IL309864A - Fin control actuation system - Google Patents

Description

FIN CONTROL ACTUATION SYSTEM This Application is a divisional application to Patent Application IL 277997.

FIELD OF THE INVENTION - The invention of the Patent Application is in the field of mechanisms used for steering and maneuvering airborne bodies, such as missiles, toward their targets, and particularly in the field of mechanisms based on fins (rudders) that protrude from the airborne body and move in the desired direction and degree in order to achieve the airborne body’s desired course of flight by aerodynamic maneuvering, also known as FAS (Fin Actuation Systems), as well as fin-based mechanical systems located in the rocket motor nozzle, and are used to steer missiles by diversion of exhaust gas (jet vanes), also known as TVC (Thrust Vector Control).

BACKGROUND OF THE INVENTION - There are known and familiar airborne bodies, such as missiles, which are steered to their target by an FAS system, which includes an assembly for actuating fins that protrude from the airborne body and controlling their angular position relative to the airborne body according to flight commands, known as FCAS (Fin Control Actuation System). Similarly, there are known and familiar missiles that are steered to their target using a TVC system (alone or in combination with FAS system).

The background of the invention of the Patent Application and an exemplifying embodiment of the invention itself will be described below in relating to a missile-type airborne body having a rocket propulsion system, and FCAS assembly which is used to steer a circumferential array of four protruding tail wings. However, a person skilled in the art would understand that the invention is also applicable to steering other airborne bodies (e.g. jet-powered cruise missiles, guided bombs, guided artillery shells, etc.), for steering a different plurality of fins (not necessarily four), and for steering other or additional types of fins (e.g. for steering a canard array of fins that are positioned while protruding from the front part of the airborne body or for steering an array of fins positioned in the middle of the airborne body). A person skilled in the art would also understand that the invention is also applicable to directing missiles, in its embodiment in a TVC system wherein the fins are implemented as jet vanes (using it alone or in combination with an FAS system).

In a rocket-propelled missile that is steered by tail control of four rear fins, the FCAS assembly includes four electro-mechanic actuators (corresponding with the four fins), and an electronic system that is connected to them, and they are all integrated, when packaged into an apparatus with a ring-like (toroidal) cross section. A ring-like apparatus, which when mounted in the missile, is positioned around the rear section of the missile motor and encompasses it and merges with the missile’s exterior line of design (the missile fuselage outer cover or case skirt).

Therefore, persons skilled in the art face the challenge of having to package the FCAS assembly given space limitations, due to the desire to make the outer diameter of the missile as compact as possible, starting with the dimensions of the missile motor in the rear (e.g. dimensions and geometry of the rocket motor's pressure control throat and gas expansion nozzle), while also having to provide adequate solution to the need of propelling the missile fins at the required torque (the need to transmit as high mechanical power as required, so that the steering of the fins will be rapid to precisely provide the missile with sharp maneuverability) with minimum backlash, and wherein the angular motion axes of the fins (the steering axes) are positioned perpendicular to the missile’s central longitudinal axis.

Reference is made to Fig. 1. Figure 1 schematically depicts in perspective the aforementioned packaging challenge (in the context of merely an exemplifying illustration) of an FCAS assembly for rocket-propelled missile 10, wherein the assembly is used to steer a circumferential array of four tail wings (not illustrated). Volume 20, having a toroidal ring like cross-section, is a geometric design constraint owing to the outer diameter D of missile 10 (a diameter that is usually sought to be minimized, e.g. for aerodynamic reasons, weight reduction, etc.), the dimensions of the missile motor in the rear section and its varying geometry (e.g. in the illustrated example – the design of nozzle 23 of rocket motor 25), the L-length dimension that can be allocated along the missile (a longitudinal dimension that is usually sought to be minimized for aerodynamic reasons, volume reduction, weight reduction, etc.), and wherein the angular motion axes (steering axes) of the fins (not illustrated), (four in the illustrated example) - 30, 35, 40, 45 are each positioned perpendicular to the central longitudinal axis 50 of the missile.

Therefore, in designing the FCAS assembly, persons skilled in the art are required to achieve high energy efficiency within the constraints of a relatively small packaging design, and which in the example in question also has a unique geometric form - a volume having a toroidal cross-section configuration with varying dimensions along its length (according to the design of the rocket motor's pressure control throat and gas expansion nozzle).

Prior to the invention which is the subject matter of the Patent Application, skilled persons addressed these challenges, for example, by positioning the electric motor axis of each of the fins parallel to the angular motion axis of that fin, and laying the gear transmission between them. Because of the volume constraints of the toroidal cross-section, such a configuration might require a longitudinal displacement of the array of motors relative to the plane of the angular motion axes of the fins. The array of motors is then positioned along the longitudinal axis of the missile, at a different plane than the plane of the angular motion axes of the fins and parallel to it, thereby requiring a gear transmissions to bridge the geometric distance between the different planes in addition to transmitting the power needed.

Reference is made to Figs. 2 and 3. Fig. 2 schematically depicts in perspective the aforesaid prior art packaging solution for missile 10 of FCAS assembly 215. Fig. 3 is a partial section side view of the prior art FCAS assembly 215 (without the fins), the array of motors (four in the illustrated example) - 250, 255, 260, 265 positioned along central longitudinal axis 50 of missile 10 in a circumferential configuration relative to central longitudinal axis 50, spanning over plane 270 that is perpendicular to central longitudinal axis 50. Plane 275 is also perpendicular to central longitudinal axis 50, on which the angular motion axes of fins 280, 285, 290, 295 extend while they are perpendicular in their directions to central longitudinal axis 50. Each of the motor axes is positioned parallel to the angular motion axis of the fin that it propels and spaced from it. Plane 270 is at a different plane than plane 275. Plane 270 is displaced from plane 275 and positioned parallel to it. The planes are spaced apart from each other at a dimension LPA, in a manner that, as mentioned, requires gear transmissions - 282, 287, 292, 297 to bridge the LPA geometric distance between the different planes.

Therefore, according to the aforementioned prior art, the FCAS assembly is actually packaged at two different planes that are displaced along the longitudinal axis of the missile, wherein gear transmissions are needed to bridge between the planes in a way that eventually reduce the volumetric efficiency and make it difficult to achieve the volumetric minimization sought by persons skilled in the art.

Moreover, according to the illustrated example, the transmission constraints call for parallel positioning of each of the motor axes in relation to the angular motion axis of the fin it propels, which also limits the ability to achieve the required compact packaging.

Moreover, as previously noted, the FCAS assembly is required to operate with minimum backlash. The mechanical precision requirements from the assembly in its operation, i.e. precision of the angular tilt of each of the fins, calls for tightening the tolerances and reducing the lost motion phenomenon (which is caused by the spaces between parts of the mechanism). According to the above prior art, the existing solution is to increase the diameter of the cog-wheel at the exit from each of the gear transmissions, in a manner that also increases dimensions, which in turn reduces volumetric efficiency and makes it difficult to achieve the volumetric minimization to which persons skilled in the art aspire.

At the same time, in the transmission field, beveloid gear transmissions (also referred to as conical involute gears) are known to be used for transmitting rotational mechanical energy from one point to another and enable producing a crossing angle or skew axes between two intermingled gears. Beveloid gears have long been used for marine applications and in the automotive field (e.g. in four-wheel drive vehicles for transmitting torque and rotational motion from the gearbox to the front axis that may not be in a parallel position).

Beveloid gears have been analyzed and discussed in the following publications: H.E. Merritt, "Gears", Pitman, London, 1955, pages 165- 170; A.S. Beam, "Beveloid Gearing", Machine Design, Vol. 26, December, 1954, pages 220-238; S.C. Purkiss, "Conical Involute Gears: Part 1", Machinery 89, 1956, pages 1403-1420; and C.C. Liu, C.B. Tsay, "Contact characteristics of beveloid gears", Mech. Mach. Theory, No. 37, 2002, pages 333-350.

Summary of the Invention - The invention solves the minimization and volumetric efficiency challenges faced by skilled persons, who are designers of mechanisms used for steering and maneuvering airborne bodies, and overcomes the shortfalls in the prior art previously discussed in the "Background of the Invention" chapter by implementing beveloid gears as a means for transmitting power from the electric motors in the assembly to the angular motion axes of the fins in the airborne body, in a manner that allows for compact packaging of all the system components (motors, transmission, axes of the fins) in a circumferential, toroidal ring like assembly, on a single plane, while enhancing propulsion performance of the airborne body’s fins, at the required torque, precisely and with minimum backlash.

In one aspect, the invention is a mechanism used to steer and maneuver airborne bodies, whether in an FCAS assembly of an airborne body (e.g. in a rocket-propelled missile, jet-powered cruise missile, guided bomb or a guided artillery shell) or in a TVC assembly in a missile. A mechanism that comprises at least one actuator, which is comprised of an electric motor having a first axis and a gear transmission for transmitting power from the electric motor to an angular motion axis of a fin (e.g. tail wing) having an angular motion around a second axis to steer the airborne body by aerodynamic maneuvering manner or TVC, as aforesaid, and wherein the mechanism in accordance with the invention, is characterized in that the said gear transmission is a beveloid gear type of gear.

In another and additional aspect of the invention, the beveloid gear transmission transmits power from the electric motor to the fin, wherein the motor axis is not parallel to the fin axis, but is positioned in creating an angle between the two axes.

In one embodiment of the invention, the mechanism, which is used to steer and maneuver airborne bodies according to the invention, is embodied as an FCAS assembly of a missile having a rocket propulsion system along its central longitudinal axis, wherein the mechanism is comprised of a circumferential array of four actuators, and is characterized in that - a. The circumferential array of the four actuators is installed in the assembly in an apparatus having a toroidal ring-like cross-section, which is adapted for installation around the rear section of the missile motor while encompasses it and merges with the missile’s exterior line of design, and b. Wherein the circumferential array of four actuators is packaged in one plane perpendicular to the central longitudinal axis of the missile, and c. The assembly is adapted for installation of four fins on top of it, each of which has an angular motion revolving around an axis by means of the circumferential array of four actuators, and d. In each of the actuators, the motor motion axis is not parallel to the fin axis, but is positioned in creating an angle between the two axes, and e. Once the assembly is installed in the missile, the four fins serve as tail wings of the missile for steering it by tail control of the four fins.

In another and additional aspect of the invention, the invention is embodied in the airborne body that comprised a mechanism, which is used for steering and maneuvering airborne bodies according to the invention, whether in an FCAS assembly of any airborne body (e.g. in a rocket-propelled missile, jet-powered cruise missile, guided bomb or a guided artillery shell), or in a TVC assembly in a missile. In other words, the invention is embodied in the airborne body in which the mechanism is installed, which is characterized in that the gear transmission used to transmit power from an electric motor to an angular motion axis of a fin having an angular motion that revolves around an axis, is gear transmission of beveloid gear type.

In another and additional aspect, the invention embodies a general method in the field of mechanisms, which are implemented to steer and maneuver airborne bodies, whether in an FCAS assembly of any airborne body (e.g. in a rocket-propelled missile, jet-powered cruise missile, guided bomb or a guided artillery shell) or in a TVC assembly in a missile. That is to say, a general method in the field of mechanical systems that are based on fins that move in the desired direction and to the desired extent in order to achieve the desired flight path of an airborne body. A method that comprise the steps of - a. Packaging the airborne body with an assembly comprised of gear transmissions of the beveloid gears type as a means for transmitting power from the electric motors in the assembly to the angular motion axes of the fins of the airborne body; and b. Steering the airborne body by transmitting power, as needed, from the electric motors in the above assembly to the angular motion axes of the fins of the airborne body through the transmissions in order to change their position in an angular motion, thereby obtaining the desired flight path of the airborne body.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings BRIEF DESCRIPTION OF THE ATTACHED FIGURES - Different aspects of at least one embodiment of the invention that is the subject of the Patent Application will be described below, with reference to the accompanying figures (while no scale should be attributed to them). The figures are presented for illustrative purposes only and for facilitating an understanding of the different aspects of the invention and the possible configurations for its actual embodiment. The figures are part of the description, but should not be construed as limiting the invention in any way. In the figures, an identical or similar element that is visually depicted in several figures could be tagged by uniform numbering. For clarity, not every element was tagged in each of the figures. In the following figures: Fig. 1 schematically depicts in perspective the packaging challenge facing a person skilled in the art in the context of merely an exemplifying illustration of an FCAS assembly of a missile having a rocket propulsion system, wherein the assembly serves for steering a circumferential array of four tail wings.

Figs. 2 and 3 schematically depict (respectively) in a perspective view and partial cross-section side view, the prior art solution for the packaging challenge described above in reference to Fig. 1.

Figs. 4 and 5 schematically depict (respectively), in a perspective view and zoom-in perspective view, an example of an FCAS assembly according to the invention, as it is installed, according to the illustrated example, in a missile having a rocket propulsion system, wherein the assembly according to the invention is used for steering a circumferential array of four tail wings (similar to the missile illustrated in Figs. 1 - 3).

Figs. 6 and 7 schematically depict (respectively) a front view and side view (in a partial cross-section) of the FCAS assembly according to the invention that is illustrated in Figs. 4 and 5.

Fig. 8 depicts an "exploded" view of components of one actuator, four of which are installed in the FCAS assembly according to the invention, which is illustrated in Figs. 4-7.

Fig. 9 depicts an "exploded" view of components of one actuator, four of which are mounted in the FCAS assembly according to the invention, that is illustrated in Figs. 4-8, alongside a bracket component that is adapted for inserting the actuator and installing it around a rear section of the missile motor, while encompassing it and merging with the exterior design line of the missile.

Fig. 10 depicts side by side, each in front view and in a side view (in a partial cross-section), the prior art solution to the packaging challenge described above in reference to Fig. 1, according to the prior art solution illustrated in Figs. 2 and 3, compared with the solution to the same challenge as provided by the FCAS assembly according to the invention, which is illustrated in Figs. 4-9.

Claims (4)

CLAIMS -

1. A mechanism for steering and maneuvering an airborne body comprised of - at least one actuator comprising - an electric motor having a first axis, and a gear transmission for transmitting power from said electric motor to an angular motion axis of a fin that has an angular motion around a second axis to steer the airborne body by aerodynamic maneuvering or TVC, and wherein the mechanism is characterized in that - said gear transmission is a beveloid gear type of transmission.

2. The mechanism for steering and maneuvering an airborne body according to claim 1, wherein - said beveloid gear transmission transmits power from said electric motor to the fin, while said first axis of the motor is not parallel to said second axis of the fin, but is positioned in creating an angle between the two axes.

3. An airborne body that comprised a mechanism for steering and maneuvering according to claim 1.

4. A method for achieving the desired flight path of an airborne body by means of fins that move in the desired direction and to the extent required for achieving the desired flight path of the airborne body by aerodynamic maneuvering or TVC, which comprise the steps of - a. packaging the airborne body with an assembly comprised of transmissions of beveloid gear type as a means for transferring power from the electric motors in the assembly to the angular motion axes of the fins of the airborne body; and b. steering the airborne body by transferring powers, as required, from the electric motors of said assembly to the angular motion axes of said fins of the airborne body through said transmissions of beveloid gear type in order to change their position in an angular motion, thereby obtaining the desired flight path of the airborne body. Webb+Co. Patent Attorneys