Vertical take-off and landing aircraft and propulsion assembly

Abstract

A vertical take-off and landing aircraft is disclosed that includes a propulsion assembly adapted to lift a load. The propulsion assembly may include a primary lift surface to provide sufficient lift for lifting the load when rotated about the central axis. The propulsion assembly may include a secondary lift surface to provide lift along a second axis to lift the propulsion assembly. The secondary lift surface may be configured to induce rotation of the primary lift surface.

Description

Technical Field

[0001] The present invention relates to a vertical take-off and landing (VTOL) aircraft and a propulsion assembly. Background Art

[0002] The problem with designing VTOL aircraft for various civilian and military applications is that, while it's preferable to keep the clearance area required for landing the aircraft as small as possible, there's a trade-off between the size of the lift system and the power required to generate thrust. Arbitrarily small thrusters will require arbitrarily large power. The limited power and energy density of the aircraft's propulsion system and power storage systems imposes a practical limit on how compact the lift system can be for a given payload.

[0003] Another problem exists in that even though surface horizontal clearance may be adequate, obstacles such as trees and power lines may protrude into the vertical clearance required for takeoff.

[0004] Existing approaches to minimizing the size of lift systems necessarily sacrifice efficiency, either through the size of the system itself or by choosing a more efficient lift system for that size, which is only practically achievable in smaller form factors (such as ducted fans). Furthermore, the clearance area for landing a VTOL aircraft is limited not only by the size of the lift system, but also by the immediate downwash generated by even a relatively efficient, smaller lift system (with correspondingly higher air speeds). Summary of the Invention

[0005] It is an object of the present invention to at least substantially address one or more of the above-mentioned disadvantages, or at least to provide a useful alternative to the VTOL aircraft discussed above.

[0006] In a first aspect, the present invention provides a propulsion assembly for lifting a load, the propulsion assembly comprising: a primary lifting surface configured to provide sufficient lift for lifting the load when rotated about a central axis; a secondary lift surface configured to provide lift along a second axis to lift the propulsion assembly, wherein the second axis is configurable between a lift configuration in which the secondary lift surface lifts the propulsion assembly and a thrust configuration in which the secondary lift surface induces rotation of the primary lift surface.

[0007] Preferably, the primary lifting surface is movable between a stowed configuration and a deployed configuration, wherein the footprint of the primary lifting surface is smaller in the stowed configuration than in the deployed configuration.

[0008] Preferably, the primary lifting surface is movable between the stowed configuration and the deployed configuration while being lifted by the secondary lifting surface.

[0009] Preferably, the second axis of the secondary lift surface is capable of continuously moving between the lifting position and the thrust position, so that the proportion of the lift of the secondary lift surface used to lift the propulsion assembly continuously decreases as the lift generated by the main lift surface increases, and the lift generated by the main lift surface increases as the rotational speed of the main lift surface around the central axis increases.

[0010] Preferably, the propulsion assembly further comprises a lifting surface control system to provide periodic and collective control of the primary lifting surface.

[0011] Preferably, the lifting surface control system comprises servo tabs.

[0012] Preferably, the propulsion assembly further comprises a tether for connecting the propulsion assembly to the load, wherein the tether is adapted to transfer power from the load to the propulsion assembly to power the propulsion assembly.

[0013] Preferably, the tether is retractable.

[0014] Preferably, the propulsion assembly further comprises a first docking hub located at the central axis, the first docking hub being configured to engage the load when the tether is fully retracted.

[0015] Preferably, the tether is connected to the propulsion assembly by a bearing to reduce the torque applied by the tether to the propulsion assembly when tension is applied to the tether.

[0016] Preferably, the main lifting surface comprises a rotor, preferably the rotor provides orientation control of the propulsion assembly.

[0017] Preferably, the secondary lifting surface comprises a rotor rotatable about the second axis, preferably the rotor provides orientation control of the propulsion assembly.

[0018] Preferably, the propulsion assembly further comprises an emergency power reserve to provide power to the propulsion assembly in case of power reduction.

[0019] Preferably, the secondary lifting surface comprises a plurality of secondary lifting surfaces.

[0020] Preferably, the tether includes an attachment interface connecting the tether to the propulsion assembly.

[0021] Preferably, the attachment interface is the non-flexible and non-rotating endpoint of the tether.

[0022] Preferably, the propulsion assembly includes a system for determining spatial parameters of the propulsion assembly relative to the load.

[0023] Preferably, the spatial parameters include absolute and relative orientation parameters of the propulsion assembly relative to the load.

[0024] Preferably, the system comprises a magnetometer and / or a gyroscope to determine the spatial parameter.

[0025] Preferably, the system includes an encoder positioned between the propulsion assembly and the attachment interface to determine the spatial parameter.

[0026] Preferably, the attachment interface includes aerodynamic surfaces and / or thrusters to control the heading of the tether.

[0027] Preferably, the tether includes a second attachment interface connecting the tether to the payload to allow the propulsion assembly to be flown at high angles relative to the horizontal, thereby allowing faster flight speeds.

[0028] Preferably, the second attachment interface comprises an articulating frame capable of changing its orientation during flight to allow the payload to remain horizontal when the propulsion assembly is tilted and to allow the propulsion assembly to fly at high angles of attack relative to the horizontal and provide faster flight speeds.

[0029] Preferably, the payload comprises an aerodynamic surface capable of providing lift during level flight.

[0030] In a second aspect, the present invention provides a vertical take-off and landing aircraft, comprising: a body having a load-bearing cavity or area for a load; The propulsion assembly according to the first aspect is used to lift the body; and A power generation assembly is located in or on the body, and is configured to provide power to the propulsion assembly.

[0031] Preferably, the aircraft further comprises one or more directional thrusters attached to the body, the directional thrusters acting in respective directions that are non-parallel to the central axis.

[0032] Preferably, the aircraft further comprises one or more directional thrusters attached to the body, the directional thrusters acting in respective directions parallel to the central axis.

[0033] Preferably, the directional thruster comprises a ducted fan, a rotor, a jet thruster and / or a pulse thruster.

[0034] Preferably, the body has a centre of gravity and includes a winch for retracting the tether, wherein the uppermost control point of the tether on the body is above the centre of gravity of the body.

[0035] Preferably, the center of gravity of the attachment interface is positioned above and spatially related to the center of gravity of the body to promote stable flight and control.

[0036] Preferably, the body further comprises a second docking hub configured to engage the first docking hub when the tether is fully retracted.

[0037] Preferably, the body further comprises one or more control surfaces for setting a preferred orientation relative to the direction of travel and / or controlling the orientation of the aircraft relative to the direction of travel.

[0038] Preferably, the moveable surface may be used to assist in changing the direction of travel.

[0039] Preferably, the vehicle comprises wheels on the body and motors driving the wheels for propelling the vehicle on the ground. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic front view of an aircraft having a propulsion assembly according to a preferred embodiment of the present invention.

[0041] Figure 2 yes Figure 1 A schematic front view of an aircraft with the propulsion assembly in a stowed configuration.

[0042] Figure 3 yes Figure 1 A schematic front view of an aircraft with the propulsion assembly in a deployed configuration.

[0043] Figure 4 yes Figure 1 Schematic front view of an aircraft in which the propulsion assembly initiates rotation of the primary lift surface.

[0044] Figure 5 yes Figure 1 Schematic front view of an aircraft with the propulsion assembly lifting the body.

[0045] Figure 6 yes Figure 1 Schematic front view of the vehicle, showing the position control of the directional thrusters.

[0046] Figure 7 yes Figure 1Schematic front view of an aircraft with the body retracted towards the propulsion assembly.

[0047] Figure 8 yes Figure 1 Schematic front view of an aircraft with the body docked to the propulsion assembly in flight.

[0048] Figure 9 A perspective view of an aircraft according to a second embodiment of the invention is shown.

[0049] Figure 10 Shown Figure 9 A spacecraft with the propulsion assembly docked.

[0050] Figure 11 Shown Figure 9 An aircraft wherein the propulsion assembly is undocked and in a stowed configuration.

[0051] Figure 12 Shown Figure 9 An aircraft wherein the propulsion assembly moves toward a deployed configuration.

[0052] Figure 13 Shown Figure 9 An aircraft wherein the propulsion assembly is in a deployed configuration.

[0053] Figure 14 Shown Figure 9 An aircraft wherein the propulsion assembly generates thrust using a primary lift surface and wherein the secondary lift surface generates thrust orthogonal to the primary lift surface. DETAILED DESCRIPTION

[0054] According to Figures 1 to 8 The aircraft 200 of the preferred embodiment shown includes a propulsion assembly 100. The propulsion assembly 100 is adapted to lift a payload 10 and is configured to be powered by the payload 10. Figure 1 As shown, the propulsion assembly 100 includes a main lift surface 110 that is configured to provide sufficient lift for lifting the load 10 when rotating about the central axis 102. In a preferred embodiment, the main lift surface 110 includes a large rotor blade 112 that is divided by a joint 114 into a central section 112a and a peripheral section 112b that is articulated relative to the central section 112a. In this way, the main lift surface 110 can be used in various applications such as Figure 1 The stowed configuration shown has a smaller footprint than the Figure 3The main lift surface 110 is configured to move between the stowed and deployed configurations, which have a larger footprint. Preferably, movement of the main lift surface 110 between the stowed and deployed configurations is accomplished by an actuator. As shown in these figures, the footprint of the main lift surface 110 (as defined by the swept area of ​​the main lift surface 110 as it rotates about the central axis 102 in a plane perpendicular to the central axis 102) is smaller in the stowed configuration than in the deployed configuration. Other methods may be employed to enable movement of the main lift surface 110 between the stowed and deployed configurations. For example, the joints 114 may be arranged as accordion-shaped or telescoping prismatic joints. The joints 114 may include vertical, horizontal, or diagonal pivots, including bearings (not shown), hinges (not shown), locking mechanisms (not shown), and / or actuators (not shown). Multiple joints 114 may be present. In the deployed configuration, the radius of the main lift surface 110 is in the range of 5 to 12 m, more preferably approximately 8.25 m. In the stowed configuration, the radius of the primary lift surface 110 is less than 3 m, preferably about 2.5 m. In another embodiment, the primary lift surface 110 has a radius of more than 12 m in the deployed configuration to provide an aerial crane. In yet another embodiment, the primary lift surface 110 has a radius of less than 5 m in the deployed configuration to provide a lower load version of the aircraft 100.

[0055] Return to Figure 1The propulsion assembly 100 further includes a secondary lift surface 120 configured to provide sufficient lift to elevate the propulsion assembly 100 and / or provide a torque to rotate the propulsion assembly 100 when rotating about a second axis 122. Preferably, the secondary lift surface 120 is located a distance from the central section 112a of the primary lift surface 110 such that the thrust generated by the secondary lift surface 120 creates a torque. In another embodiment, the secondary lift surface 120 is located on the central section 112a and configured to create a torque about the central axis 102. Most preferably, the secondary lift surface 120 is located at the distal end of the primary lift surface 110 as a tip thruster. In one embodiment, the secondary lift surface 120 is located at the distal end of the primary lift surface 110 when the primary lift surface is in the stowed configuration. In another embodiment, the secondary lift surface 120 is located at the distal end of the primary lift surface 110 when the primary lift surface is in the deployed configuration. The secondary lift surface 120 is preferably driven by at least one motor (or multiple motors) to achieve sufficient lift to lift the payload 10 off the ground. The motor may include a propeller. Preferably, the motor or motors in combination have a total peak electrical power of 50 kW to 150 kW, more preferably 80 kW to 85 kW, and a total continuous electrical power of 50 kW to approximately 70 kW, preferably approximately 55 kW. In a preferred embodiment, the secondary lift surface 120 includes one or more rotorlets 124 that rotate about respective second axes 122. The second axes 122 of the at least one rotorlet 124 or rotorlets 124 are adjustable, preferably continuously adjustable, to control the direction of the lift generated by the secondary lift surface 120. If the second axis 122 is adjusted non-parallel to the central axis 102, the lift of the secondary lift surface 120 induces the primary lift surface 110 to rotate about the central axis 102. In other embodiments, the lift surfaces 110, 120 can be positioned so that the second axis 122 does not need to be non-parallel to the first axis 102. By adjusting, preferably continuously adjusting, the direction of the second axis 122, the proportion of the lift of the secondary lift surface 120 used to lift the propulsion assembly 100 can be reduced or increased, and the proportion of the lift of the secondary lift surface 120 used to induce rotation of the primary lift surface 110 about the central axis 102 can be correspondingly increased or decreased. Thus, by controlling moment induction using the direction of the second axis 202 and the amount of thrust generated by the secondary lift surface 120, the thrust generated by the secondary lift surface 120 in the direction of the second axis 122 can be used to control the lift and orientation of the propulsion assembly 100. Preferably, the secondary lift surface 120 is configured to operate at peak efficiency when inducing rotation of the primary lift surface 110 to lift the load 20, which is the most common operating envelope of the secondary lift surface 120. In other preferred embodiments, the secondary lifting surface 120 comprises a jet propulsion, a ramjet, or an impulse device, such as a rocket.In some embodiments, the secondary lift surface 120 does not necessarily need to rotate about the second axis 122, but rather provides thrust along the second axis 122. Preferably, the thrust of the secondary lift surface 120 can be increased within a limited time period, preferably about 300 seconds, to exceed the design thrust by a certain performance margin. Preferably, the performance margin is up to 30%. For example, Figure 3 As shown, the primary lift surface 110 may move between a stowed configuration and a deployed configuration while being lifted by the secondary lift surface 120 .

[0056] The propulsion assembly 100 may further include a lifting surface control system (not shown) including servo tabs (not shown), such as those implemented on the Kaman K-MAX helicopter, to provide periodic and collective control of the primary lifting surface 110. In other embodiments, the lifting surface control system may include a blade pitch pivot. This allows for control of the position of the primary lifting surface 110 in addition to controlling its rotational speed.

[0057] like Figure 2 As shown, propulsion assembly 100 may further include a tether 140 for connecting propulsion assembly 200 to payload 10. Tether 140 is preferably connected to propulsion assembly 100 using a bearing (not shown), such as a universal joint, a pivot bearing, or other device suitable for preventing tension applied to tether 140 from inducing torque in propulsion assembly 100. Preferably, the bearing is positioned near or juxtaposed with the center of mass of propulsion assembly 100 when primary lift surface 110 is in the deployed configuration, and provides lift to elevate propulsion assembly 100 by providing lift induced by rotation of secondary lift surface 120. Tether 140 is suitable for transmitting power from payload 10 to propulsion assembly 100 to power propulsion assembly 200, for example, via a power line including electrical power carrying low-voltage alternating current and / or high-voltage direct current. Tether 140 is also suitable for transmitting control signals from payload 10 to propulsion assembly 100, although propulsion assembly 100 may also include a backup flight computer, flight sensors, and a telecommunications system for independent control, if desired. For example, the tether 140 may include a separate data cable for transmitting control signals. Preferably, the tether 140 is retractable. The propulsion assembly 100 may further include a first docking hub 150, preferably located at the central axis 102. The first docking hub 150 is configured to engage the payload 10 when the tether 140 is fully retracted, preferably to secure the payload during cruising operation of the propulsion assembly 100 or when on the ground.

[0058] The propulsion assembly 100 may further include an emergency power reserve (not shown) to power the propulsion assembly 100 during a powered descent. In one embodiment, the emergency power reserve is sized to provide sufficient power for a period corresponding to a powered descent of the propulsion assembly 100 carrying the payload 10 from its maximum design cruising altitude, noting that a portion of this descent may be unpowered due to the autorotation of the primary lift surface 110. In another embodiment, the emergency power reserve is sized to provide sufficient power for a period corresponding to a powered descent of the propulsion assembly 100 alone (without the payload 10) from an altitude corresponding to the length of the tether 140. In one embodiment, power transmitted from the tether 140 is fed into the emergency power reserve, which then powers the secondary lift surface 120. Thus, the propulsion assembly 100 can be indirectly powered by the tether 140.

[0059] return Figure 1Aircraft 200 is preferably a vertical take-off and landing (VTOL) aircraft and includes a body 210 having a load-bearing cavity or area 212. Body 210 may further include an access door (not shown), a cargo hatch (not shown), and / or windows (not shown). Body 210 may further include cushioning devices (not shown), damping devices (not shown), and / or a suspension (not shown) to reduce the impact experienced by body 210 during landing. In another embodiment, a rack (not shown) may be provided to accommodate aircraft 200 during landing. In one embodiment, the rack may include a fuel or recharging station to recharge the energy source of aircraft 200. Body 210 may include wheels 260 to allow aircraft 200 to move during landing. In one embodiment, wheels 260 may include motors (not shown), such as electric motors, such as wheel hub motors, to propel aircraft 200 on the ground as a vehicle, preferably over a limited distance, such as from a target landing site 14 to a storage area (not shown) of aircraft 200. In one embodiment, wheels 260 may be retractable to improve the aerodynamic efficiency of aircraft 200 during cruise conditions. In another embodiment, wheels 260 may include fixed wheels to reduce weight and mechanical complexity. In one embodiment, wheels may include one or more of skis, snowboards, and floats. In one embodiment, the support may be provided with wheels 260 to propel the aircraft on the ground as a vehicle. In one embodiment, movement of the support using wheels 260 may be remotely controlled. For the purposes of the above discussion, body 210 (including any contents or attached payload) may be considered payload 10. Aircraft 200 includes propulsion assembly 100 as described above, and a power generation assembly (not shown) configured to provide power to propulsion assembly 200. When landed, aircraft 200 may be connected to ground power or an external power generation assembly. The power generation assembly may include batteries, fuel cells, supercapacitors, and / or generator power. Preferably, the generator power is provided by an internal combustion engine (such as a Wankel engine). Preferably, the aircraft includes supercapacitors to provide high current in short periods of time, which would degrade the Li-ion batteries or require oversizing the generator. The aircraft 200 may also include one or more directional thrusters 230 mounted on the body 210. Each directional thruster 230 acts in a corresponding thruster direction 232 that is preferably not parallel to the central axis 102. In one embodiment, the thruster direction 232 is adjustable. In a preferred embodiment, the directional thrusters 230 include ducted fans. In other embodiments, the directional thrusters 230 include rotors, jet thrusters and / or pulse thrusters, such as cold gas thrusters, ultra-high temperature or other chemical pulse systems.When the propulsion assembly 200 suspends the payload 10, directional thrusters 230 can be used to manipulate the payload 10 in roll, pitch, yaw, and / or translation relative to the propulsion assembly. For example, the directional thrusters 230 can be mounted on the side of the aircraft 200 to redirect the payload 10 similar to the tail rotor of a helicopter. The directional thrusters 230 can be aligned vertically in a multi-rotor configuration, or non-parallel to gravity, or some combination thereof. The directional thrusters 230 can be parallel to the central axis 112 or non-parallel to the central axis 112. In a preferred embodiment, the directional thrusters 230 include three pairs of parallel, opposing thrusters aligned orthogonally to each other so that the combination of thrust and torque couples allows full motion in the longitudinal, lateral, roll, pitch, and yaw directions. In one embodiment, the directional thrusters 230 can include a tail rotor (not shown) mounted to the aircraft 200. In one embodiment, the payload 10 can include an aerodynamic surface capable of providing lift during horizontal flight, such as a wing, tail, canard, or the like.

[0060] Aircraft 200 may include a camera (not shown) for identifying target landing site 14. Aircraft 200 may also include a controller (not shown) that operates a control system configured to detect target landing site 14 using one or more of designated markings, geometric shapes, colors, landing lights, apron colors, or the letter "H." In addition to or in lieu of using a camera, aircraft 200 may further include one or more of a LIDAR sensor (not shown) and an ultrasonic rangefinder to detect obstacles around target landing site 14. Aircraft 200 may engage an instrument landing system (ILS) to land aircraft 200. In addition to or in lieu of one or more of a LIDAR sensor, ultrasonic rangefinder, camera, and radar (not shown), aircraft 200 may include an altitude and / or airspeed sensor (not shown) in propulsion assembly 100 and / or body 210 for use by the control system to adjust altitude and airspeed.

[0061] like Figure 5As shown, body 210 has a center of gravity 214 and may further include a winch (not shown), preferably an electric winch. The winch preferably includes a locking mechanism (not shown) to prevent the uncontrolled release of tether 140. The winch may also include an emergency mechanism (not shown) to cut or release tether 140. Aircraft 200 may further include a safety mechanism (not shown) for payload 20 in the event of its release by the emergency mechanism. Body 210, winch, and tether 140 are configured such that the uppermost control point 236 of tether 140 on body 210 is located above center of gravity 214, allowing body 210 to be suspended in a stable position below propulsion assembly 100. Body 210 may further include a second docking hub 240, preferably located at central axis 102. Second docking hub 240 is configured to engage first docking hub 150 when tether 140 is fully retracted. The engagement between first and second docking hubs 150, 240, can provide multiple degrees of freedom between the first and second docking hubs 150, 240. For example, the first docking hub 150 may include a dome, wherein the second docking hub 240 has a conforming dome-shaped recess.

[0062] The body 210 may further include one or more control surfaces (not shown), such as a rudder or tail or teardrop shape, to provide a smooth and steady motion along the Figure 8 The illustrated direction of travel 12 generates a corrective force toward the preferred orientation to set the preferred orientation of body 210 during flight. One or more control surfaces may also be used to help change and / or control direction of travel 12 by generating drag and / or lift forces that are not parallel to direction of travel 12.

[0063] Body 210 may further include a ballistic parachute (not shown) for use in emergency situations. In an emergency, propulsion assembly 100 may be used to attempt an autorotational landing, or disconnected from body 210 to allow the body to land using the ballistic parachute. Propulsion assembly 100 may optionally attempt a powered or unpowered landing, or deploy a separate ballistic parachute (not shown) or other impact-damping mechanism, such as deployable airbags or a crash zone. If an emergency occurs at a higher altitude, an autorotational descent may be performed first, with the aforementioned actions being taken closer to ground level.

[0064] Figures 9 to 14 A second embodiment of an aircraft 200 and propulsion assembly 100 is shown, demonstrating some of the embodiments discussed previously.

[0065] The use of various embodiments of a VTOL aircraft 200 having a propulsion assembly 100 will now be discussed.

[0066] Figure 12. For takeoff, the docking hub 150, 240 (if used and / or desired) is disconnected and the propulsion assembly 100 is lifted upward using the lift generated by the rotation of the secondary lift surface 120 about the second axis 122, as shown in FIG. Figure 2 If multiple secondary lift surfaces 120 are used, the differential thrust between these secondary lift surfaces can be used for pitch and / or attitude control. At an altitude that can be predetermined, commanded, or assessed to be safe based on sensor input, the primary lift surface 110 is moved from the stowed configuration to the deployed configuration by articulating the peripheral segments 112b about the joints 114, as shown. Figure 3 As shown. Once the primary lift surface 110 is in the deployed configuration, the second axis 122 rotates to create a moment arm about the central axis 102 so that the lift generated by the secondary lift surface 120 induces rotation of the primary lift surface 110. The rotation or movement of the second axis 122 can be performed as an actual rotation of the secondary lift surface 120, or as a change in the contribution to lift of multiple differently oriented secondary lift surfaces 120 so that the resultant lift vector changes direction. As the rotational speed of the primary lift surface 110 increases, the lift generated by the primary lift surface 110 increases, thereby allowing the second axis 122 to rotate further so that a smaller proportion of the lift generated by the secondary lift surface 120 is used to lift the propulsion assembly 200, while a larger proportion is used to induce rotation of the primary lift surface 110. Once the lift generated by the primary lift surface 110 exceeds the weight of the aircraft 200, the body 210 lifts off the ground, as shown. Figure 5 In another embodiment, the body 210 is lifted by actuation of a winch. When the body 210 is suspended below the propulsion assembly 100 on the tether 140, the body 210 may require position and / or orientation control, which is provided by a combination or selection of directional thrusters 230 and the lifting surface control system 130 of the propulsion assembly 100, as shown. Figure 6 The tether 140 can be retracted using a winch, so that the distance between the body 210 and the propulsion assembly 100 is reduced, thereby reducing the range of motion of the body 210, such as Figure 7As shown. Preferably, the tether 140 is fully retracted so that the docking hubs 240, 150 engage to connect the body 210 to the propulsion assembly 100, however, in other embodiments, the payload 10 or the body 210 may remain suspended below the propulsion assembly 100. The aircraft 200 can now fly as a helicopter, and in other embodiments, the aircraft 200 can fly as a helicopter with a suspended payload, preferably having a cruising speed of preferably over 200 km h-1, more preferably up to 300 km h-1, and a cruising range of between 300 km and 500 km, with an endurance of approximately 2 hours, carrying a payload 10 weighing between 200 kg and 420 kg, and a noise level between 105 dBA and 115 dBA.

[0067] The above steps may be performed in reverse order to land vehicle 200. If target landing site 14 is sufficiently unrestricted, vehicle 200 may be landed without extending tether 140 and / or disconnecting from propulsion assembly 100.

[0068] Advantages of various embodiments of aircraft 200 will now be discussed.

[0069] Because the footprint of the main lift surface 110 is smaller in the stowed configuration, the propulsion assembly 100 can lift off at ground level while providing relatively little clearance and deploy the main lift surface 110 required to lift the aircraft 200 at an obstacle-safe altitude, reducing downwash and noise experienced at ground level. The main lift surface 110 can be significantly larger than a helicopter in the deployed configuration, as the only limiting factor is the stowed footprint of the main lift surface. Additionally, the smaller footprint allows for much less rotor droop, thereby improving ground clearance requirements and reducing the likelihood of rotor ground strikes.

[0070] The use of the secondary lifting surface 120 to both lift the propulsion assembly 100 and induce rotation of the primary lifting surface 110 desirably reduces the number of components and systems required in the propulsion assembly 100, thereby reducing weight and complexity. Gradual control of the direction of the second axis 122 allows the secondary lifting surface 120 to smoothly transition between the tasks of lifting the propulsion assembly 100 and powering the primary lifting surface 110. The use of the lifting surface control system 130 allows for orientation and position control of the propulsion assembly 100 without multiple primary lifting surfaces 110 providing differential thrust (such as in a quadcopter configuration). For the planned route length of the aircraft 200, it is desirable to use rotors for both the primary and secondary lifting surfaces 110. Because the primary lifting surface 110 is driven by the secondary lifting surface 120, which effectively acts as a pulse transfer device from the ambient air to the primary lifting surface 110, the opposing force acting to drive the primary lifting surface 110 does not travel through the hub 150 but is instead exerted on the ambient air. As a result, there is virtually no need for the tail rotor required on a direct drive main rotor. The use of multiple secondary lift surfaces 120 allows the impulses of these surfaces to cancel each other out by being driven in opposite directions, and directional thrusters 230 can be used to account for any residual torque due to imperfect balance or friction in the various bearings.

[0071] The use of a tether 140 to transmit power from the body 210 to the propulsion system 100 reduces redundancy in the power system and allows the propulsion system 100 to be of very low weight, enabling it to be lifted by the secondary lift surface 120 and preferably carrying an emergency power reserve 160 only in case the connection between the body 210 and the propulsion system 100 is damaged. The retractability of the tether 140 allows the body 210 and propulsion system 100 to be reconnected, thereby increasing the stability of the aircraft 200. The use of docking hubs 240, 150 facilitates disconnection and reconnection of the body 210 and the propulsion system 100.

[0072] The use of directional thrusters 230 allows positional control of body 210 while it is suspended by tether 140. Directional thrusters 230 can also be used to steer aircraft 200 during flight. Using ducted fans for directional thrusters 230 increases the safety of directional thrusters 230 and increases the aerodynamic efficiency of the design performance envelope of directional thrusters 230. Directional thrusters 230 can be used in place of a tail rotor to counteract undesirable torques acting on aircraft 200.

[0073] A major limitation of helicopters is that their construction limits their maximum speed due to adverse flow across the retreating blades in horizontal flight. Tilt-rotor aircraft avoid this by allowing their rotors to tilt forward to near horizontal, causing the oncoming air to approach parallel to the rotor axis. Currently, this technology is being adapted and expanded to tethered propulsion assemblies by adding the ability to tilt and shift downward, until the tethered assembly guides the load, pulling it like a tugboat. As a result, the direction of travel, and therefore the air entering the propulsion assembly, is largely aligned with the propulsion assembly's axis of rotation.

[0074] To achieve this, the payload is preferably equipped with a pivoting tether mount, allowing the propulsion assembly to change its angle under tether tension while the payload remains horizontal. The pivoting mount requires a tether linkage and hinge point, preferably aligned axially with the center of mass, and may include a tether force sensor, locking mechanism, or actuator. The propulsion assembly is preferably equipped with a mechanism for directing the propulsion assembly's primary lifting surface downstream to achieve the appropriate angle of attack relative to the oncoming wind.

[0075] During rotational flight, the propulsion assembly has no fixed heading relative to the load. The propulsion assembly's aerodynamic surfaces apply control inputs in a continuously rotating reference frame, which need to be modulated relative to any absolute desired heading to maintain effective control. Helicopters address this issue using periodic control, in which rotor pitch inputs are indexed relative to a reference angle applied to the slide plate. Because a tether cannot apply torque along the axis of rotation, a different approach must be used.

[0076] In a preferred embodiment, tether 140 may include an attachment interface that connects the tether to propulsion assembly 100. The attachment interface may be a non-flexible, non-rotating endpoint of tether 140. The attachment interface may be co-located within docking hub 150. Alternatively, the attachment interface may be located external to docking hub 150 on propulsion assembly 100. Those skilled in the art will appreciate that tether 140 needs to rotate at the attachment interface (i.e., at the connection with propulsion assembly 100) to prevent tether 140 from winding. Further, the center of gravity of the attachment interface is positioned above and spatially relative to the center of gravity of body 210 to promote stable flight and control.

[0077] A system for determining spatial parameters of the propulsion assembly 100 relative to the payload 10 is also provided. The spatial parameters include absolute and relative orientation parameters of the propulsion assembly 100 relative to the payload 10. To determine the spatial parameters, the system may include a magnetometer and / or a gyroscope. Additionally, the system may include an encoder (such as a Hall effect sensor or similar absolute orientation sensor) positioned between the propulsion assembly 100 and the attachment interface to determine the spatial parameters.

[0078] A combination of inertial and magnetic reference frames is used to determine the heading of the payload 10 and the heading of the propulsion assembly 100, and thus calculate relative orientation so that the correct control inputs can be calculated to provide the desired trajectory in flight. Since constant rapid rotation can make inertial and magnetic system measurements unreliable, a heading reference system can be provided on the attachment interface connected to the tether 140. An encoder can determine the orientation of the propulsion assembly relative to the attachment interface, and as described above, the encoder is provided between the attachment interface and the propulsion assembly. The attachment interface can optionally be stabilized with aerodynamic surfaces (such as a tail, control surfaces, or thrusters) to maintain the desired heading relative to the payload.

[0079] The tether 140 may include a second attachment interface at an opposite end of the tether 140 that connects the tether 140 to the payload 10. The second attachment interface may be co-located within the hub 240 on the payload 10 or at a location external to the hub 240. The second attachment interface may include an articulated frame that can change its orientation during flight to allow the payload 10 to remain level when the propulsion assembly 100 is tilted. The articulated frame also allows the propulsion assembly to fly at high angles of attack relative to the horizontal and provide faster flight speeds.

[0080] Using a computer or similar system, the relative rotation between the propulsion assembly and the attachment interface is calculated, and from this the orientation relative to the payload 10 and the surrounding environment can be calculated. Thus, for any given orientation of the propulsion assembly 100, the attachment interface, and the payload 10, appropriate control signals can be calculated to steer the propulsion assembly 100 in the desired direction.

[0081] Reference numerals:

Claims

1. A propulsion assembly for lifting a load, the propulsion assembly comprising: a primary lifting surface configured to provide sufficient lift for lifting the load when rotated about a central axis; a secondary lift surface configured to provide lift along a second axis to lift the propulsion assembly, wherein the second axis is configurable between a lift configuration in which the secondary lift surface lifts the propulsion assembly and a thrust configuration in which the secondary lift surface induces rotation of the primary lift surface.

2. The propulsion assembly of claim 1, wherein: The primary lifting surface is movable between a stowed configuration and a deployed configuration, wherein the primary lifting surface occupies a smaller footprint in the stowed configuration than in the deployed configuration.

3. The propulsion assembly of claim 1, wherein: The primary lifting surface is movable between the stowed configuration and the deployed configuration while being lifted by the secondary lifting surface.

4. The propulsion assembly of claim 1, wherein: The second axis of the secondary lift surface is capable of continuously moving between the lifting position and the thrust position, so that the proportion of the lift of the secondary lift surface used to lift the propulsion assembly continuously decreases as the lift generated by the primary lift surface increases, and the lift generated by the main lift surface increases as the rotational speed of the main lift surface about the central axis increases.

5. The propulsion assembly of claim 1, wherein: The propulsion assembly further includes a lifting surface control system to provide periodic and collective control of the primary lifting surface.

6. The propulsion assembly of claim 5, wherein: The lifting surface control system includes servo tabs.

7. The propulsion assembly of claim 1, wherein: The propulsion assembly further comprises a tether for connecting the propulsion assembly to the payload, wherein the tether is adapted to transfer power from the payload to the propulsion assembly to power the propulsion assembly.

8. The propulsion assembly of claim 7, wherein: The tether is retractable.

9. The propulsion assembly of claim 7, wherein: The propulsion assembly further includes a first docking hub located at the central axis, the first docking hub configured to engage the load when the tether is fully retracted.

10. The propulsion assembly of claim 7, wherein: The tether is connected to the propulsion assembly through a bearing to reduce torque applied by the tether to the propulsion assembly when tension is applied to the tether.

11. The propulsion assembly of claim 1 , wherein: The main lifting surface includes a rotor, which preferably provides orientation control of the propulsion assembly.

12. The propulsion assembly of claim 1, wherein: The secondary lifting surface comprises a rotor rotatable about the second axis, preferably the rotor providing orientation control of the propulsion assembly.

13. The propulsion assembly of claim 1, wherein: The propulsion assembly further includes an emergency power reserve to provide power to the propulsion assembly against power reduction.

14. The propulsion assembly of claim 1, wherein: The secondary lift surface includes a plurality of secondary lift surfaces.

15. The propulsion assembly of claim 7, wherein: The tether includes an attachment interface that connects the tether to the propulsion assembly.

16. The propulsion assembly of claim 15, wherein: The attachment interface is the non-flexible and non-rotating endpoint of the tether.

17. The propulsion assembly of claim 16, comprising a system for determining spatial parameters of the propulsion assembly relative to the load.

18. The propulsion assembly of claim 17, wherein: The spatial parameters include absolute orientation parameters and relative orientation parameters of the propulsion assembly relative to the load.

19. The propulsion assembly of claim 16, wherein: The system includes a magnetometer and / or a gyroscope to determine the spatial parameter.

20. The propulsion assembly of claim 18, wherein: The system includes an encoder positioned between the propulsion assembly and the attachment interface to determine the spatial parameter.

21. The propulsion assembly of claim 15, wherein: The attachment interface includes aerodynamic surfaces and / or thrusters to control the heading of the tether.

22. The propulsion assembly of claim 15, wherein: The tether includes a second attachment interface connecting the tether to the payload to allow the propulsion assembly to fly at a high angle relative to the horizontal, thereby allowing faster flight speeds.

23. The propulsion assembly of claim 22, wherein: The second attachment interface includes an articulating frame that is capable of changing its orientation during flight to allow the payload to remain level when the propulsion assembly is tilted, and to allow the propulsion assembly to fly at high angles of attack relative to the horizontal and provide faster flight speeds.

24. The propulsion assembly of claim 1, wherein: The load includes aerodynamic surfaces capable of providing lift during level flight.

25. The propulsion assembly of claim 5, wherein: These control surfaces can be effectively flown downstream for faster axial flight.

26. A vertical take-off and landing aircraft, comprising: a body having a load-bearing cavity or area for a load; The propulsion assembly according to any one of claims 1 to 25, which is used to lift the body; and A power generation assembly is located in or on the body, and is configured to provide power to the propulsion assembly.

27. The aircraft of claim 26, further comprising one or more directional thrusters attached to the body, the directional thrusters acting in respective directions that are non-parallel to the central axis.

28. The aircraft of claim 26, further comprising one or more directional thrusters attached to the body, the directional thrusters acting in respective directions parallel to the central axis.

29. The aircraft of claim 27, wherein: The directional thrusters include ducted fans, rotors, jet thrusters and / or pulse thrusters.

30. An aircraft as claimed in claim 26 when dependent on claim 7, wherein The body has a center of gravity and includes a winch for retracting the tether, wherein an uppermost control point of the tether on the body is above the center of gravity of the body.

31. An aircraft as claimed in claim 30 when dependent on claim 15, wherein The center of gravity of the attachment interface is positioned above and spatially related to the center of gravity of the body to promote stable flight and control.

32. An aircraft as claimed in claim 26 when dependent on claim 8, wherein The body further includes a second docking hub configured to engage the first docking hub when the tether is fully retracted.

33. The aircraft of claim 26, wherein: The body further comprises one or more control surfaces for setting a preferred orientation relative to the direction of travel and / or controlling the orientation of the vehicle relative to the direction of travel.

34. The aircraft of claim 32, wherein: The movable surface may be used to assist in changing the direction of travel.

35. The aircraft of claim 26, wherein: The vehicle includes wheels on the body and motors driving the wheels for propelling the vehicle on the ground.

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