Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Missile or spacecraft guidance
Reexamination Certificate
2002-09-11
2004-04-20
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Missile or spacecraft guidance
C244S003100, C244S003110, C244S003140, C244S003150, C244S003190
Reexamination Certificate
active
06724341
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to munitions, and it particularly relates to an orientation referencing system designed to measure a munitions angular orientation and position (distance from a ground point) with absolute onboard referencing. This orientation referencing system offers advantages to the guidance and control of smart munitions. Other advantages of the orientation referencing system implementation include: (1) the capability of a smart munition with such a sensing system to be capable of determining its position and orientation while in flight with respect to a point on the ground, (2) the capability of a munition to have autonomous orientation as a single munition (no requirements to triangulate with other munitions) to provide the capability of one hit, one kill, and (3) the sensing system will be minimally intrusive and consume relatively very low power.
2. Background of the Invention
Future combat systems will require a significant reduction in weight and a significant increase in performance for both platforms and munitions. Significant gains have been achieved in the areas of Micro-Electro-Mechanical (MEMs) technologies which, in turn, have made possible a significant reduction in the size and weight of accelerometer mechanisms and substantial performance enhancement of these devices under extreme operating conditions.
To take advantage of these advances and to meet the requirements of the U.S. Army's future needs in the areas of precision-guided direct-and indirect-fire munitions, it is important to develop sensors with unique characteristics that can be integrated reliably and economically into small-and medium-caliber munitions as well as long-range munitions. In particular, it is desirable to embed electromagnetic sensors in the munitions to enhance the guidance and control of munitions in flight and improve their accuracy. These sensors will provide real-time information on the orientation, rotation and position of munitions as well as define the orientation vectors of the center of mass. Such real-time information, used alone or in conjunction with gyroscopes and inertial measurement units (IMUs) will enable the deployment of a new generation of affordable munitions characterized by highly-steerable guidance and navigation control systems that will guide them to their targets with unprecedented accuracy, delivering heretofore unimaginable lethality with a minimal expenditure of ammunition.
Radar-based guidance of munitions is currently based upon the use of radio frequency (RF) antennas printed or placed on the surface of munitions to reflect RF energy emanating from a ground-based radar system. The reflected energy is then used to track the munition or the stream of bullets on the way to the target. In this scenario, the targeting radar illuminates both the munition and the target. Energy reflected from the munition and target provides tracking information. The radar measures the time difference between the return signals from the munitions in flight and from the target to determine munition angle information and to determine of the munition″s rotation and up-down reference.
RF antennas receive and radiate energy as a function of their size and geometric shape. Typically, a tracking radar is in the Ku band with a nominal frequency range of 12.4 GHz to 18 GHz and a freespace wavelength of 1.67cm-2.4 cm. This largely defines the size of the antennas that can be used. A narrow beam width of the reflected signal is important in achieving the required measurement of the difference between the pulse received from the illuminating radar and the target return and an accurate measurement of the roll angle for the munition.
Maximizing the magnitude of the return from the munition is important to distinguish the munition from “clutter.” However, it is quite challenging to shape the antenna radiation pattern and its beam width for a munition. In particular, methods that rely of measuring the reflected radar energy currently require that the sensors (RF antennas) be placed on the surface of the munition. The added requirement that the antennas be gun-hardened and survivable during the extreme launch environment characteristic of small and medium caliber munitions greatly limits the effectiveness of the current generation of antennas.
Corrections to a munition″s flight path are currently possible but only if the munitions are equipped with an additional suite of internal sensors such as Inertia Measurement Unit (IMU″s), accelerometers, and gyroscopes. These sensors are relatively complex and inaccurate for the intended purpose herein. In addition, these sensors require inputs from a Global Positioning System (GPS) to define the munition″s orientation vectors.
The inherent problems associated with these components are manifold. The position of the munition is determined by a double integration of the acceleration signals sensed by onboard accelerometers. Integration errors and accelerometer drift interject various inaccuracies that become intolerable when these sensed and processed signals are used to determine the error signal for the control system of the munition.
Error signals should not depend on the signals being sensed or processed outside the munition while in flight. The dependency on onboard accelerometers, IMUs, gyroscopes, or other inertial sensing mechanisms that require other external calibration and correction signals, make the feedback loop so large that the resulting onboard error signal does not accurately represent the midcourse correction needed to strike the intended target. Moreover, reliance on GPS as part of the control system is problematic as GPS can be electronically jammed.
Hence, the current suite of electromagnetic sensors and even electromagnetic sensors augmented by accelerometers, IMUs, gyroscopes, and GPS, are incapable of meeting the increasingly stricter requirements for precision delivery of munitions. A new generation of sensors is thus required to meet this need.
These new sensors should be capable of providing onboard information about the angular orientation of the munition, i.e., its pitch, yaw, and roll angles, as well as its absolute position relative to a ground command station or the target (moving or stationary).
It is also desirable to have the capability to configure the sensory systems to provide onboard information about the position and orientation of the munition relative to an incoming target so that they can be used as a homing sensor. To achieve this goal, the sensors should require minimal or no computational and signal processing capability at the ground (command) station. By minimizing the role of the ground or command station in the guidance and control loop, the related sources of error and system and operational complexity that are otherwise introduced into the overall system can generally be minimized or eliminated.
In particular, the feedback loop needs to be kept as small as possible, thus requiring an autonomous onboard referencing orientation and position sensor system. In addition, the development of affordable guidance and control technologies is dependent on the development of accurate and reliable position and orientation sensors that are inexpensive to produce as well as easy to integrate into various munitions.
Currently, there is no means of meeting these requirements. Thus, there is a great and still unfulfilled need for a system of efficaciously and economically embedding guidance and control components in gun-fired munitions.
SUMMARY OF INVENTION
The development of an autonomous onboard absolute position and orientation referencing system (also referred to herein as “the referencing system”) of the present invention fills this void by providing a means of efficaciously and economically embedding guidance and control components into the fins of supersonic, highly maneuverable small, medium-caliber and long range munitions. Embedded resonant cavities, which are an integral part of the on-board guidance and control s
Niver Edip
Pereira Carlos M.
Rastegar Jahangir S.
Gregory Bernarr E.
Moran John F.
Sachs Michael C.
The United States of America as represented by the Secretary of
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