DESCRIPTION Title

Inflatable structural support for propulsion and control systems of UAVs

(Unmanned Aerial Vehicle)

Introduction

The invention consists in an inflatable structural support for propulsion systems, control system and supply of a UAV, in particular for rotary-wing drones, multicopters or similar, technological context

Today drones or UAVs on the market are typically based on a metal, carbon fiber or rigid plastic frame, on which propulsion systems, cabling and power supply system would be installed.

As a result, flying object is quite heavy and can be very dangerous in case of a fall on people from a certain height.

The technology used to realize airtight inflatable objects, allows, after inflation, to hold a rigid form for a certain period. The most widely used technology for joining airtight parts of the article is that in high-frequency welding, or gluing with specific glues that provide a secure and lasting connection between the parts.

Manufactured inflatable objects are made from different types of material, which must however have the following characteristics: sufficient resistance for the inflation and for general and/or specific use, melting point appropriate for artifacts airtight, good characteristics sealing air or gas used.

Generally, the materials used are PVC or PVC / PU coated nylon. The thickness part from 0.18 mm to 1.00 mm or more. Most of the products used falls within this range. For example, the material used for the majority of inflatable toys has a thickness between 0.18 mm and 0.24 mm PVC, while the airbeds use at least 0.50 mm PU / PVC.

Inflatable products have several advantages including ease of preparation, reduced maintenance, ease of storage.

The limitations are basically the form they can created, as manufactured inflatable structures can not present sharp edges as rigid materials and it is difficult to allow the creation of flat surfaces.

The most economic material with which are made inflatable products is PVC (polyvinyl chloride). This is a form of flexible rubber without any support of fabric that is usually used to make boats of different sizes. The quality of PVC without fabric support varies greatly depending on the formulation and thickness.

The technologies concerning lighter than air inflatable objects, have been proposed in several patents, such as in US6527223 related to an airship platform or in US6837458 B2 related to an airship.

Patents related to flying platforms or flying robotic systems based on rigid structure are for example: EP2599718 (Al), WO2010128489 (A2),

WO2007141795 (Al), DE20051014949 and US5419514 A.

A recent patent describing the use of LTE (lighter than air) technology to acquire aerial images is US2013119188.

Systems for the active control of aerostatic platforms or airships are described in several patents such as US7156342 (B2).

The U.S. Army Research Laboratory, Aberdeen (USA) published in January 2012 a document entitled "Lighter-Than-Air and Pressurized Structures Technology for Unmanned Aerial Vehicles (UAVs)", which describes in detail the various existing technologies to develop inflatable structures flying.

Methods to reduce the footprint of a UAV radar are described in EP2532588

(Al). Purpose and summary of the Invention

An airtight inflatable structure for UAV represents an innovation of technology, consisting in a typical configuration of an appropriate layer of elastic material of reduced thickness such as PVC (polyvinyl chloride), EVA (ethylene vinyl acetate), TPE (thermoplastic elastomers), co-polymers, possibly with inserted reinforcing fibers such as LCP (liquid crystal polymer) and other materials suitable for the purpose.

The sheets of elastic material, adapted to be inflated, are made with thin layers of material overlaid so as to prevent gas leakage through the micro pores of the material.

A single layer is composed of two superimposed sheets of elastic material that are welded together along appropriate lines, which create closed volumes, with appropriate valves positioned in each of them in order to allow filling with air, helium or other lighter than air gases.

The structure, in a different embodiment, is constituted by a double layer where the outer cover is made from a flexible and light as spinnaker fabric and the inner layer consisting of one or more lightweight bags made of inflatable materials.

The inner and outer layers are welded along appropriate lines, creating some volumes or closed bags, with appropriate valves located in each of the inner layers to allow for filling with air or helium or other lighter than air gases. The lines of welding or gluing also define the areas in which are inserted the propulsion systems and the control system.

In a typical single layer embodiment, each square meter of the sheet made from PVC material of thickness of 0.2 mm weighs about 280gr at a cost that is usually less than 1€ / kg, With advanced composite materials, the weight can be significantly lower, resulting in a very light and inexpensive support structure described in the invention. In a typical embodiment the external shape of the inflatable support structure is circular or polygonal with rounded corners and suitable cavities inside of this form in order to accommodate the propulsion systems and the control system.

At the top of the inflatable support structure are specific links to additional devices, such as vertical inflatable wings with appropriate form, or inflatable LTA (Lighter Than Air) balloons that allow a further reduction of the total weight of the UAV, making it a structure NLTA (Near Lighter Than Air) or LTA.

The power supply system is made from one or more sources of electrical energy, in a typical embodiment batteries or a hybrid power system consisting of batteries, super capacitors and / or fuel cells.

The hybrid power system is particularly useful when the flying vehicle has NLTA features, because it allows flights longstanding and is a method for optimizing the operation of the station for long duration missions.

The propulsion system in case of multicopter is typically made of ducted propellers or propellers protected with suitable structures in general.

In a typical embodiment each ducted propeller can have its own power electronics, with an appropriate wiring for the control electronics. Each ducted propeller is inserted into a specific cavity positioned within the inner inflatable part.

In the center of the inflatable support structure there are one or more appropriate cavities where the control electronics and the power supply system would be inserted, all contained in suitable boxes with appropriate holding mechanism connected to the inflatable structure, and an optional payload such as a camera with or without pivoting support (gimbal) and / or data acquisition systems.

A further advantage of the invention is to minimize the transmission of vibration from the propulsion system to electronics and payload due to the mechanical properties of the inflatable structural support. To transport the inflatable support structure may be deflated and the ducted propellers can be stacked together with electronics and batteries creating a compact cylinder for efficient storage.

The invention also allows minimizing the spectral signature of the UAV for the following reasons: The inflatable structure may be made of low reflection materials, the metal parts are very few and the shape minimizes reflections. The invention allows to realize a vehicle almost invisible, thanks to the possibility to use a combination of transparent/opaque materials for the inflatable support structure, propellers, rotors and containers of electronics parts.

Description of the drawings

Following is a description of an embodiment of the invention, made with reference to the accompanying drawings.

Fig 1 is a general view of the invention from below.

Fig 2 is a top view and the section AA of this view.

Fig 3 is BB sectional view with the propulsion system and the electronics installed.

Fig 4 is a view of the invention disassembled for transport.

Figure 5 is an overview of the invention with the optional inflatable wings.

Follows the description of an embodiment of the invention.

Fig 1 represents a typical shape with four cavities for propeller systems, and a central cavity for the control electronics, power system and payload. Other representations could have 3, 6, 8 or more propeller systems.

In fig. 1, the reference No. 10 indicates the outer inflatable ring, which can be made of more than one circular or polygonal cross-section to increase the resilience to the potential damage to the inflatable structure.

In fig. 1, the reference No. 11 indicates the inner inflatable part, which can be made of more than a circular cross section, in order to increase the resistance to the damage to the inflatable structure. In this embodiment the propulsion system consists of four helices.

In fig. 1, references No. 12, 13, 14, 15 indicate the cavities in which they must be inserted propeller systems, which in this embodiment of the propulsion system is again constituted by four propellers.

In fig. 1, the reference No. 16 indicates the cavity in which it must be inserted, the control electronics, and No, 17 indicates the cavities in which must be entered the system of power contained in a suitable box and reference No. 20 indicates an optional payload such as a camera with or without universal joints and / or data acquisition systems.

Fig. 1, the references No. 18 and No. 19 indicate valves used to inflate the closed volumes. In this embodiment there are two closed volumes, one for the outer ring and one for the inner part.

Fig. 2 shows a top view of a typical form of the invention with four cavities in which they must be inserted propeller systems, and a central cavity in which should be inserted into the control electronics and the power supply system. Fig. 2 also demonstrates Section A - A of this view, in which we see a typical figure of the inflated structural support, The outer ring is typically of a diameter greater than the height of the propellers or electronics + power supply system, the inner circle has a height sufficient to securely hold in position the propeller systems, the control electronics, and the supply system. In a preferred embodiment plastic inserts can be glued or welded inside the cavity to keep these parts in position.

Fig. 3 is represents Section B - B of Fig. 2, where No. 10 indicates the outer inflatable ring, which can be made of more than one circular or polygonal cross- section to increase the resilience to damage to the inflatable section.

In fig. 3 the reference No. 11 indicates the inflatable inner circle, which can be made of more than a circular cross sections, in order to increase the reliability of the structure in case of potential damage to single cross section. In this embodiment the propulsion system consists of four unit of comprised of propeller and engine referenced as 12, 13, 14, 15, which are electrically connected with the reference 17.

In fig. 3 the reference 16 indicates the volume in which are positioned one or more sources of electrical power, where the power system is composed of a typical embodiment of batteries or a hybrid power system consisting of batteries, supercapacitors and / or fuel cells. The hybrid power system allows managing high peak currents with supercapacitors, having batteries for efficient storage of energy and fuel cells to recharge the battery, and is particularly useful when the drone has NLTA features, because it allows longer distance flights and is a method for optimizing the operation of the station for long duration missions.

In fig. 3, the reference No. 17 indicates the volume in which they are placed one or more electronic subsystems/modules for flight control and image processing, a GPS sensor, an altitude sensor, accelerometers, gyroscopes and compass, and a radio communications system, other sensors for measuring the wind direction and speed, and other specific sensors.

In fig. 3 reference No. 20 indicates the volume in which is positioned an optional payload optional such as one or more cameras in the visible or infrared spectrum, with or without pivoting support [gimbal) and / or different acquisition systems.

The references 16 and 17 are connected together with a holding mechanism and an electrical connection.

The references 20 and 17 are connected together with a holding mechanism and an electrical connection.

In fig. 4 is shown a preferred method of storage and transport of the references numbered 12, 13, 14, 15, 16, 17, 20 stacked and connected together with appropriate mechanisms, with the inflatable structure in deflated state, reference 10 and 11 wrapped around them, creating a compact cylinder.

The fig. 5 is a typical form of the invention with two additional devices, reference No. 21 and No. 22 demonstrates vertical inflatable wings with lighter than air in appropriate form, or in different embodiment inflatable balloons lighter than air, which allow a further reduction of total weight of the UAV, resulting in the whole NLTA Drone structure. The wings or inflatable balloons are attached to the UAV under them with specific linkage. Links allow movements of pitch and roll of the inflatable drone.

The inflatable lighter than air Balloons may be only one, two or more than two, depending on the characteristics of the operations and the materials available. The weight lifted by lighter than air inflatable balloons, in a typical

implementation is less than the weight of the inflatable UAV itself, when it is inflated with helium or other lifting equipment.

A further advantage of the invention is to minimize the transmission of vibrations, usually in the range 50 ... 400 Hz, from the propulsion system electronics and payload thanks to the mechanical properties of the inflatable structure characteristics.

The invention allows minimizing the radar signature of the unmanned aerial vehicle for the following reasons: the material of the inflatable structure may be low reflection, the metal parts are reduced in number and size and the shape of the inflatable part minimizes reflections.

The invention allows to realize a vehicle almost invisible, thanks to the possibility to use a combination of transparent/opaque materials for the inflatable support structure, propellers, rotors and boxes for electronics.