JPH0494883A - Method for controlling working by robot - Google Patents

Abstract

PURPOSE:To improve operating efficiency and to entrive for a good automation by retreating a torch once when a torch is detected to be brought into contact with a work, then, returning the mutual distance between the torch and the work to the reference distance. CONSTITUTION:When the work is worked by a robot RB, a contact state is detected by a distance sensor HS irrespective of by the actual mutual contact between the torch T and the work or by the contact based on an erroneous detection. Then, the torch T is operated to retreat by a fixed distance once unconditionally in such a direction that the torch T is separated from the work W. After the retreatment, the torch position is controlled by a torch distance controller again to return the mutual distance between the torch T and the work W to the working reference distance and since the work W is continued to be worked continuously in control of the torch T, the robot RS is not stopped whenever the contact state is detected by the distance sensor HS and the working is performed continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a processing tool for processing a workpiece surface on a robot side.
The present invention relates to a processing control method for a robot that performs processing work on a workpiece while keeping the tip at a predetermined distance suitable for processing.

(Prior technology) As a robot that works on press-formed sheet metal, etc.
For example, automatic cutting robots that use laser beams are widely used. In order to perform cutting work using such an automatic cutting robot, teaching data regarding the virtual cutting line of the workpiece to be worked is taught to the automatic cutting robot in advance. ,
The processing torch moves according to this teaching data and operates to draw a three-dimensional smooth cutting line.

However, the surfaces of a large number of works of the same type do not necessarily have exactly the same unevenness, and the unevenness usually differs from one workpiece to another due to causes such as strain caused by pressing. However, as a result, if the distance between the torch and the workpiece surface is not constant, the relationship between the focus of the laser beam and the workpiece surface may shift, making it difficult to cut the workpiece well.

So, follow the teaching data!・When moving the torch, control is also performed to keep the distance between the torch and the workpiece surface constant. A distance sensor is provided that measures 4 times according to changes in , and this distance sensor measures 1
・-Detects the distance between the torch and the work surface, moves the torch so that this distance is approximately constant, controls the mutual distance to a predetermined distance, and determines the relationship between the focus of the laser beam and the work surface. A method was adopted to maintain the desired level.

Additionally, when the torch inadvertently touches or approaches the surface of the workpiece while the robot is cutting the workpiece, a sensor output signal from the distance sensor side indicating the contact state, that is, a contact detection signal, is transmitted. Based on this contact detection signal, the control unit of the robot determines a contact error, stops the operation of the robot, and interrupts the cutting operation.

(Problem to be Solved by the Invention) However, the above-mentioned contact detection signal does not always occur due to true contact between the torch and the workpiece, but when it is generated by chance due to the atmosphere around the tip of the torch, for example, when the contact detection signal is generated by cutting the workpiece. A contact detection signal may also be generated depending on the capacitance value when the powder is blown up, and a contact detection signal due to this false detection would also cause the robot to stop operating and interrupt cutting work, as described above. . Particularly when cutting thick plates, there is a large amount of cutting powder blown back, and as mentioned above, there is a high risk of contact detection signals being generated due to false detection, resulting in frequent interruptions of cutting work and a decrease in work efficiency. Additionally, there is a drawback that smooth automation cannot be achieved due to the robot's operation being stopped.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a robot machining control method that can improve work efficiency and achieve good automation.

(Means for solving the problem) The technical means for achieving the above [1] is the sensor output of a distance sensor that detects the mutual distance between the processing torch of the robot and the surface of the workpiece facing it. It is equipped with a torch distance control device that maintains the distance between them at a predetermined processing reference distance according to the signal, and the torch distance control device operates on the surface of the workpiece while controlling the tongue position to process the workpiece. In a robot machining control method, when a distance sensor detects a contact state between the first torch and the workpiece during the machining operation of the workpiece, the torch is temporarily retracted a certain distance in a direction away from the workpiece surface side. , after evacuation, 1 again
- The distance between the torch and the workpiece is returned to a predetermined machining reference distance by the torch distance control device, and the machining operation is continued.

(Function) According to the present invention, the distance sensor detects the contact state during the processing of the workpiece by the robot, regardless of whether it is due to true contact between the torch and the workpiece or due to false detection. When detected, the torch is unconditionally retracted by a certain distance in the direction away from the surface of the workpiece, and after retracting, the torch distance control device again controls the torch position to close the distance between the torch and the workpiece. Since the distance returns to the predetermined processing reference distance and the workpiece continues to be processed while controlling the torch, the robot does not stop each time the distance sensor detects a contact condition, and processing continues. .

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an overall schematic perspective view of a Cartesian coordinate type laser cutting robot as an example of a robot to which the present invention is applied. In the figure, the robot RB is equipped with a moving table 2 on a base 1, which can be moved freely in the X direction (horizontal direction) by a motor M1 (not shown). is placed.

Columns 3 are erected on both sides of the base 1, and a beam 4 is installed between the tops of both columns 3.

The beam 4 includes a moving column 5 which extends in the Z direction (vertical direction) in the figure and is movable along the longitudinal direction of the beam 4, that is, in the Y direction (horizontal direction perpendicular to the X direction) by a motor M2. is installed.

A swivel base 6 is provided at the lower end of the moving column 5, and is movable up and down in the Z direction by a motor M3. There is.

Further, an arm 7 is provided in a downwardly protruding manner from the bottom surface of the swivel base 6 which is offset to one side from the rotation center of the swivel base 6, and the arm 7 is moved around the rotation center, that is, in the θ direction by the rotation operation of the swivel base 6. It is said to be able to be rotated freely.

A processing laser torch T is mounted on the lower end side of the arm 7 and is rotatable around a horizontal axis, that is, in the ψ direction by a motor M5 (not shown). Using this torch T, a hide sensor H3 (described later) is configured as a distance sensor that detects the distance between the torch T and the surface of the workpiece.

A laser oscillation device 8 supplies a laser beam to the torch T side through a laser guide pipe 9.

Reference numeral 10 denotes a control device incorporating a torch distance control circuit, a microcomputer, etc., which will be described later, and an operation panel 11 equipped with a keyboard, a display, etc. Further, the external computer 12 is used to input/output various data and perform data processing, and includes a CRT 13, a keyboard 14, and the like.

FIG. 2 shows a schematic block diagram of the electrical configuration of the robot RB, and the microcomputer 21 built into the control device 10 is connected to the motors M1 to M1 through the bus BL.
M5, and a mechanism drive system 23 including encoders E1 to E5 (not shown in FIG. 1) that detect rotation angles of these motors M-M. Laser oscillation device 8. Operation panel 11
．． An external computer 12 etc. is connected.

A laser beam is guided to the laser torch T from a laser oscillation device 8, and a hide sensor H8 provided at the tip of the laser torch T is used to guide the laser torch T and the workpiece W.
The distance between the torch and the torch is detected by the torch distance control circuit 22. Note that this system can also be operated under the control of an upper host system (not shown).

FIG. 3 is a partial sectional view showing details of the laser torch T. In the figure, the lower part of the cylindrical housing 30 of the laser torch T is a nozzle tip 32 whose inner and outer diameters decrease conically toward a torch hole 31 at its lower end. The outer periphery of the nozzle tip 32 in the 1-chi hole 31 portion is a hide sensor H8 in which the plane area of the portion facing the workpiece W is increased. In addition, the housing 30
A lens 33 is provided inside, and the laser oscillation device 8
The laser beam LB guided from the laser beam LB is focused by the lens 33 and irradiated onto the workpiece W.

The hide sensor I (S) is a sensor that detects the clearance p (mutual distance) between the workpiece W and the nozzle tip 32 by a change in capacitance when the laser torch T is directed toward the workpiece W. In other words, the laser torch With respect to the mutual distance between T and workpiece W, when they approach each other, the capacitance increases, and conversely, when they move away from each other, the capacitance decreases.

Therefore, by electrically insulating the laser torch T and the arm 7 and comparing the capacitance detected by the hide sensor H8 with a predetermined reference value, the actual mutual distance between the laser torch T and the workpiece W can be determined. It can be determined whether the distance is smaller or larger than a preset mutual distance.

FIG. 4 is a block diagram showing the configuration of the torch distance control device. In the figure, encoders E,' of the mechanism drive system 23
(1-1 to 5) are configured to include a speed detector TG realized by, for example, a tachometer generator, and a phase detector PG realized by, for example, a pulse generator. Furthermore, the mechanism drive system 23 is connected to a speed controller that feeds back the speed signal α from the speed detector TG.
and a position controller 2 for feeding and distributing the position signal α from the phase detector PG. Note that the mechanism drive system 23 is supplied with a position correction signal ΔαI (described later) from the torch distance control section 22 as well as a position setting signal αIo from the microcomputer 21.

On the other hand, the torch distance control circuit 22 is connected to the hide sensor H8 at the tip of the laser torch T, and the sensor amplifier 2 is used to measure the capacitance between the hide sensor H8 and the workpiece W.
21, main controller 222, main controller 22
The coordinate conversion circuit 223 converts a distance correction signal 9 (described later) given from 2 to a position correction signal Δα.

The sensor amplifier 221 outputs a sensor output signal V depending on the capacitance between the hide sensor H8 and the workpiece W, for example, as an analog voltage.
is input to the signal processing circuit 222a in the main controller 222.

In addition, if the capacitance detected by the hide sensor (S) exceeds a preset threshold value, a sensor output signal indicates that the laser chip T and workpiece W have contacted or approached abnormally. , outputs a contact detection signal S that indicates a so-called contact state, and as described above, the main controller 22
The signal is input to the signal processing circuit 222a in 2. In addition, a contact detection circuit is provided that is connected to the partner of the hide sensor H8 and the workpiece W, and when the resistance value between the hide sensor H8 and the workpiece W becomes approximately zero, it is possible to detect that the laser torch T and the workpiece W have come into contact with each other. A configuration may also be adopted in which a contact detection signal SL notifying the user of the contact detection signal SL is output. When the sensor output signal V 2 corresponding to the actual distance p between the hide sensor s and the workpiece W is input to the signal processing circuit 222a, the signal processing circuit 222a converts the sensor output signal V 2 into a distance signal Sp. On the other hand, a reference distance signal Spo corresponding to the machining reference distance 11o (for example, 2 mm) specified by the operator is input from the microcomputer 21 to the signal processing circuit 222a, and from the signal processing circuit 222a, as shown in the following equation,
distance signal S, cl and reference distance signal S,.

The difference between the distance and the distance is output as a distance correction signal Δρ.

Δ, e-sIl -sρ0 Then, the distance correction signal Δg is converted to each coordinate value α+(+-1 to 5°, specifically x
, y, z, θ, and ψ coordinate values are shown. ) is converted into a position correction signal Δα indicating the correction amount. For example, when the attitude of the laser torch T is vertical, the position correction signal Δα
1 is a driving amount instruction signal for moving the laser torch T in the Z direction in FIG.
1-1 to 5) is a signal applied to the servo system of motor M3. As described above, the movement of the laser torch T is controlled by the mechanical drive system 23, and when the actual distance I becomes equal to the processing reference distance fIo, the distance correction signal Δg becomes zero. This constitutes a torch distance control device that is controlled so that the laser torch T is always kept at a constant distance 11o from the workpiece W.

Further, when the contact detection signal S1 is manually input to the signal processing circuit 222a, the signal processing circuit 222a unconditionally outputs a predetermined distance correction signal Δg, and the laser torch T is moved through the coordinate conversion circuit 223 and the mechanism drive system 23. A certain distance fI (for example, 1
~2IIl11) is saved. A predetermined distance correction signal Δp is set so that this retracted fixed distance of 1° corresponds to a distance within the range of the mutual distance between the laser torch T and the workpiece W, which are capable of cutting the workpiece W.

FIG. 5 is a flowchart of a processing control method for the robot RB that controls the distance between the laser beam T and the workpiece W during automatic cutting of the workpiece W by the robot I-RB. When the robot RB is activated (step Sl) to start automatic cutting of the workpiece W, the laser torch T is moved based on the teaching data 1 with a predetermined machining reference distance Ro from the workpiece W, and cuts the workpiece W. I'll go. In this cutting process, it is determined in step S2 whether the hide sensor H3 detects the contact state between the laser torch T and the work W.

If no contact state has been detected, the process moves to step S3;
The torch distance control circuit 221 and mechanism drive system 23 control the laser torch T and workpiece W to be maintained at a predetermined processing reference distance 11o.

On the other hand, if a contact state is detected, the process moves to step S4, and the laser torch T is unconditionally moved a certain distance p from the surface side of the workpiece W by the torch distance control circuit 221 and mechanism drive system 23.
will be evacuated.

Thereafter, the process moves to step S5, and it is determined whether or not the cutting work has been completed. If the cutting work has not been completed, the process returns to step S2 and the above operations are repeated. When the cutting operation is completed, the process moves to step S6, the operation of the robot RB is stopped, and the automatic cutting operation is ended here.

According to the processing control method of this embodiment, if the contact detection signal St is not output during the automatic cutting operation of the workpiece W, 1. The distance control circuit 221 and mechanism drive system 23 adjust the distance between the laser torch T and the workpiece W to a predetermined distance Ω. The cutting operation is performed based on the teaching pig while maintaining the same position.

Further, when the contact detection signal St is output during the automatic connection work, the contact detection signal S is output from the hide sensor H3 side based on step S4.

Once the laser torch T is unconditionally set at a certain distance ρ through the torch distance control circuit 221 and mechanism drive system 23,
If the contact detection signal S1 is canceled after the evacuation, the distance between the laser torch T and the workpiece W is set to the predetermined processing reference distance p again based on step S3. The position of the laser chip T is controlled so as to be returned, and the cutting operation is continued while maintaining the predetermined processing reference distance 1o. Note that if the contact detection signal St is not canceled after the evacuation, the operation of step S4 is repeated until the contact detection signal S is canceled.

Therefore, even if the contact state is erroneously detected by the hide sensor H8 due to blowing up of cutting powder from the workpiece W during automatic cutting of the workpiece W by the robot RB, the operation of the robot RB will not be stopped and the cutting operation will not be stopped. Work can be done continuously, improving work efficiency, and robot RB
The automation function of cutting work can be demonstrated well. In addition, if a contact state is detected due to actual contact between the laser torch T and the workpiece W, the laser torch T is unconditionally retracted by a certain distance g, so that damage to the laser torch T is effectively prevented. It can be prevented. Furthermore, since the retraction distance p of the laser torch T is within the mutual distance that allows the warp W to be cut, the processing reference distance ρ after retraction is
. The return will be swift.

FIG. 6 is a flowchart showing a second embodiment of the machining control method of the robot RB. As described above, when the robot RB is operated (step Sl) and automatic cutting of the workpiece W is started, the laser torch T is and the predetermined addition and reference distance ρ. The workpiece W is cut while holding the . In this cutting work process, step S2, which will be described later,
The count value N of the counter of the knob S9 is reset to zero, and then, in step S3, it is determined whether the hide sensor H8 detects the contact state between the laser torch T and the workpiece W.

If no contact state has been detected, the process moves to step S4;
As described above, the laser torch T and workpiece W are controlled to be maintained at a predetermined processing reference distance, Qo. after that,
Proceeding to step S5, it is determined whether or not the cutting work has been completed. If the cutting work has not been completed, the process returns to step S2. When the cutting work is completed, the process moves to step S6.
The operation of robot RB stops.

On the other hand, if a contact state is detected in step S3, the process moves to step S7, and the robot is evacuated by a certain distance p as described above.

After the evacuation, it is determined in step S8 whether the hide sensor H3 detects a contact state between the laser torch T and the workpiece W.

If no contact state has been detected, the process moves to step S4;
If a contact state is detected, the process moves to step S9, where 1 is added to the count @N of the counter, and then in step SIO, a predetermined number of times a( For example, it is determined whether a=4) or not.

If the count value N has not reached the set number of times a, the process returns to step S7 and the above operation is repeated. Further, when the count value N reaches the set number of times a, the process moves to step S6, and the robot RB stops.

According to this processing control method, the operation of the robot RB is stopped only when the continuous contact detection signal SL is detected a predetermined number of times a, and there is an advantage that stopping of the robot FRB more than necessary can be effectively prevented.

Note that the processing reference distance 11o may be appropriately determined according to cutting conditions such as the power and focal length of the laser beam LB, the material and thickness of the workpiece W, and the processing speed.

Furthermore, the retraction distance p 1 may be set within a predetermined mutual spacing distance that allows for good machining operations such as cutting, that is, within a predetermined capacitance range suitable for machining operations. Furthermore, the processing work is not limited to cutting work, but may also be welding work or the like. Further, the distance sensor is not limited to a capacitance sensing type, and magnetic or optical distance measuring means or the like may be used.

(Effects of the Invention) As described above, according to the robot machining control method of the present invention, when the contact state between the torch and the workpiece is detected by the distance sensor during the workpiece machining operation, the torch is first moved toward the surface of the workpiece. This method involves retracting a certain distance away from the workpiece, and after retracting, the mutual distance between the torch and the workpiece is returned to the predetermined machining reference distance using the torch distance control device, and the work is continued. The robot is not stopped every time a condition is detected, and work can be performed continuously, so work efficiency can be improved and good automation can be achieved.

[Brief explanation of drawings]

FIG. 1 is an overall schematic perspective view of a robot to which the present invention is applied;
FIG. 2 is a block diagram showing the electrical configuration of the robot in FIG. 1, FIG. 3 is a partial sectional view showing the detailed configuration of the laser torch, FIG. FIG. 5 is a flowchart showing the first embodiment of the present invention, and FIG. 6 is a flowchart showing the second embodiment. 10...control device, 11...operation panel, 1
2... External computer, 21... Microcomputer, 22... Torch distance control circuit, 23... Mechanism drive system, 221... Sensor amplifier, 222... Main controller, 222a... Signal Processing circuit, 223...Coordinate transformation circuit, RB...Robot,
T...Laser torch, -W...Work,] 9 H8...Hide sensor

Claims (1)

[Claims] (1) Torch distance control device that maintains the distance between the processing torch of the robot and the workpiece surface at a predetermined processing reference distance according to the sensor output signal of the distance sensor that detects the distance between the processing torch and the surface of the workpiece facing the robot. In the processing control method for a robot, which processes a workpiece by moving the torch on the surface of the workpiece while controlling the torch position with a torch distance control device, during the processing of the workpiece, a distance sensor controls the distance between the torch and the workpiece. When a contact condition is detected, the torch is moved a certain distance away from the workpiece surface, and
A method for controlling machining of a robot, characterized in that after evacuation, the distance between the torch and the workpiece is returned to a predetermined machining reference distance by a torch distance control device to continue machining work.