Communications: radio wave antennas – Antennas – Antenna components
Reexamination Certificate
1999-06-11
2001-11-06
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Antenna components
C343S912000, C052S111000
Reexamination Certificate
active
06313811
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to support structures, such as but not limited to those for deploying energy directing surfaces (e.g., reflectors), in either terrestrial or space applications, and is particularly directed to a new and improved compactly stowable support architecture, having both radial and circumferential structural elements, that are configured to be compactly foldable, and to be controllably driven so as deploy an unfurlable medium, such as a mesh-configured reflector. The compact packaging configuration of the invention lends itself to being efficiently transported by and deployed by a spacecraft to support large reflector apertures. Scalability permits use in small aperture applications where compact launch volume is required.
BACKGROUND OF THE INVENTION
The use of large reflector structures for satellite communication networks is becoming more widespread as demand for mobile communications increases. As the required aperture size or number of reflectors per space-deployed communication site increases, the availability of lightweight, compactly packaged antenna structures is a key element in continuing industry growth.
A non-limiting example of an umbrella type and folded rib mesh reflector that has been deployed by the National Aeronautics and Space Administration (NASA) for over a quarter of century is the Tracking Data Relay System (TDRS) reflector antenna system. In its deployed state, the metallic mesh reflector structure of the TDRS system measures 4.8 meters in diameter; however, when folded, it readily fits within a cylindrical volume approximately one meter in diameter and three meters in length. Each satellite in the deployed TDRS constellation employs two such antennae. In addition to the TDRS antenna system, commercial mobile communications systems that employ two mesh reflectors, each having an aperture size of twelve meters are also in production. Each of these reflectors, with folding ribs, is sized to fit within a cylindrical volume approximately one meter diameter and four and one-half meters in length. By folding the ribs, the same TDRS-configured volume, moderately lengthened, can package a reflector over twice the TDRS size.
There are varieties of other reflector designs in which rigid elements are oriented in either a radial direction from the reflector center or a circumferential direction at the reflector periphery, and may employ foldable rigid elements to improve packaging. Non-limiting examples of such prior art antenna structures include the following U.S. Patents: U.S. Pat. Nos. 5,787,671; 5,635,946; 5,680,145; 5,451,975; 5,446,474; 5,198,832; 5,104,211; and 4,989,015.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a new and improved structure geometry, either deployable or non-deployable, that includes both radial and circumferential structural support members to support a reflecting surface, such as a mesh-configured antenna surface. Employing both radial and circumferential support members allows the invention to adapt to a wide variety of geomtries and is not limited to only symmetric structures. The invention may be applied to any structure requiring a generally polygonal shape having a unique geometry at its periphery. As described herein, the support structure of the invention may be implemented in either of two embodiments or configurations. Both employ a regular polygonal inner hoop and generally radial struts. The difference between the two configurations involves the location and design of the tips or distal ends of the radial struts.
In the first configuration, distal ends of adjacent radial struts are hinged together in pairs to form the corner of a triangle, a subtended side of which is one side of an interior hoop structure. In the second configuration distal ends of radial struts are not hinged together. Interconnecting distal ends of the radial struts in the first configuration reduces internal member loads for structures having a relatively small (generally less than six) number of sides. The second configuration (where the radial struts are not joined together) facilitates implementing relatively large architectures (having four or more sides); however, there is an increase in internal member loads.
Due to the high cost to place systems in space, the structure's deployment reliability must be ensured to the maximum extent possible. This reliability can be achieved through slow, controlled, synchronous deployment. By synchronizing the hinges, the position of each rigid element in the structure is known and predictable throughout all stages of deployment. This enhances reliability and reduces dynamics. Moreover, the rate of deployment can be more readily controlled by design of the hinge mechanism and drive system.
In accordance with the first embodiment of the invention, distal ends of respective pairs of adjacent upper radial struts that extend from corner joints of a segmented or multi-sided foldable hoop support structure are hinged together. Mid-points of alternate upper segmented radial strut elements are hinged together by folding mid-strut hinge joints. The mid-strut hinge joints allow the hinged together upper radial strut pairs to be folded about hoop structure corner hinge joints and stowed generally parallel to a respective hoop element of the foldable hoop structure. The upper radial struts are connected to corner joints of the hoop structure by multi-axis, synchronously driven hinges. As will be described, these synchronously driven corner hinges may employ relatively non-complex pin joints, so as to allow the structure to be deployed into a three-dimensional shape with relative simple kinematics. In addition, all driven hinges are tied together via torsion tubes and gears, so that the hinges are effectively synchronized. This allows all hinges to be driven by a single motor to deploy the entire support structure. Alternatively, multiple motors may be installed for deployment redundancy. The drive motor may be installed at any convenient location along the torsion tubes.
As a non-limiting example, the multi-sided foldable hoop structure of the first embodiment of the invention may contain six rigid hoop members or legs, the length of each of which is approximately the same as the length of a respective upper radial strut. The hoop members are hinge-connected to one another in end-to-end fashion at the driven hinge joints, so as to define a generally polygonal (e.g., hexagon)-shaped hoop structure. In addition to providing attachment points to the hoop corner joints for upper radial struts, a respective hinge joint is coupled to an additional radial, bottom strut.
Tensioned cords of an upper tensioning ring tie together distal ends of successive ones of the plurality of upper radial strut. Lower cords of a lower tensioning ring tie together distal ends of the lower (i.e. bottom) radial struts. Additional, tension-only cord elements interconnect distal ends of the upper radial struts with distal ends of the lower radial struts. The tensioning cord elements and the upper and lower tensioning rings stabilize the distal ends of the radial struts and impart stiffness to the support structure.
In the second embodiment of the present invention, distal ends of radial strut elements are not hinged together to form outer perimeter hinged corner joints. Instead, distal ends of the upper radial strut elements are coupled to tensioning cords of an upper tensioning ring. Also, distal ends of lower radial strut elements are coupled to tensioning cords of a lower tensioning ring. In addition, a respective side of the hoop structure is segmented into a pair of hoop elements that are joined together at midpoint by means of a driven mid-strut hinge joint. The upper and lower radial struts are coupled to corner joints of the hoop structure by multi-axis driven hinge joints. Each of the driven corner and mid-strut hinge joints is synchronously driven to enable the structure to fold in a manner consistent with powered, synchronous deployment. Additional tens
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Le Hoang-anh
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