JP2871109B2 - Line sensor readout method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reading a line sensor, and more particularly to a method for extracting a plurality of frequency components in a distance measuring device using a spatial filter without changing the hardware configuration.

[0002]

2. Description of the Related Art Conventionally, in the autonomous traveling of an automatic guided vehicle or the like, a method of laying an electromagnetic induction wire or an optical reflective tape on a traveling path to form a traveling guide, or attaching an encoder or a tachogenerator to an axle or a measuring wheel. 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 construction work must be performed every time the traveling path is changed, which is complicated. In addition, accurate measurements could not be made due to unevenness of the road surface, slippage due to external force and wheel wear.

For this reason, a distance measuring method using a spatial filter has been developed as a method of measuring the moving distance without contact without external guidance and without contact.

[0005] The distance measuring method using the spatial filter is performed by the apparatus configuration shown in FIG. That is, as shown in the figure, the reflected light from the road surface 1 is detected by a line sensor (CCD) 3 via an optical system 2, sampled at a predetermined cycle, and changed 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 photoelectric conversion elements are arranged one-dimensionally according to a traveling method, and sequentially outputs signals corresponding to light and dark.

An output signal P from the line sensor 3 passes through a read 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 the 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 flow chart shown in FIG. 6, first, CCD data D _i (i = 1,
2,... N) are read together with the sin load function S _i (i = 1, 2,... N), and the products of the same subscript are sequentially added n times to perform a product-sum operation, and the product-sum value S _b is required. Here, the sin load function S _i is a product of the sine function and the Hanning function as shown in FIG. This sine function 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 cos weighting function C _i (i = 1, 2,... N) is read, it is determined that the subscripts are equal to those of the CCD data D _i (i = 1, 2,. product-sum operation is performed by the product is added sequentially n times, Sekiwachi S _a is obtained. Here, the cos load function C _i is a product of the cosine function and the Hanning function as shown in FIG.

Further, since the sum-of-product values S _a, S _b are obtained for each sampling, the sum-of-product values S _a1, S of the previous sampling are obtained.
_b1 and the product-sum values S _{a2 and} S _{b2 of} the current sampling. By doing so, the sum of products S _a1, S _b1 , S
Vectors t _{1 and} t ₂ at each sampling time in a phase space in which _{a2 and Sb2} are two-dimensional coordinates are shown in FIG. Therefore, the rotation angle Δφ during one sampling is obtained by the phase calculation unit 7 as in the following equation.

[0009]

(Equation 1)

Here, the moving distance x ₀ and the rotation angle △ φ are in a comparative relationship, and the proportional constant is a filter pitch p (=
L / n) and 2π, the moving distance X ₀ and the speed V are obtained as follows.

[0011]

(Equation 2)

(Equation 3)

[0012]

As described above, in the distance measuring device using a spatial filter, a weighting function is used to extract a specific frequency from an analog signal output from the line sensor 3 and corresponding to the shading of the road surface. Is prepared in advance as data, and a specific one type of frequency component is extracted by individually performing a product-sum operation on the load function data and each pixel output of the line sensor.

However, conventionally, since only one frequency is extracted, the frequency component set in the analog signal may be absent or extremely small depending on the detection road surface. In this case, a velocity vector cannot be generated. In some cases, the vector length becomes extremely short even if it is made, and the rotation angle cannot be calculated.

To solve such a problem, it is sufficient to extract a plurality of frequency components, but this causes a new problem. That is, increasing the frequency components to be extracted means that the load function data for extraction must also be increased. For this reason, it is necessary to secure a memory area for storing the increased weighting function. However, at present, it is difficult to increase the storage area due to hardware limitations.

The present invention has been made in view of the above circumstances, and provides a method of reading a line sensor capable of extracting a plurality of frequency components without changing the hardware configuration.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a line sensor disposed on a vehicle body for detecting light reflected on a traveling road surface and converting the light into an electric signal, and a predetermined period from the line sensor. And a spatial filter operation for extracting an arbitrary frequency component by multiplying an electrical signal sequentially output from the readout circuit by a sine wave and a cosine wave and integrating within a predetermined range. And a calculation unit for calculating a moving distance of the vehicle body from a rotation angle of the vector having two signals extracted by the spatial filter calculation unit as a two-dimensional coordinate and centered on an origin on a phase plane. In a distance measurement device using a spatial filter, of the signals output from the respective pixels of the line sensor, the spatial filter operation unit uses the signal of a pixel skipped by a predetermined pixel. And performing.

[0017]

The output from the line sensor is not used for the sum-of-products calculation for all pixels, but is skipped every few pixels.

[0018]

The method of the present invention will be specifically described below. The method of the present invention is applied to the apparatus shown in FIG. FIG. 1 shows an output signal p of the line sensor 3, and FIG. 2 shows an output obtained by A / D converting the output signal p for one scan cycle. The case where the number of pixels of the line sensor 3 constituted by the CCD is 2048 pixels in total, the weight function storage area of the spatial filter 5 is 2048 bytes, and four frequency components are extracted will be described. In the spatial filter 5, instead of performing a product-sum operation on all pixel data, a 2048 pixel is skipped every three pixels from the first pixel and taken out. That is, as shown by hatching in FIG. 2, the product-sum operation is performed on each of the first, fifth, ninth, thirteenth, seventeenth, ..., and 2048th pixel data with four weight function data.

As described above, since the pixel data is skipped every three pixels, the weighting function data is 204
Only 1/4 of 8 bytes, that is, 512 bytes is required. Since four frequencies are extracted, the weighting function data for the four frequencies is 512 × 4 = 2048 bytes, which is just stored in the weighting function storage area of the spatial filter calculation unit 5.

Since the four types of frequency components are extracted as described above, the component having the largest amplitude among the frequency components is sequentially selected and used for distance calculation. Therefore, the autonomous traveling of the unmanned vehicle can always be performed accurately regardless of the road surface condition. That is, even if one frequency component is lost or reduced, the accuracy of autonomous traveling of the unmanned vehicle can be improved by calculating the speed or distance using the other frequency components. Moreover, a plurality of frequency components can be extracted from the road surface pattern only by changing the software without changing the hardware configuration. It should be noted that even when a wide field of view is viewed with a CCD line sensor having a large number of pixels, the entire wide area can be used for calculation by skipping pixels.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, (a) In the first scan cycle, the product-sum operation is performed for each of the first, fifth, ninth, thirteenth, seventeenth, ..., and 2048th pixel data. (B) In the second scan cycle, the second, sixth, and first
The product-sum operation is performed on each of the 0th, 14th, 18th,..., 2045th pixel data. (C) In the third scan cycle, the third, seventh, and first
The product-sum operation is performed for each of the 1,15th, 19th... 2046th pixel data. (D) In the fourth scan cycle, the fourth, eighth, and first
The product-sum operation is performed on each of the 2, 16, 20th,..., 2047th pixel data. (E) In the fifth scan cycle, the same pixel data as in the first scan cycle is calculated again, and thereafter, similarly, pixel data used for one calculation is shifted for each scan.

In this way, all pixels can be used. Further, when a specific CCD of the line sensor 3 is out of order, when no shift is performed,
When pixel data is obtained from D and the calculation is performed, the accuracy is greatly deteriorated. However, when the pixel data is shifted for each scan as in this embodiment, the error is diluted and high accuracy can be maintained.

[0023]

According to the present invention, as described above in detail with the embodiments, the speed and distance can be calculated by extracting a plurality of frequencies by changing only the software without changing the hardware configuration. Can be.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing an output waveform of a line sensor.

FIG. 2 is a waveform diagram showing a waveform obtained by A / D exchange of a line sensor output.

FIG. 3 is a waveform diagram showing a waveform obtained by A / D exchange of a line sensor output.

FIG. 4 is a block diagram showing a distance measuring device using a spatial filter.

FIG. 5 is an explanatory diagram showing a phase space.

FIG. 6 is a flowchart showing a process of calculating a moving distance / speed.

FIG. 7 is a graph showing a spatial filter load function.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Road surface 2 Optical system 3 Line sensor 4 Readout circuit 5 Spatial filter operation part 6 A / D converter 7 Phase difference operation part

Claims (1)

(57) [Claims] 1. A line sensor disposed on a vehicle body for detecting light reflected on a traveling road surface and converting the light into an electric signal, a reading circuit for sampling the line sensor at a predetermined cycle and sequentially outputting the signal, and A spatial filter operation unit that extracts an arbitrary frequency component by multiplying the electric signal output in order by a sine wave and a cosine wave and integrates within a predetermined range, and two signals extracted by the spatial filter operation unit And a calculation unit for calculating the moving distance of the vehicle body from a rotation angle about the origin on the phase plane of a vector having two-dimensional coordinates, and a distance measurement device using a spatial filter, A method for reading out a line sensor, comprising: performing a calculation in a spatial filter calculation unit using a signal of a pixel skipped by a predetermined pixel among output signals. .