JPS6277178A - Detecting method for seam line - Google Patents

Abstract

PURPOSE:To detect a seam line without being effected by the surface state and vibration by moving a contact sensor by crossing the seam line of a work, by differentiating the output of after the movement starting initial period and by detecting the seam line from the coordinate by finding the coordinate of the position that the differential value becomes more than the prescribed value. CONSTITUTION:The sensing is performed by moving with contact a contact sensor 16 so as to cross a seam line 13 at plural places of a work 11. And in each sensing the output of the contact sensor 16 at the initial sensing start time is masked, the output after the lapse of masking time is differentiated and the seam detecting signal is obtd. when the differential output thereof is more than the prescribed value, and by storing the robot coordinate at the time when the seam detecting signal thereof is transmitted the weld line is detected by connecting these plural detection spots. The weld line can therefore be detected without being effected by the surface state of the bend, waviness, minute projection, etc. of the work 11, the humidity and disturbance light nor effected by the vibration of the robot 12 at the initial sensing time and the inclination of the sensing direction and work 11.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a seam line detection method.

(Prior Art) For example, in a car body assembly process, joint lines of workpieces are automatically arc welded by a robot. When arc welding the seam line of a workpiece using a robot, it is necessary to teach the seam line as position data in order to move the welding torch along the seam line. An example of this is shown in Figure 8. Bracket 3 that holds welding torch 2 of robot 1
A laser sensor 4 having a laser light source that generates invisible light and a light receiving element is attached to the workpiece 5, and the laser sensor 4 is moved horizontally to the workpiece 5 by the robot 1 so as to intersect the seam line 6 of the workpiece 5. By projecting invisible light onto the workpiece 5 and receiving the reflected light with a light receiving element, the seam (welding start point and end point) is detected from the change in output, that is, the change in the amount of reflected light, and the coordinates of the seam are determined. There is a system in which position data regarding the seam line 6 is obtained from the seam line 6.

(Problems to be Solved by the Invention) However, the seam line detection method using the laser sensor 4 shown in FIG. In addition, since it is a non-contact type, it is easily affected by the surface condition of the workpiece 5, humidity, and ambient light.
There is also the problem that seams cannot be detected accurately. Further, the laser sensor 4 is expensive and its handling is extremely restricted, and its large size restricts the torch posture, causing the welding position to shift in the middle of the welding line.

Further, as shown in Fig. 9, the laser sensor 4 is moved horizontally to the workpiece 5 from the position Since the seam detection signal is generated from the device 7 and the position x 1 is detected as a seam, vibration may occur when the laser sensor 4 starts moving (when sensing starts), and the workpiece 5 may be curved, undulated, or have small protrusions. etc., or if the sensing direction and the workpiece 5 are not parallel, there is a problem of false detection.

This invention was made by focusing on these conventional problems, and is capable of always accurately detecting seam lines, is small and inexpensive, and can therefore be easily applied to welding robots, etc., and is easy to teach. The purpose of this invention is to provide a seam line detection method that can be used to

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a contact sensor is moved in a direction intersecting the seam line while contacting the workpiece at multiple locations on the workpiece having a seam line, and each Differentiate the output of the contact sensor at the movement point except for the initial stage of contact movement, determine the coordinates of the workpiece position where the differential output exceeds a predetermined value as the joint position, and detect the joint line from the coordinates of these multiple joint positions. do.

(Function) Here, at each moving point of the contact sensor, that is, the sensing point, removing the output of the contact sensor at the beginning of contact with the workpiece will remove the vibration component at the start of sensing, and By differentiating the output of , and obtaining a differential output of a predetermined value or more, it is possible to remove the effects of curvature, waviness, minute protrusions of the workpiece, inclination of the sensing direction and the workpiece, and the like.

(Example) FIG. 1 shows an embodiment of the present invention.

In this example, on the car body (work) assembly line,
The joint line 13 is detected in order to automatically arc weld a predetermined part of the workpiece 11 (in this example, the rear end of the beam-off panel) by the robot 12. A bracket 14 is provided at the tip of the robot 12, and a welding torch 15 and a differential transformer type contact sensor 16 that outputs a stroke change as an electric signal are attached to the bracket 14 in a predetermined positional relationship. The robot 12 is connected to a robot controller 18 via a robot cable 17, and the welding torch 15 is connected to an arc welder 20 via a welding cable 19. Further, the contact sensor 16 is connected to the robot controller 18 via a signal line cable 21, a sensor controller 22, and a sensor information cable 23.
Connect to.

In this embodiment, the robot 12 is controlled by the robot controller 18 so that FIG. 2A shows an enlarged view of the rear end of the rear quarter panel, and FIG. First, the contact sensor 16 is brought into contact with the workpiece 11 and sensed by moving it horizontally from point a to point a'. Based on the output, the edge 24 of the workpiece 11 is detected by the sensor controller 22, and the detection signal is is supplied to the robot controller 18 to set the reference position of the robot 12 with respect to the workpiece 11. Next, according to a predetermined program based on this reference position, the points passing through the joint line 13 and point b', between point C and C', and between point d and point d' are Sensing is performed in the same way at a plurality of locations, and in each of these sensing, the sensor controller 22 detects the seam from the output of the contact sensor 16, and supplies the seam detection signal to the robot controller 18. The robot controller 18 stores the three-dimensional coordinates of the robot 12 at the time when the seam detection signal is supplied from the sensor controller 22 in each sensing, and connects these detection points to synthesize the seam line 13 and determine the point e. The welding line from to point f is three-dimensionally detected and taught. Thereafter, while controlling the robot 12 and the arc welding machine 20 by the robot controller 18, welding is performed using the welding torch 15 based on the position data of the welding line and the data representing the relative positional relationship between the contact sensor 16 and the welding torch 15. Trace and weld the lines.

FIGS. 3A and 3B show the contact sensor 16 in sensing.
This figure shows an example of the operation and its output level.

First, the contact sensor 16 is moved from the robot origin P to the workpiece 1.
Positioning is performed at the first sensing start point P2. At this point, the contact sensor 16 is not in contact with the workpiece 11, and after this positioning, the robot controller 18 supplies a sensing start signal to the sensor controller 22, so that the sensor controller 22 can receive the output of the contact sensor 16. At the same time, the contact sensor 16 is connected to the workpiece 11.
thrust in a direction almost perpendicular to the When the contact sensor 16 contacts the workpiece 11 and the output reaches the reference level S at the contact point P3, the sensor controller 22 supplies a plunge completion signal to the robot controller 18, thereby causing the contact sensor 16 to contact the workpiece 11. Ends the thrusting motion. Thereafter, while the contact sensor 16 is brought into contact with the workpiece 11 in the direction intersecting the seam line 13 through the point P and the seam point P until the sensing end point P6, the workpiece 11 is
1, and a seam detection signal is supplied from the sensor controller 22 to the robot controller 18 based on the change in output at the seam point P5, whereby the three-dimensional robot coordinates at that point are stored in the robot controller 18. do. The contact sensor 16 moves to the sensing start point P6, and during this time the sensor controller 22
When the seam detection signal is not output from the contact sensor 16
is returned to the sensing starting point P2 again and the above operation is repeated, and when the seam detection signal is output, the contact sensor 16 is moved to the retreat point P7 and the sensing is finished.

Note that when the robot controller 18 receives the seam detection signal from the sensor controller 22 at the seam point P5, the contact sensor 16 can be immediately moved to the escape point P7.

FIG. 4 shows a circuit configuration of an example of the sensor controller 22. As shown in FIG. The output of the contact sensor 16 is sent to the filter circuit 2
5, high frequency components are removed, and the output thereof is supplied via a switching circuit 26 to a predetermined stroke achievement detection circuit 27 and a sensing start vibration removal circuit 28, respectively. The switching circuit 26 is controlled by the robot controller 18 via an external input/output interface circuit 29, and is turned on by a sensing start signal from the robot controller 18 and turned off by a sensing end signal.

The predetermined stroke achievement detection circuit 27 has a comparator 30,
Here, when the output of the contact sensor 16 reaches a reference level S at a predetermined reference stroke, a plunge completion signal is outputted, and this is sent to the external input/output interface circuit 2.
9 and is supplied to the robot controller 18.

The sensing start vibration removal circuit 28 is the switching circuit 3
1 and a timer circuit 32, from the time when the timer circuit 32 issues a sensing start signal, the output of the contact sensor 16 reaches the set value S, and then the contact sensor 16
The switching circuit 31 is turned off to mask the output of the contact sensor 16 for a predetermined period of time immediately after starting to move approximately parallel to the workpiece 11, and after this masking time has elapsed, the switching circuit 31 is turned on to mask the output of the contact sensor 16.
The output of is supplied to the differentiating circuit 33.

Differentiation circuit 33 includes switching circuit 34 and sample circuit 3
5. It has registers 36, 37 and a subtracter 38, and a sampling circuit 35 controls the switching circuit 34 to sample the output of the contact sensor 16 at a predetermined sampling period and supply it to the register 36. The output of register 36 is supplied to register 37 and also to the inverting input terminal of subtracter 38. The output of the register 37 is supplied to the non-inverting input terminal of the subtracter 38, and the workpiece 11 is differentiated by calculating the difference between successive sampling outputs.
The slope is determined and the output thereof is supplied to the binarization circuit 39.

The binarization circuit 39 has a comparator 40, where the differentiating circuit 3
The output of the comparator 40 is compared with the reference level, and when the output of the differentiating circuit 33 exceeds the reference level, it outputs logic "0", otherwise it outputs logic "1", and the output of this comparator 40 is The signal is supplied to the detection circuit 41.

The seam detection circuit 41 has a comparator 42, which compares whether the output of the binarization circuit 39 is logic "0" or not.
At this time, a seam detection signal is generated and supplied to the robot controller 18 via the external human output interface circuit 29.

In this configuration, as shown in FIG. 5A, when the contact sensor 16 is brought into contact with the workpiece 11 from the sensing start point P2 and moved from the contact point P3 to the sensing end point P6 via the joint point P5, the output level changes. For example, the fifth
-3. That is, at the curved portion 11a of the workpiece 11, the curve changes gently, and therefore the slope is small, and at the joint point P, it changes rapidly, and therefore the slope is large. In addition, in FIG. 5B, the symbol S indicates noise due to disturbance, and time t. indicates the mask time from the start of sensing in the timer circuit 32.

The output of the contact sensor 16 shown in FIG. 5B is supplied to a predetermined stroke achievement detection circuit 27 and a sensing start vibration removal circuit 28. Mask time t until immediately after the contact sensor 16 contacts the point P3 of the workpiece 11 with a predetermined stroke and starts moving toward the sensing end point P6. output is removed. Therefore, the mask time t. The output after the lapse of time is differentiated in a differentiating circuit 33, and exchanged into a binary signal in a binarizing circuit 39. Thus, the mask time t. If the output of the contact sensor 16 after the elapsed time is differentiated and binarized, the fifth
As shown in FIG. The detection circuit 41 can obtain a seam detection signal that accurately corresponds to the seam point P as shown in the fifth diagram.

In this way, in this embodiment, the contact sensor 16 is used and sensed by moving it into contact with the workpiece 11 at multiple locations so as to intersect the seam line 13, and in each sensing, the output of the contact sensor 16 at the initial stage of sensing is is masked, the output after the mask time has passed is differentiated, and when the differentiated output is greater than a predetermined value, a seam detection signal is obtained.
By memorizing the robot coordinates at the time when this seam detection signal is issued, weld lines can be detected three-dimensionally by connecting these multiple detection points. etc., the vibration of the robot 12 at the beginning of sensing, the sensing direction, and the workpiece 11.
The weld line can always be detected with high accuracy without being affected by the slope of the weld line. In addition, the contact sensor 16 has a simple structure, is small, inexpensive, and easy to maintain, and the sensing point can be visually confirmed, making teaching easy. Furthermore, since the use of the contact sensor 16 allows freedom in the sensing angle, the contact sensor 16 can be made smaller, and the torch can take any posture without affecting the torch posture. Therefore, the detected welding line can always be accurately traced by the welding torch 15.

FIG. 6 shows another circuit configuration of the sensor controller 22 described above. In this example, a stroke display circuit 45, a sensing condition setting circuit 46, and a protect circuit 47 are added to the circuit configuration shown in FIG. The stroke display circuit 45 is configured to calculate the stroke of the contact sensor 16 from the output of the filter circuit 25 and display it.

The sensing condition setting circuit 46 also includes a mask time setting circuit 48 that sets a mask time in the timer circuit 32 of the sensing start vibration removal circuit 28, and a differentiation circuit 33.
a sample time setting circuit 49 that sets the sampling period in the sample circuit 35; a stroke setting circuit 50 that sets the reference level S to the comparator 30 of the predetermined stroke achievement detection circuit 27; and a comparator 40 of the binarization circuit 39.
A protection circuit 4 includes a level setting circuit 51 for setting a reference level to
7 to set each sensing condition.

As described above, by providing the sensing condition setting circuit 46, it is possible to easily change the sensing conditions, and by controlling the change of the conditions by the protection circuit 47, it is possible to prevent erroneous operations when there is no need to change the sensing conditions. be able to.

Further, by providing the stroke display circuit 45, the teaching operation can be easily performed.

FIG. 7 shows another circuit configuration of the differential circuit constituting the above-mentioned sensor controller, which includes a high-speed sampler 55 and a data buffer 56. The high-speed sampler 55 samples the output from the contact sensor 16 at a cycle faster than the sampling cycle 1 set by the sample circuit 35 (see Figure 4) or the sample time setting circuit 49 (see Figure 6), and The data is stored at the address Be of the data buffer 56 and supplied to the inverting input terminal of the subtracter 38. Further, the data buffer 56 supplies the data stored at address Be-1 one sampling period before the set sampling period to the non-inverting input terminal of the subtracter 38, and also supplies each address stored in synchronization with sampling by the high-speed sampler 55. The data of (eo)←(B1
)−−−−−(Bt−+)←(Bt)−−−(B−+)
Shift to ←(B@).

By sampling using the high-speed sampler 55 in this manner, the inclination of the workpiece 11 can be determined with higher accuracy, and therefore the accuracy of seam detection can be further improved.

Note that this invention is not limited to the above-mentioned embodiments, and can be modified or modified in many ways. for example,
In the above-described embodiment, a differential transformer type contact sensor 16 was used, but it may also be a linear potentiometer that outputs the amount of displacement in a linear direction, or a rotary potentiometer or rotary potentiometer that converts linear motion into rotational motion. An encoder can also be used. In addition, the sensing points for the seam can be set at any number of points depending on the seam line, and instead of connecting the detection points and composing the seam line, coordinate transformation is used to three-dimensionally detect the seam line. You can also. Furthermore, by attaching a sealing nozzle or the like in place of the welding torch, it can be applied to other seam joining and bonding applications. Furthermore, the seam line is not limited to three-dimensional detection, but can also be detected two-dimensionally depending on the shape and posture of the workpiece.

(Effects of the Invention) As described above, according to the present invention, the seam line of the workpiece can always be detected with high precision without being affected by the surface condition of the workpiece, the atmosphere, or undesirable vibrations. In addition, the device can be made smaller and cheaper, and it can be applied to welding robots and the like without any problems, and the teaching thereof can be easily performed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIGS. 2A and B are partially enlarged views and sectional views of FIG. 1, and FIGS. 3A and B show the operation of the contact sensor during sensing and its output level. 4 is a circuit configuration diagram of an example of the sensor controller; FIGS. 5A-D are diagrams for explaining its operation; FIG. 6 is a circuit configuration diagram of another example of the sensor controller; FIG. 7 is a circuit configuration diagram of another example of the differential circuit constituting the sensor controller, and FIGS. 8 and 9 are diagrams for explaining conventional examples. 11...Work 12...Robot 1
3... Seam line 14... Bracket 15
...Welding torch 16...Contact sensor 18.
...Robot controller 20...Arc welding machine 22...Sensor controller 25...Filter circuit 26...Switching circuit 27...Predetermined stroke achievement detection circuit 28...
Sensing start vibration removal circuit 29...External input/output interface circuit 30...Comparator 31.
...Switching circuit 32...Timer circuit 3
3...Differentiating circuit 34...Switching circuit 35.
...Sample circuits 36, 37...Register 38
...Subtractor 39...Binarization circuit 40...
Comparator 41... Seam detection circuit 42... Comparator 45... Stroke display circuit 46... Sensing condition setting circuit 47... Protect circuit 48... Mask time setting circuit 49... Sample time Setting circuit 50...Stroke setting circuit 51...Level setting circuit 55...High speed sampler 56...Data buffer Patent applicant Nissan Motor Co., Ltd. Representative Patent Attorney Akatsuki Sugimura Masashi Patent Attorney Kosuke Sugimura Figure 2 Figure 3 A Figure 5 Figure 9

Claims (1)

[Claims] 1. Move the contact sensor in a direction intersecting the seam line while making contact with the workpiece at multiple locations on the workpiece having a seam line, and at each of the moving locations, output after the contact movement of the contact sensor to the workpiece begins at the initial stage. A method for detecting a seam line, characterized in that the workpiece position where the differential output is equal to or greater than a predetermined value is determined as a seam position, and its coordinates are determined, and the seam line is detected from the coordinates of a plurality of seam positions.