Systems and methods for modular aircraft

Abstract

Systems and methods involving aircraft are provided. In some embodiments, a rotorcraft (drone) made up of one or more ducted blade enclosures is provided.

Description

SYSTEMS AND METHODS FOR MODULAR AIRCRAFTCross-Reference to Related Applications

[0001] This application claims priority to U.S. Provisional Application No. 63 / 618.276, filed on January 5, 2024, now pending, U.S. Provisional Application No. 63 / 618,277, filed on January' 5, 2024, now pending, U.S. Provisional Application No. 63 / 618,279, filed on January 5, 2024, now pending, the disclosures of which are incorporated herein by reference.Field of the Disclosure

[0002] The present invention relates to systems and methods for fixed-wing and / or rotary-wing aircraft, including, for example, modular aircraft (i.e., aircraft having a reconfigurable structure) and techniques for controlling modular aircraft.Background of the Disclosure

[0003] It has been known for nearly a century that ducted propeller blades are far more efficient than open-blade configurations. While there are some rotary-w ing drones with ducted blades, current fixed-wing and most rotary-wing aircraft have open-blade configurations. And the few rotary-wing drones with ducted blades have incorporated ducts primarily for safety purposes and not to achieve greater efficiencies. The reason fixed-wing and most rotary-wing aircraft do not utilize ducted blades is because the efficiency gains from ducting the blades is offset by losses resulting from the increased w eight of the ducted-blade structure (the “Weight Penalty”). Indeed, because of the increased weight of the ducts, in many cases, rotary-wing drones with ducted blades have decreased flight times compared to open-blade counterparts.

[0004] The Weight Penalty of traditional enclosures for ducted-blade structures is the result of: (i) the manufacture of ducts using rigid structural members for strength; and (ii) the additive nature of the enclosure, i.e., the duct is designed and incorporated independently of the overall structure of the drone, and, therefore, adds to the overall structure and weight of the drone.

[0005] Additionally, current fixed-wing and rotary -wing aircraft have “fixed” constructions, in which, for example, the number of power sources cannot be increased or decreased. Because of this fixed construction, if an operator needs to lift more than the capacityof, for example, a particular rotary-wing drone, then the user must use a different, larger rotary - wing drone that has more lifting capacity. And conversely, if the user has a large rotary-wing drone but only needs to lift a small object, then the extra power and lifting capacity of that large rotary-wing drone is wasted. Similarly, the fixed construction limits the ability to affect other aircraft characteristics such as speed, maximum flight duration, etc.

[0006] Accordingly, there is a need for aircraft which allow for changes in configuration in order to meet changing flight requirements.Description of the Drawings

[0007] For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:Figure 1 shows an illustration of a ducted-blade enclosure according to an embodiment of the present disclosure;Figure 2 shows simplified schemative of a drone made up of four ducted-blade enclosures of the present disclosure;Figure 3 is a cross-sectional view of a nm of a ducted-blade enclosure where the rim has an I-beam-like cross-section;Figure 4 shows a rim configured as a truss according to another embodiment;Figure 5 shows a rim configured as a truss according to another embodiment;Figure 6 is a photo of an exemplary drone having four ducted-blade enclosures according to another embodiment of the present disclosure.Figure 7 is a perspective view of an exemplary power module for an aircraft;Figure 8A is a perspective view of an exemplary payload module for an aircraft;Figure 8B is a shaded version of the view of Figure 8A;Figure 9A is a perspective view of an aircraft embodiment having six power modules;Figure 9B is a top view of the aircraft of Figure 9A;Figure 10A is a perspective view of another aircraft embodiment having six power modules and further including a payload module;Figure 10B is a top view of the aircraft of Figure 10A;Figure 11 A is a perspective view' of another aircraft embodiment having of six pow er modules and configured as a flying wdng;Figure 1 IB is a top view of the aircraft of Figure 11 A;Figure 12A is a perspective view of an aircraft embodiment having four power modules; Figure 12B is a top view of the aircraft of Figure 12A;Figure 13 A is a perspective view of an aircraft embodiment having twelve power modules; Figure 13B is a top view of the aircraft of Figure 13 A;Figure 14 is a graph showing an example of pay load fraction of battery vs. desired flight time vs. Drone weight; andFigures 15A-15C drag curves for airfoils of different Re.Detailed Description of the Disclosure

[0008] In some embodiments, the present disclosure provides a novel ducted-blade enclosure made up of (i) a central hub with the motor and gear assembly and / or a frameless direct drive motor and attachment points to incorporate flexible spokes; (ii) blades attached to such central hub; (iii) a rim that has multiple functions, i.e., (1) it is a duct and (2) it has attachment points in order to easily attach to other rims and (3) it has other attachment areas to incorporate flexible spokes and (4) it is the structural element connecting the drone together; and (iv) flexible spokes (tension members) that provide tensioned structure to the ducted-blade enclosure by threading through the central hub and the rim. The numerous flexible spokes help maintain a tight propeller tip to rim clearance aiding aerodynamic efficiency, while allowing a relatively flexible and light rim structure, compared to a traditional sparsely supported and stiffer duct. The flexible spokes, rim, hub, housings, shaft cany' torsional, twisting loads along an axis perpendicular to the axis of rotation of the propeller, leading back to the center of the drone that normally a drone motor arm would cany, and forces generated from P-factor and gyroscopic effects.

[0009] The presently disclosed ducted-blade enclosure provides a much lighter (as much as 50% or more reduction in weight compared to traditional drones) structure and, because the rim acts as both a duct and a structural element, there is no Weight Penalty, rather there is a significant gain in structural efficiency.

[0010] In some embodiments, the present disclosure is embodied as a ducted-blade enclosure 10 for a multi-rotor drone. The ducted-blade enclosure 10 includes a motor 12 connected to a propeller (a blade) 14. The motor may be directly connected to the propeller orindirectly connected to the propeller (by way of, for example, gears, chains, belts, etc) The motor 12 is configured to rotate the propeller 14. Rotation of the propeller defines a circumference (a propeller circumference). A rim 20 surrounds and is spaced apart from the propeller circumference. By spaced apart from the propeller circumference, a gap exists between the rotating tip(s) of the propeller blade(s) and the rim. This gap has a size which is selected according to the application at hand. The rim 20 may have a wall which extends in the axial direction with respect to the axis of rotation of the propeller (the “wall height”). The wall height may be sufficiently large to extend from a top side of the propeller to a bottom side of the propeller. In other embodiments, the wall height may be as large as the full extent of the propeller.

[0011] A plurality of tension members 22 secure the rim 20 at a fixed position relative to the motor 12. For example, the tension members may secure the rim directly to the motor, may secure the rim indirectly to the motor (for example, via one or more housings, brackets, shafts, etc., or combinations), or a combination of direct and indirect attachment. The tension members may be made from a flexible material. For example, the tension members are strings, yams, monofilament fibers, multifilament fibers, rope, cables, cords, wires, and / or the like (collectively, referred to herein as a filament). The tension members may be made from any suitable material or combinations of materials, such as, for example, polymers(s), metal(s), carbon fiber, etc. By suitable, the material of the tension members is selected to withstand forces in tension so as to maintain the rim as fixed to the motor. In some embodiments, each tension member is a separate component. In other embodiments, the tension members may be formed by lacing one or more filaments. For example, an end of a filament may be attached to the rim, may extend to the motor (or structure attached to the motor) and extend back to the rim — thereby forming two tension members by lacing a filament between the rim and the motor. Additional tension members may be made up from a single filament (e.g, three, four, or more tension members). In some embodiments, all of the tension members are formed by lacing a single filament between the rim and the motor. In some embodiments, various tensioning or auto tensioning devices will adjust filament tension.

[0012] In some embodiments, a subset of the tension members are affixed from the rim to the motor on a first side of the propeller (i.e., above the propeller); and a second subset of the tension members are affixed from the rim to the motor on a second side of the propeller (i.e., below the propeller).

[0013] In some embodiments, the rim is configured to flex in the axial direction (along the axis of rotation of the propeller — orthogonal to the plane of rotation of the propeller). In such embodiments, the tension members may be configured to allow some axial movement of the rim. The rim is configured to be rigid in a radial direction (i.e., to maintain a gap with the circumference formed by the rotating propeller). In some embodiments, the tension members allow the rim to rotate a small amount around the centroid of the shape, allowing axial movement of the rim up or down. The amount of rotation is determined by the arrangement of the tension members, the cross-sectional shape of the rim (including variations in the thickness and shape of such cross-sectional shape), vertical spacing of the filament attachment points at the rim, the material selection for the rim, and / or the material selected for the tension members.

[0014] In an example embodiment, the rim of the enclosure is configured as an I-beam shape (shown in Figure 3 as a cross-section view). In this way, the rim 102 is rigid in the radial direction as it is secured by the tension members 104 running between the rim 102 and the motor (hub 106). Figure 4 depicts another rim structure configured as a truss and similar to an I-beam in effect. Figure 5 depicts another rim structure configured as a truss having a triangular crosssection. Other configurations are possible and within the scope of the present disclosure. The use of tension members allows for sufficient structural rigidity despite the low weight of the rim (e.g., low weight relative to traditional ducts).

[0015] In some aspects, the present disclosure may be embodied as a rotorcraft (drone) made up of one or more of the ducted blade enclosures described above. For example, Figure 2 depicts a rotorcraft 50 may be formed by attaching four of the ducted-blade enclosures 52 (only the rim of the ducted-blade enclosure is shown for simplicity). In such an embodiment, the rim of each ducted-blade enclosure is attached to the rims of two adjacent ducted blade enclosures so as to form a rectangular configuration. In this way, the rims make up a structural component of the rotorcraft, thereby reducing or eliminating the need for additional structure (and its corresponding weight). In another embodiment, six ducted blade enclosures may be joined to form a rotorcraft having a hexagonal configuration. In another embodiment, eight ducted blade enclosures may be joined to form a rotorcraft having an octagonal configuration. The number of filaments can be changed to accommodate different numbers of faces of the outer shape of the rim. Other configurations having fewer or more ducted blade enclosures (including odd numbers of ducted blade enclosures) are possible and within the scope of the present disclosure. For example, frame types compatible with the Ardupilot, PX4, Betaflight, or similar closed and opensource control platforms may be used. In some embodiments, systems may incorporate additional surfaces (e.g., flaps, fins, control surfaces), counter-rotating propellers, and / or small stabilizing motors and propellers around a single ducted blade enclosure. In some embodiments, counter-rotating propellers may be contained within the rim. In some embodiments, the propeller(s) may be variable pitch propeller(s). In some embodiments, a drone may include one or more ducted propellers (e.g., as disclosed herein) as well as one or more unducted propellers. In some embodiments, the ducted blade enclosures need not be the same size. For example, a drone may include multiple ducted blade enclosures, wherein at least one of the ducted blade enclosures has a different size (e g, diameter) from the other ducted blade enclosures.

[0016] Figure 6 depicts a portion of a drone constructed with four ducted-blade enclosures of the present disclosure. The embodiment demonstrates the structural support provided by the rims of the disclosure and reducing / eliminating the need for additional structural components. In this example, a flight controller is mounted to a minimal platform at the center of the drone (betw een the rims of the enclosures). A flight controller can also be mounted off-center from the center of the drone in the center of one of the ducted-blade enclosures, and the other ducted-blade enclosures could have accelerometers, IMU’s, additional sensors and function as slave modules to the master module w ith the flight controller.Reconfiguration of Aircraft

[0017] Previously available flight and speed control systems enable the control of devices within an aircraft. For example, in a current rotary -wing drone the flight controller’s function is to direct the RPM of each motor in response to input. A command from the pilot for the multi-rotor to move forward is fed into the flight controller, which determines how to manipulate the motors accordingly in order to move forward (z.e., the front rotors will decrease RPMs and the rear rotors will increase RPMs relative to the front rotors).

[0018] However, none of these previous flight and speed controller systems in current fixed and / or rotary-wing aircraft (including rotary-w ing drones) are capable of dynamically addressing the removal or addition of aircraft components such as power sources, energy' sources, and the actual change of the structure of the aircraft due to such removal and / or addition of power sources and / or energy sources.

[0019] Some embodiments of the present disclosure provide a system for controlling an aircraft that is capable of detecting, analyzing, and accommodating a reconfiguration of the aircraft. For example, in a modular aircraft, the controller may detect the removal or addition of power modules and / or energy modules to the plant, and may alter the control of the aircraft’s modules to accommodate the changed power modules, energy modules, and structure of the new plant. Such changes may occur on the ground or in-flight.

[0020] In another aspect, the present disclosure may be embodied as a method controlling an aircraft having a plurality of modules. The method includes detecting a change in presence of one or more modules of the aircraft. For example, the aircraft may have a communication bus to which the aircraft modules are connected, and the method may include querying each module on the communication bus to obtain status data of the respective modules. Status data may include one or more of, for example, the location of the module within the aircraft structure, module type (e.g., power module, energy module, cargo module, combinations, etc.), current operational status, maximum power output available, state of charge, voltage available, cell count, etc. Changes in presence may be detected when new modules respond, or previously present modules fail to respond.

[0021] The method includes updating a manifest of the aircraft modules, wherein the manifest includes status data for each module of the aircraft. The manifest may be stored in a file or other non-volatile storage accessible by a controller of the aircraft. In some embodiments, the manifest is stored in RAM accessible by the controller (i.e., volatile memory). Other techniques for maintaining the manifest will be apparent to one skilled in the art in light of the present disclosure. Such techniques may be used individually, in combination, or used together for redundancy.

[0022] The method includes determining aircraft operational parameters based on the updated manifest. Figure 7 depicts an example of a power module 200 suitable for a multiple rotor aircraft. The power module may be, for example, a ducted enclosure such as a rim module as described above. Figures 8A and 8B depict an example of a cargo module — a modular component configured to cany' cargo — suitable for such an aircraft. It can be seen that the modules have circumferential geometries which allow for interconnection with additional modules in various configurations. According to the digital manifest of a first exemplary aircraft, the aircraft includes seven power modules configured as shown in Figures 9A and 9B. Accordingto the manifest of a second exemplary aircraft depicted in Figures 10A and 10B, six power modules and one cargo module are configured in a similar overall shape as the aircraft of Figure 9A. Each aircraft would have different flight characteristics, and therefore, the method includes determining the operational parameter for the relevant aircraft. Using the examples, the operational parameters of the first aircraft would likely include lower power output for each module as compared to the power output of the power modules in the second aircraft (which includes fewer power modules and a cargo module which may result in a heavier aircraft).

[0023] In a third example shown in Figures 11 A and 11 B, six power modules are configured in a linear “flying wing" configuration. Even though this third example includes the same number of power modules as the third example, the linear configuration will result in very different operational parameters. For example, the power output would likely be lower than in the second module (due to the lack of a cargo module), and the rotational direction of each rotor may need to be designed to accommodate an instability caused by the linear configuration. Other operational parameters that may be determined include moment of inertia, rotor rotation, load distribution, structural loading limits, thrust, energy consumption, aerodynamic parameters.

[0024] In the method, instructions are sent to at least each affected module of the aircraft based on the aircraft operational parameters. By affected module, it is meant that in some configurations, not all modules will need to receive instructions. For example, a cargo module may not require any instructions for the aircraft to achieve a desired operational state. An exemplary instruction to a power module may include commands related to rotor rotational direction, rotational speed, blade pitch, etc.

[0025] Also, if there are other performance needs, such as speed or duration of flight time, then the number of energy modules versus power modules (as defined below) can be added or dropped to meet those performance needs.

[0026] In some aircraft, sensors may be included to determine aircraft and / or flight conditions such as altitude, speed, geographic orientation, attitude, temperature, etc. The method may include receiving sensor data and the step of determining operational parameters may further be based on the received sensor data.

[0027] The present disclosure may be embodied as an aircraft having a controller programmed to perform any embodiment of the method disclosed herein. Such an aircraft maybe a rotary-wing, fixed-wing, or other (e.g., tilt-rotor) configuration. The aircraft may be modular and may be configured for dynamic reconfiguration, wherein one or more modules may be added to, removed from, or moved within, the aircraft structure.As described above, feedback control systems are provided for fixed-wing or rotary-wing aircraft designs that enable a user to rapidly add or drop the number of power sources and energy sources to match the actual capacity and / or performance needs. The feedback control system is capable of detecting the changes in the number of power sources, energy sources, and the new structure of the plant (here, an aircraft) - and then the control system can automatically control, stabilize, and optimize the new plant structure based on the new number of power sources and / or energy' sources and the new structure of the plant.

[0028] In another example, a method of flight control in which commands are computed based on changes in the aircraft structure producing error in many control parameters relative to the new structure of the aircraft and commands may utilize a control system configured to:• detect and determine location of a module relative to the position of other modules; and• detect and determine the aerodynamic operational parameters of the new plant.• detect the location of the new module added to the new plant structure (i.e., the location of the new module in relation to the other modules already part of the structure) and determination of the new plant structure:• detect the identity' of the module (i.e., is it a power module or energy' module) and obtain information from the module (i.e., current operational status of module, power output available, energy module configuration (state of charge, voltage available, cell count) and other information needed for the flight controller to determine how and to what extent to use such module);• determine and analyze operational control performance parameters such as: o which power modules rotate counter-clockwise and which should rotate clockwise; o calculation of new moments of inertia;o detection of structural issues of new plan and steps to mitigate such structural issues (e.g., if all the weight of the payload is in the center, then the system would not focus thrust at the edges of the new plant and depending on new plant structure, then determination of structural limits during maneuvers); o thrust and energy consumption based on payload and number of modules; o aerodynamic parameters of new plant (e.g.. if as in Figure 11A, it is a flying wing configuration, then there is lift produced by the new plant structure).

[0029] Definitions.• A “power module” is a power source unit that can be added or removed from the aircraft. For example, for a rotary-wing drone, the “module” could be a rotary-wing unit such as depicted in Figure 7 that is linked to other power modules of the aircraft.• An “energy module” is a battery, fuel, or any other energy source that can be added or removed from the aircraft.• A “module” can be either a power module or an energy module.• The “plant” means the aircraft, whether fixed or rotary-wing.• The “new plant” means the plant with newly added power module and / or energy module.

[0030] For example, if the number of power modules increases from 4 to 6 for a rotary- wing drone, an exemplary flight control system of the present disclosure may:• Through an ITC bus (or other bus design) cycle through each module on a timed basis, which provides status data for each such module, in order to detect that the modules are power modules and / or energy modules and, based on the new structure of the new plant, determine new operational parameters such as: o a battery management system, which w ould respond with the state of the battery for that energy module;o current flight time based on available charge in the energy module by measuring the voltage and current draw, current state of charge in energy module(s), current discharge rate, etc.; o sensors to detect the amount of thrust necessary to accelerate the mass of each module;• Calculate the new moment of inertia for the new 6-power module rotary-wing structure based on the geometry of all modules.• Determine the rotation of the rotors in each power module;• Determine whether and how much structural issues must be mitigated, e.g., the location of the pay load relative to location of the power modules will determine how much thrust each power module should produce in order to avoid structural failure.

[0031] In an aspect, the present disclosure may be embodied as a computer-implemented method for dynamically controlling an aircraft having a plurality of physical modules. For example, the aircraft may have physical modules including one or more power modules, one or more energy modules, one or more cargo modules, or combinations of these and / or other modules.

[0032] The method may include detecting, using a processor, a change in presence of one or more physical modules of the aircraft. For example, at least one physical module may be added or at least one physical module may be removed. Addition or removal of a physical module may occur in mid-flight or while stationary on the ground. The change may be detected by, for example, querying each physical module on a communication bus to obtain status data. The processor updates a digital manifest of the physical modules of the aircraft. Updating the digital manifest may include receiving status data from each of the one or more changed (added / removed) physical modules. In some embodiments, updating the digital manifest includes copying the digital manifest or portions of the digital manifest. The digital manifest may include real-time status data for each physical module of the aircraft. Operation module information may include, for example, one or more of module type, power output, state of charge, voltage available, cell count.

[0033] Based on processing the updated digital manifest, one or more modified aircraft operational parameters are determined by the processor. The aircraft operational parameters may include moment of inertia, rotor rotation, load distribution, structural loading limits, thrust, energy consumption, aerodynamic parameters, or combinations of these and / or other such parameters.

[0034] Control instructions are electronically transmitted by the processor to each physical module of the aircraft. The control instructions are based on the modified aircraft operational parameters. The control instructions cause real-time adjustments to operation of the physical modules.

[0035] In some embodiments, the processor may receive sensor data from one or more sensors of the aircraft. The method may include determining, based on the received sensor data, one or more modified aircraft operational parameters

[0036] In another aspect, the present disclosure may be embodied as a modular aircraft. The aircraft includes a plurality of physical modules and a processor in electronic communication with each physical module of the plurality of physical modules. The processor is programmed to perform any of the methods disclosed herein. For example, the processor may be programmed to: detect a change in presence of one or more physical module of the plurality of physical modules of the aircraft; update a digital manifest of the physical modules of the aircraft, wherein the manifest includes real-time status data for each physical module of the aircraft; determine, based on processing the updated digital manifest, one or more modified aircraft operational parameters; and electronically transmit control instructions to each physical module of the aircraft based on the modified aircraft operational parameters, wherein the control instructions cause real-time adjustments to operation of the physical modules.Variable Pitch Propeller

[0037] It has been known for nearly a century that changing the pitch of a propeller in response to changing rotational speed and air speed will increase the efficiency and / or power delivery of a propeller. For example, in general, a low-pitch blade is most efficient and able to deliver the most power for low-speed acceleration of an aircraft, while a high-pitch blade is most efficient for high-speed performance.

[0038] There have been many atempts to optimize the variable pitch of propeller blades. One such atempt, which is used widely in the airplane industry, is called a “constant speed propeller / ’ As the name suggests, this technique automatically adjusts the pitch of the propeller blades but maintains a constant rotational speed (rotations per minute, or RPM). Other aircraft use constant-pitch propellers and have systems to adjust the RPM based on parameters which change the weight of the airplane during the flight — for example, fuel used, fuel bum rate, etc.

[0039] Unlike fixed-wing airplanes, rotary-wing drones face a complex and constantly changing environment and demands, which require constant adjustment of gear ratio, motor power, and RPM in order to optimize the efficiency of the motors on a rotary -wing drone.

[0040] In addition, cunent fixed-wing and rotary-wing aircraft have “fixed” constructions, in which, for example, the number of power sources cannot be increased or decreased. Because of this “fixed construction,” if an operator needs to lift more than the capacity of, for example, a particular rotary-wing drone, then the user must use a different, larger rotary-wing drone that has more lifting capacity. And conversely, if the user has a large rotary- wing drone but only needs to lift a small object, then the extra power and lifting capacity of that large rotary -wing drone is wasted. Similarly, the fixed construction limits the ability7to affect other aircraft characteristics such as speed, maximum flight duration, etc.

[0041] Variable pitch propellers can help in three ways in general. As a propeller moves faster through the air, the ideal pitch to keep the blade airfoil cross section at its ideal lift-to-drag ratio changes and becomes steeper, because the vector sum of propeller RPM and forward flight speed changes the incident angle of atack of the blade. Adjusting the blade to a steeper pitch allows the propeller to use the minimum amount of power necessary to produce the necessary thrust, since the blade airfoil angle of atack can be set to the optimum. In a fixed pitch propeller, increasing the RPM has the effect of increasing the airfoil angle of atack because of the sum of vectors, but the motor can only increase RPM so far, and electric motors and speed controllers have an ideal RPM range power product and have maximum speeds. Additionally, the motor and speed controller performance changes as the batery voltage decreases. With lower voltages, high power production occurs at lower RPM, and variable pitch can put more load on the motor such that the motor RPM decreases, thus allowing higher power output than fixed pitch would allow at low batery voltages. Li-Ion bateries have a much larger portion of the discharge profile where voltage is decreasing from 3 Volts to 2.5 Volts, variable pitch mitigates this adversecharacteristic by changing the system’s optimal RPM. Variable pitch allows the motor and speed controller to operate at (or closer to with respect to fixed pitch) their ideal operating point at all battery voltages, and the propeller airfoil to operate at (or closer to with respect to fixed pitch) its ideal lift to drag ratio. This results in the minimum power used, and therefore longer flight times, even at fast forward flight speeds.

[0042] The third way that variable pitch improves the performance of a rotary -wing aircraft is it allows for instantaneous variation of thrust output without changing RPM. Normally, the thrust is changed by changing the RPM, and this introduces lag time to achieve a measured output because of the inertia of the propeller and time to spool up or down. This is exemplified in variable pitch tail-rotors in Radio Control (RC) helicopters, where instant changes are required to point the nose. Variable pitch allows the most aggressive control laws to stabilize rotary-wing aircraft, which aids fighting wind gusts etc. Multiple input, multiple output control laws are the most advanced, and a control strategy where RPM, power output, and variable pitch are simultaneously controlled allows for the least power used, most aggressive control laws and therefore most stable flight, high payload capacity at all battery voltages, and longest flight times.

[0043] Many current rotary wing drones have the ability to modulate the rotational speed of their propellers. A small number of commercially available drones incorporate the use of variable-pitch propellers. However, because of the complexities of variable pitch systems and the difficulties of managing gear ratio, motor pow er, RPM, and variable pitch for a rotary-wing drone, none of the existing systems are capable of managing all of these parameters in real time and at the same time in order to achieve high efficiency for a given amount of thrust in a given scenario.

[0044] A modular aircraft would make variable-pitch systems even more complicated because the addition or subtraction of power sources and thrust sources would change the amount and duration of pitch needed for the overall aircraft plant. However, none of these previous variable-pitch systems in current fixed and / or rotary-wing aircraft (including rotary- wing drones) are capable of dynamically addressing the removal or addition of aircraft components such as power sources, energy sources, and the actual change of the structure of the aircraft due to such removal and / or addition of power sources and / or energy sources.

[0045] The present disclosure provides a system utilizing a multiple-input, multipleoutput control system having sensors and methods to: (i) detect multiple input parameters (e.g., environmental parameters of temperature and air density, plant parameters of the RPMs of the motor and propeller, addition or subtraction of power sources or thrust sources, etc.) and output parameters (e.g., pitch, throttle, gear ratio, etc.) of the rotary-wing drone plant; (ii) compare the output parameters against pre-defined efficiency parameters (e.g., 3-D matrices showing the intersections of throttle, RPM, power produced, blade angle, etc. compared to an optimized combination of output parameters, etc.); and (iii) change any or all aircraft parameters including, for example, gear ratio, motor power, RPMs, and blade pitch to meet those pre-defined efficiency parameters, all in real time. An objective of the control system is to attempt to optimize the ratio of thrust to input power. In a particular example, in response to an operator of a rotary-wing drone demanding a particular amount of thrust, this requested amount may be achieved in one of at least two different ways: o The blade pitch may be set fine (i.e., a low blade angle) and the gear ratio may be set such that the motor has a high RPM. This would improve overall efficiency because electric motors are much more efficient at higher RPMs. However, there would be less power available from the motor at such higher motor RPMs. o The blade pitch could be set coarse (i.e., a high blade angle), and the gear ratio set for a lower RPM of the motor. The motor may be less efficient at this setting.

[0046] While it may appear that this second option would not be used because of motor efficiency concerns, this may be the optimal setting for certain atmospheric conditions such as, for example, less dense and colder air, higher payloads, and other scenarios.

[0047] Note also that there are a spectrum of variations and combinations of blade pitch, gearing ratios, and motor RPM settings (and therefore efficiency) in real time — literally millisecond to millisecond changes.

[0048] Some embodiments of the present control system are configured to utilize an infinitely -variable ratio gearing system to select the most optimum RPM within a defined RPM range for the particular motor used in the aircraft. Other embodiments may be configured to utilize alternative gearing systems. For example, another embodiment may be configured to use a gearing system having two spur gears — a small pinion gear on the electric motor and a large spurgear attached to the propeller shaft. Such a gearing system may have an inner and outer arrangement of the gears — i.e., gearing teeth on outside diameter and gearing teeth on the inside circle of the gear, such that, in order to use the large spur gear attached to the blade, (i) the small pinion gear would disengage and reengage the inner or outer gearing teeth using a solenoid or other driver, and (ii) spin the motor clockwise or counter-clockwise as applicable.

[0049] The present solution will provide high payload / empty weight capabilities for at least short flight times. Simulations show that 3-6 hour flight times may be possible. See, e.g. Figure 14.

[0050] As show n in Figure 14, low speeds and small blade widths cause the airfoil (and thus each blade and the whole propeller) to operate at a low Reynolds number. Re. Airfoils behave somewhat strangely at low Re. The lower the Re, the lower the lift / drag ratio, L / D. See Figs. 15A-15C. But still, in general, the simulations have shown that lower propeller RPM’s provide increased efficiency.

[0051] As such, there is a very small range of angle of attack for the blades that is in the “low drag bucket” — considered to have low drag. For high efficiency, it is advantageous to position the angle of attack in this low drag bucket. However, if, for example, the payload increases and more thrust is required, such additional thrust is provided via a combination of blade angle, the RPM of the propeller, and the power going into the propeller.

[0052] In another example, a method of variable-pitch control in which commands are computed based on changes in the aircraft structure which in turn require changes in many variable-pitch control parameters relative to the new structure of the aircraft and commands may utilize a control system configured to:• detect and determine location of a module relative to the position of other modules;• detect and determine the aerodynamic operational parameters of the new plant;• detect the location of the new module added to the new plant structure (i.e., the location of the new module in relation to the other modules already part of the structure) and determination of the new plant structure;• detect the identity of the module (i.e., is it a power module or energy module) and obtain information from the module (i.e., current operational status of module, power output available, energy module configuration (state of charge, voltage available, cell count) and other information needed for the flight controller to determine how and to what extent to use such module);• determine and analyze operational control performance parameters such as which power modules rotate counter-clockwise and which should rotate clockwise and calculation of new moments of inertia;• determine and analyze the amount and duration of variable-pitch required to achieve output parameters, e.g., thrust based on the above input parameters (and / or other applicable input parameters).

[0053] For example, if there were the following input parameters of (i) adding thrust sources to the plant, (ii) airspeed sensor / pitot tube, and (iii) GPS, an exemplary variable-pitch control system of the present disclosure will:• Through an I2C, CAN bus, UART, ethemet, serial bus (or other bus design or communication protocol) cycle through each module on a timed basis, which provides status data for each such module• Determine new operational parameters such as (based on the new structure of the new plant): o a battery management system, which would respond with the state of the battery for that energy module; o current flight time based on available charge in the energy module by measuring; o the voltage and current draw, current state of charge in energy module(s), current discharge rate, etc. ;• Calculate the new moment of inertia for the new 6-power module rotary-wing structure based on the geometry of all modules.• Determine the rotation of the rotors in each power module;• Determine whether and how much structural issues must be mitigated, e.g., the location of the payload relative to location of the power modules will determine how much thrust each power module should produce in order to avoid structural failure.

[0054] In an aspect, the present disclosure may be embodied as a control system for a multi-rotor aircraft having variable-pitch propellers. The control system includes a plurality of sensors configured to measure flight dynamics parameters and / or propulsion system parameters of the aircraft; an electronic storage unit configured to store a pre-defined set of efficiency parameters. The control system may include a plurality of flight controls. The flight controls may include one or more electronic speed controllers (ESCs) configured to control motor pow er and RPMs; one or more actuators (e.g.. servo motors) configured to adjust blade pitch angles of the variable-pitch propellers; and a transmission configured to modify gear ratios between motors and propellers.

[0055] A processor is in electronic communication with each sensor of the plurality’ of sensors and the electronic storage unit. The processor is programmed to receive real-time output parameters from the plurality of sensors. The plurality of sensors may include, for example, at least one accelerometer or inertial measurement unit (IMU) and at least one airspeed sensor. The real-time parameters may be received at a sampling rate. For example, the processor may receive data from the plurality of sensors at a sampling rate of 100 Hz or more (although lower sampling rates are possible and within the scope of the disclosure). The processor retrieves the pre-defined efficiency parameters from the electronic storage unit. The received output parameters may be compared with the received pre-defined efficiency parameters by the processor. For example, a feedback control algorithm may be used to determine control settings for current flight conditions. Control signals may be transmitted by the processor to the flight controls according to the determined control settings. The processor operates continuously and in real-time.

[0056] The pre-defined set of efficiency parameters may include power consumption curve(s), blade pitch angles corresponding to different flight conditions.

[0057] In some embodiments, the processor is further programmed to: retrieve a digital manifest describing a dynamic configuration of physical modules of the aircraft; and further adjust the control settings based on the dynamic configuration from the digital manifest.

[0058] In an aspect, the present disclosure may be embodied as a control system for a multi-rotor aircraft having variable-pitch propellers. The control system includes a plurality of sensors configured to measure flight dynamics parameters and / or propulsion system parameters of the aircraft: an electronic storage unit configured to a machine learning model trained on historical flight data comprising sensor measurements and corresponding control outputs. The control system may include a plurality of flight controls. The flight controls may include one or more electronic speed controllers (ESCs) configured to control motor power and RPMs; one or more actuators (e.g, servo motors) configured to adjust blade pitch angles of the variable-pitch propellers; and a transmission configured to modify gear ratios between motors and propellers.

[0059] A processor is in electronic communication with each sensor of the plurality of sensors and the electronic storage unit. The processor is programmed to receive real-time output parameters from the plurality of sensors. The plurality of sensors may include, for example, at least one accelerometer or inertial measurement unit (IMU) and at least one airspeed sensor. The real-time parameters may be received at a sampling rate. For example, the processor may receive data from the plurality of sensors at a sampling rate of 100 Hz or more (although lower sampling rates are possible and within the scope of the disclosure). The processor processes the received real-time output parameters into a feature vector compatible with the machine learning model. The processor inputs the feature vector into the machine learning model to generate control values for motor power, gear ratios, RPMs, and blade pitch angles. Control signals may be transmitted by the processor to the flight controls according to the determined control settings. The processor operates continuously and in real-time.

[0060] In some embodiments, the processor is further programmed to retrieve a digital manifest describing a dynamic configuration of physical modules of the aircraft. The input feature vector may then include information from the digital manifest.

[0061] In the present disclosure, the term drone is used broadly to refer to unmanned aerial systems, whether autonomous, manually controlled, or a combination of control. The terms “above,” “below,” “top,” and “bottom” are used with reference to the orientation of the drone during flight.

[0062] The term processor is intended to be interpreted broadly. For example, in some embodiments, the processor includes one or more modules and / or components. Each module / component executed by the processor can be any combination of hardware-basedmodule / component (e.g, graphics processing unit (GPU), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a digital signal processor (DSP)), software-based module (e.g., a module of computer code stored in the memory and / or in the database, and / or executed at the processor), and / or a combination of hardware- and softwarebased modules. Each module / component executed by the processor is capable of performing one or more specific functions / operations as described herein. In some instances, the modules / components included and executed in the processor can be, for example, a process, application, virtual machine, artificial intelligence, neural network, and / or some other hardware or software module / component. The processor can be any suitable processor configured to run and / or execute those modules / components. The processor can be any suitable processing device configured to run and / or execute a set of instructions or code. For example, the processor can be a general-purpose processor, a central processing unit (CPU), an accelerated processing unit (APU), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), graphics processing unit (GPU), microprocessor, controller, microcontroller, and / or the like. The processor may be located on (e.g., within) an aircraft, at a ground and / or mobile station, in a cloud service, or combinations of these or other locations.

[0063] Although the present disclosure has been described with respect to certain embodiments, it will be understood that other embodiments of the present disclosure may be made without departing from the spirit and scope of the present disclosure.

Claims

What is claimed is:

1. A ducted blade enclosure for a multi-rotor aircraft, comprising: a motor connected to a propeller, wherein rotation of the propeller defines a circumference; a rim surrounding and spaced apart from the propeller circumference; a plurality of flexible tension members securing the rim to the motor, wherein the rim is located at a fixed position relative to the motor; and wherein the rim includes one or more couplers for attachment to one or more adjacent rims.

2. The ducted blade enclosure of claim 1, wherein the rim is configured to be attached to each of the one or more adjacent rims using one or more couplers.

3. The ducted blade enclosure of claim 1, wherein a first subset of the flexible tension members is affixed from the rim to the motor on a first side of the propeller; and a second subset of the flexible tension members is affixed from the rim to the motor on a second side of the propeller.

4. The ducted blade enclosure of claim 1, wherein the flexible tension members are made from a flexible material, resistant to tension.

5. The ducted blade enclosure of claim 4, wherein the flexible tension members are strings, yams, filaments, rope, cables, cords, wires, or combinations of these.

6. The ducted blade enclosure of claim 1, wherein the motor comprises a motor housing, and the flexible tension members are attached to the motor by way of the motor housing.

7. The ducted blade enclosure of claim 1, wherein the plurality of flexible tension members are formed by lacing one or more filaments between the rim and the motor.

8. The ducted blade enclosure of claim 1, wherein the rim is configured to flex in an axial direction which is orthogonal to a plane of rotation of the propeller.

9. The ducted blade enclosure of claim 1, wherein the rim is configured to be rigid in a radial direction thereby maintaining a fixed gap with the propeller circumference.

10. A multi-rotor aircraft comprising:Two or more rim modules, each rim module comprising: a motor connected to a propeller, wherein rotation of the propeller defines a respective propeller circumference; a rim surrounding and spaced apart from the propeller circumference; and a plurality of flexible tension members securing the rim to the motor, wherein the rim is located at a fixed position relative to the motor; and wherein adjacent rim modules of the two or more rim modules are directly attached to each other.

11. The multi-rotor aircraft of claim 10, wherein each rim includes a plurality of couplers, and the adjacent rim modules are directly attached to each other by way of one or more couplers of the plurality of couplers.

12. The multi-rotor aircraft of claim 10, comprising four rim modules, wherein each rim of each rim module is coupled to the rims of two adjacent rim modules, such that the rim modules form a quadrilateral configuration, for example, a rectangular configuration.

13. The multi-rotor aircraft of claim 10, comprising six rim modules, wherein each rim of each rim module is coupled to the rims of two adjacent rim modules, such that the rim modules form a hexagonal configuration.

14. The multi-rotor aircraft of claim 10, comprising seven rim modules, wherein each rim of each rim module is coupled to the rims of three adjacent rim modules, such that the rim modules form a hexagonal configuration.

15. The multi-rotor aircraft of claim 10, comprising eight rim modules, wherein each rim of each rim module is coupled to the rims of two adjacent rim modules, such that the rim modules form a octagonal configuration.

16. The multi-rotor aircraft of claim 10, comprising more than 20 rim modules, for example, more than 100 rim modules or more than 1000 rim modules.

17. The multi-rotor aircraft of claim 10, comprising an arbitrary number of partially constrained or loosely connected rim modules, and further comprising a flight controller configured to modulate a thrust of each motor of each rim module to maintain stable flight of the aircraft.

18. The multi-rotor aircraft of claim 10, wherein each rim module connects to an adjacent rim module at or near one or more vertices of the rims of such rim modules.

19. The multi-rotor aircraft of claim 10, wherein one or more of the rim modules are configured to join with at least one additional rim module during flight of the aircraft.

20. The multi-rotor aircraft of claim 10, wherein one or more of the rim modules are configured to separate from the other rim modules during flight of the aircraft.

21. A computer-implemented method for dynamically controlling an aircraft having a plurality of physical modules, the method comprising: detecting, using a processor, a change in presence of one or more physical modules of the aircraft; updating, by the processor, a digital manifest of the physical modules of the aircraft, wherein the manifest includes real-time status data for each physical module of the aircraft; determining, based on processing the updated digital manifest, one or more modified aircraft operational parameters; and electronically transmitting control instructions to each physical module of the aircraft based on the modified aircraft operational parameters, wherein the control instructions cause real-time adjustments to operation of the physical modules.

22. The computer-implemented method of claim 21, wherein the one or more physical modules are selected from power modules, energy modules, and cargo modules.

23. The computer-implemented method of claim 21 , wherein at least one physical module is added.

24. The computer-implemented method of claim 23, wherein updating the manifest comprises receiving status data from each of the one or more changed physical modules.

25. The computer-implemented method of claim 21, wherein at least one physical module is removed.

26. The computer-implemented method of claim 21, wherein the parameter information comprises one or more of module type, power output, state of charge, voltage available, cell count.

27. The computer-implemented method of claim 21, wherein the aircraft operational parameters are one or more of moment of inertia, rotor rotation, load distribution, structural loading limits, thrust, energy consumption, aerodynamic parameters.

28. The computer-implemented method of claim 21, wherein detecting a change in one or more physical modules of the aircraft comprises querying each physical module on a communication bus to obtain status data.

29. The computer-implemented method of claim 21, further comprising receiving sensor data from one or more sensors of the aircraft.

30. A modular aircraft, comprising: a plurality of physical modules; a processor in electronic communication with each physical module of the plurality of physical modules, wherein the processor is programmed to: detect a change in presence of one or more physical module of the plurality of physical modules of the aircraft; update a digital manifest of the physical modules of the aircraft, wherein the manifest includes real-time status data for each physical module of the aircraft; determine, based on processing the updated digital manifest, one or more modified aircraft operational parameters; and electronically transmit control instructions to each physical module of the aircraft based on the modified aircraft operational parameters, wherein the control instructions cause real-time adjustments to operation of the physical modules.

31. The modular aircraft of claim 30, wherein the one or more physical modules are selected from power modules, energy modules, and cargo modules.

32. The modular aircraft of claim 30, wherein at least one physical module is added.

33. The modular aircraft of claim 32, wherein updating the manifest comprises receiving status data from each of the one or more changed physical modules.

34. The modular aircraft of claim 30, wherein at least one physical module is removed.

35. The modular aircraft of claim 30, wherein the parameter information comprises one or more of module type, power output, state of charge, voltage available, cell count.

36. The modular aircraft of claim 30, wherein the aircraft operational parameters are one or more of moment of inertia, rotor rotation, load distribution, structural loading limits, thrust, energy' consumption, aerodynamic parameters.

37. The modular aircraft of claim 30, wherein detecting a change in one or more physical modules of the aircraft comprises querying each physical module on a communication bus to obtain status data.

38. The modular aircraft of claim 30, further comprising one or more sensos in communication with the processor, and wherein the processor is further programmed to: receive sensor data from the one or more sensors; and determine, based on the received sensor data, one or more modified aircraft operational parameters.

39. A control system for a multi-rotor aircraft having variable-pitch propellers, comprising: a plurality’ of sensors configured to measure flight dynamics parameters and / or propulsion system parameters of the aircraft; an electronic storage unit configured to store a pre-defined set of efficiency parameters; a plurality' of flight controls comprising: one or more electronic speed controllers (ESCs) configured to control motor power and RPMs; one or more actuators (e.g., servo motors) configured to adjust blade pitch angles of the variable-pitch propellers; and a transmission configured to modify gear ratios between motors and propellers; a processor in electronic communication with each sensor of the plurality of sensors and the electronic storage unit, wherein the processor is programmed to: receive real-time output parameters from the plurality of sensors; retrieve the pre-defined efficiency parameters from the electronic storage unit; compare the received output parameters with the received pre-defined efficiency parameters using a feedback control algorithm to determine control settings for current flight conditions; and transmit control signals to the flight controls according to the determined control settings;wherein the processor operates continuously and in real-time.

40. The control system of claim 39, where the plurality of sensors comprises at least one accelerometer or inertial measurement unit (IMU) and at least one airspeed sensor.

41. The control system of claim 39, wherein the processor receives output parameters from the plurality of sensors at a sampling rate.

42. The control system of claim 39, wherein the sampling rate is greater than or equal to 100 Hz.

43. The control system of claim 39, wherein the pre-defined set of efficiency parameters includes power consumption curve(s), blade pitch angles corresponding to different flight conditions.

44. The control system of claim 39, wherein the processor is further programmed to: retrieve a digital manifest describing a dynamic configuration of physical modules of the aircraft; and further adjust the control settings based on the dynamic configuration from the digital manifest.

45. A control system for a multi-rotor aircraft having variable-pitch propellers, comprising: a plurality of sensors configured to measure flight dynamics parameters and / or propulsion system parameters of the aircraft; an electronic storage unit configured to store a trained machine learning model, wherein the machine learning model is trained on historical flight data comprising sensor measurements and corresponding control outputs; a plurality of flight controls comprising: one or more electronic speed controllers (ESCs) configured to control motor power and RPMs; one or more actuators (e.g., servo motors) configured to adjust blade pitch angles of the variable-pitch propellers; and a transmission configured to modify gear ratios between motors and propellers; a processor in electronic communication with each sensor of the plurality of sensors and the electronic storage unit, wherein the processor is programmed to: receive real-time output parameters from the plurality of sensors;process the received real-time output parameters into a feature vector compatible with the machine learning model; input the feature vector into the machine learning model to generate control values for motor power, gear ratios, RPMs, and blade pitch angles; transmit control signals to the flight controls according to the determined control values; wherein the processor operates continuously and in real-time.

46. The control system of claim 45, wherein the processor is further programmed to validate the control values from the machine learning model against pre-defined safety constraints.

47. The control system of claim 45, where the plurality of sensors comprises at least one accelerometer or inertial measurement unit (IMU) and at least one airspeed sensor.

48. The control system of claim 45, wherein the processor receives output parameters from the plurality of sensors at a sampling rate.

49. The control system of claim 48, wherein the sampling rate is greater than or equal to 100 Hz.

50. The control system of claim 45, wherein the processor is further programmed to retrieve a digital manifest describing a dynamic configuration of physical modules of the aircraft; and the input feature vector includes information from the digital manifest.

51. A computer-implemented method of controlling a multi -rotor aircraft having variable-pitch propellers, comprising: receiving, by a processor, real-time output parameters from a plurality of sensors, wherein plurality of sensors configured to measure flight dynamics parameters and / or propulsion system parameters of the aircraft; retrieving a pre-defined set of efficiency parameters from an electronic storage unit; comparing the received output parameters with the received pre-defined efficiency parameters using a feedback control algorithm to determine control settings for current flight conditions; and transmitting control signals to a plurality of flight controls according to the determined control settings, wherein the plurality of flight controls comprises: one or more electronic speed controllers (ESCs) configured to control motor power and RPMs;one or more actuators (e.g., servo motors) configured to adjust blade pitch angles of the variable-pitch propellers; and a transmission configured to modify gear ratios between motors and propellers.

52. A computer-implemented method of controlling a multi-rotor aircraft having variable-pitch propellers, comprising: receiving, by a processor, real-time output parameters from a plurality of sensors, wherein plurality of sensors configured to measure flight dynamics parameters and / or propulsion system parameters of the aircraft; processing the received real-time output parameters into a feature vector compatible with a stored machine learning model; inputting the feature vector into the machine learning model to generate control values for motor power, gear ratios, RPMs, and blade pitch angles; transmitting control signals to a plurality' of flight controls according to the determined control values, wherein the plurality of flight controls comprises: one or more electronic speed controllers (ESCs) configured to control motor power and RPMs; one or more actuators (e.g., servo motors) configured to adjust blade pitch angles of the variable-pitch propellers; and a transmission configured to modify gear ratios between motors and propellers.

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