(19) United States
`(12) Patent Application Publication (10) pub. NO.: US 200610144994 A1
`Jul. 6,2006
`Spirov et al.
`(43) Pub. Date:
`
`(54) HOMEOSTATIC FLYING HOVERCRAFT
`
`Related U.S. Application Data
`
`(76)
`
`Inventors: Peter Spirov, Minneapolis, MN (US);
`Brad Pedersen, Minneapolis, MN (US)
`
`Correspondence Address:
`PATTERSON, THUENTE, SKAAR &
`CHRISTENSEN, P.A.
`4800 IDS CENTER
`80 SOUTH 8TH STREET
`MINNEAPOLIS, MN 55402-2100 (US)
`
`(21) Appl. No.:
`
`101526,153
`
`(22) PCT Filed:
`
`Sep. 2, 2003
`
`(86) PCT No.:
`
`PCTlUS03127415
`
`(60) Provisional application No. 601407,444, filed on Aug.
`30, 2002.
`
`Publication Classification
`
`(51) Int. C1.
`B64C 39/00
`(2006.01)
`(52) U.S. C1. ................................................................ 244162
`
`(57)
`
`ABSTRACT
`
`A homeostatic flying hovercraft preferably utilizes at least
`two pairs of counter-rotating ducted fans to generate lift like
`a hovercraft and utilizes a homeostatic hover control system
`to create a flying craft that is easily controlled. The homeo-
`static hover control system provides true homeostasis of the
`craft with a true fly-by-wire flight control and control-by-
`wire system control.
`
`Parrot Ex. 1007
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`Signal Interpreter
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`HOMEOSTATIC FLYING HOVERCRAFT
`
`FIELD OF THE INVENTION
`
`[0001] The present invention relates generally to the field
`of heavier-than-air aeronautical craft that are sustained in air
`by the force of a fluid such as air. More particularly, the
`present invention relates to a homeostatic flying hovercraft
`and to a radio controlled flying saucer toy employing the
`principals of a homeostatic flying hovercraft.
`
`BACKGROUND OF THE INVENTION
`
`[0002] Ever since the term "flying saucer" was first intro-
`duced in 1947, the concept of a circular flying craft has
`become a staple of popular culture. Unlike conventional
`aircraft in which lift is produced by the difference between
`the air flowing over the top versus the bottom of a wing,
`most flying saucers have proposed using the aerodynamic
`effect of a spinning disc to at least partially generate the lift
`required for the craft. The flying disc toy known as the
`Frisbee@ is perhaps the best example of this principal. While
`numerous concepts relating to spinning, flying disc-shaped
`craft have been put forth in a variety of patents and publi-
`cations, a practical embodiment of a self-powered flying
`saucer has yet to be developed.
`[0003] The concept of a heavier-than-air craft supported
`by a fluid instead of wings or rotors predates even the Wright
`brother's first flight. U.S. Pat. No. 730,097 issued in June
`1903 described an airplane controlled by a jet propulsion
`arrangement that proposed using a pendulum valve to con-
`trol the operation of the jets as an automatic means to keep
`the craft in equilibrium. Despite numerous attempts to
`realize the concept of a craft suspended by downward
`directed jets, it was more than sixty years later before the
`Harrier jump jet actually achieved this goal with the first
`practical vertical-take-off-and-landing (VTOL) aircraft.
`Even so, the difficulty in controlling and maneuvering such
`a VTOL aircraft on both take-offs and landings, as well as
`transitions from vertical to horizontal flight, continues to
`plague the general acceptance of VTOL aircraft as evi-
`denced by the ongoing difficulties with the US Marine
`Corp's V-22 Osprey aircraft.
`[0004] Various attempts have been made to use the inher-
`ent stability of a spinning disc or multiple spinning disc
`arrangement in order to stabilize a fluid suspended flying
`craft Examples of the use of jet propulsion in connection
`with a spinning disc are shown in U.S. Pat. Nos. 3,199,809,
`3,503,573, 3,946,970, 4,566,699, 5,351,911, 6,050,250,
`6,302,229, 6,371,406, 6,375,117, 6,572,053, and 6,575,401.
`Other examples of spinning annular rings or discs in a
`saucer-shaped craft are shown in U.S. Pat. Nos. 2,863,261,
`4,214,720, 4,273,302, 4,386,748, 4,778,128, 5,072,892,
`5,259,571, 6,053,451, 6,270,036, and 6,398,159.
`[0005] Another approach to supporting a heavier-than-air
`craft has involved the use of ducted fans, instead of jets or
`rotors, to provide the necessary thrust for supporting and
`propelling the craft. Patents directed to the use of ducted
`fans to support a heavier-than-air craft date back to as early
`as 1872 and include craft that relied solely on ducted fans
`(e.g., U.S. Pat. Nos. 129,402, 905,547, 931,966, 996,627,
`and 1,816,707), as well as craft that used ducted fans in
`combination with wings (e.g., U.S. Pat. Nos. 1,291,345,
`1,405,035, 1,959,270, 2,461,435, 2,968,453 and 6,547,180)
`
`or craft using ducted fans in a helicopter-like craft (e.g. U.S.
`Pat. Nos. 1,911,041, 2,728,537, 3,199,809, 5,503,351,
`6,402,488, and 6,450,446).
`
`[0006] The first non-spinning disc shaped aerial craft with
`a single central ducted fan arrangement, as described in U.S.
`Pat. No. 2,567,392, used shutters to control airflow and
`orientation of the craft. The problem with this arrangement
`is similar to the problems encountered with helicopters,
`namely the rotation of a single fan imparts a one-way spin
`or torque that must somehow be counteracted in order for the
`craft to remain stable. Most central ducted fan arrangements
`have since utilized the concept of two counter-rotating
`blades spinning on the same axis in opposite directions to
`overcome this single-fan torque problem. The most famous
`application of this concept was the 1950's Hiller flying
`platform as described in U.S. Pat. No. 2,953,321 that was
`based on work dating back to 1947 by Zimmerman. The
`Hiller flying platform was controlled by having the operator
`shift his weight to alter the center of gravity of the craft.
`
`[0007] Other craft that use the co-axial counter-rotating
`blades for a central ducted fan arrangement have used vanes,
`louvers and duct arrangements to control airflow from the
`ducted fans in order to control orientation of the craft (e.g.,
`U.S. Pat. Nos. 2,728,537, 3,442,469, 3,677,503, 4,795,111,
`4,804,156, 5,178,344, 5,203,521, 5,295,643, 5,407,150,
`6,450,445, and 6,588,701). Patents also have described craft
`that use a pivoting central ducted fan arrangement to control
`airflow and orientation (e.g., U.S. Pat. Nos. 2,730,311,
`2,876,965, 2,968,318, 5,421,538 and 6,224,452). Still other
`patents have described central ducted fan craft that used
`variable pitch angle blades to control the airflow and orien-
`tation of the craft (e.g., U.S. Pat. Nos. 2,968,318,3,002,709,
`and 3,395,876). The addition of tail fins and tail rotors or tail
`jet engines to a central ducted fan craft has been described
`in several patents (e.g., U.S. Pat. Nos. 2,988,301,4,796,836,
`5,035,377, 5,150,857, 5,152,478, 5,277,380, 5,575,438,
`5,873,545, 6,270,038, 6,457,670, and 6,581,872). The addi-
`tion of a gyroscope mounted to and rotated by the propellers
`of the ducted fan to aid in stabilization of the craft has been
`described in U.S. Pat. Nos. 4,461,436 and 6,604,706. Com-
`binations of one or more of the control techniques have also
`been proposed in many of these patents as well as in U.S.
`Pat. No. 4,196,877.
`
`[0008] Ever since the 1950's, there have been sporadic
`research projects sponsored primarily by various military
`organizations on the design of enclosed rotorcraft vehicles.
`All of these designs to date have utilized a single-axis rotor
`inside a cowl or protective ring arrangement that forms a
`ducted fan. The most successful implementation of a single-
`axis counter-rotating ducted fan arrangement has been the
`CypherTM unmanned air vehicle (UAV) from United Tech-
`nologies Corp. that operates as a single-axis VTOL craft.
`The CypherTM has been effectively used as a drone surveil-
`lance probe by the military when remotely piloted by
`experienced UAV pilots.
`
`[0009] Recently, the military has started funding develop-
`ment of smaller unmanned air vehicles known as Organic
`Air Vehicles (OAVs) that are intended to be small ( ~ 2 4 "
`diameter)
`field-deployable
`remote
`controlled
`flying
`vehicles. Two multi-million dollar research and develop-
`ment contracts were granted in 2001 for the OAV program.
`Both contracts sought to extend the single-axis VTOL
`
`

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`Jul. 6,2006
`
`concept that is the basis for all military enclosed rotorcraft
`into a number of smaller sizes. The VTOL craft for the OAV
`program is designed to be oriented upright for takeoff and
`landings and transition into a sideways orientation for flight.
`As one might expect, the trickiest part of controlling this
`craft occurs during the transitions between vertical and
`horizontal orientations.
`
`[0010]
`In March 2002, the OAV design from Honeywell
`known as the Kestrel was selected for further funding. The
`Kestrel design is a conventional VTOL single axis rotorcraft
`that looks like a 5 pound coffee can with bunny ears and legs
`and is powered by a gas engine in the center and a pair of
`fuel canyingipayload bearing pods mounted on the sides.
`The Kestrel design has three sizes from 9-29 inches, with
`payloads ranging from 8 ounces to 18 pounds and an
`expected price tag of $10,000-$25,000 per unit. Available
`information indicates that these OAV's are being designed
`for automated self-piloting based on GPS coordinates and
`complex object recognition vision systems. Currently avail-
`able information indicates that the smaller OAV models of
`the Kestrel project are still not ready for use. For more
`information on the current status of unmanned aircraft
`development, see "Future of Unmanned Aviation," Popular
`Science, June, 2003.
`
`[0011] One alternative to the VTOL central ducted fan
`arrangement is the use of a pair of counter-rotating ducted
`fan arrangements that has been proposed in both side-to-side
`and front-and-back positions in a craft (e.g., U.S. Pat. Nos.
`2,077,471, 2,988,301, 3,752,417, 5,049,031, 5,064,143,
`5,213,284, 5,746,930, 5,890,441, and 6,464,166). A very
`early proposal for a ducted fan craft using more than a pair
`of ducts was described in 1911 by Gridley in U.S. Pat. No.
`1,012,63 1. Grindley showed the use of four ducted fans to
`produce a balanced (even) effect on the plane of the body of
`the craft, but no control arrangement for the fans was
`described. U.S. Pat. No. 4,795,111 described an alternate
`embodiment of a UAV that employed four ducts and briefly
`proposed altering fan pitch control or throttle control as a
`means for controlling this embodiment. U.S. Pat. Nos.
`6,179,247 and 6,254,032 describe proposed flying passenger
`craft that use ten or more ducted fans arranged in an
`equidistant manner in a ring around the craft. Both patents
`briefly describe a control system that varies the throttle
`control of different engines. U.S. Pat. No. 6,179,247 also
`proposes the use of a moveable paddle system to deflect air
`for purpose of control, whereas U.S. Pat. No. 6,254,032 also
`proposes that each ducted fan is individually pivotable to
`control airflow direction.
`
`[0012] Until recently, most development efforts in
`heavier-than-air craft that are fluid sustained using ducted
`fans of the like have been focused on larger passenger
`aircraft of UAVs. Recent advances in battery technology
`have generated a renewed interest in the field of remote
`controlled aircraft and smaller OAVs. Instead of conven-
`tional gas-powered engines, a combination of high-powered
`batteries and light-weight electrical motors have been used
`as replacement engines for model airplanes and model
`helicopters. While this represents an improvement in terms
`of simplicity and operability, model airplanes, and particu-
`larly model helicopters, are still expensive, complicated,
`temperamental and fragile hobby toys that can require
`months to build, learn, rebuild and master.
`
`2 .
`
`[0013] Various powered spinning disc toys and models
`have attemvted to address the control and stabilitv vroblems
`associated with model airplanes and model helicopters using
`many of the same approaches described above. These
`include single rotor model craft (e.g., U.S. Pat. Nos. 3,394,
`906, 3,477,168, 3,528,284, 3,568,358, 3,608,033,4,065,873
`and 5,429,542), dual counter-rotating rotor model craft (e.g.,
`U.S. Pat. Nos. 2,949,693, 5,071,383, 5,634,839, 5,672,086,
`and 6,053,451) and even rocket or jet-powered models (e.g.,
`U.S. Pat. Nos. 3,508,360 and 4,955,962). U.S. Pat. No.
`5,297,759 describes a disc-shaped model craft that uses two
`conventional aircraft propellers mounted at an angle of
`about 30 degrees on the surface of the disc to rotate the disc
`to provide both lift and propulsion.
`[0014] More recently, variations on the conventional
`model helicopter have been introduced utilizing multiple
`main rotors, each powered by a separate electrical motor.
`The HoverflyB I1 is perhaps the best example of such a craft
`that utilizes three main rotors and a tail rotor in a classic
`helicopter format. The Ultimate Flying SaucerTM, the Gyro-
`SaucerTM and the DraganFlyer IIITM utilize four rotors (two
`pairs of counter-rotating rotors) in a helicopter-like fashion
`to provide lift for the model craft, but do not have a separate
`tail rotor. Instead, the DraganFlyer IIITM uses three piezo-
`electric oscillation gyros to transmit flight data to an on-
`board computer to provide balanced reciprocal thrust among
`the rotors. Another variation on this approach is the Vec-
`tronTM Blackhawk that integrates a rotating outer ring with
`three rotor blades to provide lift for the craft.
`[0015] Unfortunately, each of these craft is still difficult to
`control and maneuver and all of these craft rely on multiple
`conventional helicopter rotors to provide aerodynamic lift,
`rotors that are easily damaged in the event of a crash. Like
`all exposed rotor craft, these multi-rotor models are also
`inherently dangerous due to the exposed spinning rotors.
`[0016] The most extensive research project using ducted
`fans instead of rotor blades was conducted by a research
`group at Stanford University for a NASA project to design
`miniature flying craft to be used for aerial mapping of Mars.
`The design known as a "mesocopter" calls for a very tiny
`battery-powered four rotor craft less than two inches across.
`In one version, the four tiny rotors are each shrouded in a
`protective ring. While the research is interesting, the project
`has no practical guidance on how to make a model-sized RC
`flying craft for here on Earth because of the differences in
`gravity and air density as compared to Mars.
`
`[0017] A design concept for a model flying hovercraft
`powered by ducted fans has been proposed by a student at
`MIT. Although his design proposed the use of counter-
`rotating ducted fans to power the craft, he has never been
`able to make the design work. Control of his 4 ducted fan
`design was to be achieved by using three separately con-
`trolled fins, one for yaw, one for left-right and one for
`back-forth. While some interesting concepts were proposed,
`a workable prototype was never achieved and no further
`work on the project has been reported.
`
`[0018] Whether the craft is a single-axis VTOL, ducted
`fan UAV or OAV, a multi-rotor model RC craft, or a multiple
`ducted fan craft, the main challenges with all of the existing
`designs for fluid sustained aircraft are ease of control and
`stability of flight. Manually flying any of these craft requires
`extensive training and skills. Unfortunately, the automated
`
`

`

`Jul. 6,2006
`
`self-piloting systems capable of attempting to assist with
`flying any of these craft are all based on the complicated and
`expensive inertial guidance auto-pilot systems used in air-
`planes today.
`
`[0019] Existing autopilot systems, such as the state-of-the-
`art Honeywell Fault-Tolerant Air Data Inertial Reference
`System (FTIADIRS), use one or more gyroscopes to sense
`rotation about an axis in the form of angular velocity
`detection. The FTIADIRS, for example, is comprised of a
`six-sided structure holding six ring laser gyros and six
`accelerometers. A myriad of backup and redundant power
`supplies and computer systems are integrated with this
`system to prevent a mid-flight failure.
`
`[0020] The basic reason for the use of very high precision
`laser ring gyros and multiple redundancies is that existing
`inertial guidance systems all rely on an initial static deter-
`mination of the gravitational reference to be used by the
`system. In the case of an autopilot system, the gravitational
`reference or ground horizon reference is established when
`the plane is on the ground. This process, commonly referred
`to as boresighting, establishes the gravitational reference for
`-
`down. Once this gravitational reference is established, it is
`essentially static and unchanging and the auto-pilot system
`uses the gyros to keep very precise track on a dead-
`reckoning basis of all changes in the attitude of the craft
`from the point of the ground plane reference. This compli-
`cated referencing to a static ground plane reference can be
`augmented dynamically by obtaining positional information
`from a global positioning satellite (GPS) system, but GPS
`systems are not precise enough to detect small changes in
`attitude of a craft on a continual basis.
`
`[0021]
`Ideally, the ground plane reference could be
`dynamically updated on a continual basis when the craft was
`in the air, thus eliminating the need for the complicated gyro
`based inertial guidance systems. Unfortunately, mechanical
`sensors such as pendulums, gyros and piezo-accelerometers
`do not function the same in dynamic situations where the
`sensors are continually subjected to multiple acceleration
`fields. The impact of precession on those sensors means that
`the sensor readings will provide an incorrect ground plane
`reference. By example, a pendulum is a very simple and
`effective gravitational sensor in a static context. If a pendu-
`lum is subjected to a centripetal acceleration in addition to
`gravitational acceleration by swinging the pendulum in a
`circle, for example, then the "reading" of the pendulum will
`not point down. Instead, the pendulum will point in a
`direction that is a combination of both the gravitational
`acceleration and the centripetal acceleration. This phenom-
`enon is further complicated in situations where the craft is in
`a parabolic dive, for example, when the tilt of the craft is
`equal to the rate of acceleration of the dive. In this situation,
`referred to as the "death spiral," the forces on sensor are
`balanced so that the sensors typically give no useful output
`readings in this situation.
`
`[0022] U.S. Pat. No. 5,854,843 describes a virtual navi-
`gator inertial angular measurement system that uses gyros to
`sense angular velocity and piezo-accelerometers to correct
`for drift in the gyros. While the piezo-accelerometers are
`referred to in this patent as "absolute" references, it is
`understood that these piezo-accelerometers are absolute
`only with respect to the initial gravitational ground plane
`established by a boresighting process. The need for this
`
`initial boresighting is confirmed by the fact that the inven-
`tion touts the advantage of being stable for long periods of
`time. If an inertial guidance system were able to dynamically
`update its initial gravitational ground plane, then the need
`for "stability" over extended periods of time is eliminated.
`[0023] Examples of current state of the art inertial navi-
`gational reference systems for aviation that use a gyro-based
`angular rate sensing arrangement similar to that described in
`U.S. Pat. No. 5,854,843 are shown in U.S. Pat. Nos. 5,440,
`817,5,676,334,5,988,562,6,227,482,6,332,103,6,421,622,
`6,431,494, and 6,539,290. While certain references indicate
`that a gyro sensor can be a gravitational detector of down,
`it must be understood that this statement is valid only under
`static conditions or in a limited set of acceleration circum-
`stances where the output of the sensor is not compromised
`by the acceleration fields. U.S. Pat. No. 6,273,370 attempts
`to overcome these limitations by trying to keep track of
`different states of the sensor system and determining a
`course of action based on the different state conditions. Still,
`if the sensor system loses track of the state of the sensor
`system, even this arrangement cannot dynamically deter-
`mine an inertial gravitational reference to use as a reference.
`[0024] What is needed is a heavier-than-air flying craft
`that has the ability to hover and to perform vertical air
`movements like a conventional model helicopter, yet is
`easier to operate and more durable than existing flying
`machines.
`
`SUMMARY OF THE INVENTION
`
`[0025] The present invention is a homeostatic flying hov-
`ercraft that preferably utilizes at least two pairs of counter-
`rotating ducted fans to generate lift like a hovercraft and
`utilizes a homeostatic hover control system to create a flying
`craft that is easily controlled. The homeostatic hover control
`system provides true homeostasis of the craft with a true
`fly-by-wire flight control and control-by-wire system con-
`trol.
`[0026]
`In one embodiment, the flying hovercraft is a flying
`saucer shaped over-powered skirtless hovercraft capable of
`upldown, lateral and yaw, pitch and roll flight maneuvers by
`mimicking the position of the craft to the position of a
`remote controller. Preferably, control is fluidly intuitive by
`seamlessly utilizing a series of pre-established operational
`orientations associated with each of the positions of the craft
`that result in balanced and controlled flight positions. The
`homeostatic hover control system removes the need for the
`pilot to be concerned with moment-to-moment balance1
`stabilization and control of the craft and focus instead only
`on the intended motion in which the craft is to be directed.
`[0027]
`Instead of trying to use the rotation of the craft or
`the spinning of rotor blades to provide aerodynamic lift, the
`preferred embodiment of the homeostatic flying saucer uses
`four battery-powered ducted fans housed completely inside
`the craft to produce four controlled cones of thrust beneath
`the craft. A novel control system balances the four cones of
`thrust to keep the craft stable and to cause the craft to move
`in a desired direction. The fan blades are specially designed
`to make the most efficient use of the increased power
`provided by permanent magnet motors while also reducing
`fan noise both because the blades spin somewhat slower
`than conventional blades and because of the unique aero-
`dynamic design features of the ducted fan blades.
`
`

`

`Jul. 6,2006
`
`[0028] The homeostatic control system of the preferred
`embodiment incorporates many different features to enable
`the craft to achieve homeostasis or self-stabilization. The
`ducted fans are angled slightly outward such that the four
`cones of thrust have an inherent balancing effect, much like
`the bottom of a WeebleB toy that wobbles but doesn't fall
`over. The four ducted fans are actually two pairs of counter-
`rotating fans on opposite sides of the craft. The counter-
`rotation eliminates the need for anything like a tail rotor to
`prevent spinning of the craft caused by the spinning of the
`fans. A hover control system manages the amount of thrust
`produced by each ducted fan via four speed controllers. The
`hover control system uses an XYZ sensor arrangement and
`associated control circuitry that dynamically determines an
`inertial gravitational reference for use in automatically and
`continuously determine the speed needed for each fan in
`order to keep the craft at a desired orientation. Other
`embodiments of the hover control system support collision
`avoidance sensors and the ability to automatically change
`the way the flying hovercraft operates depending upon
`whether the craft is indoors or outdoors.
`[0029] In a preferred embodiment, light-weight, high-
`torque permanent magnet motors power the ducted fans. The
`preferred embodiment of such permanent magnet motors are
`described in U.S. Pat. Nos. 6,236,561 and 6,342,746, the
`disclosures of which are hereby incorporated by reference.
`Unlike conventional electric motors that use electromag-
`netic force created by a series of wound coils within the
`motor to rotate a shaft, these permanent magnet motors
`control the flow of magnetic flux from powerful permanent
`magnets to rotate the shaft of the motor. Consequently, when
`these permanent magnet motors are used to turn a heavy load
`the motor does not draw additional current from the battery.
`These one-of-a-kind electric motors provide a combined
`total in excess of % horsepower to the shafts of the four
`ducted fans, enabling an anticipated thrust-to-weight ratio of
`greater than 2:l and preferably greater than 3:l for an
`unloaded saucer. As a result, the saucer of the preferred
`embodiment is able to fly longer and farther than if it were
`powered by conventional motors that draw increasing
`amounts of current from the battery in response to increasing
`loads on the motor.
`
`[0030] The unique and intuitive one-handed bee controller
`also includes an XY sensor arrangement and associated
`control circuitry that allows the craft to mimic the position
`of the controller in terms of yaw, pitch, roll and lateral flight
`maneuvers. In one embodiment, control of the craft is fluidly
`intuitive by seamlessly utilizing a series of pre-established
`operational orientations associated with each of a set of
`positions for the craft that result in balanced and controlled
`flight orientations. Together, the homeostatic control system
`and the bee controller eliminate the need for the pilot to be
`concerned with moment-to-moment balancelstabilization. In
`one embodiment, the bee controller also features a USB
`connection port to permit downloading of software updates
`from the web via an Internet connection.
`
`[0031] Unlike existing RC models that use inexpensive
`low frequency one-way communications, the preferred
`embodiment of the present invention incorporates state of
`the art radio frequency communications. A unique 900 MHz
`communication chip provides a two-way, multi-channel
`communication link between the controller and the saucer.
`This high speed multi-channel communication link allows
`
`multiple saucers to fly in the same area and communicate
`with each other to make advanced gaming and coordinated
`control possible. It also permits extensive data communica-
`tions both to and from the saucer. Video images and other
`high bandwidth sensor inputs can be communicated from the
`saucer to the controller over this link.
`
`[0032] In the preferred embodiment, multiple onboard
`microprocessors receive commands from another micropro-
`cessor in the bee controller and, in response, instruct the
`homeostatic control system on a desired orientation, angle
`and thrust for the craft. Preferably, radio communications
`between the microprocessor and the bee controller are used
`to keep the craft within a programmed maximum distance
`from the controller and the microprocessor automatically
`slows and reverses the craft when it approaches the maxi-
`mum range from the controller. For one embodiment of an
`RC craft, the maximum distance is 500 feet from the bee
`controller and the maximum speed is about 25 mph.
`
`[0033] In a preferred embodiment, instead of heavier,
`conventional NiCad rechargeable batteries, state-of-the-art
`Lithium Polymer rechargeable batteries are used as the
`electrical power source for powering the permanent magnet
`motors. Lithium Polymer batteries provide the long-life and
`high power capacity required for this technology in the
`lightest and smallest package.
`[0034] In a preferred embodiment, the flying hovercraft is
`an RC flying saucer that is constructed of a single EPP foam
`shell weighing between 30-42 ounces unloaded. Although
`light-weight, the saucer is designed to withstand free falls of
`up to 5 feet without damage. Even though it is as lightweight
`as styrofoam, the advanced EPP foam that forms the shell is
`actually able to bend and still return to its original shape
`without breaking.
`
`BRIEF DESCRIPTION OF THE FIGURES
`
`[0035] FIG. 1 is a cross-sectional side view of the craft in
`accordance with one embodiment of the present invention.
`[0036] FIG. 2 is a detailed cross-sectional view of the fan
`rotation of the embodiment of FIG. 1 .
`[0037] FIG. 3 is a schematic diagram of the remote
`controller and the craft of the embodiment of FIG. 1 .
`
`[0038] FIG. 4a is a schematic diagram of a general
`confirmration of 4 lift motorlducted fans and an XY axis
`mercury tilt switch stabilizer transducer of the embodiment
`of FIG. 1 .
`
`u
`
`[0039] FIG. 4b is a schematic diagram of XYZ axis
`piezoelectric gyros of the embodiment of FIG. 1 .
`
`[0040] FIG. 5 is a schematic diagram of a general con-
`figuration of 4 motors, speed controllers and motor enable
`counter of the embodiment of FIG. 1 .
`
`[0041] FIG. 6 is a timing diagram of a general duty cycle
`for operating the speed controllers and motor enable counter
`of FIG. 5 .
`
`[0042] FIG. 7 is a top view of a general configuration of
`the XY axis tilt switch stabilized transducer of the embodi-
`ment of FIG. 1 .
`
`[0043] FIG. 8 is a block diagram of the systems of the
`embodiment of FIG. 1 .
`
`

`

`Jul. 6,2006
`
`[0044] FIG. 9 is a block diagram of the avionics of the
`embodiment of FIG. 1.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`[0045] FIG. 10 is a schematic diagram of a general
`configuration of an XY axis tilt switch stabilized transducer
`circuit of the embodiment of FIG. 1 .
`
`[0046] FIG. 11 is a schematic diagram of the homeostatic
`stabilizer circuit of the embodiment of FIG. 1 .
`
`[0047] FIG. 12 is a schematic diagram of the piezoelectric
`gyro output for the embodiment of FIG. 1 .
`
`[0048] FIG. 13 is schematic diagram of the control system
`for the motor controllers incorporating the outputs of the
`stabilizer circuits and the gyr