JPH0259032B2 - - 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 occur rarely due to an abnormal protrusion on the workpiece or a teaching error (that is, forgetting to count the welding points).

However, when an industrial robot is incorporated into a production line and processes a large number of workpieces in sequence, a single abnormal workpiece may stop the entire production line, including the robot, resulting in a significant drop in production capacity. invite.

In view of the above-mentioned circumstances, the present invention provides the workpiece itself and/or
Or, in an industrial robot that is equipped with an abnormality detection means for detecting an abnormality related to a teaching error, and that automatically processes multiple workpieces in sequence while controlling the relative positions of the workpiece and the processing tool using an appropriate control means. , the processing tool faces the processing start point of the workpiece from a set reference point set at an appropriate distance from the workpiece, and when an abnormality is detected by the abnormality detection means between the processing start point and the processing end point, processing is performed. It stops the work and returns to the reference point by following the path up to that point, and if no abnormality is detected, returns directly to the reference point from the processing end point, and returns to the reference point of the processing tool regardless of whether or not an abnormality is detected. The robot is characterized in that the processing operation for the next workpiece is started upon the return of the robot, and even if the above-mentioned abnormality occurs during automatic processing, the processing operation for the abnormal workpiece is simply stopped without stopping the operation of the robot. The purpose of this invention is to provide a control method for an industrial robot, with the purpose of moving on to machining work on the next workpiece and avoiding a decrease in production capacity as much as possible.

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 formed in a loop shape, which intermittently circulates and transfers a large number of pallets 2. During the intermittent stop of the conveyor 1, unwelded parts are automatically or manually transported to a workpiece loading area (not shown). Workpieces W are loaded onto pallets 2, and the workpieces W loaded on each pallet 2 are sequentially automatically welded by an articulated welding robot 3 disposed on the side of the roller conveyor 1 downstream from the workpiece loading location in the transport direction. The welded workpieces W are taken out from the pallet 2 at a workpiece unloading location (not shown) set further downstream, and the empty pallet 2 is returned to the workpiece loading location. Reference numeral 4 denotes a locking device for positioning and fixing the pallet 2 at a predetermined position in front of the welding robot 3. When the rod is extended by the actuating cylinder 4a, the rod fits into the hole 2a drilled in the side surface of the pallet 2. The pallet is positioned and fixed. Although not shown, the locking device 4 is equipped with a pallet presence/absence detection function for detecting when the rod comes into contact with the pallet 2.

The multi-jointed welding robot 3 has a final control axis 3a.
Welding torch 5 (hereinafter referred to as torch 5) 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, and 8, a control unit with a built-in microcomputer that comprehensively controls the roller conveyor 1, the welding robot 3, 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 supply 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 supply roller 11, passed through the flexible tube 12, and then passed through the flexible tube 12. It is fed to the torch 5, and the tip protruding from the torch 5 becomes the welding point.

FIG. 2 is a schematic explanatory diagram mainly showing a circuit block diagram of the power supply device 6. As shown in FIG. In FIG. 2, reference numerals 13 and 14 are voltage applying means and energization state detecting means built into the power supply device 6. Of these, the voltage applying means 13 is connected to the welding power source 13a and the sensor power source 1.
3b, abnormal approach detection power supply 13c, one end connected to electrode 7
A changeover switch 13d is connected to the welding power source 13a and the sensor power source 13b to selectively connect it to either the welding power source 13a or the sensor power source 13b. electrically insulated) and connect it to the power supply 13c for timely abnormal approach detection.
It consists of a normally open on/off switch 13e connected to the .

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.
Energization state detection circuits 14a, 14b for sensors and abnormal approach detection connected to the workpiece W (or the pallet 2 electrically connected to the workpiece W) together with the anti-changeover switch 13d side of a, and respective energization state detection circuits 14a, 14b, respectively. an energization state detection output circuit 14 for sensors and abnormal approach detection that inputs a change in the energization state (current, voltage, or a change in both) as a detection signal and transmits it to the control means 8;
c, 14d.

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 any operation of the on/off switch 13e,
is closed and a detection voltage (this is high voltage and low current at the same level as the sensor voltage) is applied to the mantle 5a, and an abnormal approach detection power source 13c, an on/off switch 13e, an energization state detection circuit 14b, The abnormality detection means constituted by the energization state detection output circuit 14d and the jacket 5a is kept in an operable state at all times.

The remote control panel 9 is additionally provided with a backtracking push button (not shown), which is used to detect teaching errors during teaching and test operations.
Alternatively, when it is desired to start teaching again, the movement of the torch 5 is temporarily stopped, and the torch 5 is moved back for each step of the already taught point. Therefore, by continuing to press the backtracking push button, the torch 5 can finally be returned to the initial teaching point (ie, the reference point).

During all operations of the welding robot 3,
When the mantle 5a of the torch 5 abnormally approaches the workpiece W, current is applied between the mantle 5a and the workpiece W, and discharge occurs, and the change in voltage and/or current is detected by the energization state detection circuit 14b, and the energization state is detected. The control means 8 outputs the "energization" signal from the state detection output circuit 14d.
Upon receiving this signal, the control means 8 issues a command to each drive source of the welding robot 3 to stop driving.
As a result, the movement of the torch 5 is immediately stopped, and collision between the torch 5 and the workpiece W is instantly avoided. If this abnormality is detected during an operation other than automatic welding, the welding robot 3 remains in a stopped state, so the torch 5 can be retracted manually or the backtracking push button can be operated to move the torch 5 away. Work until W
The robot retreats to the desired teaching point by following a route that has been confirmed to be safe without colliding with the robot.

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

The workpieces W to be welded are of the same type,
It is formed by butting a convex plate Wa and a concave plate Wb,
As shown in Fig. 4, welding start point P ₁ , intermediate point
Automatic welding shall be performed along the welding line connecting P ₂ and welding end point P ₃ .

In addition, the microcomputer built in the control means 8 is programmed to control the reference point _P0 , which is set appropriately above the height position of the workpiece W on the roller conveyor 1, through each of the points _P1 , _P2 , _{P3, and} then again to the reference point. A user program such as the route back to P ₀ , the posture of the torch 5 at each point P ₀ , P ₁ , P ₂ , P ₃ , welding conditions, etc. is input, and the microcomputer is activated in auto mode and The above program is output step by step as command information.

Further, in the initial state of the roller conveyor 1, the first pallet 2 carrying unwelded workpieces W is placed in front of the welding robot 3, and the pallet 2 and the workpieces W are positioned and fixed by the locking device 4. do.

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

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

(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 _P0 .

(4) If it is not located, move torch 5 to the reference point
Command the positioning operation to P ₀ .

(5) Determine whether the workpiece W is placed at a predetermined position. The locking device 4 determines ``YES'' when the rod is extended in the operating cylinder 4a and the rod is in contact with the pallet.

(6) Command the operation to position the torch 5 at the welding start point _P1 .

(7) Next, command execution of welding work. As a result, the torch 5 moves from the welding start point P ₁ to the intermediate point P ₂ →
Perform automatic welding along the welding line at welding end point _P3 .

(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 _P3 . 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 is given to return the torch 5 from the welding end point _P3 to the reference point _P0 .

(11) Command the lock device 4 to be deactivated. As a result, the lock 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 performs one-pitch drive, and the pallet 2 on which the welded workpiece W is loaded leaves the welding robot 3, and the pallet 2 on which the unwelded workpiece W is newly loaded or the empty pallet 2 on which no workpiece W is loaded is replaced. reaches in front of the welding robot 3, and the locking device 4 is activated again in sequence to position and fix the pallet 2.

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

If, as shown in Fig. 5, there is an abnormal protrusion Ws near the welding line of the workpiece W, and the mantle 5a of the torch 5 comes very close to the abnormal protrusion Ws during automatic welding, current will flow between the two and a discharge will occur. However, since the energization state detection output circuit 14d issues the "energization" signal, the determination in step 8 becomes "YES".

(14) Therefore, a command is given to stop the welding work, the torch 5 is stopped at the abnormality point Pi, the changeover switch 13d is switched to the sensor power supply 13b, and as the feed roller 11 stops rotating, the electrode 7 is turned off. Feeding will also be stopped.

(15) Next, backtrack the torch 5 from the abnormality point Pi to the reference point _P0 .
As a result, the torch 5 as shown in FIG.
Abnormality point Pi is intermediate point _P2 and welding end point
If it is between Pi → _{P 2 →} P ₁ → P ₀ , it will return safely to the reference point P ₀ by retracing the route it has traveled so far.

The step 15 is the same as the step 1.
Continues between 0 and 11.

In the above-mentioned embodiment, the workpieces W are transported by the roller conveyor 1, and automatic welding is sequentially performed on the workpieces W each time the roller conveyor 1 stops intermittently. However, as shown in FIGS. The control method of the present invention can also be effectively applied when processing several works as one lot.

That is, in FIGS. 6 and 7, the welding robot 10
A workpiece mounting table 102 is installed in front of the workpiece 3, and a plurality of workpieces are positioned and fixed as one lot on the workpiece mounting table 102, and automatic welding is performed in sequence. In Fig. 6, three workpieces W1, W2, and W3 are set as one lot, and one reference point _P01 is set.
When the welding start point and welding end point of each work W1 to W3 are P ₀₂ , P ₀₃ , P ₀₄ , P ₀₅ , P ₀₆ , P ₀₇ , the teaching path of the torch 105 is
P ₀₁ →P ₀₂ →P ₀₃ →P ₀₁ →P ₀₄ →P ₀₅ →P ₀₁ →P ₀₆ →P ₀₇
→P ₀₁ . Also, Figure 7 shows four workpieces W1.
0, W20, W30, W40 as one lot,
Reference points P 10 and P ₂₀ are set for the workpieces W10, W20 and W30, W40, respectively, and the welding start point and welding end point of each workpiece W10 to W40 are set as _{P 11 ,} P ₁₂ , P ₁₃ , P ₁₄ , P ₁₅ ,P ₁₆ ,
In the case of P ₁₇ and P ₁₈ , the teaching path of the torch 105 is P ₁₀ →P ₁₁ →P ₁₂ →P ₁₀ →P ₁₃ →P ₁₄ →
P ₁₀ →P ₂₀ →P ₁₅ →P ₁₆ →P ₂₀ →P ₁₇ →P ₁₈ →P ₂₀ →P ₁₀
shall be. As in the previous embodiment, if an abnormality is detected during the welding operation, the welding apparatus returns to the reference point by back tracking and continues the next step.

In each of the above-mentioned embodiments, the abnormality detection means was designed to detect an "abnormality" when the torch mantle approaches an abnormally protruding part of the workpiece. The present invention can be similarly implemented using other abnormality detection means such as means for detecting abnormalities in the workpiece or means for detecting abnormalities in the workpiece using a television camera.

As detailed above, according to the control method of the present invention, a reference point is set for each workpiece, and under normal conditions, after the machining operation is completed, the process returns to the reference point and moves on to the machining operation for the next workpiece. When an abnormality is detected during the automatic machining process, the machining operation is stopped and the path taken up to that point is returned to the reference point to proceed to the machining operation on the next workpiece.This prevents abnormalities from occurring in the workpieces when automatically machining multiple workpieces one after another. However, the entire robot does not stop operating even when the robot is in use, and the decline in production efficiency can be kept to a minimum.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a welding robot including a production line as an example of implementing the control method of the present invention, FIG. 2 is a circuit block diagram mainly of a power supply device of the welding robot, and FIG. 3 is a welding robot shown in FIG. 1. 4 and 5 are explanatory diagrams showing the movement of the torch in normal and abnormal conditions, respectively, and FIGS. 6 and 7 are schematic explanatory diagrams for explaining another embodiment. In the diagram, 1 is a roller conveyor, 2 is a pallet, and 3 is a roller conveyor.
is a welding robot, 5 is a torch, 5a is a mantle, 6 is a power supply device, 7 is an electrode, 8 is a control means, W is a workpiece, Ws is an abnormal protrusion, P ₀ is a reference point, P ₁ is a welding start point, P ₃ indicates the welding end 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 using appropriate control means, the processing tool is moved from a reference point set at an appropriate distance from the workpiece. It faces the machining start point of the workpiece, and when the abnormality detection means detects an abnormality between the machining start point and the machining end point, it stops the machining operation and returns to the reference point by following the path up to that point. In addition, if no abnormality is detected, the processing tool returns directly to the reference point from the processing end point, and regardless of whether or not an abnormality is detected, the processing tool returns to the reference point and starts processing the next workpiece. A control method for an industrial robot, characterized by: