JPH01173206A - Robot teaching method - Google Patents

Abstract

PURPOSE:To fix the attitude at a work point to teach a robot by obtaining a new coordinate transformation matrix coinciding with the attitude at the present work point based on a coordinate transformation matrix and a movement vector to calculate new state data of each joint. CONSTITUTION:A base coordinate system O0 fixed to a base 26 and a hand coordinate system Oe fixed to a work point TCP on a work 15 are defined for an arc welding robot 14, and coordinate systems O1-O6 are defined for respective joints. Coordinate transformation matrices between respective joints are obtained from state data of respective joints, and the position of the present work point is calculated based on these matrices and a movement vector to the position of the next work point is obtained. New state data of respective joints are calculated based on coordinate transformation matrices and the movement vector. Thus, the attitude at the work point is fixed to teach the robot,and the operation speed of the robot at the time of play-back is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a robot teaching method, and more particularly, the present invention relates to a robot teaching method, in which the position of a working point of an end effector of a robot is changed while the posture is fixed with respect to a workpiece. Concerning the robot teaching method that has been made possible.

[Background of the Invention] For example, when performing a predetermined work on a work using an industrial robot, it is necessary to move an end effector attached to the tip of the robot along a predetermined path. In this case, the route is generally taught by a teaching box. Here, the teaching box used for teaching the robot is equipped with input means for selecting command values for driving each joint of the robot, a coordinate system as a reference for teaching, or a setting means for setting the operating speed of the robot. The operator teaches the robot by operating these means according to predetermined specifications.

By the way, when performing work such as painting, sealing, arc welding, etc. on a workpiece using such an industrial robot, the attitude of the end effector with respect to the workpiece becomes extremely important. Here, when the position of the end effector of the multi-joint robot is set by teaching, when the end effector is moved to a predetermined position, each joint is displaced and the posture of the end effector with respect to the workpiece changes. Therefore, after setting the position of the end effector, a work is usually performed to correct the posture of the end effector with respect to the workpiece.

In this case, for example, if an end effector configured to rotate around the tip of the robot's arm is used, the position of the work point of the end effector relative to the workpiece may change when the end effector is rotated. . Therefore, when the posture of the end effector with respect to the workpiece is corrected, the position of the work point must also be corrected, which has been pointed out to be a disadvantage in that the work becomes extremely troublesome.

Therefore, in order to improve the workability of the teaching described above, the position of the end effector's work point and its posture with respect to the workpiece are memorized during teaching, and the position and posture of the robot are adjusted based on the position and posture data of the end effector during play pack. A technical concept for operating a robot by calculating the positions of joints, etc. is disclosed in Japanese Patent Application Laid-Open No. 59-167713. However, in this case, the robot is operated by calculating the data of each joint to correct the position of the displaced work point by changing the posture of the work point, so it takes a long time to position the robot. It has been pointed out that there is an inconvenience that the operation speed during play hacking decreases.

[Object of the Invention] The present invention has been made in order to overcome the above-mentioned disadvantages, and it uses a coordinate transformation matrix set from state data of each joint constituting an articulated robot and movement of the working point of an end effector. By calculating the state data of each joint when the end effector is moved using the vector, it is possible to perform teaching with the posture of the work point fixed, and also improve the operating speed of the robot during playback. The purpose is to provide a teaching method for robots that can perform the following tasks.

Means for Achieving Object 1] In order to achieve the above object, the present invention calculates a coordinate transformation matrix between each joint from state data of each joint constituting an articulated robot, and calculates a coordinate transformation matrix between the joints based on the coordinate transformation matrix. After calculating the position of the current work point by the end effector and then determining the movement vector from the current work point position to the next work point position, based on the coordinate transformation matrix and the movement vector, A new coordinate transformation matrix between the joints is determined so that the posture of the new work point to be calculated matches the posture of the current work point, and new state data of each joint is calculated from the new coordinate transformation matrix. It is characterized by

[Embodiments] Next, preferred embodiments of the robot teaching method according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a welding system to which the robot teaching method according to the present embodiment is applied. In this welding system 10, an arc welding robot 14 is driven based on sequence control by a sequencer 12, and a clamp device 16 is driven. A predetermined welding operation is performed on the workpiece 15 positioned on the jig stand 17. In this case, the arc welding robot 14 is taught its operation by the teaching box 18, and is driven and controlled by the hydraulic unit 22 and the welding controller 24 via the robot controller 20.

The arc welding robot 14 is installed on a base 26, and the moving part 28 is moved in the direction of the arrow with respect to the base 26 by a hydraulic motor 30, and the rotating part 32 is moved to the moving part 28 by a hydraulic motor 34. On the other hand, it is configured to be able to turn in the direction of the arrow. Further, one end portion of an arm member 36 is pivotally attached to the rotating portion 32, and this arm member 36 is attached to the rotating portion 32.
It is configured to be movable up and down in the direction of the arrow by a hydraulic cylinder 38 attached to. On the other hand, a mounting member 42 having a hydraulic motor 40 is attached to the other end of the arm member 36, and a welding torch 46 as an end effector is connected to the mounting member 42 via a hydraulic motor 44. In this case, the welding torch 46 is centered around the hydraulic motor 44.
0, the hydraulic motor 44 rotates in the direction of the arrow.
It is configured to be rotatable in the direction of the arrow. The hydraulic unit 22 described above drives and controls the hydraulic motors 30, 34, 40 and 44 and the hydraulic cylinder 38 that constitute the arc welding robot 14. Further, the welding controller 24 achieves welding current control between the welding torch 46 and the workpiece 15.

Here, the base coordinate system 0° fixed to the base 26 with respect to the arc welding robot 14, and the hand coordinate system 08 fixed to the work point TCP with respect to the workpiece 15 of welding 1.
At the same time, coordinate systems OI to 06 are defined for each joint of the arc welding robot 14.

The base coordinate system O8 consists of three orthogonal axes Xo, Yo, and Zo, and the rotation directions around each axis are Ao, B, and Co, respectively. Hand coordinate system 08 is orthogonal 3 of X8, Y, , Z
It consists of axes, and the rotation directions around each axis are A, , B, respectively.
,C,. The coordinate system 0 is a coordinate system that is displaced with respect to the base coordinate system 0° by the hydraulic motor 30, and the coordinate system 0
2 is a coordinate system rotated with respect to coordinate system 01 by a hydraulic motor 34, and coordinate system 03 is a coordinate system rotated with respect to coordinate system 02 by a hydraulic cylinder 38.

Further, the coordinate system 04 is a coordinate system fixed to the coordinate system 03, and is added to explain the arc welding robot eye 4 as a 6-axis robot. Furthermore, the coordinate system 0
5 is a coordinate system that rotates with respect to the coordinate system 04 by the hydraulic motor 40, and a coordinate system 06 is a coordinate system that rotates with respect to the coordinate system 05 by the hydraulic morph 44.

On the other hand, the teaching box 18 is configured as shown in FIG. That is, the teaching box 18 basically includes a main body section 52 that performs teaching etc. to the arc welding robot 14, and a display section 54 that displays the operating method of the teaching box 18 and the like.

The main body 52 is connected to the robot controller 20 via a connection cable 55, and on the top thereof there is a mode changeover switch 56 for switching between a teach mode, a play mode, etc., which will be described later, and a mode switch 56 for manually operating the arc welding robot 14. A joystick 58 for controlling the arc welding robot 14, numeric keys 60 and 1 for selecting functions, inputting data, etc., and an emergency stop button 62 for stopping the operation of the arc welding robot 14 in an emergency are provided. In this case, joystick 5
8 is tiltable in the directions of arrows α and β, and is tiltable in the directions of arrows α and β.
The correspondence between the tilting direction or rotation direction and the driving direction of the arc welding robot 14 is set using the numeric keypad 60. The operating speed of the arc welding robot 14 is controlled by the joystick 58.
It is set by the inclination angle or rotation angle of. Note that the tip of the joystick 58 is the operation switch 6.
4 is provided, and by pressing this operation switch 64, the arc welding robot 14 becomes operable.

The main body portion 52 includes a pair of arm members 6 that protrude diagonally upward.
6a, 66b, and these arm members 66a
, 66b through mounting screws 68a, 68b, the display section 54 is rotatably mounted in the direction of arrow θ. In this case, the display section 54 has an LCD display 70, on which the operating method of the teaching box 18 selected by the mode changeover switch 56 and the numeric keypad 60 is displayed.

The welding system to which the robot teaching method according to the present embodiment is applied is basically configured as described above. Next, the teaching method using this system will be described.

First, the power of the teaching pendant 18 is turned on. In this case, a main menu screen 80 shown in FIG. 3 is displayed on the LCD display 70 of the teaching box 18. In this main menu screen 80, rTE
AcHJ is a teaching mode in which the arc welding robot 14 is taught using the joystick 58, and [PLAYJ is a teaching mode in which the arc welding robot 14 is operated by calling up desired teaching data using a keyboard (not shown) of the robot controller 1-roller 20, etc. It is play mode. Further, rAUTOJ is an AUTO mode in which the play mode is automatically executed based on a request from the sequencer 12, etc., and the actual welding work of the workpiece 15 by the arc welding robot 14 is performed in this auto mode.

rED IT is an editing mode for editing (stereoscopic shift, copying, etc.) the teaching data stored in the teaching box 18, and "PARAJ" is a parameter setting mode for setting parameters such as the dimensions of the welding torch 46 in the arc welding robot 14. mode.

Next, when the operator selects the teach mode from the main menu screen 80 and sets the mode selector switch 56 to the [1] position, the teach mode menu screen 82 shown in FIG. 4 is displayed on the LCD display 70.

In this case, rJOINT 123J is a mode in which the hydraulic motors 30, 34 and hydraulic cylinders 38 that constitute the arc welding robot 14 are driven in response to the movement of the joystick 58 in the arrow α, β, and T directions. Further, "rJOINT 456" is a mode in which the hydraulic motors 40 and 44 are driven in response to the movement of the joystick 58 in the directions of arrows α and β. rBAsEX
YZJ is the X of the base coordinate system 0° where the work point TCP of the welding torch 46 is based on the base 26 with respect to the operation of the joystick 58. , y, and z directions, respectively. Furthermore, rBASE ABCJ is the working point TC of the welding torch 46 relative to the movement of the joystick 58.
P is the rotation A around Xo, Yo, and Zo of the base coordinate system Oo. , B, , This is a mode of rotation in the C8 direction. On the other hand, rHAND
, is a mode that moves in the direction. Similarly, rHAND
ABC, the working point TCP of the welding torch 46 is in the Hunt coordinate system 0. (7) Around X, , y, , ze A, , B, ,
This is a mode of rotation in the C direction. rBASE MD
1. and “HAND MDI” are respectively welding torch 4.
This is a mode in which the work point TCP No. 6 moves based on teaching data input with the base coordinate system 0° or the hand coordinate system Oe as a reference. And rMEMORI
ZEJ indicates a mode for importing the current state of the arc welding robot 14 into a storage unit (not shown) of the robot controller 20 as teaching data.

Therefore, for example, when "3" is input from the numeric keypad 60, the "rBAsE XYZ" mode is selected from the teach mode. Next, while pressing the operation switch 64, the operator tilts or rotates the joystick 58 by a predetermined amount in the directions of arrows α, β, and T. in this case,
Data regarding the tilt direction, rotation direction, tilt angle, and rotation angle of the joystick 58 are transferred to the robot controller 20 via the connection cable 55. Based on the selected rBASE XYZJ mode, the robot controller 20 generates a pulse signal corresponding to the movement amount of each coordinate system 01 to 06 of the arc welding robot 14 from the above data and outputs it to the hydraulic unit 22. Based on the pulse signal, the hydraulic unit 22 converts the working point T'CP of the welding torch 46 in the arc welding robot 14 into a base coordinate system O8.
Accordingly, the workpiece 15 is moved to the desired welding position. In this case, the work point TCP is moved to Z by tilting the joystick 58 in the direction of the arrow α.

By moving in the direction of the arrow β and tilting in the direction of the arrow β, it moves in the Xo force direction, and by rotating in the direction of the arrow T, it moves in the Y direction. move in each direction.

Here, when the welding path on the workpiece 15 continues for a predetermined length or more in a plane, in order to accurately perform arc welding, it is necessary not only to accurately set the position of the working point TCP of the welding torch 46 (with respect to the workpiece 15 It is necessary to keep the posture of the welding torch 46 constant. In this case, in the rBASE The method of moving the welding torch 46 will be explained based on the flowchart shown in FIG.

First, the robot controller 20 is an arc welding robot)
・Each hydraulic motor 30.34.40.44 that constitutes 14
And the current pulse P+ (i-1, 2,...
・6) is taken in, and from this pulse P, the adjacent coordinate system 0. The current angle r of each joint with respect to 06 is determined as (i=1.2, . . . 6) (STPI). Here, k+ is a parameter related to the resolution and reduction ratio of the potentiometer in the thread 01. k2i is the coordinate system 0. When a reference midpoint is set for the range of motion of the joint in , this is an offset amount for expressing the pulse P obtained by the potentiometer as an increase or decrease with respect to the reference midpoint. Further, k3i is a parameter for converting an angle (deg) into radians. Note that in this embodiment, since the coordinate system 04 is fixed with respect to the coordinate system 03, the pulse P4 is set to 0.

Next, a transformation matrix T is calculated from the current angle r calculated based on equation (1) (SrF2).

In this case, the transformation matrix T is the coordinate system 0.degree. with respect to the base coordinate system 0.degree. The position and orientation of the transformation matrix T are set by jmn (m=1.2.3, n=1.2.
3.4). Here, the transformation matrix T is expressed as T= [A:,b]...(
3), the current position C of the work point TCP is calculated as follows using the transformation matrix T (SrF3). Note that A is the transformation matrix T
b is the component of the left side 4 rows and 3 columns of the transformation matrix T, and b is the right side 4
The components in row and column 1 are shown.

Further, h is a vector indicating the amount of offset of the work point TCP with respect to the coordinate system 06, and is X with respect to the base coordinate system 0°. , y, , zo force direction component as h+ , hz ,
As ha, it is defined as.

Next, the robot controller 20 determines whether there is an input from the joystick 58 on the teaching box 18 (5TP4), and if there is no input, the current pulse P is held as is (SrF2).

On the other hand, when the joystick 58 is tilted or rotated by a predetermined amount in the directions of the arrows α, β, and γ while the operation switch 64 is pressed, the robot controller 20 receives voltage signals from each potentiometer (not shown) connected to the joystick 58. (2) Calculate the amount of movement ΔC1 for each axis X0, Yo, and Zo of the base coordinate system 0° based on .

In this case, if the gain of each potentiometer is g, the movement amount ΔC3 can be found as J (SrF6). Note that j=1 is X.

The direction, j=2, is Y. The direction, j=3, is Z. Each corresponds to the amount of movement in the direction.

Next, a new position C' of the work point TCP is determined using the movement amount ΔCj calculated in step 6 (SrF2). In other words, the new position C' of the work point TCP moved by the joystick 58 changes each component of the current position C to C.
5. Letting each component of the new position C' be 04', (6
) using the formula, Cj'-Cj-ΔC47k4 ・(7)(j
-1, 2, 3). Note that k4 is a coefficient related to the resolution and reduction ratio of a potentiometer (not shown) of the joystick 58.

Here, the transformation matrix T' when moving the work point TCP to position C' is "r' - (A':, 'b')
...(8), the work point TCP is from position C to C
In order for the posture to be fixed when moving to ′, (3
), it is necessary that A-A' (9). Therefore, the new position C' of the work point TCP is C' -A-h O+ 'b' ・00
), and the transformation matrix T' is found as (SrF8).

Therefore, by inversely transforming this transformation matrix T', each coordinate system 0
．． The next angle rt'(
i=1.2,...6) can be found (SrF
2). As a result, from said angle r,' the next pulse p %
is determined as (i-1, 2, . . . 6) . . 02) (STPIO).

Next, the robot controller 20 outputs the pulse p % obtained in step 10 to the hydraulic unit 22 to instruct the arc welding robot 14 to move (STPII). In this case, the welding torch 46 of the arc welding robot 14 has its position fixed at the work point TCP, and only its position changes according to the amount of tilt or rotation of the joystick 58. Therefore, the numeric keypad 60 of the teaching pendant 18
If O and I are input at the same time, the pulse P' of each joint obtained in step 10 is stored as teaching data in the storage means (not shown) of the robot controller 20 (SrF12).

By repeating the above process for each desired welding point,
The working point TCP of the welding torch 46 is translated to a predetermined position on the workpiece 15.

In addition, in the embodiment described above, a case has been described in which the work point TCP is moved in parallel with the base coordinate system 0° as a reference, but the work point TCP is moved in parallel with the hand coordinate system 0° set at the work point TCP as a reference. It is also possible to move it. Therefore, the operator selects the rHAND XYZJ mode from the teach mode menu screen 82 displayed on the LCD display 70 and tilts or rotates the joystick 58 in a predetermined direction. In this case, the work point TCP is changed based on the hand coordinate system 0° fixed at the work point TCP, so the operator can perform teaching more easily than when using the base coordinate system 0°. Become. In addition, in the processing procedure in this case, after setting the amount of movement in each axis X, Y, Z8 direction of the hand coordinate system 08 in step 6 shown in FIG. By converting the measured movement amount Δcs (see equation (6)) and performing the processing from step 7 onwards, desired pulses for each joint can be obtained.

When the teaching work of the arc welding robot 14 is completed as described above, the operator returns the screen of the LCD display 70 of the teaching box 18 to the main menu screen 80 shown in FIG. 3. Next, the mode changeover switch 56 is set to play mode [2], and the arc welding robot 14 is caused to perform a play hack operation and the teaching data is confirmed.

Next, arc welding lobe 4 according to the teaching data
When the operation confirmation is completed, the operator returns the screen of the LCD display 70 to the main menu screen 80, and then selects [3] on the numeric keypad 60 to enter the auto mode. In this case, the arc welding robot 14 is connected to the sequencer 12.
A desired welding operation is performed on the workpiece 15 based on the teaching data output from the robot controller 20 under the control of the robot controller 20 . Note that the robot controller 20 controls each hydraulic motor 30 .
34, 40, 44 and the hydraulic cylinder 38, the arc welding robot 14
Data can be output at high speed. Therefore, it becomes possible to perform the arc welding work at high speed.

[Effects of the Invention] As described above, according to the present invention, the posture of the work point is fixed using the coordinate transformation matrix of each joint constituting the articulated robot and the movement vector of the work point by the end effector. The end effector is being moved. Therefore, the end effector can be moved in a constant posture relative to the workpiece. Moreover, the state data of each joint can be easily calculated at the time of teaching using a new coordinate transformation matrix set by the coordinate transformation matrix and the movement vector. Therefore, not only the data calculation time during teaching is shortened, but also the operation speed of the robot during play hacking is improved.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a welding system to which the robot teaching method according to the present invention is applied, FIG. 2 is a perspective view of the configuration of a teaching box in the welding system shown in FIG. 1, and FIGS. 3 and 4 are FIG. 2 is an explanatory diagram of each menu screen displayed on the teaching box, and FIG. 5 is a flowchart showing the procedure of the teaching method for the robot 1 according to the present invention. 10... Welding system 12... Sequencer 1
4... Arc welding robot 18... Teaching box 20... Robot controller 22... Hydraulic unit 24... Welding controller 52... Main body part 54... Display part 5
6...Mode selector switch 58...Joystick 60...Numeric keypad 62
...Emergency stop button 64...Operation switch 70
・・・LCD display

Claims (1)

[Claims] (1) Obtain a coordinate transformation matrix between the joints from the state data of each joint that constitutes the articulated robot, calculate the current working point position of the end effector based on the coordinate transformation matrix, and then After determining the movement vector from the position of the work point to the position of the next work point, the new work point attitude calculated based on the coordinate transformation matrix and the movement vector is the current work point attitude. A method for teaching a robot, characterized in that a new coordinate transformation matrix between the joints is determined so that they match, and new state data for each joint is calculated from the new coordinate transformation matrix.