System and method for propeller thrust protection

Abstract

The present disclosure relates generally to flight control of electric aircrafts and other powered aircrafts. In one embodiment, a method is disclosed, comprising: receiving a descent rate command from a pilot input device; determining a proximity of each of the at least two propellers to a vortex ring state; and controlling a descent rate of the aircraft to be less than the commanded descent rate when at least one of the at least two propellers is within a first threshold proximity to the vortex ring condition.

Description

Cross Reference to Related Applications

[0001] The present disclosure claims priority to U.S. Provisional Application No. 63 / 512,784, filed July 10, 2023, entitled “SYSTEMS AND METHOD FOR FLIGHT CONTROL OF EVTOL AIRCRAFT,” (Attorney Docket No. 16499.6006-00000), the contents of which are incorporated herein in their entirety for all purposes. TECHNICAL FIELD

[0002] The present disclosure relates generally to powered aerial vehicles. More particularly, but not by way of limitation, the present disclosure relates to innovations in aerial vehicles driven by electric propulsion systems. Certain aspects of the present disclosure relate generally to systems and methods for flight control of aerial vehicles driven by electric propulsion systems, as well as in other types of aircraft, and for aerial vehicles in flight simulators and video games. Other aspects of the present disclosure relate generally to improvements in flight control systems and methods that provide particular advantages in aerial vehicles and can be used in other types of aircraft. BACKGROUND

[0003] The inventors have recognized herein several problems that can be associated with flight control of aerial vehicles, including tilt-rotor aerial vehicles that use electric or hybrid electric propulsion systems (hereinafter electric propulsion units or “EPUs”). For example, when an aerial vehicle descends while its rotors and / or propellers are operating, the EPU propellers are at risk of entering a vortex ring state (VRS). During descent of the aerial vehicle, air can begin to flow upward through the propellers and increase as the rate of descent increases. If the forward airspeed at the propellers is not sufficient to cancel the wake created by the descent, one or more propellers can enter a vortex ring state in which they ingest their own wake and are unable to generate sufficient thrust to support the aerial vehicle. This problem can be particularly pronounced in aerial vehicles with multiple propellers (e.g., multicopter aerial vehicles), which are a common configuration in many electric aerial vehicles. The airflow dynamics at each propeller in a multicopter aerial vehicle can vary based on maneuvers of the aerial vehicle and / or the tilt angle of the propellers. Thus, in a multicopter aerial vehicle, some propellers can enter a vortex ring state while others are unaffected, resulting in an unstable aerial vehicle.

[0004] In addition to VRS being a more serious problem on multicopter aircraft, detecting and resolving VRS can be particularly challenging. It can be difficult to detect which propeller is closest to entering VRS because the proximity of each propeller to VRS and the risk of VRS dynamically changes with the aircraft’s maneuvers and / or the tilt angle of the propellers. Furthermore, it can be difficult to determine what change in the aircraft’s maneuvers will help avoid VRS. It will also be appreciated that VRS can affect non-electric aircraft, and the techniques discussed herein can be applied to electric, hybrid-electric, or non-electric aircraft as well as other flying vehicles. SUMMARY

[0005] The present disclosure relates generally to flight control of electric aircraft and other powered aerial vehicles. More particularly, but not by way of limitation, the present disclosure relates to innovations for tilt-rotor aircraft using electric propulsion systems. Certain aspects of the present disclosure relate to detecting the proximity of each propeller on an aircraft to a vortex ring state. Other aspects of the present disclosure relate to automatically controlling an aircraft to avoid one or more propellers from entering a vortex ring state. Still other aspects of the present disclosure relate to automatically controlling an aircraft to escape a vortex ring state after detecting that one or more propellers have entered a vortex ring state. The term “propeller” is used to refer to any aircraft component having rotating blades to support flight, and includes rotors, propellers, and the like.

[0006] One aspect of the present disclosure relates to a method comprising: receiving a descent rate command from a pilot input device; determining a proximity of each of at least two propellers to a vortex ring state; and controlling a descent rate of an aircraft to be less than the commanded descent rate when at least one of the at least two propellers is within a first threshold proximity to the vortex ring state.

[0007] Another aspect of the present disclosure relates to a control system comprising at least one processor configured to execute instructions to: receive a descent rate command from a pilot input device; determine a proximity of each of at least two propellers to a vortex ring state; and control a descent rate of an aircraft to be less than the commanded descent rate when at least one of the at least two propellers is within a first threshold proximity to the vortex ring state.

[0008] Another aspect of the present disclosure relates to an aircraft comprising at least one processor configured to execute instructions to: receive a descent rate command from a pilot input device; determine a proximity of each of at least two propellers to a vortex ring state; and control a descent rate of an aircraft to be less than the commanded descent rate when at least one of the at least two propellers is within a first threshold proximity to the vortex ring state.

[0009] Yet another aspect of the present disclosure relates to a computer readable storage medium storing instructions that, when executed by at least one processor, cause the at least one processor to: receive a descent rate command from a pilot input device; determine a proximity of each of at least two propellers to a vortex ring state; and control a descent rate of an aircraft to be less than the commanded descent rate when at least one of the at least two propellers is within a first threshold proximity to the vortex ring state. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 An exemplary vertical takeoff and landing (VTOL) aircraft is shown consistent with the disclosed embodiments.

[0011] Figure 2 An exemplary VTOL aircraft is shown consistent with the disclosed embodiments.

[0012] Figure 3 An exemplary top plan view of a VTOL aircraft is shown consistent with the disclosed embodiments.

[0013] Figure 4 An exemplary propeller rotation of a VTOL aircraft is shown consistent with the disclosed embodiments.

[0014] Figure 5 An exemplary electrical power connection in a VTOL aircraft is shown consistent with the disclosed embodiments.

[0015] Figure 6 An exemplary architecture of an electric propulsion unit is shown consistent with the disclosed embodiments.

[0016] Figure 7 An exemplary top plan view of a VTOL aircraft is shown consistent with the disclosed embodiments.

[0017] Figure 8 An exemplary flight control signaling architecture is shown consistent with the disclosed embodiments.

[0018] Figure 9A 、 Figure 9B 、 Figure 9C 、 Figure 9D and Figure 9E An exemplary top plan view of a VTOL aircraft is shown consistent with the disclosed embodiments.

[0019] Figure 10 A functional block diagram of an exemplary control system of an electric VTOL aircraft is shown consistent with the disclosed embodiments.

[0020] Figure 11 An example of a propeller entering a vortex ring state is shown consistent with embodiments of the present disclosure.

[0021] Figure 12 An exemplary block diagram for incorporating control limits is shown in accordance with embodiments of the present disclosure.

[0022] Figure 13A Figure 13B Figure 13C An exemplary block diagram for determining control limits is shown in accordance with embodiments of the present disclosure.

[0023] Figure 14A Figure 14B Figure 14C Figure 14D Figure 14E Figure 14F Figure 14G An exemplary illustration of a propeller closest to a vortex ring state and corresponding control limits is shown in accordance with embodiments of the present disclosure.

[0024] Figure 15A Figure 15B Figure 15C Figure 15D Figure 15E Figure 15F Figure 15G Figure 15H Figure 151 Figure 15J Figure 15K Figure 15L Analog results for determining a propeller closest to a vortex ring state and corresponding control limits are shown in accordance with embodiments of the present disclosure.

[0025] Figure 16 An exemplary illustration of different actions that can be taken based on proximity to a vortex ring state is shown in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION

[0026] ​​​​​​​​​​​​​​​​​​​The present disclosure presents systems, components, and techniques primarily for aircraft. The aircraft can be a manned aircraft, an unmanned aircraft (e.g., UAV), drone, helicopter, and / or airplane. The aircraft includes a fuselage and one or more components configured to allow the aircraft to fly (e.g., wings, tail, propellers). The aircraft can include any configuration that includes at least one propeller. In some embodiments, the aircraft is driven (e.g., provides thrust) by one or more electric propulsion systems (hereinafter “electric propulsion units” or “EPUs”), which can include at least one engine, at least one rotor, at least one propeller, or any combination thereof. The aircraft can be all-electric, hybrid, or fuel-powered. For example, in some embodiments, the aircraft is a tilt-rotor aircraft configured for frequent (e.g., more than 50 flights per workday), short-duration flights (e.g., less than 100 miles per flight) over, into, and out of densely populated areas. The aircraft can be configured to carry 4 to 6 passengers or commuters who desire a comfortable experience with low noise and low vibration.

[0027] The disclosed embodiments provide new and improved configurations of some of the aircraft components that are not observed in conventional aircraft, and / or identified design criteria for components that are different from those of conventional aircraft. This alternative configuration and design criteria, in combination, address the shortcomings and challenges of conventional components to produce various embodiments of configurations and designs for components of aircraft driven by propulsion systems (e.g., electric aircraft or hybrid electric aircraft) disclosed herein.

[0028] In some embodiments, the aircraft driven by propulsion systems of the present disclosure can be designed to be capable of both vertical takeoff and landing and conventional takeoff and landing, with a distributed propulsion system enabling vertical flight, horizontal and lateral flight, and transitions (e.g., between vertical and horizontal flight). The aircraft can generate thrust by supplying high-voltage electric power to multiple engines of the distributed propulsion system, which can include components that convert the high-voltage electric power to mechanical shaft power to rotate propellers.

[0029] Embodiments can include power engines (e.g., motors) connected to an onboard power source, which can include a device capable of storing energy, such as a battery or a capacitor, and can optionally include one or more systems for harnessing or generating power, such as a fuel-powered generator or a solar panel array. In some embodiments, the aircraft can comprise a hybrid-electric aircraft configured to power the distributed propulsion system using at least one of an electric-based energy source or a fuel-based energy source. In some embodiments, the aircraft can be powered by one or more batteries, internal combustion engines (ICEs), generators, turbine engines, or ducted fans.

[0030] The engines can be mounted directly to the wings, or to one or more booms attached to the wings. The amount of thrust produced by each engine can be controlled by a flight control system (FCS) sending torque commands to each engine over a digital communication interface. Embodiments can include front engines (and associated propellers) capable of changing their direction or tilt.

[0031] The engines can cause the propellers to rotate in either a clockwise or counterclockwise direction. In some embodiments, the difference in propeller rotation direction can be achieved using the direction in which the engines rotate. In other embodiments, the engines can all rotate in the same direction, and a gear arrangement can be used to achieve different propeller rotation directions.

[0032] In some embodiments, the aircraft can have a quantity of engines in various combinations of front engine configurations and tail engine configurations. Front engines can be considered engines that are primarily positioned toward the leading edge of the wing. Tail engines can be considered engines that are primarily positioned toward the trailing edge of the wing. For example, the aircraft can have six front engines and six tail engines, five front engines and five tail engines, four front engines and four tail engines, three front engines and three tail engines, two front engines and two tail engines, or any other combination of front engines and tail engines, including embodiments in which the number of front engines and tail engines is not equal.

[0033] In some embodiments, for vertical takeoff and landing (VTOL) missions, the front engines and tail engines can provide vertical thrust during takeoff and landing. During flight phases in which the aircraft is moving forward, the front engines can provide horizontal thrust, while the propellers of the tail engines can be stowed at fixed positions in order to minimize drag. The tail engines can be actively stowed using position monitoring.

[0034] Transitions from vertical flight to horizontal flight and from horizontal flight to vertical flight can be accomplished via a tilting propeller subsystem. The tilting propeller subsystem can redirect thrust between a primarily vertical direction during a vertical flight phase (e.g., hover phase or "hovering") and a horizontal or near-horizontal direction during a forward flight cruise phase based on tilting of one or more propellers (e.g., determining directionality of one or more propellers). A variable pitch mechanism can change a propeller hub assembly blade collective angle of the forward engine for operation during flight phases such as a hover phase, a transition phase, and a cruise phase. Vertical lift can be thrust in a primarily vertical direction (e.g., during a hover phase). Horizontal thrust can be thrust in a primarily horizontal direction (e.g., during a cruise phase).

[0035] In some embodiments, a "phase of flight" or "flight mode" (e.g., hover, cruise, forward flight, takeoff, landing, transition) can be defined by a combination of flight conditions (e.g., a combination of flight conditions within a particular range), which can include one or more of: airspeed, altitude, pitch angle (e.g., of the aircraft), tilt angle (e.g., of one or more propellers), roll angle, rotational speed (e.g., of a propeller), torque value, pilot command, or any other value indicative of a current or requested (e.g., commanded) state of at least a portion of the aircraft.

[0036] In some embodiments, in a conventional takeoff and landing (CTOL) mission, the forward engine can provide horizontal thrust for wing-borne takeoff, cruise, and landing, and the wings can provide vertical lift. In some embodiments, the aft engine can not be used to generate thrust during a CTOL mission and the aft propeller can be stowed in place. In other embodiments, the aft engine can be used at reduced power to shorten the length of a CTOL takeoff or landing.

[0037] As detailed herein, embodiments of the aircraft can include a number of movable structural flight elements that allow a pilot to safely control the aircraft. Rotation and direction control of the lift propellers and the tilting propellers provide the lift needed for vertical takeoff and hovering. In addition, rotation and direction of the tilting propellers provide the forward thrust needed to move the aircraft through the air. Thus, the propellers are critical to the controllability, safety, and stability of the aircraft. One or more propellers entering a vortex ring state where they cannot provide sufficient thrust can compromise the safety and stability of the aircraft.

[0038] The disclosed embodiments prevent aircraft propellers from entering vortex ring states by detecting the proximity of one or more propellers to a vortex ring state and controlling the aircraft to avoid the vortex ring state. For example, the disclosed embodiments can provide warnings to the pilot and / or limit the aircraft maneuver settings requested by the pilot and / or autopilot commands based on the proximity to a vortex ring state. In addition, the disclosed embodiments can detect that one or more propellers are in a vortex ring state and control the aircraft in a manner that removes the affected propeller from the vortex ring state and / or avoids other propellers from entering the vortex ring state. For example, the disclosed embodiments can provide warnings to the pilot and / or limit the aircraft maneuver settings requested by the pilot and / or autopilot commands based on determining that one or more propellers have entered a vortex ring state.

[0039] Reference will now be made in detail to the example embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which the same numbers represent the same or similar elements between the several figures. The implementation set forth in the following description of example embodiments is not meant to be an all-inclusive implementation of all aspects with respect to the disclosure. Rather, it is a description of example devices and methods consistent with aspects related to the subject matter claimed in the following claims.

[0040] Figure 1 is an illustration of a perspective view of an example VTOL aircraft consistent with the disclosed embodiments. Figure 2 is another illustration of a perspective view of an example VTOL aircraft in an alternative configuration consistent with embodiments of the disclosure. Figure 1 and Figure 2 VTOL aircraft 100, 200 in a cruise configuration and a vertical takeoff, landing, and hover configuration (also referred to herein as a "lift" configuration), respectively, consistent with embodiments of the disclosure are shown. As Figure 1 and Figure 2 Corresponding elements can bear similar reference numbers and refer to similar elements of aircraft 100, 200. Aircraft 100, 200 can include a fuselage 102, 202, a wing 104, 204 mounted to the fuselage 102, 202, and one or more rear stabilizers 106, 206 mounted to a rear of the fuselage 102, 202. A plurality of lift propellers 112, 212 (also referred to as "lifters") can be mounted to the wing 104, 204 and can be configured to provide lift for vertical takeoff, landing, and hovering. A plurality of tilt propellers 114, 214 (also referred to as "tilters") can be mounted to the wing 104, 204 and can be tilted (e.g., configured to tilt or change direction) between a lift configuration in which the plurality of tilt propellers provide a portion of the lift required for vertical takeoff, landing, and hovering, as Figure 2As shown, in the cruise configuration, the plurality of tilt rotors provide forward thrust to the aircraft 100 for horizontal flight, as Figure 1 As used herein, a tilt rotor lift configuration refers to any tilt rotor orientation in which the tilt rotor thrust primarily provides lift to the aircraft, and a tilt rotor cruise configuration refers to any tilt rotor orientation in which the tilt rotor thrust primarily provides forward thrust to the aircraft.

[0041] In some embodiments, the lift rotors 112, 212 can be configured to provide lift only, with all horizontal propulsion provided by the tilt rotors. For example, the lift rotors 112, 212 can be configured with fixed positions and can only generate thrust during the takeoff, landing, and hover phases of flight. Meanwhile, the tilt rotors 114, 214 can be tilted upward into a lift configuration in which the thrust from the rotors 114, 214 is directed downward to provide additional lift.

[0042] For forward flight, the tilt rotors 114, 214 can be tilted from their lift configuration to their cruise configuration. In other words, the orientation of the tilt rotors 114, 214 can be changed from a direction in which the tilt rotor thrust is directed downward (to provide lift during vertical takeoff, landing, and hovering) to a direction in which the tilt rotor thrust is directed rearward (to provide forward thrust to the aircraft 100, 200). The tilt rotor assemblies for a particular electric engine can be tilted about an axis of rotation defined by the mounting points that connect the booms and the electric engines. When the aircraft 100, 200 is in full forward flight, lift can be provided entirely by the wings 104, 204. Meanwhile, in the cruise configuration, the lift rotors 112, 212 can be turned off. The blades 120, 220 of the lift rotors 112, 212 can be held in a low-drag position for aircraft cruising. In some embodiments, the lift rotors 112, 212 can each have two blades 120, 220 that can be, for example, locked in a minimum-drag position when the aircraft is cruising, in which one blade is directly in front of the other blade, as Figure 1 As shown, in the cruise configuration, the plurality of tilt rotors provide forward thrust to the aircraft 100 for horizontal flight, as Figure 1 and Figure 2 As shown, the lift rotors 112, 212 can each include, for example, two blades, while the tilt rotors 114, 214 can each include more blades, for example, the five blades shown. In some embodiments, each of the tilt rotors 114, 214 can have from 2 to 5 blades, and possibly more, depending on the design considerations and requirements of the aircraft.

[0043] In some embodiments, the aircraft can include a single wing 104, 204 on each side of the fuselage 102, 202 (or a single wing extending across the entire aircraft). At least a portion of the lift propellers 112, 212 can be located aft of the wing 104, 204 (e.g., from a bird's eye view, the point of rotation of the propeller is aft of the wing), while at least a portion of the tilt propellers 114, 214 can be located forward of the wing 104, 204 (e.g., from a bird's eye view, the point of rotation of the propeller is forward of the wing). In some embodiments, all of the lift propellers 112, 212 can be located aft of the wing 104, 204, and all of the tilt propellers 114, 214 can be located forward of the wing 104, 204. According to some embodiments, all of the lift propellers 112, 212 and tilt propellers 114, 214 can be mounted to the wing - i.e., none of the lift propellers or tilt propellers can be mounted to the fuselage. In some embodiments, all of the lift propellers 112, 212 can be located aft of the wing 104, 204, and all of the tilt propellers 114, 214 can be located forward of the wing 104, 204. According to some embodiments, all of the lift propellers 112, 212 and tilt propellers 114, 214 can be positioned inboard of the ends of the wing 104, 204.

[0044] In some embodiments, the lift propellers 112, 212 and tilt propellers 114, 214 can be mounted to the wing 104, 204 via booms 122, 222. The booms 122, 222 can be mounted below the wing 104, 204, on top of the wing, and / or can be integrated into the wing profile. In some embodiments, the lift propellers 112, 212 and tilt propellers 114, 214 can be mounted directly to the wing 104, 204. In some embodiments, each boom 122, 222 can be mounted with one lift propeller 112, 212 and one tilt propeller 114, 214. The lift propeller 112, 212 can be mounted at the aft end of the boom 122, 222, and the tilt propeller 114, 214 can be mounted at the forward end of the boom 122, 222. In some embodiments, the lift propeller 112, 212 can be mounted in a fixed position on the boom 122, 222. In some embodiments, the tilt propeller 114, 214 can be mounted to the forward end of the boom 122, 222 via a hinge. The tilt propeller 114, 214 can be mounted to the boom 122, 222 such that the tilt propeller 114, 214 is aligned with the body of the boom 122, 222 when in its cruise configuration, thereby forming a continuous extension of the forward end of the boom 122, 222 that minimizes drag for forward flight.

[0045] In some embodiments, the aircraft 100, 200 can include one wing on each side of the fuselage 102, 202, or a single wing extending across the aircraft, for example. According to some embodiments, at least one wing 104, 204 is a high wing mounted to the upper side of the fuselage 102, 202. According to some embodiments, the wings include control surfaces, such as flaps, ailerons, and / or flaperons (e.g., configured to perform the function of both flaps and ailerons). According to some embodiments, the wings 104, 204 can have been designed with a profile that reduces drag during forward flight. In some embodiments, the wing tip profile can be curved and / or tapered to minimize drag.

[0046] In some embodiments, the rear stabilizers 106, 206 include control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wings can have any suitable design for providing lift, directionality, stability, and / or any other characteristics that benefit the aircraft. In some embodiments, the wings have tapered leading edges.

[0047] In some embodiments, the lift propellers 112, 212 or tilt propellers 114, 214 can be tilted relative to at least one other lift propeller 112, 212 or tilt propeller 114, 214, where tilt refers to the relative orientation of the rotation axis of the lift / tilt propeller about a line parallel to the fore-aft direction, similar to the roll degree of freedom of the aircraft.

[0048] In some embodiments, one or more lift propellers 112, 212 and / or tilt propellers 114, 214 can be tilted relative to the cabin of the aircraft, such that the rotation axis of the propellers in the lift configuration is angled away from an axis perpendicular to the top surface of the aircraft. For example, in some embodiments, the aircraft is a flying wing aircraft, as shown in Figure 9E below, and some or all of the propellers are tilted away from the cabin.

[0049] Figure 3 is a diagram of a top plan view of an exemplary VTOL aircraft consistent with embodiments of the present disclosure. The aircraft 300 shown in the figure can be the aircraft 100, 200, respectively, in Figure 1 and Figure 2An overhead plan view of the aircraft 100, 200 is shown. As discussed herein, the aircraft 300 can include twelve electric propulsion systems distributed across the aircraft 300. In some embodiments, the distribution of electric propulsion systems can include six forward electric propulsion systems 314 and six aft electric propulsion systems 312 mounted on booms at the forward and aft portions of the main wings 304 of the aircraft 300. In some embodiments, the forward electric propulsion systems can be mounted to the wings 304 through booms 322. In some embodiments, the aft electric propulsion systems can be mounted to the wings 304 through booms 324. In some embodiments, the length from the wings 304 to the aft ends of the booms 324 of the lift propellers (part of the electric propulsion systems 312) can include similar boom 324 aft end lengths across the multiple aft ends of the booms. In some embodiments, the boom aft end lengths can vary, for example, across the six aft ends of the booms. Further, Figure 3 An exemplary embodiment of a VTOL aircraft 300 is depicted with forward propellers (part of the electric propulsion systems 314) for horizontal flight in a horizontal orientation and aft propeller blades 320 in a stowed position for forward flight phases.

[0050] Figure 4 is a schematic diagram showing exemplary propeller rotation of a VTOL aircraft consistent with the disclosed embodiments. The aircraft 400 shown in the figure can be the aircraft 300 shown in Figure 1 , Figure 2 and Figure 3A top plan view of the aircraft 100, 200, and 300 shown. The aircraft 400 can include six forward electric propulsion systems, with three of the forward electric propulsion systems having the CW type 424 and the remaining three forward electric propulsion systems having the CCW type 426. In some embodiments, three aft electric propulsion systems can have the CCW type 428, while the remaining three aft electric propulsion systems can have the CW type 430. Some embodiments can include an aircraft 400 with four forward electric propulsion systems and four aft electric propulsion systems each having two CW types and two CCW types. In some embodiments, the aircraft 400 can include a fuselage 402, a wing 404 mounted to the fuselage 402, and one or more aft stabilizers 406 mounted to the rear of the fuselage 402. In some embodiments, each forward electric propulsion system can include a propeller blade 416. In some embodiments, each aft electric propulsion system can include a propeller blade 420. In some embodiments, the electric propulsion systems can be mounted to the wing 404 by a boom 422. In some embodiments, the propellers can counter-rotate relative to adjacent propellers to cancel the torque reversal experienced by the fuselage or wing of the aircraft from the rotation of the propellers. In some embodiments, the difference in rotation direction can be achieved using the direction of engine rotation. In other embodiments, the engines can all rotate in the same direction and a gear arrangement can be used to achieve the different propeller rotation directions.

[0051] Some embodiments can include an aircraft 400 with forward electric propulsion systems and aft electric propulsion systems, where the amount of CW type 424 and CCW type 426 is not equal among the forward electric propulsion systems, among the aft electric propulsion systems, or among the forward electric propulsion systems and the aft electric propulsion systems.

[0052] Figure 5is a schematic diagram illustrating exemplary electrical connections in a VTOL aircraft consistent with the disclosed embodiments. The VTOL aircraft can have multiple electrical systems connected to diagonally opposite electrical propulsion systems. In some embodiments, the electrical systems can include high voltage electrical systems. Some embodiments can include high voltage electrical systems connected to electrical engines via high voltage channels. In some embodiments, the aircraft 500 can include six electrical systems (e.g., battery packs), including electrical systems 526, 528, 530, 532, 534, and 536 stored within the wings 570 of the aircraft 500. The electrical systems can power the electrical propulsion systems and / or other electrical components of the aircraft 500. In some embodiments, the aircraft 500 can include six forward electrical propulsion systems with six electrical engines 502, 504, 506, 508, 510, and 512 and six aft electrical propulsion systems with six electrical engines 514, 516, 518, 520, 522, and 524. In some embodiments, one or more electrical systems (e.g., battery packs) can include a battery management system (“BMS”) (e.g., one BMS per battery pack). Although Figure 5 six electrical systems are shown in FIG. 6, the aircraft 500 can include any number and / or configuration of electrical systems.

[0053] In some embodiments, one or more battery management systems can be in communication with a flight control system (“FCS”) (e.g., FCS 612 shown in FIG. 6) of the aircraft. For example, the FCS can monitor the status of one or more battery packs and / or provide commands to one or more battery management systems that make corresponding adjustments to the high voltage power supply. Figure 6

[0054] Figure 6 is a block diagram illustrating exemplary architecture and design of an electrical propulsion unit 600 consistent with the disclosed embodiments. The exemplary electrical propulsion unit 600 includes an electrical propulsion system 602, which can be configured to control an aircraft propeller. The electrical propulsion system 602 can include an electrical engine subsystem 604, which can supply torque via an axial propeller subsystem 606 to produce thrust of the electrical propulsion system 602. Some embodiments can include the electrical engine subsystem 604 receiving low voltage direct current (LV DC) power from a low voltage system (LVS) 608. In some embodiments, the electrical engine subsystem 604 can be configured to receive high voltage (HV) power from a high voltage power system (HVPS) 610, which includes at least one battery or other device capable of storing energy. HV power can refer to power that is lower in voltage than the voltage provided by the low voltage system (LVS) 608.

[0055] ​Some embodiments can include an electric propulsion system 602 that includes an electric engine subsystem 604 that receives signals from and sends signals to a flight control system 612. In some embodiments, a flight control system (FCS) 612 can include a flight control computer (FCC) that can use controller area network ("CAN") data bus signals to send commands to and receive status and data from the electric engine subsystem 604. Consistent with the disclosed embodiments, the FCC can include an apparatus configured to perform one or more operations (e.g., computational operations) on the aircraft, such as at least one processor and a memory component that can store instructions executable by the at least one processor to perform the operations. It should be appreciated that while CAN data bus signals are used between the flight control computer and the electric engine, some embodiments can include any form of communication that has the ability to send and receive data from the flight control computer to the electric engine. Some embodiments can include an electric engine subsystem 604 that can receive and communicate operational parameters from and to the FCC in the FCS 612, including speed, voltage, current, torque, temperature, vibration, propeller position, and / or any other value of an operational parameter.

[0056] In some embodiments, the flight control system 612 can also include a tilting propeller system ("TPS") 614 that can send and receive analog discrete data to and from the electric engine subsystem 604 of the tilting propeller. The tilting propeller system (TPS) 614 can include a device that can communicate operational parameters to the electric engine subsystem 604 and articulate the direction of the propeller subsystem 606 to redirect the thrust of the tilting propeller during various phases of flight using mechanical members (e.g., a gearbox assembly, a linear actuator, and any other configured component) to alter the direction of the propeller subsystem 606. In some embodiments, the electric engine subsystem can communicate the direction of the propeller system (e.g., the angle between lift and forward thrust) to the TPS 614 and / or the FCS 612 (e.g., during flight).

[0057] In some embodiments, the flight control system can include a system that can control control surfaces in an example VTOL aircraft and their associated actuators. Figure 7 is an illustration of a top plan view of an example VTOL aircraft consistent with embodiments of the present disclosure. In addition to the aircraft components described above with reference to Figure 3 The aircraft 700 shown in the figure can be an example of the aircraft described in U.S. Patent Application No. 62 / 649, 1 10, filed March 30, 2018, and U.S. Patent Application No. 62 / 649, 1 1 1, filed March 30, 2018, respectively. Figure 1 and Figure 2The diagram shows top-view plans of aircraft 100 and 200. In aircraft 700, in addition to the propeller blades discussed previously, the control surface may also include flaperon 712 and rudder 714. The flaperon 712 may combine the functions of one or more flaps, one or more ailerons, and / or one or more spoilers. The rudder 714 may combine the functions of one or more rudders and / or one or more elevators. Alternatively or additionally, the control surface may include separate rudders and elevators. In aircraft 700, in addition to the electric propulsion system discussed previously, the actuators may also include control surface actuators (CSAs) associated with the flaperon 712 and rudder 714, as referenced below. Figure 8 Further discussion.

[0058] Figure 8 The diagram illustrates a flight control signaling architecture for controlling control surfaces and associated actuators, according to various embodiments. Although... Figure 7 The diagram shows twelve EPU inverters and associated propeller blades, six tilt propeller actuators (TPAC), six battery management systems (BMS), four flaps and associated control surface actuators (CSA), and six directional elevators and associated CSA; however, aircraft according to various embodiments may have any suitable number of these various elements. Figure 8 As shown, the control surfaces and actuators can be controlled by a combination of four flight control computers (FCCs)—left FCC, channel A (L FCC-A), left FCC, channel B (L FCC-B), right FCC, channel A (R FCC-A), and right FCC, channel B (R FCC-B)—but any other suitable number of FCCs can be used. Each FCC can control all control surfaces and actuators independently, or in any combination of each other. In some embodiments, each FCC can contain one or more hardware computing processors. In some embodiments, each FCC can utilize single-threaded or multi-threaded computing processes to perform the calculations required to control the control surfaces and actuators. In some embodiments, all calculations required to control the control surfaces and actuators can be performed by a single flight control computer on a single computing thread.

[0059] The FCCs can provide control signals, e.g., voltage or current control signals, to the control surface actuators, and the control information can be encoded in the control signals in binary, digital, or analog form. In some embodiments, the bus systems can each be a CAN bus system, e.g., left CAN bus 1, left CAN bus 2, right CAN bus 1, right CAN bus 2, center CAN bus 1, center CAN bus 2 (see Figure 8 ). In some embodiments, multiple FCCs can be configured to provide control signals via each CAN bus system, and each FCC can be configured to provide control signals via multiple CAN bus systems. In the example architecture shown, for example, LFCC-A can provide control signals via left CAN bus 1 and right CAN bus 1, LFCC-B can provide control signals via left CAN bus 1 and center CAN bus 1, RFCC-A can provide control signals via center CAN bus 2 and right CAN bus 2, and RFCC-B can provide control signals via left CAN bus 2 and right CAN bus 2. Figure 8

[0060] Figure 9A To FIG. 9F is an illustration of a top plan view of an example VTOL aircraft, consistent with embodiments of the present disclosure. There can be many design considerations (cost, weight, size, performance capabilities, etc.) that can impact the number and / or combination of tilt propellers and lift propellers in a VTOL aircraft. As described further below, the number and orientation of propellers (and other effectors or actuators) can impact how a flight control system controls the aircraft to avoid instability and uncontrollability caused by propellers entering a vortex ring state. For example, in some embodiments, in aircraft configurations with more propellers, the flight control system can allow propellers to approach (or enter) the vortex ring state boundary. In contrast, in aircraft configurations with fewer propellers, the flight control system can be more conservative in controlling the aircraft to avoid propellers entering the vortex ring state.

[0061] Figure 9A An arrangement of electric propulsion units is shown, consistent with embodiments of the present disclosure. Referring to Figure 9A ​The aircraft shown in the figure may be a top plan view of an exemplary aircraft (e.g., a VTOL aircraft). The aircraft may contain twelve electric propulsion systems distributed across the aircraft. In some embodiments, the distribution of electric propulsion systems may include six forward electric propulsion systems (901, 902, 903, 904, 905, and 906) and six tail electric propulsion systems (907, 908, 909, 910, 911, and 912). In some embodiments, the six forward electric propulsion systems may be operatively connected to a tilting propeller, and the six tail electric propulsion systems may be operatively connected to a lift propeller. In other embodiments, the six forward electric propulsion systems and multiple tail electric propulsion systems may be operatively connected to a tilting propeller, and the remaining tail electric propulsion systems may be operatively connected to a lift propeller. In other embodiments, all forward and tail electric propulsion systems may be operatively coupled to a tilting propeller.

[0062] Figure 9B An alternative arrangement of the electric propulsion unit consistent with embodiments of this disclosure is shown. Reference Figure 9B The aircraft shown in the figure may be a top plan view of an exemplary aircraft (e.g., a VTOL aircraft). The aircraft may include eight electric propulsion systems distributed across the aircraft. In some embodiments, the distribution of electric propulsion systems may include four forward electric propulsion systems (913, 914, 915, and 916) and four tail electric propulsion systems (917, 918, 919, and 920). In some embodiments, the four forward electric propulsion systems may be operatively connected to a tilting propeller, and the four tail electric propulsion systems may be operatively connected to a lift propeller. In other embodiments, the four forward electric propulsion systems and multiple tail electric propulsion systems may be operatively connected to a tilting propeller, and the remaining tail electric propulsion systems may be operatively connected to a lift propeller. In other embodiments, all forward and tail electric propulsion systems may be operatively coupled to a tilting propeller.

[0063] Figure 9C An alternative arrangement of the electric propulsion unit consistent with embodiments of this disclosure is shown. Reference Figure 9C, the aircraft shown in the figure can be a top plan view of an exemplary aircraft (e.g., a VTOL aircraft). The aircraft can include six electric propulsion systems distributed across the aircraft. In some embodiments, the distribution of electric propulsion systems can include a first set of four electric propulsion systems 921, 922, 923, and 924 that are coplanar in a first plane and a second set of two electric propulsion systems 925 and 926 that are coplanar in a second plane. In some embodiments, the first set of electric propulsion systems 921-924 can be operably connected to tilt propellers and the second set of electric propulsion systems 925 and 926 can be operably connected to lift propellers. In other embodiments, the first set of electric propulsion systems 921-924 and the second set of tail electric propulsion systems 925 and 926 can all be operably connected to tilt propellers.

[0064] Figure 9D An alternative arrangement of electric propulsion units consistent with embodiments of the present disclosure is shown. Referring to FIG. 9, Figure 9D , the aircraft shown in the figure can be a top plan view of an exemplary aircraft (e.g., a VTOL aircraft). The aircraft can include four electric propulsion systems distributed across the aircraft. In some embodiments, the distribution of electric propulsion systems can include four coplanar electric propulsion systems 927, 928, 929, and 930. In some embodiments, all of the electric propulsion systems can be operably connected to tilt propellers.

[0065] Figure 9E An alternative arrangement of electric propulsion units consistent with embodiments of the present disclosure is shown. Referring to FIG. 9, Figure 9E , the aircraft shown in the figure can be a top plan view of an exemplary aircraft (e.g., a VTOL aircraft). The aircraft can include six electric propulsion systems distributed across the aircraft. For example, in some embodiments, the aircraft can include four forward electric propulsion systems 931, 932, 933, and 934 operably connected to tilt propellers and two aft ducted fans 935 and 936 operably connected to lift propellers. In some embodiments, the aircraft can include ten electric propulsion systems distributed across the aircraft. For example, in some embodiments, the aircraft can include six forward electric propulsion systems operably connected to tilt propellers and four aft electric propulsion systems operably connected to lift propellers. In some embodiments, some or all of the aft electric propulsion systems can be operably connected to tilt propellers.

[0066] As Figure 9EAs shown, in some embodiments, the aircraft can have a flying wing configuration, such as a tailless fixed-wing aircraft without a fixed fuselage. In some embodiments, the aircraft can have a flying wing configuration, with the fuselage integrated into the wing. In some embodiments, the tilting propellers can rotate in a plane above the aircraft fuselage when the tilting propellers are operating in the lift configuration.

[0067] FIG. 9F illustrates an alternative arrangement of electric propulsion units consistent with embodiments of the present disclosure. Referring to FIG. 9F, the aircraft can be a top plan view of an example aircraft. In some embodiments, the aircraft can include a set of ducted fans 936, 937, 938, and 939 operably connected to an electric propulsion system. In some embodiments, the aircraft can include a set of ducted fans on each wing of the aircraft, and the set of ducted fans can be connected to tilt together (e.g., between a lift configuration and a forward thrust configuration). In some embodiments, the aircraft includes a left front wing and a right front wing, as well as a left rear wing and a right rear wing. In some embodiments, each wing of the aircraft includes a set of connected ducted fans. In some embodiments, each set of connected ducted fans is tiltable (e.g., between lift and forward thrust), while in other embodiments, only the set of fans on the front wings are tiltable.

[0068] As disclosed herein, the forward electric propulsion systems and the aft electric propulsion systems can be of a clockwise (CW) type or a counterclockwise (CCW) type. Some embodiments can include a variety of forward electric propulsion systems with a mix of both CW and CCW types. In some embodiments, the aft electric propulsion systems can have a mix of CW and CCW type systems among the aft electric propulsion systems. In some embodiments, each electric propulsion system can be fixed as either a clockwise (CW) type or a counterclockwise (CCW) type, while in other embodiments, one or more electric propulsion systems can vary between clockwise (CW) rotation and counterclockwise (CCW) rotation.

[0069] Figure 10 A functional block diagram of an example control system 1000 of an aircraft consistent with the disclosed embodiments is shown. The system 1000 can be implemented by at least one processor (e.g., at least one microprocessor-based controller) configured to execute software code stored in a storage medium (e.g., a computer-readable medium, a non-transitory computer-readable medium) to implement the functionality described herein. The system 1000 can also be implemented in hardware or a combination of hardware and software. The system 1000 can be implemented as part of a flight control system of an aircraft (e.g., as part of the FCS 612 in FIG. 6), and can be configured to repeatedly perform a single step or sequence until a desired or commanded result is achieved. It should be understood that, for ease of description, Figure 6 Figure 10 ​Many of the routine functions of the control system are not shown. The system 1000 further includes one or more storage media which store models, functions, tables, and / or any information used to perform the disclosed processes. As further described below, any or each block indicative of a command model (e.g., 1004, 1006, 1008, and 1010), feedback (1012, 1016, 1018, and 1022), feedforward (1014, 1020), outer loop allocation (1024, 1026), inner loop control law 1028, and control allocation 1029 can represent or include modules, scripts, functions, applications, and / or programs executed by a processor and / or microprocessor of the system 1000. It should be appreciated, Figure 10 The complexity and interconnectivity of the functional block diagram of FIG. 10 makes it impossible for a human user to effectively implement the method, or at least impractical, especially when considering implementing these functions while the aircraft is in flight, including takeoff or landing.

[0070] In some embodiments, the control system 1000 can be configured based on one or more flight control laws. The flight control laws can include a set of algorithms, models, and / or rules configured to manage the behavior of the aircraft (e.g., control or affect one or more effectors of the aircraft) in response to one or more pilot inputs and external factors. In some embodiments, the flight control laws can be configured to achieve at least one of a desired flight characteristic, stability, or performance. For example, the flight control laws can be configured to ensure stability and controllability of the aircraft by controlling how the aircraft responds to at least one of one or more pilot inputs, aircraft dynamics (e.g., disturbances, such as turbulence, gusts, etc.), or changes in flight conditions (e.g., altitude, airspeed, angle of attack).

[0071] The system 1000 can detect one or more inputs, e.g., from pilot input devices configured to receive at least one pilot input and generate or affect a signal. Pilot inputs can be generated by and / or received from input devices or mechanisms of the aircraft, such as buttons, switches, joysticks, sliders, levers, or any other device configured to generate or affect a signal based on a physical action from a pilot. For example, the pilot input devices can include one or more of a right lever (e.g., move right lever 1002a left / right and / or move right lever 1002e forward / backward), a left lever (e.g., move left lever 1002c left / right and / or move left lever 1002g forward / backward), and / or a left lever switch 1002f. In some embodiments, the pilot input devices can include an interface with an autopilot system (e.g., a display screen, switches, buttons, control sticks, and / or other interfaces). Optionally, the system 1000 can further detect inputs from the autopilot system, such as an autopilot roll command 1002b, an autopilot climb command 1002d, and / or other commands for controlling the aircraft.

[0072] In some embodiments, the one or more inputs can include at least one of: a position and / or rate of a right lever and / or a left lever, a signal received from a switch on a lever (e.g., in response to a type change command, trim input, reference input, backup control input, etc.), a measurement of an aircraft state and environmental conditions based on data received from one or more sensors of the aircraft (e.g., a measured load coefficient, airspeed, roll angle, pitch angle, actuator state, battery state, aerodynamic parameter, temperature, gust, etc.), an obstacle (e.g., presence or absence of other aircraft and / or debris), and an aircraft mode (e.g., ground taxi, takeoff, airborne). For example, right lever L / R 1002a can include a lateral position and / or rate of a right lever (e.g., a lever positioned to the right of another lever and / or a lever positioned to the right of a pilot area), autopilot roll command 1002b can include a roll signal received in autopilot mode, left lever L / R 1002c can include a lateral position and / or rate of a left lever (e.g., a lever positioned to the left of another lever and / or a lever positioned to the left of a pilot area), autopilot climb command 1002d can include a climb signal received in autopilot mode, right lever F / A 1002e can include a longitudinal position and / or rate of a right lever, left lever switch 1002f can include a signal from a switch for enabling or disabling an automatic transition function 1003, and left lever F / A 1002g can include a longitudinal position and / or rate of a left lever.

[0073] Each input can contain data as listed above (e.g., signals from switches, measurements of aircraft states, aircraft modes, etc.). Actuator states can contain actuator hardware limits, such as travel limits, speed limits, response time limits, etc., and can contain actuator health indicators, which can indicate a degradation in actuator performance that can limit the ability of a given actuator to meet an actuator command. Actuator states can be used to determine bounds (e.g., min / max) for individual actuator commands. Battery states can correspond to the remaining energy of the battery packs of the aircraft, which can be monitored when control allocation 1029 considers balancing battery pack energy states. Aerodynamic parameters can be parameters derived from aerodynamic and acoustic modeling and can be based on actuator Jacobian matrices and actuator states. Each input received from a control stick can indicate a corresponding adjustment to the pilot’s heading or power output.

[0074] Command models 1004, 1006, 1008, and 1010 can be configured to determine a shape of an ideal aircraft response (e.g., aggressiveness, turn rate, damping, overshoot, etc.). For example, each of command models 1004, 1006, 1008, and 1010 can be configured to receive and interpret at least one of inputs 1002a, 1002b, 1002c, 1002d, 1002e, 1002f, and 1002g, and in response, calculate a corresponding change in direction, heading, and propulsion, or a combination thereof, of the aircraft using an integrator (not shown). In some embodiments, right control stick L / R 1002a and autopilot roll command 1002b can be fed into turn rate command model 1004, left control stick L / R 1002c can be fed into lateral velocity command model 1006, autopilot climb command 1002d and right control stick F / A 1002e can be fed into climb command model 1008, and left control stick F / A 1002g can be fed into forward velocity command model 1010. In some embodiments, an output from automatic transition function 1003 can be fed into at least one of climb command model 1008 or forward velocity command model 1010. For example, based on receiving an enable signal from left control stick switch 1002f, automatic transition function 1003 can automatically determine at least one of a climb signal or a forward velocity signal for transmission to at least one of climb command model 1008 or forward velocity command model 1010.

[0075] The turn rate command model 1004 can be configured to output a desired position and / or turn rate command, and can also be configured to calculate a desired heading of the aircraft assuming the manipulator is brought back to a centered position (i.e., in a detent). The lateral velocity command model 1006 can be configured to output a desired position and / or lateral velocity command. The climb command model 1008 can be configured to output at least one of a desired altitude, vertical velocity, or vertical acceleration command. The forward velocity command model 1010 can be configured to output at least one of a desired position, longitudinal velocity, or longitudinal acceleration command. In some embodiments, one or more of the command models can be configured to output an acceleration generated in response to a change in a velocity command. For example, the climb command model 1008 can be configured to output a vertical acceleration generated in response to a change in a vertical velocity command.

[0076] The feed forwards 1014 and 1020 can each receive as input one or more desired changes (e.g., desired position, velocity, and / or acceleration) from the corresponding command model 1004, 1006, 1008, or 1010 and data received from one or more aircraft sensors (e.g., airspeed, aircraft orientation, aircraft load factor, measured acceleration, aircraft mass and inertia, air density, altitude, aircraft mode, etc.) and can be configured to output for each desired change a corresponding force to achieve the desired change. In some embodiments, the feed forwards 1014 and 1020 can be configured to use a simplified model of the aircraft dynamics to determine the corresponding force. For example, based on a known mass of the aircraft (e.g., a stored value) or a determined mass, the feed forwards 1014 and 1020 can be configured to determine a force to cause the aircraft to follow a desired acceleration command. In some embodiments, the feed forwards 1014 and 1020 can be configured to use a model to predict an amount of drag generated on the aircraft as a function of velocity in order to determine a force needed to follow a desired velocity command signal.

[0077] Feedback 1012, 1016, 1018, and 1022 can each receive as input one or more desired changes (e.g., desired position, velocity, and / or acceleration) from command models 1004, 1006, 1008, and 1010 and data indicative of aircraft dynamics 1030 received from aircraft sensing 1031. For example, sensed aircraft dynamics 1030 can include the physics and / or natural dynamics of the aircraft, and aircraft sensing 1031 sensor measurements can capture how the aircraft moves in response to pilot input, propulsion system output, or environmental conditions. In some embodiments, aircraft dynamics 1030 can represent control of different flight elements (e.g., electric propulsion systems and / or control surfaces) and corresponding effects on the flight elements and aircraft dynamics. Additionally or alternatively, data received from aircraft sensing 1031 can include error signals generated by one or more processors based on extraneous disturbances (e.g., velocity disturbances caused by wind gusts). In some embodiments, feedback 1012, 1016, 1018, and 1022 can be configured to generate feedback forces (e.g., at actuators) based on the received error signals. For example, feedback 1012, 1016, 1018, and 1022 can generate feedback forces to counteract the effects of external disturbances. Additionally or alternatively, feedback 1012, 1016, 1018, and 1022 can be configured to generate feedback forces based on modeling errors. For example, if an incorrect aircraft mass is input into feedforward 1014 or 1020, the acceleration of the aircraft can be faster or slower than the desired change. Based on determining a difference between the desired acceleration and the measured acceleration, one or more processors (e.g., included in aircraft sensing 1031) can generate an error signal that can be looped into feedback 1012, 1016, 1018, or 1022 to determine additional forces needed to correct the error.

[0078] In some embodiments, feedback 1012, 1016, 1018, or 1022 can be disabled. For example, in response to losing position and / or ground speed feedback due to an interruption in global positioning system (GPS) communications, system 1000 can be configured to operate without feedback 1012, 1016, 1018, or 1022 until the GPS communications reconnect.

[0079] In some embodiments, feedback 1012, 1016, 1018, or 1022 can receive, as input, multiple measurements and a trust value for each measurement indicating whether the measurement is valid. For example, one or more processors of system 1000 can assign a Boolean (true / false) value to each measurement used in system 1000 to indicate that the measurement is valid (e.g., is) or that the measurement can be invalid (e.g., is not). Based on one or more processors identifying a measurement as invalid, feedback 1012, 1016, 1018, or 1022 can disregard the measurement for further processing. For example, in response to one or more processors identifying a heading measurement as invalid, feedback 1012, 1016, 1018, or 1022 can disregard subsequent heading measurements when determining feedback forces.

[0080] In some embodiments, feedback 1012, 1016, 1018, or 1022 can determine one or more feedback forces based on actuator state information received from one or more sensors (e.g., included in aircraft sensing 1031). For example, in response to actuator state information indicating that there is an actuator failure, one or more processors of system 1000 can update one or more processes of system 1000 and determine alternative commands for achieving a desired change. For example, one or more processors of system 1000 can adjust one or more models, functions, algorithms, tables, inputs, parameters, thresholds, and / or constraints based on (e.g., in response to) a change in state (e.g., a failure) of an actuator (or other aircraft component, such as an engine or battery, for other examples). An alternative command (e.g., a yaw, pitch, roll, thrust, or torque) can be determined based on the adjustment. Additionally or alternatively, in response to actuator state information indicating that one or more actuators are at a maximum, one or more processors of system 1000 can update one or more processes of system 1000 (e.g., as described above) and determine alternative commands for achieving a desired change.

[0081] A total desired force can be calculated based on outputs of feedback 1012, 1016, 1018, and 1022 and feedforward 1014 and 1020. For example, one or more processors of system 1000 can calculate a desired turn rate force by summing outputs of feedback 1012 and feedforward 1014. Additionally or alternatively, one or more processors of system 1000 can calculate a desired lateral force by summing outputs of feedback 1016 and feedforward 1014. Additionally or alternatively, one or more processors of system 1000 can calculate a desired vertical force by summing outputs of feedback 1018 and feedforward 1020. Additionally or alternatively, one or more processors of system 1000 can calculate a desired longitudinal force by summing outputs of feedback 1022 and feedforward 1020.

[0082] The lateral / orientation outer loop allocation 1024 and the longitudinal outer loop allocation 1026 can each be configured to receive as inputs one or more desired forces and data (e.g., airspeed, aircraft orientation, aircraft load factor, measured acceleration, aircraft mass and inertia, indication of working / failing actuators, air density, altitude, aircraft mode, whether the aircraft is in the air or on the ground, weight on wheels, etc.) received from the aircraft sensing 1031. Based on the inputs, the outer loop allocations 1024 and 1026 can be configured to command roll, command yaw, command pitch, demand thrust, or output a combination of different commands / demands to achieve one or more desired forces.

[0083] The lateral / orientation outer loop allocation 1024 can receive as inputs a desired turn rate force and / or a desired lateral force, and can command roll or command yaw. In some embodiments, the lateral / orientation outer loop allocation 1024 can determine the output based on a determined flight mode. The flight mode can be determined using pilot input (e.g., a selected mode on a pilot's controls) and / or sensed aircraft information (e.g., airspeed). For example, the lateral / orientation outer loop allocation 1024 can determine a flight mode of the aircraft using at least one of a determined (e.g., sensed or measured) airspeed or an input received at a pilot's controls button (e.g., an input indicating that the aircraft is to fly according to a particular flight mode). In some embodiments, the lateral / orientation outer loop allocation 1024 can be configured to prioritize pilot controls button input over measured airspeed when determining the flight mode (e.g., the pilot controls button is associated with a higher weight or higher priority than the measured airspeed). In some embodiments, the lateral / orientation outer loop allocation 1024 can be configured to blend (e.g., using a weighted sum) the determined airspeed and the pilot controls button input to determine the flight mode of the aircraft. In a hover flight mode, the lateral / orientation outer loop allocation 1024 can utilize roll commands (e.g., roll angle, roll rate) to achieve a desired lateral force, and can utilize yaw commands to achieve a desired turn rate force. In some embodiments, such as in a hover flight mode, the aircraft can be configured to be unable to accelerate outside of a predetermined hover envelope (e.g., a hover speed range). In a forward flight mode (e.g., level flight), the lateral / orientation outer loop allocation 1024 can utilize yaw commands to achieve a desired lateral force, and can utilize roll commands to achieve a desired turn rate force. In the forward flight mode, the lateral / orientation outer loop allocation 1024 can be configured to determine the output based on a sensed airspeed. In a transition between the hover flight mode and the forward flight mode, the lateral / orientation outer loop allocation 1024 can use a combination of roll commands and yaw commands to achieve the desired forces.

[0084] The longitudinal outer loop allocation 1026 can receive the desired vertical force and / or the desired longitudinal force as inputs and can output at least one of a pitch command (e.g., a pitch angle) or a thrust vectoring requirement. The thrust vectoring requirement can include a longitudinal thrust (e.g., a mix of nacelle tilting propeller thrust and forward propeller thrust) and a vertical thrust (i.e., a combination of forward and aft thrust). In some embodiments, the longitudinal outer loop allocation 1026 can determine the output based on the determined flight mode. For example, in a hover flight mode, the longitudinal outer loop allocation 1026 can achieve the desired longitudinal force by lowering the pitch attitude and by using longitudinal thrust, and can achieve the desired vertical force with vertical thrust. In a forward flight mode, the longitudinal outer loop allocation 1026 can achieve the desired longitudinal force with longitudinal thrust (e.g., forward propeller thrust). In a cruise flight mode, the longitudinal outer loop allocation 1026 can achieve the desired vertical force by commanding pitch (e.g., raising the pitch attitude) and requiring thrust (e.g., increasing longitudinal thrust).

[0085] The inner loop control law 1028 can be configured to determine a moment command based on at least one of a roll command, a yaw command, or a pitch command from the lateral / orientation outer loop allocation 1024 or the longitudinal outer loop allocation 1026. In some embodiments, the inner loop control law 1028 can depend on sensed aircraft dynamics (e.g., from aircraft sensing 1031). For example, the inner loop control law 1028 can be configured to compensate for disturbances at the attitude and rate level to stabilize the aircraft. Additionally or alternatively, the inner loop control law 1028 can account for the period of a natural mode (e.g., a phugoid mode) affecting the pitch axis and can control the aircraft appropriately to compensate for such natural modes of the aircraft. In some embodiments, the inner loop control law 1028 can depend on aircraft inertia.

[0086] The inner-loop control law 1028 can determine the moment commands using one or more stored dynamic models that reflect the motion characteristics of the aircraft (e.g., the aerodynamic damping and / or inertia of the aircraft). In some embodiments, the inner-loop control law 1028 can use a dynamic model (e.g., a low-order equivalent system model) to capture the motion characteristics of the aircraft and determine one or more moments that will cause the aircraft to achieve the commanded roll, yaw, and / or pitch. Some embodiments can include determining (e.g., by the inner-loop control law 1028 or other component) the moment commands based on at least one received command (e.g., a roll command, a yaw command, and / or a pitch command) and a determined (e.g., measured) state of the aircraft. For example, the difference between the commanded state of the aircraft and the measured state of the aircraft can be used to determine the moment commands. By way of further example, the difference between the commanded roll angle and the measured roll angle can be used to determine the moment commands. As described below, the control allocation 1029 can control the aircraft (e.g., by the flight elements) based on the determined moment commands. For example, the control allocation 1029 can control one or more electric propulsion systems (e.g., the electric propulsion systems 602 shown in FIG. 6) of the aircraft (e.g., transmit one or more commands to the one or more electric propulsion systems), which include tilt actuators, electric engines, and / or propellers. The control allocation 1029 can further control one or more control surfaces (e.g., control surfaces such as the flaperons 712 and the rudder elevators 714 shown in FIG. 6) of the aircraft, including flaperons, rudder elevators, ailerons, spoilers, rudders, and / or elevators. Figure 6 Figure 7

[0087] While the embodiments shown in FIG. 6 include both the inner-loop control law 1028 and the outer-loop allocations 1024 and 1026, in some embodiments, the flight control system can not include the outer-loop allocations 1024 and 1026. Thus, the pilot's control stick inputs can create roll, yaw, pitch, and / or thrust commands. For example, the right control stick can control roll and pitch, and the left control stick and / or pedals can control yaw and thrust. Figure 10

[0088] The control allocation 1029 can accept as inputs one or more of the following: force and moment commands, data received from one or more aircraft sensors, envelope protection limits, scheduling parameters, and optimizer parameters. The control allocation 1029 can be configured to determine actuator commands based on the inputs by minimizing an objective function that includes one or more primary objectives, such as satisfying (e.g., responding to, conforming to, resolving, providing output based on) the commanded aircraft forces and moments, and one or more secondary objectives, which can include minimizing acoustic noise and / or optimizing battery pack usage. ​​​

[0089] In some embodiments, the control allocation 1029 can be configured to calculate limits for individual actuator commands based on actuator states and envelope protection limits. The envelope protection limits can include one or more boundaries within which the aircraft should operate to ensure safe and stable flight. In some embodiments, the envelope protection limits can be defined by one or more of velocity, altitude, angle of attack, or load factor. For example, the envelope protection limits can include one or more bending moments and / or one or more load constraints. In some embodiments, the control allocation 1029 can use the envelope protection limits to automatically adjust one or more control surfaces or control settings. Doing so can prevent the aircraft from experiencing undesirable conditions, such as a stall or structural strain or failure. In normal operation, the minimum command limit for a given actuator can include the maximum of: a minimum limit based on hardware and a minimum flight envelope limit; and the maximum command limit for a given actuator can include the minimum of: a maximum limit based on hardware and a maximum flight envelope limit. In the event of a failure of an actuator, the command limits for the failed actuator correspond to a failure mode.

[0090] The control allocation 1029 sends commands to one or more flight elements to control the aircraft. The flight elements will move in accordance with the control commands. Various sensing systems and associated sensors that are part of the aircraft sensing 1031 can detect the movement of the flight elements and / or the dynamics of the aircraft and provide information to the feedback 1012, 1016, 1018, 1022, the outer loop allocation 1024 and 1026, the inner loop control law 1028, and the control allocation 1029 to incorporate into the flight control.

[0091] As described above, the aircraft sensing 1031 can include one or more sensors to detect aircraft dynamics. For example, the aircraft sensing 1031 can capture how the aircraft moves in response to pilot input, propulsion system output, or environmental conditions. Additionally or alternatively, the aircraft sensing 1031 can detect errors in the aircraft response based on extraneous disturbances (e.g., a wind gust induced speed disturbance). Further, the aircraft sensing 1031 can include one or more sensors to detect propeller speed, such as a magnetic sensor (e.g., a Hall effect or inductive sensor) or an optical sensor (e.g., a tachometer) configured to detect the rotor speed of the aircraft engine (and, thereby, the speed of the propeller). The aircraft sensing 1031 can include one or more sensors to detect the nacelle tilt angle (e.g., in a lift configuration (e.g., Figure 2 ) and a forward thrust configuration (e.g., Figure 1The tilt angle can be provided to the system 1000. Additionally, one or more pitot tubes, accelerometers, and / or gyroscopes can detect the pitch angle of the aircraft, which can be provided to the system 1000. In some embodiments, aircraft sensing 1031 can combine the tilt angle sensor measurements and the aircraft pitch measurements to determine the overall nacelle tilt angle of the propeller.

[0092] Aircraft sensing 1031 can include one or more sensors configured to detect engine torque and / or thrust, such as one or more current sensors or voltage sensors, strain gauges, load cells, and / or propeller vibration sensors (e.g., accelerometers).

[0093] Aircraft sensing 1031 can include one or more sensors configured to detect aircraft movement and / or aircraft orientation (e.g., accelerometers, 3-axis accelerometers, gyroscopes, 3-axis gyroscopes, and / or tilt position sensors for determining the angle of the engine) and airspeed sensors (e.g., pitot tube sensors). Aircraft sensing 1031 can further include one or more inertial measurement units (IMUs) to determine the aircraft state based on these measurements. The aircraft state can refer to the forces experienced by the aircraft, the orientation of the aircraft, the position (e.g., altitude) of the aircraft, and / or the movement of the aircraft. For example, the aircraft state can include at least one of the following: the position of the aircraft (e.g., yaw angle, roll angle, pitch angle, and / or any other orientation across one or two axes), the speed of the aircraft, the angular rate of the aircraft (e.g., roll, pitch, and / or yaw rate), and / or the acceleration of the aircraft (e.g., longitudinal, lateral, and / or vertical acceleration) or any physical property of the aircraft or one of its components.

[0094] In some embodiments, aircraft sensing 1031 can include an inertial navigation system (INS) and / or air data and / or an attitude and heading reference system (ADAHRS). The inertial navigation system (INS) and / or attitude and heading reference system (ADAHRS) can include one or more inertial measurement units (IMUs) and corresponding sensors (e.g., accelerometers, gyroscopes, tri-axial gyroscopes, and / or tri-axial accelerometers). In some embodiments, the INS and / or ADAHRS can filter and / or otherwise process sensor measurements to determine aircraft states (e.g., accelerations or angular rates). For example, in some embodiments, the INS and / or ADAHRS can determine angular rates based on gyroscope measurements, and can determine accelerations based on measurements from accelerometers.

[0095] In some embodiments, as described further below, VRS avoidance 1033 can determine a closeness of a state of one or more propellers to a vortex ring state. Based on one or more of the determined closenesses, VRS avoidance 1033 can input a control limit to ensure that a set number or all of the aircraft propellers are avoided from entering a vortex ring state. In some embodiments, the control limit can include a descent rate limit, e.g., a maximum allowable descent rate at which the aircraft can fly while avoiding propellers from entering a vortex ring state. In some embodiments, VRS avoidance 1033 can input this descent rate limit into climb command model 1008. Accordingly, climb command model 1008 can determine a desired altitude, vertical speed, and / or vertical acceleration that does not exceed the descent rate limit.

[0096] In some embodiments, the limit can include a forward speed limit, e.g., a minimum forward speed at which the aircraft can fly while avoiding propellers from entering a vortex ring state. In some embodiments, VRS avoidance 1033 can be configured to input this forward speed limit into forward speed command model 1010. Accordingly, forward speed command model 1010 can determine a desired position, longitudinal speed, and / or longitudinal acceleration that does not fall below the forward speed limit.

[0097] In some embodiments, the limit can include a turn rate limit, e.g., a maximum turn rate at which the aircraft can fly while avoiding propellers from entering a vortex ring state. In some embodiments, VRS avoidance 1033 can be configured to input this maximum turn rate limit into turn rate limit command model 1004. Accordingly, turn rate limit command model 1004 can determine a desired position and / or turn rate command that does not exceed the maximum turn rate limit.

[0098] In some embodiments, the limits can include a yaw rate limit, e.g., a limit setting a maximum yaw rate in one or more directions. For example, the yaw rate in the direction of the propeller as the state approaches the vortex ring state can be limited. In some embodiments, the VRS avoidance 1033 can be configured to input this yaw rate limit to the inner loop control law 1028. Thus, the inner loop control law 1028 can determine aircraft movements (e.g., moments) that do not exceed the yaw rate limit.

[0099] In some embodiments, the limits can include a roll rate limit, e.g., a limit setting a maximum roll rate in one or more directions. For example, the roll rate in the direction of the propeller as the state approaches the vortex ring state can be limited. In some embodiments, the VRS avoidance 1033 can be configured to input this roll rate limit to the inner loop control law 1028. Thus, the inner loop control law 1028 can determine aircraft movements that do not exceed the roll rate limit.

[0100] In some embodiments, the limits can include a pitch rate limit, e.g., a limit setting a maximum pitch rate. For example, the pitch rate toward the ground can be limited. In some embodiments, the VRS avoidance 1033 can be configured to input this pitch rate limit to the inner loop control law 1028. Thus, the inner loop control law 1028 can determine aircraft movements that do not exceed the pitch rate limit.

[0101] Based on applying the above-described limits to the command models (1004, 1006, 1008, and / or 1010) and / or the inner loop control law 1028, the system 1000 sends moment commands corresponding to these limits to the control allocation 1029. The control allocation 1029 can then control the aircraft (e.g., the aircraft dynamics control 1030) in accordance with these limits. For example, the control allocation 1029 can control the aircraft propeller speeds and / or tilt directions to implement the moment commands that comply with the determined limits.

[0102] In some embodiments, the limits can include propeller torque or propeller speed limits for one, some, or all of the aircraft propellers. In some embodiments, the VRS avoidance 1033 can be configured to input this torque or speed limit to the control allocation 1029. Thus, the control allocation 1029 can determine propeller commands that do not exceed the torque or speed limit.

[0103] As further described below, in some embodiments, the VRS avoidance 1033 can determine any combination of limits that the system 1000 can use to control operation of the aircraft (e.g., override and limit pilot commands). For example, in some embodiments, the VRS avoidance 1033 can limit a descent rate. In some embodiments, the VRS avoidance 1033 can limit a propeller torque or speed. In some embodiments, the VRS avoidance 1033 can limit a yaw rate, a roll rate, and / or a pitch rate. In some embodiments, the VRS avoidance 1033 can limit a descent rate, a turn rate, a forward speed, a yaw rate, a roll rate, and / or a pitch rate.

[0104] In some embodiments, as further described below, the limited aircraft maneuver corresponds to a change in maneuver requested by the pilot and / or autopilot (e.g., through a pilot's controls). For example, if the pilot requests a change in descent through the controls, the VRS avoidance 1033 can limit the descent rate. For example, if the pilot requests a roll through the controls, the VRS avoidance 1033 can limit the roll rate. In some embodiments, the VRS avoidance 1033 can determine the requested aircraft maneuver through one or more models, such as the turn rate command model 1004, the lateral velocity command model 1006, the climb command model 1008, and / or the forward speed command model 1010. The system 1000 can apply the limits dynamically and quickly during flight (e.g., vertical descent), thereby improving the safety of the aircraft while still allowing it to operate within tolerable control limits.

[0105] Figure 11 A propeller entering a vortex ring state is shown according to embodiments of the disclosure. During normal flight 1101, air flow moves down through the propeller. As the aircraft descends 1102, some air flow can overcome the downward thrust from the propeller rotation and move up through the propeller. When the aircraft propeller enters a vortex ring state 1103, the wake from the upward flowing air begins to be drawn back down, creating a vortex 1104. In the vortex ring state 1103, the aircraft can experience vibrations and can not produce enough thrust to support the aircraft. Furthermore, in the vortex ring state 1103, the condition can be exacerbated by attempts to increase thrust, as an increase in propeller rotation can cause more upward air flow to be drawn back into the propeller.

[0106] As described above, propellers are more likely to enter a vortex ring state at higher descent rates, as there is more upward air flow through the propeller. Furthermore, propellers are more likely to enter a vortex ring state at lower forward airspeeds, as the aircraft is less likely to break out of the wake caused by the upward air flow, such that the wake is more likely to be drawn back into the propeller in the vortex 1104.

[0107] Figure 12 A block diagram for incorporating control limitations is shown in accordance with embodiments of the present disclosure. It should be appreciated that the steps of the example method depicted in Figure 12 would not be possible, or at least impractical, especially when considering frequent (e.g., continuous) implementation of these functions while the aircraft is in flight (including takeoff or landing), and / or dynamic implementation of these functions based on (e.g., in response to) received signals (e.g., aircraft sensors, changing state measurements, pilot input devices). In general, it should be understood that Figure 12 Any / all steps of the example method of FIG. 12 can be performed or executed, e.g., by at least one processor (e.g., FCS, FCC) in accordance with one or more instructions stored on a computer-readable medium (e.g., non-transitory computer-readable medium).

[0108] At step 1201, pilot commands can be transmitted to the flight control system (e.g., through the left and / or right yoke). For example, the pilot commands can indicate a flight path angle, a turn rate, a lateral speed, a climb rate (e.g., an ascent or descent rate), a forward speed, a roll rate, and / or a yaw rate. In some embodiments, the autopilot system can transmit one or more of these commands to the flight control system (e.g., system 1000). At step 1206, the VRS avoidance 1033 can receive and / or measure a state of the aircraft (e.g., quantities related to the aircraft). In some embodiments, the measured quantities can include an airspeed V 空速 In some embodiments, the measured quantities can further include other measurements indicative of airflow pulled through the propeller, such as revolutions per minute (rpm) Ω measured by an engine sensor (e.g., a Hall effect sensor, an inductive sensor, or an optical sensor), torque Q measured by a circuit sensing device (e.g., a phase current sensor), thrust measured by a strain gauge and / or load cell, and / or vibration measured by an accelerometer. In some embodiments, the measured quantities can further include air density p (e.g., as measured by a pressure sensor and a temperature sensor). In some embodiments, the measured quantities can further include a current state of the aircraft, such as a current pitch angle, a roll angle, a sideslip angle, a turn rate, a lateral speed, a climb rate (e.g., an ascent or descent rate), a forward speed, a roll rate, a yaw rate, and / or an acceleration (e.g., longitudinal and / or lateral acceleration). In some embodiments, the measured quantities can further include a nacelle tilt angle and / or a blade tilt angle (e.g., a pitch angle) of one or more propellers. For example, the measured quantities can include a nacelle tilt angle of the electric propulsion unit 114 shown. Figure 1 In some embodiments, the measured quantities can further include a current state of the aircraft, such as a current pitch angle, a roll angle, a sideslip angle, a turn rate, a lateral speed, a climb rate (e.g., an ascent or descent rate), a forward speed, a roll rate, a yaw rate, and / or an acceleration (e.g., longitudinal and / or lateral acceleration). In some embodiments, the measured quantities can further include a nacelle tilt angle and / or a blade tilt angle (e.g., a pitch angle) of one or more propellers. For example, the measured quantities can include a nacelle tilt angle of the electric propulsion unit 114 shown.

[0109] At step 1205, the VRS avoidance 1033 can calculate one or more limits on the commanded aircraft state (e.g., commanded descent rate indicated by the descent rate command) based on the proximity of the one or more propellers to the multi-dimensional vortex ring state boundary, as described further below with respect to Figures 14A to 14G Further described below. For example, the VRS avoidance 1033 can store one or more characteristics for the propellers, such as propeller torque constants and constants associated with the propeller and / or aircraft geometry. In addition, the VRS avoidance 1033 can store one or more models and / or lookup tables (e.g., multi-dimensional lookup tables) to determine one or more propeller-local airspeeds V x , V y (e.g., horizontal airspeed parallel to the propeller disk and vertical airspeed perpendicular to the propeller disk) and induced airspeed V h at hover based on the measured quantities received at step 1206. The VRS avoidance 1033 can determine the proximity of the one or more propellers to the vortex ring state by dividing the local airspeeds by the induced airspeed at hover (e.g., V x / V h .V y / V h ) and comparing to an established vortex ring state boundary Boundary = F(V x , V y , V h ) (e.g., stored as a model and / or a lookup table of values). For example, as described further below, in some embodiments, the VRS avoidance 1033 can determine the propeller closest to the vortex ring state. Based on the propeller state of the propeller closest to the vortex ring state and its determined proximity, control limits can be established. In some embodiments, the VRS 1033 can determine a second, third, and / or fourth propeller closest to the vortex ring state and can establish control limits based on that propeller.

[0110] The control limits can change dynamically based on the measured quantities (e.g., propeller speed, airspeed) to avoid the vortex ring state. “Propeller speed” can refer to the rotational speed of the propeller (e.g., RPM or blade tip speed (e.g., tip Mach number)). For example, more restrictive limits (e.g., lower maximum descent rate) can be set at higher propeller speeds where the wake is more likely to be drawn back into the propeller. Similarly, more restrictive limits (e.g., lower maximum descent rate) can be set at lower forward airspeeds where the wake is less likely to be removed by forward movement of the aircraft. In some embodiments, the control limits can be correlated to the measured quantities (e.g., airspeed) such that an increase in the measured quantity results in an increase in the constraints imposed by the system.

[0111] In some embodiments, at step 1205, the VRS avoidance 1033 can detect the airspeed (e.g., the longitudinal airspeed) of the aircraft. If the airspeed is above a stored threshold, the VRS avoidance 1033 can not determine any control limits or disengage commands. The airspeed threshold can be set based on a model and / or experimental data that determines that the likelihood of a propeller entering a vortex ring state is low (e.g., less than 5% or 10%) if above the airspeed. In some embodiments, the VRS avoidance 1033 can detect the propeller speed of the propellers of the aircraft. If the propeller speed (e.g., the maximum or average of the propeller speed) is below a set threshold, the VRS avoidance 1033 can not determine any control limits or disengage commands. The propeller speed threshold can be set based on a model and / or experimental data that determines that the likelihood of a propeller entering a vortex ring state is low (e.g., less than 5% or 10%) if below the propeller speed.

[0112] In some embodiments, at step 1205, the VRS avoidance 1033 can detect whether the aircraft is in a powered lift state. For example, the VRS avoidance 1033 can determine whether a tilting propeller (e.g., the tilting propeller 114) is in a lift configuration and / or within a threshold proximity (e.g., 45 degrees, 30 degrees, 15 degrees) of a lift configuration, and / or whether a lift propeller (e.g., the lift propeller 112) is rotating. If the aircraft is not in a powered lift state, the VRS avoidance 1033 can not determine any control limits or disengage commands.

[0113] In some embodiments, the VRS avoidance 1033 can detect that one or more propellers have entered a vortex ring state. In some embodiments, the VRS avoidance 1033 can determine that one or more propellers have entered a vortex ring state based on detected vibrations (e.g., by the aircraft sensing 1031 and associated accelerometers). The VRS avoidance 1033 can store one or more vibration models and / or vibration lookup tables that indicate a vortex ring state. For example, the VRS avoidance 1033 can store accelerometer amplitude and / or frequency measurements and / or ranges using a lookup table and / or model that indicate expected measurements of a propeller in a vortex ring state. These values that indicate a vortex ring state can be based on historical data and / or models of propeller behavior in a vortex ring state at one or more propeller speeds and / or airspeeds. In some embodiments, the VRS avoidance 1033 can determine that one or more propellers have entered a vortex ring state based on a propeller state crossing a boundary of a vortex ring state, as described below with reference to FIG. 13. Figures 14A to 14G Further described.

[0114] In some embodiments, based on the VRS avoidance 1033 detecting that one or more propellers have entered a vortex ring state, the VRS avoidance 1033 can adjust the limits set by the determined proximity of the propellers to the vortex ring state, as described above. For example, the VRS avoidance 1033 can make the limits more restrictive (e.g., further limit the rate of descent by 5%, 10%, 15%, etc.) based on the duration and / or significance (e.g., intensity) of the vibrations indicative of the vortex ring state.

[0115] In some embodiments, the VRS avoidance 1033 can additionally or alternatively take other actions upon determining that one or more propellers have entered a vortex ring state. In some embodiments, the VRS avoidance 1033 can send a command to perturb the nacelle tilt of one or more propellers to exit the vortex ring state. For example, the VRS avoidance 1033 can adjust the angle of the axis of rotation (nacelle tilt angle) of a propeller that has entered a vortex ring state to remove the wake. Further, in some embodiments, the VRS avoidance 1033 can send multiple commands to constantly change the nacelle tilt angle between an upper angle and a lower angle. Further, in some embodiments, the VRS avoidance 1033 can send commands for other rotors to adjust their nacelle tilt angle and / or thrust to counteract the adjustments made to the propeller that has entered a vortex ring state.

[0116] In some embodiments, the VRS avoidance 1033 can send a command to increase the forward airspeed of the aircraft upon detecting that one or more propellers have entered a vortex ring state. For example, the VRS avoidance 1033 can increase the forward airspeed of the aircraft (e.g., further increase the forward airspeed by 5%, 10%, 15%, etc.) based on the duration and / or significance of the vibrations indicative of the vortex ring state.

[0117] At step 1202, the VRS avoidance 1033 can input limits (or disengage commands) into one or more segments of the flight control system, thereby limiting the effect of the commands received at step 1201. For example, the limits (or disengage commands) can be input into one or more of the control laws, functions, models, and / or algorithms described above with respect to Figure 10 As described above, based on the limits, the system 1000 can calculate the commands input into the control allocation (e.g., control allocation 1029) in the control laws, functions, models, and / or algorithms described above with respect to Figure 10 At step 1203, the control allocation 1029 can determine flight element commands based on the input commands. For example, the control allocation 1029 can send commands (e.g., torque or thrust commands) to aircraft flight elements such as control surfaces, tilt actuators, and / or propellers. Thus, the flight elements are controlled in accordance with the determinations made by the VRS avoidance 1033.

[0118] Furthermore, in some embodiments, one or more limits (or disengagement commands) established by VRS Avoidance 1033 at step 1205 can be directly input into the control assignment at step 1203. VRS Avoidance 1033 can determine the forces, torques, actuator signals, thrust, nacelle tilt angle, propeller speed (e.g., rpm), and / or propeller torque required to avoid vortex ring state, and input those limits directly into control assignment 1029. Similarly, flight elements are controlled within the limits (or commands) established by VRS Avoidance 1033. For example, flight elements can be controlled at yaw rates, pitch rates, descent rates, and / or roll rates lower than those requested by pilot command 1201 to ensure that the aircraft is controlled within the established limits and to prevent one or more propellers from entering vortex ring state.

[0119] Figures 13A to 13B Block diagrams illustrating the determination of control limits according to embodiments of the present disclosure are shown. These diagrams may further illustrate the limit determination performed by VRS avoidance 1033. For example, these block diagrams may further illustrate the above regarding... Figure 12 Steps 1206 and 1205 are shown.

[0120] Figure 13A A first block diagram is shown for determining control limits according to an embodiment of the present disclosure. In some embodiments, the steps in block 1310 may be performed for each propeller. At step 1311, VRS avoidance 1033 may calculate the propeller torque by using a first reference model. The first reference model may be configured to receive a measured quantity 1312 as input. For example, the measured quantity 1312 may include the propeller speed (e.g., RPM Ωi as measured by a Hall effect sensor and / or an inductive sensor) and the electric motor phase current Ii (e.g., as measured by a current sensor). Based on the measured quantity 1312 and stored characteristics (e.g., torque constant K), VRS avoidance 1033 may calculate the propeller torque using a model, a function (e.g., Qi=f(Ωi,Ii,K)) and / or one or more lookup tables providing torque based on Ωi, Ii, and / or K.

[0121] At step 1313, VRS avoidance 1033 can be achieved by using a second reference model based on the input torque Q. i The thrust value T is calculated using the measured quantity 1314. i (For example, associated with a propeller). For example, the measured quantity 1314 may include the aircraft airspeed (e.g., determined by a pitot tube and / or GPS) and the aircraft longitudinal acceleration (e.g., determined by an accelerometer). Based on the measured quantity 1314, the characteristics of the thrust function can be determined. For example, the characteristic T can be...0_i dT / dQ and / or Q 0i Stored in one or more lookup tables as functions of aircraft airspeed and / or aircraft longitudinal acceleration. Based on relevant characteristics (e.g., T...). 0_i , dT / dQ, Q 0i VRS avoids the use of models and functions (e.g., T) to prevent 1033 from being used. i =T 0_i +dT / dQ (Q i -Q 0i )) and / or based on T 0_i dT / dQ and / or Q 0i Provide thrust value T i One or more lookup tables are used to calculate the thrust value T. i In some embodiments, T is calculated. i This may involve referencing models (linear or nonlinear), functions, and / or lookup tables that vary based on flight phases (e.g., hovering, transition, forward flight, aircraft orientation (pitch, roll, etc.)), airspeed, propeller tilt angle, propeller tilt relative to the local airflow of one or more propellers, and / or total pitch angle.

[0122] At step 1315, VRS avoidance 1033 can be achieved by using a third reference model based on the input torque T. i The induced velocity V generated by the propeller speed during hovering is calculated using the measured quantity 1316. h For example, the measured quantity 1316 may include the air density ρ. 空气 Based on the measured quantity 1316 and the stored geometric parameter A representing the propeller disk area. prop VRS avoids 1033 by using models and functions (e.g., , and / or based on ρ 空气 and / or A prop Provide V h (One or more lookup tables) are used to calculate the induced velocity during hovering.

[0123] At step 1317, the VRS avoidance 1033 can calculate a velocity component (e.g., the velocity associated with a particular propeller) based on the measured quantity 1318. For example, the measured quantity 1318 may include the nacelle tilt angle τ. i (e.g., measured by a Hall effect sensor), the aircraft pitch angle α and / or the aircraft sideslip angle β. Based on the measured quantities 1318 and the stored geometric parameters, the local airspeed component V can be determined. x_i and V y_i (For example, the horizontal airspeed parallel to the propeller disk and the vertical airspeed perpendicular to the propeller disk).

[0124] At step 1319, VRS avoidance 1033 can calculate a proximity from the propeller state (e.g., based on one or more measured quantities) to a VRS boundary. For example, VRS avoidance 1033 can calculate a distance from the propeller state to the VRS boundary and / or another constant representing a proximity to the VRS boundary (e.g., a time until entering the VRS boundary). The VRS boundary can be a function, expression, lookup table, or model. In some embodiments, once the propeller state exceeds the VRS boundary, it enters the vortex ring state and is unable to provide sufficient thrust. The VRS boundary can be based on historical data and / or a model showing propeller states at which propellers enter the vortex ring state (e.g., V h , V x , V z ). In some embodiments, VRS avoidance 1033 can store multiple VRS boundaries based on the positioning and / or geometry of the aircraft propellers. In some embodiments, a different VRS boundary can be stored and referenced for each set of one or more propellers having similar positioning and / or geometry. In some embodiments, a first VRS boundary is used for all front propellers, and a second VRS boundary is used for all rear propellers. In some embodiments, a single VRS boundary is used for all aircraft propellers regardless of their positioning / orientation. In some embodiments, the measured distance to the boundary can be a function of the aircraft trajectory, as described further below with respect to Figures 14A to 14F In some embodiments, steps 1311-1317 can be repeated for each propeller.

[0125] At step 1320, VRS avoidance 1033 can determine which propeller state is closest to the vortex ring state boundary. In some embodiments, control limits can be set based on the state of the propeller closest to the vortex ring state boundary. In some embodiments, control limits can be set based on the propeller states of the second, third, and / or fourth closest propellers to the vortex ring state boundary. As described further below, in some embodiments, based on the current trajectory of the propeller, the control limits can be based on the intersection of the propeller state with the vortex ring boundary.

[0126] Figure 13BA second block diagram for determining control limits is shown, in accordance with an embodiment of the disclosure. In some embodiments, the steps in block 1330 can be performed for each propeller. At step 1331, the VRS avoidance 1033 can calculate the torque of the propeller by using a first reference model. The first reference model can be configured to receive measured quantities 1332 as input. For example, the measured quantities 1332 can include propeller speed (e.g., RPMs 0i as measured by a Hall effect sensor and / or an inductance sensor) and electrical engine phase current Ii (e.g., as measured by a current sensor). Based on the measured quantities 1332 and stored characteristics (e.g., torque constant K), the VRS avoidance 1033 can calculate the torque of the propeller using a model, a function (e.g., Qi = f(0i, Ii, K)), and / or one or more lookup tables based on 0i, Ii, and / or K. i

[0127] At step 1333, the VRS avoidance 1033 can calculate the speed components based on measured quantities 1334 by using a second reference model. For example, the measured quantities 1334 can include nacelle tilt angle T i (e.g., as measured by a Hall effect sensor), aircraft pitch angle a, and / or aircraft sideslip angle b. Based on the measured quantities 1318 and stored geometric parameters, the local airspeed components V x_i and V y_i may be determined.

[0128] At step 1335, the VRS avoidance 1033 can calculate the propeller thrust value T i based on the input torque Q x , speed components (V z , V i ), and measured quantities 1336 by using a third reference model. For example, the measured quantities 1336 can include vehicle speed V inf . In some embodiments, the VRS avoidance 1033 can calculate the thrust value T i using a function T i =F(0 x_i , V z_i , V i ), a model that determines T x_i based on 0 z_i , V i , and / or V i , or a lookup table that determines T x_i based on 0 z_i , V i , and / or V i . In some embodiments, the function, model, and / or lookup table are specific to the determined measured vehicle speed V inf ​In some embodiments, the lookup table can be one or more multidimensional lookup tables generated based on computational fluid dynamics (CFD) data and / or wind tunnel (WT) data. In some embodiments, the multidimensional lookup table can include a machine learning model, such as a neural network configured to predict thrust. In some embodiments, the thrust T i References to models, functions, and / or lookup tables that vary based on a flight phase (e.g., hover, transition, or forward flight) can be involved.

[0129] At step 1337, the VRS avoidance 1033 can calculate the induced velocity V i resulting from the propeller speed in hover based on the input torque T h and the measured quantities 1338 using a fourth reference model. For example, the measured quantities 1338 can include air density p 空气 . Based on the measured quantities 1338 and stored geometric parameters A prop representing the propeller disc area, the VRS avoidance 1033 can use a model, function (e.g., , and / or lookup table based on p 空气 and / or A prop to calculate the induced velocity in hover. h

[0130] At step 1339, the VRS avoidance 1033 can calculate the proximity of the propeller state (e.g., based on one or more measured quantities) to the VRS boundary. The VRS boundary can be a function, lookup table, or model. In some embodiments, once the propeller state exceeds the VRS boundary, it enters a vortex ring state and is unable to provide sufficient thrust. The VRS boundary can be based on historical data and / or a model showing propeller states (e.g., V h , V x , V z ) at which propellers enter a vortex ring state. In some embodiments, the VRS avoidance 1033 can store multiple VRS boundaries, which can be based on the positioning of the aircraft propellers, the geometry of the aircraft propellers, and / or the design of the aircraft (e.g., weight, size, wing shape). Different VRS boundaries can be stored and referenced for each set of one or more propellers with similar positioning and / or geometry. In some embodiments, a first VRS boundary is used for all front propellers, and a second VRS boundary is used for all rear propellers. In some embodiments, the measured distance to the boundary can be a function of the aircraft trajectory, as further detailed below. In some embodiments, steps 1331-1339 can be repeated for each propeller.

[0131] ​At step 1340, VRS avoidance 1033 can determine which propeller state is closest to the vortex ring state boundary. In some embodiments, control limits can be set based on the state of the propeller closest to the vortex ring state boundary. In some embodiments, control limits can be set based on the propeller states of a second, third, and / or fourth propeller close to the vortex ring state boundary.

[0132] Figure 13C A third block diagram is shown for determining control limits according to embodiments of the present disclosure. In some embodiments, the control limit determination and associated control may be triggered by a threshold propeller speed (e.g., a threshold propeller RPM or a threshold blade tip speed (e.g., the Mach number at the blade tip)). For example, at lower propeller speeds, vortex ring state may not be a problem. However, at higher propeller speeds, control limits may be initiated when the propeller is at risk of ingesting its own wake. The threshold propeller speed can be set based on experimental data or by modeling the effect of propeller speed on vortex ring state. For example, the threshold can be set to a value corresponding to a tip speed in one or more ranges of [13.5-27.2] m / s, [30.2-60.8] mph, or Mach [0.04-0.08].

[0133] In some embodiments, the steps in block 1310 can be performed for each propeller. At step 1342, the VRS avoidance 1033 can calculate the induced velocity V generated by the hovering propeller based on the input reference value 1341. h For example, reference value 1341 may include reference air density ρ. 空气 (e.g., air density at sea level), reference torque T during hovering h and reference area A prop In some embodiments, for each propeller having the same physical characteristics (e.g., propeller size, geometry, angle, blade spacing, and / or any characteristics affecting its performance), the reference torque T at hover is... h They can be the same. For example, all lift propellers can have a first reference torque when hovering (e.g., when the aircraft is in the hovering phase of flight), and all tilt propellers can have a second reference torque when hovering. For example, propellers with different numbers of blades, different blade sizes, different blade shapes, and / or different hub caps can have different reference torques T when hovering. h Based on the reference value of 1341, VRS avoidance of 1033 can be achieved using models and functions (e.g., (and / or one or more lookup tables to calculate the induced velocity during hovering.)

[0134] As described above, at step 1344, VRS avoidance 1033 can calculate a velocity component (e.g., a velocity associated with a particular propeller) based on the measured quantities 1318. For example, the measured quantities 1318 can include a nacelle tilt angle τ i (e.g., as measured by a Hall effect sensor), an aircraft pitch angle a, and / or an aircraft sideslip angle β. Based on the measured quantities 1318 and stored geometric parameters, a local airspeed component V x_i and V z_i (e.g., a horizontal airspeed parallel to a propeller disk and a vertical airspeed perpendicular to a propeller disk) can be determined.

[0135] At step 1345, VRS avoidance 1033 can calculate a proximity to the VRS boundary from the propeller state. For example, VRS avoidance 1033 can calculate a distance from the propeller state to the VRS boundary and / or another constant representing a proximity to the VRS boundary (e.g., a time until entering the VRS boundary). The VRS boundary can be a function, expression, lookup table, or model. In some embodiments, once the propeller state exceeds the VRS boundary, it enters a vortex ring state and is unable to provide sufficient thrust. The VRS boundary can be based on historical data and / or a model showing propeller states at which propellers enter a vortex ring state (e.g., V x_i , V z_i ).

[0136] In some embodiments, VRS avoidance 1033 can store multiple VRS boundaries based on physical characteristics of the aircraft propellers. In some embodiments, different VRS boundaries can be stored and referenced for each set of one or more propellers having similar positioning and / or geometry. In some embodiments, a first VRS boundary is used for all lift propellers and a second VRS boundary is used for all tilt propellers. In some embodiments, a single VRS boundary is used for all aircraft propellers regardless of their physical characteristics. In some embodiments, the proximity to the boundary can be a function of the aircraft trajectory as described further below with respect to Figures 14A to 14F In some embodiments, steps 1341-1345 can be repeated for each propeller.

[0137] At step 1346, VRS avoidance 1033 can determine which propeller state is closest to the vortex ring state boundary. In some embodiments, control limits can be set based on the state of the propeller closest to the vortex ring state boundary. In some embodiments, control limits can be set based on the propeller state of the second, third, and / or fourth propeller closest to the vortex ring state boundary. As described further below, in some embodiments, based on the current trajectory of the propeller, the control limits can be based on an intersection of the propeller state with the vortex ring boundary.

[0138] Consistent with the disclosed embodiments (e.g., as described above with respect to the example Figures 12 to 13C The proximity of each of the at least two propellers to the vortex ring state is determined based on at least one of: a thrust of the propeller, a torque of the propeller, a propeller speed, or a vibration of the propeller. Additionally or alternatively, the proximity of each of the at least two propellers to the vortex ring state is determined based on an airspeed of the aircraft, a pitch angle of the aircraft, and a pitch of the propeller.

[0139] Figures 14A to 14G A diagram is shown for determining the propeller closest to the vortex ring state and corresponding control limits according to embodiments of the disclosure. In some embodiments, Figures 14A to 14F The diagram shown in FIG. 13A further illustrates determining the proximity of the propeller state to the VRS boundary and determining one or more limits, as in Figure 13A steps 1319-1320 and Figure 13B steps 1339-1340 in FIG. 13B. Figures 14A to 14G Each of the dashed trajectories illustrate a projected propeller state. In some embodiments, the trajectory of the propeller state can be interpolated based on past determined values (e.g., V x , V z , and / or V h ) over a set time window. In some embodiments, the trajectory of the propeller state can be determined by inputting pilot and / or autopilot commands into one or more reference models. As shown in Figures 14A to 14G The VRS boundary is a multi-dimensional boundary that varies based on changes in Vx, Vz, and / or Vh, as shown in FIG. 13A.

[0140] While the determination of the distance between the propeller state and the vortex ring state boundary is described, in some embodiments, other values can also represent the proximity to the vortex ring state boundary. For example, in some embodiments, the time of entry into the VRS boundary can be used to determine the propeller closest to the VRS boundary and the associated control limits. The time of entry into the VRS can be calculated by considering the propeller trajectory and the propeller state (e.g., the horizontal and / or vertical acceleration of the propeller).

[0141] Figure 14A A state of the aircraft propellers relative to the VRS boundary is shown when the horizontal airspeed at each propeller is approximately constant and the rate of descent at each propeller is increasing. Because the propeller state trajectory is at a constant V x / V h value, the vertical distance between the propeller state (A-F) and the boundary will be the relevant distance. Propeller F is closest to the VRS boundary, so the limits on movement of the aircraft can be based on the intersection value (V z / Vh ) and (V x / V h ).

[0142] Figure 14B shows the state of the aircraft propellers relative to the VRS boundary when the horizontal airspeed at each propeller is decreasing and the rate of descent at each propeller is approximately constant. Because the propeller state trajectory is at a constant V z / V h value, the horizontal distance between the propeller state (A-F) and the boundary will be the relevant distance. Propeller F is closest to the VRS boundary, so the limit on aircraft movement can be based on the intersection value (V z / V h ) and (V x / V h ).

[0143] Figure 14C shows the state of the aircraft propellers relative to the VRS boundary when the horizontal and vertical airspeed at each propeller is changing at a constant trajectory. The distance between the propeller state and the VRS boundary along the trajectory will be the relevant distance. Propeller F is closest to the VRS boundary, so the limit on aircraft movement can be based on the intersection value (V z / V h ) and (V x / V h ).

[0144] Figure 14D shows the state of the aircraft propellers relative to the VRS boundary when the aircraft is turning at a constant vertical airspeed V z . The distance between the propeller state and the VRS boundary along the horizontal trajectory will be the relevant distance. Propeller F is closest to the VRS boundary, so the limit on aircraft movement can be based on the intersection value (V z / V h ) and (V x / V h ).

[0145] Figure 14E shows the state of the aircraft propellers relative to the VRS boundary when the aircraft is rolling at a constant vertical airspeed V z . The distance between the propeller state and the VRS boundary along the vertical trajectory will be the relevant distance. Propeller E is closest to the VRS boundary, so the limit on aircraft movement can be based on the intersection value (V z / V h ) and (V x / V h ).

[0146] Figure 14FStates of the aircraft propellers relative to the VRS boundary are shown as the aircraft is rolling and turning. As shown, each trajectory for each propeller state can be different based on the side of the aircraft the propeller is on and the positioning of the propeller along the wing. The distance between the propeller state and the VRS boundary along the respective trajectory of the propeller will be the distance for that propeller. Propeller E is closest to the VRS boundary, so the limit on aircraft movement can be based on the intersection value (V z / V h ) and (V x / V h ).

[0147] Figure 14G States of the aft aircraft propellers relative to the VRS boundary are shown as the aircraft is pitching up. The distance between the propeller state and the VRS boundary along the arc of the trajectory will be the relevant distance. Propeller F is closest to the VRS boundary, so the limit on aircraft movement can be based on the intersection value (V z / V h ) and (V x / V h ).

[0148] In some embodiments, based on the determined propeller state trajectory (e.g., Figures 14A to 14G ) and the intersection point (V z / V h ) and / or (V x / V h ) of the propeller closest to the vortex state boundary, the aircraft movement can be controlled to avoid the propeller entering the vortex state. In some embodiments, a second, third, and / or fourth intersection point of a propeller closest to the vortex state boundary will be determined, and the control limit will be based on this determined intersection point.

[0149] In some embodiments, the VRS avoidance 1033 can place a limit V z_max on the vertical airspeed component of the propeller, where V z_max = (V z / V h ) V h and V z / V h correspond to the intersection point of the propeller closest to the vortex state boundary. In some embodiments, the VRS avoidance 1033 can determine a descent rate, roll rate, and / or pitch rate limit based on V z_max . For example, the descent rate, roll rate, and / or pitch rate can be limited to avoid exceeding V z_max .

[0150] In some embodiments, the descent rate limit can be set to V z_maxIn some embodiments, the roll rate limit can be set as where r w is the distance from the center of the aircraft to the tip of the wing. In some embodiments, the pitch rate limit can be set as where r n is the distance from the center of the aircraft to the nose of the aircraft.

[0151] In some embodiments, the flight control system (e.g., system 1000 in Figure 10 ) can store one or more weighting functions to determine the associated limits on the descent rate, roll rate, and / or pitch rate when the pilot requests more than one of these maneuvers.

[0152] In some embodiments, the VRS avoidance 1033 can set a limit V x_max where V x_max = (V x / V h ) V h and V x / V h correspond to the intersection point of the propeller closest to the vortex ring state boundary. In some embodiments, the VRS avoidance 1033 can determine the forward speed, turn rate, and / or yaw rate limits based on V x_max . For example, the forward speed, turn rate, and / or yaw rate can be limited to avoid exceeding V x_max .

[0153] In some embodiments, the forward speed limit can be set as V x_max . In some embodiments, the turn rate and / or yaw rate limit can be set as r 转弯 = V x_max / r w where r w is the distance from the center of the aircraft to the tip of the wing.

[0154] Figures 15A to 15L Example simulation results for determining the propeller closest to the vortex ring state and corresponding control limits are shown in accordance with embodiments of the present disclosure.

[0155] Figure 15A Example states of the aircraft propeller relative to the VRS boundary when the aircraft is in a departure transition are shown. In the shown departure transition, the aircraft is ascending and accelerating laterally into forward flight. The propeller starts in a stationary hover, where V x / V h and V z / V hThe value is close to zero. When the aircraft transitions to forward flight, the tilting propellers (e.g., Figure 2 (The tilting propeller 214) is in a lift configuration (e.g., as...) Figure 2 (as shown) to forward flight configuration (e.g., as shown) Figure 1 The transition between (as shown) and becomes less prone to experiencing vortex ring states. Lift propellers (e.g., Figure 2 The lift propeller 212 remains stationary and accelerates laterally as the aircraft accelerates and V... x / V h It becomes less likely to experience the vortex ring state as it increases.

[0156] Figure 15B This illustrates exemplary states of the aircraft propellers relative to the VRS boundary as the aircraft tumbles at different points during the departure transition. As shown, the propeller on the descent side of the aircraft will approach the VRS boundary due to the decrease in Vz / Vh, while the propeller on the ascent side of the aircraft will move away from the VRS boundary due to the increase in Vz / Vh.

[0157] Figure 15C Exemplary scenarios are shown illustrating that roll rate limits can vary and can be indicated by different propellers at different points during the departure transition. At some points during the departure transition, the outermost propellers on the descent side may limit the roll rate because they experience a maximum decrease in Vz / Vh. For example, at the start of the departure transition, the outermost EPUs 1 and 7 or 6 and 12 (depending on the roll direction) provide the maximum limit on the aircraft's roll rate. Furthermore, in some embodiments, the outermost lift propellers may limit the roll rate as the departure transition progresses. For example, as the departure transition progresses, EPUs 12 and 7 (depending on the roll direction) provide the maximum limit on the aircraft's roll rate. As shown, the limit can vary at different points during the departure transition. For example, as the aircraft transitions to a more vertical climb, the roll rate limit may become less restrictive as the airflow is pushed downwards through the propellers. In some embodiments, as described above... Figures 13A to 13C In detail, the most restrictive roll rate limits at different points during the departure transition will be used as restrictions on aircraft control.

[0158] Figure 15D This illustrates exemplary states of the aircraft propellers relative to the VRS boundary as the aircraft descends at different points during the departure transition. As shown, due to the decrease in Vz / Vh, all propellers approach the VRS boundary during descent. Figure 15E The demonstration shows that the descent rate limit can be varied and can be indicated by different propellers at different points during the departure transition. When the aircraft transitions to forward flight, the tilting propellers can transition to a forward flight configuration (e.g., as shown in the diagram). Figure 1 (As shown in the diagram) and the lifting propeller can limit the descent rate. Furthermore, as regarding...Figure 15D As described, the descent rate limit can become less restrictive as the aircraft transitions to a more vertical climb.

[0159] Figure 15F Exemplary states of the aircraft propellers relative to the VRS boundary are shown as the aircraft performs a roll maneuver at different points in the departure transition. In this example, the extrapolated propeller states do not intersect the VRS boundary, and no roll rate limit is imposed. However, under other conditions, such as when the aircraft is turning in forward flight in a manner that reduces the absolute magnitude of Vx / Vh, a roll rate limit can be imposed to ensure that the propellers of the aircraft avoid vortex ring states.

[0160] Figure 15G Exemplary states of the aircraft propellers relative to the VRS boundary are shown as the aircraft is in the arrival transition. In the arrival transition shown, the aircraft is descending while decelerating. During deceleration, the nose of the aircraft is tilted upward and the tilted propellers are behind the vertical line. After deceleration, the aircraft enters a vertical descent.

[0161] Figure 15H Exemplary states of the aircraft propellers relative to the VRS boundary are shown as the aircraft rolls at different points in the arrival transition. As described above, the propellers on the descending side of the aircraft will approach the VRS boundary, and will provide a roll rate limit for the aircraft.

[0162] Figure 151 Exemplary scenarios are shown demonstrating that the roll rate limit can vary and can be indicated by different propellers at different points in the arrival transition. The roll rate limit can be more restrictive during the arrival flight than during the departure flight because the propellers are operating at lower torque and the aircraft is descending. As shown in FIG. 18, at some points in the arrival transition, the outermost propellers on the descending side can limit the roll rate because they experience the greatest reduction in Vz / Vh. Figure 15C As shown in FIG. 18, the limit can vary at different points in the arrival transition. For example, as the aircraft transitions to a more vertical descent, the roll rate limit can become more restrictive as the airflow is pushed upward through the propellers. In some embodiments, as detailed above with respect to FIG. 17, the most restrictive roll rate limit at different points in the arrival transition will be used as the limit on aircraft control.

[0163] As shown in FIG. 18, the limit can vary at different points in the arrival transition. For example, as the aircraft transitions to a more vertical descent, the roll rate limit can become more restrictive as the airflow is pushed upward through the propellers. In some embodiments, as detailed above with respect to FIG. 17, the most restrictive roll rate limit at different points in the arrival transition will be used as the limit on aircraft control. Figures 13A to 13C As shown in FIG. 18, the limit can vary at different points in the arrival transition. For example, as the aircraft transitions to a more vertical descent, the roll rate limit can become more restrictive as the airflow is pushed upward through the propellers. In some embodiments, as detailed above with respect to FIG. 17, the most restrictive roll rate limit at different points in the arrival transition will be used as the limit on aircraft control.

[0164] Figure 15J Exemplary states of the aircraft propellers relative to the VRS boundary are shown as the aircraft descends at different points in the arrival transition. As described above with respect to FIG. 18, all of the propellers approach the VRS boundary due to the reduction in Vz / Vh. Figure 15D As shown in FIG. 18, the limit can vary at different points in the arrival transition. For example, as the aircraft transitions to a more vertical descent, the roll rate limit can become more restrictive as the airflow is pushed upward through the propellers. In some embodiments, as detailed above with respect to FIG. 17, the most restrictive roll rate limit at different points in the arrival transition will be used as the limit on aircraft control. Figure 15KIt is shown that the limits can vary and can be indicated by different propellers at different points of the approach transition. Further, as described with respect to Figure 151 the descent rate limit can become more restrictive as the aircraft transitions to a more vertical descent.

[0165] Figure 15L It is shown that exemplary states of the aircraft propellers relative to the VRS boundary when the aircraft performs a yaw maneuver at different points of the approach transition. In this example, the extrapolated propeller states do not intersect the VRS boundary, and no yaw rate limit is employed. However, under other conditions, such as when the aircraft is turning in forward flight in a manner that reduces the absolute magnitude of Vx / Vh, a yaw rate limit can be employed to ensure that the propellers of the aircraft avoid a vortex ring state.

[0166] Figure 16 It is shown a diagram of different actions that can be taken based on proximity to a vortex ring state, in accordance with embodiments of the present disclosure. In some embodiments, VRS avoidance 1033 can determine the proximity of the propeller state to one or more different warning boundaries around the vortex ring state boundary using the methods described above with respect to Figures 14A to 14G In some embodiments, VRS avoidance 1033 can determine whether the propeller state exists within one or more warning zone ranges. In some embodiments, the warning boundaries (e.g., the 1stwarning and / or 2ndwarning boundaries) can dynamically change based on different aircraft operating conditions. In some embodiments, propeller states outside of the first warning boundary can represent a safe zone for VRS avoidance (e.g., a probability of entering the VRS of approximately 0%, a probability of entering the VRS below some threshold). In some embodiments, propeller states within the first warning boundary and before the second warning boundary can contain, for example, a probability of entering the vortex ring state of approximately 0-50%. In some embodiments, propeller states within the second warning boundary and before the VRS boundary can contain, for example, a probability of entering the VRS of approximately 50-100%. In some embodiments, Figures 14A to 14G The limits set in the middle of

[0167] In some embodiments, in response to detecting that one or more propellers are in at least one of the first warning zone, the second warning zone, the flight control system can perform one or more preventative actions. The preventative actions can include generating a warning to the pilot on an output device. For example, the output device can include any suitable device configured to provide output to the pilot, such as a display, one or more lights, a touchscreen, a haptic device, a virtual / augmented reality display, or one or more speakers. In some embodiments, the warning provided by the output device can vary based on proximity to the VRS. For example, the output device can be a display showing the proximity of the propeller state to the VRS boundary and / or the warning boundary. The output device can be controlled to provide a warning (e.g., associated with the proximity of the propeller state to the VRS boundary and / or the warning boundary), such as by changing color, increasing emitted light, and / or increasing text size based on one or more propeller states being closer to the VRS boundary and / or entering one or more warning zones. Additionally or alternatively, the output device can be controlled to increase the volume and / or intensity of haptic feedback based on one or more propeller states being closer to the VRS boundary and / or entering one or more warning zones.

[0168] The preventative actions can further include controlling the aircraft to prevent the propellers from entering the VRS by modifying pilot commands and / or limiting pilot commands. As described above, controlling the aircraft based on one or more limitations can include limiting propeller torque, propeller speed, descent rate, turn rate, forward speed, yaw rate, roll rate, and / or pitch rate. In some embodiments, a warning is provided based on one or more aircraft propellers entering the first warning zone. In some embodiments, flight controls are modified (e.g., by limiting pilot commands) based on one or more aircraft propellers entering the second warning zone closer to the vortex ring state. In some embodiments, as described above, flight controls are modified to implement a breakout procedure (e.g., change the cabin tilt) based on one or more aircraft propellers entering the vortex ring state.

[0169] Additional aspects of the present disclosure can be further described via the following clauses: 1. A computer-implemented method for an aircraft, comprising: receiving a descent rate command from a pilot input device; determining a proximity of each propeller of at least two propellers to a vortex ring state; and controlling a descent rate of the aircraft to be less than the commanded descent rate when at least one propeller of the at least two propellers is within a first threshold proximity to the vortex ring state.

[0170] 2. The method of clause 1, wherein the proximity of each propeller of the at least two propellers to the vortex ring state is determined based on at least one of an airspeed of the aircraft, and a pitch angle of the propeller or a tilt angle of the propeller.

[0171] 3. The method of clause 2, wherein the proximity of each propeller of the at least two propellers to the vortex ring state is determined based on at least one of a thrust of the propeller, a torque of the propeller, a propeller speed, or a vibration of the propeller.

[0172] 4. The method of clause 1, wherein the proximity of each propeller of the at least two propellers to the vortex ring state is determined based on an airspeed of the aircraft, a pitch angle of the propeller, and a pitch of the propeller.

[0173] 5. The method of any one of clauses 1-4, wherein the proximity of each propeller of the at least two propellers to the vortex ring state is determined based on a thrust value.

[0174] 6. The method of clause 5, wherein the thrust value is a thrust provided by a corresponding propeller when the aircraft is in a hover phase.

[0175] 7. The method of clause 5 or 6, wherein the thrust value varies based on a type of the corresponding propeller.

[0176] 8. The method of any one of clauses 5-7, wherein: the at least two propellers include a lift propeller and a tilt propeller; and the thrust value of the lift propeller is different than the thrust value of the tilt propeller.

[0177] 9. The method of any one of clauses 1-8, wherein determining the proximity of each propeller of the at least two propellers to the vortex ring state includes determining a proximity of a state of the propeller to a multi-dimensional vortex ring state boundary.

[0178] 10. The method of any one of clauses 1-9, wherein controlling the descent rate includes: determining a maximum allowable descent rate; inputting the maximum allowable descent rate and a descent rate command of the pilot into a model that generates a descent rate command; and controlling one or more of the flight elements of the aircraft based on the generated descent rate command.

[0179] 11. The method of any of clauses 1-10, wherein controlling the rate of descent includes determining a maximum allowable rate of descent based on at least one of a roll of the aircraft, a pitch of the aircraft, or a forward speed of the aircraft.

[0180] 12. The method of any of clauses 1-11, further comprising: providing a warning to the pilot based on at least one of the at least two propellers being within a second threshold proximity to the vortex ring state; wherein the second threshold proximity is different than the first threshold proximity; and wherein the warning includes at least one of a display of text, a turning on of a light, a change in color of a light, an audible notification, or a haptic notification.

[0181] 13. The method of any of clauses 1-12, wherein the second threshold proximity is further from the vortex ring state than the first threshold proximity.

[0182] 14. The method of any of clauses 1-13, further comprising controlling at least one of a propeller tilt angle, an aircraft roll angle, an aircraft pitch angle, or a propeller speed based on at least one of the at least two propellers being within the threshold proximity to the vortex ring state.

[0183] 15. The method of any of clauses 1-14, further comprising detecting an airspeed of the aircraft, wherein the determining the proximity of each of the at least two propellers to the vortex ring state is performed upon determining that the airspeed is below a threshold speed.

[0184] 16. The method of any of clauses 1-15, further comprising detecting an airspeed of the aircraft, wherein the controlling the rate of descent of the aircraft to be less than the commanded rate of descent is performed upon determining that the detected airspeed is less than a threshold.

[0185] 17. The method of any of clauses 1-16, further comprising detecting whether the aircraft is receiving powered lift support, wherein the determining the proximity of each of the at least two propellers to the vortex ring state is performed upon detecting that the aircraft is receiving powered lift support.

[0186] 18. The method of any of clauses 1-17, wherein controlling the rate of descent includes controlling the aircraft based on the determined maximum allowable rate of descent.

[0187] 19. The method of clause 18, further comprising detecting a vibration of at least one of the at least two propellers, wherein the maximum allowable rate of descent is reduced based on the detected vibration exceeding a threshold vibration.

[0188] 20. The method of any one of clauses 1-19, wherein the pilot input device is at least one control device.

[0189] 21. The method of any one of clauses 1-20, further comprising: determining that at least one of the at least two propellers has entered a vortex ring state; and controlling the tilt angle of at least one of the at least two propellers based on the determination.

[0190] 22. The method of any one of clauses 1-21, further comprising: receiving an aircraft maneuver rate command from the pilot input device; determining a proximity of each of the at least two propellers to a vortex ring state; and controlling a maneuver rate of the aircraft to be less than the commanded maneuver rate based on at least one of the at least two propellers being within a threshold proximity to the vortex ring state; and wherein the maneuver rate is at least one of a yaw rate, a roll rate, or a pitch rate.

[0191] 23. The method of any one of clauses 1-22, wherein the at least two propellers include at least one propeller located on an opposite side of a fuselage of the aircraft from another propeller.

[0192] 24. The method of any one of clauses 1-23, wherein the at least two propellers include a lift propeller and a tilt propeller.

[0193] 25. The method of any one of clauses 1-24, wherein the at least two propellers include at least four propellers.

[0194] 26. A control system comprising at least one processor configured to execute instructions to cause the system to perform the method of any one of clauses 1-25.

[0195] 27. A computer-readable storage medium storing instructions that, when executed by at least one processor, cause the at least one processor to perform the method of any one of clauses 1-25.

[0196] 28. An aircraft, comprising at least one processor configured to perform the method of any of clauses 1-25.

[0197] 29. The aircraft of clause 28, further comprising the pilot input device and the at least two propellers.

[0198] 30. The aircraft of clause 29, wherein the at least two propellers comprise at least one propeller located on an opposite side of a fuselage of the aircraft from another propeller.

[0199] 31. The aircraft of clause 29 or 30, wherein the at least two propellers comprise a lift propeller and a tilt propeller.

[0200] 32. The aircraft of any of clauses 29-31, wherein the at least two propellers comprise at least four propellers.

[0201] The foregoing description has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and adaptations of the disclosure will be apparent from consideration of the specification and practice of the disclosed embodiments of the application. The features and advantages of the disclosure are apparent from the detailed specification, and thus, it is the intention that the appended claims cover all systems and methods falling within the true spirit and scope of the disclosure. As used herein, the indefinite articles "a" and "an" mean "one or more." Similarly, unless the use of a plural term is expressly clear in a given context, it does not necessarily mean plural. Unless specifically indicated otherwise, words such as "and" or "or" mean "and / or." As used herein, "based on" can include dependent on, interdependent on, related to, defined at least in part by, derived from, affected by, or responsive to, unless expressly stated otherwise. As used herein, "related to" can include comprising, denoted by, indicated by, or based on. Furthermore, as numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents can be resorted to as falling within the scope of the disclosure.

[0202] Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. The structures and circuit arrangements shown in the figures are intended to be illustrative only and are not intended to be limiting as to the specific arrangements and circuit arrangements as described and shown in the figures. The specification and examples are intended to be exemplary, with the true scope and spirit of the application being indicated by the appended claims. The foregoing description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and adaptations of the embodiments disclosed herein will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The step sequences shown in the figures are also intended to be illustrative only and are not intended to be limiting as to any particular step sequence. Thus, those skilled in the art can appreciate that these steps can be performed in different sequences while still carrying out the same methods.

Claims

1. A computer-implemented method for an aircraft, comprising: Receive descent rate command from the pilot input device; Determine the proximity of each of at least two propellers to the vortex ring state; as well as When at least one of the at least two propellers is within a first threshold of the vortex ring state, the aircraft's descent rate is controlled to be less than the commanded descent rate.

2. The method according to claim 1, The proximity of each of the at least two propellers to the vortex ring state is determined based on at least one of the aircraft's airspeed and the aircraft's pitch angle or the propeller's tilt angle.

3. The method according to claim 2, The proximity of each of the at least two propellers to the vortex ring state is determined based on at least one of the propeller thrust, the propeller torque, the propeller speed, or the propeller vibration.

4. The method of claim 1, wherein the proximity of each of the at least two propellers to the vortex ring state is determined based on the airspeed of the aircraft, the pitch angle of the aircraft, and the pitch of the propellers.

5. The method according to any one of claims 1 to 4, wherein the proximity of each of the at least two propellers to the vortex ring state is determined based on the thrust value.

6. The method of claim 5, wherein the thrust value is the thrust provided by the corresponding propeller when the aircraft is in a hovering phase.

7. The method according to claim 5 or 6, wherein the thrust value varies based on the type of the corresponding propeller.

8. The method according to any one of claims 5 to 7, wherein: The at least two propellers comprise a lift propeller and a jib propeller; and The thrust value of the lifting propeller is different from that of the tilting propeller.

9. The method according to any one of claims 1 to 8, wherein determining the proximity of each of the at least two propellers to the vortex ring state comprises determining the proximity of the propeller state to the boundary of the multidimensional vortex ring state.

10. The method according to any one of claims 1 to 9, wherein controlling the descent rate comprises: Determine the maximum allowable rate of descent; The maximum permissible descent rate and the pilot's descent rate command are input into the model that generates the descent rate command; as well as The aircraft's flight elements are controlled based on the generated descent rate command.

11. The method according to any one of claims 1 to 10, wherein controlling the descent rate comprises determining a maximum permissible descent rate based on at least one of the aircraft's roll, the aircraft's pitch, or the aircraft's forward speed.

12. The method according to any one of claims 1 to 11, further comprising: The pilot is warned based on at least one of the at least two propellers being within a second threshold of the vortex ring state. Wherein the second threshold proximity is different from the first threshold proximity; and The warning includes at least one of the following: display of text, turning on a light, changing the color of a light, an auditory notification, or a tactile notification.

13. The method according to any one of claims 1 to 12, wherein the second threshold proximity is further from the vortex ring state than the first threshold proximity.

14. The method according to any one of claims 1 to 13, further comprising controlling at least one of the following based on at least one of the at least two propellers being within the threshold proximity to the vortex ring state: propeller tilt angle, aircraft roll angle, aircraft pitch angle, or propeller speed.

15. The method according to any one of claims 1 to 14, further comprising detecting the airspeed of the aircraft, wherein determining the proximity of each of the at least two propellers to the vortex ring state is performed upon determining that the airspeed is below a threshold speed.

16. The method according to any one of claims 1 to 15, further comprising detecting the airspeed of the aircraft, wherein upon determining that the detected airspeed is less than a threshold, the step of controlling the descent rate of the aircraft to be less than the descent rate of the command is performed.

17. The method of any one of claims 1 to 16, further comprising detecting whether the aircraft is receiving powered lift support, wherein upon detecting that the aircraft is receiving powered lift support, the determination of the proximity of each of the at least two propellers to the vortex ring state is performed.

18. The method according to any one of claims 1 to 17, wherein controlling the descent rate comprises controlling the aircraft based on a determined maximum permissible descent rate.

19. The method of claim 18, further comprising detecting vibration of at least one of the at least two propellers, wherein the maximum permissible descent rate is reduced based on the detected vibration exceeding a threshold vibration.

20. The method according to any one of claims 1 to 19, wherein the pilot input device is at least one control device.

21. The method according to any one of claims 1 to 20, further comprising: Determine that at least one of the at least two propellers has entered the vortex ring state; as well as The tilt angle of at least one of the at least two propellers is controlled based on the determination.

22. The method according to any one of claims 1 to 21, further comprising: Receive aircraft maneuver rate commands from the pilot input device; Determine the proximity of each of at least two propellers to the vortex ring state; as well as Based on the fact that at least one of the at least two propellers is within a threshold proximity to the vortex ring state, the aircraft's maneuver rate is controlled to be less than the commanded maneuver rate; and The maneuvering rate is at least one of yaw rate, roll rate, or pitch rate.

23. A control system comprising at least one processor configured to execute instructions to cause the system to perform the method according to any one of claims 1 to 22.

24. A computer-readable storage medium storing instructions that, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 22.

25. An aircraft comprising at least one processor configured to perform the method according to any one of claims 1 to 22.

26. The aircraft of claim 25, further comprising: The pilot input device and the at least two propellers.

27. The aircraft of claim 26, wherein the at least two propellers include at least one propeller located on the side of the fuselage of the aircraft opposite to the other propeller.

28. The aircraft of claim 26 or 27, wherein the at least two propellers comprise a lift propeller and a jib propeller.

29. The aircraft according to any one of claims 26 to 28, wherein the at least two propellers comprise at least four propellers.

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