JPH033545B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for an industrial robot that sequentially automatically processes a plurality of workpieces.

Generally, industrial robots are equipped with various abnormality detection means, and when an abnormality is detected during automatic processing, the processing operation is immediately stopped. For example, in the case of welding robots, accidents in which a processing tool collides with a workpiece rarely occur due to an abnormal protrusion on the workpiece or a teaching error (that is, forgetting to teach the welding point). However, as industrial robots are incorporated into production lines,
When processing a large number of workpieces in sequence, the operation of the entire production line including the robot may be stopped due to just one abnormal workpiece, resulting in a significant reduction in production capacity.

The present applicant previously proposed in Japanese Patent Application No. 58-151161 that a reference point is set for the processing tool at an appropriate distance from the workpiece, the processing tool is directed from this reference point to the processing start point, and after the processing operation, the processing tool is directed from the processing end point to the reference point. If an abnormality occurs during processing, the processing tool will be returned to the reference point and the processing tool will be returned to the reference point by retracing the route taken up to that point. We proposed a control method that allows the production line to continue operating even if there is an abnormality in only one workpiece, minimizing the decline in production efficiency by moving to the next workpiece upon return.

However, while the aforementioned control method is effective for workpieces whose machining time is relatively short, for workpieces whose machining time is several hours long, if an abnormality occurs near the end of machining, the machining equipment will not be able to operate for a long time. Since it is necessary to return to the reference point by retracing the route taken up to that point, the above-mentioned feature of suppressing a decline in production efficiency is lost.

In view of the above-mentioned circumstances, the present invention sets a reference point where the processing tool waits and returns after processing is appropriately spaced from the workpiece, and provides at least one return relay point on the route from the processing start point to the processing end point. When an abnormality is detected by the abnormality detection means on the above-mentioned route, the processing tool will stop the processing operation, retrace the previous route, return to the reference point from the nearest return relay point, and return to the reference point after the abnormality is detected. The feature is that the processing operation for the next workpiece begins when the processing tool returns to the reference point, regardless of whether or not the processing tool returns to the reference point.If an abnormality occurs during the processing operation, the processing tool can safely and quickly return to the reference point. The purpose of this invention is to provide a control method for an industrial robot that can return to the next workpiece and minimize the decline in production efficiency even when an abnormality occurs in a workpiece that requires a long machining time.

Prior to a specific explanation of the present invention, a production line including a welding robot as an industrial robot that is the background of the present invention will be sequentially explained.

In FIG. 1, reference numeral 1 denotes a roller conveyor constituting a loop-shaped production line, which intermittently circulates and transfers a large number of pallets 2. During the intermittent stop of the conveyor 1, a roller conveyor 1 is conveyed automatically or manually at a workpiece loading location (not shown). Unwelded workpieces W are loaded onto pallets 2 during the work, and the workpieces W loaded on each pallet 2 are sequentially welded by an articulated welding robot 3 installed on the side of the roller conveyor 1 downstream from the workpiece delivery location in the transfer direction. Automatic welding is performed, and the welded workpieces W are taken out from the pallet 2 at a workpiece delivery location (not shown) set further downstream, and the empty pallet 2 is returned to the workpiece delivery location. Reference numeral 4 designates a locking device for positioning and fixing the pallet 2 at a predetermined position in front of the welding robot 3, and a flange engagement member 4b formed at the tip of the rod is drilled into the side surface of the pallet 2 by the rod extension operation of the operating cylinder 4a. The pallet 2 is fitted into the provided hole 2a and is pressed by the collar against the guide roller 1a disposed on the opposite side surface, thereby positioning and fixing the pallet.
Although not shown, the locking device 4 has a pallet presence/absence detection function for detecting that the engaging member 4b has come into contact with the pallet 2.

The multi-jointed welding robot 3 has a final control axis 3.
A welding torch 5 (hereinafter referred to as torch 5) is attached to a as a processing tool. Reference numeral 6 denotes a power supply device for applying voltage and supplying current to the electrodes 7, etc. of the torch 5; 8, a built-in microcomputer controller for comprehensively controlling the roller conveyor 1, the welding robot 5, the power supply device 6, etc.; Means 9 is a remote control panel derived from the control means 8, which remotely controls the movement and operation of each part by manual operation, performs teaching operations on the workpiece W, and stores data in the memory (not shown) in the control means 8. It inputs the user program.

Reference numerals 10 and 11 denote an electrode supply roll and a pair of electrode feed rollers attached to the power supply device 6, and the electrode 7 is pulled out from the supply roll 10 by the rotation of the feed roller 11, and passed through the flexible tube 12 to the torch. 5
The tip protruding from the torch 5 becomes the welding point.

Reference numerals 13 and 14 denote voltage applying means and energization state detecting means built into the power supply device 6, of which the voltage applying means 13 is connected to the welding power source 13a and the sensor power source 13.
b. Abnormal approach detection power source 13c, one end of which is connected to the electrode 7, and a changeover switch 13d that selectively connects to either the welding power source 13a or the sensor power source 13b, one end of which is made of the conductor of the torch 5; It consists of a regular open/close switch 13e, etc., which is connected to the mantle 5a (however, the mantle 5a is electrically insulated from the electrode 7) and is connected to a power source 13c for abnormal approach detection at appropriate times.

The energization state detection means 14 has one end connected to the sensor power source 13b and the abnormal approach detection power source 13c, and the other end connected to the welding power source 13c.
Palette 2 along with the anti-changeover switch 13d side of 3a
The energization state detection circuits 14a and 14b for sensors and abnormal approach detection are connected to the roller conveyor 1 which is electrically connected to the workpiece W via It consists of energization state detection output circuits 14c and 14d for a sensor and for abnormal approach detection, which input the change in both as a detection signal and transmit it to the control means 14.

Therefore, when sensing the welding line of the workpiece W using the electrode 7 protruding from the torch 5 as a sensor,
Welding robot 3 during teaching, during tests to check the posture, movement speed, welding conditions, etc. of the torch 5 according to the program obtained through teaching, when manually moving the torch 5, etc., and during automatic welding, etc.
During all operations, the open/close switch 13e is always closed and a detection voltage (this is a high voltage, low current at the same level as the sensor voltage) is applied to the mantle 5a, and the abnormal approach detection power source 13c is opened/closed. The abnormality detection means constituted by the switch 13e, the energization state detection circuit 14b, the energization state detection output circuit 14d, and the jacket 5a is kept in an operable state at all times.

Below, the welding robot 3 mentioned above is the roller conveyor 1.
A case in which a large number of workpieces W are sequentially automatically welded in cooperation with each other will be explained with reference to the flowchart shown in FIG.

The workpieces W are of the same type, and as shown in Fig. 1, the welding start point Ps, the points _P1 , _P2 , _P3 , _P4 , _P5 ,
It is assumed that automatic welding is performed along a zigzag developed welding line connecting P ₆ , P ₇ and the welding end point Pe.

In addition, the microcomputer built in the control means 8 is programmed to control the reference point Po, which is set appropriately above the height position of the workpiece W on the roller conveyor 1, through each of the points Ps, _P1 to _P7 , Pe, and then back to the reference point. Po
, the posture of the torch 5 at each point, the welding conditions, the welding speed, and the welding start point Ps and points P ₂ , P ₄ , P ₆ (in addition ,point
P ₂ , P ₄ , P ₆ are collectively referred to as return relay point Pi), etc.), and the microcomputer is activated in auto mode,
Accordingly, the aforementioned program is output step by step as command information. In addition, the return point P ₂ ,
It is assumed that P ₄ and P ₆ are approximately equally spaced, and that it has been confirmed by visual inspection at the time of tinching that it is safe to return to the reference point Po in a straight line without any obstruction.

Furthermore, in the initial state of the roller conveyor 1, the first pallet 2 on which unwelded workpieces W are already loaded is
is placed in front of the welding robot 3, and the pallet 2 and workpiece W are positioned and fixed by a locking device 4.

Below, the steps in the automatic welding mode will be explained one by one.

(1) First, determine whether the program includes welding command information.

(2) If it is included, command the operation to switch the changeover switch 13d to the welding power source 13a.

(3) Determine whether the torch 5 is located at the reference point Po.

(4) If it is not located, move torch 5 to the reference point
Command the positioning operation to Po.

(5) Determine whether the workpiece W is placed at a predetermined position. When the rod of the actuating cylinder 4a in the locking device 4 is extended and the engaging member 4b is detected to be in contact with the pallet, a determination of ``YES'' is made.

(6) Command the operation to position the torch 5 at the welding start point Ps.

(7) Next, command execution of welding work. As a result, the torch 5 changes from Ps→P ₁ →P ₂ →P ₃ →P ₄ →P ₅ →P ₆ →
Perform automatic welding along the welding line of P ₇ →Pe.

(8) During the execution of the welding work, it is determined whether an abnormality is detected for each unit movement amount (step amount) of the torch 5.
“Electricity” is output from the energization state detection output circuit 14d.
If there is no signal, it is judged as "NO".

(9) Next, it is determined whether the torch 5 has reached the welding end point Pe. If "YES", a command is given to stop the welding work. As a result, the changeover switch 13d is switched to the sensor power supply 13b,
Further, by stopping the rotation of the feeding roller 11, feeding of the electrode 7 is stopped.

(10) Next, command the return movement of the torch 5 from the welding end point Pe to the reference point Po.

(11) Command the release of pallet 2. This results in
The locking device 4 releases the fixed position of the pallet 2 by the rod shortening operation of the operating cylinder 4a.

(12) Next, command conveyor 1 to be driven one pitch. As a result, the roller conveyor 1 is driven one pitch, and the pallet 2 carrying the welded work W leaves in front of the welding robot 3, and the pallet 2 carrying the new unwelded work W arrives in front of the welding robot 3. , the locking device 4 is operated again in sequence to position and fix the pallet 2.

(13) Determine whether to move to the next work W.
If ``YES'', the process returns to steps (1) and (2) and automatically welds the work W in sequence.

If, as shown in FIG. 1, there is an abnormal protrusion t in the middle of the welding line of the workpiece W, for example between points P ₆ and P ₇ , the mantle 5a of the torch 5 comes extremely close to the abnormal protrusion t during automatic welding. Then, the current flows between the two and discharges, and the energization state detection output circuit 14d issues a signal of "energization", so the determination in step (8) becomes "YES".

(14) Therefore, the order is given to stop the welding work. As a result, the torch 5 stops at the abnormality point Pt, and the changeover switch 13d changes to the sensor power supply 1.
3b, and as the feeding roller 11 stops rotating, feeding of the electrode 7 also stops.

(15) Next, command torch 5 to perform back tracking. As a result, the torch 5 retraces the path it has traveled from the abnormality occurrence point Pt to that point, as shown in FIG.

(16) Determine whether the torch 5 has reached the welding start point Ps or the return relay point Pi. For example, torch 5
reaches the nearest return point P ₆ and decides "YES".

(17) Command the torch 5 to return to the reference point Po. As a result, the torch 5 returns directly from the return point ^P6 to the reference point Po.
This step (17) is similar to the steps (10) and (11) above.
continues in between.

By making some changes to the program, in step (17) mentioned above, when the torch 5 approaches an obstacle while returning from point P ₆ to Po, it will return from that point and return to the next nearest point from point P ₆ . It is also possible to return to the reference point Po from the return point _P4 .

Furthermore, in the above-mentioned embodiment, the abnormality detection means provided in the welding robot 3 detects as an "abnormality" when the torch mantle approaches an abnormal protrusion of the workpiece W. The present invention can be similarly implemented using other abnormality detection means, such as means for detecting a defect in the bevel or means for detecting an abnormality in the workpiece using a television camera.

Furthermore, in the above-mentioned embodiment, the workpieces W are transported by the roller conveyor 1, and the workpieces W are automatically welded one after another every time the roller conveyor 1 stops intermittently. The control method of the present invention can also be effectively applied when a lot of workpieces are placed on a workbench and processed.

As detailed above, according to the control method of the present invention, a reference point is set at which the processing tool waits and returns after processing is completed, and at least one Because a return relay point is set, even if the machining time for the workpiece is long and an error occurs near the end of machining, the workpiece can quickly return to the reference point from the return relay point closest to the point where the error occurred during backtracking operation. , it is possible to minimize the decline in production efficiency due to the occurrence of an abnormality, and to continue operating the robot.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of a welding robot including a production line as an example of implementing the control method of the present invention, and FIG. 2 is a control flowchart employed in the welding robot of FIG. 1. In the diagram, 1 is a roller conveyor, 2 is a pallet, and 3 is a roller conveyor.
is a welding robot, 4 is a locking device, 5 is a torch,
5a is a jacket, 6 is a power supply device, 7 is an electrode, 8 is a control means, W is a workpiece, Po is a reference point, Ps is a welding start point, Pe is a welding end point, Pi is a return relay point,
t is an abnormal protrusion, and Pt is an abnormal occurrence point.

Claims (1)

[Claims] 1 Equipped with an abnormality detection means for detecting abnormalities related to the workpiece itself and/or teaching mistakes,
In an industrial robot that automatically processes a plurality of workpieces in sequence while controlling the relative positions of the workpiece and the processing tool by appropriate control means, a reference point where the processing tool waits and returns after processing is completed. is set at an appropriate distance from the workpiece, and at least one return relay point is set on the route from the processing start point to the processing end point, and when the processing tool detects an abnormality on the route by the abnormality detection means, At the same time as stopping the machining operation, the previous route is returned to the reference point from the nearest return relay point, and regardless of whether or not an abnormality is detected, the processing tool returns to the reference point and starts the next workpiece. A control method for an industrial robot, which is characterized in that it moves to processing work.