JP3184248B2 - Robot control device and control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a welding robot, and particularly, a hot start for improving welding quality.
It can be used for welding crater fillers.

[0002]

2. Description of the Related Art Conventionally, sensor control (Japanese Patent Laid-Open No. Sho 62-166)
078), there is position control in the welding torch length direction (arc length), but this control is effective when the robot has welding with an interpolation path (at the time of interpolation operation). Sensor control cannot be performed when there is no robot interpolation path, such as during a hot start or crater filler. This is because the length direction of the torch is the synthetic direction of X, Y, and Z of the robot wrist, and therefore, the rising is bad when the wrist moves in the torch direction unless the wrist is constantly driven by the interpolation operation. In addition, the constant control of the arc length is performed by a welding method such as MAG welding in which electrodes are consumed.
There was no special important control.

[0003]

In recent years, in TIG welding, which is a non-consumable electrode welding method, the need for which has been increasing, the importance of constant control of the arc length has been increasing in order to stabilize the arc while maintaining welding quality. Is coming. For this reason, even in the case of a hot start, a crater filler, or the like, which conventionally does not require the arc length control (sensor control), it is necessary to perform the arc length constant control when the robot is in an operation standby state before moving.

An object of the present invention is to make sensor control effective during a robot playback (automatic operation) operation in a robot operation standby state, and to perform sensor control during a robot standby time during an arc unstable period such as at the start of welding. The purpose is to stabilize the arc by performing the welding and to smoothly shift to the main welding.

[0005]

The above object is achieved by TIG welding.
State of the welding torch provided at the tip of the robot
The TIG by the constant arc length control
Sensor control processing to convert to position correction amount of welding robot
And the welding torch in the specified direction from the current position in the standby state.
For moving a distance smaller than the welding torch tip diameter
The moving distance is determined in advance as an interpolation instruction amount, and the TIG welding is performed.
Outputs the interpolation instruction amount when the robot is in the operation standby state.
Interpolation command processing unit, the position correction amount and the interpolation instruction amount
From the current position of the standby state of the welding torch
The distance between the specified distances separated by the interpolation instruction amount is
Interpolation operation that performs interpolation calculation at the specified minimum nearby interpolation speed
Before inputting the result of the interpolation operation of the arithmetic processing unit and the interpolation operation processing unit
Servo system that generates command value to TIG welding robot
This can be achieved by providing a control unit . In particular,
This can be achieved by giving a pseudo-interpolation instruction amount of the minimum distance and the minimum speed considered as stopped as a robot operation command, and determining the operation direction at that time from the torch posture of the robot.

[0006]

The robot can maintain the operation standby state by giving the interpolation instruction amount of the pseudo interpolation path. On the other hand, since the interpolation operation is actually performed, the sensor control operation can be easily achieved.

[0007]

An embodiment of the present invention will be described below.

In the embodiment, the robot has a structure capable of operating the torch by sensor control for performing constant control of the arc length for TIG welding. In this case, a sensor that detects a current corresponding to the arc of the torch or that directly looks at the arc length is used. In the constant control of the arc length, the robot detects the arc state at that time when the actual welding work has a waveform distortion as shown by the solid line in FIG. 5 with respect to the path of the teaching line indicated by the dotted line in FIG. The operation position of the robot is controlled so that the torch height (△ 11, Δ12, Δ13) is kept constant. In the constant control of the arc length, if there is a sensor control instruction (step 6) at the time of the interpolation operation command (step 1) in the control flow of FIG. 1, the sensor control is enabled in step 7 and the interpolation is executed in step 8. Then, the position to be interpolated is added with a correction amount for the displacement detected by the sensor, and the robot position is controlled so that the torch goes to a position where the arc length becomes constant. End of sensor control is Step 4
Specifically, this is performed by time-up control specified by the user or by input of an end signal from the outside .

FIG. 2 shows the position and control relationship of each processing unit when performing the above control. Regarding the direction of control at this time,
This is performed for the A vector (vertical direction vector) of the tool attachment coordinate system shown in the control direction of FIG. This control direction differs depending on the wrist posture at that time when viewed from the control direction of the wrist of the robot. Therefore, the sensor control processing unit 10
The control direction of the wrist is determined by taking in the current wrist posture.

The arithmetic operation will be described. Assuming that the sensor detected analog value in FIG. 2 is a, the A / D converter 13 performs the arithmetic operation shown in the following equation.

[0011]

(Equation 1)

Here, the symbol C is an A / D conversion coefficient, and D is a digitally converted detection amount. Although the analog value a for sensor detection is not particularly specified, a device that detects a welding voltage of a TIG welding machine, filters the voltage, and converts the voltage to an analog voltage of 0 to 10 V is used in the embodiment.

Next, the sensor control processing unit 10 shown in FIG. 2 converts the detection amount D into a correction amount h. The operation expression is as follows.

[0014]

(Equation 2)

Here, A indicates the direction of the vector A in FIG. The constant control of the arc length is controlled by adding the correction amount h to the robot position.

In this embodiment, in order to realize sensor control while the robot is stopped at an arbitrary position, the symbol b in FIG. 2, that is, the interpolation instruction amount b is a distance 0.1 m that can be regarded as a stop by the naked eye.
m (a value sufficiently smaller than the welding torch tip diameter) to the pseudo route, and the interpolation speed at this time is set to the lowest speed at which zero suppression or the like does not occur in the calculation (0.01 mm in the embodiment).
/ Sec), and by making the interpolation operation processing section 11 function, it is possible to realize the same performance as sensor control by normal interpolation operation processing. In the embodiment, the interpolation direction is the horizontal R vector in FIG. 4 and the O vector direction in the tool attachment coordinate system. The minimum values of the interpolation distance and the speed are used, but the interpolation is completed after a lapse of time. Therefore, when the interpolation is completed, the interpolation is performed in a direction opposite to the direction currently being executed (R vector direction). An interpolation instruction is issued, and minute interpolation is continuously performed on the pseudo interpolation path. Therefore, based on the generation of the interpolation completion signal, the interpolation command processing unit 12 supplies the interpolation command generator 12a (1) that continuously generates the next interpolation command amount b in the reverse direction.
7a) is provided. The pseudo-interpolation path in this case is a pseudo-path, and may be arbitrary, and examples thereof include a reciprocating operation, a circular operation, and a square operation.

Further, in the embodiment, there are a system in which the end of the sensor control is terminated by time-up of a time designated by the user (which can be arbitrarily set) and a system in which the sensor control is terminated by an external end signal (FIG. 1). (Fig. 2).

FIG. 3 shows a position control vector amount C calculated by the sensor control processing unit 15 without the intervention of the arithmetic processing unit 16 by interpolation. The structure which implement | achieves is shown.

FIG. 6 is a block diagram for calculating the correction amount during the constant arc length control shown in FIG. 23 is a generator for receiving a sensor detection amount and generating a horizontal sensor control signal;
Reference numeral 24 denotes a generating unit that receives the signal and generates a correction amount in the A direction. Reference numeral 25 denotes a generator for generating a horizontal signal in response to the horizontal adjustment amount of the relative movement direction of the torch and the welding work, and reference numeral 26 denotes a generator for generating an N-direction correction amount in response to the signal.

FIG. 7 shows a case in which the welding is immediately shifted to the main welding at the point where the arc is emitted. If the arc length is long, the arc becomes unstable and easily cut, and if the heat input to the work is insufficient. Cannot maintain high welding quality. As in the case of performing welding (hot start) as shown in FIG. 8, the work is heated immediately after the arc is generated without immediately shifting to the main welding to improve the penetration and then the main welding is performed. It is effective to perform constant control (sensor control) on the welding quality. In the above embodiment, the arc length can be stably controlled by performing constant control (sensor control) on the arc length by a pseudo interpolation operation, and the arc can be shifted in a stable state when shifting to the main welding. Therefore, high welding quality can be obtained.

The welding operation shown in FIG. 9 (crater filler)
If the torch does not move up and down, the arc length will be shortened by overlaying the deposited metal,
When the build-up end is formed (crater filler) at the final stage of welding in which the torch does not move horizontally, the torch 21 and the build-up portion are short-circuited, resulting in an electrode short-circuit. According to this embodiment, FIG.
As shown in FIG.
Since it is possible to move up and down from the build-up portion of No. 2, the arc length is kept constant even at the time of the crater filler forming the build-up end in the final stage, and a crater filler with good welding results can be realized.

The above two methods are methods in which the sensor control is completed in a time-up manner. Next, a system that can be realized by using a method of ending sensor control by inputting an external end signal will be described with reference to FIGS.

FIG. 11 shows a system in which the cylindrical workpiece 102 is rotated by a positioner or the like, and the robot is welded by the torch 103 while stopping at the position shown in the figure. In the case of this system, when the cylinder is a perfect circle and the center of rotation is not the center of the perfect circle, the arc length varies when the cylinder is rotated. In this embodiment, the sensor can be controlled at this time, and the arc length can be kept constant. Further, by configuring the system to generate an external end signal by operating the external switch 101 when the cylinder makes one rotation, ideal cylindrical welding can be performed in TIG welding.

Further, in the case of a work 105 having a long welding distance as shown in FIG. 12, sensor control can be performed even when a system for performing welding by sliding the work side horizontally is assembled. In this case, a switch (not shown)
Is to generate an external end signal.

[0025]

According to the present invention, the sensor control that is effective at the time of the interpolation operation is made effective in the operation standby state of the robot, and the sensor control is performed in the robot standby state when the arc is unstable such as at the start of welding. It is possible to smoothly shift to the main welding.

[Brief description of the drawings]

FIG. 1 is a flowchart of sensor control showing one embodiment of the present invention.

FIG. 2 is a sensor control processing logic circuit diagram also using interpolation.

FIG. 3 is another sensor control processing logic circuit diagram that also uses interpolation.

FIG. 4 is an explanatory diagram showing each control direction during constant arc length control.

FIG. 5 is an explanatory diagram of an operation during constant arc length control.

FIG. 6 is an explanatory diagram of a correction amount calculation in the constant arc length control.

FIG. 7 is an explanatory diagram of a conventional example of hot start execution.

FIG. 8 is an explanatory diagram of an embodiment of the present invention in which hot start is performed.

FIG. 9 is an explanatory diagram of an operation of a conventional example of crater filler enforcement.

FIG. 10 is an explanatory diagram of an operation of the embodiment of the present invention in which the crater filler is enforced.

FIG. 11 is an explanatory view of an embodiment of the present invention at the time of cylindrical welding using a positioner.

FIG. 12 is an explanatory view of an embodiment of the present invention when welding a workpiece having a long welding distance.

[Explanation of symbols]

10: sensor control processing unit, 11: interpolation calculation processing unit, 12
... interpolation command processing unit, 12a ... interpolation command generator, 13 ... A
/ D conversion unit, 14 servo control processing unit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sumio Washio 7-1-1 Higashi Narashino, Narashino-shi, Chiba Hitachi Keiyo Engineering Co., Ltd. (72) Inventor Tsukasa Shiina 7-1-1, Higashi-Narashino, Narashino-shi, Chiba Hitachi Keiyo Engineering Co., Ltd. (72) Inventor Masaharu Yaginuma 7-1, 1-1 Higashi Narashino, Narashino City, Chiba Prefecture Hitachi Keiyo Engineering Co., Ltd. (72) Inventor 1 Shibuya 7-1, 1-1 Higashi Narashino, Narashino City, Chiba Prefecture Hitachi, Ltd. Narashino Works (56) References JP-A-63-207473 (JP, A) JP-A-61-186170 (JP, A) JP-A-59-76677 (JP, A) JP-A-48-18135 (JP) , A) Japanese Patent Publication No. 50-40390 (JP, B2) Japanese Patent Publication No. 6-13149 (JP, B2) (58) (Int.Cl. ^7, DB name) B23K 9/127 B23K 9/12 B25J 9/10

Claims (3)

(57) [Claims] 1. A TIG welding robot provided at a tip thereof.
Sensor signal indicating the arc state of the welding torch (21)
(A) The robot for TIG welding by constant arc length control
Sensor control processing unit for converting to the position correction amount (h) of the unit
(10) and the specified direction from the current position in the standby state with the welding torch (21)
(R or O) less than the welding torch tip diameter
The movement distance for the movement is specified as the interpolation instruction amount (b).
In the operation standby state of the TIG welding robot.
The interpolation command processing unit (1) that outputs the interpolation command amount (b)
2) Input the position correction amount (h) and the interpolation instruction amount (b)
From the current position of the standby state of the welding torch (21)
In the designated direction (R or O), the interpolation instruction amount (b)
Interpolated speed of specified minimum nearby speed between separated distances
And an interpolation calculation processing unit (11) for performing an interpolation calculation by the interpolation processing unit (11).
Servo control processing to generate command value to IG welding robot
For controlling a robot, comprising a control unit (14)
apparatus. 2. The apparatus according to claim 1 , wherein the interpolation command processing section (12) is configured to execute the TI
In the operation standby state of the G welding robot, the interpolation calculation is performed.
When the interpolation by the processing unit (11) is completed, the interpolation command
The control device for a robot according to claim 1, wherein the amount is continuously generated by changing the amount (b) so that the moving direction is the opposite direction . 3. A TIG welding robot provided at the tip of the robot.
Sensor signal indicating the arc state of the welding torch (21)
A method of controlling a robot for performing route interpolation operation so as to perform the arc length constant control by (a), the position correction of the TIG welding robot said sensor signal
Is converted into the quantity (h), and the welding torch (21) is visually detected from the current position in the standby state.
A pseudo route having a distance that can be regarded as a stop is determined on the pseudo route.
The moving distance for moving the object is set as the interpolation instruction amount (b).
The interpolation is performed when the TIG welding robot is in an operation standby state.
The instruction amount (b) is output, and the position correction amount (h) and the supplementary amount are output.
Before the welding torch (21) by inputting the distance indication amount (b)
A specified direction from the current position in the standby state on the pseudo route
At the specified minimum interpolation speed
Interpolating the distance given by the quantity (b),
The command value to the TIG welding robot is calculated based on the result.
A method for controlling a robot, characterized in that it occurs.