Control systems and methods for rotating systems

In one embodiment, a local control system for a rotor assembly of an apparatus includes a first actuator disposed in the rotor assembly and configured to control motion of a first controllable element in the rotor assembly. The rotor assembly is mounted to the apparatus and is rotated responsive to torque and rotational energy provided thereto. The local control system also includes a first sensor disposed in the rotor assembly and configured to provide position feedback in relation to the first controllable element. The local control system also includes a first local control computer disposed in the rotor assembly and communicably coupled to a first central control computer disposed in the apparatus external to the rotor assembly, where the first local control computer is configured to transmit a control signal to the first actuator and receive a feedback signal from the first sensor.

BACKGROUND

Technical Field

The present disclosure relates generally to control systems and methods and more particularly, but not by way of limitation, to control systems and methods for rotating systems.

History of Related Art

Fixed-wing aircraft, such as airplanes, are capable of flight using wings that generate lift responsive to the forward airspeed of the aircraft, which is generated by thrust from one or more jet engines or propellers. The wings generally have an airfoil cross section that deflects air downward as the aircraft moves forward, generating the lift force to support the aircraft in flight. Fixed-wing aircraft, however, typically require a runway that is hundreds or thousands of feet long for takeoff and landing.

Unlike fixed-wing aircraft, vertical takeoff and landing (VTOL) aircraft do not require runways. Instead, VTOL aircraft are capable of taking off, hovering and landing vertically. One example of a VTOL aircraft is a helicopter which is a rotorcraft having one or more rotors that provide lift and thrust to the aircraft. The rotors not only enable hovering and vertical takeoff and landing, but also enable forward, backward and lateral flight. These attributes make helicopters highly versatile for use in congested, isolated or remote areas. Helicopters, however, typically lack the forward airspeed of fixed-wing aircraft due to the phenomena of retreating blade stall and advancing blade compression.

Tiltrotor aircraft attempt to overcome this drawback by utilizing proprotors that can change their plane of rotation based on the operation being performed. Tiltrotor aircraft typically have a pair of nacelles mounted near the outboard ends of a fixed wing with each nacelle housing a propulsion system that provides torque and rotational energy to a proprotor. The nacelles are rotatable relative to the fixed wing such that the proprotors have a generally horizontal plane of rotation providing vertical thrust for takeoff, hovering and landing, much like a conventional helicopter, and a generally vertical plane of rotation providing forward thrust for cruising in forward flight with the fixed wing providing lift, much like a conventional propeller driven airplane. It has been found, however, that forward airspeed induced proprotor aeroelastic instability is a limiting factor relating to the maximum airspeed of tiltrotor aircraft in forward flight.

SUMMARY

In one embodiment, a local control system for a rotor assembly of an apparatus includes a first actuator disposed in the rotor assembly and configured to control motion of a first controllable element in the rotor assembly. The rotor assembly is mounted to the apparatus and is rotated responsive to torque and rotational energy provided thereto. The local control system also includes a first sensor disposed in the rotor assembly and configured to provide position feedback in relation to the first controllable element. The local control system also includes a first local control computer disposed in the rotor assembly and communicably coupled to a first central control computer disposed in the apparatus external to the rotor assembly, where the first local control computer is configured to transmit a control signal to the first actuator and receive a feedback signal from the first sensor.

In one embodiment, a method is performed by a local control computer in a rotor assembly of an apparatus. The method includes transmitting a control signal to an actuator in the rotor assembly. The rotor assembly is mounted to the apparatus and is rotated responsive to torque and rotational energy provided thereto. The actuator is configured to control motion of a first controllable element in the rotor assembly. The method also includes receiving a feedback signal from a sensor in the rotor assembly, the feedback signal including position feedback in relation to the first controllable element.

In one embodiment, a control system for an apparatus includes a local control system disposed in a rotor assembly of the apparatus. The rotor assembly is mounted to the apparatus and is rotated responsive to torque and rotational energy provided thereto. The local control system includes an actuator configured to control motion of a controllable element in the rotor assembly. The local control system also includes a sensor configured to provide position feedback in relation to the controllable element. The local control system also includes a local control computer configured to transmit a control signal to the actuator and receive a feedback signal from the sensor. In addition, the control system includes a first central control computer disposed in the apparatus external to the rotor assembly and communicably coupled to the local control computer, where the first central control computer is configured to transmit a command to the local control computer.

DETAILED DESCRIPTION

While the making and using of various embodiments of the present disclosure are discussed in detail below, it should be appreciated that the present disclosure provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative and do not delimit the scope of the present disclosure. In the interest of clarity, not all features of an actual implementation may be described in the present disclosure. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, members, apparatuses, and the like described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. In addition, as used herein, the term “coupled” may include direct or indirect coupling by any means, including moving and/or non-moving mechanical connections.

Referring toFIGS. 1A-1Din the drawings, a tiltrotor aircraft is schematically illustrated and generally designated10. Aircraft10includes a fuselage12, a wing14and a tail assembly16including control surfaces operable for horizontal and/or vertical stabilization during forward flight. Located proximate the outboard ends of wing14are pylon assemblies18a,18bthat are rotatable relative to wing14between a generally vertical orientation, as best seen inFIG. 1A, and a generally horizontal orientation, as best seen inFIGS. 1B-1D. Pylon assemblies18a,18beach house a portion of the drive system that is used to rotate proprotor assemblies20a,20b, respectively. Each proprotor assembly20a,20bincludes a plurality of proprotor blades22that are operable to be rotated, as best seen inFIGS. 1A-1B, operable to be feathered, as best seen inFIG. 1Cand operable to be folded, as best seen inFIG. 1D. In the illustrated embodiment, proprotor assembly20ais rotated responsive to torque and rotational energy provided by engine24aand proprotor assembly20bis rotated responsive to torque and rotational energy provided by engine24b. Engines24a,24bare located proximate an aft portion of fuselage12. Engines24a,24bare operable in a turboshaft mode, as best seen inFIGS. 1A-1Band a turbofan mode, as best seen inFIGS. 1C-1D.

FIG. 1Aillustrates aircraft10in VTOL or helicopter flight mode, in which proprotor assemblies20a,20bare rotating in a substantially horizontal plane to provide a lifting thrust, such that aircraft10flies much like a conventional helicopter. In this configuration, engines24a,24bare operable in turboshaft mode wherein hot combustion gases in each engine24a,24bcause rotation of a power turbine coupled to an output shaft that is used to power the drive system coupled to the respective proprotor assemblies20a,20b. Thus, in this configuration, aircraft10is considered to be in a rotary flight mode.FIG. 1Billustrates aircraft10in proprotor forward flight mode, in which proprotor assemblies20a,20bare rotating in a substantially vertical plane to provide a forward thrust enabling wing14to provide a lifting force responsive to forward airspeed, such that aircraft10flies much like a conventional propeller driven aircraft. In this configuration, engines24a,24bare operable in the turboshaft mode and aircraft10is considered to be in the rotary flight mode.

In the rotary flight mode of aircraft10, proprotor assemblies20a,20brotate in opposite directions to provide torque balancing to aircraft10. For example, when viewed from the front of aircraft10in proprotor forward flight mode (FIG. 1B) or from the top in helicopter mode (FIG. 1A), proprotor assembly20arotates clockwise, as indicated by motion arrows26a, and proprotor assembly20brotates counterclockwise, as indicated by motion arrows26b. In the illustrated embodiment, proprotor assemblies20a,20beach include three proprotor blades22that are equally spaced apart circumferentially at approximately 120 degree intervals. It should be understood by those having ordinary skill in the art, however, that the proprotor assemblies of the present disclosure could have proprotor blades with other designs and other configurations including proprotor assemblies having four, five or more proprotor blades. In addition, it should be appreciated that aircraft10can be operated such that proprotor assemblies20a,20bare selectively positioned between proprotor forward flight mode and helicopter mode, which can be referred to as a conversion flight mode.

A flight control computer30is schematically shown in fuselage12, but it should be appreciated that the flight control computer30may take a number of forms and exist in a variety of locations within aircraft10. Similarly, although flight control computer30is illustrated singly, flight control computer30can be illustrative of two, three, four or any other suitable number of flight control computers in aircraft10, which computers can be located in same, similar or different locations within fuselage12or elsewhere in aircraft10.

Flight control computer30is configured to control and communicate with various systems within aircraft10including, for example, local control systems28aand28b. Local control systems28aand28bare schematically shown in the proprotor assemblies20aand20b, respectively. The local control systems28aand28bcan each be communicably coupled to the flight control computer30and provide closed-loop control of controllable elements located within the proprotor assemblies20aand20b. The controllable elements within the proprotor assemblies20aand20bcan include any structural feature operable to move and/or effect change such as, for example, blade locks, a gimbal lock, trailing-edge flaps, twistable blades, independently controllable elements attached or connected to blades, combinations of the foregoing and/or the like.

The local control systems28aand28bcan include, inter alia, actuators that control motion of the controllable elements in the proprotor assemblies20aand20b, sensors that provide feedback data related to the controllable elements and control computers that operate the actuators, for example, by transmitting control signals to the actuators. As will be illustrated in greater detail with respect toFIGS. 4-6, the flight control computer30and the local control systems28aand28bcan collaboratively provide a variety of redundant control methods relative to the controllable elements in the proprotor assemblies20aand20b.

FIG. 1Cillustrates aircraft10in transition between proprotor forward flight mode and airplane forward flight mode, in which engines24a,24bhave been disengaged from proprotor assemblies20a,20band proprotor blades22of proprotor assemblies20a,20bhave been feathered, or oriented to be streamlined in the direction of flight, such that proprotor blades22act as brakes to aerodynamically stop the rotation of proprotor assemblies20a,20b. In this configuration, engines24a,24bare operable in turbofan mode wherein hot combustion gases in each engine24a,24bcause rotation of a power turbine coupled to an output shaft that is used to power a turbofan that forces bypass air through a fan duct to create forward thrust enabling wing14to provide a lifting force responsive to forward airspeed, such that aircraft10flies much like a conventional jet aircraft. Thus, in this configuration, aircraft10is considered to be in a non-rotary flight mode.FIG. 1Dillustrates aircraft10in airplane forward flight mode, in which proprotor blades22of proprotor assemblies20a,20bhave been folded to be oriented substantially parallel to respective pylon assemblies18a,18bto minimize the drag force generated by proprotor blades22. In this configuration, engines24a,24bare operable in the turbofan mode and aircraft10is considered to be in the non-rotary flight mode. The forward cruising speed of aircraft10can be significantly higher in airplane forward flight mode versus proprotor forward flight mode as the forward airspeed induced proprotor aeroelastic instability is overcome.

Even though aircraft10has been described as having two engines fixed to the fuselage each operating one of the proprotor assemblies in the rotary flight mode, it should be understood by those having ordinary skill in the art that other engine arrangements are possible and are considered to be within the scope of the present disclosure including, for example, having a single engine that provides torque and rotational energy to both of the proprotor assemblies. In addition, even though proprotor assemblies20a,20bare illustrated in the context of tiltrotor aircraft10, it should be understood by those having ordinary skill in the art that the proprotor assemblies disclosed herein can be implemented on other tiltrotor aircraft including, for example, quad tiltrotor aircraft having an additional wing member aft of wing14, unmanned tiltrotor aircraft or other tiltrotor aircraft configurations.

Referring toFIGS. 2A-2Gof the drawings, a mechanism for transitioning a tiltrotor aircraft between rotary and non-rotary flight modes is depicted and generally designated100. In the illustrated embodiment, a rotor assembly102is depicted as a gimbal mounted, three bladed rotor assembly having a gimballing degree of freedom relative to a mast104. Rotor assembly102includes a rotor hub106that is coupled to and operable to rotate with mast104. Rotor hub106has a conical receptacle108extending from a lower portion thereof. Rotor hub106includes three arms110each of which support a rotor blade assembly112, only one being visible in the figures. Each rotor blade assembly112includes a cuff114and a rotor blade116that is pivotably coupled to cuff114by a connection member depicted as pin118. As discussed herein, rotor blade assembly112has a pitching degree of freedom during rotary flight and a folding degree of freedom during non-rotary flight.

The pitching and folding degrees of freedom of rotor blade assembly112are realized using the highly reliable operation of swash plate120. Swash plate120includes a non-rotating lower swash plate element122and a rotating upper swash plate element124. Swash plate element124is operably coupled to each rotor blade assembly112at cuff114via a pitch link126and a pitch horn128, only one such connection being visible in the figures. A control system including swash plate actuators (not pictured) is coupled to swash plate element122. The control system operates responsive to pilot input to raise, lower and tilt swash plate element122and thus swash plate element124relative to mast104. These movements of swash plate120collectively and cyclically control the pitch of rotor blade assemblies112during rotary flight and fold rotor blade assemblies112during non-rotary flight.

Transitioning mechanism100includes a gimbal lock130that is coupled to and operable to rotate with mast104. Gimbal lock130includes a conical ring132, an actuation ring134and an actuator136including a lift ring138. Gimbal lock130is operable to selectively enable and disable the gimballing degree of freedom of rotor assembly102relative to mast104. As best seen inFIG. 2A, gimbal lock130is disengaged from rotor assembly102, which enables the gimballing degree of freedom of rotor assembly102. In this configuration, there is an axial separation between conical ring132of gimbal lock130and conical receptacle108of rotor hub106such that any teetering or flapping motion of rotor assembly102is not impacted by gimbal lock130. When it is desired to transition the tiltrotor aircraft from the rotary flight mode and the non-rotary flight mode, actuator136is operated to cause lift ring138to raise actuation ring134, which in turn raises conical ring132into conical receptacle108of rotor hub106. In this configuration, as best seen inFIG. 2B, gimbal lock130is engaged with rotor assembly102, which disables the gimballing degree of freedom of rotor assembly102relative to mast104for non-rotary flight. In the illustrated embodiment, conical ring132has a conical geometry that is configured to mate with a similar geometry of receptacle108thus disabling the gimballing degree of freedom of rotor assembly102relative to mast104. It should be appreciated, however, that the exact mating geometry of conical ring132and receptacle108is implementation specific and not limited to the illustrated geometry.

Transitioning mechanism100also includes a blade stop assembly140that is coupled to and operable to rotate with mast104. Blade stop assembly140includes three arms142that correspond to the three rotor blade assemblies112of rotor assembly102. In the illustrated embodiment, blade stop assembly140is integrated with gimbal lock130and shares actuation ring134, actuator136and lift ring138therewith, such that operation of blade stop assembly140occurs together with the operation of gimbal lock130. It should be appreciated, however, that a blade stop assembly and a gimbal lock for use with the embodiments disclosed herein could alternatively operate independent of one another. As best seen inFIG. 2A, arms142of blade stop assembly140have a radially contracted orientation, which provides clearance for rotor blade assemblies112during rotary flight. When it is desired to transition the tiltrotor aircraft from the rotary flight mode and the non-rotary flight mode, actuator136is operated to cause lift ring138to raise actuation ring134, which in turn shifts arms142from the radially contracted orientation to a radially extended orientation, as best seen inFIG. 2B. In this configuration, arms142of blade stop assembly140will each engage a cuff114of a rotor blade assembly112upon feathering the rotor blade assemblies112responsive to lowering swash plate120, as best seen inFIG. 2C. In this manner, blade stop assembly140provides a positive stop for rotor blade assemblies112.

Referring additionally toFIGS. 3A-3E, transitioning mechanism100includes three blade lock assemblies150, only one being visible in the figures. Each blade lock assembly150is selectively operable to enable and disable the folding degree of freedom and the pitching degree of freedom of the respective rotor blade assembly112. As illustrated, each blade lock assembly150includes a crank152that is rotatably coupled to cuff114and rotatable with pitch horn128via a connection member depicted as pin154. In this manner, rotation of crank152is responsive to the rise and fall of swash plate120in non-rotary flight. Each blade lock assembly150also includes a link156that is rotatably coupled to rotor blade116at lug158via a connection member depicted as pin160. Crank152and link156are coupled together at a pivot joint162. In the illustrated embodiment, coincident with pivot joint162, link156includes a pair of outwardly extending flanges164each having a roller element166rotatably coupled thereto. Each flange164is receivable in a seat168of cuff114when it is desired to disable the folding degree of freedom of rotor blade assembly112. Preferably, an arch shaped geometry of the contact surface of each seat168is sized such that a fully engaged flange164seated therein will have two points of contact therewith providing a stiff connection, thereby minimizing any vibrations and/or relative movement between the parts.

Each blade lock assembly150further includes a blade lock170having a fold lock position securing pivot joint162to cuff114and a pitch lock position securing cuff114to arm142of blade stop assembly140. More specifically, each blade lock170includes a fold lock172and a pitch lock174. Each fold lock172consists of a pair of arms176that are rotatably coupled to respective seats168of cuff114via connection members depicted as pins178. Each arm176includes a wedge180having a bearing surface that contacts a respective roller element166and provides maximum contact force when fold lock172is fully engaged, as best seen inFIG. 3A. Each pitch lock174includes a hasp182that is rotatably coupled to a pair of lugs184of cuff114via a connection member depicted as pin186. Each hasp182includes a central opening operable to selectively receive and retain a tab188of cuff114and a tab190of arm142therein, as best seen inFIG. 3C. In the illustrated embodiment, fold lock172and a pitch lock174are coupled together by a pair of adjustable connecting rods192such that a single actuator194is operable to shift blade lock170between the fold lock position, depicted inFIG. 3A, and the pitch lock position, depicted inFIG. 3B. It should be appreciated, however, that a fold lock and a pitch lock for use with the embodiments disclosed herein could alternatively operate independent of one another.

The operation of transitioning mechanism100will now be described with reference to an exemplary flight of tiltrotor aircraft10. For vertical takeoff and hovering in helicopter flight mode, as best seen inFIG. 1A, and low speed forward flight in proprotor forward flight mode, as best seen inFIG. 1B, tiltrotor aircraft10is in rotary flight mode. To achieve this operational mode, engines24a,24bare in turboshaft mode to provide torque and rotational energy to proprotor assemblies20a,20b, gimbal lock130is in the disengaged position enabling the gimballing degree of freedom of rotor assemblies102, as best seen inFIG. 2A, arms142of blade stop assembly140are in the radially contracted orientation providing clearance for rotor assemblies102, as best seen inFIG. 2A, and each of the blade lock assemblies150is enabling the pitching degree of freedom and disabling the folding degree of freedom of rotor blade assemblies112, as best seen inFIG. 3A. In this configuration, swash plate120collectively and cyclically controls the pitch of rotor blade assemblies112responsive to pilot input.

When it is desired to transition tiltrotor aircraft10from low speed forward flight in proprotor forward flight mode, as best seen inFIG. 1B, to high speed forward flight in airplane forward flight mode, as best seen inFIG. 1D, transitioning mechanism100is used to safely achieve this result. As a preliminary step, engines24a,24bare transitioned from turboshaft mode to turbofan mode until forward thrust is solely generated by engines24a,24band tiltrotor aircraft10is in non-rotary flight mode. Swash plate120is now used to collectively shift the pitch of rotor blade assemblies112to the feathering position, as best seen inFIG. 1C, wherein rotor blades116act as brakes to aerodynamically stop the rotation of rotor assemblies102. To disable the gimballing degree of freedom of rotor assembly102, actuator136is operated to cause lift ring138to raise actuation ring134, which in turn raises conical ring132into conical receptacle108of rotor hub106, as best seen inFIG. 2B. At the same time, responsive to lift ring138raising actuation ring134, arms142shift from the radially contracted orientation to the radially extended orientation, as best seen inFIG. 2B, to provide a positive stop for rotor blade assemblies112.

Next, actuators194are operated to shift blade locks170from the fold lock position, depicted inFIG. 3A, to the pitch lock position, depicted inFIG. 3C. Actuator194simultaneously causes hasp182to rotate relative to lugs184of cuff114about pin186and arms176to rotate relative to seats168of cuff114about pins178, as best seen inFIG. 3B. At the end of travel, hasp182has received tab188of cuff114and tab190of arm142in a central opening, as best seen inFIG. 3C, which disables the pitching degree of freedom of rotor blade assemblies112. Also, at the end of travel, wedges180have cleared the lower portion of seats168, which enables the folding degree of freedom of rotor blade assemblies112. Swash plate120is now used to collectively shift rotor blade assemblies112from the radially outwardly extending feathering position, as best seen inFIG. 1C, to a folded orientation, as best seen inFIGS. 1D and 2G.

With the pitching degree of freedom disabled, rise and fall of swash plate120now rotates pitch horn128relative to cuff114, which in turn causes rotation of crank152. The rotation of crank152causes rotation of link156relative to lug158about pin160, rotation in pivot joint162, which disengages flanges164from seats168, and rotation of rotor blade116relative to cuff114about pin118, as best seen inFIGS. 2F and 3D. Continued operation of swash plate120causes continued rotation of pitch horn128, crank152, link156and rotor blade116until rotor blade116reaches its desired folded orientation, as best seen inFIGS. 2G and 3E. Tiltrotor aircraft10is now in airplane flight mode, which is the high speed forward flight mode of tiltrotor aircraft10and is a non-rotary flight mode. In this operational mode, engines24a,24bare in turbofan mode providing no torque and rotational energy to proprotor assemblies20a,20b, gimbal lock130is in the engaged position disabling the gimballing degree of freedom of rotor assemblies102, arms142of blade stop assembly140are in the radially extended orientation providing a position stop and coupling for rotor blade assemblies112, and each of the blade lock assemblies150is disabling the pitching degree of freedom and enabling the folding degree of freedom of rotor blade assemblies112.

When it is desired to transition back to proprotor forward flight mode, as best seen inFIG. 1B, from airplane forward flight mode, as best seen inFIG. 1D, transitioning mechanism100is used to safely achieve this result. With the pitching degree of freedom disabled, lowering swash plate120rotates pitch horn128relative to cuff114, which in turn causes rotation of crank152, link156and the unfolding of rotor blade116, as best seen inFIGS. 2F and 3D. Continued operation of swash plate120causes continued rotation of pitch horn128, crank152, link156and rotor blade116until rotor blade116reaches its desired radially outwardly extending orientation, as best seen inFIG. 2E. In this position, crank152and link156are generally aligned such that flanges164have entered seats168, as best seen inFIG. 3C.

Next, actuators194are operated to shift blade locks170from the pitch lock position, depicted inFIG. 3C, to the fold lock position, depicted inFIGS. 2D and 3A. Actuator194simultaneously causes hasp182to rotate relative to lugs184of cuff114about pin186and arms176to rotate relative to seats168of cuff114about pins178, as best seen inFIGS. 2D and 3B. At the end of travel, hasp182is remote from tab188of cuff114and tab190of arm142, as best seen inFIG. 3A, which enables the pitching degree of freedom of rotor blade assemblies112. Also, at the end of travel, wedges180have contacted roller element166seating flanges164tightly within seats168and disabling the folding degree of freedom of rotor blade assembly112, as best seen inFIG. 3A. Swash plate120may now be used to collectively shift rotor blade assemblies112from the feathering position, as best seen inFIG. 1C, to a windmilling orientation.

To enable the gimballing degree of freedom of rotor assembly102, actuator136is operated to cause lift ring138to lower actuation ring134, which in turn lowers conical ring132out of engagement with conical receptacle108of rotor hub106, as best seen inFIG. 2A. At the same time, responsive to lift ring138lower actuation ring134, arms142shift from the radially extended orientation to the radially contracted orientation, as best seen inFIG. 2A, to provide clearance for rotor blade assemblies112. Next, engines24a,24bare transitioned from turbofan mode to turboshaft mode such that forward thrust is provided by proprotor assemblies20a,20band tiltrotor aircraft10is in the rotary flight mode. From this configuration, tiltrotor aircraft10may now be transitioned to helicopter mode when it is desired to hover and/or land the aircraft.

FIG. 4illustrates an example of a control system400for controllable elements in a rotor assembly of a tiltrotor aircraft. The control system400includes a local control system1028, a slip ring1040and a flight control computer1030. The local control system1028can be considered an example of each of the local control systems28aand28bofFIGS. 1A-1D. In that way, the local control system1028can be mounted or otherwise disposed in a rotor assembly of a tiltrotor aircraft in similar fashion to the local control systems28aand28b. Also, the flight control computer1030can be considered an example of the flight control computer30ofFIGS. 1A-1D, and thus can be located or disposed outside of, or external to, the rotor assembly in which the local control system1028is disposed or mounted.

In the illustrated embodiment, the local control system1028includes a control loop1032that is managed by a local control computer1038. The local control computer1038can communicate with the flight control computer1030using any form of network or data communication, such as serial communication (e.g., RS-422, RS-485, etc.). The local control computer1038is connected to the flight control computer1030via the slip ring1040. The slip ring1040can provide electrical connections and other connections between the local control computer1038, which rotates with the rotor assembly, and the flight control computer1030, which is external the rotor assembly and therefore does not rotate with rotor assembly. The slip ring1040can include, for example, non-rotating brushes conductively coupled to one side of each connection and slidingly engaging rotating rings that are conductively coupled to the other side of each connection.

The control loop1032includes an actuator1034, such as a motor, paired with a feedback sensor1036. The actuator1034and the feedback sensor1036can each be connected to the local control computer1038via an analog or digital connection. In general, the actuator1034, when operated, controls motion of a controllable element within the rotor assembly in which the local control system1028is disposed or mounted. The local control computer1038can operate the actuator1034, for example, by transmitting control signals, such as electric current, to the actuator1034in order to produce proportional motion. In an example, the actuator1034can be similar to the actuator136described above relative toFIGS. 2A-2G, such that it is operated to engage or disengage a gimbal lock such as the gimbal lock130, thereby enabling or disabling a gimballing degree of freedom of the rotor assembly in which the local control system1028is disposed or mounted. In another example, the actuator1034can be similar to the actuators194described above relative toFIGS. 3A-3E, such that it is operated to shift blade locks from a pitch lock position to a fold lock position or from a fold lock position to a pitch lock position. Other examples of actuators will be apparent to one skilled in the art after reviewing the present disclosure.

In some cases, the local control computer1038can transmit the control signals to the actuator1034in response to receiving corresponding control commands transmitted through the slip ring1040by the flight control computer1030. The local control computer1038can report received feedback to the flight control computer1030. In addition, or alternatively, the local control computer1038can transmit the control signals to the actuator1034on its own initiative based on software or other control logic resident thereon. The feedback sensor1036, in turn, can measure position, speed and/or other appropriate characteristics of the controllable element and provide, to the local control computer1038, a feedback signal that includes, for example, information related to or derived from the measured characteristic(s). In a typical embodiment, the control loop1032is fully contained in the rotor assembly within which the local control system1028is disposed or mounted and thus may be considered “locally closed” relative to the rotor assembly.

In various embodiments, locally-closed control loops such as the control loop1032can provide various technical advantages. For example, wiring for communications related to locally-closed control loops such as the control loop1032can be contained to the rotor assembly in which the local control computer1038is mounted, and need not pass through the slip ring1040to the flight control computer1030. This can decrease the amount of wiring through the slip ring1040and reduce susceptibility, for example, to electromagnetic interference. Furthermore, in certain embodiments, fault management and other functions can be performed locally by the local control computer1038, thereby reducing communication overhead related to communicating with the flight control computer1030and relieving the flight control computer1030of the corresponding computational expense. For example, the local control computer1038can identify a fault in the rotor assembly, determine one or more remediation steps and utilize the control loop1032to implement the one or more remediation steps, for example, by transmitting a control signal to an actuator such as the1034.

For illustrative purposes, the control loop1032, the actuator1034, the feedback sensor1036, the local control computer1038and the flight control computer1030are each illustrated singly. However, in various embodiments, each of these illustrated components can be representative of plural such components in order to implement greater redundancy and reliability. For example, in certain embodiments, the local control computer1038can manage multiple control loops similar to the control loop1032, each loop including a pairing of a distinct actuator and a distinct sensor similar to the actuator1034and the feedback sensor1036, respectively, for purposes of providing redundant control paths for the same controllable element. According to this example, if, for instance, an actuator in one control loop were to experience failure, any one of the other redundant control loops would be sufficient to control motion of the controllable element.

In another example, the local control computer1038can be representative of more than one local control computer. According to this example, management of multiple control loops, for the same or different controllable elements, can be appropriately distributed among the local control computers. In some cases, according to this example, more than one of the local control computers can be configured to manage the same control loops, different control loops or overlapping sets of control loops. In addition, or alternatively, the flight control computer1030can be representative of more than one flight control computer. In an example, multiple flight control computers similar to the flight control computer1030could each communicate with and/or send commands to the same local control computers, different local control computers or overlapping sets of control computers.

FIG. 5illustrates an example of a control system500for a tiltrotor aircraft such as the aircraft10ofFIGS. 1A-1D. For illustrative purposes, the control system500is shown to include a local control system528that further includes two local control computers, namely, local control computers1138aand1138b, and eight control loops, namely, control loops1132a(1),1132b(1),1132c(1),1132d(1),1132a(2),1132b(2),1132c(2) and1132d(2) (collectively, control loops1132) and auxiliary sensor(s)1142. The control system500further includes three flight control computers, namely, flight control computers1130a,1130band1130c, a slip ring1140and a remote computer1152.

The control loops1132can each include a pairing of an actuator and a feedback sensor in a rotor assembly as described relative to the control loop1032ofFIG. 4. More particularly, in the control system500, the control loops1132are organized into four pairs, namely, control loops1132a(1)-(2),1132b(1)-(2),1132c(1)-(2) and1132d(1)-(2), such that, within each pair, the control loops supply redundant control paths for the same controllable element. For example, the control loops1132a(1) and1132a(2) can each include an actuator that controls motion of a first controllable element in the rotor assembly and a sensor that provides feedback relative to that controllable element. In that way, two actuators from two different control loops can be configured to control motion of the first controllable element, and two sensors from those two different control loops can be configured to provide feedback relative to the first controllable element. In like fashion, control loops1132b(1)-(2),1132c(1)-(2) and1132d(1)-(2) can each collectively include two actuators and two sensors relative to second, third and fourth controllable elements, respectively.

For example, in the three-blade illustrative example ofFIGS. 1A-3E, control loops1132a(1)-(2),1132b(1)-(2) and1132c(1)-(2) can each correspond to a different proprotor blade and provide control and feedback relative to the shifting of blade locks from a pitch lock position to a fold lock position, or vice versa, in the fashion described above relative toFIGS. 3A-3E. Further, according to this example, control loops1132d(1)-(2) can control and provide feedback relative to the engaging or disengaging of a gimbal lock in the fashion described above relative toFIGS. 2A-2G.

The auxiliary sensor(s)1142can serve a disambiguation function relative to the control loops1132. As described previously, the example four pairs of control loops shown inFIG. 5, namely, the control loops1132a(1)-(2),1132b(1)-(2),1132c(1)-(2) and1132d(1)-(2), may each include two sensors that provide feedback relative to first, second, third and fourth controllable elements, respectively. In some cases, two sensors in a given control-loop pair might provide inconsistent feedback for the same controllable element, for example, due to a malfunction in one of the sensors. In certain embodiments, the auxiliary sensor(s)1142can resolve these discrepancies by providing an additional set of feedback of the same type provided by the other two sensors. The additional set of feedback can be used to identify erroneous feedback. In certain embodiments, the auxiliary sensor(s)1142can include four auxiliary sensors so that there is one auxiliary sensor for each of the four controllable elements. Advantageously, in certain embodiments, when an ambiguity or discrepancy occurs relative to the sensors of one of the control loops1132a(1)-(2),1132b(1)-(2),1132c(1)-(2) and1132d(1)-(2), a corresponding one of the auxiliary sensor(s)1142can be used to indicate which of the first two sensors is correct, thereby providing improved fault tolerance. An output of the auxiliary sensor(s)1142can be provided to one or both of the local control computers1138aand1138b.

The local control computer1138aincludes a driver1144a, storage1146a, a communication interface1148aand a terminal connection1150a. In similar fashion, the local control computer1138bincludes a driver1144b, storage1146b, a communication interface1148band a terminal connection1150b. In general, the local control computers1138aand1138bcan each operate as described with respect to the local control computer1038ofFIG. 4, with management of the control loops1132being distributed between the two. In the illustrated example ofFIG. 5, the first loop of each control-loop pair, namely, the control loops1132a(1),1132b(1),1132c(1) and1132d(1), is managed by the local control computer1138a, with control signals being sent from, and feedback signals being received by, the driver1144a. The second loop of each control-loop pair, namely, the control loops1132a(2),1132b(2),1132c(2) and1132d(2), is shown as being managed by the local control computer1138b, with control signals being sent from, and feedback signals being received by, the driver1144b.

In certain embodiments, the local control computers1138aand1138bcan collaborate in the management, for example, of the four controllable elements to which the control loops1132relate. For example, the local control computers1138aand1138bcan share data and reach an agreed-upon decision regarding what control signal should be transmitted to which actuator. Data sharing and decision making can occur in various fashions. For example, in certain embodiments, the local control computer1138acan perform disk operations, such as read and write operations, on the storage1146bof the local control computer1138b. Similarly, the local control computer1138bcan perform disk operations, such as read and write operations, on the storage1146aof the local control computer1138a. In addition, or alternatively, the local control computers1138aand1138bcan exchange data related to controllable elements, such as received feedback, via the communication interfaces1148aand1148b. In various embodiments, the agreed-upon decision about a given control signal can reached as a result of each of the local control computers1138aand1138bexecuting parallel logic based on the same information, as a result of the decision of a designated “master” or “primary” computer, combinations of the same and/or the like.

The local control computers1138aand1138bcan remotely receive updates from a remote computer1152via the terminal connections1150aand1150b, respectively. In various embodiments, the remote computer1152can provide firmware or software updates, modify variable parameters stored in the storage1146aand1146b, retrieve fault codes from the storage1146aand1146b, combinations of the same and/or the like. In addition, in some embodiments, the terminal connections1150aand1150bcan be used by the remote computer1152as instrumentation ports.

In general, the flight control computers1130a,1130band1130ccan function and communicate through the slip ring1140in the fashion described relative to the flight control computer1030ofFIG. 4. The flight control computers1130a,1130band1130care shown to include first communication channels1130a(1),1130b(1) and1130c(1), respectively, and second communication channels1130a(2),1130b(2) and1130c(2), respectively.

In the example ofFIG. 5, the flight control computers1130a,1130band1130ccollectively provide three paths for communicating with the local control computer1138aand three paths for communicating with the local control computer1138b. The local control computer1138ais communicably coupled, through the slip ring1140, to the first communication channels1130a(2),1130b(2) and1130c(2), respectively, of the flight control computers1130a,1130band1130c. The local control computer1138bis shown to be communicably coupled, through the slip ring1140, to the second communication channels1130a(2),1130b(2) and1130c(2) of the flight control computers1130a,1130band1130c, respectively. In that way, all of the flight control computers1130a,1130band1130ccan communicate a command, or receive feedback from, one or both of the local control computers1138aand1138b.

The slip ring1140can operate as described with respect to the slip ring1040ofFIG. 4and thereby facilitate the above-described communications between the local control computers1138aand1138band the flight control computers1130a,1130band1130c. Additionally, the local control computers1138aand1138bcan be powered, through the slip ring1140, by buses1154aand1154b, respectively.

Furthermore, the flight control computers1130a,1130band1130care electrically connected to signal generators1156a,1156band1156c, respectively, which generators are controllable by the flight control computers1130a,1130band1130c. The signal generators1156a,1156band1156ccan produce an electrical or logical signal that enables the drivers1144aand1144b. In the illustrated embodiment, the signal generators1156a,1156band1156care shown in a daisy-chain configuration in which any one of the flight control computers1130a,1130band1130ccan enable or disable the driver1144aand/or the driver1144b. In certain embodiments, if, for example, a fault or other adverse situation in the rotor assembly is detected by one of the flight control computers1130a,1130band1130c, any of the flight control computers1130a,1130band1130ccan disable, or terminate the control function of, the driver1144aand/or the driver1144bvia the signal generators1156a,1156band1156c.

FIG. 6illustrates an example of a control system600for a tiltrotor aircraft such as the aircraft10ofFIGS. 1A-1D. For illustrative purposes, the control system600is shown to include a local control system628that further includes three local control computers, namely, local control computers1238a,1238band1238c, and twelve control loops, namely, control loops1232a(1),1232a(2),1232a(3),1232b(1),1232b(2),1232b(3),1232c(1),1232c(2),1232c(3),1232d(1),1232d(2) and1232d(3) (collectively, control loops1232). The control system600further includes three flight control computers, namely, flight control computers1230a,1230band1230c, a slip ring1240and a remote computer1252.

The control loops1232can each include a pairing of an actuator and a feedback sensor in a rotor assembly as described relative to the control loop1032ofFIG. 4and the control loops1132ofFIG. 5. In the control system600, the control loops1232are organized into four sets, namely, control loops1232a(1)-(3) (collectively, control loops1232a),1232b(1)-(3) (collectively, control loops1232b),1232c(1)-(3) (collectively, control loops1232c) and1232d(1)-(3) (collectively, control loops1232d), such that, within each set, the control loops supply redundant control paths for the same controllable element. For example, the control loops1232acan each include an actuator that controls motion of a first controllable element in the rotor assembly and a sensor that provides feedback relative to that controllable element. In that way, three actuators from three different control loops can be configured to control motion of the first controllable element, and three sensors from those three different control loops can be configured to provide feedback relative to the first controllable element. In like fashion, the control loops1232b,1232cand1232dcan each collectively include three actuators and three sensors relative to second, third and fourth controllable elements, respectively.

For example, in the three-blade illustrative example ofFIGS. 1A-3E, the control loops1232a,1232band1232ccan each correspond to a different proprotor blade and provide control and feedback relative to the shifting of blade locks from a pitch lock position to a fold lock position, or vice versa, in the fashion described above relative toFIGS. 3A-3E. Further, according to this example, the control loops1232dcan control and provide feedback relative to the engaging or disengaging of a gimbal lock in the fashion described above relative toFIGS. 2A-2G. In contrast to the control system500ofFIG. 5, no auxiliary sensors are illustrated in the control system600. In certain embodiments, the disambiguation function served, for example, by the auxiliary sensor(s)1142ofFIG. 5, is unnecessary in the control system600due to the fact that the control loops1232a,1232b,1232cand1232deach include, in total, three sensors, thereby providing built-in fault tolerance when, for example, a single sensor malfunctions.

The local control computers1238a,1238band1238cinclude, respectively, drivers1244a,1244band1244c, storage1246a,1246band1246c, communication interfaces1248a,1248band1248c, and terminal connections1250a,1250band1250c. In general, the foregoing example components of the local control computers1238a,1238band1238ccan perform similarly to the components of the same name that are shown and described with respect to the local control computers1138aand1138bofFIG. 5. Likewise, the local control computers1238a,1238band1238ccan each operate as described with respect to the local control computer1038ofFIG. 4, with management of the control loops1232being distributed among the three computers.

In the illustrated example ofFIG. 6, the first loop of each control-loop set, namely, the control loops1232a(1),1232b(1),1232c(1) and1232d(1), is managed by the local control computer1238a, with control signals being sent from, and feedback signals being received by, the driver1244a. The second loop of each control-loop set, namely, the control loops1232a(2),1232b(2),1232c(2) and1232d(2), is shown as being managed by the local control computer1238b, with control signals being sent from, and feedback signals being received by, the driver1244b. Further, the third loop of each control-loop set, namely, the control loops1232a(3),1232b(3),1232c(3) and1232d(3), is shown as being managed by the local control computer1238c, with control signals being sent from, and feedback signals being received by, the driver1244c.

For simplicity of illustration, direct connections between the local control computer1238aand the local control computer1238care not explicitly shown inFIG. 6. However, it should be appreciated that the connections shown, for example, between the storage1246aand the storage1246b, can also exist between the storage1246aand the storage1246c. Similarly, the connections shown, for example, between the communication interface1248aand the communication interface1248b, can likewise exist between the communication interface1248aand the communication interface1248c.

In certain embodiments, the local control computers1238a,1238band1238ccan collaborate in the management of the four controllable elements to which the control loops1232relate. For example, the local control computers1238a,1238band1238ccan share data and reach an agreed-upon decision regarding what control signal should be transmitted to which actuator. Data sharing and decision making can occur in various fashions. For example, in certain embodiments, the local control computer1238acan perform disk operations, such as read and write operations, on the storage1246bof the local control computer1238band/or the storage1246cof the local control computer1238c. Similarly, the local control computer1238bcan perform disk operations, such as read and write operations, on the storage1246aof the local control computer1238aand/or the storage1246cof the local control computer1238c. In addition, or alternatively, the local control computers1238a,1238band1238ccan exchange data related to controllable elements, such as received feedback, via the communication interfaces1248a,1248band1248c. In various embodiments, the agreed-upon decision about a given control signal can reached as a result of each of the local control computers1238a,1238band1238cexecuting parallel logic based on the same information, as a result of the decision of a designated “master” or “primary” computer, combinations of the same and/or the like.

The local control computers1238a,1238band1238ccan remotely receive updates from the remote computer1252via the terminal connections1250a,1250band1250c, respectively. In various embodiments, the remote computer1252can provide firmware updates, modify variable parameters stored in the storage1246a,1246band1246c, retrieve fault codes from the storage1246a,1246band1246c, combinations of the same and/or the like. In addition, in some embodiments, the terminal connections1250a,1250band1250ccan be used by the remote computer1252as instrumentation ports.

In general, the flight control computers1230a,1230band1230ccan function and communicate through the slip ring1240in the fashion described relative to the flight control computer1030ofFIG. 4. The flight control computers1230a,1230band1230care shown to include first communication channels1230a(1),1230b(1) and1230c(1), respectively, and second communication channels1230a(2),1230b(2) and1230c(2), respectively.

In the example ofFIG. 6, the flight control computers1230a,1230band1230ccollectively provide multiple redundant paths for transmitting commands, or receiving feedback relative to, the four controllable elements controlled via the control loops1232. The local control computer1238ais communicably coupled, through the slip ring1240, to both the first communication channel1230a(1) and the second communication channel1230a(2) of the flight control computer1230a. The local control computer1238bis shown to be communicably coupled, through the slip ring1240, to both the first communication channel1230b(1) and the second communication channel1230b(2) of the flight control computer1230b. The local control computer1238cis shown to be communicably coupled, through the slip ring1240, to both the first communication channel1230c(1) and the second communication channel1230c(2) of the flight control computer1230c. In that way, all of the flight control computers1230a,1230band1230ccan communicate a command, or receive feedback relative to, any of the four controllable elements controlled by the control loops1232.

The slip ring1240can operate as described with respect to the slip ring1040ofFIG. 4and thereby facilitate the above-described communications between the local control computers1238a,1238band1238cand the flight control computers1230a,1230band1230c. Additionally, the local control computers1238a,1238band1238ccan be powered, through the slip ring1240, by buses1254a,1254band1254c, respectively.

Furthermore, the flight control computers1230a,1230band1230care electrically connected to signal generators1256a,1256band1256c, respectively, which generators are controllable by the flight control computers1230a,1230band1230c. The signal generators1256a,1256band1256ccan produce an electrical or logical signal that enables the drivers1244a,1244band1244c, respectively. In certain embodiments, if, for example, a fault or other adverse situation in the rotor assembly is detected by one of the flight control computers1230a,1230band1230c, the flight control computer1230acan disable, or terminate the control function of, the driver1244a. The flight control computers1230band1230ccan take similar action relative to the drivers1244band1244c, respectively.

FIG. 7illustrates an example of a computer system200. In some cases, the computer system200can be representative, for example, of a flight control computer such as, for example, the flight control computer1030ofFIG. 4, the flight control computers1130a,1130band1130cofFIG. 5, and/or the flight control computers1230a,1230band1230C ofFIG. 6. In addition, in some cases, the computer system200can be representative, for example, of a local control computer such as, for example, the local control computer1038ofFIG. 4, the local control computers1138aand1138bofFIG. 5, and the local control computers1238a,1238band1238cofFIG. 6.

The computer system200includes an application222operable to execute on computer resources202. The application222can include, for example, logic for determining what control signal to send, which actuator should send a control signal, whether a fault has occurred, what action to take in light of a fault, combinations of the foregoing and/or the like. In particular embodiments, the computer system200may perform one or more actions described or illustrated herein. In particular embodiments, one or more computer systems may provide functionality described or illustrated herein. In particular embodiments, encoded software running on one or more computer systems may perform one or more actions described or illustrated herein or provide functionality described or illustrated herein.

The components of the computer system200may include any suitable physical form, configuration, number, type and/or layout. As an example, and not by way of limitation, the computer system200may include an embedded computer system, a system-on-chip (SOC), a single-board computer system (SBC) (such as, for example, a computer-on-module (COM) or system-on-module (SOM)), a desktop computer system, a laptop or notebook computer system, an interactive kiosk, a mainframe, a mesh of computer systems, a mobile telephone, a personal digital assistant (PDA), a wearable or body-borne computer, a server, or a combination of two or more of these. Where appropriate, the computer system200may include one or more computer systems; be unitary or distributed; span multiple locations; span multiple machines; or reside in a cloud, which may include one or more cloud components in one or more networks.

In the depicted embodiment, the computer system200includes a processor208, memory220, storage210, interface206, and bus204. Although a particular computer system is depicted having a particular number of particular components in a particular arrangement, this disclosure contemplates any suitable computer system having any suitable number of any suitable components in any suitable arrangement.

Processor208may be a microprocessor, controller, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to execute, either alone or in conjunction with other components, (e.g., memory220), the application222. Such functionality may include providing various features discussed herein. In particular embodiments, processor208may include hardware for executing instructions, such as those making up the application222. As an example, and not by way of limitation, to execute instructions, processor208may retrieve (or fetch) instructions from an internal register, an internal cache, memory220, or storage210; decode and execute them; and then write one or more results to an internal register, an internal cache, memory220, or storage210.

In particular embodiments, processor208may include one or more internal caches for data, instructions, or addresses. This disclosure contemplates processor208including any suitable number of any suitable internal caches, where appropriate. As an example, and not by way of limitation, processor208may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory220or storage210and the instruction caches may speed up retrieval of those instructions by processor208. Data in the data caches may be copies of data in memory220or storage210for instructions executing at processor208to operate on; the results of previous instructions executed at processor208for access by subsequent instructions executing at processor208, or for writing to memory220, or storage210; or other suitable data. The data caches may speed up read or write operations by processor208. The TLBs may speed up virtual-address translations for processor208. In particular embodiments, processor208may include one or more internal registers for data, instructions, or addresses. Depending on the embodiment, processor208may include any suitable number of any suitable internal registers, where appropriate. Where appropriate, processor208may include one or more arithmetic logic units (ALUs); be a multi-core processor; include one or more processors208; or any other suitable processor.

Memory220may be any form of volatile or non-volatile memory including, without limitation, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), flash memory, removable media, or any other suitable local or remote memory component or components. In particular embodiments, memory220may include random access memory (RAM). This RAM may be volatile memory, where appropriate. Where appropriate, this RAM may be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, where appropriate, this RAM may be single-ported or multi-ported RAM, or any other suitable type of RAM or memory. Memory220may include one or more memories220, where appropriate. Memory220may store any suitable data or information utilized by the computer system200, including software embedded in a computer readable medium, and/or encoded logic incorporated in hardware or otherwise stored (e.g., firmware). In particular embodiments, memory220may include main memory for storing instructions for processor208to execute or data for processor208to operate on. In particular embodiments, one or more memory management units (MMUs) may reside between processor208and memory220and facilitate accesses to memory220requested by processor208.

As an example, and not by way of limitation, the computer system200may load instructions from storage210or another source (such as, for example, another computer system) to memory220. Processor208may then load the instructions from memory220to an internal register or internal cache. To execute the instructions, processor208may retrieve the instructions from the internal register or internal cache and decode them. During or after execution of the instructions, processor208may write one or more results (which may be intermediate or final results) to the internal register or internal cache. Processor208may then write one or more of those results to memory220. In particular embodiments, processor208may execute only instructions in one or more internal registers or internal caches or in memory220(as opposed to storage210or elsewhere) and may operate only on data in one or more internal registers or internal caches or in memory220(as opposed to storage210or elsewhere).

In particular embodiments, storage210may include mass storage for data or instructions. As an example, and not by way of limitation, storage210may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a Universal Serial Bus (USB) drive or a combination of two or more of these. Storage210may include removable or non-removable (or fixed) media, where appropriate. Storage210may be internal or external to the computer system200, where appropriate. In particular embodiments, storage210may be non-volatile, solid-state memory. In particular embodiments, storage210may include read-only memory (ROM). Where appropriate, this ROM may be mask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. Storage210may take any suitable physical form and may include any suitable number or type of storage. Storage210may include one or more storage control units facilitating communication between processor208and storage210, where appropriate.

In particular embodiments, interface206may include hardware, encoded software, or both providing one or more interfaces for communication (such as, for example, packet-based communication) among any networks, any network devices, and/or any other computer systems. As an example, and not by way of limitation, communication interface206may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network and/or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network.

Depending on the embodiment, interface206may be any type of interface suitable for any type of network for which computer system200is used. As an example, and not by way of limitation, computer system200can include (or communicate with) an ad-hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, computer system200can include (or communicate with) a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network, an LTE network, an LTE-A network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or any other suitable wireless network or a combination of two or more of these. The computer system200may include any suitable interface206for any one or more of these networks, where appropriate.

In some embodiments, interface206may include one or more interfaces for one or more I/O devices. One or more of these I/O devices may enable communication between a person and the computer system200. As an example, and not by way of limitation, an I/O device may include a keyboard, keypad, microphone, monitor, mouse, printer, scanner, speaker, still camera, stylus, tablet, touchscreen, trackball, video camera, another suitable I/O device or a combination of two or more of these. An I/O device may include one or more sensors. Particular embodiments may include any suitable type and/or number of I/O devices and any suitable type and/or number of interfaces206for them. Where appropriate, interface206may include one or more drivers enabling processor208to drive one or more of these I/O devices. Interface206may include one or more interfaces206, where appropriate.

Bus204may include any combination of hardware, software embedded in a computer readable medium, and/or encoded logic incorporated in hardware or otherwise stored (e.g., firmware) to couple components of the computer system200to each other. As an example, and not by way of limitation, bus204may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or any other suitable bus or a combination of two or more of these. Bus204may include any number, type, and/or configuration of buses204, where appropriate. In particular embodiments, one or more buses204(which may each include an address bus and a data bus) may couple processor208to memory220. Bus204may include one or more memory buses.

Herein, reference to a computer-readable storage medium encompasses one or more tangible computer-readable storage media possessing structures. As an example, and not by way of limitation, a computer-readable storage medium may include a semiconductor-based or other integrated circuit (IC) (such, as for example, a field-programmable gate array (FPGA) or an application-specific IC (ASIC)), a hard disk, an HDD, a hybrid hard drive (HHD), an optical disc, an optical disc drive (ODD), a magneto-optical disc, a magneto-optical drive, a floppy disk, a floppy disk drive (FDD), magnetic tape, a holographic storage medium, a solid-state drive (SSD), a RAM-drive, a SECURE DIGITAL card, a SECURE DIGITAL drive, a flash memory card, a flash memory drive, or any other suitable tangible computer-readable storage medium or a combination of two or more of these, where appropriate.

Particular embodiments may include one or more computer-readable storage media implementing any suitable storage. In particular embodiments, a computer-readable storage medium implements one or more portions of processor208(such as, for example, one or more internal registers or caches), one or more portions of memory220, one or more portions of storage210, or a combination of these, where appropriate. In particular embodiments, a computer-readable storage medium implements RAM or ROM. In particular embodiments, a computer-readable storage medium implements volatile or persistent memory. In particular embodiments, one or more computer-readable storage media embody encoded software.

Although various illustrative examples are described above relative to tiltrotor aircraft, it should be appreciated that the principles described herein can similarly be applied to other rotorcraft such as helicopters, cyclocopters, autogyros, gyrodynes and rotor kites. It should also be appreciated that, in various embodiments, the control principles described herein can also be applied to non-rotorcraft machines and apparatus that include rotor assemblies. For example, in certain embodiments, a local control system can be disposed in a rotor assembly of a wind or water turbine and can include one or more local control loops of the type described with respect toFIGS. 4-6. Further, the local control system can communicate with one or more central control computers similar to the flight control computers described above, except that such computers would control operational aspects of wind or water turbines instead of flight. The one or more central control computers can be located, for example, external to the rotor assembly on the wind or water turbine. The one or more central control computers can also be located external to the wind or water turbine, for example, in cases where the one or more central control computers communicate with groups or collections of wind or water turbines.

Herein, reference to encoded software may encompass one or more applications, bytecode, one or more computer programs, one or more executables, one or more instructions, logic, machine code, one or more scripts, or source code, and vice versa, where appropriate, that have been stored or encoded in a computer-readable storage medium. In particular embodiments, encoded software includes one or more application programming interfaces (APIs) stored or encoded in a computer-readable storage medium. Particular embodiments may use any suitable encoded software written or otherwise expressed in any suitable programming language or combination of programming languages stored or encoded in any suitable type or number of computer-readable storage media. In particular embodiments, encoded software may be expressed as source code or object code. In particular embodiments, encoded software is expressed in a higher-level programming language, such as, for example, C, Perl, or a suitable extension thereof. In particular embodiments, encoded software is expressed in a lower-level programming language, such as assembly language (or machine code). In particular embodiments, encoded software is expressed in JAVA. In particular embodiments, encoded software is expressed in Hyper Text Markup Language (HTML), Extensible Markup Language (XML), or other suitable markup language. The foregoing description of embodiments of the disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure. The embodiments were chosen and described in order to explain the principals of the disclosure and its practical application to enable one skilled in the art to utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the embodiments without departing from the scope of the present disclosure. Such modifications and combinations of the illustrative embodiments as well as other embodiments will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.

Depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. Although certain computer-implemented tasks are described as being performed by a particular entity, other embodiments are possible in which these tasks are performed by a different entity.