Redundant driveline for pylon-mounted rotors

Abstract

The pylon is coupled to the wing. A tilt rotor having a range of motion is coupled to the wing via a pylon such that the tilt rotor is located aft of the wing. The tilt rotor includes a redundant driveline including a plurality of motors and a plurality of motor controllers, the redundant driveline driving one or more blades included in the tilt rotor.

Description

[0001] Cross-references to other applications This application claims priority to U.S. Provisional Patent Application No. 62 / 912,872, filed on October 9, 2019, entitled “FIXED WING AIRCRAFT WITH TILT ROTORS,” which is incorporated herein by reference for all purposes. Background Art

[0002] New aircraft are being developed that can take off and land in dense urban areas, open up new transportation corridors, and avoid congestion on the road. For example, Kitty Hawk is developing a new electric vertical take-off and landing (eVTOL) tiltrotor aircraft that can take off and land in a footprint of approximately 30 feet by 30 feet. Early prototypes have been built and tested, and further improvements in the performance of the vehicle (e.g., improved safety and / or reduced mass) would be desirable. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Various embodiments of the invention are disclosed in the following detailed description and accompanying drawings.

[0004] Figure 1A is a perspective view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors.

[0005] Figure 1B is a top view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors.

[0006] Figure 2A is a bottom view of an embodiment showing boundary layer thickness with the motor turned off.

[0007] Figure 2B is a bottom view of an embodiment showing boundary layer thickness with the motor turned on.

[0008] Figure 3A is a diagram illustrating an example of a tilt-wing configuration with corresponding lift vector, thrust vector, and drag.

[0009] Figure 3B is a diagram illustrating an example of a fixed wing configuration with a leading edge mounted tilt rotor and corresponding lift vector, thrust vector, and drag.

[0010] Figure 3C is a diagram illustrating an embodiment of a fixed wing configuration with a trailing edge mounted tilt rotor and corresponding lift vector, thrust vector, and drag.

[0011] Figure 4 is a diagram showing an embodiment of the airflow generated when a trailing edge mounted tilt rotor on a main wing is closed.

[0012] Figure 5 is a diagram showing an embodiment of a forward swept and tapered wing and a straight wing for comparison.

[0013] Fig. 6A is a diagram showing an embodiment of a takeoff tilt transition from a hovering position to a cruise position.

[0014] Figure 6B is a diagram showing an embodiment of a landing tilt transition from a cruise position to a hovering position.

[0015] Figure 7 is a diagram showing an embodiment of a velocity tilt map.

[0016] Fig. 8A is a front view of an embodiment of a redundant drive train system with a belt drive shaft.

[0017] Figure 8B is a side view of an embodiment of a redundant drive train system with a belt drive shaft.

[0018] Figure 8C is a top view of an embodiment of a redundant drive train system with a belt drive shaft.

[0019] Fig.8D is a perspective view of an embodiment of a redundant drive train system having a belt drive shaft.

[0020] Fig. 9 is a diagram showing an embodiment of a pylon mounted tiltrotor in a hovering position.

[0021] Fig. 10A is a front view of an embodiment of a redundant drive train system configured to fit into a pylon having a geared drive shaft.

[0022] Fig. 10B is a side view of an embodiment of a redundant drive train system configured to fit into a pylon having a geared drive shaft.

[0023] Fig. 10C is a top view of an embodiment of a redundant drive train system configured to fit into a pylon having a geared drive shaft.

[0024] Fig. 10D is a perspective view of an embodiment of a redundant drive train system configured to fit into a pylon having a geared drive shaft.

[0025] Fig.11A is a front view of an embodiment of a redundant drive train system configured to fit into a pylon having a drive train in a coaxial arrangement.

[0026] Fig. 11B is a top view of an embodiment of a redundant drive train system configured to fit into a pylon having a drive train in a coaxial arrangement.

[0027] Fig. 11C is a perspective view of an embodiment of a redundant drive train system configured to fit into a pylon having a drive train in a coaxial arrangement. DETAILED DESCRIPTION

[0028] The present invention can be implemented in a variety of ways, including as: a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer-readable storage medium; and / or a processor, for example, a processor configured to execute instructions stored on a memory connected to the processor and / or provided by the memory. In this specification, these embodiments or any other form that the present invention may take may be referred to as technology. In general, within the scope of the present invention, the order of the steps of the disclosed process may be changed. Unless otherwise stated, a component described as being configured to perform a task (such as a processor or memory) may be implemented as a general component temporarily configured to perform a task at a given time or as a specific component manufactured to perform the task. As used herein, the term "processor" refers to one or more devices, circuits, and / or processing cores configured to process data (such as computer program instructions).

[0029] A detailed description of one or more embodiments of the present invention is provided below together with the accompanying drawings that illustrate the principles of the present invention. The present invention is described in conjunction with such embodiments, but the present invention is not limited to any embodiment. The scope of the present invention is limited only by the claims, and the present invention encompasses many alternatives, variations and equivalents. Many specific details are set forth in the following description in order to thoroughly understand the present invention. These details are provided for the purpose of example, and the present invention can be implemented according to the claims without some or all of these specific details. For the sake of clarity, technical materials known in the technical field related to the present invention are not described in detail so that the present invention is not unnecessarily concealed.

[0030] Various embodiments of redundant drive train systems are described herein. In a redundant drive train, there are multiple drive trains, which include multiple motors and multiple motor controllers. As will be described in more detail below, the redundant drive train system can reduce the total weight of the drive train and, in some cases, allow the remaining (multiple) operating drive trains to output at least some thrust from the propeller. In some embodiments, the system includes a pylon, wherein the pylon is coupled to a wing (e.g., a main wing or a canard) and a tilt rotor, wherein the tilt rotor has a range of motion, the tilt rotor is coupled to the wing via the pylon so that the tilt rotor is located at the rear of the wing, and the tilt rotor includes a redundant drive train, the redundant drive train includes multiple motors and multiple motor controllers, and the redundant drive train drives one or more blades included in the tilt rotor.

[0031] First, an exemplary tiltrotor vehicle is described, where an initial prototype uses a non-redundant drive train for each propeller or rotor. As will be described in more detail below, the uniqueness of the exemplary vehicle imposes a unique set of constraints on the redundant drive train systems that can be used therein. It should be noted that the redundant drive train systems described herein can be used in vehicles other than the exemplary tiltrotor vehicle.

[0032] Figure 1A is a perspective view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors. Figure 1B 1 is a top view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors. In the example shown, the main wings (100a and 100b) are fixed wings that are attached to the fuselage (102a and 102b) in a fixed manner or position. In other words, the main wings are not tilt-rotors that can rotate. The main wings (100a and 100b) are also forward-swept (e.g., relative to the pitch axis). For example, for an aircraft embodiment with canard wings (as shown here), the forward sweep angle can be between about 14° and 16°. 掠 , or for an aircraft embodiment without canards, the forward sweep angle can be as high as 35°.

[0033] In this example, the main wings (100a and 100b) have six rotors (104a and 104b) attached to the trailing edge of the main wings. Rotors or propellers in this configuration are sometimes referred to as pusher propellers (e.g., because at least when the propellers are in their forward flight position, the propellers are behind the wings and "push" the vehicle forward). The forward flight mode is sometimes referred to as the cruise mode in this article. For clarity, these rotors on the main wings are sometimes referred to as main wing rotors (e.g., to distinguish them from rotors attached to canards). Of course, the number of rotors shown here is merely exemplary and is not meant to be limiting.

[0034] In addition to the six main wing rotors, there are two rotors (106a and 106b) attached to the canards (108a and 108b). These rotors are sometimes called canard rotors. The canards are thinner than the main wings, so unlike the main wing rotors, the canard rotors are attached to the far end of the canards, rather than to the trailing edge of the canards.

[0035] All rotors in this example are tilt-rotors, which means that they can tilt or otherwise rotate between two positions. In the accompanying drawings shown here, the rotors are in a cruising (e.g., forward flight, backward facing, etc.) position. In this position, the rotors rotate around (e.g., substantially) a longitudinal axis of rotation so that they provide (substantially) backward thrust. When the rotors are in this position, the lift that keeps the tilt-rotor vehicle in the air comes from the airflow above the main wing (100a and 100b) and the canard (108a and 108b). In this particular example, the rotation range of the tilt-rotor range has a minimum angular position of approximately 0°-5° and a maximum angular position of approximately 90°-95°. This range is specific to the design and / or implementation.

[0036] The rotors can also be tilted downward to be in a hovering (e.g., vertical takeoff and landing, downward facing, etc.) position (not shown). In this second position, the rotors rotate about a (e.g., substantially) vertical axis of rotation so that they provide (substantially) downward thrust. In this configuration, the lift that keeps the tilt-rotor vehicle airborne comes from the downward airflow of the rotors.

[0037] Generally speaking, the tiltrotors, when oriented to output thrust substantially downward, allow the aircraft to perform vertical takeoff and landing (VTOL). This mode or configuration (e.g., in terms of the manner in which the aircraft as a whole flies and / or in terms of the position of the tiltrotors specifically) is sometimes referred to as hovering. The ability to perform vertical takeoff and landing allows the aircraft to take off and land in areas without airports and / or runways. Once airborne, the tiltrotors (if desired) change position to output thrust (substantially) backward instead of downward. This allows the aircraft to fly in a more efficient manner for forward flight; this mode or configuration is sometimes referred to as cruising.

[0038] Canards are useful because they can stall first (e.g., before the main wings), thereby generating a large pitching moment and not losing much lift when stalled, whereas a main wing stall loses a large amount of lift for each change in pitch moment (e.g., causing the entire aircraft to drop or fall). Therefore, a stall with a canard may be more benign than without it. Canard stall behavior is particularly beneficial in conjunction with a forward-swept wing, because a stall of the main wing can generate an adverse pitching moment if at the wing root, and a large and dangerous rolling moment if at the wing tip. In addition, the canard can generate lift at low airspeeds and increase CL 最大(ie, maximum lift coefficient), and struts are provided to hold or otherwise attach the canard motors.

[0039] In some embodiments, the pylons (110a and 110b) for attaching the rotor to the canard and / or main wing include some hinges and / or rotation mechanisms so that the tilt rotor can rotate between the two positions shown. Any suitable hinge mechanism can be used. For example, for ultralight aircraft, there are very strict weight requirements, and therefore a lightweight solution may be desired. Alternatively, a fixed tilt solution can also be used to meet very strict weight requirements.

[0040] In some embodiments, the aircraft is designed so that the main wings (100a and 100b) and canards (108a and 108b) can provide sufficient lift to perform a glider-style landing if needed during an emergency. For example, some ultralight standards or specifications require the ability to land safely in the event of one or more rotor failures, and the ability to perform a glider-style landing would satisfy that requirement. One benefit of using a fixed wing for the main wing (e.g., as compared to a tilt-rotor wing) is that there is no danger of the wing getting stuck in the wrong position (e.g., a hovering position) where a glider-style landing is not possible because the wing position is not suitable for a glider-style landing.

[0041] Another benefit of a fixed wing with a trailing edge mounted tiltrotor is the stalling behavior (or lack thereof) during the transition from a hover position to a cruise position (or vice versa). With a tiltwing, during the transition, the angle of attack of the tiltwing changes, which increases the risk of stalling. A fixed wing with a trailing edge mounted tiltrotor does not change the wing angle of attack (e.g., even if the rotor is turned off / on or the tiltrotor is displaced). In addition, this configuration increases the dynamic pressure and circulation over the main wing, which greatly improves the behavior during the transition (e.g., from a hover position to a cruise position or vice versa). In other words, a fixed wing with a trailing edge mounted tiltrotor can perform transitions more quickly and / or more efficiently than a tiltwing (as an example).

[0042] Another benefit associated with a fixed-wing vehicle with a tiltrotor (e.g., compared to a tiltwing) is that a smaller fraction of mass is used for the tilt actuator(s). That is, the multiple actuators for the multiple tiltrotors (still) comprise a smaller fraction of mass than a single heavy actuator for the tiltwing. The tiltrotor also has fewer points of failure because there are multiple actuators compared to a single (and heavy) actuator for the tiltwing. Another benefit is that the fixed wing makes transitions (e.g., between a cruise mode or position and a hover mode or position) more stable and / or faster than a tiltwing design.

[0043] In some embodiments, the rotor is a variable pitch propeller having different blade pitches when the rotor is in a hovering position and a cruise position. For example, different blade pitches (ranges) can achieve more efficient operation or flight when in a cruise position and a hovering position. When the rotor is in a cruise position, adjusting the blade pitch to a "cruise pitch" (e.g., approximately 26°) achieves a lower frontal area (e.g., lower drag) that is beneficial to cruising. When the rotor is in a hovering position, adjusting the blade pitch to a "hover pitch" (e.g., approximately 6°) achieves a higher rotor disc area that is beneficial to hovering. In other words, one blade pitch may be very suitable for a cruise mode, but not for a hover mode, and vice versa. The use of a variable pitch propeller achieves better (e.g., overall) efficiency, resulting in less power consumption and / or increased flight range.

[0044] The following figure shows the Figure 1A and 1B Various benefits are associated with the exemplary aircraft shown in FIG.

[0045] Figure 2A 2 is a bottom view of an embodiment showing boundary layer thickness with the motor off. In this example, laminar flow extension lines 200a, 202a, and 204a show the extension of laminar flow at different regions of the main wing. In this example, it is assumed that the aircraft is cruising (e.g., flying in a substantially forward direction). Figure 1A and 1B As shown in , in this embodiment, the main wing rotor (206) is attached to the trailing edge of the main wing (208). The figure below shows the boundary layer thickness when the rotor is turned on.

[0046] Figure 2B is a bottom view of an embodiment showing boundary layer thickness with the motor on. In this example, the motor is on and the rotor has an exit air velocity of 30 m / s. With the motor on, a low pressure area is formed toward the rear of the wing, which increases the laminar extension over the main wing. For example, see the corresponding Figure 2A 200a, 202a and 204a in FIG. 200b, 202b and 204b. Comparison of the two groups shows that the laminar flow stretch increases in the first two positions (i.e., at 200a / 200b and 202a / 202b). The last position (i.e., 204a / 204b) has only a slightly longer laminar flow stretch due to interference from the canard rotor (210).

[0047] The drag from the main wing rotor (or more precisely, the drag from the pylons used to attach the main wing rotor to the main wing) is hidden in the wake of the airflow from the main wing. See, for example, Figure 2A, which more clearly shows that the pylon (220) is connected or otherwise attached to the rear of most of the laminar flow extension (222). For the embodiment shown here, the pylon is also able to remain away from some of the boundary layer thickness of the main wing, which means that the pylon has lower drag per unit surface area. This improves drag compared to some other alternative designs or configurations. The following figures describe this in more detail.

[0048] Figure 3A is a diagram showing an example of a tilt-wing configuration with corresponding lift vectors, thrust vectors, and drag. In this example, a fixed rotor (300) is attached to a tilt-wing (302) at a fixed position or angle. This is an alternative arrangement to the above-described aircraft embodiment(s). In order to direct the airflow generated by the fixed rotor (300) rearward or downward, the tilt-wing (302) rotates. As shown here, for this configuration, there is drag (304) at the trailing edge of the tilt-wing, which is undesirable.

[0049] Also shown here is the lift (306) and thrust (308) for this configuration, with the tilt-wing shown in the middle of a transition (e.g., between a cruise position and a hover position). As shown here, the lift (306) and thrust (308) are substantially orthogonal to each other, which is inefficient. In other words, the tilt-wing is inefficient during its transition.

[0050] Figure 3B is a diagram showing an example of a fixed wing configuration with a leading edge mounted tiltrotor and corresponding lift vector, thrust vector and drag. In this example, the tiltrotor (320) is attached to the leading edge of the fixed wing (322). This is another alternative arrangement for the above-described aircraft embodiment(s). The corresponding drag (324) and thrust (326) for this arrangement are also shown. No useful lift is generated with this configuration, and therefore the lift vector is not shown here.

[0051] Figure 3C is a diagram showing an embodiment of a fixed wing configuration with a trailing edge mounted tiltrotor and corresponding lift vectors, thrust vectors, and drag. In this example, the tiltrotor (340) is attached to the trailing edge of a fixed wing (342). In this configuration, the drag due to the trailing edge mounted tiltrotor (e.g., primarily due to its pylon, not shown) is hidden in the wake of the airflow from the main wing. Thus, there is no drag (at least due to the tiltrotor (340)).

[0052] The position of the trailing edge mounted tilt-rotor (340) relative to the fixed wing (342) also draws air (344) over the fixed wing, after which the air turns or bends through the rotor and downward. This flow turning over the wing creates a relatively large induced lift (346), as shown here. Also shown here is the thrust vector (348) generated by the rotor. It should be noted that the induced lift (346) and the thrust (348) are substantially in the same direction (i.e., both are pointed substantially upward), which is a more efficient arrangement, including during transition. In other words, using a fixed wing with a trailing edge mounted tilt-rotor creates less drag and improved efficiency during transition (e.g., because the lift and thrust vectors are now pointed substantially in the same direction) compared to other rotor and wing arrangements. For example, please note that respectively Figure 3A and Figure 3B Resistance 304 and resistance 324, and Figure 3A The orthogonal positions of lift 306 and thrust 308 in FIG.

[0053] The following figures illustrate embodiments of flow diversion in more detail.

[0054] Figure 4 is a diagram showing an embodiment of airflow generated when a trailing edge mounted tiltrotor on a main wing is closed. In this example, a tiltrotor aircraft (400) is shown, but for comparison purposes, the main wing rotor is closed. With the rotor closed, the airflow inflow (402) and the airflow outflow (404) move substantially in the same direction. That is, the airflow does not turn (e.g., downward) as it passes over the rotor.

[0055] Tiltrotor 420 shows the same vehicle as tiltrotor 400, except that the rotors are open. In this example, the airflow inflow (422) and the airflow outflow (424) have significantly different directions, and there is a significant turn or bend in the airflow as it passes over the rotors of the exemplary tiltrotor shown. As described above, this causes significant lift, which is desirable because less power is consumed and / or the range of the tiltrotor is increased.

[0056] In this example, the main wing rotors (426) are in a hovering position. As shown here, these rotors are slightly pitched or otherwise tilted (e.g., with the top of the main wing rotor pointing slightly forward and the bottom pointing slightly backward). In this figure, the amount of tilt is shown as θ 俯仰(428), and in some embodiments is approximately a 90° range of rotation or movement (e.g., ~3° upward from horizontal when in the cruise position (e.g., for minimum drag) and ~93° downward from horizontal when in the hover position, which yields a ~96° range of rotation). Although such canting or pitching of the rotors is not absolutely necessary for flow steering to occur, in some embodiments, the main wing rotors are canted or otherwise pitched to some extent to increase or otherwise optimize the amount of flow steering. In some embodiments, the canard rotors are similarly pitched. It should be noted that the tiltrotor 420 is shown in a nose-up position, and thus the vertical axis (e.g., relative to the tiltrotor) is not perpendicular to the ground and / or reference frame.

[0057] In some embodiments, when the rotor is in the hovering position, the rotor (e.g., main wing rotor and / or canard rotor) is slightly turned outward away from the fuselage or otherwise tilted. In some embodiments, the turning (e.g., outward) is about 10° to obtain greater yaw authority.

[0058] In some embodiments, the main wing, in addition to being forward swept, is also tapered (eg, the wing narrows outwardly toward the wing tip). The following figures describe various wing and / or tail embodiments.

[0059] Figure 5 5 is a diagram showing an embodiment of a swept and tapered wing and a straight wing for comparison. In the example shown, wing 500 is a straight wing without tapering (e.g., the wing is the same width from center to wing tip). An exemplary rotor (502) is shown at the trailing edge of the straight wing (500).

[0060] The center of thrust (504), indicated by the dashed line, is determined by the location or arrangement of the rotors and extends through the center of the main wing rotor (502). For simplicity, the canard rotors are ignored in this example. The center of lift is based on the shape of the wing. For a rectangular wing such as wing 500, the center of lift (506), indicated by the solid line, extends along the center of the wing. The calculation of the aerodynamic center is more complex (e.g., the aerodynamic center depends on the cross-section of the wing, etc.), and the aerodynamic center 508, indicated by the dashed line, is exemplary and / or typical for this type of wing.

[0061] As shown here, the arrangement of a straight wing (500) and its corresponding main wing rotor (502) creates a center of thrust (504) that is relatively far from both the center of lift (506) and the aerodynamic center. This separation is undesirable. More specifically, when the main wing rotor (502) is in a hovering position, if the center of thrust (504) is far from the center of lift (506), then the transition (e.g., in the context of the aircraft moving as a whole, such as switching from substantially upward flight to substantially forward flight, or vice versa) will produce very large moments and may capsize the vehicle or prevent acceleration or stability and / or require a bulky and / or non-optimal propulsion system. In cruise, if the center of thrust (504) is far from the center of lift (506), it is less important (e.g., because the thrust moment is smaller and more easily balanced by the aerodynamic moment), but it is still undesirable.

[0062] In contrast, the arrangement of a forward-swept and tapered wing (520) and its corresponding rotor (522) along the trailing edge produces a center of thrust (524), center of lift (526), ​​and aerodynamic center (528) that are closer to one another. For example, the forward sweep of the wing moves the rotor forward to varying degrees. This causes the center of thrust to move forward (e.g., toward the leading edge and toward the other centers). The tapering of the wing prevents the aerodynamic center and the center of lift from being displaced too far forward (and, more importantly, away from the center of thrust) due to the forward sweep. For example, for a forward-swept wing (not shown) without tapering, the center of thrust would move forward by approximately the same amount as the aerodynamic center and the center of lift, and would result in a greater separation between the three centers than is shown here in wing 520.

[0063] Some other benefits of a forward-swept and tapered wing include better visibility for the pilot, and a better location for the fuselage to main wing junction (e.g., allowing the main spar to pass behind the pilot's seat, rather than through the pilot). In addition, the taper reduces wing moments and brings the motor's center of thrust closer to the wing-to-fuselage attachment when referenced to the direction of flight, so there is less moment carried from the wing to the fuselage, a shorter tail boom (e.g., which reduces the weight of the aircraft), and improved pitch stability.

[0064] The following figures describe exemplary tilt transitions of the rotor between the cruise position and the hover position.

[0065] Fig. 6Ais a diagram illustrating an embodiment of a takeoff tilt transition from a hover position to a cruise position. In some embodiments, an exemplary tiltrotor aircraft performs this transition shortly after takeoff (e.g., substantially vertically). It should be noted that this tilt transition is optional, and the aircraft can be flown entirely with the rotors in the hover position (although not at optimal performance). This may be done, for example, if a tilt maneuver is risky and is best performed at a higher altitude.

[0066] Tilt rotor 600 shows an exemplary aircraft after it performs a vertical takeoff. In this state shown here, the main wing rotor and the canard rotor are in a hovering position (e.g., rotating around a substantially vertical axis of rotation so that the rotor generates substantially downward thrust).

[0067] The tiltrotor then transitions from a completely upward direction of movement to a direction of movement with at least some forward motion, wherein the rotors continue in a hovering position until the tiltrotor reaches a certain desired altitude at which to begin the transition (602). In other words, the vehicle transitions first, and then changes the tilt of the rotors. In one example, the altitude at which the tiltrotor begins the change in rotor tilt from the hovering position to the cruise position is a sufficiently high altitude so that there is time to recover in the event of a problem during the transition. Switching the rotors between the hovering position and the cruise position is a riskier time, where the likelihood of problems (e.g., rotor failure, rotor jamming, etc.) is higher. Although the tiltrotor may have systems and / or techniques for recovery (e.g., compensating for rotor failure by causing the remaining rotors to output more thrust, deploying a parachute, etc.), these systems and / or techniques require time (i.e., sufficient altitude) to work.

[0068] From position 602, the tiltrotor aircraft flies substantially forward and moves the tiltrotors from a hovering position (e.g., wherein thrust is substantially output downward) to a cruise position. Once in cruise position 604, the rotors rotate about a substantially longitudinal axis so that they output rearward thrust.

[0069] Figure 6B is a diagram illustrating an embodiment of a landing tilt transition from a cruise position to a hover position. For example, an exemplary tiltrotor aircraft may perform this transition prior to a vertical landing. As with the previous transitions, this transition is optional. For example, if desired, an exemplary tiltrotor aircraft may maintain the tiltrotor in a cruise position and perform a glider-style landing instead of a vertical landing.

[0070] Tiltrotor 610 shows the rotor in a cruise position. When flying in a substantially forward direction, the tiltrotor moves from the cruise position shown at 610 to a hovering position shown at 612. With the tiltrotor in the hovering position (612), the tiltrotor descends to position 614 (at least in this example) with some forward movement, thereby keeping power usage (much) lower and retaining better options in the event of a motor or other component failure (e.g., the tiltrotor can add power to the rotor and exit the landing process or path) until it finally lands on the ground.

[0071] Figure 7 700 is a diagram illustrating an embodiment of a velocity-tilt graph. In the illustrated diagram, the x-axis illustrates the forward velocity of the aircraft, and the y-axis illustrates the tilt (e.g., the position or angle of the tilt-wing or tilt-rotor) ranging from a (e.g., minimum) cruise position (700) to a (e.g., maximum) hover position (702).

[0072] The first operational envelope (704), shown with a solid line border and filled with a grid pattern, is associated with a tilt-rotor aircraft. Figure 4 The tiltrotor 400 and Figure 3A 302 and fixed rotor 300 in FIG. 2. A second operational envelope (706), shown with a dashed border and gray fill, is associated with a (e.g., similar) aircraft having a forward-swept and fixed wing with a trailing-edge mounted tilt-rotor. See, for example, the above embodiments.

[0073] In the diagram shown here, the tiltrotor operating envelope (706) is a superset of the tiltrotor operating envelope (704), indicating that the former aircraft configuration is safer and / or more airworthy than the latter, and is also able to fly faster and slower at similar tilt positions. For fixed wings, the wings are already (and / or always) pointed in the (forward) direction of travel. When the tiltrotor is in or near the (e.g., maximum) hover position (702), the vehicle can fly almost all the way to the stall speed (e.g., V2) without having to tilt the motor up to the cruise position. It should be noted that, for example, the tiltrotor operating envelope (706) can stay in the (e.g., maximum) hover position (702) until V2. This greatly increases the operating states of the tiltrotor operating envelope (706) compared to the tiltrotor operating envelope (704). For example, please note all the gray areas above the tiltrotor operating envelope (704).

[0074] Another effect that may contribute to the extended operating envelope of a tiltrotor configuration in or near a hover position includes flow steering (see, e.g., Figure 4). The flow turning over the main wing causes some additional lift. In some embodiments, this flow turning and the lift it produces is amplified or optimized by tilting the main wing rotors from directly downward to a slightly backward angle when in normal hover (e.g., in the minimum tilt position 700).

[0075] In contrast, the tilt-wing presents a larger frontal area when it is tilted upward in the (e.g., maximum) hover position (702). Therefore, the tilt-wing cannot fly forward at any suitable speed until it is in or near the full (e.g., minimum) cruise position (700) or nearly so.

[0076] Early prototypes of the tiltrotor vehicle were used for proof of concept and development of an airworthy vehicle. To this end, for simplicity, each propeller had a single drive train. The following figures describe various embodiments of redundant drive train systems that can be used with an exemplary tiltrotor vehicle or other vehicles.

[0077] Fig. 8A is a front view of an embodiment of a redundant drive train system with a belt drive shaft. Figure 8B-Figure 8D The same drive train embodiment is shown in side, top and perspective views, respectively. In the example shown, a redundant drive train is used to drive the blades of a tiltrotor, as described above, where the tiltrotor is coupled to the wing or canard via a fixed pylon. The rotor disks (800a-800d) are small enough to fit within the pylon subsystem.

[0078] A first transmission system (802a-802d) including a first motor and a first motor controller and a second transmission system (804a-804d) including a second motor and a second motor controller drive a shaft (806a-806d) holding a propeller. In this example, both transmission systems drive the shaft via a belt (808a-808d).

[0079] for Figure 1A-1B In the vehicle shown in FIG, there will be a total of 16 drive trains, of which the redundant drive trains are Figure 8A-8D As shown. If one of the 16 drive trains fails, the other drive trains will need to support 1.15 times their normal load in hover (e.g., assuming a simple control scheme, the opposing unit will not be able to contribute much). Assume that one of the outermost motors or controllers on the left side of the main wing fails. In this case, to maintain balance, in the simplest control scheme, the opposing rotor (i.e., the outermost rotor on the right side of the main wing) will only be able to provide as much thrust as the rest of the rotors on the left wing. Without redundant systems, one rotor on the left side will provide no thrust, and one rotor on the right side will also provide no thrust. With redundancy, both can provide about half of the normal thrust.

[0080] In contrast, for the previous powertrain architecture with a total of 8 powertrain units, if one of the powertrains fails, the other drivetrains will need to support 1.33 times its normal load in hover. The redundant drivetrain for each propeller reduces the power output required for each propeller in the event of a failure. This in turn allows the total mass of the (redundant) drivetrain to be reduced, resulting in a mass saving of 1 / 6 of the total mass of the drivetrain (e.g., because the total mass is driven by the failure condition). Some of this saving may be offset by the increase in the following aspects, for context, in this example, the stack height of the motors is half that of the original drivetrain architecture (e.g., with one drivetrain per propeller).

[0081] An attractive feature of a belt-driven redundant drive train system (such as shown here) is that drive train failures are more benign, since no rotor must come to a complete stop. This can make a belt-driven drive train an acceptable choice for some applications, even though the belt drive is not as efficient as a direct drive, and the side-by-side arrangement of the motors results in a wider pylon housing, which in turn increases drag. The efficiency loss (e.g., ~5% loss) and the drag increase (e.g., ~10%-15%) may be an acceptable tradeoff to have a partially driven propeller.

[0082] The uniqueness of the exemplary tiltrotor vehicle described above means that there are certain design constraints that the redundant drive train system used in such a vehicle needs to meet. For example, the redundant drive train system must fit within a pylon-mounted tiltrotor. The following figure shows a more detailed example of a pylon-mounted tiltrotor.

[0083] Fig. 9 is a diagram showing an embodiment of a pylon mounted tiltrotor in a hovering position. In the example shown, the front pylon portion (900) fits around a wing or canard (902). The rear of the pylon is the tiltrotor portion (904), shown here in a hovering position. The tiltrotor in this example is an early version with a single motor (906) that drives a shaft (908) and in turn drives propeller blades (910). It would be desirable to have a redundant drive train system (substantially) fit into the existing footprint shown here, as increasing the size of the front pylon portion (900) or the rear tiltrotor portion (904) would increase the surface area, which in turn would increase drag. For context, the diameter of the tiltrotor (904) is 160 mm, and the length from the front surface (912) to the plane of the blades (910) is 600 mm.

[0084] Apart from Figure 8A-8D In addition to the belt drive embodiment shown in , redundant drive trains can be implemented in various embodiments. The following figures show some alternatives.

[0085] Fig. 10A is a front view of an embodiment of a redundant drive train system configured to fit into a pylon having a geared drive shaft. Figure 10B-10D The side view, top view and perspective view of the same transmission system embodiment are shown respectively. Figure 8A-8D As in the example of , the size and power output of the motor are reduced by reducing the stack height in half (e.g., compared to the original architecture with a single powertrain per propeller). Similar to the previous examples, the components shown are located within a cylindrical space (1000a-1000d), such as a conical, cylindrical tilt rotor, which is located rearward of a fixed pylon portion that connects the tilt rotor to a wing or canard. The first drive train (1002a-1002d) and the second drive train (1004a-1004d) rotate a gear drive shaft (1006a-1006d), which in turn drives the propeller. In some applications, relatively low losses in the gear drive train (e.g., ~2% or less) can make such an embodiment attractive, even though certain types of failures may prohibit the remaining and operating drive train from driving the shaft via the gears.

[0086] Fig.11A is a front view of an embodiment of a redundant drive train system configured to fit into a pylon having a coaxially arranged drive train. Figure 11B-Figure 11C A top view and a perspective view, respectively, of the same powertrain embodiment are shown.

[0087] In the example shown here, the diagrams on the left (1100a-1100c) show a single, non-redundant drive train for comparison purposes.

[0088] The center diagrams (1102a-1102c) show redundant drive train embodiments of equal power where the motor diameter remains the same but the stack height is halved.

[0089] The figures on the right (1104a-1104c) show a configuration where the diameter is reduced and the stack height is increased a little compared to the original design (e.g., as shown in Figures 1100a-1100c). In some embodiments, this configuration is used for a side-by-side configuration (see, e.g., Figure 8A-8D and Figures 10A-10D ), reducing the pylon width and therefore aerodynamic drag at the expense of weight, since this way of splitting the motor would lead to an increase in the weight of the entire drive train.

[0090] While the non-redundant drive train (1100a-1100c) has a single drive train (1102a-1102c), the reduced height redundant drive train examples (1110a-1110c) and reduced diameter redundant drive train examples (1120a-1120c) both have a first drive train (1112a-1112c and 1122a-1122c) and a second drive train (1114b-1114c and 1124b-1124c). In some embodiments, the two drive trains have completely separate electrical systems (e.g., separate batteries) with the drive trains arranged coaxially with the motors turning the same shaft, which in turn is connected to the propellers (blades).

[0091] With the coaxial arrangement shown here, the losses due to belts or gears are eliminated. Another advantage is that, since the motors are arranged along a common axis, the pylon width remains unchanged and the pylon length is essentially the same. Therefore, the (overall) resistance is almost the same as the original design.

[0092] In some applications, redundant drive train systems are not deployed on a vehicle in a uniform and / or homogeneous manner. Figure 1A-1B In the exemplary vehicle shown in , only the outermost tiltrotors have redundant drive trains, while the other (e.g., inboard) tiltrotors have only a single drive train each, because in the event of a failure, the outermost tiltrotors are the most difficult to compensate due to their longer moment arms in the rollover orientation. Alternatively, in some embodiments, the canard tiltrotors have a coaxially arranged, reduced diameter redundant drive train system, while the other (i.e., main wing) tiltrotors have a coaxially arranged, reduced height redundant drive train system, because it is easier to embed a thicker pylon into the main wing rather than at the end of a thinner canard while maintaining low drag.

[0093] Although the foregoing embodiments have been described in detail for the purpose of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways to implement the invention. The disclosed embodiments are illustrative rather than restrictive.

Claims

1. A system comprising: An inboard tilt-rotor subsystem, the inboard tilt-rotor subsystem comprising: Inboard hanger; Inboard tiltrotor; and A single, non-redundant drive train; and An outboard tilt-rotor subsystem, the outboard tilt-rotor subsystem comprising: an outboard pylon, wherein the outboard pylon is coupled to a wing; Outboard tiltrotor, where: The outboard tiltrotor has a range of motion; and The outboard tilt-rotor is coupled to the wing via the outboard pylon so that the outboard tilt-rotor is located rearward of the wing; a redundant drive train comprising a plurality of motors and a plurality of motor controllers, the redundant drive train driving one or more blades; and The one or more blades.

2. The system according to claim 1, wherein: The system is included in an electric vertical take-off and landing (eVTOL) tiltrotor vehicle.

3. The system according to claim 1, wherein: The outboard tiltrotor subsystem is the outermost tiltrotor subsystem.

4. The system of claim 1, wherein: The plurality of motors include a first motor and a second motor; and The first motor and the second motor are individually powered by a first battery and a second battery, respectively.

5. The system according to claim 1, wherein: The outboard tiltrotor subsystem further includes a belt drive shaft.

6. The system of claim 1, wherein: The outboard tiltrotor subsystem further includes a belt and a shaft; The plurality of motors include a first motor and a second motor; and The first motor and the second motor rotate about non-coaxial rotation axes and drive the shaft via the belt.

7. The system according to claim 1, wherein: The redundant drive train includes a gear drive shaft.

8. The system of claim 1, wherein: The outboard tiltrotor subsystem further includes at least one gear and shaft; The plurality of motors include a first motor and a second motor; and The first motor and the second motor rotate about non-coaxial rotation axes and drive the shaft via the at least one gear.

9. The system of claim 1, wherein: The outboard tiltrotor subsystem further includes a shaft; The plurality of motors include a first motor and a second motor; and The first motor, the second motor and the shaft are coaxial.

10. A method comprising: An inboard tilt-rotor subsystem is provided, the inboard tilt-rotor subsystem comprising: Inboard hanger; Inboard tiltrotor; and A single, non-redundant drive train; and An outboard tilt-rotor subsystem is provided, the outboard tilt-rotor subsystem comprising: an outboard pylon, wherein the outboard pylon is coupled to a wing; Outboard tiltrotor, where: The outboard tiltrotor has a range of motion; and The outboard tilt-rotor is coupled to the wing via the outboard pylon so that the outboard tilt-rotor is located rearward of the wing; a redundant drive train comprising a plurality of motors and a plurality of motor controllers, the redundant drive train driving one or more blades; and The one or more blades.

11. The method according to claim 10, wherein: The inboard tiltrotor subsystem and the outboard tiltrotor subsystem are in an electric vertical take-off and landing (eVTOL) tiltrotor vehicle.

12. The method according to claim 10, wherein: The outboard tiltrotor subsystem is the outermost tiltrotor subsystem.

13. The method of claim 10, wherein: The plurality of motors include a first motor and a second motor; and The first motor and the second motor are individually powered by a first battery and a second battery, respectively.

14. The method according to claim 10, wherein: The outboard tiltrotor subsystem further includes a belt drive shaft.

15. The method of claim 10, wherein: The outboard tiltrotor subsystem further includes a belt and a shaft; The plurality of motors include a first motor and a second motor; and The first motor and the second motor rotate about non-coaxial rotation axes and drive the shaft via the belt.

16. The method according to claim 10, wherein: The redundant drive train includes a gear drive shaft.

17. The method of claim 10, wherein: The outboard tiltrotor subsystem further includes at least one gear and shaft; The plurality of motors include a first motor and a second motor; and The first motor and the second motor rotate about non-coaxial rotation axes and drive the shaft via the at least one gear.

18. The method of claim 10, wherein: The outboard tiltrotor subsystem further includes a shaft; The plurality of motors include a first motor and a second motor; and The first motor, the second motor and the shaft are coaxial.

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