BACKGROUND OF THE INVENTION

&null;0002&null; 1. Field of the Invention

&null;0003&null; The present invention relates to control of miniature unmanned aircraft, wherein directional control is remotely controlled, and other aspects of flight such as instantaneous attitude and altitude conditions are automatically controlled from within the aircraft.

&null;0004&null; 2. Description of the Prior Art

&null;0005&null; Small, unmanned aircraft operate under certain constraints imposed by the government. Aircraft weighing less than fifty-five pounds, not able to reach speeds of two hundred miles per hour, and having flight direction controlled from the ground need not be licensed by civil air authorities. Because small, unmanned aircraft are capable of many civilian uses in gathering aerial data and transmitting data, it is extremely desirable to use them in place of larger, manned aircraft which operate at much greater costs, are subject to severe restrictions, and are susceptible to creating much more severe hazards in the event of mishaps.

&null;0006&null; Small unmanned remotely controlled aircraft, popularly known as &null;model&null; aircraft, have been utilized by hobbyists for years. Such aircraft, when built to sufficient scale, would be adequate in some ways to play a role in data acquisition and transfer. However, traditional model aircraft are intended to be flown within a limited radius from a person controlling the aircraft, under visual line-of-sight control, and usually over areas dedicated to that purpose. Utilizing small, unmanned aircraft over greater areas, for example by radio line-of-sight, on missions demanding greater precision in flight control imposes demands which cannot be met by traditional model aircraft.

&null;0007&null; One severe problem is that of maintaining appropriate attitude. When, for example, taking a sequence of optical scans, such as multispectral &null;pushbroom&null; scans, the data becomes much more useful, or more immediately useful, if taken from the same vantage point. Otherwise stated, it is desirable to maintain the data acquisition platform at a constant orientation to the surface of the earth. This is next to impossible to accomplish if relying upon the &null;line of sight&null;, from the ground control methods of traditional model aircraft.

&null;0008&null; Constant orientation relative to the surface of the earth requires close control over both attitude and altitude of the aircraft. Flight control of aircraft could be entirely automated using sufficient sensors, combined with microprocessors and data inputs such as by the Global Positioning System (hereinafter, GPS) and by preprogrammed flight instructions. Particularly addressing civilian uses in the United States, it is highly desirable to have an unmanned aircraft which is light enough to avoid the fifty-five pound limit which is a threshold above which severe restrictions on use of an aircraft are imposed, and which cannot operate under sustained independent directional control. There exists a need art for aircraft which have minimized the burden of flight control imposed on external supervision by performing certain tasks internally, while still having directional control originating remotely, thereby avoiding undue restrictions on unmanned, miniature aircraft.

SUMMARY OF THE INVENTION

&null;0009&null; The present invention sets forth a method and apparatus for meeting the fore stated need. To this end, small, unmanned aircraft are provided with certain onboard flight sensors, radio reception capability, and an onboard microprocessor capable of processing internally generated positional and attitude data and externally generated directional control to arrive at attitude, altitude, and directional control sufficient to meet the needs of long range data acquisition and transfer. Directional control is derived from remote signals, while attitude and altitude control are provided in conjunction with other flight control aspects internally within the aircraft. The necessary apparatus is sufficiently small and light that the aircraft can accommodate many forms of data acquisition sensors and data conversion, retain data in memory, and transmit data to the ground, while still having significant range and altitude capabilities.

&null;0010&null; Accordingly, it is one object of the invention to provide a miniature, unmanned aircraft suitable for acquiring and transferring data, which can maintain flight stability automatically while operating under remote control as to flight path.

&null;0011&null; It is another object of the invention to minimize types of control which must be generated remotely, and limit this control to directional or flight path control.

&null;0012&null; It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.

&null;0013&null; These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWING

&null;0014&null; Various other objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawing, which is a diagrammatic, side elevational view of an aircraft equipped to practice the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

&null;0015&null; The drawing figure shows a miniature, unmanned aircraft 10, the principal purpose of which is to acquire or transmit data or both. Acquisition of data signifies that aerial images of ground characteristics and other data may be obtained by sensors such as, for example, digital cameras from the air. Aircraft 10 has an airframe including a fuselage 12, a wing 14, a reciprocating piston internal combustion engine 16 and associated fuel supply system (not separately shown) carried aboard the airframe, and a propeller 18 drivably connected to engine 16. The engine will be understood to include a fuel supply system (not separately shown) carried aboard the airframe. The airframe supports control surfaces such as elevator, rudder, flaps, and ailerons. The latter are shown representatively by rudder 20. Each control surface has a servomechanism, shown representatively as servomechanism 22.

&null;0016&null; Aircraft 10 is capable of acquiring data or transmitting data or both acquiring and transmitting data. To this end, a mission data handling apparatus 24 disposed selectively to acquire data or transmit data or to both acquire and transmit data is provided. Apparatus 24 may be, for example, a multispectral instrument, an infrared or near infrared sensor, or any other sensor which may be carried aboard miniature, remotely controlled data gathering or transmitting aircraft.

&null;0017&null; Aircraft 10 has a remotely controlled guidance system having a microprocessor 26 disposed to manage flight, a radio frequency transceiver 28 carried aboard the aircraft and disposed to receive remotely generated flight direction commands and to communicate flight direction commands to microprocessor 26, a Global Positioning System (GPS) receiver 30, and a plurality of sensors disposed to sense data relating to stabilization and altitude of aircraft 10. These sensors include flight stabilization sensors including a roll sensor 32, a pitch sensor 34, and a yaw sensor 36, and redundant altitude sensors including a laser or acoustic altimeter 38 and a barometric pressure altimeter 40. A pitot tube 42 serves as a velocity sensor. A flux gate compass 44 determines direction of aircraft 10. The functions of pitot tube 42 and flux gate compass 44 may be redundantly supplemented by calculations using GPS signals considered with respect to time.

&null;0018&null; Microprocessor 26 will be understood to be a complete system including all necessary programming and memory devices (neither separately shown).

&null;0019&null; In operation, aircraft 10 is controlled from a suitable ground station (not shown) or other source of radio frequency command signals. These signals include directional commands which constitute the only source of directional instruction. No programming contained within microprocessor 26 includes predetermined directional instruction. However, programming provided within microprocessor is capable of processing inputs from the attitude and altitude sensors, and of generating command signals which are then transmitted to servomechanisms represented by servomechanism 22. In the preferred embodiment, microprocessor 26 can, by considering inputs from the various sensors and also GPS receiver 30, determine its location, attitude, altitude, and velocity. These characteristics may be transmitted to the ground station via transceiver 28. This arrangement avoids the restrictions which may be imposed on aircraft capable of guiding their own flight, since although the ground station operator knows where aircraft 10 is, where aircraft 10 is headed, and its velocity, only attitude and altitude data and internally derived command signals are generated within aircraft 10.

&null;0020&null; The invention is a method of controlling aircraft 10 such that flight stabilization is automatically performed within aircraft 10, and flight direction is performed exclusively by external remotely generated signals. The method comprises an initial step of providing aircraft 10 in the form described above.

&null;0021&null; A subsequent step is that of receiving remotely generated radio frequency flight direction commands on transceiver 28 and transmitting the flight direction commands to microprocessor 26.

&null;0022&null; Another step is that of causing at least one and preferably all of the flight stabilization sensors 32, 34, 36 to transmit sensed data to microprocessor 26. A further step is that of causing microprocessor 26 to process flight direction commands and sensed data relating to stabilization to generate stabilization and directional command signals, and transmitting generated stabilization and directional command signals to each of the servomechanisms represented by servomechanism 22.

&null;0023&null; A further step is that of determining the stabilization command signals to be transmitted to each servomechanism (e.g., servomechanism 22) at least in part from data sensed by the flight stabilization sensors.

&null;0024&null; Another step is that of determining directional command signals transmitted to each servomechanism based entirely and exclusively on direction commands received by transceiver 28.

&null;0025&null; The basic method set forth above may be expanded to include further steps of, first, receiving GPS signals on GPS receiver 30; next, processing received GPS signals within microprocessor 26 to determine altitude of aircraft 10; and next, generating altitude control commands for maintaining a selected altitude under control of microprocessor 26 and transmitting generated altitude control commands to each servomechanism (e.g., servomechanism 22).

&null;0026&null; A step of providing a plurality of attitude sensors of different types may be practiced. This is satisfied by providing roll sensor 32, a pitch sensor 34, and yaw sensor 36, or any other sensors providing equivalent function.

&null;0027&null; The basic method may be modified by adding a further step of providing an altitude sensor, such as laser or acoustic altimeter 38 or a barometric pressure altimeter 40 or both.

&null;0028&null; An advantageous additional step is that of limiting the gross weight of the aircraft to fifty-five pounds. Suitable construction for achieving this weight limit is set forth in copending application entitled, MINIATURE, UNMANNED AIRCRAFT WITH INTERCHANGEABLE DATA MODULE, Ser. No. , to which the reader is referred.

&null;0029&null; It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.