Field of the invention Embodiments of the present invention relate generally to control systems for fluid borne vehicles, and more particularly to control systems for use with Vertical and/or Short Take-Off and Landing (V/STOL) air vehicles.

Background to the invention

Vertical and/or Short Take-off and Landing (V/STOL) aircraft are aircraft that can take off and land either with a reduced ground roll relative to conventional fixed wing aircraft, or vertically. This classification includes a variety of types of aircraft including some fixed wing types as well as helicopters and other powered aircraft, such as cyclogyros, tiltwings and tiltrotors. Often, aircraft of this type have the ability to hover.

V/STOL vehicles direct airflow downwards to generate lift in order to lift the vehicle off the ground and support the vehicle in hover (if the vehicle has a hovering capability). Various types of V/STOL aircraft use various systems to produce the control forces and moments necessary for stable take-off, landing, hovering, and translational flight. Many of these systems come at a considerable size, weight and/or power cost, and may introduce unwanted mechanical complexity to the vehicle design.

V/STOL vehicles may be manned, optionally manned, or may be Unmanned Air Vehicles (UAVs). In particular, the use of V/STOL UAVs is increasing amongst military, law enforcement and civilian operators for a number of applications including, for example, inspection, surveillance, and photography. Many of these applications can benefit from a vehicle having a small profile and/or footprint, for example for operation in dense or cluttered environments and in confined spaces. A reduced profile/footprint may have further advantages, for example facilitating easier transport, storage and/or launching of vehicles. Such benefits apply also to other fluid borne vehicles, such as manned, optionally manned or Unmanned Underwater Vehicles (UUVs).

It is an object of the present invention to provide any or all of the advantages described above.

Summary of the invention The invention generally comprises a control system for a vehicle, a vehicle with such a control system, and methods for controlling a vehicle using such a control system.

The vehicle will generally have one or more means to induce a flow of an ambient fluid, each means inducing a flow predominantly in a single direction defining a thrust axis for said means, in order to produce forces, moments or a combination of forces and moments acting on the vehicle, and one or more of the means to induce a flow being vane controlled means. The control system comprises two or more arrays of vanes arranged in proximity to the thrust axis of a vane controlled means, each array of vanes arranged to interact with flow of fluid from the vane controlled means in order to influence the forces and moments acting on the vehicle, wherein an array of vanes is rotatable about an axis which is not substantially parallel to the thrust axis of the vane controlled means.

In a preferred embodiment, an axis of rotation of an array of vanes is substantially offset from the thrust axis of the corresponding vane controlled means.

In a preferred embodiment, an axis of rotation of an array of vanes is located in or in proximity to the periphery of said induced flow of ambient fluid. In a preferred embodiment, a means to induce a flow of fluid is a ducted fan.

In a preferred embodiment, an axis of rotation of an array of vanes is substantially adjacent to a tangent of or substantially tangential to an outer lip or edge of a duct of a ducted fan. In a preferred embodiment, an array of vanes is rotatable about an axis which is substantially perpendicular to the thrust axis of a corresponding vane controlled means.

In a preferred embodiment, a means to induce a flow of fluid is an open rotor. In a preferred embodiment, the vanes of an array of vanes have aerofoil cross sections.

In a preferred embodiment, an array of vanes is positioned on a downstream side of the flow inducing means. In a preferred embodiment, an array of vanes is positioned on an upstream side of the flow inducing means. In a preferred embodiment, an array of vanes is substantially rigid.

In a preferred embodiment, one or more vanes of an array of vanes are rotatable relative to the vane supporting structure of said array of vanes.

In a preferred embodiment, one or more vanes of an array of vanes is resiliently deformable relative to the vane supporting structure of said array of vanes.

In a preferred embodiment, the vehicle has a vehicle body, the body having roll and pitch axes each being perpendicular to a thrust axis and to each other.

In a preferred embodiment, an array of vanes is rotatable from a first position in which it is substantially within the duct of a ducted fan to a second position in which a substantial portion of the array is outside said duct. Preferably in the first position the force vector produced therefrom substantially intersects the roll axis and in the second position the force vector produced therefrom does not intersect the roll axis.

In a preferred embodiment, an array is rotatable from a position in which the force vector produced therefrom substantially intersects the roll axis to a position in which the thrust vector produced therefrom does not substantially intersect the roll axis.

In a preferred embodiment, the arrays of vanes are arranged so that the force vectors produced by the respective arrays of vanes produce in operation a moment about the roll axis substantially only in a clockwise or anticlockwise direction.

In a preferred embodiment, the vehicle comprises one or more arrays of vanes which in operation produce a moment about the roll axis in a clockwise direction and one or more arrays of vanes which in operation produce a moment about the roll axis in an anticlockwise direction.

In a preferred embodiment, the vehicle comprises arrays of vanes arranged to produce force vectors in operation in respective directions that produce a moment about the yaw axis.

In a preferred embodiment, the vehicle comprises arrays of vanes arranged to produce force vectors in operation in respective directions to produce a moment about both the roll axis and the yaw axis. In a preferred embodiment, the vehicle comprises arrays of vanes arranged to produce force vectors in operation in respective directions to produce a moment about the roll axis but not the yaw axis or a moment about the yaw axis but not the roll axis. In a preferred embodiment, the vehicle has arrays of vanes arranged to produce force vectors in operation in respective directions to produce a moment about the pitch axis.

In a preferred embodiment, the vehicle has arrays of vanes arranged to produce force vectors in operation in respective directions to produce a net force substantially perpendicular to the yaw axis.

In a preferred embodiment, the vehicle further comprises one or more arrays of vanes which are not rotatable relative to the vehicle body. In a preferred embodiment, the vehicle body is generally planar, having a longest dimension in a direction of the roll axis and a longest dimension in a direction of the pitch axis which are each greater than twice a longest dimension in a direction of the yaw axis.

In a preferred embodiment, the arrays of vanes are generally planar.

In a preferred embodiment, the vanes have aerofoil cross sections. In a preferred embodiment, the vehicle has two flow inducing means. In a preferred embodiment, the vehicle is a tandem ducted fan vehicle.

In a preferred embodiment, the vehicle has three or more flow inducing means.

In a preferred embodiment, there are two or more vane controlled flow inducing means.

Optionally, the vehicle has rigid wings.

Optionally, the vehicle is articulated. Brief description of the drawings A more complete understanding of the present invention may be had by reference to the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein: FIG. 1 is a perspective view of a tandem ducted fan UAV with a vane array arrangement according to the present invention.

FIG. 2 is a perspective view of a duct and vane array arrangement according to the present invention.

FIG. 3 is another view of a ducted fan UAV.

FIG. 4 and FIG. 4a show cross sections of vane array arrangements. FIG. 5 is a diagram showing forces exerted on a duct by a vane array.

FIG. 6 is a diagram showing forces exerted on a duct by a vane array and by an alternative louvre system. FIG. 7 is a diagram showing an example control scheme.

FIG. 8 is a plan view of an articulated quad rotor arrangement. FIG. 9 shows an arrangement with fixed wings.

FIG. 10 and FIG. 10a show diagrams of a first mechanism acting on a vane array wherein each vane of the vane array is resiliently deformable.

FIG. 11 and FIG. 11a show diagrams of a second mechanism acting on a van array wherein each vane of the vane array is resiliently deformable.

Detailed description of drawings

Referring now to FIG. 1 , there is shown a tandem ducted fan vehicle (100) including a generally planar vehicle body (101 ). The vehicle includes two ducted fans (120) each comprising a duct (121) and a fan (123). The fans (123) induce a flow of air through the ducts (121) from an upper inlet side of the ducts (121 ) to a lower outlet side in a downward direction along the fan thrust axes (110) in order to generate thrust and cause a net upward force acting on the vehicle in a direction of the yaw axis (113) which is centrally disposed between the ducted fans (120). The vehicle has a roll axis (111 ) and a pitch axis (112) each perpendicular to the yaw axis (113) and to each other. The vehicle has a number of vane arrays (130) arranged in proximity to the outlet side of the ducts (121 ), each being rotatable about an axis substantially perpendicular to the thrust axis (110) of the ducted fan (120) to which it is mounted. The operation of said vane arrays (130) will be discussed with reference to the following figures. Referring now to FIG. 2, there is shown a duct (121 ) with a vane array (130) arrangement according to the present invention. The vane array (130) is rotatable by an actuator (132) about an array rotation axis (133).

Referring now to FIG. 3, there is shown a duct (121 ) viewed along the roll axis (111). The vane arrays (130), which have a generally planar shape in this embodiment, have been rotated about their respective array rotation axes to a position wherein the plane of the vehicle body and the respective planes of the vane arrays are not substantially parallel.

Referring now to FIG. 4 and FIG.4a, there are shown cross sections of embodiments of vane arrays (130). In the preferred embodiment shown, vane arrays comprise a number of aerofoil vanes (131 ) arranged over a generally planar vane array (130) and supported by a frame or vane support structure of the vane array. In a preferred embodiment, the vanes (131) are arranged so that the chords of the aerofoils are substantially perpendicular to the plane of the vane arrays (130). It will be appreciated by one skilled in the art that the vanes (131 ) may be of any suitable design in order to generate suitable lift and drag forces, and may be angled with respect to a vane array plane, and that the vane arrays may be non-planar without diverging from the spirit of the invention.

FIG. 5 shows the forces caused by a preferred embodiment of the vane array (130) at various angles of rotation. When the vane array (130) is deflected, the aerodynamic surfaces of each vane in the array acquire an angle of attack relative to the substantially vertical flow (160) through the duct (121 ), leading to an aerodynamic force (F) on the vane (130). In a vane array embodiment similar to that shown in FIG 4, the angle of the force vector (F) from the horizontal plane closely follows the angle of deflection of the vane array (130) up to a significant angle, that angle depending on the aerodynamic characteristics of the vane array. It can be seen that the aerodynamic force (F) on the vane arrays (130) changes as the angle of attack of the individual vanes relative to the flow (160) through the duct changes. In the preferred embodiment shown, the force increases as the vane array (130) rotates from a position in which the vane array plane is substantially perpendicular to the fan thrust axis (110), shown as the uppermost position in FIG. 5, to a position in which the vane array is at a significant angle to a plane perpendicular to the fan thrust axis (110).

FIG. 6 is a diagram showing forces exerted on a duct (121) by a vane array (130) and those exerted by an alternative louvre system comprised of a number of louvres (200) housed within the duct (121). In a louvre system, as a substantially vertical flow of air passes through the duct a net aerodynamic force (Fl) acts on the louvres (200). The angle of the louvres (200) can be altered in order to change the magnitude and direction of this force. Likewise, using the vane array system of the present invention, as a substantially vertical flow of air passes through the duct a net aerodynamic force (Fv) acts on the vane array (130). The vane array (130) can be rotated as a whole in order to change the magnitude and direction of this force. Each of the vane array force (Fv) and the louvre force (Fl) produces a moment (M) about the axis (114) in the anticlockwise direction, the magnitude of which depends on the magnitude of the force and the moment arm at which the force acts. It will be appreciated that these forces (Fv, Fl) can be resolved into their horizontal and vertical components in order to assess the resultant moments they produce about an axis (114) which may be, for example, the roll or pitch axis of a vehicle. The vane array force (Fv) horizontal component and vertical component act at moment arms (Mavh) and (Maw) respectively to produce moments about the axis (114) in an anticlockwise direction. The louvre force (Fl) horizontal component acts at a moment arm (Malh) to produce a moment about the axis (114) in an anticlockwise direction. In this setup, since the louvres are collectively actuated and arranged symmetrically about the axis (114), the vertical component of the louvre force (Fl) does not produce a net moment about the axis (114). It can be seen that because the vane array rotates out of the plane (124) of the duct, the horizontal component of the vane array force (Fv) acquires a larger moment arm than the horizontal component of the louvres.

It should be noted that advantageously the vane array rotational axis is offset from the thrust axis (110) to produce a greater moment arm (Maw) for the vertical component of the vane array force. Advantageously, the vane array rotational axis is offset from the thrust axis (110) far enough so that the horizontal and vertical components of the vane force (Fv) act to produce moments in the same direction about an axis, for example axis (114). Still referring to FIG. 6, it should be noted that the effective moment arm of the horizontal component of the louvre force (Fl) could be increased by arranging the louvres further from the plane (124) of the duct. However since the louvres (200) are mounted inside the duct, this would require the duct to be taller. Advantageously, the vane array system is able to produce forces with significant horizontal component moment arms while maintaining a short duct and hence allowing a vehicle to have a reduced frontal profile and lower mass. It should be further noted that a louvre system can produce a vertical component with a beneficial moment arm if the louvres are not arranged symmetrically about the relevant axis, for example if the louvres (200) were arranged only on one side of the duct (121) of FIG. 6. However such an arrangement is still unable to take advantage of the increased moment arm of the horizontal component of the vane array system. Thus, for a given duct size, the vane array arrangement is able to produce greater moments around the relevant axes than the louvre system described.

Still referring to FIG. 6, the louvre system shown requires each of the louvres to rotate to create the desired force. Typically, the louvres will be collectively actuated using a mechanical system, examples of which will be known to one skilled in the art. Alternatively, the louvres could be individually actuated, however this would require a large number of actuators. Advantageously, the vane array system described herein facilitates rotation of the vane arrays to the desired positions using a single actuator and further advantageously the vane arrays can be made substantially rigid and do not require mechanical joints or linkages. FIG.7 shows an example control scheme for a tandem ducted fan vehicle, for example that shown in FIG. 1. It will be appreciated by one skilled in the art with reference to the preceding description that suitably designed and positioned vane arrays can be used to produce forces which result in moments about each of the roll, pitch, and yaw axes. FIG. 7 shows a number of vane array (130) positions relative to forward (FWD) and aft (AFT) ducts (121) of a tandem ducted fan vehicle, which vehicle may be of a similar configuration to that shown in FIG. 1. In the configuration labelled (300a), the right side vanes have been rotated relative to their respective ducts to substantially the same extent. Thus, assuming equal fluid flow through each duct, the vane arrays will each cause a substantially equal moment in the same direction about the roll axis (111 ), causing the vehicle to roll with its right side moving downward, in a clockwise direction when facing the forward (FWD) side of the vehicle. Furthermore, it will be appreciated that if the vane arrays are arranged in complementary positions about the yaw axis (113), as in FIG. 1 , the substantially equal forces acting on each of the vane arrays will act to induce equal but opposite moments about the yaw axis (113). Thus, the configuration labelled (300a) will produce a moment about the roll axis but no moment about the yaw axis (113). Likewise, the configuration labelled (300b) will cause a rolling moment opposite to that of (300a) with no yaw moment. Similarly, the configurations labelled (300c) and (300d) respectively will produce moments around the yaw axis (113) without producing substantial moments about the roll axis (111).

It will be appreciated by one skilled in the art that suitable arrangements of vane arrays will allow control about each of the roll, pitch, and yaw axes independently. It will be appreciated that combining rotation angles on various vane arrays on a vehicle will allow a desired combination of control forces. It will be further appreciated that vane arrays can be arranged to produce forces in the direction of the roll, pitch and/or yaw axes without producing a substantial moment about the other axes or all of the axes.

FIG. 8 shows an articulated vehicle comprising four ducted fans. The present invention may advantageously allow for vehicles which are articulated and comprise a number of joints (140) about which sections of a vehicle can translate and/or rotate relative to each other. This may allow, for example, a vehicle to change from the configuration shown in figure 8 to a configuration in which the thrust axes of all the ducted fans are aligned or to any other relative rotational position.

FIG. 9 shows a vehicle further comprising fixed wings (150). One skilled in the art will appreciate that this may allow the vehicle to translate horizontally with reduced power for a given vehicle mass.

FIG. 10 and FIG. 10a show an alternative vane array (130) embodiment wherein the arrays of vanes (130) are in a resiliently deformable louvre arrangement. In this arrangement the vanes (131) are resiliently deformable, allowing an edge (134) of the vanes (131 ) to be moved by an appropriate mechanism, whilst another edge (135) of the vanes remains fixed to the frame of the vane array (130), to allow the vanes (131) to take on a curved shape, meaning the shape of the vanes (131) is not fixed relative to the vane array frame. Such an arrangement allows the exit angles of the vanes (131 ) to vary relative to the angle of the flow of fluid to a differing degree than would be achieved by varying only the angle of a vane array (130) as a whole. Thus, with the vanes arrays (130) deflected to a given position this may advantageously allow the vane arrays (130) to deflect the flow to varying degrees.

Comparing this deformable louvre vane array arrangement to the rigid arrangement shown in FIG. 4, this may, for example, advantageously allow the vane arrays (130) to deflect air through a relatively small or substantially no angle when at a small angle relative to a vehicle body, for example the uppermost position in FIG. 5, whilst allowing the vane arrays (130) to deflect the air through a greater angle when the vane arrays (130) are at a larger angle, for example the lowermost position in FIG. 5, than would be possible by simply rotating the rigid vane array (130) of FIG. 4 through the same angle. This may advantageously allow the vane arrays (130) to provide a greater force at an angle of deflection without having vanes (131) which are at an angle to the fluid flow when the vane arrays (130) are not deflected, for example the vane array (130) arrangement of FIG. 4a. This may advantageously result in a vane array (130) arrangement which produces less drag at some vane array position(s) whilst also allowing large forces to be created at the same or other vane array positions.

The deformabie louvre vane array (130) arrangement may be rotated about an axis (133) by a single actuator. In this arrangement, a linkage (136) is used to deflect the vanes (131) relative to the vane array (130) structure as the whole vane array (130) is rotated about the axis (133). This may allow the mechanism to achieve the advantages described in the preceding paragraph without requiring further actuators over, for example, the arrangement shown in FIG. 4. It will be appreciated that various mechanisms may be employed to actuate the vanes (131) and vane arrays (131) with a single actuator. Such arrangements will be known by one skilled in the art.

FIG. 11 and FIG. 11a show an alternative arrangement in which vane arrays (130) have one or more actuators (137) to actuate the vanes (131) within the vane array (130) in addition to any actuators used to rotate the vane array (130) as a whole. This may advantageously allow the angles of the vanes (131) to be selectively altered independently of the angle of the vane arrays (130) as a whole. One skilled in the art will appreciate that such an arrangement may allow selecting of appropriate combinations of forces and moments acting on the body of a vehicle.

It will be appreciated that the vanes may be resiliently deformabie or rigid, may rotate within the vane arrays about a pivot point, and may be individually rotatable within the vane arrays without departing from the spirit of the invention. Although in the embodiments shown the vane arrays are positioned in the outlets of the ducts, it will be appreciated that vane arrays may be positioned in the inlets of the ducts in addition to or instead of the outlets without departing from the spirit of the invention.

One skilled in the art will appreciate that the present invention encompasses arrangements wherein a vane array comprises a grid, lattice or other arrangement of aerodynamic surfaces. One skilled in the art will appreciate that the angle of incidence of the vane array aerodynamic surfaces relative to the plane of the vane array, and the angle of rotation of the vane array at which the vane array produces its minimum aerodynamic force, may be selected to produce a desired behaviour.

One skilled in the art will appreciate that embodiments of the present invention are not limited to substantially planar vehicles, nor to tandem ducted fan vehicles.

One skilled in the art will appreciate that the present invention is not limited to embodiments that direct air flow substantially downwards, but may equally be applied to embodiments that direct air flow in a substantially horizontal direction, for example to generate forward thrust.

One skilled in the art will appreciate that the present invention is not limited to embodiments wherein the vehicle is an air vehicle. For example, it will be appreciated that the present invention may be embodied in an underwater vehicle.

As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. It is accordingly intended that the claims shall cover all such modifications and applications that do not depart from the spirit and scope of the present invention.

Other aspects, objects and advantages of the present invention are evident from the disclosure, drawings, and claims.