JP2009262275A - Robot control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smooth a robot stop action after detecting contact in displacement detection action. <P>SOLUTION: A robot control apparatus includes a command position generation part 2 for calculating a command position for detecting displacement of a workpiece W by a working tool T mounted on a robot R, a drive control part 3 for moving the working tool T based on the command position, a stop processing part 8 for outputting a stop signal Ts by detecting the contact of the working tool T with the workpiece W, a contact position calculation part 7 for storing a contact position Dv when the working tool T comes in contact with the workpiece W, and a position correction part 9 for correcting teaching data Td by calculating a position displacement amount. By the input of the stop signal Ts, the current position of the working tool T which the drive control part 3 recognizes is made to be the contact position Dv, the command position which the command position generation part 2 outputs is made to be an inertia moving position Sv, and an inertia moving distance correction route for allowing the working tool T to run back from the inertia moving position Sv to the contact position Dv is calculated so that the working tool T is made to be stopped at the original contact position Dv. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a robot control device that detects a displacement of a workpiece such as arc welding.

  2. Description of the Related Art Conventionally, a contact detection device is widely known as a device for detecting a displacement of a workpiece (hereinafter referred to as a workpiece). For example, in the field of arc welding robots, a position detection method using a welding wire protruding from an arc welding torch as an input device of a contact detection device is widely used (for example, see Patent Documents 1 and 2).

  FIG. 3 is a block diagram showing a configuration of a conventional arc welding robot apparatus using a contact detection device. As shown in the figure, the arc welding robot apparatus 20 includes a robot R that performs arc welding work, a portable operating device TP that is used when an operator performs teaching work, and a robot control apparatus RC that controls the operation of the robot R. Generally composed.

  The portable operation device TP includes a display unit 41 on which the teaching data Td is displayed, a keyboard 42 for inputting the teaching data Td, an emergency stop switch (not shown) for emergency stopping the robot R, and the like. The teaching data Td input from the keyboard 42 is transmitted to the robot controller RC via an interface circuit (not shown) and stored in the hard disk 4. In the robot R, an arc welding torch T is attached to the wrist tip as a work tool. The robot controller RC controls the operation of the robot R based on the input teaching data Td.

  Each part of the robot controller RC will be described. The CPU 6 is a central processing unit, the RAM 5 is a temporary calculation area, and the hard disk 4 is a non-volatile memory for storing teaching data Td and the like. The hard disk 4 also stores a contact position Dv indicating the position of the workpiece when the contact detection device TC detects contact. Although not shown in the drawing, the amount of displacement of the workpiece, which is the difference between the contact position Dv and the teaching data Td, is also stored in the hard disk 4.

  The main control unit 1 is a control center of the robot control device RC. The main control unit 1 interprets the teaching data Td and outputs the interpretation result to the command position generation unit 2, as well as a control signal for controlling a welding power source (not shown) and the like. Is output.

  The command position generation unit 2 plans the path of the arc welding torch T based on the interpretation result of the teaching data Td in the main control unit 1 and calculates the command position that is the amount of movement of each axis of the robot R. The command position is output as a position command signal to the drive control unit 3 described later.

  The drive control unit 3 outputs a servo control signal for controlling the rotation of each servo motor of the robot R based on the position command signal, thereby driving each axis of the robot R to set a control point of the arc welding torch T. Move along the route. Further, the drive control unit 3 can recognize the current position of the control point of the arc welding torch T by feeding back information from an encoder (not shown).

  The stop processing unit 8 monitors the contact detection signal Tc from the contact detection device TC, and outputs the stop signal Ts to the command position generation unit 2 to stop the robot R when the contact detection signal Tc is input. .

  The contact detection device TC includes a discharge high-voltage power source as a contact detection power source electrically connected to the welding wire Wr of the arc welding torch T, and a current sensor for detecting energization (both not shown). ). Hereinafter, these are collectively referred to as a contact detection device TC. When arc welding is performed, the welding wire Wr and the workpiece W are in an electrically conductive state. A device for generating a potential difference between the welding wire Wr and the workpiece W is a contact detection device TC. When the contact detection device TC is operated to generate a voltage between the welding wire Wr and the workpiece W, current flows when the welding wire Wr is in contact with the workpiece W, and the welding wire Wr is separated from the workpiece W. When it is, no current flows. That is, the contact between the welding wire Wr and the workpiece W can be detected based on the state of the current flowing through the welding wire Wr.

  The contact position calculation unit 7 calculates the contact position Dv based on each shaft angle when the arc welding torch T stops after the stop signal Ts is input. Further, the position correction unit 9 calculates the amount of positional deviation of the workpiece W based on the contact position Dv and the teaching data.

  Next, the action at the time of detecting and correcting misalignment in the arc welding robot apparatus 20 described above will be described.

  The main control unit 1 interprets a command for executing a displacement detection operation described in the teaching data Td. The command position generation unit 2 calculates a path for detecting the positional deviation of the workpiece based on the analysis result of the main control unit 1, calculates the command position to follow this path, and outputs the command position to the drive control unit 3. The calculation and output of the command position is performed at every predetermined calculation cycle defined by the robot controller RC. Then, the drive control unit 3 operates the robot R according to the route.

  When the welding wire Wr contacts the workpiece W, the contact detection device TC outputs a contact detection signal Tc. The stop processing unit 8 outputs a stop signal Ts to the command position generation unit 2. As a result, the drive control unit 3 stops the robot R. Thereafter, the contact position calculation unit 7 calculates the contact position Dv based on each axis angle when the robot R is stopped.

  After the detection operation is completed, the position correction unit 9 calculates the amount of displacement of the workpiece W based on the contact position Dv and the reference position data in the teaching data Td, and corrects the teaching data Td.

  By the way, after the stop signal Ts is input to the command position generation unit 2, the robot R does not stop immediately due to a position deviation amount described below.

  There is a positional deviation amount between the command position output from the command position generation unit 2 to the drive control unit 3 and the current position where the drive control unit 3 actually drives the robot R. The position deviation amount is stored in a variable called a deviation counter (not shown) in the drive control unit 3. The deviation counter is a counter that adds the movement amount of each axis of the robot in accordance with the command position from the command position generation unit 2 and subtracts the actual movement amount of each axis of the robot. The speed and amount of movement are determined. When the value of the deviation counter is 0, the robot speed is 0. In other words, after the stop signal Ts is actually input to the command position generation unit 2, the robot R stops after stroking by the amount of position deviation stored (remaining) in the deviation counter. .

  FIG. 4 is a diagram showing a state of coasting due to the positional deviation amount. The figure shows an example in which the arc welding torch T moves in the detection operation direction Sd in order to detect the displacement of the workpiece W by the welding wire Wr. In the figure, a position P1 is a position where the welding wire Wr actually contacts the workpiece W. Originally, it is desirable to stop immediately at the position P1, but due to the above-described positional deviation amount, the arc welding torch T coasts to the position P2 and stops. As a result, a coasting distance Dd is generated. Although not shown, since the welding wire Wr is pressed against the workpiece W by coasting and stopping after coasting, the stress from the workpiece W is continuously applied to the welding wire Wr, and the welding wire Wr is bent.

  As described above, in the position detection method using the contact detection device TC, a delay (cogging distance Dd) from when the contact detection device TC detects contact with the workpiece W until the robot R stops. ) Occurs. Since the position where the robot R stops is recognized as the contact position Dv and the amount of displacement is calculated, the position of the workpiece W recognized by the robot controller RC and the actual position of the workpiece W are between. An error occurred, and it was originally impossible to detect the position to be welded. Furthermore, as described with reference to FIG. 4, in the case of an arc welding robot, the welding wire Wr may bend due to the coasting distance Dd, so that the target position during welding may be shifted.

  Therefore, conventionally, in order to reduce the amount of positional deviation (running distance), the speed during the detection operation has been reduced. However, if the speed at the time of the detection operation is lowered, the time required for the detection operation becomes longer, so that productivity is lowered. As a method of reducing the position deviation amount, it is conceivable to increase the calculation capability of the CPU or the like mounted on the robot control device RC and shorten the cycle for monitoring the contact detection signal Tc from the contact detection device TC. This leads to an increase in cost.

  Means for solving the above problems is disclosed in Patent Document 2. In Patent Document 2, when the contact detection device TC detects contact, the value of the deviation counter in the drive control unit 3 is replaced with 0, so that the contact detection device TC detects contact with the workpiece W. The robot R is stopped immediately and the coasting distance is set to zero.

Japanese Patent Publication No.56-5634 Japanese Patent Application Laid-Open No. 07-237164

  However, the prior art described in Patent Document 2 has a problem that abnormal noise or vibration occurs when the robot R stops because the robot R stops suddenly when contact is detected. Due to these abnormal noises, vibrations, etc., the robot life may be shortened. Further, Patent Document 2 discloses a method of smoothly stopping and simultaneously shortening the coasting distance, but this method can smoothly stop the robot, but the coasting distance still occurs. For this reason, the arc welding robot has a problem that the target position at the time of welding described above is shifted.

  Therefore, the present invention provides an arc welding robot that uses a welding wire as a contact detection device while smoothing the stop operation of the robot after detecting the contact during the detection operation when detecting the displacement of the workpiece. An object of the present invention is to provide a robot control device capable of reducing the bending of a welding wire caused by coasting after detection.

In order to achieve the above object, the first invention provides:
In a robot control device that detects a positional shift of the work by bringing a work tool attached to the robot into contact with the work,
A command position generation unit that calculates a path for detecting the positional deviation based on teaching data and outputs a command position on the path;
A drive control unit that drives the robot according to the command position while recognizing the actual position of the work tool;
A stop processing unit that outputs a stop signal for stopping the robot when a contact detection signal indicating that the work tool has contacted the workpiece is input from a contact detection unit;
When the stop signal is input, the actual position of the work tool recognized by the drive control unit is stored as a contact position, and the command position output by the command position generation unit is a coast position. A contact position calculation unit that stores
A displacement amount calculation unit that calculates a displacement amount of the workpiece based on the contact position and the teaching data;
The command position generation unit calculates a coasting distance correction path for moving the work tool from the coasting position to the contact position when the stop signal is input, and controls the driving of the command position. The robot control apparatus according to claim 1, wherein the work tool is moved along the coasting distance correction path and stopped at the contact position.

  According to a second aspect of the present invention, in the robot control apparatus, the robot is an arc welding robot, and the work tool is an arc welding torch.

  According to the first aspect of the invention, when the position detection of the workpiece is detected by the contact detection device, after the contact is detected, the workpiece is advanced and stopped in the reverse direction by the coasting distance. Since the position deviation amount is set to 0 as in the prior art, the robot is not stopped suddenly, so that the robot can be smoothly stopped.

  According to the second invention, particularly when the welding wire of the arc welding robot is applied as the contact detection device, the effect of the first invention can be exhibited. Furthermore, it is possible to prevent the welding wire from being pressed against the workpiece and bent due to the coasting during the contact detection operation.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on examples with reference to the drawings.

  FIG. 1 is a block diagram showing an arc welding robot apparatus 10 of the present invention. In the figure, the difference from FIG. 3 shown as the prior art is the contact position calculation unit 7, the command position generation unit 2, the drive control unit 3, and the coast position Sv stored in the hard disk 4. Hereinafter, these will be described. The other parts are the same as those shown in FIG.

  The contact position calculation unit 7 is configured to receive a stop signal Ts from the stop processing unit 8. When the stop signal Ts is input, the contact position calculation unit 7 refers to the current position of the work tool recognized by the drive control unit 3 and stores it in the hard disk 4 as the contact position Dv. At the same time, the command position output by the command position generator 2 when the stop signal Ts is input is referred to and stored in the hard disk 4 as the coasting position Sv. The contact position Dv and the coast position Sv may be configured to be temporarily stored in the RAM 5 instead of the hard disk 4.

  When the stop signal Ts is input, the command position generation unit 2 stops the calculation and output of the command position necessary for the position shift detection operation and stops the position shift detection operation. Subsequently, a route based on the coast position Sv and the contact position Dv stored in the hard disk 4 is calculated. More specifically, a coasting distance correction path for moving the arc welding torch T from the coasting position Sv to the contact position Dv is calculated. Then, the command position on the coasting distance correction route is calculated and output to the drive control unit 3.

  In the stage where the stop signal Ts is input, the drive control unit 3 still has the position deviation amount at the time of the position deviation detection operation. For this reason, the remaining command position is processed as the position deviation amount (the robot R is driven). Thereafter, the robot R is driven based on the command position on the coasting distance correction route input from the command position generation unit 2. As a result, the arc welding torch T stops at the contact position Dv.

  FIG. 2 is a diagram illustrating how the coasting distance is corrected according to the present invention. This figure shows a case where the workpiece W moves in the detection operation direction Sd in order to detect the positional deviation of the workpiece W by the welding wire Wr of the arc welding torch T. In the drawing, a position P1 'indicates a position where the welding wire Wr actually contacts the workpiece W, and a position P2' indicates a position when coasting according to the position deviation amount.

  In the present invention, the position P1 'is the contact position Dv, and the position P2' is the coast position Sv. The contact position Dv (position P1 ') is a position when the stop signal Ts is input (current position recognized by the drive control unit 3). The coast position Sv (position P2 ') is a command position output by the command position generator 2 when the stop signal Ts is input.

  The command position generation unit 2 calculates a coasting distance correction path Tk for moving the arc welding torch T from the coasting position Sv to the contact position Dv and outputs the command position to the drive control unit 3. Then, the drive command unit 3 drives each axis of the robot R and stops the arc welding torch T at the contact position Dv.

  As described above, when detecting the position deviation of the workpiece by the contact detection device, after detecting the contact, the position deviation amount is not set to 0, but is advanced in the reverse direction by the amount of the position deviation amount and stopped. As a result, the stopping operation of the robot can be smoothed. Furthermore, it is possible to improve the detection accuracy of the displacement.

  In addition, the present invention can exert the above-described effects particularly when a welding wire of an arc welding robot is applied as a contact detection device. Furthermore, it is possible to prevent the welding wire from being pressed against the workpiece and bent during the contact detection operation.

It is a block diagram which shows the structure of the arc welding robot apparatus of this invention. It is the figure which showed a mode that the coasting distance was correct | amended by this invention. It is a block diagram which shows the structure of the conventional arc welding robot apparatus. It is the figure which showed a mode that it coasts by the cause of a positional deviation amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main control part 2 Command position generation part 2 Command position generation part 3 Drive control part 4 Hard disk 7 Contact position calculation part 8 Stop processing part 9 Position correction part 10 Arc welding robot apparatus 20 Arc welding robot apparatus 41 Display part 42 Keyboard Dd 惰Travel distance Dv Contact position P1 Position P1 ′ Position P2 Position P2 ′ Position R Robot RC Robot controller Sd Detection direction Sv Coasting position T Arc welding torch Tc Contact detection signal TC Contact detection device Td Teaching data Tk Stop path TP Portable Operating device Ts Stop signal W Work Wr Welding wire

Claims (2)

In a robot control device for detecting a positional deviation of the workpiece by bringing a work tool attached to the robot into contact with the workpiece,
A command position generation unit that calculates a path for detecting the positional deviation based on teaching data and outputs a command position on the path;
A drive control unit that drives the robot according to the command position while recognizing the actual position of the work tool;
A stop processing unit that outputs a stop signal for stopping the robot when a contact detection signal indicating that the work tool has contacted the workpiece is input from a contact detection unit;
When the stop signal is input, the actual position of the work tool recognized by the drive control unit is stored as a contact position, and the command position output by the command position generation unit is a coast position. A contact position calculation unit that stores
A displacement amount calculation unit that calculates a displacement amount of the workpiece based on the contact position and the teaching data;
The command position generation unit calculates a coasting distance correction path for moving the work tool from the coasting position to the contact position when the stop signal is input, and controls the driving of the command position. The robot controller according to claim 1, wherein the work tool is moved according to the coasting distance correction route and stopped at the contact position.   The robot control apparatus according to claim 1, wherein the robot is an arc welding robot, and the work tool is an arc welding torch.

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