An unmanned aerial vehicle

Abstract

The present invention relates to an unmanned aerial vehicle comprising, a vehicle body; a plurality of rotors, each rotor having a rotational axis; and pivotal rotor couplings configured to facilitate pivotal adjustment of an orientation of the rotational axis of a respective rotor around a respective pivot axis. The vehicle has a UAV configuration in which the rotational axis of each rotor has an upright orientation, and a USV configuration in which the rotational axis of at least some rotors has a non-upright orientation. The vehicle is configured to be switched between the UAV configuration and the USV configuration via the pivotal rotor couplings. The plurality of rotors is located above a water surface when the vehicle floats on water in the USV configuration. At least some rotors have different horizontal orientations in the USV configuration. The invention further relates to a method of operating such a vehicle.

Description

[0001] AN UNMANNED AERIAL VEHICLE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to an unmanned aerial vehicle and a method for operating such an unmanned aerial vehicle, in particular in the context of operation near or at a water surface, for example to perform measurements.

[0004] BACKGROUND OF THE INVENTION

[0005] Unmanned aerial vehicles have numerous applications including facilitation and performance of various measurements.

[0006] During operation of an unmanned aerial vehicle, it can be necessary to operate the unmanned aerial vehicle near a water surface, such as the surface of a lake, the ocean, or a river. Such operation may for example be required to perform specific measurements, for example measurements requiring water contact, such as hydrology or bathymetry measurements.

[0007] Here, hydrology is the study of movement, distribution, and management of water on Earth, and bathymetry is the study of underwater depth of ocean floors, lake floors, and river floors.

[0008] Generally, performance of such operation and such measurements suffer from a number of problems.

[0009] A sensor may need to be in contact with or near water to perform a given measurement. For a conventional unmanned aerial vehicle, this can be difficult to stably accomplish in practice.

[0010] Furthermore, some water bodies such as smaller rivers may offer very limited space and manoeuvrability, for example due to vegetation or other obstacles in or near the water. This can severely constraint size and operation of unmanned aerial vehicles.

[0011] In addition, any operation of an unmanned aerial vehicle will generally be subjected to wind and / or water flow. This can prohibit accurate positioning or maintaining a specific desired position. SUMMARY OF THE INVENTION

[0012] On the above background, it is an object of preferred embodiments of the present disclosure to provide an unmanned aerial vehicle which generally has improved manoeuvrability at water surfaces, for example in the context of performing measurements near or at water surfaces. More specifically, it is an object of preferred embodiments to provide improved manoeuvrability under practical circumstances, where it can be necessary to accurately position and reposition the unmanned aerial vehicle when subject to wind, water flow, and obstacles such as vegetation in or near water.

[0013] A first aspect of the present disclosure relates to an unmanned aerial vehicle comprising : a vehicle body configured to permit the unmanned aerial vehicle to float on water; a plurality of rotors, wherein each rotor of the plurality of rotors has a rotational axis; and one or more pivotal rotor couplings, each of the respective pivotal rotor couplings configured to facilitate pivotal adjustment of an orientation of the rotational axis of a respective rotor of the plurality of rotors around a respective pivot axis transverse to the rotational axis of the respective rotor of the plurality of rotors, wherein the unmanned aerial vehicle has a UAV configuration in which the rotational axis of each rotor of the plurality of rotors has an upright orientation permitting the plurality of rotors to generate a vertical thrust allowing the unmanned aerial vehicle to fly in the UAV configuration, wherein the unmanned aerial vehicle has a USV configuration in which the rotational axis of at least some rotors of the plurality of rotors has a non-upright orientation permitting the plurality of rotors to generate a horizontal thrust while the unmanned aerial vehicle floats on water via the vehicle body in the USV configuration, wherein the unmanned aerial vehicle is configured to be switched between the UAV configuration and the USV configuration by pivotal adjustment of at least some rotors of the plurality of rotors via at least some of the pivotal rotor couplings, wherein the plurality of rotors is positioned on the unmanned aerial vehicle such that the plurality of rotors is located above a water surface when the unmanned aerial vehicle floats on water in the USV configuration, wherein at least some rotors of the plurality of rotors have different horizontal orientations in the USV configuration.

[0014] The unmanned aerial vehicle according to the present disclosure generally provides improved manoeuvrability at water surface, for example in the context of performing measurements near or at water surfaces. Upon landing on a water surface in the UAV configuration, the unmanned aerial vehicle can be switched from the UAV configuration to the USV configuration by pivotal adjustment of at least some rotors of the plurality of rotors. In the USV configuration, the unmanned aerial vehicle is capable of manoeuvring on the water surface by horizontal thrust of the rotors. By positioning the rotors above the water surface, vegetation, or other obstacles in the water itself may be avoided.

[0015] Since some of the rotors have different horizontal orientations in the USV configuration, the unmanned aerial vehicle can be manoeuvred accurately, for example to reposition the vehicle or to maintain the vehicle at a specific desired position while subject to wind and water flow. In contrast, in case the rotors had the same horizontal orientation, it would be difficult to reposition the vehicle or to maintain the vehicle at a specific desired position. For example, if such an unmanned aerial vehicle and its rotors are oriented to counteract water current, it is not possible to counteract a gust of wind, or to reposition the vehicle transversely without reorienting the entire vehicle. With rotors having different horizontal orientations, water flow / current, wind, and repositioning can be addressed accurately, dynamically, and simultaneously.

[0016] Generally, the term of an unmanned aerial vehicle can be abbreviated as UAV and the term of an unmanned surface vehicle can be abbreviated as USV. Hence the terminology of a UAV configuration and a USV configuration. An unmanned surface vehicle generally refers to a vehicle that operates on the surface of water without a crew.

[0017] The UAV configuration may also be referred to as a first (vehicle) configuration, and the USV configuration may also be referred to as a second (vehicle) configuration.

[0018] When switching between the UAV configuration and the USV configuration, the pivotal adjustment of the pivotal rotor couplings may, for example, be facilitated by one or more rotor actuators, or by motor / rotor torque in combination with an offset between a rotational axis of a rotor and a pivot axis of the pivotal rotor couplings. In principle, the pivotal adjustment may also be performed manually, although preferably, it is performed automatically by means of rotor actuators, motor / rotor torque, or some combination thereof.

[0019] Each of the pivotal rotor couplings may be associated with a USV pivotal engagement mechanism and / or a UAV pivotal engagement mechanism, which releasably locks an associated rotor and its rotational axis at the non-upright orientation of the USV configuration and / or the upright orientation of the UAV configuration, respectively. Such engagement mechanisms may be based on a tongue and a groove loosely fitting a rotor pivotally to, e.g., a mast structure connecting the rotor to the rest of the unmanned aerial vehicle.

[0020] Preferably, in the UAV configuration, the unmanned aerial vehicle has six degrees of freedom. That is, the unmanned aerial vehicle can be translated in three perpendicular axes and reoriented by rotation around these three axes. Motion along the three perpendicular axes is generally referred to as motion forward / backward (surge), up / down (heave), and left / right (sway), and reorientation around these three axes are generally referred to as yaw (normal axis), pitch (transverse axis), and roll (longitudinal axis).

[0021] Generally, in the UAV configuration, surge and sway motion may require a reorientation of the unmanned aerial vehicle. For example, a surge may require a pitch. Thus, forward movement may be associated with pitch. Similarly, sideways movement may be associated with roll.

[0022] In the USV configuration, the different horizontal orientations of the rotors provide thrust in different directions of a horizontal plane and the unmanned aerial vehicle obtains at least two translational degrees of freedom, corresponding to motion in these two different directions, inter alia in a forward / backward direction and in a left / right direction. In contrast, a vehicle in which the rotors have just one horizontal orientation, will typically only have a single translational degree of freedom corresponding a single direction in a horizontal plane provided by the unitary horizontal orientation of all rotors. Further, in the USV configuration, the unmanned aerial vehicle further preferably has a least one orientational degree of freedom corresponding to yaw. In principle, some degree of pitch and roll may also be possible, but such reorientation will generally be counteracted by buoyancy.

[0023] Preferably the different horizontal orientations of at least some rotors of the plurality of rotors in the USV configuration differ by an angle of at least 30 degrees, for example at least 45 degrees, for example at least 60 degrees, for example at least 75 degrees, such as 90 degrees. This angle is measured between the rotational axes of the rotors. A further advantage of providing different horizontal orientations in the USV configuration is that this may enable simplified control instructions in relation to operation of the unmanned aerial vehicle and in particular in relation to operation of the unmanned aerial vehicle in the USV configuration. This concept will be explained further below.

[0024] In the context of the present disclosure, control instructions may be understood as the set of signals which determines which rotors accelerate or operate to perform a given manoeuvre, such as surge, heave, sway, yaw, pitch, and roll. Such control instructions may thereby comprise respective acceleration instructions to respective rotors.

[0025] As an example, simultaneous and similar acceleration of all rotors may provide a heave motion of the unmanned aerial vehicle in the UAV configuration. Such operation may be facilitated by heave control instructions. As another example, considering an unmanned aerial vehicle with four rotors arranged in a quadcopter configuration, simultaneous acceleration of two diagonally opposite rotors (and, optionally, simultaneous deceleration of the two other rotors) may provide a yaw reorientation of the unmanned aerial vehicle in the UAV configuration.

[0026] Generally, control instructions may be programmed onto or facilitated by a programmable logic circuit and / or stored in a digital storage of the unmanned aerial vehicle. The programmable logic circuit may then be configured to adjust currents to the relevant motors upon execution of control instructions.

[0027] In examples according to the present disclosure, the unmanned aerial vehicle comprises one or more pivotal rotor actuators, each configured to pivotally adjust the orientation of the rotational axis of a respective rotor of the plurality of rotors via the pivotal rotor couplings.

[0028] Such pivotal actuators may ensure that the unmanned aerial vehicle can be reliably switched between the UAV configuration and the USV configuration.

[0029] As an example, each rotor may be accompanied by a pivotal actuator. Such a pivotal actuator can optionally be positioned to pivot together with the rotor during pivotal adjustment of the rotor. A pivotal actuator can also be fixed relative to the vehicle body, for example in a mast structure next to a rotor. A single pivotal actuator may also be arranged to pivotally adjust several rotors, for example to pivotally adjust all rotors of the plurality of rotors. For example, the actuator may be located in the vehicle body from where at can pivotally adjust several rotors by means of one or more belts mechanically the pivotal actuator with the rotors. In practice, a pivotal rotor actuator may be implemented as, e.g., an electric motor, such as an electromechanical actuator, a linear motor, or a rotary motor.

[0030] In examples according to the present disclosure, the respective rotational axis of a respective rotor of the plurality of rotors has an offset to the respective pivot axis of the respective pivotal rotor coupling coupled to that respective rotor.

[0031] In examples according to the present disclosure, the offset between the rotational axis and the pivot axis is arranged such that when a respective rotor of the plurality of rotors generates a thrust, this thrust provides a torque around the pivot axis associated with this respective rotor to support orientation of this respective rotor from the non-upright orientation to the upright orientation.

[0032] By positioning the rotors such that the rotational axis is offset to the pivot axis, rotation of the rotor to generate a thrust will simultaneously generate a torque around the pivot axis. This in turn can be used to support or even facilitate the switch between the UAV configuration and the USV configuration. For example, a thrust of a rotor below a certain threshold is used during operation in the UAV configuration and / or the USV configuration, while a thrust above this threshold will initiate a switch between the UAV configuration and the USV configuration. Such a threshold may for example be linked to the mechanical tightness of an engagement mechanism releasably locking the rotor at the non-upright orientation of the USV configuration and / or the upright orientation of the UAV configuration.

[0033] In case the rotor is configured to rotate in both directions, a switch between the UAV configuration and the USV configuration can be performed both ways.

[0034] Although the offset between pivot axis and rotational axis can in principle be implemented in any way, the rotational axis is preferably arranged such that a thrust of the rotor provides a torque which support orientation of this rotor from the non-upright orientation towards the upright orientation (and not the other way around). In case of a rotor configured to rotate in both directions, the relevant thrust to consider here is the thrust used to allow the unmanned aerial vehicle to fly in the UAV configuration.

[0035] By such an implementation, the thrust which is generated during operation in the UAV configuration may ensure that the rotors are properly upheld in the upright orientation during operation and may ensure that the pivotal adjustment when switching from USV configuration to UAV configuration is reinforced. In examples according to the present disclosure, at least some of the rotors of the plurality of rotors are oriented inwardly when the unmanned aerial vehicle is in the USV configuration such that a centre of mass of each of these respective rotors is located closer to a central upright axis of the unmanned aerial vehicle in the USV configuration than in the UAV configuration.

[0036] By orienting the rotors inwardly when the unmanned aerial vehicle is in the USV configuration, collisions with or interference from surrounding obstacles, such as vegetation, can be reduced in the USV configuration.

[0037] In examples according to the present disclosure, the rotational axes of the plurality of rotors are located in different planes when the unmanned aerial vehicle is in the USV configuration.

[0038] In examples according to the present disclosure, at least some of the rotors of the plurality of rotors have an orientation below a horizontal orientation when the unmanned aerial vehicle is in the USV configuration such that this orientation of these at least some of the rotors has a downwards vertical component.

[0039] In examples according to the present disclosure, each rotor of the plurality of rotors has an orientation below a horizontal orientation when the unmanned vehicle is in the USV configuration such that this orientation of each rotor of the plurality of rotors has a downwards vertical component.

[0040] In examples according to the present disclosure, in the USV configuration, the horizontal component is greater than the vertical component for at least some rotors of the plurality of rotors, preferably for all rotors of the plurality of rotors.

[0041] In case all rotational axes are located in the same plane in the USV configuration, the unmanned aerial vehicle may suffer from unwanted tilting during operation. This can be a result of the torque relative to the centre of mass that each rotor generates.

[0042] By providing rotational axes located in different planes, the torque relative to the centre of mass is reduced, and thereby unwanted tilting may also be reduced.

[0043] Preferably these different planes may be provided such that the angle between the rotational axis to the centre of mass of the unmanned aerial vehicle is reduced relatively to a rotational axis being located in an absolutely horizontal plane. This corresponds to providing the rotational axis or the rotor with a downwards vertical component. Yet, relatively, the horizontal component should preferably be greater than the vertical component to ensure that a horizontal thrust can still efficiently be generated.

[0044] In context of the present disclosure, a horizontal orientation may be defined by the water surface when the unmanned aerial vehicle is floating without thrust, water current, and wind.

[0045] In examples according to the present disclosure, the unmanned aerial vehicle comprises first pitch control instructions associated with forward movement of the unmanned aerial vehicle in the UAV configuration, wherein the unmanned aerial vehicle comprises second pitch control instructions associated with forward movement of the unmanned aerial vehicle in the USV configuration, wherein the first pitch control instructions and the second pitch control instructions both comprise acceleration instructions associated with relative acceleration of the same set of rotors of the plurality of rotors.

[0046] In examples according to the present disclosure, the unmanned aerial vehicle comprises first yaw control instructions associated with rotation of the unmanned aerial vehicle in the UAV configuration, wherein the unmanned aerial vehicle comprises second yaw control instructions associated with rotation of the unmanned aerial vehicle in the USV configuration, wherein the first yaw control instructions and the second yaw control instructions both comprise acceleration instructions associated with relative acceleration of the same set of rotors of the plurality of rotors.

[0047] In addition, each of the first yaw control instructions and the second yaw control instructions may comprise acceleration instructions associated with relative acceleration of different sets of rotors of the plurality of rotors.

[0048] For example, considering an unmanned aerial vehicle having six rotors, the first set of control instructions may comprise acceleration instructions associated with relative acceleration of three rotors, and the second set of control instructions may comprise acceleration instructions associated with relative acceleration of two rotors, wherein the first yaw control instructions and the second yaw control instructions both comprise acceleration instructions associated with relative acceleration of just one rotor of the plurality of rotors. Thereby, the first set of control instructions comprise acceleration instructions associated with relative acceleration of two rotors which are not accelerated by the second set of control instructions, and the second set of control instructions comprise acceleration instructions associated with relative acceleration of one rotor which is not accelerated by the first set of control instructions.

[0049] By providing such control instructions, yawing may efficiently be implemented to permit simplified control of the unmanned aerial vehicle, for example to ensure that the vehicle may efficiently yaw in both the UAV configuration and the USV configuration, preferably substantially independently from translation of the unmanned aerial vehicle.

[0050] In examples according to the present disclosure, the unmanned aerial vehicle comprises first roll control instructions associated with sideways movement of the unmanned aerial vehicle in the UAV configuration, wherein the unmanned aerial vehicle comprises second roll control instructions associated with sideways movement of the unmanned aerial vehicle in the USV configuration, wherein the first roll control instructions and the second roll control instructions both comprise acceleration instructions associated with relative acceleration of the same set of rotors of the plurality of rotors.

[0051] In the context of the present disclosure, a set of rotors can be one rotor, or it can be more rotors.

[0052] Generally, the provision of separate control instructions in the UAV configuration and in the USV configuration which comprise acceleration instructions directed at the same set of rotors can simplify programming and operation of the unmanned aerial vehicle.

[0053] In examples according to the present disclosure, the unmanned aerial vehicle comprises a sensor arranged at a lower surface of the vehicle body such that the sensor is below a water surface when the unmanned aerial vehicle floats on water in the USV configuration.

[0054] Such a sensor may be configured to perform measurements in relation to hydrology or bathymetry. It may for example be a water depth sensor, such as an ultrasonic water level sensor. In examples according to the present disclosure, the plurality of rotors is at least four rotors, for example at least six rotors.

[0055] An advantage of having six rotors instead of four is that this may simplify yaw reorientation in the USV configuration.

[0056] In contrast, an unmanned aerial vehicle with four rotors arranged in a quadcopter configuration, in which the four rotors pivot inwardly towards the centre of the unmanned aerial vehicle when switching to the USV configuration would be challenging to yaw in the USV configuration.

[0057] By having six rotors, the orientation of the rotational axis of some of the rotors can be naturally offset from a central vertical axis of the unmanned aerial vehicle. Thereby, these rotors can provide a torque around this central axis, which in turn can yaw the unmanned aerial vehicle in the USV configuration.

[0058] In examples according to the present disclosure, the vehicle body comprises a watercraft hull associated with a hull orientation indicative of hydrodynamical drag, wherein the watercraft hull has a first drag coefficient along the hull orientation, and the watercraft hull has a second drag coefficient transverse to the hull orientation, each of the first drag coefficient and the second drag coefficient evaluated based on water flow when the unmanned aerial vehicle floats on water in the USV configuration, wherein the second drag coefficient is greater than the first drag coefficient.

[0059] For example, the second drag coefficient can be greater than the first drag coefficient by a factor of 1.2, for example a factor of 1.5, such as a factor of 1.8.

[0060] Alternatively, instead of a watercraft hull, the vehicle body may comprise one or more floats, such as two floats.

[0061] By having separate drag coefficients along different directions of the unmanned aerial vehicle, the unmanned aerial vehicle may autonomously orient itself along any current in the water upon which it floats. With such autonomous orientation relative to water current, manoeuvring in the water can be simplified, since forward / backward motion and left / right motion can be separately associated with motion in the direction of the current and motion transverse to said current.

[0062] In examples according to the present disclosure, the vehicle body is configured to permit the unmanned aerial vehicle to float on water via buoyancy. In examples according to the present disclosure, the unmanned aerial vehicle may have a greater number of rotors oriented along the hull orientation than transverse to the hull orientation in the USV configuration, for example four rotors oriented along the hull orientation and two rotors oriented transverse to the hull orientation.

[0063] Since the unmanned aerial vehicle may orient itself along a current when subject to the current, having a greater number of rotors oriented along the hull orientation is advantageous. Generally, a greater thrust may be required to counteract a water current, e.g., to maintain a specific position, than required to transverse the current.

[0064] In examples according to the present disclosure, the unmanned aerial vehicle may have a first set of USV control instructions and a second set of USV control instructions, wherein the first set of USV control instructions is directed at operation under conditions with substantial water flow, such as in a river, and the second set of USV control instructions is directed at operation under conditions with no substantial water flow, such as in a lake in calm weather conditions. The two sets of control instructions enable the unmanned aerial vehicle to perform optimal in different situations and may potentially reduce the power consumption. Particularly, the second set of control instructions may utilize the rotors less aggressively and thereby improve the expected operation time without recharging.

[0065] A further, third set of USV control instructions may correspond to a fast movement of the vehicle or increased thrust of one or more of the rotors of the vehicle, for example in comparison with the first set of USV control instructions and / or the second set of USV control instructions. To obtain a higher speed on water, one or more of the rotors may be oriented to provide an increased vertical thrust and thereby reduce a submergence level of the watercraft hull. This condition can be activated manually by a human operator, or automatically. For automatic activation, the vehicle may comprise a sensor determining a the submergence level or depression of the watercraft hull into water or detecting that the speed is insufficient for keeping the planned route or a steady position. This could be due to strong currents.

[0066] In some embodiments, the third set of USV control instructions utilize a subset of the rotors have an non-upright orientation for providing primarily a horizontal thrust and thus the horizontal speed of the UAV, and another subset of the rotors have an upright orientation for providing primarily a vertical thrust and thereby lift the watercraft hull.

[0067] Such a third set of USV control instructions may be compatible with the vehicle in the USV configuration, or it may be associated with an auxiliary USV configuration separate from the (main) USV configuration. The UAV may comprise hydrofoils arranged to provide a lift out of water and prevent diving of the watercraft hull. Such hydrofoils can be arranged just above a waterline when the UAV moves at slow speed such that the hydrofoils contact water only at high speed when the hull is sucked further into the water due to the speed. Accordingly, the hydrofoils works only when necessary to prevent diving. Alternatively, the hydrofoil can be arranged below the waterline or water surface when the vehicle floats on water.

[0068] In examples according to the present disclosure, the watercraft hull has a deck which is shaped to provide an opening for air flow along the rotational axis of each rotor of the plurality of rotors when the unmanned aerial vehicle is in the UAV configuration.

[0069] In other words, the watercraft hull may have a deck which is shaped not to block air flow from the rotors in the UAV. The opening for air may be defined by straight air passages, e.g., holes extending vertically through the hull and thereby allow an airflow from the rotors from a point above the hull to a point below the hull. The holes may particularly have the shape as tunnels, e.g. having a circular cross section.

[0070] Generally, a watercraft hull can obstruct air flow generated by the rotors, thereby reducing the actual thrust generated upon rotation of the rotors in the UAV configuration.

[0071] Such a thrust reduction may be reduced by shaping the deck of the hull to provide an opening for air flow along the rotational axis of each of the rotors.

[0072] In examples according to the present disclosure, the unmanned aerial vehicle comprises a plurality of mast structures, wherein each mast structure of the plurality of mast structures has an upright orientation and comprises a first end and a second end distal relative to the first end, wherein the first end connects to the vehicle body, and the second end is connected to a respective rotor of the plurality of rotors, for example such that the plurality of rotors is positioned on the unmanned aerial vehicle such that the plurality of rotors is located above a water surface when the unmanned aerial vehicle floats on water in the USV configuration.

[0073] In examples according to the present disclosure, each rotor of the plurality of rotors is positioned above a floatation height relative to a water surface when the unmanned aerial vehicle floats on water in the USV configuration, wherein the floatation height is at least a diameter of the rotors.

[0074] Thereby, preferably, the ratio of floatation height to diameter of the rotors is at least 1.0, for example at least 1.2, for example at least 1.4, such as 1.6. In examples according to the present disclosure, the unmanned aerial vehicle defines a longitudinal centre line and a transverse centre line, wherein at least some of the rotors are displaced relative to both the longitudinal centre line and the transverse centre line.

[0075] Such an arrangement of the rotors relative to centre lines may generally improve manoeuvrability. For example, it may enable or improve yaw reorientation when the unmanned aerial vehicle is in the USV configuration. Further, it may enable or improve forward / backward motion and left / right motion in the USV configuration.

[0076] A second aspect of the present disclosure relates to method of operating an unmanned aerial vehicle according to the first aspect, the method comprising the steps of: operating the unmanned aerial vehicle in the UAV configuration to position the unmanned aerial vehicle over a water surface; landing the unmanned aerial vehicle on the water surface such that the unmanned aerial vehicle floats on the water surface; switching the unmanned aerial vehicle from the UAV configuration to the USV configuration by pivotal adjustment of at least some rotors of the plurality of rotors via at least some of the pivotal rotor couplings; and operating the unmanned aerial vehicle in the USV configuration on the water surface.

[0077] Generally, methods according to the present disclosure may be carried out via manual remote control of the unmanned aerial vehicle, by fully autonomous operation of the unmanned aerial vehicle, or by some combination thereof.

[0078] Remote control may, for example, be performed via a UAV remote controller. Such UAV remote controllers are generally well known. However, UAV remote controllers in the context of the present disclosure may further comprise a toggling means such as a mechanical or digital switch for controlling the switching between the UAV configuration and the USV configuration. A UAV remote controller can further be used to control the unmanned aerial vehicle in the USV configuration. In particular, one or more control instructions for various movement patterns can be at least partially reused in both the UAV configuration and the USV configuration. Accordingly, control of the vehicle in the USV configuration may be implemented similarly on a UAV remote controller as the control of the vehicle in the UAV configuration. Autonomous operation may, for example, be performed by manually pre-programming a trajectory of the unmanned aerial vehicle (including switches between the UAV configuration and the USV configuration), and / or performed via a positioning system of the unmanned aerial vehicle, upon which a trajectory is automatically generated, for example to perform a bathymetry measurement across a body of water such as a river. Relevant positioning systems include satellite navigation systems (such as the Global Positioning System), camera-based vision systems, lidar systems, and combinations thereof.

[0079] To obtain high accuracy in smaller bodies of water, the positioning system may be based on measurements of seaside objects, such as plantation, rocks, man-made structures, etc. This may facilitate operation and navigation via a Simultaneous localization and mapping (SLAM) algorithm.

[0080] In examples according to the present disclosure, the unmanned aerial vehicle comprises a sensor positioned below the water surface when the unmanned aerial vehicle floats on the water surface, wherein the method comprises a step of performing at least one measurement below the water surface using the sensor.

[0081] In examples according to the present disclosure, the at least one measurement is at least one depth measurement.

[0082] In examples according to the present disclosure, the step of performing at least one measurement is a step of performing a series of measurements, wherein the unmanned aerial vehicle is repositioned via horizontal thrust of at least one rotor of the plurality of rotors while in the USV configuration between each measurement of the series of measurements.

[0083] By repositioning via horizontal thrust, in contrast to repositioning while in the UAV configuration, a series of measurements can be performed far more efficiently.

[0084] The series of measurement and / or the repositioning of the unmanned aerial vehicle between each measurement of the series of measurements may optionally be based on water flow and / or a positioning system as described above.

[0085] In examples according to the present disclosure, the series of measurements is performed across a body of water to provide a bathymetry measurement of the body of water, for example across a water river to provide a bathymetry measurement of the water river, for example a bathymetry measurement of the water river transverse to a flow direction of the water river. The aspects disclosed herein are particularly well-suited for such use.

[0086] In examples according to the present disclosure, the respective rotational axis of a respective rotor of the plurality of rotors has an offset to the respective pivot axis of the respective pivotal rotor coupling coupled to that respective rotor such that a thrust of a respective rotor of the plurality of rotors provides a torque around the pivot axis due to the offset to thereby support orientation of this respective rotor from the non-upright orientation towards the upright orientation.

[0087] BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Embodiments of the invention will now be further described by reference to the accompanying drawings, in which:

[0089] Fig. 1 illustrates an unmanned aerial vehicle in the UAV configuration according to the present disclosure,

[0090] Fig. 2 illustrates an unmanned aerial vehicle in the USV configuration according to the present disclosure,

[0091] Figs. 3a-b illustrate pivotal adjustment of a respective rotor between an upright position and a non-upright position according to the present disclosure,

[0092] Fig. 4 illustrates a top-view indicating rotational axes of an unmanned aerial vehicle in the USV configuration according to the present disclosure,

[0093] Fig. 5 schematically illustrates a method of operating an unmanned aerial vehicle to perform a series of measurements below a water surface,

[0094] Fig. 6 illustrates a top-view indicating inward orientation of a rotor of an unmanned aerial vehicle in the USV configuration according to the present disclosure, and

[0095] Fig. 7 illustrates two rotors providing thrust in two different directions in a horizontal plane. DETAILED DESCRIPTION

[0096] Fig. 1 illustrates an unmanned aerial vehicle 1 in the UAV configuration 7 according to the present disclosure.

[0097] The unmanned aerial vehicle 1 comprises a vehicle body 2 in the form of a watercraft hull configured to permit to unmanned aerial vehicle to float on water via buoyancy. Generally, like with many conventional watercraft vehicles, the watercraft hull is substantially filled with air or any other buoyancy-providing medium to thereby promote floating on the water.

[0098] Further, the unmanned aerial vehicle comprises six mast structures 10 disposed around the periphery of the vehicle body 2. Each mast structure 10 has an upright orientation and comprises a first end and a second end distal relative to the first end, the first end connecting to the vehicle body 2 and the second end connecting to a respective rotor 3. Thereby, the unmanned aerial vehicle 1 comprises six rotors 3.

[0099] Each rotor 3 is connected to a respective mast structure 10, and thereby to the vehicle body 2, via a respective pivotal rotor coupling 5 having a respective pivot axis. Each pivotal rotor coupling 5 thereby facilitates pivotal adjustment of an orientation of a respective rotor 3 around the respective pivot axis. This pivot axis has a transverse orientation relative to a respective rotational axis of the respective rotor 3. Here, the rotational axis is the axis around which the rotor 3 rotates to generate a thrust during operation of the unmanned aerial vehicle 1.

[0100] In the present illustration, the plurality of rotors 3 and their rotational axes have an upright orientation. This permits the rotors to generate a vertical thrust, which allows operation of the unmanned aerial vehicle 1 in the UAV configuration 7 to fly. While the unmanned aerial vehicle 1 is in this configuration, it can be operated as any other conventional unmanned aerial vehicle having six rotors, commonly referred to as a hexacopter configuration. Similarly, unmanned aerial vehicles according to the present disclosure having another number of rotors, such as three, four, or eight rotors, can also be operated by conventional methods while in the UAV configuration.

[0101] The unmanned aerial vehicle 1 further comprises a centrally located post structure 11 which can host, e.g., one or more antennas, for example to allow remote control and / or measurements. Fig. 2 illustrates an unmanned aerial vehicle 1 in the USV configuration 8 according to the present disclosure. The vehicle 1 is the same is the one illustrated in Fig. 1, but in a different configuration.

[0102] The unmanned aerial vehicle 1 is configured to be switched between the UAV configuration 7 as illustrated in Fig. 1 and the USV configuration 8 as illustrated in Fig. 2 by pivotal adjustment of the rotors 3 around their respective pivot axes 6 of the respective pivotal rotor couplings 5. In this example, each pivotal rotor coupling 5 comprises a pivotal rotor actuator to adjust the orientation of the rotor 3 associated therewith. The pivotal rotor actuator is positioned together with the motor of each rotor 3, such that the pivotal rotor actuator pivots together with the rotor 3 when switching between the UAV configuration 7 and the USV configuration 8. Thereby, the pivotal rotor actuator can be placed in the vicinity of the rotor

[0103] 3 which simplifies the construction, while minimally compromising air flow of the rotor 3 in one or both configurations 7, 8.

[0104] In the USV configuration 8 illustrated in Fig. 2, each of the rotors 3 and their respective rotational axes has a non-upright orientation permitting the rotors 3 to generate a horizontal thrust. Thus, when the unmanned aerial vehicle 1 floats on water, this horizontal thrust can be used to accurately steer and position the vehicle 1. In particular, the rotors and their respective rotational axes have different horizontal orientations, which grants the unmanned aerial vehicle 1 in the USV configuration 8 with thrust in different horizontal directions. Particularly with three simultaneous degrees of motional freedom including two simultaneous translational degrees of freedom and a rotational degree of freedom (yaw) on the water surface. In particular, these degrees of freedom are independent of each other. The thrust in different horizontal directions corresponds to the horizontal component of the thrust vector from rotors being oriented in different directions with respect to the horizontal component of the rotational axes.

[0105] Figs. 3a-b illustrate pivotal adjustment of a respective rotor 3 between an upright position and a non-upright position according to the present disclosure. Both Figures provides a sideview of a rotor 3 and the associated mast structure 10. In Fig. 3a, the rotor 3 and its rotational axis 4 has an upright orientation, corresponding to the UAV configuration of the unmanned aerial vehicle illustrated in Fig. 1, and in Fig. 3b, the rotor 3 and its rotational axis

[0106] 4 has a non-upright orientation, corresponding to the USV configuration of the unmanned aerial vehicle illustrated in Fig. 2.

[0107] In both Fig. 3a and Fig. 3b, a pivot axis 6 is indicated. In these figures, the pivot axis has an orientation perpendicular to the plane of the drawing. In comparison, the rotational axis 4 of the rotor, indicated by an arrow, has an orientation parallel to the plane of the drawing in both figures.

[0108] The pivot axis 6 is the axis around which the rotor 3 pivots to switch the unmanned aerial vehicle between the UAV configuration and the USV configuration. This is also illustrated in Figs. 3a and 3b, in which it is apparent that the rotor has pivoted around the pivot axis between the two figures.

[0109] The figures also illustrate an offset 9 between the rotational axis 4 and the pivot axis 6. A dashed line parallel with the rotational axis 4 and extending from the pivot axis 6 has been drawn so as to more clearly illustrate this offset 9.

[0110] In practice, a pivot axis 6 which has an offset 9 relative to the rotational axis 4 can ensure that thrust generated by the rotor can be used to support a specific orientation of the rotor and its rotational axis 4.

[0111] According to the present example, thrust generated by the rotor 3 will generate a torque at the pivot axis 6, which in turn will support orientation of the rotor 3 towards the upright orientation illustrated in Fig. 3a.

[0112] Fig. 3b further illustrates that the rotational axis 4 of the rotor 3 may have a vertical component when the unmanned aerial vehicle is in the USV configuration. In other words, in the USV configuration, the rotational axis does not have a perfect horizontal orientation. Yet, the horizontal component is preferably greater than the vertical component in this configuration, as is the case in the illustrated example. This can ensure a more smooth operation of the vehicle in the USV configuration, due to a reduced torque at the centre of mass of the unmanned aerial vehicle.

[0113] The angle between the rotational axis 4 of the rotor 3 in the upright orientation of the UAV configuration and the rotational axis 4 of the same rotor 3 in the non-upright orientation of the USV configuration is approximately 90 degrees. However, in other examples, the angle may be greater, for example to reduce the horizontal component of the rotational axis in the upright orientation. However, an angle of approximately 90 degrees can simplify design and implementation of the pivotal rotor coupling.

[0114] Fig. 4 illustrates a top-view indicating rotational axes 4a-4f of an unmanned aerial vehicle 1 in the USV configuration 8 according to the present disclosure. The illustration indicates the orientation of the rotational axes 4a-4f of each of the six rotors of the illustrated vehicle 1. These rotational axes also indicate the direction in which each rotor provides additional thrust upon acceleration of the respective rotor.

[0115] In a conventional unmanned aerial vehicle, yaw reorientation is typically implemented by accelerating rotors rotating in one direction (for example clockwise), while optionally decelerating rotors rotating in another direction (for example counterclockwise). Using a quadcopter as an example, two rotors rotating clockwise and positioned opposite to each other relative to the centre of the vehicle can be accelerated to rotate the vehicle in a counterclockwise direction. Similarly, the two other rotors of the quadcopter rotating counterclockwise and also positioned opposite to each other relative to the centre of the vehicle can also accelerated to rotate the vehicle in a clockwise direction.

[0116] Similar considerations can apply to an unmanned aerial vehicle with six rotors, which may be referred to as a hexacopter. Considering rotors located circumferentially around the perimeter of such a vehicle, every second rotor may rotate clockwise, and these may be accelerated to rotate the vehicle in a counterclockwise direction. The remaining three rotors then rotate counterclockwise and can be accelerated to rotate the vehicle in a clockwise direction.

[0117] Returning to the unmanned aerial vehicle 1 in the USV configuration 8 illustrated in Fig. 4, a yaw reorientation in the USV configuration 8 may be implemented by an acceleration pattern which is different from that in the UAV configuration. For example, the two rotors associated with the rotational axes labelled 4a and 4d positioned opposite to each other relative to the centre of the unmanned aerial vehicle 1 can be accelerated to implement counterclockwise rotation of the unmanned aerial vehicle 1. Similarly, the two rotors associated with the rotational axes labelled 4b and 4c positioned opposite to each other relative to the centre of the unmanned aerial vehicle 1 can be accelerated to implement clockwise rotation of the unmanned aerial vehicle 1.

[0118] Thereby, yaw control instructions related to rotation of the unmanned aerial vehicle in the UAV configuration can comprise acceleration instructions associated with relative acceleration of the same and / or different set(s) of rotors as yaw control instructions related to rotation of the unmanned aerial vehicle in the USV configuration.

[0119] Acceleration of, e.g., rotors at the rotational axes labelled 4c and 4d can be associated with forward movement (upwards direction of the drawing) of the unmanned aerial vehicle 1 in both the UAV configuration and in the USV configuration. Thus, pitch control instructions related to forward movement of the unmanned aerial vehicle in the UAV configuration can comprises acceleration instructions associated with relative acceleration of the same set of rotors as pitch control instructions related to forward movement of the unmanned aerial vehicle in the USV configuration. Correspondingly, the rotors at the rotational axes labelled 4a and 4b can be associated with backwards movement of the unmanned aerial vehicle 1 in both the UAV configuration and the USV configuration.

[0120] Furthermore, acceleration either of the rotor at the rotational axis labelled 4e or of the rotor at the rotational axis labelled 4f can be associated with sideways movement of the unmanned aerial vehicle 1 in both the UAV configuration and in the USV configuration. Hence, roll control instructions related to sideways movement of the unmanned aerial vehicle in the UAV configuration can comprises acceleration instructions associated with relative acceleration of the same set of rotors as roll control instructions related to sideways movement of the unmanned aerial vehicle in the USV configuration.

[0121] Fig. 4 further illustrates a hull orientation 12 as indicated by an arrow. This hull orientation 12 is associated with the watercraft hull of the vehicle body 2 and indicates a direction of small hydrodynamical drag, whereas the direction transverse to the hull orientation 12 large hydrodynamical drag.

[0122] In case the unmanned aerial vehicle 1 floats on water in which a water current is present, the unmanned aerial vehicle 1 will tend to align the hull orientation 12 along the direction of the current. Thereby, the rotors at the rotational axes labelled 4a and 4b and / or the rotors at the rotational axes labelled 4c and 4d can be used to accelerate and operate the unmanned aerial vehicle along the direction of the current, whereas the rotors at the rotational axes labelled 4e and 4f can be used to accelerate and operate the unmanned aerial vehicle transversely to the direction of the current.

[0123] Fig. 5 schematically illustrates a method of operating an unmanned aerial vehicle 1 to perform a series of measurements 14a, 14b below a water surface 16. In the illustration, the same unmanned aerial vehicle 1 is illustrated in three different consecutive vehicle locations 17a-17c supplemented by arrows which indicate that the vehicle 1 moves between these locations 17a-17c.

[0124] Initially, the unmanned aerial vehicle 1 is operated in the UAV configuration 7 to thereby move the vehicle by means of flying as indicated by the vehicle 1 illustrated in the UAV configuration in the first location 17a.

[0125] Next, the unmanned aerial vehicle 1 is landed on the water surface 16 such that the vehicle 1 floats on the water surface 16, as illustrated by the vehicle 1 being present in the second vehicle location 17b. On the water surface 16, the unmanned aerial vehicle 1 is switched from the UAV configuration 7 to the USV configuration 8 by pivotal adjustment of the plurality of rotors via pivotal rotor couplings. In the illustrations, the vehicle 1 in the second vehicle location 17b is thus illustrated in the USV configuration 8, in which it can then be operated.

[0126] In the second vehicle location 17b, the unmanned aerial vehicle 1 performs a first measurement 14a indicated by schematically illustrated wavefronts in the figure. In the present example, the vehicle utilizes a sensor 13 in the form of an ultrasonic water level sensor to perform a measurement 14a in the form of an ultrasonic water level measurement, which provides an indication of the water depth at the location of the vehicle 1, i.e., at the second vehicle location 17b.

[0127] After having performed the first measurement 14a, the unmanned aerial vehicle is repositioned via horizontal thrust of at least one rotor of the plurality of rotors of the vehicle 1. The vehicle moves from the second vehicle location 17b to the third vehicle location 17b.

[0128] In the third vehicle location 17c, the unmanned aerial vehicle 1 performs a second measurement 14b using the sensor to obtain an indication of the water depth at the third vehicle location.

[0129] In this manner, the unmanned aerial vehicle 1 according to the present example is capable of performing a series of measurements 14a, 14b, in which the vehicle 1 is repositioned via horizontal thrust of at least one rotor while in the USV configuration between measurements of the series of measurements 14a, 14b. In particular, the vehicle 1 is not switched between the USV configuration 8 and the UAV configuration 7 between consecutive measurements 14a, 14b.

[0130] Fig. 6 illustrates a top-view indicating inward orientation of a rotor 3 of an unmanned aerial vehicle 1 in the USV configuration 8 according to the present disclosure.

[0131] In the presently illustrated embodiment, the rotors 3 are oriented inwardly when the unmanned aerial vehicle 1 is in the USV configuration 8. Thus, the centre of mass of each of the respective rotors 3 of the vehicle 1 is located closer to a central upright axis 18 in the USV configuration 8 than in the UAV configuration.

[0132] This concept is detailed further in the Fig. 6 in which various guiding lines 19, 20 are drawn to distinguish between inward orientation versus non-inward orientation.

[0133] Firstly, the figure indicates a central upright axis 18, which is located at the geometric centre of the unmanned aerial vehicle 1, and which in the present illustration has an orientation perpendicular to the plane of the illustration. Furthermore, a pivot axis 6 of a pivotal rotor coupling associated with a rotor 3 is illustrated, along with the rotational axis 4 of that rotor 3.

[0134] When the unmanned aerial vehicle 1 is switched from the UAV configuration to the USV configuration, the rotor 3 is pivotally adjusted around the pivot axis 6, and accordingly, the centre of mass of the rotor 3 is also moved. Considering the projection of the direction of movement of this centre of mass in the illustration plane, the direction of movement when switching to the USV configuration is the same direction as the direction of the illustrated rotational axis 4, i.e., perpendicular to the axis 6. That is, in the plane illustrated in Fig. 6, the centre of mass moves downward when switching to the USV configuration. As a result, the centre of mass in the USV configuration is closer to the central upright axis 18 than in the UAV configuration.

[0135] In other examples within the scope of the present disclosure, the direction of movement of the centre of mass can be different than illustrated in Fig. 6. Whether an orientation of a rotor can be considered as being inward, can be evaluated by considering guiding lines 19, 20 as those illustrated in Fig. 6.

[0136] A centre-to-rotor guiding line 19 is drawn from the central upright axis 18 to the centre of the pivot axis 6, where a projection of the rotational axis 4 intersects the pivot axis 6. In addition, an inward threshold guiding line 20 is drawn through this same intersection and perpendicular to the centre-to-rotor guiding line 19.

[0137] The inward threshold guiding line 20 serves as a threshold as to whether a rotor can be considered as to have an inward orientation. If the rotational axis 4 and the central upright axis 18 are located on the same side of the inward threshold guiding line 20, then the rotor 3 has an inward orientation (as is the case in the present illustration). If, in contrast, the rotational axis 4 had been on one side of the inward threshold guiding line 20 and the central upright axis 18 had been on the opposite side of this guiding line 20, then the rotor 3 would not have an inward orientation. This would, for example, be the case if the rotational axis 4 was orientated towards the right-hand side or oriented upwards relative to the plane of the illustration. This is exemplified in Fig. 6 by the arrow denoted by reference numeral 21, which indicates an exemplary outwards rotor orientation 21. If the rotational axis 4 had this outwards rotor orientation 21, then it would not have an inward orientation.

[0138] Fig. 7 illustrates two rotors providing thrust in two different directions in a horizontal plane 22. The horizontal thrust of one of the rotors is illustrated with a first dotted line 23, and the horizontal thrust of the other rotor is illustrated with a second dotted line 24. The thrusts 23, 24 in two different directions in a horizontal plane is a result of the different horizontal orientations in the USV configuration and provides two translational degrees of freedom corresponding to the directions of the thrust indicated by the dotted lines 23, 24. Further a rotational degree of freedom can be obtained by, e.g., a horizontal orientations of rotors or thrusts 23, 24 being offset relative to a centre of the vehicle, such as offset relative to a central upright axis.

[0139] List of figure references:

[0140] 1 unmanned aerial vehicle

[0141] 2 vehicle body

[0142] 3 rotor

[0143] 4 rotational axis

[0144] 5 pivotal rotor coupling

[0145] 6 pivot axis

[0146] 7 UAV configuration

[0147] 8 USV configuration

[0148] 9 offset

[0149] 10 mast structure

[0150] 11 post structure

[0151] 12 hull orientation

[0152] 13 sensor

[0153] 14 measurement

[0154] 15 water

[0155] 16 water surface

[0156] 17 vehicle location

[0157] 18 central upright axis

[0158] 19 centre-to-rotor guiding line

[0159] 20 inward threshold guiding line

[0160] 21 outwards rotor orientation

[0161] 22 horizontal component of thrust from one rotor in USV configuration

[0162] 23 horizontal component of thrust from another rotor in USV configuration

[0163] 24 horizontal plane

Claims

CLAIMS1. An unmanned aerial vehicle comprising : a vehicle body configured to permit the unmanned aerial vehicle to float on water; a plurality of rotors, wherein each rotor of the plurality of rotors has a rotational axis; and one or more pivotal rotor couplings, each of the respective pivotal rotor couplings configured to facilitate pivotal adjustment of an orientation of the rotational axis of a respective rotor of the plurality of rotors around a respective pivot axis transverse to the rotational axis of the respective rotor of the plurality of rotors, wherein the unmanned aerial vehicle has a UAV configuration in which the rotational axis of each rotor of the plurality of rotors has an upright orientation permitting the plurality of rotors to generate a vertical thrust allowing the unmanned aerial vehicle to fly in the UAV configuration, wherein the unmanned aerial vehicle has a USV configuration in which the rotational axis of at least some rotors of the plurality of rotors has a non-upright orientation permitting the plurality of rotors to generate a horizontal thrust while the unmanned aerial vehicle floats on water via the vehicle body in the USV configuration, wherein the unmanned aerial vehicle is configured to be switched between the UAV configuration and the USV configuration by pivotal adjustment of at least some rotors of the plurality of rotors via at least some of the pivotal rotor couplings, wherein the plurality of rotors is positioned on the unmanned aerial vehicle such that the plurality of rotors is located above a water surface when the unmanned aerial vehicle floats on water in the USV configuration, wherein at least some rotors of the plurality of rotors have different horizontal orientations in the USV configuration.

2. An unmanned aerial vehicle according to claim 1, wherein the unmanned aerial vehicle comprises one or more pivotal rotor actuators, each configured to pivotally adjust the orientation of the rotational axis of a respective rotor of the plurality of rotors via the pivotal rotor couplings.

3. An unmanned aerial vehicle according to any of the preceding claims, wherein the respective rotational axis of a respective rotor of the plurality of rotors has an offset to the respective pivot axis of the respective pivotal rotor coupling coupled to that respective rotor.

4. An unmanned aerial vehicle according to claim 3, wherein the offset between the rotational axis and the pivot axis is arranged such that when a respective rotor of the plurality of rotors generates a thrust, this thrust provides a torque around the pivot axis associated with this respective rotor to support orientation of this respective rotor from the non-upright orientation to the upright orientation.

5. An unmanned aerial vehicle according to any of the preceding claims, wherein at least some of the rotors of the plurality of rotors are oriented inwardly when the unmanned aerial vehicle is in the USV configuration such that a centre of mass of each of these respective rotors is located closer to a central upright axis of the unmanned aerial vehicle in the USV configuration than in the UAV configuration.

6. An unmanned aerial vehicle according to any of the preceding claims, wherein the rotational axes of the plurality of rotors are located in different planes when the unmanned aerial vehicle is in the USV configuration.

7. An unmanned aerial vehicle according to any of the preceding claims, wherein at least some of the rotors of the plurality of rotors have an orientation below a horizontal orientation when the unmanned aerial vehicle is in the USV configuration such that this orientation of these at least some of the rotors has a downwards vertical component.

8. An unmanned aerial vehicle according to any of the preceding claims, wherein each rotor of the plurality of rotors has an orientation below a horizontal orientation when the unmanned vehicle is in the USV configuration such that this orientation of each rotor of the plurality of rotors has a downwards vertical component.

9. An unmanned aerial vehicle according to any of the preceding claims, wherein, in the USV configuration, the horizontal component is greater than the vertical component for at least some rotors of the plurality of rotors, preferably for all rotors of the plurality of rotors.

10. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle comprises first pitch control instructions associated with forward movement of the unmanned aerial vehicle in the UAV configuration, wherein the unmanned aerial vehicle comprises second pitch control instructions associated with forward movement of the unmanned aerial vehicle in the USV configuration, wherein the first pitch control instructions and the second pitch control instructions both comprise acceleration instructions associated with relative acceleration of the same set of rotors of the plurality of rotors.

11. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle comprises first yaw control instructions associated with rotation of the unmanned aerial vehicle in the UAV configuration, wherein the unmanned aerial vehicle comprises second yaw control instructions associated with rotation of the unmanned aerial vehicle in the USV configuration, wherein the first yaw control instructions and the second yaw control instructions both comprise acceleration instructions associated with relative acceleration of the same set of rotors of the plurality of rotors.

12. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle comprises first roll control instructions associated with sideways movement of the unmanned aerial vehicle in the UAV configuration, wherein the unmanned aerial vehicle comprises second roll control instructions associated with sideways movement of the unmanned aerial vehicle in the USV configuration, wherein the first roll control instructions and the second roll control instructions both comprise acceleration instructions associated with relative acceleration of the same set of rotors of the plurality of rotors.

13. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle comprises a sensor arranged at a lower surface of the vehicle body such that the sensor is below a water surface when the unmanned aerial vehicle floats on water in the USV configuration.

14. An unmanned aerial vehicle according to any of the preceding claims, wherein the plurality of rotors is at least four rotors, for example at least six rotors.

15. An unmanned aerial vehicle according to any of the preceding claims, wherein the vehicle body comprises a watercraft hull associated with a hull orientation indicative of hydrodynamical drag, wherein the watercraft hull has a first drag coefficient along the hull orientation, and the watercraft hull has a second drag coefficient transverse to the hull orientation, each of the first drag coefficient and the second drag coefficient evaluated based on water flow when the unmanned aerial vehicle floats on water in the USV configuration, wherein the second drag coefficient is greater than the first drag coefficient.

16. An unmanned aerial vehicle according to any of the preceding claims, wherein the vehicle body is configured to permit the unmanned aerial vehicle to float on water via buoyancy.

17. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle may have a greater number of rotors oriented along the hull orientation than transverse to the hull orientation in the USV configuration, for example four rotors oriented along the hull orientation and two rotors oriented transverse to the hull orientation.

18. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle may have a first set of USV control instructions and a second set of USV control instructions, wherein the first set of USV control instructions is directed at operation under conditions with substantial water flow, such as in a river, and the second set of USV control instructions is directed at operation under conditions with no substantial water flow.

19. An unmanned aerial vehicle according to any of the preceding claims, wherein the watercraft hull has a deck which is shaped to provide an opening for air flow along the rotational axis of each rotor of the plurality of rotors when the unmanned aerial vehicle is in the UAV configuration.

20. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle comprises a plurality of mast structures, wherein each mast structure of the plurality of mast structures has an upright orientation and comprises a first end and a second end distal relative to the first end, wherein the first end connects to the vehicle body, and the second end is connected to a respective rotor of the plurality of rotors, for example such that the plurality of rotors is positioned on the unmanned aerial vehiclesuch that the plurality of rotors is located above a water surface when the unmanned aerial vehicle floats on water in the USV configuration.

21. An unmanned aerial vehicle according to any of the preceding claims, wherein each rotor of the plurality of rotors is positioned above a floatation height relative to a water surface when the unmanned aerial vehicle floats on water in the USV configuration, wherein the floatation height is at least a diameter of the rotors.

22. An unmanned aerial vehicle according to any of the preceding claims, wherein the unmanned aerial vehicle defines a longitudinal centre line and a transverse centre line, wherein at least some of the rotors are displaced relative to both the longitudinal centre line and the transverse centre line.

23. An unmanned aerial vehicle according to any of the preceding claims, wherein, in said USV configuration, the rotational axis of a first subset of rotors of the plurality of rotors has the upright orientation and the rotational axis of a second subset of rotors of the plurality of rotors has the non-upright orientation, wherein the second subset of rotors is configured to provide a vertical thrust while to first subset of rotors provide a horizontal thrust.

24. An unmanned aerial vehicle according to any of claims 1-22, wherein the unmanned aerial vehicle has an auxiliary USV configuration in which the rotational axis of a first subset of rotors of the plurality of rotors has the upright orientation and in which the rotational axis of a second subset of rotors of the plurality of rotors has the non-upright orientation, wherein the second subset of rotors is configured to provide a vertical thrust while to first subset of rotors provide a horizontal thrust, wherein the unmanned aerial vehicle is configured to be switched between an auxiliary USV configuration and any of the USV configuration and the UAV configuration.

25. A method of operating an unmanned aerial vehicle according to any of the preceding claims, the method comprising the steps of: operating the unmanned aerial vehicle in the UAV configuration to position the unmanned aerial vehicle over a water surface;landing the unmanned aerial vehicle on the water surface such that the unmanned aerial vehicle floats on the water surface; switching the unmanned aerial vehicle from the UAV configuration to the USV configuration by pivotal adjustment of at least some rotors of the plurality of rotors via at least some of the pivotal rotor couplings; and operating the unmanned aerial vehicle in the USV configuration on the water surface.

26. A method according to claim 25, wherein the unmanned aerial vehicle comprises a sensor positioned below the water surface when the unmanned aerial vehicle floats on the water surface, wherein the method comprises a step of performing at least one measurement below the water surface using the sensor.

27. A method according to claim 26, wherein the at least one measurement is at least one depth measurement.

28. A method according to any of claims 26-27, wherein the step of performing at least one measurement is a step of performing a series of measurements, wherein the unmanned aerial vehicle is repositioned via horizontal thrust of at least one rotor of the plurality of rotors while in the USV configuration between each measurement of the series of measurements.

29. A method according to claim 28, wherein the series of measurements is performed across a body of water to provide a bathymetry measurement of the body of water, for example across a water river to provide a bathymetry measurement of the water river, for example a bathymetry measurement of the water river transverse to a flow direction of the water river.

30. An method according to any of claims 25-29, wherein the respective rotational axis of a respective rotor of the plurality of rotors has an offset to the respective pivot axis of the respective pivotal rotor coupling coupled to that respective rotor such that a thrust of a respective rotor of the plurality of rotors provides a torque around the pivot axis due to the offset to thereby support orientation of this respective rotor from the non-upright orientation towards the upright orientation.

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