WO2007141795A1

WO2007141795A1 - Unmanned air vehicle system

Info

Publication number: WO2007141795A1
Application number: PCT/IL2007/000693
Authority: WO
Inventors: Eliezer Barnea
Original assignee: Israel Aerospace Industries Ltd.
Priority date: 2006-06-08
Filing date: 2007-06-07
Publication date: 2007-12-13
Also published as: IL176200A0; IL176200A

Abstract

An unmanned air vehicle (UAV) system (10), is provided including a ground station (70), a platform (20) configured for carrying a payload (40) and having a propulsion system (30) for enabling the platform at least to selectively sustain a predetermined altitude above the ground station when in flight mode, and also including a tether (50) operatively coupling the ground station with the platform, the tether providing electrical communication between the platform and the ground station.

Description

UNMANNED AIR VEHICLE SYSTEM

FIELD OF THE INVENTION

This invention relates to air vehicles, in particular to unmanned air vehicles.

BACKGROUND OF THE INVENTION

Unmanned Air Vehicles (UAV) come in a variety of configurations each adapted for the specific design mission it is intended to be used for. For example, some

UAVs are configured for surveillance, observation or monitoring of a ground-level zone from an altitude, and may circle the zone continuously until fuel limitations force the UAV to leave and eventually land at base.

Heavier that air UAVs rely on powerplants and aerodynamic surfaces for maintaining the UAV at an altitude over the ground at a lift sustaining airspeed.

Some UAVs are configured for independent VTOL operation, for example the Kestrel UAV, which is powered by a liquid fuel powered by two tilt-fan engines and may be suitable for surveillance missions.

Lighter-than-air (LTA) unmanned vehicles, such as balloons and blimps, are also known for use in surveillance, and some varieties thereof are tethered to a fixed ground location. No power is requited to keep the LTA vehicle at a predetermined altitude; deployment and retrieval of the LTA vehicle is relatively slow. Such LTA vehicles are relatively large, and their buoyancy is sensitive to small losses in the working gas, typically Helium. Another known system for surveillance, observation or monitoring of a ground- level zone from an altitude includes surveillance equipment mounted at the top of a tall pole, tower or the like, which are static structures, and limited in the maximum height from which surveillance may be carried out. Telescopic poles provide control over this height, and such systems are routinely employed on trucks for providing TV coverage of events at moderate heights. However, such telescopic systems are complex, costly, heavy, and more limited in the maximum height that they can provide for the surveillance equipment. SUMMARY OF THE INVENTION

The present invention relates to tethered airborne platforms, in particular to such platforms that are heavier-than-air air vehicles, and that may be applied for uses including surveillance from a static or moving ground station. According to a first aspect of the invention, an unmanned air vehicle (UAV) system is provided, comprising a ground station; a platform configured for carrying a payload and comprising a propulsion system for enabling said platform at least to selectively sustain a predetermined altitude above a ground station when in flight mode; a tether operatively coupling said ground station with said platform, said tether configured for providing electrical communication between said platform and said ground station.

In particular, the propulsion system is electrically powered and is provided with electrical power from the ground station, which is configured with an electrical power source, via said tether.

In disclosed embodiments, the platform is configured for hovering or powered flight, wherein the lifting forces for the platform, in hover and at least partially in flight, is provided directly by the propulsion system, which provides a lifting force which is partially or fully vectored to balance directly the weight of the platform. Thus, the platform is free from the need of, or indeed does not comprise, any aerodynamic lifting surfaces for balancing the weight of the platform during operation thereof, at least when hovering. The ground station may comprise a housing for receiving and accommodating said platform when said flight mode is terminated, and a spool system for reversibly winding said tether thereto. The spool system may be configured to release or wind said tether in a substantially tensile free manner, according to a distance between said platform and said ground station.

The platform may comprise a payload including an observation system for observing an environment in an area circumscribing said ground station. The observation system may comprise at least one imaging device for imaging a scene external to said system in at least one of; the visible spectrum; infra red frequencies; ultraviolet frequencies. The ground station may be adapted for being reversibly or permanently connected to a mother vehicle, said vehicle capable of transport over a surface at least during operation of the system. The mother vehicle may be self-propelled, or may be towed via another vehicle. The propulsion system is electrically powered, and may comprise at least one electrical motor coupled to a fan.

The platform may comprise an upper-facing first side and a downward facing second side, and a plurality of through-openings therebetween, wherein the propulsion system may comprise a ducted fan arrangement accommodated in each said through- opening. The fans may be of variable pitch or of fixed pitch.

The payload may be downwardly-depending from said second side at a location at or generally close to a center of gravity of said platform. The tether may be connected to said platform via a distal connection point at a location at or generally close to a center of gravity of said platform. The payload may be enclosed in a casing comprising apertures for enabling operation of imaging devices, and wherein said distal connection point comprises a spacer arrangement for routing a distal portion of said tether to said platform around a portion of said payload via an eyelet located below said center of gravity.

The platform may comprise a landing arrangement configured for minimizing landing impact forces with respect thereto.

The system may comprise a suitable control system for maintaining stability of said platform when in said flight mode with respect to maintaining said altitude within predetermined thresholds.

The ground station may comprise an electrical power generator for supplying electrical power to said platform via said tether.

The platform may comprise a suitable electrical backup system for providing emergency power to said platform. The backup system may be configured for providing emergency power to said propulsion system for enabling said platform to be landed in a generally safe manner with respect to said ground station. The backup system may comprise a high capacitance system capable of storing and delivering sufficient electrical power to said propulsion system for operating the same for a short duration of time correlated to landing said platform in a generally safe manner with respect to said ground station. The system may further comprise a control interface for enabling a user to operate said system. The interface may comprise at least one of a position control station, a payload control station, and a payload monitor station.

The system may comprise a suitable control system configured for controlling said propulsion system when in said flight mode, such as to maintain said platform within a predetermined distance and/or altitude with respect to said ground station, while said ground station is being transported over a surface.

Thus, according to the first aspect of the invention, a platform is provided for carrying a payload and comprising a propulsion system for enabling said platform at least to selectively sustain a predetermined altitude above a ground station when in flight mode, said platform being configured for being connected to a tether to provide electrical communication between said platform and a ground station, said propulsion system being electrically powered and configured for being provided, in operation, with electrical power from the ground station via the tether, wherein said propulsion system is further configured to provide, in operation, a lifting force which is at least partially vectored to balance directly a weight of said platform.

According to a second aspect of the invention, a vehicle is provided, comprising a system according to the first aspect of the invention. The vehicle may be self- propelled, having its own powerplant and capable of locomotion, typically over a surface, such as a ground surface and/or a water surface. Alternatively, the vehicle may be trailer or the like.

According to a third aspect of the invention a building structure, comprising a system according to the first aspect of the invention. The building structure may be an observation post, for example. According to a fourth aspect of the invention, a method is provided for extending enhancing a viewing vantage point of an observer, comprising; providing a system according to the first aspect of the invention; causing said platform to hover with respect to the observer at a desired altitude above the observer; acquiring surveillance data of the surrounding environment via said payload.

In other embodiments of the invention, a vectored or tilting fan arrangement may be used as the powerplant, and the angle of the fan may be changed in order to further control operation of the platform. Optionally, aerodynamic control surfaces may be provided to the platform for further controlling operation of the platform.

A feature of the ducted fan arrangement for the disclosed embodiment is that it provides noise reduction and better safety, as compared with using unducted propellers and the like.

Noise reduction may be further enhanced by having the turning axes of the fans substantially vertically, so that the noise generated by the fans is directed towards the ground directly below and to the sky directly above the platform, and thus minimizes projection of fan noise in directions around the system itself. Optionally, some embodiments of the platform may comprise one or a plurality of illumination lights, which may be used for illuminating the area in the immediate vicinity of the ground station, or indeed for illuminating specific spots distanced from the ground station. This may be of particular assistance for general or frontier policing activities at night, for example. While embodiments of the system, and particularly the platform, is described herein as being used as an aerial surveillance platform, it may also have other uses in addition or in stead of thereof. For example, the platform may be used as an aerial illumination platform, comprising a plurality of search lights or the like. Alternatively, the platform may be used as a relay station for the broadcast or relay of radio, television and any other transmissions, providing a similar effect as a relay station atop a tower or pole, but with the versatility of deploying and retracting the same as required.

Alternatively, embodiments of the system may be configured for use in anti- terrorist activities. For example, as an aerial surveillance platform, it may be flown towards a high floor of a building, under tethered power and control, to assume a position enabling it to look into a window thereof of an apartment in which suspects are operating. Further, the platform, in particular the payload, may be equipped with anti- terrorist measures, for example a mechanical arrangement or mechanism, for example a mechanical arm or probe, to test suspicious packages or the like for bombs, where such packages are not readily accessible with regular tracked robots, for example. Similarly, the system may be used for scanning a minefield for unexploded mines, while the operator is at a safe distance. In fact, by coupling the system to a moving vehicle, the vehicle can traverse a minefield by deploying the platform ahead of the vehicle, the platform scanning and plotting a safe path for the vehicle, wherever possible.

Thus, the system according to aspects of the invention may comprise a payload including any suitable equipment as needed for a variety of missions. A feature of embodiments of the invention is that in operation the platform according to the invention can assume a hovering position, -with respect to the ground station, which may be static or moving, at a relatively high enough altitude, such as to enable data obtained by the payload to be transmitted over a long distance, optionally to a receiving station independent of the system itself. Additionally or alternatively, the platform can also be configured for being displaced from the ground station in a horizontal direction.

Another feature of embodiments of the invention is that no working fluid, for example helium for buoyancy or liquid fuel supply, needs to be provided to the airborne platform itself. Another feature of the invention is that no special take off or landing area needs to be prepared in advanced at any particular site. Rather, the take-off and landing occurs with respect to the ground station, which is a part of the system, and which can be placed on a vehicle roof, or on the top or other location of an observation post, for example. Deployment of the platform according to the invention may be accomplished in an automated manner, enabling the operator to remain secure within the vehicle or post and thus not exposing the operator to sniper fire, mines, booby traps and so on.

Another feature of embodiments of the invention is that it enables the ground station to be in the form of a relatively shallow box, which can be placed on a vehicle roof, for example, or concealed or incorporated in a generally non-obtrusive manner in the general form or structure of the mother vehicle.

The system of the invention finds application in military use, police use, and civilian use.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1 is a partial cross-sectional side view of the system according to the invention.

Fig. 2 is a bottom view of the embodiment of Fig. 1.

Fig. 3 is a bottom isometric view of the embodiment of Fig. 1. Fig. 4 schematically illustrates the embodiment of Fig. 1 in flight mode, in use with a self-propelled ground vehicle.

Fig. 5 schematically illustrates the embodiment of Fig. 1 in flight mode, in use with a self-propelled sea vehicle.

Fig. 6 schematically illustrates the embodiment of Fig. 1 in stored mode, in use with a non-self propelled ground vehicle.

DETAILED DESCRIPTION OF EMBODIMENTS

A first embodiment of the system of the invention is illustrated in Figs. 1 to 3 and generally designated with numeral 10, comprises a platform 20, tether 50 and ground station 70.

The platform 20 comprises a heavier-than-air mobile unmanned air vehicle (UAV) adapted for providing hovering and optionally flight performance in up to six degrees of freedom, including translations and/or rotations with respect to one or more of three orthogonal axes, i.e., with respect to any one of or combinations of vertical, horizontal (forward, backward) and lateral (side to side) movement, having a propulsion system 30 and a payload 40. In the illustrated embodiment, the platform 20 comprises a generally rectangular plan form, having a substantially flat upward facing upper side 22 and a substantially flat downward facing lower side 24, joined one to another via peripheral side walls 26, which are relatively shallow, minimizing the cross-section of the platform 20 as observed from a sideways or front/back direction. In other variations of this embodiment, the plan form of the platform 20 may be different, for example triangular, polygonal, elliptical, circular, and so on.

The propulsion system 30 comprises a ducted fan arrangement comprising four electrically powered ducted fans, 35a, 35b, 35c, 35d, referred to herein collectively by the numeral 35, one accommodated in each of four substantially similar cylindrical through-openings 32 provided in a symmetrically spaced manner between the upper side 22 and the lower side 24. Each ducted fan 35 comprises a propeller or fan 36 powered by an electrical motor 37 held concentrically within the corresponding opening 32 via a plurality of struts 38, the location of the fan 35 dividing the opening 32 into an upstream intake opening 3 land a downstream exhaust outlet 33. The rotational axes of the fans 35 are substantially parallel one with another, and substantially orthogonal to said upper side 22 and/or lower side 24, and when the platform is hovering the rotational axes may be vertical or close thereto. Thus, the propulsion system 30 is configured for providing a lifting force that at least is partially vectored, i.e., comprises at least a force component in the upward vertical direction, to balance directly the weight of the platform, enabling the platform to hover, as well as move, without the need of aerodynamic lifting surfaces such as wings, for example.

Each motor and corresponding fan may be configured for rotation in the same direction, and thus are substantially identical in construction. Alternatively, two of the fans 35 (for example two diagonally spaced fans 35a, 35c) with their corresponding motors may be configured for rotating in one direction, while the other two fans (for example 35b, 35d) with their corresponding motors may be configured for counter- rotation, i.e., for rotating in the opposite direction to the first two fans, and thus provide rotational stability to the platform when all fans are working. The rotational speed of the fans 35 may be individually controlled, enabling differentials in fan speed to provide desired rotational movement of the platform 20. The fans 35 may each comprise a plurality of fixed pitch blades for simplicity and low weight. However, in other embodiments, variable pitch blades may be used for better efficiency.

Each exhaust outlet 33 further comprises at least one set, and preferably two sets of orthogonally arranged variable control vanes 39, set for pivoting along two mutually orthogonal axes lying on a plane substantially coplanar with the said upper side 22 and/or lower side 24, and controllably deflectable to provide maneuverability to said platform 20 when in flight mode. .

The vanes 39 and the fans 35 may be controlled by means of an on-board flight computer 90, which in turn may receive command inputs from the ground station 70 via the tether 50 or via wireless communication, and enable the platform 20 to be maneuvered into any desired or necessary direction, altitude, elevation, angle of attack with respect to the direction of motion along the ground of the platform (where applicable), and provides any desired or required pitch, roll or yaw, and/or any displacement along any direction as required or desired.

Each electric motor 37 may comprise, by way of non-limiting example, 600V, 1500W brushless DC type motor. High voltage motors may be better than low voltage motors of the same weight and wattage, as they allow the electrical power cables of the tether 50 to be thinner, and thus less heavy, than they would otherwise need to be. The motors are preferably able to provide peak power at about 300% of the nominal design power, enabling relatively fast powered maneuvering in response to gusts and so on, providing better safety to the platform 20. This peak power capability also enables the platform to be landed safely in the event that one or two motors have to be shut down, and powered flight continued via the remaining motors. The motors 37 are further preferably designed with a high mean time between failures (MTBF), for example, 10,000 hours. Such brushless DC motors may each comprise two independent rotors, and thus in the event of failure of one rotor, the other rotor may continue to operate, providing some measure of control and power to the platform 20. Optionally, the motors 37 may each comprise a thermocouple for enabling monitoring, typically continuously, of the motor temperature via the flight computer 90. Motor malfunction can be detected by the computer 90 as a rise in motor temperature, and steps can be taken for an emergency landing before the motor fails completely. This provides a safety aspect to operation of the system 10 and minimizes potential damage to the motor which may happen if allowed to continue working to full failure.

In other embodiments there may be less than four or more than four ducted fans and/or the ducted fans may be replaced with other suitable propulsion units, for example unducted propellers and so on. The platform 20 further comprises a suitable electrical backup system for providing emergency power to the platform, in particular to the motors 37 for enabling said platform to be landed in a generally safe manner with respect to said ground station 70. Such a situation may be contemplated, for example, when the regular electrical power provided to the platform via the tether 50 fails. In the illustrated embodiment, the backup system comprises a high capacitance system 29 capable of storing and delivering sufficient electrical power to said propulsion system for operating the same for a short duration of time correlated to landing said platform in a generally safe manner with respect to the ground station. The high capacitance system may comprise, by way of non-limiting example, one or a plurality of ultracapacitors, supercapacitors, electrochemical capacitors, electrical double layer capacitors (EDLC) and the like, in which a substantially large amount of charge may be discharged in a short time, say between about 3 seconds and about 30 seconds, at high efficiency. Suitable high capacitance systems are commercially available, and are currently used in applications such as hybrid automobiles.

The platform 20, or indeed any other part of the system 10, may comprise a Global Positioning System (GPS) antenna 48, for receiving and relaying GPS data to the computer 90, and thus determining the platform's or the system's position. This may be useful in enabling the computer 90 to control the platform to position and orientation of the payload 40 where required, within limits, in cooperation with the location of the ground station 70. The computer 90 may be configured with two or more CPU's and two or more inertial navigation systems or AINS sensors, for redundancy, and may be configured for operating and flying the platform 20 autonomously, without operator intervention, within predefined parameters.

The platform 20 further comprises a payload 40, the nature of which will generally depend on the mission for which the particular system 10 is envisaged. In one particular application of the invention, the system 10 is contemplated as an observation platform for providing information of the surrounding environment with respect to the ground station 70, which may be static or moving, including at ground level or in the air. Thus, in this embodiment the payload 40 includes imaging equipment enclosed in a generally spherical protective casing 42, enabling the platform 20 to operate as an aerial observation platform. The imaging equipment may include one or a plurality of cameras or the like, configured for acquiring discrete optical, thermal or other images and/or including video images, optionally in real time, in any desired frequency, typically including the visible electromagnetic spectrum, but optionally also at infrared and/or ultraviolet frequencies. Optionally, the payload 40 may also comprise laser and/or radar equipment for range-finding, surveillance or other uses. In particular, the payload 40 may comprise LADAR (laser radar) detectors for detecting the presence of low objects such as power lines, bridges and so on, in the path of the platform 20 or tether 50, when the system is coupled to a traveling vehicle, for example. The LADAR is operatively connected to computer 90 and/or computer 100, which can then calculate and control evasive maneuvers for the platform. Such a feature also allows using the system atop a vehicle even at night or in other low- visibility conditions while in flight mode, and also facilitates continued operation of the platform 20, in particular providing surveillance data therefrom, even while the ground station 70 is moving with the vehicle.

The casing 42 may have a plurality of lookout ports 43 strategically located about the surface thereof, through which the various imaging and other equipment in the casing 42 may view or receive their respective data from the surrounding environment. For example, at least some of these ports may be downward-looking with respect to a zone in the ground at some distance from the ground station, when the platform 20 is at a predetermined altitude from the ground station. Optionally, the casing may be mounted on a frame (not shown) that enables the payload 40 to be rotated about one axis (e.g. a vertical axis) or about two orthogonal axes, enabling the position of the ports 43 to be selectively changed, and thus enabling the zone being observed via the equipment therein to be chosen. The on-board computer 90 may be operatively connected to a suitable arrangement of attitude and acceleration sensors (not shown), and configured for enabling the platform and/or payload to face in a particular direction or towards a particular point (for example a ground target) regardless of the position of the platform 20 and of the wind conditions when in flight mode.

The maximum weight of the payload 40 generally depends on the nominal power-to-weight ratio of the propulsion system 30, the power rating thereof, and on the weight of the platform 20 and of the length of deployed tether 50. By way of non- limiting example, the payload 40 may comprise a weight of between about 7Kg and about 10Kg. Clearly, in other embodiments of the invention, the payload may have a weight less than 7Kg or more than 10 Kg.

The payload may additionally or alternatively also comprise a mechanical arm or probe, for example, for causing a desired mechanical effect, for example, grabbing, probing and so on, responsive to manual commands from the operator, or to automatic commands according to preset rules governing causing such effects.

The payload 40 may be in the form of a removable module, and thus may be interchangeable with a number of similar modules, each of which is set up for a different mission profile. The payload 40 module may thus comprise reversible connection/disconnection mechanism for connecting the payload to the main body of the platform 20, with a suitable interface for connecting/disconnecting power lines, data lines and so on of the payload 40 to the platform 20 and thence to the tether 50. The payload 40 may be located directly below, or at least near to, the center of gravity CG of the platform 20, and thus downwardly depends from the center of the lower side 24 of the platform 20. Such an arrangement aids in the stability of the platform 20 when in flight mode. Other arrangements may be provided as needed. The platform 20 also comprises suitable undercarriage or landing gear for cushioning the landing impact to the platform 20 when landing the same with respect to the ground station 70, or indeed any other landing surface, at the end of normal flight operations. In the illustrated embodiment, the landing gear may comprise four spaced struts 44, each strut 44 being cantilevered from a point on the lower side 24, outwardly diverging and ending at a free end comprising a rounded pad 45 or the like, for example. The struts 44 may be made from high tensile composite fiber, for example, which can absorb landing impact stresses by bending. The struts may be configured for absorbing nominal impact accelerations of 3g, for example. Alternatively, the landing gear may comprise skis, wheels and so on, which may be retractable, semi retractable or permanently deployed.

The payload 40, or at least some of the imaging devices thereof, may be configured to rotate or otherwise move with respect to the platform, enabling any field of view to be brought into the line of sight of the imaging devices, regardless of the position, orientation or attitude of platform, and also enabling any filed of view, previously possibly obscured by one of the struts 44, to become visible, for example by also maneuvering the platform 20 as required.

Optionally, the platform 20 and/or the ground station 70 may be equipped with an inflatable shock-absorbing system, for example one or a series of balloons, that may be inflated at or near landing to cushion the landing of the platform. This may be provided, for example, as an emergency measure should the undercarriage fail or the on-board computer determine (via suitable sensors, for example) that the landing acceleration exceeds the safety limit or structural limit for the undercarriage, or as an alternative form of the undercarriage therefor.

The tether 50 primarily comprises one or a plurality of cables 55 configured for supplying electrical power to the motors 37 and other electrical or electronic equipment in the platform 20, for example the payload 40 and the computer 90. The cables 55 are preferably highly flexible and are of low weight. For example, one or two cables 55 may be provided, configured for^' high voltage, for example 300V or 600V, and thus enabling the cable diameter to be low, adding to the flexibility and low weight of the tether 50. Further, by use of suitable low- weight materials, for example aluminium alloys, the weight of the cables 55 may be further reduced. Optionally, a tension- carrying safety line 56 may be comprised in the tether to relieve tensile loads on the cables 55, and/or to ensure that the platform remains mechanically connected to the ground station 70, even if the cables 55 fail mechanically. The tether 50 may also comprise communication links, for example fiber optic cables or electrical cables 57, for transmitting data from the pay load 40 to the ground station 70, and/or for transmitting commands and other data from the ground station 70 to the platform 20. A distal end 58 of the tether 50 is connected to the lower side 24 of the platform

20 via a proximal connection point 59, preferably at or close to the CG thereof, which may aid in providing stability, or at least in reducing potential instability in the platform, due to the tether 50. Other arrangements may be provided as needed. In the illustrated embodiment, the payload 40 is also close to the CG at the lower side 24, and the distal end 58 of the tether 50 is connected to the platform 20 via a spacer arrangement 60 which effectively displaces the point at which the tether is freely suspended from the bottom side 24, from the proximal connection point 59, to a position immediately below the payload 40 and CG. The spacer arrangement 60 in this embodiment comprises a hook-shaped support 62, anchored close to the distal connection point 59, which is close to the base of the payload 40 with respect to the lower side 24, and circumvents the surface of the casing 42 towards a free end thereof comprising an eyelet 64, located immediately below the payload and CG. The distal end 58 of the tether 50 is routed from the distal connection point 59 through the eyelet 64, and thence towards the ground station 70. The length of the tether 50 may be as long as desired, generally limited by the weight of the extended length thereof between the ground station 70 and the platform 20 that can be supported by the platform 20 (in addition to its own weight including that of the payload 40) when the platform 20 is in simple hovering mode or in flight mode. By way of non-limiting example, the nominal maximum extended length of the tether may be between about 50m and about 100m. Clearly, according to the specific details of the embodiment of the invention, the nominal maximum extended length of the tether may be less than 50m or more than 100m. Optionally, the proximal end 52 of the tether 50 may be connected to a winch or spool 80, located at the ground station 70. The spool 80 may be electrically powered and enables the tether 50 to be controllably and selectively released from, or wound onto, a spool, allowing deployment or retraction, respectively, of the platform 20 with respect to the ground station 70. Thus, the winch or spool 80 releases the tether 50 when the platform 20 rises, and collects the tether when the platform comes down. The platform 20 may also be configured to pull the tether with some force so as to control the tension in the tether 50. A suitable ground computer 100, operatively connected to the spool 80, can monitor the tension in the tether 50 (for example by means of suitable strain gauges), and can control the deployed length of tether in real time to minimize tensile stresses in the tether 50. Further, the ground computer 100 can be further adapted to wind-in the tether under controlled conditions to facilitate and stabilize the landing of the platform 20 with respect to the ground station at the end of the flight mode. Thus, during the landing phase, the spool 80 may actually pull the platform 20 towards the ground station 70 in a swift and secure manner, while the platform is still in flight mode.

Optionally, the tether 50 may be reversibly connected to the platform 20 and/or to the ground station 70 in a manner such as to enable relatively quick connection and disconnection with respect thereto. This may be a useful feature when requiring to replace the tether in battlefield conditions, for example.

Further optionally, the tether 50 may comprise an emergency quick-release system, enabling the tether 50 to be severed from the platform 20 and/or from the ground station 70, controlled manually by the operator of the system 10, and/or according to pre-set rules by means of one or both computers 90, 100. By way of non- limiting example, the quick release system may comprise a magnetic connector (not shown) for selectively locking or releasing the main body of the tether 50 from the distal end 58 thereof, at or near the eyelet 64, for example. The magnetic connector may thus comprise a male element, for example, attached to the main body of the tether 50, and a complementary female element comprised on the distal end 58, such that when the male and female elements of the connected are brought together and magnetically locked, the main body of the tether 50 and the distal end 58, which can be two coaxial parts of the tether, are brought together to provide electrical, data, and mechanical continuity to the tether 50. The magnetic connector may be caused to become disconnected, and thus sever the platform 20 from the main body of the tether 50 and thus from the ground station 70, when, for example, the tether becomes entangled and is endangering the platform 20 and/or the vehicle, or wherein the platform 20 cannot be brought back down to the ground station, or for any other suitable reason. Such disconnection may be performed by the user on a discretionary basis, by means of the interface 150. However, there may be instances where the computers 90 and/or 100 may automatically disconnect the platform under predefined conditions. For example, if the computers detect that there has been an electrical power interruption but data continues to flow via the tether 50, then there may be no need to disconnect as it may be assumed that the computers (having their own back-up battery for such an event) are still operational, and may land the platform 20 safely, using the aforesaid emergency high capacitance system, while still tethered. On the other hand, if there is no power or data transfer along the tether 50, this may be indicating that the platform 20 may be damaged, and may thus fall onto the ground station 70, possibly causing injury and/or damage, and, particularly when attached to a moving vehicle, it may be prudent to disconnect the platform 20 to avoid such a scenario.

Similar arrangements may be made regarding the proximal end 52 of the tether 50, mutatis mutandis, as there may situations in which it may be desired to disconnect the tether 50 close to or at the ground station 70, for example if the tether were to become entangled in a tree or power lines.

The ground computer 100 may estimate the altitude of the platform 20, for example by monitoring the length of tether 50 that has been released from the spool. The ground computer 100 may also comprise its own GPS antenna 77, and thus enable the position of the ground station to be accurately tracked. Furthermore, the GPS data obtained for the ground station 70 may be used, together with GPS data from the computer 90, to determine and control the position of the platform 20 with respect to the ground station 70, for example so that the platform 20 maintains a hovering position within a predetermined radius about the ground station 70, whether the latter is static or moving while the platform is in flight mode. The differential between the GPS data obtained for the ground station 70 and the GPS data from the computer 90, may provide positional accuracies in the order of about 0.5m, for example.

The ground station 70 comprises a housing 71 for accommodating the platform 20 on landing, and for protecting the same from the environment in stored mode, while not in operation. The ground station 70 also serves as a launch site for the platform 20, and serves to channel electrical power thereto via the tether 50 when in flight mode. The ground station 70 comprises an open-box like structure, having a base 72 and peripheral side walls 74, of a shape and size sufficient to accommodate the platform 20 therein. Optionally, the side walls 74 are pivotably hinged with respect to the base 72, and may be rotated away from the base 72, manually or in an automated manner, particularly for landing mode and takeoff mode, to minimize possible contact between the walls 74 and the platform 20 due to possible sideways drifting of the platform when near the ground station 70. The housing 71 also comprises a cover 78 that can be placed over the open- box structure of the base 72 and walls 74, particularly after the platform 20 has been safely stowed therein. Optionally, clamps (not shown) may be provided on the base 72 to reversibly clamp the platform thereto. The housing 71 may also be relatively shallow in depth to minimize its bulk, particularly when carried by a vehicle.

The ground station 70 also comprises an electrical power inlet 79, in electrical communication with the cables 55 of the tether 50 via spool 80, for connecting the cables 55 to an electrical power source such as an electrical generator 250. Optionally, the ground station 70 comprises such a generator 250.

Optionally, the system 10 may further comprise a proximity detection system, comprising suitable proximity sensors, operatively connected to one or both of computers 90, 100. Such sensors may be based, for example, on laser or radar range finding devices, which are configured for determining, accurately, the distance, and optionally also the direction, between the platform 20 and the ground station 70, and further optionally also the attitude of the platform 20. In one particular embodiment of the proximity detection system, a suitable camera may be provided on one of the platform 20 or ground station 70, that is configured to maintain the other one of the platform 20 or ground station 70 in view at all times, given the maximum radius of operation of the platform 20 relative to the ground station 70. Such a camera (not shown), for example mounted on the ground station 70, may comprise a wide angle lens, for example, or may include a suitable arrangement to keep its line of sight always aligned with the platform 20 (or indeed vice versa). Further, the component of the system 10 not comprising the camera, in such an example, the platform 20, may comprise a plurality of targets (e.g. LED's) in a set pattern that is identifiable from any orientation, magnification, or distortion due to wide angle lenses and so on. Accordingly since the location of the targets with respect to the platform 20 is known then by analysing the corresponding pattern of the targets in images obtained via the camera, the distance between the platform and camera (and thus the ground station 70), and the attitude and orientation of the platform 20 may be determined in a accurate manner. The proximity detection system may be useful as a back-up to the positional data obtained with the GPS antennas 48, 77 and further enables landing progress to be monitored accurately when GPS data s not available or subject to inaccuracies.

Further optionally, the system 10 may comprise an upward/lateral looking capability, enabling the platform 20 to provide image data in a substantially upwards and/or forward direction from the vantage point of the upper side 22. This may be useful in detecting aircraft and the like above the platform 20 when deployed, but may also provide image data or other information of the environment around the platform 20 and ground station 70, when the platform 20 is accommodated in the ground station 70. The aforesaid capability may be provided in a variety of ways. For example, the payload 40 may comprise one or more upward/lateral looking imaging devices, which relay data to the operator in the same manner as for the other imaging and other devices of the payload 40. Thus, the payload may be located on the upper side or on a forward, rearward or lateral side of the platform, or an auxiliary payload may be provided on the upper side or on a forward, rearward or lateral side of the platform. Alternatively, a periscope arrangement may be provided in the platform and/or the ground station, which is brought into alignment at least one imaging device of the payload 40 disposed below the lower side 24, at least when the payload is landed on the ground station. The periscope arrangement has an optical surface that protrudes past the top of the platform and/or of the ground station enabling the upper field of view to be seen by the imaging devices via the lower optical surface thereof facing the imaging device. Optionally, the upper optical surface of the periscope arrangement may be configured to rotate or otherwise move to enable the fled of view thereof to be altered.

Optionally, the platform 20 and/or the ground station 7On and/or the tether 50 may be painted with any camouflage colors and/or designs, as desired. Referring to Figs. 4 and 6, the ground station 70 may be removably or integrally connected to a carrier or mother vehicle 200 that is self-propelled, for example a car, Jeep, Hummer, truck, tank, or any other self-propelled ground vehicle (Fig. 4), or indeed a sea-faring vehicle 300 such as a ship (Fig. 5), or any hybrid vehicle such as an amphibian vehicle or hovercraft. In such cases, the ground station 70 may be located atop the vehicle, for example the roof, turret or any other suitable location thereof, and optionally, the vehicle powerplant may be used for generating the electrical power necessary for operation of the system 10. Alternatively, and referring to Fig. 6, the ground station 70 may be removably or integrally connected to a mother or carrier vehicle 400 that is not self propelled, for example a trailer, trolley, cart and so on, which may comprise wheels or the like, and which may be transported by hooking the same onto a suitable self-propelled vehicle.

Alternatively, the ground station 70 may be removably or integrally connected to a fixed location such as for example a building, tower, or other site or structure, which comprises a suitable powerplant for supplying the electrical power needs of the system 10, or alternatively which provides the electrical power from a power grid such as the electric mains.

According to one aspect of the invention, the system 10 may be removed from one carrier vehicle or location and fixed to another carrier vehicle or location, according to need or desire.

Referring back to Fig. 1, the system 10 further comprises a control interface 150 for enabling control of the system 10, and for retrieving and dealing with data received from the platform 20 and other components of the system 10. The interface 150 may be operatively coupled to the ground computer 100, which can receive operator commands and coordinate operation of the spool 80 and computer 90, accordingly.

The control interface 150 may comprise a position control station 151, a payload control station 152, and a payload monitor station 153, at least some of which allow interactive operation by the user. The position control station 151 is configured for providing the user with the ability to control the height or altitude of the platform 20 above the ground station 70. The position control station 151 may thus comprise a computer station, with suitable software such as drop-down menus enabling the user to choose the operational altitude of the platform 20, and the ground computer 100 and flight computer 90 subsequently control the operation of the platform in flight mode to enable the platform to remain, say, within about Im to about 5m of this altitude. Further, other drop down menus may also be used for enabling the user to initiate deployment and landing of the platform 20, at the beginning and end, respectively, of a particular flight operation. Further options in the drop-down menus may allow the user to command the platform to take evasive action, such as reducing height, sideways maneuvering and so on, when in the vicinity of low cables, trees, bridges and so on. However, in normal operation suitable sensors in the payload 40 may detect the presence of low-height obstacles in the path of the platform 20 and/or tether, and corrective evasive action may be taken automatically under the control of the computers 90, 100 to avoid the same. For example, the platform 20 may be temporarily winched in to a lower height sufficient to clear the overhead obstacle, and once cleared, the platform 20 is automatically winched out to the nominal operating altitude. Similarly, the platform may be automatically or manually controlled to take evasive maneuvers in battlefield situations or when under fire. For example rather than taking the shortest route between two points, for example landing, taking off, traveling along the path of the carrier vehicle, and so on, corresponding zig-zag paths are computed and followed by the platform 20 to increase survivability. The ground computer 100 and flight computer 90 automatically take into account the speed and direction of the carrier vehicle, if this is traveling while the platform is deployed. While, optionally, a joystick may be provided for inputting user commands to the system 10, a drop-down menu system can be used universally with less skill required of the user.

The payload control station 152 is configured for providing the user with the ability to control the operation of the payload 40, for example the line of sight of various imaging units therein, zooming thereof, electromagnetic frequency range, and so on. The payload control station 152 may thus comprise a computer station, optionally the same computer station used as the position control station 151, with suitable software such as drop-down menus enabling the user to control the line of sight, zoom and so on thereof.

The payload monitor station 153 is configured for providing the user with the data from the payload, and optionally to store and/or transmit the data to another location. The image or other data may be viewed on a screen, optionally the same computer screen of the aforementioned computer station. In one particular example of the system 10, the platform 20 has a nominally square planform, with sides of about 160cm in length, and has a weight of about 30Kg, not including the payload B40B which may comprise a weight of about 8kg. The platform 20 comprises four said ducted fans 35, each including a 63.5cm diameter (25 inch) propeller, driven by one of four motors 37, each of which is a brushless DC electric motor rated at 1.5KW and weighing about 1.8 Kg. The tether 50 comprises at least one 8-gauge electrical cable, rated at 200V₅ and the platform 20 may be raised to a height of about 50m by means of the ducted fans 35, and kept in flight mode, or at least hovering, indefinitely so long as power is supplied thereto from the ground station, so long as the system is neither damaged nor malfunctions.

Operation of the system 10, when carried on a vehicle, for example as illustrated in Figs. 4 or 5, or when towed behind a vehicle, for example using a trailer as illustrated in Fig. 6, may be as follows. When it is desired to deploy the platform 20, the operator commands the system

10, via the position control station 151, to do so, inputting or choosing a desired operational height for the platform 20 above the ground station 70, for example 100m. After performing standard checks for the system 10, and determining that everything is in order, one or both of the computers 90, 100, automatically start the motors 37, the cover 78 having been removed and optionally the side walls 74 having been pivoted away from the platform 20 in an automated or manual manner. Then, computer 100 controls unwinding of the tether 50 from the spool 80, checking the deployed length with the altitude attained by the platform 20 as this is raised by means of the ducted fan arrangement. If the vehicle is moving, the GPS antennas on the platform 20 and ground station 70 provide data to the computers 90, 100, which then control the power provided to the motors 37 and/or control the vanes 39 to maintain the platform above the vehicle or trailer, or above a particular location with respect thereto, within a radius of operation, which may be, for example, 1 to 10 meters. The platform 20 is then in flight mode (also referred to as hover mode), and maintains a hovering attitude above the vehicle. At this point the user may interact with the payload control station 152, to scan, survey or otherwise image a particular part of the environment in the vicinity of the moving vehicle, or this may be automatically programmed into the system 10. Optionally, the payload 40 may be controlled to automatically scan a number of fields of view around the vehicle continuously, or on a rotation basis, for example. The payload monitor station 153 provides the user with surveillance data, including images, of the surrounding environment, continuously, and the platform 20 can remain airborne nominally indefinitely, subject to being damaged or becoming inoperational, having substantially unlimited endurance, as long as the ground station 70 provides the required electrical power, i.e., until there is an interruption in the electrical supply thereto, or until it is desired to discontinue operation of the system 10.

Deployment of the platform 20 can be a very quick operation, in some embodiments in a matter of seconds, and this quick reaction time with respect to the appropriate user commands enables the platform to be deployed only when needed, and thus avoid deployment with the increased chance of giving away the position or movement of the vehicle, unless absolutely necessary. For example, in hostile situations when under attack by artillery or mortar fire, the platform may be deployed quickly, and the source of fire quickly identified by scanning the environment around the vehicle from the vantage point of the platform's altitude. The surveillance information thus obtained may be relayed to suitable counter-offensive means, and/or may be used to plan an escape route out of range of the artillery or mortar fire.

In non-hostile situations, the platform may be deployed continuously in flight mode without such fear of being discovered. As the vehicle travels over a particular landscape (or seascape, for example), the

Ladar system in the payload 40 continually looks out for possible obstacles that could pose a threat to the payload 20 and/or the tether 50, and where necessary the computers 90 and/or 100 command the platform 20 to decrease height, and even land on the base 72, in order to try to avoid colliding with such obstacles. In other situations, for example in urban scenarios, it may be desired to observe the ground scene behind a building or in the next street before actually traveling thereto, and the platform 20 may be controlled, by means of the position control station 151, to displace away from the vehicle and towards a vantage point that would allow the scene of interest to be observed without exposing or endangering the vehicle itself. Similarly, whenever an obstruction is encountered, the platform 20 may be controlled to move in a substantially lateral manner, for example, to better view the scene obscured by the obstruction.

Operation of the platform 20 in flight mode can be modified to enable the platform to react in a safe manner to some windy or gusty conditions that may exist near the ground station 70. For example, the computer 90 and/or computer 100 may increase the power supply to the motors 37 to their maximum safe limit, which may be 300% of the design power, enabling the platform 20 to rapidly accelerate away from the turbulent ground zone. The ability to provide surplus power to the motors 37 may also be used for handling unexpected turbulence near buildings, for example.

Surveillance or other observation data provided by the payload 40 may be continually viewed via the payload monitor station 153. The images thus obtained are in an upright orientation relative to the user, since the payload is in a relatively similar position with respect to the scene that it is monitoring as is the user, but at a greater height. Accordingly, little time is wasted in trying to interpret the scene in terms of the current vantage point of the user, and thus even untrained personnel can identify a target position, type and so on from the images with relative ease. Optionally, the interface 150, in particular the payload control monitor 153, may be configured for processing successive images to detect any changes therebetween, and thus alert when, for example, a target enters the field of view as observed by the payload 40. While this type of surveillance may be conducted when the system 10 is located at one place statically, for example when the vehicle on which it is mounted is stopped, or when mounted to a building structure, it can also be adapted for use with a moving platform, for example when the vehicle on which the system 10 is mounted is moving, and/or when the surveillance uses a movable camera, for example mounted on a turret system, scanning a particular field of view (for example 360 degrees around the platform 20) continuously. In each case, suitable software for this purpose is provided. Operation of the system 10 may be carried out in flight mode with the tether 50 being untensioned, other than due to the weight thereof as hanging from the platform, and thus hangs freely therefrom to the ground station 70. Alternatively, operation of the system 10 may be carried out in flight mode with the tether 50 being under tension, which tension may be provided by winching the tether via spool 80, and/or by raising the altitude of the platform 20, such that the tension in the tether is greater than that derivable from the weight of the deployed length of tether.

Intended termination of flight mode is carried out via the position control station 151, which via user interaction commands one or both of the computers 90, 100 to power down the motors 37 to lose height, and to concurrently bring in the tether 50 correspondingly until the platform 20 lands safely on base 72 and is secured thereon. This is followed by closing of the sides 74 and covering the housing 71 with cover 78.

Unintended termination of flight mode may occur when there is an interruption of the electrical power supply from the ground station via tether 50. The computer 90 and/or computer 100 are configured for sensing such a power interruption, and immediately bring on-line electrical power from the high capacitance system 29 to the platform 20, in particular the motors 37. The motors 37, now powered by the high capacitance system 29, provide an emergency landing on the base 72, and the tether 50 is brought in a similar manner to intended termination of flight mode, though possibly faster, as the high capacitance system 29 can in general only supply sufficient power for a short time. The high capacitance system 29 may be fully charged at the beginning of each flight operation of the platform 20, and adds to the safety and survivability of the system 10. Operation of the system 10 when used on a static structure rather than a vehicle is similar to that described above, mutatis mutandis, with the exception that while in general no evasive maneuvers are required for avoiding power lines and so on, they may still be useful in avoiding air-borne objects, such as for example birds and so on, to avoid collision therewith. In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not imply any particular order of performing the steps.

Finally, it should be noted that the word "comprising" as used throughout the appended claims is to be interpreted to mean "including but not limited to". While there has been shown and disclosed example embodiments in accordance with the invention, it will be appreciated that many changes may be made therein without departing from the spirit of the invention.

Claims

T/IL2007/00069324CLAIMS:

1. An unmanned air vehicle (UAV) system, comprising a ground station; a platform configured for carrying a payload and comprising a propulsion system for enabling said platform at least to selectively sustain a predetermined altitude above a ground station when in flight mode; a tether operatively coupling said ground station with said platform, said tether providing electrical communication between said platform and said ground station.

2. A system according to claim 1, wherein said propulsion system is electrically powered and in operation is provided with electrical power from said ground station via said tether, said ground station comprising a suitable electrical power source.

3. A system according to claim 1 or claim 2, wherein said propulsion system is configured to provide a lifting force which is at least partially vectored to balance directly the weight of the platform.

4. A system according to any one of claims 1 to 3, wherein said ground station comprises a housing for receiving and accommodating said platform when said flight mode is terminated, and a spool system for reversibly winding said tether thereto.

5. A system according to claim 4, wherein said spool system is configured to release or wind said tether in a substantially tensile free manner, according to a distance between said platform and said ground station.

6. A system according to any one of claims 1 to 5, wherein said platform comprises a payload including an observation system for observing an environment in an area circumscribing said ground station.

7. A system according to claim 6, wherein said observation system comprises at least one imaging device for imaging a scene external to said system in at least one of; the visible spectrum; infra red frequencies; ultraviolet frequencies.

8. A system according to any one of claims 1 to 7, wherein said ground station is adapted for being reversibly or permanently connected to a mother vehicle, said vehicle capable of transport over a surface at least during operation of the system.

9. A system according to claim 8, wherein said mother vehicle is self-propelled.

10. A system according to any one of claims 1 to 9, wherein said propulsion system comprises at least one electrical motor coupled to a fan.

11. A system according to any one of claims 1 to 10, wherein said platform comprises an upper-facing first side and a downward facing second side, and a plurality of through-openings therebetween, and wherein said propulsion system comprises a ducted fan arrangement accommodated in each said through-opening.

12. A system according to any one of claims 1 to 11, wherein said payload is downwardly-depending from said second side at a location at or generally close to a center of gravity of said platform.

13. A system according to claim 12, wherein said tether is connected to said platform via a distal connection point at a location at or generally close to a center of gravity of said platform.

14. A system according to claim 13, wherein said payload is enclosed in a casing comprising apertures for enabling operation of imaging devices, and wherein said distal connection point comprises a spacer arrangement for routing a distal portion of said tether to said platform around a portion of said payload via an eyelet located below said center of gravity.

15. A system according to claim 14, further comprising imaging devices having their lines of site aligned with said apertures.

16. A system according to any one of claims 1 to 15, said payload comprises a mechanical arrangement for causing a desired mechanical effect responsive to manual commands from the operator.

17. A system according to any one of claims 1 to 16, wherein said platform comprises a landing arrangement configured for minimizing landing impact forces with respect thereto.

18. A system according to any one of claims 1 to 17, wherein said system comprises a suitable control system for maintaining stability of said platform when in said flight mode with respect to maintaining said altitude within predetermined thresholds.

19. A system according to any one of claims 1 to 18, wherein said ground station comprises an electrical power generator for supplying electrical power to said platform via said tether.

20. A system according to any one of claims 1 to 19, wherein said platform comprises a suitable electrical backup system for providing emergency power to said platform.

21. A system according to claim 20, wherein said backup system is configured for providing emergency power to said propulsion system for enabling said platform to be landed in a generally safe manner with respect to said ground station.

22. A system according to claim 21, wherein said backup system comprises a high 5 capacitance system capable of storing and delivering sufficient electrical power to said propulsion system for operating the same for a short duration of time correlated to landing said platform in a generally safe manner with respect to said ground station.

23. A system according to any one of claims 1 to 22, further comprising a control interface for enabling a user to operate said system.

10 24. A system according to claim 23, wherein said interface comprises at least one of a position control station, a payload control station, and a payload monitor station.

25. A system according to any one of claims 1 to 24, wherein said system comprises a suitable control system configured for controlling said propulsion system when in said flight mode, such as to maintain said platform within a predetermined

15 distance and/or altitude with respect to said ground station, while said ground station is being transported over a surface.

26. A vehicle, comprising a system according to any one of claims 1 to 25.

27. A vehicle according to claim 26, wherein said vehicle is self-propelled.

28. A vehicle according to claim 26, wherein said vehicle is trailer or the like.

20 29. A building structure, comprising a system according to any one of claims 1 to 25.

30. A building structure according to claim 29, wherein said building is an observation post.

31. A platform for carrying a payload and comprising a propulsion system for 25 enabling said platform at least to selectively sustain a predetermined altitude above a ground station when in flight mode, said platform being configured for being connected to a tether to provide electrical communication between said platform and a ground station, said propulsion system being electrically powered and configured for being provided, in operation, with electrical power from the ground station via the tether, 30 wherein said propulsion system is further configured to provide, in operation, a lifting force which is at least partially vectored to balance directly a weight of said platform.

32. A method for extending enhancing a viewing vantage point of an observer, comprising; providing a system according to any one of claims 1 to 25; causing said platform to hover with respect to the observer at a said altitude above the observer; acquiring surveillance data of the surrounding environment via said payload.