JPS5997889A - Method of controlling attitude of wrist of industrial robot - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to trajectory control of an industrial robot, and particularly to a method of controlling the wrist posture during parallel movement of the wrist tip position.

As shown in FIG.
4) In industrial robots equipped with a wrist consisting of three axes: a bending axis (5) and a second torsion axis (6), tools such as painting guns and welding torches that are attached to the tip of the wrist ( When moving the tip position of item 7) in parallel, there was no effective algorithm, so we applied technical constraints such as ``The tip position of the tool must be on the axis of the final axis (6).'' I was going. In addition, if the tool (7) is a tool that has a directional coating pattern, such as a painting gun, move the painting gun in parallel in the direction of the arrow from position 7a to position 7b as shown in Figure 2. Even if the axial direction of the gun is preserved, the twisting around the gun's axis is
Since the n-direction of the gun screw was not controlled, the coating pattern (8) could not be substantially translated in parallel as shown.

The present invention is an attempt to solve these problems, and is an industrial robot with three wrist axes.
Assuming two unit vectors that intersect at a point and are independent of the tip axis coordinate guide, and controlling the direction of the plane containing these two unit vectors, the axial direction of the tool attached to the tip axis and the screw n This is a wrist posture control method for an industrial robot that can control the posture in two directions, eliminating restrictions on the mounting position and direction of the tool installed on the torsion shaft at the tip, and preventing any mounting force from being applied. Even if it is a tool,
Control of its direction and twist around the tool axis? This made it possible.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 3, an articulated industrial robot has a rotation axis θI (1
1. Three arms consisting of a longitudinal axis θ2 (2), a vertical axis θ3 (3), a first torsion axis θ4 (4), and a bending axis θ6 (
5) The wrist consists of three axes, the second torsion axis θ6 (6) being the tip axis, and the three axes of the wrist intersect at one point.

Then, the ground coordinate e (X, 7% 2), the coordinate on the rotation axis θ1 (11% 71, Zt), the coordinate on the longitudinal axis θ2 (Xa, y2, z2), and the coordinate on the vertical axis θ3' t(
"Coordinates on a, y3, θ6'!k(xa, y6, Za)
It is stipulated that Furthermore, the torsion axis θ6 at the tip is an independent unit vector K (0, 1, O) machining P (0,
0,1). Ground coordinates Cx5 of these vectors
y% 2] is as follows.

(Here, Ca is the coordinate transformation matrix around the a-axis of the θ1-axis.) Also, since axes 0, θ5, and θ6 of the three wrist axes intersect at one point, the tip axis ( 6) The two independent vectors defined by , and the plane defined by P (9
) moves in parallel, the movement position of the wrist center A is A1
, if the moving position of the tip position B is B', then AAl and B B
' are parallel and have equal length. The amount of movement of the wrist center A is equal to the amount of movement of the tip position B, and one posture of the tool with respect to the ground, which has a constant positional relationship with the plane (9), is preserved.

Next, an algorithm in the present invention will be described.

(a) Find the coordinates of the current wrist position (point A).

Here Si stop sin θ soil 01=
=cos θI Si+j A 5in(θ1 + θj)C! i
10j =: coθ(θi + θj)11,
E2 is the arm length.

(See Figure 3) (b) Find the current vector using PI formulas (1) and (2).

(C) The amount of parallel movement is Xs, 7s, Zs (!:
Find the coordinates of point A1 ([1) Equation (3) Find the position of the 3 axes of F arm θ-
- θ1·θ1 is determined.

(θ) ii obtained by changing equations (1) and (2) (Here, it is the inverse matrix of the C-xtr1 matrix Ca) J: 9
θ4, θ5, and θ6 of each axis of the wrist can be determined.

According to the present invention, the following effects can be achieved as described above.

1. There are no restrictions on how to attach tools to a robot with three wrist axes.

2. The tool posture and tip position during parallel movement can be controlled.

3. Even in 3D shifting when working in synchronization with the conveyor, the posture of the tool can be preserved and shifted.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional industrial robot, Fig. 2 is an explanatory diagram of the movement state of the wrist of a conventional robot, Fig. 3 is a schematic diagram for explaining the present invention in detail, and Fig. 4 is a diagram of the present invention. FIG. 3 is an explanatory diagram of the movement status of the wrist according to the invention. (4), (5), (6)... Each axis of the wrist (9)
・・・・・・・・・・・・・・・・・・Plane P, K・
・・・・・・・・・・・・Patent attorney Hector Kawa
Junji Uchi

Claims (1)

[Claims] In an industrial robot with a 3-axis wrist, the 3-axis wrist
The axes of the shafts intersect at one point, and two independent points are created within the tip axis coordinate system.
A wrist posture control method for an industrial robot, the method comprising assuming two unit vectors and controlling the direction of a plane containing the two unit vectors.