JPS62295115A - Control method for robot - Google Patents

Abstract

PURPOSE:To speed up arc locus arithmetic operations by setting a two-dimensional coordinate system to an arc plane in a three-dimensional space, calculating the center and radius of the arc and converting them into values in the three-dimensional coordinate system. CONSTITUTION:A robot to be controlled is constituted by fitting a lower arm 2, an upper arm 3 and a wrist 4 on a robot main body 1 in that order. The lower arm 2 and the main body 1, the upper and lower arms 3 and 2, the wrist 4 and the upper arm 3 are provided turnably (slew) and rotatably. A robot control part gives required drive control signals to drive systems phi1-y6 for six axes, and angles that a detector for slew angles detects are inputted. This control is made so that the tip of the wrist 4 can move on a desired arc in the three-dimensional space. This means that first three points P1-P3 are taught, and second the two-dimensional coordinate system (arc interpolation coordinate system) is set on the arc plane including the three points, and the center and radius of the arc are calculated and converted into robot coordinate systems X0-Z0 by vector calculation.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to a robot control method, and particularly to a robot control method that simplifies the control algorithm by using vector operations. .

[Conventional technology]

Conventionally, when attempting to draw a three-dimensional arc trajectory from robot i, a two-dimensional coordinate system fixed on the three-dimensional arc trajectory is considered, and the arc trajectory to be drawn is calculated on this two-dimensional coordinate system. The two-dimensional coordinates were transformed into the robot's coordinate system by performing a three-dimensional top rotation transformation. For this reason, very complicated calculations involving many exterior angle functions are required, and the amount of calculations also increases, so there is a problem in that it is not possible to increase the speed of the robot's arc trajectory calculation process.

[Problem that the invention seeks to solve]

As described above, the conventional robot control method when attempting to draw a three-dimensional arcuate trajectory by the robot requires a very large amount of calculation, and requires a large amount of time in the arcuate trajectory calculation process. This poses a problem in applications that require high-speed calculations, such as robot control.

Therefore, it is an object of the present invention to provide a robot control method that reduces the amount of calculation when drawing a three-dimensional arc trajectory, thereby increasing the speed of the robot's arc trajectory calculation process.

[Means for solving problems]

According to this invention, a two-dimensional coordinate system is set on a predetermined arc plane in a three-dimensional space, and the center, radius, and arc locus of the arc are calculated in this two-dimensional coordinate system,
These calculated values are converted into values in a three-dimensional coordinate system using vector operations, and the robot is controlled based on these converted values.

[Effect]

Therefore, according to the present invention, the conversion from the two-dimensional coordinate system to the robot coordinate system is performed using vector calculations, which greatly reduces the amount of calculations and speeds up the arc trajectory calculation process.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Fig. 1 shows an overview of a robot control device to which the robot control method of the present invention is applied, and Fig. 2 shows an overview of the robot to be controlled by the invention and an example of its control. It is.

In FIG. 2, the robot to be controlled in this embodiment has a lower arm 2 attached to a robot body 1.
The upper arm 3 is attached to the upper arm 3, and the wrist 4 is further attached to the upper arm 3. The lower arm 2 is pivotable and rotatable relative to the robot body 1 (ψ1 direction and ψ2 direction).
The upper arm 3 is made rotatable and rotatable relative to the lower arm 2 (in the ψ3 direction and ψ4 direction), and the wrist 4 is allowed to rotate and rotate relative to the upper arm 3 (in the ψ5 direction and ψ6 direction). has been done. In other words, this robot can rotate in the ψ1 direction, rotate in the ψ2 direction, rotate in the ψ3 direction, and rotate in the ψ3 direction with respect to the arm.
4 axes of rotation in 4 directions, rotation in ψ5 directions about the wrist, ψ
It is constructed with a total of six axes of freedom, two axes of rotation in six directions.

In FIG. 1, the robot control unit 1o includes drive systems for the six axes, namely, a swing drive system 11 that drives turning in the ψ1 direction, a lower arm bending drive system 12 that drives bending rotation in the ψ2 direction, and a lower arm bending drive system 12 that drives turning in the ψ2 direction. An upper arm bending drive system 13 that drives bending rotation, an upper arm rotation drive system 14 that drives rotation in the ψ4 direction,
Required drive control signals are applied to the wrist bending drive system 15 that drives bending rotation in the ψ5 direction and the wrist rotation drive system 16 that drives rotation in the ψ6 direction, respectively, and the rotation drive system 1
1, the turning angle ψ1 is detected by the turning angle detector 21, the lower arm bending angle ψ2 by the lower arm bending drive system 12 is detected by the lower arm bending angle detector 22, and the upper arm bending angle ψ3 by the upper arm bending drive system 13 is detected by the lower arm bending angle ψ3. The upper arm bending angle detector 23 detects the upper arm rotation angle ψ4 caused by the upper arm rotation drive system 14, which is detected by the upper arm rotation angle detector 2.
4, the wrist bending angle ψ is detected by the wrist bending drive system 15.
5 is detected by the wrist bending angle detector 25, and the wrist rotation angle ψ6 caused by the wrist rotation drive system 16 is detected by the wrist rotation angle detector 26, and each is applied to the robot control device IO.

The robot control device 10 forms required drive signals for each axis, that is, each of the drive systems 11 to 16, based on the data of the teaching points taught in response to the teaching designation from the teaching box 30.

By the way, in the robot of this embodiment, the tip of the robot's hand 4 is controlled to move on a desired circular arc in a three-dimensional space. Specifically, as shown in FIG. 2, three points P1, p2. P3 is taught, a two-dimensional coordinate system (circular interpolation coordinate system) is set on the circular arc plane including these three points, and this circular interpolation coordinate system is used to calculate the center and radius of the arc and interpolate the position on the arc. The calculated values are used in vector operations to create the robot coordinate system XO, YO.

Convert to Zo value.

FIG. 3 shows the control flow for implementing the il;I+1 method described above. In FIG. 3, first, in step 31, three teaching points P1 and P2 are set.
．． An X'-Y' coordinate system is set on the arc plane including P3.

The setting operation of this X'-Y' coordinate system is performed as follows. First, as shown in FIG. 4, three teaching points p1, p2. Consider a plane (arc plane) determined by p3, and set the teaching point P1 on this plane. P2. Set the point P1 (the first point of the arc, the starting point of the arc locus) in P3 as the origin, set the direction of the line segment p+P2 as the X' axis, orthogonal to this X' axis, and set the point P3 (the third point of the arc, the starting point of the arc The Y' axis is determined so that the end point of the trajectory is in the first or second quadrant. With this setting, Pl (
The arc locus passing through (first point of the arc) - P2 (second point of the arc) - P3 (third point of the arc) always rotates counterclockwise. Therefore, determination of the rotation direction is unnecessary in the following processing.

In addition, in FIG. 4, the teaching point Pi.

p2. The coordinates of p3 in the robot coordinate system Xo -Yo-Zo are (x+, Yl, zl) and (X2゜y2.Z, respectively)
2), (X3. y3. Z3) and line segment P2
The length of P3 is Dl, the length of line segment P3P is D 2 ,
The length of the line segment Pi p2 is D3, and the length of ZP3P1P2 is θ.

Next, in step 32, teaching points P1°P2.
Coordinate data in the robot coordinate system of P3 (xl, Yl, z
l), (X2.Y2.Z2), (X3.Y3.23) into X'-Y' coordinate system Teno coordinate data (0, O), (a2.
O), (a3°b3). As is clear from FIG. 5, this conversion can be performed by the following calculation.

That is, in Fig. 5... (1) D 2 ox... (2) ... (3) The X' coordinate a2 of the teaching point P2 is a2 =
D3...(5) X' coordinate tF'l a 3, Y' coordinate b3 of teaching point P3
are respectively a3=D2co; θ 1, -(6)b3
=D2m completed 1...(7).

Next, in step 33, the arc radius R of the arc center O in the X'-Y' coordinate system is calculated as (aq, bo). That is, as is clear from FIG. 6, one mark (ao, bo) of the arc center O in the X'-Y' coordinate system can be found from aQ=□ (8). Further, the radius R of the circular arc can be found from R-a□"10bo"-(10).

Subsequently, in step 34, unit vectors eX and ey in the x'-y' coordinate system are calculated. Considering the E-M fi system and the X'-Y' drifting system in which the X'-Y' coordinate system is translated in parallel so that the origin is the arc center O in Fig. 6, the unit vector ex on the X' axis is given by, and the unit vector ey on the Y' wheel axis is... (
12) is given by. Therefore, the unit vector ex.

each ey ...(13) ...(14) becomes.

Next, in step 35, X'-Y' of the arc center O
Convert coordinate data in the coordinate system to coordinate data in the robot coordinate system. This conversion is performed by vector calculation using the unit vector obtained in step 34. As is clear from FIG. 8, the position vector PO indicating the arc center O is Po-11+P10 - (15).

Therefore, the position vector PO is P□−P1+a□ ex
+b□ ey −(16).

Therefore, the coordinate data of the arc center O in the robot coordinate system (
XO+yo+zo) can be determined from the following relationship using coordinate data (ao, bo) in the x'-y' coordinate system.

(17) The above steps, ie, steps 31 to 35, are the initial processing for performing this circular trajectory control. After execution of this initial processing, robot arc trajectory control processing is performed.

In step 36, a point P'(t) on the mouth trajectory is calculated in the X'-Y' coordinate system. This calculation is performed as follows. That is, as shown in FIG. 9, the rotational direction of the arc locus is set counterclockwise starting from point P1. Therefore, if the rotation angle at any time t from the point P1 is θ(1), then the point P (t) on the arc at any time t can be expressed in the X'-Y' coordinate system as shown below. It will be done.

P'' (t) = (x' (t), y' (
t))-(18) Here, x' (t), y' (t
) are respectively X″(t) ″Rcos (θR+θ(
t))...(19)y' (t) -Rsin (
θR+θ(t) )−(20). However, θR is the angle of OPl viewed from the x'-y' coordinate system.

Next, in step 37, arithmetic processing is performed to convert the data at point P'(t) into data P(t) in the robot coordinate system. The arithmetic processing in step 37 is executed using vector Kn. Referring to Figure 10, first
The position vector PR'(t) of point P(t) on the arc in the '-Y' coordinate system is PR'(t) -x'(t)
・ex +yJ (t) @ eY... (21) Expressing this position vector 1PR'(t) in the robot coordinate system, PR(t)-x' (t) ・ex-'', y' (
t) ・ey...(22) Therefore, the position vector F D) of point P (t) in the robot coordinate system is P (t) −Po + 1PR(t) −F□ +x'
(t) aex +y' (t) pot ey...
・It is expressed as (23).

Therefore ...(24) The relationship between

Here, XO, yO, 20 have been previously determined in step 35 using equation (17), and x'(t)+y'(t
) are obtained in step 36 using equations (19) and (20), and e XX, e Xy,
e XZ and e yx, e yy, e yz
has been determined in advance in step 34 using equations (13) and (14), so the coordinate data x(t) of the robot coordinate system for performing circular trajectory control.

y(t) and z(t) can be found.

These steps 36 and 37 are repeatedly processed when performing circular interpolation.

The robot control device 10 shown in FIG. 1 executes the above arithmetic processing, and obtains coordinate data x(t),
Once y(t) and z(t) are determined, each axis, namely the rotation drive system 11, lower arm bending drive system 12, upper arm bending drive system 13, upper arm rotation Desired drive signals are applied to the drive system 14, the wrist bending drive system 15, and the wrist rotating section/dynamic system 16. As a result, the tip of the robot's pole lamp 4 is controlled to move along a desired circular arc.

In the above embodiment, the present invention is applied to a 6-axis welding robot with 4 arms and 2 wrists, but it is of course applicable to other types of robots as well.

〔Effect of the invention〕

As described above, according to the present invention, by effectively using vector calculations, the amount of calculation required for arc trajectory calculation processing can be significantly reduced, and the speed of circular arc trajectory calculation processing of the robot can be increased.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing an embodiment of a robot control device to which the robot control method of the present invention is applied, and Fig. 2 explains an example of the robot of this embodiment and the control principle. FIG. 3 is a flowchart showing the operation of this embodiment.
FIGS. 4 to 10 are diagrams illustrating arithmetic processing in the same embodiment. 1...Body, 2...Lower arm, 3...Upper arm, 4...
Wrist, 5...Tool, 6...Circular plane, 7...Round bar, 10...Robot control device, 30...Teaching box〇in O Fig. 2 Fig. 3 Fig. 6 v'' Figure 7 Figure 9

Claims (4)

[Claims] (1) Set two-dimensional coordinates on a predetermined arc plane in three-dimensional space, calculate the center, radius, and arc locus of the above-mentioned arc in this two-dimensional coordinate system, and calculate these calculated values using vector calculation. A robot control method characterized by converting values into values in a dimensional coordinate system and controlling the robot based on the converted values. (2) The robot control method according to claim (1), wherein the two-dimensional coordinate system is an arc coordinate system. (3) The predetermined arc plane is defined by three points P_ in the control space.
The two-dimensional coordinate system is determined by teaching P_1, P_2, and P_3, and the two-dimensional coordinate system has point P_1 as the origin, and coordinates the X-axis and A method for controlling a robot according to claim (1), wherein the Y-axis is set. (4) The calculation of the circular arc trajectory is performed at the teaching point P_1.
, P_2, and P_3, the robot control method is performed by performing circular interpolation based on P_2 and P_3.