WO2017103867A1

WO2017103867A1 - Drone with rotors comprising hinged blades

Info

Publication number: WO2017103867A1
Application number: PCT/IB2016/057700
Authority: WO
Inventors: Arthur GARDIN; Florent ROQUE
Original assignee: Evodrone
Priority date: 2015-12-17
Filing date: 2016-12-16
Publication date: 2017-06-22
Also published as: FR3045566A1; FR3045566B1

Abstract

The invention relates to a multirotor drone (1) comprising a fuselage and a plurality of engine units driving a plurality of rotors (4), each rotor comprising two blades (5) mounted in a facing arrangement on either side of a blade tilting axis BP, such that each of the blades (5) has one rotational degree of freedom about said blade tilting axis BP.

Description

DRONE WITH ROTORS COMPRISING ARTICULATED BLADES

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a drone. It relates more particularly to a multirotor drone comprising a fuselage and a plurality of powertrains driving a plurality of rotors.

STATE OF THE PRIOR ART

With the permanent miniaturization of electronics, a new type of drone has emerged for a small decade in the category of mini drones (MTOW <25kg): drones multirotors. These rotary wing aircraft consist of several rotors (at least three) whose different thrusts allow lift and control of the drone. The main advantage of this configuration, compared to conventional helicopters, lies in its simplicity: just a few motors directly driving rotors, controlled by an inertial unit and controlled by a small computer, to fly almost any object , similar to a helicopter.

[0003] These multirotor drones, used primarily as recreational vehicles, have seen their fields of use diversify considerably: they are now professionally exploited to perform a wide variety of missions. These missions can take the form of objects to be transported / raised in the air, or of information gathering in all their forms by means of sensors embedded in the aircraft (aerial shooting, mapping, surveys of all kinds). , etc.).

These professional applications require both optimal flight performance (range, maneuverability and embedded load of the drone), as well as exemplary reliability.

The search for ever better performance guides the designers of multirotors to increase the bearing surface of their rotors, and therefore the diameter of the latter. This increase is inevitably accompanied by an amplification of certain perverse effects, which until now were often neglected on small diameter rotors. In particular, the large diameter rotors generate significant gyroscopic efforts and incompatible with onboard mechanics, vibration damping systems or the very light structures of some multirotors. From Negative consequences of the transmission of gyroscopic forces from the rotor to the structure of the drone, we can cite some examples: premature fatigue of rotating parts of the rotor head due to the introduction of significant cyclic forces, large displacements, even crossing stops of a powertrain mounted in a flexible manner (vibration isolation) during the inclination of the drone or excessive loading of the structure of the drone, because of the transmission thereto of vibrations and gyroscopic forces generated by the large diameter rotor.

To overcome these disadvantages, the invention provides different technical means.

SUMMARY OF THE INVENTION

The object of the invention is to provide a multirotor drone rotor head architecture for limiting the transmission of gyroscopic forces from the rotor to the structure of the drone.

To do this, the invention provides a multirotor drone comprising a fuselage and a plurality of powertrains driving a plurality of rotors each of which contributes to a significant fraction of the lift, characterized in that the rotors are variable pitch, each rotor comprises two blades, the blades being mounted in opposition on either side of a pivot axis BP of the blades, so that the rotor has a degree of freedom in rotation about said axis of rotation BP of the rotor and in the blades each have a hinge of pitch around an axis AP of articulation of the blades made using two spherical ball joints.

The blades being arranged free to tilt, they minimize the transmission of the generated forces of the rotor to the structure, including gyroscopic and aerodynamic forces.

Fixing the blades with the two spherical ball joints allows obtaining a degree of freedom around the axis AP passing through the center of the ball joints, with a rigid behavior in the other directions.

Such an architecture has several advantages: simplicity and robustness are increased compared to a conventional system consisting of radial contact bearings and thrust bearings. The very rigid retention of the blades thus avoids dynamic imbalances of the rotor in flight. The ratio of Mass / Robustness / Price is particularly interesting, especially in small dimensions compatible with drones which is the object of this invention and improved maintainability due to the simplicity of assembly.

Such an architecture allows, with a compact and lightweight system, a blade mobility along a single axis AP, retaining rigidity in all other directions.

This solution also provides excellent resistance to stress, in particular centrifugal. The solution provides a good dynamic behavior of the rotor and a good positioning of the blades. In addition, this solution is particularly compact and lightweight, and corresponds well to small scales related to drones.

According to an advantageous embodiment, the BP tilting axis, which is defined as the axis passing through the anchor points of the blade pitch controls, forms a Delta angle with respect to the AP axis. articulation of the blades.

Also advantageously, the value of the Delta angle is provided to vary the angle of incidence of the blades as a function of their tilting. Such an architecture allows to bring the blades in the plane perpendicular to the axis of rotation.

Advantageously, the Delta angle is included:

between -90 ° <0 <0 ° or; 0 ° <δ <90 ° and more preferably between -80 ° ≤ o≤-30 ° or; 30 ° ≤ô≤80 ° and even more preferably between -60 ° ≤ o≤-40 ° or; 40 ° ≤ô≤60 °.

According to another advantageous embodiment, the drone comprises a pitch control implemented by a kinematic chain comprising an actuator connected to a control rod passing through a rotary cage motor.

The invention advantageously provides that the end of the control rod is connected to two connecting rods, located opposite the actuator of pitch relative to the engine, each link being connected to a blade, thus controlling the pivoting of the blades around the axis AP, thus making it possible to vary the pitch angle.

According to an advantageous embodiment, a blade articulation insert is integrated in the blade root and comprises two bores housing the two spherical ball joints, and a threaded hole for fixing the anchor point of the order. to not. DESCRIPTION OF THE FIGURES

All the details of embodiment are given in the description which follows, supplemented by FIGS. 1 to 9C, presented solely for purposes of non-limiting examples, and in which:

FIGS. 1A and 1B are diagrammatic representations illustrating an example of pivoting of the blades around a pivot axis BP;

FIG. 1C is a perspective view of an example of a drone;

FIG. 2 is a view from above of an exemplary implementation of a rocking rotor;

FIG. 3 shows the arrangement of FIG. 2 seen in perspective;

FIGS. 4A, 4B and 4C make it possible to illustrate the effect of tilting of the blades;

FIG. 5 illustrates a portion of a rotor with spherical ball joints;

FIG. 6 illustrates a blade with a hinge insert;

FIGS. 7a and 7b illustrate an example of a sliding bearing arrangement;

FIGS. 8a and 8b illustrate an exemplary pitch control system with a through rod;

FIGS. 9a to 9c illustrate an example of an elastic connecting piece.

DETAILED DESCRIPTION OF THE INVENTION

DEFINITIONS

"UAV" means a remotely piloted aircraft as defined in the decree of 1 April 2012 on "the design of civil aircraft that circulate without any person on board, the conditions of their employment and the required capabilities people who use them. " In short, it is any aircraft capable of unmanned flight on board, which is controlled either by a computer (on board or on the ground) or by an operator on the ground, used for recreational purposes, competitions , or professional.

By "multirotors" is meant any rotary wing aircraft whose air lift is obtained by means of the use of at least three non-coaxial rotors, each of which participates in a significant fraction of the lift. total required for the flight.

By "rotary wing" is meant any drone whose lift in the air is obtained by means of the use of at least one rotor, allowing the drone to perform hovering. The invention relates preferentially to multirotor drones equipped with three to eight rotors. The invention preferably on multirotors equipped with four to six rotors 4.

The invention relates more preferably to multirotor drones with variable pitch, the control of which is obtained by means of the modification of the collective pitch of at least three of their rotors 4.

ROTORS BIPALES

The described invention relates only to multirotor drones equipped with two-bladed rotors, or rotors 4 equipped with two blades 5 diametrically opposed.

ROTOR TILTING JOINT

The invention relates to a rotor 4 hinged so that the two blades 5 can rock together relative to their axis of rotation. In this way, the plane in which the trajectory of the blades 5 is inclined may incline with respect to the main rotation axis 6 of the rotor: this plane is therefore not systematically normal to this axis of rotation.

The axis of this joint must also be carefully selected to meet the following constraints: allow the tilting of the blades 5 relative to their axis of rotation and not introduce additional vibrations because of this new degree of freedom .

For this, according to a first embodiment as shown in Figures 1A and 1B, the tilting axis BP is positioned in compliance with these three rules: be inscribed in a plane orthogonal to the axis of rotation 6 main rotor, do not be parallel to the axis of the pitch pitch of the blades 5 and be positioned so that the center of inertia of the parts can tilt (blades 5, blade feet, rotor head 10, etc.) or coincide with the axis in question.

The advantage of this joint lies in the following: the entire rotor 4 is free to tilt at the mercy of external stresses (aerodynamic solicitation and gyroscopic effects induced by an inclination of the drone in space) regardless of movements of its main axis of rotation. For example, when the drone 1 tilts in space, the gyroscopic forces generated by the rotor 4 tend to keep the orientation of the rotor disk constant in space, despite the inclination of the drone 1. tilting articulation 7 makes it possible not to force the rotor 4 to follow the inclination of the drone 1, but use centrifugal forces and some aerodynamic efforts to restore the orientation of the rotor disc. Thus, it is not the structure that counteracts the gyroscopic forces by reaction to them, but external forces (centrifugal force and aerodynamic forces). The transmission of gyroscopic forces is greatly reduced.

DELTA ANGLE COUPLING TILT - NOT

Beyond the centrifugal forces that naturally tend to bring the rotor to its equilibrium position (ie in a plane orthogonal to the main axis of rotation of the rotor), one can also introduce aerodynamic forces to counteract the gyroscopic forces. For this, as shown in Figure 2, it is sought to ensure that the tilting of the blades 5 relative to their axis of rotation is coupled with a change in their pitch, which tends to combat this tilting. To obtain this effect, we study the orientation of the hinge axis AP pitch of the blades, with respect to the direction formed by the two anchoring points 8 of the pitch control of the blades. The angle formed by these two directions is called Delta.

It is then found that if this angle is different from 90 °, the tilting of the blades 5 causes a change in their pitch in one direction or the other, depending if the axis of articulation of the blades is located forward or backward of the anchor point of the pitch control. By convention, it will be said that the angle Delta is positive when the anchoring point of the pitch control 8 is situated in front of the axis of the pitch articulation (on the leading edge side of the blade 5 ), and negative in the other direction. Note finally that in the extreme case where this angle would be zero, the tilting of the blades is no longer possible. This case of the present invention is therefore excluded.

If we observe the behavior of a blade 5 in the case of a positive Delta angle, we see, as shown in Figures 4A, 4B and 4C, a tilting upward (Figure 4B ) of the blade has the effect of reducing his pace. FIG. 4C represents this effect with an arrow P illustrating the lift, pointing downwards. Conversely, a downward tilt (Figure 4C) has the effect of increasing its pitch. FIG. 4B represents this effect with an arrow P illustrating the lift, pointing upwards. The desired effect is obtained: the tilting of the blades generates an aerodynamic force tending to bring the rotor back into a plane perpendicular to its axis of rotation. Finally, note that the lower the Delta angle, the greater the effect obtained; conversely, the closer the Delta angle is to 90 °, the lower the effect obtained. Finally, it is noted that the use of a negative Delta angle (anchor point of the hinge of pitch located behind the axis of the hinge pitch, or the side of the trailing edge of the blade ) makes it possible to obtain an equivalent result, mainly because of complex dynamic phenomena that we will not detail in this document.

Therefore, the angle Delta is preferably chosen in the following ranges:

ARTICULATION OF NOT

The pitch articulation, only present on drones multirotors with variable pitch, is the pivot connection between a blade 5 and the rotor head 10. It allows the modification of the collective pitch of the rotor. The invention preferably relates to multirotor drones with variable pitch, the rotors of which have a pitch joint made using two spherical ball joints 19.

In the embodiment of Figure 3, the pitch control is implemented by a kinematic chain comprising an actuator January 1, connected to a control rod 12 through the rotating cage motor 9. On the opposite side of the motor, above the rotor head 10, the control rod end 13 is connected on each side of the rotor head 10 to a connecting rod 14, each being connected to a blade, and controlling the pivoting blades around the axis AP, thus allowing to face vary the pitch angle. Other modes of variable pitch actuation may be used within the scope of the present invention.

JOINT OF SIMPLIFIED BLADE

A simplified blade articulation insert 16 makes it possible to ensure that each blade integrates into its own geometry a means of positioning the following elements between them, precisely, definitively and without adjustments: the wing, the two ball joints spheres and the anchor point of the pitch control. An embodiment of such a blade is shown in Figure 6, where there are two bores 18 for positioning the two spherical ball joints, and the threaded hole 17 for securing the anchor point of the step command.

This architecture is obtained advantageously by means of a single insert around which the wing is molded, as shown in Figure 6.

This blade architecture is of multiple interest, especially small scales characteristic of multi-rotor drones provided according to the invention, namely drones of a few kilograms:

-It allows optimal use of spherical ball joints, which themselves have multiple advantages:

Particularly rigid transmission of the forces generated by the blade (in particular centrifugal forces, drag stresses, lift forces).

-High strength and durability of the system due to an optimal solicitation of spherical bearings (radial force dominating due to centrifugal force).

-High accuracy and repeatability of positioning the blade on the rotor head.

Such an architecture also allows the blade to perform multiple functions which, in the state of the art, are often provided by multiple parts:

-Articulation of pitch of the blade,

-Positioning the blade on the rotor head,

-Positioning the anchor point of the pitch control,

Local reinforcement of the blade in a particularly stressed area (blade root).

Such architecture is particularly simple, lightweight, robust and durable, significantly limiting the number of parts needed and avoiding the use of fragile and unsustainable elements such as miniature ball bearings. This has the direct consequence of simplifying the assembly and maintenance of the system.

TILT JOINT ON SMOOTH BEARING

FIGS. 7a and 7b show an advantageous exemplary embodiment of tilting articulation carried out by means of plain bearings 20. These plain bearings have several advantages over the connection elements commonly encountered in the state of the invention. art: -They greatly limit the transmission of forces to the structure by allowing a quasi-free movement of the rotor, unlike the elastomeric links of model-reduced helicopters, which exert a strong restoring force for small deviations. They are particularly adapted to the tilting movement generated by the rotor, with respect to ball-bearing type connections. Indeed, it is a reciprocating movement in low amplitude rotation which tends to greatly degrade the service life of the ball bearings by premature local wear of the bearing tracks.

-They are particularly resistant to hostile environments (presence of water, sand, salt ...).

SLIDING COMBINATION SLIDER AND INDEX

FIG. 3 shows an exemplary embodiment of a system comprising a rotary cage and hollow shaft motor 9, as well as an indexed pitch control with respect to the rotating shaft of the motor, the step actuator 1 1 being located opposite the rotor relative to the engine (notion of control passing through the engine).

This architecture has the advantage of being particularly simple and compact by gathering all the control elements in the immediate vicinity of the rotary cage motor. It also makes the control system not particularly robust and accurate by advantageously limiting game sources and complex efforts in fragile links.

STEAM CONTROL SYSTEM WITH INDEPENDENT MECHANICAL SHUTTERS OF THE ACTUATOR

Figures 8a and 8b show an advantageous embodiment of a pitch control system with stops 21 limiting its stroke mechanically. This feature has several advantages:

-protect the actuator against overtravel that may damage it.

avoid the blocking of the pitch control in a position not provided for by the kinematics of the system.

-Limit the pitch range of the rotor to a range aerodynamically compatible with the flight range of the drone.

SERVO-COUPLING SOFT CONNECTION

Figures 9a, 9b and 9c show an advantageous embodiment of a system with a resilient connecting piece connecting a rotary actuator, servo-type, to the slider previously described. This elastic connecting piece 22, provided with a deformation zone 23, is sufficiently flexible in bending to absorb the small deformations caused by the transformation of the rotational movement of the actuator in a translation movement of the slider, while being rigid enough to transmit the pitch control efforts.

This architecture has the advantage of simplifying the pitch control system by advantageously replacing a complex articulation of rigid elements by a single flexible element. As a result, the system is more robust and its assembly and maintenance are simplified.

MONOBLOC MOTOR CONTROL UNIT

FIG. 10 shows an advantageous exemplary embodiment of a drone equipped with powertrains (GMP) in which each GMP comprises a one-piece frame 26, gathering around a single piece all the organs of the GMP to be precisely positioned between them (motor positioning zones 24, positioning zone of the pitch actuator 25, fixing the GMP to the cell 27).

This one-piece frame 26 has the double advantage of limiting the number of parts required for the relative positioning of each member of the GMP, and to release the cell (structure of the drone) from all dimensional constraints related to the integration of a GMP with variable pitch.

Reference numbers used on Drone figures

Fuselage

Powertrain

Rotor

blades

Rotor shaft

Tilt Articulation

Anchor points for step commands

Engine

Rotor head

actuator

Step control rod

End of step control rod

Connecting rod

Support

Joint insert

Threaded hole

bore

Spherical ball

Plain bearing

stopper

Elastic connecting piece

Deformation zone

Positioning area

Monobloc frame

Attachment of the GMP to the cell

Claims

1. A multirotor drone (1) comprising a fuselage (2) and a plurality of powertrains (3) driving a plurality of rotors (4) each of which contributes a significant fraction of the lift, characterized in that the rotors are variable pitch, each rotor (4) comprises two blades (5), the blades being mounted in opposition on either side of a pivot axis LP of the blades, so that the rotor has a degree of freedom in rotation about said axis of rotation. BP tilting of the rotor and in that the blades each have a hinge of pitch around an axis AP of articulation of the blades made using two spherical ball joints (19).

2. Drone according to claim 1, wherein the BP tilting axis forms a Delta angle with respect to the axis of articulation of the blades.

The drone of claim 2, wherein the Delta angle is comprised:

4. Drone according to any one of the preceding claims, comprising a pitch control implemented by a kinematic chain comprising an actuator (1 1), connected to a control rod (12) passing through the rotary cage motor (9). .

5. Drone according to claim 4, wherein the end of the control rod is connected to two connecting rods, located opposite the pitch actuator relative to the motor, each link being connected to a blade , thus controlling the pivoting of the blades around the axis AP, thus making it possible to vary the pitch angle.

6. Drone according to one of the preceding claims, comprising a blade articulation insert (16), integrated root blade and comprising two bores (18) housing the two spherical ball joints (19), and a threaded hole (17) for fixing the anchor point of the pitch control.