JP2519442B2 - Work line tracking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a work for operating a predetermined machine tool (for example, an industrial robot) by following a work line attached to the surface of a workpiece. Regarding the line tracking method.

(Prior art and its problems) As a cutting robot capable of cutting a workpiece having a complicated three-dimensional shape such as a press-formed sheet metal into a desired shape, the present applicant has filed an application,
Various types such as the plasma cutting robot disclosed in JP-A-57-96791 have already been proposed and put into practical use. Then, in such a robot, it is necessary to manually mark the machining line such as the cutting line on the work or the teaching model in advance and perform the teaching along the marking line.

As a method for automatically teaching along such a processing line, there is a method disclosed in, for example, JP-A-61-100808. In this way, the eleventh
As shown in the figure as a schematic diagram, three or more spot light sources 101 to 103 are provided in the vicinity of the end effector of the robot, and light spots P _{1 to} P ₃ emitted from these spot light sources 101 to 103 on the surface of the work W are provided. Image with the TV camera 104. Then, the spatial relative relationship between the robot and the work W is obtained based on the positional relationship of the light spots P _{1 to} P ₃ on the screen of the CRT (not shown), and the posture of the robot is adjusted accordingly. Further, in this state, the image of the marking line C is captured, the robot is moved following the position of the marking line C, and the teaching data is taken in.

Therefore, in this method, three or more spot lights,
An illumination light (not shown) that illuminates a certain area on the surface of the work piece at a time in order to illuminate the image of the marking line C;
Different kinds of light are projected onto the surface of the work. However,
As shown in Fig. 12, the light spot (for example, P ₁ ) is the scribe line C.
If it exists above, the image of the ruled line C and the image of the spot light P ₁ will overlap. Therefore, it is difficult to distinguish these two types of images, and as a result, there is a problem in that the accuracy of the tracking operation is limited. This can be dealt with by making the above two types of light different in intensity and performing multi-valued image processing, but the multi-valued image processing device has a drawback that it is expensive.

Such a problem is common not only when teaching the robot, but also when the machine tool is made to follow the machining line using the optical means.

(Object of the Invention) The present invention is intended to overcome the above-mentioned problems in the prior art, and an image of a pattern light such as a spot light and a processed line can be obtained without using an expensive device such as a multi-valued image processing device. It is an object of the present invention to provide a machining line tracking method capable of clearly distinguishing from the image of No. 1 and improving tracking accuracy without significantly increasing cost.

(Means for Achieving the Object) In order to achieve the above-mentioned object, the present invention provides a method in which a predetermined pattern light is applied to the surface of the workpiece from a pattern light irradiation means attached to a predetermined machine tool. Image data of the surface is taken in, the level of the image data is compared with a first threshold value to obtain the position of the image of the pattern light on the surface, and the machining is performed based on the position of the image of the pattern light. A first step of adjusting a spatial relationship between a device and a surface of the workpiece, and irradiating the surface with predetermined illumination light for illuminating an image of a working line attached to the surface of the workpiece. Capture the image data of the surface in the state of
A second step of comparing the level of the image data with a second threshold value to detect the position of the image of the working line;
A third step of changing the spatial relationship between the machine tool and the workpiece along the direction in which the work line extends, and repeating the first to third steps to obtain the work line. (A) The intensity of the pattern light is set to be greater than the intensity of the illumination light, and (b) is intended for a work line tracking method of following the operation of the machine tool.
The first threshold value is set to a level between the image level of the image of the pattern light and the image level of the image of the processing line, and the second threshold value is set to the image of the processing line. Set to a level lower than the image level of (c)
When capturing the image data of the surface in the second step, the irradiation of the pattern light is stopped.

The “workpiece” in the present invention is not limited to the product itself, but is a term that includes a dummy or the like representing a work target such as a teaching model of a robot.

Further, the operation of the machine tool may be various operations such as an actual machining operation itself or an operation of manually moving, in addition to an operation for fetching data such as teaching.

(Embodiment) A. Outline of mechanical structure of embodiment FIG. 1 shows a machine of a Cartesian laser cutting robot as an example of a machine tool to which the present invention is applied to follow a marking line (working line). It is a schematic perspective view which shows a dynamic structure.
In the figure, the laser cutting robot RB is mounted on a base 1 by a motor M ₁ (not shown) in the X direction (horizontal direction).
1 has a movable base 2 which is movable, and a work (not shown) is placed on the movable base 2. A beam 4 is erected on the top of a column 3 which is erected vertically on both sides of the base 1, and the beam 4 extends in the Z direction (vertical direction) in the drawing and is moved in the Y direction by a motor M ₂ . A movable column 5 that is movable is provided. A light source device 14 incorporating two types of light sources, which will be described later, is attached to the moving column 5.

Further, a motor M _{4 which} moves up and down in the Z direction by the motor M ₃ is provided at the lower end of the moving column 5. Accordingly, the arm 6 provided at a position eccentric from the center axis of the moving column 5 rotates in the θ direction in the drawing. Further, a motor M ₅ is provided on the lower side of the arm 6,
This allows the laser torch T as an end effector.
Rotates in the ψ direction in the figure. Furthermore, this laser torch T
Adjacent to the sensor head for optical marking line tracking
SH (described later) is placed.

Among these, the laser beam from the laser oscillator 7 is applied to the laser torch T through the laser guide pipe 8. Further, the control device 9 has an image processing device, a microcomputer, and the like, which will be described later, built therein.
The 10 is provided with a keyboard and a display. Further, the external computer 11 is for performing input / output of various data and data processing, and includes a CRT 12, a keyboard 13, and the like. Then, the image from the sensor head SH is monitored on the CRT 12.

B. Outline of Electrical Configuration of Embodiment FIG. 2 is a schematic diagram of the electrical configuration of the robot RB shown in FIG. In FIG. 2, the following devices and the like are connected to the microcomputer 21 built in the control device 9 via the bus BL.

Mechanism drive system 23 including the motors M _{1 to} M ₅ and encoders E _{1 to} E ₅ (not shown in FIG. 1) for detecting the rotation angles of the motors M _{1 to} M ₅ , laser oscillation Device 7, operation panel 10, external computer 11, light source device 14.

On the other hand, the sensor head SH facing the workpiece W as the workpiece receives illumination light for illuminating the workpiece W and illuminating the ruled line C from the illumination light source 24 via the optical fiber 26 during teaching. Given. Further, the light for giving the spot light used for maintaining the relative distance / posture relationship (spatial relationship) between the sensor head SH and the work W in a predetermined relationship during teaching is also emitted from the laser diode light source 25. It is given to the sensor head SH via the fiber 27.

Further, from the sensor head SH, an image signal in the vicinity of the marking line C is taken in by the image processing device 22 and is displayed on the CRT 12 in FIG. 1 under the control of the microcomputer 21. However, the image processing device 22 is configured as a device that performs binary image processing. This system can be operated under the control of a host system (not shown).

C. Detailed Configuration of Sensor Head SH FIG. 3 is a partial cross-sectional view showing the details of the above-described sensor head SH, and FIG. 4 is a cross-sectional view taken along the line AA ′. In these figures, the sensor head SH is provided in parallel with the laser torch T, and during teaching, the laser torch T is rotated 90 ° in the α direction from the direction shown and retracted.

Further, in the reproduction mode, the laser torch T is returned in the direction shown in the figure, and the sensor head SH is rotated 180 ° in the γ direction (the same as the α direction) and retracted. Further, in the reproduction mode, the laser torch T and the sensor head SH can be rotated 180 ° in the β direction around the axis of the arm 6 so that the laser torch T can move to the position shown in the sensor head SH. These rotations may be performed manually or by a motor. A broken line I shown below the sensor head SH in FIG. 3 indicates a position corresponding to the tip portion of the laser torch T when rotating in the β direction.

3 and 4, the light emitting ends of three optical fibers 26 (26a to 26c) connected to the illumination light source 24 of FIG. 2 are provided at the lower end of the housing 30 of the sensor head SH. ing. Then, from this light projecting end, illumination light L for illuminating the area G on the surface of the work W in a planar manner is emitted. Further, the light supplied from the laser diode light source 25 by the three optical fibers 27 (27a to 27c) is given to the projectors 31a to 31c having a microlens (not shown) at the tip thereof, and these projectors 31a to 31c. The surface of the work W is irradiated from 31c as three spot lights.

These projectors 31a~31c, as shown in FIG. 5, the spot beam L _a ~L _c from them are arranged to intersect at one point O, the relative distance between the sensor head SH and the workpiece W · The following light spot groups are formed on the work W according to the posture relationship. That is, when the sensor head SH maintains a predetermined distance and posture with respect to the surface of the work W (the fifth
(When the surface indicated by W _a in the figure is the surface of the workpiece W)
6A, the _three light spots P _{1 to} P ₃ on the work W are formed in the reference positions Q _{1 to} Q ₃ , respectively. On the other hand, these relative distances and postures are W _{b in} FIG.
~ When it shifts as shown by W _d , Fig. 6 (b) ~
As shown in (d), the positions are displaced from the reference positions Q _{1 to} Q ₃ .

Therefore, the positions of the light spots P _{1 to} P ₃ and the reference position Q ₁ to
If the distance / attitude control is performed so that the relationship with Q ₃ is always the relationship shown in FIG. 6 (a), teaching is performed while maintaining the relative distance between the sensor head SH and the work W and the attitude at predetermined values. be able to. Such control can be performed by operating the keyboard 12 while visually observing the screen of the CRT 12, or can be automatically performed by the microcomputer 21 based on the output of the image processing device 22.

Returning to FIG. 3, the illumination light L from the optical fibers 26a to 26c
The surface image of the work W (especially the image of the marking lines on the surface) illuminated by the light and the distance / posture detection spots P _{1 to} P ₃ formed on the surface of the work W by the projectors 31a to 31c are the housing. CC through the lens 32 provided in 30
The light enters the D image sensor (ITV camera) 33 and forms an image on its surface. However, as described later, since the spot light L _a ~L _c repeated blinking progresses the following, an image of the light spot P ₁ to P ₃ are imaged only at a particular time (details will be described later). Then, the image data thus obtained is given to the image processing device 22 of FIG. 2 through the image transmission line 34,
It undergoes image processing as described below. As a result, while detecting the ruled line C formed in advance as an image, the sensor head SH moves following it and the teaching data is taken in.

D. Teaching Operation Therefore, hereinafter, the processing when the teaching operation is performed using such a device will be described with reference to FIG. The following processes are performed under the control of the microcomputer 21 and the external computer 11 shown in FIG.

First, in step S1 of FIG. 7, the laser diode light source 25 is turned on and the illumination light source 24 is also turned on. Thus both the spot light L _a ~L _c and the illumination light L is turned on. Therefore, as shown in FIG. 8 (a), the spot light P ₁
The image of ~ P _{3 and} the image of the score line C can be observed on the surface of the work W. The mark images (white circles) indicating the reference positions Q _{1 to} Q ₃ are created in the image processing device 22,
It is displayed on the screen of CRT12 after being combined with the image actually observed.

Of the image data read in such a state, the image level of the pixel on the I-I line in FIG. 8 (a) is shown in FIG. 9 (a). As can be seen from FIG. 9A, a peak is formed at the image level in the region corresponding to the light spot P ₃ and the ruled line C.

7 view of the next step S2, spot light L _a ~L _c threshold V _H strength first which is predetermined in accordance with the
Are set in the image processing device 22. This first threshold
V _H is set to a level between the image level of the light spots P _{1 to} P _{3 and} the image level of the image of the ruled line C. In other words, this threshold value V _H has an intermediate value between the two peaks in FIG. 9 (a). Further, the first threshold value V _H is higher than a second threshold value V _L for detecting a marking line which will be described later. It is because the spot light L _a ~L _c given by emitting a laser diode, whereas the light intensity is larger, as the illumination light source 24 for providing illuminating light L, such as incandescent lamps It corresponds to using a light source having a relatively small light intensity.

In the next step S3 in FIG. 7, the image data (FIG. 9A) picked up by the CCD image pickup device 33 is taken into the image processing device 22. Then, in step S4, the level of each pixel of this image data is compared with the above threshold value V _H, and the image data is binarized by this, and the screen of pixels having a level higher than the threshold value V _H is displayed. Identify the top position. As a result, the positions on the screen of the light spots P _{1 to} P _{3 in} FIG. 8A can be known. Further, a drive command signal is given to the mechanism drive system 23 of the robot RB so that the deviation between the positions of the light spots P _{1 to} P ₃ thus obtained and the reference positions Q _{1 to} Q ₃ becomes zero. . Thereby, the robot RB is driven, and the distance between the sensor head SH and the work W and the attitude of the sensor head SH are controlled so that the light spots P _{1 to} P ₃ match the reference positions Q _{1 to} Q ₃ , respectively. (Step S5).
An image after such control is performed is shown in FIG.
FIG. 9 (b) shows the image level on the line II-II.

In the next step S6 in FIG. 7, the laser diode light source 25 is turned off. However, the illumination light source 24 is kept on. Whereby the irradiation of the spot light L _a ~L _c is stopped, the illumination light L for illuminating the whole within the angle of the CCD image sensor 33
Only the surface of the work W is irradiated. Then, as shown in FIG. 8 (c), an image of only the score line C comes to be observed. At this time, since the spot lights L _{a to} L _c are extinguished, the light spots P ₁ to L ₁ as shown in FIGS.
P ₃ is not observed. The image level on the line III-III in FIG. 8 (c) is as shown in FIG. 9 (c).

As described above, the intensity of the illumination light L spot beam L _a ~L _c
Has a smaller value than the strength of. Therefore, the seventh
In step S7 in the figure, a relatively low second threshold value V _L is set in the image processing device 22. The level of the second threshold value V _L is lower than the image level (peak value) of the image of the ruled line C and higher than the noise level V _N. Then, in the next step S8, the image data of FIG. 8 (c) is fetched, and in step S9 the low level threshold V _L (FIG. 9 (c)) is compared with the image level of each pixel to obtain an image. The data is binarized. Based on this, the positions of the pixels having the level equal to or higher than the threshold value V _L are specified, and the positions of these pixels correspond to the position of the ruled line C. In this process, since the irradiation of the spot light L _a ~L _c is stopped, the image that is taken out by comparison with a threshold value V _L is only the image of the scribed line C.

In the next step S10, as shown in FIG. 8 (c), a predetermined number (N) of scanning lines and ruled lines C on the screen.
The position of the target point F is determined as the point where and intersect, and this target point F is displayed on the screen as a "+" mark. These target points F are points that are candidates for teaching points.

Then, in step S11, how much the point selected from the plurality of target points F by the predetermined rule deviates from the center of the screen is obtained. Then, according to the amount of deviation, the current position / orientation data of the sensor head SH is corrected, and the corrected position / orientation data is fetched as teaching data. This completes the teaching process at one teaching point.

When that point is not the final teaching point, the process proceeds from step S12 to S13, and the sensor head SH is moved by a predetermined distance along the direction in which the ruled line C extends. Then, the process returns to step S1, the above-described operation is repeated, and when the final teaching point is reached, the teaching process is completed. As a result, the sensor head SH automatically follows the ruled line C, and automatic teaching is executed.

In this iterative process, when adjusting the position and orientation of the sensor head SH only spot light L _a ~L _c is removed by the high-level threshold V _H. Further, when detecting the position of the ruled line C, only the illumination light L is emitted. Thus when specifying a position of the light spot P ₁ to P _3, the light spot P ₁ ~
Even if the image of P _{3 and} the image of the marking line C are simultaneously observed and the image data having the spatial level distribution as shown in FIG. 10 (a) is captured, only the image of the light spot P ₃ should be captured. You can

Further, when determining the position of the image of the scribed line C, in order to spot light L _a ~L _c for forming a light spot P ₁ to P ₃ is turned off, 10 view of (a) Such image data is not captured, and it is possible to clearly capture only the image of the ruled line C as shown in FIG. 10 (b). Therefore, the sensor head SH accurately follows the ruled line C.

When detecting the ruled line C, the illumination light L
It is also conceivable to irradiate only the spot light, and on the other hand, when spot light is detected, the illumination light is turned off and only the spot light is irradiated. In this case, both images can be binarized with a single threshold value (for example, the above threshold value V _L ). However, in the case of such a technique, the illumination light L for whole surface illumination has to be blinked in a complicated manner. However, incandescent lamps and halogen lamps used as the light source of the illumination light L have a slow flashing response speed, and their lifespan is significantly shortened if the flashing is repeated. On the other hand, according to the present invention, only spot light (pattern light) that can be formed by using a light source such as a laser diode that has a high blinking response and whose life does not become too short even if blinking is repeated. Therefore, there is also an advantage that such a problem does not occur.

E. Modifications One embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment, and the following modifications are possible.

The processing line is not limited to a simple scribe line, and may be, for example, a line in which fluorescent paint or the like is applied in a band shape on the surface of the work W and scribed on it. In this way, the ruled lines appear more clearly on the image, which is more suitable for automatic tracking. Further, it may be a processed line drawn with a paint on the surface of the work W, or one in which a tape is attached and a thin cut line is provided on the tape.

In the above embodiment, the case where three spot lights are used as the pattern light is shown, but four or more spot lights may be used. The present invention is also applicable to the case where light having a linear or mesh pattern, for example, is applied to the surface of the work instead of the spot light and the spatial relationship between the work and the sensor head is adjusted based on the image. Is applicable. It is not essential to attach a light source of illumination light to a processing device such as a robot, and it may be provided at an external position.

In order to follow the machining line, the relative spatial relationship between the sensor head and the work need only be changed, so the sensor head is spatially fixed and only the position / orientation of the work W side is changed. The present invention can also be applied to.

INDUSTRIAL APPLICABILITY The present invention is applicable not only to robot teaching but also to various machine tools that perform desired processing while following the marking lines.

(Effect of the Invention) As described above, according to the present invention, each of the detection of the position of the image of the pattern light and the detection of the position of the processing line can be performed by the binary image processing, and both of them can be performed. Since it is possible to clearly capture only the image required for detection, it is possible to obtain a machining line tracking method capable of improving the tracking accuracy without significantly increasing the cost.

[Brief description of drawings]

1 is a perspective view showing an outline of a mechanical structure of an embodiment in which the present invention is applied to teaching of an industrial robot, FIG. 2 is a schematic block diagram showing an electric structure of the robot of FIG. 1, FIG. 3 is a partial sectional view showing the detailed structure of the sensor head, FIG. 4 is a sectional view taken along the line AA ′ of FIG. 3, and FIGS. 5 and 6 are the principle of controlling the relative distance / posture between the sensor head and the workpiece. Explanatory diagram of an example, FIG. 7 is a flowchart showing the operation of the embodiment, FIG. 8 is a diagram showing an example of an image captured in the embodiment, and FIGS. 9 and 10 are image data captured in the embodiment. FIG. 11 and FIG. 12 are diagrams for explaining the relationship between the level and the threshold value, and FIG. 11 and FIG. RB ... Laser cutting robot, 9 ... Control device, 10 ... Operation panel, 11 ... External computer, 22 ... Image processing device,
T ...... laser torch, SH ...... sensor head, W ...... workpiece, C ...... scribed line (processing line), L _a ~L _c ...... spotlight (pattern light), P ₁ ~P ₃ ...... light spot, L ...... illumination light, V _H ...... first threshold, V _L ...... second threshold

Claims (2)

(57) [Claims] 1. The image data of the surface is taken in a state in which the surface of the workpiece is irradiated with a predetermined pattern light from a pattern light irradiation means attached to a predetermined machine tool, and the level of the image data and the first The position of the image of the pattern light on the surface is compared with the threshold value, and the spatial relationship between the machine tool and the surface of the workpiece is adjusted based on the position of the image of the pattern light. A first step; capturing image data of the surface in a state in which the surface is irradiated with predetermined illumination light that illuminates an image of a work line applied to the surface of the workpiece, and the level of the image data is acquired. And a second threshold value to detect the position of the image of the working line, and the spatial relationship between the machine tool and the workpiece along the direction in which the working line extends. And the third step to change Wherein, by repeating the first to third step,
In the work line tracking method of operating the machine tool by following the work line, the intensity of the pattern light is set to be larger than the intensity of the illumination light, and the first threshold value of the image of the pattern light is set. A level between the image level and the image level of the image of the processing line is set, and the second threshold is set to a level lower than the image level of the image of the processing line, A method of following a working line, wherein irradiation of the pattern light is stopped when the image data of the surface is captured in the second step. 2. The machine tool is an industrial robot, the follow-up is a follow-up for teaching processing of the industrial robot, the work line is a marking line, and the pattern lights are different from each other. The work line tracking method according to claim 1, wherein the spot light has three or more angles.