JP2009279725A - Robot control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate an operation by automatically setting a coordinate system suitable for a manual operation when correcting teaching points forming a circular-arc route. <P>SOLUTION: In this robot control device, the teaching points A to C forming the circular-arc route K are corrected in terms of a position by moving a work tool T mounted on a robot in accordance with a directional instruction inputted from an operation means. A perpendicular line length St and an intersection Sp are calculated by drawing a perpendicular line Sv in relation to a center axis Kr of the circular-arc route K from a present position D of the work tool T. A manual operation coordinate system Cm having a first coordinate axis Xs determined based on a direction of the center axis Kr and a second coordinate axis Ys determined based on a direction of the perpendicular line Sv is set. In accordance with the directional instruction inputted from the operation means, the work tool T is moved in the first coordinate axis direction Xs, in the second coordinate axis direction Ys or in the circular-arc route direction having the intersection Sp as a center and the perpendicular line Sv as a radius. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a robot control apparatus for correcting a taught arc path.

  When processing operations such as arc welding and spot welding are realized by a robot, a method called teaching playback is generally adopted. In the teaching playback method, a workpiece is set at a predetermined position, the robot is moved manually to a desired position using portable operation means, and the moved position is stored as a teaching point. In this method, the work route is taught, and the taught data (hereinafter referred to as “teaching data”) is repeatedly reproduced to continuously process workpieces of the same type. As the above-described work route, it is possible to teach a desired route such as a straight line route or an arc route (see, for example, Patent Documents 1 and 2).

  FIG. 4 is a general block diagram of a conventional arc welding robot apparatus. In the figure, a robot R includes an arc welding torch T at the wrist as a work tool for processing a workpiece W. The base coordinate system Cb is an orthogonal coordinate system unique to the robot R having the X, Y, and Z coordinate axis directions, and is stored as a constant in the robot controller RC. Actually, the origin is arranged at the base portion of the robot R, but for convenience of explanation, it is expressed in the illustrated position.

  The teach pendant TP as an operation means is a device for an operator to teach the work path of the robot R with respect to the work W, and a direction instruction unit 4 for moving the robot R is provided on the board surface. Yes. The direction indicating unit 4 is equipped with a plurality of buttons corresponding to the coordinate axis directions (± X, ± Y, ± Z) of the base coordinate system Cb. More specifically, the direction indicating unit 4 includes a button 4x for moving in the ± X coordinate axis direction, a button 4y for moving in the ± Y coordinate axis direction, and a button 4z for moving in the ± Z coordinate axis direction. I have.

  Then, by pressing each button, the operator moves the robot R to a desired position and teaches a work route for performing the machining work. Then, the position and orientation coordinate values of the robot R at the teaching point on the work path are stored in the robot controller RC as teaching data. The robot controller RC controls the drive motor of the robot R based on the teaching data and current position information from an encoder (not shown), and moves the arc welding torch T to the teaching point.

  FIG. 5 is a diagram for explaining the relationship between the moving direction of the robot and the coordinate system at the time of teaching, and shows an image viewed from the direction of the arrow H in FIG. In the figure, the robot R, the workpiece W and the base coordinate system Cb are the same as those shown in FIG. For convenience of explanation, X + and Y + in the axial direction are represented by arrows, and the other axial directions are omitted. The circular arc path K is a part of a path necessary for machining the workpiece W, and is formed by the teaching point A, the teaching point B, and the teaching point C.

  The operator moves the robot R to a desired position, teaches the position, confirms the work route, and corrects the position if necessary. However, the operation of each button when performing position correction is complicated. For example, in order to correct the arc path K, it is assumed that the robot R is moved from the teaching point B that is the current position to the correction point B ′ that is the desired correction position. If the direction from the teaching point B to the correction point B ′ is completely coincident with the X + direction of the base coordinate system Cb, for example, the operator only has to operate the button 4x to the + side. However, as shown in the figure, the coordinate axis direction of the base coordinate system Cb and the direction in which it is desired to move are almost the same. In such a case, the operator needs to move the robot R by operating the button 4x, the button 4y, etc. in combination. If the workpiece W is large or complicated, the operation for moving the robot R becomes even more complicated.

  Patent Document 1 discloses a method of setting a weld line coordinate system at each teaching point on an arc path. When correcting the position, manual operation is performed with reference to the weld line coordinate system, and the operation is complicated. It has been suggested that this could be reduced. However, when performing manual operation on the basis of the weld line coordinate system disclosed in Patent Document 1, there are problems to be described later.

  Further, Patent Document 2 discloses a method that can reduce the position correction operation of the straight path by defining a non-orthogonal weld line coordinate system with reference to the teaching point on the straight path. No mention is made of the case.

JP 62-194513 A Japanese Patent No. 3665344

  FIG. 6 is a diagram for explaining the axial direction when the weld line coordinate system is set at the teaching point on the circular arc path. In the figure, for example, the origin of the welding line coordinate system Cw at the teaching point B and the direction of each coordinate axis are as follows. The origin Wo is the same as the position of the teaching point B, the + direction of the coordinate axis Zj is a tangential direction in the arc path K, and the + direction of the coordinate axis Xj is the normal direction of the plane including the arc path K (from the back of the drawing). The + direction of the coordinate axis Yj is a direction that is perpendicular to the coordinate axes Zj and Xj and follows the right-handed coordinate system. The + direction of the coordinate axis Yj coincides with the direction from the center point Ko of the circular arc path K toward the teaching point B.

  If the welding line coordinate system Cw is set and the manual operation is performed while the arc welding torch T is at the teaching point B, the arc welding torch T is moved by simple operations in the ± Xj, ± Yj, and ± Zj directions. be able to. In other words, when the direction to be moved from the teaching point B coincides with, for example, the direction away from the center point Ko of the circular arc path K (+ Yj) or the normal direction (+ Xj) of the circular arc path K, etc. The weld line coordinate system Cw set in B is very effective.

  However, it is assumed that the arc welding torch T is manually operated in the welding line coordinate system Cw when the arc welding torch T is at the non-teaching point D between the teaching point B and the teaching point C. In the welding line coordinate system Cw, since the coordinate axis direction set at the teaching point B does not change, the coordinate axis directions at the non-teaching point D remain ± Xj, ± Yj, and ± Zj as shown. Therefore, for example, when moving the position of the non-teaching point D in the direction of the center point Ko of the arc path K (in the direction of the dotted arrow), the combination operation of the button 4x and the button 4y is required. That is, at positions other than the teaching point, there is a problem that even if the manual operation is performed with reference to the welding line coordinate system Cw, the operation becomes complicated.

  Further, when the button 4z is pressed with the welding line coordinate system Cw as a reference, the movement is made in the tangential direction Zj. However, there is little opportunity to move the teaching point in the tangential direction to correct the position, so the button 4z is difficult to use. There were also challenges.

  Accordingly, the present invention provides a robot control device that can automatically set a coordinate system suitable for manual operation when correcting teaching points forming an arc path and facilitate the operation. With the goal.

In order to achieve the above object, the first invention provides:
A robot that corrects the position of a pre-taught arc path by moving a work tool attached to the robot in accordance with an instruction input from an operating means having a first direction instruction section, a second direction instruction section, and a third direction instruction section In the control device,
A perpendicular length and an intersection point are calculated from the current position of the work tool with respect to the central axis of the circular arc path to calculate a perpendicular length and an intersection point, and the first coordinate axis determined based on the direction of the central axis and the direction of the perpendicular A coordinate system setting unit for setting a manual operation coordinate system having a second coordinate axis determined based on the coordinate system;
When an instruction is input from the first direction instruction unit, the work tool is moved in the direction of the first coordinate axis, and when an instruction is input from the second direction instruction unit, the work tool is moved to the second direction. An operation control unit for moving the work tool on an arc path centered on the intersection point and having the perpendicular length as a radius when an instruction is input from the third direction indicating unit.
A robot control apparatus comprising:

  According to a second aspect of the invention, in the robot according to the first aspect, the manual operation coordinate system is calculated when the instruction input is input or when the work tool stops after the instruction input. It is a control device.

  According to the first invention, a coordinate system optimum for manual operation is set based on the teaching point forming the circular arc path and the current position of the work tool, and the work tool is set in accordance with the direction instruction input from the operation means. Is caused to perform at least one of movement in the normal direction of the arc path, movement in the direction toward the center of the arc path, and rotational movement with the arc center axis as the rotation center. It is possible to facilitate manual operation when correcting the teaching.

  According to the second invention, the manual operation coordinate system is automatically set when a direction instruction input from the operation means is input or when the work tool stops moving after the direction instruction is input. . That is, since the manual operation coordinate system can be automatically set without performing a special operation, in addition to the effect of the first invention, the number of work steps can be reduced.

  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 of an arc welding robot apparatus to which a robot control apparatus according to the present invention is applied. As shown in the figure, the arc welding robot apparatus 20 includes a robot R that performs arc welding work, a teach pendant TP as an operation means used when an operator performs teaching work, and a robot control apparatus that controls the operation of the robot R. Roughly composed of RC.

  The teach pendant TP is a device for an operator to teach the work path of the robot R with respect to the work W. On the board surface, a direction indicating unit 4 for moving the robot R is provided as in the prior art. The direction instructing unit 4 is the same as that given the same reference numerals in FIG. That is, a plurality of buttons corresponding to each coordinate axis direction (± X, ± Y, ± Z) in a predetermined coordinate system are provided, and a button 4x, a button 4y, and a button 4z are provided. The teach pendant TP also includes a display unit 41 for displaying the teaching data Td, a keyboard 42 for inputting the teaching data Td, an emergency stop switch (not shown) for stopping the robot R in an emergency, 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 7. An arc welding torch T as a work tool is attached to the tip of the wrist of the robot R. 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, the hard disk 7 is a non-volatile memory for storing teaching data Td, a manual operation coordinate system Cm described later, and the like. The teaching processing unit 1 stores the teaching data Td input from the teach pendant TP in the hard disk 7. The display processing unit 11 displays the teaching data Td, the coordinate system used as a reference in manual operation, and the like on the teach pendant TP as necessary.

  The operation control unit 2 outputs a position command signal for moving the robot R in a designated direction to the drive control unit in response to an instruction input from the teach pendant TP. The drive control unit 3 outputs a servo control signal for controlling rotation of each servo motor of the robot R based on the position command signal, drives each axis of the robot R, and moves a control point of the arc welding torch T. .

  Next, the manual operation coordinate system setting unit 8 will be described. The manual operation coordinate system setting unit 8 performs the following processing based on the teaching points forming the circular arc path, and automatically sets a coordinate system suitable for manual operation (manual operation coordinate system Cm).

  FIG. 2 is a diagram for explaining the manual operation coordinate system. In the drawing, an arc path K is formed by the teaching point A, the teaching point B, and the teaching point C. The position correction mode for correcting the arc path K is selected, and the control point of the arc welding torch T is positioned at the non-teaching point D. When an instruction is input from the direction instruction unit 4 in this state, the manual operation coordinate system setting unit 8 performs the following processing to set the manual operation coordinate system Cm before driving each axis of the robot R.

  First, the central axis Kr of the arc path K is calculated based on the three teaching points A, B, and C that form the arc path K. Subsequently, the perpendicular direction Sv, the perpendicular length St, and the intersection point Sp are calculated from the non-teaching point D that is the current position of the arc welding torch T with respect to the central axis Kr.

  Then, the coordinate axis Xs (first coordinate axis) coinciding with the direction of the central axis Kr is determined with the non-teaching point D as the origin. Further, the coordinate axis Ys (second coordinate axis) is determined based on the perpendicular direction Sv. At this time, an axis orthogonal to the coordinate axis Xs and the coordinate axis Ys may be determined as the coordinate axis Zs.

  As described above, the manual operation coordinate system Cm having at least the coordinate axis Xs and the coordinate axis Ys is set and stored in the hard disk 7. Instead of the hard disk 7, it may be stored in the RAM 5.

  Following the above, the operation control unit 2 performs the following process to move the work tool in response to a direction instruction input from the direction instruction unit 4.

  FIG. 3 is a diagram for explaining a moving direction when the manual operation is performed in the manual operation coordinate system. As shown in the figure, when an instruction is input from the button 4x, the arc welding torch T is moved from the current position in the direction of the coordinate axis Xs. When an instruction is input from the button 4y, the arc welding torch T is moved from the current position in the direction of the coordinate axis Ys.

  When an instruction is input from the button 4z, the arc welding torch T is moved from the current position in the arc path direction Ks with the intersection Sp on the center axis Kr as the center and the perpendicular length St as the radius. More specifically, while the button 4z is pressed, the movement target position (movement target position in the next control cycle) is calculated momentarily according to the following equation and a position command signal is output to the drive control unit 3. .

When the movement target position is Qn, the intersection is Sp, the vector of the central axis Kr is Krv, the movement speed at the time of manual operation is Ms, the control period is Dt, and the vector of the perpendicular length St is Stv.
Movement target position Qn = Sp + Rot (Krv, Ms · Dt / Stv) · Stv

  In the above, the manual operation coordinate system Cm is set at the timing when the instruction input from the direction indicating unit 4 is performed, but the arc welding torch T is moved and stopped in response to the instruction input from the direction indicating unit 4. You may make it set after doing.

  As described above, the optimum coordinate system for manual operation is set based on the teaching point forming the circular arc path and the current position of the work tool. Then, according to the direction instruction input, the work tool performs at least one of movement in the normal direction of the arc path, movement in the direction toward the center of the arc path, and rotational movement with the arc center axis as the rotation center. By doing so, it is possible to facilitate manual operation when teaching and correcting the arc path.

  The manual operation coordinate system is automatically set when a direction instruction input from the operation means is input or when the work tool stops moving after the direction instruction is input. That is, since the manual operation coordinate system can be automatically set without performing a special operation, in addition to the above effects, the work man-hours can be reduced.

1 is a block diagram of an arc welding robot apparatus to which a robot control apparatus according to the present invention is applied. It is a figure for demonstrating a manual operation coordinate system. It is a figure for demonstrating the moving direction at the time of manual operation in a manual operation coordinate system. It is a general block diagram of the conventional arc welding robot apparatus. It is a figure for demonstrating the relationship between the moving direction of a robot at the time of teaching, and a coordinate system. It is a figure for demonstrating the axial direction when a welding line coordinate system is set in the teaching point on a circular arc path | route.

Explanation of symbols

A Teaching point B Teaching point B 'Correction point C Teaching point Cb Base coordinate system Cm Manual operation coordinate system Cw Welding line coordinate system D Non-teaching point H Arrow K Circular path Ko Center point Kr Central axis Ks Circular path direction Qn R Robot RC Robot controller Sp Intersection St Perpendicular length Sv Perpendicular direction T Arc welding torch Td Teaching data TP Teach pendant W Work Wo Origin Xj Coordinate axis (weld line coordinate system)
Xs coordinate axis (manual operation coordinate system)
Yj coordinate axis (weld line coordinate system)
Ys coordinate axis (manual operation coordinate system)
Zj coordinate axis (weld line coordinate system)
Zs coordinate axis (manual operation coordinate system)
DESCRIPTION OF SYMBOLS 1 Teaching process part 2 Operation control part 3 Drive control part 4 Direction instruction | indication part 4x Button 4y Button 4z Button 5 RAM
6 CPU
7 Hard Disk 8 Manual Operation Coordinate System Setting Unit 11 Display Processing Unit 20 Arc Welding Robot Device 41 Display Unit 42 Keyboard

Claims (2)

A robot that corrects the position of a pre-taught arc path by moving a work tool attached to the robot in accordance with an instruction input from an operating means having a first direction instruction section, a second direction instruction section, and a third direction instruction section In the control device,
A perpendicular length and an intersection point are calculated from the current position of the work tool with respect to the central axis of the circular arc path to calculate a perpendicular length and an intersection point, and the first coordinate axis determined based on the direction of the central axis and the direction of the perpendicular A coordinate system setting unit for setting a manual operation coordinate system having a second coordinate axis determined based on the coordinate system;
When an instruction is input from the first direction instruction unit, the work tool is moved in the direction of the first coordinate axis, and when an instruction is input from the second direction instruction unit, the work tool is moved to the second direction. An operation control unit for moving the work tool on an arc path centered on the intersection point and having the perpendicular length as a radius when an instruction is input from the third direction indicating unit.
A robot control device comprising:   The robot control apparatus according to claim 1, wherein the manual operation coordinate system is calculated when the instruction is input or when the work tool is stopped after the instruction is input.

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