WO2018025122A2

WO2018025122A2 - Damage mitigating, modular system for multirotor airframes

Info

Publication number: WO2018025122A2
Application number: PCT/IB2017/054503
Authority: WO
Inventors: Jonathan Michael HEANEY
Original assignee: Heaney Jonathan Michael
Priority date: 2016-08-01
Filing date: 2017-07-25
Publication date: 2018-02-08
Also published as: GB201613253D0; WO2018025122A3

Abstract

A drone (y.1) comprises an airframe and multiple arms (b) that are attached to the airframe with a motor and rotor (j) attached to each of the arms (b) at a position remote from the airframe. Some, but preferably all of the arms (b) are pivotally attached to the airframe, to pivot relative to the airframe from an operational position of the arm (b) in a deflection direction and each arm (b) has a bias element (c, d, R) that is configured to bias the arm (b) to pivot in a return direction that is opposite to its deflection direction, to return the arm (b) to its operational position.

Description

DAMAGE MITIGATING, MODULAR SYSTEM FOF MULTIROTOR AIRFRAMES

FIELD OF THE INVENTION

This invention relates to unmanned multirotor aerial vehicles or craft (also commonly known as "drones").

BACKGROUND TO THE INVENTION

Drones are often operated in close proximity to obstacles, which often results in collisions and damage to the airframe and /or components of the drone. Racing drones are particularly prone to these collisions, because they are typically designed for speed rather than durability and are flown at high speeds through tight courses. As structural strength is sacrificed in favour of reduced mass, breakage is a frequent event in current designs. The present invention seeks: to reduce the likelihood of damage or mitigate damage to the craft and/or its components; to provide for quick and cost-effective repairs, requiring minimal tools; to provide structural strength, rigidity and protection of internal components of the craft; to provide light weight craft; and/or to provide for selection and substitution of components.

SUMMARY OF THE INVENTION

According to the present invention there is provided an aircraft comprising:

an airframe;

a plurality of arms that are each attachable to the airframe; and

at least one rotor attached to each of said arms at a position remote from the airframe;

wherein one or more of said arms are pivotally attachable to the airframe, to be pivotable relative to the airframe, to pivot from an operational position of each arm in a deflection direction of the arm, each of said pivotable arms having a first bias element that is configured to bias the arm to pivot in a return direction that is opposite to its deflection direction. The aircraft may have a front and a rear and may be configured to travel predominantly forward, and the arms and first bias elements may be configured so that the arms" deflection directions are rearward in relation to the airframe.

One or more (preferably all) of the arms may be releasably attachable to the airframe and one or more of them (preferably all) may be held in attachment to the airframe, by a single component that serves as a detent. One of more of the first bias elements may be configured to bias a plurality of the arms to pivot in their respective return directions.

The aircraft may include one or more bumper elements that are each movably supported on the airframe, to move relative to the airframe from an operational position in a deflection direction of each bumper element and the aircraft may further include one or more second bias element that are each configured to bias one of the bumper elements to move in a return direction that is opposite to its deflection direction.

Each bumper element may have an elongate shape and may be configured to slide longitudinally relative to the airframe, in its deflection direction and return direction, and one or more of the bumper elements may protrude from the airframe in its return direction.

The second bias elements may be configured to dissipate impact energy from movement of the bumper elements in their deflection directions.

One or more of the arms may include one or more elongate structural elements that are removably attached to the arm and the structural elements may be rigid rods. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how it may be put into effect, the invention will now be described by way of non-limiting example, with reference to the accompanying drawings in which:

Figure 1 shows top and perspective views of a first embodiment of a motor arm according to the present invention;

Figure 2 shows top and perspective views of the motor arm of Figure 1 with three support rods removed;

Figure 3 shows a top view of four of the motor arms of Figure 1 in an array suitable for a quad multi-rotor aircraft;

Figure 4 shows a top view of a first embodiment of a multi-rotor aircraft according to the present invention;

Figures 5 and 6 show side views of the aircraft of Figure 4, with a top section shown in position in Figure 5 and shown pivoted upwards in Figure 6;

Figure 7 shows a perspective view of a rod clamp of the aircraft of Figure 4;

Figure 8 shows a threaded attachment pillar and graduated locking disc of the aircraft of Figure 4;

Figures 9 and 10 show an exploded perspective view and an exploded side view, respectively, of a thumb screw of the aircraft of Figure 4;

Figure 1 1 shows top, side and top perspective views of the assembled thumbscrew of Figures 9 and 10.

Figure 12 shows bottom and bottom perspective views of the assembled thumbscrew of

Figures 9 and 10;

Figure 13 shows a front view of a second embodiment of a multi-rotor aircraft according to the present invention;

Figure 14 shows a top view of the aircraft of Figure 13;

Figure 15 shows a rear view of the aircraft of Figure 13; and

Figure 16 shows an exploded view of a motor arm of the aircraft of Figure 13.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Figures 1 to 3, a first embodiment of an arm or motor arm according to the present invention comprises a support component (b) and elongate structural elements in the form of rods (f) supported in the support component. The motor arm is intended to support a motor (a) with a propeller (j) for an aircraft such as a drone.

In the illustrated embodiment of Figures 1 to 3, three of the rods (f) are removably fitted in the support component (b) and the rods are preferably of a rigid, lightweight material such as carbon fibre. However, in other embodiments, the numbers of rods (f) can vary depending on the design and the rods have been omitted in Figure 2, for illustration.

Various other configurations of support components and rods can be used and in particular, each arm need not include a unitary support component. In other embodiments, the motor arm could include one or more support elements and each support element could be configured: as a spacer to keep the rods in position, as a holder for the motor (a), as an attachment to other components of the drone, and/or the like.

The support component (b) is of a lightweight construction and in the illustrated embodiment it is a unitary element of a resilient material such as injection moulded plastic, milled aluminium or carbon fibre. The support component (b) defines splits (n) around apertures in which the rods (f) are received and the splits allow the apertures to expand slightly so that the rods can be inserted in the apertures. The rods (f) are secured in the support component (b) with screws (m) that close the splits (n) to clamp the rods, but various other fasteners or anchoring arrangements could be used.

The rods (f) provide much of the structural strength of the motor arm, but in the event of an accident such as the drone colliding with an object, the rods are likely to receive significant impact and they are exposed to a risk of damage. However, the rods (f) can easily be interchanged, to replace a damaged rod, or to provide different strengths and weights of rods, for different purposes (e.g. for training or for racing). The rods (f) are also relatively inexpensive and can be replaced repeatedly and in most cases, installation of new rods after a collision, while reusing the support component (b), will provide a motor arm of adequate structural integrity. In the illustrated embodiment, the rods (f) are cylindrical and could be hollow or solid and these types of rods are commercially available at relatively low cost. However, other variations of rods could be used instead, such as elongate elements with different cross-sectional profiles - as long as they are elongate in shape, strong and cost- effective.

Figure 3 shows a top view of four of the motor arms in an array suitable for a quad multi-rotor drone and shows how the motor arms could be orientated and attached to a central airframe of the drone. The same design of motor arm can be used in all four positions of the drone - each supporting a motor (a) and rotor or propeller (j), although in other embodiments, the different motor arm may be configured differently, e.g. the front arms and rear arms may be identical, or may be mirror-images of one another. The arrow (k) shows the direction of forward flight of the drone and on contact during a collision with an object, the motor arms are intended to pivot backwards around their attachment points (I) to the airframe.

Referring to Figures 4 to 12, a first embodiment of a multi-rotor aircraft according to the present invention is generally identified by reference (y.1 ) and is referred to as a drone. The drone (y.1 ) includes four motor arms that can have a similar construction to the motor arms shown in Figures 1 to 3, or the motor arms could have a different construction and in Figures 4 to 6, each motor arm is shown as a unitary element and is identified by reference (b), because the motor arm essentially comprises a support component, as described with reference to Figures 1 to 3, without the splits and rods. This simplified construction of the motor arms is shown largely for the sake of simplicity of illustration and the drone y.1 could preferably be used with different configurations of motor arms, such as those shown in Figures 1 to 3, or other variants described above. Other features that are common between the Figures 1 to 3 and Figures 4 to 7 are identified by like reference symbols - although suffixes are used to identify some individual features in Figures 4 to 6. Referring to Figures 4 to 6, each of the motor arms (b) is pivotally attached to the airframe of the drone (y.1 ) to pivot generally in a plane that would be generally horizontal when the drone is in hovering normal flight. The pivotal attachment of each motor arm (b) is by attaching it on a pin (x) that extends from the airframe and that is received in an aperture at the attachment point (I) of each motor arm, so that a pivot axis is formed at the attachment point (I). This pivotal attachment of the motor arms (b) allows each of them to pivot relative to the airframe of the drone (y.1 ) from an operational position that it would occupy during normal operation of the drone (as shown in Figure 4), in a deflection direction. The deflection directions of each of the motor arms (b) are shown by arrows in Figure 4 and in each case, pivotal movement of the motor arm (b) results in movement of the motor (a) at the remote end of the motor arm, being aft, relative to the drone (y.1 ). The direction of forward travel of the drone (y.1 ) is identified by reference (k), in Figure 4. In other embodiments, motor arms b could be configured to pivot in more directions than those shown in the drawings.

The pivotal attachment of the motor arms (b) to the airframe of the drone (y.1 ) is preferably releasable, so each motor arm can quickly and easily be removed from its pin (x) and can be returned or replaced - which allows for quick repairs or modifications.

The two forward motor arms (b.1 and b.2) are attached to a first bias element in the form of an extension coil spring (c) that extends between them and that pulls them towards each other, forward of their pivot points (I), so that the spring (c) biases them to pivot opposite to the deflection direction, in a return direction, towards their operational positions.

Similarly, each of the two aft motor arms (b.3 and b.4) has a first bias element in the form of an extension coil spring (d.1 and d.2) that is fitted laterally on the airframe and pulls its associated motor arm forward, in a return direction, against the deflection direction. Each of the springs (c and d) could be replaced with a variety of other bias elements, such as elastomeric elements, pneumatically compressible elements, etc. and similarly, the pivotal attachment of each motor arm (b) to the airframe could be in a variety of ways, e.g. the end of each motor arm that is remote from the motor (a) could simply be received in a socket that is formed in the airframe.

Referring to Figure 4 in forward flight of the drone (y.1 ), if a motor (a), motor arm (b) or propeller (j) were to collide with an object, the arm would deflect and pivot backwards (in the deflection direction) about its pivot axis (I), decelerating against the tension of the spring (c), in the case of the forward arms, or one of the springs (d), in the case aft arms. Ideally the impact forces received by the motor arms (b) would largely be absorbed or dissipated in the deflection of these motor arms against the bias of the springs (c and d).

The drone (y.1 ) includes bumper elements in the form of elongate bumpers (h) at forward ends of compression rods (z) that are supported on the airframe and can move relative to the airframe. The compression rods (z) move relative to the airframe by sliding longitudinally in containment tubes (g) defined in the airframe and their range of sliding motion is limited by an arrester jacket (i) that is attached to each compression rod and that is held captive inside its associated containment tube (g). Each bumper (h) and its compression rod (z) can slide longitudinally from their operational positions (shown in Figures 4 to 6) in deflection directions. Second bias elements in the form of compression springs (e) are provided at the end of each compression rod (z) and bias its associated compression rod and bumper (h) to slide in a return direction, opposite to the deflection direction.

Various other configurations of bumper elements and second bias elements can be used, e.g. a bumper element can be a tab that is pivotally attached to the airframe and is pneumatically biased to push the airframe away from an impinging object. Referring to Figure 5, upper compression rods (Z.2 and Z.3) are positioned at angles most likely to protect the drone (y.1 ) from collisions based on the attitude the drone most commonly attains to achieve forward flight. The lowest compression rod (z.4) is configured as to protect a battery (B) of the drone (y.1 ). Referring to Figures 4 to 6, the compression rods (z) and bumpers (h) are preferably configured to receive impacts longitudinally, so that the impacts can be transferred to the springs (e) and are preferably absorbed or dissipated. To this end, the bumpers (h) also preferably protrude from the airframe - each protruding in its return direction - i.e. each protruding in the direction opposite to the direction in which it is expected to be deflected during impact.

Depending on the specific airframe design, the compression rods (z) and bumpers (h) at their ends, are configured to deflect the drone (y.1 ) away from an impinging object, to allow it to continue in flight, if the situation allows.

In the event of a glancing collision off the side of the drone (y.1 ), especially against one of the aft motor arms (b.3 or b.4), there is a possibility that the drone could continue in flight, as the motor arm would almost immediately be pulled back into its normal operating position by its spring (c or d) after impact, allowing for normal operation to resume.

In the case of a head-on, or near head-on collision, the forward motor arms (b.1 and b.2) would pivot aft (in the deflection direction) until one of the bumpers (h) came into contact with the object. Thereafter the connecting rod (z) and its connected absorption devices, in this example, the bumper (h) and spring (e) will either bring the drone (y.1 ) to a complete stop or deflect it off the object. Either way, a large part of the impact forces would be absorbed into the strongest part of the airframe and away from more fragile components, thus reducing the chance of damage. The arrester jackets (i) allow the compression rods (z) limited, longitudinal movement while preventing them from being ejected from the airframe after an impact. The arrested jackets (i) also allow for the compression rods (z) to be easily replaced if damaged.

Referring to Figures 5 and 6, a top part of the airframe is connected to a bottom part of the airframe by a hinge (q) and is held in an operating position (shown in Figure 5), against pivotal movement about the hinge (q), by a locking device such as a locking thumbscrew (v). The top part of the airframe acts as detent by holding the pivoting ends of each of the motor arms (b) in position on its pin (x). By removing the thumbscrew (v) the top part of the airframe can pivot upwards allowing quick access to inner components as well as allowing the motor arms (b) to be removed off their pins (x), as shown in Figure 6.

A recess (p) is defined in the bottom part of the airframe and is aligned with the centre of an internal flight controller (not shown). A balance board (o) is provided, which includes a rounded protruding ridge that is receivable in the recess (p). When the airframe is supported on the balance board (o) with its ridge in the recess (p), the airframe will tilt forward or aft, under gravity, depending on whether the centre of mass of the drone is forward or aft of the recess (p). Ideally, the centre of mass of the drone is aligned with the centre of the internal flight controller and the balance board (o) and recess (p) thus assists a user when making adjustments to the drone to ensure a proper mass balance.

A camera (r) is secured to camera mount (s) on the airframe by a releasable attachment such as hook-and-loop straps (u) (also known by the trade name "Velcro") and the camera mount is attached via a slide mechanism to the top part of the airframe. The slide mechanism allows linear forward and aft adjustment of the mount (s), which is held in place relative to the slide mechanism by a small thumbscrew.

The battery (B) is secured to the airframe via a battery slider mechanism (t) which also has limited, linear forward and aft adjustability with a thumbscrew. By adjusting the position of the two slide mechanism, to move the camera (r) and battery (B) forward and aft, in conjunction with the balance board (o), the centre of mass of the drone (y.1 ) can be set directly below the flight controller. This can make the drone (y.1 ) more stable when flying with various payloads of cameras, batteries etc.

Figure 7 shows the basic design of one of the arrester jackets (i), which clamps the compression rod (z) using a screw (m) and integrated threading. The arrester jackets (i) are positioned in easily accessible recesses within the airframe to allow limited linear movement of each arrester inside the bounds of its recess during longitudinal sliding of its compression rod (z) in its deflection direction while compressing the spring (e). The arrested jacket (i) also prevents the spring (e) from ejecting the compression rod (z) once impact pressure on the bumper (h) has dissipated. Ease of accessibility allows for the compression rods (z) to be replaced and adjusted quickly. Referring to Figure 8, a threaded post (w) protrudes through the hinged, top portion of the airframe and forms an attachment point for the locking thumbscrew (v). The central threaded post (w) originates from the bottom part of the airframe and extends up through the hinged top part of the airframe. The graduated disk around the base of the post (w) is part of the top part of the airframe and provides purchase for locking protrusions protruding from the base of the locking thumbscrew (v), described below.

Figures 9, 10, 1 1 and 12 show an example of a locking thumbscrew (v). The assembled thumbscrew (Figures. 1 1 & 12) screws onto the threaded post (w) (shown in Figure.8) with a female screw thread defined in a top mechanism (III). Compression springs (IV) press down on a circular mechanism (V) which has four angular tipped protrusions which penetrate through slots in a bottom mechanism (VII). The top (III) and bottom (VII) mechanisms contain the compression springs and circular protrusion mechanism (V) and are joined together by a set of screws (II). A release bar (I) fits over the top mechanism (III) and connects to the circular protrusion mechanism (V) by a different set of screws (VI). In use, the locking thumbscrew (v) operates as follows: The assembled thumbscrew (v) is placed onto a threaded post (w) and rotated to tighten it by conventional screw- threaded operation. When the thumbscrew (v) has travelled far enough down the post (w), the angled protrusions (V) come into contact with the graduated disk of the post (w) (shown in Figure 8). The angular ends of the protrusions (V) allow them to be pushed upwards against the spring (IV) by wedge action when the thumbscrew (v) is rotated to tighten, but to purchase or dig in when rotated in the opposite direction, thus arresting any 'unscrewing' motion due to vibrations caused by the motors. To unscrew the thumbscrew (v), the release bar (I) is pulled upwards, withdrawing the protrusions (V) and allowing the thumbscrew (v) to rotate.

In keeping with the use of compression rods (f) in the motor arms (b) and compression rods (z) on the airframe, the central core of the threaded post (w) can consist of a replaceable rod that extends all the way up through a central aperture in the release bar (I). Since this rod is rooted in the bottom part of the airframe it provides a solid central pillar to support surrounding structural elements.

The drone (y.1 ) shown in Figures 1 to 12 uses a system of rods (f and z), support structures and dissipation devices (c, d and e), integrated into the airframe, which deflect collision forces away from the vital components of the drone and into purpose built features where it can be safely dissipated, thus reducing the chance of damage to the drone and/or its components.

In the event that the airframe does suffer catastrophic damage, individual components can be quickly replaced. Additionally the rods (f and z) can be made up from a multitude of materials allowing a user to select rods suitable for specific circumstances.

The present invention mitigates the degree of damage a drone is likely to suffer in a collision and thus reduces the cost of repairs. When repairs are needed, they can typically be carried out quickly and with minimal tools due to the modular construction of the drone (y.1 ). The structure of the drone (y.1 ) is versatile in that various versions of the motor arm (b) can share a common pivot point, operational position and range of motion allowing them to be interchanged between airframes.

The hinged operation of the upper part of the airframe about its hinge (q) to act as common detent with a single securing element in the form of the thumbscrew (v) to secure all four motor arms (b), allows speedy access to internal components of the drone (y.1 ) as well as replacement of the motor arms.

The rods (f and z) and their associated connections provide substantial rigidity to the motor arms (b) and airframe, which reduces the need for additional structural components and allows a light weight construction of the drone (y.1 ) and which allows the rest of the motor arms and airframe to be made of lighter, cheaper materials. The rods (f and z) preferably have standardised sizes, which allows them to be replaced easily and to lock them in place easily.

The components of the drone (y.1 ) are preferably modular in design so that elements such as different shaped outer shells or camera mounts (s) can be interchanged between different airframes, allowing for multiple configurations. The modular construction also preferably allows for removal of non-essential components from the airframe when power to weight performance is the priority.

Referring to Figures 13 to 1 6, a second embodiment of a multi-rotor aircraft or drone according to the present invention is generally identified by reference (y.2). The drone (y.2) shares many features with that of the drone (y.1 ) shown in Figures 1 to 12 and only some of the most pertinent differences are mentioned below.

The drone (y.2) does not use a common spring to bias the two forward motor arms (b.1 and b.2) forward and does not use separate springs to bias the aft motor arms (b3 and b4) forward. Instead, the drone (y.2) uses a bias element in the form of an elastic tensile element, e.g. a rubber band (R), which is attached to forward protuberances (P) on each of the motor arms (b.2 and b.4) on the starboard side of the drone. The rubber band (R) simultaneously biases both the aft (b.4) and forward (b.2) arms forward. A similar bias element is used on the port side of the drone (y.2), but is not shown and other configurations of shared or individual bias elements can be used in other embodiments of the invention.

Each of the motor arms of the drone (y.2) comprises a support component (b) that is split between an upper support component (b.2i) and a bottom support component (b.2ii). Instead of three rods (f), each of the motor arms shown in Figures 13-16 includes only two rods. The use of only two rods (z) in each of the motor arms is partly to allow the motor (a) to be installed inside the support component (b) between the rods (z) - which protect it, with only the shaft and propeller (j) protruding above the support component.

The motor arm shown in Figure 16 also includes a base plate (C) and the motor is attached to the base plate, rather than to the support component (b). Different baseplate shapes are provided to allow for motors of various heights and screw configurations to be used on the motor arm. The base plate (C) can be attached to the support component (b) by screws, in clip-fashion, or any other suitable manner.

Another motivation for using only two rods (x) in the motor arm, is so that an electronic speed controller (ESC) of the drone (y.2) can be installed in a well-protected space within the arm while still benefiting from the cooling effect of being under the propeller wash. (ESCs handle the massive fluctuations of power going to the motor so they are prone to overheating and burning out.)

Claims

An aircraft (y.1 ) comprising:

an airframe;

a plurality of arms (b) that are each attachable to the airframe; and at least one rotor (j) attached to each of said arms (b) at a position remote from the airframe;

characterised in that at least one of said arms (b) is pivotally attachable to the airframe, to be pivotable relative to the airframe, to pivot from an operational position of the arm (b) in a deflection direction of the arm (b), said arm (b) having a first bias element (c,d, R) that is configured to bias the arm (b) to pivot in a return direction that is opposite to its deflection direction.

An aircraft (y.1 ) according to claim 1 , which has a front and a rear and is configured to travel predominantly forward, characterised in that the arm (b) and first bias element (c,d,R) are configured so that the arm's (b) deflection direction is rearward in relation to the airframe.

An aircraft (y.1 ) according to claim 1 or claim 2, characterised in that at least some of the arms (b) are releasably attachable to the airframe.

An aircraft (y.1 ) according to claim 3, characterised in that a plurality of the releasably attachable arms (b) are held in attachment to the airframe, by a single detent.

An aircraft (y.1 ) according to any one of the preceding claims, characterised in that at least one said first bias elements (c,R) is configured to bias a plurality of the arms (b) to pivot in the return directions of each of the arms (b).

6. An aircraft (y.1 ) according to any one of the preceding claims, characterised in that said aircraft (y.1 ) includes at least one bumper element (h) that is movably supported on the airframe, to move relative to the airframe from an operational position of the bumper element (h) in a deflection direction of the bumper element (h), said aircraft (y.1 ) further including at least one second bias element

(e) that is configured to bias the bumper element (h) to move in a return direction that is opposite to its deflection direction.

7. An aircraft (y.1 ) according to claim 6, characterised in that said bumper element (h) has an elongate shape and is configured to slide longitudinally relative to the airframe, in its deflection direction and return direction.

8. An aircraft (y.1 ) according to claim 7, characterised in that said bumper element (h) protrudes from the airframe in its return direction.

9. An aircraft (y.1 ) according to any one of claims 6 to 8, characterised in that the second bias element (e) is configured to dissipate impact energy from movement of the bumper element (h) in its deflection direction.

10. An aircraft (y.1 ) according to any one of the preceding claims, characterised in that at least one of the arms (b) includes at least one elongate structural element

(f) that is removably attached to said arm (b).

1 1 . An aircraft (y.1 ) according to claim 10, characterised in that said elongate structural element (f) is a rigid rod.