the distance detectors A and C is made equal to the distance between the light irradiation points by the distance detectors B and D, the distance detectors A and B or the distance detector C are obtained. The positional relationship of D does not need to be aligned perpendicular to the moving direction as shown in FIG. 13 (top view).

Further, since the unevenness information necessary for speed measurement may be measured by the change, the distance detectors do not substantially match the distance to the object to be measured, and the distance to the object to be measured is The distance detectors may be different, that is, the distance detectors need not all be on the same plane substantially parallel to the surface of the object to be measured as shown in FIG. 13 (side view).
As long as the distance between each distance detector and the object to be measured does not matter, the three and four distance detectors are arranged on the same line parallel to the moving direction when viewed from the top. The same applies to cases such as FIG. 1 (top view) and FIG. 11 (top view).

Here, the disposition intervals of the distance detectors are required accuracy as a speed measuring device, measurement range, frequency response characteristics of the light emitter / receiver, allowable characteristics of deviation amount of light irradiation point in each distance detector, The determinants are the spatial frequency characteristics of irregularities and undulations on the surface of the object to be measured, and the appearance and shape of the device.

In particular, the allowable characteristic of the deviation amount of the light irradiation point in each distance detector, that is, the moving direction of the light irradiation point on the surface of the object to be measured in each pair of distance detectors performing the correlation calculation and the right angle thereto. There is a problem with the allowable characteristic of the amount of deviation in the forming direction. In other words, when the distance between the distance detectors of each set for performing the correlation calculation, that is, d becomes too large, in the change of the moving speed and the moving direction, and the changing process,
The light irradiation points of these distance detectors, which should detect the unevenness information at the same point, do not pass through the same point but have a certain amount of deviation, and the allowable range of the amount of deviation in this case becomes a problem.

Further, in the case where the speed measuring device of the present invention is mounted on a vehicle, if the distance between two distance detectors for performing the difference calculation becomes too large, the distance detector will be the same as the distance detector due to the influence of pitching or the like. Noise is no longer added and the speed error increases.

In consideration of the above points, it is necessary to determine the arrangement interval of the distance detectors and select an advantageous type as the arrangement position.

In the embodiment, the speed measuring device moves,
It can be used even when the speed measurement device is fixed and the measured object moves. Even in this case, the in-phase noise of the DUT and the velocity measuring device can be removed. Further, in the embodiment, the difference calculation is (a)-(b), but (b)-
It goes without saying that the order of the difference calculation may be reversed from that of (a) and the like.

Further, in the embodiment, the projection beam is applied to the plane of the object to be measured substantially at a right angle, but it may be applied obliquely as long as the variation of the unevenness information necessary for speed measurement can be measured. Also, the light projecting means and the light receiving means may be separated by a considerable distance. However, when considering the measurement error, it is desirable to project and receive light at a substantially right angle.

[0044]

The in-phase noise has various specific frequencies due to its cause, and the signal obtained from the unevenness of the surface of the object to be measured changes depending on the moving speed of the object to be measured. According to the present invention, the common-mode noise can be cut regardless of the relationship between the common-mode noise and the frequency of the uneven signal.

Although an electric filter may be used as a method of cutting noise, this method involves some signal deterioration of necessary information in the process of cutting in-phase noise. According to the present invention, unlike the method using the filter, in the process of cutting the in-phase noise, a disadvantage in applying the correlation calculation, that is, the loss of necessary information from the uneven signal of the surface of the DUT. There is no fear of.

That is, according to the configuration of the present invention, the combined unevenness information of the surface of the object to be measured at the light irradiation point by the two distance detectors of the same set in which the in-phase noise is eliminated, this unevenness information and the detection time. It is possible to obtain the unevenness information in which the amplitude and the phase are substantially the same just with the shift. Then, by performing a correlation calculation between these pieces of unevenness information, it becomes possible to obtain a highly accurate correlation. Therefore, since the delay time due to the difference in the positions of the light irradiation points can be calculated with high accuracy, it is possible to calculate the moving speed with high accuracy.

Further, it can be used even in an environment where a large amount of common-mode noise is added, and it is possible to realize a highly accurate speed measuring device which is not affected by the influence of common-mode noise under wider usage conditions. Further, since the present invention is based on the unevenness information of the surface of the object to be measured, it is possible to fill the weak points of the conventional method of calculating the speed based on the light and dark information.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a speed measuring device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a distance detector according to an embodiment of the present invention.

FIG. 3 is a block diagram of an arithmetic processing system from distance detection to speed calculation according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an embodiment of speed measurement in an example of the present invention.

FIG. 5 is a diagram showing output signal waveforms from distance detectors A, B, and C when there is no in-phase noise.

FIG. 6 is a difference signal (a) -by the differential calculator of the speed measuring device which is the method of the embodiment of the present invention when there is no in-phase noise.
It is a figure which shows the waveform of (b) and difference signal (b)-(c).

FIG. 7 is a diagram showing a result of a correlation calculation between the conventional method and the method of the present invention when there is no in-phase noise.

FIG. 8: Distance detectors A, B, C when in-phase noise is included
It is a figure which shows the output signal waveform from.

FIG. 9 is a difference signal (a) − by the differential calculator of the speed measuring device which is the method of the embodiment of the present invention when the common-mode noise is included.
It is a figure which shows the waveform of (b) and difference signal (b)-(c).

FIG. 10 is a diagram showing a result of correlation calculation between the conventional method and the method according to the present invention when common-mode noise is included.

FIG. 11 is a diagram showing a modification in which four distance detectors are used.

FIG. 12 is a diagram showing a modified example when four distance detectors are used.

FIG. 13 is a diagram showing a modified example in which four distance detectors are used.

FIG. 14 is a diagram showing a configuration of a conventional speed measuring device.

[Explanation of symbols]

A, B, C, D ... Distance detector, 1 ... Distance detector, 2 ... L
ED, 21 ... Projection lens, 3 ... PSD, 31 ... Focusing lens, 4 ... DUT, 41 ... Irradiation point, 51 ... Differential calculator, 52 ... Differential calculator, 6 ... Correlation / speed Calculator, 61 ...
Correlation calculator, 62 ... Speed calculator.

Claims (5)

[Claims] 1. By irradiating an object to be measured that moves in a predetermined direction with light and receiving reflected light from the object to be measured,
First, second, and third distance detecting means for obtaining distance information to the first, second, and third light irradiation points of the measured object, and distance information from the first distance detecting means, respectively. A first differential calculator for performing a difference calculation with distance information from the second distance detecting means; distance information from the second distance detecting means and distance information from the third distance detecting means A second differential arithmetic unit that performs a difference calculation of the first differential arithmetic unit and an output of the first differential arithmetic unit and an output of the second differential arithmetic unit. A correlation calculator for calculating the delay time between the output of the calculator and the output of the second differential calculator, and the speed of the object to be measured based on the delay time obtained by the correlation calculator. A speed calculator, and the first, second, and third light irradiation points are on an axis parallel to the predetermined direction, and Light irradiation point, the first with respect to the predetermined direction 1
A predetermined distance behind the light irradiation point of the second light irradiation point, and the third light irradiation point is the second light irradiation point with respect to the second direction with respect to the predetermined direction.
2. The speed measuring device, characterized in that the predetermined distance is provided behind the light irradiation point. 2. The distance detecting means comprises a light projecting means for projecting a light beam onto an object to be measured, a light receiving lens for detecting the direction of light reflected from the object to be measured, and a light incident position detecting element. The speed measuring device according to claim 1, further comprising: a light receiving unit that outputs distance information to the object to be measured based on the principle of triangulation. 3. By irradiating a measured object moving in a predetermined direction with light and receiving reflected light from the measured object,
First, second, third, and fourth distance detecting means for obtaining distance information to the first, second, third, and fourth light irradiation points of the measured object, and the first distance detection A first differential calculator for calculating a difference between the distance information from the distance detector and the distance information from the second distance detector, the distance information from the third distance detector, and the fourth distance detector A second differential calculator that performs a difference calculation with distance information from the means, and a cross-correlation calculation between the output of the first differential calculator and the output of the second differential calculator, A correlation calculator that calculates a delay time between the output of the first differential calculator and the output of the second differential calculator, and the measured object based on the delay time obtained by the correlation calculator. And a velocity calculator for calculating the velocity of the object, wherein the third light irradiation point passes through the first light irradiation point and is flat in the predetermined direction. On a different axis and at a predetermined distance behind the first light irradiation point with respect to the predetermined direction, the fourth light irradiation point passes through the second light irradiation point, and A velocity measuring device, characterized in that the velocity measuring device is on the axis parallel to the predetermined direction and at a predetermined distance behind the second light irradiation point with respect to the predetermined direction. 4. An axis passing through the first and third light irradiation points,
The speed measuring device according to claim 3, wherein the axis passing through the second and fourth light irradiation points is the same axis. 5. The distance detecting means includes a light projecting means for projecting a light beam onto the object to be measured, a light receiving lens for detecting the direction of light reflected from the object to be measured, and a light incident position detecting element. The speed measuring device according to claim 3 or 4, further comprising: a light receiving unit that outputs distance information to the object to be measured based on the principle of triangulation.