JPH0134716B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for detecting that the robot deviates from a taught welding line for trajectory correction in a welding robot to which an arc sensor method is applied. It is related to.

[Conventional technology]

A welding robot using the teaching playback method welds along the taught welding line when the workpiece is positioned accurately and has little variation, but when the workpiece accuracy or positioning accuracy is poor, the welding robot performs arc welding. The welding trajectory is corrected using sensors.

A welding method using this arc sensor is described in Japanese Patent Laid-Open No. 51-91851. This welding method follows the consumable electrode arc welding method by welding the consumable electrode while weaving, detects the arc current at both left and right ends of the weaving, and adjusts the weaving motion source so that the arc currents at both ends are approximately equal. This is to move the holding part.

This welding method based on arc current is called arc sensor welding, and is advantageous in that it detects the current during welding and provides a correction signal to the robot, and does not require an external sensor. It does not necessarily match the corrected direction and may deviate from the welding line.

Causes of abnormal conditions in arc sensor welding methods include arc breakage, wire breakage, gas outage Unstable welding conditions (unbalanced current, voltage, and speed) Unstable arc current due to bead sagging Arc current due to tearing An abnormality in the current detector may be an issue.

[Problem that the invention seeks to solve]

In the case of and, the abnormality can be detected by receiving an external abnormality signal, similar to an external sensor system such as a TV camera (for example, see Japanese Patent Laid-Open No. 55-5109). but,
In an arc sensor that uses the welding current itself as an information source, it is difficult to detect . In particular, it is difficult to distinguish whether the phenomenon is due to misalignment information or unstable conditions. In addition, once the bead drips down, weaving welding within the groove, which is a prerequisite for the arc sensor, is no longer possible, so incorrect correction may be made and an abnormal state may occur. In most cases, the arc current is disturbed at the groove due to the gap, which causes incorrect correction, resulting in breakage.

Conventionally, there is no software-based method for detecting this, but a method using a torch cup short-circuit has been adopted in some cases. However, this cannot be detected unless the torch cup touches the work or surrounding objects.

An object of the present invention is to detect that the robot has deviated from the trajectory without the torch cup or the like touching the workpiece or its surroundings in order to correct the trajectory.

[Means for solving problems]

To achieve this objective, the present invention monitors the distance between the taught welding line and the current position of the torch during welding in a welding method that collects positional deviation information from the arc current and performs a corrective action of the torch. , the deviation signal is generated when the distance exceeds a preset tolerance value.

〔Example〕

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

In FIG. 1, it is assumed that the welding line P ₁ P ₂ ---→ should be welded, but in reality, the welding is performed at a point P _N that is shifted.

In addition, the current position of the robot's torch x, y, z
is already determined in a separate routine for each time the RPG clock, that is, the pulse to operate the robot, is sent out.

FIG. 2 is a geometric explanatory diagram for calculating the amount of deviation of the actual welding point P _N from the taught welding line P ₁ P ₂ --→.

First, when the robot reaches P ₁ (x ₁ , y ₁ , z ₁ ), the direction cosines A, B, and C of P ₁ P ₂ ---→ are determined by the following procedure. However, P ₂ is the next coordinate point taught in advance, and the coordinates are x ₂ , y ₂ , z ₂ .

Δx ₁ =x ₂ −x ₁ Δy ₁ =y ₂ −y ₁ Δz ₁ =z ₂ −z ₁ DP=√ ₁ ² + ₁ ² + ₁ ² A=Δx _{1 /DP B=Δy 1 /} DP C=Δz ₁ /DP Next, the current position of the torch during welding P _N (x _N , y _N ,
z _N ) and the direction cosines L, M, and N of P ₁ .

Δx _N =x _N −x ₁ Δy _N =y _N −y ₁ Δz _N =z _N −z ₁ DL=√ _N ² + _N ² + _N ² L=Δx _N ／DL M=Δy _N ／DL N=Δz _N /DL From the direction cosine of this P ₁ P ₂ ---→ and the direction cosine of P ₁ P _N ---→, the angle between the welding line P ₁ P ₂ and the current position P _N of the torch ∠P _N P ₁ P ₂ ---→ Find (θ), and calculate θ and P ₁ P _N --
-→Welding line from the current position of the torch according to the length DL
Find the length H of the perpendicular drawn to P ₁ P ₂ .

cosθ=L・A+M・B+N・C θ=cos ^-1 (L・A+M・B+N・C) H=DL・sinθ Tolerance value PRM set by this H and parameters
is compared every RPG clock, and when the value of H exceeds the allowable value, it is detected that the welding torch has deviated from the welding line.

When the deviation is detected, the robot stops welding and generates an alarm. In addition, as the allowable value PRM,
Any numerical value from 0 to 65000 μm can be set as a parameter.

FIG. 3 is a processing flowchart by a microcomputer for performing the above calculation.

〔Effect of the invention〕

As mentioned above, according to the invention, the distance between the taught welding line and the current position of the torch during welding is monitored and a deviation signal is generated when the distance exceeds a preset tolerance value. It is said that Since the current position of the torch during welding is monitored in this way, deviations can be detected with high accuracy without the uncertainty seen in conventional cup short circuit detection. Furthermore, since the allowable value can be set using parameters, the range of deviation can be set arbitrarily.

[Brief explanation of drawings]

FIG. 1 is a perspective view for explaining an example of trajectory deviation of a welding torch detected by the present invention, FIG. 2 is a diagram for explaining the calculation according to the present invention, and FIG. 3 is a flowchart showing the calculation process. be.

Claims (1)

[Claims] 1 In a welding method that collects positional deviation information from the arc current and performs corrective torch operations, the distance between the taught welding line and the current position of the torch during welding is monitored, and the distance is set to a preset tolerance value. A sensing deviation detection method characterized in that a deviation signal is generated when the deviation exceeds.