JP2921180B2 - Light guide line detection method using line sensor - 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 detecting a light guide line using a line sensor, and more particularly to a method for accurately detecting a light guide line.

[0002]

2. Description of the Related Art An unmanned vehicle is a device that travels along a traveling path in various factories, warehouses, offices, and the like, and conveys parts, products, small articles, and the like. There is a light guiding type as one method of guiding an unmanned vehicle along a traveling path by unmanned traveling. In the light-guided type,
Draw a white line on the floor or attach a light reflective tape, and detect the white line or the light reflective tape with an unmanned vehicle's optical sensor to detect the white line and the light reflective tape (both are collectively referred to as "light guide lines").
Drive unmanned along.

FIG. 7 is a plan view showing an example of a light guiding type. A white line 2 serving as a light guiding line is drawn on a floor surface 1, and an unmanned vehicle 3 is provided with a line sensor 4. The light emitted from the unmanned vehicle 3 side and reflected by the floor surface 1 and the white line 2 is received by the line sensor 4, and the electric charge of the n photoelectric conversion elements (CCD) of the line sensor 4 is 1 The nth element (for example, the right end) in order from the element (for example, the left end)
Is read out.

FIG. 8 shows an output signal (voltage) of the line sensor 4.
A shows an example of C, which receives reflected light from the floor surface 1
The output of the CD is small and the CC receiving the reflected light from the white line 2
The output of D is large. The output signal A shown in FIG.
Is binarized at a threshold level V _S. FIG. 9 shows the binarized signal a. The unmanned vehicle 3 can travel unmanned along the white line 2 by steering the controller so that the high level portion of the signal a, that is, the portion indicating the white line 2 is located at the center of the line sensor 4.

[0005]

However, since unmanned vehicles are used in various situations, the difference in contrast between the light guide line and the floor may be reduced in the middle of the traveling route depending on the place of use. is there. Also, due to dirt or the like, the reflectance on the light guide line and the floor surface is low, so that the amount of light received by the sensor is small and the sensor output value may be reduced as a whole.

That is, when the contrast difference is small, the output of the line sensor 4 becomes as shown in FIG.
If the level of the signal indicating the white line 2 and the level of the signal indicating the floor 1 are close to each other and the threshold level V _S is not set to an optimum position between the two signal levels, the floor 1 and the white line 2 may be distinguished from each other. Cannot be binarized. If the entire signal A shown in FIG. 10 is amplified, the level difference between the signal indicating the white line 2 and the signal indicating the floor 1 increases, so that the threshold level can be easily set.
At first glance. However, since the output of the line sensor 4 includes a direct current component, amplifying the entire signal to such an extent that the level difference between the signal indicating the white line 2 and the signal indicating the floor surface 1 becomes considerably large is difficult in a normal operational amplifier or the like. Impossible and unrealistic.

[0007] When the reflectivity on the light guide line or the floor surface decreases, the entire output of the line sensor 4 decreases as shown in FIG. At this time, unless the threshold level is changed from V _S to V _S ″, binarization cannot be performed so that the floor surface 1 and the white line 2 can be distinguished. However, the threshold level is changed to the optimum position and instantaneously. It is extremely difficult to do.

According to the present invention, in consideration of the above prior art, even if the contrast between the light guide line and the floor is not so clear or the contrast changes suddenly during traveling, the light guide line can be reliably detected. An object of the present invention is to provide a light guide line detection method using a line sensor.

[0009]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems is provided in an unmanned vehicle traveling along a light guide line installed on a floor, and is provided with light reflected on the floor and the light guide line. In a method of detecting a light guiding line based on an output signal output from a line sensor that receives light, a gain is adjusted by removing a direct current component from an output signal of the line sensor and adjusting a gain of the output signal from which the direct current component is removed. By making the peak value of the adjusted output signal the same as the preset peak command value, and comparing the gain-adjusted output signal with a threshold level that is smaller than the peak command value by a certain level, the gain-adjusted output signal is binarized. It is characterized in that

[0010]

According to the present invention, since the DC component is removed from the output signal of the line sensor, the output signal after removing the DC component can be greatly amplified to increase the difference between the signal indicating the floor surface and the signal indicating the light guiding line. Since the peak value of the amplified output signal is made constant, the threshold level can be fixed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, a line sensor 4 is provided in an unmanned vehicle, and has a configuration in which CCDs are linearly arranged. The line sensor 4 receives the light reflected by the floor surface 1 and the white line 2 and generates an electric charge according to the amount of light received. This electric charge is read out by the line sensor readout circuit 5 and the line sensor output signal A (FIG. a)).

The DC cut circuit 6 has a subtraction section 6a and integration functions 6b and 6c. In the blocks showing the integration functions 6b and 6c, S represents a Laplace operator and K and K ₁
Represents a constant. Although the specific circuit configuration of this DC component cut circuit 6 will be described later, this DC component cut circuit 6 cuts the DC component of the output signal A (FIG. 2A) of the line sensor 4 and ), An output signal A ° having no DC component is output. Focusing on the output signal A °, the signal portion indicating the white line 2 has the highest level as a level.
Always on the plus side.

The gain adjustment circuit 7 has a multiplication unit 7a, a positive peak hold unit 7b, a subtraction unit 7c, and an integration function 7d. In the block showing the integration function 7d, S represents a Laplace operator, and K ₂ and K ₃ represent constants.
The plus direction peak hold unit 7b detects the peak P (see FIG. 2C) of the output signal A ° from which the DC component has been cut. Although a specific circuit configuration of the gain adjustment circuit 7 will be described later,
The gain adjustment circuit 7 controls the output signal A ° so that the peak value of the output signal becomes a preset peak command value P °.
And outputs an output signal A "(see FIG. 2D) whose gain is adjusted. That is, even if the peak value level of the output signal A ° changes, the peak value of the output signal A" always becomes the peak command value P. °, automatic gain adjustment (AGC) is performed.

The comparator 8 has a threshold level V _S ° which is smaller by a fixed value than the peak command value P °.
(See FIG. 2D). Then, the output signal A ″ whose gain has been adjusted becomes the threshold level V _S
When it is larger than °, the output of the comparator 8 becomes high level, otherwise, it becomes low level and binarization is performed. The high-level signal portion indicates the white line 2,
The low-level signal portion indicates the floor 1.

As described above, in this embodiment, the direct current component is removed from the output signal of the line sensor 4 and the line sensor output signal without the direct current component is amplified, so that the signal indicating the white line and the floor surface are compared. A large level difference from the indicated signal can be obtained. Further, when the DC component is removed from the output signal of the line sensor 4 and amplified, the peak value of the amplified signal A ″ is always adjusted to the peak command value P °, so that the threshold level V _S ″ becomes the peak value. It can be a fixed value smaller than the command value P ° by a fixed value.

As shown in FIG. 10, the present invention removes the DC component even when the difference between the signal level indicating the white line and the signal level indicating the floor is small as shown in FIG. Therefore, the difference between the level indicating the white line and the level indicating the floor can be made large, and binarization can be easily performed. Also, as shown in FIG. 11, even when the level of the output signal A is entirely low, the peak of the signal amplified after removing the DC component is adjusted to the peak command value P °, so that the threshold level V _S ° can be binarized even if it is a fixed value.

FIG. 3 shows a specific configuration of the DC cutoff circuit 6. The DC component cut circuit 6 includes a subtraction section 6a, an amplification section 6d, an averaging (integration) circuit 6e, an addition section 6f, and a sample hold circuit 6g. Averaging circuit 6
e corresponds to the integrating function 6b in FIG. 1, and the fact that the integration of the discrete value system is realized by the sample-hold circuit 6g and the adding unit 6f corresponds to the integrating function 6c in FIG. Then, the output signal A is averaged, sampled and held, and the output signal A is subtracted from the compensation voltage V _H to obtain an output signal A ° in which a DC component is cut. Further, the operation will be described in detail with reference to FIG. 4A shows the output signal A, and FIG. 4B shows the output obtained by integrating the output signal A by the integration function 6b (FIG. 1), that is, the sample-and-hold circuit 6g (FIG. 3). Then, the line sensor output A from pixel 0 to pixel n (time from t1 to t2) is integrated, and the final value Z (n) is held as a sample hold value. If the integrated value of the line sensor, that is, the average of the magnitude is discretized and the average value is controlled to be zero, the DC component of the line sensor output A can be removed. Therefore, a closed loop is formed.

Next, a specific configuration of the gain adjustment circuit 7 is shown in FIG. The gain adjustment circuit 7 includes a multiplication unit 7a, a full-wave rectification / peak hold circuit 7e, a sample hold circuit 7f, a subtraction unit 7c, an amplification unit 7g, an addition unit 7h, and a sample hold circuit 7i. The full-wave rectification / peak hold circuit 7e corresponds to the positive peak hold section 7b in FIG. 1, and forms a discrete closed loop with the amplifier section 7g, the addition section 7h, and the sample hold circuit 7i.
This corresponds to the integration function 7d in FIG. Next, the operation will be described with reference to FIG. 6A shows a DC cut output signal A °, FIG. 6B shows a waveform obtained by full-wave rectifying the signal A °, and FIG. 6C shows a peak hold value of the full-wave rectified signal. . Therefore, the peak value is held from pixel 0 to n pixels, the final value is held by the sample hold circuit 7f, the final hold value is compared with the peak command value P °, and the command value P ° and the held peak are held. The gain of the multiplier 7a is made variable so that the values become the same.

Although the embodiment of FIG. 1 shows an example in which the white line 2 is detected, even if the light guide line is a light reflecting tape, the line can be detected exactly in the same manner as the white line 2.

[0020]

According to the present invention, the contrast between the light guide line and the floor surface is reduced in the middle of the traveling route, or the level of the output signal of the line sensor is reduced. Even if it is lower overall,
The output of the line sensor can be surely binarized (binarized as indicated separately from the floor surface and the light guide line), and the light guide line can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing an output signal of the embodiment.

FIG. 3 is a block diagram showing a specific configuration of a DC component cut circuit.

FIG. 4 is a waveform diagram showing a signal waveform in the DC component cut circuit.

FIG. 5 is a block diagram showing a specific configuration of a gain adjustment circuit.

FIG. 6 is a waveform diagram showing a signal waveform in the gain adjustment circuit.

FIG. 7 is a plan view showing an unmanned vehicle and a floor.

FIG. 8 is a waveform diagram showing an output signal according to the related art.

FIG. 9 is a waveform diagram showing a binarized output signal.

FIG. 10 is a waveform chart showing a waveform of an output signal.

FIG. 11 is a waveform diagram showing a waveform of an output signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Floor surface 2 White line 3 Unmanned vehicle 4 Line sensor 5 Line sensor reading circuit 6 DC cut circuit 7 Gain adjustment circuit 8 Comparator A, A °, A ″ Output signal P ° Peak command value V _S ° Threshold level

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-228307 (JP, A) JP-A-64-74915 (JP, A) JP-A-61-818 (JP, A) JP-A-1- 120208 (JP, A) JP-A-61-169910 (JP, A) JP-A-51-5790 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G05D 1/02

Claims (1)

(57) [Claims] An unmanned vehicle running along a light guide line installed on a floor is provided on an unmanned vehicle based on an output signal output from a line sensor that receives light reflected on the floor and the light guide line. A method for detecting a light guiding line, comprising: removing a DC component from an output signal of a line sensor, and adjusting a gain of the output signal from which the DC component has been removed to thereby set a peak value of the output signal whose gain has been adjusted to a preset peak command value. The light using the line sensor is characterized by binarizing the gain-adjusted output signal by comparing the gain-adjusted output signal with a threshold level smaller than the peak command value by a certain level. Guidance line detection method.