Aéronef

Abstract

Title: Aircraft The invention relates to an aircraft comprising a carrier structure (1) and at least three propellers (21, 22, 23) attached to the carrier structure (1), each propeller (21, 22, 23) being configured to generate a thrust vector in at least one direction, said aircraft being characterized in that each propeller (21, 22, 23) is orientable independently of the other propellers (21, 22, 23), so as to form a combination of thrust vectors such that the carrier structure (1) can be kept stationary at any pitch angle θ, the pitch angle θ being defined between a yaw axis (z) of a frame (O, x, y, z) relative to the carrier structure (1) and a reference axis (Z) of an absolute frame (O, X, Y, Z). The invention also relates to a method for controlling the flight of such an aircraft. See Fig. 3 for the abstract.

Description

Title of the invention: Aircraft technical field

[0001] The present invention relates to the field of aeronautical transport. Its application is particularly advantageous in the production of aircraft, especially aerostats, with enhanced flight capabilities. STATE OF THE ART

[0002] Aircraft typically include "heavier-than-air" devices, called aerodynes, and "lighter-than-air" devices, called aerostats. The aerodyne generates a dynamic force to balance its weight (this is the case of a helicopter, for example), while the aerostat uses a static force to balance at least partially its weight (this is the case of a dirigible, for example).

[0003] Aircraft are essentially used to move through the air in all directions of space. In an absolute (O, X, Y, Z) coordinate system of the flight space, an aircraft can move in translation along X and / or Y and / or Z. Some aircraft cannot move along Z independently of their movement along X. This is typically the case for airplanes, which use the lift generated by airspeed to maintain their flight. To steer, aircraft use, in particular, aerodynamic control surfaces that allow certain rotational movements. These rotational movements are generally described in a (O, x, y, z) coordinate system relative to the aircraft's structure. A rotation around the x-axis of this relative coordinate system corresponds to a roll movement. A rotation around the y-axis of this relative coordinate system corresponds to a pitch movement. A rotation around the z-axis of this relative coordinate system corresponds to a yaw movement.

[0004] In addition to their movement capabilities, some aircraft can also perform hovering. In this case, translational movements along the axes (X, Y, Z) of the absolute frame of reference (O, X, Y, Z) are made independent.

[0005] An airship, for example, has the ability to move through the surrounding space thanks to its propellers and aerodynamic control surfaces. Complete rotation around the z-axis, known as the yaw axis, is possible, notably by using a bow thruster. Rotation around the x-axis, known as the roll axis, is limited. Rotation around the y-axis, known as the pitch axis, is limited. In practice, airships can control their attitude within a pitch angle θ between -20° and +20°. The pitch angle θ is defined between the yaw axis z of the relative frame of reference (O, x, y, z) and the vertical reference axis Z of the absolute frame of reference.

[0006] The aircraft's movement capabilities therefore remain limited.

[0007] One object of the present invention is to overcome at least in part the disadvantages of known solutions.

[0008] In particular, an object of the present invention is to propose an aircraft exceeding the displacement limitations of current aircraft and / or offering extensive hovering capabilities.

[0009] Another object of the present invention is to propose a method for flight control of such an aircraft.

[0010] The other objects, features and advantages of the present invention will become apparent from an examination of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0011] To achieve this objective, a first aspect of the invention relates to an aircraft comprising a carrier structure and at least three non-collinear thrusters attached to the carrier structure, each thruster being configured to generate a thrust vector in at least one direction.

[0012] Advantageously, each thruster is steerable independently of the other thrusters. Each thruster is steerable independently of the other thrusters so as to form a combination of vector thrusts such that the supporting structure can be maintained stationary at any pitch angle 0. For a given range of pitch angles 0, the pitch angle 0 is defined between a yaw axis of a frame relative to the supporting structure and a reference axis of an absolute frame, typically linked to the flight space.

[0013] Thus, the aircraft can typically be positioned "on its side," in hover. Such positioning is only possible if the thrusters can be oriented and controlled independently of each other. In particular, the combination of thrust vectors is configured to produce a force moment opposing the gravitational restoring moment exerted on the supporting structure, with an equal or greater magnitude. These extended flight capabilities offer a wide range of applications. In the field of photography, for example, for inspection or imaging, a camera carried as part of the aircraft's payload can be directed in any direction without the aircraft's supporting structure acting as a shield. When the aircraft is used for inspections, it can get as close as possible to the surface to be inspected by positioning itself "on its side."When the aircraft is used for advertising or communication purposes, it can perform much more "rich" and complex maneuvers than those expected of a conventional helicopter or airship. The combinations of translation and / or rotation, while moving or hovering, are far more numerous with such an aircraft.

[0014] Preferably, the combination of vector thrusts allows complete rotations of the supporting structure around each of the yaw, roll, and pitch axes of the frame of reference relative to the supporting structure, and translations of the supporting structure along each of said axes of the relative frame of reference. Advantageously, such an aircraft does not use control surfaces for orientation.

[0015] According to a preferred embodiment, the aircraft is an aerostat. The supporting structure typically includes an envelope configured to contain a gas lighter than the air surrounding the supporting structure. This allows for the partial or total compensation or balancing of the gravitational force acting on the supporting structure. The thrust vector of each propellant can be reduced.

[0016] Another aspect of the invention relates to a method for controlling the flight of such an aircraft, comprising at least one of the following movements: • a rotational movement about the yaw axis combined with a translational movement along a direction in a plane normal to the yaw axis, the yaw axis preferably forming a 90° angle with the reference axis. The aircraft typically moves like a wheel in the flight space. This movement of the aircraft typically occurs along a horizontal axis, combined with a rotation about an axis perpendicular to the horizontal axis of movement. • A 180° rotational movement around a pitch or roll axis of the reference frame relative to the supporting structure, so as to flip the supporting structure while remaining in a hover. Such a movement is similar to a "turn-on-the-spot" maneuver of the aircraft. It differs from a loop or a roll performed by a moving aircraft, such as an airplane. • a translational movement along the Z-axis, with the yaw axis forming a 90° angle with the Z-axis. The aircraft typically moves on its side during climbs and / or descents. This helps reduce drag during climbs / descents. BRIEF DESCRIPTION OF THE FIGURES

[0017] The aims, objects, features and advantages of the invention will become clearer from the detailed description of embodiments thereof, which are illustrated by the following accompanying drawings in which:

[0018] [Fig.1] Fig.1 illustrates the different reference frames, in this case an absolute reference frame (O, X, Y, Z) linked to the flight space, and a relative reference frame (O, x, y, z) linked to the supporting structure, according to an embodiment of the present invention.

[0019] [Fig.2] Figure [Fig.2] illustrates in perspective an aircraft according to an embodiment of the present invention.

[0020] [Fig.3] Fig.3 illustrates in perspective an aircraft according to another embodiment of the present invention.

[0021] [Fig.4] Fig.4 illustrates a propulsion unit linked to a supporting structure according to an embodiment of the present invention.

[0022] [Fig.5] The [Fig.5] illustrates in perspective an aircraft according to another embodiment of the present invention.

[0023] [Fig.6] [Fig.7] Figures 6 and 7 illustrate in perspective a propulsion system according to a embodiment of the present invention.

[0024] [Fig.8] Fig.8 illustrates the movement of an aircraft according to an embodiment of the present invention.

[0025] [Fig.9] Fig.9 illustrates the movement of an aircraft according to another embodiment of the present invention.

[0026] [Fig.10A][Fig.10B][Fig.10C] Figures 10A to 10C illustrate stages of an aircraft movement, according to an embodiment of the present invention.

[0027] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of the principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the dimensions of the various elements (supporting structure, casing, propulsion systems, etc.) may vary from the proportions illustrated in the schematic diagrams. DETAILED DESCRIPTION

[0028] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:

[0029] According to one example, each thruster is orientable in any direction in space. According to another example, the thrust vector of each thruster is individually controllable. Preferably, the thrust vector is individually controllable in magnitude and direction.

[0030] According to one example, the aircraft is configured so that the combination of thrust vectors produces a moment of force greater than the gravitational restoring moment exerted on the supporting structure. This makes it possible, in particular, to position the aircraft in hover.

[0031] In one example, the given pitch angle range is between 0° and 60°. In another example, the given pitch angle range is between 0° and 90°. The aircraft can thus exhibit any pitch angle while hovering.

[0032] According to one example, the thrusters are identical to each other and arranged on the load-bearing structure such that, for any 0 pitch angle in the range of 0 pitch angles, the combination of vector thrusts simultaneously counterbalances the weight of the aircraft and counterbalances the gravitational restoring moment exerted on the load-bearing structure.

[0033] In one example, the thrusters are identical. In another example, the aircraft comprises four thrusters equally distributed on the supporting structure. In another example, the thrusters are diametrically opposed around the supporting structure, in pairs. In another example, the thrusters have a barycenter defining a center of pressure P, the supporting structure has a center of gravity G, and the center of pressure P and the center of gravity G are coincident or separated by a distance d such that

[0034] [Math.l]

[0035] with m the mass of the aircraft, g the acceleration due to gravity, T the maximum thrust vector exerted by each thruster, and L the distance between the center of thrust P and each thruster. When this condition is met, the thrust available from all the thrusters typically compensates for the gravitational restoring moment acting on the aircraft and simultaneously provides lift. Such a distance d is thus sufficiently small so that the combination of thrust vectors can keep the supporting structure stationary at any pitch angle, particularly when the aircraft is on its side, i.e., at a pitch angle of 90°. Preferably, the distance d is sufficiently small so that the combination of thrusts generates a moment greater than the gravitational restoring moment exerted on the supporting structure.The thrust combination is configured to support the weight of the aircraft and to compensate for the gravitational restoring moment, so that the stationary position can be maintained at any pitch angle.

[0036] According to one example, the combination of vector thrusts allows complete rotations of the supporting structure respectively around each of the yaw axis z, roll axis x and pitch axis y of the frame relative to the supporting structure, and translations of the supporting structure respectively along each of said axes x, y, z of the relative frame.

[0037] According to one example, the supporting structure includes an envelope configured to contain a gas lighter than the air surrounding the supporting structure. This makes it possible to at least partially compensate for the weight of the supporting structure and / or the aircraft. The aircraft is typically in this case an aerostat. The supporting structure thus typically has a center of buoyancy F. According to one example, the center of pressure P and the The center of buoyancy F is essentially coincident. In the case where the center of buoyancy F and the center of gravity G are coincident or separated by a distance d, the above formula [Mathl] is applicable. Part of the weight is relieved due to the buoyancy of the aerostat. For the sizing of the propulsion systems, it is therefore possible to introduce a "virtual" mass m' into the formula [Mathl], strictly less than m, to account for the buoyancy of the aerostat.

[0038] According to one example, the envelope has a rotational symmetry around the yaw axis of the frame relative to the supporting structure.

[0039] In one example, the envelope has a toroidal shape defining a central volume. In one example, the central volume is at least partially occupied by a payload. In one example, the central volume is configured to accommodate a payload. Preferably, the aircraft includes receiving means (platform, attachment loop, beams) for housing a payload within the central volume. In one example, the payload is entirely housed within the central volume. Thus, the payload does not protrude outside the central volume. In one example, the central volume is at least partially faired.

[0040] According to one example, each of the propellers comprises a frame and four propellers fixed to the frame, each propeller being controllable independently of the other propellers, the frame being articulated with respect to the supporting structure with two degrees of rotational freedom. Preferably, the frame is articulated with respect to the supporting structure by means of a spherical finger joint.

[0041] According to one example, the aircraft comprises three first thrusters defining a first plane PI, and three second thrusters defining a second plane P2 parallel to the first plane PI. According to one example, the first three thrusters of the first plane PI are distributed at 120° to each other about the yaw axis of the frame of reference relative to the supporting structure, the three second thrusters of the second plane P2 are distributed at 120° to each other about said yaw axis, and the first three thrusters of the first plane PI are offset by 60° about the yaw axis with respect to the three second thrusters of the second plane P2.

[0042] According to one example, the first and second planes PI, P2 are located at an equal distance on either side of an equatorial plane of the supporting structure, the equatorial plane being normal to the yaw axis of the frame relative to the supporting structure.

[0043] According to one example, the thrusters are all in the same plane PO parallel to an equatorial plane of the supporting structure, the equatorial plane being normal to the yaw axis of the frame of reference relative to the supporting structure, said plane PO preferably being located at a non-zero distance from the equatorial plane. This makes it easier, for example, to access the thrusters when the aircraft is on the ground, for example for maintenance.

[0044] According to one example, the aircraft typically includes a control system configured to control the thrusters, in orientation and thrust. According to an example, the control system is configured to control the thrusters in such a way as to stabilize the aircraft's attitude, preferably automatically, i.e. without human intervention.

[0045] According to one example, the aircraft includes at least one sensor called a pitch sensor, configured to measure at least one parameter relating to the pitch of the aircraft.

[0046] Except in cases of incompatibility, it is understood that all the above optional features can be combined to form an embodiment that is not necessarily illustrated or described. Such an embodiment is obviously not excluded from the invention. The features of one aspect of the invention, for example the aircraft, can be adapted mutatis mutandis to another aspect of the invention, for example the flight method.

[0047] It is specified that, within the framework of the present invention, the terms "on", "overcomes", "covers", "underlying", "opposite" and their equivalents do not necessarily mean "in contact with".

[0048] An element "based" on a material A is understood to be an element comprising only that material A or that material A and possibly other materials, for example, alloying elements. Thus, a carbon-based load-bearing structure is typically understood to be a load-bearing structure based on carbon fibers and a binder. An aluminum-based load-bearing structure is understood to be a load-bearing structure based on aluminum or an aluminum alloy. A nylon- or Kevlar-based sheath may comprise the polymer alone or the polymer with reinforcements or additives.

[0049] Several embodiments of the invention implementing successive steps of the flight control method are described below. Unless explicitly stated, the adjective "successive" does not necessarily imply, although this is generally preferred, that the steps follow each other immediately; intermediate steps may separate them.

[0050] Furthermore, the term "step" refers to the execution of a part of the process, and can designate a set of sub-steps.

[0051] Furthermore, the term "step" does not necessarily mean that the actions carried out during a step are simultaneous or immediately successive. Certain actions of a first step may, in particular, be followed by actions related to a different step, and other actions from the first step may be repeated later. Thus, the term "step" does not necessarily imply unitary actions that are inseparable in time and in the sequence of phases of the process.

[0052] A frame of reference relative to the supporting structure, preferably orthonormal, and comprising the x, y, z axes, is shown in the accompanying figures. An absolute frame of reference, preferably orthonormal, and comprising the X, Y, Z axes, is also used in this illustration. request.

[0053] The terms "vertical", "vertically" refer to a direction along Z. The relative terms "on", "surmounts", "under", "underlying", "intercalated" refer to positions taken along the direction z.

[0054] The absolute reference frame (O, X, Y, Z) corresponds to the reference frame of the flight space. In practice, it is the reference frame linked to the ground. X and Y are typically oriented according to cardinal points; for example, X is oriented north, and Y is oriented west. Z is oriented vertically. This reference frame allows the position and movement of the aircraft relative to the ground to be determined.

[0055] The (O, x, y, z) reference frame relative to the aircraft allows the aircraft's orientation to be determined with respect to the absolute reference frame. By convention, the x-axis is oriented towards the "front" of the aircraft, and the y-axis towards the left of the aircraft.

[0056] The heading of the aircraft is defined by the angle between the x-axis and the reference X-axis.

[0057] The aircraft's attitude is defined by the angle 0 between the z-axis and the reference Z-axis.

[0058] The aircraft's bank angle is defined by the angle between the y-axis and the reference Y-axis.

[0059] The z-axis is called the yaw axis, the x-axis is called the roll axis, and the y-axis is called the pitch axis.

[0060] In the context of the present invention, "hovering," "hovering," or "stationary" refers to the ability to maintain a stationary position in the absolute frame of reference, independent of weather conditions (wind gusts, air pockets, etc.). In particular, an aircraft in hover does not move in translation in the absolute frame of reference. Aircraft such as a helicopter or airplane cannot perform looping or barrel roll maneuvers while stationary.

[0061] The term "vector thrust" refers to a thrust provided by one of the propulsion units, defined in magnitude and direction, and representable by a force vector. In the following, the terms "vector thrust" and "thrust" are used interchangeably.

[0062] The gravitational restoring moment is determined with respect to the aircraft's center of gravity. The resulting torque resulting from the combination of the thrust vectors is determined with respect to the center of thrust, i.e., with respect to the center of gravity of the thrusters.

[0063] The center of pressure is not necessarily the same as the center of gravity or the center of buoyancy. The center of buoyancy is the point at which the buoyant force acts. However, for the sake of clarity and conciseness, the center of pressure and the center of buoyancy are considered to be the same in the following text. This does not limit the aircraft embodiments to such a configuration. Other embodiments may be considered.

[0064] A particular application of the invention relates to an aircraft, more specifically- A monolithic aircraft, capable of performing all translational and rotational movements in the absolute frame of reference, and all rotational movements around the three axes of the relative frame of reference, independently or in combination. Such an aircraft can advantageously be placed in all positions with respect to the absolute frame of reference, statically or dynamically.

[0065] Figure 1 schematically illustrates the absolute frame of reference O, X, Y, Z and the relative frame of reference O, x, y, z. The angle θ formed between the Z-axis of the absolute frame of reference and the z-axis of the relative frame of reference corresponds to the aircraft's pitch angle. By convention, the front of the aircraft is directed along the x-axis of the relative frame of reference, even though, in the practical case of a toroidal aircraft such as the one illustrated in Figure 1, the front is not necessarily clearly identifiable. The aircraft's positions are determined in the absolute frame of reference O, X, Y, Z. The aircraft can move in translation and / or rotation about the X, Y, Z axes of the absolute frame of reference. The aircraft can also perform, for a given fixed position in the absolute frame of reference O, X, Y, Z, one or more rotations about the x, y, z axes of the relative frame of reference.

[0066] In the following, only the relative frame O, x, y, z is represented on the figures, for the sake of clarity.

[0067] Figure 2 illustrates an aircraft according to a first embodiment of the invention. The aircraft preferably has a height dimension along the z-axis that is smaller than its dimensions along the x and y-axis. From an aerodynamic point of view, this facilitates the aircraft's movement parallel to the xy-plane. In this example, the aircraft is typically an aerostat. The aircraft here comprises a supporting structure 1 formed by a toroidal envelope 10. The envelope 10 typically comprises a lifting gas lighter than air, for example, helium, which gives the aerostat a certain buoyancy. The buoyant force acting on the aerostat can be viewed as a force applied at the center of buoyancy F. The envelope 10 can have various shapes, with or without rotational symmetry about the z-axis, for example, an oval or ovoid, discoidal, triangular, polygonal shape, etc.

[0068] Alternatively, the load-bearing structure 1 may be without an envelope 10. In this case, the aircraft typically corresponds to an aerodyne. The load-bearing structure 1 may resemble a fuselage or a frame, faired or unfaired. The load-bearing structure 1 may include elements that improve the aircraft's aerodynamics.

[0069] The supporting structure 1 is configured in particular to support the aircraft's thrusters 21, 22, 23. The thrusters 21, 22, 23 are therefore attached to the supporting structure 1 by a connection which is detailed below. The aircraft comprises at least three thrusters 21, 22, 23. In one example, the aircraft may comprise four thrusters. In another example, the aircraft may comprise six thrusters. In one possibility, the thrusters are in the same plane, regularly distributed around the z-axis. Alternatively, the thrusters are not all in the same plane, and / or are not regularly distributed around the z-axis. Specific examples are described below, without limitation. Other configurations or arrangements of thrusters may be considered, without departing from the principle of the invention.

[0070] Each of the thrusters 21, 22, 23 is configured to generate a thrust vector in different directions. The combination of the thrust vectors of the thrusters 21, 22, 23 can be viewed as a force and a moment of force applied at the center of thrust P. The thrusters 21, 22, 23 are typically controlled in orientation and thrust by an onboard or remote control system. The thrusters 21, 22, 23 can be oriented independently of each other with respect to the supporting structure 1. Their thrusts can be controlled independently of each other. The independent control of the different thrusts and orientations of the thrusters 21, 22, 23 advantageously allows the aircraft to be moved or maneuvered in any rotation in the relative frame O, x, y, z, and / or in any translation and / or rotation in the absolute frame O, X, Y, Z.Independent control of the various thrusts and directions of the propellers 21, 22, 23 advantageously allows any attitude angle to be maintained during movement or hovering. The aircraft may typically include an attitude sensor configured to determine the aircraft's attitude in real time.

[0071] The load-bearing structure 1 can be configured to carry a payload 12. In one configuration, this payload 12 is housed in the center of the load-bearing structure 1. For example, the payload 12 is housed in the central volume 11 delimited by the toroidal-shaped envelope 10, as illustrated in [Fig. 2]. The payload 12 can be used for imaging or data acquisition instruments. It can be used for transporting freight or disseminating information. Other applications are also possible.

[0072] In the case illustrated in [Fig.2], the center of gravity G, the center of thrust P and the center of buoyancy F are substantially coincident, due in particular to the symmetrical design of the supporting structure 1 and / or the envelope 10.

[0073] Figure 3 illustrates an aircraft according to a second embodiment of the invention. This second embodiment differs from the first embodiment essentially in that the volume at the center of the toroidal envelope 10 is at least partially enclosed by one or more fairing elements 13 on either side of the envelope along the z-axis. This improves the aircraft's aerodynamics by promoting laminar airflow parallel to these fairing elements 13. Part of the payload 12' can exit through one or more fairing elements 13, for example, to avoid obscuring a camera lens. The enclosed central volume can be used to increase the available carrier gas volume and / or to house a carrier gas expansion compensation system, such as a balloon.

[0074] In the case illustrated in [Fig. 3], the center of pressure P and the center of buoyancy F remain essentially coincident. The center of gravity G is no longer coincident with the center of pressure P and the center of buoyancy F, due to the protruding portion of the payload 12'. The center of gravity G is thus separated from the center of buoyancy F by a distance d. The buoyant force, which is a first vertical force directed upwards, acts on the center of buoyancy F. The weight of the aerostat, which is a second vertical force directed downwards, acts on the center of gravity G. The torque resulting from these first and second forces typically generates a gravitational restoring moment of magnitude mgdsin(0) with respect to the center of buoyancy F, where m is the mass of the aircraft and g is the acceleration due to gravity. The thrusters 21, 22, 23 can be oriented so as to generate a moment of force aimed at compensating for the gravitational restoring moment.As an example, the maximum torque generated by two diametrically opposed thrusters, each generating a maximum thrust T, and separated from the center of thrust P by a distance L, corresponds to 2LT. For the gravitational restoring moment to be compensated by this maximum torque for any pitch angle θ, mgd must be less than 2LT. The aircraft is preferably sized to satisfy these conditions. In particular, the distance d is chosen to be sufficiently small, d < 2LT / mg, to allow compensation of the gravitational restoring moment by the torque generated by the aircraft's thrusters. The maximum thrust T of the thrusters 21, 22, and 23 is to be determined, notably as a function of the aircraft's mass m. As an example, the maximum thrust T of each thruster is on the order of a few hundred Newtons (N), for example, on the order of 300 N.If the aircraft is configured to maintain a hovering pitch angle of 0° within a limited range between 0° and 0max, it is sufficient that the relationship mgdsin(0max) < 2LT be satisfied. For example, if 0max is less than 90°, the maximum thrust T of each thruster can thus be reduced.

[0075] Figure 4 illustrates a thruster 23 mounted on the envelope 10 by means of a connecting arm 31 and rigid suspension lines 61a, 61b. In one illustrated configuration, the "upper" rigid suspension lines 61a are longer than the "lower" rigid suspension lines 61b. The PO plane of the thrusters is then offset below the aircraft's median plane M, also known as the equatorial plane. Access to the thrusters from the ground is simplified. This facilitates thruster maintenance.

[0076] In the illustrated example, the aircraft comprises three thrusters 21, 22, 23 spaced 120° apart about the z-axis. Alternatively, the aircraft comprises four thrusters in the same plane, spaced 90° apart. around the z-axis. According to another possibility, the aircraft comprises four thrusters distributed in two planes parallel to the aircraft's equatorial plane M. According to another possibility illustrated in [Fig. 5], the aircraft comprises six thrusters distributed in two planes PI, P2 parallel to the aircraft's equatorial plane M. For example, three thrusters 21, 22, 23 are distributed in the first plane PI at 120° to each other around the z-axis, three other thrusters 24, 25, 26 are distributed in the second plane P2 at 120° to each other around the z-axis, and the thrusters 21, 22, 23 of the first plane PI are offset by 60° around the z-axis relative to the thrusters 24, 25, 26 of the second plane P2. Other configurations are also possible. The thrusters are not necessarily evenly distributed around the z-axis. The number and arrangement of the thrusters may vary.

[0077] Figure 6 illustrates a particular embodiment of a thruster 21, 22, 23. In this example, the thrusters 21, 22, 23 comprise four propellers 41, 42, 43, 44 fixed on a frame 40, and the frame 40 is mounted by a spherical finger joint 30 on the connecting arm 31. This allows two degrees of rotational freedom, around the axes U, V, for the frame 40 with respect to the connecting arm 31 and, consequently, with respect to the supporting structure. According to a preferred possibility, the frame 40 is mounted freely with respect to the connecting arm 31, and the four propellers 41, 42, 43, 44 are driven independently of each other to orient the frame 40 with respect to the connecting arm 31. The orientation and modulation of the thrust amplitude of the propeller are then obtained by independently modulating the rotational speed of the four propellers 41, 42, 43, 44.According to another possibility, the orientation of the frame 40 relative to the connecting arm 31 is controlled by means of jacks and / or gears at the connection 30. The rotational speed can then be identical for the four propellers 41, 42, 43, 44. In this case, only the amplitude of the thrust of the propeller is modulated by the rotational speed of the four propellers 41, 42, 43, 44.

[0078] Figure 7 illustrates in more detail the connection 30 with respect to the connecting arm 31. One or more housings 50 for batteries 51 are preferably provided, for example on the frame 40, to power the propellers 41, 42, 43, 44. The housings 50 for batteries 51 are preferably mounted close to the connection 30, to minimize the inertia of the frame 40 due to the weight of the batteries 51, when the frame 40 is oriented with respect to the connecting arm 31. The balance of masses around the central point of rotation is optimized.

[0079] In this embodiment of the propulsion unit, the thrust of the propulsion unit, resulting from the thrust of the four propellers 41, 42, 43, 44, is typically applied at the linkage 30. Other types of propulsion units can be considered, for example turbines.

[0080] Figures 8, 9, 10A-10C illustrate different modes of movement and flight control of the aircraft.

[0081] As illustrated in [Fig. 8], the aircraft can be positioned "on its side," that is, so that the xy plane of the relative frame is substantially parallel to the vertical Z axis of the absolute frame. The aircraft can then move on its side in any direction within the flight space, for example, in the XY plane of the absolute frame, as illustrated. In particular, the aircraft can move on its side along the vertical Z axis, climbing or descending. This minimizes the drag associated with this vertical movement. The energy required for movement is thus reduced.

[0082] As illustrated in [Fig.9], the aircraft can position itself on its edge and perform a combination of rotation around the z-axis and translation along the X-reference axis. The aircraft then moves by virtually "rolling", like a wheel.

[0083] As illustrated in Figures 10A, 10B, and 10C, the aircraft can rotate 180° on its own axis so as to turn around, either at a fixed position in the absolute reference frame or while moving in the absolute reference frame. This allows, for example, the payload 12—typically a camera—to be oriented upwards without being screened by the aircraft. This improves the possibility of shooting upwards, for example, for inspection under a bridge.

[0084] From the above, it is clear that such an aircraft has increased flight capabilities, usable in many fields of application such as, for example and without limitation, photography, inspection, imaging, communication, advertising etc.

[0085] The invention is not limited to the embodiments described above. In particular, different forms of load-bearing structure can be envisaged, without departing from the principle described in this application.

Claims

Demands

1. Aircraft comprising a load-bearing structure (1) and at least three non-collinear thrusters (21, 22, 23) attached to the load-bearing structure (1), each thruster (21, 22, 23) being configured to generate thrust vectors in at least one direction, said aircraft being characterized in that each thruster (21, 22, 23) is steerable independently of the other thrusters (21, 22, 23), so as to form a combination of thrust vectors such that the load-bearing structure (1) can be maintained stationary at any pitch angle 0, for a given range of pitch angles 0, the pitch angle 0 being defined between a yaw axis (z) of a frame (0, x, y, z) relative to the load-bearing structure (1) and a reference axis (Z) of an absolute frame (0, X, Y, Z), and in that each of the propellers (21, 22, 23) comprises a frame (40) and four propellers (41, 42, 43, 44) fixed to the frame (40), each propeller (41, 42, 43,44) being controllable independently of the other propellers, and the frame (40) being articulated with respect to the supporting structure (1) with two degrees of rotational freedom.

2. Aircraft according to the preceding claim wherein each thruster (21, 22, 23) is steerable in any direction in space, and wherein the thrust vector of each thruster (21, 22, 23) is individually controllable.

3. Aircraft according to any one of the preceding claims configured so that the combination of vector thrusts produces a moment of force greater than the gravitational restoring moment exerted on the supporting structure (1).

4. Aircraft according to any one of the preceding claims in which the given pitch angle range 0 is between 0° and 90°.

5. Aircraft according to any one of the preceding claims wherein the thrusters (21, 22, 23) are identical to each other and arranged on the supporting structure (1) such that, for any pitch angle 0 of the pitch angle 0 range, the combination of vector thrusts simultaneously counterbalances the weight of the aircraft and counterbalances the gravitational restoring moment exerted on the supporting structure (1).

6. Aircraft according to any one of the preceding claims wherein the propulsion units (21, 22, 23) are identical to each other and have a center of gravity defining a center of thrust P, the structure carrier (1) having a center of gravity G, such that the center of thrust P and the center of gravity G are coincident or separated by a distance d such that: _ n2+ \ 2T 7 \ 2TL / with m the mass of the aircraft, g the acceleration due to gravity, T the maximum vector thrust exerted by each thruster, and L the distance separating the center of thrust P and each thruster (21, 22, 23).

7. Aircraft according to any one of the preceding claims wherein the combination of vector thrusts permits complete rotations of the carrier structure (1) respectively around each of the yaw (z), roll (x) and pitch (y) axes of the frame relative to the carrier structure (1), and translations of the carrier structure (1) respectively around each of said axes (x, y, z) of the relative frame.

8. Aircraft according to any one of the preceding claims wherein the supporting structure (1) comprises an envelope (10) configured to contain a gas lighter than air surrounding the supporting structure (1).

9. Aircraft according to any one of claims 6 to 7 wherein the envelope (10) has a rotational symmetry about the yaw axis (z) of the frame relative to the supporting structure (1).

10. Aircraft according to any one of claims 6 to 8 wherein the envelope (10) has a toroidal shape defining a central volume (11), and wherein the central volume (11) is at least partly occupied by a payload (12, 12').

11. Aircraft according to any one of the preceding claims wherein the frame (40) is articulated vis-à-vis the supporting structure (1) by means of a spherical finger joint (30).

12. Aircraft according to any one of the preceding claims comprising three first thrusters defining a first plane PI, and three second thrusters defining a second plane P2 parallel to the first plane PI, wherein the first three thrusters of the first plane PI are spaced 120° apart about the yaw axis (z) of the frame of reference relative to the supporting structure (1), the three second thrusters of the second plane P2 are spaced 120° apart about said yaw axis (z), and the first three thrusters of the first plane PI are offset by 60° about the yaw axis (z) with respect to the three second thrusters of the second P2 plan.

13. Aircraft according to the preceding claim in which the first and second planes PI, P2 are located at an equal distance on either side of an equatorial plane (M) of the supporting structure (1), the equatorial plane (M) being normal to the yaw axis (z) of the frame relative to the supporting structure (1).

14. Aircraft according to any one of claims 1 to 10 wherein the thrusters (21, 22, 23) are all in the same plane PO parallel to an equatorial plane (M) of the supporting structure (1), the equatorial plane (M) being normal to the yaw axis (z) of the frame relative to the supporting structure (1), said plane PO preferably being located at a non-zero distance from the equatorial plane (M).

15. Aircraft according to any one of the preceding claims comprising at least one sensor called a pitch sensor, configured to measure at least one parameter relating to the pitch of the aircraft.

16. A method for controlling the flight of an aircraft according to any one of the preceding claims, comprising at least one of the following displacements: • a rotational displacement about the yaw axis (z) combined with a translational displacement along a direction of a plane normal to the yaw axis (z), the yaw axis (z) preferably forming an angle of 90° with the reference axis (Z). • a rotational displacement of 180° about a pitch axis (y) of the frame of reference relative to the supporting structure (1), so as to invert the supporting structure (1) while remaining in hover. • a translational displacement about the reference axis (Z), the yaw axis (z) forming an angle of 90° with the reference axis (Z).

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