Aeronautics and astronautics – Aircraft structure – Fuel supply
Reexamination Certificate
2002-12-30
2003-12-30
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft structure
Fuel supply
C356S005010, C356S152100, C356S139030, C250S206100, C250S206200
Reexamination Certificate
active
06669145
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to radiation reflectors, and, more particularly, to frequency discrimination between multiple modulated reflectors for simultaneous remote position sensing, such as for in-flight refueling of aircraft.
BACKGROUND OF THE INVENTION
Retroreflectors are well-known devices in the field of electromagnetic and optical radiation. A retroreflector, such as a corner reflector or corner cube, made by arranging three reflecting surfaces at mutual 90 degree angles, is often used as a cooperative target for locating and ranging because its signal return decreases as 1/R
2
, where R is range, instead of 1/R
4
, the performance of a normal flat mirror. Retroreflectors receive radiation energy and reflect such energy back in the direction from which the radiation energy came. Without modification, a retroreflector will return the radiation energy with the same general characteristics of amplitude versus time behavior as the incident radiation. Methods of modulating the characteristics of the amplitude versustime behavior of reflective radiation signals have been developed using modulated retroreflectors in different applications.
Presently, any modulation of radiation signals reflected from a retroreflector is caused by changing some characteristic of the retroreflector to alter its performance. For example, U.S. Pat. No. 6,233,088 to Roberson et al. discloses modulating a radiation signal by deforming a reflecting surface of the retroreflector.
By example only, one application of modulated retroreflectors is in the field of in-flight aircraft refueling. Pilots in manned aircraft use visual cues to locate, approach, and station a receiving aircraft relative to a tanker aircraft, at which point personnel on the tanker manipulate a boom to mate with the proper receptacle on the refueling aircraft or the pilot of the receiving aircraft approaches and mates to a drogue trailing from the tanker. This type of in-flight refueling operation requires skilled pilots in both aircraft to position and orient the aircraft and either a skilled boom operator to control the position of the refueling boom relative to the receiving aircraft or a skilled pilot to control the position of the receiving aircraft relative to the drogue. Because refueling operations are manually controlled at least in part, the chance of pilot or operator error increases the potential for a collision between the two aircraft or between the receiving aircraft and the refueling boom or drogue. Automation of these processes for unmanned aircraft requires location of cueing features on the tanker or drogue so an unmanned aircraft can perform the same process of locating a tanker and positioning itself relative to the tanker so that a skilled operator on the tanker may guide the boom into the desired position or relative to the drogue.
Other prior art systems for in-flight refueling of aircraft use optical systems with multiple reflectors. Each reflector may be distinguished from another by the pattern of their placements. Another method to distinguish the position of each of several retroreflectors is modulation of each reflected radiation signal at a different frequency. The different frequencies of modulation of the reflected radiation signals allow a frequency selective position measuring system to separately interpret the information provided by each reflected radiation signal in order to obtain precise measurement of the position of each retroreflector and, thus, the orientation of the structure upon which the retroreflectors are mounted. Presently, systems for simultaneously measuring positions of several reference points use an imaging system to observe positions of an array of retroreflectors distinguished by placement in a characteristic pattern. An alternative prior art method is the use of a non-imaging position measuring sensor system such as a duo-lateral photodiode position sensor that separately measures the different frequencies of modulation of radiation signals using electrical modulation of sources such as a light emitting diodes. This method can be extended to an array of retroreflectors by using electrical modulation of corner reflectors with a deformable reflecting surface, each at a characteristic frequency.
Typically two methods are used for implementing cooperative remote sensing: modulated or continuous light sources in a known array on the target, or modulated or unmodulated retroreflectors in a known array on the target. Unmodulated sources emit continuous wave signals and reflectors reflect incident signals back to an imaging position-sensing radiation detector and position determining system, which could be a pilot's eyes or a video camera and image processor. Image sensors, such as video cameras, respond only to the intensity (and perhaps color) of light, as their frame rate is too slow to respond to modulation frequencies above a few hertz. Modulated sources and reflectors emit or reflect modulated signals back to non-imaging sensors. Non-imaging position sensors such as duo-lateral photodiodes have much faster speed of response, so they can measure the position of multiple sources if they are modulated at different frequencies so that the measurements can be separated based on frequency.
One prior art duo-lateral photodiode position sensor system uses light emitting diodes (LEDs), each emitting light modulated at different frequencies to enable a remote sensing device to measure the exact coordinate of each LED. However, using LEDs to create a coordinated source array requires electrical power and wiring to energize and modulate the emitted light of the LEDs. Another method of modulating a radiation signal is disclosed in U.S. Pat. No. 6,233,088 to Roberson et al. The Roberson method consists of selectively mechanically deforming at least a portion of a reflective surface of a reflector. As when using LEDs to produce a modulated radiation signal, the Roberson method, too, requires electrical power to produce a modulated reflected radiation signal. The necessity of a power source and the associated wiring to provide modulation for a remote sensing system can be a substantial disadvantage to implementing an automated remote sensing system for aerial refueling.
In order to reduce the risk of human life, unmanned air vehicles (UAV) have been employed and are being further developed for surveillance and smart weapon technology. An extension of an unmanned air vehicle is the use of such an aircraft for offensive and defensive combat strikes. The unmanned combat air vehicle (UCAV) was designed and is being further developed as a safe and affordable weapon system to expand the capabilities of an air defense and strike system. The goal of a successful UCAV design would provide the strength, features, and functionalities of a current strike fighter with limited human intervention by automating tasks that would have previously required human control. Ideally, a UCAV could perform all the tasks if not more tasks of a manned combat air vehicle, with limited or no human intervention required. For example, in order to be able to operate a UCAV during prolonged periods of time without landing, the vehicle would need to be refueled from a tanker aircraft. Thus it would be advantageous to design an automatic positioning system that is reliable enough to enable a UCAV to automatically position itself in relation to a tanker aircraft for refueling.
BRIEF SUMMARY OF THE INVENTION
A fluid-motion-powered modulated retroreflector is therefore provided to modulate radiation signals in a unique manner to permit each retroreflector in an array to be discriminated and individually located. Such fluid-motion-powered modulated retroreflectors include a chopping wheel or a pair of polarizing filters, or polarizers, that may modulate the reflected radiation and a propeller to rotate a chopping wheel or one of the polarizing filters. Motion of the propeller through a fluid such as air causes rotational velocity of the propeller and eliminates the need for an independent
Alston & Bird LLP
Barefoot Galen L.
The Boeing Company
LandOfFree
Apparatus, method and system for fluid-motion-powered... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus, method and system for fluid-motion-powered..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus, method and system for fluid-motion-powered... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3129521