Gear cutting – milling – or planing – Milling – Including means to infeed rotary cutter toward work
Reexamination Certificate
2001-06-05
2003-01-07
Wellington, A. L. (Department: 3722)
Gear cutting, milling, or planing
Milling
Including means to infeed rotary cutter toward work
C409S235000, C409S211000, C409S216000, C408S236000, C074S479010, C074S490080, C248S653000, C901S023000
Reexamination Certificate
active
06503033
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a parallel mechanism structure for controlling three-dimensional position and orientation.
BACKGROUND ART
As well known, generally, a parallel mechanism structure for controlling three-dimensional position and orientation has been chiefly studied for a work machine for processing a work object and a robot manipulator for assembling and transferring an object.
By way of example, the work machine functions to process a material, so that the material takes a desired shape or form. The work machine is composed of a machine body and a tool, in which the machine body operates by virtue of power-and a cutting tool works the material. At this time, it is essentially required that three-dimensional position and orientation of the tool for the working material be controlled in the work machine.
First, an explanation of a serial mechanism structure developed before a parallel mechanism structure has been emerged will be described.
FIG. 1
is an exemplary view illustrating a conventional serial mechanism structure. As shown, the conventional serial mechanism structure, each link from a base
11
to a main spindle
12
has a cantilever structure at a perpendicular angle. The serial mechanism structure has some advantages that the working space is large and the software and control devices for controlling the structure are configured in a simple manner. When compared with the conventional serial mechanism structure, however, the parallel mechanism structure where the base and the main spindle are connected by means of a plurality of links has the following advantages. By these reasons, the studies for the newly proposed parallel mechanism structure have been dynamically made.
The advantages of the parallel mechanism structure are as follows: First, as the mass of inertia of a moving part decreases, the velocity and the acceleration thereof can increase; Second, as the main spindle and the base are connected by means of the plurality of links and only a tension force and a compressing force, instead of a bending force, are applied to each link, the stiffness of the machine can increase; Third, as the error of each link of the parallel mechanism structure is reflected to the main spindle on the average, the accuracy thereof can be more improved, when compared with the serial mechanism structure where the error of each link is accumulated; and Forth, when compared with most of the work machine adopting the serial mechanism structure are three-axis right angled coordinate machine, the parallel mechanism structure is basically configured to carry out six degree-of-freedom(d.o.f) motions, which can at a time work five-face and five-axis in a complete shape.
FIG. 2
is an exemplary view illustrating a hexapod structure as the conventional parallel mechanism structure. As shown, in the hexapod structure the main spindle
22
and the base
21
are connected by means of six links, and the expansion of the links enables the six d.o.f motions. The hexapod structure is called ‘Stewart platform’. The parallel mechanism work machine adopting the ‘Stewart platform’ has been manufactured by Giddings & Lewis Co. in U.S.A. The work machine achieves the six d.o.f motions, but has the disadvantages that the working space is very small and particularly, the main spindle is inclined up to about 15° and cannot continuously sweep the lateral surfaces of the workpiece over a full 360 degree range.
Also, an ‘octahedral hexapod’ structure has been developed by the co-operation of the Ingersoll inc. and NIST in U.S.A. The structure is reverse to the ‘Stewart platform’ structure. In this case, the working space is narrow and the main spindle has the inclination angle of 30° and additionally, the work bench is inclined at the angle of 15°. However, it is noted that the whole inclination of the ‘octahedral hexapod’ structure is the angle of 45°. The limitation of the hexapod structure is due to the problems that the six links connected to the main spindle interfere with each other and the rotating angle of the ball joint connecting the main spindle and the link is fixed.
A newly developed parallel mechanism structure where the inclination angle of the main spindle extends up to an angle of 90° is disclosed in Korean Patent No. 237553 filed by the same applicant.
FIGS. 3
a
and
3
b
are exemplary views illustrating the conventional parallel mechanism structure where the main spindle is inclined up to an angle of 90°, wherein
FIG. 3
a
shows the main spindle of the inclination angle of 0° and
FIG. 3
b
shows the main spindle of the inclination angle of 90°.
As shown, three links
73
,
74
and
75
connected to a main spindle
72
are transferred vertically along corresponding rectilinear vertical guides
83
,
84
and
85
, and the three vertical guides
83
,
84
and
85
are transferred along a round horizontal guide
76
for the horizontal transfer at an angle of 360°. The three links
73
,
74
and
75
are connected by S-R-P joints from the main spindle
72
, and the vertical guides
83
,
84
and
85
are connected by a P′ joint with the circular horizontal guide
76
. The P joint and the P′ joint are driven and thus, by the six driving joints, the six d.o.f motions of the main spindle
72
can be achieved.
In this case, the ‘S’ represents a spherical joint for a three-dimensional rotation. the ‘R’ represents a revolution joint for an one-dimensional rotation, the ‘P’ represents a prismatic joint for an one-dimensional rectilinear transfer, and the ‘P′’ represents the prismatic joint for a circular transfer.
In the parallel mechanism structure as shown in
FIGS. 3
a
and
3
b
, any (for example, the reference numeral ‘
85
’) of the vertical guides
83
,
84
and
85
is arranged downward on the basis of the horizontal guide
76
and the other vertical guides
83
and
84
are arranged upward on the basis of the horizontal guide
76
. The arrangement of the three horizontal guides
83
,
84
and
85
in the different directions enables the limitation of the working space to be overcome, thereby ensuring a large working area.
In the parallel mechanism structure as shown in
FIGS. 3
a
and
3
b
, also, the six d.o.f motions of the main spindle can be carried out with three actuators for horizontally transferring the rectilinear vertical guides
83
,
84
and
85
on the vertical guide
76
and three actuators for vertically transferring the three links
73
,
74
and
75
connected to the main spindle on the rectilinear vertical guides
83
,
84
and
85
. With
With the conventional parallel mechanism structure as shown in
FIGS. 3
a
and
3
b
, the inclination angle of the main spindle is an angle of 90°, as shown in
FIG. 3
b
and thereby, the five-face work except the bottom face is possible.
However, even in case of the inclination angle of 90° of the main spindle, the bottom-face work for the material is not possible. Therefore, there is a need for the extension of the inclination angle of the main spindle.
Additionally, the conventional parallel mechanism structure has limitations as a motion simulator for simulating a real motion, due to the restriction of the inclination angle of the main spindle.
DISCLOSURE OF THE INVENTION
An object of the invention is to provide a parallel mechanism structure for controlling three-dimensional position and orientation which is capable of extending the inclination angle of a main spindle in the parallel mechanism structure as shown in
FIGS. 3
a
and
3
b
, whereby in the case where it is applied in a work machine, the bottom-face work for a material is possible and in the case it is applied in a motion simulator, the inclination angle of the main spindle rotates at ±360°.
To accomplish this and other objects of the present invention, there is provided a parallel mechanism structure for controlling three-dimensional position and orientation in which three links are connected to a main spindle of the mechanism and driven in two directions, namely, vertical and horizontal directions, thereby achieving
Han Young-Oh
Hwang Jae Chul
Kim Jin-Sung
Kim Jong-won
Park Chongwoo
Cadugan Erica E
Dickstein , Shapiro, Morin & Oshinsky, LLP
Kim Jongwon
Wellington A. L.
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