JP2500222Y2 - Distance measuring device with spatial filter - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a distance measuring device using a spatial filter, which is improved to improve the measurement accuracy.

B. Outline of the device In the distance measuring device using the spatial filter, when the traveling speed becomes fast, the phase difference in the phase space during one sampling becomes 180 ° or more, and it is impossible to judge whether the vehicle has moved forward or backward.

Therefore, in the present invention, by moving the load function at the moving speed at the time of the previous sampling, the relative speed to the measurement object is reduced to calculate the phase difference in the phase space at the time of this sampling. Since the moving distance and speed at the current sampling are calculated by adding the phase difference at the time of the previous sampling, the moving distance and speed can be reliably calculated even when the measurement target moves at high speed. it can.

C. Conventional technology Conventionally, when automatically driving an automated guided vehicle, a method of laying an electromagnetic induction wire or an optical reflection tape on the road to form a travel guide, or attaching an encoder or tacho generator to the axle or measuring wheel is used. There is a method of measuring the speed and moving distance of an unmanned vehicle from a pulse or analog voltage according to the rotation of the wheel.

However, these methods require the work of laying a reflective tape or the like on the road surface, and the work must be performed every time the traveling road is changed, which is complicated, and the unevenness of the road surface
Accurate measurement could not be performed due to slip 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 a moving distance in a non-contact manner without requiring guidance from the outside.

The distance measuring method using this 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 transmitted through the optical system 2 to the line sensor (CC
D) 3 is detected, sampled at a predetermined cycle, and converted into an electric signal. The optical system 2 and the line sensor 3 are attached to the bottom surface of the vehicle body (not shown). The line sensor 3 is formed by temporarily arranging optical conversion elements along the traveling direction, and sequentially outputs signals according to light and dark.

The output signal P from the line sensor 3 passes through the read circuit 4, is converted into CCD data of a digital signal by the A / D converter 6, and then is input to the spatial filter calculation unit 5. The spatial filter calculation 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, and from the temporal and temporal change, the fourth frequency component is extracted. The vector corresponding to the moving distance is obtained in the phase space shown in the figure. That is, CCD data D _i (i = 1, 2, ...) From the line sensor 3 consisting of N pixels
N) is read together with the weighting function data S _i (i = 1, 2, ... N), and products of equal subscripts are sequentially added N times to perform a product-sum operation, and a product-sum value S _b Is required. Here, the weighting function data S _i is, as shown in FIG. 5, the CCD of the product of the sine wave and the Hanning (window) function.
It is sampled at the same cycle as the data. This sine wave has n wave numbers in the length L of the line sensor, and its wavelength p (= L / n) is hereinafter referred to as a filter pitch.

Next, when the weighting function data C _i (i = 1,2, ... N) is read, even if the subscripts are equal to the CCD data D _i (i = 1,2, ... N). The product-sum operation is performed by sequentially adding the products n times, and the product-sum value S _a is obtained. Here, the weight function data C _i is, as shown in FIG. 5, the product of the cosine wave and the Hanning function, which is sampled at the same period as the CCD data. Weight function data S _i , C _i
Are respectively given from the weight function memories 15a and 15b.

Further, since the product sum values S _a and S _b are obtained for each sampling, the product sum values of the previous sampling are set to S _a1 and S _b1, and the product sum values of this sampling are set to S _a2 and S _b2. To do.
By doing so, the vectors A ₁ and A ₂ at 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 as in FIG. . Therefore, 1
The phase difference Δφ between the samplings is calculated by the phase difference calculator 7 as the following equation.

Here, the moving distance x ₀ and the rotation angle Δφ are in a proportional relationship, and the proportional constant is a filter pitch p (= L / n) and 2
Since it is a ratio with π, the moving distance x ₀ and the speed V are obtained as follows.

However, the phase difference during one sampling is within one rotation.

Therefore, after that, the phase difference Δφ is summed up by the accumulator 8 and (p / 2π) is accumulated by the multipliers 9 and 10 to obtain the moving distance x ₀ and the velocity V, respectively.

D. Problems to be Solved by the Invention As described above, the distance measuring device using the spatial filter is characterized by non-contact and highly accurate measurement.

However, when the moving speed of the automated guided vehicle increases and the moving distance during one sampling increases, the phase difference Δφ in the phase space exceeds 180 °, and it may have rotated in the positive direction, or may have reversed and rotated in the negative direction. I couldn't judge whether it turned to. In other words, it is impossible to know whether the automated guided vehicle has moved forward or backward. For example, the moving speed of the automated guided vehicle is high, and the phase difference Δφ per sampling is Δφ.
Becomes 270 °, or it retreats and the phase difference Δφ is −9.
I don't know if it reached 0 °.

Therefore, if the reading interval of the line sensor (CCD) 3 and the calculation speed for processing the data are improved, the above-mentioned inconvenience is improved, but there is a limit to the improvement of the calculation speed, etc. could not.

The present invention has been made in view of the above prior art, and an object of the present invention is to provide a distance measuring device using a spatial filter that can reliably determine the moving distance and speed even when the moving speed of the measuring object is high. It is what

E. Means and Actions for Solving the Problem In the present invention, a phase difference memory for storing the phase difference calculated by the distance measuring device at the time of the previous sampling,
A weight function memory for storing a sine wave and a cosine wave whose phase is advanced by the phase difference stored in the phase difference memory as a weight function at the time of this sampling is provided.

Therefore, the weight function moved at the moving speed at the previous sampling is stored in this weight function memory. Therefore, the relative speed of the weight function stored in the weight function memory and the object to be compared is reduced by the moving speed at the previous sampling.

Then, based on the weighting function stored in the weighting function memory, if calculated by the spatial filter calculating unit and the phase difference calculating unit, the moving distance when it is estimated that the moving speed is the same as the moving speed at the previous sampling is calculated. The corresponding phase difference is determined.

Therefore, if an adder that adds the phase difference at the previous sampling to this phase difference and outputs it as the phase difference at the current sampling, the moving distance at the current sampling is calculated.

Therefore, even if the phase difference in the phase space is 180 ° or more between the previous sampling and the current sampling, the moving distance can be measured reliably.

F. Embodiment Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. Incidentally, the same parts as those of the above-mentioned conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows an embodiment of the present invention. As shown in the figure, in this embodiment, the phase of the weighting function at the current sampling is advanced according to the phase difference at the previous sampling.

That is, the reflected light from the road surface 1 enters the line sensor 3 provided on the bottom surface of the vehicle body via the optical system 2. The CCD provided as the line sensor 3 has a large number of photoelectric conversion elements arranged one-dimensionally along the traveling direction.
A signal P corresponding to light and dark is read from each photoelectric conversion element by a read circuit 4, converted into CCD data D ₁ of a digital signal by an A / D converter 6, and then input to a spatial filter operation unit 5. The spatial filter calculation unit 5 extracts an arbitrary frequency component and obtains the sum of products S _a S _b as described above. That is, the weight function data C _i , S _i stored in the weight function memories 15a and 15b.
And the CCD data D _i are sum-of-products calculated by the sum-of-products value S _a S
_b is obtained, and the sum of products S _a S _b is input to the phase difference calculation unit 7, and the phase difference Δφ is obtained by the above-mentioned equation (1).

Here, a phase difference memory 11 that stores the phase difference Δφ _s at the time of the previous sampling is provided, and the phase difference Δφ _s at the time of the previous sampling is input to the address converter 12. The address converter 12 calculates a value for changing the address of the weighting function data according to the phase difference Δφ _s according to the following equation.

Where p = L / n, so In other words, this is the number of elements of the line sensor per unit cycle (N / n) and multiplying the phase difference [Delta] [phi _s, is obtained by a number of elements corresponding to the phase difference [Delta] [phi _s. However, N is the number of elements of the line sensor (CCD).

This ΔN is stored in the memory 13 and input to the read address circuit 14. The read address circuit 14 reads the addresses, which are sequentially added one by one from a predetermined start address, from the sine wave data N times to read the load function data C and D.
Is stored in the weight function memories 15a and 15b as

Here, in the read address circuit 14, the start address provided with ΔN is used as a new start address. Therefore, the weighting function stored in the weighting function memories 15a and 15b has a phase shifted by Δφ _s from that in the previous sampling, as shown in FIG. Therefore, as the sum of products calculation in the spatial filter calculator 5, the weight function data C _i , S _i and the CCD data D _i whose subscripts are shifted by ΔN are sequentially summed.

The spatial filter calculation unit 5 and the phase difference calculation unit 7 calculate Δφ using the sum of products S _a S _b as described above.

If the phase difference Δφ is zero, it means that the distance has been estimated to have moved at the speed calculated and calculated at the previous sampling until the current sampling. Therefore, the distance moved between the previous sampling and the current sampling also matches the distance obtained at the previous sampling. Further, when the phase difference Δφ is not zero, it means that the distance estimated to move at the speed calculated at the previous sampling and the distance actually moved to the current sampling do not match.

Therefore, the adder 16 adds the phase difference Δφ _s at the previous sampling to this Δφ and outputs it as the phase difference Δφ _a at the current sampling, which is accumulated by the accumulator 8 and the multiplier 9 The distance traveled and the speed are calculated by multiplying by 10 and 10. The phase difference Δφ _s at the previous sampling is stored in the phase difference memory 11, and after this phase difference Δφ _s is output, the phase difference memory 11 stores the phase difference Δφ _a at this sampling as the previous sampling value. To do.

As described above, in this embodiment, the phase of the weighting function at the time of this sampling is advanced according to the phase difference at the time of the previous sampling, so that a phase difference of 180 ° or more in the phase space can be obtained during one sampling. Even when moving at high speed, it is possible to easily calculate the moving distance and speed by determining whether the vehicle has moved forward or backward.

In the above embodiment, the load function data S _i and C _i are
As shown in FIG. 2, since the Hanning function is not multiplied in advance, it is advisable to multiply the CCD data by the Hanning function.

G. Effect of the Invention As described above in detail based on the embodiments, the present invention estimates the phase in the phase space at the current sampling time from the moving speed at the previous sampling time and the estimated phase. Since the phase difference between one sampling is calculated from the actual phase, even when moving at high speed,
It is possible to reliably calculate the moving distance and the speed.

[Brief description of drawings]

FIG. 1 is a block diagram of a spatial filter distance measuring device according to a first embodiment of the present invention, FIG. 2 is a graph showing spatial filter output waveforms at the time of the previous sampling and the present sampling, and FIG. Configuration diagram of the spatial filter distance measuring device,
FIG. 4 is an explanatory view showing a phase space, and FIG. 5 is a graph showing a product of a weighting function and a Hanning function. In the drawings, 1 is a road surface, 2 is an optical system, 3 is a line sensor, 4 is a readout circuit, 5 is a spatial filter operation unit, 6 is an A / D converter, 7 is a phase difference operation unit, 8 is an accumulator, Reference numerals 9 and 10 are multipliers, 11 is a phase difference memory, 12 is an address conversion circuit, 13 is a memory, 14 is an address read circuit, and 15a and 15b are weight function memories.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-266606 (JP, A) JP-A-2-278312 (JP, A) JP-A 58-3483 (JP, A) JP-B 61- 36161 (JP, B2) JP-B 4-67613 (JP, B2) JP-B 61-43641 (JP, B2) JP-B 6-50728 (JP, Y2)

Claims (1)

(57) [Scope of utility model registration request] 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 for each sampling from the readout circuit. A sine wave and a cosine wave are separately multiplied as a weighting function and integrated within a predetermined range, and a spatial filter calculation unit that extracts an arbitrary frequency component, and two signals extracted by the spatial filter calculation unit A phase difference computing unit that computes a phase difference centered on the origin on the phase plane of a vector that is two-dimensional coordinates, and a moving distance that is proportional to the phase difference obtained by the phase difference computing unit. In a distance measuring device using a spatial filter having a distance calculating unit, a phase difference memory for storing the phase difference calculated by the distance measuring device at the time of the previous sampling. A weight function memory that stores a sine wave and a cosine wave whose phase is advanced by the phase difference stored in the phase difference memory as a weight function at the time of this sampling, and a weight function stored in the weight function memory. Based on the spatial filter calculation unit, the phase difference calculated by the phase difference calculation unit is added with a phase difference at the time of the previous sampling, and an adder for outputting the phase difference at the time of the current sampling is provided. A distance measuring device using a spatial filter, wherein the distance calculating unit calculates a moving distance based on the output phase difference.