(12)
`
`United States Patent
`Barr
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 7,219,861 B1
`May 22, 2007
`
`US007219861B1
`
`(54) GUIDANCE SYSTEM FOR
`RADIO-CONTROLLED AIRCRAFT
`
`(75) Inventor: Howard Barr, Encinitas, CA (US)
`
`.
`
`_
`
`.
`
`.
`
`(73) Asslgnee. ilggll‘lt international, Inc., Carrollton,
`(U )
`
`.
`
`( * ) Not1ce:
`
`.
`
`.
`
`.
`
`.
`
`Subject to any d1scla1mer, the term ofth1s
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 774 days.
`
`.
`
`(21) Appl. No.: 09/611,177
`
`(22) Flled:
`
`Jul‘ 6’ 2000
`
`(51) Egg-‘£53m?
`
`(2006 01)
`
`9/1993 Stern
`5,249,272 A
`7/1994 Orton et 31.
`5,329,213 A
`4/1995 Singhai
`5,407,149 A
`6/1995 Moberg
`5,425,750 A
`8/1995 Slmonoif
`H1469 H
`9/1995 Nakada et a1.
`5,452,901 A
`4/l996 Yang
`5,507,455 A
`5,577,154 A 11/1996 Orton
`
`5,672,086 A
`
`5 730 394 A *
`537853281 A
`5,789,677 A
`5,904,724 A *
`
`9/1997 D'
`
`3/l998 C522; et a1‘
`7/1998 Peter et a1‘
`8/1998 McEachern
`5/1999 Margolin
`
`DE
`JP
`W0
`
`FOREIGN PATENT DOCUMENTS
`196 14 987 A1
`4/1996
`2000-5451
`11/2000
`WO 94/08847
`4/1994
`
`(52) US. Cl. .................................................... .. 244/190
`(58) Field of Classi?cation Searcl214Z/.i.9..(.)...i.7.. 1
`See application ?le for complete search history.
`
`* cited by examiner
`Primary ExamineriTien Dinh
`(74) Attorney’ Agent’ or FirmiKnObbe Martens Olson &
`Bear LLP
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`7/1964 Rhoads et a1.
`3,141,634 A *
`3,154,266 A * 10/1964 Sheppard et a1.
`4,038,590 A
`7/1977 Knowlton
`4,206,411 A
`6/1980 Meyer
`4,522,072 A
`6/1985 Sulouif et a1.
`4,725,956 A *
`2/1988 Jenkins
`4,821,572 A
`4/1989 Hulsing, II
`4,964,598 A 10/1990 Berejik et a1.
`5,058,824 A 10/1991 Cycon et a1.
`5,067,674 A 1l/1991 Heyche et a1.
`5,195,920 A
`3/1993 Collier
`
`(57)
`
`ABSTRACT
`
`A method and system are described for controlling the ?ight
`pattern of a remote controlled aircraft. The system includes
`a microcontroller that is linked to an accelerometer for
`determining the attitude of the aircraft and modifying signals
`to the aircraft’s ?ight control system in order to prevent a
`crash. In addition, several preset ?ight patterns are stored in
`a memory so that upon activation, the aircraft Will enter a
`preset ?ight pattern.
`
`23 Claims, 6 Drawing Sheets
`
`10\‘
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`24B
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`24A-/
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`Parrot Ex. 1005
`
`

`

`U.S. Patent
`
`May 22, 2007
`
`Sheet 1 0f 6
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`U.S. Patent
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`May 22, 2007
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`U.S. Patent
`
`May 22, 2007
`
`Sheet 4 0f 6
`
`US 7,219,861 B1
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`4 U2 '\
`I START )
`1f
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`STORE SIGNAL PROPERTIES CORRESPONDING
`TU LEVEL FLIGHT TO A MEMORY
`v
`RECEIVE SIGNAL FROM TRANSMIITEG
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`( END )
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`FIG. 4
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`MODIFY SIGNALS
`435 \
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`STORE MODIFIED
`SIGNALS TU MEMORY
`
`

`

`U.S. Patent
`
`May 22, 2007
`
`Sheet 5 0f 6
`
`US 7,219,861 B1
`
`502%
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`READ SIGNALS FROM
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`TO REGISTERS
`
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`
`FIG. 5
`
`=
`
`‘:
`
`

`

`U.S. Patent
`
`May 22, 2007
`
`Sheet 6 6f 6
`
`US 7,219,861 B1
`
`(START )/ 600
`
`540
`f
`
`1r
`‘\
`CALCULATE MOTOR SPEED, ROLL AND PITCH
`
`614R
`USE TRANSMITTED
`SERVO COMMANDS
`
`DOES SPEED, ROLL RTTD PITCH
`EXCEED PREPRDDRAMMED
`LIMITS
`?
`
`61m
`
`MODIFY SERi/D COMMANDS
`
`END
`
`612
`
`FIG. 6
`
`700 SENSOR
`"""—' / CONDITION
`VOLTAGE /?02 mommy
`REFERENCE
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`FIG. 7
`
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`
`CONVERTER
`
`

`

`US 7,219,861 B1
`
`1
`GUIDANCE SYSTEM FOR
`RADIO-CONTROLLED AIRCRAFT
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates to control systems for radio-con
`trolled aircraft. More speci?cally, this invention relates to
`methods and systems for modifying the ?ight path of a
`radio-controlled aircraft.
`2. Description of the Related Art
`The sport of ?ying radio-controlled aircraft has increased
`in popularity over the past several years. Many hobbyists
`spend a tremendous amount of time building and ?ying
`these radio-controlled aircraft. As is known, these aircraft
`are ?oWn by a pilot that sends control signals from a
`transmitter to a receiver in the aircraft.
`A remote controlled airplane changes direction by move
`ment around one or more of its three axes of rotation: lateral
`axis, vertical axis, and longitudinal axis. These axes are
`imaginary lines that run perpendicularly to each other
`through the exact Weight center of the airplane. The air
`plane’s rotation around them is termed pitch, roll, and yaW.
`The pilot guides the airplane by sending control signals to
`servos Within the airplane that change the pitch, roll, and
`yaW by moving the elevators, ailerons, and rudder of the
`airplane.
`Conventional remote controlled aircraft use radio fre
`quency signals that are sent from the pilot’s transmitter to a
`receiver in the airplane, Which in turn generate a sequence
`of frequency modulated signals. Each control surface in the
`airplane is moved by a servo that receives these frequency
`modulated signals. By, for example, increasing the fre
`quency of the signal that controls the elevator servo, the pilot
`can cause the airplane to ascend or descend. In the same
`manner, changing the pulse-Width of the signals to the
`aileron servo Will cause the airplane to turn.
`Unfortunately, the chance that a beginner Will success
`fully complete their ?rst ?ight can be less than 1 in 10. This
`fact not only deters potential hobbyists from joining the
`sport, but also adds to the cost of taking up this sport since
`so many aircraft are destroyed during the learning stages.
`One reason that so many aircraft are destroyed during the
`learning stage of ?ying remote-controlled aircraft is that no
`inexpensive and convenient system exists for assisting a
`novice pilot to maneuver the plane or recover from unstable
`?ight situations. Some systems do exist for pilotless military
`aircraft, such as one described in US. Pat. No. 4,964,598
`(’598) to Berejik et al. The system described in the ’598
`patent relies on feedback signals from gyroscopes in the
`airplane to control the bank-angle and actual rate of climb of
`the aircraft. While such a system might be appropriate for
`military drones, such a system is complex and Would not
`provide a cost effective solution for radio-controlled airplane
`hobbyists.
`What is needed in the art is a simple and inexpensive
`system that can be incorporated into radio-controlled aircraft
`systems in order to give novice pilots the ability to ?y radio
`controlled aircraft Without risking a crash. The present
`invention ful?lls such a need.
`
`20
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`60
`
`SUMMARY OF THE INVENTION
`
`One embodiment of the invention is a control system for
`remote-controlled aircraft. This embodiment includes: a
`receiver for receiving control signals from a transmitter; a
`control module in communication With said receiver and at
`
`65
`
`2
`least one aircraft ?ight control system, Wherein said control
`module comprises instructions that, When executed, send
`modi?ed control signals to said ?ight control system; and a
`positioning module in communication With said control
`module, said positioning module providing positioning sig
`nals representing the current attitude of the aircraft to said
`control module.
`Another embodiment of the invention is a system for
`preventing crashes of a remote controlled aircraft that
`includes: a positioning module that determines the attitude
`of said remote controlled aircraft during ?ight; a control
`module in communication With said positioning module and
`With control signals received from a transmitter; and said
`control module comprising instructions for determining
`When said aircraft is at risk of crashing and, responsive to
`said determination, providing modi?ed control signals to at
`least one aircraft ?ight control system, Wherein said modi
`?ed control signals reduce said risk of crashing said aircraft.
`Yet another embodiment of the invention is a method of
`modifying the ?ight pattern of a remote controlled aircraft.
`The method includes: reading control signals from a trans
`mitter; reading positioning signals corresponding to the
`attitude of said aircraft from a positioning module; deter
`mining if said control signals Will place the airplane outside
`of de?ned performance parameters; and modifying said
`control signals so that performance of said airplane is Within
`said de?ned performance parameters.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic diagram of a remote-controlled
`aircraft.
`FIG. 2 is a block diagram illustrating one embodiment of
`the circuitry for controlling a remote-controlled aircraft.
`FIG. 3 is a timing diagram illustrating processed servo
`signals Within one embodiment of the circuitry of FIG. 2.
`FIG. 4 is a ?oW diagram illustrating a process for sending
`modi?ed signals to servos in a remote-controlled aircraft.
`FIG. 5 is a ?oW diagram illustrating the modify signals
`process of FIG. 4.
`FIG. 6 is a ?oW diagram illustrating the ?ight assist
`process of FIG. 5.
`FIG. 7 is a block diagram illustrating an embodiment of
`a sensor conditioning circuit.
`
`DETAILED DESCRIPTION
`
`1. OvervieW
`Embodiments of the present invention relate to a loW
`cost, electronic guidance system that is incorporated into a
`remote controlled airplane and is capable of modifying the
`?ight control signals sent by the pilot to the airplane. This
`embodiment functions by modifying the control signals that
`are sent by the pilot to the airplane. For example, if the pilot
`moves a control lever on the transmitter, the frequency of the
`signals being sent to a receiver in the aircraft are altered. The
`receiver in the aircraft then outputs pulse-Width modulated
`signals to a microcontroller Which analyZes the signals and
`outputs and, after making any necessary modi?cations,
`outputs the pulse-Width modulated signals to the servos that
`control ?ight. Each movement of the control stick by the
`pilot causes signals at one or more frequencies to be trans
`mitted to a receiver in the aircraft. These signals are con
`verted to pulse-Width modulated signals for controlling
`di?ferent servos or settings of the aircraft.
`Each command transmitted by the pilot to the aircraft
`affects the position of either a servo, or other ?ight control
`
`

`

`US 7,219,861 B1
`
`3
`system on the aircraft. In one embodiment, if the pilot
`changes the ?ight path by modifying, for example, the
`elevator servo, a microcontroller analyzes the request, along
`With data from an accelerometer or other level sensing
`device such as an inclinometer, to determine Whether the
`maneuver might lead to an unstable ?ight. If the maneuver
`is one that might lead to an unstable ?ight, this system can
`modify the pulse-Width of the signal from the receiver
`before being transmitted to the ?ight control servos, so that
`the airplane does not go out of control.
`In use, the circuitry described beloW detects the intended
`position of each ?ight control system (aileron, engine, ?aps,
`etc.) Within the aircraft, and then modi?es that position
`based on the current pitch and roll of the aircraft. The ?ight
`control systems include the mechanisms for poWering and
`steering the aircraft, such as the servos, engine, ailerons,
`rudder and elevators.
`In one embodiment, a plurality of accelerometers, here
`used as inclinometers, are located Within the aircraft and
`provide sensed information to a microcontroller concerning
`the current attitude of the aircraft. Instructions stored Within
`the microcontroller read the intended position of each servo
`from the frequencies transmitted by the ground transmitter
`and thereafter modify the pulse-Width of the signals to
`prevent the plane from crashing, or to enter a pre-planned
`?ight pattern, if signaled to do so by the pilot.
`In addition to the above-referenced embodiment, other
`embodiments of the system are available. For example, an
`emergency ?ight mode is provided Which alloWs the pilot to
`press an “emergency” button on the radio transmitter that
`sends a signal to the ?ight control circuitry instructing it to
`place the airplane in upright, level ?ight. The ?ight control
`circuitry determines the current position of the aircraft
`through the accelerometers, and calculates the proper servo
`positions of the elevators, ailerons and rudder to place the
`aircraft in level ?ight. Thus, the emergency button Will right
`the aircraft from any position and place it in level ?ight.
`Another embodiment of the invention includes a button
`that sends a command to the ?ight control circuitry to
`execute a constant ?ight path based on the current pitch and
`roll condition. By depressing this button, or otherWise
`executing a command to the ?ight control circuitry on the
`aircraft, the current pitch and roll condition is detected and
`stored to a memory. The microcontroller Within the system
`then continually monitors the pitch and roll of the aircraft
`and makes any necessary adjustment in the servos to main
`tain the current attitude of the airplane.
`Another embodiment of the system includes a “preset”
`?ight mode. Upon activation by the pilot, the plane Will
`execute a pre-programmed ?ight path based upon the current
`pitch and roll information. For example, the pre-pro
`grammed ?ight path might be a Wide-sWeeping circle. Thus,
`should the hobbyist get in trouble during a ?ight, this button
`on the transmitter can be activated to instruct the plane to
`correct itself from any current position. The plane Will then
`enter a sloW, circular loop until deactivated by the pilot.
`Once the “preset” ?ight mode has been entered, the plane
`Will continue With the preset ?ight pattern until instructed to
`discontinue the pattern by receipt of a signal from the ground
`transmitter.
`The preset ?ight mode might include speci?c patterns,
`such as a ?gure of “8”, loop or spin. Thus, the pilot could
`enter aerobatic or complicated ?ight movements into a
`memory in the ?ight control system so that these movements
`could be repeated over and over Without risk of error.
`Another embodiment of the invention includes an ultra
`sonic ranging system that is integrated into the airplane
`
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`4
`electronics. In this embodiment, the ultrasonic sensor detects
`objects, such as Walls, and can turn to avoid them. Thus, an
`airplane that could ?y indoors by turning When a Wall as
`detected is anticipated. In one embodiment, the aircraft
`includes a series of transducers and drive electronics for
`determining the distance of the aircraft from other objects.
`For example, the Polaroid Ultrasonics (NeWton, Mass.)
`Model 6500 Series sonar ranging module can be integrated
`into the aircraft ?ight control system to report distances from
`other objects. Using this module, the distance from an object
`can be calculated based on the time of a transmit signal and
`the leading edge of the returning echo signal. The distance
`is then calculated as the transit time/speed of sound. The
`onboard central processor in the aircraft Would then make an
`evaluation of What, if any, evasive maneuver to take based
`on the distance to the object.
`2. System
`Referring to FIG. 1, a radio-controlled ?ight system 10 is
`illustrated. The system includes a remote transmitter 20 that
`provides joysticks 22A,B and buttons 24AiC for sending
`frequency or amplitude modulated signals 25 to a remote
`controlled aircraft 30. The aircraft 30 receives the signals 25
`via a receiver (not shoWn). The received signals are fed
`through the ?ight control circuitry, as described beloW in
`FIG. 2, in order to control a set of ailerons 35A,B a rudder
`40 and an elevator 45.
`As can be imagined, adjusting the joysticks 22A,B or
`depressing the buttons 24AiC on the transmitter 20 sends
`signals 25 to the radio-controlled aircraft 30 that normally
`move the servos Which control the ailerons, rudder and
`elevators.
`FIG. 2 is a block diagram of a ?ight control system 100
`that is mounted Within the remote controlled airplane 30. As
`indicated, the ?ight control system 100 includes a radio
`control receiver 105 that is linked to an antenna 110 for
`receiving frequency modulated signals in the frequency
`modulated system from the radio-control transmitter 20. The
`received servo signal commands are separated by the
`receiver 105 into servo signal paths 112 to a signal-condi
`tioning circuit 115 that translates the servo signals into
`appropriate digital pulse-Width modulated signals (typically
`3V) by, for example, level shifting and transition sharpening
`the signal from the receiver. The signal conditioning circuit
`115 preferably converts the incoming analog Waveforms into
`sharp square Waves having a (LSV min-max. This prevents
`any pulse-Width errors from entering the ?ight control
`system and affecting the airplane performance. In one
`embodiment, the signal conditioning circuit is a Texas
`Instruments (Dallas, Tex.) 74 HCT14 integrated circuit,
`folloWed by a 74 HC14.
`The square Wave pulse-Width modulated signals are then
`sent to a one-of-eight selector circuit 120 that selects each
`conditioned frequency channel in a serial manner. As is
`shoWn, each frequency channel controls a separate servo, or
`other component such as the engine, Within the airplane 30.
`Thus, a transmitter 20 might transmit frequency modulated
`signals along eight separate frequency channels for control
`ling the ailerons, propeller speed, elevator, rudder, etc. of the
`aircraft 30. The selector circuit 120 individually selects each
`servo channel so that the system 100 can analyZe and modify
`one channel at a time prior to outputting it to a servo. The
`selector 120 chooses each channel on the leading edge of the
`square Wave pulse, and thereafter Waits for the trailing edge
`of the same channel before moving on to select the next
`channel in line to analyZe. In this manner, the selector 120
`serially transmits each channel being transmitted to the
`receiver 105. As each channel is selected from the selector
`
`

`

`US 7,219,861 B1
`
`5
`120, it is fed into a microcontroller 130 that processes all of
`the incoming signal data. In one embodiment, the micro
`controller is a Motorola (Austin, Tex.) MC 68 HC711D3.
`This microcontroller includes four kilobytes of on-board
`Programmable Read Only Memory (PROM) for storing
`instructions, and 192 bytes of on-chip Random Access
`Memory (RAM).
`Also feeding into the microcontroller 130 is a tWo-axis
`accelerometer 140 that provides pulse-Width modulated sig
`nals 142, 144 corresponding to the present X and Y dimen
`sional acceleration of the airplane 30, Which corresponds to
`the airplane’s pitch and roll. Several inclinometers could be
`used as accelerometers. For example, a Model LCL (The
`Fredricks Company, Huntingdon Valley, Pa.) or Biaxial
`Accelerometer Model LA02-0201-1 from Humphrey (San
`Diego, Calif.) are useful for embodiments of an accelerom
`eter or an inclinometer. HoWever, preferably the accelerom
`eter is an Analog Devices (NorWood, Mass.) ADXL 202
`Model accelerometer. The ADXL202 is a complete 2-axis
`accelerometer With a measurement range of :2 g. The
`ADXL202 can measure both dynamic acceleration (e.g.,
`vibration) and static acceleration (e.g., gravity). The outputs
`of the ADXL202 are Duty Cycle Modulated (DCM) signals
`Whose duty cycles (ratio of pulse-Width to period) are
`proportional to the acceleration in each of the 2 sensitive
`axes. These outputs may be measured directly With a micro
`processor counter. The DCM period is adjustable from 0.5
`ms to 10 ms via a single resistor (RSET). If an analog output
`is desired, an analog output proportional to acceleration is
`available from the XFILT and YFILT pins, or may be recon
`structed by ?ltering the duty cycle outputs. Furthermore,
`?lter capacitors external to these outputs are set to the
`appropriate bandWidth. This helps stabiliZe control of the
`airplane due to vibrations from the motor affecting the
`readings from the inclinometer.
`Because of the design of this system, the microcontroller
`130 thus receives input from the receiver 105 and the
`accelerometer 140. Within the PROM of the microcontroller
`130 are instructions for receiving signals from the acceler
`ometer 140 and selector 120 and determining the proper
`output signals to transmit to the servos. This process Will be
`discussed more completely beloW in the folloWing ?gures.
`The microcontroller 130 also has inputs from a “Zero”
`sWitch 150 that is used to set the level ?ight angle for the
`aircraft 30 before take-off. By depressing the Zero sWitch
`150, the microcontroller 130 samples the current tWo-axis
`accelerometer position and determines the level ?ight posi
`tion for the aircraft. This Zero position can be used later
`during ?ight by the microcontroller 130 to determine the
`appropriate yaW and pitch for the aircraft When level ?ight
`is required.
`The microcontroller 130 also communicates through a
`softWare-generated I2C bus With a temperature sensor 160
`that provides temperature compensation for the accelerom
`eter 140 and other sensing electronics. In one embodiment,
`the temperature sensor is a National Semiconductor (Santa
`Clara, Calif.) Model LM75 temperature sensor.
`Also connected to the microcontroller 130 are a pair of
`serial memory circuits 165A,B that can store ?ight infor
`mation during the ?ight or store pitch and yaW data for
`future maneuvers. As Will be discussed With regard to FIG.
`3, the microcontroller 130 buffers incoming pulse-Width
`modulated signals from the transmitter in order to present
`the signals to the servos in a parallel manner, instead of
`serially. In one embodiment, the serial memory is an Atmel
`(San Jose, Calif.) Model AT25256, a 256K bit memory
`device.
`
`20
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`30
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`35
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`Also connected to the microcontroller 130 is a ZERO
`READY indicator light 170, a FAULT indicator 175 and a
`POWER indicator light 180. In use, the ZERO READY
`indicator light ?ashes to indicate When the system is ready
`to be Zeroed by the pilot. Pressing the Zero sWitch 150 then
`sets the current state of the accelerometer to a memory in the
`microcontroller 130. The FAULT indicator light 175 is
`illuminated Whenever a fault or error is detected Within the
`?ight control system 100. The POWER indicator light 180
`is illuminated Whenever poWer is applied to the ?ight control
`system 100.
`The microcontroller 130 outputs signals to the servos
`along a group of output connections. The output connections
`?rst pass through a digital signal conditioning circuit 190,
`and then to an aileron servo 200, tail servo 205, motor speed
`output 210 and rudder servo 215.
`Referring noW to FIG. 3, a timing diagram is shoWn,
`illustrating an RF signal 301 received by the ?ight control
`system, and the same servo signals 303 once they have been
`processed by the ?ight control system and are sent to the
`servos. In particular, the timing signals for each servo are
`provided serially from the transmitter 20 to the receiver 105
`in the airplane 30. For example, a signal 300 is transmitted
`along frequency channel 1 in order to manipulate servo 1
`that controls the rudder. The signal 300 includes a leading
`edge 302 and trailing edge 304. The pulse-Width of the
`signal is de?ned as X, and is used by the ?ight control
`system to calculate the angle of movement for servo 1
`(rudder). The larger the pulse-Width varies from nominal, the
`more that servo 1 moves from its Zero angle.
`As also indicated, a signal 310 corresponding to servo 2
`(ailerons) is transmitted along frequency channel 2. Signal
`310 includes a leading edge 312 and trailing edge 315. The
`pulse-Width of the signal 310 is de?ned as Y As shoWn,
`because the analog signals from the transmitter 20 are sent
`serially, the trailing edge 304 of signal 300 aligns With the
`rising edge 312 of signal 310. As illustrated, the rising and
`falling edges of the signals 320 and 325, corresponding to
`servos 3 and 4, respectively, also folloW one another in a
`serial manner.
`For this reason, and as illustrated in FIG. 3B, the outputs
`from the signal-conditioning device 190 (FIG. 2) process the
`incoming signals so that the signals sent to the server in
`embodiments of this invention are aligned in parallel. As
`illustrated, the leading edge 302 of the signal 300 aligns With
`the leading edge 312 of the signal 310. This is also true of
`the leading edges of the other signals 320 and 325. Thus, the
`servos that are controlled by these signals are moved simul
`taneously.
`Referring noW to FIG. 4, a process for receiving and
`sending signals to servos Within the ?ight control system is
`illustrated. The process 400 begins at a start state 402 and
`then moves to a state 404 Wherein signal properties corre
`sponding to level ?ight for the aircraft are stored to the serial
`memory 165 Within the ?ight control system 100. The
`process 404 is normally activated by pressing the Zero
`sWitch 150 in order to indicate that the current settings for
`the aircraft correspond to level ?ight. The current settings
`from the accelerometer are then stored to a memory in the
`microcontroller. The aircraft is then launched from the
`ground and, at the state 410, signals are received from the
`transmitter 20. The process 400 then moves to a state 415
`Wherein the current yaW and pitch of the aircraft are captured
`by the microcontroller 130 from the accelerometer 140.
`Once the yaW and pitch have been captured by the micro
`controller 130, and any signals corresponding to ?ight
`requests have been received from the transmitter 20, the
`
`

`

`US 7,219,861 B1
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`7
`process 400 moves to a state 420 Wherein all of the signals
`can be stored to one of the serial memories 165A,B.
`Once the signals have been stored to a memory at the state
`420, the process 400 moves to a decision state 425 Wherein
`a determination is made Whether the signals coming from
`the transmitter 20 need to be modi?ed before being sent to
`the servos. This decision process is normally undertaken by
`instructions Within, or communicating With, the microcon
`troller 130. For example, softWare instructions and algo
`rithms for analyZing the accelerometer signals and transmit
`ter signals are preferably stored in the PROM of the
`microcontroller.
`A determination to modify the pulse-Width of the signals
`from the transmitter 20 is based on the requested servo
`positions from the transmitter 20, along With the data input
`from the accelerometer 140. For example, if the data coming
`from the transmitter indicates a sharp, diving right turn, the
`microprocessor may determine based on the yaW and pitch
`from the accelerometer that such a maneuver might lead to
`unstable ?ight or an aircraft crash.
`If a determination is made at the decision state 425 that
`signal modi?cations are needed prior to transmitting the
`signals to the servos, the process 400 moves to a process
`state 430 Wherein the signals are modi?ed. The process of
`modifying signals is described more speci?cally in FIG. 5.
`Once the signals have been modi?ed at the process state 430,
`the modi?ed signals are stored to the serial memory 165A,B
`at a state 435. The process 400 then moves to a state 437
`Wherein the leading edges of all the signals are aligned. The
`process 400 then moves to a state 440 Wherein all of the
`aligned signals are transmitted to the servos and any other
`aircraft ?ight control system. Thus, the modi?ed, aligned
`signals are sent to the servos Which thereafter modify the
`?ight path of the aircraft. The process then ends at an end
`state 450.
`Referring to FIG. 5, the process 430 of modifying signals
`prior to being sent to the aircraft’s ?ight control systems is
`explained. The process 430 begins at a start state 500 and
`then moves to a state 502 Wherein the signals are read from
`a memory storage. Once this information has been read, the
`process 430 moves to a decision state 504 Wherein a
`determination is made Whether any system intervention has
`been requested by the pilot. System intervention can be
`requested by, for example, pressing a button on the trans
`mitter, or otherWise sending a signal to the receiver in the
`aircraft. In one embodiment, an extra servo channel can be
`used to signal the system by introducing preselected pulse
`Widths. If system intervention has been requested, the pro
`cess 430 moves to a decision state 506 in order to determine
`Whether the type of intervention requested Was an emer
`gency mode. Such an emergency mode might be requested
`When the pilot can no longer control the aircraft. If a
`determination is made at the decision state 506 that an
`emergency mode has not been requested, the process 430
`moves to a decision state 508 in order to determine Whether
`a ?ight assist mode has been requested. As described above,
`a ?ight assist mode is used by the pilot in order to prevent
`the pilot from making mistakes during the ?ight. The ?ight
`assist mode alloWs the pilot to ?y the plane freely, but
`prevents any actions such as a steep dive, roll, etc. that could
`lead to a crash.
`If a determination is made that the ?ight assist mode has
`not been requested, the process 430 moves to a decision state
`512 to determine Whether a ?ight storage mode has been
`requested. A ?ight storage mode is requested When the pilot
`Wishes to save the ?ight pattern of the aircraft to a memory
`in order to doWnload it later to a computer for revieW. If a
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`determination is made at the decision state 512 that the ?ight
`storage mode has not been requested, the process 430 moves
`to a decision state 514 to determine Whether preprogrammed
`?ight has been requested. Such preprogrammed ?ight might
`be, for example, When the pilot Wishes to ?y the plane in a
`preprogrammed con?guration, such as a circle, ellipse or
`oval pattern. If a determination is made that preprogrammed
`?ight has not been requested, the process 430 moves to a
`state 520 Wherein the current ?ight commands for the
`aircraft are stored to registers Within the ?ight control
`system 100. The process 430 then executes the stored ?ight
`commands by sending them to the appropriate servos at a
`state 522. The process then terminates at an end state 530.
`If a determination had been made at the decision state 504
`that no system intervention Was requested, the process 430
`moves to a state 532 Wherein the signals transmitted by the
`pilot to the aircraft are stored to registers Within the ?ight
`control system 100. The process 430 then moves to the state
`522 to execute the servo commands.
`If a determination had been made at the decision state 506
`that an emergency mode Was requested by the pilot, the
`process 430 moves to a state 534 Wherein the difference
`betWeen the current pitch and roll of the aircraft and a Zero
`setting are calculated. As is knoWn, the Zero setting Would
`correspond to straight and level ?ight parameters. The
`process 430 then moves to a state 536 Wherein a corrective
`servo command is calculated in order to return the aircraft to
`a Zero (level ?ight) position. The process 430 then moves to
`the state 520 to store those calculated ?ight commands to
`registers Within the ?ight control system 100.
`If a determination Was made at the decision state 508 that
`a ?ight assist mode had been requested, the process 430
`moves to a ?ight assist process state 540, as described beloW
`in reference to FIG. 6. The process 4