UAV WITH FRANGIBLE AIRFRAME STRUCTURES
1. A mechanical joiner for an airframe, comprising:
- a joiner core having a first side with a first cradle shaped to hold a first structural member and a second side with a second cradle shaped to hold a second structural member;
a first cap shaped to mate to the first side of the joiner core and clamp the first structural member into the first cradle, wherein the joiner core includes a first hole for a first mechanical fastener to extend through and across the first cradle to secure the first cap to the joiner core; and
a second cap shaped to mate to the second side of the joiner core and clamp the first structural member into the second cradle, wherein the second cap includes second holes for second mechanical fasteners, distinct from the first mechanical fastener, to secure the second cap to the joiner core.
A mechanical joiner for an airframe includes a joiner core and first and second caps. The joiner core has a first side with a first cradle shaped to hold a first structural member and a second side with a second cradle shaped to hold a second structural member. The first cap is shaped to mate to the first side and clamp the first structural member into the first cradle. The joiner core includes a first hole for a first mechanical fastener to extend through and across the first cradle and secure the first cap to the joiner core. The second cap is shaped to mate to the second side and clamp the first structural member into the second cradle. The second cap includes second holes for second mechanical fasteners, distinct from the first mechanical fastener, to secure the second cap to the joiner core.
- 1. A mechanical joiner for an airframe, comprising:
a joiner core having a first side with a first cradle shaped to hold a first structural member and a second side with a second cradle shaped to hold a second structural member; a first cap shaped to mate to the first side of the joiner core and clamp the first structural member into the first cradle, wherein the joiner core includes a first hole for a first mechanical fastener to extend through and across the first cradle to secure the first cap to the joiner core; and a second cap shaped to mate to the second side of the joiner core and clamp the first structural member into the second cradle, wherein the second cap includes second holes for second mechanical fasteners, distinct from the first mechanical fastener, to secure the second cap to the joiner core.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- 11. An unmanned aerial vehicle (UAV), comprising:
a wing assembly including a wing spar; a boom assembly including a boom and a plurality of motor mounts secured to the boom; and a spar-boom joiner for mechanically securing the wing spar to the boom, the spar-boom joiner including; a joiner core having a first side with a spar cradle shaped to hold the wing spar and a second side with a boom cradle shaped to hold the boom; a spar cap shaped to mate to the first side of the joiner core and clamp the wing spar into the spar cradle, wherein a spar fastener extends through the wing spar and secures the spar cap to the joiner core; and a boom cap shaped to mate to the second side of the joiner core and clamp the boom into the boom cradle, wherein second mechanical fasteners, distinct from the spar fastener, secure the boom cap to the joiner core.
- View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
This disclosure relates generally to unmanned aerial vehicles, and in particular but not exclusively, relates to airframes of unmanned aerial vehicles.
An unmanned vehicle, which may also be referred to as an autonomous vehicle, is a vehicle capable of travel without a physically-present human operator. An unmanned vehicle may operate in a remote-control mode, in an autonomous mode, or in a partially autonomous mode.
When an unmanned vehicle operates in a remote-control mode, a pilot or driver that is at a remote location can control the unmanned vehicle via commands that are sent to the unmanned vehicle via a wireless link. When the unmanned vehicle operates in autonomous mode, the unmanned vehicle typically moves based on pre-programmed navigation waypoints, dynamic automation systems, or a combination of these. Further, some unmanned vehicles can operate in both a remote-control mode and an autonomous mode, and in some instances may do so simultaneously. For instance, a remote pilot or driver may wish to leave navigation to an autonomous system while manually performing another task, such as operating a mechanical system for picking up objects, as an example.
Various types of unmanned vehicles exist for various different environments. For instance, unmanned vehicles exist for operation in the air, on the ground, underwater, and in space. Unmanned aerial vehicles (UAVs) are becoming more popular in general. Their use over populated areas, such as suburban and urban localities, means that designed in safety measures and components are increasingly important.
Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Not all instances of an element are necessarily labeled so as not to clutter the drawings where appropriate. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described.
Embodiments of a system, apparatus, and method of operation for a structural joiner having a frangible design that preferentially decouples kinetic energy between linked structures in the event of a collision of a threshold magnitude are described herein. In the following description numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Embodiments described herein describe mechanical joiners and techniques for securing airframe structures to each other in a “frangible” manner that permits these structures to fail in the event of a collision, thereby decoupling kinetic energy between linked structures in a controlled failure mode. The mechanical structures are designed to break in a specified manner in specified locations to control where the impact kinetic energy is directed. These mechanical joiners are well suited for use in aerial vehicles, such as unmanned aerial vehicles (UAVs). An UAV refers to any autonomous or semi-autonomous vehicle that is capable of performing some functions without a physically present human pilot. A UAV can take various forms, such as a fixed-wing aircraft.
UAVs have structural elements that operate as a skeleton or frame, to which other elements are mounted, for carrying load forces during operation. Examples of such structural elements include wing spars, booms, and the like. These elements should be strong while also lightweight. To achieve a balance between strength and weight, these structural elements are often hollow (e.g., tubular) members fabricated of materials such as metal (e.g., aluminum), fiberglass, carbon fiber (e.g., filament wound carbon fiber tubes), or otherwise.
Accordingly, embodiments described herein contemplate mechanical joiners that break upon impact and separate the high mass components of the fuselage from elongated mechanical structures. This separation prevents the kinetic energy and deceleration force of the fuselage from being directed down a boom or rod upon a catastrophic impact. This separation of the higher mass components from the elongated, high strength and slender airframe components improves safety and reduces property damage in the event of crash landings of a UAV. Instead of directing the energy of the collision to the tip of the boom, the collision energy of the fuselage is dissipated in the collision of the fuselage itself, which is a broad, blunt object. In various embodiments, the fuselage is modular and the individual sections are also joined with frangible mechanical joiners that are design to break on impact, further dissipating collision energy.
The illustrated embodiment of UAV 100 includes a fuselage 104. In one embodiment, fuselage 104 is modular and includes a battery module, an avionics module, and a mission payload module. These modules are detachable from each other and mechanically securable to each other to contiguously form at least a portion of the fuselage or UAV main body.
The battery module includes a cavity for housing one or more batteries for powering aerial vehicle 100. The avionics module houses flight control circuitry of aerial vehicle 100, which may include a processor and memory, communication electronics and antennas (e.g., cellular transceiver, wifi transceiver, etc.), and various sensors (e.g., global positioning sensor, an inertial measurement unit (IMU), a magnetic compass, etc.). The mission payload module houses equipment associated with a mission of aerial vehicle 100. For example, the mission payload module may include a payload actuator for holding and releasing an externally attached payload. In another embodiment, the mission payload module may include a camera/sensor equipment holder for carrying camera/sensor equipment (e.g., camera, lenses, radar, lidar, pollution monitoring sensors, weather monitoring sensors, etc.).
The illustrated embodiment of UAV 100 further includes horizontal propulsion units 106 positioned on wing assembly 102, which can each include a motor, shaft, motor mount, and propeller, for propelling UAV 100. The illustrated embodiment of UAV 100 includes two boom assemblies 110 that secure to wing assembly 102. In one embodiment, wing assembly 102 includes a wing spar 203 (see
The illustrated embodiments of boom assemblies 110 each include a boom housing 111 in which a boom 214 (see
During flight, UAV 100 may control the direction and/or speed of its movement by controlling its pitch, roll, yaw, and/or altitude. For example, the stabilizers 108 may include one or more rudders 108a for controlling the UAV'"'"'s yaw, and wing assembly 102 may include elevators for controlling the UAV'"'"'s pitch and/or ailerons 102a for controlling the UAV'"'"'s roll. As another example, increasing or decreasing the speed of all the propellers simultaneously can result in UAV 100 increasing or decreasing its altitude, respectively.
Many variations on the illustrated fixed-wing aerial vehicle are possible. For instance, aerial vehicles with more wings (e.g., an “x-wing” configuration with four wings), are also possible. Although
It should be understood that references herein to an “unmanned” aerial vehicle or UAV can apply equally to autonomous and semi-autonomous aerial vehicles. In a fully autonomous implementation, all functionality of the aerial vehicle is automated; e.g., pre-programmed or controlled via real-time computer functionality that responds to input from various sensors and/or pre-determined information. In a semi-autonomous implementation, some functions of an aerial vehicle may be controlled by a human operator, while other functions are carried out autonomously. Further, in some embodiments, a UAV may be configured to allow a remote operator to take over functions that can otherwise be controlled autonomously by the UAV. Yet further, a given type of function may be controlled remotely at one level of abstraction and performed autonomously at another level of abstraction. For example, a remote operator may control high level navigation decisions for a UAV, such as specifying that the UAV should travel from one location to another (e.g., from a warehouse in a suburban area to a delivery address in a nearby city), while the UAV'"'"'s navigation system autonomously controls more fine-grained navigation decisions, such as the specific route to take between the two locations, specific flight controls to achieve the route and avoid obstacles while navigating the route, and so on.
As mentioned above, mechanical joiners 216 and/or 235 may be frangible structures designed to break apart to decouple the kinetic energy between linked structures in the event of a catastrophic impact or crash landing. This controlled failure mode improves safety and reduces property damage in the event of crash landings of UAV 100 by diverting impact energy way from booms 214 and/or wing spar 203. In one embodiment, the mechanical fasteners 240, which structurally join the rear avionics module to the middle mission payload module, are selected and/or designed to shear or otherwise fail upon impact of fuselage 104. In one embodiment, mechanical fasteners 245, which structurally join the middle mission payload module to the front battery module, are also selected and/or designed to shear or otherwise fail upon impact of fuselage 104. In one embodiment, mechanical fasteners 240 and 245 are plastic fasteners (e.g., nylon, polyetheretherketone, etc.).
Spar-boom joiner 300 is a mechanical bracket or joiner that secures structural members of airframe 200 to each other. In particular, spar-boom joiner 300 secures one of booms 214 to wing spar 203 with sufficient strength and rigidity to withstand the linear, shear, and torsional forces that arise during ordinary operation of UAV 100. The illustrated embodiment of joiner core 305 includes boom cradle 345 on its lower side that conforms to and clamps around one of booms 214 to hold it securely in place. Similarly, joiner core 305 further includes spar cradle 340 on its upper side (opposite its lower side) that conforms to and clamps around wing spar 203 to hold it securely in place. Although
In one embodiment, spar-fastener 320 is a metal fastener (e.g., bolt and nut) that extends through hole 350 (
The illustrated embodiment of boom cap 315 includes boom cradle 370 that mates to boom cradle 345 in joiner core 305, which collectively conform to the cross sectional shape of a given boom 214. Boom cap 315 is secured to joiner core 305 with four boom fasteners 330, which serve to clap boom 214 between boom cap 315 and joiner core 305. Additionally, boom cap 315 includes hole 375 through which anti-rotation pin 325 inserts into boom 214 to prevent rotational movement of boom 214 within boom cradle 345. In one embodiment, anti-rotation pin 325 is a plastic screw (e.g., nylon) that threads through tapped hole 375 into boom 214. In one embodiment, hole 375 is an untapped hole and anti-rotation pin 325 is secured in place with adhesive. In yet another embodiment, anti-rotation pin 325 is a pin or boss molded into boom cap 315. In yet other embodiments, anti-rotation pin 325 may run all the way through boom 214 and spar 203 replacing spar fastener 320. Due to the fabrication tolerances, in some embodiments, a layer of adhesive (e.g., cyanoacrylate, etc.) is also applied to the inside surface of boom cap 315 that conforms with and mates to boom 214 (i.e., boom cradle 370 on boom cap 315) to maintain a precise rotational position without slop. However, in these embodiments, the adhesive is not applied to boom cradle 345 on joiner core 305. Bonding boom 214 to boom cap 315 while not bonding to joiner core 305 controls the failure mode to a separation of boom cap 315 and boom 214 from the remainder of spar-boom joiner 300 and wing spar 203.
Spar-boom joiner 300 includes a number of “frangible” design features that allow wing spar 203 (and thus fuselage 104) to separate from booms 214 in the event of a collision impacting the end of one or both booms 214. The first feature includes isolating the pin structure (i.e., anti-rotation pin 325) that prevents rotation of boom 214 within boom cradle 345 from the pin structure (i.e., spar fastener 320) that prevents rotation of wing spar 203 within spar cradle 340. This enables lesser/different strength material to be used with anti-rotation pin 325 than spar fastener 320. In the event of collision, anti-rotation pin 325 shears off well before failure of spar fastener 320.
The second feature includes the use of lesser shear strength mechanical fasteners for implementing boom fasteners 330 compared to spar-cap fasteners 335 and/or spar fastener 320. For example, each of the four boom fasteners 330 are fabricated of a material having a lesser shear strength than spar fastener 320, which secures wing spar 203 into spar cradle 340. As a result, boom fasteners 330 are selected to fail (e.g., shear or tensile failure) in a boom collision, which releases the grip boom cap 315 has on boom 214. This release prevents the inertia associated with wing spar 203 and fuselage 104 from being carried through to the tips of booms 214. In one embodiment, boom fasteners 330 are plastic screws. One type of suitable plastic for boom fasteners 330 is polyetheretherketone (PEEK). Other types of plastics or materials (e.g., aluminum) may be implemented as well.
Additional frangible features may be integrated into spar-boom joiner 300. For example, joiner core 305 may be designed as the frangible link itself with integrated failure points to allow joiner core 305 to break apart upon impact as opposite to a separation of boom cap 315.
The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.
These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.