JPH0650728Y2 - Distance measuring device with spatial filter - Google Patents

Description

[Detailed Description of the Device] A. Field of Industrial Application The present invention is an improved distance measuring device using a spatial filter.

B. Outline of the device In the distance measuring device using the spatial filter, the frequency component of the spatial filter to be noticed decreased because the reflected light from the road surface suddenly changed, and as a result, the absolute value of the vector on the phase plane corresponding to the moving distance. However, in the present invention, sinusoidal waves with different phases,
Since the two types of spatial filters based on cosine waves are used, it is possible to improve the measurement accuracy by using a vector having a large absolute value in the phase space.

C. Conventional technology Conventionally, in automatic driving of unmanned guided vehicles, 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 tacho-generator 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 according to the rotation of the axle.

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

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

A distance measuring method using this spatial filter is shown in FIG.
This will be described with reference to FIG.

As shown in FIGS. 5 and 6, the reflected light from the road surface 1 is captured by the optical system 2, and the line sensor (CCD) 3
Thus, it is sampled at a predetermined cycle and converted into an electric signal. Here, although the reflected light from the road surface 1 is composed of a combination of various kinds of frequencies,
If the materials and surrounding environment are constant, the combination is considered to be almost constant. Then, the optical system 2 and the line sensor 3
If the above is provided on the bottom surface of the vehicle (not shown), the fluctuation will be slightly repeated as the vehicle travels.

The output from the licensor 3 passes through the read circuit 4 and is then 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 signal P that has passed through the read circuit 4 is converted into a digital signal by the A / D converter 6, but when expanded into a Fourier series, it becomes as follows.

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

The Fourier class A _i (x _o ), B _i (x _o ) is given by the following equation.

A _i (x _o ) = (2 / L) ・ ▲ ∫ ^L _o ▼ P ・ cos (k ・ i ・ x) dx
… (2) B _i (x _o ) ＝ (2 / L) ・ ▲ ∫ ^L _o ▼ P ・ sin (k ・ i ・ x) dx
(3) These signals P are each multiplied by a cosine wave and sine waves S ₁ and S ₂ of a specific frequency shown in the following equations as spatial filters, and integrated in a predetermined range.

_{S 1 = F · cos (n} · k · x) ... (4) S 2 = F · sin (n · k · x) ... (5) a (X o = ▲ ∫ L o ▼ P · S 2 d x = F ・ B _n (X _o ) ・ L / 2…
(6) b (X _o = ▲ ∫ ^L _o ▼ P ・ S ₁ d _x = F ・ A _n (X _o ) ・ L / 2…
(7) Here, if the output P from the line sensor is due to reflected light having a constant condition such as a road surface or environment, a certain nth-order component should change continuously in a triangular function. Yes, for example, as shown in the following formula.

P _n (l) = G · sin (n · k · l + φ) (8) Therefore, the n-th order Fourier coefficients A _n and B _n are obtained as follows.

A _n (X _o ) ＝ (2 / L) ・ ▲ ∫ ^L _o ▼ P _n (x _o ＋ x) ・ cos (k ・
n · x) dx = 2 / L ▲ ∫ L o ▼ Gsin {n · k (x o + x) + φ} · cos (k
・ N ・ x) dx = G / L ▲ ∫ ^L _o ▼ sin (2nkx ＋ nkx _o ＋ φ) ＋ sin (nkx _o ＋
φ) dx = G / L ・ L ・ sin (nkx _o + φ) = G ・ sin (nkx _o + φ) (9) Similarly, B _n (x _o ) = G ・ cos (nkx _o + φ) (10) (9) ) Equation (10) is substituted into the above equations (6) and (7), and arranged as follows.

a (x _o ) = (FL / 2) ・ Gcos (nkx _o + φ) (11) b (x _o ) = (FL / 2) ・ Gsin (nkx _o + φ) (12) Obtained in this way a (x _o ), b (x _o ) vibrate like a trigonometric function, and are then input to the moving distance calculation unit 7.

Here, the moving distance calculation unit 7 determines the rotation angle ρ about the origin on the phase plane shown in FIG. 8 of the vector A whose two-dimensional coordinates are a (x _o ), b (x _o ). Ask. That is, as shown in FIG. 8, a vector A having two-dimensional coordinates of a (x _o ) and b (x _o ) rotates at a rotation angle nkx _o proportional to the movement distance X _o . Therefore, the following relational expression holds from FIG.

nkx _o + φ = 2πm + ρ (13) where m is the number of revolutions around the origin, ρ = arctaR (b (x _o ) / a (x _o )), (O ≦ ρ ≦ 2π) φ is the initial value ρ _{t = 0} .

Therefore, if the equation (13) is modified, the moving distance x _{o to be obtained} is given by the following equation.

x _o = m · p + (ρ−φ) p / 2π (14) where p is the filter pitch (= L / n). C in Fig. 5
The PU8, RAM9, and ROM10 constitute the spatial filter calculation unit 5 and the moving distance calculation unit. Further, the moving distance x _o is differentiated with time to obtain the velocity.

D. Problem to be Solved by the Invention However, in the above-described conventional method, when the reflected light from the road surface is irregular or suddenly changes, the output of the frequency component of interest is reduced, and the phase plane shown in FIG. Vector A in
The absolute value of was to be reduced. Even if the absolute value of the vector A becomes small, the measurement of the rotation angle ρ and the rotation speed m of the vector A does not have any problem theoretically, but in reality, the absolute value of the vector A cannot be small. The higher the accuracy, the lower the measurement accuracy.

The present invention relates to a distance measuring device using a spatial filter that can improve measurement accuracy by using a larger vector in a phase plane even when reflected light from a road surface becomes irregular and suddenly changes. .

E. Means and Actions for Solving the Problems In the present invention, two types of spatial filter arithmetic units having different phases of the sine wave and the cosine wave used as the spatial filter are provided and obtained by these spatial filter arithmetic units. The moving distance is calculated using the one having the larger absolute value out of the two vectors. Therefore, even if one vector becomes smaller as a result of the part where the reflected light changes abruptly within the phase-shifted range of the spatial filter, the other vector is used, so that the measurement accuracy is improved.

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

FIG. 1 shows an embodiment of the present invention. As shown in the figure,
In this embodiment, first and second spatial filter arithmetic units 9 and 10 are provided. That is, the reflected light from the road surface 1 is reflected by the optical system 2
Are photographed by the line sensor 3, sampled at a predetermined cycle by the line sensor 3, passed through the readout circuit 4, converted into a digital signal by the A / D converter 6, and then processed by the first spatial filter calculation unit 9 and the second spatial filter calculation. Input to part 10. First
Since the first and second spatial filter calculation units 9 and 10 have the same configuration as the above-described conventional spatial filter calculation unit 5, the calculation process will not be repeated, but the sine wave and cosine wave used as the spatial filter will not be repeated. Are out of phase. That is,
In the conventional spatial filter, the sine wave a and the cosine wave b cover the entire range of the licensor as shown in FIG.
In this embodiment, the entire range of the line sensor is covered by partially overlapping the sine waves C and D and the cosine waves E and F whose phases are shifted by two cycles. In FIGS. 3 and 7, the sine wave and the cosine wave are passed through the Hanning window so that they converge at the front and rear portions of the measurement range, but such a Hanning window may not be passed.

As shown in FIG. 2, the flow chart of the first and second spatial filter arithmetic units 9 and 10 sequentially performs arithmetic processing of the first spatial filter and the second spatial filter, and the linear sensor (CC
Repeat for the number of elements in D).

The signals a _n , b _n , c _n , and d _n thus obtained are passed through the low-pass filters 11, 12, 13, and 14, respectively, and then the previous value a
It is input to the phase calculators 15 and 16 together with _n-1 , b _n-1 , c _n-1 , and d _n-1 . Here, the subscript of the signal indicates the number of times of sampling.

The phase difference calculators 15 and 16 have a rotation angle Δ corresponding to the moving distance from the last sampling to the current sampling.
ρ ₁ and Δρ ₂ are calculated. First, regarding Δρ ₁ ,
As shown in FIG. 6B, the absolute values of the inner product and outer product of the vector (a _n , b _n ) and the vector (a _n-1 , b _n-1 ) are obtained.

Similarly, Δρ ₂ is obtained as follows.

On the other hand, the signals a _n , b _n , c _n , and d _n are input to the amplitude calculation units 17 and 18, and the absolute value of the vector A ₁ having (a _n and b _n as coordinate values) and (c _n , d _n The absolute value of the vector A ₂ with the coordinate value of is calculated as follows.

The absolute values A ₁ and A ₂ pass through the low pass filters 19 and 20, respectively, and are compared by the comparator 21. Comparator 21
Is, A ₁ is turned on the switch for selecting (as shown in FIG. 1 (b) (c)) Δρ 1 if Re larger than A _2, is A ₁ in the opposite
If it is smaller than A _2, the switch for selecting Δρ ₂ is turned on. The selected Δρ ₁ or Δρ ₂ is integrated by the accumulator 22 to obtain ρ. After that, the moving distance is obtained in the same manner as the above-mentioned conventional technique. The above calculation is performed according to the flowchart of FIG.

Here, Δρ ₁ and Δρ ₂ are logically the same value,
If the absolute value of the vector is small, the error becomes relatively large,
If the moving distance is calculated using this, the accuracy will decrease. Especially when the reflected light from the road surface changes abruptly, the output of the frequency component of interest decreases, and as a result, the absolute value of either vector may decrease, but if Δρ by the other vector is used, The measurement accuracy does not decrease. On the contrary, when the output of the frequency component of interest increases due to the sudden change of the reflected light and the absolute value of either vector increases, Δ
The measurement accuracy using ρ will be improved. The comparator 21 may compare the vector absolute values A ₁ and A ₂ for each sampling.

G. Effect of Device As described above in detail with reference to the embodiments, in the present invention, two kinds of spatial filter operation units having different phases of the spatial filter are provided, and Since the one having the larger absolute value is used to calculate the moving distance, the accuracy can be maintained or improved even in a place where the reflected light suddenly changes.

[Brief description of drawings]

1 (a) is a block diagram showing an embodiment of the present invention, FIGS. 1 (b) and (c) are explanatory diagrams showing rotation of a vector in a phase plane, and FIG. 2 is a first and a second space. FIG. 3 is a flow chart of the filter calculation unit, FIG. 3 is a graph showing the spatial filter of the present invention, FIG. 4 is a flow chart for calculating the rotation angle ρ corresponding to the moving distance, and FIG. FIG. 6 is a block diagram of the device, FIG. 7 is a graph showing a conventional spatial filter, and FIG. 8 is an explanatory diagram showing a vector and its rotation angle in a phase plane. In the drawing, 1 is a road surface, 2 is an optical system, 3 is a licensor, 4 is a readout circuit, 6 is an A / D converter, 9 is a first spatial filter operation unit, 10 is a second spatial filter operation unit, 11, 12 , 13, 14, 19, 20 are low-pass filters, 15, 16 are phase difference calculation units, 17, 18 are amplitude calculation units, 21 is a comparator, and 22 is an accumulator.

Claims (1)

[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 sine wave and a cosine wave are respectively multiplied, and an arbitrary frequency component is extracted by integrating within a predetermined range, and a sine wave and a cosine wave signal a and b oscillating at the frequency are obtained. A travel distance calculation unit for calculating the moving distance of the vehicle body from the rotation angle of the vector A ₁ having two-dimensional coordinates of the sine wave and cosine wave signals a and b from the filter calculation unit about the origin on the phase plane In a distance measuring device using a spatial filter having, a sine wave whose phase is different from that of the sine wave or cosine wave in the electric signal from the photodetection conversion unit,
The cosine wave is multiplied, and the same frequency component as the above frequency is extracted by integrating within a predetermined range, and a sine wave vibrating at the frequency and a cosine wave signal c, d are added to the spatial filter calculation section, and the sine wave is added. A comparator for comparing the absolute value of the vector A ₂ having the two-dimensional coordinates of the wave and cosine wave signals c and d with the absolute value of the vector A ₁ is provided, and the vector A ₁ or A _{2 having} a large absolute value is provided.
A distance measuring device using a spatial filter, wherein the travel distance calculation unit calculates the travel distance of the vehicle body by selectively using