FIELD OF THE INVENTION
[0001] The present invention relates to the field of antenna systems, and is more particularly
concerned with pointing systems for steerable antennas.
BACKGROUND OF THE INVENTION
[0002] It is well known in the art to use steerable (or tracking) antennas to communicate
with a relatively moving target over a scan angle. Especially in the aerospace industry
when the antenna is on board of a spacecraft, such steerable RF (Radio Frequency signal)
antennas preferably need to have precise pointing, high gain, low mass, and high reliability.
[0003] Satellites often contain two (2) degree of freedom pointing devices to communicate,
sense, etc. with other satellites or bodies. Since the distances are large, the pointing
accuracy and resolution is critical.
[0004] The payload of these pointing devices is variable. Some payloads are full antennas,
portions of an antenna, sensors, etc.
[0005] Many different pointing devices have been devised in the past. The simplest one being
two rotary actuators (RA) assembled in a sequential chain and holding the payload,
such as a reflector, as shown in Figures 1a and 1b. Especially when relatively small
scan angles are required, such as below +/- 30 degrees for example, these types of
pointing devices have many disadvantages, or at least a few, among the following list:
- high profile;
- heavy mass, structurally inefficient;
- high cost;
- low accuracy;
- low resolution;
- low reliability;
- need for Hold down and Release Mechanisms (HRM);
- requires fixed predetermined stowed position for launch;
- need for moving harness (RF rotary joint, electrical wiring, etc.); and/or
- reduced RF performance in the case of a reflector pointing mechanism.
[0007] Accordingly, there is a need for an improved antenna pointing system.
SUMMARY OF THE INVENTION
[0008] It is therefore a general object of the present invention to provide an improved
antenna pointing system that solves the above-mentioned problems.
[0009] Advantages of the antenna pointing system of the present invention are:
- 1. lower profile;
- 2. lower mass, structurally efficient;
- 3. lower cost;
- 4. higher accuracy;
- 5. higher resolution;
- 6. higher reliability;
- 7. eliminates need for Hold down and Release Mechanisms (HRM);
- 8. allows for last minute selection of stowed position for launch;
- 9. eliminated need for moving harness (RF rotary joint, electrical wiring, etc.);
and/or
- 10. improved RF performance in the case of a reflector pointing mechanism.
[0010] The above first three (3) points are main advantages when using rotary actuators.
[0011] According to the present invention there is provided an antenna pointing system according
to claim 1.
[0012] Conveniently, the flexible mounting structure is a universal joint, including bearings,
flexures or the like, preferably located near a geometric center of the payload.
[0013] In one embodiment, there are two rotary actuators with essentially the two second
ends of the connecting rods connecting adjacent a perimeter of the payload, the two
actuators being angularly spaced from one another relative to a rotation center of
the flexible mounting structure, typically by an angle sufficient to make use of the
full angular displacement range of the payload about the flexible mounting structure.
[0014] In one embodiment, there are first and second rotary actuators connecting to respective
said connecting rod with said second ends of said connecting rods movably connecting
to corresponding first and second attachment points of the payload.
[0015] Typically, the first and second attachment points are angularly spaced from one another
relative to a rotation center of the flexible mounting structure, and the first and
second attachment points are substantially adjacent a perimeter of the payload.
[0016] Conveniently, the first and second attachment points are substantially 90 degrees
apart from one another relative to the rotation center of the flexible mounting structure.
[0017] Other objects and advantages of the present invention will become apparent from a
careful reading of the detailed description provided herein, within appropriate reference
to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In the annexed drawings, like reference characters indicate like elements throughout.
Figures 1a and 1b are side and rear elevation views, respectively, of an antenna reflector mounted
with a prior art two-axis gimbal pointing system;
Figure 2 is a top perspective view of an embodiment of an antenna pointing system in accordance
with the present invention movably supporting an antenna reflector payload;
Figure 3 is an enlarged top perspective view of a rotary actuator of the embodiment of Figure
2;
Figure 4 is a partially broken enlarged top perspective view of a universal joint of the embodiment
of Figure 2; and
Figure 5 is a partially broken top plan view of the embodiment of Figure 2.
DETAILED DESCRIPTION OF THE INVENTION
[0019] With reference to the annexed drawings the preferred embodiments of the present invention
will be herein described for indicative purpose and by no means as of limitation.
[0020] Referring to Figures 2 and 3, there is shown a schematic diagram of an embodiment
of the low profile high resolution and torque antenna pointing system 10. In the case
presented, the pointing system 10 points a reflector, part of an RF (Radio Frequency
signal) antenna 12 mounted on board of a spacecraft, represented by the mounting surface
14 situated in orbit. The pointing system 10 consists of using rotary actuators 20
in conjunction with cranks 22 and connecting rods 24 to impart rotations to a payload
structure 26, such as an antenna reflector assembly, which is movably held in place
by a flexible mounting structure 28 as a universal joint structure or the like. An
example of the complete system 10 is shown in Figure 2.
[0021] In the embodiment 10, the RF performance is improved because the generally orthogonal
first 30 and second 31 rotation axes of the universal joint 28 intersects a point
proximate the geometric center of the reflector 26, to define the rotation center
R thereof. The system 10 uses two rotary actuators 20 to drive two degrees of freedom.
Both rotary actuators 20 have their fixed part secured to the base plate 14 eliminating
any mobile harnessing, such as RF rotary joint, electrical wiring, etc. A crank 22
is assembled on the output of the moving part of both rotary actuators 20. A rotary
actuator 20 with its crank 22 is shown in Figure 3.
[0022] An elongated connecting rod 24 has a first proximal end 32 movably connected to the
shaft 23 of the crank 22 and the opposite second distal end 34 movably connected to
the payload 26, at an attachment point 27 typically adjacent a perimeter thereof.
Typically, both ends 32, 34 are connected through spherical bearings 35, flexures
or the like in order to allow angular displacements thereof between respective connecting
elements. The payload 26 is movably mounted on the surface 14 using the universal
joint 28 typically consisting of one to two (1-2) static brackets 36 securable to
the surface 14 and movably supporting a cross 38 about the first rotation axis 30
via at least one first bearing 40, flexure or the like, and one to two (1-2) moving
brackets 42 extending from or secured to the payload 26 and movably supported by the
cross 38 about the second rotation axis 31 via at least one second bearing 44, flexure
or the like, as shown in Figure 4.
[0023] As best seen in Figure 5, the two attachment points 27 connecting to the two second
distal ends 34 of the respective connecting rods 24 are typically angularly spaced
from one another relative to the rotation center R of the flexible mounting structure
28, as illustrated by angle A. Angle A is typically sufficient to make use of the
full angular displacement range of the payload 26 about the flexible mounting structure
28. To this end, angle A is preferably around 90 degrees.
1. An antenna pointing system (10) for selectively moving a payload (26) relative to
a mounting surface (14), said system (10) comprising a flexible mounting structure
(28) for movably attaching the payload (26) to the mounting surface (14), and
being characterized by:
- at least one rotary actuator (20) having a moving part (22) being movable relative
to a fixed part adapted for being secured on the surface (14); and
- a connecting rod (24) movably connecting to a crank (22) assembled on the moving
part (22) at a first end (32) thereof, and adapted for movably connecting to the payload
(26) at a second end (34) thereof.
2. The antenna pointing system (10) of claim 1, wherein the at least one rotary actuator
includes first and second rotary actuators (20) connecting to respective said connecting
rod (24) with said second ends (34) of said connecting rods (24) being adapted for
movably connecting to corresponding first and second attachment points (27) of the
payload (26).
3. The antenna pointing system (10) of claim 2, wherein the first and second rotary actuators
(20) are angularly spaced (A) from one another relative to a rotation center (R) of
the flexible mounting structure (28).
4. The antenna pointing system (10) of claim 3, wherein the first and second rotary actuators
(20) are adapted to be adjacent a perimeter of the payload (26).
5. The antenna pointing system (10) of claim 2, wherein the first and second rotary actuators
(20) are substantially 90 degrees apart (A) from one another relative to the rotation
center (R) of the flexible mounting structure (28).
6. The antenna pointing system (10) of claim 1, wherein the flexible mounting structure
(28) is adapted to be located adjacent a geometric center of the payload (26).
7. The antenna pointing system (10) of claim 1, wherein the flexible mounting structure
is a universal joint structure (28).
1. Antennenpositionierungssystem (10) zum selektiven Bewegen einer Nutzlast (26) in Bezug
auf eine Befestigungsfläche (14), wobei das System (10) eine flexible Halterungskonstruktion
(28) zur beweglichen Befestigung der Nutzlast (26) an der Befestigungsfläche (14)
aufweist und
gekennzeichnet ist durch:
- wenigstens ein Drehstellglied (20), das ein bewegliches Teil (22) aufweist, das
in Bezug auf ein feststehendes Teil beweglich ist, das dafür ausgelegt ist, an der
Fläche (14) gesichert zu werden; und
- eine Pleuelstange (24), die beweglich mit einer Kurbel (22) verbunden ist, die an
dem beweglichen Teil (22) an einem ersten Ende (32) davon angebracht ist und dafür
ausgelegt ist, beweglich mit der Nutzlast (26) an einem zweiten Ende (34) davon verbunden
zu werden.
2. Antennenpositionierungssystem (10) nach Anspruch 1, wobei das wenigstens eine Drehstellglied
erste und zweite Drehstellglieder (20) beinhaltet, die jeweils mit der Pleuelstange
(24) verbunden sind, wobei die zweiten Enden (34) der Pleuelstangen (24) dafür ausgelegt
sind, beweglich mit entsprechenden ersten und zweiten Befestigungspunkten (27) der
Nutzlast (26) verbunden zu werden.
3. Antennenpositionierungssystem (10) nach Anspruch 2, wobei das erste und zweite Drehstellglied
(20) in Bezug auf ein Rotationszentrum (R) der flexiblen Halterungskonstruktion (28)
in Umfangsrichtung mit einem Abstand (A) voneinander angeordnet sind.
4. Antennenpositionierungssystem (10) nach Anspruch 3, wobei das erste und zweite Drehstellglied
(20) dafür ausgelegt sind, an einen Umfang der Nutzlast (26) anzugrenzen.
5. Antennenpositionierungssystem (10) nach Anspruch 2, wobei das erste und zweite Drehstellglied
(20) in Bezug auf das Rotationszentrum (R) der flexiblen Halterungskonstruktion (28)
im Wesentlichen um 90 Grad (A) voneinander entfernt sind.
6. Antennenpositionierungssystem (10) nach Anspruch 1, wobei die flexible Halterungskonstruktion
(28) dafür ausgelegt ist, angrenzend an eine geometrische Mitte der Nutzlast (26)
angeordnet zu werden.
7. Antennenpositionierungssystem (10) nach Anspruch 1, wobei die flexible Halterungskonstruktion
eine Kardangelenkkonstruktion (28) ist.
1. Système de pointage d'antenne (10) pour déplacer sélectivement une charge utile (26)
par rapport à une surface de montage (14), ledit système (10) comprenant une structure
de montage flexible (28) pour fixer de manière amovible la charge utile (26) à la
surface de montage (14), et étant
caractérisé par :
- au moins un actionneur rotatif (20) ayant une partie mobile (22) étant déplaçable
par rapport à une partie fixe adaptée pour être fixée sur la surface (14) ; et
- une tige de raccordement (24) se raccordant de manière mobile à une manivelle (22)
assemblée sur la partie mobile (22) au niveau d'une première extrémité (32) de cette
dernière, et adaptée pour se raccorder de manière mobile à la charge utile (26) au
niveau d'une second extrémité (34) de cette dernière.
2. Système de pointage d'antenne (10) selon la revendication 1, dans lequel au moins
un actionneur rotatif inclut un premier et un second actionneur rotatif (20) se raccordant
à une dite tige de raccordement respective (24) avec lesdites secondes extrémités
(34) desdites tiges de raccordement (24) étant adaptées pour se raccorder de manière
mobile au premier et second points de fixation respectifs (27) de la charge utile
(26).
3. Système de pointage d'antenne (10) selon la revendication 2, dans lequel le premier
et le second actionneur rotatif (20) sont espacés angulairement (A) l'un de l'autre
par rapport à un centre de rotation (R) de la structure de montage flexible (28).
4. Système de pointage d'antenne (10) selon la revendication 3, dans lequel le premier
et le second actionneur rotatif (20) sont adaptés afin d'être adjacents à un périmètre
de la charge utile (26) .
5. Système de pointage d'antenne (10) selon la revendication 2, dans lequel le premier
et le second actionneur rotatif (20) sont substantiellement espacés de 90 degrés (A)
l'un de l'autre par rapport au centre de rotation (R) de la structure de montage flexible
(28).
6. Système de pointage d'antenne (10) selon la revendication 1, dans lequel la structure
de montage flexible (28) est adaptée afin d'être juxtaposée à un centre géométrique
de la charge utile (26).
7. Système de pointage d'antenne (10) selon la revendication 1, dans lequel la structure
de montage flexible est une structure de joint universel (28).