JPS6111807A - Compensating method of backlash - Google Patents

Abstract

PURPOSE:To improve the working accuracy of a joint type robot by always monitoring the neutral position of a W axis, and at the passage of the leading part of the robot through the neutral position, compensating its backlash. CONSTITUTION:A numeral control (NC) system using a backlash compensating method is constituted of a processor 30 to which memories 31, 32, a teaching operation board 33, a CRT display device 35, etc. are connected, a joint type robot 39, a welding machine 40 which is a working object, etc. In the backlash compensation, the angles of respective joints are calculated from the coordinates of the leading position of the robot 39 and the angles of the joints after moving a robot arm are calculated on the basis of said calculated results. When the W axis passes the neutral position, positional information after the movement is calculated and the information discriminates whether the W axis passes the neutral position or not. When passing the neutral position, an increment pulse is applied from a backlash compensating port 44 to a servo circuit 38 to execute the backlash compensation of the W axis. A theta axis also is similarly compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a backlash correction method, and particularly relates to an articulated robot capable of correcting backlash at a point where the direction of gravity applied to an arm changes. This invention relates to a backlash correction method.

(Prior Art) Recently, articulated robots have come to be used as welding robots and the like. FIG. 4 is a perspective view of such a robot. In the figure, 1 is a servo motor installed on the base, 2 is a W-axis unit, 3 is a W-axis arm, 4 is a U-axis arm, 4
The electric shaft is the bearing of the U-axis arm 4. Furthermore, FIG. 5 is a mechanical diagram of such an articulated robot. In the figure, θ=0° indicates the front face of the robot, W is the W axis, U is the U axis, α is the rotation axis of the wrist,
β is the axis of vertical movement of the wrist.

(Problems with the prior art) In the above-mentioned joint disc/boot, in particular, when the direction of the gravity applied to the arm of the pot changes,
When the W-axis and the tip position of the robot move past the neutral position of the W-axis, backlash occurs and there is a problem in that accurate control in response to the command value to the robot cannot be performed immediately.

(Objective of the Invention) The present invention constantly monitors the neutral position of the %W axis and corrects backlash when the W axis and the tip position of the robot move past the neutral position of the W axis. The purpose of the present invention is to provide a bar-so-classy correction method for an articulated robot that can accurately follow command values and improve work accuracy.

(Summary of the Invention) The present invention provides a backlash correction method for an articulated robot, in which (1) the joint O angle is determined from the tip position information of the articulated robot; (3) If the W axis passes through the neutral position t, determine the tip position information of the arm of the robot after the arm has moved; (4)
It is configured to determine whether or not the tip position information has passed through the neutral position of the W-axis, and (5) to correct backlash by increasing the angular increment Δθ of the W-axis when the information has passed through the neutral position. .

Also, when the direction of movement of the θ-axis changes, the backlash of the θ-axis is corrected.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to eight drawings.

FIG. 1 is a block diagram of an embodiment of a numerical control (NC) system employing a back two-seven tool correction method according to the present invention. In the figure, 30 is a processing device, and this processing device 30 includes:
Memory 611 consisting of ROM Memory 32 consisting of RAM
．． Teaching operation panel 35, operation panel 34% CRT display device 35.
A tape reader 35 is connected. The memory 31 stores various control programs to be executed by the processing device 30. The memory 32 includes a teaching operation panel 33J and an operation panel 34.
, data input from a tape reader 35, etc., and the results and data of calculations performed by the processing device 30. The desk teaching operation panel 33 has a numerical display, lamps, and operation buttons necessary for operating the articulated robot.

The operation panel 64 has various keys such as a numeric keypad and a function key, and inputs various data to the tNC device from the outside. . 37 is an axis controller including an interpolator that controls a plurality of axes, 38 is a servo circuit that controls the drive source of the articulated robot 39, and 4o is the work object that the articulated robot 39 works on, sb, for example, a welding machine. is. Reference numeral 42 denotes an input/output circuit which inputs and outputs signals to and from the workpiece 40 via a relay unit 43'Ik. 44 is a backlash correction boat. Reference numeral 41 denotes a work object interface for interfacing with the work object 4o, and 45 represents a path line.bThe position of each axis of this articulated robot 39 is controlled in an incremental manner.

FIG. 2 is a mechanical diagram of an articulated robot for explaining backlash correction according to the present invention, and FIG. 3 is a 70-chart for explaining the backlash correction.

A method of backlash correction using these caps will be explained.

(al First, the coordinates of the tip of the articulated robot (XOl
Each joint angle is calculated from Yo, Zo). That is, from the coordinates (Xo, Yo, Zo) θ, A
Find y I Au.

Here, R= 1'Xo" + Yo"・
・・・・・・・・・・・・(1) M = R” + Zo
” ・・・・・・・・・・・・(2) A=
M −Lv” + Lu” =-・(3) B, =
M+Lv”-Lu2 ・・・・・・・・・・・・(4
)C=t'4-Lv"Lt+"(M-Lv"j,"u
')' ---(5), each angle of θ, W, [J is e = jan-1(Yo/Xo)
-... (6) W = tan-"Ki l 2 l rainbow tan -... (7) Zo・B+ R-C Tonashi, above (6), (7 ), by substituting the above (1) to (5)'t- into equations (8), the angles of θ, -W, and U can be obtained.

(b) Next, calculate each joint angle after the arm moves. As shown in FIG. 2, the position of the tip of the arm is Xt.

If we move to Yi and Zi, the above equation (1),
(2).

(6), (7), (8) KXi, Yi,
Zi f SotLf' FL Substitution Suruko and calculation of each joint angle after arm movement.

(C) Next, in Φ) above, it is determined whether the moving direction of the θ-axis changes. As a result, when the direction of movement of the θ-axis changes, the angular increment Δ of the θ-axis is
Backlash correction is performed by adding θ (−0,05°). When the θ-axis backlash correction is completed, the process proceeds to the W-axis backlash correction. same,
The θ-axis backlash correction can be omitted if it is not necessary.

(dl Next, it is determined whether the W-axis has passed the neutral position (W=0°°). As a result, if the W-axis has passed the neutral position, the angular increment Δw of the W-axis ( o, is°)
Packlashny correction is performed by increasing . .

(e) Next, θ-axis angle increment Δθ, W-axis angle increment ΔW
and the coordinates of the tip of the arm (Xi') from the value of the angle U of the U axis.

yi, z*) in total x-t-le. That is, Xi lYl
1Zl is Xi = cosθ(Lv sin W'
+ Lu cos U ) Yi = sinθ(Lv
5inW+:Lu cosU)Zi=L
v cosW −Lt+ sin[J: It can be obtained by dividing.

(fl Next, increment each axis X, Y, Zv.

By adding the coordinate conversion error and the irregularity in robot positioning, the baraccuracy correction is completed.

For example, the coordinate conversion error is 05 in width,
Positioning of Robo Soto 2 (The width is 0.4
With wn.

Here, in order to simplify calculations, it is assumed that the β-axis is always directed downward, the load is always applied to the front side of the U-axis, and backlash can be ignored.

Next Vcj A numerical control system for performing the above-mentioned backlash correction will be explained with reference to FIG.

First, to perform full backlash correction for the W axis, store the neutral position (W = 0°) information in the memory 52 & CW axis, and perform backlash correction on the W axis and arm tip position information obtained from the servo circuit 38. input into the boat 44, the processing unit 1it30 executes calculations at each stage, and compares the obtained values with the neutral position information to determine whether the W-axis and arm tip position information is at the neutral position (w'=o If the angle exceeds 0.15°, the W-axis backlash is corrected by applying an incremental pulse from the backlash correction port 44 to the every-bo circuit 38 in order to completely increase the W-axis angle increment (+0.15=).

Similarly, the θ-axis power crash compensation means is used to compensate for pack lash when the moving direction of the machine moving parts of a normal machine tool is reversed.
'I-Cancellation means is sufficient, so the explanation will be omitted here (
For example, JP-A-59-. 3 (see Publication No. 5808, Publication I#Kaian 5B-68111, Japanese Patent Application Laid-open No. 139820/1984, etc.).

In the above embodiment, the balaclancy of an articulated robot has been described, but it goes without saying that the present invention is not limited to this and can be applied to backlash of a robot having a single joint. In this case, it is only necessary to monitor the passage of the W-axis through the neutral position.

(Effects of the Invention) According to the present invention, the neutral position of the W-axis of the articulated robot is monitored, and when the W-axis and the tip position of the arm pass through the neutral position, the three gravitational forces acting on the arm and arm are If the direction changes, this can be quickly detected.

Since backlash correction can be performed, even if the direction of gravity acting on the robot's arm changes, accurate control can be performed that quickly follows the command value to the robot. Therefore, it is possible to improve the accuracy of the robot's work.

Furthermore, correct teaching information can be given when teaching the robot.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of an NC system using the backlash correction method according to the present invention, FIG. 2 is a mechanical diagram of an articulated robot for fully explaining the backlash correction according to the present invention, and FIG. The figure is a flowchart explaining backlash correction, and Figure 4 is a perspective view of an articulated robot.
FIG. 5 is a mechanical diagram of the articulated robot. X...Y axis, Y...Y axis, 2...Z axis, W...
W axis, U...U@, θ...θ axis, 30... Processing device, 38... Servo circuit, 39... Joint robot, 44... Backlash correction boat.

Claims (3)

[Claims] (1) In the backlash correction method for an articulated robot, the joint angle is determined from the tip position information of the arm of the articulated robot, the joint angle after the arm is moved is determined based on the joint angle, and the W-axis When passes through the neutral position, obtain the tip position information of the robot after the arm movement, determine whether or not the tip position information has passed the neutral position of the W axis, and if the tip position information has passed the neutral position, W A backlash correction method characterized by correcting backlash by increasing the angular increment of the shaft. (2) The backlash correction method according to claim (1), wherein the backlash of the θ-axis is corrected when the moving direction of the θ-axis of the articulated robot changes. (3) The backlash correction method according to claims (1) and (2), wherein the articulated robot has a plurality of joints.