JPH0673745B2 - Control method for industrial robot - Google Patents

Description

Detailed Description of the Invention

(Field of Industrial Application) The present invention relates to a sensor for detecting a work by applying a detection voltage to electrodes. (Prior Art and Problems Therewith)
In 3, we 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 in response to a welding command or a sensor command from the control means, and the electrodes are not The welding state of the work is searched by detecting the energization state with the work. However, when a consumable electrode is used as the electrode, the protruding length of the electrode from the torch is usually different at the end of each welding due to the difference in the penetration of the electrode during welding. Further, generally, the electrode between the electrode supply reel and the torch is inserted into the flexible tube, but in this case, the protruding length of the electrode is not necessarily changed due to the change in the bending state of the flexible tube accompanying the movement of the torch. Since it is not kept constant and the accurate welding line of the workpiece is not detected even if sensing is performed in this state, naturally good welding results cannot be expected in automatic welding performed based on such inaccurate sensing. . Therefore, when sensing the next welding line of the work after welding, it is necessary to set the electrode projection length of the torch to a predetermined length in advance, prior to actual sensing. Conventionally, the regulation of the electrode protrusion length is performed by setting a reference position on the outer edge of the work fixture, with the torch electrode slightly retracted each time the sensing is performed, and the virtual welding point of the torch tip being set based on the command of the control means. Aligning with the reference position, send out the electrode in this state, stop the electrode sending out by obtaining the energization signal between the electrode and the work fixture, or finish the automatic welding of the part with the work and move to the next sensing Before
The procedure was performed in the same manner as described above in the vicinity of the welding end point previously programmed (often near the next sensing and welding point). However, in the former case, the relative position between the workpiece attachment and the virtual welding point of the torch must be position-controlled each time sensing is performed, so the time required for sensing also increases, especially when the torch travel distance is long,
In the latter case, the reference position of the work, which was set in advance to regulate the length of the electrode protrusion due to manufacturing and mounting errors of each work, is not always accurate for all works, and the position deviation The error directly appears as an error in the protruding length of the electrode, but in any case, the accurate protruding length of the electrode is not always obtained. (Means for Solving Problems) A control method according to the present invention teaches an electrode protrusion length regulation point at an appropriate position on a work, stores a correction value of at least one-dimensionally sensed position information for each work, and corrects the correction value. It is characterized in that the position information of the electrode protrusion length regulation point is corrected by the value. (Example) Hereinafter, it demonstrates in full detail based on the Example shown in drawing. FIG. 1 is an overall schematic view of a rectangular coordinate welding robot RO adopted as an industrial robot which is the background of the present invention. Reference numeral 1 is a vertical axis configured at a terminal of a known rectangular coordinate (X, Y, Z) robot RO (details not shown), and supports a first arm 2 so as to be rotatable around the vertical axis 1 (arrow α). I am doing it. Reference numeral 3 denotes a second arm supported by the tip of the first arm 2 so as to be rotatable around the oblique axis 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 dorch 4 are configured to intersect at a point P. Further, the torch 4 is set so that its welding operation point may coincide with the point P. Thus, by controlling the rotation angles in the directions of the arrows α and β, the attitude angle θ and the turning angle φ (so-called Euler angle) of the torch 4 with respect to the vertical axis 1 can be controlled with the point P fixed. Reference numeral 5 is a fixed work table as a work mounting tool, and two work pieces are provided on the upper left and right by appropriately using the clamp jigs 5a and 5b.
Fix W1 and W2 as a pair. The workpieces W1 and W2 are composed of horizontal plates W1a and 2Wa and standing plates W1b and W2b that are temporarily attached in an upright shape along the edges of the horizontal plates.Each workpiece W1 and W2 is expected to have a manufacturing error. It is also inevitable that the clamp jigs 5a and 5b will cause an error in attachment to the work table 5. Reference numerals 6a and 6b denote an electrode supply roll and a pair of feed rollers. By controlling the rotation of the feed roller 6b, the electrode 4a is pulled out from the supply roll 6a and fed to the torch 4 through the flexible tube 6c. is there. Reference numeral 7 is a welding power supply device, which is a voltage applying means 7a and an energization state detecting means.
7b is built in, of which the voltage applying means 7a is a welding power source 7a.
₁ , a power source for detection 7a ₂ , a changeover switch for connecting one end to the electrode 4a and selectively connecting to either of the power sources 7a ₁ and 7a ₂ at appropriate times
Composed of 7a ₃ . Also, the energization state detection means 7b is made conductive state detection circuit 7b ₁ energized state detection output circuit 7b ₂ Prefecture,
Of these, the energization state detection circuit 7b ₁ has one end connected to the detection power supply 7
a ₂ and the other end of the welding power source 7a ₁ together with the non-changeover switch 7a ₃ side to the work table 5 which is always in conduction with the works W1 and W2, and the energization state detection output circuit 7b ₂ inputs a change in the energized state in the energization state detection circuit 7b ₁ (current, voltage or both of them changes,) as a detection signal. Reference numeral 8 denotes a computer as a control means for comprehensively controlling the entire welding robot RO, including a CPU and a memory, and the bus line B of the computer 8 has the welding power source device 7 and each axis servo system SX of the robot RO. The remote control box 9 for SY / SZ / Sα / Sβ and teaching is connected. The remote control box 9 is required to input numbers of "0" to "9", a group of keys for inputting various kinds of pre-assigned information, and an interactive type so that the teaching work can be sequentially performed. It comprises a display 9a for displaying a message and information corresponding to a key operation. The predetermined procedure for teaching is pre-programmed in the memory of the computer 8 and
Controls the display 9a based on this program and the operator's key operation. Then, the operator appropriately cuts the electrode 4a protruding from the torch 4 into a regular protruding length L ₀ using a cutting tool prior to the teaching work. Now, the weld lines of the fillets of the horizontal plates W1a and W2a and the vertical plates W1b and W2b of the workpieces W1 and W2, respectively.
It is intended to perform horizontal fillet welding for WL1 and WL2. Then, the operator operates the remote control box 9 to move the torch 4 to perform the following teaching work. (1) First, the electrode tip P of the torch 4 is arranged at the first sensing start point P ₁ near the welding start point P ₄ of the welding line WL _{1, and} the position information (X, Y, Z axes) at the position P ₁ is set, The posture information (α and β axes) and the fillet weld line sensing command information are taught and the sensing is executed. That is, in this sensing, the torch 4 moves in the vertical direction toward the horizontal plate W1a and in the horizontal direction toward the standing plate W1b to move to the horizontal plate W1a.
And the surface of the vertical plate W1b are detected, and the welding line WL1
Take in position P ₂ of. (2) Next, the torch 4 is moved from the welding start point P ₄ to the standby position P ₃ appropriately separated from the welding start point P ₄ and further to the welding start point P _4, and the position information, attitude information, and both positions P at the respective positions P ₃ and P ₄ are moved. ₃
It teaches the moving speed information between P _4. In particular, at the welding start point P ₄ , a sensing correction command is taught in addition to the above information. This sensing correction command means that the welding start point P ₄ is corrected by the sensing result executed in the above (1) during the automatic welding operation on the work W1. (3) location information at that position brings the torch 4 to a welding end point P ₅ of weld lines WL1, orientation information, fillet welding conditions (current, voltage, speed, etc.), it teaches the sensing correction command. (4) Subsequently, the torch 4 is appropriately separated from the welding end point P ₅ and brought to an intermediate retreat position P ₆ located above the horizontal plate W1 so that the central axis M is vertical to the horizontal plate W1. The position information, attitude information, and electrode protrusion length regulation command at that position are taught, and the electrode protrusion length regulation work is executed. That is, the torch 4 descends in the vertical direction toward the horizontal plate W1a, detects the surface of the horizontal plate W1a, and takes in the detected position P ₇ as the electrode protrusion length regulation point. Teach the sensing correction command for the detected position P ₇ . (5) Bring the torch 4 to the second sensing start point P ₈ near the welding start point P ₁₀ of the welding line WL 2, and teach the position information, posture information, and fillet welding line sensing command information at that position P ₈ . At the same time, sensing is performed in the same manner as in (1) above, and the position P ₉ of the welding line WL2 is captured. (6) Next, move the torch 4 to the welding start point P ₁₀ ,
Position information at that position P ₁₀ , attitude information, moving speed information between the second sensing start point P ₈ and welding start point P ₁₀ ,
Also, teach the sensing correction command. (7) Bring the torch 4 to the welding end point P ₁₁ of the welding line WL 2, and position information, posture information, fillet welding conditions at that position,
Teach the sensing correction command. (8) Finally, the retracted position P ₁₂ away from the welding end point P ₁₁
Bring torch 4 to teach position information and moving speed information. This is the end of teaching. Next, among the operations performed by the welding robot RO based on the command output from the computer 8, an explanation will be given with reference to FIGS. 3 and 4, focusing particularly on the operation of adjusting the electrode protrusion length during the automatic welding operation. It should be noted that work W1 ′ ・
W2 ′ has substantially the same shape and size as the workpieces W1 and W2 during teaching, but some misalignment is expected. [1] First, the torch 4 positions the first sensing start point P ₁ to perform sensing, and the computer 8 obtains the point P ₂ ′ of the welding line WL 1 from the sensing result, and determines the point P ₂ at the time of teaching. The difference ΔP ₂ is calculated and stored as the correction value ΔPn (process PR1). Then, the computer 8 corrects the welding start point P ₄ , the welding end point P ₅ , and the electrode protrusion length regulation point P ₇ during the teaching with the sensing correction command by the correction value ΔPn, and the point P ₄ after the position end. ′ · P ₅ ′ · P ₇ ′ is calculated and stored (process PR2). [2] The torch 4 is in the standby position P ₃ after performing the sensing.
'Go to, the welding start point P _4' more welding start point P ₄ performs horizontal fillet welding to the welding end point P ₅ 'than, after the end of welding, retracted to an intermediate retracted position P _6. At the end of this welding, the protruding length L ₁ of the electrode 4a of the torch 4 is generally slightly shorter than the normal protruding length L ₀ due to the melting of the electrode 4a (fourth
(See (a) figure). [3] From the state of FIG. 4 (a), the electrode 4a is processed by the treatment PR3.
Retracts into the torch 4 (Fig. 4 (b)). [4] By the process PR4, the changeover switch 7a ₃ turns the detection power source 7a
Switch to ₂ . [5] Next, the virtual tip P of the torch 4 is processed by the process PR5.
So that is located at the corrected electrode protrusion length regulation point P ₇ ′,
For example, it moves downward as shown in FIG. 4 (c). With this, the tip of the torch 4 and the horizontal plate W1 of the workpiece W1 '
The distance to the surface of a'just corresponds to the regular electrode protrusion length L ₀ (see FIG. 4 (c)). [6] Subsequently, the electrode 4a is fed by the process PR6,
The electrode 4a again projects from the tip of the chip toward the horizontal plate W1a '. Then, the tip of the electrode 4a discharges close to the horizontal plate W1a 'to detect the surface of the horizontal plate W1a' (Fig. 4 (d)),
Computer 8 receives the "energization" signal from the energization state detection output circuit 7b _2, delivery of the electrode 4a by treatment PR7 · PR8 moves back to its original intermediate retracted position P ₆ is stopped (the 4 (e ) Figure). As a result of this movement return, as shown in FIG. 4 (e), the electrode tip of the torch 4 exactly coincides with the position P ₆ , and the electrode projection length from the torch 4 is set equal to the regular electrode projection length L _0. It is in the state of being [8] Subsequently, the torch 4 moves to the second sensing start point P ₈ , and the welding line is obtained from the sensing result as in the above [1].
Find point P ₉ ′ on WL2 and calculate the difference from point P ₉ during teaching △ P ₉
Is stored as a correction value ΔPn (processing PR1). Then, the computer 8 corrects the welding start point P ₁₀ and welding end point P ₁₁ at the time of teaching with a sensing correction command by the correction value ΔPn, and calculates and stores the point P ₁₀ ′ · P ₁₁ ′ after position correction. Yes (Process PR2).

[9] After that, the changeover switch 7a ₃ is switched to the welding power source 7a ₁ by the process PR9. [10] Subsequently, the torch 4 performs horizontal fillet welding from the welding start point P ₁₀ ′ to the welding end point P ₁₁ ′, and after the welding is completed, retracts to the retracted position P ₁₂ and these workpieces W1 ′ and W2 ′ Complete the automatic welding work for. The present invention can also be modified as described below in addition to the above-described embodiment. (1) The robot may be a robot having another mechanical structure such as a multi-joint welding robot, in addition to the Cartesian welding robot as in the above embodiment. (2) In the above embodiment, the regulation of the electrode protrusion length prior to teaching was described as a manual work using a cutting tool, but a reference point of the work table 5 may be set in advance and automatically performed. Good. (3) In the above-described embodiment, the electrode protrusion length regulation point during welding is set to one place. However, if a large number of works are individually attached by jigs and the relative positions between the works may shift, the electrode The protrusion length regulation point is set at a plurality of positions in the already welded work (position-corrected) in sequence and near the welding start point of the next work. (4) In the above-described embodiment, the torch 4 is used both as a welding torch and a sensor, but it can be naturally implemented as a sensor for use with other processing tools such as a welding torch, fusing torch, grinder and the like. (Effects of the Invention) As described above, when the control method of the present invention is used,
The arbitrary point on the work is taught as the electrode protrusion length regulation point, and the previous electrode protrusion length regulation point is corrected using the compensation value of the workpiece sensing prior to automatic welding. There is no need to return to the reference position of the work fixture or the like, which is located far away each time the length regulation work is performed, and the regulation work can be performed near the next welding start point, which can shorten the overall welding time. Even if the electrode is shortened due to melting when welding is interrupted, there is no risk of adversely affecting the accuracy of the next electrode protrusion length regulation, and accurate electrode protrusion length regulation work is always guaranteed, and welding is started smoothly thereafter. It has a great effect such as obtaining.

[Brief description of drawings]

FIG. 1 is an overall schematic view of a welding robot adopting the present invention,
FIGS. 2 (a) and 2 (b) are operation explanatory views showing work for adjusting the length of the electrode protrusion during teaching, and FIG. 3 is a flow chart.
FIGS. 4 (a) to 4 (e) are operation explanatory views showing an electrode protrusion length adjusting operation during the automatic welding operation. In the figure, 4 is a torch, 4a is an electrode, 5 is a work table, 7
Is a welding power source device, and 8 is a computer.

Claims (1)

[Claims] 1. An industrial robot comprising: a sensor having an electrode capable of expanding and contracting in the direction of the central axis; a means for applying a detection voltage to the electrode; and a means for detecting the energized state of the electrode. The electrode protrusion length regulation point is taught in a proper position, the correction value of the position information sensed in at least one dimension for each work is stored, and the position information of the electrode protrusion length regulation point is corrected by the correction value. A method for controlling an industrial robot characterized by the above.