JP2680298B2 - Position correction method for robot equipped with automatic guided vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an unmanned guided vehicle-equipped robot in which a robot is mounted on an unmanned guided vehicle so that the robot can be moved to a plurality of distant locations for work. Position correction method. [Prior Art] An automated guided vehicle-mounted robot completes a given task by repeating a series of operations in which the automated guided vehicle conveys the robot to a work position, and then the robot performs work. Some robots of this type are designed to memorize teaching points preliminarily taught with respect to a workpiece and follow this memory for playback, which is called a teaching / playback type robot. . When making a teaching / playback robot work, the robot operation point (generally the arm tip)
The relative position between the work and the work must be constantly known, and for this purpose, the automatic guided vehicle must be stopped at a fixed position with respect to the work. Conventionally, the following two methods have been adopted as a stopping method for realizing this. (1) A mechanical positioning device at the stop position of the automatic guided vehicle,
For example, a device for pressing an automated guided vehicle against a rail or a cone is provided and positioning is performed by this. (2) The position of the work is confirmed using the visual sensor, and the teaching point is corrected and operated based on the amount of deviation from the position when the automatic guided vehicle is at the regular position. [Problems to be Solved by the Invention] By the way, the conventional position correction method described above has the following drawbacks. (A) In the method of (1) above, since the automated guided vehicle is driven by tires, lateral positioning is difficult. Also, since the positioning device must be installed in all work positions,
Space and money are large. Furthermore, positioning is impossible where a positioning device cannot be installed. (B) In the method of (2), the visual sensor that can accurately grasp the position of the work becomes extremely expensive. Moreover, since image processing must be performed, a high level of technical skill and investment are required. The present invention has been made under such a background,
An object of the present invention is to provide a position correction method for a robot equipped with an automated guided vehicle, which does not require a mechanical positioning device and does not require complicated image processing. [Means for Solving the Problems] In order to solve the above problems, the present invention conveys a robot mounted on an automatic guided vehicle to a plurality of work positions, and the robot is previously set for each of the plurality of work positions. In an unmanned guided vehicle-mounted robot that operates according to the taught points,
The automatic guided vehicle is provided with a mark recorded at a predetermined position of a work placement table placed at each of the plurality of work positions, and an image detection unit attached to a tip end portion of an arm of the robot. Stop near each of multiple work positions,
After causing the robot to reproduce the mark reading operation taught in advance, the mark is detected by the image detecting means,
A conversion formula is created based on the amount of deviation between the mark position at this time and the mark position at the time of teaching, and the teaching point of the robot is corrected by this conversion formula. [Operation] According to the above configuration, the image detecting means may be any one that can capture a simple mark (for example, two points). Also,
The position can be easily corrected using the mark as a reference. Therefore,
Position correction can be performed without complicated image processing. Example An example of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is an automatic guided vehicle. This automatic guided vehicle may be either a guided unmanned vehicle that travels along a guide line laid on the ground or a so-called self-guided unmanned vehicle that travels without a guide line. A robot 2 is mounted on the automatic guided vehicle 1. The robot 2 has an arm 3 that can horizontally rotate, rotate forward and backward, and rotate vertically. The image input device 4 and the handle 5 are integrally attached to the tip of the arm 3 so that they can be swung and twisted. Image input device 4
Is a solid-state imaging device such as a CCD (charge coupled device). The hand 5 is for gripping the work 6. It should be noted that the work 6 is drawn to be larger than that of the robot 2. The work 6 is placed on a frame 7a formed in the central portion of the upper surface of the work table 7 so as to receive the work of the robot 2. A mark 8 composed of two points 8a and 8b is written in the corner of the work table 7. In such a configuration, the automated guided vehicle 1 travels between a plurality of worktables 7 to perform work. In this case, the stop accuracy of the automatic guided vehicle 1 is low, and the position must be corrected in the following procedure. (1) First, when teaching, which is done prior to work,
Teaching to read the mark 8. That is, the image input device 4 is moved right above the mark 8 and the position is taught.
In this case, for example, a horizontal Cartesian coordinate system XY having the origin at the center of the bottom of the leg of the robot 2 and the X axis in the direction parallel to the horizontal scanning line of the image input device 4, and the point of the mark 8 in this coordinate system is taken. The coordinates of 8a and 8b are (Xa, Ya) and (Xb, Yb), respectively.
(FIG. 2 (a)). (2) Next, at the position when the automated guided vehicle 1 is stopped, the reading playback taught above is performed, and the mark 8 is displayed.
Read. That is, after the robot is made to reproduce the mark reading operation taught in advance, the image input device 4 reads the mark 8. In this case, the position and the shape of the arm 3 with respect to the automated guided vehicle 1 are the same as those at the time of teaching.
However, the stop position of the automated guided vehicle 1 is different from that at the time of teaching, and the XY coordinate system shifts to the UV coordinate system shown in FIG. 2 (a). Therefore, the teaching point Pi taught in the XY coordinate system
By converting the coordinates (Xi, Yi) in (1) to the coordinates (Ui, Vi) in the UV coordinate system, the correct control for the work 6 can be performed. Hereinafter, this conversion method will be described in detail. In the following description, the point 8a of the mark 8 in the UV coordinate system
Let (Ua, Va) be the coordinates of and the coordinates of the point 8b be (Ub, Vb). In such a setting, the coordinates of the teaching point Pi in the UV coordinate system will be obtained by the procedure shown in FIGS. 2 (b) to (d). (I) The point 8a is the origin, and x- is parallel to the XY coordinate system.
The coordinates (xi, yi) of the point Pi in the y coordinate system are as follows (Fig. 2 (b)). xi ＝ Xi−Xa yi ＝ Yi−Ya (1) If this is expressed in the determinant system, Becomes Here, Zi and zi are the coordinates in the height direction of the point Pi in the XY and xy coordinate systems, respectively, and these are invariant. Let A be the determinant of the above equation (2). That is, (II) Next, the coordinates of the point 8b of the mark 8 in the xy coordinate system are obtained as shown in FIG. 2 (b). That is, from the formula (1), it becomes (Xb-Xa, Yb-Ya). Also,
The coordinate of the point 8b rotated clockwise by Δθ is (Ub-Ua, V
b-Va). This translates the U-V coordinate system,
A coordinate system whose origin is (Ua, Va) (this is the u-
v coordinate system) and the coordinates of the point 8b. These two coordinates (Xb-Xa, Yb-Ya), and (Ub-U
a, Vb−Va) and the straight line connecting the origin with the x axis are α and β, tan α = (Yb−Ya) / (Xb−Xa) tan β = (Vb−Va) / ( Ub-Ua) ... (4) is obtained. Further, since Δθ = β−α, tan Δθ can be obtained by using the tangent addition theorem as follows. tan Δθ = S / T (5) where S = (Xb−Xa) (Vb−Va) − (Yb−Ya) (Ub−Ua) T = (Xb−Xa) (Ub−Ua) − ( Yb−Ya) (Vb−Va) From this, the angular deviation amount Δθ can be obtained by the following equation. Δθ = Arctan S / T (6) (III) As shown in FIG. 2 (c), the xy coordinate system is rotated by an angle deviation amount Δθ to form a new coordinate system uv. Coordinates of point Pi in this uv coordinate system (ui, vi)
Is ui = (cosΔθ) xi− (sinΔθ) yi vi = (sinΔθ) xi + (cosΔθ) yi (7) If this transformation is expressed in determinant as above, it becomes as follows. (IV) As shown in FIG. 2 (d), the uv coordinate system is translated to form a UV coordinate system, and a point Pi in this coordinate system is set.
The coordinates (Ui, Vi) of are calculated as follows. Ui = ui + Ua Ui = vi + Va (9) If this transformation is expressed by a determinant, Becomes (V) The teaching point Pi is converted using the above determinant. The coordinates of the point Qi after conversion can be calculated by Qi = C · B · APi (11). In the case of three dimensions, the marks may be three-dimensionally independent three points, and these may be read by two or more image input devices. Then, the calculation according to the two-dimensional case is performed. That is, it suffices to obtain a conversion formula based on the positional shift amount in each coordinate axis direction and the angular shift amount, and perform coordinate conversion based on these. [Effects of the Invention] As described above, according to the present invention, a robot mounted on an automated guided vehicle is conveyed to a plurality of work positions, and the robot is operated at each of the plurality of work positions in accordance with a teaching point taught in advance. In an unmanned guided vehicle-equipped robot, a mark recorded at a predetermined position of a work placement table placed at each of the plurality of work positions and an image detection means attached to a tip portion of an arm of the robot are provided. The unmanned guided vehicle is stopped near each of the plurality of work positions, the mark reading operation taught by the robot is reproduced, and the mark is detected by the image detecting means. Since a conversion formula is created based on the amount of deviation between the mark position at the time of teaching and the mark position at the time of teaching, and the teaching point of the robot is corrected by this conversion formula, the following effects can be obtained. You. (1) No external positioning device is required. (2) High-precision position correction can be performed without performing complicated image processing. (3) Since the mark is provided on the work placement table, rough teaching of a teaching point in a state where there is no work at the work position, for example, when loading the work onto the work stand, or of the robot after teaching is performed. It is also possible to check the operation, and when multiple workpieces are placed on the table, processing of these multiple workpieces can be handled with a single mark detection, thus reducing the number of marks and reducing the time and effort required to record marks. It can be drastically reduced. (4) When the mark is read, the robot is made to reproduce the mark reading operation taught in advance, and the image is read by the image detecting means attached to the tip of the rear arm. Therefore, the image detecting means can easily read the mark. It is possible to read the mark in a state where the mark is moved to the position, and it is possible to improve the mark detection accuracy and thus the position correction accuracy, and it is possible to obtain the excellent effects of increasing the degree of freedom of the mark position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing the configuration of an embodiment of the present invention,
FIG. 2 is a graph for explaining the coordinate conversion. 1 ... Automated guided vehicle, 2 ... Robot, 4 ... Image input device, 6 ... Work, 8 ... Mark.

Continuation of front page    (56) References JP-A-60-54011 (JP, A)                 JP-A-60-237504 (JP, A)                 JP-A-59-189415 (JP, A)                 JP 59-182076 (JP, A)                 JP 58-114892 (JP, A)                 JP-A-60-229109 (JP, A)                 JP-A-60-167787 (JP, A)

Claims (1)

(57) [Claims] An automated guided vehicle-equipped robot that conveys a robot mounted on an automatic guided vehicle to a plurality of work positions and causes the robot to work according to a teaching point previously taught for each of the plurality of work positions, A mark recorded at a predetermined position on the work placement table placed and an image detection means attached to the tip of the arm of the robot, and the automatic guided vehicle for each of the plurality of work positions. Stop near,
After causing the robot to reproduce the mark reading operation taught in advance, the mark is detected by the image detecting means,
A position correction method for a robot equipped with an automated guided vehicle, characterized in that a conversion formula is created based on a deviation amount between a mark position at this time and a mark position at the time of teaching, and the teaching point of the robot is corrected by this conversion formula.