JPH07284933A - Method for controlling position of robot - Google Patents

Abstract

PURPOSE:To appropriately set the final arrival position where an electrode of the fixing side fixed to a welding gun supported with robot arms reaches the final arrival position for reaching the material to be welded in a good balance without using an equalizing mechanism having spring, etc., and prevent the lowering of maintainability and economics of the welding gun. CONSTITUTION:A fixing side electrode 7 fixed to the welding gun fixedly supported in the industrial robot arm and a moving side electrode 6 are provided and the interval (d) required for moving the interval of successive welding points between the tip part of the fixing side electrode 7 and the surface of the material is set, and the consumed quantity (c) of the fixing side electrode 7 is detected. Firstly, the tip part of the fixing side electrode 7 is moved to a first command position P1 having the interval (d) from the welding point of the material, and further moved to a second command position P2 adding the interval (d) and the consumed quantity (c) of the fixing side electrode 7 to the first command position P1 to return back the fixing side electrode 7 to the first command position P1 after welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed side electrode supported by a welding gun supported by an industrial robot arm, and a movable side electrode movably supported by the welding gun toward the fixed side electrode. The present invention relates to a resistance welding technique using a welding gun having two pairs of electrodes, such as a C-shaped welding gun or an X-shaped welding gun for sandwiching and holding a welding object with pressure, and is particularly suitable for a robot when welding and pressing. The present invention relates to a position control method.

[0002]

2. Description of the Related Art When an industrial robot that carries out a welding operation by attaching a resistance welding gun moves between welding points on the surface of an object to be welded, the conventional robot position control method attaches the welding gun to the robot by fixing it. If this happens, the positioning error of the robot, teaching error, the accuracy of the welding target and jig, the deflection of the welding gun, the wear of the fixed electrode, the displacement of the pressing position of the fixed electrode tip due to the thermal distortion of the welding target, etc. Occurs, and at each welding point, due to these accumulated errors, welding is performed in a state in which the welding target is forcibly pushed one-sided, that is, the state where mechanical distortion is applied to the welding target, resulting in poor welding. However, there is a problem in that the welded object after welding has a large distortion or indentation.

Therefore, in order to move between welding points on the surface of the object to be welded by an industrial robot which carries out a welding operation by attaching a resistance welding gun, a fixed side electrode supported by the welding gun supported by the robot arm is used. Although a space is required between the welding target and the welding target, conventionally, in order to reach the welding target by moving the fixed side electrode through the gap at the welding point, an equalizing mechanical mechanism using a spring or an equalizing cylinder, For example, the main body of the welding gun is supported by a robot arm so as to be movable in the axial direction of the electrode via a spring, and when the robot arm moves, the welding gun is pressed in one direction by the force of the spring to maintain a fixed position, and the robot arm moves. This fixed position cannot be moved by the change in acceleration due to
Moreover, a mechanism was provided so that the main body of the welding gun could freely move in the axial direction of the electrode with respect to the robot arm when a force exceeding the spring pressure was applied. During the welding operation, first, the robot arm and the welding gun main body reach the teaching position having the above-mentioned interval between the fixed electrode and the welding object. Next, the welding gun starts operating from the open state to the closed state. At this time, the fixed-side electrode is pressed against the object to be welded, the spring is deflected by the reaction force of the object to be welded, and then the moving-side electrode is also pressed against the object to be welded, and the spring force and the electrode pressure force are The welding gun is moved to a balanced position, in other words, the welding gun is regulated and follows the position of the object to be welded, thereby correcting the error in the pressing position of the electrode. After the welding at the welding point is completed, the welding gun operates from the closed state to the open state, and the movable electrode is returned to the original position.

In the Equalize mechanical mechanism using such springs and Equalize cylinders, it is only possible to mechanically correct how much the tip of the fixed electrode approaches or goes too far with respect to the object to be welded. For this reason, the one-sided pushing force of the electrodes is not completely removed structurally, and it is unavoidable that an imbalance in the applied pressure corresponding to the spring pressure remains between both electrodes. In addition, the influence of gravity was unavoidable, and the welding characteristics changed depending on the position of the welding gun. Further, since the fixed electrode first presses the object to be welded and bends the spring, the pressing operation is started, so that the cycle time of the welding operation of the robot becomes long.

[0005]

As described above, in the Equalize mechanical mechanism using the spring, the Equalize cylinder, etc., the maintainability and economy of the welding gun are deteriorated, and if the final position of the fixed electrode is inappropriate, Excessive stress was applied to the object to be welded, causing deformation and noise at the time of collision becoming loud. And correct the final reaching position of the fixed side electrode during welding work,
It was impossible or very difficult to adjust. Japanese Patent Application Laid-Open No. 2-30477 filed by the present applicant discloses a method of detecting the amount of wear of each electrode and correcting the position of the robot, but it is fixed to a welding gun supported by a robot arm. There was no means for the side electrode to reach the welding object, and there was no means for adjusting the final reaching position of the fixed side electrode.

An object of the present invention is to finally reach a fixed object electrode fixed to a welding gun supported by a robot arm to reach an object to be welded without using an equalizing mechanical mechanism having a spring or an equalizing cylinder. It is an object of the present invention to provide a robot position control method capable of appropriately setting a position without imbalance and preventing deterioration of maintainability and economy of a welding gun by having a conventional Equalize mechanical mechanism. Another object of the present invention is to obtain good welding characteristics irrespective of the position of the welding gun, shorten the cycle time of the welding operation of the robot, and input one teaching position for each welding point in advance. It is to provide a robot position control method that is sufficient. Another problem of the present invention is that, due to the improper fixed-side electrode final position, the welding object is prevented from being deformed by giving excessive stress, and the fixed-side electrode and the welding object. It is an object of the present invention to provide a robot position control method capable of preventing noise at the time of collision and further correcting and adjusting the final arrival position of the front fixed side electrode during welding work.

[0007]

Therefore, according to the present invention, the fixed side electrode fixed to the welding gun fixedly supported by the arm of the industrial robot and the welding gun movably supported toward the fixed side electrode. And a movable side electrode, the fixed side electrode and the movable side electrode can be arranged at positions sandwiching the welding object, and a welding point continuous between the fixed side electrode tip and the surface of the welding object. Set a necessary interval when moving between and store in the robot, the consumption of the fixed electrode is detected and stored in the robot, first the tip of the fixed electrode to the first of the welding object surface Second command position obtained by adding the distance and the wear amount of the fixed electrode to the first command position and moving the fixed-side electrode tip to the first command position having the interval with respect to the welding point Move to the above Characterizing that the electrode is moved to hold the welding target under pressure with the fixed-side electrode for welding, and after the welding, the movable-side electrode is returned, and then the fixed-side electrode is returned to the first command position. The above-mentioned problems of the prior art have been solved by providing a robot position control method.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the attached FIGS. FIG. 1 is a block diagram showing a configuration of a robot controller used in a robot position control method according to an embodiment of the present invention, and FIG. 2 is a side view of a fixed side electrode supported by a welding gun fixedly supported by a robot arm of FIG. Fig. 2 (b) to (f) shows the operation of the moving side electrode during welding work, and Fig. 2 (b ') to (f') shows the state of electrode wear. I will show each of them. FIG. 3 is a flowchart for explaining the operation during welding work by the robot position control method according to the embodiment of the present invention.

According to one embodiment of the robot position control method of the present invention, the fixed side electrode 7 fixed to the welding gun 2 fixedly supported by the arm of the industrial robot 1 and the movable side electrode 7 are movably welded. The movable side electrode 6 supported by the gun 2 is provided, and the fixed side electrode 7 and the movable side electrode 6 can be arranged at positions sandwiching the welding target, and the fixed side electrode 7 and the welding target surface are disposed between the fixed side electrode 7 tip and the welding target surface. The distance d required when moving between consecutive welding points is set and stored in the robot 1, the consumption amount c of the fixed side electrode 7 is detected and stored in the robot 1, and the tip of the fixed side electrode 7 is first stored. The tip of the fixed electrode 7 is moved to a first command position P1 having a space d with respect to the first welding point on the surface of the object to be welded, and the tip of the fixed electrode 7 is spaced from the first command position P1 and the wear amount c of the fixed electrode 7 is c. Is moved to the second command position P2, and the moving side electrode 6 is The object to be welded is pressed and held with the fixed-side electrode 7 to be welded, and after welding, the movable-side electrode 6 is returned and then the fixed-side electrode 7 is returned to the first command position P1. .

More specifically, with reference to FIG. 2, it is assumed that the electrodes are in a worn state. Like the conventional method, the robot 1
When the program 9 is created, the clearance or distance d required for moving from the welding point where the robot 1 is between the welding target and the fixed electrode 7 to the continuous welding point (see FIG. 2 (b))
Then, the distance d is stored in the fixed side electrode clearance memory 16. Prior to welding work, for example, Japanese Patent Laid-Open No. 2-30
As disclosed in Japanese Patent No. 477, the wear amount c of the fixed-side electrode 7 is measured by a measuring device outside the robot, and the wear amount c is input to the fixed-side electrode wear amount detection circuit 14. In order to correct the tip position of the fixed-side electrode 7 as a tool error of No. 3, it is stored in the fixed-side electrode consumption amount memory 15. The robot 1 reads the program 9 with the program data reading circuit 10 and the robot position command creating circuit 11 has a first command position having a distance d between the tip of the fixed electrode 7 before wear and the first welding point on the surface of the object to be welded. The position command data P1 of P1 is created, and the robot is driven by the robot drive circuit 12. When it is determined that the current position P read by the robot position coincidence detection circuit 13 and the command position P1 match (see FIG. 2 (b ')), the command position P1 is replaced with the wear amount c in the fixed side electrode wear amount memory 15 and the clearance. Taking into account the distance d in the memory 16,
The command position P2 is created, and the robot drive circuit 12 drives the robot.

When it is judged that the current position P read by the robot position matching detection circuit 13 and the command position P2 match (see FIG. 2 (c ')), a welding start signal is sent to the welding machine 18 and a welding completion signal is returned. Wait on the spot until you come (Fig. 2 (d ') →
See (e ′). Close the gun with the air cylinder → open). When the welding completion signal is received, the robot drive circuit 12 drives the robot by using the position command P1 again. When it is judged that the current position P read by the robot position coincidence detection circuit 13 coincides with the command position P1 (see FIG. 2 (f ′)), the robot moves to the next welding point, and FIG. 2 (b ′) → (f ′) repeat. In short, it teaches only one position P1 where the fixed side electrode distance is kept between the welding target and the position P2 that makes suitable contact with the welding target, and automatically adjusts the fixed side electrode clearance and the fixed side electrode consumption amount. It is generated, and the robot is operated as if three points such as P1 → P2 → P1 were taught.

The operation will be described with reference to the flowchart of FIG. Here, the movement / closing / opening modes switched by the robot position command switching circuit 18 indicate the following movement modes. Movement: A mode in which the fixed-side electrode 7 is moved to the position command P1 separated from the object to be welded by the distance d for welding. Closing: A mode in which the fixed-side electrode 7 is moved to the closed position P2 at a position where the fixed-side electrode 7 and the moving-side electrode 6 can be closed. Opening: A mode in which the fixed electrode 7 is moved to the position command P1 in order to prepare the welding gun 2 to move to the next work point after the moving electrode 6 is opened. First, the program 9 is read by the program data reading circuit 10, and the command position data P1 is created by the robot position command creating circuit 11 (step 32). The position command data P1 is stored in the robot position command memory 17 (step 33). The switch of the robot position command switching circuit 18 is switched to "move" (step 34). The robot drive circuit 12 outputs a robot position command (step 35). The robot position coincidence detection circuit 13 loops until the position coincides (current position = command position) (step 36).

If position matching is detected and the switch of the robot position command switching circuit 18 is "move", the process branches to step 38 (step 37). Contents of robot command position memory 17
The command position data P2 is created by adding the consumption amount c in the fixed side electrode consumption amount memory 15 and the interval d in the clearance memory 16 to P1 (step 38). Robot position command switching circuit 18
Switch the switch to "close" (step 39). The robot drive circuit 12 outputs a robot position command (step 35). Loop until the robot position match detection circuit 13 matches the position (current position = command position) (step 3
6).

If position matching is detected and the switch of the robot position command switching circuit 18 is "closed", the process branches to step 41 (step 40). A welding start signal is sent to the welding machine 18 (step 41), and a welding completion signal is received on the spot (step 42). The switch of the robot position command switching circuit 18 is switched to "open" (step 43). The robot drive circuit 12 outputs the robot position command P1 (step 35). The robot position coincidence detection circuit 13 loops until the position coincides (current position = command position) (step 36).
If the position coincidence is detected and the switch of the robot position command switching circuit 18 is neither "move" nor "closed", the process branches to step 44 (step 40). Robot position command switching circuit 18
Switch the switch to "move" (step 44). When the above is completed, the process proceeds to the next welding point and the processes of steps 31 to 45 are repeated.

[0015]

As described above, according to the present invention, the gap between the fixed electrode and the object to be welded which allows the robot to move between the continuous welding points is set, and the amount of wear of the electrode is reduced. In addition, since it can be positioned at a suitable position, the final reaching position where the fixed-side electrode supported by the robot arm reaches the welding target without using the Equalize mechanical mechanism that has a spring, Equalize cylinder, etc. The present invention provides a robot position control method that can be appropriately set without balance and that does not reduce the maintainability and economy of the welding gun by having a conventional Equalize mechanical mechanism. Further, according to the present invention, good welding characteristics can be obtained irrespective of the posture of the welding gun, the cycle time of the welding operation of the robot can be shortened, and one teaching position can be input in advance for each welding point. , It is possible to minimize the deformation of the welding target by applying excessive stress to the welding target due to the improper fixed electrode end position, and also to prevent the noise when the stationary electrode and the welding target collide. Further, the present invention provides a robot position control method capable of correcting and adjusting the final reaching position of the fixed-side electrode during welding work.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a robot controller used in a robot position control method according to an embodiment of the present invention.

FIG. 2 shows the operation of the fixed side electrode and the moving side electrode supported by the welding gun fixedly supported by the robot arm of FIG. 1 during welding work, and FIGS. 2 (b) to 2 (f) show that the electrodes are consumed. 2 (b ') to 2 (f') in the state where the electrodes are not worn, and those in the state where the electrodes are worn out, respectively.

FIG. 3 is a flowchart illustrating an operation during welding work by the robot position control method according to the embodiment of the present invention.

[Explanation of symbols]

 1 Robot 2 Welding gun 2 6 Moving side electrode 7 Fixed side electrode c Fixed side electrode wear amount d Interval P1 1st command position P2 2nd command position

Claims (1)

[Claims] 1. An industrial robot having a fixed side electrode fixed to a welding gun fixedly supported by the arm, and a movable side electrode movably supported by the welding gun toward the fixed side electrode, The fixed-side electrode and the moving-side electrode can be arranged at positions sandwiching the object to be welded, and an interval required when moving between continuous welding points between the fixed-side electrode tip and the surface of the object to be welded. The fixed side electrode tip is set and stored in the robot, the fixed side electrode consumption amount is detected and stored in the robot, and the fixed side electrode tip has the interval with respect to the first welding point on the welding target surface. No. 1 command position, the fixed-side electrode tip is moved to the second command position obtained by adding the distance and the wear amount of the fixed-side electrode to the first command position, and the moving-side electrode is moved. Let the welding target A robot position control method characterized in that the fixed side electrode is pressed and held for welding, the movable side electrode is returned after welding, and then the fixed side electrode is returned to the first commanded position.