GB2483785A

GB2483785A - Small unmanned aerial vehicle

Info

Publication number: GB2483785A
Application number: GB1115948.0A
Authority: GB
Inventors: Franz Maier; Alfred Scha Tti
Original assignee: LFK Lenkflugkoerpersysteme GmbH
Current assignee: LFK Lenkflugkoerpersysteme GmbH
Priority date: 2010-09-17
Filing date: 2011-09-15
Publication date: 2012-03-21
Anticipated expiration: 2031-09-15
Also published as: FR2964946A1; GB201115948D0; DE102010045858A1; GB2483785B; DE102010045858B4; FR2964946B1

Abstract

A small unmanned aerial vehicle has a fuselage 1 with aerodynamically active surfaces or wings 2 arranged on the fuselage 1. Control surfaces 7 are located to the rear of the wings and are pivotable at right angles to the longitudinal axis X of the small aerial vehicle. At least one propeller 42,52 is arranged to be drivable by a drive motor 40,50. In order to make the aerial vehicle more controllable in strong winds, at least one region of the control surfaces 7 is arranged directly behind the propellers 42,52 in the direction of the air flow produced by them.

Description

Small unmanned aerial vehicle

TECHNICAL FIELD

The present invention relates to a small unmanned aerial vehicle according to the preamble of claim 1. Small unmanned aerial vehicles of this kind are used for short-range reconnaissance or combat and can be carried in the equipment baggage of small task forces or on vehicles.

BACKGROUND OF THE INVENTION

Miniature aerial vehicles suitable for hover flight and sufficiently quick cruise fiiqht have, owing to their design, for example because of their large contact surface relative to the wind, considerable wind susceptibility and high energy consumption. To compound the situation, the controllability in situations with wind is frequently reduced, for example because the oncoming flow at the control surfaces is no longer ideal.

Classical rotorcraft and quattrocopters or systems with at least three propellers arranged remotely from one another on a structure are distinguished by a good hovering ability, but limited cruising ability and manoeuvrability.

Owing to the iack of aerodynamic lift surfaces, the cruise flight is not energy-efficient either. Systems which consist essentially of a downward-discharging engine with control surfaces arranged below it have the same characteristics, namely good hover flight properties and limited cruise flight properties.

PRIOR ART

A small unmanned aerial vehicle according to the generic kind is known, for example, from DE 10 2007 018 188 Al.

This vehicle can be converted from cruise flight to hover flight by means of a front propeller driven by a battery-operated electric motor and control surfaces arranged at the tail. This known small aerial vehicle can be launched and land vertically and in addition can cruise, as well as hover over a location on the ground.

To that end, this known small aerial vehicle is provided with an electric-motor-driven propeller arranged at the nose of the fuselage. Aerodynamic wings are attached laterally to the fuselage and at their rear ends pivotable control surfaces are provided. However, practical use of this small unmanned aerial vehicle, which is also called a "mini-drone", has revealed that the transition from the vertical flying state during launching or hover flight to cruise flight and from this back to the vertical flying state for the purpose of landing is problematical.

Particularly in the event of a crosswind influence, the controllability of this small unmanned aerial vehicle is not always reliably ensured. Also during certain essential flight manoeuvres, such as vertical descent, difficult conditions arise on account of the unfavourable flow conditions.

A small unmanned aerial vehicle with foldout wings and control surfaces is known from DE 2004 061 977 Al. This vehicle can be converted by means of a battery-operated electric-motor-driven tail propeller from cruise flight to hover flight by changing the direction of rotation of the propeller. In the case of this known small unmanned aerial vehicle, too, the controllability particularly in the transition phase between cruise flight and hover flight has proved to be difficult.

SUMMARY OF THE INVENTION

It is therefore desirable to provide a small unmanned aerial vehicle of the generic kind which is reliably controllable in the transition phases between hover flight and cruise flight and between cruise flight and hover flight, as well as during manoeuvres with difficult oncoming-flow conditions, and also in the event of any crosswind influence which may occur.

According to the invention, which is defined in ciaims 1, at least one region of the control surfaces is arranged directly behind a propeller in the direction of the air flow produced by the propeller.

ADVANTAGES

This configuration of the arrangement of the control surfaces in relation to the propeller ensures that the control surfaces are directly subjected to an oncoming flow by the propellers, so that there is still a sufficient oncoming flow at the pivotable control surfaces even if a constant or gusty crosswind strikes the small unmanned aeriai vehicle.

This small unmanned aerial vehicle is particularly suitable for carrying out tactical assignments and can perform the hover-and cruise-flight phases and also the transition between these flight phases even under difficult environmental conditions. The ability to accomplish the two flight phases makes it possible to perform demanding operations, such as rapid flight to a defined target position and subseguent observation in hover flight.

Vertical descent is also easily possible by means of this arrangement. Arming of the aerial body is also conceivable.

Preferably, the drive motor is arranged in the fuselage, preferably in the tail region, so that the drive motor is aerodynamically covered by the fuselage casing.

Furthermore, the drive motor is preferably in the form of an electric motor. The batteries or accumulators required for supplying the electric motor can be provided in the fuselage or inside the aerodynamic active surfaces arranged on the fuselage. This configuration of the small aerial vehicle with an electric drive enables reliable and unproblematical use even in extremely difficult environments.

Preferably, the drive motor is arranged coaxially with respect to the roll axis of the small aerial vehicle; this axle will usually coincide with the longitudinal axis of the elongate fuselage. By this means, a particularly advantageous configuration of the small aerial vehicle with regard to flight mechanics is achieved.

In a preferred development of the small unmanned aerial vehicle, a second propeller, which is arranged coaxially with respect to the first propeller and rotates in the opposite direction, is provided. The second propeller can be drivable either by the existing drive motor of the first propeller via gearing, preferably coaxial gearing, or alternatively it can be drivable by a second drive motor which is likewise preferably arranged coaxially with respect to the roll axis of the small aerial vehicle.

These two alternative configurations with propellers rotating in opposite directions ensure that the torques exerted on the small aerial vehicle by the respective propellers compensate each other, so that the attitude of the aerial body about the roll axis is stabilised.

Preferably, the pivotable control surfaces are mounted on four control surface axles arranged in a Cartesian or orthogonal manner about the longitudinal axis of the aircraft. In the case of this variant, the control surfaces are each spaced apart from one another in the circumferential direction by 9Q0. Alternatively, the pivotable control surfaces can also be mounted on three control surface axles which extend in a star shape away from the longitudinal axis of the small aerial vehicle and are spaced apart from one another in the circumferential direction by 1200 each. Other preferably equidistantly spaced arrangements are possible.

It is particularly advantageous when the steering gear provided to actuate each control surface is integrated into the associated control surface in such a way that only a pivotable control surface lever projects from the control surface. This lever is then connected to a structural element of the small aerial vehicle. In this way, the steering gear required to actuate the control surface is aerodynamically covered by the control surface itself.

Preferably, the small aerial vehicle has a launching and landing frame arranged at the tail. By means of this landing frame, the small aerial vehicle can be launched from any desired location without requiring a separate launching device and be landed safely again in the same way.

In this case, it is advantageous to provide at least one pivot bearing of a respective control surface in the launching and landing frame. Each pivot bearing can for this purpose be provided in or on the respective control surface axle associated with the control surface and is fixed to the launching and landing frame.

Preferred embodiments of the invention with additional design details and further advantages are described and explained in more detail below with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings: Fig. 1 shows a side view of a small unmanned aerial vehicle according to the invention, and Fig. 2 shows a basic diagram of control software for this small unmanned aerial vehicle.

DESCRIPTION OF EMBODIMENTS

In Fig. 1, a small unmanned aerial vehicle according to the invention is illustrated in a side view. The vehicle is generally rotationally symmetric and has a fuselage 1, at the rear end of which there are rigidly attached four aerodynamic active surfaces which form wings 2 of the small aerial vehicle. These wings 2 are arranged in a Cartesian manner about the longitudinal axis X of the aerial vehicle and are thus oriented at right angles to one another. The aerial vehicle shown in Fig. 1 is thus designed as a cross-winged vehicle with four half-wings. The fuselage structure and the wing structure are made of lightweight materials, preferably foamed plastics.

In the rear region of the radially outer wing ends 20 of each wing 2, supporting legs 30 of a launching and landing frame 3 are attached, which extend in the direction of the longitudinal axis X of the aerial vehicle rearwards beyond the wings 2. At the rear free end of the supporting legs of the launching and landing frame 3, there are provided balloon-like supporting feet 32 which are preferably composed of elastic material. Connecting struts 34 connect each pair of adjacent supporting legs 30. These connecting struts 34 can be either straight or curved in the form of a circular segment, so that the struts 34 as a whole form a ring connecting the supporting legs or feet 30 to one another.

A first drive motor 40 of a first drive unit 4 is arranged in the tail region 10 of the fuselage 1. The drive motor 40 is preferably in the form of an electric motor and is supplied with electrical energy by electrical energy storage devices provided in the fuselage 1 and/or the wings 2, these devices being illustrated merely schematically in the drawing and denoted by the reference symbol 6. Instead of fitting the electrical energy storage device 6, which may be in the form of a battery or accumulator, in the fuselage as shown, it is also possible for one or more electrical storage devices to be provided on the outside of the fuselage.

A tail skid 12, which passes axially through the drive motor 40 and the propeller 42, is fixed to the fuselage 1.

A second, preferably electrical, drive motor 50 of a second drive unit 5 is provided on the tail skid 12 behind the first propeller 42 and drives a second propeller 52 which is likewise rotatably mounted on the tail skid 12. The axes of rotation of the drive motors 40, 50 and thus also of the propellers 42, 52 lie on the longitudinal axis X of the small aerial vehicle and, since the small aerial vehicle is constructed symmetrically about the longitudinal axis X, this axis corresponds to the dynamic roll axis X' of the small aerial vehicle. The drive motors 40, 50 and the propellers 42, 52 are thus arranged coaxially with respect to the roll axis X' of the small aerial vehicle.

The propellers 42, 52 rotate in opposite directions of rotation, so that the torques induced by the propellers 42, 52 on the small aerial vehicle about the roll axis X' cancel each other out. The air flow produced by the propellers 42, 52 is directed substantially rearwards in relation to the aerial vehicle (downwards in Fig. 1) and produces propulsion for the small aerial vehicle.

Instead of the two coaxial motors 40, 50 illustrated in Fig. 1, which are each in the form of an electric motor and each drive one of the propellers 42, 52, it is alternatively also possible to provide a single drive motor which drives both propellers 42, 52 in opposite directions via gearing. This gearing is preferably in the form of coaxial gearing which is mounted on the tail skid 12 behind the drive motor. The drive motors can be in the form of brushless electric motors which are controllable in their rotational speed by a corresponding regulating device (rotational speed controller or governor), so that the propulsion of the unmanned aerial vehicle can be controlled or regulated. It is, of course, also possible to use internal combustion engines, or hybrid systems consisting of electric motor(s) and internal combustion engine(s), instead of electric motors.

Directly behind the arrangement consisting of the two propellers 42, 52, i.e. behind the second propeller 52, four pivotable control surfaces 7 are provided in the downwind area of the air flow produced by the propellers 42, 52. Each of the control surfaces 7 is pivotably mounted on an associated control surface axle 70 which extends between the tail skid 12 and a supporting leg 30 of the launching and landing frame 3, radially outwards in relation to the longitudinal axis X of the aerial vehicle.

The pivotable control surfaces 7 are thus pivotably mounted on four control surface axles 70 arranged in a Cartesian manner about the longitudinal axis X of the vehicle.

To actuate each control surface 7, there is provided a steering gear 72 which is integrated into the associated control surface 7 in such a way that only a pivotable control surface lever (not shown) projects from the control surface. This lever is connected to a structural element of the small aerial vehicle, for example to the control surface axle 70.

The guidance electronics, which are required for controlling the aerial vehicle and include a basic flight guidance sensor system consisting, for example, of an inertial measurement unit (IM[J), acceleration sensors and rotational rate sensors, are accommodated in the fuselage 1 and/or the wings 2. Furthermore, a satellite navigation receiver and pressure sensors, ultrasonic sensors, rotational speed sensors, temperature sensors and/or operating voltage sensors, as well as data transmission equipment, are also provided there.

In the front section 14 of the fuselage 1, a space for a payload is formed. This payload can be, for example, a camera and/or a seeker head. Furthermore, it can also include weapons.

Since the small aerial vehicle according to the invention is preferably provided for short-range use and is to be portable by individual task force personnel, it is preferably constructed in a modular fashion, so that it can be fitted together. By way of example, the length of the entire vehicle is usually between 50 cm and 1.3 m, the diameter of the fuselage structure is between 5 cm and cm and the total weight is between 1 kg and 6 kg. One embodiment of the small aerial vehicle according to the invention has a length of 70 cm, a fuselage diameter of 7 cm and a total weight of 1 kg. A second embodiment of the aerial vehicle according to the invention, suitable for longer flying times and/or greater payload transportation, has a length of 1.2 m, a fuselage diameter of 12 cm and a total weight of 5 kg.

The small aerial vehicle can be launched either directly from the launching frame 3 and land thereon or it can be launched from a launching container 8, illustrated merely schematically in Fig. 1. The launching container 8 reduces impairment during storage and preparation of the mission and reliably prevents the aerial vehicle from toppling over during the launching process, for example in the presence of strong winds.

The small aerial vehicle according to the invention is part of a system which includes, in addition to the vehicle itself, a ground or operating station which is connected via radio to a corresponding transmit/receive device in the small aerial vehicle for unidirectional or bidirectional data transmission. The operator of the system can transmit commands to the vehicle by suitable control elements via the operating station, for example commands for position control of the vehicle. Furthermore, information on the flying state and/or the surroundings of the vehicle (e.g. pictures taken or videos recorded by a camera present in the vehicle) can be transmitted by the vehicle to the operating station and displayed on a screen there.

Fig. 2 shows in a block diagram the data flow between the operator and the aerial vehicle, as well as the interaction of the aerial vehicle with the environment which surrounds it.

In the attitude control mode, the software included in the guidance electronics determines in the navigation module 112 the estimated attitude of the small aerial vehicle for the purpose of its attitude control. An attitude control module 110 compares the estimated attitude with the data input into the operating station 102 by the operator 101 and transmitted to the guidance electronics of the aerial vehicle via the data transmission equipment 103, 104.

The guidance electronics can likewise be commanded in the so-called position control mode by a position control module 107. In this case, an altitude controller 108 compares the altitude or height above ground estimated in the navigation module 112 with the commanded altitude and from this determines thrust commands for the drive unit 109. The position control module 107 compares the position estimated by the navigation module with the commanded position and from this determines corresponding attitude and altitude commands. The commanded positions for the position control module are obtained from the path data preset by the operator 101 and provided via the operating station 102, the data transmission equipment 103, 104 and by online path planning 105. These path data can consist, for example, of a single point if the small aerial vehicle is to maintain its position at a location, but they can also be preset relative to a current position, this being typical of a flight based on camera images or, when visibility is good, by control commands sent by the operator to the small unmanned aerial vehicle. The path data can, however, also be preset by a flight path which has been preset and stored in a mission data memory.

Higher-level moding defines the operating modes of the small unmanned aerial vehicle and of the software modules of the guidance electronics in dependence on the operator presettings and on sensor and module information, for example about GPS availability, navigation accuracy or charging state of the batteries in the case of an electrical drive. A scheduler 106 determines the calling sequence and calling frequency of the individual modules.

Reference numerals in the claims, descripticn and drawings serve merely for a better understanding of the invention and are not intended to limit the scope of protection.

List of reference symbols 1 fuselage 2 wings 3 launching and landing frame 4 first drive unit second drive unit 6 electrical energy storage device 7 control surfaces 8 launching container tail region 12 tail skid 14 front section radially outer wing ends supporting legs 32 supporting feet 34 connecting struts 40, 50 drive motor 42, 52 propeller control surface axle 72 steering gear 101 operator 102 operating station 103, 104... data transfer device online path planning 106 scheduler 107 position control module 108 altitude controller 109 drive unit bearing control module 112 navigation module X longitudinal axis roll axis