JPH01113177A - Method for controlling industrial robot - Google Patents

Abstract

PURPOSE:To shorten the welding time by teaching an optional place of a work as a regulating point of electrode wire extension and using a corrected value by sensing of the work to correct said regulating point of the electrode wire extension and carrying out regulating work at a place close to a welding starting point. CONSTITUTION:An electrode 4a is brought into a torch 4 and a changeover switch is changed over to a power source for detection. The virtual tip P of the torch 4 falls and moves so that it is located at the regulating point P7' of the electrode wire extension after being corrected. Hereby, the distance between the chip tip of the torch 4 and the surface of a horizontal plate W1a' of the work is exactly coincident with the regular electrode wire extension L0. Continuously, the electrode 4a is fed and again projected toward the horizontal plate 1a' from the chip tip and the tip approaches the horizontal plate 1a' and discharges electricity to detect the surface of the horizontal plate W1a'. A computer 8 receives an electrification signal from an electrified state detection output circuit and the electrode 4a returns to the original intermediate shunting position P6. The electrode tip of the torch 4 is coincident with the position P6 and the electrode wire extension is in a state regulated to be equal to the regular extension L0.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a sensor that detects a workpiece by applying a detection voltage to an electrode. (Prior art and its Q problems) The present applicant previously filed Japanese Patent Application Laid-open No. 54-15441 and
No. 4-64853 presented an automatic welding device that uses the torch electrode itself as a sensor. In this automatic welding device, a welding voltage and a sensor voltage are selectively applied to the electrodes of the torch through a special voltage application means according to a welding command or a sensor command from a control means as appropriate, and the electrodes and sensor voltages are applied selectively to the torch electrodes during sensing. This detects the current state between the workpiece and the weld line of the workpiece. However, when a consumable electrode is used as the electrode, the length of the electrode protruding from the torch usually differs at the end of each weld due to the difference in the degree of penetration of the electrode during welding. Also,
Generally, the electrode between the electrode supply reel and the torch is inserted into a flexible tube, but in this case, the protruding length of the electrode is not necessarily constant due to changes in the bending state of the flexible tube as the torch moves. Even if sensing is performed in this state, the accurate weld line of the workpiece will not be detected.
Naturally, good welding results cannot be expected from automatic welding performed based on such inaccurate sensing. Therefore, when sensing the next weld line on the workpiece after welding is completed, it is necessary to regulate the protruding length of the electrode of the torch to a predetermined length in advance of actual sensing. Conventionally, this electrode protrusion length has been regulated by setting a reference position on the outer edge of the workpiece fixture, and commanding the control means with the torch electrode slightly retracted each time sensing is performed. Based on this, the virtual welding point at the tip of the torch is aligned with the reference position, the electrode is fed out in this state, and an energization signal is obtained between the electrode and the workpiece fixture to stop the electrode feeding, or automatic After finishing welding and before moving on to the next sensing, welding was carried out in the same manner as described above near the previously programmed welding end point (often at a place close to the next sensing and welding point). However, in the former case, the relative position of the virtual welding point between the workpiece fixture and the torch must be controlled each time sensing is performed, which increases the time required for sensing, especially if the torch travels a long distance. In this case, the reference position of the workpiece set in advance for regulating the electrode protrusion length is not necessarily accurate for all workpieces due to errors in manufacturing and mounting each workpiece, and the positional deviation error may occur. However, in any case, it was not always possible to obtain an accurate electrode protrusion length, for example, this directly appeared as an error in the protrusion length of the electrode. (Means for Solving Problems) The control method according to the present invention teaches an electrode protrusion length regulation point at a suitable location on a workpiece, stores a correction value of position information sensed in at least one dimension for each workpiece, and stores the correction value of position information sensed in at least one dimension for each workpiece. The present invention is characterized in that the positional information of the electrode protrusion length regulation point is corrected depending on the value. (Example) Hereinafter, a detailed description will be given based on an example shown in the drawings. FIG. 1 is an overall schematic diagram of a rectangular coordinate type welding robot (RO) employed as an industrial robot that forms the background of the present invention. 1 is a vertical axis constructed at the terminal of a known rectangular coordinate (X, Y, Z) robot) RO (details not shown), and the first arm 2 is rotatable around the vertical axis 1 (arrow α). I support it. 3 is a second arm supported at the tip of the first arm 2 so as to be pivotable around an oblique shaft 3a (arrow β). A torch 4 as an end effector is attached to the tip of the second arm 3, and the torch 4 has a function as a sensor as described later. The vertical axis 1, the oblique axis 3a, and the central axis M of the torch 4
are constructed so that they intersect at one point P. Further, the torch 4 is set so that its welding operating point can coincide with the point P. Thus, by controlling the rotation angle in the directions of the arrows α and β, the attitude angle θ and the turning angle ψ (so-called Euler angle) of the torch 4 with respect to the vertical axis 1 can be controlled while fixing the point P. Reference numeral 5 denotes a fixed workpiece pull as a workpiece fixing device, and the two works W1 and W2 are fixed as a pair on the left and right sides of the upper surface using appropriate clamping jigs 5a and 5b. In addition, work W1・
W2 consists of horizontal plates W1a-W2a and vertical plates Wlb-W2b temporarily attached in an upright manner along the edge of each horizontal plate, and each workpiece W1 and W2 is expected to have manufacturing errors, and also has a clamp jig 5a. - Errors are unavoidable when attaching to the work table 5 using 5b. 6a and 6b are an electrode supply roll and a pair of feed rollers, and the electrode 4a is transferred to the feed roll 6 by controlling the rotation of the feed roller 6b.
Pull out the torch 4 from a and pass through the flexible tube 6C.
There is -ζ as if it were to be sent to . Reference numeral 7 denotes a welding power source device which incorporates a voltage applying means 7a and an energization state detecting means 7b, of which the voltage applying means 7a is connected to a welding power source 7a1. Detection power source 7a2. A changeover switch that connects one end to the electrode 4a and selectively connects it to either of the two types of sources 7a, 7az at an appropriate time? Consists of az. The energization state detection means 7b includes an energization state detection circuit 7b and an energization state detection output circuit 7b2, of which the negative end of the energization state detection circuit 7b is connected to the detection power supply 7az,
The other end of the welding power source 7a is connected to the work table 5, which is always in electrical continuity with the workpieces W1 and W2, together with the opposite switch 7a, and the energization state detection output circuit 7
b2 inputs a change in the energization state (change in current, voltage, or both) in the energization state detection circuit 7b as a detection signal. Reference numeral 8 denotes a computer as a control means for comprehensively controlling the entire welding robot (RO), and includes a CPU and a memory.
．． Each axis servo system of robot RO 5x-sy-sz-sy
・Connect Sβ and remote control box 9 for teaching. The remote control box 9 includes keys for inputting numbers from "0" to "9" as well as a group of keys for inputting various information assigned in advance, as well as a set of keys for inputting various information assigned in advance, as well as a set of keys required for interactive teaching work. The device is equipped with a display 9a for displaying messages and information corresponding to key operations. A predetermined procedure for teaching is preprogrammed in the memory of the computer 8 and
controls the display 9a based on this program and key operations by the operator. Therefore, prior to the teaching operation, the operator uses an appropriate cutting tool to cut the electrode 4a protruding from the torch 4 to a regular protrusion length. Cut into. Now, the horizontal plates W1a-W of the works W1 and W2 are respectively
Fillet welding conditions LI/WL between 2a and standing plate Wlb-W2b
2, horizontal fillet welding is to be performed. Then, the operator performs the following teaching work while operating the remote control box 9 and moving the torch 4. (1) First, welding 'fullAWL, welding starting point P of 1
The electrode tip P of the torch 4 is placed at the first sensing starting point P, which is close to P, and the position information (X, Y, Z axes), posture information (α, β axes), and fillet at that position P are obtained. The welding condition sensing command information is taught and the sensing is executed. That is, in this sensing, the torch 4 moves vertically toward the horizontal plate Wla and horizontally toward the vertical plate W1b, detects the surfaces of the horizontal plate Wla and the vertical plate Wlb, and determines the position of the welding line WLI from each detection position. Take in P2. (2) Next, the torch 4 is moved to a standby position P3 appropriately spaced from the welding start point P4 and then to the welding start point P4, and the position information and posture information 1 at each position P3 and P4 are
The moving speed information between both positions P and pi is taught. In particular, at the welding start point P4, in addition to the above information, a sensing correction command is taught. This sensing correction command means correcting the welding start point P4 based on the sensing result executed in (1) above during automatic welding work on the workpiece W1. (3) Bringing the torch 4 to the welding end point P of the welding line WLI, position information, posture information, fillet welding conditions (
Current, voltage, speed, etc.) and sensing correction commands are taught. (4) Subsequently, the torch 4 is appropriately spaced from the welding end point P and brought to an intermediate weeping position P6 located above the horizontal plate W1 so that the central axis M is perpendicular to the horizontal plate W1, Teach the position information, posture information, and electrode protrusion length regulation command at that position, and create the electrode protrusion length regulation.
carry out the work. That is, the torch 4 descends in the vertical direction toward the horizontal plate Wla, detects the surface of the horizontal plate Wla, and takes the detected position P7 as the electrode protrusion length regulation point. A sensing correction command for the detected position P7 is taught. (5) Bring the torch 4 to the second sensing start point P8 close to the welding start point P1° of the welding line WL2, and
The position information, posture information, and fillet weld line sensing command information at a are taught, and sensing is performed in the same manner as in step 11 above to capture the position P of the weld line WL2. (6) Next, the torch 4 Move to the welding start point PIG,
Position information and posture information at the position P1°, the second
Sensing start point P8 - Teach moving speed information between welding start point P1° and sensing correction command. (7) Bring the torch 4 to the welding end point pH of the welding line WL2, and teach the position information, posture information, fillet welding conditions, and sensing correction command at that position. (8) Finally, the retreat position Pl away from the welding end point pH
Bring the torch 4 to □ and teach position information and movement speed information. This completes the teaching. Next, among the operations performed by the welding robot RO based on the command output from the computer 8, the operation of regulating the electrode protrusion length during the automatic welding operation will be particularly emphasized and explained with reference to FIGS. 3 and 4. In addition, with this, the workpiece Wl to be automatically welded
It is assumed that 'W2' has substantially the same shape and size as the workpieces W1 and W2 at the time of teaching, but some positional deviation is expected. [1] First, the torch 4 is positioned at the first sensing starting point P1 and sensing is performed, and the computer 8 determines the point 22' of the welding line WLI from the sensing result,
The difference ΔP2 from the point P2 at the time of teaching is calculated and stored as a correction value ΔPn (processing PR1). Then, the computer 8 corrects the welding start point Pa, welding end point Ps, and electrode protrusion length regulation point P1 at the time of teaching with the sensing 'correction command using the correction value ΔPn, and points 2 after position correction.
4'·p, l·p, and l are calculated and stored (processing PR2). [2] After performing the sensing, the torch 4 moves from the standby position P to the welding start points p and l, and moves from the standby position P to the welding start points p and l.
, Perform horizontal fillet welding from / to the welding end point P,',
After welding is completed, it retreats to the intermediate retreat position P6. At the end of this welding, the protruding length of the electrode 4a of the torch 4 is
Generally, the protrusion length Lo is slightly shorter than the normal protrusion length Lo due to the welding in a (see Fig. 4(a)). [3] From the state shown in FIG. 4(a), the electrode 4a is retracted into the torch 4 by process PR3 (FIG. 4(b)). [4] Through process PR4, the changeover switch 7az is switched to the detection power supply 7a2. [5] Next, in process PR5, the virtual tip P of the torch 4 is moved downward, for example, as shown in FIG. 4(C), so that it is located at the corrected electrode protrusion length regulation point p7j. With this, the distance from the tip end of the torch 4 to the surface of the horizontal plate Wla' of the workpiece W1' exactly corresponds to the normal electrode protrusion length Lo (see FIG. 4(C)). [6] Subsequently, in process PR6, the electrode 4a is fed, and the electrode 4a again protrudes from the tip end toward the horizontal plate Wla'. Then, the tip of the electrode 4a is horizontal FiW1
a' to detect the surface of the horizontal plate W1a' (FIG. 4(d)), the computer 8 receives the "energization" signal from the energization state detection output circuit 7bz, and processes PR7 and P.
At H1, feeding of the electrode 4a is stopped and the electrode 4a returns to the original intermediate retracted position P6 (FIG. 4(e)). With this movement return, as shown in FIG. 4(e), the electrode tip of the torch 4 exactly coincides with the position P, and the electrode protrusion length from the torch 4 is regulated to be equal to the normal electrode protrusion length LO. is in a state of [8] Next, the torch 4 moves to the second sensing starting point pg
, calculate the points p and l of the welding line WL2 from the sensing results as in [1] above, and calculate and store the difference ΔP from the point P at the time of teaching as a correction value ΔPn (process P
R1). Then, the computer 8 corrects the welding start point PIG and welding end point Pl+ at the time of teaching with the sensing correction command using the correction value ΔPn, calculates and stores the point PIO' and pH' after the position correction (processing PR2 >.

[9] Thereafter, the changeover switch 7a is switched to the welding power source 7a by process PR9. [10] Next, the torch 4 is moved to the welding starting point P. Horizontal fillet welding is performed from ' to the welding end point pH', and after welding is completed,
Retreat to the retreat position "11 P + z, and these pictures W
Complete automatic welding work for 1' and W2'. In addition to the embodiments described above, the present invention can also be modified as described below. (1) The robot may be a robot of other mechanical configuration, such as an articulated welding robot, in addition to the rectangular coordinate type welding robot as in the above embodiment. (2) In the above embodiment, the electrode protrusion length was regulated manually using a cutting tool prior to teaching.
The reference point of the work table 5 may be determined in advance, and the process may be performed automatically. (3) In the above embodiment, the length of the electrode protrusion during welding was set at one point, but if a large number of workpieces are attached individually using jigs and there is a risk that the relative positions of the workpieces may shift, The protrusion length regulation points are successively set in the previously welded workpieces (position corrected) and close to the welding start point of the next workpiece, resulting in a plurality of points. (4) In the above-mentioned embodiment, the torch 4 is used both as a welding torch and as a sensor, but it can also be used exclusively as a sensor for use with a processing tool such as a welding torch, a fusing torch, or a grinder. (Effect of the invention) As explained above, when using the control method of the present invention,
An arbitrary location on the workpiece is taught as the electrode protrusion length regulation point, and the correction value obtained by sensing the workpiece prior to automatic welding is used to correct the previous electrode protrusion length regulation point. There is no need to return to the reference position of a distant workpiece fixture each time the length adjustment work is performed, and the adjustment work can be performed at a location close to the next welding start point, reducing the overall welding time. Even if the electrode becomes short due to penetration during welding interruption, there is no risk of adversely affecting the accuracy of the next electrode protrusion length adjustment, ensuring accurate electrode protrusion length adjustment at all times, and making subsequent welding starts smoothly. It can be used with great effect.

[Brief explanation of the drawing]

Figure 1 is an overall schematic diagram of a welding robot adopting the present invention.
Figures 2 (a) and (b) are action explanatory diagrams showing the electrode protrusion length regulation work during teaching, Figure 3 is a flow chart, and Figures 4 (a) to (e) are electrodes during automatic welding work. FIG. 7 is an explanatory diagram showing the operation of protrusion length regulation work. In the figure, 4 is a torch, 4a is an electrode, 5 is a work table,
7 is a welding power supply device, and 8 is a computer.

Claims (1)

[Claims] An industrial robot including a sensor equipped with an electrode that is expandable and retractable in the central axis direction, means for applying a detection voltage to the electrode, and means for detecting the energization state of the electrode,
Teach the electrode protrusion length regulation point at an appropriate location on the workpiece, store a correction value of positional information sensed in at least one dimension for each workpiece, and correct the positional information of the electrode protrusion length regulation point using the correction value. A method of controlling an industrial robot, which is characterized by the ability to control robots.