Unmanned aerial vehicle with center of mass displacement

Abstract

The disclosure regards an unmanned aerial vehicle (UAV) comprising a main body, a frame, a plurality of propeller units attached to the frame, and a displacement mechanism configured to displace with three translational degrees of freedom the main body of the UAV with respect to the frame, thereby adjusting the center of mass of the 5 UAV in any spatial direction.

Description

[0001] Unmanned aerial vehicle with center of mass displacement

[0002] The present disclosure relates to a novel unmanned aerial vehicle (UAV) system that can perform center of mass displacement for various tasks, such as high-force tool manipulation to non-horizontal surfaces at heights and landing on water.

[0003] Background

[0004] Unmanned Aerial Vehicles (UAVs) are utilized in a wide range of applications, including surveillance, delivery, inspection, and search and rescue operations. Depending on the specific use case, UAVs are designed with particular structural configurations, propulsion systems, and control mechanisms to optimize their performance for a given task. For any given task, manoeuvrability and stability of the UAV are critical parameters. For example, high-force tool manipulation at heights, such as drilling or cutting, requires enhanced stability and force output, which existing UAVs struggle to achieve. Similarly, landing on water demands a specific balance and buoyancy control that most UAVs are not designed for. Therefore, there is a need for a novel UAV design that can enable the use of UAVs in operations that are not currently feasible, as well as enable UAVs to be used for multiple tasks.

[0005] Summary

[0006] The present inventor has realized that one factor that significantly affects manoeuvrability and stability, is the center of mass (CoM) of the UAV, because the CoM of a UAV affects various flight dynamics, such as stability, control responsiveness, energy efficiency, and handling of specific tasks.

[0007] One objective of the present disclosure is therefore to enable the use of an adjustable center of mass (CoM) of a UAV in order to enable the UAV to conduct work that cannot be performed by conventional UAVs. In an embodiment, the present disclosure relates to a UAV comprising a main body, a frame, a plurality of propeller units attached to the frame, and a displacement mechanism configured to displace with three translational degrees of freedom the main body of the UAV with respect to the frame. Hence, thereby having the capability of adjusting the center of mass of the UAV in any spatial direction. In conventional UAV designs, the CoM is typically fixed, meaning that each UAV is built with a specific CoM arrangement tailored for its intended application. However, different tasks may benefit from different CoM configurations. For instance, a UAV used for precision hovering may require a different CoM positioning than one optimized for high-speed forward flight or payload transportation. This limitation means that UAVs must often be custom-designed for each specific application, resulting in increased development and manufacturing costs, reduced operational flexibility, and inefficiencies in deployment.

[0008] An example highlighting a task that UAVs are currently unable to perform is provided below. The state of the art in the field of construction and maintenance of building surfaces at heights involves construction or maintenance workers that need to manually access the surface and perform the required operations to service the building surface. Such a solution is well established, however it involves various disadvantages, as the risk of an accident is significant, and the cost of hiring personnel to perform such tasks can be high. To substitute manual labor for such tasks, unmanned aerial vehicles (UAV) have been tested in monitoring operations of a surface. For example, a UAV with a camera installed has been utilized to capture a video of a building surface, with the aim of investigating whether the surface needs to be serviced or not. Such a solution prevented personnel from working at heights, reducing the risk of an accident. However, when high-force operations are required to be performed at elevated surfaces, such as drilling, soldering or any other high-force operation, workers are still required to manually perform such tasks, as no aerial robotic solution exists.

[0009] With the presently disclosed UAV, having a main body, a frame, a plurality of propeller units attached to the frame, the flexibility comes from the displacement mechanism configured to displace with three translational degrees of freedom the main body of the UAV with respect to the frame.

[0010] The frame of the UAV may be utilized to attach on it the various parts of the UAV. The displacement mechanism may translate the main body of the UAV with respect to the frame, towards any spatial direction. For example, the displacement mechanism may be able to translate the main body longitudinally, vertically, or transversely, or in a combination of the three, at any random three-dimensional vector. As a result, the CoM of the UAV can be adjusted, in order to optimize the UAV for various operations. For instance, the process of landing a body on water can be achieved by lowering the center of mass vertically, possibly lower than the propeller units. By lowering the center of mass, it is possible to increase the stability of the UAV against disturbances of the water surface, such as waves. Stability can be achieved if the center of gravity of the UAV is below the metacenter of the buoyancy, where the metacenter can be defined as the point where the line of action of the buoyancy force before rotation and the line of action of the buoyancy force after rotation intersect. As a result, by utilizing the displacement mechanism it is possible to adjust the center of mass of the UAV and adjust it to be beneath the surface of the water, thereby increasing the stability of the UAV and achieving successful landing and floating on water.

[0011] Another purpose of the present disclosure is to provide a solution to substitute manual work at heights, especially related to high-force tool manipulation, such as drilling operations, soldering metal, or any other operation that may involve the application of significant forces. To achieve such a task, one possible solution is to adapt a UAV to be capable to carry out high-force tool manipulation tasks. However, state of the art UAV solutions cannot carry out such operations, due to the limited thrust that is provided towards the direction of the task. E.g. to drill a hole into a vertical concrete hole with a drilling tool it is necessary to create a substantial horizontal force on the drilling tool. To tackle such a problem, one embodiment of the present disclosure relates to an unmanned aerial vehicle (UAV) for manipulation of (a non-horizontal) surface of a structure, for example a substantially vertical surface. The UAV comprising a plurality of propeller units for providing thrust for carrying and navigating the UAV. A main body can be provided comprising a manipulator for manipulating the non- horizontal surface. A displacement mechanism for moving the main body and the manipulator within the UAV, thereby displacing the center of mass of the UAV. In the preferred embodiment the UAV comprises a thrust control unit configured to adjust a thrust direction of at least one of the propeller units, such that a first group of the propeller units predominantly provide thrust to counteract gravity, and a second group of the propeller units can provide thrust to the manipulator, for example by predominantly providing thrust in a direction perpendicular to the non-horizontal surface. Displacing the center of mass of the UAV, towards and / or above the first group of propeller units, allows the first group of propeller units to provide thrust to counteract gravity, and preferably maintain the UAV stable in the air. Such a function allows a second group of propeller units to be released from the duty of maintaining the UAV in the air, and they can for example be oriented I rotated accordingly, e.g. in order to provide thrust in the direction of the non-horizontal surface. That thrust can be then utilized by the manipulator to perform certain tasks on the non-horizontal surface, such as drilling a hole.

[0012] For example, the main body of the UAV (typically holding the manipulator) can be displaced towards and / or above the propeller units that are positioned at the front part of the UAV, allowing the rear propeller units of the UAV to rotate and provide thrust towards the non-horizontal surface. The thrust provided by the rear propeller units can be utilized by the UAV to establish reaction forces with the environment, such as with the non-horizontal surface. These reactions forces can be utilized by the manipulator in order to carry out high-force manipulation tasks. Such tasks cannot be performed by state of the art UAVs - where all the propeller units are counteracting gravity - as the force exerted by the manipulator itself is not enough to perform these tasks. Therefore, the thrust provided by a group of propeller units, as specified herein, can be advantageous for successfully performing such high-force tasks.

[0013] The thrust control unit can adjust the individual thrust of each propeller unit, by for example keeping a group of propeller units parallel to the surface of the earth, in order to counteract gravity, and keeping a second group of propeller units at an orientation to predominantly provide thrust towards the non-horizontal surface.

[0014] In addition, the UAV may comprise a stability unit, configured to establish and / or maintain contact with the non-horizontal surface to stabilize the UAV, typically during manipulation of the surface. In an embodiment the stability unit comprises a plurality of contact points for contacting the non-horizontal surface. For example, such contact points can be a set of elongated rods.

[0015] In one embodiment the presently disclosed UAV can be seen as having 1) a fly mode where the propeller units cooperate to fly and navigate the UAV in the air, and 2) a surface manipulation mode, typically when contacting the non-horizontal surface while hovering, where the center of mass of the UAV is aligned, or at least substantially aligned, with the first group of propeller units, such that the thrust of the first group of propeller units counteracts gravity, and where the second group of propeller units is oriented to provide thrust towards the non-horizontal surface such that the second group of propeller units provide thrust to the manipulator.

[0016] Moreover, the UAV can be configured such that in the fly mode, all propeller units cooperate to navigate the UAV in the air, and in the surface manipulation mode, propellers of a first group of the propeller units revolve parallel, or at least substantially parallel, to the main body, thereby providing thrust to counteract gravity, and propellers of a second group of propeller units revolve perpendicular, or at least substantially perpendicular, to the main body, thereby providing thrust towards the non-horizontal surface. Alternatively propellers of the second group of propeller units are oriented to revolve substantially parallel to the non-horizontal surface. E.g. in case of a tilting surface, the main body may be oriented to be horizontal, but the force utilized by the manipulator may be maximized in the second group of propellers are oriented such that the propellers revolve parallel to the slanted surface.

[0017] For example, the thrust control unit can be adjusted such that in the fly mode, all the propeller units of the UAV are providing thrust to counteract gravity and navigate the UAV in the air, and in surface manipulation mode, a first group of the propeller units provide thrust to counteract gravity and a second group of the propeller units provide thrust to be used by the manipulator to perform tasks at the non-horizontal surface.

[0018] Furthermore, the present disclosure relates to a computer implemented method adjusting the thrust direction of a plurality of propeller units in a UAV, comprising: obtaining at least one propeller for providing thrust for carrying and navigating the UAV, obtaining a main body of the UAV, wherein a thrust control unit adjusts the orientation of the plurality of propeller units with respect to the main body of the UAV, such that the direction of thrust can be modified. Such a method can for example be performed by a processing unit positioned on the UAV, which can control the propeller units of the UAV. Description of drawings

[0019] Various embodiments are described hereinafter with reference to the drawings. The drawings are examples of embodiments and are intended to illustrate some of the features of the presently disclosed UAV with center of mass displacement, and are not limiting to the presently disclosed system and method.

[0020] Fig. 1 shows a schematic of the side view of an unmanned aerial vehicle (UAV) comprising four propeller units, a main body that can be displaced, and a manipulator positioned on the main body.

[0021] Fig. 2 shows a schematic of the side view of a UAV where the main body has been displaced towards a first group of propeller units.

[0022] Fig. 3 shows a schematic of the side view of a UAV where the UAV is in contact with a non-horizontal surface, and a second group of propeller units provide thrust in the direction of the non-horizontal surface.

[0023] Fig. 4 shows a schematic of the side view of a UAV describing the different angles that a propeller can operate at.

[0024] Fig. 5 shows a schematic of the side view of a UAV operating at a surface of arbitrary angle.

[0025] Fig. 6 shows a drawing of a UAV illustrating a horizontal bar on which a group of propeller units is attached to.

[0026] Fig. 7 shows an image of a UAV comprising four bi-rotor propeller units, a stability unit, a main body, a manipulator and a displacement mechanism.

[0027] Fig. 8 shows the method steps for a computer implemented method for adjusting the thrust direction of a plurality of propeller units in an UAV.

[0028] Fig. 9 shows a simulation of a UAV when approaching a non-horizontal surface.

[0029] Fig. 10 shows a schematic of forces exerted on the UAV and the torque generated when in contact to a non-horizontal surface.

[0030] Figs. 11 A, B show an example of a UAV floating on water without adjusting its center of mass.

[0031] Figs. 12 A, B show an example of a UAV floating on water that displaces its main body to adjust its center of mass.

[0032] Figs. 13 A, B show a displacement mechanism comprising a rail configured to displace the main body of the UAV along a vertical direction.

[0033] Figs. 14 A, B show a UAV where the displacement mechanism comprises a joint configured to rotate the main body along a transverse axis of the UAV. Detailed description

[0034] The present disclosure relates in a first embodiment to an unmanned aerial vehicle (UAV) comprising a main body, a frame, a plurality of propeller units attached to the frame, and a displacement mechanism configured to displace with three translational degrees of freedom the main body of the UAV with respect to the frame. Thereby preferably having the capability of adjusting the center of mass of the UAV in any spatial direction. The displacement mechanism enables controlled longitudinal, transverse, and vertical movement of the UAV’s center of mass (CoM), thereby optimizing flight dynamics for different operational requirements. By actively shifting the CoM, the UAV can improve stability, maneuverability, and adaptability across various flight and landing conditions.

[0035] In a conventional UAV design, the CoM is typically fixed, which limits the ability to adapt to changing conditions or specific tasks. However, by incorporating a displacement mechanism, the UAV can dynamically adjust its balance during flight, thereby optimizing aerodynamics and energy efficiency. For example, during highspeed forward flight, shifting the CoM forward can reduce drag and enhance propulsion efficiency. Conversely, when hovering or performing precision maneuvers, the CoM can be repositioned to improve stability and control responsiveness.

[0036] A particularly important application of vertical CoM displacement is in the ability to land the UAV on water surfaces with improved stability. When a UAV lands on water, its buoyancy is determined by the distribution of its weight relative to the waterline. If the CoM is too high, the UAV may become unstable, increasing the risk of capsizing due to minor disturbances such as waves or wind. However, by lowering the CoM, the UAV effectively reduces its metacentric height, which improves stability and prevents excessive tilting. The displacement mechanism allows for active control over the CoM, ensuring that the UAV achieves a balanced flotation posture that minimizes unwanted oscillations. By adjusting the CoM downward, the UAV can optimize the distribution of buoyant forces, ensuring that critical components — such as electrical systems or sensors — remain above the waterline. Additionally, the CoM adjustment may help counteract uneven weight distribution caused by payloads or onboard equipment, allowing for a more stable landing configuration. In scenarios where the UAV needs to take off from water, the displacement mechanism may be used to slightly raise the CoM, shifting the balance of forces to facilitate smoother lift-off.

[0037] In an embodiment, the UAV comprises a thrust control unit controlling the direction and power of the plurality of propeller units, the thrust control unit configured to individually adjust the direction of each of the plurality of propeller units, thereby causing any of the propeller units to apply a thrust vector to be directed along any arbitrary vector in three- dimensional space.

[0038] The thrust control unit enables precise maneuverability and enhanced stability by dynamically adjusting the orientation and power of each propeller. Unlike conventional UAVs, where propellers are typically fixed or have limited degrees of freedom, the ability to direct thrust along any vector allows for advanced flight modes, including hovering at unconventional angles and stable flight under varying load conditions. This feature can be particularly advantageous in applications requiring tool manipulation, precise landing on irregular surfaces, or counteracting asymmetric payload distributions.

[0039] For example, in scenarios where the UAV needs to apply force against a surface, such as in drilling, cutting, or sensor placement operations, the thrust control unit can adjust the thrust vector of individual propellers to counteract reaction forces. Additionally, in high-wind environments, the system can continuously adjust thrust directions to maintain stability, ensuring that the UAV does not drift off course. Further technical details and advantages of using a thrust control unit for high-force tool manipulation are expanded in the sections below.

[0040] In an embodiment, the displacement mechanism comprises a linear actuator configured to translate the main body along a longitudinal direction. By enabling controlled forward and backward movement of the main body relative to the UAV frame, the displacement mechanism provides additional flexibility in adjusting the center of mass (CoM) along the UAV’s primary flight axis. This adjustment can optimize the aerodynamic profile during forward flight, reduce drag, and improve energy efficiency. For example, when transitioning from a hovering mode to a cruise mode, shifting the CoM forward can help achieve a more aerodynamically efficient posture, allowing the UAV to travel longer distances with less power consumption. Additionally, longitudinal CoM adjustments can be beneficial when carrying payloads of varying weight distributions. If a UAV is transporting an elongated or asymmetric payload, shifting the main body forward or backward ensures that the total mass remains optimally balanced, reducing the risk of instability during flight.

[0041] Furthermore, the displacement mechanism may comprise a linear actuator configured to translate the main body along a transverse direction. By providing side-to-side CoM adjustment, the UAV gains the ability to counteract any possible lateral instabilities caused by external forces, such as side winds, sudden maneuvers, or asymmetric payload configurations. This is particularly useful for precision landing operations, where slight lateral shifts can help the UAV align more accurately with the intended touchdown location.

[0042] For instance, when docking with a moving platform or attaching to a vertical surface for inspection tasks, the UAV can adjust its CoM laterally to compensate for small position errors. This capability also enables enhanced evasive maneuvering, as shifting the mass distribution transversely can improve yaw and roll dynamics, allowing the UAV to quickly change direction without excessive tilting.

[0043] In embodiment, the displacement mechanism comprises a linear actuator configured to translate the main body along a vertical direction. Vertical displacement of the CoM has a direct impact on stability and hover efficiency. Lowering the CoM increases the moment of inertia, thereby reducing susceptibility to small disturbances such as gusts of wind or turbulence. On the other hand, raising the CoM can improve the UAV’s ability to perform rapid vertical maneuvers, such as quick ascents or obstacle avoidance.

[0044] A critical application of vertical CoM displacement is water landing and buoyancy control. When landing on a water surface, a UAV with a fixed CoM may experience instability due to wave motion or uneven flotation forces. However, by actively lowering the CoM, the UAV can improve its stability in the water, reducing the risk of capsizing. The metacentric height, which determines stability in floating objects, is affected by the distribution of mass relative to the buoyant forces acting on the UAV. By lowering the CoM, the UAV ensures that buoyancy forces remain symmetrically distributed, thereby minimizing tilt and oscillations. This configuration ensures that critical components, such as electronics or sensors, remain above the waterline, preventing damage or loss of functionality.

[0045] Moreover, the displacement mechanism may comprise a rail system enabling guided translation of the main body in at least one spatial direction. A rail system can ensure precise and controlled CoM adjustments, preventing unintended movement while allowing smooth transitions. The use of linear rails, tracks, or sliding mechanisms ensures that the main body remains securely constrained within its designated range of motion, reducing mechanical complexity and improving reliability. This is particularly beneficial in automated flight modes, where pre-programmed CoM adjustments can be executed without manual intervention.

[0046] In an embodiment, the displacement mechanism is configured to shift the center of mass downward thereby improving buoyancy and stability when landing on a water surface. When a UAV lands on water, the presence of waves and fluid resistance can cause instability, increasing the risk of the UAV tilting or submerging critical components. By shifting the CoM downward, the UAV increases its resistance to tilting forces, ensuring that it remains in a stable, upright orientation.

[0047] Additionally, controlling the CoM dynamically while floating allows for adaptation to varying water conditions. For example, in rough waters, the UAV can lower its CoM even further to counteract wave-induced oscillations, while in calm conditions, it may maintain a higher CoM to optimize take-off efficiency.

[0048] In an embodiment, the UAV may comprise a ballast, the ballast configured to adjust the center of mass of the UAV by rotating about a longitudinal, transverse and / or vertical axis of the UAV. A ballast system may enable fine control over UAV balance, particularly when external conditions or payload shifts require real-time CoM correction. For example, in high-force tool applications, such as drilling or cutting, the UAV can rotate its ballast to counteract the tool’s reaction forces, ensuring stability and precision.

[0049] Moreover, the displacement mechanism may comprise one or more joints configured to enable rotation of the main body around a longitudinal, transverse, and / or vertical axis of the UAV. Rotational adjustments allow the UAV to change its pitch, roll, or yaw orientation without relying entirely on propeller-based thrust adjustments, leading to more energy-efficient maneuvers.

[0050] For example, in aerial docking scenarios, the UAV can slightly pitch forward or backward by rotating the main body instead of expending additional thrust, thereby conserving energy. Similarly, for high-precision tasks such as pipeline inspection, a controlled rotational adjustment can improve positioning accuracy. In addition, the ballast may rotate around a longitudinal, transverse, and / or vertical axis of the UAV, thereby optimizing the CoM of the UAV.

[0051] Furthermore, the displacement mechanism may be configured to adjust the center of mass by rotating the main body about a longitudinal, transverse and / or vertical axis of the UAV. By incorporating rotational CoM adjustments, the UAV achieves a higher degree of control over stability and responsiveness. This is particularly advantageous in dynamic environments, such as autonomous docking, or heavy-lift operations, where real-time adjustments to mass distribution can significantly enhance overall performance.

[0052] By implementing both translational and rotational CoM adjustments, the UAV achieves a highly versatile and adaptive flight capability, making it suitable for a wide range of applications while reducing the need for specialized UAV designs.

[0053] Depending on the type of application, different configurations of center of mass adjustment may be employed. For example, the main body of the UAV may be displaced in any spatial dimension, or it may be rotated around a longitudinal, transverse or vertical axis of motion of the UAV. In addition, a further object, such as a ballast may be displaced or rotated in order to tune the center of mass of the UAV.

[0054] The present disclosure relates in an embodiment to an unmanned aerial vehicle (UAV) for manipulation of a non-horizontal surface of a structure, comprising a plurality of propeller units for providing thrust for carrying and navigating the UAV, a main body comprising a manipulator for manipulating the non-horizontal surface and a displacement mechanism for moving the main body and the manipulator within the UAV, thereby displacing the center of mass of the UAV. The UAV further comprises a thrust control unit configured to adjust a thrust direction of at least one of the propeller units, such that a first group of the propeller units predominantly provide thrust to counteract gravity, and a second group of the propeller units predominantly provide thrust in a direction perpendicular to the non-horizontal surface, such that the second group of propeller units provide thrust to the manipulator.

[0055] The propellers of the UAV revolve such that they provide thrust to counteract the gravitational pull. In fly mode roll, pitch and yaw of the presently disclosed UAV can be controlled like in any standard UAV in order to carry, navigate and balance the UAV in the air.

[0056] The main body of the manipulator may comprise a battery for providing power to the propeller units and the manipulator. A schematic of a side view of an embodiment of the presently disclosed UAV can be seen in Fig. 1 , where the UAV (100) comprises four propeller units (101) and a main body (102) on which the manipulator (103) is positioned. In this embodiment, the center of mass of the UAV is defined by the position of the main body. The downwards pointing vector (104) originating from the main body (102) corresponds to the gravitational force due to the mass of the UAV. The vectors (105) pointing upwards from the propeller units (101) correspond to the thrust provided by the propeller units (101) to counteract the gravitational force (104).

[0057] When the UAV (100) is positioned near a surface (200) which is aimed to be manipulated, the main body (102) of the UAV (101) can be displaced towards a first group of propeller units (201), as illustrated in Fig. 2. As described above, that allows the first group of propeller units (201) to fully counteract gravity, as depicted by the thrust vector (202) caused by the first group of propeller units (201). That allows a second group of propeller units (203) to be released from providing thrust to counteract gravity, allowing them to be used for other purposes.

[0058] For example, as shown in Fig. 3, the second group of propeller units (304) can be rotated such that they revolve parallel to the non-horizontal surface, thereby providing a thrust vector (300) towards the non-horizontal surface. The manipulator (301), attached to the main body by means of manipulator arm (301), such as a robotic arm, can therefore perform tasks on the non-horizontal surface using force exerted (302) by the manipulator (301) and taking advantage of the provided thrust (300) by the second group of propeller units (304).

[0059] To increase the manipulation force that the UAV can exert on the environment, it is advantageous that the centre of mass of the UAV is as close as possible to the nonhorizontal surface. Furthermore, the closer the manipulator (301) is to the nonhorizontal surface, the shorter the manipulator arm (30T) can be and as a result provide higher end-effector forces given a certain motor torque.

[0060] In an embodiment the UAV comprises a fly mode where the propeller units cooperate to fly and navigate the UAV in the air, and a surface manipulation mode when contacting the non-horizontal surface while hovering, where the center of mass of the UAV is aligned with the first group of propeller units, such that the thrust of the first group of propeller units counteracts gravity, and where the second group of propeller units is oriented to provide thrust towards the non-horizontal surface such that the second group of propeller units provide thrust to the manipulator. For example, a fly mode can be used when all the propeller units are predominantly providing thrust to counteract gravity and to navigate the UAV, as shown in the schematic of Fig. 1. An example of a UAV being in the surface manipulation mode can be seen in Fig. 3, where a UAV has a group of propeller units rotated accordingly to provide thrust towards the non-horizontal surface.

[0061] Moreover, an important aspect of high-force manipulation using a UAV is to properly stabilize the UAV before performing tasks on the non-horizontal surface. The UAV can therefore comprise a stability unit (106, 206, 306, 703), configured to establish and / or maintain contact with the non-horizontal surface to stabilize the UAV. The stability unit can comprise planar or linear elements, that are rigid or flexible, in order to facilitate contact between the UAV and a non-horizontal surface. In an embodiment, the stability unit comprises a plurality of contact points for contacting the non-horizontal surface. Such contact points can assist the propeller units in providing equilibrium and prevent the UAV from destabilizing when the manipulator performs certain tasks. Moreover, the stability unit can be loosely attached to the UAV, or it can pivot around the UAV, depending on the type of the task that is to be performed by the UAV. In another embodiment, the contact points comprise a plurality of rods for maintaining contact with the non-horizontal surface. Such rods can for example be elongated rigid cylinders (703), extending parallel to the non-horizontal surface. An example of such rods can be seen in Fig. 7.

[0062] For example, as seen in Fig. 3, the stability unit is an advantage as it provides further stability to the UAV when the manipulator performs a high-force task. Therefore, for such tasks, establishing contact using the stability unit (303) can be beneficial to ensure an improved performance of the UAV. The stability unit can be configured, comprising a plurality of hooks for providing contact and / or securing the UAV to the non-horizontal surface.

[0063] Depending on the type of the non-horizontal surface, it might be beneficial that the stability unit comprises elements that can lead to the UAV being secured to the surface. For example, if there are elements in the non-horizontal surface that can act as handles, hooks can be utilized by the UAV in order to secure the UAV to the surface. In addition, if the non-horizontal surface is magnetic, it might be possible to install magnets on the stability unit in order to attach the UAV to the surface before performing the manipulation tasks.

[0064] In an embodiment, the distance between the point of contact of the manipulator to the non-horizontal surface and the central point of contact of the stability unit to the non- horizontal surface is preferably less than 150 cm, even more preferably less than 100 cm, most preferably less than 75 cm, most preferably less than 40 cm. For example, the distance between the point that the manipulator acts on the non-horizontal surface and the center of the stability unit can be minimized, leading to increased maximum force that the UAV can sustain. Depending on the needs of each task, and the load of the UAV, different distances can be employed that suit each scenario. In addition, the area of contact between the stability unit and the non-horizontal surface can be maximized, leading to increased stability and increased maximum force that the UAV can sustain. Further details regarding that distance optimization can be found in the examples section.

[0065] In an embodiment, the thrust control unit can be configured to adjust at least one propeller to counteract gravity, and to adjust at least one propeller to provide thrust towards the non-horizontal surface. As seen in Fig. 3, the thrust control unit can adjust the front two propeller units to revolve around a vertical axis, providing thrust (303) to counteract gravity. Accordingly, the thrust control unit can adjust the rear two propeller units of Fig. 3 to revolve around a horizontal axis, providing thrust (300) towards the non-horizontal surface.

[0066] In one embodiment the thrust control unit can adjust any propeller unit such that the corresponding propeller(s) revolve around an axis, said axis forming an arbitrary angle with the earth surface. An example of that action can be seen in Fig. 4, where the two rear propeller units (400) of the UAV revolve in an arbitrary angle (p (401), defined by the earth surface (402) and the imaginary axis (403) around which the propeller revolves. A propeller revolves at an angle cp=90° when the propeller is only providing thrust to counteract gravity, as the front propeller units (40) in Fig. 4. On the other hand, a propeller revolves at an angle (p=0° when the propeller unit is tilted by 90°, as shown in the rear propeller units (304) in Fig. 3.

[0067] One purpose of choosing an arbitrary angle between 0° and 90°, is that the propeller units can provide thrust both to counteract gravity, and to provide thrust to the task performed by the manipulator. For example, if the non-horizontal surface (500) is tilted, as shown in Fig. 5, then it could be possible to tilt the rear propeller units (501) accordingly, in order to provide the optimal thrust to the manipulator and potentially also assist in stabilizing the UAV.

[0068] The schematic shown in Fig. 5 is only one of the many different propeller configurations that can be applied. Depending on the type of the non-horizontal surface, the angle of the non-horizontal surface, the task of the manipulator, and other parameters such as the weight of the UAV and the position of the center of mass, different combinations of propeller angles can be used by the thrust control unit.

[0069] Furthermore, the UAV can be configured such that the main body further comprises at least one horizontal bar on which the second group of the propeller units are attached, wherein said horizontal bar is configured to rotate around an axis defined by a longitudinal extension of the bar, thereby controlling the thrust direction of the second group of propeller units. The purpose of having such a bar is that it would be possible to simultaneously control a plurality of propeller units, such as the rear propeller units, to provide the same amount of thrust at the same direction. That can be beneficial as that ensures that no stability issues are created when rotating a group of propeller units. A schematic of a horizontal bar (600) on which a group of propeller units (601) is attached can be seen in Fig. 6. In this example, the UAV comprises four propeller units, each of which comprises of two propellers with corresponding rotors.

[0070] Propeller units

[0071] The presently disclosed UAV may comprise at least one junction positioned between a propeller unit and the main body, configured to rotate said propeller unit across the entire range of orientations within a hemisphere. The purpose of such a junction is to allow a propeller unit to oriented at any angle, allowing the UAV to navigate towards any direction, or allowing a group of propeller units to provide thrust towards a preferred direction. Such a junction can optionally be used in combination with the horizontal bar described above.

[0072] Moreover, the presently disclosed UAV may comprise at least four propeller units, wherein optionally each propeller unit comprises at least two co-axial rotors and propellers. Depending on the manipulator that is carried on the UAV, and the tasks that need to be performed, more or fewer propeller units can be mounted on the UAV to provide additional thrust to counteract gravity and to assist the manipulator in performing the tasks on the non-horizontal surface. Each propeller can comprise at least two blades, such as three, four or six blades. In addition, the UAV can be configured, such that each propeller unit provides thrust of more than two Newton. Preferably, each propeller unit can provide thrust of at least half of the total thrust that the UAV can deliver, such that it can be possible for a propeller unit to only provide thrust to counteract gravity, while the other propeller units provide thrust towards the manipulator.

[0073] Displacement mechanism of the main body

[0074] An important aspect of the present disclosure is the function of the displacement mechanism of the main body of the UAV. In one embodiment the UAV is configured such that upon contact with the non-horizontal surface, the displacement mechanism moves the main body towards the non-horizontal surface, preferably such that the center of mass of the UAV is aligned with the first group of propeller units. For example, as seen in Fig. 1 and Fig. 2, the main body (102) can be designed to also be the center of mass of the UAV. Once the UAV approaches the non-horizontal surface (200), the displacement mechanism can move the center of mass such that it is aligned with the first group of propeller units. It is advantageous that the center of mass is aligned with respect to a group of propeller units, as that can improve the stability of the UAV.

[0075] For example, if the first group of propeller units comprises four propellers, and the center of mass is shifted towards one of the four, then the stability of the UAV might not be optimal. If however the center of mass is positioned at the geometrical center defined by the four propellers, then the center of mass is aligned with the four propeller.

[0076] In certain scenarios, it may be beneficial that the center of mass is not perfectly aligned with the first group of propeller units, for example when the UAV needs to be tilted to perform a certain task.

[0077] In another embodiment, when the displacement mechanism moves the main body of the UAV towards a first group of propeller units, the second group of propeller units gradually rotate from an angle cp=90° to an angle (p=0°.

[0078] Furthermore, as also described in the sections above, the displacement mechanism can be configured to displace the main body of the UAV with three translational degrees of freedom, thereby preferably with the ability of adjusting the center of mass of the UAV in any spatial direction. The three degrees of freedom can be understood as displacing the main body of the UAV in all three spatial directions. Depending on the type of application or task that is to be carried by the UAV, the displacement mechanism may displace the center of mass (CoM) longitudinally, transversely, or vertically. Longitudinal displacement may be understood as shifting the CoM forward or backward along the UAV’s main axis, which affects its pitch characteristics and aerodynamic balance. Transverse displacement involves moving the CoM side-to-side, perpendicular to the longitudinal axis, influencing roll stability and lateral maneuverability. Vertical displacement adjusts the CoM upward or downward relative to the UAV’s frame, impacting overall stability, hover efficiency, and the UAV’s ability to counteract external forces such as wind or payload shifts. Additionally, vertical displacement may be advantageous when using the UAV to land on a fluid surface, such as water. By enabling controlled movement of the CoM in these three directions, the displacement mechanism enhances the UAV’s adaptability to different flight conditions and operational requirements.

[0079] A key advantage of vertical CoM displacement is its potential to facilitate controlled water landings. In conventional UAV designs, a fixed CoM can lead to instability when landing on water, increasing the risk of capsizing or improper flotation. By actively lowering the CoM, the UAV can achieve a more stable floating posture, reducing the likelihood of tipping over due to external disturbances such as waves or wind. Additionally, shifting the CoM downward alters the UAV’s buoyancy distribution, allowing it to maintain a desired waterline position, ensuring that flotation elements or waterproofed sections remain above the surface. Conversely, raising the CoM may assist in controlled water take-off by adjusting the UAV’s balance to optimize propulsion efficiency during lift-off. This dynamic CoM adjustment enhances the UAV’s versatility, enabling seamless operation across both aerial and aquatic environments. Specifically, by adjusting the center of mass of the UAV it is possible to achieve stability of the UAV by having the center of gravity of the UAV below the metacenter of the buoyancy. The metacenter is defined as the point where the line of action of the buoyancy force before rotation and the line of action of the buoyancy force after rotation intersect. As a result, by displacing the center of mass it is possible to have a UAV that can be stable while floating on water, even with the presence of disturbances such as waves or wind gusts.

[0080] Moreover, the UAV can be configured, such that the main body comprises a load cell configured to provide the position of the main body relative to the displacement mechanism. Such a load cell can be utilized by the thrust control unit in order to determine the amount of thrust required to counteract gravity, and therefore adjust the propeller units of the UAV accordingly. Several types of load cells can be used, such as pneumatic load cells, hydraulic load cells or strain gauge load cells. In addition, a load cell can be utilized to provide information as to where the center of mass is located in the UAV. Such information can be important, as it can be used to optimize the operation of the propeller units and the manipulator.

[0081] In an embodiment the displacement mechanism comprises at least two tracks / rails, on which the main body can be attached, such that the main body can be displaced along the tracks / rails. In another embodiment, the displacement mechanism comprises at least one linear shaft on which the main body can be attached, such that the main body can be displaced along the at least one linear shaft. Alternatively, the displacement mechanism comprises at least one periscopic extension unit on which the main body can be attached, such that the main body can be displaced along the at least one periscopic extension unit. Such mechanisms can be used to successfully displace the main body of the UAV. Any other displacement mechanism can be utilized, as long as such a displacement mechanism can carry move the main body of the UAV and provide the necessary stability.

[0082] An example of the presently disclosed UAV is shown in fig. 7. The main body (700) can be displaced along the two tracks (701) in order to displace the center of mass of the UAV and align it with a first group of propeller units (702). A stability unit (703) can also be utilized, and in this embodiment each propeller unit comprises two co-axial rotors with propellers.

[0083] Furthermore, the presently disclosed UAV may comprise a battery for powering the plurality of the propeller units, the displacement mechanism and the manipulator. Depending on the tasks to be performed by the manipulator, and the time that is needed for the UAV to navigate and perform the tasks, different battery types can be used. For example, for short tasks a smaller battery can be sufficient, while for heavyforce manipulation tasks a battery that can provide more energy may be needed. In an embodiment, additional energy can be delivered to the UAV from a ground power unit, through cable transmission.

[0084] The presently disclosed UAV can further comprise an optical sensor, such as a camera, for imaging, detecting or capturing video of the non-horizontal surface. Such a sensor can be beneficial, as it can provide feedback to a user for the status of a surface that is examined, and it can assist into optimizing the tasks to be performed by the manipulator. It may also be possible to collect video data and store them at a data storage on the main body of the UAV, which can be retrieved at a later stage by a user. Depending of the task that the UAV is performing, it is possible to stream video data directly to another computing unit, where a user can continuously monitor the data that the UAV collects. The UAV may also comprise a weight sensor, configured to measure the load of the main body and the manipulator. Other types of sensors that can be utilized are an accelerator sensor or a contact sensor, providing data as to when the UAV has been in contact with a surface.

[0085] Moreover, the UAV can comprise a sensor for measuring the force exerted by the manipulator to provide feedback for the operation of the propeller units. For example, such a sensor can provide feedback to the thrust control unit, which can then optimize the angle of each propeller and the power provided by each propeller, to properly balance the UAV during the manipulation task, and to provide the necessary thrust to the manipulator.

[0086] In an embodiment, the manipulator can be configured to perform any of the actions selected from the group comprising: drilling, soldering, screwing, spraying, painting, loading materials and unloading materials. Generally, the manipulator can be a modular unit, easily customizable to be attached with any kind of tool that might be required to perform a task in an aerial non-horizontal surface.

[0087] The present disclosure further relates to a computer implemented method for adjusting the thrust direction of a plurality of propeller units in a UAV, comprising: obtaining at least one propeller for providing thrust for carrying and navigating the UAV, obtaining a main body of the UAV, wherein a thrust control unit adjusts the orientation of the plurality of propeller units with respect to the main body of the UAV, such that the direction of thrust can be modified.

[0088] A further way that the present disclosure is fundamentally different from state of the art solutions, is that the adjustment of thrust and the displacement of the main body of the UAV can be performed in a synchronized manner, allowing to further increase the provided thrust towards a non-horizontal surface, where a high-force manipulation task is to be performed. Moreover, the synchronized motion of the main body of the UAV and the propeller units can provide further stability to the UAV. In certain situations, the propeller units can cooperate to make sure that the gravitational component of the UAV is counteracted. The propeller units’ thrust depends on the position of the center of mass of the UAV, therefore the position of the main body of the UAV can be synchronized with the propeller units, to optimize the thrust output of the propellers. Once the gravity is compensated by the propeller units, a first part of the propellers can spin at a lower rate, since the gravitational component is compensated by a second part of the propellers. The first part of the propellers can then be utilized to provide thrust to other directions, such as generating a push force acting in a forward or backward direction with respect to a non-horizontal surface that is positioned in front of the UAV. More complex mechanisms can also be utilized, in order to generated forces in arbitrary directions.

[0089] Examples

[0090] An example showing the synchronized manner of displacing the main body of the UAV and changing the direction of a number of propeller units is shown in Figure 9 A-D. In Figure 9A, a UAV (900) is initially on fly mode, where all of the four sets of propellers (901) are providing thrust to counteract gravity. Shown in Figure 9B, when the UAV moves towards a non-horizontal surface (902), the rear propellers (903) can start rotating, such that their provided thrust can be both used to counteract gravity, and to assist an operation that can be handled by the UAV. Simultaneously, the main body of the UAV (904) can be displaced towards the non-horizontal surface. The UAV can establish contact (905) with the non-horizontal surface (902), while the rear propellers have rotated further (903). As shown in Figure 9D, the main body of the UAV (904) can be displaced further towards the non-horizontal surface, while the rear propellers (903) are rotated such that they provide thrust perpendicular to the non-horizontal surface. Utilizing that thrust, a manipulator that can be equipped on the main body of the UAV (904) can perform a plurality of tasks on the non-horizontal surface.

[0091] Fig. 10A shows schematics that illustrate the limit conditions for an example of the presently disclosed UAV when it comes in contact with a non-horizontal surface. Initially, the UAV can establish contact with the non-horizontal surface (1000) having the rear propellers (1001) providing a force Fprop (1007) towards the non-horizontal surface, which is equalized by a reaction force from the surface Fc(1002) having the opposite direction but same magnitude with the FprOp. Then, when the manipulator (1003) comes into contact and possibly exerts a force to the non-horizontal surface, in equilibrium, the forces that are in play are adjusted as Fc=Fprop-Fman wherein Fman is the reaction force exerted by the non-horizontal surface due to the force of the manipulator. Accordingly, a torque is generated rc=Fman ■ decwhere dec(1008) is the distance between the center of the contact point of the stability unit (1004) and the contact point of the manipulator (1005). If the force exerted by the rear propellers is the maximum possible, then the rear propellers are in saturation, meaning that they cannot provide further thrust. Limit conditions can be incurred on the Fcand TC. In particular, if it is possible to consider the maximum force exerted by the non-horizontal surface as a reaction to the forces caused by the UAV as Fc max=FProp max-Fman ■ (dec-dcp) / dcp wherein dcp(1009) is the distance between the center of the contact point of the stability unit (1004) and the pivot point (1006). If the Fc max force is zero, that would mean that the UAV is detached from the non-horizontal surface, and the stability unit makes no contact with the non-horizontal surface. At the limit of that equation, where the two parts are equal, the maximum external force that the system can sustain is Fman=FprOp max ■ dcp / ( dec-dcp). It is possible to affect the limit of that equation, by modifying the shape of the stability unit and the distance between the manipulator and the center of the stability unit such as (dec-dcp) / dcp is as small as possible. Effectively, that would mean that the point of contact of the manipulator to the non-horizontal surface is as close as possible to the center of the stability unit. In addition, it is also possible to limit the value of Fman if allowed by the task performed, and further it is possible to increase the force exerted by the propellers.

[0092] A further use case of the present disclosure is described below. A possible use case benefitting from the center of mass displacement can be landing the UAV on a water surface. Landing on water can be achieved by lowering the center of mass lower than the propellers. In this context, considering that the UAV is able to float on water - meaning that there is a buoyant force applied to the center of buoyancy of the UAV that is floating on water - displacing the center of mass below the water surface will increase the stability of the UAV against disturbances such as waves, thereby enabling the UAV to land successfully on water and float.

[0093] Figs. 11 A-B show an example of a UAV that is floating on water, where there is no displacement of the main body of the UAV. A gravitational force W 1103 and a buoyant force Fb 1104 are applied on the UAV. Assuming that the UAV is floating, these two forces are equal. In this example, the metacenter 1100 is below the center of gravity 1101 of the UAV, leading to instability of the UAV in the presence of disturbances in the water, such as waves. Therefore, a tilt of the robot of an angle 0 1102 would lead to the UAV capsizing.

[0094] Figs. 12 A-B show an example of a UAV that is floating on water, where the main body has been displaced vertically, thereby leading to the metacenter 1200 being above the center of gravity 1201 of the UAV. As a result, the UAV can be stable in the presence of waves or wind gusts, and when tilted by an angle 0 1202 that would lead to the UAV being restored to its original balanced state. A gravitational force W 1203 and a buoyant force Fb 1204 are applied on the UAV.

[0095] Fig. 13A shows an example of a UAV where the main body is on its default position. The displacement mechanism comprises a rail 1300 wherein the main body 1301 is attached to. In fig. 13B the rail is activated, thereby displacing the main body of the UAV in a vertical direction 1302 and modifying its center of mass. In this example, the thrust control unit modifies the direction of a propeller unit 1303, in order to individually adjust the thrust vector generated by that propeller unit and provide stability on the UAV.

[0096] Fig. 14A shows an example of a UAV wherein the displacement mechanism comprises a joint 1400 configured to enable rotation of the main body around a transverse axis of the UAV. In Fig 14A the main body 1401 is on its default position, while in Fig. 14B the joint has been rotated by 90° thereby repositioning the main body and adjusting the center of mass of the UAV. As also described in the sections above, such a readjustment of the center of mass can provide stability on the UAV when floating on water, and it may also be used for a plethora of applications, such as for optimizing the thrust when performing high-force tool manipulation, or for optimizing the navigation of the UAV.

[0097] Further modifications may be done on the UAV, such as having a joint enabling the rotation of the main body around a longitudinal or around a vertical axis of the UAV.

[0098] Items

[0099] 1. An unmanned aerial vehicle (UAV) for manipulation of a non-horizontal surface of a structure, comprising:

[0100] - a plurality of propeller units for providing thrust for carrying and navigating the UAV,

[0101] - a main body comprising a manipulator for manipulating the non-horizontal surface,

[0102] - a displacement mechanism for moving the main body and the manipulator within the UAV, thereby displacing the center of mass of the UAV, wherein the UAV comprises a thrust control unit configured to adjust a thrust direction of at least one of the propeller units, such that a first group of the propeller units predominantly provide thrust to counteract gravity, and a second group of the propeller units predominantly provide thrust in a direction perpendicular to the non-horizontal surface.

[0103] 2. The UAV according to item 1 , comprising a fly mode where the propeller units cooperate to fly and navigate the UAV in the air, and a surface manipulation mode when contacting the non-horizontal surface while hovering, where the center of mass of the UAV is aligned with the first group of propeller units, such that the thrust of the first group of propeller units counteracts gravity, and where the second group of propeller units is oriented to provide thrust towards the non- horizontal surface such that the second group of propeller units provide thrust to the manipulator.

[0104] 3. The UAV according to any one of the preceding items, further comprising a stability unit, configured to maintain contact with the non-horizontal surface to stabilize the UAV.

[0105] 4. The UAV according to item 3, wherein the stability unit comprises a plurality of contact points for contacting the non-horizontal surface.

[0106] 5. The UAV according to item 4, wherein the contact points comprise a plurality of rods for maintaining contact with the non-horizontal surface.

[0107] 6. The UAV according to item 3, comprising a plurality of hooks for providing contact and / or securing the UAV to the non-horizontal surface.

[0108] 7. The UAV according to any one of the preceding items, wherein the thrust control unit is configured to adjust at least one propeller to counteract gravity, and to adjust at least one propeller to provide thrust towards the non-horizontal surface. The UAV according to any one of the preceding items, wherein the main body further comprises at least one horizontal bar on which the second group of the propeller units are attached, wherein said horizontal bar is configured to rotate around an axis defined by a longitudinal extension of the bar, thereby controlling the thrust direction of the second group of propeller units. The UAV according to any one of the preceding items, configured such that upon contact with the non-horizontal surface, the displacement mechanism moves the main body towards the non-horizontal surface, such that the center of mass of the UAV is aligned with the first group of propeller units. The UAV according to item 2, where in the fly mode, all propeller units cooperate to navigate the UAV in the air, and where in the surface manipulation mode, a first group of the propeller units revolve parallel to the main body, thereby providing thrust to counteract gravity, and a second group of propeller units revolve perpendicular to the main body, thereby providing thrust towards the non-horizontal surface. The UAV according to any one of the preceding items, wherein the main body comprises a load cell configured to provide the position of the main body relative to the displacement mechanism. The UAV according to any one of the preceding items, comprising at least one junction positioned between a propeller and the main body, configured to rotate said propeller across the entire range of orientations within a hemisphere. The UAV according to any one of the preceding items, wherein each propeller is configured to provide thrust of more than 2 Newton. The UAV according to any one of the preceding items, comprising at least four propeller units. The UAV according to any one of the preceding items, wherein each propeller unit comprises at least two co-axial rotors. 16. The UAV according to any one of the preceding items, wherein the displacement mechanism comprises at least two tracks / rails, on which the main body can be attached, such that the main body can be displaced along the tracks / rails.

[0109] 17. The UAV according to any one of the preceding items, wherein the displacement mechanism comprises at least one linear shaft on which the main body can be attached, such that the main body can be displaced along the at least one linear shaft.

[0110] 18. The UAV according to any one of the preceding items, wherein the displacement mechanism comprises at least one periscopic extension unit on which the main body can be attached, such that the main body can be displaced along the at least one periscopic extension unit.

[0111] 19. The UAV according to any one of the preceding items, comprising a battery for powering the plurality of the propeller units, the displacement mechanism and the manipulator.

[0112] 20. The UAV according to any one of the preceding items, comprising an optical sensor, such as a camera, for imaging I detecting I capturing video of the nonhorizontal surface.

[0113] 21. The UAV according to any one of the preceding items, comprising a sensor for measuring the force exerted by the manipulator to provide feedback for the operation of the propeller units.

[0114] 22. The UAV according to any one of the preceding items, wherein the manipulator is configured to perform any of the actions selected from the group comprising: drilling, soldering, screwing, spraying, painting, loading materials and unloading materials.

[0115] 23. The UAV according to any one of the preceding items, wherein the distance between the point of contact of the manipulator to the non-horizontal surface and the central point of contact of the stability unit to the non-horizontal surface is preferably less than 150 cm, even more preferably less than 100 cm, most preferably less than 75 cm, most preferably less than 40 cm. A computer implemented method for adjusting the thrust direction of a plurality of propeller units in a UAV, such as the UAV according to any of the preceding claims, comprising: obtaining at least one propeller for providing thrust for carrying and navigating the UAV, obtaining a main body of the UAV, wherein a thrust control unit adjusts the orientation of the plurality of propeller units with respect to the main body of the UAV, such that the direction of thrust can be modified. Use of a UAV to manipulate a non-horizontal surface of a structure, wherein the UAV is configured according to any of items 1-23.

Claims

Claims1. An unmanned aerial vehicle (UAV) comprising• a main body,• a frame,• a plurality of propeller units attached to the frame, and• a displacement mechanism configured to displace with three translational degrees of freedom the main body of the UAV with respect to the frame, thereby adjusting the center of mass of the UAV in any spatial direction.

2. The UAV according to claim 1 , comprising a thrust control unit for controlling the direction and power of the plurality of propeller units, the thrust control unit configured to individually adjust the direction of each of the plurality of propeller units, thereby causing any of the propellers units to apply a thrust vector to be directed along any arbitrary vector in three-dimensional space.

3. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises a linear actuator configured to translate the main body along a longitudinal direction.

4. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises a linear actuator configured to translate the main body along a transverse direction.

5. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises a linear actuator configured to translate the main body along a vertical direction.

6. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises a rail system enabling guided translation of the main body in at least one spatial direction.

7. The UAV according to any one of the preceding claims, wherein the displacement mechanism is configured to shift the center of mass downward thereby improving buoyancy and stability when landing on a water surface.

8. The UAV according to any one of the preceding claims, comprising a ballast, the ballast configured to adjust the center of mass of the UAV by rotating about a longitudinal, transverse, and / or vertical axis of the UAV.

9. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises one or more joints configured to enable rotation of the main body around a longitudinal, transverse and / or vertical axis of the UAV.

10. The UAV according to any one of the preceding claims, wherein the displacement mechanism is configured to adjust the center of mass by rotating the main body about a longitudinal, transverse and / or vertical axis of the UAV.

11. The UAV according to any one of the preceding claims, wherein the main body comprises a manipulator for manipulating a non-horizontal surface, and wherein the thrust control unit is configured to adjust a thrust direction of at least one of the propeller units, such that a first group of the propeller units predominantly provide thrust to counteract gravity, and a second group of the propeller units predominantly provide thrust in a direction perpendicular to the non-horizontal surface.

12. The UAV according to claim 11, comprising a fly mode where the propeller units cooperate to fly and navigate the UAV in the air, and a surface manipulation mode when contacting the non-horizontal surface while hovering, where the center of mass of the UAV is aligned with the first group of propeller units, such that the thrust of the first group of propeller units counteracts gravity, and where the second group of propeller units is oriented to provide thrust towards the non- horizontal surface such that the second group of propeller units providethrust to the manipulator.

13. The UAV according to any one of the claims 11-12, further comprising a stability unit, configured to maintain contact with the non-horizontal surface to stabilize the UAV.

14. The UAV according to any one of claims 11-13, wherein the stability unit comprises a plurality of contact points for contacting the non-horizontal surface.

15. The UAV according to claim 14, wherein the contact points comprise a plurality of rods for maintaining contact with the non-horizontal surface.

16. The UAV according to any one of claims 11-15, comprising a plurality of hooks for providing contact and / or securing the UAV to the non-horizontal surface.

17. The UAV according to any one of claims 11-16, wherein the thrust control unit is configured to adjust at least one propeller to counteract gravity, and to adjust at least one propeller to provide thrust towards the non-horizontal surface.

18. The UAV according to any one of the claims 2-17, wherein the main body further comprises at least one horizontal bar on which a group of the propeller units are attached, wherein said horizontal bar is configured to rotate around an axis defined by a longitudinal extension of the bar, thereby controlling the thrust direction of said group of propeller units.

19. The UAV according to any one of claims 11-18, configured such that upon contact with the non-horizontal surface, the displacement mechanism moves the main body towards the non-horizontal surface, such that the center of mass of the UAV is aligned with the first group of propeller units.

20. The UAV according to claim 12, where in the fly mode, all propeller units cooperate to navigate the UAV in the air, and where in the surface manipulation mode, a first group of the propeller units revolve parallel to the main body, thereby providing thrust to counteract gravity, and a second group of propeller units revolve perpendicular to the main body, thereby providing thrust towardsthe non-horizontal surface.

21. The UAV according to any one of the preceding claims, wherein the main body comprises a load cell configured to provide the position of the main body relative to the displacement mechanism.

22. The UAV according to any one of the preceding claims, comprising at least one junction positioned between a propeller and the main body, configured to rotate said propeller across the entire range of orientations within a hemisphere.

23. The UAV according to any one of the preceding claims, wherein each propeller is configured to provide thrust of more than 2 Newton.

24. The UAV according to any one of the preceding claims, comprising at least four propeller units.

25. The UAV according to any one of the preceding claims, wherein each propeller unit comprises at least two co-axial rotors.

26. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises at least two tracks / rails, on which the main body can be attached, such that the main body can be displaced along the tracks / rails.

27. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises at least one linear shaft on which the main body can be attached, such that the main body can be displaced along the at least one linear shaft.

28. The UAV according to any one of the preceding claims, wherein the displacement mechanism comprises at least one periscopic extension unit on which the main body can be attached, such that the main body can be displaced along the at least one periscopic extension unit.

29. The UAV according to any one of the preceding claims, comprising a battery for powering the plurality of the propeller units and the displacement mechanism and the manipulator.

30. The UAV according to any one of claims 11-29, comprising a battery for powering the manipulator.

31. The UAV according to any one of claims 11-30, comprising an optical sensor, such as a camera, for imaging I detecting I capturing video of the non-horizontal surface.

32. The UAV according to any one of claims 11-31, comprising a sensor for measuring the force exerted by the manipulator to provide feedback for the operation of the propeller units.

33. The UAV according to any one of claims 11-32, wherein the manipulator is configured to perform any of the actions selected from the group comprising: drilling, soldering, screwing, spraying, painting, loading materials and unloading materials.

34. The UAV according to any one of claims 11-33 wherein the distance between the point of contact of the manipulator to the non-horizontal surface and the central point of contact of the stability unit to the non-horizontal surface is preferably less than 150 cm, even more preferably less than 100 cm, most preferably less than 75 cm, most preferably less than 40 cm.

35. A computer implemented method for adjusting the thrust direction of a plurality of propeller units in a UAV, such as the UAV according to any of the preceding claims, comprising: obtaining at least one propeller for providing thrust for carrying and navigating the UAV, obtaining a main body of the UAV, wherein a thrust control unit adjusts the orientation of the plurality of propeller units with respect to the main body of the UAV, such that the directionof thrust can be modified.

36. Use of a UAV to manipulate a non-horizontal surface of a structure, wherein the UAV is the UAV according to any one of claims 11-34.

Images