JPH0332429B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for controlling a welding torch in a welding robot. Conventional welding robots of this type include a robot body with three orthogonal main axes (X, Y, and Z axes) and a wrist portion with two axes: bending (B axis) and swinging (S axis). There is something I did. This welding robot positions the welding torch held at the tip of the wrist at each teaching point from the start to the end of the welding line, sequentially stores the position data of each axis of the robot at that position as teaching data, and performs welding. When moving the torch tip along the welding line taught by the teaching data, calculate the position data of the two teaching points from the position data of each axis (teaching data) and the constant of the wrist part, Calculate the distance between these two points, divide it equally, determine the number of interpolation points, and then perform interpolation calculations. As a result, you can obtain interpolation that traces a straight line (or circle) between the two points. , The inverse coordinate transformation is performed on this to obtain the position data of each axis, and each axis is controlled using this position data. Also, during welding, the actual weld line is detected by a weld line detection means such as an arc sensor. death,
The output of the welding line detection means further controls each of the axes so that the welding torch follows the actual welding line. When performing multi-layer welding using such a conventional welding robot, the welding trajectory of the first layer is first taught, and then the welding trajectory of the second layer, third layer, etc. is taught sequentially, but the teaching of the second and subsequent layers is When teaching, it is necessary to assume the welding condition up to the previous layer, and this causes the welding center distance between each layer to be uneven, resulting in a problem that welding accuracy cannot be improved. This required a great deal of time for teaching work. The present invention has been made in view of the above-mentioned circumstances, and is a welding torch control that allows multilayer welding to be performed with simple teaching work, provides high welding accuracy, and shortens welding time. The purpose is to provide a method. According to this invention, the welding torch tip position is calculated from predetermined constants and variables related to each axis of the robot, and each axis is controlled so that the welding torch tip follows a welding line taught in advance by teaching data. In a welding robot that performs welding, the first layer is welded along a welding line taught in advance using teaching data, while detecting the actual welding line, and also detecting the amount of deviation between the welding line taught in advance and the actual welding line. The destination welding line is memorized by sequentially memorizing. And welding from the second layer onwards,
The predetermined constant is changed corresponding to the welding center distance of each layer, the welding torch tip position is calculated from the changed predetermined constant and variable, and each welding torch is adjusted along the memorized actual welding line. Control the axis. Furthermore, when welding an even number of layers, the stored actual welding line is read out from the terminal end to the starting end, and the welding torch is controlled to move in the opposite direction to the welding direction of the first layer. . The present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a system configuration diagram of a welding robot to which the present invention is applied, and specifically shows the welding robot. This welding robot includes a welding robot body 1, a welding robot control device 2, a field operation panel 3, a teaching box 4, a welding power supply device 5, and a welding wire box 6. The welding robot main body 1 has a wrist 7 and an arm in a rectangular coordinate system of horizontal (X), horizontal (Y), and vertical (Z), and each part is controlled by control signals from the welding robot controller 2. Position control is performed. Further, the welding robot main body 1 is provided with a welding wire feeding device 8, which feeds the welding wire 9 from the welding wire box 6 to the wrist 7. Further, appropriate welding power is supplied to the welding wire 9 from the welding power supply device 5 in response to a command from the welding robot control device 2. The field operation panel 3 is operated by an operator as appropriate, and has switches for selecting an operating mode of the welding robot main body 1, emergency stop, return to origin, etc. The teaching box 4 has a switch for moving each part of the welding robot body 1, a switch for writing position information of a teaching point into the welding robot control device 2, and the like. Figures 2a and 2b show a plan view and a side view of the wrist 7 of the welding robot 1, respectively.
This wrist 7 has a rotation axis S for swinging the wrist 7 in the X-Y plane and a rotation axis B for bending the welding torch 10, and these rotation axes S and B are connected to the welding robot control device 2. As a result of this control, the direction of the welding torch 10 (the posture of the wrist) is controlled. Further, O indicates the tip of the arm, and d ₁ to _{d 4} indicate the length of each part of the wrist 7, as shown in FIG. 2b. This welding robot uses the distance between each part of the wrist 7 as a constant, and the angles of the rotation axes S and B and the point O of the arm.
Welding torch 1 with the position of (X, Y, Z) as a variable
The position of the tip of the welding torch 10 is calculated and each axis is controlled so that the welding torch 10 follows a desired trajectory. For example, when welding a welding line L as shown in FIG. 3, the welding torch 10 is positioned at teaching points _P1 and _P2 , and the position data of each axis at these positions is stored as teaching data. Note that, as shown in FIG. 3, the welding torch 10 is taught in different postures at _P1 and _P2 . Since the tip of the welding torch 10 must move linearly between P ₁ and P ₂ , the position data of P ₁ and P ₂ is obtained from the position data of each axis, and the next After calculating the distance and dividing it into equal parts to determine the number of interpolation points, interpolation calculations are performed. As a result, interpolation that traces a straight line between P ₁ and P ₂ is obtained, and the position data of each axis for this is calculated backwards. Each axis of the robot is controlled based on this position data. Note that the broken line l is a trajectory followed by the tip O of the arm. On the other hand, since welding workpieces generally have poor processing and assembly accuracy, it is not possible to achieve good welding simply by faithfully tracing the taught welding line. The welding line is detected, and the welding torch is controlled to follow the actual welding line based on the detection output. FIG. 4 is a block diagram showing an example of the configuration of a control device for implementing the welding torch control method according to the present invention. The case of performing three-layer fillet welding as shown in FIG. 6 will now be described. The first memory 11 stores in advance teaching data (X, Y, Z, θ _S , θ _B ) for each axis of the robot body 1 at each teaching point. Also,
The third memory 12 stores multilayer stacking information shown in Table 1 for each layer.

[Table] This multilayer information is a pseudo constant of the wrist for each layer. When welding the first layer, the central processing unit (CPU) 13 receives the teaching data from the first memory 11 and the wrist constant of the first layer from the third memory 12.
Based on the output of the arc sensor 14, a movement command value for each axis is output. This movement command value is added to the subtracter 15. To the other input of the subtractor 15, a number of pulse signals corresponding to the moving distance of the shaft, that is, the rotation amount of the shaft drive motor 17, is applied from the encoder 16, and the subtractor 15 receives two input signals. The deviation is taken and led to the position deviation counter 18. The count value of the position deviation counter 18 is D/A
It is converted into an analog signal by the converter 19 and sent to the subtracter 2.
Added to 0. An analog signal corresponding to the rotational speed of the shaft drive motor 17 is applied from the speed detector 21 to the other input of the subtractor 20.
0 takes the deviation of the two input signals and leads it to the shaft drive motor 17 via the servo amplifier 22. Furthermore, the arc sensor 14 detects the actual welding line based on the arc current values at both ends of the weaving during welding, and outputs correction data so that the welding torch tip follows the actual welding line. The CPU 13 outputs movement command values for each axis based on the above correction data, controls the tip of the welding torch by tracing, and as shown in FIG. ) is stored in the third memory 23 for each position where the welding line A is equally divided by a certain fixed length (Δl).
In addition, if the sensor correction amount for each Δl is _E
The amount of deviation (ΔYi) between the trained welding line A and the actual welding line B can be expressed as ΔYi= _i 〓 ^x=1 E _X. In this way, the first layer of multilayer welding is welded. Next, the second layer welding is performed without using the arc sensor 14, using the teaching data from the first memory 11, the copying correction data from the second memory 23, and the second layer wrist constant from the third memory 12. Based on this, the movement command value for each axis is output. In this case, the teaching data and copying correction data are read from the terminal end P _N of the welding line toward the starting end P ₁ as shown in Table 2.

【table】

Claims (1)

[Claims] 1 The welding torch tip position is calculated from predetermined constants and variables related to each robot axis, and each axis is controlled so that the welding torch tip follows the welding line taught in advance by teaching data. In a welding robot that detects an actual weld line using a weld line detection means and controls the welding torch to follow the actual weld line, when performing multilayer welding, the predetermined constant is set for each layer. When welding the first layer of the weld line by storing multi-layer deposition information that has been changed by a preset amount, the welding torch is controlled based on the teaching data and the output of the weld line detection means, and the welding torch is The amount of deviation between the welding line and the actual welding line is sequentially memorized, and when welding an even number of layers, the teaching data and the amount of deviation stored are read out from the end of the welding line to the beginning of the welding line. , reads out the multi-layer deposition information corresponding to the welding layer, controls the movement of the welding torch in a direction opposite to the welding direction of the first layer based on this read data, and welds odd-numbered layers excluding the first layer. When performing this, the teaching data and the stored deviation amount are read out from the starting end of the welding line to the ending end, and
reading the multilayer deposition information corresponding to the welding layer;
The welding torch is adjusted based on this read data.
A welding torch control method characterized by controlling movement in the same direction as the welding direction of the layers.