WO2024018392A1

WO2024018392A1 - Hybrid propulsion rotorcraft uav drone

Info

Publication number: WO2024018392A1
Application number: PCT/IB2023/057351
Authority: WO
Inventors: Romano Bulgarelli
Original assignee: Romano Bulgarelli
Priority date: 2022-07-20
Filing date: 2023-07-19
Publication date: 2024-01-25

Abstract

A rotorcraft type UAV drone comprises a main body (1) which supports at least one rotor (2, 4) with blades (6) and at least one compressor (18, 20), integrated with each other and operated by the same driving force (10, 12), to generate compressed air by drawing air to be conveyed inside a main body of the UAV drone by taking external air. The at least one rotor (2, 4) is configured to support the UAV drone in flight in a substantially vertical direction. One or more exhaust nozzles (30, 34) are arranged and configured on the main body (1) for the selective expulsion of the compressed air for moving the UAV drone on a substantially horizontal plane. Preferably, the drone UAV comprises two electric motors which each generate the driving force for a respective rotor and compressor. Preferably the two compressors are connected in series to define a two-stage compression of the air taken from outside the UAV drone.

Description

HYBRID PROPULS ION ROTORCRAFT UAV DRONE

Field of invention

The present invention relates to the sector of drones or RPVs (Remotely Piloted Vehicles ) .

The invention has been developed with particular regard to a drone UAV (Unmanned Aerial Vehicle ) of the rotorcraft type , i . e . the type that sustains itsel f in flight thanks to the thrust of the air on one or more rotors . In the following, this type of vehicle will be referred to for simplicity as a UAV drone .

Technology background

The bladed rotors of rotorcraft drones currently in production constitute the only propulsion system generically and universally adopted for this type of UAV aircraft . The aeroplanes with multiple rotor propulsion, for example trirotor, multirotor, quadcopter, are signi ficantly af fected by the atmospheric conditions and above all by the thrust of the wind, with serious stabili zation problems , and are subj ect to high inclinations and angle of dri ft during flight maneuvers even in the absence of atmospheric perturbations .

The exceptions are rotorcraft drones with two coaxial rotors , which however are very complex and complicated to make , as well as to fly .

They have poor maneuverability and for this reason they have found little di f fusion .

Summary of the invention

The obj ect of the invention is to overcome the drawbacks of the known art , and to provide a UAV drone which is stable in flight . Another obj ect of the invention is to make a UAV drone that is cheap, simple to make and to use . These and other obj ects are achieved by a UAV drone having the characteristics indicated in the claims which follow .

According to a first aspect , a new propulsion concept is described for a UAV (Unmanned Aerial Vehicle ) drone which uses two counter-rotating coaxial rotors for support , i . e . which contrast the force of gravity, and which therefore determine the motion of the drone in a vertical Z direction . The two rotors are associated with two corresponding compression stages , axial or centri fugal , used to produce thrusts on the hori zontal X-Y plane , orthogonal to the vertical Z direction, and which can exploit the same driving forces used for the rotation of each rotor . The architecture of the UAV drone is such as to generate the forces necessary to ensure movement in the three axes of space in the Earth ' s atmosphere at sea level and up to an altitude of several thousand feet , as well as in the Martian atmosphere at minimum density and pressure . Stabili zation solutions similar to the attitude adj ustment of current spacecraft and satellites in Earth orbit can be adopted .

A solution incorporated in the present invention therefore consists in reserving the sole function of support to the blades of the coaxial rotors , i . e . the sole task of supporting the aircraft at high altitude , unlike the technique adopted in known rotorcraft in which the rotors also provide for propulsion, i . e . for progress or in any case to the movement of the vehicle in the hori zontal plane . In the present invention, the propulsion, and in particular the advancement of the UAV drone , is instead entrusted to a propulsion system other than the rotors . The propulsion system is implemented thanks to the compressors which are coupled to the rotors themselves and which compress a fluid, for example air, which can be made to escape on command from noz zles arranged on the body of the UAV drone . This propulsion system therefore takes care of stabili zation, acceleration and deceleration on the hori zontal plane at the relevant altitude . The propulsion system can also be arranged in such a way as to compensate , i f necessary, for any autorotation that could be triggered in the event of a failure of one of the two motors that set the rotors in rotation .

According to a particular aspect , the propulsion j ets which emerge from the various noz zles corresponding to various speci fic vectors are generated, in the simplest case , by conveyed and compressed atmosphere . However, it is also possible to use di f ferent fluids , for example an aerosol of air and distilled water, thus increasing the mass of the compressed fluid and consequently the thrust generated . Alternatively propellants of other types can be used, for example ecological propellants such as hydrogen peroxide or propane .

The conveyed and compressed fluid available aboard the UAV drone can be used to command actuators for accessories , such as loading arms , hatches , etc .

According to another particular aspect , the piloting of the UAV drone takes place remotely, for example through radio wave signals . Real-time navigation control can take place via a navigation camera, for example placed on the top, pointed in the direction of the progress vector, and which can have a variable inclination . A latest generation microcontroller can manage these instructions and also perform predefined and/or autonomous missions thanks to various sensors used for telemetry, for the collection of various data such as : air speed, barometric pressure , pressure and temperature in the central body of the UAV drone and in the distribution chamber, motors temperature and outside temperature , GNSS data, GPS data, IMU data . The microcontroller can also manage the radar to avoid obstacles during the flight and/or manage the starting of the rotors for safety reasons , and/or the recognition of obj ects and/or people . This and more can be obtained using software and firmware suitable for the purpose . Wind direction and speed can be derived from inertial data from an IMU ( Inertial Measurement Unit ) module . The peculiar characteristics of the UAV drone obj ect of this document invention make it particularly useful for civil protection, land control and rescue applications .

In particular, the UAV drone is usefully equipped with a propulsion system that can be defined as "hybrid" , since it employs two systems based on di f ferent physical principles which operate in synergy .

The first propulsion system employs blades , preferably coaxial bladed rotors used for the ascent and descent of the UAV drone in the vertical direction . The second propulsion system is of the j et type and applies Newton ' s physical principle of action-reaction . The j et system preferably employs two compression stages , which are mechanically integral with the first blade propulsion system, for displacement and navigation on the hori zontal plane .

Brief description of the drawings

Further characteristics and advantages will emerge from the detailed description which follows of a preferred embodiment , with reference to the attached drawings , given by way of nonlimiting example , in which :

Figure 1 is a perspective view of a UAV drone of the rotorcraft type , incorporating features of the present invention;

- figure 2 is a longitudinal section of the UAV drone of figure 1 , taken along a plane passing through the central vertical axis of the UAV drone ; and figure 3 is a perspective view of a detail of the j et control of the UAV drone of the previous figures .

Detailed description In the embodiment examples that follow, characteristics are described which allow the invention to be implemented . The characteristics described can be variously combined with each other, and are not necessarily limited to the precise embodiment to which the drawings and the relative description refer . In other words , a skilled technician in the sector who reads the following description will be able to obtain the information useful for knowing how to achieve one or more of the characteristics described by combining it with one or more of the other characteristics described, without the particular formulation of the description of the paragraphs , sentences or drawings constitutes a limit to the possibility of isolating one or more of the described and illustrated features in order to combine them with one or more of any of the other described and illustrated features . In more detail , in the present description any combination of any two expressly described characteristics must be understood as expressly described, even in the case in which said characteristics are individually extracted from the speci fic context in which they can be j uxtaposed or combined with other, di f ferent characteristics , taking into account the skills and knowledge of an expert technician in the sector who understands the possibility of functionally combining said characteristics without requiring the functional contribution of the other, di f ferent characteristics . Unless otherwise speci fied, each and every element , organ, means , system, component , obj ect described and illustrated in this description must be considered individually described and independently modi fiable , as well as separable from and/or combinable with each and every other element , organ, medium, system, component , obj ect described and illustrated . The materials , shapes and functions described and illustrated are not restrictive of the present invention, but are only speci fied to enable an expert technician to understand and implement the invention according to preferred but not exclusive embodiments.

With reference now to figure 1, a UAV drone of the rotorcraft type comprises a main body 1, on which two coaxial counterrotating rotors 2, 4 are mounted. In the example of figure 1 each rotor is equipped with three blades 6, but of course it is possible to provide variants in which each rotor comprises two, three or more blades with predefined geometry and angle of attack so as to optimize the thrust force, i.e. the UAV drone lift. Since the two rotors are coaxial, the resultant of the angular moments of each rotor 2, 4 is kept zero, so as not to generate auto-rotation in case of hovering (stationary flight) or translated. Only when the direction angle change is required, e.g. for the turn, the prevalence of a temporary and defined resulting angular momentum is induced in one of the two rotors, for example in a clockwise or counterclockwise direction, so as to rotate the aircraft on the vertical axis respectively to the right or to the left. This entity is obtained only by varying both rotor speeds, i.e. increasing it in one rotor and simultaneously decreasing it in the other, or vice versa, so as to keep the overall lift unchanged, and therefore the flight altitude during the rotation .

The diameter of the circumference defined by the rotation of the blades 6 can be of different values depending on the model specialization required, e.g. less for light loads and more for higher loads. Preferably, but not restrictively, the ends of the blades 6 define a circumference the diameter of which can be between approximately 900 and 1800 mm. Each blade 6 is hinged to the rotor with a joint 8 and, in the rest position on the ground, remains located on the vertical adjacent to the main body 1 of the UAV drone. When the rotors 2, 4 are set in rotation, the centrifugal force will push the respective blades 6 into the hori zontal position shown in figure 1 .

In the lower part of the main body 1 there is a housing 9 for rechargeable batteries , preferably lithium polymer, as well as the electronics necessary for their management together with the power drivers of two motors 10 , 12 ( see figure 2 ) which operate the respective rotors 2 , 4 . I rotors 2 , 4 are mechanically integral with axial or centri fugal compressors 18 , 20 , which overall form a two- stage compression system . Supports are obtained in the lower part of the main body 1

14 for the support of the UAV drone on the ground . The supports 14 are pivotally mounted so as to retract into respective grooves 16 when not in use .

As better visible in figures 2 and 3 , the two independent electric motors 10 , 12 which supply the driving force are housed in the main body 1 . The motors 10 , 12 are for example , but not limited to , of the type with IP68 insulation degree brushless technology of 37V/ 150A each, with a total power of 11 . 1 kW . The motors are housed between the two rotor/compressor assemblies . On the surface of the main body 1 , aerodynamic cooling fins can be provided in contact with the outside so as to be hit by the air flows during the advancement of the aircraft . The external air is conveyed, thanks to the geometry of the upper rotor 2 and to the possible presence of an axial duct 17 , in the impeller of the first centri fugal compressor 18 which forms the first compression stage . The compressed air collects inside the volume of the main body 1 , where the electric motors 10 , 12 are housed . The compressed air from the first stage and confined in the central area of the main body 1 is sucked in by the second centri fugal compressor 20 which forms the second compression stage and is integral with the lower rotor 4 . From the second compressor 20 , the further compressed air is expelled into a distribution chamber 22 . The total compression ratio of the two compression stages is variable from a minimum to a maximum and is directly proportional to the speed of the rotors since each of them is always integral with the impeller of the relative compressor, and therefore variable . The pressure obtained will be minimal at low altitudes while it will be maximum at high flight altitudes during which the rotors reach their maximum rotation speed to generate maximum li ft .

The distribution chamber 22 , which provides for the translation and stabili zation of the UAV drone , is located j ust above its center of mass to ensure a natural balance of the forces involved . Inside it comprises a movable sphere 24 which can rotate on its own vertical axis , controlled by a motor, for example an electric stepper motor, through a drive shaft 25 ( see figure 3 ) .

The distribution chamber 22 is equipped with openings 26 in its upper area, from which the compressed air coming from the second compression stage 20 enters . As illustrated in the example of the figures , which should not be considered limiting, the distribution chamber can be equipped of ten circular openings homogeneously distributed on a smaller circle on the upper hemisphere of the movable sphere 24 . Other configurations for the compressed air inlet openings are certainly possible and within the reach of an expert who has read and understood the present description .

The movable sphere 24 is provided with outlet holes 28 for the compressed air . The outlet holes 28 are preferably six in number, and are arranged on a smaller circle than the movable sphere 24 on its lower hemisphere . The mobile sphere 24 can be rotated in such a way that the outlet holes 28 are selectively aligned with discharge noz zles 30 , obtained on the main body of the UAV drone and better visible in figure 1 . An opening is also obtained in the mobile sphere 24 inclined 32 , which allows the angle of the thrust vector to be varied by approximately +/- 10 ° on the hori zontal plane , causing the compressed air to alternately escape from one or the other of the exhaust noz zles 30 , to respectively produce a thrust in two opposite directions , to obtain for example an acceleration or a deceleration .

The distribution chamber 22 is also equipped with compensation noz zles 34 , obtained directly on the main body 1 of the UAV drone at the four cardinal points , each equipped with a controlled and normally closed solenoid valve , which is opened i f necessary by the control software to counteract , compensating it , any unbalance of roll and pitch . There may also be two other compensation noz zles (not visible in the figures ) , also equipped with a normally closed solenoid valve , in opposition to each other, with the task of canceling the auto-rotation caused by a possible failure of one of the two motors , allowing the exit of a j et which produces a thrust in the tangential direction contrary to the rotation induced by the angular momentum produced by the rotor still in operation, thus guaranteeing the emergency landing and/or the return of the aircraft to the starting point without any damage . In a variant of the UAV drone , the thrust of an environmentally friendly propellant , such as hydrogen peroxide or distilled water, is added to the thrust generated by the compressed air, stored on board and vapori zed to generate the increased thrust . In case distilled water is used as a propellant , the UAV drone is configured to vapori ze the distilled water and expel it with compressed air in order to increase the mass of the expelled fluid .

In the speci fic case of the hydrogen peroxide propellant model , the internal surface of the distribution sphere 24 is coated with porous elements , for example metallic silver, with the function of triggering a catalytic exothermic reaction thanks to the use of an aerosol of hydrogen peroxide about 90% hydrogen . This reaction is capable of instantly generating a signi ficant amount of heat and steam expelled through the distribution chamber noz zles , to generate the necessary and required thrust vectors .

In the propellant version, a portion of the main body 1 is used as a tank 36 for the hydrogen peroxide . Preferably, the tank 36 is located in the top surrounding the axial conduit 17 and has a capacity of about 3000 cc . From the tank 36 , the hydrogen peroxide is conveyed, by means of a pipe 38 for example of a few millimeters in diameter, to two opposite inj ectors 40 located inside the sphere 24 . The pipe 38 runs along the structural shaft 42 which, also in the version without propellant of the UAV drone , runs along the entire height of the main body 1 . An electric pump controlled by the on-board electronics provides for the selective delivery of the propellant . The acceleration obtainable through the use of the propellant can reach the limit of subsonic values . The software has the task of monitoring the speed of the UAV drone with respect to the air, reading the static and dynamic pressure values in real time through sensors , thus allowing to limit the maximum speed, by interrupting the supply of the propellant , for prevent the advancing blade tip of each of the rotors from reaching or exceeding the speed of sound, so as to prevent the sonic boom from which structural damage can result , thus avoiding the danger of eventual destruction of the aircraft .

The hybrid propulsion system using the rotors and the j et of compressed air and/or propellant provides clear advantages . A small vertical take-of f UAV drone can demonstrate excellent hovering capabilities with high stability, and can reach speeds unattainable with vertical take-of f drones and cover large distances in shorter times with less flight time for the same battery capacity . with which it is equipped, combined with a greater transportable load .

It has been found that the motors of the UAV drone , in a particular embodiment of non-limiting example , can guarantee an overall payload of around 40 kg with a cylindrical form factor with a volume of about 0 . 3 m3 , and a maximum speed allowable speed of about 282 m/ sec, calculated taking into account the aerodynamic resistance compared to the standard air with the following parameters : Altitude 1000 m; Temp . 281 °K; Pressure 898 hPa ; Density 1 . 1 ; Dynamic viscosity 1 . 76 x 10-5 ) .

The availability of compressed air on board the UAV drone allows it to be equipped with compressed air accessories , such as compressed air grippers for loading, holding and releasing a load .

Variants are naturally possible which do not modi fy the operating principle described above with reference to preferred but non-limiting embodiments . For example , it is possible to make a rotorcraft UAV drone having a di f ferent combination of one or more rotors , even non-coaxial ones , connected to one or more compressors driven by the same motor or by several motors . The hybrid propulsion system can therefore be adapted to respond to the di f ferent constructive forms achievable by combining blade rotors with j ets for propulsion and/or correction and stabili zation of the UAV drone .

Naturally, the principle of the invention remaining the same , the embodiments and construction details may vary widely with respect to what has been described and illustrated, without thereby departing from the scope of the present invention .

Claims

1. An UAV drone of a rotorcraft type, comprising a main body (1) supporting at least one rotor (2, 4) with blades (6) and at least one compressor (18, 20) , each rotor (2, 4) being integral with at least one corresponding compressor (18, 20) to form a rotor/compressor assembly driven by the same driving force (10, 12) , the at least one compressor being overall configured to generate compressed air by drawing external air to be conveyed within the main body (1) of the UAV drone, the at least one rotor (2, 4) being configured to support in flight the UAV drone in a substantially vertical direction, one or more exhaust nozzles (30, 34) being arranged on the main body (1) and configured for selectively expelling the compressed air compressed by the at least one compressor for moving the UAV drone in a substantially horizontal plane.

2. An UAV drone according to claim 1, comprising a distribution chamber (22) configured to collect compressed air generated by the at least one compressor (19, 20) and selectively direct it to the one or more exhaust nozzles (30, 34) .

3. An UAV drone according to claim 2, wherein the distribution chamber (22) comprises a movable hollow sphere (24) controlled in rotation by electronics of the UAV drone, on the movable hollow sphere being provided compressed air inlet openings and compressed air outlet openings at positions configured to selectively direct, according to the rotational position of the movable hollow sphere, the compressed air towards one or more of the exhaust nozzles according to the control needs of the UAV drone and its desired direction.

4 . An UAV drone according to any one of the preceding claims , wherein the compressed air is used in a j et fashion to compensate for the attitude and stabili zation of the UAV drone during flight , the compressed air being emitted from selectively openable exhaust noz zles through normally closed solenoid valves driven by the UAV drone electronics .

5 . An UAV drone according to any one of the preceding claims , comprising a tank for an environmentally friendly propellant with a delivery system for generating propulsive thrust in addition to that generated by compressed air .

6 . An UAV drone according to claim 5 , wherein the propellant is hydrogen peroxide , the UAV drone being configured to generate an exothermic catalytic reaction using metallic silver as a catalyst .

7 . An UAV drone according to claim 5 , wherein the propellant is distilled water, the UAV drone being configured to vapori ze the distilled water and expel it with compressed air so as to increase the mass of the expelled fluid .

8 . An UAV drone according to any one of the preceding claims , comprising two electric motors each driving a blade rotor and a compressor connected to the blade rotor, the two compressors being connected in series to collectively define a two-stage compression of the compressed air taken outside the UAV drone .

9 . An UAV drone according to claim 8 , comprising an emergency j et system that intervenes to stabilise the UAV drone in the event of a failure or mal function of one of the two motors or rotors .