A joint and a method of constructing a joint for a variable geometry truss having a variable number of planes of variable length battens connected together in a triangular configuration, each plane being connected by six fixed length longerons in a Stewart platform configuration, are presented. The variable length battens allow the orientation of one end plane of the variable geometry truss to be changed to the other end plane in a controlled manner by selectively adjusting the lengths of the variable length battens. A main pivot joint pivotally connects two battens about a pivotal axis. A universal joint is pivotally connected to the main joint such that the pivotal axis of the universal joint is coextensive with the pivotal axis at the main joint. Two longerons are pivotally connected to the universal joint. Each longeron is thereby provided with three intersecting axes of rotation. Each longeron may include a revolute joint, allowing rotation about the longitudinal axis of the longeron

Horner, Garnett C.

English

NASA Technical Reports Server

NASA CASE NO.
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The invention disclosed in this document resulted from research in aeronautical and
space activities performed under programs of the National Aeronautics and Space
Administration. The invention is owned by NASA and is, therefore, available for
licensing in accordance with the NASA Patent Licensing Regulation (14 Code of
Federal Regulations 1245.2).
To encourage commercial utilization of NASA-owned inventions, it is NASA policy to
grant licenses to commercial concerns. Although NASA encourages nonexclusive
licensing to promote competition and achieve the widest possible utilization, NASA
will provide the necessary incentive to the licensee to achieve early practical
application of the invention.
Address inquiries and all applications for license for this invention to NASA Patent
Counsel, Langley Research Center, Code 212, Hampton, Virginia 23681-0001.
Serial No.: 08/325,723
10/14/94 LaRC
(NASA-Case-LAR-15136-1) JOINT FOR
A VARIABLE GEOMETRY TRUSS AND
METHOD OF CONSTRUCTING SAME Patent
Application (NASA. Langley
Research Center) 18 p
N95-14138
Unclas
G3/39 0029849
https://ntrs.nasa.gov/search.jsp?R=19950007724 2020-06-17T23:54:41+00:00Z

LAR 15136-1 - 1- PATENT APPLICATION
JOINT FOR A VARIABLE GEOMETRY TRUSS
AND METHOD OF CONSTRUCTING SAME
Origin of the Invention
5
The invention described herein was made by a U.S. Government
employee and may be manufactured and used by or for the government for
governmental purposes without the payment of any royalties thereon or
therefore.
Background of the Invention
Field of the Invention
10 This invention relates in general to deployable truss beam structures,
and specifically, to a joint suitable for a variable geometry truss able to
statically or dynamically move, in a controlled way, one end with respect to the
other end.
Description of the Related Art
15 Deployable truss beam structures that can maneuver in a serpentine
manner, i.e., are adaptive, are particularly useful in space-borne applications,
such as a robot manipulator, a berthing device between spacecraft, joints in a
crane or boom, and as a support structure for other moveable structures.
Space-based deployable structures, however, must be transported into space by
20 rocket driven vehicles, such as the U.S. space shuttle, where storage space is
LAR 15136-1 -2- PATENT APPLICATION
limited. In order for a deployable truss beam structure to be useful on such
missions, it must be possible to collapse it into a compact pacl;age for
transportation, and to extend it to its fully extendedlength during use in space.
Examples of prior deployable trusses include the two-axis gimbal and
5 geodesictrusses. However, two-axis gimbal trussesare limited in terms of the
load they cansustain and deployablegeodesictrussesare not capable of lateral
motion. A deployable truss beam structure that is maneuverable in a
serpentine manner is disclosed in a June 1985 paper entitled "Deployable
Controllable Geometry Truss Beam" by Marvin D. Rhodes and Martin M.
10 Mikulas. The Rhodes/Mikulas truss consists of cross-longeronsand battens.
The cross-longeronsareof fixed length and attach one comer of a three batten
triangle to the next plane defined by another three batten triangle. The length
of every other batten triangle can independently vary in length creating a
variable geometry truss. When the variable length battens are telescoped from
15 the fully extended position to the fully dosed position, the truss goesfrom a
completely collapsed to a fully deployed position. By changing the length of
the variable length battens, the truss can be maneuvered in a serpentine
manner. Based on the rotational requirement of the joints in the
Rhodes/Mikulas truss, two different types of joints are required which limits
20 the useability of the truss.
Summary of the Invention
25
Accordingly, it is an object of the present invention to provide a joint
for a variable geometry truss which allows the truss to statically or dynamically
move, in a controlled way, one body with respect to another body.
It is another object of the present invention to provide a single joint
LAR 15136-1 -3- PATENT APPLICATION
suitable for use at every joint location in a variable geometry truss.
It is another object of the present invention to provide a truss joint
having significant load capability.
It is a further object of the present invention to provide a simple type
5 of joint structure for avariable geometry truss.
It is still a further object of the present invention to provide a method
for constructing a joint for a variable geometry truss.
These and other objects are accomplished by a joint for a truss having
battens and longexonscomprising a first joint for pivotally connecting at least
l0 two battens forming a pivotal axis, and a secondjoint connected to said first
joint for connecting at least two longerons such that each longeron has at least
two axes of rotational freedom.
These and other objects are further accomplished by a method for
constructing a joint of a truss comprising the steps of pivotally connecting a
15 first and second batten to form a joint having a pivotal axis, and connecting
a first and second longeron to one side of the joint such that the first and
second longeron has three axes of rotational freedom, the intersection of each
axis of rotation of the first and second longeron lying on the pivotal axis of the
joint.
20 Brief Description of the Drawings
25
The present invention and the objects achieved by it will be understood
from the description herein, with reference to the accompanying drawings, in
which:
FIG. 1 is an isometric view of a simplified first embodiment of the
invention in a fully deployed variable geometry truss.
LAR 15136-1 -4- PATENT APPLICATION
FIG. 2 is an isometric view of a simplified first embodiment of the
invention as used in a variable geometry truss deployed in a serpentine
manner.
FIG. 3 is a lateral cross-sectional view of a joint for a variable length
5 batten in accordance with the first embodiment of the invention.
FIG. 4 is an isometric view of a second embodiment of the invention in
a fully deployed variable geometry truss.
FIG. 5 is an isometric view of an alternate joint according to the first or
second embodiment of the invention.
10 FIG. 6 is a lateral cross-sectional view of a joint according Fig. 5.
Detailed Description of the Preferred Embodiments
FIG. 1 is an isometric view of a variable geometry truss 10 having a joint
16 according to a first preferred embodiment of the invention. FIG. 1 is
simplified to show only those elements necessary for an understanding of the
I5 invention. A variable geometry truss is comprised of three components: a
plurality of fixed length longerons 14, a plurality variable length battens 12,
and a plurality of joints 16. Three variable length battens 12 are connected
together by the joints 16 to form a triangle. Depending on the application and
the length requirement, one or more such triangles are formed and connected
20 together by the fixed length longerons 14. In the example, as shown in FIG.
I, and as discussed herein, three such triangles are formed by two end triangles
and a center triangle. Each end triangle of variable length battens 12 is
connected to the center triangle by six fixed length longerons 14 arranged in
a so-called "Steward platform" configuration by the joints 16. In other words,
25 each point of the variable length batten I2 in each end triangle is connected
LAR 15136-1 -5- PATENT APPLICATION
by fixed length longerons 14 to two points of the adjacent variable length
battens triangle. Each point in the center triangle is connected to two other
triangles by four fixed length longerons 14.
Each variable length batten 12 can be independently lengthened and
5 shortened through the use of a hand-cranl_ 22. The hand-crank 22 is attached
to an inner rod 30 (see FIG. 3) of the variable length batten I2 through a cage
25 which forms a main pivot joint, having a main pivotal axis, with bracket 26
of another variable length batten 12. A yoke 18 is pivotally connected to the
outside of cage 25. The center triangle has two yokes 18, one on each side of
10 the joints 16. The yoke 18 rotates about the same pivotal axis as the bracket
26 in the cage 25. Each yoke 18 is provided with a rotatable rod 20 which
rotates perpendicularly to the rotation of yoke 18 forming a universal joint
having two degrees of rotational freedom. Two fixed length longerons 14 are
pivotally connected to each rotatable rod 20 by an end bracket 28. In the first
15 preferred embodiment of the invention, the end bracket 28 is free to rotate in
a direction perpendicular to the rotation of both the rotatable rod 20 and the
yoke 18 thereby providing each fixed length longeron 14 with three
intersecting degrees of rotational freedom. At one end of each fixed length
longeron 14 is a revolute joint 19 which allows rotation about the longitudinal
20 axis of the longeron 14.
FIG. 2 is an isometric view of the variable geometry truss 10 deployed
in a serpentine manner. The variable length battens 12 allow the orientation
of one end triangle with respect to the other end triangle to be changed in a
controlled manner. The length of each variable length battens 12 is controlled
25 by rotating the hand crank 22. By rotating the hand crank 22, an inner
threaded rod 30 is made to rotate against a threaded joint 24 connected to an
outer rod 29. Thus, the length of each variable length batten 12 can be
LAR 15136-1 - 6- PATENT APPLICATION
precisely controlled to displace the end triangles of the variable geometry truss
10 in both a vertical and lateral manner.
FIG. 3 is a lateral cross-section view of a variable length batten 12 with
joint 16. The hand crank 22 is connected to the inner rod 30 via a bolt 22b.
5 The inner rod 30 extends through the cage 25 and inside the outer rod 29.
The outer rod 29 is capped with the threaded joint 24. Threads 23 on the
inner rod 30 engage the threads on the threaded joint 24. A bracket 26 is
connected to the opposite end of the outer rod 23. The bracket 26 has two
end arms 27. Each end arm 27 is provided with a hole 27a to allow
10 attachment to the cage 25 of an adjacent variable length batten 12. The cage
25 of the variable length batten 12 is provided with holes 25a for pivotally
connecting, about the same axis, the yoke 18 and the end arms 27 of another
variable length batten 12 via bolt 25b. The yoke 18 is provided with opposing
holes 18a for attachment of the rotatable rod 20 via bolts 20b. The rotatable
15 rod 20 is provided with a throughhole 20a, intersecting the pivotal axis of the
yoke 18, for pivotally attaching the end brackets 28 of the fixed length
longerons 14. The cage 25, the bracket 26, the yoke 18, and the rotatable rod
20 form the joint 16.
The joint 16 pivotally connects two variable length battens 12 about a
20 main pivotal axis. The joint 16 further connects at least two fixed length
longerons 14 such that each fixed length longeron 14 has three intersecting
axes of rotation. At one end of each fixed length longeron 14 is a revolute
joint 19 which allows rotation about the longitudinal axis of the longeron 14.
FIG. 4 is an isometric view of a variable geometry truss with a joint 16
25 according to a second embodiment of the invention. FIG. 4 is simplified to
show only those dements necessary for an understanding of the invention. In
the second embodiment of the invention, the variable length battens 12 are
LAR 15136-1 -7- PATENT APPLICATION
provided with motors 32 to allow for automatic lengthening and shortening of
the variable length battens 12. The variable length battens 12 are lengthened
and shortened by the motor 32 via a standard ball screw mechanism (not
shown). It will be recognized by one sldlled in the art that other mechanisms
5 may be used, such as pneumatic or hydraulic actuators. It will also be
recognized that the invention according to the first embodiment can be
automated by replacing the hand crank 22 by an automatic drill-like
mechanism. One advantage of using the ball screw mechanism in the variable
length batten 12 is that the inner rod 30 is not required to extend through the
10 joint 26, and thus allows the use of a much more compact joint structure.
In the second embodiment, as shown in FIG. 4, the variable geometry
truss 10 is only provided with one triangle of variable length battens 12. A
pair of fixed end plates 34, upon which various structures can be attached, is
provided to form end planes for the variable geometry truss 10. The fixed
15 length longerons 14 are connected to the end plates via joints 38 which
provide two degrees of rotational freedom. In this configuration, the fixed
length longerons 14 can be attached to the rotatable rod 20 via a fixed-angle
bracket 36 which restricts the movement of the fixed length longerons 14 by
maintaining a constant angle between them. Due to the limited range of
20 available motion in this configuration, the joint 16 is provided with restriction
plates 42 to prevent over-extension of the variable geometry truss.
FIG. 5 is an isometric view of an alternate joint 16, constructed in
accordance with the first or second preferred embodiment of the invention.
As shown in FIG. 5, the joint 16 is configured to allow for multiple planes of
25 variable length batten triangles by allowing rotation as between the fixed
length longerons 14, similar to the first embodiment as shown in FIG. 1. In
this configuration, a bracket 45, forming the main pivot joint of joint 16, is
LAR 15136-I -8- PATENT APPLICATION
provided to rotatably connect the end brackets 26 of two variable length
battens 12 with two yokes 18 via a common center pin 44. Each yoke holds
a rotatable rod 20, via bolt 48, whose axis of rotation is perpendicular to and
intersects with the centerline of center pin 44. The fixed length longerons 14
5 are rotatably connected to the rotatable rod 20 via a bolt 50 whose axis of
rotation intersects the axis of rotation of center pin 44. For use in the second
embodiment, a restriction plate 42 is attached to adjacent yokes 18 to cause
the variable length battens 12 to rotate simultaneously about the center pin
44. This in turn causes the battens 12 in the adjacent batten planes to become
10 fixed length battens of equal length.
As can be seen in FIG. 5, the variable length battens 12 are driven by
a motor 32 via a belt 52. The motor 32 is held in place via a bracket 54. The
variable length battens 12 are provided with an expansion joint 46 which
protects the gap between the inner rod 30 (not shown) and the outer rod 29,
15 allowing for deployment in environmentally hostile situations.
FIG. 6 is a lateral partial cross-sectional side view of the joint 16 in
accordance with Fig. 5. An axis of rotation 56 of the common centerpin 44
lies perpendicular to and intersects with an axis of rotation 58 of the rotatable
rod 20 (not shown). Because the variable length battens 12 are activated via
20 motors 32, the joint 16 is compactly designed using easily machined parts.
The use of motors 32 to automatically adjust the length of the variable
length battens 12 enables the use of remote controllers for deployment in
environmentally hostile situations. The remote controllers can be embodied
in computerized controls that automatically adjust the relationship between
25 the end planes of the variable geometry truss 10.
In all of the embodiments of the joint 16 for the variable geometry truss
10, according to the preferred embodiments of the invention described above,
LAR 15136-1. -9- PATENT APPLICATION
the variable length battens 12 and the fixed length longerons 14 share a
common axisof rotation 56. Further, the axisof any other degreeof rotational
freedom provided to the fixed length longerons 14 preferably intersects at the
samepoint on the common axisof rotation 56. This common axis of rotation
5 56 is provided by the structure of joint 16. While two specific embodiments
have been described, it will be recognized by one sldlled in the art that other
configurations can be used. Specifically, any joint that provides rotations
about two axes, just as if there were an actual two-axis gimbal operating at the
joint, can be used. The embodiments of the invention provide a single joint
I 0 for variable geometry truss that can be retracted compactly for storage and
transportation, and has excellent structural stability during and after
deployment, while displaying great dexterity.
Numerous modifications and adaptations of the present invention will
be apparent to those sldlled in the art. Thus, the following claims and their
15 equivalents are intended to cover all such modifications and adaptations which
fall within the true spirit and the scope of the present invention.
What is claimed is:
LAR 15136-I
Abstract of the Disclosure
PATENT APPLICATION
5
10
A joint and a method of constructing a joint for a variable geometry
truss having a variable number of planes of variable length battens connected
together in a triangular configuration, each plane being connected by six fixed
length longerons in a Stewart platform configuration. The variable length
battens allow the orientation of one end plane of the variable geometry truss
to be changed to the other end plane in a controlled manner by selectively
adjusting the lengths of the variable length battens. A main pivot joint
pivotally connects two battens about a pivotal axis. A universal joint is
pivotally connected to the main joint such that the pivotal axis of the universal
joint is coextensive with the pivotal axis at the main joint. Two longerons are
pivotally connected to the universal joint. Each longeron is thereby provided
with three intersecting axis of rotation. Each longeron may include a revolute
joint, allowing rotation about the longitudinal axis of the longeron.
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Joint for a variable geometry truss and method of constructing same

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