Patent Application
20220178665
The present disclosure relates to control actuation systems and more particularly to a control plate-based control actuation system with a reduction in actuators at no loss of performance.
A typical Control Actuation System (CAS) in a missile or other projectile drives control surfaces with separate actuators. The number of separate actuators depends upon the number of control surfaces or fins that are deployed and, in some cases, includes four control surface and four corresponding actuators. These actuators tend to be expensive, including the actuator itself as well as the motor controllers, feedback sensors, and the like. To drive down the cost of the CAS it is desirable to reduce actuator count and associated electronics.
There are various existing solutions, all of which come at a loss of performance. The most common solution is to eliminate yaw control and fly in a bank-to-turn configuration where only two actuators are used. There, one actuator controls two fins to generate roll moments and the other actuator controls two fins to generate pitch. This methodology results in a reduced response rate of the maneuverability for the system and effects the ability to engage with fast maneuvering targets.
Another common approach to reducing actuator count is to tie two opposing fins together so that they can only contribute to pitch control using a single actuator. The remaining two fins each have an actuator and are responsible for roll and yaw control, respectively. This results in not being able to get full roll and yaw capabilities of independently controlling the typical four control surfaces. This methodology also reduces the system's ability to engage fast maneuvering targets.
A less common approach to reducing actuator count is to use a transmission that takes three rotational inputs from motors and using a series of gears distributes that to the four control surfaces. This is not a common solution because of the complexity, the backlash, the losses, and the increased weight of a transmission often outweighs any benefits of eliminating one actuator.
Certain solutions use rotating systems such as helicopter rotors. These systems have to be complex, heavy duty, and robust to transfer the pitch and cyclic to highly loaded and fast spinning rotor blades. Some cases have complex gear box mechanisms to generate the pitch and cyclic effects or hydraulic systems focused on a hemispherical bearing system.
Other solutions focus on bank to turn systems. In some cases, they use high frequency voice coils so that the electronics can spin with the shell while only the lifting surfaces are “derolled.” While it may be an interesting approach, it is a different problem from that solved by the present disclosure as it only results in bank to turn capability (pitch & roll), while the present approach results in skid turning capability (pitch, yaw, and roll. independently).
Wherefore it is an object of the present disclosure to overcome the above-mentioned shortcomings and drawbacks associated with the conventional control actuation systems.
One aspect of the present disclosure is A control plate-based control actuation system for steering a moving object, comprising: a control plate having at least four fin linkages for connecting at least four fins to the control plate; and three actuators configured to move the control plate to produce movement in two or more of the at least four fins; wherein the three actuators work to either push/pull or tilt the control plate control deflections of the two or more of the at least four fins.
One embodiment of the control plate-based control actuation system is wherein the three actuators are linear actuators. In certain embodiments, the three actuators work together to either push/pull or tilt the control plate according to a three-dimensional planar equation a(x−Px)+b(y−Py)+c(z−Pz)=0.
Another embodiment of the control plate-based control actuation system is wherein the control actuation system is in a tail section of the moving object. Yet another embodiment of the control plate-based control actuation system is wherein the control actuation system is in a mid-body section of the moving object.
Still yet another embodiment of the control plate-based control actuation system further comprises a guidance system for controlling the control plate-based control actuation system to steer the moving object toward a target. In some cases, combinations of pitch, yaw, and roll inputs are combined in an actuator mapping and generate pitch, yaw, and roll commands.
In certain embodiments, the control plate defines a plane and is connected to the four control surfaces via right angle linkage.
Another aspect of the present disclosure is a control plate-based control actuation system for steering a moving object, comprising: a control plate having at least four fin linkages for connecting at least four fins to the control plate; and three actuators configured to move the control plate to produce movement in two or more of the at least four fins; wherein a first actuator is configured to push or pull the control plate to move all fins simultaneously to create a roll moment in the moving object; wherein a second actuator is configured to push or pull the control plate to move a first pair of fins located opposite one another on the control plate to create a pitch moment in the moving object; and wherein a third actuator is configured to push or pull the control plate to move a second pair of fins located opposite one another on the control plate to create a yaw moment in the moving object.
One embodiment of the control plate-based control actuation system is wherein the control actuation system is in a tail section of the moving object. In some cases, the control actuation system is in a mid-body section of the moving object.
Another embodiment of the control plate-based control actuation system further comprises a guidance system for controlling the control plate-based control actuation system to steer the moving object toward a target. In certain embodiments, the first actuator, second actuator, and third actuator are linear actuators.
Yet another aspect of the present disclosure is a method of steering a moving object, comprising: providing a control plate-based control actuation system on the moving object, the control plate-based control actuation system comprising: a control plate having at least four fin linkages for connecting at least four fins to the control plate; and three actuators configured to move the control plate to produce movement in two or more of the at least four fins; wherein the three actuators work together to either push/pull or tilt the control plate to control deflections of the two or more of the at least four fins.
One embodiment of the method further comprises: pushing or pulling the control plate, via a first actuator, to move all fins simultaneously to create a roll moment in the moving object; pushing or pulling the control plate, via a second actuator, to move a first pair of fins located opposite one another on the control plate to create a pitch moment in the moving object; and pushing or pulling the control plate, via a third actuator, to move a second pair of fins located opposite one another on the control plate to create a yaw moment in the moving object.
Another embodiment of the method further comprises controlling the control plate-based control actuation system, via a guidance system, to steer the moving object toward a target. In some cases, the control actuation system is in a tail section of a round. In other cases, the control actuation system is in a mid-body section of the moving object.
Yet another embodiment of the method further comprises controlling the control plate-based control actuation system, via a guidance system, to steer the moving object toward a target.
These aspects of the disclosure are not meant to be exclusive and other features, aspects, and advantages of the present disclosure will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims, and accompanying drawings.
The foregoing and other objects, features, and advantages of the disclosure will be apparent from the following description of particular embodiments of the disclosure, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosure.
The control plate concept according to the principles of the present disclosure has the benefit of reducing the actuator count, at no loss of pitch, yaw, or roll control. The backlash of the system can be easily controlled through tolerancing of the interfaces between the control plate and the actuator and the control plate and the fin linkages. In some cases, anti-backlash gears or knuckle joints and threaded rods may be used to manage the backlash. And compliant materials (e.g., nylon bushings) can be used at any of the joint locations to eliminate any remaining backlash.
A swash plate is often used in helicopter rotors to combine two control inputs pitch (up/down) and cyclic (forward/back and left/right) inputs and rotate the individual rotor blades a specified amount versus their angular location throughout rotation. Here, three control inputs (Pitch, Yaw, and Roll) are mapped to three linear actuator deflections. In one embodiment, those deflections push/pull (if all actuators move together) and tilt (if they move proportionally) the control plate, which is connected to the control surfaces using linkages.
In one embodiment, pushing/pulling the control plate moves all of the control surfaces together, generating a roll input. Tilting the control plate moves opposing control surfaces and generates pitch and yaw inputs. Combinations of pitch, yaw and roll inputs can be combined in the actuator mapping, and generate output pitch, yaw, and roll commands. Assuming linear control (common in missile systems), combining inputs like this comes at no loss of control performance. Even outside of the linear region, the losses are small and are identical to the four actuator systems, but with all the benefits of a reduced actuator system.
In one embodiment, a missile tail kit is shown, but the present disclosure could apply to any system where three control inputs need to be mapped to four or more outputs.
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As noted previously, common CAS configuration is four motors to control four active surfaces (e.g., fins). Reduction of actuators are typically done by either limiting control axes, transmissions, or tying surfaces together. In some cases, one actuator moves two pitch fins together, and another actuator moves two roll fins together. In all cases these prior systems either limit capability in one or more axes or eliminates a control axis all together.
In one embodiment of the present disclosure, a control plate is used as a low-cost skid steer (independently controlled pitch, yaw, and roll control axes) projectile control system. The system can be built “around” any central geometry (i.e. if this is a nose mounted guidance system it can be built around a seeker, or if this is a tail mounted guidance kit it can be built around a rocket nozzle or other motor like a jet engine) while still using only three actuators. There are other missile control systems that use three actuators, but they use complicated gear boxes and cannot be built around a central geometry. Here, low cost linear actuators are used to create the motion of the control plate that translates to the control surface deflections.
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In one embodiment of the present disclosure, the control plate shape is arbitrary. It is simply a way of defining a plane that the four or more linkages and three actuators are connected to. Each fin's movement is a function only of how much its linkage point has moved. It is not affected by rotation of the control plate about the same axis that the linkage is attached. It is only affected by the push/pull of the total control plate (pitch), and the rotation about the axis 90° out of phase of the linkage points (cyclic). By each fin being sensitive to two movement directions, but not a third, enables combined Pitch, Yaw, and Roll control inputs for three independent control axes. Since the control plate is simply defining a plane, only 3 “points” are required to fully define that plane hence, only three linear actuators.
While the shape of the control plane can be somewhat arbitrary, for the control algorithms it is assumed to be a three-dimensional plane that is capable of being translated or rotated. In certain embodiments, the linkage location is distributed roughly equally to balance stresses/actuator forces. The three-dimensional points where the actuators are linked to the control planes are defined as P, Q, and R, each with unique X, Y, and Z coordinates (Px, Py, and Pz for example). The coordinates of P, Q, and R are known. The Y and Z of the actuator linkage points are defined in the design of the CAS (they represent the horizontal and vertical offsets of the actuators from the missile centerline). The X component can easily be resolved from the actuator feedback. With the knowledge of the P, Q, and R coordinates the normal vector of the control plane is defined as {right arrow over (n)}={right arrow over (PQ)}×{right arrow over (QR)}=a,b,c
. The
a,b,c
coefficients can then be used in the three-dimensional planar equation a(x−Px)+b(y−Py)+c(z−Pz)=0 to calculate the three-dimensional location of any point on this plane, including the fin linkage locations. Similar methodology can be used to transform the fin linkage location to a fin deflection, as well as going from a desired fin deflection back to required actuator commands.
The control plate-based control actuation system has several benefits, including three independent control axes using only three linear actuators. Linear actuators tend to have negligible internal backlash; therefore, the backlash of the system should be controllable via tolerance control of the “slop” in the linkage locations as described above. An arbitrary control plate shape can be built around other components such as a rocket nozzle, electronics, or rotating geometries such as a drive shaft. This concept can be applied to any number of control surfaces assuming they physically fit in the space available.
Referring to
In certain embodiments, pushing or pulling the control plate using a first actuator moves all fins simultaneously to create a roll moment in the moving object. In some cases, pushing or pulling the control plate using a second actuator moves a first pair of fins located opposite one another on the control plate to create a pitch moment in the moving object; and pushing or pulling the control plate using a third actuator moves a second pair of fins located opposite one another on the control plate to create a yaw moment in the moving object.
It is to be understood that the present invention can be implemented in various forms of hardware, software, firmware, special purpose processes, or a combination thereof. In one embodiment, the present invention can be implemented in software as an application program tangible embodied on a computer readable program storage device. The application program can be uploaded to, and executed by, a machine comprising any suitable architecture.
While various embodiments of the present invention have been described in detail, it is apparent that various modifications and alterations of those embodiments will occur to and be readily apparent to those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present invention, as set forth in the appended claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various other related ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items while only the terms “consisting of” and “consisting only of” are to be construed in a limitative sense.
The foregoing description of the embodiments of the present disclosure has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the present disclosure be limited not by this detailed description, but rather by the claims appended hereto.
A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the scope of the disclosure. Although operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.
While the principles of the disclosure have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the disclosure. Other embodiments are contemplated within the scope of the present disclosure in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present disclosure.
