Systems and methods for phased control of electric propulsion unit power-down and power-up

Abstract

Aspects of the present disclosure generally relate to systems and methods for flight control of aircrafts driven by electric propulsion systems and in other types of vehicles. Some embodiments may include a control system for controlling an aircraft, comprising at least one first electric propulsion unit (EPU); at least one second EPU; and at least one processor. The at least one processor may be configured to receive a first thrust command; command, based on the received thrust command, the at least one first EPU to a first spooling stage and the at least one second EPU to a second spooling stage different from the first spooling stage; receive a second thrust command; and command, based on the received second thrust command, the at least one second EPU to the first spooling stage.

Description

PATENTAttorney Docket No. 16499.0040-00304SYSTEMS AND METHODS FORPHASED CONTROL OF ELECTRIC PROPULSION UNIT POWER-DOWN AND POWER-UPCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 730,881, titled “Systems and Methods for Phased Control Of Electric Propulsion Unit Power-Down and Power-Up,” filed December 11, 2024, the contents of which are incorporated herein in their entirety for all purposes.TECHNICAL FIELD

[0002] This disclosure relates generally to powered aerial vehicles. More particularly, and without limitation, the present disclosure relates to innovations in aircrafts driven by electric propulsion systems. Certain aspects of the present disclosure generally relate to systems and methods for flight control of aircrafts driven by electric propulsion systems and in other types of vehicles, as well as flight control of aircrafts in flight simulators and video games. Other aspects of the present disclosure generally relate to improvements in flight control systems and methods that provide particular advantages in aerial vehicles and may be used in other types of vehicles.BACKGROUND

[0003] The inventors here have recognized several problems that may be associated with flight control of aircraft, including a tilt-rotor aircraft that uses electrical or hybrid-electric propulsion systems (hereinafter referred to as electric propulsion units or “EPUs”).

[0004] During operation of an aircraft, it may be desirable or necessary to control EPUs in a safe and stable manner while the aircraft is reducing or gaining speed and / or transitioning between stages of flight. Simply controlling EPU thrust based solely on pilot commands, however, particularly in aircraft with multiple EPUs, can lead to EPUs operating in undesirable ranges for periods of time. The undesirable ranges may be correlated with increased aircraft turbulence, instability, vibration, noise, or control difficulties. Accordingly, there is a need to reduce the operation of EPUs in these undesirable ranges while still providing smooth speed changes and phase-of-flight changes for the aircraft.PATENTAttorney Docket No. 16499.0040-00304

[0005] Therefore, there is a need for improved systems and methods for certain aircraft to control phased shutdown of aircraft components.SUMMARY

[0006] The present disclosure relates generally to flight control of electric aircraft and other powered aerial vehicles. More particularly, and without limitation, the present disclosure relates to innovations in tilt-rotor aircraft that use electrical propulsion systems. For example, certain aspects of the present disclosure relate to a control system for controlling a phased shut down of an aircraft.

[0007] Accordingly, it may be desirable for an aircraft to power down or shut down individual or groups of EPUs. Moreover, it may further be desirable or necessary to power on and power up individual or groups of EPUs while the aircraft is in flight. That is, an individual EPU or a group of EPUs may be powered on during a first portion of a flight and subsequently powered down (i.e., shutdown) during a second portion of the flight. Likewise, an individual EPU or a group of EPUs may be powered off during a first portion of a flight and subsequently powered on during a second portion of the flight.

[0008] Some EPUs may have a rotations-per-minute (RPM) avoidance range. An RPM avoidance range may be a range or band of RPM values that may be more likely to cause vibration and / or instability of the EPU or other aircraft components. Operating an EPU or a group of EPUs at an RPM within an RPM avoidance range may induce vibrations and / or instability of the aircraft, thereby affecting aircraft safety, passenger comfort, and structural integrity. For example, when an individual or a group of EPUs are shut down or powered on while the aircraft is in flight, the individual or the group of EPUs may be forced to operate in the RPM avoidance range.

[0009] In accordance with some embodiments, a computer-implemented method for controlling an aircraft is provided. The method may comprise: receiving a first thrust command; commanding; based on the received first thrust command, at least one first electronic propulsion unit, EPU, to a first spooling stage and at least one second EPU to a second spooling stage different from the first spooling stage; receiving a second thrust command; and commanding, based on the received second thrust command, the at least one second EPU to the first spooling stage.

[0010] In accordance with some embodiments, commanding at least one EPU to a first spooling stage and at least one second EPU to a different spooling stage based on a receivedPATENTAttorney Docket No. 16499.0040-00304 thrust command, as described herein, may provide improved aircraft stability during thrust transitions. By staggering spooling stages in response to thrust commands and subsequently transitioning EPUs between spooling stages, the system may reduce time spent in RPM avoidance ranges and dynamically offset thrust changes among EPUs.

[0011] In accordance with some embodiments there is provided a control system for controlling an aircraft. The control system may comprise: at least one first electric propulsion unit, EPU; at least one second EPU; and at least one processor configured to perform the aforementioned method for controlling an aircraft.

[0012] Similarly, in accordance with some embodiments there is provided a computer- readable medium storing instructions that are executable by at least one processor to perform the aforementioned method for controlling an aircraft.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Fig. 1 shows an exemplary VTOL aircraft, consistent with disclosed embodiments.

[0014] Fig. 2 shows an exemplary VTOL aircraft, consistent with disclosed embodiments.

[0015] Fig. 3 shows an exemplary top plan view of a VTOL aircraft, consistent with disclosed embodiments.

[0016] Fig. 4 illustrates exemplary propeller rotation of a VTOL aircraft, consistent with disclosed embodiments.

[0017] Fig. 5 shows exemplary power connections in a VTOL aircraft, consistent with disclosed embodiments.

[0018] Fig. 6 shows an exemplary architecture of an electric propulsion unit, consistent with disclosed embodiments.

[0019] Fig. 7 shows an exemplary top plan view of a VTOL aircraft, consistent with disclosed embodiments.

[0020] Fig. 8 shows an exemplary flight control signaling architecture, consistent with disclosed embodiments.

[0021] Figs. 9A-9F illustrate exemplary top plan views of VTOL aircraft, consistent with disclosed embodiments.

[0022] Fig. 10 illustrates a functional block diagram of an exemplary control system of an electric VTOL aircraft, consistent with disclosed embodiments.PATENTAttorney Docket No. 16499.0040-00304

[0023] Fig. 11 illustrates a functional block diagram of an exemplary phased shutdown control logic concept of an electric VTOL aircraft, consistent with disclosed embodiments.

[0024] Fig. 12 illustrates a graph of an exemplary progression of spooling-down EPUs through an RPM avoidance range, consistent with disclosed embodiments.

[0025] Fig. 13 illustrates a graph of an exemplary progression of spooling-down EPUs through a plurality of RPM avoidance ranges in a first sequence, consistent with disclosed embodiments.

[0026] Fig. 14 illustrates a graph of an exemplary progression of spooling-down EPUs through a plurality of RPM avoidance ranges in a second sequence, consistent with disclosed embodiments.

[0027] Fig. 15 illustrates a graph of an exemplary spool-down override, consistent with disclosed embodiments.

[0028] Fig. 16 illustrates a graph of an exemplary progression of spooling-up EPUs through an RPM avoidance range, consistent with disclosed embodiments.DETAILED DESCRIPTION

[0029] The present disclosure addresses systems, components, and techniques primarily for use in an aircraft. The aircraft may be an aircraft with a pilot, an aircraft without a pilot (e.g., an unmanned aerial vehicle (UAV)), a drone, a helicopter, and / or an airplane. An aircraft includes a physical body and one or more components (e.g., a wing, a tail, a propeller) configured to allow the aircraft to fly. The aircraft may include any configuration that includes at least one propeller. In some embodiments, the aircraft is driven (e.g., provided with thrust) by one or more electric propulsion systems (hereinafter referred to as electric propulsion units or “EPUs” in the plural, and also electric propulsion unit or “EPU” in the singular), which may include at least one engine, at least one rotor, at least one propeller, or any combination thereof. A “lifter” or “lifter EPU may be considered an EPU with a predominant function of providing thrust for lift, rather than forward propulsion. Additionally or alternatively, a “lifter” or “lifter EPU” may be an EPU that is not configured to tilt independently of the aircraft. A “tilter” or “tilter EPU” may be considered an EPU with a predominant function of providing thrust for forward propulsion, rather than lift. Additionally or alternatively, a “tilter” or “tilter EPU” may be an EPU that is configured to tilt independently of the aircraft, such as by using an actuator or any electrically activated tilting mechanism. The aircraft may be fully electric, hybrid, orPATENTAttorney Docket No. 16499.0040-00304 gas powered. For example, in some embodiments, the aircraft is a tilt-rotor aircraft configured for frequent (e.g., over 50 flights per work day), short-duration flights (e.g., less than 100 miles per flight) over, into, and out of densely populated regions. The aircraft may be configured to carry 4-6 passengers or commuters who have an expectation of a comfortable experience with low noise and low vibration. Accordingly, it is desirable to control the shut down of propellers in a phased and / or staggered approach to improve aircraft performance (e.g., reduce vibration and / or increase safety, stability, ride comfort, and / or structural integrity). It should be noted that while terms such as “shut down,” “powered-off,” “powered off,” and variations thereof are used herein, they do not necessarily correspond to a state of zero power or voltage. Instead, they may correspond to a power, voltage, and / or thrust state that is below a predetermined threshold (e.g., where an EPU provides little, negligible, or no thrust, such as an idle state). Similarly, terms such as “powered-on” and “powered on,” and variations thereof may correspond to a state of power, thrust, or voltage that exceeds a predetermined threshold (e.g., exceeds a non-zero threshold, is in a non-idle state).

[0030] Disclosed embodiments provide new and improved configurations of aircraft components, some of which are not observed in conventional aircraft, and / or identified design criteria for components that differ from those of conventional aircraft. Such alternate configurations and design criteria, in combination addressing drawbacks and challenges with conventional components, yielded the embodiments disclosed herein for various configurations and designs of components for an aircraft (e.g., electric aircraft or hybrid-electric aircraft) driven by a propulsion system.

[0031] In some embodiments, the aircraft driven by a propulsion system of the present disclosure may be designed to be capable of both vertical and conventional takeoff and landing, with a distributed propulsion system enabling vertical flight, horizontal and lateral flight, and transition (e.g., transitioning between vertical flight and horizontal flight). The aircraft may generate thrust by supplying high voltage electrical power to a plurality of engines of the distributed propulsion system, which may include components to convert the high voltage electrical power into mechanical shaft power to rotate a propeller.

[0032] Embodiments may include an electric engine (e.g., motor) connected to an onboard electrical power source, which may include a device capable of storing energy such as a battery or capacitor, and may optionally include one or more systems for harnessing or generating electricity such as a fuel powered generator or solar panel array. In somePATENTAttorney Docket No. 16499.0040-00304 embodiments, the aircraft may comprise a hybrid aircraft configured to use at least one of an electric-based energy source or a fuel-based energy source to power the distributed propulsion system. In some embodiments, the aircraft may be powered by one or more batteries, internal combustion engines (ICE), generators, turbine engines, or ducted fans.

[0033] The engines may be mounted directly to the wing, or mounted to one or more booms attached to the wing. The amount of thrust each engine generates may be governed by a torque command from a Flight Control System (FCS) over a digital communication interface to each engine. Embodiments may include forward engines (and associated propellers) that are capable of altering their orientation, or tilt.

[0034] The engines may rotate the propellers in a clockwise or counterclockwise direction. In some embodiments, the difference in propeller rotation direction may be achieved using the direction of engine rotation. In other embodiments, the engines may all rotate in the same direction, and gearing may be used to achieve different propeller rotation directions.

[0035] In some embodiments, an aircraft may possess quantities of engines in various combinations of forward and aft engine configurations. A forward engine may be considered an engine that is positioned predominantly towards the leading edge of a wing. An aft engine may be considered an engine that is positioned predominantly towards the trailing edge of a wing. For example, an aircraft may possess six forward and six aft engines, five forward and five aft engines, four forward and four aft engines, three forward and three aft engines, two forward and two aft engines, or any other combination of forward and aft engines, including embodiments where the number of forward engines and aft engines are not equivalent.

[0036] In some embodiments, for a vertical takeoff and landing (VTOL) mission, the forward and aft engines may provide vertical thrust during takeoff and landing. During flight phases where the aircraft is moving forward, the forward engines may provide horizontal thrust, while the propellers of the aft engines may be stowed at a fixed position in order to minimize drag. The aft engines may be actively stowed with position monitoring.

[0037] Transition from vertical flight to horizontal flight and vice-versa may be accomplished via the tilt propeller subsystem. The tilt propeller subsystem may redirect thrust between a primarily vertical direction during vertical flight phase (e.g., hover-phase) to a horizontal or near-horizontal direction during a forward-flight cruising phase, based on a tilt of one or more propellers (e.g., determining directionality of one or more propellers). A variable pitch mechanism may change the forward engine’s propeller-hub assembly blade collectivePATENTAttorney Docket No. 16499.0040-00304 angles for operation during phases of flight, such as a hover-phase, transition phase, and cruisephase. Vertical lift may be thrust in a primarily vertical direction (e.g., during a hover-phase). Horizontal thrust may be thrust in a primarily horizontal direction (e.g., during a cruise-phase).

[0038] In some embodiments, a “phase of flight” or “flight phase,” (e.g., hover, cruise, forward flight / wing-borne flight, takeoff, landing, transition) may be defined by a combination flight conditions (e.g., a combination of flight conditions within particular ranges), which may include one or more of an airspeed, ground speed altitude, pitch angle (e.g., of the aircraft), tilt angle (e.g., of one or more propellers), roll angle, rotation speed (e.g., of one or more propellers), torque value, pilot command, or any other value indicating a current or requested (e.g., commanded) state of at least part of the aircraft. A “flight state” may include a flight phase and / or forces or environmental factors experienced by the aircraft, such as at least one of weather conditions, air density, natural wind movements, humidity, a proximity of at least one component to a vortex ring state, etc. Additionally or alternatively, an “aircraft state” may include one or more aircraft operational capabilities, which may include, or be based on, states of one or more aircraft subsystems. For example, an aircraft state may include an energy state, range capability, maneuver capability, thrust capability, speed capability, etc.

[0039] “Vertical flight,” a “hover” phase of flight, or a thrust-borne phase of flight may be considered any phase of flight where lift for an aircraft is provided predominantly by engine- driven lift devices or engine thrust, such as by one or more engines (e.g., EPUs), rather than one or more wings. “Horizontal flight, a “cruise” phase of flight, or a wing-borne phase of flight may be considered any phase of flight where lift for an aircraft is provided predominantly by one or more nonrotating airfoil surfaces (e.g., wings), rather than by any engine (e.g., EPU). A “transition” phase of flight, or semi-thrust-bome phase of flight may be considered any phase of flight where an aircraft is using a combination of thrust-borne and wing-borne phases of flight (e.g., where both forms of lift are used to support the aircraft) and / or where an aircraft is shifting from vertical flight to horizonal flight, or vice versa.

[0040] In some embodiments, in a conventional takeoff and landing (CTOL) mission, the forward engines may provide horizontal thrust for wing-borne take-off, cruise, and landing, and the wings may provide vertical lift. In some embodiments, the aft engines may not be used for generating thrust during a CTOL mission and the aft propellers may be stowed in place. In other embodiments, the aft engines may be used at reduced power to shorten the length of the CTOL takeoff or landing.PATENTAttorney Docket No. 16499.0040-00304

[0041] As detailed herein, embodiments of the present disclosure may include a controller for phased shutdown of electric propulsion units to minimize vibration and maximize stability of an aircraft. Control of individual EPUs during flight is critical to safely operate a VTOL aircraft. Several factors may affect a need to toggle individual EPUs from a powered- on status to a powered-off status and vice versa (i.e., from a powered-off status to a powered- on status). For example, one or more lift propellers may be intentionally shut down during flight (i.e., placing the lift propellers in a stowed configuration) as the VTOL aircraft transitions from a vertical flight phase (e.g., hover-phase) to a forward-flight phase (e.g., cruise phase). The one or more lift propellers may be intentionally shut down to allow the VTOL aircraft to safely achieve increased forward velocities during cruise phase. In another example, a failure of an EPU on one side of an aircraft may require a shutdown of a corresponding EPU on the opposite side of the aircraft to maintain aircraft stability by operating an equal number of EPUs on each side of the aircraft. The ability to transition an EPU from a powered-on status to a powered-off status (and vice versa) during flight is critical to the safety and stability of the aircraft.

[0042] The embodiments of the present disclosure may include a control system to control the spooling-up and / or spooling-down of an individual EPU or a group of EPUs during flight. In some embodiments, a control system may include an individual controller or a plurality of controllers. In some embodiments, a control system may include an individual controller configured to control at least one EPU. In some embodiments, a control system may include a plurality of controllers configured to control at least one EPU.

[0043] The embodiments of the present disclosure may include a control system configured to control a total lifter thrust output of a group of EPUs. In some embodiments, a control system may include control logic configured to monitor the total lifter thrust demand relative to a current lifter operating condition. In some embodiments, a current lifter operating condition can be received from one or more sensors positioned on the aircraft. In some embodiments, an offline allocator monitors a total lifter thrust demand desired for the sum of all EPUs. In some embodiments, a total lifter thrust demand can be a weighted pseudoinverse. In some embodiments, a total lifter thrust demand can be a total lifter thrust already computed in an outer loop allocation.

[0044] The embodiments of the present disclosure may include a control system configured to control a total lifter thrust output of a group of EPUs based on a current lifterPATENTAttorney Docket No. 16499.0040-00304 thrust operating condition. In some embodiments, a control system configured to control a total lifter thrust output of a group of EPUs based on an RPM avoidance range or band. In some embodiments, a control system may be configured to control a total lifter thrust output of a group of EPUs based on a combination of a current lifter thrust operating condition and an RPM avoidance range.

[0045] The embodiments of the present disclosure may include a control system configured to control a lifter thrust output of an individual EPU. Like the control of a group of EPUs, the control of an individual EPU may also be configured to control a total lifter thrust output of a group of EPUs based on a combination of a current lifter thrust operating condition and an RPM avoidance range. In some embodiments, a current lifter thrust operating condition may include either a current lifter thrust operating condition of an individual EPU or a current lifter thrust operating condition of a plurality of EPUs (i.e., all of the EPUs of an aircraft).

[0046] In some embodiments, a lifter thrust output of an individual EPU or an aggregate lifter thrust output of a plurality of EPUs may be measured by at least one sensor positioned on the aircraft. In some embodiments, an RPM avoidance range may be determined by at least one sensor positioned on the aircraft.

[0047] In some embodiments, a lifter thrust output may include a lifter thrust output of an individual EPU. In some embodiments, a lifter thrust output may include a lifter thrust output of a plurality of EPUs.

[0048] Although some embodiments of the present disclosure are discussed with respect to a lifter thrust output of an individual EPU or a group of EPUs, the disclosure is not limited to this configuration. In some embodiments, the present disclosure may include a control system configured to control a total thrust output of an individual EPU or a group of EPUs. In some embodiments, a total thrust output may include a total thrust output from a plurality of lifter EPUs, a plurality of tilter EPUs (e.g., tiltable EPUs), or a combination of EPUs types. In some embodiments, a control system may include control logic configured to monitor the total thrust demand relative to a current operating condition. In some embodiments, a current operating condition can be received from one or more sensors positioned on the aircraft. In some embodiments, an offline allocator monitors a total thrust demand desired for the sum of all EPUs. In some embodiments, a total thrust demand can be a weighted pseudoinverse. In some embodiments, a total thrust demand can be a total lifter thrust already computed in an outer loop allocation.PATENTAttorney Docket No. 16499.0040-00304

[0049] In some embodiments, a total thrust output or a total thrust demand may include a total thrust output or a total thrust demand of a plurality of tilter EPUs, a plurality of lifter EPUs, and / or any combination of tilter and lifter EPUs.

[0050] In some embodiments, an RPM avoidance range is a range or band of RPM values that may be more likely to cause vibration and / or instability of the EPU or other aircraft components. Operating an EPU or a group of EPUs at an RPM within an RPM avoidance range may induce vibrations and / or instability of the aircraft, thereby affecting aircraft safety, passenger comfort, and structural integrity. For example, when an individual or a group of EPUs are shut down or powered on while the aircraft is in flight, the individual or the group of EPUs may be forced to operate in the RPM avoidance range.

[0051] In some embodiments, an RPM avoidance range may be an RPM avoidance range that is specific to an individual EPU. In some embodiments, an RPM avoidance range for each individual EPU may be the same as the other EPUs of the aircraft. In some embodiments, an RPM avoidance range for each individual EPU may be different for each EPU depending on a characteristic of the EPU. In some embodiments, an RPM avoidance range may be predetermined or static. In some embodiments, an RPM avoidance range may be dynamic based on a condition of the EPU, a condition of the aircraft, an air speed, an environmental condition, or the like. As used herein, an RPM avoidance range may also be referred to as an RPM keep-out range, an RPM keep-out zone, or an RPM avoidance zone.

[0052] In some embodiments, multiple RPM avoidance ranges may be defined. In some embodiments, any number of RPM avoidance ranges may be defined, such as one RPM avoidance range, two RPM avoidance ranges, three RPM avoidance ranges, and so on. For example, in one embodiment including a first RPM avoidance range and a second RPM avoidance range, the first RPM avoidance range may be higher (e.g., include higher RPM values) than the second RPM avoidance range. Even though some embodiments described herein may refer to a single RPM avoidance range, it is appreciated that using a plurality of RPM avoidance ranges is a possible alternative approach to using a single range.

[0053] In some embodiments, the number of RPM avoidance ranges, as well as their respective range values, may vary based on any one or any combination of operational goals, EPU conditions, aircraft characteristics or configurations, air speed, environmental conditions, or the like. In some embodiments, RPM avoidance ranges may be added, removed, or adjustedPATENTAttorney Docket No. 16499.0040-00304 dynamically to optimize performance (e.g., automatically during flight and / or during pre-flight configuration).

[0054] In some embodiments, an RPM avoidance range may be based on data derived from one or more passenger seating sensors positioned throughout the aircraft cabin, such as accelerometer or other vibration sensors positioned on or within sensing proximity of passenger seating. In some embodiments, one or more passenger seating sensors may provide vibration or acceleration measurements used to define operational limits (such as RPM avoidance ranges) for improved ride quality.

[0055] In some embodiments, an RPM avoidance range may be dynamically dependent based on the physical characteristics of an individual EPU or a group of EPUs. In some embodiments, the individual EPU or the group of EPUs may be any type of EPU, including a lifter, a tilter, and the like. In some embodiments, an RPM avoidance range may be dynamically dependent based on a size of an EPU. In some embodiments, an RPM avoidance range may be dynamically dependent based on a placement, a location, a position, or an orientation of an EPU. In some embodiments, an RPM avoidance range may be dynamically dependent based on a mass of an EPU.

[0056] In some embodiments, an RPM avoidance range may be based on at least one measured, calculated, or predicted mast moment associated with at least one EPU. In some embodiments, a mast moment may be determined based on past or current data (e.g., vibration data, accelerometer data, etc.) or based on predetermined values derived from testing or physical modeling. In some embodiments, an RPM avoidance range may be static (e.g., hard- coded). In some embodiments, an RPM avoidance range may be dynamically adjusted based on mast moment data trends or patterns.

[0057] In some embodiments, an RPM avoidance range may be dependent on noise, controllability, a predetermined flight plan, an as-flown flight plan, and the like.

[0058] In some embodiments, an RPM avoidance range may include an RPM maximum and an RPM minimum. In some embodiments, an RPM maximum and an RPM minimum may dynamically vary.

[0059] In some embodiments, an RPM avoidance range, a desired spooling behavior, and / or an idle speed may be determined based on an upper and a lower rotor torque limit sent to an online allocator. In some embodiments, an aerodynamic torque maximum limit can be determined based on at least one tilter powertrain limitation. In some embodiments, anPATENTAttorney Docket No. 16499.0040-00304 aerodynamic torque minimum limit can be determined based on at least one tilter powertrain limitation.

[0060] The embodiments of the present disclosure may include a control system configured to control an EPU or a group of EPUs based on one or more corresponding RPM avoidance ranges. In some embodiments, a control system may control an individual EPU to spool-down or spool-up more rapidly. Spooling-down corresponds to the process of transitioning an EPU from a powered-on status to a powered-off status. Spooling-up corresponds to the process of transitioning an EPU from a powered-off status to a powered-on status. Although spooling-up and spooling-down are described in reference to an EPU that is transitioning from a fully powered-off status to a fully powered-on status, spooling-up and spooling-down is not limited to this description. For example, spooling-up may also correspond to the process of transitioning an EPU from a low power status (i.e., low RPM values and low thrust output) to a high power status (i.e., high RPM values and high thrust output). Likewise, spooling-down may also correspond to the process of transitioning an EPU from a high power status (i.e., high RPM values and high thrust output) to a low power status (i.e., low RPM values and low thrust output).

[0061] The embodiments of the present disclosure may include a control system configured to control an EPU or a group of EPUs based on one or more corresponding RPM avoidance ranges. In some embodiments, a control system may be configured to reduce or minimize an amount of time that an EPU operates in its RPM avoidance range.

[0062] The embodiments of the present disclosure may include a control system configured to control a total lifter thrust output of a group of EPUs based on combination of a current lifter thrust operating condition or an RPM avoidance range. In some embodiments, a control system may dynamically control a lifter thrust output by each individual EPU of a plurality of EPUs. In some embodiments, a control system may dynamically control a lifter thrust output of an individual EPU to compensate for or at least partially offset an adjustment of another individual EPU. In some embodiments, a control system may dynamically control a lifter thrust output of a plurality of EPUs to compensate for or at least partially offset an adjustment of another plurality of EPUs. In some embodiments, a control system may dynamically control a tilter thrust output by each individual tilter EPU of a plurality of tilter EPUs.PATENTAttorney Docket No. 16499.0040-00304

[0063] In some embodiments, a control system may be configured to control an individual EPU, a pair of EPUs, or a group of EPUs. In some embodiments, a control system may dynamically vary an individual EPU, a pair of EPUs, or a group of EPUs to compensate for or at least partially offset a dynamic adjustment of another individual EPU, another paid of EPUs, or another group of EPUs.

[0064] The embodiments of the present disclosure may include a control system that may be configured to control the transition of an aircraft from a hover-phase to a cruise-phase. In some embodiments, a transition from a hover-phase to a cruise-phase may include spoolingdown one or more of the EPUs. In some embodiments, spooling-down may correspond to the process of transitioning an EPU from a powered-on status to a powered-off status.

[0065] In some embodiments, a transition from a hover-phase to a cruise-phase may include spooling-down one or more pairs of EPUs. In some embodiments, one or more pairs of EPUs may be spooled-down rapidly to reduce or minimize the amount of time spent in the avoidance range. In some embodiments, a rapid spool-down of one or more pairs of EPUs may cause a drastic change in the total thrust output by the plurality of EPUs (i.e., the total thrust output for the aircraft). In some embodiments, one or more pairs of EPUs may be dynamically varied to account for, compensate for, or at least partially offset the rapid spool-down of a different one or more pairs of EPUs. For example, commanding a second EPU to a second spooling stage may at least partially offset a reduction in total aircraft thrust caused by the command of a first EPU to a first spooling stage. Likewise, commanding a third EPU to the second spooling stage may at least partially offset a reduction in total aircraft thrust caused by the command of the second EPU to the first spooling stage.

[0066] The embodiments of the present disclosure may include a control system that may be configured to control the transition of an aircraft from a cruise-phase to a hover-phase. In some embodiments, a transition from a cruise-phase to a hover-phase may include spooling- up one or more of the EPUs. In some embodiments, spooling-up may correspond to the process of transitioning an EPU from a powered-off status to a powered-on status.

[0067] In some embodiments, a transition from a cruise-phase to a hover-phase may include spooling-up one or more pairs of EPUs. In some embodiments, one or more pairs of EPUs may be spooled-up rapidly to reduce or minimize the amount of time spent in the avoidance range. In some embodiments, a rapid spool-up of one or more pairs of EPUs may cause a drastic change in the total thrust output by the plurality of EPUs (i.e., the total thrustPATENTAttorney Docket No. 16499.0040-00304 output for the aircraft). In some embodiments, one or more pairs of EPUs may be dynamically varied to account for, compensate for, or at least partially offset the rapid spool -up of a different one or more pairs of EPUs. For example, commanding a second EPU to a first spooling stage may at least partially offset an increase in total aircraft thrust caused by the command of a first EPU to a second spooling stage. Likewise, commanding a third EPU to the first spooling stage may at least partially offset an increase in total aircraft thrust caused by the command of the second EPU to the second spooling stage.

[0068] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the subject matter recited in the appended claims.

[0069] Fig. 1 is an illustration of a perspective view of an exemplary VTOL aircraft, consistent with disclosed embodiments. Fig- 2 is another illustration of a perspective view of an exemplary VTOL aircraft in an alternative configuration, consistent with embodiments of the present disclosure. Figs. 1 and 2 illustrate a VTOL aircraft 100, 200 in a cruise configuration and a vertical take-off, landing and hover configuration (also referred to herein as a “lift” configuration), respectively, consistent with embodiments of the present disclosure. Elements corresponding to Figs. 1 and 2 may possess like numerals and refer to similar elements of the aircrafts 100, 200. The aircraft 100, 200 may include a fuselage 102, 202, wings 104, 204 mounted to the fuselage 102, 202 and one or more rear stabilizers 106, 206 mounted to the rear of the fuselage 102, 202. A plurality of lift propellers 112, 212 may be mounted to wings 104, 204 and may be configured to provide lift for vertical take-off, landing and hover. A plurality of tilt propellers 114, 214 may be mounted to wings 104, 204 and may be tiltable (e.g., configured to tilt or alter orientation) between the lift configuration in which they provide a portion of the lift required for vertical take-off, landing and hovering, as shown in Fig. 2, and the cruise configuration in which they provide forward thrust to aircraft 100 for horizontal flight, as shown in Fig. 1. As used herein, a tilt propeller lift configuration refers to any tilt propeller orientation in which the tilt propeller thrust is providing primarily lift to the aircraftPATENTAttorney Docket No. 16499.0040-00304 and tilt propeller cruise configuration refers to any tilt propeller orientation in which the tilt propeller thrust is providing primarily forward thrust to the aircraft.

[0070] In some embodiments, lift propellers 112, 212 may be configured for providing lift only, with all horizontal propulsion being provided by the tilt propellers. For example, lift propellers 112, 212 may be configured with fixed positions and may only generate thrust during take-off, landing and hover phases of flight. Meanwhile, tilt propellers 114, 214 may be tilted upward into a lift configuration in which thrust from propellers 114, 214 is directed downward to provide additional lift.

[0071] For forward flight, tilt propellers 114, 214 may tilt from their lift configurations to their cruise configurations. In other words, the orientation of tilt propellers 114, 214 may be varied from an orientation in which the tilt propeller thrust is directed downward (to provide lift during vertical take-off, landing and hover) to an orientation in which the tilt propeller thrust is directed rearward (to provide forward thrust to aircraft 100, 200). The tilt propellers assembly for a particular electric engine may tilt about an axis of rotation defined by a mounting point connecting the boom and the electric engine. When the aircraft 100, 200 is in full forward flight, lift may be provided entirely by wings 104, 204. Meanwhile, in the cruise configuration, lift propellers 112, 212 may be shut off. The blades 120, 220 of lift propellers 112, 212 may be held in low-drag positions for aircraft cruising. In some embodiments, lift propellers 112, 212 may each have two blades 120, 220 that may be locked, for example while the aircraft is cruising, in minimum drag positions in which one blade is directly in front of the other blade as illustrated in Fig. 1. In some embodiments, lift propellers 112, 212 have more than two blades. In some embodiments, tilt propellers 114, 214 may include more blades 116, 216 than lift propellers 112, 212. For example, as illustrated in Figs. 1 and 2, lift propellers 112, 212 may each include, e.g., two blades, whereas and tilt propellers 114, 214 may each include more blades, such as the five blades shown. In some embodiments, each of the tilt propellers 114, 214 may have 2 to 5 blades, and possibly more depending on the design considerations and requirements of the aircraft.

[0072] In some embodiments, the aircraft may include a single wing 104, 204 on each side of fuselage 102, 202 (or a single wing that extends across the entire aircraft). At least a portion of lift propellers 112, 212 may be located rearward of wings 104, 204 (e.g., rotation point of propeller is behind a wing from a bird’ s eye view) and at least a portion of tilt propellers 114, 214 may be located forward of wings 104, 204 (e.g., rotation point of propeller is in frontPATENTAttorney Docket No. 16499.0040-00304 of a wing from a bird’s eye view). In some embodiments, all of lift propellers 112, 212 may be located rearward of wings 104, 204 and all of tilt propellers 114, 214 may be located forward of wings 104, 204. According to some embodiments, all lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to the wings — e.g., no lift propellers or tilt propellers may be mounted to the fuselage. In some embodiments, lift propellers 112, 212 may be all located rearwardly of wings 104, 204 and tilt propellers 114, 214 may be all located forward of wings 104, 204. According to some embodiments, all lift propellers 112, 212 and tilt propellers 114, 214 may be positioned inwardly of the ends of the wing 104, 204.

[0073] In some embodiments, lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to wings 104, 204 by booms 122, 222. Booms 122, 222 may be mounted beneath wings 104, 204, on top of the wings, and / or may be integrated into the wing profile. In some embodiments, lift propellers 112, 212 and tilt propellers 114, 214 may be mounted directly to wings 104, 204. In some embodiments, one lift propeller 112, 212 and one tilt propeller 114, 214 may be mounted to each boom 122, 222. Lift propeller 112, 212 may be mounted at a rear end of boom 122, 222 and tilt propeller 114, 214 may be mounted at a front end of boom 122, 222. In some embodiments, lift propeller 112, 212 may be mounted in a fixed position on boom 122, 222. In some embodiments, tilt propeller 114, 214 may mounted to a front end of boom 122, 222 via a hinge. Tilt propeller 114, 214 may be mounted to boom 122, 222 such that tilt propeller 114, 214 is aligned with the body of boom 122, 222 when in its cruise configuration, forming a continuous extension of the front end of boom 122, 222 that minimizes drag for forward flight.

[0074] In some embodiments, aircraft 100, 200 may include, e.g., one wing on each side of fuselage 102, 202 or a single wing that extends across the aircraft. According to some embodiments, the at least one wing 104, 204 is a high wing mounted to an upper side of fuselage 102, 202. According to some embodiments, the wings include control surfaces, such as flaps, ailerons, and / or flaperons (e.g., configured to perform functions of both flaps and ailerons). According to some embodiments, wings 104, 204 may have a profile that reduces drag during forward flight. In some embodiments, the wing tip profile may be curved and / or tapered to minimize drag.

[0075] In some embodiments, 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 wing(s) may have any suitable design for providing lift, directionality, stability, and / or anyPATENTAttorney Docket No. 16499.0040-00304 other characteristic beneficial for aircraft. In some embodiments, the wings have a tapering leading edge.

[0076] In some embodiments, lift propellers 112, 212 or tilt propellers 114, 214 may be canted relative to at least one other lift propeller 112, 212 or tilt propeller 114, 214, where canting refers to a relative orientation of the rotational axis of the lift propeller / tilt propeller about a line that is parallel to the forward-rearward direction, analogous to the roll degree of freedom of the aircraft.

[0077] In some embodiments, one or more lift propellers 112, 212 and / or tilt propellers 114, 214 may canted relative to a cabin of the aircraft, such that the rotational axis of the propeller in a 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 Fig. 9E below, and some or all of the propellers are canted away from the cabin.

[0078] Fig. 3 is an illustration of a top plan view of an exemplary VTOL aircraft, consistent with embodiments of the present disclosure. Aircraft 300 shown in the figure may be a top plan view of the aircraft 100, 200 shown in Figs. 1 and 2, respectively. As discussed herein, an aircraft 300 may include twelve electric propulsion systems distributed across the aircraft 300. In some embodiments, a distribution of electric propulsion systems may include six forward electric propulsion systems 314 and six aft electric propulsion systems 312 mounted on booms forward and aft of the main wings 304 of the aircraft 300. In some embodiments, forward electric propulsion systems may be mounted to wings 304 by booms 322. In some embodiments, aft electric propulsion systems may be mounted to wings 304 by booms 324. In some embodiments, a length of the rear end of the boom 324 from the wing 304 to a lift propeller (part of electric propulsion system 312) may comprise a similar rear end of the boom 324 length across the numerous rear ends of the booms. In some embodiments, the length of the rear ends of the booms may vary, for example, across the six rear ends of the booms. Further, Fig. 3 depicts an exemplary embodiment of a VTOL aircraft 300 with forward propellers (part of electric propulsion system 314) in a horizontal orientation for horizontal flight and aft propeller blades 320 in a stowed position for a forward phase of flight.

[0079] Fig. 4 is a schematic diagram illustrating exemplary propeller rotation of a VTOL aircraft, consistent with disclosed embodiments. Aircraft 400 shown in the figure may be a top plan view of the aircraft 100, 200, and 300 shown in Figs. 1, 2, and 3, respectively. An aircraft 400 may include six forward electric propulsion systems with three of the forwardPATENTAttorney Docket No. 16499.0040-00304 electric propulsion systems being of CW type 424 and the remaining three forward electric propulsion systems being of CCW type 426. In some embodiments, three aft electric propulsion systems may be of CCW type 428 with the remaining three aft electric propulsion systems being of CW type 430. Some embodiments may include an aircraft 400 possessing four forward electric propulsion systems and four aft electric propulsion systems, each with two CW types and two CCW types. In some embodiments, aircraft 400 may include a fuselage 402, wing(s) 404 mounted to the fuselage 402, and one or more rear stabilizers 406 mounted to the rear of the fuselage 402. In some embodiments, each forward electric propulsion system may include propeller blades 416. In some embodiments, each aft electric propulsion system may include propeller blades 420. In some embodiments, electric propulsion systems may be mounted to wing(s) 404 by booms 422. In some embodiments, propellers may counter-rotate with respect to adjacent propellers to cancel torque steer, generated by the rotation of the propellers, experienced by the fuselage or wings of the aircraft. In some embodiments, the difference in rotation direction may be achieved using the direction of engine rotation. In other embodiments, the engines may all rotate in the same direction, and gearing may be used to achieve different propeller rotation directions.

[0080] Some embodiments may include an aircraft 400 possessing forward and aft electric propulsion systems where the amount of CW types 424 and CCW types 426 is not equal among the forward electric propulsion systems, among the aft electric propulsion systems, or among the forward and aft electric propulsion systems.

[0081] Fig. 5 is a schematic diagram illustrating exemplary power connections in a VTOL aircraft, consistent with disclosed embodiments. A VTOL aircraft may have multiple power systems connected to diagonally opposing electric propulsion systems. In some embodiments, the power systems may include high voltage power systems. Some embodiments may include high voltage power systems connected to electric engines via high voltage channels. In some embodiments, an aircraft 500 may include six power systems (e.g., battery packs), including power systems 526, 528, 530, 532, 534, and 536 stored within the wing 570 of the aircraft 500. The power systems may power electric propulsion systems and / or other electric components of the aircraft 500. In some embodiments, the aircraft 500 may include six forward electric propulsion systems having six electric engines 502, 504, 506, 508, 510, and 512 and six aft electric propulsion systems having six electric engines 514, 516, 518, 520, 522, and 524. In some embodiments, one or more power systems (e.g., battery packs) may includePATENTAttorney Docket No. 16499.0040-00304 a battery management system (“BMS”) (e.g., one BMS for each battery pack). While six power systems are shown in Fig. 5, the aircraft 500 may include any number and / or configuration of power systems.

[0082] In some embodiments, the one or more battery management systems may communicate with a Flight Control System (“FCS”) of the aircraft (e.g., FCS 612 shown in Fig 6). For example, the FCS may monitor the status of one or more battery packs and / or provide commands to the one or more battery management systems which make corresponding adjustments to the high voltage power supply.

[0083] Fig. 6 illustrates block diagram of an exemplary architecture and design of an electric propulsion unit 600 consistent with disclosed embodiments. Exemplary electric propulsion unit 600 includes an electric propulsion system 602, which may be configured to control aircraft propellers. Electric propulsion system 602 may include an electric engine subsystem 604 that may supply torque, via a shaft, to a propeller subsystem 606 to produce the thrust of the electric propulsion system 602. Some embodiments may include the electric engine subsystem 604 receiving low voltage direct current (LV DC) power from a Low Voltage System (LVS) 608. In some embodiments, the electric engine subsystem 604 may be configured to receive high voltage (HV) power from a High Voltage Power System (HVPS) 610 comprising at least one battery or other device capable of storing energy. HV power may refer to power that is higher in voltage than voltage provided by Low Voltage System (LVS) 608.

[0084] Some embodiments may include an electric propulsion system 602 including an electric engine subsystem 604 receiving signals from and sending signals to a flight control system 612. In some embodiments, a flight control system (FCS) 612 may comprise a flight control computer (FCC) capable of using Controller Area Network (“CAN”) data bus signals to send commands to the electric engine subsystem 604 and receive status and data from the electric engine subsystem 604. An FCC may include a device configured to perform one or more operations (e.g., computational operations) for an aircraft, such as at least one processor and a memory component, which may store instructions executable by the at least one processor to perform the operations, consistent with disclosed embodiments. It should be understood that while CAN data bus signals are used between the flight control computer and the electric engine(s), some embodiments may include any form of communication with the ability to send and receive data from a flight control computer to an electric engine. SomePATENTAttorney Docket No. 16499.0040-00304 embodiments may include electric engine subsystems 604 capable of receiving operating parameters from and communicating operating parameters to an FCC in FCS 612, including speed, voltage, current, torque, temperature, vibration, propeller position, and / or any other value of operating parameters.

[0085] In some embodiments, a flight control system 612 may also include a Tilt Propeller System (“TPS”) 614 capable of sending and receiving analog, discrete data to and from the electric engine subsystem 604 of the tilt propellers. A tilt propeller system (TPS) 614 may include an apparatus capable of communicating operating parameters to an electric engine subsystem 604 and articulating an orientation of the propeller subsystem 606 to redirect the thrust of the tilt propellers during various phases of flight using mechanical means such as a gearbox assembly, linear actuators, and any other configuration of components to alter an orientation of the propeller subsystem 606. In some embodiments, electric engine subsystem may communicate an orientation of the propeller system (e.g., an angle between lift and forward thrust) to TPS 614 and / or FCS 612 (e.g., during flight).

[0086] In some embodiments, a flight control system may include a system capable of controlling control surfaces and their associated actuators in an exemplary VTOL aircraft. Fig- 7 is an illustration of a top plan view of an exemplary VTOL aircraft, consistent with embodiments of the present disclosure. Aircraft 700 shown in the figure may be a top plan view of the aircraft 100, 200 shown in Figs. 1 and 2, respectively, in addition to the aircraft components described above with reference to Fig. 3. In aircraft 700, the control surfaces may include, in addition to the propeller blades discussed earlier, flaperons 712 and ruddervators 714. Flaperons 712 may combine functions of one or more flaps, one or more ailerons, and / or one or more spoilers. Ruddervators 714 may combine functions or one or more rudders and / or one or more elevators. Additionally or alternatively, control surfaces may include separate rudders and elevators. In aircraft 700, the actuators may include, in addition to the electric propulsion systems discussed earlier, control surface actuators (CSAs) associated with flaperons 712 and ruddervators 714, as discussed further below with reference to Fig. 8.

[0087] Fig. 8 illustrates a flight control signaling architecture for controlling the control surfaces and associated actuators, according to various embodiments. Although Fig. 7 illustrates twelve EPU inverters and associated propeller blades, six tilt propeller actuators (TPACs), six battery management systems (BMSs), four flaperons and associated control surface actuators (CSAs), and six ruddervators and associated CSAs, aircraft according toPATENTAttorney Docket No. 16499.0040-00304 various embodiments can have any suitable number of these various elements. As shown in Fig- 8, control surfaces and actuators may be controlled by a combination of four flight control computers (FCCs) — Left FCC, Lane A (L FCC-A), Left FCC, Lane B (L FCC-B), Right FCC, Lane A (R FCC-A), and Right FCC, Lane A (R FCC-B), although any other suitable number of FCCs may be utilized. The FCCs may each individually control all control surfaces and actuators or may do so in any combination with each other. In some embodiments, each FCC may include one or more hardware computing processors. In some embodiments, each FCC may utilize a single-threaded computing process or a multi -threaded computing process to perform the computations required to control the control surfaces and actuators. In some embodiments, all computing process required to control the control surfaces and actuators may be performed on a single computing thread by a single flight control computer.

[0088] The FCCs may provide control signals to the control surface actuators, including the EPU inverters, TPACs, BMSs, flaperon CSAs, and ruddervator CSAs, via one or more bus systems. For different control surface actuators, the FCC may provide control signals, such as voltage or current control signals, and control information may be encoded in the control signals in binary, digital, or analog form. In some embodiments, the bus systems may 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 Fig. 8). In some embodiments, multiple FCCs may be configured to provide control signals via each CAN bus system, and each FCC may be configured to provide control signals via multiple CAN bus systems. In the exemplary architecture illustrated in Fig. 8, for example, L FCC-A may provide control signals via Left CAN bus 1 and Right CAN bus 1, L FCC-B may provide control signals via Left CAN bus 1 and Center CAN bus 1, R FCC-A may provide control signals via Center CAN bus 2 and Right CAN bus 2, and R FCC-B may provide control signals via Left CAN bus 2 and Right CAN bus 2.

[0089] Figs. 9A-9F are illustrations of a top plan view of exemplary VTOL aircrafts, consistent with embodiments of the present disclosure. There may be a number of design considerations (cost, weight, size, performance capability etc.) that may influence the number and / or combination of tilt and lift propellers in a VTOL aircraft.

[0090] Fig. 9A illustrates an arrangement of electric propulsion units, consistent with embodiments of the present disclosure. Referring to Fig. 9A, the aircraft shown in the figure may be a top plan view of an exemplary aircraft (e.g., a VTOL aircraft). The aircraft mayPATENTAttorney Docket No. 16499.0040-00304 include twelve electric propulsion systems distributed across the aircraft. In some embodiments, a distribution of electric propulsion systems may include six forward electric propulsion systems (901, 902, 903, 904, 905, and 906) and six aft electric propulsion systems (907, 908, 909, 910, 911, and 912). In some embodiments, the six forward electric propulsion systems may be operatively connected to tilt propellers and the six aft electric propulsion systems may be operatively connected to lift propellers. In other embodiments, the six forward electric propulsion systems and a number of aft electric propulsion systems may be operatively connected to tilt propellers and the remaining aft electric propulsion systems may be operatively connected to lift propellers. In other embodiments, all forward and aft electric propulsion systems may be operatively coupled to tilt propellers.

[0091] Fig. 9B illustrates an alternate arrangement of electric propulsion units, consistent with embodiments of the present disclosure. Referring to Fig. 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, a distribution of electric propulsion systems may include four forward electric propulsion systems (913, 914, 915, and 916) and four aft electric propulsion systems (917, 918, 919, and 920). In some embodiments, the four forward electric propulsion systems may be operatively connected to tilt propellers and the four aft electric propulsion systems may be operatively connected to lift propellers. In other embodiments, the four forward electric propulsion systems and a number of aft electric propulsion systems may be operatively connected to tilt propellers and the remaining aft electric propulsion systems may be operatively connected to lift propellers. In other embodiments, all forward and aft electric propulsion systems may be operatively coupled to tilt propellers.

[0092] Fig. 9C illustrates an alternate arrangement of electric propulsion units, consistent with embodiments of the present disclosure. Referring to Fig. 9C, 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 six electric propulsion systems distributed across the aircraft. In some embodiments, a distribution of electric propulsion systems may include a first set of four electric propulsion systems 921, 922, 923, and 924 coplanar in a first plane and a second set of two electric propulsion systems 925 and 926 coplanar in a second plane. In some embodiments, the first set of electric propulsion systems 921-924 may be operatively connected to tilt propellers and second set of electric propulsion systems 925 and 926 may be operativelyPATENTAttorney Docket No. 16499.0040-00304 connected to lift propellers. In other embodiments, the first set of electric propulsion systems 921-924 and the second set of aft electric propulsion systems 925 and 926 may all be operatively connected to tilt propellers.

[0093] Fig. 9D illustrates an alternate arrangement of electric propulsion units, consistent with embodiments of the present disclosure. Referring to Fig. 9D, 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 four electric propulsion systems distributed across the aircraft. In some embodiments, a distribution of electric propulsion systems may include four coplanar electric propulsion systems 927, 928, 929, and 930. In some embodiments, all of the electric propulsion systems may be operatively connected to tilt propellers. In an alternative version of Fig. 9D (not depicted), the aircraft may have only two coplanar electric propulsion systems (e.g., electric propulsion systems 927, 928).

[0094] Fig. 9E illustrates an alternate arrangement of electric propulsion units, consistent with embodiments of the present disclosure. Referring to Fig. 9E, 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 six electric propulsion systems distributed across the aircraft. For example, in some embodiments, the aircraft may include four forward electric propulsion systems 931, 932, 933, and 934 operatively connected to tilt propellers and the two aft ducted fans 935 and 936 operatively connected to lift propellers. In some embodiments, the aircraft may include ten electric propulsion systems distributed across the aircraft. For example, in some embodiments, the aircraft may include six forward electric propulsion systems operatively connected to tilt propellers and the four aft electric propulsion systems operatively connected to lift propellers. In some embodiments, some or all of the aft electric propulsion systems may operatively connected to tilt propellers.

[0095] As shown in Fig. 9E, in some embodiments, the aircraft may have a flying wing configuration, such as a tailless fixed-wing aircraft with no definite fuselage. In some embodiments, the aircraft may have a flying wing configuration with the fuselage integrated into the wing. In some embodiments, the tilt propellers may rotate in a plane above the body of the aircraft when the tilt propellers operate in a lift configuration.

[0096] Fig. 9F illustrates an alternate arrangement of electric propulsion units, consistent with the embodiments of the present disclosure. Referring to Fig. 9F, the aircraft may be a top plan view of an exemplary aircraft. In some embodiments, the aircraft may includePATENTAttorney Docket No. 16499.0040-00304 ducted fans 936, 937, 938, and 939 operably connected to the electric propulsion systems. In some embodiments the aircraft may include a bank of ducted fans on each wing of the aircraft and the bank of ducted fans may be connected to tilt together (e.g., between lift and forward thrust configuration). In some embodiments the aircraft includes a left and right front wing and a left and right rear wing. In some embodiments, each wing of the aircraft includes a bank of connected ducted fans. In some embodiments, each bank of connected ducted fans are tiltable (e.g., between lift and forward thrust), while in other embodiments only the bank of fans on the front wing(s) are tiltable.

[0097] The embodiments of the present disclosure may include a control system (e.g., including an FCC) configured to dynamically control a spool -up process or a spool-down process on any arrangement of EPUs, such as the arrangements of EPUs illustrated in Figs.9A-9F

[0098] In some embodiments, a control system may be configured to control a spooldown process on the arrangement of EPUs illustrated in Fig. 9A. In some embodiments, a control system may control a spool-down process by controlling the spool-down of the six aft electric propulsion systems (907, 908, 909, 910, 911, and 912). In some embodiments, a control system may control a spool-down process in a staggered approach, i.e., powering down an individual or a corresponding group of electric propulsions systems in an ordered sequence. In some embodiments, a control system may dynamically adjust the order in which EPUs spool through a plurality of RPM avoidance ranges. For example, the control system may dynamically adjust the order in which EPUs spool through a plurality of RPM avoidance ranges based on at least one of a phase of flight, flight state, or aircraft state. An RPM avoidance range may be considered any group of RPM speeds at which it is undesirable for an EPU to remain at for prolonged periods of time. Additionally or alternatively, an RPM avoidance range may include any set of RPM speeds at which at least one processing device is configured to minimize the duration that an EPU operates.

[0099] In some embodiments, in further reference to an arrangement of EPUs illustrated in Fig. 9A, a control system may control a spool-down process in a staggered approach by spooling-down corresponding pairs of EPUs. In some embodiments, a control system may control a first pair of electric propulsion systems (e.g., electric propulsion systems 909 and 910) to spool down from a powered-on status (e.g., having a power, thrust, and / or voltage above a predetermined threshold) to a powered-off status (e.g., having a power, thrust,PATENTAttorney Docket No. 16499.0040-00304 and / or voltage below a predetermined threshold). The spool-down (which may be rapid) of a first pair of electric propulsion systems may be motivated by efforts to reduce or minimize the amount of time an electric propulsion system must operate in its respective avoidance range. The spool-down of a pair of electric propulsion systems may cause the total thrust output to drastically decrease (i.e., in this example, transitioning from the thrust of six electric propulsion systems to the thrust of only four electric propulsion systems). In some embodiments, a control system may compensate for the drastic decrease in total thrust output by controlling the remaining four electric propulsion systems (e.g., electric propulsion systems 907, 908, 911, and 912) to exert at least a partially offsetting increased thrust output. In some embodiments, a compensation by the remaining electric propulsion systems may decrease, minimize, offset, or cancel out the resulting change in the total thrust caused by the rapid spool-down of the first pair of electric propulsion systems.

[0100] In some embodiments, in further reference to an arrangement of EPUs illustrated in Fig. 9A, a control system may further control a spool-down process in a staggered approach by spooling-down corresponding pairs of EPUs. In some embodiments, following the spooling-down process of a first pair of electric propulsion systems, a control system may control a second pair of electric propulsion systems (e.g., electric propulsion systems 908 and 911) to rapidly spool down from a powered-on status to a powered-off status. The rapid spool down of a second pair of electric propulsion systems may be motivated by efforts to reduce or minimize the amount of time an electric propulsion system must operate in its respective avoidance range. The rapid spool-down of a second pair of electric propulsion systems may cause the total thrust output to drastically decrease (i.e., in this example, transitioning from the thrust of four electric propulsion systems to the thrust of only two electric propulsion systems). In some embodiments, a control system may compensate for the drastic decrease in total thrust output by controlling the other remaining two electric propulsion systems (e.g., electric propulsion systems 907 and 912) to exert an offsetting increased thrust output. In some embodiments, a compensation by the remaining electric propulsion systems may minimize, at least partially offset, or cancel out the resulting change in the total thrust caused by the rapid spool-down of the second pair of electric propulsion systems.

[0101] In some embodiments, a control system may be configured to dynamically adjust the tilt angle of at least one propeller blade and / or at least one EPU during spool-up or spool-down sequences, such as by adjusting blade collective, blade cyclic, and / or propeller tiltPATENTAttorney Docket No. 16499.0040-00304 angle. For example, when transitioning through one or more RPM avoidance ranges, a control system may simultaneously modify blade collective, blade cyclic, or EPU tilt to improve or optimize thrust distribution, improve aircraft stability, and / or reduce or minimize vibration. Propeller tilt angle may refer to or include the tilt angle of a tiltable EPU (e.g., a “filter”), such as the tilt angle of the nacelle of an EPU, which may be controllable through a tilt actuator, consistent with disclosed embodiments. This combined approach allows coordinated control of RPM, tilt, and collective to maintain stability and efficiency during flight mode transitions.

[0102] By way of further example, a control system may be configured to dynamically adjust the blade collective for an EPU while that EPU is spooling up or down and / or transitioning through an RPM avoidance range. As used herein, blade collective may refer to (i) a control mechanism that changes the pitch angle of all blades of a rotor or propeller simultaneously and by a same amount, rather than individually, or (ii) a quantifiable representation, such as an angle, of the pitch of all blades associated with a rotor or propeller. For example, when an EPU is increasing its RPM, the collective system may decrease the blade collective of that EPU. As another example, when an EPU is decreasing its RPM, the collective system may increase the blade collective of that EPU. Adjusting the blade collective may be configured to at least partially offset a change in thrust resulting from the EPU spooling up or down and / or transitioning through an RPM avoidance range. Such a technique may be useful to at least partially offset a change in thrust in embodiments where only one EPU group is present (e.g., where there is not another EPU group available to help accomplish such an offset), though it is not limited to such embodiments.

[0103] Although some embodiments of the present disclosure were described in reference to various features of the arrangement of Fig. 9A, the present disclosure is not limited to the arrangement of Fig. 9A. In some embodiments, a control system of the present disclosure may control a spool-down on any of the arrangements illustrated in Figs. 9A-9F. In some embodiments, a control system of the present disclosure may control a spool-up process on any of the arrangements illustrated in Figs. 9A-9F. In some embodiments, a control system of the present disclosure may control the spool-up or spool-down process of the electric propulsion systems in any order. In some embodiments, a control system of the present disclosure may control the spool-up or spool-down process of the electric propulsion systems in any order of pairs or groups (e.g., groups that may or may not have symmetric positioning with respect to the main body, wings, or fuselage of the aircraft). In some embodiments, a control system ofPATENTAttorney Docket No. 16499.0040-00304 the present disclosure may control the spool-up or spool-down process of only some electric propulsion systems, while leaving other electric propulsion systems fully operational without spooling. In some embodiments, a control system of the present disclosure may control load distribution among the plurality of electric propulsions systems, which may reduce excessive stress on any one or group of individual components. In some embodiments, load balancing and distribution commands may be based on structural constraints and / or monitored aircraft state information or aircraft component state information using one or more sensors.

[0104] In some embodiments, a control system may control a spool-down by operating a single electric propulsion system. In some embodiments, an aircraft may have an unplanned failure of at least one electric propulsion system, thereby causing an asymmetric number of electric propulsion systems to be in operation on either side of the aircraft. In some embodiments, a control system may control a corresponding electric propulsion system to rapidly spool down to compensate for or at least partially offset the unplanned failure. A corresponding electric propulsion system may include an electric propulsion system that is positioned in a corresponding position (e.g., symmetric position) with respect to the fuselage (e.g., main body, centerline) of the aircraft (i.e., electric propulsion system 907 corresponds to electric propulsion system 912, electric propulsion system 908 corresponds to electric propulsion system 911, electric propulsion system 909 corresponds to electric propulsion system 910, etc.).

[0105] As disclosed herein, the forward electric propulsion systems and aft electric propulsion systems may be of a clockwise (CW) type or counterclockwise (CCW) type. Some embodiments may include various forward electric propulsion systems possessing a mixture of both CW and CCW types. In some embodiments, the aft electric propulsion systems may possess a mixture of CW and CCW type systems among the aft electric propulsion systems. In some embodiments, each electric propulsion systems may be fixed as clockwise (CW) type or counterclockwise (CCW) type, while in other embodiments, one or more electric propulsion systems may vary between clockwise (CW) and counterclockwise (CCW) rotation.

[0106] Fig. 10 illustrates a functional block diagram of an exemplary control system 1000 of an aircraft, consistent with disclosed embodiments. System 1000 may be implemented by at least one processor (e.g., at least one a 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 functions described herein. SystemPATENTAttorney Docket No. 16499.0040-003041000 may also be implemented in hardware, or a combination of hardware and software. System 1000 may be implemented as part of a flight control system of the aircraft (e.g., part of FCS 612 in Fig. 6) and may be configured to perform a single step or sequence repeatedly until a desired or commanded outcome is achieved. It is to be understood that many conventional functions of the control system are not shown in Fig. 10 for ease of description. System 1000 further includes one or more storage mediums storing model(s), function(s), table(s), and / or any information for executing the disclosed processes. As further described below, any or each box indicating a command model (e.g., 1004, 1006, 1008, and 1010), feedback (1012, 1016, 1018, and 1022), feed forward (1014, 1020), Outer Loop Allocation (1024, 1026), inner loop control laws 1028, and control allocation 1029 may represent or include module(s), script(s), function(s), application(s), and / or program(s) that are executed by processor(s) and / or microprocessor(s) of system 1000. It is appreciated that the complexity and interconnectedness of the functional block diagram of Fig. 10 would be impossible, or at least impractical, to effectively implement by a human user, especially when considering that these functionalities are implemented while the aircraft is flying (including taking off or landing).

[0107] In some embodiments, control system 1000 may be configured based on one or more flight control laws. A flight control law may comprise a set of algorithms, models, and / or rules configured to govern a behavior of an aircraft (e.g., control or influence one or more effectors of the aircraft) in response to one or more pilot inputs and external factors. In some embodiments, a flight control law may be configured to achieve at least one of desired flight characteristics, stability, or performance. For example, a flight control law may be configured to improve stability and controllability of an aircraft by controlling how the aircraft responds to at least one of one or more pilot inputs, vehicle dynamics (e.g., disturbances, such as turbulence, gusts, etc.), or changes in flight conditions (e.g., altitude, airspeed, angle of attack).

[0108] In some embodiments, control system 1000 may be configured to perform operations without receiving any explicit pilot or system command. For example, control system 1000 may trigger adjustments and control of the spooling process based on external forces or environmental conditions (such as gust loads or turbulence). This ability may enable autonomous control and automatic avoidance of undesirable RPM ranges while not adding to pilot workload.

[0109] In some embodiments, control system 1000 may be configured to use various combinations of commands and forces, which may be represented by at least one of a phase ofPATENTAttorney Docket No. 16499.0040-00304 flight, flight state, or aircraft state, to determine one or more spooling related commands. In some embodiments, control system 1000 may be configured to trigger adjustments and control the spooling process based on one or more external forces only, one or more pilot commands only, or a combination of external forces and pilot commands. For example, control system 1000 may control a spool down process based solely on an external force, such as a wind gust. Moreover, control system 1000 may control a spool down process based solely on a pilot command, such as an acceleration or deceleration command. Control system 1000 may control a spool down process based on a combination of external forces and pilot commands. In some embodiments, control system 1000 may control a spooling process based on any one of or any combination of pilot inputs, vehicle dynamics, aircraft characteristics, flight conditions, or environmental conditions.

[0110] System 1000 may detect one or more inputs, such as from a pilot input device configured to receive at least one pilot input and generate or influence a signal. A pilot input may be generated by and / or received from an input device or mechanism of the aircraft, such as a button, a switch, a knob, a stick, a slider, an inceptor, any combination thereof, or any other device configured to generate or influence a signal based on a physical action from a pilot. For example, a pilot input device may include one or more of right inceptor(s) (e.g., moving right inceptor left / right 1002a and / or right inceptor forward / aft 1002e), left inceptor(s) (e.g., moving left inceptor left / right 1002c and / or left inceptor forward / aft 1002g), and / or left inceptor switch 1002f. In some embodiments, a pilot input device may include an interface with an autopilot system (e.g., display screen(s), switch(es), button(s), lever(s), and / or other interface(s)). Optionally, system 1000 may further detect inputs from an autopilot system, such as autopilot roll command 1002b, autopilot climb command 1002d, and / or other command(s) to control the aircraft.

[0111] In some embodiments, the one or more inputs may include at least one of a position and / or rate of a right inceptor and / or a left inceptor, signals received (e.g., response type change commands, trim inputs, reference inputs, backup control inputs, etc.) from switches on the inceptors, measurements of aircraft state and environmental conditions (e.g., measured load factor, airspeed, roll angle, pitch angle, actuator states, battery states, aerodynamic parameters, temperature, gusts, etc.) based on data received from one or more sensors of the aircraft, obstacles (e.g., presence or absence of other aircraft and / or debris), and an aircraft mode (e.g., taxiing on the ground, takeoff, in-air). For example, right inceptor L / RPATENTAttorney Docket No. 16499.0040-003041002a may comprise a lateral position and / or rate of a right inceptor (e.g., an inceptor positioned to the right of another inceptor and / or an inceptor positioned on the right side of a pilot area), autopilot roll command 1002b may comprise a roll signal received in autopilot mode, left inceptor L / R 1002c may comprise a lateral position and / or rate of a left inceptor (e.g., an inceptor positioned to the left of another inceptor and / or an inceptor positioned on the left side of a pilot area), autopilot climb command 1002d may comprise a climb signal received in autopilot mode, right inceptor F / A 1002e may comprise a longitudinal position and / or rate of the right inceptor, left inceptor switch 1002f may comprise a signal from a switch for enabling or disabling automatic transition function 1003, and left inceptor F / A 1002g may comprise a longitudinal position and / or rate of the left inceptor.

[0112] Each input may include data as listed above (e.g., signals from switches, measurements of aircraft state, aircraft mode, etc.). Actuator states may include actuator hardware limits, such as travel limits, speed limits, response time limits, etc., and can include actuator health indicators that may indicate deteriorations in actuator performance that may limit a given actuator’s ability to satisfy actuator commands. Actuator states may be used to determine the bounds (e.g., minimum / maximum values) for individual actuator commands. Battery states may correspond to remaining energy of the battery packs of the aircraft, which may be monitored when control allocation 1029 considers balancing battery pack energy states. Aerodynamic parameters may be parameters derived from aerodynamic and acoustic modeling and can be based on the actuator Jacobian matrices and actuator states. Each input received from an inceptor may indicate a corresponding adjustment to an aircraft’s heading or power output.

[0113] Command models 1004, 1006, 1008 and 1010 may be configured to determine a shape (e.g., aggressiveness, slew rate, damping, overshoot, etc.) of an ideal aircraft response. For example, each command model of command models 1004, 1006, 1008 and 1010 may be configured to receive and interpret at least one of inputs 1002a, 1002b, 1002c, 1002d, 1002e, 1002f and 1002g and, in response, compute a corresponding change to an aircraft’s orientation, heading, and propulsion, or a combination thereof using an integrator (not pictured). In some embodiments, right inceptor L / R 1002a and autopilot roll command 1002b may be fed into turn-rate command model 1004, left inceptor L / R 1002c may be fed into lateral speed command model 1006, autopilot climb command 1002d and right inceptor F / A 1002e may be fed into climb command model 1008, and left inceptor F / A 1002g may be fed into forward speedPATENTAttorney Docket No. 16499.0040-00304 command model 1010. In some embodiments, an output from automatic transition function 1003 may be fed into at least one of climb command model 1008 or forward speed command model 1010. For example, based on receiving an enable signal from left inceptor switch 1002f, automatic transition function 1003 may automatically determine at least one of a climb signal or a forward speed signal for transmission to at least one of climb command model 1008 or forward speed command model 1010.

[0114] Turn-rate command model 1004 may be configured to output a desired position and / or turn-rate command and may also be configured to compute a desired heading of the aircraft to be assumed when the inceptor is brought back to a centered position (e.g., in detent). Lateral speed command model 1006 may be configured to output a desired position and / or lateral speed command. Climb command model 1008 may be configured to output at least one of a desired altitude, vertical speed, or vertical acceleration command. Forward speed command model 1010 may be configured to output at least one of a desired position, longitudinal speed, or longitudinal acceleration command. In some embodiments, one or more of the command models may be configured to output an acceleration generated in response to changes in speed command. For example, climb command model 1008 may be configured to output a vertical acceleration generated in response to a change in vertical speed command.

[0115] Feed forward 1014 and 1020 may each receive as input one or more desired changes (e.g., desired position, speed and / or acceleration) from corresponding command models 1004, 1006, 1008 or 1010 as well as data received from the one or more aircraft sensors (e.g., airspeed, vehicle orientation, vehicle load factor, measured acceleration, vehicle mass and inertia, air density, altitude, aircraft mode, etc.) and may be configured to output, for each desired change, a corresponding force to accomplish the desired change. In some embodiments, feed forward 1014 and 1020 may be configured to determine the corresponding force using simplified models of aircraft dynamics. For example, based on a known (e.g., a stored value of) or determined mass of the aircraft, feed forward 1014 and 1020 may be configured to determine a force to cause the aircraft to follow a desired acceleration command. In some embodiments, feed forward 1014 and 1020 may be configured to use a model predicting an amount of drag on the vehicle produced as a function of speed in order to determine a force required to follow a desired speed command signal.

[0116] Feedback 1012, 1016, 1018, and 1022 may each receive as input the one or more desired changes (e.g., desired position, speed and / or acceleration) from command models 1004,PATENTAttorney Docket No. 16499.0040-003041006, 1008 and 1010 as well as data received from Vehicle Sensing 1031 indicative of Vehicle Dynamics 1030. For example, sensed Vehicle Dynamics 1030 may comprise the physics and / or natural dynamics of the aircraft, and Vehicle Sensing 1031 sensor measurements may capture how the aircraft moves in response to pilot inputs, propulsion system outputs or ambient conditions. In some embodiments, Vehicle Dynamics 1030 may represent the control of different flight elements (e.g., electric propulsion system(s) and / or control surfaces) and the corresponding effect on the flight elements and aircraft dynamics. Additionally or alternatively, data received from Vehicle Sensing 1031 may include error signals generated, by one or more processors, based on exogenous disturbances (e.g., gust causing speed disturbance). In some embodiments, feedback 1012, 1016, 1018 and 1022 may be configured to generate feedback forces (e.g., at an actuator) based on the received error signals. For example, feedback 1012, 1016, 1018 and 1022 may generate feedback forces with the intent of counteracting the effect(s) of external disturbances. Additionally or alternatively, feedback 1012, 1016, 1018 and 1022 may be configured to generate feedback forces based on modeling errors. For example, if an incorrect aircraft mass is input into either feed forward 1014 or 1020, the aircraft may accelerate faster or slower than the desired change. Based on determining a difference between the desired acceleration and the measured acceleration, one or more processors may generate an error signal (e.g., included in Vehicle Sensing 1031) which may be looped into feedback 1012, 1016, 1018 or 1022 to determine an additional force needed to correct the error.

[0117] In some embodiments, feedback 1012, 1016, 1018 or 1022 may be disabled. For example, in response to losing position and / or ground speed feedback due to disruption of global position system (GPS) communication, system 1000 may be configured to operate without feedback 1012, 1016, 1018 or 1022 until GPS communication is reconnected.

[0118] In some embodiments, feedback 1012, 1016, 1018 or 1022 may receive as input a plurality of measurements as well as a trust value for each measurement indicating whether the measurement is valid. For example, one or more processors of system 1000 may assign a Boolean (true / false) value for each measurement used in system 1000 to indicate that the measurement is trustworthy (e.g., yes) or that the measurement may be invalid (e.g., no). Based on one or more processors identifying a measurement as invalid, feedback 1012, 1016, 1018 or 1022 may omit that 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 may omit subsequent heading measurements in determining feedback force(s).PATENTAttorney Docket No. 16499.0040-00304

[0119] In some embodiments, feedback 1012, 1016, 1018 or 1022 may determine one or more feedback forces based on actuator state information received from one or more sensors (e.g., included in Vehicle Sensing 1031). For example, in response to actuator state information indicating that there is a failure of an actuator, one or more processors of system 1000 may update one or more processes of System 1000 and determine an alternative command to achieve the desired change. For example, one or more processors of system 1000 may adjust one or more model(s), function(s), algorithm(s), table(s), input(s), parameter(s), threshold(s), and / or constraint s) based on (e.g., in response to) a change in state (e.g., failure) of an actuator (or other aircraft component, such as an engine or battery, for other examples). Alternative command(s) (e.g., yaw, pitch, roll, thrust, or torque) may be determined based on the adjustment(s). Additionally or alternatively, in response to actuator state information indicating that one or more actuators are at a maximum value, one or more processors of system 1000 may update one or more processes of system 1000 (e.g., as described above) and determine an alternative command to achieve the desired change.

[0120] Total desired forces may be calculated based on outputs of feedback 1012, 1016, 1018 and 1022 and feed forward 1014 and 1020. For example, one or more processors of system 1000 may calculate a desired turn -rate force by summing the outputs of feedback 1012 and feed forward 1014. Additionally or alternatively, one or more processors of system 1000 may calculate a desired lateral force by summing the outputs of feedback 1016 and feed forward 1014. Additionally or alternatively, one or more processors of system 1000 may calculate a desired vertical force by summing the outputs of feedback 1018 and feed forward 1020. Additionally or alternatively, one or more processors of system 1000 may calculate a desired longitudinal force by summing the outputs of feedback 1022 and feed forward 1020.

[0121] Lateral / Directional Outer Loop Allocation 1024 and Longitudinal Outer Loop Allocation 1026 may each be configured to receive as input one or more desired forces and data received from Vehicle Sensing 1031 (e.g., airspeed, vehicle orientation, vehicle load factor, measured acceleration, vehicle mass and inertia, indications of working / failed actuators, air density, altitude, aircraft mode, whether the aircraft is in the air or on the ground, weight on wheels, etc.). Based on the inputs, Outer Loop Allocation 1024 and 1026 may be configured to command roll, command yaw, command pitch, demand thrust, or output a combination of different commands / demands in order to achieve the one or more desired forces.PATENTAttorney Docket No. 16499.0040-00304

[0122] Lateral / Directional Outer Loop Allocation 1024 may receive as input a desired turn-rate force and / or a desired lateral force and may command roll or command yaw. In some embodiments, Lateral / Directional Outer Loop Allocation 1024 may determine output based on a determined flight mode. A flight mode may be determined using pilot inputs (e.g., a selected mode on an inceptor) and / or sensed aircraft information (e.g., an airspeed). For example, Lateral / Directional Outer Loop Allocation 1024 may 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 inceptor button (e.g., an input instructing the aircraft to fly according to a particular flight mode). In some embodiments, Lateral / Directional Outer Loop Allocation 1024 may be configured to prioritize a pilot inceptor button input over measured airspeed in determining the flight mode (e.g., the pilot inceptor button is associated with a stronger weight or higher priority than a measured airspeed). In some embodiments, Lateral / Directional Outer Loop Allocation 1024 may be configured to blend (e.g., using weighted summation) the determined airspeed and pilot inceptor button input to determine the flight mode of the aircraft. In a hover flight mode, Lateral / Directional Outer Loop Allocation 1024 may achieve the desired lateral force with a roll command (e.g., roll angle, roll rate) and may achieve the desired turn-rate force with a yaw command. In some embodiments, such as in hover flight mode, the aircraft may be configured to not be able to accelerate outside a predetermined hover envelope (e.g., hover speed range). In a forward -flight mode (e.g., horizontal flight), Lateral / Directional Outer Loop Allocation 1024 may achieve the desired lateral force with a yaw command and may achieve the desired turn-rate force with a roll command. In forward flight mode, Lateral / Directional Outer Loop Allocation 1024 may be configured to determine output based on sensed airspeed. In a transition between hover flight mode and forward flight mode, Lateral / Directional Outer Loop Allocation 1024 may achieve desired forces using a combination of a roll command and a yaw command.

[0123] Longitudinal Outer Loop Allocation 1026 may receive as input a desired vertical force and / or a desired longitudinal force and may output at least one of a pitch command (e.g., pitch angle) or a thrust vector demand. A thrust vector demand may include longitudinal thrust (e.g., mix of nacelle tilt and front propeller thrust) and vertical thrust (e.g., combined front and rear thrust). In some embodiments, Longitudinal Outer Loop Allocation 1026 may determine output based on a determined flight mode. For example, in a hover flight mode, Longitudinal Outer Loop Allocation 1026 may achieve a desired longitudinal force byPATENTAttorney Docket No. 16499.0040-00304 lowering a pitch attitude and by using longitudinal thrust, and may achieve a desired vertical force with vertical thrust. In a forward-flight mode, Longitudinal Outer Loop Allocation 1026 may achieve a desired longitudinal force with longitudinal thrust (e.g., front propeller thrust). In a cruise flight mode, Longitudinal Outer Loop Allocation 1026 may achieve a desired vertical force by commanding pitch (e.g., raising pitch attitude) and demanding thrust (e.g., increasing longitudinal thrust).

[0124] Inner loop control laws 1028 may be configured to determine moment commands based on at least one of a roll command, yaw command, or pitch command from Lateral / Directional Outer Loop Allocation 1024 or Longitudinal Outer Loop Allocation 1026. In some embodiments, Inner loop control laws 1028 may be dependent on sensed Vehicle Dynamics (e.g., from Vehicle Sensing 1031). For example, Inner loop control laws 1028 may be configured to compensate for disturbances at the attitude and rate level in order to stabilize the aircraft. Additionally or alternatively, Inner loop control laws 1028 may consider periods of natural modes (e.g., phugoid modes) that affect the pitch axis, and may control the aircraft appropriately to compensate for such natural modes of the vehicle. In some embodiments, inner loop control laws 1028 may be dependent on vehicle inertia.

[0125] Inner loop control laws 1028 may determine moment commands using one or more stored dynamics 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 laws 1028 may 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 may include determining (e.g., by inner loop control laws 1028 or other component) a moment command based on at least one received command (e.g., a roll command, yaw command, and / or pitch command) and a determined (e.g., measured) aircraft state. For example, a moment command may be determined using a difference in the commanded aircraft state and the measured aircraft state. By way of further example, a moment command may be determined using the difference between a commanded roll angle and a measured roll angle. As described below, Control Allocation 1029 may control the aircraft (e.g., through flight elements) based on the determined moment command(s). For example, Control Allocation 1029 may control (e.g., transmit one or more commands to) one or more electric propulsion system(s) of the aircraft (e.g., electric propulsion system 602 shown in Fig. 6), including tilt actuator(s), electricPATENTAttorney Docket No. 16499.0040-00304 engine(s), and / or propeller(s). Control Allocation 1029 may further control one or more control surface(s) of the aircraft (e.g., control surfaces, such as flaperons 712 and ruddervators 714 shown in Fig. 7), including flaperon(s), ruddervator(s), aileron(s), spoiler(s), rudder(s), and / or elevator(s).

[0126] While the embodiment shown in Fig. 10 includes both Inner Loop Control Laws1028 and Outer Loop Allocations 1024 and 1026, in some embodiments the flight control system may not include Outer Loop Allocations 1024 and 1026. Therefore, a pilot inceptor input may create roll, yaw, pitch, and / or thrust commands. For example, a right inceptor may control roll and pitch and a left inceptor and / or pedal(s) may control yaw and thrust.

[0127] Control Allocation 1029 may accept as inputs one or more of force and moment commands, data received from the one or more aircraft sensors, envelope protection limits, scheduling parameter, and optimizer parameters. Control Allocation 1029 may be configured to determine, based on the inputs, actuator commands by minimizing an objective function that includes one or more primary objectives, such as meeting (e.g., responding to, satisfying, addressing, providing output based upon) commanded aircraft forces and moments, and one or more secondary, which can include minimizing acoustic noise and / or optimizing battery pack usage.

[0128] In some embodiments, control allocation 1029 may be configured to compute the limits of individual actuator commands based on the actuator states and envelope protection limits. Envelope protection limits may include one or more boundaries that the aircraft should operate within to ensure safe and stable flight. In some embodiments, envelope protection limits may be defined by one or more of speed, altitude, angle of attack, or load factor. For example, envelope protection limits may include one or more bending moments and / or one or more load constraints. In some embodiments, control allocation 1029 may use envelope protection limits to automatically adjust one or more control surfaces or control settings. Doing so may prevent the aircraft from undesirable scenarios such as stalling or structural strain or failure. In normal operation, the minimum command limit for a given actuator may include the maximum of: the minimum hardware based limit and the minimum flight envelope limit; and the maximum command limit for a given actuator may includes the minimum of: the maximum hardware based limit and the maximum flight envelope limit. In the case of an actuator failure, the command limits for the failed actuator correspond to the failure mode.PATENTAttorney Docket No. 16499.0040-00304

[0129] Control allocation 1029 sends commands to one or more flight elements to control the aircraft. The flight elements will move in accordance with the controlled command. Various sensing systems and associated sensors as part of Vehicle Sensing 1031 may detect the movement of the flight elements and / or the dynamics of the aircraft and provide the information to Feedback 1012, 1016, 1018, 1022, Outer Loop allocation 1024 and 1026, Inner Loop Control laws 1028, and Control Allocation 1029 to be incorporated into flight control.

[0130] As described above, Vehicle Sensing 1031 may include one or more sensors to detect vehicle dynamics. For example, Vehicle Sensing 1031 may capture how the aircraft moves in response to pilot inputs, propulsion system outputs or ambient conditions. Additionally or alternatively, Vehicle Sensing 1031 may detect an error in the aircraft’s response based on exogenous disturbances (e.g., gust causing speed disturbance). Further, Vehicle Sensing 1031 may include one or more sensors to detect propeller speed, such as a magnetic sensor (e.g., 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). Vehicle sensing 1031 may include one or more sensors to detect a nacelle tilt angle (e.g., a propeller rotation axis angle between a lift configuration (e.g., Fig. 2) and forward thrust configuration (e.g., Fig. 1)). For example, one or more magnetic sensors (e.g., Hall effect or inductive sensor), position displacement sensors, linear displacement sensors, and / or other sensor(s) associated with the tilt actuator may detect a tilt angle (e.g., relative to the aircraft and / or wing), which may be provided to system 1000. Further, one or more pitot tubes, accelerometers, and / or gyroscopes may detect a pitch angle of the aircraft, which may be provided to system 1000. In some embodiments, Vehicle Sensing 1031 may combine tilt angle sensor measurements and aircraft pitch measurements to determine an overall nacelle tilt angle for the propellers. Vehicle sensing 1031 may include one or more sensors configured to detect an 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). In some embodiments, detection of vibration levels may be performed using one or more vibration sensors positioned on or near one or more propellers or other structural components.

[0131] Vehicle sensing 1031 may include one or more sensors configured to detect vehicle dynamics, such as acceleration and / or pitch orientation sensors (e.g., accelerometer(s), 3-axis accelerometer(s), gyroscope(s), 3-axis gyroscope(s), and / or tilt-position sensors to determine angles of engines) and airspeed sensors (e.g., pitot tube sensors). Vehicle sensingPATENTAttorney Docket No. 16499.0040-003041031 may further include one or more inertial measurement units (IMUs) to determine an aircraft state based on these measurements. An aircraft state may refer to forces experienced by, an orientation of, a position of (e.g., altitude), and / or movement of, the aircraft. For example, an aircraft state may include at least one of: a position of the aircraft (e.g., a yaw angle, roll angle, pitch angle, and / or any other orientation across one or two axes), velocity of the aircraft, angular rate of the aircraft (e.g., roll, pitch, and / or yaw rate), and / or an acceleration of the aircraft (e.g., longitudinal, lateral and / or vertical acceleration), or any physical characteristic of the aircraft or one of its components.

[0132] In some embodiments, Vehicle Sensing 1031 may include an inertial navigation systems (INS) and / or an air data and / or an attitude heading reference systems (ADAHRS). The inertial navigation systems (INS) and / or an air data and attitude heading reference systems (ADAHRS) may include one or more inertial measurement units (IMUs) and corresponding sensors (e.g., accelerometers, gyroscopes, three-axis gyroscopes, and / or three-axis accelerometers). In some embodiments, the INS and / or ADAHRS may filter and / or otherwise process sensor measurements to determine an aircraft state (e.g., acceleration or angular rate). For example, in some embodiments, the INS and / or ADAHRS may determine angular rates based on gyroscope measurements and may determine acceleration based on measurements from an accelerometer. In some embodiments, any combination of measurements recorded by Vehicle Sensing 1031 may be used to perform dynamic adjustments and control spooling sequences.

[0133] It is appreciated that the functionality described with respect to Fig. 11 may be implemented in any of the blocks shown in Fig. 10, or in an additional block that may be connected to other blocks in Fig. 10.

[0134] Fig. 11 illustrates a functional block diagram of an exemplary phased power- up / power-down control logic of an electric VTOL aircraft, consistent with disclosed embodiments. System 1100 (e.g., control logic) may be implemented by at least one processor (e.g., at least one a 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 functions described herein. System 1100 may also be implemented in hardware, or a combination of hardware and software. System 1100 may be implemented as part of a flight control system of the aircraft (e.g., part of FCS 612 in Fig. 6) and may be configured to perform a single step or sequence repeatedly until a desired orPATENTAttorney Docket No. 16499.0040-00304 commanded outcome is achieved. It is to be understood that many conventional functions of the control system are not shown in Fig. 11 for ease of description. System 1100 further includes one or more storage mediums storing model(s), function(s), table(s), and / or any information for executing the disclosed processes. The “Q” referred to in Fig. 11 may represent and / or be associated with torque. For example, “Q” may represent aerodynamic torque and / or may be equal to, similar to, or correlated with RPM2and / or thrust.

[0135] In some embodiments, system 1100 may include an online allocator 1101, an offline “lookahead” allocator 1102, an EPU controller 1103, a spool-up / spool-down state logic 1104, a blend-in sequential spool-up / spool-down logic 1105, and an enabling sequential spool- up / spool-down logic 1106.

[0136] In some embodiments, at least one component (e.g., FCC, online allocator 1101, or all or part of system 1100) may receive a first thrust command. In some embodiments, an online allocator 1101 may receive a force and moment (FM) demand input, which may include and / or may be based on a thrust command. In some embodiments, an FM demand input and / or thrust command may include at least two force values and at least three moment values. Instead of or in addition to receiving an FM demand input, the at least one component may receive an angular acceleration input and / or an angular acceleration command. In some embodiments, an online allocator 1101 may receive at least one offline aerodynamic torque demand, at least one online aerodynamic torque achieved, or at least one aeromodel parameter.

[0137] In some embodiments, an offline “lookahead” allocator 1102 may receive an FM demand input. In some embodiments, an offline “lookahead” allocator 1102 may receive at least one offline aerodynamic torque demand, at least one online aerodynamic torque achieved, or at least one aeromodel parameter. In some embodiments, an offline “lookahead” allocator 1102 may use a pseudo-inverse. In some embodiments, an offline “lookahead” allocator 1102 may use a total lifter aerodynamic torque allocated in an outer loop. In some embodiments, an offline “lookahead” allocator 1102 may include, access, and / or receive nominal scheduled aerodynamic torque limits (e.g., stored in memory). Additionally or alternatively, offline “lookahead” allocator 1102 may generate a total offline torque demand (e.g., value representing a torque demanded by one or more lifter EPUs) and / or input the total offline torque demand to spool-up / spool-down state logic 1104. In some embodiments, offline “lookahead” allocator 1102 may generate use and / or generate nominal scheduled torque limits that are associated with (e.g., correlated with) increased weighting values (e.g., for anPATENTAttorney Docket No. 16499.0040-00304 algorithm, weighted equation, etc.) at lower speeds (e.g., lower commanded aircraft speeds, lower measured airspeeds, lower commanded EPU propeller speeds, lower measured EPU propeller speeds, etc.).

[0138] In some embodiments, an online allocator 1101 may feed one or more actuator commands to an EPU controller 1103. In some embodiments, an EPU controller 1103 may include a controller to control lifters. In some embodiments, an EPU controller 1103 may include states for lifter pairs that may be managed with respect to a spool-up or a spool-down. In some embodiments, an EPU controller 1103 may include a future fault-handling state and / or a fault-handling logic. In some embodiments, functions of an EPU controller 1103 may also be performed by spool -up / spool-down state logic 1104.

[0139] In some embodiments, system 1100 may be configured to issue commands or certain commands (e.g., spool -up / spool-down commands) to any type of EPU, or only one type of EPU (e.g., a lifter, described above). It is therefore appreciated that any reference to a “lifter” may be equally applied to a “til ter” or to any EPU, and conversely that any reference an “EPU” may be equally applied to only a “lifter” or “tilter”.

[0140] In some embodiments, an online allocator 1101 may further feed one or more actuator commands to a spool -up / spool-down state logic 1104.

[0141] In some embodiments, an offline “lookahead” allocator 1102 may feed one or more total lifter aerodynamic torque demands to a spool -up / spool-down state logic 1104.

[0142] In some embodiments, a spool-up / spool-down state logic 1104 may determine a triggering pattern for a spool-up or a spool-down, depending on an aerodynamic torque demand or an aerodynamic torque achieved. In some embodiments, a spool-up / spool-down state logic 1104 may estimate a feasible spool -up and / or spool-down rate for an individual lifter or a pair of lifters. In some embodiments, a spool-up / spool-down state logic 1104 may estimate feasible spool-up and / or spool-down rates for lifter pairs to avoid a motor torque saturation or other errors. In some embodiments, a spool-up / spool-down state logic 1104 may generate aerodynamic torque limit signals for the online allocator 1101. In some embodiments, functions of spool-up / spool-down state logic 1104 may also be performed by enabling sequential spool- up / spool-down logic 1106.

[0143] In some embodiments, a spool-up / spool-down state logic 1104 may feed one or more lifter transition states to an enabling sequential spool-up / spool-down logic 1106. In some embodiments, an enabling sequential spool-up / spool-down logic 1106 may generate dynamicPATENTAttorney Docket No. 16499.0040-00304 upper and / or lower aerodynamic torque limits. Additionally or alternatively, enabling sequential spool -up / spool-down logic 1106 may generate dynamic torque limits and / or input dynamic torque limits to blend-in sequential spool -up / spool-down logic 1105. In some embodiments, enabling sequential spool -up / spool-down logic 1106 may generate dynamic torque limits that are associated with (e.g., correlated with) reduced weighting values (e.g., for an algorithm, weighted equation, etc.) at lower speeds (e.g., lower commanded aircraft speeds, lower measured airspeeds, lower commanded EPU propeller speeds, lower measured EPU propeller speeds, etc.).

[0144] In some embodiments, an enabling sequential spool -up / spool-down logic 1106 may feed dynamic upper and / or lower aerodynamic torque limits to a blend-in sequential spool - up / spool-down logic 1105. In some embodiments, a blend-in sequential spool -up / spool-down logic 1105 may be controlled based on at least one of a threshold airspeed, an FMS contingency (e.g., land now, return home), or a nominal scheduled aerodynamic torque limit.

[0145] In some embodiments, a blend-in sequential spool -up / spool-down logic 1105 may be configured to feed online aerodynamic torque limits to an online allocator 1101, which in turn may compute and / or recompute actuator commands to transmit to at least one EPU controller and / or may compute information to transmit to the spool -up / spool-down logic.

[0146] In some embodiments, at least one component (e.g., FCC, online allocator 1101, or all or part of system 1100) may receive a first thrust command. For example, online allocator 1101 may receive an FM demand that includes the first thrust command. In some instances, a command may instruct a recipient (e.g., EPU) to maintain a current state (e.g., maintain an RPM or spooling stage). Additionally or alternatively, while one EPU may receive a thrust command to change states, another EPU may maintain a current state, regardless of whether it receives a specific command to do so, consistent with disclosed embodiments.

[0147] In some embodiments, at least one component (e.g., FCC, online allocator 1101, or all or part of system 1100) may command, based on the received first thrust command, at least one first EPU to a first spooling stage and at least one second EPU (e.g., distinct or separate from the at least one first EPU) to a second spooling stage different from the first spooling stage. For example, the first thrust command may be a command for increased thrust (e.g., when the aircraft is commanded to increase lift and / or speed), and the component may command the at least one first EPU to a first spooling stage that is associated with (e.g., is configured to cause) increased thrust relative to the second spooling stage and / or a priorPATENTAttorney Docket No. 16499.0040-00304 spooling stage of the at least one first EPU. In some embodiments, the at least one first EPU and the at least one second EPU may both be in the second spooling stage (e.g., a lower thrust spooling stage than the first spooling stage, a higher thrust spooling stage than the first spooling stage) when the thrust command is received. Commanding the at least one second EPU to a second spooling stage different from the first spooling stage may include commanding the at least one second EPU to maintain the second spooling stage. As another example, the first thrust command may be a command for decreased thrust (e.g., when the aircraft is commanded to decrease lift and / or speed), and the component may command the at least one first EPU to a first spooling stage that is associated with (e.g., is configured to cause) decreased thrust relative to the second spooling stage and / or a prior spooling stage of the at least one first EPU.

[0148] In some embodiments, at least one component may predict whether an EPU will remain in an RPM avoidance range for more than a predetermined duration of time. In some embodiments, such prediction may be implemented based on any one or any combination of inputs, such as at least one phase of flight, at least one flight state, at least one aircraft state, at least one pilot command, at least one external force, at least one environmental condition, at least one aircraft characteristic, at least one flight condition, flight plan data, historical data, or at least one model.

[0149] In some embodiments, at least one component may override or recover a spool - up / spool-down command to maintain RPM consistency and avoid unnecessary reversals. In some embodiments, the at least one component may be configured to, based on an indication that an RPM avoidance range violation would be transient or temporary, override or recover the spooling command to maintain a consistent RPM, rather than performing a full spool- up / spool-down only to then have a subsequent spooling process to reverse it. In some embodiments, an indication that an RPM avoidance violation would be transient or temporary may be based on prediction of whether an EPU will remain in an RPM avoidance range for more than a predetermined duration of time. As used herein, an override or recovery command may refer to a control action that interrupts, reverses, suspends, and / or supersedes an ongoing spool-up or spool-down command before completion, based on a determination that the RPM avoidance range violation is predicted to be transient or temporary. For example, the override may cancel or reverse the original spooling command and recover the EPU to its prior operating state to maintain RPM consistency and avoid unnecessary reversals.PATENTAttorney Docket No. 16499.0040-00304

[0150] In some embodiments, an EPU that changes from the first spooling stage to the second spooling stage, or vice versa, may pass through an RPM avoidance range, discussed above. An RPM avoidance range may include a maximum RPM value and a minimum RPM value. An RPM avoidance range may include, for example, RPMs of approximately 100-900 RPM, though other ranges are possible (e.g., 5-100 RPM, 100-500 RPM, 100-1,100 RPM, etc.). For example, in an embodiment including an EPU with an RPM avoidance range of 5- 100 RPM, the maximum RPM value of the RPM avoidance range is 5 RPM, while the minimum RPM value of the RPM avoidance range is 100 RPM. In some embodiments the RPM avoidance range may be based on a propeller configuration (e.g., a number, length, arrangement, shape, and / or tilt of one or more propellers of an EPU).

[0151] In some embodiments, the first spooling stage may include a range of RPM values above a maximum RPM of an RPM avoidance range and the second spooling stage may include a range of RPM values below a minimum RPM value of the RPM avoidance range. In some embodiments, the first spooling stage may include a range of RPM values above a maximum RPM value of a first RPM avoidance range, a second spooling stage may include a range of RPM values below a minimum RPM value of a second RPM avoidance range, and a third spooling stage may include a range of RPM values above a maximum RPM value of the second RPM avoidance range and below a minimum RPM value of the first RPM avoidance range, where a minimum RPM value of the first RPM avoidance range is greater than a maximum RPM value of the second RPM avoidance range.

[0152] In some embodiments, at least one component may be configured to command both the at least one first EPU and the at least one second EPU to the third spooling stage before commanding the at least one first EPU or the at least one second EPU to the second spooling stage. In some embodiments, at least one component may be configured to command the at least one first EPU to the second spooling stage before commanding the at least one second EPU to the third spooling stage.

[0153] Additionally or alternatively, as discussed above, when at least one EPU transitions from one spooling stage to another, at least one other EPU may be sped up or sped down (e.g., to a different spooling stage or substage), which may occur temporarily (e.g., for a calculated and / or predetermined amount of time) during the transition, which may help to at least partially offset the change in thrust (e.g., what would otherwise be a rapid and / or turbulent change in thrust) resulting from the transition.PATENTAttorney Docket No. 16499.0040-00304

[0154] In some embodiments, the at least one first EPU may include a pair of EPUs or more (i.e., two or more EPUs). Additionally, the at least one second EPU may include a pair of EPUs or more (i.e., two or more EPUs). A pair of EPUs may include one EPU on one side of the aircraft (e.g., the left side) and one EPU on the other side of the aircraft (e.g., the right side). In some embodiments, the pair of EPUs may include opposite (e.g., symmetrically opposite) EPUs. For example, with respect to exemplary Fig. 9A, EPUs 909 and 910 are opposite, 908 and 911 are opposite, and 907 and 912 are opposite.

[0155] In some embodiments, a component (e.g., FCC, online allocator 1101, or all or part of system 1100) may receive a second thrust command. For example, online allocator 1101 may receive an FM demand that includes the second thrust command. The second thrust command may be distinct from the first thrust command and / or may be a continuation of the first thrust command (e.g., a continuation of the first thrust command across a threshold period of time).

[0156] In some embodiments, a component (e.g., FCC, online allocator 1101, or all or part of system 1100) may command, based on the received second thrust command, the at least one second EPU to the first spooling stage (e.g., the same spooling stage to which the at least one first EPI was commanded based on the first thrust command).

[0157] In some embodiments, at least one processing component (e.g., FCC, online allocator 1101, or all or part of system 1100) may sequence commands to EPU groups based on the position of the EPUs in those groups. For example, at least one processing component (e.g., FCC, online allocator 1101, or all or part of system 1100) may command EPUs that are closer to the aircraft body (e.g., centerline, fuselage) to higher speed spooling stages prior to commanding EPUs that are further from the aircraft body to the same or similar higher speed spooling stages. For example, when one or more thrust commands for increased thrust are received, the component may command EPUs 909 and 910 to a higher speed spooling stage (e.g., a first or second spooling stage) prior to commanding EPUs 908 and 911 to the higher speed spooling stage. In other embodiments, the opposite may be true (e.g., a component may command EPUs that are further from the aircraft body to higher speed spooling stages prior to commanding EPUs that are closer to the aircraft body to the same or similar higher speed spooling stages).

[0158] Additionally or alternatively, a component (e.g., FCC, online allocator 1101, or all or part of system 1100) may command EPUs that are further from the aircraft body (e.g.,PATENTAttorney Docket No. 16499.0040-00304 centerline, fuselage) to lower speed spooling stages prior to commanding EPUs that are further from the aircraft body to the same or similar lower speed spooling stages. For example, when one or more thrust commands for decreased thrust are received, the component may command EPUs 908 and 911 to a lower speed spooling stage (e.g., a first or second spooling stage) prior to commanding EPUs 909 and 910 to the lower speed spooling stage. In other embodiments, the opposite may be true (e.g., a component may command EPUs that are closer to the aircraft body to lower speed spooling stages prior to commanding EPUs that are further from the aircraft body to the same or similar lower speed spooling stages). Additionally or alternatively, the component may prioritize spooling up or spooling down one or more EPUs based on one or more other factors, such as aircraft geometry, EPU mass, aircraft mass (e.g., weight), aircraft shape, EPU shape, airspeed, aircraft materials, aircraft payload, limitations of any aircraft component (e.g., acceleration limits, torque limits, and the like), environmental conditions, etc.

[0159] The embodiments described herein may be applied to any number and configuration of EPU groups. For example, three EPU groups may be designated (e.g., EPUs 909 and 910, EPUs 908 and 911, and EPUs 907 and 912), and the EPU groups may be commanded to the same or different spooling stages (e.g., two different spooling stages, three or more different spooling stages) based on one or more received thrust commands, consistent with disclosed embodiments).

[0160] In some embodiments, an EPU or a group of EPUs may be prioritized based on an amount of command authority that they provide. In some embodiments, an EPU or a group of EPUs may be prioritized based on a roll authority, a pitch authority, a yaw authority, or a combination of roll, pitch, and / or yaw authority. In some embodiment, one or more EPUs may be designated to a group based on an active maneuver or a planned maneuver. In some embodiments, an EPU or a group of EPUs may be prioritized for spooling up and / or spooling down to different spooling stages based on an active maneuver or a planned maneuver.

[0161] In some embodiments, EPUs may be designated into any number of different groups of EPUs. In some embodiments, at least one EPU may be moved or switched into a different group based on one or more factors related to aircraft and / or EPU performance, such as EPU thrust loss, EPU failure, battery capacity, loads, etc. For example, if an individual EPU in a pair or a group unintentionally fails, one or more other EPUs may be moved or switched into (e.g., by at least one processing component) a different group to compensate for the failure. In some embodiments, any number of EPUs may be designated to any number of differentPATENTAttorney Docket No. 16499.0040-00304 groups. While a “pair” of EPUs may be discussed in certain embodiments, it is appreciated that this is one example of a group of EPUs, and that other types of groups may also be used (i.e., not necessarily a pair).

[0162] In some embodiments, a component (e.g., FCC, online allocator 1101, or all or part of system 1100) may command one or more EPUs based on an indication that one or more EPUs is in a failed state (e.g., broken, disconnected, unresponsive, not achieving a performance metric, and / or unable to achieve a threshold thrust). For example, the component may adjust a sequence of EPUs or EPU groups to transition between spooling stages. By way of further example, the component may prioritize a failed EPU, or group having a failed EPU, for powering down (e.g., transitioning to a lower speed spooling stage, such as when a command for decreased thrust is received) and / or may de-prioritize a failed EPU, or group having a failed EPU, for powering up (e.g., transitioning to a higher speed spooling stage, such as when a command for higher thrust is received).

[0163] Fig. 12 illustrates a graph of an exemplary progression of spooling-down EPUs through an RPM avoidance range, consistent with disclosed embodiments. The graph depicts a staggered shutdown sequence over time, with the x-axis representing time and the y-axis representing RPM. As stated above, while certain references may be made to a “pair” of EPUs, any such reference may be equally applied to any EPU group. In some embodiments, this exemplary progression of spooling-down EPUs may correspond to spooling-down EPUs during a transition phase of flight, such as when an aircraft is transitioning from a cruise phase of flight to a hover phase of flight.

[0164] As shown in Fig. 12, the graph depicts a first spooling stage 1201, an RPM avoidance range 1202, and a second spooling stage 1203. As shown in Fig. 12, the graph depicts RPM values of various combinations of EPUs through different dashing patterns.

[0165] In some embodiments, the first spooling stage 1201 may include a range of RPM values above a maximum RPM of the RPM avoidance range 1202 and the second spooling stage 1203 may include a range of RPM values below a minimum RPM value of the RPM avoidance range 1202.

[0166] As shown in Fig. 12, the graph depicts three spool-down occurrences for corresponding to a set of single EPUs or a set of pairs of EPUs (e.g., a pair of corresponding EPUs on either side of the aircraft). In some embodiments, a control system may control a first spool-down event by commanding a first EPU or pair of EPUs (EPU 1) to transition from aPATENTAttorney Docket No. 16499.0040-00304 powered-on status in a first spooling stage 1201 (e.g., operating at an RPM above the maximum RPM value of the RPM avoidance range 1202) to a powered-off or idle status in a second spooling stage 1203 (e.g., operating at an RPM below the minimum RPM value of the RPM avoidance range 1202). The graph illustrates an exemplary RPM trajectory of the first EPU or pair of EPUs (EPU 1) while passing through an RPM avoidance range. In some embodiments, the spool-down may be rapid to reduce or minimize the amount of time spent in the RPM avoidance range, before subsequently leveling off into a powered-off or idle status. For example, at least one processing component controlling an EPU may command an EPU to change its RPM from a first value on one side of an RPM avoidance range 1202 to a second value on the other side of the RPM avoidance range 1202. Commanding the EPU to implement such a change may include instructing the EPU to change its RPM at a higher rate of change when it is operating in the RPM avoidance range than when it is not operating in the RPM avoidance range. Such a technique may be used in any of the embodiments described herein (e.g., spooling up and down EPUs, discussed with respect to Figs. 11, 12, 13, 14, and 15).

[0167] As further shown in Fig. 12, during the first (leftmost) spool-down event, the control system may simultaneously command a first EPU or first EPU group (EPU 1) to spool down and at least one second EPU or pair of EPUs to increase thrust output to compensate for or at least partially offset the sharp decrease in total thrust output caused by the first spooldown event. In some embodiments, at least one second EPU or pair of EPUs may include all remaining EPUs (e.g., the EPUs that were not spooled down during the first spool-down event). For example, as shown in Fig. 12, the control system may command a second EPU and a third EPU to increase thrust output to compensate for or at least partially offset the sharp increase in total thrust output caused by the first spool-down event. This compensation is reflected in the graph as a corresponding increase in RPM for the second EPU (or pair of EPUs) (EPU 2) and third EPU (or pair of EPUs) (EPU 3). In some embodiments, the compensation may decrease, minimize, offset, or cancel out the resulting change in total thrust caused by the rapid spooldown of the first EPU or pair of EPUs, consistent with disclosed embodiments (e.g., those discussed with respect to Fig. 11).

[0168] Following the first spool-down event, the graph illustrates a second spool-down event for another EPU or pair of EPUs (EPU 2) different from the first EPU or first pair of EPUs (EPU 1). Similar to the first spool-down event, the second spool-down event may be rapid to reduce time spent in the RPM avoidance range. During this second spool-down event,PATENTAttorney Docket No. 16499.0040-00304 the control system may simultaneously command one or more remaining EPUs or pairs of EPUs (EPU 3) to increase thrust output to compensate for or at least partially offset the reduction in total thrust. The graph shows a corresponding increase in RPM for the compensating EPUs during this second event.

[0169] Fig. 12 also illustrates a third spool-down event for another EPU or pair of EPUs (EPU 3) different from the first EPU and the second EPU (or the first pair of EPUs and the second pair of EPUs) (EPU 1 and EPU 2). In some embodiments, a third spool-down event may or may not be accompanied by a compensatory thrust adjustment by one or more additional remaining EPUs.

[0170] It is appreciated that while three exemplary spool-down events are depicted in Fig. 12, other numbers of similar spool-down events may occur with the same or different numbers of EPUs.

[0171] In some embodiments, the control system may dynamically adjust the order of spool-down events and compensation commands based on any one or any combination of at least one phase of flight, at least one flight state, at least one aircraft state, at least one operational condition, at least one pilot input, at least one aircraft characteristic, at least one load distribution target (e.g., constraint, parameter, desired state), or at least one environmental condition. In some embodiments, the spooling events may be staggered in time to maintain overall aircraft stability and reduce vibration while transitioning through RPM avoidance ranges. It is appreciated that the terms and lines corresponding to “EPU 1”, “EPU 2”, and “EPU 3” in Fig. 12 may correspond to single EPUs, pairs of EPUs, or even larger groups of EPUs (e g., 3 EPUs, 4 EPUs, etc ).

[0172] As shown in Figs. 13 and 14, a control system may dynamically adjust the order in which EPUs spool-down through a plurality of RPM avoidance ranges.

[0173] Fig. 13 illustrates a graph of an exemplary progression of spooling-down EPUs through a plurality of RPM avoidance ranges in a first sequence, consistent with disclosed embodiments. The graph depicts a staggered shutdown sequence through a plurality of RPM avoidance ranges over time, with the x-axis representing time and the y-axis representing RPM. As stated above, while certain references may be made to a “pair” of EPUs, any such reference may be equally applied to any EPU group. The changes in RPMs depicted in the graph may be caused by instructions issued to corresponding EPUs or groups of EPUs (e.g., by at least one processing device), consistent with disclosed embodiments. In some embodiments, thisPATENTAttorney Docket No. 16499.0040-00304 exemplary progression of spooling-down EPUs may correspond to spooling-down EPUs during a transition phase of flight, such as when an aircraft is transitioning from a cruise phase of flight to a hover phase of flight.

[0174] As shown in Fig. 13, the graph depicts a first spooling stage 1301, a first RPM avoidance range 1302, a third spooling stage 1303, a second RPM avoidance range 1304, and a second spooling stage 1305. As shown in Fig. 13, the graph depicts RPM values of various combinations of EPUs through different dashing patterns.

[0175] In some embodiments, the first spooling stage 1301 may include a range of RPM values above a maximum RPM value of a first RPM avoidance range 1302, the second spooling stage 1305 may include a range of RPM values below a minimum RPM value of a second RPM avoidance range 1304, and a third spooling stage 1303 may include a range of RPM values above a maximum RPM value of the second RPM avoidance range 1304 and below a minimum RPM value of the first RPM avoidance range 1302, wherein a minimum RPM value of the first RPM avoidance range 1302 is greater than a maximum RPM value of the second RPM avoidance range 1304.

[0176] As shown in Fig. 13, the graph depicts a first RPM avoidance range 1302 that is higher than a second RPM avoidance range 1304.

[0177] As shown in Fig. 13, a first sequence may include passing a plurality of EPUs or pairs of EPUs through two RPM avoidance ranges in a staggered manner. As shown in Fig. 13, a first EPU or pair of EPUs (EPU 1) passes through a first RPM avoidance range 1302, followed by a second EPU or pair of EPUs (EPU 2) passing through the first RPM avoidance range 1302, and then a third EPU or pair of EPUs (EPU 3) passing through the first RPM avoidance range 1302. After each EPU or pair of EPUs (EPU 1, EPU 2, EPU 3) has transitioned through the first RPM avoidance range 1302, the sequence continues with the first EPU or pair of EPUs (EPU 1) passing through the second RPM avoidance range 1304, followed by the second EPU or pair of EPUs (EPU 2), and then the third EPU or pair of EPUs (EPU 3).

[0178] This staggered approach may reduce vibration and maintain stability by limiting the number of EPUs simultaneously operating within an RPM avoidance range. In some embodiments, the control system may dynamically adjust the timing and order of these transitions based on any one or any combination of at least one phase of flight, at least one flight state, at least one aircraft state, at least one operational condition, at least one pilot input, at least one aircraft characteristic, at least one load distribution target (e.g., constraint,PATENTAttorney Docket No. 16499.0040-00304 parameter, desired state), or at least one environmental condition. Although Fig. 13 illustrates two RPM avoidance ranges, the disclosed concepts may apply to any number of RPM avoidance ranges, and the sequence may be adapted accordingly. Additionally, it is appreciated that the terms and lines corresponding to “EPU 1”, “EPU 2”, and “EPU 3” in Fig. 13 may correspond to single EPUs, pairs of EPUs, or even larger groups of EPUs (e.g., 3 EPUs, 4 EPUs, etc.). Moreover, it is appreciated that while three exemplary spool-down events are depicted in Fig. 13, other numbers of similar spool-down events may occur with the same or different numbers of EPUs.

[0179] In some embodiments, control of EPUs may be sequenced (e.g., by system 1100) such that only a single EPU or EPU group transitions through an RPM avoidance range during a given time period.

[0180] Fig. 14 illustrates a graph of an exemplary progression of spooling-down EPUs through a plurality of RPM avoidance ranges in a second sequence, consistent with disclosed embodiments. The graph depicts a staggered shutdown sequence through a plurality of RPM avoidance ranges over time, with the x-axis representing time and the y-axis representing RPM. As stated above, while certain references may be made to a “pair” of EPUs, any such reference may be equally applied to any EPU group. The changes in RPMs depicted in the graph may be caused by instructions issued to corresponding EPUs or groups of EPUs (e.g., by at least one processing device), consistent with disclosed embodiments. In some embodiments, this exemplary progression of spooling-down EPUs may correspond to spooling-down EPUs during a transition phase of flight, such as when an aircraft is transitioning from a cruise phase of flight to a hover phase of flight.

[0181] As shown in Fig. 14, the graph depicts a first spooling stage 1401, an RPM avoidance range 1402, a third spooling stage 1403, a second RPM avoidance range 1404, and a second spooling stage 1405. As shown in Fig. 14, the graph depicts RPM values of various combinations of EPUs through different dashing patterns.

[0182] In some embodiments, the first spooling stage 1401 may include a range of RPM values above a maximum RPM value of a first RPM avoidance range 1402, the second spooling stage 1405 may include a range of RPM values below a minimum RPM value of a second RPM avoidance range 1404, and a third spooling stage 1403 may include a range of RPM values above a maximum RPM value of the second RPM avoidance range 1404 and below a minimum RPM value of the first RPM avoidance range 1402, wherein a minimumPATENTAttorney Docket No. 16499.0040-00304RPM value of the first RPM avoidance range 1402 is greater than a maximum RPM value of the second RPM avoidance range 1404.

[0183] As shown in Fig. 14, the graph depicts a first RPM avoidance range 1402 that is higher than a second RPM avoidance rangel404. As shown in Fig. 14, the second sequence may include passing each EPU or pair of EPUs through a plurality of RPM avoidance ranges before a subsequent EPU or pair of EPUs begins its transitions. As shown in Fig. 14, a first EPU or pair of EPUs (EPU 1) passes through a first RPM avoidance range 1402 and immediately through a second RPM avoidance range 1404. After the first EPU or pair of EPUs (EPU 1) completes its transitions, the second EPU or pair of EPUs (EPU 2) passes through the first RPM avoidance range 1402 and the second RPM avoidance range 1404, followed by the third EPU or pair of EPUs (EPU 3).

[0184] This approach may be advantageous in scenarios where rapid clearance of RPM avoidance ranges for individual EPUs or pairs of EPUs is preferred, such as during high-wind conditions, rapid flight mode transitions, or when required by structural load balancing constraints. In some embodiments, the control system may dynamically adjust the timing and order of these transitions based on any one or any combination of at least one phase of flight, at least one flight state, at least one aircraft state, at least one operational condition, at least one pilot input, at least one aircraft characteristic, at least one load distribution target (e.g., constraint, parameter, desired state), or at least one environmental condition.

[0185] In some embodiments, such as those with three or more RPM avoidance ranges, an EPU may be instructed to transit multiple RPM avoidance ranges (e.g., as depicted in Fig. 14) and may also be instructed to maintain an RPM between avoidance ranges (e.g., as depicted in Fig. 13) while other EPUs transit one or more RPM avoidance ranges.

[0186] Although Fig. 14 illustrates two RPM avoidance ranges, the disclosed concepts may apply to any number of RPM avoidance ranges, and the sequence may be adapted accordingly. Additionally, it is appreciated that the terms and lines corresponding to “EPU 1”, “EPU 2”, and “EPU 3” in Fig. 14 may correspond to single EPUs, pairs of EPUs, or even larger groups of EPUs (e.g., 3 EPUs, 4 EPUs, etc.). Moreover, it is appreciated that while three exemplary spool-down events are depicted in Fig. 14, other numbers of similar spool-down events may occur with the same or different numbers of EPUs.

[0187] Fig. 15 illustrates a graph of an exemplary spool -down override, consistent with disclosed embodiments. The graph depicts a sequence of spool-down overrides or recoveriesPATENTAttorney Docket No. 16499.0040-00304 over time, with the x-axis representing time and the y-axis representing RPM. As stated above, while certain references may be made to a “pair” of EPUs, any such reference may be equally applied to any EPU group. The changes in RPMs depicted in the graph may be caused by instructions issued to corresponding EPUs or groups of EPUs (e.g., by at least one processing device), consistent with disclosed embodiments.

[0188] As shown in Fig. 15, the graph depicts a first spooling stage 1501, an RPM avoidance range 1502, and a second spooling stage 1503. As shown in Fig. 15, the graph depicts RPM values of various combinations of EPUs through different dashing patterns

[0189] As shown in Fig. 15, an EPU (EPU 1) may begin a spool-down sequence through an RPM avoidance range 1502 in response to a command and / or detected condition. However, before completing the spool-down, the control system may determine that the RPM avoidance range violation is predicted to be transient or temporary and, based on this determination, may issue an override or recovery command to cancel or reverse the spool-down command and recover the EPU to its prior operating state. An override or recovery command may help maintain RPM consistency and stability. In some embodiments, a second EPU (EPU 2) may be configured to compensate for or at least partially offset the total thrust caused by the spool-down of the first EPU (EPU 1).

[0190] In some embodiments, the control system may predict whether an EPU will remain in an RPM avoidance range for more than a predetermined duration of time. Such prediction may be based on any one or any combination of inputs, including at least one phase of flight, at least one flight state, at least one aircraft state, at least one pilot command, at least one external force (e.g., gust loads), at least one environmental condition, at least one aircraft characteristic, at least one flight condition, flight plan data, historical data, or at least one model. The control system may, based on determining that the predicted time in the RPM avoidance range is below a predetermined threshold, override the spool-down command and recover the EPU to its prior operating state, which may thereby avoid unnecessary reversals.

[0191] With respect to Fig. 15, the graph may illustrate or represent multiple scenarios where spool-down recovery occurs. For example, an EPU may begin spooling down based on to a gust-induced disturbance but then recover to its prior RPM level when the disturbance subsides. In another scenario, an EPU may begin spooling up but then recover to its prior RPM level if a transient acceleration command is detected (e.g., by at least one processing device). This approach allows the RPM to remain consistent when a keep-out zone violation would onlyPATENTAttorney Docket No. 16499.0040-00304 be temporary, reducing unnecessary transitions and improving overall system efficiency. In some embodiments, the control system may base override or recovery decisions on monitored vibration levels, airspeed, pilot acceleration or deceleration commands, or other signals indicative of transient conditions.

[0192] Additionally, it is appreciated that the terms and lines corresponding to “EPU 1”, “EPU 2”, and “EPU 3” in Fig. 15 may correspond to single EPUs, pairs of EPUs, or even larger groups of EPUs (e.g., 3 EPUs, 4 EPUs, etc.). Moreover, it is appreciated that while three exemplary spool-down events are depicted in Fig. 15, other numbers of similar spool-down events may occur with the same or different numbers of EPUs.

[0193] Fig. 16 illustrates a graph of an exemplary progression of spooling-up EPUs through an RPM avoidance range, consistent with disclosed embodiments. The graph depicts a staggered shutdown sequence over time, with the x-axis representing time and the y-axis representing RPM. As stated above, while certain references may be made to a single EPU or a “pair” of EPUs, any such reference may be equally applied to any EPU group. In some embodiments, this exemplary progression of spooling up EPUs may correspond to spooling up EPUs during a transition phase of flight, such as when an aircraft is transitioning from a hover phase of flight to a cruise phase of flight.

[0194] As shown in Fig. 16, the graph depicts a first spooling stage 1601, an RPM avoidance range 1602, and a second spooling stage 1603. As shown in Fig. 16, the graph depicts RPM values of various combinations of EPUs through different dashing patterns.

[0195] As shown in Fig. 16, the graph depicts three spool-up occurrences for corresponding to a set of single EPUs or a set of pairs of EPUs (e.g., a pair of corresponding EPUs on either side of the aircraft). In some embodiments, a control system may control a first spool-up event by commanding a first EPU or pair of EPUs (EPU 1) to transition from a powered-off or idle status in a first spooling stage 1601 (e.g., operating at an RPM below the minimum RPM value of the RPM avoidance range 1602) to a powered-on status in a second spooling stage 1603 (e.g., operating at an RPM above the maximum RPM value of the RPM avoidance range 1602). The graph illustrates an exemplary RPM trajectory of the first EPU or pair of EPUs (EPU 1) while passing through an RPM avoidance range. In some embodiments, the spool-up may be rapid to reduce or minimize the amount of time spent in the RPM avoidance range, before subsequently leveling off into a stable powered-on status. For example, at least one processing component controlling an EPU may command an EPU to change itsPATENTAttorney Docket No. 16499.0040-00304RPM from a first value on one side of an RPM avoidance range 1202 to a second value on the other side of the RPM avoidance range 1202. Commanding the EPU to implement such a change may include instructing the EPU to change its RPM at a higher rate of change when it is operating in the RPM avoidance range than when it is not operating in the RPM avoidance range. Such a technique may be used in any of the embodiments described herein (e.g., spooling up and down EPUs, discussed with respect to Figs. 11, 12, 13, 14, 15, and 16).

[0196] As further shown in Fig. 16, during the first (leftmost) spool -down event, the control system may simultaneously command a first EPU or first EPU group (EPU 1) to spool up and at least one second EPU or pair of EPUs to decrease thrust output to compensate for or at least partially offset the sharp increase in total thrust output caused by the first spool-up event. In some embodiments, at least one second EPU or pair of EPUs may include all remaining EPUs (e.g., the EPUs that were not spooled down during the first spool-down event). For example, as shown in Fig. 16, the control system may command a second EPU and a third EPU to decrease thrust output to compensate for or at least partially offset the sharp increase in total thrust output caused by the first spool-up event. This compensation is reflected in the graph as a corresponding decrease in RPM for the second EPU (or pair of EPUs) (EPU 2) and third EPU (or pair of EPUs) (EPU 3). In some embodiments, the compensation may decrease, minimize, offset, or cancel out the resulting change in total thrust caused by the rapid spool-up of the first EPU or pair of EPUs, consistent with disclosed embodiments (e.g., those discussed with respect to Fig. 11).

[0197] Following the first spool-down event, the graph illustrates a second spool -up event for another EPU or pair of EPUs (EPU 2) different from the first EPU or first pair of EPUs (EPU 1). Similar to the first spool-up event, the second spool-up event may be rapid to reduce time spent in the RPM avoidance range. During this second spool-up event, the control system may simultaneously command one or more remaining EPUs or pairs of EPUs (EPU 3) to decrease thrust output to compensate for or at least partially offset the increase in total thrust. The graph shows a corresponding decrease in RPM for the compensating EPUs during this second event.

[0198] Finally, Fig. 16 illustrates a third spool -up event for another EPU or pair of EPUs (EPU 3) different from the first EPU and the second EPU (or the first pair of EPUs and the second pair of EPUs) (EPU 1 and EPU 2). In some embodiments, a third spool -up eventPATENTAttorney Docket No. 16499.0040-00304 may or may not be accompanied by a compensatory thrust adjustment by one or more additional remaining EPUs.

[0199] In some embodiments, the control system may dynamically adjust the order of spool-up events and compensation commands based on any one or any combination of at least one phase of flight, at least one flight state, at least one aircraft state, at least one operational condition, at least one pilot input, at least one aircraft characteristic, at least one load distribution target (e.g., constraint, parameter, desired state), or at least one environmental condition. In some embodiments, the spooling events may be staggered in time to maintain overall aircraft stability and reduce vibration while transitioning through RPM avoidance ranges.

[0200] Additionally, it is appreciated that the terms and lines corresponding to “EPU 1”, “EPU 2”, and “EPU 3” in Fig. 16 may correspond to single EPUs, pairs of EPUs, or even larger groups of EPUs (e.g., 3 EPUs, 4 EPUs, etc.). Moreover, it is appreciated that while three exemplary spool-down events are depicted in Fig. 16, other numbers of similar spool-down events may occur with the same or different numbers of EPUs.

[0201] Although Figs. 13-15 refer to a spool-down process, any description of these figures may also apply to a spool-up process (i.e., transitioning EPUs from a powered-off or idle status to a powered-on status), such as depicted in Fig. 16.

[0202] Additional aspects of the present disclosure may be further described via the following clauses:1. A method for controlling an aircraft, comprising: receiving, using at least one hardware processor, a first thrust command; commanding, using the at least one hardware processor, based on the received first thrust command, at least one first EPU to a first spooling stage and at least one second EPU to a second spooling stage different from the first spooling stage; receiving, using the at least one hardware processor, a second thrust command; and commanding, based on the received second thrust command, the at least one second EPU to the first spooling stage.2. The method of clause 1, further comprising:PATENTAttorney Docket No. 16499.0040-00304 receiving, using the at least one hardware processor, a third thrust command; and commanding, using the at least one hardware processor, based on the received third thrust command, at least one third EPU to the second spooling stage.3. The method of clauses 1 or 2, wherein the first spooling stage includes a range of RPM values above a maximum RPM value of an RPM avoidance range and the second spooling stage includes a range of RPM values below a minimum RPM value of the RPM avoidance range.4. The method of clause 3, wherein the at least one processor is further configured to dynamically adjust the RPM avoidance range based on at least one of mast moment data, vibration data, at least one aircraft characteristic, or at least one environmental condition.5. The method of any one of clauses 1 to 4, wherein the first spooling stage includes a range of RPM values above a maximum RPM value of a first RPM avoidance range, the second spooling stage includes a range of RPM values below a minimum RPM value of a second RPM avoidance range, and a third spooling stage includes a range of RPM values above a maximum RPM value of the second RPM avoidance range and below a minimum RPM value of the first RPM avoidance range, wherein a minimum RPM value of the first RPM avoidance range is greater than a maximum RPM value of the second RPM avoidance range.6. The method of any one of clauses 1 to 5, further comprising dynamically adjusting, using the at least one hardware processor, the first RPM avoidance range and the second RPM avoidance range based on at least one of mast moment data, vibration data, at least one aircraft characteristic, or at least one environmental condition.7. The method of any one of clauses 1 to 5, further comprising commanding, using the at least one hardware processor, both the at least one first EPU and the at least one second EPU to the third spooling stage before commanding the at least one first EPU or the at least one second EPU to the second spooling stage.8. The method of any one of clauses 1 to 5, further comprising commanding, using the at least one hardware processor, the at least one first EPU to the second spooling stage before commanding the at least one second EPU to the third spooling stage.PATENTAttorney Docket No. 16499.0040-003049. The method of any one of clauses 1 to 8, wherein commanding the at least one second EPU to the second spooling stage at least partially offsets a reduction in total thrust caused by the command of the at least one first EPU to the first spooling stage.10. The method of clause 9, wherein commanding the at least one second EPU to the second spooling stage includes dynamically adjusting blade collective or tilt angle of the at least one second EPU.11. The method of any one of clauses 1 to 10, wherein commanding the at least one third EPU to the second spooling stage at least partially offsets a reduction in total thrust caused by the command of the at least one second EPU to the first spooling stage.12. The method of clause 11, wherein commanding the at least one third EPU to the second spooling stage includes dynamically adjusting blade collective or tilt angle of the at least one third EPU.13. The method of any one of clauses 1 to 12, further comprising: predicting, using the at least one hardware processor, a duration of time that the at least one first EPU will remain in an RPM avoidance range; comparing, using the at least one hardware processor, the predicted duration of time to a predetermined threshold duration of time; and overriding, using the at least one hardware processor, a spooling command when the predicted duration of time is below the predetermined threshold duration of time.14. The method of any one of clauses 1 to 13, wherein the prediction is based on at least one of a pilot command, an external force, an environmental condition, or flight plan data.15. The method of any one of clauses 1 to 14, further comprising dynamically adjusting, using the at least one hardware processor, the first RPM avoidance range and the second RPM avoidance range based on data derived from one or more passenger seating sensors.16. The method of any one of clauses 1 to 15, wherein the first thrust command and the second thrust command are generated based on a pilot command.17. The method of any one of clauses 1 to 16, wherein the first thrust command and the second thrust command are generated based on an external force or an environmental condition.PATENTAttorney Docket No. 16499.0040-0030418. The method of any one of clauses 1 to 17, wherein the first thrust command and the second thrust command are generated based on one or more load distribution constraints.19. A control system for controlling an aircraft, comprising: at least one first electric propulsion unit (EPU); at least one second EPU; and at least one processor configured to perform the method of any one of clauses 1-18.20. A computer-readable medium storing instructions that are executable by at least one processor to perform the method of any one of clauses 1-18.21. A control system for controlling an aircraft, comprising: at least one first electric propulsion unit (EPU); at least one second EPU; and at least one processor configured to: receive a first thrust command; command, based on the received thrust command, the at least one first EPU to a first spooling stage and the at least one second EPU to a second spooling stage different from the first spooling stage; receive a second thrust command; and command, based on the received second thrust command, the at least one second EPU to the first spooling stage.22. A control system for controlling an aircraft, comprising at least one processor configured to: receive a first thrust command; command, based on the received thrust command, at least one first EPU to a first spooling stage and at least one second EPU to a second spooling stage different from the first spooling stage; receive a second thrust command; and command, based on the received second thrust command, the at least one second EPU to the first spooling stage.23. A method for controlling an aircraft, comprising: receiving a first thrust command;PATENTAttorney Docket No. 16499.0040-00304 commanding, based on the received thrust command, at least one first EPU to a first spooling stage and at least one second EPU to a second spooling stage different from the first spooling stage; receiving a second thrust command; and commanding, based on the received second thrust command, the at least one second EPU to the first spooling stage.24. A computer-readable medium storing instructions that are executable by at least one processor to perform the method of clause 23.

[0203] The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein.

[0204] The features and advantages of the disclosure are apparent from the detailed specification, and thus, it is intended 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, the use of a plural term does not necessarily denote a plurality unless it is unambiguous in the given context. Words such as “and” or “or” mean “and / or” unless specifically directed otherwise. As used herein, unless specifically stated otherwise, being “based on” may include being dependent on, being interdependent with, being associated with, being defined at least in part by, being derived from, being influenced by, or being responsive to. As used herein, “related to” may include being inclusive of, being expressed by, being indicated by, or being based on. Further, since numerous modifications and variations will readily occur from studying the present disclosure, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.

[0205] Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the implementations disclosed herein. It is intended that the architectures and circuit arrangements shown in figures are only for illustrative purposes and are not intended to be limited to the specific arrangements and circuit arrangements as described and shown in the figures. It is also intended that the specificationPATENTAttorney Docket No. 16499.0040-00304 and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims. The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein. It is also intended that the sequence of steps shown in figures is only for illustrative purposes and is not intended to be limited to any particular sequence of steps. As such, those skilled in the art can appreciate that these steps can be performed in a different order while implementing the same method.

Claims

PATENTAttorney Docket No. 16499.0040-00304CLAIMS1. A computer-implemented method for controlling an aircraft, comprising: receiving a first thrust command; commanding, based on the received first thrust command, at least one first electronic propulsion unit, EPU, to a first spooling stage and at least one second EPU to a second spooling stage different from the first spooling stage; receiving a second thrust command; and commanding, based on the received second thrust command, the at least one second EPU to the first spooling stage.

2. The method of claim 1, further comprising: receiving a third thrust command; and commanding, based on the received third thrust command, at least one third EPU to the second spooling stage.

3. The method of claim 1 or 2, wherein the first spooling stage includes a range of RPM values above a maximum RPM value of an RPM avoidance range and the second spooling stage includes a range of RPM values below a minimum RPM value of the RPM avoidance range.

4. The method of claim 1 or 2, wherein the first spooling stage includes a range of RPM values above a maximum RPM value of a first RPM avoidance range, the second spooling stage includes a range of RPM values below a minimum RPM value of a second RPM avoidance range, and a third spooling stage includes a range of RPM values above a maximum RPM value of the second RPM avoidance range and below a minimum RPM value of the first RPM avoidance range, wherein a minimum RPM value of the first RPM avoidance range is greater than a maximum RPM value of the second RPM avoidance range.

5. The method of claim 3 or 4, further comprising dynamically adjusting any one of the RPM avoidance ranges based on at least one of mast moment data, vibration data, at least one aircraft characteristic, or at least one environmental condition.

6. The method of claim 4, further comprising dynamically adjusting both the first RPM avoidance range and the second RPM avoidance range based on at least one of mast moment data, vibration data, at least one aircraft characteristic, or at least one environmental condition.PATENTAttorney Docket No. 16499.0040-003047. The method of claim 4, further comprising commanding both the at least one first EPU and the at least one second EPU to the third spooling stage before commanding the at least one first EPU or the at least one second EPU to the second spooling stage.

8. The method of claim 4, further comprising commanding the at least one first EPU to the second spooling stage before commanding the at least one second EPU to the third spooling stage.

9. The method of any one of claims 1-8, wherein commanding the at least one second EPU to the second spooling stage at least partially offsets a reduction in total thrust caused by the command of the at least one first EPU to the first spooling stage.

10. The method of claim 9, wherein commanding the at least one second EPU to the second spooling stage includes dynamically adjusting blade collective or tilt angle of the at least one second EPU.

11. The method of claim 2, wherein commanding the at least one third EPU to the second spooling stage at least partially offsets a reduction in total thrust caused by the command of the at least one second EPU to the first spooling stage.

12. The method of claim 11, wherein commanding the at least one third EPU to the second spooling stage includes dynamically adjusting blade collective or tilt angle of the at least one third EPU.

13. The method of any one of claims 1-12, further comprising: predicting a duration of time that the at least one first EPU will remain in an RPM avoidance range; comparing the predicted duration of time to a predetermined threshold duration of time; and overriding a spooling command when the predicted duration of time is below the predetermined threshold duration of time.

14. The method of claim 13, wherein the prediction is based on at least one of a pilot command, an external force, an environmental condition, or flight plan data.

15. The method of claim 4, further comprising dynamically adjusting the first RPM avoidance range and the second RPM avoidance range based on data derived from one or more passenger seating sensors.

16. The method of any one of claims 1-15, wherein the first thrust command and the second thrust command are generated based on at least one pilot command.PATENTAttorney Docket No. 16499.0040-0030417. The method of any one of claims 1-16, wherein the first thrust command and the second thrust command are generated based on at least one of an external force or an environmental condition.

18. The method of any one of claims 1-17, wherein the first thrust command and the second thrust command are generated based on one or more load distribution constraints.

19. A control system for controlling an aircraft, comprising: at least one first electric propulsion unit, EPU; at least one second EPU; and at least one processor configured to perform the method of any one of claims 1-18.

20. A computer-readable medium storing instructions that are executable by at least one processor to perform the method of any one of claims 1-18.

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