System and method for tilt propeller with tilt actuator gearbox and integrated inverter

Abstract

A tilt propeller for a vertical take-off and landing (VTOL) aircraft includes a tilt actuation assembly for moving the tilt propeller between a climb configuration and a cruise configuration. The tilt actuation assembly may include multiple rotary actuators coupled to multiple torque paths in a tilt actuation gearbox. The rotary actuators may be coupled to each other by idler gears in the tilt actuation gearbox to evenly distribute loads and provide redundancy in the event of a failure. The tilt actuation assembly is shared between the tilt actuators, propeller motor, and propeller inverter, but may provide compact packaging that allows for easy sharing of power, control structures, and sensor information.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 378,536, filed October 6, 2022, and U.S. Provisional Application No. 63 / 378,680, filed October 7, 2022, the entire contents of each of which are incorporated by reference for all purposes.

[0002] The present disclosure relates generally to the field of powered air vehicles. More specifically, but not exclusively, the present disclosure relates to innovations in tilt propeller aircraft using electric propulsion systems. Certain aspects of the present disclosure generally relate to tilt actuator systems for tilt propellers. Other aspects of the present disclosure generally relate to improvements in tilt actuation systems that may be used in other types of vehicles but may provide particular advantages in air vehicles. Summary of the Invention

[0003] Some embodiments of the present disclosure provide a tilt actuator for tilting a propulsion system of an aircraft. The tilt actuator may include a tilt actuator having a rotor, a planetary gear set including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the rotor being coupled to the sun gear, a worm gear coaxially coupled to an output of the planetary gear set, a worm wheel meshed with the worm gear, a gear shaft coaxially coupled to the worm wheel, a pinion coaxially coupled to the gear shaft, a sector gear meshed with the pinion, and an output shaft coupled to the sector gear, the output shaft configured to be fixed to a frame of the aircraft.

[0004] Some embodiments of the present disclosure provide a tilt device for an aircraft, which may include: a first frame, a second frame movably coupled to the first frame, a propulsion system attached to the second frame, a tilt actuator coupled to the second frame, the tilt actuator including a rotor, a planetary gearset including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the rotor being coupled to the sun gear, a worm gear coaxially coupled to an output of the planetary gearset, a worm wheel coaxially coupled to the worm gear, a gear shaft coaxially coupled to the worm wheel, a pinion coaxially coupled to the gear shaft, a sector gear meshed with the pinion, and an output shaft coupled to the sector gear, the output shaft being fixed to the first frame.

[0005] Some embodiments of the present disclosure provide a tilt device for an aircraft, the tilt device including: a first frame; a second frame movably coupled to the first frame; a propulsion system attached to the second frame; a first tilt actuator coupled to the second frame, the first tilt actuator including a first rotor; a first planetary gear set including a first sun gear, a first plurality of planetary gears, a first planet carrier, and a first ring gear, the first rotor being coupled to the first sun gear; a first worm gear coaxially coupled to an output of the first planetary gear set; a first worm wheel meshed with the first worm gear; a first gear shaft coaxially coupled to the first worm wheel; a first pinion coaxially coupled to the first gear shaft; a first sector gear meshed with the first pinion; and a first gear shaft coupled to the first sector gear. a second tilt actuator having a second rotor; a second planetary gearset having a second sun gear, a second plurality of planet gears, a second planet carrier, and a second ring gear, the second rotor being coupled to the second sun gear; a second worm gear coaxially coupled to the output of the second planetary gearset; a second worm wheel meshed with the second worm gear; a second gear shaft coaxially coupled to the second worm wheel; a second pinion coaxially coupled to the second gear shaft; a second sector gear meshed with the second pinion; and a second output shaft coupled to the second sector gear, the second output shaft being fixed to the first frame.

[0006] Some embodiments of the present disclosure provide a tilt apparatus for an aircraft, which may include a first frame, a second frame movably coupled to the first frame, a propulsion system attached to the second frame, a first tilt actuator, and a tilt actuator gearbox coupled to the second frame, wherein the tilt actuator gearbox includes a first gear stage coupled to the first tilt actuator, a second gear stage coupled to the first gear stage, and a third gear stage coupled to the second gear stage and the first frame.

[0007] Some embodiments of the present disclosure provide a tilt apparatus for an aircraft, which may include: a first frame; a second frame movably coupled to the first frame; a propulsion system coupled to the second frame and configured to move with the second frame, the propulsion system including a propeller, a motor configured to rotate the propeller, and a propulsion inverter configured to supply current to the motor; and a tilt actuation system coupled to the second frame and configured to move with the second frame relative to the first frame, the tilt actuation system including a tilt actuator, a tilt actuator inverter configured to supply current to the tilt actuator, and a tilt actuator gearbox coupled to the second frame, the tilt actuator configured to tilt the second frame relative to the first frame via the tilt actuator gearbox.

[0008] Some embodiments of the present disclosure provide a method for tilting a propulsion system of an aircraft. The method may include tilting a first frame relative to a second frame using a tilt actuator, the first frame coupled to a body of the aircraft, the second frame coupled to a propeller, a motor assembly configured to rotate the propeller, and the tilt actuator. The tilt actuator may include a tilt actuator including a rotor, a planetary gearset including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the rotor coupled to the sun gear, a worm gear coaxially coupled to an output of the planetary gearset, a worm wheel coaxially coupled to the worm gear, a gear shaft coaxially coupled to the worm wheel, a pinion coaxially coupled to the gear shaft, a sector gear meshed with the pinion, and an output shaft coupled to the sector gear, the output shaft configured to be fixed to the frame of the aircraft. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 illustrates an exemplary VTOL aircraft in a cruise configuration, consistent with embodiments of the present disclosure.

[0010] [Figure 1B] 1 illustrates an exemplary VTOL aircraft in an ascent configuration, consistent with embodiments of the present disclosure.

[0011] [Figure 2A] 1 illustrates an exemplary tilting arrangement on a VTOL aircraft, consistent with embodiments of the present disclosure. [Figure 2B] 1 illustrates an exemplary tilting arrangement on a VTOL aircraft, consistent with embodiments of the present disclosure.

[0012] [Figure 3] 1 illustrates a first and second frame of a VTOL aircraft, consistent with an embodiment of the present disclosure.

[0013] [Figure 4A] 1 illustrates an exemplary tilt actuation assembly consistent with embodiments of the present disclosure. [Figure 4B] 1 illustrates an exemplary tilt actuation assembly consistent with embodiments of the present disclosure. [Figure 4C] 1 illustrates an exemplary tilt actuation assembly consistent with embodiments of the present disclosure. [Figure 4D] 1 illustrates an exemplary tilt actuation assembly consistent with embodiments of the present disclosure.

[0014] [Figure 5A] 1 illustrates an exemplary blade pitch control assembly consistent with an embodiment of the present disclosure. [Figure 5B] 1 illustrates an exemplary blade pitch control assembly consistent with an embodiment of the present disclosure. [Figure 5C] 1 illustrates an exemplary blade pitch control assembly consistent with an embodiment of the present disclosure.

[0015] [Figure 6] 1 illustrates an exemplary tilt actuation assembly consistent with embodiments of the present disclosure.

[0016] [Figure 7A] 1 illustrates an exemplary tilt actuation assembly and motor assembly consistent with embodiments of the present disclosure. [Figure 7B] 1 illustrates an exemplary tilt actuation assembly and motor assembly consistent with embodiments of the present disclosure. [Figure 7C] 1 illustrates an exemplary tilt actuation assembly and motor assembly consistent with embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present disclosure primarily addresses components of electric vertical take-off and landing (eVTOL) aircraft for use with non-traditional aircraft. For example, the eVTOL aircraft of the present disclosure may be intended for frequent (e.g., more than 50 flights per working day), short-duration flights (e.g., less than 100 miles per flight) over, into, and outside of populated areas. The aircraft may be intended to carry four to six passengers or commuters who expect a low-noise and low-vibration experience. Therefore, it may be desirable for the aircraft's components to be configured and designed to withstand frequent use without wear, for the components to generate less heat and vibration, and for the aircraft to include mechanisms for effectively controlling and managing the heat or vibration generated by the components. Furthermore, some of these aircraft may be intended to operate in close proximity to each other over congested metropolitan areas. Therefore, it may be desirable for the components to be configured and designed to generate low levels of noise both inside and outside the aircraft and to have various safety and backup mechanisms. For example, for safety reasons, it may be desirable for an aircraft to be propelled by a distributed propulsion system to avoid the risk of a single point of failure and to be capable of conventional takeoff and landing on a runway. Furthermore, it may be desirable for the aircraft to be able to safely take off and land vertically from relatively confined spaces (e.g., vertiports, parking lots, or driveways) while transporting approximately four to six passengers or commuters with associated baggage, as compared to traditional airport runways. These service requirements may impose design constraints on the size, weight, and operational efficiency (e.g., drag, energy use) of the aircraft, which may affect the design and configuration of aircraft components.

[0018] The disclosed embodiments provide new and improved configurations of aircraft components not observed in conventional aircraft and / or identified design criteria for components that differ from conventional aircraft components. Such alternative configurations and design criteria combine to address shortcomings and challenges of conventional components and result in the disclosed embodiments of various configurations and designs of eVTOL aircraft components.

[0019] In some embodiments, the disclosed eVTOL aircraft may be designed to be capable of both vertical and conventional takeoff and landing, with a distributed electric propulsion system that enables vertical flight, forward flight, and transition. Thrust may be generated by supplying high-voltage power to the electric engines of the distributed electric propulsion system, each of which may convert the high-voltage power into mechanical shaft power for rotating a propeller. The embodiments disclosed herein may involve optimizing the energy density of the electric propulsion system. The embodiments may include an electric engine connected to an onboard power source, which may include a device capable of storing energy, such as a battery or capacitor, or may include one or more systems for harnessing or generating electricity, such as a fuel-powered generator or a solar panel array. Some disclosed embodiments provide for component weight and space reduction in the aircraft, thereby increasing the aircraft's efficiency and performance. Focusing on safety in passenger transportation, the disclosed embodiments also implement new and improved safety protocols and system redundancies in the event of a failure to minimize any single point of failure in the aircraft's propulsion system. Some disclosed embodiments also provide new and improved approaches to meeting aviation and transportation laws and regulations.

[0020] In a preferred embodiment, the distributed electric propulsion system may include 12 electric engines that may be mounted on forward and aft booms of the aircraft's wings. The forward electric engines may be tiltable in flight between a horizontally oriented position (e.g., to generate forward thrust) and a vertically oriented position (e.g., to generate vertical lift). The forward electric engines may be of a clockwise or counterclockwise type relative to the direction of propeller rotation. The aft electric engines may be fixed in a vertically oriented position (e.g., to generate vertical lift). The aft electric engines may also be of a clockwise or counterclockwise type relative to the direction of propeller rotation. In some embodiments, the aircraft may have various combinations of forward and aft engine configurations. For example, the aircraft may have six forward and six aft electric engines, four forward and four aft electric engines, or any other combination of forward and aft electric engines, including embodiments in which the number of forward and aft electric engines is unequal. In some embodiments, the aircraft may have four forward propellers and four aft propellers, at least four of which include tiltable propellers.

[0021] In some embodiments, for vertical take-off and landing (VTOL) missions, the forward and aft electric engines can provide vertical thrust during take-off and landing. During flight phases in which the aircraft is in forward flight mode, the forward electric engine can provide horizontal thrust, while the propellers of the aft electric engines can be stowed in a fixed position to minimize drag. The aft electric engines can be actively stowed with position monitoring. Transitions from vertical to horizontal flight and vice versa can be achieved via a tilt propeller subsystem. The tilt propeller subsystem can redirect thrust from a primarily vertical orientation during vertical flight mode to a nearly horizontal orientation during forward flight. In some embodiments, transitional modes of flight can be utilized beyond brief changes between climb and cruise. For example, tilt propellers can be maintained at intermediate angles between substantially horizontal and substantially vertical, in combination with or independently of operating lift propellers. This may enable the aircraft to proceed at speeds much lower than the stall speed of a comparably sized conventional aircraft and transition seamlessly above and below such speeds without interrupting the passenger experience. The variable pitch mechanism may vary the collective pitch angle of the propeller hub assembly blades of the forward electric engine for operation during hover, transition, and cruise phases.

[0022] In some embodiments, for conventional take-off and landing (CTOL) missions, the forward electric engine may provide horizontal thrust for fixed-wing take-off, cruise, and landing. In some embodiments, the aft electric engine may not be used to generate thrust during CTOL missions, and the aft propeller may be stowed in place.

[0023] In some embodiments, the electric engine may be housed in or connected to the boom of the aircraft and may include a motor, an inverter, and a gearbox. In some embodiments, the motor, inverter, and gearbox may be linked together so that they share a central axis. In some embodiments, torque generated by the motor may be sent to the gearbox separately from the propeller of the propulsion system. In some embodiments, the gearbox may provide gear reduction and then send torque back to the propeller via a main shaft and through bearings located inside the motor. In some embodiments, the inverter may be attached to the back of the gearbox so that the main shaft does not pass through the inverter when outputting torque to the propeller. In some embodiments, the motor, gearbox, and inverter may be linked together so that a coolant, such as oil, may be used to maintain the motor, inverter, and / or gearbox while sharing a common heat exchanger.

[0024] In some embodiments, the tilting propeller system may include a linear or rotary actuator for changing the orientation of the propulsion system during operation. In some embodiments, the pitch of the propulsion system may be changed as a function of the orientation of the propulsion system. In some embodiments, the rotary actuator may include a motor, an inverter, and a gearbox. In some embodiments, the gearbox may include various types of gears that cooperate to provide a gear reduction that can orient the propulsion system. In some embodiments, the tilting propeller system may include a redundant configuration in which multiple motors, inverters, and gearboxes are present and cooperate using gears. In some embodiments, a configuration utilizing multiple motors, gearboxes, and inverters may allow a failed portion of the redundant configuration to be driven by a motor, inverter, and gearbox of another portion of the configuration. In some embodiments, the gearbox configuration may also allow the tilting propeller system to maintain the orientation of the propulsion system with or without the assistance of additional power provided by the system.

[0025] In some embodiments, the electric propulsion systems described herein may generate thrust by supplying high-voltage (HV) electrical power to an electric engine, which converts the HV electrical power into mechanical shaft power used to rotate a propeller. As described above, the aircraft described herein may have multiple electric engines mounted fore and aft of the wing. The amount of thrust generated by each electric engine may be controlled by torque commands from a flight control system (FCS) via a digital communication interface to each electric engine. Embodiments may include a forward electric engine, and may be capable of changing the orientation, or tilt, of the forward electric engine. Additional embodiments include a forward engine, which may be a clockwise (CW) or counterclockwise (CCW) type. The forward electric engine propulsion subsystem may consist of a multi-blade adjustable pitch propeller and a variable pitch subsystem.

[0026] In some embodiments, the aircraft may include an aft engine or lifter that may be of the clockwise (CW) or counterclockwise (CCW) type. Additional embodiments may include an aft electric engine that utilizes a multi-blade fixed pitch propeller.

[0027] As described herein, the orientation and use of the electric propulsion system may vary throughout the operation of the aircraft. In some embodiments, during vertical takeoff and landing, the forward propulsion system and the aft propulsion system may provide vertical thrust during takeoff and landing. Some embodiments may include transitioning from vertical flight to horizontal flight and vice versa. In some embodiments, the transition may be achieved via a tilt propeller system (TPS). The TPS redirects thrust between a primarily vertical direction during vertical flight mode and a primarily horizontal direction during forward flight mode. Additional embodiments may include a variable pitch mechanism that can change the collective angle of the forward propulsion system's propeller hub assembly blades for operation during hover, cruise, and transition phases. Some embodiments may include a conventional takeoff and landing (CTOL) configuration, with the tilter providing horizontal thrust for fixed-wing takeoff, cruise, and landing. The aft electric engine is not used to generate thrust during CTOL missions, and the aft propeller is stowed in place to reduce drag.

[0028] As disclosed herein, an electric engine may include an inverter and a motor, or an inverter, a gearbox, and a motor, in various configurations, such as the exemplary configurations described herein. For example, an electric engine may include an electric motor, a gearbox, and an inverter that all share the same central axis. Additionally, the central axis may be configured along the axis of the output shaft toward the aircraft's propeller. In such an exemplary configuration, the motor, gearbox, and inverter would all share the output shaft as the central axis and be oriented circularly around the output shaft. Additional embodiments may include a motor, gearbox, and inverter that are mounted together in an array or in a configuration in which some components, such as the motor and gearbox, are mounted together and other components, such as the inverter, are located elsewhere, but wiring is used to connect the electric engine.

[0029] As mentioned above, the electric engines for aircraft described herein may include some or all of a motor, an inverter, and a gearbox. Various configurations may include an inverter and a motor, such that the motor's output shaft directly provides the speed and torque of the propeller shaft. Additional embodiments of the electric engine may include a motor, an inverter, and a gearbox, where the motor's output may be transmitted through a gearbox connected to the output shaft for the propeller, or a motor, an inverter, and a gearbox, where the output from the motor is decoupled from the propeller and transmitted through the gearbox, and the output shaft for the propeller re-enters the propeller through the gearbox and the motor. As described herein, the electric engine may contemplate any combination or orientation of some or all of the motor, inverter, and gearbox. Additionally, each configuration or orientation of the electric engine disclosed herein may include cooling via air cooling, a coolant, or a mixture of both.

[0030] For example, an electric engine configuration may include a motor and inverter, with the motor located between the aircraft propeller and the inverter. Additionally, the motor may include a gearbox. Furthermore, the inverter may share the same central axis as the motor, and the inverter may be located in an enclosure that cantilevers away from the rear of the motor and may be air-cooled. It is recognized that such an inverter orientation may not be an optimal configuration in terms of the enclosure required to achieve such a cantilevered orientation. Additionally, a motor in this configuration utilizing air cooling may include potting material, and air fins to assist in cooling the motor may result in a further significant increase in system mass.

[0031] Some embodiments may include an electric engine where the inverter module may be mounted outside the motor enclosure. Additional embodiments may include an electric engine where the inverter may be mounted above the electric motor such that the inverter's air cooling fins are below the propeller. Further embodiments may include the inverter mounted at the back of the motor with the air cooling fins facing radially outward, the inverter mounted at the front of the motor with the air cooling fins facing radially outward, the inverter mounted on the motor where the inverter is cooled by a liquid such as oil, or any other position of the inverter relative to the motor.

[0032] Embodiments of the electric motor may include a stator enclosure, a wound stator assembly, a rotor, various bearings, and any additional components that assist in transferring the speed and torque generated by the motor to the propeller.

[0033] It is understood that electric engines may generate heat during operation and may include thermal management systems to ensure that components of the electric engine do not fail during operation. In some embodiments, a coolant may be used and circulated throughout individual components of the engine, such as the inverter, gearbox, or motor, through some of the components, or through all of the engine's components, to help manage the heat present within the engine. Additional embodiments may include using air-cooling methods to cool the electric engine, or using a mixture of coolant and air to manage the heat generated by the electric engine during operation. In some embodiments, the coolant used may also be the same liquid used as a lubricant throughout the inverter, gearbox, or motor. For example, the inverter, gearbox, and motor may be cooled using liquid or air, or a mixture of air and liquid, such as using air cooling to cool the motor, using liquid cooling on the inverter and gearbox, or any other combination of air and liquid cooling throughout the inverter, gearbox, and motor, or even a subset of these components.

[0034] In some embodiments, oil may be used as a lubricant throughout the electric engine and as a coolant fluid to help manage heat generated by the engine during operation. Further to this example, various amounts of oil may be used to function as both a lubricant and a coolant fluid in the electric engine, such as less than 1 quart, less than 2 quarts, or any other amount of oil required to lubricate and cool the electric engine, with or without the assistance of air cooling. As disclosed herein, the electric engine may have different primary functions, such as being used only for ascent and landing and thus only in one orientation, or being used during all phases of flight, such as ascent, landing, and flight. An engine used during all phases of flight may experience various orientations throughout flight and may contain more lubricant and coolant than an engine used in only one orientation.

[0035] Certain flight design considerations have particular importance in the fields of electric and VTOL aircraft. For example, in VTOL design, it may be important to configure the system to be lightweight, simple, energy-efficient, and fail-safe. Thus, it may be desirable to configure the system with a simple and robust design, for example, by eliminating heavy actuators, power sources, and control components, as well as wiring, tubing, or other conduits and electrical connections. Such simplification may serve the dual purpose of reducing weight and eliminating points of failure.

[0036] For example, it may be desirable to provide a simple and robust tilt actuation system for moving tilt propellers between climb and cruise configurations. However, it may also be desirable to provide a backup system or other form of redundancy in the event of failure of the primary tilt actuation system. Furthermore, it may be desirable to provide a system that can maintain a sufficient level of control over the tilt gear in the event of a failure, rather than simply preventing the complete loss of the tilt propellers. Balancing these competing interests within a compact, lightweight, and reliable design can be difficult.

[0037] Embodiments of the present disclosure may provide a tilt actuation system with one or more rotary actuators. For example, in some embodiments, a tilt actuation system may include two rotary actuators, each with a dedicated load path, and a gear reduction system. The gear reduction system may couple the two rotary actuators so that either rotary actuator can transmit torque through both load paths if the other rotary actuator fails. The gear reduction system may include a worm gear or other gear configured to achieve a high gear reduction and prevent or reduce backdriving. The rotary actuator design may allow the actuator to be co-packaged with other elements, such as the inverter of a tilt propeller motor assembly, to share power and control components. Thus, tilt actuation systems according to embodiments of the present disclosure may be compact, lightweight, and fail-safe.

[0038] Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like numbers in different drawings represent the same or similar elements, unless otherwise indicated. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with the present disclosure. Instead, they are merely examples of apparatus and methods consistent with aspects related to the subject matter set forth in the appended claims.

[0039] 1A-1B illustrate a VTOL aircraft 100 in a cruise configuration and a vertical takeoff, landing, and hovering configuration (also referred to herein as a "climb" configuration), respectively, consistent with an embodiment of the present disclosure. Aircraft 100 may include a fuselage 102, wings 104 attached to fuselage 102, a tail 105, and one or more aft stabilizers 106 attached to tail 105 or the rear of fuselage 102. Multiple lift propellers 112 may be attached to wings 104 and configured to provide lift for vertical takeoff, landing, and hovering. The multiple tilt propellers 114 may be mounted on the wings 104 and may be tiltable between a cruise configuration, as shown in FIG. 1A , in which the multiple tilt propellers 114 provide forward thrust to the aircraft 100 for horizontal flight, and a climb configuration, as shown in FIG. 1B , in which the multiple tilt propellers 114 provide a portion of the lift required for vertical takeoff, landing, and hovering. As used herein, the climb configuration may refer to an orientation of the tilt propellers in which the tilt propeller thrust continues to provide primarily lift to the aircraft. The cruise configuration may refer to an orientation of the tilt propellers in which the tilt propeller thrust continues to provide primarily forward thrust to the aircraft. Alternatively, the cruise configuration may refer to a configuration in which the lift propellers are stowed.

[0040] In some embodiments, lift propellers 112 may be configured to provide only lift, with all propulsion being provided by tilt propellers. Thus, lift propellers 112 may be in a fixed position and generate thrust only during takeoff, landing, and hovering. Meanwhile, tilt propellers 114 may tilt into a lift configuration in which the thrust of tilt propellers 114 is directed downward to provide additional lift.

[0041] For forward flight, tilt propeller 114 may tilt from a tilt propeller 114 climb configuration to a tilt propeller 114 cruise configuration. In other words, the tilt angle of tilt propeller 114 may change from an orientation in which tilt propeller thrust is directed downward (to provide lift during vertical takeoff, landing, and hovering) to an orientation in which tilt propeller thrust is directed rearward (to provide forward thrust to aircraft 100). The tilt propeller may tilt about an axis that may be perpendicular to the forward direction of aircraft 100. When aircraft 100 is in full forward flight during the cruise configuration, lift may be provided entirely by wings 104. Meanwhile, lift propeller 112 may be stopped. Blades 120 of lift propeller 112 may be locked in a low-drag position for aircraft cruise. In some embodiments, lift propellers 112 may each have two blades 120 that can be locked for cruising in a minimum-drag position with one blade immediately ahead of the other, as illustrated in FIG. 1A. In some embodiments, lift propellers 112 have three or more blades. In some embodiments, tilt propellers 114 include more blades 118 than lift propellers 112. For example, as illustrated in FIGS. 1A-1B, lift propellers 112 may each include, for example, two blades, and tilt propellers 114 may each include, for example, five blades. In some embodiments, tilt propellers 114 may have, for example, two to five blades.

[0042] In some embodiments, the aircraft may include only one wing 104 on each side of the fuselage 102 (or a single wing extending across the entire aircraft), and at least a portion of the lift propellers 112 may be located aft of the wing 104 and at least a portion of the tilt propellers 114 may be located forward of the wing 104. In some embodiments, all of the lift propellers 112 may be located aft of the wing 104 and all of the tilt propellers 114 may be located forward of the wing 104. According to some embodiments, all of the lift propellers 112 and tilt propellers 114 may be mounted on the wing, i.e., no lift propellers or tilt propellers may be mounted on the fuselage. In some embodiments, all of the lift propellers 112 may be located aft of the wing 104 and all of the tilt propellers 114 may be located forward of the wing 104. According to some embodiments, all of the lift propellers 112 and tilt propellers 114 may be positioned inboard of the wing tips 109 .

[0043] In some embodiments, the lift propellers 112 and tilt propellers 114 may be attached to the wing 104 by a boom 122. The boom 122 may be attached below the wing 104, above the wing, and / or integrated into the wing profile. In some embodiments, one lift propeller 112 and one tilt propeller 114 may be attached to each boom 122. The lift propeller 112 may be attached to the aft end of the boom 122, and the tilt propeller 114 may be attached to the forward end of the boom 122. In some embodiments, the lift propeller 112 may be attached in a fixed position on the boom 122. In some embodiments, the tilt propeller 114 may be attached to the forward end of the boom 122 via a hinge. The tilt propeller 114 may be mounted on the boom 122 such that when in the cruising configuration, the tilt propeller 114 is aligned with the body of the boom 122, forming a continuous extension of the forward end of the boom 122 that minimizes drag for forward flight.

[0044] In some embodiments, the aircraft 100 may include, for example, one wing on each side of the fuselage 102 or a single wing extending across the aircraft. According to some embodiments, the at least one wing 104 is a high wing mounted on the upper side of the fuselage 102. According to some embodiments, the wing includes control surfaces such as flaps, ailerons, or flaperons. According to some embodiments, the wing may have curved wing tips 109 to reduce drag during forward flight.

[0045] In some embodiments, the aft stabilizer 106 includes control surfaces such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wing(s) may have any suitable design. For example, the wing has a tapered leading edge or a tapered trailing edge. In some embodiments, the wing may have a substantially straight leading edge in a center section of the wing 104.

[0046] Aircraft 100 may include at least one door 110 for passenger ingress and egress. In some embodiments, door 110 may be located below and forward of wing 104, as seen in Figures 1A-1B.

[0047] Further description of VTOL aircraft can be found in U.S. Patent Publication No. 2021 / 0362849, which is incorporated by reference in its entirety for all purposes.

[0048] As explained above, it may be desirable to provide a simple and robust tilt actuation system for, for example, moving a tilt propeller between a climb configuration and a cruise configuration. Embodiments of the present disclosure may provide a rotary actuator design that is compact, lightweight, efficient, and fail-safe.

[0049] A. Exemplary Tilt Propeller Embodiment 2A-2B illustrate an exemplary tilting arrangement in a VTOL aircraft 200 consistent with embodiments of the present disclosure. VTOL aircraft 200 may be similar to, for example, VTOL aircraft 100 of FIGS. 1A-1B. In FIGS. 2A-2B and below, corresponding or similar elements may be labeled with corresponding numbers using the number of this figure as the leading digit(s). For example, in some embodiments, boom 222 of FIGS. 2A-2B may be similar to boom 122 of FIGS. 1A-1B. In some cases, corresponding numbers may represent unrelated features.

[0050] 2A illustrates the tilting apparatus in a lift configuration (top) and a cruise configuration (bottom). The tilting apparatus may include, for example, a tilt propeller 214, a motor assembly 230 coupled to the lift propeller and configured to rotate the lift propeller 214 about a propeller rotation axis 292, and a nacelle (omitted for clarity) around the motor assembly 230. The motor assembly 230 and the tilt propeller 214 may comprise the tilting apparatus's propulsion system 215. The tilting apparatus may further include a first frame 223 mounted on a structure of the VTOL aircraft. For example, the first frame 223 may be mounted to the boom 222. The second frame 224 may be movably coupled to the first frame 223 at a pivot 225. The second frame 224 may be configured to support, for example, the motor assembly 230 and the tilt propeller 214. The tilting device may further include a tilt actuation assembly 240 configured to tilt the second frame 224 relative to the first frame 223 about the pivot 225. For example, the tilt actuation assembly 240 may include one or more actuators and a gear reduction system configured to apply a torque to the first frame 223 about the pivot 225 to tilt the second frame 224. The tilt actuation assembly 240 may be capable of actuating the motor assembly 230 and tilt propeller 214 without excessive external connections to the boom for supplying power, control signals, or even mechanical actuation. For example, compared to providing a linear actuator between the first frame 223 and the second frame 224, the tilt actuation assembly 240 may provide a compact design that leaves sufficient space for airflow, for example, in the cruising configuration (as schematically illustrated by the solid arrow at the bottom of FIG. 2A ). Additionally, the tilt actuation assembly 240 may be powered and controlled locally by components supported on the second frame 224 to minimize cumbersome connections between the first and second frames and eliminate potential points of failure.

[0051] 2B illustrates an exploded view of the tilting device of FIG. 2A. As described further below, tilt actuation assembly 240 may be mounted to second frame 224 and coupled to first frame 223 at pivot 225. Tilt actuation housing 241 may engage second frame 224 to cover tilt actuation assembly 240 and protect second frame 224 from the external environment. As shown by the dashed lines, first frame 223 may be coupled to, for example, the front of boom 222 or another structure of VTOL aircraft 200, and second frame 224 may be attached to the bottom of motor assembly 230, such as by bolts or other fasteners.

[0052] FIG. 3 illustrates an expanded view of first frame 323 and second frame 324 of an aircraft, such as VTOL aircraft 100, consistent with embodiments of the present disclosure. First frame 323 and second frame 324 may include corresponding bores at pivot 325 and may be joined together by, for example, an output shaft, as described below. In some embodiments, second frame 324 may include additional bores, for example, to support components of a tilt actuation assembly or to accommodate a blade pitch control assembly. For example, in some embodiments, the blade pitch control assembly may include a linked tilt pitch configured to passively actuate the collective blade pitch of the propeller as a function of the tilt angle of the tilt actuation assembly. In some embodiments, second frame 324 may include cam bore 363 for mounting a gear shaft of the tilt actuation assembly or a camshaft for supporting a cam of the blade pitch control assembly. In some embodiments, a single shaft may include the gear shaft and camshaft passing through cam bore 363, and the bore may comprise a through-hole formed in the element. In some embodiments, the second frame 224 may further include a pitch control bore 364 configured to accommodate, for example, a pitch control rod of a blade pitch control assembly.

[0053] B. Exemplary TPS Gearbox Embodiments 4A-4D illustrate an exemplary tilt actuation assembly in an aircraft, such as the VTOL aircraft 100, consistent with embodiments of the present disclosure. For example, FIG. 4A illustrates an exploded view of an exemplary tilt actuation assembly 440. The exploded view illustrates only the first (left) torque path from the first actuator 442 through the first gear reduction system to the first pivot 425. The first gear reduction system may include various gears and shafts, as well as bearings and structural support, disposed along the first torque path between the first actuator 442 and the first pivot 425, as described further below. Such gears, shafts, and other components may include a planetary gear set 450, a worm gear 455, a worm wheel 456, a gear shaft 457, a pinion 458, a bearing 468, a sector gear 459, and an output shaft 460. The gear reduction system described herein may alternatively be referred to as a tilt actuator gearbox. Additionally, while only the first (left-hand) torque path is shown, it should be understood that the symmetrical and opposite second (right-hand) torque path may comprise similar components and may be appropriately represented by the description of the elements in the exploded view of FIG. 4A . For example, providing multiple actuators along multiple torque paths may provide redundancy in the event of actuator, gear, or other component failure. Additionally, this arrangement may help evenly distribute torque to multiple pivots 425 on the first frame or allow for the use of smaller-sized actuators. In some embodiments, the tilt actuation assembly may comprise a single torque path from a single actuator, as further described below with respect to FIG. 6 . Close-up views of a portion of the tilt actuation assembly 440 are shown in FIGS. 4B-4D .

[0054] The tilt actuation assembly 440 may include an actuator 442. The actuator 442 may include, for example, a rotary actuator having a rotor 445 housed within a stator 446. For example, the actuator 442 may include, for example, an induction motor, a synchronous motor, or another electric motor or any other type of rotary actuator. In some embodiments, the actuator 442 may include, for example, a linear actuator adapted to generate rotary motion using a slider, a lead screw, a rack and pinion, or other mechanical system. In some embodiments, the actuator 442 may include, for example, a hydraulic motor or an air motor. The rotor shaft of the actuator 442 may be coupled to a gear, such as a sun gear 443. The actuator 442 may be mounted to an adjacent structure of the tilt actuation assembly 440 by, for example, a mounting bracket 439, which may also support a second tilt actuator in some embodiments. An actuator cap 444 may be configured to cover the actuator 442 to enclose the actuator 442 within the tilt actuation housing 441.

[0055] The actuator 442 may be coupled to the planetary gear set 450. For example, the planetary gear set 450 may include a sun gear 443, a plurality of planet gears 452, a planet carrier 453, and a ring gear 454. As described above, the rotor shaft of the actuator 442 may be coupled to the sun gear 443 such that the rotor shaft extends from the tilt actuator 442 to the sun gear 443. The sun gear may be configured to mesh with inner sides (i.e., sides facing the center of the planet carrier 453) of the plurality of planet gears 452 to rotate the plurality of planet gears 452. The plurality of planet gears 452 may be coupled to the planet carrier 453 and configured to mesh with the ring gear 454 along outer sides of the plurality of planet gears 452. Thus, when the actuator 442 is energized, the actuator 442 may apply torque via the sun gear 443 as an input to either the planet carrier 453 or the ring gear 454 via the plurality of planet gears 452 as an output. For example, as seen in FIG. 4A , torque may be output at planet carrier 453 to worm gear 455. The planetary gear set may comprise the first gear stage of tilt actuation assembly 440. In some embodiments, the first gear stage may comprise a gear reduction ratio of approximately, for example, 2:1 to 5:1. In some embodiments, the first gear stage may comprise a gear reduction ratio of approximately, for example, 3:1 to 4:1. It should be understood that these gear ratios are exemplary and non-limiting, and other gear ratios may be used in the first gear stage.

[0056] The worm gear 455 may be coaxially coupled to the output of the planetary gear set 450, such as the planet carrier 453. The worm wheel 456 may be configured to mesh with the worm gear 455. The worm wheel 456 may be coaxially coupled to a gear shaft 457, such that, for example, when the actuator 442 is energized, the worm gear 455 rotates the worm wheel 456 and the gear shaft 457, thereby transferring torque about the axis of the actuator 442 to an orthogonal torque about the axis of the gear shaft 457. The worm gear 455, the worm wheel 456, and the gear shaft 457 may comprise a second gear stage of the tilt actuation assembly 440. In some embodiments, the second gear stage may comprise a gear reduction ratio of, for example, about 20:1 to 40:1. In some embodiments, the second gear stage may comprise a gear reduction ratio of, for example, about 28:1 to 35:1. It should be understood that these gear ratios are exemplary and non-limiting and that other gear ratios may be used in the second gear stage.

[0057] The worm gear configuration of the second gear stage may offer several advantages. For example, as described above, a worm gear / worm wheel arrangement may provide a high reduction ratio in a compact space. The reduction ratio may be based on the number of teeth 476 of the worm wheel 456 divided by the number of individual threaded filaments 475, or gaps, on the worm gear 455. For example, as seen in FIG. 4B , the worm gear 455 may include a single filament 475 that wraps continuously around the worm gear 455. Each full rotation of the worm gear 455 may move the worm wheel 456 by one tooth 476. Thus, a 40-tooth worm wheel and a single filament worm gear may achieve a high gear reduction of 40:1 in a tight space.

[0058] Additionally, the worm gear may be configured with a self-locking feature to prevent backdriving. Backdriving may occur, for example, when a downstream gear farther from the actuator along the torque path drives an upstream gear closer to the actuator. For example, backdriving may refer to the worm wheel 456 driving the worm gear 455 without reversing direction as a result of a force acting on the worm wheel 456. For example, the weight of the motor assembly and propeller may backdrive the worm gear 455 toward the cruise configuration, overriding any self-locking feature. Alternatively, the thrust of the rotating propeller may backdrive the worm gear 455 toward either the climb or cruise configuration, depending on the relationship between the propeller's thrust line and the hinge line about which the propeller tilts. For example, with reference to FIG. 2A , the thrust line may represent the direction of thrust of the propeller 214. For purposes of this description, the thrust line may be considered to be substantially coincident with the propeller rotation axis 292. When thrust line 292 is offset from the hinge line extending out of the page through pivot 225, propeller thrust can generate a moment about the hinge line to apply a torque to pivot 225. Thus, when thrust line 292 is below pivot 225 when viewed in the cruise configuration, torque about pivot 225 can backdrive the worm gear, tilting propeller 214 up toward the climb configuration. The opposite can occur when thrust line 292 is above pivot 225 when viewed in the cruise configuration. Torque about pivot 225 can backdrive the worm gear, tilting propeller 214 down toward the cruise configuration.

[0059] Backdriving can be prevented, reduced, or controlled by appropriate design of the worm gear 455 and the thrust line 292. For example, the tilting device can be designed so that the thrust line 292 is offset from the pivot 225 by a predetermined threshold and direction. This can generate a moment about the pivot 225 when thrust is generated. In some embodiments, the thrust line 292 can pass substantially through the pivot 225 to minimize propeller-induced backdriving. This can help prevent runaway tilt in the event of an actuator failure or can help maintain some control by reducing the load requirements on the remaining actuators. In some embodiments, the thrust line 292 can pass under or over the pivot 225 so that thrust urges the tilting propeller toward a climb or cruise configuration, respectively. For example, in some embodiments (as shown in FIG. 2A ), the thrust lines 292 may extend below the pivot 225 to slightly bias the tilt propellers 214 toward the climb configuration by their own thrust. The climb configuration may be considered a safer mode than the cruise configuration for emergency flight situations, or may be the most preferred placement when design constraints prevent the thrust lines from passing directly through the pivot 225. In some embodiments, it may be desirable to slightly bias the tilt propellers 214 toward the cruise configuration to allow conventional flight, for example, in the event of an actuator failure, which may enable greater energy efficiency and longer flight times.

[0060] Additionally, referring back to FIG. 4B , to control backdriving, an appropriate lead angle θ can be selected for the filaments of the worm gear 455. The lead angle θ may refer to the angle made by the inclined helical surfaces 475a of the filaments 475, measured from a plane perpendicular to the rotation axis 455a of the worm gear 455. If this lead angle is reduced (e.g., so that the filaments are approximately perpendicular to the rotation axis of the filaments), the frictional force between the worm gear 455 and the worm wheel 456 may be too great to allow backdriving by the worm wheel 456. However, because the filaments 475 of the worm gear can slide against the teeth 476, the worm gear 455 may be able to overcome the sliding frictional force and drive the worm wheel 456 via the actuator 442. This self-locking feature may be useful for allowing a tilt propeller to be driven to any desired tilt angle and held there without requiring an excessive amount of energy to do so. Self-locking can also be useful in the event of actuator 442 failure, as it can reduce or eliminate abrupt changes in tilt angle that could cause damage to or loss of control of the tilt propeller. In some embodiments, as described further below, the sizing of actuator 442 and the design of worm gear 455 can be selected to achieve desired operational specifications at a minimal weight penalty. In some embodiments, worm gear 455 can comprise a spherical gear, as seen at the bottom of FIG. 4B . In a spherical configuration, filars 475 conform to arc 456a of worm wheel 456 and more closely mesh with teeth 476, which can lead to higher power transmission and reduced backlash.

[0061] Returning to FIG. 4A , the gear shaft 457 may further be coaxially coupled to a pinion 458. In some embodiments, the pinion 458 may include, for example, a helical gear or a spur gear. A further end of the gear shaft may be received in a side panel 441 a of the tilt actuation housing 441, for example, via a rotational bearing 468. The rotational bearing may include, for example, a ball bearing, a cylindrical roller bearing, a needle roller bearing, or other rotational bearing. The pinion 458 may be configured to mesh with a sector gear 459. In some embodiments, the sector gear 459 may include, for example, a spur gear or a helical gear. The sector gear 459 may be coaxially coupled to an output shaft 460, which may be fixed to a first frame (not shown) at a pivot 425. For example, the output shaft may include a spline section 460 a for fixing the output shaft to the first frame. The output shaft 460 may be rotatably coupled to the second frame 424, for example, via the tilt actuation housing 441. Thus, the sector gear 459 and output shaft 460 may remain stationary relative to the first frame, while the second frame may be able to rotate about the output shaft 460 and pivot 425. The necessary torque to achieve this rotation may be provided at the interface between the pinion 458 and the sector gear 459. For example, when the gear shaft 457 is driven by the actuator 442 via the first and second gear stages, the movable pinion 458 may roll along the teeth of the stationary sector gear 459, tilting the entire tilt actuation assembly 440, second frame 424, motor assembly, and propeller (not shown). Thus, the tilt actuation assembly 440 may be fully mounted to the second frame 424 and configured to tilt the second frame 424 relative to the first frame. Additionally, sector gear 459 may limit the tilt range of second frame 424 to prevent the propeller blades from colliding with the surface of VTOL air vehicle 100. For example, sector gear 459 may set the maximum tilt angle of the tilt actuator to maintain clearance CL (see, e.g., FIG. 2A ) between VTOL air vehicle 100 and the propeller of the propulsion system.

[0062] As can be seen in FIG. 4A , pinion 458 and sector gear 459 may comprise the third gear stage of tilt actuation assembly 440. In some embodiments, the third gear stage may comprise a gear reduction ratio of approximately, for example, 2:1 to 5:1. In some embodiments, the third gear stage may comprise a gear reduction ratio of, for example, 3:1 to 4:1. It should be understood that these gear ratios are exemplary and non-limiting, and other gear ratios may be used in the second gear stage. In some embodiments, the first, second, and third stages may have a combined gear reduction of, for example, 250:1 to 500:1, although other combined gear ratios are contemplated. This may allow for the employment of relatively smaller actuators, reducing the overall mass of tilt actuation assembly 440 and VTOL aircraft 400 and increasing energy efficiency.

[0063] In some embodiments, tilt actuation assembly 440 may include cam 462 (see, e.g., FIG. 4A). For example, cam 462 may be coaxially coupled to gear shaft 457, e.g., via cam bore 463 in second frame 424 (similar to cam bore 363 in FIG. 3). In this manner, cam 462 may rotate through an angle that may have a fixed relationship to the tilt angle of the tilt propeller. This relationship may be used, for example, to adjust propeller blade pitch as a function of tilt angle. For example, cam 462 may be designed with an outer profile that acts against a pitch control rod (not shown) as the cam rotates. As described further below, the shape of the outer profile of cam 462 may be selected to move the pitch control rod a desired amount for a given tilt angle of the propeller. Alternatively, or in addition, the cam profile may be used to measure the tilt angle of the propeller, e.g., as described below.

[0064] FIG. 4C illustrates exemplary components of the first, second, and third gear stages of tilt actuation assembly 440 in an assembled state consistent with embodiments of the present disclosure. The view in FIG. 4C may more clearly illustrate the interlocking between the various gears in tilt actuation assembly 440. For example, as seen in FIG. 4C , actuator 442 may be coaxially aligned with the input and output of planetary gear set 450, which may be coaxially aligned with worm gear 455. Rotation of worm gear 455 about the actuator axis may rotate worm wheel 456 along the axis of rotation of gear shaft 456, which may be generally perpendicular to the actuator axis. Gear shaft 456 may rotate pinion 458 such that pinion 458 may roll along the teeth of sector gear 459, while sector gear 459 remains stationary relative to the first frame (not shown). For example, sector gear 459 may be coaxially coupled to output shaft 460, which may be secured to the first frame by spline section 460a. Thus, all of the illustrated elements along the torque path between actuator 442 and pinion 458 may be rotated about output shaft 460 by one or more actuators 442.

[0065] 4C may illustrate dual torque paths that may be achieved consistent with embodiments of the present disclosure. For example, the first and second actuators 442 may each rotate their own planetary gear set 450, worm wheel 455, etc. along two parallel torque paths. In some embodiments, the torque paths may be coupled by an idler gear 461, described below.

[0066] FIG. 4D illustrates a further view of tilt actuation assembly 440 consistent with embodiments of the present disclosure. Idler gear 461 may couple first and second actuators 442 together, for example, via the outputs of first and second planetary gear sets 450. For example, idler gear 461 may be configured to mesh with first and second planetary carriers 453 when planetary carrier 453 is configured as an output of planetary gear set 450. As can be seen in the lower right of FIG. 4D , when planetary carrier 453 rotates clockwise, as indicated by the solid arrow, the idler gear rotates counterclockwise following planetary carrier 453. During normal operation of tilt actuation assembly 440, the idler gear may simply progress along the two planetary gear sets 450 without transferring substantially significant loads between the two torque paths. However, idler gear 461 may nevertheless perform a load sharing function to equalize any minor differences between the left and right torque paths. Furthermore, if one actuator fails, the remaining actuator may be able to distribute its torque substantially equally between the two torque paths via idler gear 461 to prevent excessive torsional loads or imbalance.

[0067] The extent to which a single actuator may be capable of driving the entire propulsion system may depend on actuator sizing. For example, in some embodiments, two actuators may be sized to be fully redundant, in that either actuator may be capable of tilting the propulsion system at normal operating speeds for extended periods of time. However, such a system may involve high cost and excessive weight, which may reduce the flight range of the VTOL aircraft or necessitate the elimination of other important features. Additionally, specifications or flight standards may not require such full redundancy. In some embodiments, actuator 442 may be sized such that a single actuator 442 may be capable of tilting the propulsion system at a reduced speed.

[0068] In some embodiments, the actuators 442 may be sized such that a single actuator 442 can replace or be combined with the worm gear 455 to maintain stability of the tilt propulsion system. For example, if one actuator fails, another actuator may be able to backdrive the torque path of the failed actuator, even if the other actuator is not sized to support the entire tilt actuator load. Such a configuration may advantageously reduce weight in the VTOL aircraft while maintaining a safe flight mode. For example, this configuration may further enable the propulsion system to be held stable or even to operate from a cruise configuration to a safer climb configuration, even though a single actuator may not be optimally suited to perform this operation without assistance from another source of tilt torque, such as the propulsion system. In some embodiments, for example, the lift propeller may be driven to provide additional lift power to assist the remaining actuator 442 in tilting the propulsion system to a safer tilt angle. This may be made possible by appropriate design of the thrust lines and pivots, as described above. Alternatively, the functioning actuator may apply an opposing torque to the idler gear 461 and rely on flight-induced vibrations to propel the gear forward, thereby achieving a suitable amount of backdriving during a failure mode without adding excessive weight to the aircraft.

[0069] Additionally, under normal conditions when both actuators are operating, greater stability may be achieved by opposing the two actuators. For example, the left planetary carrier 453 may operate in the positive direction indicated by the solid arrow while the right planetary carrier 453 operates in the negative direction indicated by the dashed arrow. The first torque in the positive direction and the second torque in the negative direction may be substantially equal and opposite. The opposing forces, especially when used in combination with the self-locking feature of the worm gear 455, may achieve a high level of stability with low energy consumption.

[0070] Additionally, as shown in FIG. 4D , tilt actuation assembly 440 may include a tilt sensor 469 configured to sense the tilt angle of the propulsion system. In some embodiments, a previously unused surface of tilt actuation assembly 440 may be configured in combination with tilt sensor 469 to sense the tilt angle. For example, a rear surface 479 of sector gear 459 may be formed with a predetermined cam profile. Tilt sensor 469 may include a proximity sensor configured to sense proximity to rear surface 479. In this manner, the gap distance between tilt sensor 469 and rear surface 479 may vary according to a known relationship with the tilt angle. In some embodiments, other sensor configurations may be used. For example, another surface may be used in place of rear surface 479 of sector gear 459, as long as the surface can be configured to vary with a known relationship to the tilt angle. Furthermore, rear surface 479 may be configured as other than a cam profile. For example, rear surface 479 may be configured with a grating or other indicia, and tilt sensor 469 may comprise, for example, an optical encoder. Alternatively, a resolver or other angle sensor may be disposed on rear surface 479. It is also contemplated that other types of tilt sensors that do not rely on gap measurements may be used to determine the tilt angle.

[0071] As further illustrated in FIG. 4D , the shafts in the tilt actuation assembly may be continuous or may be divided into left and right torque paths. For example, output shaft 460 may comprise separate segments (segments 460 on either side of center gap G) as shown, or may include a single shaft 460 as shown in long dashed lines. Similarly, gear shaft 457 may be continuous as shown, or may comprise separate segments as shown in short dashed lines. A continuous shaft may be preferred for added torque stability and distribution, while separate segments may be preferred to reduce weight or create space to accommodate other components. In some embodiments, a continuous gear shaft 457 may be preferred when mounting cam 462, as described below.

[0072] 5A-5C illustrate an exemplary blade pitch control assembly 572 in an aircraft such as VTOL aircraft 100, consistent with an embodiment of the present disclosure. Blade pitch control assembly 572 may be integrated with a tilt actuation assembly, for example, as described above. Cam 562 and gear shaft 557 may correspond, for example, to cam 462 and gear shaft 457 of FIGS. 4A-4D . In VTOL aircraft 100, it may be desirable to achieve a low blade pitch angle in a climb configuration for optimal thrust and a high blade pitch angle for optimal efficiency in cruise. As previously described and shown in FIG. 5A , cam 562 may rotate with the tilt of second frame 524 about pivot 525. The outer profile of cam 562 may press against roller 565 coupled to slider 567, which may move pitch control rod 566 along propeller axis of rotation 592. Pitch control rod 566 may be further rotationally separated from slider 567 by pitch control rod bearing 590 to allow pitch control rod 566 to rotate about its axis with propeller 514. By selecting an appropriate profile shape for cam 562, pitch control rod 566 may operate to control the pitch angle of the blades as a function of the tilt angle of the propeller.

[0073] For example, as shown in FIG. 5B , pitch control rod 566 may pass through second frame 524 and motor assembly 530 and be coupled to propeller yoke 591. Propeller yoke 591 may be movably mounted inside hub 531 so that propeller yoke 591 may move along propeller rotation axis 592. Propeller yoke 591 may be coupled to each propeller blade 518, such as by an eccentrically located pin or protrusion 593 a in blade actuation cup 593. As propeller yoke 591 moves along rotation axis 592 by pitch control rod 566, propeller blade 518 may rotate about its longitudinal axis (as indicated by the circular arrow and dashed line) to change the pitch angle of propeller blade 518. Thus, the blade pitch angle may be mechanically correlated to the tilt angle of second frame 524. This may enable design tradeoffs by exchanging pitch control flexibility for reduced complexity, weight, and an independent control architecture. For example, if blade pitch angle is automatically adjusted as a function of propeller tilt angle, there is no need to provide a dedicated system for adjusting blade pitch. Eliminating components associated with such control also eliminates a potential source of failure. Further embodiments of such linked tilt-pitch systems may be found in U.S. Patent Application Nos. 18 / 098,417 and 18 / 478,980, which are incorporated by reference in their entireties for all purposes. Additionally, as seen in FIG. 5A, cam 562 may be utilized as a sensing surface for tilt sensor 569 in the same manner as described above with respect to tilt sensor 469 of FIG. 4D.

[0074] FIG. 5C illustrates a further embodiment of a blade pitch control assembly 572 consistent with embodiments of the present disclosure. In the embodiment of FIG. 5C , a dedicated pitch control actuator 542p may be provided, for example, to actuate the pitch control rod 566. For example, the pitch control actuator 542p may include a rotary actuator having a lead screw LS configured to move the slider 567, a linear actuator, a hydraulic actuator, or another actuator configured to move the slider 557 or the pitch control rod 566. The pitch control actuator 542p may be configured so that the lead screw LS does not interfere with the gear shaft 557, for example, by positioning the pitch control actuator 542p between the gear shaft 557 and the pitch control rod 566. Alternatively, the lead screw LS may avoid interference with the gear shaft 557 by positioning the lead screw LS to pass vertically above or below the gear shaft 557, as seen in the cruise configuration. For example, an alternative arrangement is further shown in FIG. 5C , in which pitch control actuator 542p is located on the opposite side of gear shaft 557 from slider 567, such that lead screw LS passes underneath gear shaft 557. In some embodiments, pitch control actuator 542p can be accommodated by providing gear shaft 557 in two separate segments, as described with respect to FIG. 4D , such that a portion of pitch control actuator 542p can be located in the gap between the segments. In some embodiments, another type of actuator can be configured to impart linear motion to pitch control rod 566.

[0075] FIG. 6 illustrates an exemplary tilt actuation assembly in an aircraft, such as the VTOL aircraft 100, consistent with embodiments of the present disclosure. In FIG. 6, a single actuator 442 (see, e.g., FIG. 4A) may be configured to tilt the second frame 624 along a single torque path to the pivot 625. The single torque path may correspond, for example, to one side of the dual torque paths described above, but may be appropriately sized to function on its own. In some embodiments, the single actuator 442 may be configured to tilt the second frame 624 along dual torque paths connected by an idler gear (see, e.g., FIG. 4C). When there is only one actuator in a dual torque path configuration (e.g., coupled to the left planetary gearset 450 in FIG. 4D), a complete second planetary gearset may not be required because there is no need to provide a gear reduction from the second actuator. For example, the planet carrier 453 or the idler gear 461 may instead include a secondary load path gear configured to transfer torque to the second torque path.

[0076] Returning to FIG. 6 , a single actuation system may lack the redundancy of dual torque paths, but may provide other safety or backup features while reducing the weight and cost of tilt actuation assembly 640. For example, linear damper 627 may be provided to reduce the tilt rate of second frame 624 in the event of a failure of actuator 642. Linear damper 627 may be coupled between second frame 624 and another frame, such as, for example, first frame 623 or another structural element of VTOL aircraft 600. In some embodiments, the linear damper may be further supported by bulkhead 695, such as bulkhead 295 of FIG. 2B .

[0077] If actuator 642 becomes disconnected from second frame 624 or otherwise fails, damper 627 can dissipate energy, thereby limiting the rate of change of tilt of second frame 624 and preventing catastrophic failure. Damper 627 can comprise a known damper configuration, such as a balanced hydraulic or pneumatic cylinder comprising a piston configured to slide within a cylinder and including multiple openings through which fluid can flow as the piston moves within the cylinder. Damper 627 can include a passive damper configured to apply a force (hydraulic or pneumatic) to second frame 624 only when the tilt angle of a propeller (not shown) is changing (i.e., no bias is applied when the propeller is stationary). In some embodiments, an additional redundant actuator 642 can be provided in addition to a damper mechanism such as damper 627. Damper 627 can be configured to limit the rate of change of the tilt angle of second frame 624 in both the upward and downward tilt directions. Damper 627 can be positioned such that the force vector of damper 627 can extend below the tilt axis of the propeller, such as the tilt axis of pivot 625. In some embodiments, damper 627 can be configured to limit the rate of change of the tilt angle of the propeller below a predetermined threshold if actuator 642 becomes disconnected from second frame 624 or otherwise fails.

[0078] Further aspects of the linear damper are described in the above-incorporated U.S. Patent Application No. 18 / 098,417. Additionally, although not readily shown in other figures, second frame 624 may include hard stops 671 configured to prevent tilt propeller blades from colliding with a surface of VTOL aircraft 100, such as boom 622. For example, hard stops 671 may set a maximum tilt angle for the tilt actuator to maintain clearance CL between boom 622 or another surface of the aircraft and the propellers of the propulsion system (see, e.g., FIG. 2A ). While the ability of hard stops to prevent collisions may be limited in propulsion systems that may accelerate rapidly during a malfunction, other features according to embodiments of the present disclosure may slow the acceleration to a point where hard stops 671 become effective. For example, linear dampers 627, or a self-locking worm gear as described above, may slow the acceleration sufficiently so that the propulsion system can be stopped by hard stops 671.

[0079] 7A-7C illustrate an exemplary integrated tilt actuation assembly 440 and motor assembly 730 in an aircraft, such as a VTOL aircraft 100, consistent with embodiments of the present disclosure. The embodiment according to Figures 7A-7C illustrates various schemes for co-packaging various elements of the tilting device, such as the tilt actuation assembly 740 and motor assembly 730, and for sharing resources, such as inverter architectures and other power and control systems. Additional description of power and control systems can be found in U.S. Patent Application No. 18 / 363,535, which is incorporated by reference in its entirety for all purposes.

[0080] In some embodiments, the inverter may receive high-voltage direct current (DC) power from a high-voltage power system and may receive torque commands, for example, from an aircraft flight control system. The inverter may also receive low-voltage DC power from a low-voltage system, such as a low-voltage power system used to power an engine control processor. In some embodiments, the low-voltage power may include, for example, 28 volts. However, this is merely an example, and other low voltages may be used. In some embodiments, the inverter may be responsible for receiving aircraft torque commands and engine mode commands, generating AC current in the stator phase winding sets to output rotor torque, monitoring voltage, current, shaft speed, torque, and temperature in the electric engine, fault detection and adjustment, and / or transmitting status and faults to the aircraft.

[0081] The motor assembly 730 may include various modules, such as, for example, a motor 735, a gearbox 736, and a propulsion inverter 737. For example, the modules may be arranged in the order shown or in another order. The propulsion inverter 737 may be configured to provide AC current to the drive motor 735 and may be further configured to control the motor 735 based on, for example, commands from a flight control system of the VTOL aircraft, sensor feedback signals, etc. As illustrated in FIGS. 7A-7B , the propulsion inverter 737 may be mounted adjacent to the tilt actuation assembly 740 via a second frame 724. In some embodiments, the second frame 724 may include a central void CV such that the interior of the tilt actuation housing 741 may be integrated with the inverter housing 786 of the propulsion inverter 737 to create a common housing with a contiguous volume in which electrical components may be co-packaged or shared. Thus, in some embodiments, the components of the propulsion inverter 737 and the tilt actuation assembly 740 may be included within a common housing. For example, as described above, tilt actuation inverter 748, tilt actuation wiring 747, tilt actuator 742, or various gears and shafts may be included in a common housing with propulsion inverter 737. However, embodiments of the present disclosure are not limited thereto. For example, in some embodiments, one or more similar advantages to those described in this section may be achieved even if propulsion inverter 737 is separated from actuator 742 or tilt actuation assembly 740 by, for example, motor 735, gearbox 736, second frame 724, or a partition.

[0082] For example, power may be delivered to input and DC filter module 781 from one or more external battery packs of VTOL aircraft 700, as illustrated schematically by HV DC lines 780. Input and DC filter module 781 may provide DC power to both propulsion inverter 737 and tilt actuation inverter 748, which may provide current to one or more actuators 742 via tilt actuator wiring 747. For example, tilt actuator wiring 747 may include multiple phase leads. In some embodiments, multiple tilt actuation inverters 748 may be provided to provide current to multiple actuators 742. As illustrated in FIG. 7A , both propulsion inverter 737 and tilt actuation inverter 748 may be coupled to a common bus bar 783 to provide a common voltage from input and DC filter module 781 to both systems. Propulsion inverter 737 and tilt actuation inverter 748 may be further configured to share sensor information from various sensors 787 or share feedback control or communication signals, for example. Sensors 787 may include, for example, sensors for monitoring electrical, mechanical, dynamic, or thermal properties of motor assembly 730, propellers (not shown), or other elements of the propulsion system. In some embodiments, propulsion inverter 737 may share a sampling rate with tilt actuated inverter 748 for synchronization purposes. In some embodiments, propulsion inverter 737 may be configured to supply current to tilt actuator 742. In some embodiments, tilt actuated inverter 748 may comprise a subcomponent of propulsion inverter 737 or may otherwise be integrated with propulsion inverter 737. In some embodiments, an integrated housing configuration may support internal coordination of thrust vectoring between propulsion inverter 737 and tilt actuated inverter 748. Additional embodiments of an integrated housing arrangement may include an integrated or shared controller 788. For example, controller 788 may include a shared controller configured to control both propulsion inverter 737 and tilt actuated inverter 748.Alternatively, controller 788 may include an integrated tilt actuator controller within propulsion inverter 737 that is configured to control tilt actuated inverter 748. In some embodiments, tilt actuated inverter 748 may include the tilt actuator controller. In some embodiments, an integrated housing arrangement may allow a common circuit board to be shared between propulsion inverter 737 and tilt actuated inverter 748. This close location or integration of the control and power architecture for the propulsion system and tilt actuation assembly 740 may help minimize the length, mass, and complexity of the electrical connections while reducing the overall volume and mass of the packaging structure.

[0083] In some embodiments, tilt actuator wiring 747 may run either externally or internally through or along tilt actuation housing 741. Because actuator 742 may be co-packaged with its power and control components rather than leaving them fixed to the first frame, boom, or other stationary structure of VTOL aircraft 700, tilt actuation inverter 748 and actuator 742 may remain in a fixed relationship throughout the entire tilt range between the climb and cruise configurations. Thus, tilt actuation assembly 740 may operate without requiring complex flexible cables or wiring arrangements. Additionally, such component proximity may reduce failure modes associated with excessive cabling, as well as save production costs, weight, volume, and electromagnetic radiation due to cable leakage.

[0084] Further, as shown in FIG. 7B , in some embodiments, the actuator 742 can be located inside the tilt actuation housing 741, such as between the worm gear 755 and the inverter 737. For example, in some embodiments, the tilt actuator 742 can be located between the motor 735 and a gear of the tilt actuator gearbox, such as the worm gear 755 or worm wheel 756, as shown in FIG. 7B . For example, in some embodiments, the tilt actuator inverter 748 can be located between the motor 735 and a gear of the tilt actuator gearbox, as shown in FIG. 7B . In such a case, the tilt actuator wiring 747 can be further shortened, the overall volume of the tilt actuation assembly 740 can be reduced, and packaging mass can be further eliminated. For example, because the actuator cap 744 is not necessary to protect the actuator 742 from the external environment outside the tilt actuation housing 741, the actuator cap 744 can be modified, or in some cases, eliminated. Thus, embodiments of the present disclosure may provide compact packaging with reduced mass, simpler power and control connections, fewer relative moving parts, and less cabling.

[0085] FIG. 7C illustrates a system for synchronizing a propulsion system 715 and a tilt actuation assembly 740 consistent with embodiments of the present disclosure. The propulsion system 715 may include, for example, a propeller 714, a motor 735, and an inverter 737. The propulsion system 715 may include additional elements, such as, for example, a gearbox (not shown). The tilt actuation assembly 740 may include, for example, an actuator 742 and a tilt actuation inverter 748. The tilt actuation assembly 740 may include additional elements, such as, for example, a tilt actuator gearbox with gears and associated mechanical components (see, for example, FIG. 4A). To support compliant operation with multiple switching modules, such as, for example, the propulsion inverter 737, the tilt actuation inverter 748, or additional systems, a synchronization pulse 798 may be generated in some embodiments. For example, one or more microprocessors 784 of the propulsion inverter 737 may receive an analog sample signal 797 from the coil of the motor 735 via an HV bridge 785. The microprocessor 784 of the propulsion inverter 737 may generate a synchronization pulse 798 to notify the tilt operated inverter 748 that the propulsion inverter 737 is currently in an electrically quiet (i.e., not switching) period, as shown by waveform 735a. This information may be used to coordinate and trigger analog signal sampling in the tilt operated inverter 748 by one or more additional microprocessors 796 and the pulse-width modulation and sample control 789, as shown by waveform 742a. ​​Thus, the propulsion inverter 737 may share a sampling rate with the tilt operated inverter 748. For example, in some embodiments, the microprocessor 796 and the pulse-width modulation and sample control 789 may synchronize their sampling rate to the sampling rate of the microprocessor 784 of the propulsion inverter 737. In some embodiments, the microprocessor 796 or the pulse-width modulation and sample control 789 may synchronize their internal clocks to the internal clock of the microprocessor 784 of the propulsion inverter 737.Synchronizing the sampling rates between the propulsion inverter 737 and the tilt inverter 748 may minimize or eliminate corruption of analog measurements due to, for example, switching-related noise.

[0086] Embodiments of the present disclosure may be further described by the following clauses. 1. A tilt actuator for tilting a propulsion system of an aircraft, the tilt actuator comprising: a tilt actuator having a rotor; a planetary gear set including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the rotor being coupled to the sun gear; a worm gear coaxially coupled to the output of the planetary gear set; a worm wheel meshed with the worm gear; a gear shaft coaxially coupled to the worm wheel; a pinion coaxially coupled to the gear shaft; a sector gear meshed with the pinion; an output shaft coupled to the sector gear and configured to be fixed to a frame of the aircraft. 2. A tilt actuation device as described in clause 1, wherein the planet carrier comprises an output of a planetary gear set coupled to a worm gear. 3. A tilt actuator as described in clause 1 or 2, wherein the worm gear comprises a spherical gear. 4. A tilt actuator as described in any one of clauses 1 to 3, wherein the worm gear is configured to support the tilt actuator at a fixed tilt angle. 5. A tilt actuator as described in any one of clauses 1 to 4, wherein the pinion includes a helical gear. 6. A tilt actuator as described in any one of clauses 1 to 5, wherein the sector gear includes a helical gear. 7. A tilt actuator as described in any one of clauses 1 to 6, wherein the sector gear includes a spur gear. 8. A tilt actuation device as described in any one of clauses 1 to 7, further comprising a cam coupled to the gear shaft and configured to actuate the pitch control rod in accordance with rotation of the gear shaft. 9. A tilt actuator as described in any one of clauses 1 to 8, wherein the pinion drives the sector gear to rotate the propulsion system about the pivot position. 10. A tilt actuator as described in any one of clauses 1 to 9, wherein the maximum tilt angle of the tilt actuator is configured to maintain clearance between the aircraft and the propulsion system propeller. 11. A tilt actuator as described in any one of clauses 1 to 10, wherein the tilt actuator is located between the worm gear and the propulsion system. 12. A tilt actuator as described in any one of clauses 1 to 11, further comprising a linear damper configured to damp tilt movement of the propulsion system. 13. A tilt actuator as described in any one of clauses 1 to 12, further comprising a tilt angle sensor configured to detect a tilt angle of the tilt actuator. 14. The tilt actuator of clause 13, wherein the tilt angle sensor includes a proximity sensor. 15. An idler gear coupled to the output of the planetary gear set; a secondary load path gear coupled to the idler gear; a second worm gear coaxially coupled to the output of the secondary load path gear; a second worm wheel meshed with the second worm gear; a second gear shaft coaxially coupled to the second worm wheel; a second pinion coaxially coupled to the second gear shaft; a second sector gear meshed with the second pinion; A tilt actuator as described in any one of clauses 1 to 14, further comprising: a second output shaft coupled to the second sector gear and configured to be fixed to a frame of the aircraft. 16. A second tilt actuator with a second rotor; a second planetary gear set including a second sun gear, a second plurality of planet gears, a second planet carrier, and a second ring gear, the second rotor being coupled to the second sun gear; 16. The tilt actuator of clause 15, wherein the secondary load path gear comprises an output of a second planetary gear set. 17. Further comprising a controller configured to apply a first torque from the first tilt actuator to the idler gear and a second torque from the second tilt actuator to the idler gear; Clause 17. The tilt actuator of clause 16, wherein the first torque and the second torque are substantially equal and opposite. 18. The tilt actuator of clause 16, wherein either the first tilt actuator or the second tilt actuator is configured to drive the tilt actuator without the other of the first tilt actuator or the second tilt actuator. 19. The tilt actuator of clause 15, wherein the gear shaft includes a second gear shaft. 20. An aircraft tilt device, a first frame; a second frame movably coupled to the first frame; a propulsion system mounted on the second frame; a tilt actuator coupled to the second frame, the tilt actuator connecting the rotor and a planetary gear set including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the rotor being coupled to the sun gear; a worm gear coaxially coupled to the output of the planetary gear set; a worm wheel meshed with the worm gear; a gear shaft coaxially coupled to the worm wheel; a pinion coaxially coupled to the gear shaft; a sector gear meshed with the pinion; a tilting device including an output shaft coupled to the sector gear and fixed to the first frame; 21. A motor for a propulsion system; 21. The tilting device of clause 20, further comprising an inverter configured to drive the motor. 22. The tilting device of clause 20 or 21, further comprising a tilt actuator controller configured to control the tilt actuator. 23. A tilting device as described in clause 22, wherein the inverter comprises a tilt actuator controller. 24. The tilting device of clause 22, wherein the inverter comprises a sensor configured to provide feedback information to the tilt actuator controller. 25. The tilting device of clause 24, wherein the sensor comprises a tilt angle sensor, the tilt angle sensor including a proximity sensor configured to measure a relative distance to the cam surface. 26. A tilt device as described in any one of clauses 21 to 25, wherein the inverter is configured to supply power to the tilt actuator. 27. A tilt device as described in any one of clauses 21 to 26, wherein the inverter is configured to supply a common voltage to the motor and the tilt actuator. 28. A tilting device as described in any one of clauses 21 to 27, wherein the inverter comprises a common bus bar electrically coupled to the motor and the tilt actuator. 29. A tilting device as described in any one of clauses 21 to 28, wherein the planetary gear set has a gear reduction ratio of between 2:1 and 5:1. 30. A tilting device as described in any one of clauses 21 to 29, wherein the worm gear and worm wheel have a gear reduction ratio of 20:1 to 40:1. 31. A tilting device as described in any one of clauses 21 to 30, wherein the second frame comprises a housing for a planetary gear set, a worm gear, a worm wheel, a gear shaft, a pinion, a sector gear, or an output shaft. 32. A tilting device as described in any one of clauses 21 to 31, further comprising a housing configured to house an inverter and one of a planetary gear set, a worm gear, a worm wheel, a gear shaft, a pinion, a sector gear, or an output shaft. 33. An aircraft tilt device, a first frame; a second frame movably coupled to the first frame; a propulsion system mounted on the second frame; a first tilt actuator coupled to the second frame and including a first rotor; a first planetary gear set including a first sun gear, a first plurality of planet gears, a first planet carrier, and a first ring gear, wherein the first rotor is coupled to the first sun gear; a first worm gear coaxially coupled to the output of the first planetary gear set; a first worm wheel meshed with the first worm gear; a first gear shaft coaxially coupled to the first worm wheel; a first pinion coaxially coupled to the first gear shaft; a first sector gear meshed with the first pinion; a first output shaft coupled to the first sector gear and fixed to the first frame; a second tilt actuator having a second rotor; a second planetary gear set including a second sun gear, a second plurality of planet gears, a second planet carrier, and a second ring gear, the second rotor being coupled to the second sun gear; a second worm gear coaxially coupled to the output of the second planetary gear set; a second worm wheel meshed with the second worm gear; a second gear shaft coaxially coupled to the second worm wheel; a second pinion coaxially coupled to the second gear shaft; a second sector gear meshed with the second pinion; a second output shaft coupled to the second sector gear and fixed to the first frame; and a tilting device. 34. An aircraft tilt device, a first frame; a second frame movably coupled to the first frame; a propulsion system mounted on the second frame; a first tilt actuator; a tilt actuator gearbox coupled to the second frame; The tilt actuator gearbox a first gear stage coupled to the first tilt actuator; a second gear stage coupled to the first gear stage; a tilting device comprising a second gear stage and a third gear stage coupled to the first frame; 35. A tilting device as described in clause 34, wherein the first gear stage has a gear reduction ratio of 2:1 to 5:1. 36. A tilting device as described in clause 35, wherein the first gear stage has a gear reduction ratio of 3:1 to 4:1. 37. A tilting device as described in any one of clauses 34 to 36, wherein the second gear stage has a gear reduction ratio of between 20:1 and 40:1. 38. A tilting device as described in clause 37, wherein the second gear stage has a gear reduction ratio of 28:1 to 35:1. 39. A tilting device as described in any one of clauses 34 to 38, wherein the third gear stage has a gear reduction ratio of between 2:1 and 5:1. 40. A tilting device as described in clause 39, wherein the third gear stage has a gear reduction ratio of 3:1 to 4:1. 41. A tilting device as described in any one of clauses 34 to 40, wherein the tilt actuator gearbox has a gear reduction ratio of between 250:1 and 500:1. 42. The first gear stage is A tilting device as described in any one of clauses 34 to 41, comprising a first planetary gear set comprising a first sun gear, a first plurality of planetary gears, a first planet carrier, and a first ring gear, wherein a first rotor of a first tilt actuator is coupled to the first sun gear. 43. The second gear stage is a first worm gear coaxially coupled to the output of the first planetary gear set; a first worm wheel meshed with the first worm gear; 44. The tilting device according to any one of clauses 34 to 43, comprising: a first gear shaft coaxially coupled to the first worm wheel. 44. The third gear stage a first pinion coaxially coupled to the first gear shaft; a first sector gear meshed with the first pinion; 44. The tilting device according to any one of clauses 34 to 43, comprising: a first output shaft coupled to the first sector gear and fixed to the first frame. 45. Further comprising a second tilt actuator; The gearbox is a fourth gear stage coupled to the second tilt actuator; a fifth gear stage coupled to the fourth gear stage; and 45. The tilting device of any one of clauses 34 to 44, further comprising a fifth gear stage and a sixth gear stage coupled to the first frame. 46. ​​The first gear stage and the fourth gear stage have substantially equal gear ratios; the second gear stage and the fifth gear stage have substantially equal gear ratios; Clause 46. A tilting device as described in clause 45, wherein the third gear stage and the sixth gear stage have substantially equal gear ratios. 47. An aircraft tilt device, a first frame; a second frame movably coupled to the first frame; a propulsion system coupled to the second frame and configured to move with the second frame, propeller, a motor configured to rotate a propeller; and a propulsion system comprising a propulsion inverter configured to supply current to the motor; a tilt actuation system coupled to the second frame and configured to move with the second frame relative to the first frame, Tilt actuator, a tilt actuator inverter configured to supply current to the tilt actuator; and a tilt actuation system comprising a tilt actuator gearbox coupled to the second frame; A tilting device, wherein the tilt actuator is configured to tilt the second frame relative to the first frame via the tilt actuator gearbox. 48. The tilting device of clause 47, further comprising a DC input and filter module configured to provide power to the propulsion inverter and the tilt actuator inverter. 49. The tilting device of clause 48, wherein the DC input and filter module is configured to supply a common voltage to the propulsion inverter and the tilt actuator inverter. 50. A tilting device as described in any one of clauses 47 to 49, wherein the propulsion inverter and the tilt actuator inverter are coupled to a common busbar. 51. A tilting device as described in any one of clauses 47 to 50, wherein the propulsion inverter and tilt actuation system components are co-packaged in a common housing. 52. A tilt device as described in clause 51, wherein the tilt actuation system components comprise one of a tilt actuator, tilt actuator wiring, a tilt actuator inverter, or a gear in a tilt actuator gearbox. 53. A tilting device as described in any one of clauses 47 to 52, wherein the tilt actuator is located between the motor and the tilt actuator gearbox. 54. A tilting device as described in any one of clauses 47 to 53, wherein the tilt actuator inverter is located between the motor and the tilt actuator gearbox. 55. A tilting device as described in any one of clauses 47 to 54, further comprising a second tilt actuator further configured to tilt the second frame relative to the first frame via a tilt actuator gearbox. 56. A tilting device as described in clause 55, wherein the gearbox comprises a first torque path from the tilt actuator to the first frame and a second torque path from the second tilt actuator to the first frame. 57. A method for tilting a propulsion system of an aircraft, comprising: tilting the first frame relative to the second frame using a tilt actuator; a first frame coupled to a body of the aircraft; a second frame coupled to the propeller, the motor assembly configured to rotate the propeller, and the tilt actuator; The tilt actuator a tilt actuator having a rotor; a planetary gear set including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the rotor being coupled to the sun gear; a worm gear coaxially coupled to the output of the planetary gear set; a worm wheel meshed with the worm gear; a gear shaft coaxially coupled to the worm wheel; a pinion coaxially coupled to the gear shaft; a sector gear meshed with the pinion; an output shaft coupled to the sector gear, the output shaft configured to be fixed to a frame of the aircraft. 58. The method of clause 57, wherein the planet carrier comprises an output of a planetary gear set coupled to a worm gear. 59. The method of clause 57 or 58, wherein the worm gear comprises a spherical gear. 60. A method according to any one of clauses 57 to 59, wherein the worm gear is configured to support the tilt actuator at a fixed tilt angle. 61. The method of any one of clauses 57 to 60, wherein the pinion comprises a helical gear. 62. The method of any one of clauses 57 to 61, wherein the sector gear comprises a helical gear. 63. The method of any one of clauses 57 to 62, wherein the sector gear includes a spur gear. 64. The method of any one of clauses 57-63, further comprising a cam coupled to the gear shaft, the cam configured to actuate the pitch control rod in accordance with rotation of the gear shaft. 65. A method according to any one of clauses 57 to 64, wherein the pinion drives the sector gear so as to rotate the propulsion system about a pivot location. 66. A method according to any one of clauses 57 to 65, wherein the maximum tilt angle of the tilt actuator is configured to maintain clearance between the body of the aircraft and the propeller. 67. A method according to any one of clauses 57 to 66, wherein the tilt actuator is located between the worm gear and the propulsion system. 68. The method of any one of clauses 57 to 67, further comprising a linear damper configured to damp tilting motion of the propulsion system. 69. The method of any one of clauses 57-68, further comprising a tilt angle sensor configured to detect the tilt angle of the tilt actuator. 70. The method of clause 69, wherein the tilt angle sensor includes a proximity sensor. 71. The tilt actuator an idler gear coupled to an output of the planetary gear set; a secondary load path gear coupled to the idler gear; a second worm gear coaxially coupled to the output of the secondary load path gear; a second worm wheel meshed with the second worm gear; a second gear shaft coaxially coupled to the second worm wheel; a second pinion coaxially coupled to the second gear shaft; a second sector gear meshed with the second pinion; 71. The method of any one of clauses 57 to 70, further comprising: a second output shaft coupled to the second sector gear and configured to be fixed to a frame of the aircraft. 72. A second tilt actuator with a second rotor; a second planetary gear set including a second sun gear, a second plurality of planet gears, a second planet carrier, and a second ring gear, the second rotor being coupled to the second sun gear; 72. The method of clause 71, wherein the secondary load path gear comprises an output of a second planetary gearset. 73. Further comprising a controller configured to apply a first torque from a first tilt actuator to the idler gear and a second torque from a second tilt actuator to the idler gear; 73. The method of clause 72, wherein the first torque and the second torque are substantially equal and opposite. 74. The method of clause 72, wherein either the first tilt actuator or the second tilt actuator is configured to drive the tilt actuation device without the other of the first tilt actuator or the second tilt actuator. 75. The method of clause 71, wherein the gear shaft includes a second gear shaft.

[0087] The foregoing description has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise form or embodiments disclosed. Modifications and adaptations of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the invention disclosed herein.

Claims

1. 1. A tilt actuator for tilting a propulsion system of an aircraft, comprising: a tilt actuator having a rotor; a planetary gear set including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the rotor being coupled to the sun gear; a worm gear coaxially coupled to the output of the planetary gear set; a worm wheel meshed with the worm gear; a gear shaft coaxially coupled to the worm wheel; a pinion coaxially coupled to the gear shaft; a sector gear meshed with the pinion; an output shaft coupled to the sector gear and configured to be fixed to a frame of the aircraft.

2. The tilt actuator of claim 1 , wherein the planet carrier comprises the output of the planetary gear set coupled to the worm gear.

3. The tilt actuator of claim 1 or 2, wherein the worm gear comprises a spherical gear.

4. The tilt actuator according to any one of claims 1 to 3, wherein the worm gear is configured to support the tilt actuator at a fixed tilt angle.

5. The tilt actuator according to any one of claims 1 to 4, wherein the pinion includes a helical gear.

6. The tilt actuator according to any one of claims 1 to 5, wherein the sector gear includes a helical gear.

7. The tilt actuator according to any one of claims 1 to 6, wherein the sector gear includes a spur gear.

8. The tilt actuator of any one of claims 1 to 7, further comprising a cam coupled to the gear shaft and configured to actuate a pitch control rod in accordance with rotation of the gear shaft.

9. A tilt actuator according to any preceding claim, wherein the pinion drives the sector gear to rotate the propulsion system about a pivot location on the frame.

10. The tilt actuator of any one of claims 1 to 9, wherein a maximum tilt angle of the tilt actuator is configured to maintain clearance between the aircraft and a propeller of the propulsion system.

11. The tilt actuation device according to any one of claims 1 to 10, wherein the tilt actuator is located between the worm gear and the propulsion system.

12. The tilt actuator of any one of claims 1 to 11, further comprising a linear damper configured to damp tilt movement of the propulsion system.

13. The tilt actuator of any one of claims 1 to 12, further comprising a tilt angle sensor configured to detect a tilt angle of the tilt actuator.

14. The tilt actuator of claim 13 , wherein the tilt angle sensor includes a proximity sensor.

15. an idler gear coupled to the output of the planetary gear set; a secondary load path gear coupled to the idler gear; a second worm gear coaxially coupled to the output of the secondary load path gear; a second worm wheel meshed with the second worm gear; a second gear shaft coaxially coupled to the second worm wheel; a second pinion coaxially coupled to the second gear shaft; a second sector gear meshed with the second pinion; A tilt actuator according to any one of claims 1 to 14, further comprising: a second output shaft coupled to the second sector gear and configured to be fixed to the frame of the aircraft.

16. a second tilt actuator having a second rotor; a second planetary gear set including a second sun gear, a second plurality of planet gears, a second planet carrier, and a second ring gear, the second rotor being coupled to the second sun gear; The tilt actuator of claim 15 , wherein the secondary load path gear comprises an output of the second planetary gearset.

17. a controller configured to apply a first torque to the idler gear from a first tilt actuator and a second torque to the idler gear from the second tilt actuator; 17. The tilt actuator of claim 16, wherein the first torque and the second torque are substantially equal and opposite.

18. 17. The tilt actuator of claim 16, wherein either the first tilt actuator or the second tilt actuator is configured to drive the tilt actuator without the other of the first tilt actuator or the second tilt actuator.

19. The tilt actuator of claim 15 , wherein the gear shaft includes the second gear shaft.

20. A tilt device for an aircraft, comprising: a first frame; a second frame movably coupled to the first frame; a propulsion system coupled to the second frame and configured to move with the second frame, propeller, a motor configured to rotate the propeller; and a propulsion system comprising a propulsion inverter configured to supply current to the motor; a tilt actuation system coupled to the second frame and configured to move with the second frame relative to the first frame, Tilt actuator, a tilt actuator inverter configured to supply current to the tilt actuator; and a tilt actuation system comprising a tilt actuator gearbox coupled to the second frame; The tilt actuator is configured to tilt the second frame relative to the first frame via the tilt actuator gearbox.

21. 21. The tilting device of claim 20, further comprising a DC input and filter module configured to provide power to the propulsion inverter and the tilt actuator inverter.

22. 22. The tilting apparatus of claim 21, wherein the DC input and filter module is configured to supply a common voltage to the propulsion inverter and the tilt actuator inverter.

23. A tilting arrangement according to any one of claims 20 to 22, wherein the propulsion inverter and the tilt actuator inverter are coupled to a common busbar.

24. A tilting arrangement according to any one of claims 20 to 23, wherein the propulsion inverter and tilt actuation system components are co-packaged in a common housing.

25. 25. The tilting apparatus of claim 24, wherein the components of the tilt actuation system comprise one of a tilt actuator, tilt actuator wiring, the tilt actuator inverter, or gears of the tilt actuator gearbox.

26. A tilting device according to any one of claims 20 to 25, wherein the tilt actuator is located between the motor and a gear of the tilt actuator gearbox.

27. A tilting device according to any one of claims 20 to 26, wherein the tilt actuator inverter is located between the motor and a gear of the tilt actuator gearbox.

28. The tilting device of any one of claims 20 to 27, further comprising a second tilt actuator further configured to tilt the second frame relative to the first frame via the tilt actuator gearbox.

29. 29. The tilting apparatus of claim 28, wherein the gearbox comprises a first torque path from the tilt actuator to the first frame and a second torque path from the second tilt actuator to the first frame.

30. A tilting apparatus according to any one of claims 20 to 29, wherein the propulsion inverter and the tilt operation inverter share the same sampling rate.

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