JP2573135Y2 - Moving distance detector - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance detector using a spatial filter and an encoder, which is improved so as to improve measurement accuracy.

[0002]

2. Description of the Related Art Conventionally, in the automatic traveling of an automatic guided vehicle or the like, a traveling guide is formed by laying an electromagnetic induction wire or an optical reflecting tape on a traveling path, or an encoder or a tachogenerator is attached to wheels and measuring wheels. There is a method of measuring the speed and moving distance of an unmanned vehicle from a pulse or an analog voltage according to the rotation of a wheel.

However, these methods require construction work for laying a reflective tape or the like on the road surface, so that the work must be performed every time the traveling path is changed, which is troublesome. Accurate measurement was not possible due to wheel wear. For this reason, external guidance is unnecessary, and as a method of measuring the moving distance without contact,
A method using a gyro has been considered, but a gyro with high accuracy is expensive at present, and as another method, a distance measuring method using a spatial filter has been developed.

FIG. 7 shows an apparatus configuration for implementing the distance measuring method using the spatial filter. As shown in FIG. 1, the reflected light from the road surface 1 is transmitted through the optical system 2 to the line sensor (CC).
D) It is detected by 3 and is sampled at a predetermined cycle and converted into an electric signal. The optical system 2 and the line sensor 3 are mounted on the bottom surface of a vehicle body (not shown). The line sensor 3 is one in which optical conversion elements are temporarily arranged along the traveling direction, and signals according to light and dark are sequentially output.

An output signal P from the line sensor 3 passes through a readout circuit 4 and is converted by an A / D converter 6 into a digital signal CCD.
After being converted into data, it is input to the spatial filter operation unit 5. The spatial filter operation unit 5 integrates this output signal within a predetermined range to extract an arbitrary frequency component from the reflected light composed of optically random frequencies, The vector corresponding to the moving distance in the phase space shown in FIG. That is,
As shown in the flowchart of FIG. 9, the CCD data D _i (i = 1, 2,... N) from the line sensor 3 composed of N pixels
Is read together with the load function data S _i (i = 1, 2,... N), and a product-sum operation is performed by sequentially adding N times the products having the same suffix to obtain a product-sum value S _b Can be

[0006] Here, the weighting function data S _i, the product of the sine wave and the Hanning (window) function, is obtained by sampling by the CCD data and the same cycle. This sine wave has n wave numbers in the length L of the line sensor, and the wavelength p (= L / n) is hereinafter referred to as a filter pitch.

Next, when the load function data C _i (i = 1, 2,... N) is read, a subscript is added to the CCD data D _i (i = 1, 2,... N). product-sum operation is performed by the product of equal of added sequentially n times, Sekiwachi S _a is obtained. Here, the weighting function data C _i for the product of the cosine wave and the Hanning function is obtained by sampling by the CCD data and the same cycle. The load function data S _i and C _i are respectively given from the load function memory.

Further, since the sum-of-product values S _a and S _b are obtained for each sampling, the sum-of-product values of the previous sampling are S _a1 and S _b1, and the sum-of-product values of the current sampling are S _a2 and S _a2 , respectively.
Let it be S _b2 . In this way, the vectors t _{1 and} t ₂ at the time of each sampling in the phase space in which the product sum values S _a1 , S _b1 , S _a2 and S _b2 are two-dimensional coordinates are shown in FIG. Accordingly, the phase difference Δφ between one sampling is obtained by the phase difference calculation unit 7 as in the following equation. Δφ = arctan ｛(S _a1 · S _b2 −S _a2 · S _b1 ) / (S _a1 · S _a2 + S _b1 · S _b2 )｝… (1)

Here, the moving distance x ₀ and the rotation angle Δφ are in a proportional relationship, and the proportional constant is represented by a filter pitch p (=
Since the L / n) and the ratio of the 2 [pi, it is determined as follows from the moving distance x ₀ and speed V. Δx ₀ = V = (p / 2π) · Δφ (2) x ₀ = (p / 2π) · ΣΔφ (3) However, the phase difference between one sampling is within one rotation.

Accordingly, the spatial filter distance calculating section 8 integrates (p / 2π) to obtain the moving distance Δx _{0 in} one sampling, that is, the velocity V, and further sums up by the accumulator 9 to calculate the moving distance. x ₀ is determined.

[0011]

As described above, a distance detector using a spatial filter has a feature that non-contact and high-precision detection is possible. However, when the reflected light from the road surface is irregular, suddenly changed, or glossy, the frequency components to be extracted decrease and the amplitude of the output of the spatial filter operation unit 5 decreases. In some cases, the absolute values of the vectors t ₁ and t ₂ in space become small, and accurate measurement may not be performed.

That is, since the distance detector using the spatial filter depends on the frequency component included in the reflected light from the road surface, accurate measurement may not be performed if the road surface condition is poor. In addition, combining the travel distance measurement with the spatial filter and the travel distance measurement with the encoder,
When the amplitude of the spatial filter is smaller than a certain reference value, switching to the measurement of the moving distance by the encoder may be performed. However, in an automatic guided vehicle or the like, the wheels wear as the vehicle travels, which causes an error in measurement by the encoder. Similarly, when the wheel diameter decreases due to the wear of the wheels, the line sensor 3 and the Road surface 1
However, there is a problem that an error occurs in the measurement of the moving distance by the spatial filter because the distance changes.

The present invention has been made in view of the above prior art, and uses both a distance measurement using a spatial filter and a distance measurement using an encoder, and selectively uses the output of the spatial filter according to its amplitude. It is another object of the present invention to provide a distance detector capable of eliminating an error caused by wheel wear.

[0014]

According to an aspect of the present invention, there is provided a photoelectric conversion device for converting incident light into an electric signal, and a reading circuit for sampling the photoelectric conversion device at a predetermined period and sequentially outputting the signals. A spatial filter operation unit for extracting an arbitrary frequency component by multiplying the electric signal sequentially output from the readout circuit for each sampling by a sine wave and a cosine wave as a weighting function and integrating them within a predetermined range. A phase difference calculator for calculating, for each sampling, a phase difference centered on an origin on a phase plane of a vector having two signals extracted by the spatial filter calculator as two-dimensional coordinates; and A distance detector having a spatial filter distance calculator for calculating a moving distance proportional to the phase difference obtained by the calculator, and outputting a pulse corresponding to the rotation speed of the wheel. Encoder, an encoder distance calculation unit that calculates a moving distance based on an output from the encoder, and based on a change in a diameter of the wheel due to wear of the wheel and a change in a distance between the photoelectric conversion element and a road surface due to the change. When an error occurs between the moving distance by the encoder calculating unit and the moving distance by the spatial filter calculating unit, a correction coefficient calculating circuit for correcting the error, and a distance between the photoelectric conversion element and the mounting position of the encoder are used. ,
When an error occurs between the moving distance by the encoder calculating unit and the moving distance by the spatial filter calculating unit, a distance converter for converting one moving distance into the other moving distance, and a signal from the spatial filter calculating unit An amplitude comparator that compares the amplitude of the spatial filter with the reference amplitude, and when the amplitude comparator detects that the amplitude of the signal from the spatial filter arithmetic unit is smaller than the reference amplitude, the spatial filter distance arithmetic unit And a moving distance selector that outputs an output from the encoder distance calculating unit as a moving distance in place of the output of the encoder.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. Note that the same parts as those of the above-described conventional technology are denoted by the same reference numerals, and description thereof will be omitted. 1 to 6
1 shows an embodiment of the present invention. As shown in both figures, an automatic guided vehicle 10 has a moving distance detector 12 using a spatial filter.
And a moving distance detector 11 using an encoder. The automatic guided vehicle 10 has a structure having one front wheel 13 and two rear wheels 14, in which the front wheel 13 is a driving steering wheel and the rear wheel 14 is a driven wheel. A steering motor 13a and a drive motor 13b are attached to the front wheel 13. The wheel base between the front wheel 13 and the rear wheel 14 is L.

An encoder 15 is mounted on the front wheel 13,
The encoder 15 outputs a pulse corresponding to the rotation speed of the front wheel 13 to the moving distance detector 11. On the other hand, a line sensor (CCD) 16 is disposed between the rear wheels 14, and the reflected light from the road surface is detected by the line sensor 16 via an optical system (not shown), sampled at a predetermined cycle, and The signal is converted into a signal and input to a moving distance detector 12 using a spatial filter. As the moving distance detector 12 using a spatial filter, an amplitude calculator 17 is added to the conventional device shown in FIG. 7 as shown in FIG.

That is, as shown in FIG. 3, the output signal P from the line sensor 3 passes through the readout circuit 4 and the A / D converter 6
Is converted into CCD data of a digital signal, and then input to the spatial filter operation unit 5. The spatial filter operation unit 5 integrates this output signal within a predetermined range to extract an arbitrary frequency component from the reflected light composed of optically random frequencies, A vector corresponding to the movement distance in the phase space shown in FIG. That is, as shown in the flowchart of FIG. 9, the CCD data D _i (i = 1,
2,... N) are read together with the load function data S _i (i = 1, 2,... N), and a product-sum operation is performed by sequentially adding N times the products of the same subscript. Sekiwachi S _b is required.
Here, the sine wave and the weighting function data S _i and Hanning (window)
The product with the function is sampled at the same cycle as the CCD data.

Next, when the load function data C _i (i = 1, 2,... N) is read, a subscript is added to the CCD data D _i (i = 1, 2,... N). product-sum operation is performed by the product of equal of added sequentially n times, Sekiwachi S _a is obtained. Here, the weighting function data C _i as shown in FIG. 9, the product of the cosine wave and the Hanning function is obtained by sampling by the CCD data and the same cycle.

Further, since the sum-of-product values S _a and S _b are obtained for each sampling, the sum-of-product values of the previous sampling are S _a1 and S _b1, and the sum-of-product values of the current sampling are S _a2 and S _a2 , respectively.
Let it be S _b2 . In this way, the vectors t _{1 and} t ₂ at the time of each sampling in the phase space in which the product sum values S _a1 , S _b1 , S _a2 and S _b2 are two-dimensional coordinates are shown in FIG. Accordingly, the phase difference Δφ between one sampling is obtained by the phase difference calculation unit 7 as in the following equation. Δφ = arctan ｛(S _a1 · S _b2 -S _a2 · S _b1 ) / (S _a1 · S _a2 + S _b1 · S _b2 )｝ ... (1) Therefore, the moving distance ΔI _{s in} one sampling is expressed by the following equation. (P / 2π) is calculated by the spatial filter distance calculation unit 8 based on the calculated values. ΔI _s = V = (p / 2π) · Δφ (2) These results are output to the moving distance selector 18 shown in FIG.

On the other hand, assuming that the amplitudes of the sum of products S _a and S _b are E and F, respectively, the weighted average G of the amplitudes is
The calculation is performed by the amplitude calculator 17 as follows. G = (E ² + F ² ) ^1/2 (4) The result is output to the amplitude comparator 19 shown in FIG.
The amplitude comparator 19 compares the weighted average G of the amplitude with an amplitude H serving as a preset reference. When the weighted average G of the amplitudes is larger than the reference amplitude H, the amplitude comparator 19 sends the moving distance ΔI _s detected by the moving distance detector 12 using the spatial filter to the moving distance selector 18.
Is output, on the contrary, when the weighted average G of the amplitudes is smaller than the reference amplitude H, the moving distance ΔI _e from the moving distance detector 11 by the encoder is output.
Is output.

In accordance with the selection signal from the amplitude selector 19, the moving distance selector 18 detects the moving distance detected by the moving distance detector 12 by the spatial filter or the moving distance ΔI _e from the moving distance detector 11 by the encoder. Is selected and output to the accumulator 21.

However, the driving wheels 1 in the automatic guided vehicle 10
If 3 is worn and its diameter becomes k times, the moving distance detected by the encoder 15 becomes 1 / k times. Also,
As shown in FIG. 6, the drive wheel 13 is worn and its diameter is k.
If it is doubled, the moving distance detected by the spatial filter is H / {H + (k-1) Q} times. However, the height from the road surface to the line sensor 16 is H, and the wheel radius is Q. Therefore, the moving distance _Ie measured by the moving distance detector 11 by the encoder and the moving distance Is measured by the moving distance detector 12 by the spatial filter are _equal to the driving wheel 1.
3 includes an error caused by wear.

In order to correct this error, a correction coefficient calculator 24 is provided. This correction coefficient calculator 2
In No. 4, the rate of change k of the drive wheels 13 is determined by the following procedure, and a correction coefficient is determined for each of them based on this. That is, the output of the moving distance detector 12 by the spatial filter is normal,
In addition, the unmanned carrier 10 travels straight and travels a certain distance I
The measures a moving distance I _e measured by the moving distance detector 11 by the encoder is compared with the movement distance I _s measured by the moving distance detector 12 by the spatial filter,
The following relationship is derived. I = _Ie · k = ｛1+ (k−1) Q / H｝ _Is (5) Therefore, k = ｛(1−Q / H) _Is ｝ / ｛1− (Q / H) _Is …… (6)

As described above, since the change rate k of the wheel radius can be obtained by measuring the moving distance I in a certain section, the correction coefficient calculator 24 calculates the detected moving distance _Ie obtained by the encoder as follows. multiplied by the rate of change k as the correction coefficient, also for detecting moving distance I _s obtained by the spatial filter, {1+ (k-1) Q / H}
Is multiplied as a correction coefficient to obtain an actual moving distance I excluding an error caused by wheel wear. Correction coefficient for encoder: k Correction coefficient for spatial filter: 1+ (k-1) Q / H

Further, a moving distance detector 1 using an encoder
A moving distance [Delta] I _e is detected by 1, the moving distance [Delta] I, which is detected by the moving distance detector 12 by the spatial filter
_{In s} , an error occurs because the position where the encoder 15 is mounted and the position where the line sensor 16 is mounted are different. Therefore, the moving distance converter 20 converts the moving distance according to the following equation. Note that the moving distance ΔI _e , Δ
I _s is the distance traveled in one sampling. (Δψ / ΔI _e ) = (sin θ / L) (7) ΔI _s = ΔI _e · cos θ (8) However, as shown in FIG. 4, L is the length of the wheel base, and I _e is detected by the encoder. Is the steering angle, θ is the steering angle, and ψ is the inclination of the vehicle body with respect to the course.

Therefore, in the position converter 20, the moving distance ΔI detected by the moving distance detector 11 by the encoder is used.
_e is multiplied by cosθ, and the moving distance detector 1 using a spatial filter
2 by converting the moving distance [Delta] I _s at the position to be detected. After that, it is accumulated by the accumulator 21 and output as the moving distance of the automatic guided vehicle 10. I _s = ΣΔI _s = (p / 2π) · ΣΔφ (9) Note that the reading circuit 4, the A / D converter 6,
Spatial filter operation unit 5, phase difference operation unit 7, spatial filter distance operation unit 8, amplitude comparator 19, moving distance selector 18,
Specifically, the distance converter 20, the correction coefficient calculator 24, and the like include a CCD drive circuit 25, choppers 26 and 27, a DSP 28, a CPU 29, and the like, as shown in FIG. In addition, the automatic guided vehicle 10 of the present embodiment is also provided with a contact image sensor 30, a CCD drive circuit 31, a battery 32, and the like.

[0027]

As described above in detail, based on the embodiments, the present invention uses both distance measurement using a spatial filter and distance measurement using an encoder, and outputs the output by the amplitude of the spatial filter. When the reflected light from the road surface is irregular, suddenly changed, or glossy, the frequency components to be extracted are reduced, and when the amplitude of the output of the spatial filter operation unit is reduced, the encoder is used selectively. Thus, the distance can be detected, and extremely accurate position detection becomes possible. Further, it is possible to calculate an accurate distance by absorbing an error based on a difference between the mounting position of the encoder and the mounting position of the photoelectric conversion element. Furthermore, since an error between the moving distance by the encoder and the moving distance by the spatial filter due to the wear of the wheels can be eliminated, a more accurate moving distance can be measured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a distance detector according to an embodiment of the present invention.

FIG. 2 is an encoder and a CCD according to an embodiment of the present invention;
It is a top view of the automatic guided vehicle to which was attached.

FIG. 3 is a configuration diagram of a moving distance detector using a spatial filter according to an embodiment of the present invention;

FIG. 4 is an explanatory diagram showing a phase space.

FIG. 5 is a perspective view of the automatic guided vehicle according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between a wheel diameter and a distance between a CCD camera and a road surface.

FIG. 7 is a configuration diagram of a moving distance detector using a spatial filter according to the related art.

FIG. 8 is an explanatory diagram showing a phase space.

FIG. 9 is a flowchart illustrating a process of a product-sum operation using a spatial filter.

[Description of Signs] 1 Road surface 2 Optical system 3 Line sensor 4 Readout circuit 5 Spatial filter operation unit 6 A / D converter 7 Phase difference operation unit 8 Accumulator 10 Automatic guided vehicle 11 Moving distance detector by encoder 11a Encoder Position detector 12 Moving distance detector by spatial filter 12a Position detector by spatial filter 13 Front wheel 14 Rear wheel 15 Encoder 16 CCD 17 Amplitude calculator 18 Moving distance selector 19 Amplitude comparator 20 Moving distance converter 21 Accumulator 22 Position calculator 23 Amplitude comparator 24 Correction coefficient calculator 25 CCD drive circuit 26, 27 Chopper 28 DSP 29 CPU 30 Contact image sensor 31 CCD drive circuit 32 Battery

Continuation of the front page (56) References JP-A-2-81104 (JP, A) JP-A-4-109322 (JP, U) JP-A-4-30405 (JP, U) JP-A-4-29813 (JP , U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01C 22/00 G05D 1/02

Claims (1)

(57) [Scope of request for utility model registration] 1. A photoelectric conversion element for converting incident light into an electric signal, a readout circuit for sampling the photoelectric conversion element at a predetermined cycle and sequentially outputting the electric signal, and an electric signal sequentially output from the readout circuit for each sampling A spatial filter operation unit that extracts an arbitrary frequency component by separately multiplying a sine wave and a cosine wave as a weight function and integrating within a predetermined range; and two signals extracted by the spatial filter operation unit. A phase difference calculation unit that calculates a phase difference of the vector as a two-dimensional coordinate centered on the origin on the phase plane for each sampling, and calculates a movement distance proportional to the phase difference obtained by the phase difference calculation unit An encoder that outputs a pulse corresponding to the number of rotations of a wheel, based on an output from the encoder. An encoder distance calculating unit that calculates a moving distance, based on a change in the diameter of the wheel due to the wear of the wheel and a change in the distance between the photoelectric conversion element and a road surface due to the change, a moving distance by the encoder calculating unit, When an error occurs in the moving distance by the spatial filter calculating unit, a correction coefficient calculating circuit for correcting the error, based on the distance between the photoelectric conversion element and the mounting position of the encoder, the moving distance by the encoder calculating unit, A distance converter for converting one moving distance into the other moving distance when an error occurs with the moving distance by the spatial filter calculating unit; and an amplitude for comparing the amplitude of the signal from the spatial filter calculating unit to a reference amplitude. A comparator, when the amplitude comparator detects that the amplitude of the signal from the spatial filter operation unit is smaller than the reference amplitude. A moving distance selector which outputs an output from the encoder distance calculating unit as a moving distance in place of the output from the spatial filter distance calculating unit.