JPH0635538A - Method and device for calibration of stop position of mobile object - Google Patents

Abstract

PURPOSE:To reduce the necessary frequency of calibration even with use of plural mobile objects. CONSTITUTION:When plural mobile objects are operated in a yard where plural stations are set, the errors caused to the positioning markers 8 and 8 of a positioning table 11 when a main body 1 is correctly stopped at each station are detected as the calibration amounts for calibration of the mobile objects. Then the error caused to the stop position of the table 11 when each station correctly stops at the markers 8 put on the floor in an operating area with use of one of those calibrated mobile objects is detected as a calibration amount for calibration of the mobile objects. Thus the calibration amount is detected by a single mobile object and all other mobile objects are calibrated with a calibration amount equal to that of the preceding mobile object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning calibration method for a moving body, specifically, an automatic guided vehicle, a mobile robot for work, and the like. The present invention relates to a positioning calibration method for stopping each moving body at a predetermined stop position when using the moving body such as a robot.

[0002]

2. Description of the Related Art A moving body such as an automated guided vehicle or a mobile robot needs to be accurately stopped at a stop position of a station which is a working position. For example, in the case of an unmanned guided vehicle, even when the article is transferred from the unmanned guided vehicle to the station at the station, and vice versa, even if there is a slight deviation depending on the type and size of the article. Then, the transfer of the article may be hindered. Further, in the case of the work robot, if the stop position at the station is deviated, the work there may not be performed smoothly.

On the other hand, the stop accuracy of the moving body is generally about ± 10 mm in the traveling direction and the direction orthogonal thereto and about ± 1 ° in the rotating direction around the vertical axis.
In this way, it is inevitable that a certain degree of error will occur in the stopping accuracy of the moving body. However, for example, in the case of an automated guided vehicle that automatically transfers and conveys articles in a semiconductor manufacturing factory or the like, a problem occurs even with the above-mentioned deviation, so a structure that eliminates the deviation each time the moving object is stopped is used. Alternatively, it is necessary to provide one or both of the devices for transferring articles to and from the moving body, and further to further improve the stopping accuracy of the moving body.

The following method is known as a known method for improving the stopping accuracy of such a moving body.
That is, a plurality of hydraulic jacks are provided on the side of the moving body, and a conical female hole is formed at the tip of the rod protruding toward the floor surface side. On the other hand, on each station side, a plurality of positioning projections having a conical male portion are provided at regular stop positions on the floor corresponding to the mounting positions of the hydraulic jacks on the moving body side. Then, when the moving body stops at the station, the hydraulic jacks are advanced from the side of the moving body, and the hydraulic jacks are externally fitted to the positioning protrusions for positioning. In such a method, the moving body is lifted from the floor surface and positioned at the regular stop position.

However, in such a method,
Since the positioning projections hinder the traveling of the moving body and a large number of additional equipment such as a hydraulic power source is required on the moving body side,
This will increase costs and complicate the structure. Further, in the above method, the positioning is performed by the engagement between the female hole and the male portion, so that the accuracy of the positioning deteriorates over time due to the wear of the female hole and the male portion, and dust is generated. For example, it cannot be used in an environment where the positioning accuracy and cleanliness are strictly controlled, such as in a semiconductor manufacturing factory.

Under these circumstances, the applicant of the present application has previously applied for the invention of Japanese Patent Application Laid-Open No. 1-186459. This JP 1-18
According to the invention of No. 6459, the positioning means is provided on the loading platform in two directions in the horizontal plane and in three directions of the rotation around the vertical axis, the above-mentioned deviation is detected, and the positioning correction value for canceling the deviation is calculated. Then, by positioning the loading platform based on the calculated positioning correction value, the relative stop position between the loading platform and the transfer device can be positioned with a simple structure, non-contact, inexpensively and highly accurately. In order to provide a positioning method for a vehicle, which has a loading platform on which an article is placed, and which automatically travels and stops with a positioning mark as a target, in two directions in a horizontal plane and around a vertical axis. Positioning means for the loading platform in three directions of the rotation direction of
An optical sensor for detecting the positioning mark is provided on the transport vehicle, the optical sensor detects a shift amount between the transport vehicle and the positioning mark, and based on the shift amount, the shift amount in the loading platform described above. It is characterized in that a positioning correction value, which is a movement amount in the three directions to be reduced, is calculated, and the positioning means in the three directions is driven based on the positioning correction value to move the loading platform.

The following is the premise of the present invention, Japanese Patent Laid-Open No. 1-186459.
The invention of the issue will be described.

FIG. 1 is a left side view of a carrier vehicle as a moving body according to the invention of the above-mentioned Japanese Patent Laid-Open No. 1-186459, showing a state in which it is stopped on a certain station. It should be noted that this transport vehicle has its traveling direction in the left direction (the direction indicated by the white arrow) in FIG.

In FIG. 1, reference numeral 1 is a main body of a transport vehicle, which is a pair of left and right driving wheels 2 (right driving wheel is not shown) and auxiliary wheels 3 and 3 (one each on the front, rear, left and right) (right side). The auxiliary wheels are supported by (not shown).

The drive wheels 2 are mounted on the central portion of the main body 1 so as to be appropriately separated from each other on the right and left sides, and drive motors (not shown) are coaxially directly connected to the respective drive motors. The main body 1 is steered and driven by the drive of each of these drive motors to move forward and backward and turn right and left. Further, the auxiliary wheels 3 and 3 are attached to the front and rear portions of the main body 1 so as to be rotatable around a vertical axis of the main body 1 while being appropriately separated from each other.

A loading table 4 for placing articles to be conveyed is provided on the top of the main body 1. The loading table 4 is attached with its center and the center of the main body 1 aligned with each other, and a positioning table 11 is interposed between the two. The positioning table 11 has three layers, each of which is provided in the central portion of the main body 1 and performs positioning in three directions, that is, a traveling direction y of the main body 1, a direction x orthogonal to the traveling direction, and a rotation direction θ around the vertical axis of the main body 1. The positioning means 5x, 5y, and 5θ are formed, and the loading platform 4 is fixed to the uppermost positioning means 5θ. Therefore, the loading table 4 is attached to the main body 1 so as to be movable and rotatable in three directions.
Also, the positioning means for the positioning table 11 in each direction 5x,
y, 5θ is 3 depending on the driving unit 6x, 6y, 6θ in each direction.
It can be driven independently in each direction.

On the other hand, CCD cameras 7 and 7 for detecting the stop position of the main body 1 are attached to the front and rear of the center of the main body 1 at equal distances from the center of the main body 1 downward.

Positioning markers 8, 8 as stop targets for indicating the stop position and direction at each station are installed on the floor surface 10 of each station. These positioning markers 8 and 8 have a black circle drawn in the center of a white square, and the CCD camera installed in the main body 1 of the transport vehicle.
It is drawn directly on the floor surface 10 at the same intervals as 7, 7, or a prepared sheet is attached.

In the main body 1 of the transport vehicle, these positioning markers 8 and 8 are imaged by CCD cameras 7 and 7, respectively, and the position where the vehicle should stop is detected based on the information obtained from the images. Also, after stopping, CCD camera 7, 7
From the position on the image of the positioning markers 8, 8 imaged by, the deviation amount in each of the three directions of the traveling direction y of the main body 1, the direction x orthogonal to the traveling direction, and the rotation direction θ of the main body 1 around the vertical axis is obtained. Therefore, each drive unit 6x, 6 of the positioning table 11 is calculated according to the calculation of the deviation amount in the three directions and the result thereof.
Positioning control device 9 which gives drive signals to y and 6θ is the main body 1
It is provided in.

Various configuration examples can be considered for each of the drive units 6x, 6y, 6θ, and thus detailed description thereof will be omitted. However, the point is that when an automated guided vehicle stops at each station,
Positioning markers 8, 8 provided there are CCD cameras
Images are taken with 7, 7 and the relative positional relationship between the main body 1 and both positioning markers 8, 8 is obtained from the images taken by the CCD cameras 7, 7, that is, the amount of deviation between the correct stop position is calculated. In order to eliminate the amount of deviation, the positioning control device 9 drives each drive unit 6x,
By driving 6y, 6θ, each positioning means 5x, 5y,
Positioning means provided at the top by moving 5
Match the center of y with the center of the station.

By such an operation, when the main body 1 of the transport vehicle is stopped at the station, the loading platform 4 is positioned at the correct position, so that the transfer of the article between the station and the loading platform 4 is accurate. And it is done smoothly.

Although the automatic guided vehicle is provided with a loading platform 4 for loading and transporting articles, the positioning means (5θ in the example of FIG. 1) of the uppermost layer is used as it is as the loading platform 4. It may be used, or a separate loading platform 4 may be precisely positioned and fixed on the uppermost positioning means 5θ.

Further, as a driving method by the driving units 6x, 6y, 6θ for the respective positioning means 5x, 5y, 5θ, there is disclosed in Japanese Patent Laid-Open No. 1-1864.
In the invention of No. 59, the eccentric cam is rotated by the motor, and the eccentric rotation motion of the eccentric cam caused thereby linearly moves both the positioning means 5x and 5y in the x direction and the y direction respectively, and the positioning means 5θ is parallel to the floor surface 10. It is configured to rotate and move in a plane.

However, it goes without saying that the above-mentioned structure is an example, and various structures such as a rack and pinion, a worm gear, a direct drive by a linear motor, and the like are possible.

Furthermore, the positioning markers 8 and 8 installed in each station do not have to be limited to the above configuration,
It suffices if the position and direction at which the main body 1 of the transport vehicle should stop can be specified. For example, an arrow or a simple rectangular marker is installed and detected by one CCD camera. But it's okay.

FIG. 2 is a flow chart showing the control procedure of the above-mentioned conventional positioning method for the guided vehicle, and FIG. 3 is a schematic diagram for explaining the method for calculating the positioning correction value.

The guided vehicle is self-propelled toward the stations by a predetermined guiding device, and the black circles at the centers of the positioning markers 8, 8 provided at the respective stations are located at the positions where the visual fields of the CCD cameras 7, 7 can be captured. Stop at. When the transport vehicle stops, the positioning markers 8 and 8 are imaged by the CCD cameras 7 and 7 (step S1), the intermediate position G of both positioning markers 8 and 8 is set as the origin based on the imaging result, and the installation direction is set to X.
Between the center position PA, PB of the CCD camera 7, 7 field of view and the center position PA ', PB' of the positioning marker 8, 8 in the coordinate system with the Y axis as the direction orthogonal to this X axis. Distance d _XA ,
d _YA , d _XB and d _YB are obtained (step S2).

Next, the obtained distances d _XA , d _XB ,
Positioning correction values Δx, Δy, and Δθ are calculated from d _YA and d _YB by a calculation method described later (step S3). Then, the positioning correction values Δx, Δ calculated in step S3
The drive units 6x, 6y, 6θ are driven in accordance with y, Δθ (step S4), whereby the positioning means 5x, 5y, 5θ move. As described above, the positioning means of the uppermost layer of the positioning table 11 is maintained with the main body 1 of the transport vehicle being stopped.
5θ, that is, the loading platform 4 moves relative to the main body 1 of the transport vehicle and is positioned at the correct position with respect to the station.

On the other hand, each positioning correction value Δx, Δy, Δθ
Is calculated by the positioning control device 9 as follows. First, both CCD cameras 7, which are indicated by the two-dot chain line in Fig. 3,
When the position of the center of gravity of the positioning markers 8, 8 is captured within the visual field of 7, the distances d _XA , d _YA , d _XB , d _XY described above are obtained. Then, the respective positioning correction values Δx, Δy, Δθ are obtained by the following equations (1), (2) and (3).

ΔX = {(d _XA + d _XB ) / 2} (1) d _Y = d _YA −d _YB Δy = (d _Y / 2) + d _YB = {(d _YA −d _YB ) / 2} + d _YB = (d _YA + d _YB ) / 2 (2) Δθ = sin ^-1 (d _Y / 2L) = sin ^-1 {(d _YA -d _YB ) / 2L} (3) However, 2L: Both positioning markers 8, 8 installation distance

Since the respective positioning correction values Δx, Δy, Δθ are obtained by the above equations (1) to (3), the respective driving units 6x, 6y, Δy are calculated in accordance with the obtained respective positioning correction values Δx, Δy, Δθ.
By driving 6θ, the uppermost layer positioning means 5θ
However, in other words, the loading platform 4 is positioned at the regular stop position.

[0027]

As described above, the unmanned guided vehicle as the moving body of the invention of Japanese Patent Laid-Open No. 1-186459, which is a conventional example, is a pair provided on the floor of the station at the stop position. Each marker is imaged by a pair of CCD cameras, and positioning is performed with respect to the station to eliminate the stop error according to the information obtained from the imaged images. However, it is inevitable that an error will occur in the position where the marker is installed at each station. For this reason, in reality, a pair of positioning markers are imaged by a pair of CCD cameras with the main body stopped at an accurate position for each moving body at each station, and that state is used as a regular stop position for the positioning table. It is necessary to perform calibration to move the to the correct position.

Therefore, conventionally, for example, it is necessary to calibrate all of a plurality of moving bodies used in the same factory at all stations, and the required number of calibrations is given by the following equation (4). .

N = R × S (4) where N: number of calibration required R: number of moving objects S: number of stations

Therefore, there has been a problem that the required number of calibrations rapidly increases as the number of moving bodies and the number of stations increase. Such a problem further increases the manufacturing cost because it is necessary for the manufacturer of the moving body to carry in all the moving bodies to the customer (user of the moving body) and actually perform calibration. Further, on the user side, when a station is newly installed or when the position of the station is changed, there arises a problem that it becomes necessary to calibrate all moving bodies.

The present invention has been made in view of the above-mentioned circumstances, and a method for calibrating a stop position of a moving body which can reduce the required number of calibrations even when a plurality of moving bodies are used, and a method of using the method. The purpose of the present invention is to provide a calibration device.

[0032]

A method for calibrating a stop position of a moving body according to the present invention is a method of calibrating a plurality of moving bodies when operating the plurality of moving bodies in an operation area in which a plurality of stopping positions are set. For each of them, the error with respect to the stop target of the table when each main body correctly stops at the stop target is detected as a calibration amount and calibrated, and one of the moving bodies calibrated in this way is used. For each stop position in the operating area, the error with respect to the stop position of the table when the stop target correctly installed on the floor of each stop position is detected as a calibration amount and calibrated. With the same calibration amount detected by one moving object, all other Body, characterized in that calibrating the.

The calibration device according to the present invention is characterized by including a stop target installed on the floor and an image pickup device provided above the vicinity of the center of the stop target.

[0034]

In the moving body stop position calibration method according to the present invention, for each of a plurality of moving bodies, an error with respect to the stop target of the table is detected as a calibration amount when each main body correctly stops at the stop target. If one of the moving objects that has been calibrated in this way and is calibrated in this way is used to correctly stop at the stop target installed on the floor at each stop position for each stop position in the operation area The error with respect to the stop position of the table is detected and calibrated as the calibration amount, and the same calibration amount as the calibration amount detected by one moving body is obtained without obtaining the calibration amount for each moving body. All other mobiles have been calibrated at That.

Further, in the calibration device according to the present invention, the image of the stop target and the image of the table when the main body of each moving body stops at the stopping target are picked up by the image pickup device, and from these images, the moving target of each moving body is picked up. The error between the stop target and the table when the main body correctly stops at the stop target is obtained as a calibration amount for the moving body of each table.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments thereof.

FIG. 4 is a schematic diagram showing the structure of a calibration station as a calibration device used for carrying out the method for calibrating the stop position of a moving body to which the method of the present invention is applied, and the moving body stopped there. Is.

The moving body is basically constructed in the same manner as the conventional example shown in FIG. That is, although not shown in FIG. 4, a main body 1 having a traveling system composed of drive wheels, which are attached to the central portion of the wheel at right and left positions and auxiliary wheels provided at front, rear, left and right, respectively. And this body 1
It is composed of a positioning table 11 mounted on the top.

The loading table is provided on the upper surface of the positioning table 11 if the moving body is an unmanned guided vehicle, and various actuators are provided if it is a mobile robot, but they are omitted in FIG.

On the main body 1 of the moving body, a pair of positioning markers as shown in FIG. 1 which are originally installed on the floor of the station where the moving body should be stopped at appropriate intervals.
The CCD cameras 7 and 7 for picking up images of 8 and 8 are also provided, which is similar to the above-mentioned conventional example. Further, on the upper surface of the positioning table 11 of the moving body, a pair of markers 22 to be described later is
Is provided.

On the other hand, on the floor of the calibration station, the CCD provided in the main body 1 of the moving body described above.
A pair of calibration markers 21, 21 are installed at positions so as to be within the visual fields of the cameras 7, 7. In addition,
The installation interval of the pair of calibration markers 21, 21 is the same as that of the pair of positioning markers 8, 8 in the normal station shown in FIG. 1, and the installation interval is also the positioning markers 8, 8. Are equal. Further, a calibration CCD camera 20 is installed at a position immediately above the center of a straight line connecting the centers of gravity of the pair of calibration markers 21, 21.

In the calibration station, the straight line connecting the centers of gravity of the pair of calibration markers 21 and 21 is defined as the Y-axis, and the straight line orthogonal to the center of the calibration markers 21 and 21 is the X-axis. The coordinate system of the calibration station (hereinafter referred to as the calibration coordinate system) is set.

FIG. 5 is a schematic diagram showing the relationship between the marker 22 installed on the upper surface of the positioning table 11 and the coordinate system of the positioning table 11. The coordinate system of the positioning table 11 (hereinafter referred to as a table coordinate system) is an orthogonal coordinate system in which the moving direction of the moving body is the y axis and the orthogonal direction is the x axis, and the origin of the coordinate system of the positioning table 11 is A pair of markers 22, 22 are arranged at equal intervals on both sides of the y-axis sandwiching them.

The procedure of executing the method for calibrating the stop position of a moving body according to the present invention will be described below with reference to the flowchart of FIG.

In the method for calibrating the stop position of the moving body of the present invention, the calibration CCD as described above is used.
At the calibration station in which the camera 20 and the calibration markers 21, 21 are installed, first, the positioning tables 11 of all moving bodies are calibrated (step S11).

The moving body is stopped at the calibration station so that the field of view of the pair of CCD cameras 7, 7 of the moving body can image the pair of calibration markers 21, 21. Next, the positioning by the positioning table 11 is performed.

The calibration CCD camera 20 images the markers 5, 5 on the positioning table 11 of the moving body,
From the image obtained as a result, the position of the origin of the table coordinate system with respect to the calibration coordinate system and the inclination of the y-axis are obtained.

Since the data thus obtained becomes an error with respect to the positioning markers 8, 8 in the station of the positioning table 11 of each moving body, this is input to the positioning control device 9 of each moving body as a calibration amount. To do. When the calibration amount is input to the positioning control device 9 in this way, the moving body sets the reference position of the positioning table 11 based on the calibration amount. This calibrated state becomes the position of error 0 with respect to the main body 1 of the positioning table 11, that is, the reference position.

Therefore, after that, the positioning table 11 is positioned with the calibrated state as a reference.

Regarding one of the moving bodies for which the positioning table 11 has been calibrated in this way,
Calibration is performed at all stations in the yard where a plurality of moving bodies including this moving body are used.
The calibration at this time is a calibration of the relative error of the positioning markers 8, 8 installed in each station with respect to the station.

As a result of calibration by this one moving body, positioning markers at all stations
Since the calibration amounts for correcting the error of the installation positions of 8 and 8 can be obtained, the calibration amounts of these respective stations are input to the positioning control devices 9 of all other moving bodies. As a result, the error of each positioning table 11 with respect to the main body 1 has already been calibrated in all the moving bodies in the calibration station, and therefore, in each station in accordance with the calibration amount already obtained for each station. Positioning table 11
Is set, and the position of the positioning table 11 can be corrected at each station based on this reference position.

The amount of movement of each of the x, y and θ axes of the positioning table 11 is obtained by the following equations (5), (6) and (7).

X = Δx + rx + Sxi (5) y = Δy + ry + Syi (6) θ = Δθ + rθ + Sθi (7) where x, y, θ: movement of the positioning table 11 in the x, y, θ directions. Amount Δx, Δy, Δθ: Error amount of moving body stop position with respect to station marker rx, ry, rθ: Calibration amount of moving body error Sx, Sy, Sθ: Calibration amount at each station i: Station number

Therefore, by individually calibrating the error of the positioning table 11 with respect to the main body 1 of each moving body and the error of the positioning markers 8 and 8 at each station, the required number of calibrations is as follows. It decreases as in equation (8).

N = R + S (8) where N: number of calibration required R: number of mobile units S: number of stations

Furthermore, if the positioning markers 8, 8 can be installed in each station without error, calibration at each station becomes unnecessary, so that only the error peculiar to each moving body can be calibrated. It improves, and the above equation (8) becomes N = R.

[0057]

As described above in detail, according to the moving body stop position calibration method of the present invention, the number of calibrations when using a plurality of moving bodies in a yard having a plurality of stations is reduced. You can
In particular, when the number of moving bodies and the number of stations are large, it can be greatly reduced, and when the marker installation position at each station is accurate, calibration at each station becomes unnecessary. .

Therefore, the manufacturer does not need the calibration conventionally required for all moving bodies at each station to which the moving body is delivered, which contributes to cost reduction.

Further, since the calibration CCD camera of the calibration station is used to detect the relative positional relationship between the marker and the marker installed on the positioning table of the moving body, strict positional accuracy is ensured. Never required. Therefore, the relative positional relationship between the calibration CCD camera and the pair of markers may be fixed only until the calibration of the moving body used in the same yard is completed.

[Brief description of drawings]

FIG. 1 is a left side view of a conventional transport vehicle as a moving body, showing a state in which it is stopped on a certain station.

FIG. 2 is a flowchart showing a control procedure of a conventional method for positioning a carrier vehicle.

FIG. 3 is a schematic diagram illustrating a conventional method for calculating a positioning correction value for a carrier vehicle.

FIG. 4 is a schematic diagram showing a configuration of a calibration station as a calibration device used for carrying out a method for calibrating a stop position of a moving body to which the method of the present invention is applied, and the moving body stopped there. .

FIG. 5 is a schematic diagram showing a relationship between a marker installed on the upper surface of a positioning table and a coordinate system of the positioning table.

FIG. 6 is a flow chart showing a procedure of executing the method of the present invention.

[Explanation of symbols]

 1 Transport vehicle body 5x x-direction positioning means 5x y-direction positioning means 5x θ-direction positioning means 6x x-direction driving section 6x y-direction driving section 6x θ-direction driving section 7 CCD camera 8 Positioning marker 11 Positioning table 20 CCD camera for calibration 21 Marker for calibration 22 Marker

Claims (2)

[Claims] 1. A linear movement in a horizontal plane with respect to the self-propelled main body in order to correct a stop error with respect to the stop position when the self-propelled main body recognizes a stop target installed on the floor at the stop position and stops. And a method for calibrating the stop position of each moving body when operating a plurality of moving bodies provided with a rotatable table in an operation area in which a plurality of stopping positions are set, for each of the plurality of moving bodies. , Calibrates by detecting an error of the table with respect to the stop target when the main body correctly stops at the stop target as a calibration amount, and for each stop position in the operation area, the calibrated plurality of Table stop position when one of the moving objects correctly stops at the stop target installed on the floor at each stop position The calibration is performed by detecting an error as to a calibration amount, and calibrating all other moving bodies with the same calibration amount as the calibration amount detected by the one moving body. Body stop position calibration method. 2. The stop target installed on a floor, and an imaging device provided above the vicinity of the center of the stop target, wherein the imaging device correctly stops the main body of each moving body at the stop target. In order to determine the error between the stop target and the table as a calibration amount for the moving body of each table, the image of the stop target and the table of the table when the main body of each moving body stops at the stop target. The calibration device used in the method for calibrating a stop position of a moving body according to claim 1, wherein the calibration device is configured to capture an image.