Patent ID: 12240591

The drawing figures do not limit the disclosure to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the disclosure.

DETAILED DESCRIPTION

The following detailed description references the accompanying drawings that illustrate specific embodiments in which the current disclosure can be practiced. The embodiments are intended to describe aspects in sufficient detail to enable those skilled in the art to practice those embodiments of the disclosure. Other embodiments can be utilized, and changes can be made without departing from the scope of the current disclosure. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the disclosure is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

In this description, references to “one embodiment,” “an embodiment,” or “embodiments” mean that the feature or features being referred to are included in at least one embodiment of the technology. Separate references to “one embodiment,” “an embodiment,” or “embodiments” in this description do not necessarily refer to the same embodiment and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments but is not necessarily included. Thus, the technology can include a variety of combinations and/or integrations of the embodiments described herein.

Generally, embodiments of the present disclosure are directed to fly-by-wire (FBW) servo actuators. FBW allows for pilot movement of flight controls to be converted into electronic signals used to control actuators to move control surfaces to a desired position based on the pilot's input. The FBW servo actuators may be used for primary flight control (e.g., control of ailerons, elevators, rudder) of aircraft. The FBW servo actuator may comprise multiple redundancies to allow for continued operation of the actuator in the event of failure of one or more components of the actuator. The failures may be due gear locking or jamming in the drivetrain of the servo actuator and/or motor failure, for example. The multiple redundancies may allow for a single servo actuator to be used to actuate a control surface rather than requiring two servo actuators. The use of a single servo actuator may be advantageous in that all components can be contained with a single housing, which improves installation and serviceability of the actuator. Furthermore, crosstalk between actuators is eliminated.

The FBW servo actuator may comprise at least one output arm coupled to and rotationally driven by an output shaft. The at least one output arm may be coupled to a pushrod, for example, that actuates a control surface. The output shaft may be driven by a first and second differential.

The first differential may comprise a harmonic gear, a first gear, and a second gear. The first gear may be driven by a first motor and may drive a circular spline of the harmonic gear. The second gear may be driven by a second motor and may drive a wave generator of the harmonic gear. A flex spline of the harmonic gear may be coupled to an outer shaft that is in turn coupled to the output shaft to actuate the output arm. The second differential may mirror the first differential and comprise a harmonic gear with a circular spline driven by a third gear (corresponding to the first gear) that is driven by a third motor. A wave generator of the harmonic gear may be driven by a fourth gear (corresponding to the second gear) that is driven by a fourth motor. A flex spline of the harmonic gear may be coupled to a second outer shaft that is likewise coupled to the output shaft of the FBW servo actuator via a second outer shaft. In some embodiments, direct drive motors may be used in place of the second and/or fourth motors to drive the wave generators.

By connecting each differential to the output shaft via the outer shafts, the speed of the first differential and the second differential may be mechanically linked. The motor speeds may be adjusted based such that the combined motor speeds of the first and second motors driving the first differential equals the combined motor speeds of the third and fourth motors driving the second differential. Thus, if the third motor fails, for example, the speed of the fourth motor can be increased to compensate for the failed motor. Accordingly, the FBW servo actuator allows for failure in gears, motors, differentials, or a combination thereof, to be compensated for by the remaining components of the actuator to ensure that flight operations are not impacted. Thus, no single point of failure exists.

FIGS.1and2illustrate a perspective and a cross-sectional view, respectively, of a drivetrain100for an FBW servo actuator for some embodiments of the present disclosure. The drivetrain100may comprise a front end102aand a rear end102b. An output arm104may be disposed at the front end102a. The output arm104may be controlled by the drivetrain100via an inner output shaft106to thereby control movement of a pushrod or the like coupled to the output arm104(seeFIG.11). The output arm104may rotate about106to adjust the position of the pushrod. The pushrod, in turn, may control movement of a control surface, such as an aileron, elevator, or rudder. The shaft106may have a threaded end108for coupling to a nut110, such as a castle nut or the like, to secure output arm104to shaft106. The shaft106may extend from front end102ato rear end102b.

Drivetrain100may further comprise a front or first differential112acomprising a first harmonic gear114a, a first outer gear116a, and a first inner gear116b. The first harmonic gear114acomprises a first wave generator118a, a first flex spline120a, and a first circular spline122a. Rearward from first differential112ais a rear or second differential112bcomprising a second harmonic gear114b, a second outer gear124a, and a second inner gear124b. The second harmonic gear114blikewise comprises a second wave generator118b, a second flex spline120b, and a second circular spline122b. Gears116a,116bmay be driven to drive first differential112a, and gears124a,124bmay be driven to drive second differential112b. First differential112amay be coupled to a first outer shaft126a, and second differential112bmay be coupled to a second outer shaft126a. As best seen inFIG.2, shaft106may be received through each outer shaft126a,126b. Accordingly, rotational output of differentials112a,112bmay cause corresponding rotation of the respective shafts126a,126bthat is in turn transferred to shaft106to actuate output arm104.

Each differential112a,112bmay be coupled to a shaft126a,126bvia one or more fasteners128, thereby providing a fixed connection that mechanically links the rotation of outer shafts126a,126bto one another. In some embodiments, differentials112a,112bare coupled to outer shafts126a,126bvia the flex spline120a,120bsuch that rotation of flex spline120a,120bcauses rotation of outer shafts126a,126b. Accordingly, the rotational speed of differentials112a,112bmay be equal (or near equal) even in the event of a failed component. For example, when fully operational, each differential112a,112bmay rotate a respective outer shaft126a,126bat the same speed. If, for example, first differential112afails, second differential112bmay still be operational to drive second outer shaft126band, thereby, shaft106.

Drivetrain100may also comprise an encoder130located rearward from the second outer gear124a. The encoder130may be an absolute encoder. The encoder130may also be coupled to a resolver132. Both the encoder130and the resolver132may be used for feedback control of drivetrain100and may measure angular position and/or speed of shaft106.

Turning now toFIG.3, a cross-sectional view of the first differential112ais illustrated for some embodiments. Second differential112bmay be substantially similar to second differential112a. Second differential112bmay be a mirror of first differential112a. First differential112acomprises first harmonic gear114a, first outer gear116a, and first inner gear116bas discussed above. The first flex spline120ais fixed to an outer surface of the first wave generator118aand has external teeth (not shown) that extend radially around first flex spline120aand mesh with corresponding interior teeth of the first circular spline122a. The first wave generator118ahas an elliptical shape, and first flex spline120aflexes to deform to this elliptical shape when affixed to first wave generator118a. Accordingly, when driven, two regions of teeth of the first flex spline120aare in contact with the circular teeth of first flex spline120a. The two regions are on opposing sides of the major axis of the ellipse. The use of differentials112a,112bcomprising harmonic gears114a,114bis advantageous because the harmonic gears114a,114bhave zero backlash. The harmonic gears114a,114balso provide space savings as compared to planetary gear differentials, among other advantages as will be apparent to one of skill in the art. However, it is contemplated that a planetary gear differential may be used to drive shaft106without departing from the scope hereof.

The gears116a,116bare coupled to the first harmonic gear114asuch that the first harmonic gear114afunctions as a differential. Thus, each gear116a,116bmay be driven by a respective motor (seeFIG.4) to provide rotational inputs to the first harmonic gear114a. In some embodiments, first outer gear116adrives first circular spline122a, and first inner gear116bdrives first wave generator118a. For example, first outer gear116may be coupled to an outer surface of first circular spline122asuch that rotation of first outer gear116acauses corresponding rotation of first circular spline122a, which then rotates first flex spline120adue to the gear mesh between circular spline122aand flex spline120a. First inner gear116bmay be coupled to an inner structure134that is coupled to the wave generator118a, thereby allowing first inner gear116bto drive first wave generator118a. The inner structure134may be a hollow sleeve or the like that allows shaft106to pass therethrough. Bearings136may allow rotation of inner structure134. A wall137aof the flex spline120amay receive fasteners128to couple flex spline120ato first outer shaft126asuch that the rotation of first flex spline120amay be transferred to the first outer shaft126aand from the first outer shaft126ato the shaft106. In some embodiments, gears116a,116brotate in the same direction. In some embodiments, gears116a,116brotate in opposite directions.

As previously mentioned, second differential112bmay mirror first differential112asuch that the frontmost component of first differential112a(i.e., wall137a) is the rearmost component (wall137b) of second differential112b, as shown inFIG.3. Accordingly, on second differential112b, second outer gear124amay be connected to the circular spline122b, and second inner gear124bmay be connected to wave generator118bvia a corresponding inner structure134. In some embodiments, gears124a,124brotate in the same direction. In some embodiments, gears124a,124brotate in opposite directions. In some embodiments, differentials112a,112brotate outer shafts126a,126bin the same direction. In some embodiments, differentials112a,112brotate outer shafts126a,126bin opposite directions.

Turning now toFIGS.4-7, a number of views of an FBW servo actuator138are illustrated in accordance with embodiments of the present disclosure. Specifically,FIG.4is a perspective view,FIG.5is a top-down view,FIG.6is a side view, andFIG.7is a cross-sectional side view of FBW servo actuator138. As shown, FBW servo actuator138may comprise a front wall140coupled to a base plate142. Shaft106may extend out of front wall140. Drivetrain100may be coupled to base plate142. Base plate142may comprise one or more mounting holes144for receiving a fastener therein to couple the FBW servo actuator138to another surface or structure, such as within an aircraft, for example. Similarly, front wall140may comprise one or more mounting holes146for receiving a fastener therein to fasten front wall140to another structure, such as a housing for the FBW servo actuator138as shown inFIGS.8-9.

As previously discussed, each gear116a,116b,124a,124bmay be driven by a separate motor to provide redundancy in the event of failure. Thus, by providing four motors for the four input gears116a,116b,124a,124b, if one of the motors fails, only a single gear116a,116b,124a,124bis affected. If a motor does fail, all or a subset of the working motors may adjust (e.g., increase or decrease) the speed (or other motor parameter, such as power or torque) to compensate for the failed motor.

In some embodiments, FBW servo actuator138comprises a first outer gear motor148afor driving first outer gear116a, a first inner gear motor148bfor driving first inner gear116b, a second outer gear motor150afor driving second outer gear124a, and a second inner gear motor150bfor driving second inner gear124b. In some embodiments, first outer gear motor148ais substantially similar to second outer gear motor150a. In some embodiments, first inner gear motor148bis substantially similar to second inner gear motor150b. In some embodiments, first motors148a,148bcollectively are configured to operate at the same speed as second motors150a,150b. That is, the sum of the motor speed for the first motors148a,148bmay equal or be substantially equal to (e.g., within a 5% range) of the motor speed of the second motors150a,150b. Thus, for example, if second outer gear motor150afails, second inner gear motor150bmay be configured to increase the output speed to match the combined output speeds of first motors148a,148b. Alternatively, one or both of first motors148a,148bmay decrease the output speed such that the combined output speed of motors148a,148bmatches the output speed of second inner gear motor150b. Adjustments to the motor speeds of motors148a,148b,150a,150bmay occur likewise in the event of failure of any of the motors148a,148b,150a,150b. Each motor148a,148b,150a,150bmay drive at least one output gear152that is meshed (either directly or indirectly) to the corresponding input gear116a,116b,124a,124b. Each motor148a,148b,150a,150bmay also be mounted to base plate142via motor mounts154. As shown inFIG.7, one or more fasteners156may be inserted through base plate142to couple motor mounts154to base plate142and base plate142to front wall140.

Reference is now made toFIGS.8-10, depicting an FBW servo actuator138′ in accordance with embodiments of the present disclosure. Servo actuator138′ is substantially similar to FBW servo actuator138discussed above; however, motors148a,148b,150a,150b(denoted as motors148a′,148b′,150a′, and150′) are arranged on a single side of drivetrain100as seen best inFIG.10.FIG.8illustrates a top-down cross-sectional view of FBW servo actuator138′ depicting inner enclosures for some embodiments.FIG.9depicts a top-down cross-sectional view of FBW servo actuator138′ with inner and outer enclosures of FBW servo actuator138′ for some embodiments.FIG.10illustrates a perspective view of the FBW servo actuator138′ illustrated inFIGS.8and9with the enclosures hidden.

As shown inFIG.8, FBW servo actuator138may comprise a front inner enclosure156a, a middle inner enclosure156b, and a rear inner enclosure156c. Collectively, enclosures156a,156b,156cmay house drivetrain100. The front inner enclosure156amay house first differential112a, and the rear inner enclosure156cmay house second differential112b. Front inner enclosure156amay be coupled to front wall140. The middle inner enclosure156bmay house at least a portion of motor mounts154and front inner gear116band rear inner gear124bin some embodiments. Shaft106may extend through each inner enclosure156a,156b,156c. It will be appreciated that more or fewer than the three inner enclosures156a,156b,156cmay be employed without departing from the scope hereof. For example, a single inner enclosure may be used that encompasses drivetrain100.

As shown inFIG.9, an outer enclosure158may enclose the inner enclosures156a,156b,156c. Outer enclosure158may also house the various electronics for FBW servo actuator138. For example, cables160(e.g., motor cables, encoder cables etc.) may be housed within outer enclosure158. In some embodiments, cables160are at least partially housed within inner enclosures156a,156b,156cand outer enclosure158and may be connected to the corresponding components within enclosures156a,156b,156c, as will be appreciated by one of skill in the art. Outer enclosure158may present a substantially box-like enclosure. Outer enclosure158may also house one or more PCBs162. In some embodiments, outer enclosure158comprises three PCBs162. Fewer or more PCBs162may be employed without departing from the scope hereof. PCBs162may store the necessary computer-executable instructions to control the operations of FBW servo actuator138. For example, PCBs162may be communicatively coupled to motors148a,148b,150a,150bto control the operations thereof.

As previously discussed, providing a single FBW servo actuator138that is self-continued may reduce latency for FBW operations as crosstalk between FBW servo actuator138and a second servo actuator is eliminated. The use of a single actuator per control surface also provides space savings compared to using two actuators and increases the ease of installation and maintenance of the actuators.

It is one advantage of the present disclosure that drivetrain100and FBW servo actuator138may be assembled using conventional assembly techniques that ease assembling, installation, and service of FBW servo actuator138. As discussed above, one or more fasteners128, which may include screws bolts, pins, and the like, may be used to couple various components of drivetrain100to one another. For example, flex splines120a,120bmay be coupled to outer shafts126a,126bas shown. Fasteners128may also be used to couple gears116b,124bto inner structure134and inner structure134to wave generators118a,118b. Thus, the removable fasteners128may allow for ease of servicing drivetrain100in the event of failure in a gear116a,116b,124a,124b, for example. Likewise, as discussed with respect toFIG.7, fasteners156may be used to secure base plate142to front wall140and motor mounts154. Adhesives (e.g., epoxy) may also be used to secure various components of FBW servo actuator138. For example, adhesives may be used to secure PCBs162within outer enclosure158.

FIGS.11-14illustrate a second FBW actuator200for some embodiments of the present disclosure. Like FBW servo actuator138discussed above, FBW actuator200may comprise a drivetrain202comprising a first differential204aand a second differential204b. In contrast to FBW servo actuator138, differentials204a,204bmay be on a first side206aand a second side206b, respectively, of second FBW actuator200. Each differential204,206may comprise a harmonic gear208a,208b. First harmonic gear208acomprises first wave generator210a, first flex spline212a, and first circular spline214a, and second harmonic gear208blikewise comprises second wave generator210b, second flex spline212b, and second circular spline214b.

Differentials204a,204bmay drive an output shaft216. Rotation of output shaft216may cause rotation of output arms218, which are located between (e.g., equidistantly from) differentials204a,204b. As shown, output shaft216is coupled to two output arms218, which provides further redundancy in the event of a failure in one of the output arms218. The output arms218, in turn, may be coupled to a pushrod220. The pushrod220may be configured to actuate a control surface, as previously discussed. It is contemplated that output arms218may couple to more than one pushrod220to provide additional redundancy if a pushrod fails. Furthermore, it is contemplated that other mechanisms for actuating control surfaces, such as capstans, or other mechanical linkages, may be used without departing from the scope hereof.

In some embodiments, a first motor222aand a second motor222bare configured to drive first differential204a. First motor222amay be connected to a gear set224configured to mesh with an input gear226for driving first differential204a. Similar to gears116a,124adiscussed above, input gear226may provide input to circular spline214a. Second motor222bmay be a direct drive motor that drives wave generator210a. Flex spline212amay serve as the output for differentials204a,204b. Flex spline212amay be coupled to an outer shaft228athat rotates output shaft216. Input gear226and second motor222bmay rotate in the same direction or in opposite directions.

Second side206bmay be substantially similar to first side206a. A third motor230amay correspond to first motor222aand drive a gearset232that drives an input gear234. Input gear234may be substantially similar to input gear226and may provide input to a circular spline214b. Likewise, a fourth motor230bmay be a direct drive motor that drives a wave generator210b. The flex spline212bof may be coupled to an outer shaft228bto drive output shaft216. Input gear234and fourth motor230bmay rotate in the same direction or opposite directions. Differentials204a,204bmay cause rotation of outer shafts228a,228bin the same direction or opposite directions.

As with FBW servo actuator138, the use of four motors222a,222b,230a,230bprovides for redundancy in second FBW actuator200. Thus, if a motor222a,222b,230a,230bfails, a corresponding motor can increase the output thereof to compensate for the loss of the failed motor. Additional redundancy is provided by way of multiple output arms218and/or multiple pushrods220.

FIG.13illustrates second FBW actuator200with a housing236, andFIG.14illustrates second FBW actuator200with the housing236shown transparently as indicated by the dashed lines. In some embodiments, housing236is a two-piece housing coupled together by fasteners238. For example, a first housing piece may house first side206a, and a second housing piece may house second side206b. Fasteners238may couple the first housing piece to the second housing piece. In some embodiments, output arms218and pushrod220are not contained within housing236.

FIG.15schematically depicts an aircraft250having a FBW system252in accordance with embodiments of the present disclosure. FBW system252may comprise control module254, servo actuators256, control surfaces258, sensors/feedback control260, or any combination thereof. Servo actuators256may correspond to FBW servo actuators138,138′,200discussed above. Operations of servo actuators256may be controlled by control module254to actuate control surfaces258. Control surfaces258may be control surfaces for primary flight control such as the ailerons, rudders, and elevators. Feedback control260may include sensor data and/or feedback information relating to the position/operation of control surfaces258that may be provided to control module254to adjust the operations of servo actuators256. Thus, for example, failure and/or improper operations of gears or motors within actuators256may be communicated to control module254by feedback control260, and control module254may instruct servo actuators256to adjust the operations thereof accordingly. Control module254may instruct servo actuators256to actuate control surfaces258to a desired position based on input262received from an operator (e.g., a pilot or autopilot system).

Although current disclosure has been described with reference to the embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed, and substitutions made herein without departing from the scope of the disclosure as recited in the claims.

Having thus described various embodiments, what is claimed as new and desired to be protected by Letters Patent includes the following.