UNITED STATES PATENT AND TRADEMARK OFFICE
`__________________________
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`__________________________
`
`DJI EUROPE B.V.
`Petitioner
`v.
`TEXTRON INNOVATIONS INC.
`Patent Owner.
`
`___________________
`
`IPR2023-001104
`U.S. Patent No. 8,682,505
`_____________________
`
`DECLARATION OF DR. WILLIAM SINGHOSE IN SUPPORT OF
`PETITION FOR INTER PARTES REVIEW OF U.S. PATENT NO. 8,682,505
`
`Mail Stop PATENT BOARD
`Patent Trial and Appeal Board
`U.S. Patent & Trademark Office
`P.O. Box 1450
`Alexandria, VA 22313-1450
`
`DJI-1003
`IPR2023-01104
`
`

`

`TABLE OF CONTENTS
`
`I. 
`QUALIFICATIONS .................................................................................... 2 
`UNDERSTANDING OF RELEVANT LEGAL PRINCIPLES ................. 8 
`II. 
`’505 PATENT ............................................................................................ 11 
`III. 
`A.  Technical Background ............................................................................ 11 
`1.  Pilot Controls ..................................................................................... 14 
`2.  Sensors ............................................................................................... 16 
`3.  Actuators and Control Surfaces ......................................................... 18 
`4.  Aircraft Movement ............................................................................. 20 
`5.  Flight Control Systems ...................................................................... 25 
`a.  Model ............................................................................................ 28 
`b.  Equations of Motion ..................................................................... 30 
`c.  Coordinate Systems ...................................................................... 33 
`6.  Navigation .......................................................................................... 34 
`B.  Overview of the ’505 Patent ................................................................... 37 
`C.  Level of Ordinary Skill in the Art ........................................................... 45 
`D.  Prosecution History ................................................................................. 48 
`1.  U.S. Prosecution ................................................................................. 48 
`2.  European Prosecution ........................................................................ 51 
`E.  Claim Construction ................................................................................. 55 
`IV.  GROUND 1: GOLD RENDERS CLAIMS 1-2, 5-6, 8-9, 11-12,
`15-16, AND 18-19 OBVIOUS. ................................................................. 56 
`A.  Overview of Gold .................................................................................... 56 
`B. 
`Independent Claim 1 ............................................................................... 59 
`1.  Preamble [1P] ..................................................................................... 60 
`2. 
`“Longitudinal Control Architecture” [1B]. ....................................... 61 
`3. 
`“Lateral Control Architecture” [1A]. ................................................ 67 
`4. 
`“Control Yaw Movement … ” [1C] .................................................... 73 
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`TABLE OF CONTENTS
`(continued)
`
`C. 
`
`Page
`5. 
`“Continuously Moves” [1D] ............................................................... 80 
`Independent Claim 11 ............................................................................. 81 
`1.  Preamble [11P] ................................................................................... 82 
`2. 
`“Sensing” Limitation [11A] ............................................................... 82 
`3. 
`“Determining” Limitation [11B] ....................................................... 85 
`4. 
`“Selectively Controlling” Limitation [11C] ....................................... 89 
`5. 
`“Continuously Moves” [11D] ............................................................. 91 
`D.  Dependent Claims ................................................................................... 91 
`1. 
`“Directional Controller” (Claims 2 and 12) ...................................... 91 
`2. 
`“Lateral Control Architecture” (Claims 5 and 15) ............................ 95 
`a. 
`“Lateral Sideward Groundspeed Control Loop”
`[5A]/[15A] .................................................................................... 97 
`“Lateral Roll Attitude Control Loop” [5B]/[15B] ...................... 102 
`b. 
`“Lateral Roll Rate Control Loop” [5C]/[15C] ............................ 105 
`c. 
`“Lateral Controller” (Claims 6 and 16) .......................................... 107 
`“Longitudinal Control Architecture” (Claims 8 and 18) ................. 109 
`a. 
`“Longitudinal Forward Speed Control Loop”
`[8A]/[18A] .................................................................................. 111 
`“Longitudinal Pitch Angle Control Loop” [8B]/[18B] .............. 115 
`b. 
`“Longitudinal Pitch Rate Control Loop” .................................... 119 
`c. 
`“Longitudinal Controller” (Claims 9 and 19) ................................. 121 
`5. 
`V.  GROUND 2: THE COMBINATION OF GOLD AND
`SKONIECZNY RENDERS CLAIMS 3 AND 13 OBVIOUS. ............... 124 
`A.  Overview of Combination ..................................................................... 124 
`1.  Skonieczny ....................................................................................... 124 
`
`3. 
`4. 
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`TABLE OF CONTENTS
`(continued)
`
`Page
`2.  Motivation to Combine Gold and Skonieczny ................................ 128 
`B.  “Directional Control Architecture” (Claims 3 and 13) ........................ 132 
`1. 
`“Directional Heading Control Loop” [3A.1]/[13A] ........................ 135 
`2. 
`“Directional Turn Coordination Control Loop”
`[3A.2]/[13B]. .................................................................................... 139 
`“Directional Yaw Rate Control Loop” [3A.3]/[13C] ...................... 142 
`3. 
`“Directional Control Latch” (Claims 4 and 14) .............................. 146 
`4. 
`VI.  GROUND 3: THE COMBINATION OF GOLD AND ADAMS
`RENDERS CLAIMS 7, 10, 17 AND 20 OBVIOUS. ............................. 148 
`A.  Overview of the Combination ............................................................... 149 
`1.  Adams .............................................................................................. 149 
`2.  Motivation to Combine Gold and Adams ........................................ 152 
`B.  “Lateral Control Latch” (Claims 7 and 17) .......................................... 155 
`C.  “Longitudinal Control Latch” (Claims 10 and 20) ............................... 157 
`VII.  CONCLUSION ........................................................................................ 159 
`
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`
`U.S. Patent 8,682,505
`USS. Patent 8,682,505
`IPR2023-001104
`IPR2023-001104
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`U.S. Patent No. 8,682,505
`IPR2023-001104
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`
`
`
`I, Dr. Singhose, declare as follow:
`1.
`I have been engaged by Perkins Coie LLP on behalf of DJI Europe
`
`B.V. (“Petitioner”), to provide this Declaration concerning technical subject matter
`
`relevant to the petition for Inter Partes Review (“Petition”) of U.S. Patent
`
`8,682,505 to Christensen (“the ’505 patent”).
`
`2.
`
`I am over 18 years of age. I have personal knowledge of the facts
`
`stated in this Declaration and could testify competently to them if asked to do so. I
`
`have reviewed and am familiar with the specification and the claims of the ’505
`
`patent. In general, I will cite to the specification of a United States patent using the
`
`following formats: (Patent No., Col:Line Number(s)) or (Patent No., Paragraph
`
`Number(s)). For example, the citation (’505 patent, 1:1-10) points to the ’505
`
`patent specification at column 1, lines 1-10. Also, for convenience, I use italics to
`
`denote limitations from the challenged claims.
`
`3.
`
`All of the opinions contained in this Declaration are based on the
`
`documents I reviewed and my knowledge and professional judgment. In forming
`
`the opinions expressed in this Declaration, I reviewed the documents listed in the
`
`attached Appendix. I have also reviewed and am familiar with any other document
`
`referred to in this Declaration.
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`
`
`I have been asked to provide my technical opinions regarding how a
`
`U.S. Patent No. 8,682,505
`IPR2023-001104
`
`4.
`
`person of ordinary skill in the art would have understood the claims of the ’505
`
`patent at the time of the alleged invention, which I have been asked to assume is
`
`the 2011 timeframe. For purposes of whether the teachings of the prior art render
`
`the claims of the ’505 patent obvious, I have been asked to assume the date of
`
`March 30, 2011. I have also been asked to provide my technical opinions on how
`
`concepts in the ’505 patent specification relate to claim limitations of the ’505
`
`patent. In reaching the opinions provided herein, I have considered the ’505 patent,
`
`its prosecution history, and the references cited in the Appendix. I have also drawn
`
`on my own education, training, research, knowledge, and personal and professional
`
`experience.
`
`I. Qualifications
`5.
`I believe I am well qualified to render useful opinions on this matter. I
`
`will briefly summarize my knowledge, training, and experience here. A more
`
`detailed summary of my background, education, experience, and publications is set
`
`forth in my curriculum vitae (CV), which is submitted as DJI-1004.
`
`6.
`
`I am being compensated for my time at my standard consulting rate. I
`
`am also being reimbursed for expenses that I incur during the course of this work.
`
`My compensation is not contingent upon the results of my study and analysis, the
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`
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`substance of my opinions, or the outcome of any proceeding involving the ’505
`
`U.S. Patent No. 8,682,505
`IPR2023-001104
`
`patent. I have no financial interest in the outcome of this matter or in any litigation
`
`involving the ’505 patent.
`
`7.
`
`Based on my education, research, and work experience, I am
`
`knowledgeable about the subject matter of the ’505 patent and the related prior art.
`
`Specifically, my qualifications as an expert in the control of rotary aircraft, and
`
`other similar machines, stem from my prior work experience, as well as my
`
`experience as a Professor in the Woodruff School of Mechanical Engineering at
`
`Georgia Tech performing research, teaching, working, and consulting. I have
`
`hundreds of publications that are directed toward understanding and improving the
`
`control of rotorcraft and other machinery.
`
`8.
`
`Regarding my education, I received a B.S. in Mechanical Engineering
`
`from the Massachusetts Institute of Technology (“MIT”) in 1990. I then received
`
`an M.S. in Mechanical Engineering from Stanford University in 1992. Finally, I
`
`received a Ph.D. in Mechanical Engineering from MIT in 1997. After receiving my
`
`Ph.D., I was a postdoctoral researcher at MIT before becoming a professor at
`
`Georgia Tech in 1998.
`
`9.
`
`At Georgia Tech, I have taught a graduate-level course on advanced
`
`control system design and implementation since 2001. I have co-authored a
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`

`
`
`textbook entitled “Command Generation for Dynamic Systems”, which focuses on
`
`U.S. Patent No. 8,682,505
`IPR2023-001104
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`designing control commands to move machines. The textbook presents numerous
`
`examples of various machines to which the theoretical concepts are applicable,
`
`including cranes, robots, and satellites. I have also developed a series of remote-
`
`operated experimental cranes and aerial lifts used extensively in educational
`
`activities.
`
`10. My research focuses on the dynamics and control of machines. I have
`
`researched, developed experimental platforms, and published several papers
`
`relevant to aircraft and flight control. For example, I conducted research directed at
`
`controlling rotorcraft sling load operations which was sponsored by the National
`
`Rotorcraft Technology Center. This project involved researching the effects of
`
`suspended loads on the control of rotorcraft and techniques to reduce the swinging
`
`of the load and improve the response of such systems. The results of my research
`
`were presented in several papers. One such paper, “Dynamic Modeling and
`
`Simulation of a Remote-Controlled Helicopter with a Suspended Load”, studied
`
`the dynamic effects of loads suspended below the helicopter by cables and created
`
`a dynamic model of the loaded system. The paper documented the difficulty of
`
`maintaining a steady hover position after a horizontal movement of the helicopter
`
`while carrying a suspended load.
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`
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`11. My paper “Input-Shaping and Model-Following Control of a
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`U.S. Patent No. 8,682,505
`IPR2023-001104
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`Helicopter Carrying a Suspended Load” studied the effects of a heavy load
`
`suspended from a helicopter. The paper analyzed how the swinging of a suspended
`
`load can create challenges for model-following control architectures used in
`
`modern helicopter flight control systems due to the degradation of the tracking of
`
`the prescribed model dynamics, thereby degrading the control effectiveness. The
`
`paper described the use of input shaping with model-following control to reduce
`
`helicopter payload swing and improve the tracking of the prescribed model. The
`
`paper illustrates the design of an attitude-command flight control system that
`
`combines input-shaping and model-following control using dynamic models of a
`
`Sikorsky S-61 helicopter. It also shows the simulation results of the system for
`
`longitudinal and lateral repositioning movements.
`
`12. My paper “Reducing Swing of Model Helicopter Sling Load Using
`
`Input Shaping” studied techniques for suppressing the swinging of a load
`
`suspended beneath a helicopter to improve safety and productivity. Specifically,
`
`the paper discusses the formation of a dynamic model to characterize the
`
`translational response of a model helicopter and sling load to lateral control inputs
`
`in order to investigate the use of input shaping on helicopters.
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`13. While I have addressed a few of the relevant papers above, other
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`U.S. Patent No. 8,682,505
`IPR2023-001104
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`papers that I have published on rotorcraft include the following:
`
` J. J. Potter and W. Singhose, A Planar Experimental Remote-
`Controlled Helicopter with a Suspended Load, IEEE/ASME
`Transactions on Mechatronics, vol. 20, no. 5, pp. 2496-2503, 2015,
`doi: 10.1109/TMECH.2014.2386801.
`
` J. J. Potter, C. J. Adams, and W. Singhose, An Experimental Remote
`Controlled Helicopter with Suspended Load, in 2013 Int. Symp. on
`Mechatronics and its Applications, Amman, Jordan, 2013.
`
` N. Johnson and W. Singhose, Dynamics and Modeling of a Quadrotor
`with a Suspended Payload, in AIAA Aviation Forum Applied
`Aerodynamics Conference, Atlanta, GA, 2018
`
` C. Adams, J. Potter, and W. Singhose, Modeling and Input Shaping
`Control of a Micro Coaxial Radio-Controlled Helicopter Carrying a
`Suspended Load, in Int. Conference on Control, Automation and
`Systems, Jeju, Korea, 2012.
`
` S. Ichikawa, A. Castro, N. Johnson, H. Kojima, and W. Singhose,
`Dynamics and Command Shaping Control of Quadcopters Carrying
`Suspended Loads, in 14th IFAC Workshop on Time Delay Systems
`TDS (IFAC-PapersOnLine), Budapest, Hungary, 2018, vol. 51, no.
`14, pp. 84 - 88.
`In addition to conducting research on rotorcraft dynamics and control,
`
`14.
`
`I have also performed research on air traffic control that was sponsored by NASA.
`
`That research program produced several publications directed to optimizing flight
`
`paths and reducing the taskload of air traffic controllers, such as:
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`

`U.S. Patent No. 8,682,505
`IPR2023-001104
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`
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` Vela, A., J. P. Clarke, E. Feron and W. Singhose (2011). The Relative
`Value of Trajectory Prediction and Conflict-Resolution Algorithms.
`IEEE/AIAA 30th Digital Avionics Systems Conference, Seattle, WA,
`2011.
`
` Vela, A., K. Feigh, S. Solak, W. Singhose and J.-P. Clarke (2012).
`Formulation of Reduced-Taskload Optimization Models for Conflict
`Resolution. IEEE Trans. on Systems, Man, and Cybernetics 42(6):
`1552- 1561.
`
` Vela, A., S. Solak, E. Feron, K. Feigh, W. Singhose and J.-P. Clarke
`(2009). A Fuel Optimal and Reduced Controller Workload
`Optimization Model for Conflict Resolution. Digital Avionics
`Systems Conference, Orlando, Florida.
`
` Vela, A., S. Solak, W. Singhose and J.-P. Clarke (2009). A Mixed
`Integer Program for Flight-Level Assignment and Speed Control for
`Conflict Resolution. IEEE Conference on Decision and Control,
`Shanghai, China.
`
` Vela, A. E., E. Feron, W. Singhose and J.-P. Clarke (2010). Control of
`Holding Patterns for Increased Throughput and Recovery of
`Operations. Digital Avionics Systems Conference, Salt Lake City,
`UT.
`
` Vela, A. E., E. Salaun, E. Feron, W. Singhose and J.-P. Clarke (2011).
`Bounds on Controller Taskload Rates at an Intersection for Dense
`Traffic. 2011 American Control Conference, San Francisco, CA.
`
` Vela, A. E., S. Solak, J.-P. Clarke, W. Singhose, E. Barnes and E.
`Johnson (2010). Near Real-Time Fuel-Optimal En Route Conflict
`Resolution. IEEE Trans. on Intelligent Transportation Systems 11(4):
`826-837.
`15. Finally, I am a named inventor on six (6) US patents directed at
`
`improving control systems:
`
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`

`U.S. Patent No. 8,682,505
`IPR2023-001104
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`
`
` Singhose, W., Singer, N., Rappole, W., Derezinski, S., and Pasch, K.,
`“Methods and Apparatus for Minimizing Unwanted Dynamics in a
`Physical System,” U.S. Patent 5,638,267, granted June 10, 1997.
`
` R. Eloundou, W. Singhose, “Command Generation Combining Input
`Shaping and Smooth Baseline Commands,” U.S. Patent 6,920,378,
`granted July 19, 2005.
`
` K. L. Sorensen, W. Singhose, and S. Dickerson, “Combined feedback
`and command shaping controller for multistate control with
`application to improving positioning and reducing cable sway in
`cranes,” U.S. Patent 7,970,521, granted June 28, 2011.
`
` W. Singhose and D. Kim, “Methods and Systems for Double-
`Pendulum Crane Control,” U.S. Patent 8,235,229, granted August 7,
`2012.
`
` W. Singhose and Joshua Vaughan, “Methods and Systems for
`Improving Positioning Accuracy,” U.S. Patent 8,975,853, granted
`March 10, 2015.
`
` W. Singhose and Chen Chih Peng, “Crane Control Systems and
`Method,” U.S. Patent 9,132,997, granted September 15, 2015. •
`Khalid Sorensen and W. Singhose, “Crane Motion Control”, U.S.
`Patent 9,776,838, granted Oct. 3, 2017.
`
`16. The combination of my education, research, and work experience in
`
`the area of rotorcraft control enables me to provide clarifying analysis and
`
`confident opinions on the subject matter of this IPR.
`
`II. Understanding of Relevant Legal Principles
`17.
` I am not a lawyer, and I will not provide any legal opinions. Although
`
`I am not a lawyer, I have been advised certain legal standards are to be applied by
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`
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`technical experts in forming opinions regarding the meaning and validity of patent
`
`U.S. Patent No. 8,682,505
`IPR2023-001104
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`claims.
`
`18.
`
`I understand that a patent claim is invalid if it is anticipated or obvious
`
`in view of the prior art, and that a claim can be unpatentable even if all of the
`
`requirements of the claim cannot be found in a single prior-art reference. I further
`
`understand that invalidity of a claim requires that the claim be anticipated or
`
`obvious from the perspective of a person of ordinary skill in the art at the time the
`
`invention was made.
`
`19.
`
`I have been informed that a patent claim is invalid if it would have
`
`been obvious to a person of ordinary skill in the art. In analyzing the obviousness
`
`of a claim, I understand the following factors may be taken into account: (1) the
`
`scope and content of the prior art; (2) the differences between the prior art and the
`
`claims; (3) the level of ordinary skill in the art; and (4) any so called “secondary
`
`considerations” of non-obviousness, if they are present. I am not aware of any
`
`evidence of secondary considerations of non-obviousness relevant to the ’505
`
`patent. I reserve the right to supplement this Declaration if Patent Owner (“PO”)
`
`introduces evidence of secondary considerations of non-obviousness.
`
`20.
`
`I understand that to prove that prior art or a combination of prior art
`
`renders a patent obvious, it is necessary to:
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`U.S. Patent No. 8,682,505
`IPR2023-001104
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`
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`identify the particular references that, singly or in combination, make
`the patent obvious;
`
`specifically identify which elements of the patent claim appear in each
`of the asserted references; and
`
`(1)
`
`(2)
`
`(3) explain why a person of ordinary skill in the art would have combined
`the references, and how they would have done so, to create the
`inventions claimed in the patent. I further understand that exemplary
`rationales that may support a conclusion of obviousness include:
`
` combining prior art elements according to known methods to yield
`predictable results;
`
` simple substitution of one known element for another to obtain
`predictable results;
`
` use of known technique(s) to improve similar devices (methods or
`products) in the same way;
`
` applying a known technique to a known device (method or product)
`ready for improvement to yield predictable results;
`
` “obvious to try” – choosing from a finite number of identified,
`predictable solutions with a reasonable expectation of success;
`
` known work in one field of endeavor may prompt variations of the work
`for use in either the same field or a different field based on design
`incentives or other market forces if the variations are predictable to a
`person of ordinary skill in the art; and
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`U.S. Patent No. 8,682,505
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`
`
` some teaching, suggestion, or motivation in the prior art that would
`have led a person of ordinary skill in the art to modify the prior art
`reference or to combine prior art reference teachings to arrive at the
`claimed invention.
`
`21.
`
`I have been informed that, in considering obviousness, hindsight
`
`reasoning derived from the patent-at-issue may not be used.
`
`III.
`
`’505 Patent
`22. The ’505 patent “relates generally to flight control systems, and more
`
`particularly, to a flight control system having flight control laws which enable
`
`precise aircraft maneuvering relative to the ground.” (DJI-1001, 1:7-10.) The ’505
`
`patent focuses its discussion on “[a]ircraft that can hover and fly at low speeds”
`
`including “rotorcraft, such as helicopters and tilt rotors, and jump jets.” (DJI-1001,
`
`1:13-15.) As I discuss below in the Technical Background section, use of a flight
`
`control system using control laws that enable maneuvering relative to the ground
`
`was extremely well-known and in use by the earliest possible priority date of the
`
`’505 patent (March 30, 2011).
`
`A. Technical Background
`23. Because the ’505 patent is directed to rotorcraft, I focus my discussion
`
`in this section on rotorcraft. The main characteristic of a rotorcraft is the use of
`
`rotary wings to produce the thrust necessary for motion. A helicopter typically uses
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`two engine driven rotorsa main rotor and a tail rotor. These two rotors are shown
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`U.S. Patent No. 8,682,505
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`in the figure below. The main rotor produces thrust, primarily for vertical lift, but
`
`also for directional control. The tail rotor is used to control the heading1 of the
`
`helicopter. Changes in the angle of the main rotor produce propulsive forces for
`
`longitudinal and lateral motion.
`
`
`
`Rotorcraft Flying Handbook, Figure 1-7
`
`24. A useful reference system for an aircraft (e.g., a helicopter) consists of
`
`three mutually perpendicular lines (axes) that intersect at the center of gravity of
`
`the aircraft. As shown in the figure below, the longitudinal axis passes through the
`
`nose and the tail of the aircraft. Rotation about the longitudinal axis is referred to
`
`
`1 The heading of an aircraft is the direction in which the nose of the aircraft
`
`points during flight. (DJI-1016, 1-6.)
`
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`
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`as roll and is used for lateral control. The lateral axis extends from left to right.
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`U.S. Patent No. 8,682,505
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`Rotation about the lateral axis is referred to as pitch and is used for longitudinal
`
`control. The vertical axis passes vertically through the center of gravity. Rotation
`
`about the vertical axis is referred to as yaw and is used to control the direction that
`
`the nose of the aircraft is pointing.
`
`
`
`Helicopter Aerodynamics - Aircraft Theory of Flight (DJI-1024)
`25. Attitude is the set of three angles that define the orientation of an
`
`aircraft (the rotation relative to the Earth-fixed coordinate system), and consist of
`
`pitch, roll, and yaw as described above. Therefore, attitude is a function of the
`
`helicopter’s rotation about its axes. Attitude rates are the angular speeds of the
`
`aircraft, or the rates at which the orientation of the aircraft changes. These consist
`
`of pitch rate, roll rate, and yaw rate (sometimes called heading rate).
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`U.S. Patent No. 8,682,505
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`1. Pilot Controls
`26. Helicopter cockpits often come equipped with the following
`
`controllers used by a pilot to control movement of the aircraft: a cyclic stick, a
`
`collective stick, and foot pedals. Each of these input devices allows a pilot to move
`
`the helicopter in a different way. (See, e.g., DJI-1015, 4-1.) A cyclic stick can
`
`move forwards and backwards, as well as left and right. A cyclic stick is typically
`
`used for changing the helicopter’s pitch and roll attitude angles by controlling the
`
`main rotor disk angle. Cyclic pitch control tilts the main rotor disc by changing
`
`pitch angle of the rotor blades in their cycle of rotation. (DJI-1015, 4-2.) When the
`
`main rotor disc is tilted, the horizontal force component moves the helicopter in the
`
`direction of the tilt. (DJI-1015, 4-2.) For example, if the cyclic stick is moved
`
`forward, the rotor disc tilts forward, resulting in forward acceleration. (DJI-1015,
`
`4-3.) If it is moved aft, the disc tilts aft, resulting in backward acceleration. (DJI-
`
`1015, 4-3.) Change in the pitch angle is very strongly correlated with longitudinal
`
`motion; therefore, pitch control is generally synonymous with longitudinal control.
`
`To summarize very simply, the forward-backward movement of the cyclic stick
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`controls longitudinal motion.
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`27. Rotation about the longitudinal axis (rolling the helicopter left or
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`right) alters the helicopter’s roll attitude, resulting in a sideward motion. Roll
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`control is generally synonymous with lateral control. Therefore, the left-right
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`motions of the cyclic stick controls lateral motion.
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`28. The pedals control the pitch of the tail rotor blades. (DJI-1015, 4-3.)
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`In addition to counteracting torque of the main rotor, the tail rotor controls the
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`heading of the helicopter. (DJI-1015, 4-3.) That is, the pedals cause the helicopter
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`to rotate about the vertical axis (when it is in level flight) to change its yaw angle.
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`29. As shown in the figure below, thrust of the tail rotor depends on pitch
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`angle of the tail rotor blades. (DJI-1015, 4-3.) The pitch angle can be positive,
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`negative, or zero. (DJI-1015, 4-3.) A high positive pitch angle tends to move the
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`tail to the right; a low positive or negative pitch angle moves the tail to the left; and
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`a medium pitch keeps the tail in line and maintains the yaw angle. (DJI-1015, 4-3.)
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`Rotorcraft Flying Handbook, Figure 4-6
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`30. Collective pitch control changes the pitch angle of all main rotor
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`blades simultaneously (collectively). (DJI-1015, 4-1.) The collective stick controls
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`the total thrust generated by the main rotor. Therefore, it generally controls the
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`vertical motion of the helicopter.
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`31. Although the above description of helicopter controls is
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`representative, some helicopters may combine the cyclic stick and pedals into a
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`single three-axis stick (movement forward and backwards, left and right, and
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`rotational). Others may combine the cyclic stick, collective stick, and pedals into a
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`single four-axis stick (movement forward and backwards, left and right, up and
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`down, and rotational). Alternatively, others may separate the functionality of the
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`cyclic stick into two sticks. All of these configurations are known configurations
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`for helicopter controls.
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`2. Sensors
`32. Helicopters are equipped with a range of sensors to provide pilots and
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`flight control systems with the measurements and information necessary to safely
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`complete their missions. These sensors include Inertial Measurement Units
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`(IMUs), GPS, Pitot tubes, altitude sensors, radar, as well as other advanced sensor
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`systems.
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`33.
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`IMUs are typically a combination of gyroscopes and accelerometers
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`that provide measurements for attitude, attitude rate, relative velocity, and position.
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`They also sometimes include magnetometers, which measure orientation relative to
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`the Earth’s magnetic field. The raw outputs of the gyroscopes, accelerometers, and
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`magnetometer are processed (via filtering and sensor fusion) to give the more
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`useful measurements of aircraft states like pitch, roll, and yaw angles, as well as
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`relative velocity and position.
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`34. Pitot tubes, which measure fluid velocity, are used to provide airspeed
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`measurements, like in fixed-wing aircraft. For helicopters, these devices are
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`typically used for longitudinal velocity measurements (DJI-1023, 30-35.)
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`35. GPS is used for position measurements, from which velocity and
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`heading can be estimated. The accuracy and error depend on civilian versus
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`military grade GPS. GPS and IMU outputs can be combined via sensor fusion to
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`provide better position and velocity estimates, as well as to allow for absolute
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`position to be determined correcting for any error in measurement from the IMU
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`accelerometers. IMU and GPS sensors can be packaged as integrated sensor
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`systems.
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`36. Altitude is measured using a combination of barometric altimeters,
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`which measure static pressure, and temperature sensors. At low altitudes, radar can
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`also be used to obtain more accurate measurements (DJI-1020, 125). Modern
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`helicopters may also be equipped with Air Data Computers (ADCs) that combine
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`measurements from Pitot tubes, altimeters, and other sensors to determine air
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`speed, altitude, and other air and flight parameters.
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`3. Actuators and Control Surfaces
`37. The pilot commands issued through the pilot’s controller (e.g., cyclic
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`stick, collective stick, and foot pedals) are applied to control surfaces including the
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`main and tail rotors through actuators or servos. The actuators move the control
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`surfaces based on the received commands. In modern digital fly-by-wire flight
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`control systems, the pilot commands are monitored by a flight computer which
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`then issues commands to actuators to move the control surfaces.
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`38. The actuators move the various control surfaces of the aircraft that
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`change the collective or cyclic pitch of the rotor blades. One common control
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`surface is a swash plate which transmits control inputs to the main rotor blades.
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`(DJI-1015, 5-5.) For example, a “stationary swash plate is mounted around the
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`main rotor mast.” (DJI-1015, 5-6.) While it is restrained from rotating, it is able to
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`tilt in all directions and move vertically through use of a series of pushrods. (DJI-
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`1015, 5-6.) In older helicopters, these systems may have included mechanical
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`linkages and/or hydraulic boost actuators directly connected to the control surfaces.
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`39. The collective pitch of the tail rotor is changed using a “pitch change
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`mechanism on the tail rotor gearbox.” (DJI-1015, 4-3.) The exact composition of
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`this mechanism and the servo actuator supplying power (e.g. hydraulic vs.
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`electromechanical) varies between helicopters, although a linear hydraulic actuator
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`is often used. The same principle used to change the collective pitch of the main
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`rotor can be applied to the tail rotor as illustrated in the following figure. (DJI-
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`1015, 4-1.)
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`Rotorcraft Flying Handbook, Figure 4-1
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`40. Actuators can include servo-controlled valves for hydraulic syste