JPH04169909A - Robot attitude correcting system - Google Patents

Abstract

PURPOSE:To improve the reliability of online teaching work by rotating a working point in the approach direction to correct the attitude of a robot at the time when the robot is in the vicinity of a peculiar point. CONSTITUTION:Values of axes of a robot 2 beta, gamma are obtained in accordance with data of positions and attitudes of teaching points W1 to W3, and it is judged whether the robot 2 is in the vicinity of a peculiar point or not based on values of axes beta, gamma; and when the robot 2 is in the vicinity of a peculiar point, teaching points W1 to W3 are rotated at a prescribed angle in the approach direction of teaching points, and values of axes of the robot 2 beta, gammaare obtained again in accordance with data of positions and attitudes of teaching points W1 to W3 rotated at the prescribed angle. The attitude of the robot 2 is corrected based on these obtained values of axes beta, gamma. That is, attitudes of teaching points W1 to W3 are changed to prevent the robot 2 from being in the vicinity of the peculiar point. Thus, the robot 2 is never at the peculiar point, and an unnecessary operation at the peculiar point is eliminated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a robot posture correction method used for offline teaching, and particularly to a robot posture correction method that prevents the robot from taking a singular point. .

[Conventional technology]

In recent years, offline programming methods have been introduced to robot teaching.

In this offline programming method, the teaching point is mainly created in a Cartesian coordinate system, and the value of each axis of the robot is determined based on the position and orientation data of the teaching point in the Cartesian coordinate system. The robot's posture is determined accordingly.

Depending on its posture, a robot may assume a singularity.

[Problem to be solved by the invention]

However, when a robot is at a singularity, it performs useless movements.

For example, if there is a singular point near 0 degrees on the robot's β-axis, and the robot takes a value near 0 degrees on the β-axis, the T-axis will rotate 360 degrees instead of just a small angle. In other words, the robot's wrist turns around.

If the robot were to perform such movements, such as during arc welding or spot welding, the cables would wrap around the robot and the cycle time would be longer than necessary. As a result, the working efficiency of the robot is significantly reduced.

Conventional teaching work has problems such as these,
The reliability of the teaching work was low.

The present invention has been made in view of these points, and it is an object of the present invention to provide a robot posture correction method that prevents the robot from performing unnecessary operations at singular points.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention uses an off-line robot posture correction method to obtain the values of each axis of the robot from data on the position and posture of the teaching point, and to calculate the A singular point determination is performed to determine whether or not the robot is near the singular point, and when the robot is near the singular point, the teaching point is rotated by a predetermined angle around the approach direction of the teaching point, and the teaching point is rotated by the predetermined angle. The robot posture is characterized in that the values of each axis of the robot are calculated again from data on the position and posture of the taught point, and the posture of the robot is corrected based on the recalculated values of each axis. A modification scheme is provided.

[Effect]

The values of each axis of the robot are found from the position and orientation data of the teaching point. Based on the values of each axis, it is determined whether the robot is near the singularity. When the robot is near the singular point, the teaching point is rotated by a predetermined angle around the approach direction of the teaching point. The values of each axis of the robot are again determined from the position and orientation data of the teaching point rotated by a predetermined angle. The robot's posture is corrected based on the recombined values of each axis. That is, the posture of the teaching point is changed so that the robot does not take a position near the singular point. For this reason, the robot never reaches a singularity, nor does it perform unnecessary operations at a singularity.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram for explaining a robot posture correction method according to the present invention. The figure shows one screen of a CRT.

Screen 1 on the right side shows the input procedure. First, the cursor is positioned on the first line 10 of screen 1. At this time, specify the robot name using the keyboard. As a result, the target robot and tool are selected.

Next, the cursor moves to the second line 11. At this time,
Specify the name of chain C using the keyboard. Chain C has a working point (teaching point) Wl as shown in the following equation (1).
, W2, and W3.

Chain C=(Wl→W2→W3) (1) By the way, the work point W (Wl, W2, W3) consists of position and orientation data.

Here, each vector with respect to the reference coordinates of the work point W is defined as follows.

Normal vector N = (NxSNy, Nz) Orient vector O = (○x, Oy, Oz) Approach vector A = (Ax, Ay, Az) Location vector L = (Lx, Ly, Lz) At this time, the working point W The position and orientation data are expressed by the determinant W of the following equation (2).

Chain C (= (Wl-W2-W3)) is composed of data of each work point expressed by this determinant W and the order of each work point.

When you finish specifying chain C, the cursor moves to line 3, 1.
Move to 2. At this time, press the execution key on the keyboard.

When the execution key is pressed, based on the information of chain C,
First, the position and orientation data of the first work point W1 are obtained.

Next, from the position and orientation data, each axis of the robot 2 (for example α, β, T1θ
, 6 axes of WSU).

In this case, the robot 2, at the position of the work point W1,
The robot takes a posture such that the Z direction (approach direction) of the work point W1 is the Z direction of the torch 3 of the robot 2. Note that the Z direction of the work point W1 is a direction perpendicular to the surface of the workpiece 4.

In this way, the posture of the robot 2 is determined, and a singularity determination is performed to determine whether or not the robot 2 is near the singularity.

Here, the singular point is, for example, near 0 degrees of the β axis. At this singular point, the T-axis only needs to rotate by a small angle, but instead of 36
There is a problem that it rotates by 0 degrees.

When the robot 2 is near the singular point, the coordinate axis of the work point W1 is rotated by a predetermined angle α degree around the Z axis so as to remove the singular point. Data on the position and orientation of the work point W1 when rotated by a predetermined angle α degree is obtained. From that data,
Find the values of each axis of robot 2 again. The posture of the robot 2 is corrected based on the values of each axis.

Note that although the Z direction (approach direction) of the torch 3 is determined, the rotation of the remaining axis is not determined, and the rotation angle can be set arbitrarily.

Furthermore, it is determined whether the robot 2 whose posture has been corrected interferes with peripheral devices. If there is no interference, the work point rotated by a predetermined angle α degree is set as a new work point, and the next work point W2 is moved to, and singularity determination is performed in the same manner.

When there is interference, the predetermined angle α of the work point is adjusted until there is no interference.
The posture of the robot 2 is repeatedly corrected by rotation. This repetition is performed until the work point has rotated 360 degrees around two axes. If a posture that does not interfere even after 360 degree rotation is not found, it is determined as an error and the process moves to the next work point W2.

FIG. 2 is a flowchart for carrying out the invention. In the figure, the number following S indicates the step number.

[S1] Specify the names of chain C and robot 2.

[S2] Based on the information of chain C, obtain position and orientation data of work point Wn.

[S3] Values for each axis of the robot 2 are determined from the position and posture data of the work point Wn.

[S4] It is determined whether the robot 2 is near a singular point. If it is not near the singularity, the process goes to S5; if it is, the process goes to S7.

[S5] Move the work point Wn to the next work point Wn+1.

[S6] It is determined whether singularity determination has been performed at all work points of chain C. Once executed, exit the program. Otherwise, return to S2.

[S7] The coordinate axis of the work point Wn is rotated by a predetermined angle α degree around the Z axis.

[S8] It is determined whether the coordinate axis of the work point Wn has rotated 360 degrees or more around the Z-axis. If it has rotated, proceed to S5; if not, proceed to S9.

[S9] It is determined whether the robot 2 is interfering with a peripheral device at the work point Wn rotated by a predetermined angle α degree. If there is interference, the process returns to S7; if there is no interference, the process proceeds to S5.

As described above, when the robot 2 is near the singular point, the work point W is rotated around two axes (approach direction) to change the posture of the work point W, and the robot 2
The posture of the person was also corrected. For this reason, the robot 2 never reaches a singular point and does not perform any unnecessary operations at a singular point. Therefore, offline teaching work can be performed with higher reliability.

Furthermore, the work point W at which the robot 2 after posture correction does not interfere with peripheral devices is set as a new work point. Therefore, even if the robot 2 corrects its posture, it does not interfere with peripheral devices, and the reliability of the teaching work is further increased in this respect as well.

FIG. 3 is a diagram showing a schematic configuration of an offline programming system to which the present invention is applied.

The robot control device 20 has a microprocessor configuration and controls the robot 2 by driving a servo motor built into the arc welding robot 2.

A workstation is used as the offline program device 40, and the operation program for the robot 2 can be created offline. For this purpose, the coordinate system of the robot 2 is downloaded from the robot control device 20 to the offline programming device 40. Furthermore, accurate information on the tip point of the tool (torch) 3 of the robot 2 is required, and the coordinates of the tip point of the tool 3 have also been downloaded to the offline programming device 40.

Work points WL W2 and W3 of the work 4 constitute a chain C. The robot 2 performs singularity determination in the order of Wl-W2-W3 based on the information of the chain C.

FIG. 4 is a diagram showing a schematic configuration of an offline programming device that implements the present invention.

The processor 51 controls the operation of the entire apparatus according to the robot posture correction method program of the present invention stored in the ROM 52. ROM52 is EPROM or E
Consists of EPROM.

The RAM 53 is composed of a DRAM or the like, and temporarily stores various data including data related to chain C of the work 4 and data for arithmetic processing.

The floating point arithmetic processor 54 performs various calculations such as coordinate transformation.

The graphic control circuit 55 converts the digital signal into a display signal and supplies it to the CRT 56.

The hard disk 58 has a storage capacity of 140 Mbytes or more for storing various data, and is controlled by the hard disk controller 57.

The input/output board 59 is used to input and output various types of data, and a keyboard 60 and mouse 61 are connected thereto. These components are coupled together by a bus 50.

〔Effect of the invention〕

As explained above, in the present invention, when the robot is near the singular point, the work point is rotated around the approach direction, and the posture of the robot is corrected accordingly.

For this reason, the robot never reaches a singularity, nor does it perform unnecessary operations at a singularity. Therefore, offline teaching work can be performed with higher reliability.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the robot posture correction method of the present invention, FIG. 2 is a flowchart for carrying out the present invention, and FIG. 3 is a schematic configuration of an offline programming system to which the present invention is applied. FIG. 4 is a diagram showing a schematic configuration of an offline programming device that implements the present invention. 2...--1 Robot 3 ゛ Torch 4 --- Work 20 Robot control device 40 ゛ Off-line program device W1, W2
, W3 Working point (teaching point) C Chain patent applicant Fanuc Co., Ltd. agent Patent attorney Takeshi Hattori

Claims (6)

[Claims] (1) In the offline robot posture correction method, the values of each axis of the robot are determined from data on the position and posture of the teaching point, and based on the values of each axis, whether the robot is near a singular point or not. When the robot is near the singular point, the teaching point is rotated by a predetermined angle around the approach direction of the teaching point, and the position and orientation of the teaching point rotated by the predetermined angle are determined. A robot posture correction method, characterized in that the values of each axis of the robot are determined again from data, and the posture of the robot is corrected based on the values of each axis determined again. (2) It is characterized in that it is determined whether or not the robot whose posture has been corrected interferes with a peripheral device of the robot, and when there is no interference, the teaching point rotated by the predetermined angle is set as a new teaching point. The robot posture correction method according to claim 1. (3) Determine whether or not the robot whose posture has been corrected will interfere with peripheral devices of the robot, and if it interferes,
2. The robot posture correction method according to claim 1, wherein the robot posture is repeatedly corrected by rotating the teaching point by a predetermined angle until there is no interference. (4) The robot posture correction method according to claim 3, wherein the robot posture correction is performed until the teaching point rotates 360 degrees around the approach direction. (5) The robot posture correction method according to claim 1, wherein the singularity determination is performed for each teaching point of a teaching point group that is a collection of teaching points in a predetermined order. (6) The robot posture correction method according to claim 1, wherein the singular point is near 0 degrees of the β axis of the robot.