JPS6213276A - Control method in automatic seam welding equipment - Google Patents

Abstract

PURPOSE:To control with correction a trailing track and to operate the corect seam welding of a welding equipment by providing a strain gage on the wrist part is operation end of the work holding robot of an automatic seam welding equipment and by detecting the torque deviation at the robot operation time. CONSTITUTION:A work W is held by the work holder 10 at the arm tip wrist part 8 of the robot 7of a seam welding machine 1 and its position is controlled by the rotation of the wrist shaft 9 by a motor 15. The flange Wa of the work W is welded with the pinching electrification of electromagnetic roll 2. In case of the welding direction of the flange Wa of the work W being slipped off against the electrode roll 2 the strain gage 17 interposed on the wrist shaft 9 detects the deviation for the normal torque. The feedback control is performed so as to make the torque deviation zero by varying the rotary speed and progressing direction of the roll 2, 2 according to the torque deviation thereof.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a control method for an automatic seam welding device that can automatically seam weld workpieces such as fuel tanks for two-wheeled vehicles using a robot. .

(Prior Art) The applicant of the present application previously disclosed in Japanese Patent Application No. 58-227829 that a workpiece is held by a vertical wrist shaft provided at the wrist at the operating end of the robot via a workpiece holder. An automatic seam welding device has been proposed in which the welded portion is guided by the movement of each stationary member of the robot including the wrist shaft and fed between a pair of upper and lower electrode rolls provided in a seam welding machine.

(Problem to be Solved by the Invention) In a seam welding machine, the welded part of the workpiece is forcibly fed by an electrode roll, so in the above device, the robot is operated in synchronization with the rotation of the electrode roll. However, due to slippage between the workpiece and the electrode roll, the actual feed stone of the workpiece by the electrode roll and the amount of workpiece feed by the robot movement may not match, and as a result, the There is a problem in that the moving direction of the electrode roll deviates from the normal direction, causing the electrode roll to come off the welded portion or interfere with the workpiece.

The present invention provides a control method that solves the above problems by automatically detecting a mismatch between the actual feed amount of the workpiece by the electrode roll and the feed distance of the workpiece due to the movement of the robot and correcting the trajectory. Its purpose is to provide.

(Means for Solving Problem +2) In the present invention, in order to achieve the above object, the actual torque applied to the vertical wrist shaft that holds the workpiece via the workpiece holder, and the actual torque applied to the workpiece by the electrode roll. The deviation between the normal torque acting on the wrist axis and the rotation of the electrode roll is detected when the feeding distance and the movement of the robot match the feeding distance of the workpiece. The speed and direction of movement of the electrode roll relative to the workpiece can be changed.

(Function) Torque related to the movement of the workpiece sent in the horizontal direction by the electrode rolls acts on the vertical wrist axis, which is offset from the part where the workpiece is held between the pair of upper and lower electrode rolls. If the actual feed of the workpiece by the electrode roll does not match the feed rate of the workpiece by the movement of the robot, for example, if the former feed rate decreases from the latter feed rate due to workpiece slipping, the electrode roll A reaction force corresponding to the difference between the two feed rates acts in the opposite direction to the workpiece feed direction, and thus the actual torque acting on the wrist shaft is smaller than the normal torque when the two feed rates match. By detecting the deviation between the two torques, the difference between the two feed amounts is detected.

Then, by changing the rotational speed of the electrode roll according to this torque deviation, both feed amounts will match, and by changing the direction of movement of the electrode roll with respect to the workpiece, the welding trajectory of the electrode roll can be adjusted to the normal trajectory. Accurate seam welding can be achieved by restoring the seam.

(Example) Referring to FIG. 1, (1) shows seam welding, and a pair of upper and lower electrode rolls (21) (2
2) and drive motors (31) (32) for the respective rolls (21) (22) are provided at the rear thereof, where the upper electrode roll (21) is an electrode holder that is raised and lowered by a pressure cylinder (4). The drive motor (31) is pivotally supported by (51).
The lower electrode roll (22) is pivotally supported by an immovable electrode holder (52) and rotationally driven by a drive motor (32), and the welding 11! A robot (7) is mounted on the upper surface of (1), and a workpiece holder (11) is attached to a vertical wrist @ (9) that is pivoted on the wrist (8) at the operating end of the robot (7). A welded part W consisting of a butt flange around the workpiece W, holding a workpiece W consisting of a fuel tank for a two-wheeled vehicle.
a to the lower electrode roll (2) at a predetermined welding start point.
2) With the upper electrode roll (21) placed on
and a welded part Wa between the two rolls (21) and (22).
Rotating the two arms (2+) (22) while sandwiching them, and in synchronization with this, move each movable member of the robot (7) including the wrist shaft (9) according to the taught data, The welding part Wa was continuously fed between the two rings (2d (22)) to perform automatic seam welding.

In addition, the robot shown in the figure (υ is a seam welding machine (1
) Both electrode rolls (21) are attached to the base at+ fixed on the top surface of
(22) The robot body (+21, etc., the robot body ab
A first arm (13) extending forward, which is pivotably mounted on the top of the first arm (13), and a second arm (a) extending downward, which is disposed at the tip of the first arm (a3), so as to be swingable in the front-rear direction. A wrist part (8) is attached to the lower end of the second arm a@ so as to be always held in a constant posture by an appropriate parallel mechanism.
is attached, and a wrist shaft (9) which is rotatably driven by a drive motor (19) mounted on the wrist part (8) via an internal bevel gear (not shown) is vertically installed.
9) A workpiece holder 0G was attached to the lower end via a cross joint ae.

In the automatic seam welding apparatus configured as described above, according to the present invention, the actual feed amount of the workpiece W by the electrode roll (2+) (22) matches the feed rate of the workpiece W by the movement of the robot (7). The deviation between the normal torque acting on the wrist axis (9) and the actual torque acting on the wrist axis (9) when
The rotation speed of the electrode rolls (21) and (22) and the direction of movement of the electrode rolls (21) and (22) relative to the work W are changed.

To explain this further, electrode roll (2+) (22)
When the workpiece W is sent in the direction of arrow A in Fig. 2,
The workpiece W slips with respect to the rolls (21) (22) and the workpiece W due to the rolls (21) (22)
Even if the feed interval of the robot (D) is reduced, the wrist axis (9) will not be able to feed the workpiece W by the rolls (2+) (22) as shown in the imaginary line in Fig. 2 because the robot (D) is operated as instructed. The workpiece W is moved in advance in the workpiece feeding direction, and the workpiece W is moved by the roll (
2d (22) is tilted using the holding part O as a fulcrum, and the direction of movement of the rolls (21) and (22) with respect to the workpiece W deviates from the normal direction.

At this time, a reaction torque acts on the wrist shaft (9) in the opposite direction to the workpiece feeding direction, that is, in the counterclockwise direction in FIG.
The actual torque acting on the wrist shaft (9) increases by the counter torque amount from the above-mentioned normal torque, and as a result, by detecting the deviation between the actual torque and the normal torque,
The feed m of the work W due to the movement of the robot (7) and the electrode [
The difference between the actual feeding distance of the workpiece W by the rolls (21) and (22) is detected, and the rotational speed and traveling direction of the rolls (2+) and (22) are determined according to this torque deviation. If the feedback ai control is performed so that the torque deviation becomes zero by changing the angle, the welding trajectory of 0-rule (2+) (22) returns to the normal trajectory and accurate seam welding is performed.

Note that the direction of movement of the rolls (21) and (22) is such that the rotation axis X of the robot main body (2) is located on a vertical line passing through the clamping part O, so that the main body aδ is turned and the workpiece W is held in the clamping part. It can be easily changed by tilting using part 0 as a fulcrum.

Here, the torque deviation can be detected, for example, from the change in the drive current of the drive motor (1!11) of the hand wheel (9), that is, the a line in Fig. 3 is caused by the electrode roll (21) (22). Between feeds of workpiece W and workpiece W by robot (7)
If the change characteristics of the drive current are normal when the feed gauges match, there will be a difference between the two feed rates and the wrist axis (9)
When the actual torque acting on the motor becomes larger than the normal torque as described above, the drive current correspondingly becomes larger than the normal current value as shown by the b line, and thus the change characteristics of the a line are memorized. If the deviation between this and the actual drive current is detected, the torque deviation can be detected.

In addition, as shown in Fig. 4, a strain gauge (+
It is also possible to detect the torque deviation by attaching the elastic material (9a) to the middle part of the wrist shaft (9), as shown in Fig. 5. A relatively large torsion corresponding to the elastic member (9a) is generated, and a strain gauge surface is attached to the circumferential surface of the elastic member (9a) so that the torque can be detected with good sensitivity.

(Effects of the Invention) As described above, according to the present invention, the rotation speed and direction of movement of the electrode roll are changed depending on the deviation between the actual torque and the normal torque acting on the wrist axis. Even if the welding trajectory of the electrode roll deviates from the normal trajectory due to a mismatch between the actual feed rate of the workpiece by the electrode roll and the feed stone of the workpiece due to robot movement, this is automatically returned to the normal trajectory to ensure accurate seaming. It has the effect obtained by performing welding.

[Brief explanation of drawings]

Figure 1 shows one example of automatic seam welding equipment to which the method of the present invention is applied.
A side view of the example, Fig. 2 is a diagram explaining the principle of action of torque on the wrist shaft, Fig. 3 is a change characteristic diagram of the drive current of the drive motor, and Fig. 4 is an example in which a strain gauge is attached to the wrist shaft. FIG. 5 is an enlarged side view of the main parts of the wrist.

Claims (1)

[Claims] 1. A workpiece is held via a workpiece holder on a vertical wrist shaft provided at the wrist at the operating end of the robot, and the workpiece is moved by each movable member of the robot including the wrist shaft. This is a control method for an automatic seam welding device in which the welded part is guided between a pair of upper and lower electrode rolls provided in a seam welding machine, and the control method is based on the actual feed amount of the workpiece by the electrode rolls and the robot The deviation between the normal torque that acts on the wrist axis and the actual torque that acts on the wrist axis when the feed amount of the workpiece due to movement matches is detected, and the electrode roll is adjusted according to this deviation. 1. A control method for an automatic seam welding apparatus, characterized in that the rotation speed and the direction of movement of the electrode roll relative to a workpiece are changed. 2. A control method for an automatic seam welding apparatus according to claim 1, wherein the torque deviation of the wrist shaft is detected from a change in the drive current of a drive motor of the wrist shaft. . 3. A control method for an automatic seam welding apparatus according to claim 1, wherein the torque deviation of the wrist shaft is detected using a strain gauge attached to the wrist shaft.