JP2004086453A - Guidance device for automatic guided vehicles - Google Patents

Abstract

An unmanned conveyance that can improve position detection accuracy without increasing the number of sensors, and that can cope with a moving path having a branch, and does not cause a response delay even when traveling at high speed. To provide a vehicle guidance device.
In an automatic guided vehicle guiding device for detecting the position of a guide tape installed along a movement path on an unmanned transport vehicle side, a plurality of guide tapes installed on the unmanned transport vehicle side in a direction intersecting with the guide tape are provided. , Detecting means for specifying two adjacent sensors enclosing the edge of the guide tape from output voltages of the plurality of sensors, reference voltage setting means for setting a reference voltage, and the two adjacent sensors And calculating means for calculating a position corresponding to the reference voltage as a position of an edge of the guide tape from a relationship between each position and each output voltage.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automatic guided vehicle (AGV) guidance device that is guided by a guide mark installed on a floor surface and travels in a factory or a warehouse along a desired movement route.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a technique relating to guidance of an automatic guided vehicle, for example, there is a method for detecting a displacement of a self-propelled vehicle disclosed in Japanese Patent No. 2857703, which has a patent right of the present applicant. In this method, the strength of a magnetic field generated by a guide magnet installed on the floor is detected by a plurality of magnetic sensors arranged in a line in the left-right direction on the self-propelled vehicle. Then, the waveform obtained by connecting the detection outputs of the plurality of magnetic sensors is subjected to discrete Fourier transform using the length from the magnetic sensor located at the left end to the magnetic sensor located at the right end of the plurality of magnetic sensors as one cycle of the fundamental wave. By detecting the amount of displacement between the self-propelled vehicle and the magnet for guiding based on the phase of the fundamental wave, high resolution is achieved with a small number of magnetic sensors.
[0003]
Japanese Unexamined Patent Application Publication No. 9-269820 discloses an unmanned transport that detects a guide tape laid along a moving path on a side of an unmanned transport vehicle by a plurality of sensors arranged in a line in a direction intersecting the guide tape. A vehicle guidance device is disclosed. In this apparatus, the vehicle travels while continuously detecting the edge portion of the guide tape with the sensor, so that it is possible to cope with a branched moving path. Also, by narrowing the arrangement intervals of the sensors facing the edge portion of the guide tape, the detection accuracy is improved, and the swing width in the left and right direction of the automatic guided vehicle during traveling is reduced to improve the stopping accuracy. I have.
[0004]
[Problems to be solved by the invention]
However, with the diversification and sophistication of user needs for the automatic guided vehicle, problems that cannot be dealt with by the conventional automatic guided vehicle guiding device as described above have been pointed out, and it has been demanded to overcome them. For example, in the method for detecting a displacement of a self-propelled vehicle described in Japanese Patent No. 2857703, since the center position of the guide magnets installed at intervals on the moving path is recognized, the branched moving path is , Could not respond. Further, since the Fourier transform is required, the calculation process is complicated and the calculation speed is slow, and it cannot be applied to an unmanned guided vehicle running at high speed.
[0005]
On the other hand, in the automatic guided vehicle guidance device disclosed in Japanese Patent Application Laid-Open No. 9-269820, since the detection accuracy is determined by the interval between the sensors, many sensors are required to increase the detection accuracy, and the cost increases. Had become. Furthermore, the resolution of the sensor is limited due to the limited size of the sensor.
[0006]
Therefore, an object of the present invention is to improve the position detection accuracy without increasing the number of sensors, to be able to cope with a moving route having a branch, and to cause a response delay even when traveling at high speed. It is an object of the present invention to provide an automatic guided vehicle guidance apparatus that does not have any problem.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is an automatic guided vehicle guiding device that detects a position of a guide tape installed along a movement path on an unmanned transport vehicle side. A plurality of sensors installed in a direction intersecting the guide tape, detection means for specifying two adjacent sensors enclosing the edge of the guide tape from output voltages of the plurality of sensors, and a reference for setting a reference voltage The configuration includes a voltage setting unit and an arithmetic unit that calculates a position of an edge of the guide tape based on output voltages and positions of the two adjacent sensors and the reference voltage.
[0008]
According to a second aspect of the present invention, in addition to the configuration of the first aspect, the calculating means linearly interpolates the relationship between the output voltage and the position of the two adjacent sensors and determines a position corresponding to the reference voltage. It is configured to calculate.
[0009]
According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, a magnetic tape is used as a guide tape installed along a movement path, and a magnetic sensor is used as a sensor. I have.
[0010]
[Action]
According to the first aspect of the present invention, the position corresponding to the reference voltage is calculated as the position of the edge of the guide tape from the relationship between each position of the two adjacent sensors surrounding the edge of the guide tape and each output voltage. Because of the calculation means, the position of the edge of the guide tape can be specified with a fineness equal to or greater than the interval between the sensors.
[0011]
According to the second aspect of the present invention, in addition to the operation of the first aspect of the present invention, each position and each output voltage of two adjacent sensors enclosing the edge of the guide tape are linearly interpolated as the arithmetic means, Since the position corresponding to the reference voltage is calculated, the calculation speed is increased.
[0012]
According to the third aspect of the invention, in addition to the operation of the first or second aspect of the invention, a magnetic tape is used as the guide tape and a magnetic sensor is used as the sensor, so that the work of laying the moving path is easy. In addition, a guiding error due to contamination of the guide tape or the like is avoided.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual diagram schematically showing an entire automatic guided vehicle guidance apparatus according to the present invention. A guide mark G made of a magnetic tape is laid on the floor along the movement path. In the automatic guided vehicle 100 (the so-called AGV), caster wheels 110 are arranged at four corners, and a magnetic sensor array 120 in which a plurality of magnetic sensors are arranged in a line is arranged between the front and rear caster wheels. . In addition, a traveling wheel 130 that is rotationally driven by a traveling motor 140 is installed at substantially the center of the left and right sides of the automatic guided vehicle 100. In this embodiment, the magnetic sensor array 120 uses Hall elements arranged in a line at ± 10 mm at intervals of 10 mm.
[0014]
Next, a mechanism in which the automatic guided vehicle guidance device of the present invention detects the position of the guide tape laid on the floor will be described with reference to FIGS. FIG. 2 shows an output of each magnetic sensor when the magnetic sensor arrays are arranged so as to be orthogonal to each other with the center aligned on a magnetic tape having a width of 50 mm laid on a floor surface (iron plate having a thickness of 3.2 mm). Is shown. The measurement was performed while changing the distance between the magnetic sensor array and the magnetic tape to 20, 30, and 40 mm, and the respective measurement results are shown on the same graph. The smaller the distance between the magnetic sensor array and the magnetic tape is, the larger the output can be obtained, which is preferable. However, if the distance is up to about 40 mm, there is no practical problem.
[0015]
As is clear from this figure, the output of the magnetic sensor array forms a waveform that peaks at the center of the magnetic tape and rises sharply at both ends of the magnetic tape. In a conventional automatic guided vehicle guidance device, the position of the magnetic sensor where the sign of the output of the magnetic sensor array changes is recognized as the end of the magnetic tape. Therefore, the resolution of positioning was limited to 10 mm in the interval between sensors, that is, in the case of the magnetic sensor array described above.
[0016]
In the present invention, the end of the magnetic tape is recognized by the following method. First, a reference voltage for calculating the end of the magnetic tape is determined from the measurement results in FIG. In the case of this embodiment, the output voltage of the magnetic sensor at the end of the magnetic tape is about 0.2 to 0.4 V, but keeps a substantially constant value even when the distance between the magnetic tape and the magnetic sensor array changes. The indicated 0.3 V was set as the reference voltage VL.
[0017]
Next, by comparing the output voltage of each sensor of the magnetic sensor array with the reference voltage, two adjacent magnetic sensors whose output voltage shows two values including the reference voltage value are specified. Then, based on the positions (XM, XN) and the output voltages (VM, VN) of the two magnetic sensors (SM, SN), a position XL corresponding to the reference voltage VL is calculated by the following equation.
XL = {(VN−VL) · XM + (VL−VM) · XN} / (VN−VM)
[0018]
The calculated XL is recognized as the end of the magnetic tape. The above calculation formula is nothing but the fact that a point which internally divides the distance (XN-XM) between the two sensors by the ratio of (VN-VL) :( VL-VM) is obtained. That is, as shown in FIG. 3, the relationship between the position (XM, XN) and the output voltage (VM, VN) of two adjacent magnetic sensors (SM, SN) is linearly interpolated, and the position corresponding to the reference voltage VL is obtained. The end of the magnetic tape is specified by calculating XL.
[0019]
The center XC of the magnetic tape is calculated by performing a weighted average of the position Xi of the magnetic sensor Si indicating a positive output voltage and the output voltage Vi based on the following equation.
XC = ΣXi · Vi / ΣVi
Here, the reason why the weighted average magnetic sensor is limited to the magnetic sensor indicating a positive output voltage is that the output voltage of the sensor fluctuates greatly in the vicinity of the end of the magnetic tape, so that the center of the magnetic sensor array is If the sensor width is shifted from the center of the magnetic tape, there is no problem if the sensor width is infinite, but in reality, since the sensor width is finite, the integrated negative value is biased left and right, This is because the error of the calculated XC increases.
[0020]
Next, the right end position, the left end position, and the center position of the magnetic tape were calculated by the above method using the magnetic tapes arranged as shown in FIG. FIG. 5 shows the results together with actual values.
[0021]
As is clear from FIG. 5, the center position is correctly calculated in the linear portion (the range of y = 0 to 50 mm) of the magnetic tape. In addition, the right end position and the left end position of the magnetic tape have an error of about 9 mm from the actual value, but the value is constant in the entire measurement area. This is an error caused by setting the voltage reference value to 0.3 V. Prior to the implementation, the voltage reference value is once adjusted (zero point adjustment) so that the calculated value matches the actual value. This makes it possible to reduce the error. In the case of the present embodiment, the error between the calculated value and the actual value could be made 1 mm or less.
[0022]
On the other hand, in the branch area of the magnetic tape (y = 50 to 300 mm), the calculated value at the center position is different from the actual value. This is because the magnetic sensor array measures the two magnetic tapes after branching in the branch area. However, in the branch area, the magnetic tape travels while following the right end position or the left end position of the magnetic tape according to the traveling route (the right route or the left route after the branch), so that there is no operational problem.
[0023]
In FIG. 5, the reason why the tape right end position is constant at 300 mm at y = 250 mm or more is that the sensor width is set to 300 mm, so that further calculation is not possible.
[0024]
In the present embodiment, two adjacent magnetic sensors (SM, SN) indicating two values including the reference voltage value are specified, and the positions (XM, XN) and output voltages (VM, VN) of the two magnetic sensors are specified. ) Is linearly interpolated to calculate the position XL corresponding to the reference voltage VL, thereby obtaining the right end position or the left end position. However, it is also possible to interpolate using a quadratic curve or a cubic curve using the spline interpolation method. It is possible. However, as described above, when the sensor interval is set to 10 mm, a linear interpolation provides a positioning accuracy of 1 mm corresponding to one-tenth of the sensor interval, so that linear interpolation is practically sufficient. Moreover, linear interpolation is preferable because the calculation method is simple and the calculation processing speed can be increased.
[0025]
Further, in the present embodiment, an example of a magnetic induction type using a magnetic tape as a guide tape and a magnetic sensor as a sensor is described, but the same applies to an optical induction type using a reflection tape and an optical sensor. Applicable to
[0026]
【The invention's effect】
According to the first aspect of the present invention, the position corresponding to the reference voltage is calculated as the position of the edge of the guide tape from the relationship between each position of the two adjacent sensors surrounding the edge of the guide tape and each output voltage. With the configuration including the calculation means, the position of the edge of the guide tape can be specified with a fineness equal to or greater than the interval between the sensors.
[0027]
According to the second aspect of the present invention, in addition to the effect of the first aspect, as the calculating means, each position and each output voltage of two adjacent sensors enclosing the edge of the guide tape are linearly interpolated, Since the position corresponding to the reference voltage is calculated, a resolution of 1/10 or more of the sensor interval can be achieved without reducing the calculation speed.
[0028]
According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, a magnetic guiding system using a magnetic tape as a guide tape and a magnetic sensor as a sensor is employed, so that a moving path is laid. The work is facilitated, and guidance errors due to contamination of the guide tape or the like are avoided.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an automatic guided vehicle guiding device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a relationship between a sensor output and a guide tape of the automatic guided vehicle guiding device of the present invention.
FIG. 3 is a diagram illustrating linear interpolation according to the present invention.
FIG. 4 is a diagram showing the arrangement of magnetic tapes and sensors used in a positioning accuracy test of the present invention.
FIG. 5 is a diagram showing a result of a positioning accuracy test of the present invention.
[Explanation of symbols]
100: automatic guided vehicle 110: caster wheel 120: magnetic sensor array 130: running wheel 140: running motor G: guide tape

Claims (3)

In an automatic guided vehicle guidance device that detects the position of the guide tape installed along the movement path on the automatic guided vehicle side,
On the automatic guided vehicle side,
A plurality of sensors installed in a direction intersecting with the guide tape,
Detecting means for specifying, from output voltages of the plurality of sensors, two adjacent sensors that enclose the edge of the guide tape;
Reference voltage setting means for setting a reference voltage;
Calculating means for calculating a position corresponding to the reference voltage as a position of an edge of the guide tape from a relationship between each position of the two adjacent sensors and each output voltage. Guidance device. 2. The automatic guided vehicle guidance device according to claim 1, wherein the calculation unit linearly interpolates output voltages and positions of the two adjacent sensors to calculate a position corresponding to the reference voltage. 3. 3. The automatic guided vehicle guidance device according to claim 1, wherein the guide tape is a magnetic tape, and the sensor is a magnetic sensor.

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