JP2500174Y2 - Distance measuring device with spatial filter - Google Patents

Description

[Detailed Description of the Invention] A. Industrial Field of Application The present invention is to improve the S / N ratio by increasing the output of the spatial filter in the distance measuring device using the spatial filter.

B. Outline of the device In the distance measuring device using the spatial filter, the frequency component of the spatial filter of interest decreases due to the sudden change of the reflected light from the road surface. The electric signal may be relatively low, but the phase of the electric signal from the photodetection conversion unit is delayed and / or advanced by a positive integer multiple of one period of the sine wave and the cosine wave used in the spatial filter calculation unit. Is added to this electrical signal, the amplitude of only the frequency component of interest increases relative to the noise, so the S / N ratio is improved and accurate measurement can be performed.

C. Conventional technology Conventionally, in automatic driving of an automated guided vehicle, a method of laying an electromagnetic induction wire or an optical reflection tape on the road to form a running guide, or attaching an encoder or tachogenerator to the axle or measuring wheel. Then, there is a method of measuring the speed and moving distance of the unmanned vehicle from a pulse or analog voltage corresponding to the rotation of the wheel.

However, these methods require the processing of a traveling path by laying a guide wire, a reflective tape, etc. on the road surface, and the processing work is troublesome. I couldn't make good measurements.

For this reason, a distance measuring method using a spatial filter has been developed as a method of measuring a moving distance in a non-contact manner without requiring guidance from the outside.

A distance measuring method using this spatial filter will be described with reference to FIGS. 7 to 10.

As shown in FIG. 7, the reflected light from the road surface 1 is taken by the optical system 2, sampled at a predetermined cycle by the line sensor (CCD) 3, and converted into an electric signal. Here, the reflected light from the road surface 1 is composed of a combination of various kinds of frequencies, but if the material of the road surface 1 and the surrounding environment are constant, the combination is considered to be substantially constant. If the optical system 2, line sensor 3 and the like are provided on the bottom surface of the vehicle (not shown), slight fluctuations will be repeated as the vehicle travels.

The output from the line sensor 3 passes through the read circuit 4 and then is input to the spatial filter calculation unit 5. The spatial filter calculation unit 5 extracts an arbitrary frequency component from the reflected light composed of optically random frequencies, and obtains a vector corresponding to the moving distance in the phase space from the time series change thereof. . That is, the read circuit 4
The signal V that has passed through is converted into a digital signal by the A / D converter 6, and is expanded to the Fourier series as follows.

However, x ₀ is the position of the vehicle at time t, x is the position in the line sensor read from the reading circuit, and x = ₀ is the reference, k = 2π / L, i = 0,1,2 ..., L Is the measurement range of the line sensor.

The Fourier coefficients A _i (x ₀ ) and B _i (x ₀ ) are given by the following equation.

_{A i (x 0) = (} 2 / L) · ∫ 0 L V · cos (k · i · x) dx ... (2) B i (x 0) = (2 / L) · ∫ 0 L V · sin (K · i · x) dx (3) These signals V are spatial filters, respectively, which are multiplied by cosine waves and sine waves S ₁ and S ₂ of specific frequencies shown in the following equations,
Integrate within a predetermined range.

S ₁ = F ・ cos (n ・ k ・ x) (4) S ₂ = F ・ sin (n ・ k ・ x) (5) S _a (x ₀ ) = ∫ ₀ ^L V ・ S ₂ d _x = F ・ B _n (x ₀ ) ・ L / 2 (6) S _b (x ₀ ) ＝ ∫ ₀ ^L V ・ S ₁ d _x ＝ F ・ A _n (x ₀ ) ・ L / 2 (7) As shown in FIG. 9, the cosine wave S ₁ and the sine wave S ₂ used as the spatial filter can be expressed as L / n for one period 2π / nk of them.
(= L / n). Here, the output V from the line sensor should change continuously in a trigonometric function with respect to a certain n-th order component V _n if the condition such as the road surface or the environment is due to reflected light. , For example, as shown in the following formula. However, l = x ₀ + x, and φ is an initial value.

Therefore, the nth-order Fourier coefficients A _n and B _n are obtained as follows.

In the same way Substituting equations (9) and (10) into equations (6) and (7) and rearranging gives the following equation.

S _a (x ₀ ) and S _b (x ₀ ) thus obtained are the tenth
As shown in Figure (a), it changes in a trigonometric function, and when the position x ₀ changes in the vehicle with the passage of time, its waveform spatiotemporally flows to the right in the figure. Is. Then, as shown in the phase plane of FIG. 10 (b), the trajectory of the vector having S _a and S _b as two-dimensional coordinates is
The rotation angle of the vector is proportional to the moving distance x ₀ , and it can be seen from the equations (11) and (12) that the proportional constant is 2π / P. Therefore, in order to obtain the moving distance x ₀ , the rotation angle of the vector may be multiplied by P / 2π. Actually, the signals S sampled by the line sensor 3 in a predetermined cycle determine the above S _a and S _b. Therefore, in the following, the subscript of the sampling number n is added so that they can be distinguished for each sampling number. It will be displayed as S _an and S _bn . The signals S _an and S _bn obtained in this way pass through a low-pass filter (not shown) and
It is input to the moving distance calculation unit 6 together with S _an-1 and S _bn-1 . The moving distance calculation unit 6 includes a phase difference calculation unit 7, an accumulator 8, and a multiplier.
It is composed of 9 and 10. The phase difference calculator 7 calculates the angle difference Δφ on the phase plane corresponding to the moving distance from the previous sampling time n−1 to the current sampling time n, as shown in FIG. That is, the absolute value of the inner product and outer product of the vector (S _an-1 , S _bn-1 ) and the vector (S _an , S _bn ) shown in FIG. 8 is obtained according to the following formula, and the ratio thereof is calculated.

This angular difference Δφ is summed by the accumulator 8 (ΣΔφ),
Then, the multiplier 9 multiplies it by P / 2π and outputs it as the moving distance x ₀ . Further, the velocity V can be obtained by multiplying P / 2π in the multiplier 10 without summing the angular differences Δφ.

D. Problems to be Solved by the Invention However, the frequency component of interest decreases in an irregular or sudden change on the road surface, and the signal S _an shown in FIGS. 10 (a) and 10 (b) decreases. , The amplitude of S _bn was sometimes small. As a result, the S / N ratio of the output deteriorates, and accurate measurement may not be possible.

The present invention has been made in view of the above prior art,
It is an object of the invention to provide a distance measuring device using a spatial filter capable of obtaining an output signal having a good S / N ratio.

E. Means and Actions for Solving the Problem In the present invention, a positive integer multiple of the spatial filter pitch P,
Delay the phase of the electrical signal from the photodetection converter, and /
Alternatively, one or more advanced electrical signals are added to this electrical signal, so that only the amplitude of the frequency component specified by the spatial filter increases relative to the noise, which improves the S / N ratio. To do.

F. Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1 (a), (b) and (c) show an embodiment of the first invention of the present application. As shown in the figure, the road surface 1
The reflected light from is taken by the optical system 2, and is sampled at a predetermined cycle by the photodetection conversion unit including the line sensor 3 and the readout circuit 4 to become the electric signal V (x ₀ ), which is A /
It is digitized by the D converter 6. Thereafter, the signal V (x ₀ ) is input to each of the phase delay circuits 11 provided in a plurality of stages (N stages in the figure). Each phase delay circuit 11 generates a delay signal V (x ₀ −P), V (x ₀ −2P), ... V (x ₀ −NP) whose phase is delayed by a positive integer multiple of the spatial filter pitch P. , These delayed signals are summed and input to the spatial filter operation unit 5 together with the signal V (x ₀ ). Although the contents of the calculation in the spatial filter calculation unit 5 are as described above, the explanation will be explained. In short, the frequencies specified by the spatial filter have the same phase and their outputs strengthen each other. Required output S _an , S
The amplitude of _bn will increase. On the other hand, the frequency and noise that are not specified by the spatial filter do not always have the same phase with the signal V (x ₀ ) and the delayed signal V (x ₀ −iP) (where i = 1, 2 ... N). It is not constructive, but it is certain that its amplitude will increase to some extent. However, when the amplification factor of the amplitude for the frequency specified by the spatial filter is N stages as in the above embodiment, (N + 1) is doubled, while at other frequencies, it is approximately Since it is about double, the amplitude of the specific frequency becomes relatively large and the S / N ratio is improved. Therefore, the amplitudes of S _an and S _bn are sufficiently large even on irregular roads,
This will enable accurate measurement. For example, as shown in FIG. 2 when the signals S _an and S _bn are obtained by computer simulation in the case of N = 1, the amplitude is smaller than that in the conventional example of FIG. 9 showing the case of the same conditions. About 2
It is twice as big.

The configuration after the spatial filter calculation unit 5 is the same as that shown in FIG. 7 and has the same operation and effect, so the description thereof will be omitted.

Next, the third embodiment of the second invention of the present application will be described.
It will be described with reference to the drawings.

In this embodiment, a phase advance circuit 12 is provided in place of the phase delay circuit 11 of the above embodiment, and other configurations are the same. Each phase lead circuit 12 has a spatial filter pitch P.
The lead signals V (x ₀ + P), V (x ₀ + 2P), ... V (x ₀ + NP) that are advanced by the phase of the signal V (x ₀ ) by a positive integer multiple of are generated. Therefore, although there is a difference between advancing and delaying the phase, it is still deviated by a positive integer multiple of the spatial filter pitch P, and the frequencies specified by the spatial filter become the same phase and reinforce each other. Produces the action and effect of. As shown in FIGS. 4 (a) and 4 (b), the computer simulation results of the signals S _a and S _b when N = 1 show that the amplitude is about twice that of the conventional one. I understand.

Further, for the signal V (x ₀ ), the subscript indicating the number of times of sampling is omitted, but this is because the same result is obtained at any number of times.

FIG. 5 shows an embodiment according to the third invention of the present application. In this embodiment, the phase delay circuit 11 and the phase advance circuit
Except that each of the 12 stages has multiple stages (N stages in the figure),
The configuration is the same as that of the above-described embodiment, and the same operational effect is obtained. For example, as shown in FIG. 6, the computer simulation results for S _a and S _b when N = 1
Its amplitude is about three times that of the conventional one.

In the above embodiment, the phase delay circuit 11, the phase advance circuit
Although 12 is provided between the A / D converter 6 and the spatial filter operation section 5, theoretically it may be provided between the read circuit 4 and the A / D converter 6.

G. Effect of the Invention As described concretely based on the above embodiments, in the present invention, by providing the phase delay circuit and / or the phase advance circuit, the phase of the electric signal from the photodetection conversion unit can be set to the spatial filter pitch P. Since it is delayed by a positive integer multiple of or added to the original electric signal when advanced, it is possible to selectively increase the amplitude for the frequency specified by the spatial filter, thus improving the S / N ratio. The measurement accuracy can be improved.

[Brief description of drawings]

1 (a), (b) and (c) respectively relate to an embodiment of the first invention of the present application, and FIG. 1 (a) is its configuration diagram and FIG. 1 (b).
Is a graph showing a delayed signal, FIG. 6 (c) is a graph showing a sum of delayed signals, FIG. 2 (a) is a graph showing spatiotemporal changes of signals S _a and S _b , and FIG. 2 (b) is Graphs showing the phase space of the signals S _a and S _b , FIGS. 3 (a), (b) and (c) respectively relate to the embodiment of the second invention of the present application, and FIG. 4B is a graph showing a lead signal, FIG. 4C is a graph showing a summed lead signal, and FIG. 4A is a signal.
A graph showing the spatiotemporal changes of S _a and S _b , FIG. 4 (b) is a graph showing the phase space of the signals S _a and S _b , and FIGS. 5 (a) and 5 (b).
(C) is related to the embodiment of the third invention of the present application, FIG. (A) is its configuration diagram, (b) is a graph showing a lead signal and a delayed signal, (c) is the sum. graph showing the signal and the delay signal advances, FIG. 6 (a) is the signal S _a, the graph showing the spatial variation when S _b, FIG. 6 (b) is the signal S _a, S _b
FIG. 7 is a graph showing a phase space of a moving distance measuring device using a conventional spatial filter, and FIG. 8 is a diagram showing signals S _an and S.
_{bn, S an-1, S} bn-1 of a graph showing a phase space, the graph Figure 9 is showing a spatial filter, FIG. 10 (a) is a conventional signal
S _a, graph showing spatial variation when S _b, Fig. 10 (b) is a graph showing the phase space of the signals S _a, S _b. In the drawings, 1 is a road surface, 2 is an optical system, 3 is a line sensor (CCD), 4
Is a reading circuit, 5 is a spatial filter operation unit, 6 is a moving distance operation unit, 7 is a phase difference operation unit, 8 is an accumulator, 9 and 10 are multipliers,
Reference numeral 11 is a phase delay circuit, and 12 is a phase advance circuit.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-1-266606 (JP, A) JP-A-2-278312 (JP, A) JP-A 58-3483 (JP, A) JP-A 63- 177066 (JP, A) JP 61-36161 (JP, B2) JP 4-67613 (JP, B2) JP 61-43641 (JP, B2) JP 6-50728 (JP, Y2)

Claims (3)

(57) [Scope of utility model registration request] 1. A light detecting and converting unit which is arranged on the bottom surface of a vehicle body and which captures light reflected on a traveling road surface, samples the light at a predetermined period and converts it into an electric signal, and an electric signal from the light detecting and converting unit. A spatial filter calculating section for multiplying a sine wave and a cosine wave, respectively, and integrating within a predetermined range to extract an arbitrary frequency component, and obtaining a sine wave and a cosine wave signal vibrating at the frequency, and the spatial filter calculating section. Distance measurement by a spatial filter having a travel distance calculation unit for calculating the travel distance of the vehicle body from a rotation angle of a vector having two-dimensional sine and cosine wave signals as coordinates from the origin on the phase plane In the apparatus, one or two or more phase delay circuits for delaying the phase of the electric signal from the photodetection conversion unit by a positive integer multiple of one cycle of the sine wave and the cosine wave are provided, and the delay electric circuit from the phase delay circuit is provided. Belief Distance measuring device according to a spatial filter, characterized in that the input by adding to an electric signal from the optical detector converting unit to the spatial filter operation section. 2. A photodetection conversion unit arranged on the bottom surface of a vehicle body for capturing light reflected on a traveling road surface, sampling at a predetermined cycle and converting it into an electric signal, and an electric signal from the light detection conversion unit. A spatial filter calculating section for multiplying a sine wave and a cosine wave, respectively, and integrating within a predetermined range to extract an arbitrary frequency component, and obtaining a sine wave and a cosine wave signal vibrating at the frequency, and the spatial filter calculating section. Distance measurement by a spatial filter having a travel distance calculation unit for calculating the travel distance of the vehicle body from a rotation angle of a vector having two-dimensional sine and cosine wave signals as coordinates from the origin on the phase plane In the apparatus, one or two or more phase advance circuits for advancing the phase of the electric signal from the photodetection conversion unit by a positive integer multiple of one cycle of the sine wave and cosine wave are provided, and the advance electric signal from the phase advance circuit is provided. signal Distance measuring device according to a spatial filter, characterized in that the input by adding to an electric signal from the optical detector converting unit to the spatial filter operation section. 3. A light detecting and converting unit which is arranged on the bottom surface of a vehicle body and which captures light reflected on a traveling road surface, samples it at a predetermined cycle and converts it into an electric signal, and an electric signal from the light detecting and converting unit. A spatial filter calculating section for multiplying a sine wave and a cosine wave, respectively, and integrating within a predetermined range to extract an arbitrary frequency component, and obtaining a sine wave and a cosine wave signal vibrating at the frequency, and the spatial filter calculating section. Distance measurement by a spatial filter having a travel distance calculation unit for calculating the travel distance of the vehicle body from a rotation angle of a vector having two-dimensional sine and cosine wave signals as coordinates from the origin on the phase plane In the apparatus, a phase delay circuit that delays the phase of the electric signal from the photodetection conversion unit by a positive integer multiple of one cycle of the sine wave and the cosine wave is provided, and the electric signal from the photodetection conversion unit is provided. A phase lead circuit for advancing the phase of the signal by a positive integer multiple of one cycle of the sine wave and cosine wave is provided, and the delayed electric signal from the phase delay circuit and the lead electric signal from the phase lead circuit are provided. Is added to the electric signal from the photodetection conversion unit and is input to the spatial filter calculation unit.