JP2812078B2 - Positioning control device for spot welding robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically correcting the position of a spot welding gun to an optimum position in accordance with the amount of deformation of the spot welding gun caused by the pressing force of the electrode tip on the workpiece. And a control device for the spot welding robot.

[0002]

2. Description of the Related Art At present, spot welding performed on a vehicle body is performed by a dedicated spot welding gun mounted on a robot. As an example of this welding gun, the one shown in FIG. 6 can be exemplified. In this spot welding gun 1, one of the electrode tips 2 is moved up and down in the directions A and B by a servomotor 3. This vertical movement is performed by a ball screw 4 engaged with the servo motor 3. In such a spot welding gun 1 using the servo motor 3 as a drive source, the positioning with respect to the spot where the spot welding is performed can be accurately performed by using the correction function of the robot. When a pressing force is applied to an object,
As shown in FIG. 6, the gun arm 5 is elastically deformed outward in the figure according to the pressing force. For this reason, at the time of pressurization, it is necessary to push in by the servomotor 3, and this pushing is absorbed or corrected by the floating mechanism 6 having a structure as shown in FIG.

[0003]

However, in a spot welding robot using such a floating mechanism 6, although a certain degree of position correction can be performed by using a correction function on the robot side, it is very accurate. It is not suitable for positioning, and there is a problem that the provision of such a mechanism leads to an increase in size, cost and weight.

The present invention has been made in view of such problems of the prior art, and has as its object to provide a low-cost, low-weight spot welding robot positioning control apparatus capable of accurate positioning. .

[0005] The present invention for achieving the above object, scan
The support position of the pot welding gun is determined based on the teaching data.
In a spot welding robot configured to spot-weld an object to be welded, a relationship between a pressing force applied to the object to be welded by an electrode tip in the spot welding gun and an amount of deformation of the spot welding gun. Based on the relationship stored in the storage means.
From the pressing force applied to the workpiece.
Means for calculating the amount of deformation of the welding gun,
The teaching is performed in accordance with the deformation amount calculated by the shape amount calculating means.
Correction means for correcting the display data.
You .

According to the present invention having the above-mentioned configuration, the correcting means includes a pressing force applied to the workpiece to be welded to the electrode tip, the deformation amount of the spot welding gun being stored in the storage means, and the spot welding gun . Based on the relationship with the amount of gun deformation
Calculate and scan the teaching data according to the calculated amount of deformation.
Pot welding gun is supported at the optimal position where no stress occurs
Correction as follows .

For this reason, it is not necessary to provide a floating mechanism as in the prior art, so that highly reliable spot welding can be performed with an improvement in positioning accuracy, and cost and size can be reduced. Become. Further, the operating performance is improved as the weight is reduced.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a spot welding robot.

As shown in the drawing, the operation of the illustrated spot welding robot 10 is controlled by a robot controller 11. The spot welding robot is of a seven-axis type, and a spot welding gun 1 is mounted on a working end thereof. The first axis turns the entire spot welding robot 10 in the J1 direction, and the second axis moves the working end in the vertical direction, that is, the J2 direction with reference to the first axis. The third axis similarly moves the working end in the vertical direction, that is, in the J3 direction with reference to the second axis. The fourth axis is for turning the working end in the J4 direction in the drawing with reference to the third axis. The fifth axis is for moving the working end in the J5 direction in the drawing with reference to the fourth axis. The sixth axis is for turning the working end in the J6 direction in the drawing with reference to the fifth axis. The seventh axis moves the electrode tip 2 of the spot welding gun 1 attached to the working end up and down in the J7 direction in the figure. The spot welding gun 1 is not supported by the floating mechanism, but is directly mounted on the sixth shaft.

The robot controller 2 comprehensively controls the operations of the above seven axes based on data taught in advance, and positions the electrode tip 2 at a predetermined position with respect to the workpiece. Spot welding is performed at that position.

FIG. 2 is a schematic block diagram of a positioning control device for a spot welding robot according to the present invention. The robot controller 11 includes a control unit 15 as a correction unit that comprehensively controls the operation of the spot welding robot 10, and based on a signal from the control unit 15, performs the operation of each of the seven axes. Servo control units 20A to 20G are provided for each control. The six servo control units 20A to 20F control the operation of each axis arm of the main body of the spot welding robot 10, and the servo control unit 20G is an electrode tip of the spot welding gun 1. The second operation is controlled. In the control unit 15,
A storage unit 16 is provided as storage means for storing the relationship between the pressure applied to the electrode tip 2 and the amount of deformation of the gun arm 5.

FIG. 3 is a detailed block diagram of the servo control unit. The servo control section controls the operation amount of the connected servo motor 3, and the operation amount of the servo motor 3 is fed back by a signal from the encoder 19. The encoder 19 gives position feedback to the control unit 15 and also gives feedback of a position command and a speed command to the servo control unit itself.

The servo control section calculates the rotational speed of the servo motor 3 based on the position command output from the control section 15, and calculates a command for a current flowing through the servo motor 3 based on the speed command. Based on this current command, a predetermined voltage is applied to the servo motor 3 and a predetermined current is supplied. The current controller 21 controls the servo motor 3 based on the current limiting command output from the control unit 15 so that the servo motor 3 is not supplied with a current equal to or greater than the current limit. It has a function of notifying the control unit 15. Since this current value is proportional to the pressing force of the electrode tip 2 to the workpiece, the control unit 15 calculates a correction amount based on the deformation of the gun arm 5 based on this current value.

FIG. 4 is a structural view of a spot welding gun 1A controlled by the apparatus of the present invention. This gun 1A
Has the same basic structure as that shown in FIG.
The cancer 1A is different in that attached to its sixth axis directly without a floating mechanism 6 to cormorants good conventional.

The apparatus of the present invention is configured as described above. This apparatus operates as follows based on the flowchart of FIG.

First, the controller 15 of the robot controller 11
Controls the operation of the servo control unit of each axis based on data taught in advance, and
The electrode tip 2 is positioned at a predetermined pressure point on the workpiece, that is, a welding point (S1). When the positioning is completed, the servo motor 3 is driven to narrow the interval between the electrode tips 2 and press the workpiece with a predetermined pressure. Since this pressing force is proportional to the value of the current flowing through the servomotor 3, the control unit 15 grasps the pressing force based on the current monitor feedback signal from the current controller 21 (S2). The correction of the deformation amount of the gun arm 5 that is deformed by the pressing force is performed based on the data stored in the storage unit 16. Specifically, the storage unit 16 stores the pressing force of the electrode tip 2 and the deformation amount of the gun arm 5 associated with the pressing force.
The correction amount is calculated with reference to the deformation amount parameter stored in 6 (S3). The control section 15 corrects the position data of each axis based on the deformation amount parameter, and positions the electrode tip 2 at a predetermined calculation position (S4, S5). With the above-described processing, it is possible to completely eliminate the displacement of the electrode tip 2 due to the deformation of the gun arm 5 that occurs when the electrode tip 2 is pressed against the workpiece.

The above-mentioned flowchart may be processed in real time for each step,
Further, the steps S2 to S4 may be performed in advance offline.

[0018]

As described above, according to the present invention, the teaching data is spot-welded in accordance with the pressure of the electrode tip.
Correct the gun so that it is supported in a stress-free position
Therefore, it is not necessary to provide a floating mechanism as in the related art, and highly reliable spot welding can be performed with an improvement in positioning accuracy, and cost and size can be reduced. Further, the operating performance is improved as the weight is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a spot welding robot.

FIG. 2 is a schematic block diagram of a positioning control device for a spot welding robot according to the present invention.

FIG. 3 is a detailed configuration diagram of a servo control unit shown in FIG. 2;

FIG. 4 is a structural view of a spot welding gun of the spot welding robot according to the present invention.

FIG. 5 is a flowchart of the apparatus of the present invention.

FIG. 6 is a structural view of a conventional spot welding gun.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Spot welding gun 2 ... Electrode tip 3 ... Servo motor 4 ... Ball screw 5 ... Gun arm 11 ... Robot control device 15 ... Control unit 16 ... Storage unit 19 ... Encoder 20A to 20F ... Servo control unit 21 ... Current controller

Claims (1)

(57) [Claims] 1. A teaching position for supporting a spot welding gun.
The spot welding robot is configured to spot-weld the object to be welded based on the data to be applied to the object to be welded. A storage unit that stores a relationship with the deformation amount, and based on the relationship stored in the storage unit ,
The spot welding is performed based on the pressure applied to the workpiece.
A deformation amount calculating means for calculating the deformation amount of the contact gun, and a deformation amount calculated by the deformation amount calculating means.
Correction means for correcting the teaching data.
Positioning control device for spot welding robot.