JPH08271269A - Dislocation detection method of self-propelled vehicle - Google Patents

Abstract

PURPOSE: To provide a dislocation detection method, of a self-propelled vehicle, in which the dislocation amount of the self-propelled vehicle from a reference position can be detected at low costs. CONSTITUTION: The intensity of a magnetic field to be generated by a magnet 3, for guidance, which is installed on a floor face is detected by a plurality of magnetic sensors 21 which are installed at a self-propelled vehicle 1 in its right and left directions. While a length up to the magnetic sensor 21 situated on the other side from the magnetic sensor 21 situated on one side of the plurality of magnetic sensors 21 is used as one cycle of fundamental waves, a waveform obtained by connecting respective detection outputs by the plurality of magnetic sensors 21 is discrete-Fourier-transformed, and the displacement amount S (Δx) of the self-propelled vehicle 1 from the magnet 3 for guidance is detected on the basis of the phase of the fundamental waves.

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 positional deviation between a self-propelled vehicle guided by guide magnets installed at a predetermined distance on a floor and a guide magnet. .

[0002]

2. Description of the Related Art A self-propelled vehicle guided along guide magnets installed at predetermined intervals on a floor detects the amount of positional deviation with respect to the guide magnets when passing through the installed guide magnets. The steering amount is determined based on the position shift amount, and the vehicle travels autonomously up to the guide magnet, which is the next traveling target. At this time, due to unevenness of the floor surface during running, or slip between the wheel and the floor,
When the self-propelled vehicle reaches the target guide magnet, a positional deviation of about ± 100 mm may occur depending on the installation distance of the guide magnet.

Therefore, as a method of detecting such a positional deviation amount, conventionally, a method of analogly taking out the differential output of a magnetic sensor arranged in a vehicle in a direction orthogonal to the traveling direction, or A method of digitally detecting by the on / off state of a plurality of magnetic detection switches arranged in a line in the direction orthogonal to the traveling direction, or as another method, a method of detecting the magnetic field in a direction orthogonal to the traveling direction of the vehicle There is a method of arranging dozens of magnetic sensors (Hall elements) and detecting the reversal position of the direction of the magnetic field generated by the guide magnet.

[0004]

However, in the case of detecting the above-mentioned conventional positional deviation amount, the first method described above provides a linear positional detection range of ± 30 m with respect to the positional deviation. narrow. Therefore, it is necessary to shorten the installation interval of the guide magnet so that the positional deviation between the self-propelled vehicle and the guide magnet does not exceed ± 30 mm, which requires an extremely large number of guide magnets, which increases the installation cost. There's a problem.

In the second method, the resolution for detecting the positional deviation amount is restricted by the size of the magnetic detection switch,
The limit is 2-3 mm, and there is a problem when trying to steer a self-propelled vehicle smoothly with high accuracy.

Further, in the third method, it is possible to detect a positional deviation of about ± 100 mm with a resolution of about 1 mm, but it is necessary to arrange an extremely large number of Hall elements, so the signal processing circuit is complicated. Therefore, there is a problem that the cost is extremely high.

In view of the above problems, it is an object of the present invention to provide a method for detecting a positional deviation of a self-propelled vehicle that can detect the positional deviation of the self-propelled vehicle at low cost.

[0008]

According to a first aspect of the present invention, there is provided a method for detecting a displacement of a self-propelled vehicle by detecting the strength of a magnetic field generated by a guide magnet installed on a floor surface on which the self-propelled vehicle travels. In a method for detecting a positional deviation of a self-propelled vehicle, the lateral displacement between the self-propelled vehicle and a guide magnet is detected by a plurality of magnetic sensors arranged in a row in the left-right direction of the self-propelled vehicle. ,
The waveform obtained by connecting the detection outputs of the magnetic sensor is subjected to discrete Fourier transform with the length from the magnetic sensor located on one side to the magnetic sensor located on the other side as one cycle of the fundamental wave to obtain the phase of the fundamental wave. It is characterized in that the amount of positional deviation is detected based on this.

A method of detecting a positional deviation of a vehicle according to a second aspect of the present invention is characterized in that the positional deviation amount is determined when the sign of the total sum of the detection outputs of the magnetic sensor is reversed.

[0010]

The function of calculating the positional deviation amount will be described. When N magnetic sensors provided in the left-right direction detect the strength of the magnetic field generated by the guide magnets, the respective detection outputs of the N magnetic sensors have the vertical axis as the magnetic sensor detection output and the horizontal axis as the magnetic field. As shown in FIG. 1 in which the sensor number is used, the larger the guide magnet, the larger. When the waveform obtained by connecting the detection outputs of the N magnetic sensors is discrete-Fourier-transformed with the length of the arrangement of the N magnetic sensors as one cycle of the fundamental wave −π to + π, the phase of the fundamental wave becomes When the guide magnet is located at the center of the N magnetic sensors, it becomes zero, and when a positional deviation occurs between the magnetic sensor and the guide magnet, the phase of the fundamental wave changes in accordance with the amount of positional deviation.

Therefore, by calculating the following equation (1), the phase shift amount S can be detected by calculating the phase of the fundamental wave corresponding to the magnetic sensor located at the center.

[0012]

[Equation 1]

Next, the principle of detecting the time when the magnetic sensor passes just above the guide magnet will be described based on the magnetic field distribution of the guide magnet. The guide magnet has a predetermined area, but if this is used as a magnetic dipole and the magnetic field distribution is approximately determined, the magnetization intensity H of the magnetic dipole at the magnetic moment m is expressed by polar coordinates, Hr = 2m · cos θ / 4πr ³ (2) Hθ = m · sin θ / 4πr ³ (3) Therefore, the y-direction component of the magnetic field is calculated from these equations, Hy = yz / (x ² + y ² + z ² ) ^5/2 . (4) is obtained.

Here, x is a lateral distance based on the magnetic dipole, y is a traveling direction distance of the self-propelled vehicle based on the magnetic dipole, z is a vertical distance based on the magnetic dipole, and r
Is the radius from the magnetic dipole, and θ is the rotation angle with respect to the magnetic dipole.

In a three-dimensional diagram, the lateral direction is the displacement amount Δx with the guide magnet as the reference, the traveling direction is y with the guide magnet as the reference, and the magnetization distribution in the vertical direction with the guide magnet as the reference ( 2 is shown as relative value). The y-direction component of the strength of magnetization becomes exactly 0 when y = 0,
It gradually increases as it goes away from y = 0, and then gradually starts to decrease when it exceeds a predetermined point. Similarly, in a negative y region, a negative distribution is shown, and it is symmetrical with respect to the x axis.
It also decreases as the absolute value of x increases.

As described above, the y-direction component of the magnetization intensity becomes 0 at the center (y = 0) of the guide magnet 3, and the magnetization direction is reversed before and after that. Therefore, the position detection sensor 2 is calculated by calculating the sum Σf (i) (i = 0, 1 ... N-1) of the detection output f (i) of each magnetic sensor and detecting the inversion of the sign of the sum of the detection outputs. Can be detected just above the guide magnet 3.

Then, when the self-propelled vehicle 1 is positioned directly above the guide magnet 3 and the sign of the sum of the detection outputs of the magnetic sensor is reversed, the detected positional deviation amount is determined. This allows
The displacement of the vehicle can be detected using a small number of magnetic sensors. Further, the amount of positional deviation when the self-propelled vehicle is positioned directly above the guide magnet can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 3 is a schematic plan view showing the relationship between the position sensor and the guide magnet provided in the vehicle. A self-propelled vehicle 1 that is guided by a guide magnet 3 installed on the floor to travel.
Moves in the traveling direction indicated by the arrow, and ideally, the center of the self-propelled vehicle 1 is steered so as to pass through the center of the guide magnet 3. A position sensor 2 is attached to the self-propelled vehicle 1 in a direction in which the longitudinal direction is orthogonal to the traveling direction, that is, in the left-right direction. The position sensor 2 has magnetic sensors 21, 21 ... Are arranged in parallel. The magnetic sensors 21 are installed at a predetermined height from the guide magnets 3, and are arranged in a row at appropriate intervals in a direction in which the strength of the traveling direction component of the self-propelled vehicle 1 in the magnetic field generated by the guide magnets 3 is detected. For example, 10 to 20 pieces are arranged in a length of 400 mm. The guide magnet 3 has a disk shape so that the same magnetic field distribution can be obtained regardless of which direction the vehicle 1 passes.

FIG. 4 is a block diagram showing the construction of an apparatus for carrying out the method for detecting the positional deviation of the vehicle according to the present invention. N
The detection outputs of the magnetic sensors 21, 21 ... Composed of Hall elements are sequentially selected by the multiplexer 4 and input to the analog / digital (A / D) converter 6 through the amplifier 5 and converted into digital signals for arithmetic processing. CPU7
The CPU 7 outputs the calculation result of the positional deviation amount S.

Next, the detection of the amount of positional deviation between the self-propelled vehicle and the guide magnets by the apparatus configured as described above will be described with reference to the flow chart shown in FIG. 5, which shows the control contents of the CPU. The CPU 7 takes in the detection outputs of the N magnetic sensors 21 (i = 0, 1 ... N-1) (S1). Then, the position shift amount S is calculated by the above-mentioned equation (1) (S2). Then, the total sum of the detection outputs of the magnetic sensor 21 (i = 0, 1 ... N-1) is calculated (S3). Then, it is determined whether or not the sign of the total sum of the respective detection outputs of the magnetic sensor 21 is reversed (S4), and the calculation of the positional deviation amount S is continued until it is reversed. When the sign is reversed, it is the time when the vehicle, that is, the position sensor 2 is positioned on the guide magnet 3 as described above.

Therefore, if it is determined that the sign is reversed, the position shift amount S at the time of the determination is determined (S5). As a result, the lateral displacement amount S between the self-propelled vehicle 1 and the guide magnet 3 at the position of the guide magnet 3 can be determined. And
The CPU 7 outputs the signal of the determined position deviation amount S. Subsequently, it is determined whether or not the traveling operation is completed (S6), and the positional deviation amount S is determined every time the self-propelled vehicle 1, that is, the position sensor 2 is located on the guide magnet 3 until it is determined that the traveling operation is completed. CPU
Output from 7. When it is determined that the traveling operation is completed, the control operation for calculating the positional deviation amount S is completed.

FIG. 6 shows the actual positional deviation Δx = S between the center of the vehicle and the guide magnet, z = 50 mm, L = 400 mm, N
The calculation result of the positional deviation amount S obtained as = 10 is shown with the distance y as a parameter. As the position sensor 2 approaches the guide magnet 3 and y becomes smaller, it exhibits good linearity in a wide range. Therefore, when the position sensor 2 passes immediately above the guide magnet 3 (y = 0), the calculation result of the amount of positional deviation according to the above equation (1) is calculated.
By outputting to the steering control circuit (not shown), the vehicle 1 can be steered according to the amount of positional deviation. The above
The calculation of equation (1) can be easily performed by an inexpensive one-chip microcomputer.

By arranging 10 to 20 magnetic sensors over the entire length of 400 mm, the positional deviation amount S can be detected with the same accuracy without using the hundreds of magnetic sensors as in the prior art.

In the present embodiment, the time when the sign of the total sum of the detection outputs is detected is detected. However, among the magnetic sensors 21, the magnetic sensor showing the maximum detection output is focused and the detection output is determined from the peak value. You may detect the time when it starts to decrease. Although the number of magnetic sensors is 10 to 20 in the present embodiment, it goes without saying that the number of magnetic sensors may be increased or decreased according to the width of the range for detecting the positional deviation or the required resolution.

[0025]

As described above in detail, in the method for detecting the position deviation of the self-propelled vehicle according to the present invention, the waveform obtained by connecting the detection outputs of the magnetic sensors arranged at the predetermined intervals is obtained from one position sensor to the other position. Discrete Fourier transform is performed with the length to the sensor as one cycle of the fundamental wave, and the amount of positional deviation is calculated based on the phase of the fundamental wave component.Therefore, a small number of magnetic sensors and a one-chip microcomputer are used. Since it can be realized, a large cost reduction can be achieved. Further, since the fundamental wave component is obtained and calculated, the present invention has excellent effects such as being able to avoid the influence of offset error due to geomagnetism and the like.

[Brief description of drawings]

FIG. 1 is a graph showing a detection output of each magnetic sensor.

FIG. 2 is a graph showing the distribution of the y-direction component of magnetization in a three-dimensional manner.

FIG. 3 is a schematic plan view showing the relationship between a magnetic sensor and a guide magnet that are applied to implement the positional deviation detection method according to the present invention.

FIG. 4 is a block diagram of an apparatus for carrying out the positional deviation detection method according to the present invention.

FIG. 5 is a flowchart showing the control contents of the CPU.

FIG. 6 is a graph showing the calculation result of the positional deviation amount.

[Explanation of symbols]

 1 Self-propelled vehicle 2 Position sensor 21 Magnetic sensor 3 Guide magnet 4 Multiplexer 5 Amplifier 6 A / D converter 7 CPU

Claims (2)

[Claims] 1. A self-propelled vehicle that detects the strength of a magnetic field generated by a guide magnet installed on a floor on which the self-propelled vehicle travels,
In a method for detecting a positional deviation of a self-propelled vehicle, which detects the positional deviation in the left-right direction between the self-propelled vehicle and the guide magnet by detecting with a plurality of magnetic sensors arranged in a line in the left-right direction, the detection of the magnetic sensor The waveform obtained by connecting the outputs is discrete Fourier transformed with the length from the magnetic sensor located on one side to the magnetic sensor located on the other side as one cycle of the fundamental wave, and the amount of positional deviation based on the phase of the fundamental wave. A method for detecting a positional deviation of a self-propelled vehicle, which comprises detecting 2. The method for detecting a positional deviation of a vehicle according to claim 1, wherein the positional deviation amount is determined when the sign of the total sum of the detection outputs of the magnetic sensor is reversed.