WO2017055818A2 - Guidance system for an aircraft or vehicle and a method of use thereof - Google Patents

Abstract

A guidance system is provided for a vehicle or aircraft. The system comprises optical emitting means for emitting at least one optical beam therefrom in use. The optical emitting means are provided on or associated with one of a first vehicle/aircraft or at a first locality. The first locality is different, separate, independent and/or remote to the first vehicle /aircraft. Optical receiving means are provided for receiving said at least one optical beam in use. The optical receiving means are provided on or associated with the other of the first vehicle/ aircraft or first locality. Processing means are provided on or associated with the optical receiving means for sensing and/or calculating an intensity of said at least one received optical beam and/or an incident angle of said at least one received optical beam to allow positional and/or orientation information of the vehicle/ aircraft with respect to the first locality to be calculated.

Description

Guidance System for an Aircraft or Vehicle and a Method of Use Thereof

This invention relates to a guidance system for an aircraft or vehicle and to a method of use thereof.

Although the following description refers almost exclusively to a guidance system for aircraft in the form of hovering drone type aircraft, it will be appreciated by persons skilled in the art that the guidance system of the present invention can be used with any vehicle, aircraft, any hovering device and/ or the like.

It is known to use unmanned aerial vehicles (UAVs), also called drones, in both military and civilian applications. Such vehicles range in size and weight from heavily armed fighter jets to lightweight surveillance crafts weighing only a few pounds. The small and lightweight UAVs are attractive for many civilian applications but significant barriers to adoption of such vehicles are the operator skill level required to control the vehicle in use, the cost of manufacturing and running such vehicles, safety concerns, the limited flight time that is possible with the vehicles and the public perception of the vehicles, particularly from a privacy perspective.

Conventional UAVs can be either of a fixed wing type or a rotary wing type, and the current trend is towards making these vehicles more complex with greater mission capability. Typical vehicle functions include flying pre-set trajectories using GPS (Global Position System) guidance, remote control using a real time video feed from the vehicle, autonomous object recognition and target engagement, automatic return-to-base for refuelling and/or the like. In order to allow UAVs to be used in a wider number of applications and more frequently, there is a need to provide a much simpler UAV which overcomes the abovementioned problems.

It is therefore an aim of the present invention to provide a guidance system for an aircraft or vehicle, and particularly, but not necessarily exclusively, to a guidance system for a hovering aircraft or hovering UAV.

It is a further aim of the present invention to provide a method of using a guidance system for an aircraft or vehicle, and particularly, but not necessarily exclusively, to a method of using a guidance system for a hovering aircraft or hovering UAV. According to a first aspect of the present invention there is provided a guidance system for a vehicle or aircraft, said system comprising optical emitting means for emitting at least one optical beam therefrom in use; said optical emitting means provided on or associated with one of a first vehicle/aircraft or at a first locality; the first locality being different, separate, independent and/or remote to the first vehicle/ aircraft; and optical receiving means for receiving said at least one optical beam in use; said optical receiving means provided on or associated with the other of the first vehicle/aircraft or first locality; and wherein processing means are provided on or associated with the optical receiving means for sensing and/or calculating an intensity of said at least one received optical beam and/or an incident angle of said at least one received optical beam to allow positional and/ or orientation information of the vehicle/ aircraft with respect to the first locality to be calculated.

Thus, the Applicants have recognized that a large number of applications, particularly civilian applications, could be carried out by much less sophisticated aircraft or vehicles, if the simple guidance system of the present invention is used to detect the movement, orientation and/or position of the vehicle /aircraft. The present invention uses a simple optical beam emitting means or mechanism and an optical beam receiving means or mechanism to allow movement, positional and/ or orientation information of the aircraft or vehicle with respect to at least a first locality to be calculated or detected, and this positional and/or orientation information can, in turn, optionally be used to control the position, orientation and/ or movement of the aircraft or vehicle in use.

In one embodiment the guidance system is arranged to communicate with control means or a control mechanism to allow movement, positional and/or orientation control of the aircraft/ vehicle using said sensed and/or calculated movement, positional and/ or orientation information generated by the guidance system. The movement, positional and/or orientation control of the aircraft/vehicle is preferably undertaken automatically by the aircraft/vehicle.

Preferably the control means or mechanism controls one, two and/or three axes of movement or the pitch, roll and/ or yaw of the aircraft/ vehicle in use. Preferably the aircraft/ vehicle is an unmanned aerial vehicle (UAV), a drone, hovering vehicle and/ or the like.

In one example, the air craft/ vehicle only has hovering capability in terms of airborne flight. This has the advantage that the hovering aircraft can operate without any operator skill or training. In addition, no conventional aircraft pilot flight controls are required. An aircraft that is arranged to hover in free space in substantially one location is intrinsically safer than an aircraft that is designed to fly over pre-determined distances on its own. Furthermore, it allows the aircraft to be optionally tethered to a ground surface, fixed location, first locality and/or the like. This optionally enables power to be provided to the aircraft for indefinite flight times.

Preferably the first location is a spaced distance apart from the aircraft/vehicle when the latter is moving, is airborne and/ or is in an operational condition.

Preferably the aircraft or vehicle has rotary means or a rotary mechanism for generating a lifting force for the aircraft or vehicle to allow the aircraft or vehicle to move between a non-airborne or non-operational condition and an air-borne or operational condition in use.

The aircraft/ vehicle can be adjacent to the first locality when in the non-airborne or non-operational condition. The aircraft/ vehicle is typically a spaced distance apart from the first locality when in the air borne, is moving and/or is in an operational condition.

Preferably the rotary means or mechanism is a rotor or rotary wing type and further preferably is a single rotor or single rotary wing type. However, multiple rotors can be used if required. Use of a single rotor or single rotary wing type has the advantage of providing the aircraft/ vehicle with mechanical and aerodynamic stability, in contrast to multiple rotors which make an aircraft intrinsically unstable and rely upon electronics being provided in the aircraft to keep the rotors the right way up. In addition, a single relatively large rotor is typically more efficient than multiple relatively smaller rotors, thereby extending the flight time of the aircraft significantly. Furthermore, in the event of a power failure, a single rotor can "auto- rotate" to allow a safe unpowered landing, whereas a multi-rotor aircraft will simply fall from the sky. Preferably the aircraft or vehicle has power means provided thereon or associated therewith to power the aircraft/vehicle, power the rotary means and/or the like. The power means can include battery power, fuel power, solar power and/or the like.

The at least one optical beam is typically any optical beam capable of being detected by optical receiving means. For example, the at least one optical beam could include ultra violet light, visible light and/or infra-red light.

In a preferred embodiment the at least one optical beam is in the form of at least one infra-red (IR) beam. Preferably the optical emitting means is an infra-red emitting means.

In one embodiment the optical emitting means emits a plurality of optical beams.

Preferably the optical emission means emits three or more optical beams and preferably three or more infra-red beams.

Preferably the optical receiving means and/ or processing means are able to sense and/or calculate the intensity of one of the received optical beams relative to the intensity of at least one other received optical beam or stored optical data. A change in the relative intensity of a particular optical beam being sensed and/or calculated by the optical receiving means and/or processing means is indicative of a change in orientation, direction and/ or movement of the aircraft/ vehicle in use.

Preferably the, or each of the plurality of, optical beams is independently identifiable so that the specific change in orientation, direction and/ or movement of the aircraft/ vehicle relative to each optical beam can be identified.

In one embodiment one optical beam can be distinguished from another optical beam or the plurality of optical beams and/or from visible ambient light via identification means, data, device or object. For example, the identification means, data, device or objectcan include or consist of a unique code, a different carrier frequency, a unique time or sequence position within a timed sequence, a different wavelength, a different colour, pulsing at a different frequency and/ or the like. In one embodiment the plurality of optical beams are emitted simultaneously or substantially simultaneously and/or preferably in a continuous or substantially continuous manner when in an operational condition.

In an alternative embodiment the plurality of optical beams are emitted in a predetermined sequence and preferably are emitted in a repetitive pre-determined sequence, and/or in a pulsed manner (i.e. the beams are rapidly moved between on and off conditions). This latter embodiment has the advantage that less power is used. Thus, each optical beam can be emitted for a relatively short period of time or is pulsed and then is switched off while another optical beam is emitted and/ or the like. The timing of the detection of a beam within the sequence can be used to determine which beam of the plurality of beams has been detected. If the position or intensity of the beam and the timing of the beam are known, the position of the aircraft with respect to the beam can be calculated. Preferably this calculation is undertaken by the processing means.

Preferably two or more or the plurality of infra-red beams or the plurality of optical beams overlap or substantially overlap in use.

Preferably the degree of overlap of the optical beams is equal or substantially equal. Thus, for example, each beam overlaps with an adjacent beam by a substantially equal amount.

Preferably the plurality of optical beams is arranged in a pre-determined spatial arrangement so that the intensity of radiation within each beam can be measured.

Preferably each optical beam is shaped so that it is relative narrow in shape and/ or dimensions at the optical emitting means and is relative broader in shape and/ or dimensions a spaced distance from the optical emitting means.

In one embodiment each optical beam is substantially cone shaped or a truncated cone shape, with an apex or truncated apex of the cone located at the optical emitting means and a broader base of the cone or truncated cone located a spaced distance above, below or apart from the optical emitting means. Thus, in one example, the optical beam diverges outwardly from the optical emitting means. In one example, a cross section taken through the optical beam cone perpendicular or substantially perpendicular to a longitudinal or central axis of the beam or cone is preferably circular or substantially circular in shape.

Preferably the intensity of the optical beam is greatest along a central or longitudinal axis/point or substantially central or longitudinal axis/point of the beam or cone shape (at any cross section taken perpendicular or substantially perpendicular to the longitudinal or central axis). Further preferably the intensity of the optical beam decreases in a direction travelling radially or linearly outwardly from the central or longitudinal axis/point. As such, the optical receiving means and/or processing means can determine the position and/or orientation of the aircraft within a particular optical beam based on the intensity of the optical beam being detected.

Preferably the intensity of the optical beam changes along the central or longitudinal axis or substantially central or longitudinal axis of the beam or cone shape, with a greater optical intensity the closer to the optical emitting means and a lower intensity the further from the optical emitting means. As such, the optical receiving means and/or processing means can determine the height and/or distance of the aircraft from the optical emitting means based on the intensity of the optical beam being detected.

In one embodiment three optical beams are provided.

Preferably each of the three optical beams are arranged to be 120 degrees with respect to an adjacent beam. Thus, each beam provides a 120 degree or substantially 120 degree cone shape or pattern. For example, if a chord was taken in the area of overlap of three optical beams from the circumferential point of overlap of two adjacent beams to a central point where the three or more chords meet, each chord would be at an angle of 120 degrees to an adjacent chord. Preferably the three beams in combination provide coverage over 360 degrees or substantially 360 degrees of a central point, position or location.

In one example, each optical beam of the three optical beams, can be slanted towards one corner of an equilateral triangle. In one example, each optical beam, or each of the three optical beams, is arranged at 30 degrees to a vertical axis. Thus, the longitudinal or central axis of each optical beam is arranged at 30 degrees or substantially 30 degrees to a vertical axis.

Preferably the area of overlap of three optical beams is detected as a central or substantially central position of the aircraft which the aircraft attempts to maintain when in an operational condition.

The intensity of light within each optical beam typically varies with position and therefore the intensity of light being sensed by the optical receiving means allows the relative position of the aircraft/ vehicle with respect to an optical beam to be calculated.

In one embodiment at least one or only one upwardly, downwardly and/or outwardly optical divergent beam is emitted from the optical emitting means.

In a preferred embodiment, where only one optical divergent beam is generated by the optical emitting means, the optical emitting means is provided on or adjacent the first locality or ground and the optical receiving means is provided on or associated with the aircraft. However, it will be appreciated that the optical emitting means could be provided on the aircraft/vehicle and the optical receiving means could be provided on the first locality or ground if required.

Preferably where only one optical divergent beam is generated by the optical emitting means, this beam or beams is omni- directional.

Preferably the optical divergent beam is an infra-red beam and further preferably is a sinusoidally modulated infrared beam generated from one or more LEDs. Preferably the frequency of the infrared beam is approximately 13KHz.

Preferably in the embodiment where only one optical divergent beam is generated by the optical emitting means, the optical receiving means includes or comprises an incident angle detection means or sensor.

Preferably the incident angle detection means can measure angles of incidence of + /- 60 degrees. Since linear aircraft movement is proportional to the tangent of the incidence angle, the aircraft's or vehicle's working range in each direction can be increased by a factor of 5 compared to other embodiments described herein.

Preferably the incident angle detection means includes one or more sensors, and preferably two sensors for each horizontal axis. For example, two sensors are provided for each of the two horizontal axes (X, Y and/or Z axes) in a three dimensional space, thereby providing four sensors in total.

Preferably one of the pair of incident angle detection sensors are provided to sense side to side positioning of the aircraft/ vehicle and preferably the other pair of incident angle detection sensors are provided to sense front to back positioning of the aircraft/ vehicle.

Preferably the incident angle detection sensor or sensors are arranged so that each sensor, or different parts of the same sensor, are arranged at an acute angle to a horizontal axis, such as for example 30 degrees, or approximately or substantially at 30 degrees, to the horizontal.

Preferably the two incident angle detection sensors are provided and each are arranged at an acute angle to the horizontal and in opposing directions (i.e. they diverge outwardly from each other relative to a central point).

Preferably the incident angle detection sensor or sensors are flat, planar or substantially flat or substantially planar in form.

In one embodiment the tilt of the aircraft/ vehicle is measured using inertial sensing means or mechanism. A measurement of tilt or angle of title of the aircraft/ vehicle obtained from the inertial sensing means or mechanism can be used and is subtracted from the total incident angle measured by the incident angle detection sensor or sensors. The resulting value represents the position of the aircraft/ vehicle only.

In one embodiment the incident angle detection means, sensor or sensors are mounted on levelling means on the vehicle or levelling means, such as for example a gimbal or actively levelling gimbal. The levelling means allows the incident angle detection means, sensor or sensors to be kept in a horizontal or substantially horizontal position at all times during operation of the vehicle/ aircraft. Preferably the levelling means can be controlled by inertial sensing means.

In one embodiment the optical receiving means are provided on the aircraft/ vehicle and the optical emitting means are provided at the first locality. Preferably the processing means and/or control means are also provided on the aircraft/vehicle. The advantage of having the optical receiving means, processing means, and/or control meansprovided on the aircraft/ vehicle is that one or more control signals generated therefrom can be direcuy used by the aircraft/vehicle to control the same.

In an alternative embodiment the optical receiving means are provided at the first locality and the optical emitting means are provided on the aircraft/vehicle. In this embodiment further communication means may be required to communicate one or more control signals from the first locality to the aircraft/ vehicle to control the aircraft/vehicle. In one embodiment the first locality is a ground location, stationary location or a non-airborne location.

In an alternative embodiment the first locality is a mobile or movable location, other vehicle, other aircraft, air-borne location and/ or the like.

In one embodiment the guidance system includes directional means or a directional mechanism which allows the direction of movement of the aircraft or vehicle with respect to the first locality to be determined at any particular time. In one example, the directional means is arranged to emit a further or at least a fourth optical beam therefrom or from an optical beam source. Preferably further optical receiving means are provided for receiving the further or fourth optical beam.

Preferably the further or at least fourth optical beam is in the form of at least one polarised light beam.

Preferably the further optical receiving means is a polarised light beam receiving means or device.

In one embodiment a pair of polarised light beam receiving means is provided, each receiving means having filter means associated therewith which are angled at 90 degrees or substantially 90 degrees with respect to each other. When the polarised light receiving means are orientated in a central angle or substantially central angle with respect to a polarised light beam, each filter means is typically orientated at 45 degrees or substantially 45 degrees with respect to a horizontal or vertical axis or substantially horizontal or vertical axis of the polarised light beam and the intensity of the light beam being received by each of the receiving means is equal or substantially equal. If the receiving means are rotated in a direction away from the central position, one of the receiving filter means will become more aligned with the polarised light beam whereas the other of the receiving filter means will become less aligned with the polarised light beam. The receiving means associated with the filter means will detect different intensities of polarised light as a result of the different alignment of the filter means with respect to the beam and this detection can be used to control and/ or adjust the direction of rotation of the aircraft accordingly.

Preferably the polarised light beam is emitted from the first locality and the polarised light beam receiving means is provided with the aircraft/ vehicle.

In one embodiment the aircraft or vehicle or system has tethering means provided on or associated therewith to allow the aircraft/ vehicleto be retained at a fixed or substantially fixed location when not in use and/or when in an operational airborne condition. In one example, the aircraft is tethered via the tethering means at or adjacent the first locality.

In one embodiment power means or one or more power cables are provided on, are associated with or form the tethering means. The power means or one or more power cables can provide power to the aircraft/ ehicle if required. In one example, this can increase the flight time of the aircraft/ vehicle and/or make the flight time indefinite. The power can come from battery means, mains power supply, generator means and/ or the like.

In one embodiment of the present invention the aircraft/vehicle is movable between a substantially stationary, ground based and/or inoperable condition to a substantially movable, airborne and/or operable condition. Preferably the air craft/ vehicle is undergoing a hovering motion when in an airborne and/or operable condition. Preferably the aircraft or vehicle can be moved between an inoperable condition or grounded condition and an operable condition or air borne condition by moving the at least one optical beam in a particular direction.

Preferably compensation means, dimming means and/or automatic gain means can be provided or associated with the optical emitting means to adjust changes in optical beam intensity with decreasing and/or increasing height of the aircraft or vehicle.

In one embodiment safety equipment may be provided on or associated with the aircraft or vehicle. This is particularly the case in the present invention as it is significantly lightweight compared to conventional UAVs. The safety equipment could, for example, include parachute means and/ or the like.

The optical receiving means can be any or any combination of one or more sensors that allow detection of an optical beam or optical signal in use. The polarised light receiving means can be any or any combination of one or more sensors that allow detection of a polarised light beam or signal in use.

Different filter means or devices can be provided on or associated with the optical receiving means to allow different optical beams to be detected.

According to a second independent aspect of the present invention there is provided a guidance system for a vehicle or aircraft, said system comprising polarising light emitting means for emitting at least one polarised light beam therefrom in use and locatable on one of a first aircraft/ vehicle or at a first locality, the first locality being different, separate, independent and/ or remote to the first aircraft/ vehicle; and polarised light receiving means for receiving said at least one polarised light beam in use, said polarised light receiving means locatable on the other of the first aircraft/ vehicle or first locality, and wherein processing means are provided and/or associated with the polarised light receiving means for sensing and/or calculating an intensity of said at least one polarised light beam to allow movement, positional and/ or orientation information of the aircraft/ vehicle with respect to the first locality to be calculated.

According to a third aspect of the present invention there is provided a method of using a guidance system for a vehicle or aircraft, said method including the steps of emitting at least one optical beam from optical emitting means; said optical emitting means provided on or associated with one of a first vehicle/ aircraft or at a first locality; the first locality being different, separate, independent and/ or remote to the first vehicle/ aircraft; receiving said at least one optical beam using optical receiving means, said optical receiving means provided on or associated with the other of the first vehicle/ aircraft or first locality; and sensing and/or calculating an intensity of said at least one received optical beam and/ or an incident angle of said at least one received optical beam using processing means to allow positional and/or orientation information of the vehicle /aircraft with respect to the first locality to be calculated. According to a further aspect of the present invention there is provided an aircraft or vehicle including a guidance system.

The resulting aircraft/ vehicle utilising the guidance system of the present invention is significantly simplified compared to conventional aircraft/vehicles and it is therefore less expensive to produce and use. The aircraft/ vehicle of the present invention could be used for example, the help find injured people in an emergency, provide aerial sports footage, take overhead photographs of land and/ or buildings for sale purposes, surveying purposes, repair purposes and/or the like, it could allow road accident circumstances to be documented and/ or the like.

An aircraft/vehicle utilising the guidance system of the present invention does not require GPS and magnetic compassing to locate and orient itself as is required by many conventional UAVs. GPS is not totally reliable, as it is adversely affected by tall buildings, trees, weather, external interference and/or malicious jamming. In addition, many conventional UAVs rely on radio control signals to be transmitted between a base station and the vehicle. Radio communications are also subject to interference and jamming. As a result, accidents have occurred with conventional UAVs as a result of the abovementioned vulnerabilities.

Embodiments of the present invention will now be described with reference to the accompanying figures, wherein:

Figure la is a simplified view of a guidance system according to an embodiment of the present invention;

Figure lb is a simplified view of directional means that can form part of the guidance system shown in figure la; Figure 2 is a graph showing a spatial radiation pattern for an IR beam shown in Figure la;

Figure 3 is a simplified view of a guidance system according to a further embodiment of the present invention;

Figure 4 is a simplified view of a guidance system according to a yet further embodiment of the present invention;

Figure 5 is a simplified plan view of the IR beams from above in the embodiment in figure la;

Figure 6 is a simplified view of a guidance system according to an embodiment of the present invention;

Figure 7 is a simplified view showing beam angle of incidence for different aircraft tilts for the embodiment in figure 6;

Figures 8a and 8b show the arrangement of the angle of incidence sensors for use in the embodiment shown in figure 6 with light from the light beam arriving 8a) direcdy below the sensors and 8b) obliquely with respect to the sensors respectively; and

Figure 9 shows a typical graph of incidence angle sensor measurement output against the incidence angle of light hitting the sensor.

Referring firstly to figures la and 5, there is illustrated a UAV in the form of a hovering aircraft 2 capable of undergoing hovering motion when in an operable condition. More particularly, the aircraft 2 comprises a vehicle body 4 having a single rotor blade 6 mounted centrally thereof to a top surface of body 4 and capable of undergoing rotary motion around pivot point 8. Two wing members 10 extend outwardly from opposite side walls of body 4. The distal free ends of wing members 10 each have propeller members 12 attached thereto to allow the yaw of the aircraft to be controlled in use. Landing leg supports 14 extend outwardly from a base of body to allow the aircraft to be supported when on the ground in a substantially non-operable or non-airborne condition.

In accordance with the present invention, a guidance system is provided that allows the position, direction and/or orientation of the aircraft 2 to be calculated and subsequently controlled with respect to a first locality or ground surface. More particularly, the guidance system utilises the detection and calculation of intensities of optical beams to allow the movement, position and/or orientation of the aircraft to be calculated. The aircraft guidance system aims to maintain a plurality of spatially arranged optical beams at equal intensities so as to maintain the aircraft in a required position in operational use. Optical emitting means in the form of an Infra Red (IR) beacon 16 is provided at the first locality on a ground surface or non- airborne location. The IR beacon 16 emits three upwardly divergent IR beams 18, 20, 22 (represented by the different hatching). Each beam forms a substantial cone shape as it diverges from the point of emission and each cone is arranged substantially 120 degrees with respect to an adjacent cone shaped beam to provide 360 degree coverage. In addition, each beam 18, 20, 22 is angled at 30 degrees to a vertical axis.

Figure 5 shows the three IR beams 18, 20, 22 in plan view from above looking towards the IR beacon 16. Each beam has a longitudinal or substantially central axis 18', 20', 22'. A cross section taken through each beam substantially perpendicular to this central axis will be substantially circular in shape. A chord 19, 21, 23 taken from the circumferential point of overlap with an adjacent optical beam to a point where all three chords meet 25 is such that the chords are arranged at 120 degrees with respect to each other.

The aircraft 2 has a non-directional downward pointing IR receiving sensor 34 which can independently detect the intensity of each IR beam 18, 20, 22. According to the relative intensity of each IR beam that is detected, the aircraft can determine its position within the known and pre-determined 120 degree pattern. For example, if the aircraft 2 is located substantially centrally of the 120 degree pattern, the sensor detects an equal IR intensity for each IR beam 18, 20, 22 and can determine it is in the required position.

Figure 2 shows the spatial radiation pattern for each IR beam being emitted from beacon 16. As can be seen, each IR beam produces a substantially cone shaped distribution on the graph with % relative intensity on the 'y' axis against angular displacement on the axis. The % relative intensity of the beam radiation falls off steadily with increasing angle displacement from a central or longimdinal axis of the beam, with the % intensity reaching almost zero at 60 degrees angular displacement from the central or longitudinal axis. By directing the three beams at 30 degrees from the vertical, the aircraft hovering above will detect each beam at about 84% relative intensity based on the graph. If the aircraft 2 moves from the central position, where all three beams overlap (shown by area 27 in figure 5), the aircraft will detect an increase in relative intensity of some beams and a reduction in relative intensity in other beams, thereby allowing the movement of the aircraft to be measured. An automated control system provided on the aircraft can be set so that the aircraft tries to maintain relative constant overall intensity of all three IR beams during operation. Each beam can be independently identifiable so that the processing means can determine where the aircraft is relative to each beam.

The height of the aircraft can also be measured and controlled according to the absolute intensity of the beam pattern reaching the sensors. If a change in intensity of the beam pattern is detected by the sensors, the aircraft can be controlled to adjust its height accordingly. In addition, the intensity of the IR beams can be adjusted and this change will also be detected by the aircraft and can be used to control the height of the aircraft. For example, dimming circuitry can be used to adjust the beam intensity being emitted from the optical emitting means or beacon 16, thereby allowing the height of the aircraft to be adjusted to a required height.

The direction of movement and/or height of the aircraft can be controlled automatically by the aircraft once the sensors on the aircraft have detected a change in intensity of the IR beams detected. This has the advantage that no additional communication is required for flight/ aircraft control, such as for example there is no requirement for radio communication which improves the stealth nature of the aircraft since radio signals are easily detectable. Control of the aircraft is typically along three axes, pitch, roll and yaw and any suitable control means can be used to provide this control.

The aircraft 2 can distinguish the IR beams for each other by use of differing carrier frequencies for each IR beam. Alternatively, a scheme can be used in which each of the three IR beams is activated separately in a rapid repeating sequence.

Such as for example, ABC, ABC, ABC, ABC From the timing of the sequence, each individual IR beam can be identified. The system also includes directional means to allow the direction of travel of the aircraft 2 to be determined and/ or controlled with respect to the three IR beams 18, 20, 22. The directional means in this example includes a fourth beam which transmits polarised light from the ground beacon 16. A pair of polarised light receiving sensors are provided on aircraft 2 (not shown) to detect the polarised light beam. Each receiving sensor is fitted with a polarising filter, 26, 28 in front of the sensor and each filter is orientated at right angles to the other. In figure lb, the vertical shading represents the iUumination beam of light 24 polarised in a vertical direction up and down the page. The polarising filters 26, 28 are aligned in a 45 degree clockwise direction and a 45 degree anti-clockwise direction in relation to the polarised light beam 24. In this situation, each receiving sensor associated with the polarising filters 26, 28 will detect a substantially equal polarised beam intensity. If the direction of the aircraft 2 changes from a central position with respect to the fourth beam 24, one sensor will become more aligned to the polarised light beam while the other sensor will become less aligned to the polarised light beam. The sensors will then detect differing intensities of polarised light, thereby allowing the direction of the aircraft movement to be corrected using the aircraft control means.

The aircraft can be moved from a non-operational condition, wherein the aircraft is not airborne, to an operational condition, wherein the aircraft is airborne. The aircraft can be guided between the non-operational condition and the operational condition by moving the IR beams in a required direction. Rotation of the beams can be used to change the yaw of the aircraft.

Compensation may be required in order to adjust for a reduction in beam intensity with increasing height of the aircraft. This can be done using automatic gain within the receiving circuitry of the aircraft or via logarithmic signal processing. The latter method results in beam intensity ratios rather than differences which are independent of absolute intensity. Compensation may also be required to adjust for IR beam divergence. As the height of the aircraft increases, a given distance subtends a smaller angle. This is a proportional effect and can be compensated by factoring in the known height of the aircraft.

Figure 3 illustrates a further embodiment of the present invention in which a single wide angle IR beam 30 is emitted from ground beacon 16. An array of sensors 32 or a camera are provided on a lower surface of aircraft 2 and these sensors are able to detect and measure the angle of incidence of single beam 30 from the beacon 16. The angle of incidence changes with a change in aircraft position with respect to a substantially central position. This embodiment has the advantage that the incident angle measured is in relation to the aircraft 2 and so it is not necessary to measure the direction of movement of the aircraft, as is required with the embodiment in figure 1, in order to make position corrections for the aircraft. A disadvantage of the embodiment is that the angle of incident will change when the aircraft tilts so compensation may be required using additional sensors, such as gyros and/or accelerometers. A further disadvantage is that the aircraft cannot be guided between a non- irborne condition and an airborne condition by moving the IR beam as was possible in the previous embodiment.

Figure 4 illustrates a yet further embodiment of the present invention in which an optical emitter in the form of an IR beacon 16 is provided on the aircraft 4 for emitting one or more IR beams 18 therefrom towards a ground surface 32. A plurality of ground sensors 34 are provided on the ground for detecting the relative intensity of the IR beams 18 emitted from the aircraft. The system works in a similar manner to that previously described. However, a disadvantage associated with this embodiment is that the positional information generated by sensors 34 is processed on the ground 32 and not on the aircraft 4. As such, this positional information then needs to be transmitted back to the aircraft 4 to enable correction of the position of the aircraft. The transmission of the aircraft control signals from the ground to the aircraft will typically require additional equipment that is not required in the previously described embodiments. In addition, since these control signals are most likely to be communicated by one or more radio signals and/or the like, such signals are easily detectable and reduce the stealth qualities of the aircraft. A further disadvantage is that the ground sensors 34 will need to be located in an upwardly direction so they would need to operate accurately in all weather conditions, such as in bright sunshine. This is in contrast to the earlier described embodiments in which the aircraft sensors point can be located in a substantially downwardly facing direction and are therefore substantially sheltered from different weather conditions, such as bright sunlight. A yet further disadvantage is that in order for aircraft control to operate over a relatively long range (i.e. for the aircraft to reach a required height above the ground) considerable optical transmission power will be required to transmit the IR beam to the ground sensors. The power supply for the optical transmission would have to be carried by the aircraft and this would increase the weight of the aircraft and thus the fuel required to power the aircraft.

Figures 6-9 illustrate a yet further embodiment of the present invention. As with the embodiment shown in figure 3, a single wide angle beam 30 is emitted from ground beacon 16. The beam 30 is omni-directional. The aircraft hovers above the beacon 16 as previously described, and the incident angle Θ degrees of the arriving beam is measured in order to determine the aircraft's position. An array of sensors are provided on a lower surface of aircraft 2 and these sensors are able to detect and measure the angle of incidence of single beam 30 from the beacon 16. The angle of incidence changes with a change in aircraft position with respect to a substantially central position.

In some instances, the embodiment shown in figures 1-5 has a number of potential shortcomings. These are as follows: a) non-linearities in the beam polar intensity distribution can cause the three beam embodiment to work inadequately for some directions of aircraft movement. It is necessary to add an extra beam to create a 4-beam system in order to make it work well. This adds cost and power consumption to the optical guide system. b) The beam spreads of available infra-red LEDs or optical beams are typically relatively narrow, such that useable angular range of aircraft movement above the ground beacon is often restricted to approximately 20 degrees away from a central axis in any direction. Movements of the aircraft beyond this angle limit can cause aircraft control malfunction. c) The aircraft's directional frame of reference is established according to the fixed beam angles and therefore flight control of the aircraft is very sensitive to any movement of the ground beacon in use, particularly tilt movements. This can be a problem if, for example, the ground beacon is accidentally kicked, knocked over or blown over in use. d) If one of the optical beams fails for any reason, the aircraft is likely to fly out of control. e) In order for the aircraft to fly in the right direction to correct its position above the beacon, the heading of the aircraft in relation to the beacon must be known. This can add complexity to the system in the form of the polarized beam describe above.

The embodiment shown in figures 6-9 overcomes these problems that can be associated with the embodiment shown in figures 1-5. The aircraft 2 hovers above the ground beacon 16 as before, and the incident angle Θ is measured in order to determine the aircraft's position. This method has the following advantages: a) the incident angle does not depend on the orientation of the ground beacon, which is simply a point source of light. If the ground beacon is omni-directional then it makes no difference if the ground beacon is accidentally moved, kicked, is blown over and/ or the like. b) the angle of incidence is measured in relation to the aircraft, there is no requirement for a separate heading measurement. c) the ground beacon can be provided with one or more further light sources to provide redundancy in case the main ground beacon fails. d) the optical receiving means on the aircraft is significantly simplified because there is only a single optical beam frequency to monitor/measure. e) the incident angle detection means can have a much wider usable angular range than the 4 optical beam beacon embodiment, such as for example +/-60 degrees compared to +/-20 degrees. Since the corresponding linear aircraft movement is proportional to the tangent of the incidence angle, the aircraft's working range in each direction is increased by almost a factor of 5. The wider range is because the incident angle detection means is made from flat sensors, as is described in more detail below, rather than lens focused LEDs typically used in the 4 beam beacon embodiment. f) if the horizontal operating range of the aircraft with respect to the ground beacon is exceeded (as limited by the sensor's 60 degree maximum incident beam angle in one example), control degradation is much more gradual than with the 4 optical beam embodiment, making recovery of the aircraft more likely. The actual maximum operating range of the aircraft depends on the aircraft height, since the maximum angle of 60 degrees subtends a greater horizontal distance as the height increases. The maximum distance (away from a centre) is given by h tan 60, where h is the height. This works out to 1.73h in one example.

In the embodiment shown in figures 6-9, in using a single optical beam, the incident angle measured by the aircraft depends not only on the aircraft's position, but also on its angle of inclination. As the aircraft tilts, the measured angle of incidence Θ also changes. For example, with reference to figure 7, the incident angle of aircraft 2' when in a horizontal position is θ_ΐ5 whereas the incident angle of aircraft 2' when in a tilted position is θ₂, even though both aircraft are in the same position in space. This can be handled in two ways:

1. The tilt of the aircraft can be measured using inertial sensors. The measured angle of tilt can be subtracted from the total measured incident angle so that the remaining angle value represents the position only.

2. The optical incident angle sensor can be mounted on levelling means in the form of an actively levelled gimbal mechanism, to keep the optical incident angle sensor horizontal. The gimbal can be actively controlled by inertial sensors as per 1) above.

The advantage of 2) above is that it allows the full angular range of the incident angle sensor to be used for aircraft position measurement. With method 1) some of the incident sensor's angular range must be reserved for the aircraft tilt. For example, if the incident angle sensor can measure angles up to +/-60 degrees and the aircraft is allowed to tilt up to +/-30 degrees, then the allowable range of aircraft position is only + / -30 degrees.

The actively levelling gimbal can include, for example, a pair of brushless electric motors directly driving the pitch and roll axes of the gimbal. This allows the gimbal to rotate smoothly and substantially silently. To provide tilt information, a 2 axis sensor is placed directly on the gimbal. The sensor outputs are used to keep the gimbal horizontal in both horizontal axes by providing negative feedback to the motors.

Figure 8 shows an example of an angle of incidence sensor that can be used in the present embodiment. A pair of flat incidence sensors 36, 36' can be provided at an acute angle relative to the horizontal, each sensor in an opposing diverging arrangement from a central point. More particularly, in the illustrated embodiment the sensors 36, 36' are a pair of flat photodiode sensors, each mounted at an angle of 30 degrees to the horizontal and in opposing diverging positions. In figure 8a, light (shown by arrows 38) arrives directly below in a vertical orientation and illuminated both photodiode sensors 36, 36' equally. In figure 8b, light (shown by arrows 38) arrives obliquely and illuminates sensor 36 more than sensor 36'. Each photodiode sensor 36, 36' produces a maximum output when the light strikes it orthogonally. When the light hits the photodiode sensors 36, 36' obliquely, the output is reduced in proportion to the cosine of the angle away from perpendicular, due to the reduced receiving area presented to the beam.

In figure 8a, the light 38 strikes the sensors 36, 36' at 30 degrees from perpendicular. The sensors therefore produce an equal output. In figure 8b, the light 38 strikes sensor 36 orthogonally, and sensor 36' at a steeply inclined angle. The two outputs therefore differ, and their ratio is used as a measure of incident angle of the light.

Figure 9 shows a typical graph of incidence angle sensor measurement output against the incidence angle of light hitting the sensor. It is linear or substantially linear over a range of +/-60 degrees. More particularly, the graph illustrates the difference between the two sensor output signal strengths. The maximum signal difference at 60 degrees generates a 87% signal output (i.e. one sensor is angled at 60 degrees to the light beam (87% output) and the other sensor is parallel to the light beam (0% output).

Claims

Claims

1.A guidance system for a vehicle or aircraft, said system comprising optical emitting means for emitting at least one optical beam therefrom in use; said optical emitting means provided on or associated with one of a first vehicle/ aircraft or at a first locality; the first locality being different, separate, independent and/or remote to the first vehicle/ aircraft; and optical receiving means for receiving said at least one optical beam in use; said optical receiving means provided on or associated with the other of the first vehicle/aircraft or first locality; and wherein processing means are provided on or associated with the optical receiving means for sensing and/or calculating an intensity of said at least one received optical beam and/ or an incident angle of said at least one received optical beam to allow positional and/or orientation information of the vehicle/aircraft with respect to the first locality to be calculated.

2. The guidance system of claim 1 wherein the guidance system is arranged to communicate with control means to allow movement, positional and/ or orientation control of the vehicle/ aircraft in use using said sensed and/or calculated positional and/ or orientation information of the vehicle/ aircraft.

3. The guidance system of claim 2 wherein the control means controls one, two and/or three axes of movement, or the pitch, roll and/or yaw of the vehicle/ aircraft in use.

4. The guidance system of claim 1 wherein the vehicle/ aircraft is an unmanned aerial vehicle UAV), a drone or a hovering vehicle.

5. The guidance system of claim 1 wherein the vehicle or aircraft has rotary means for generating a lifting force for the vehicle or aircraft to allow the same to move between a non-airbome, stationary or non-operational condition and an air borne, movable or operational condition.

6. The guidance system of claim 5 wherein the rotary means includes a single rotor or rotary wing, or multiple rotors or rotary wings.

7. The guidance system of claims 1 or 5 wherein power means are provided on or associated with the vehicle or aircraft to power the same in use.

8. The guidance system of claim 1 wherein the at least one optical beam is any or any combination of ultraviolet light, visible light or infra-red light.

9. The guidance system of claim 1 wherein the optical receiving means and/or processing means is able to sense and/ or calculate the intensity of one of the received optical beams relative to the intensity of at least one other received optical beams or stored optical data.

10. The guidance system of claim 1 wherein the, or each, optical beam is independently identifiable via identification means.

11. The guidance system of claim 1 wherein the optical emitting means emits a plurality of optical beams and said optical beams are emitted, simultaneously, substantially simultaneously, continuously and/or substantially continuously when in an operational condition.

12. The guidance system of claim 1 wherein the optical emitting means emits a plurality of optical beams and said optical beams are emitted in a predetermined sequence and/ or in a pulsed manner.

13. The guidance system of claim 1 wherein the optical emitting means emits a plurality of optical beams.

14. The guidance system of claim 13 wherein two or more or all of the plurality of optical beams overlap or substantially overlap.

15. The guidance system of claim 14 wherein the degree of overlap of the optical beams is equal or substantially equal.

16. The guidance system of claim 1 wherein each optical beam is shaped so that it is relatively narrow in shape and/or dimensions at the optical emitting means and is relatively broader in shape and/ or dimensions with increasing distance away from the optical emitting means.

17. The guidance system of claim 1 wherein the intensity of an optical beam is greatest along a central or longitudinal axis/point thereof at any cross section taken perpendicular to the central or long^mdinal axis/point and decreases in a direction radially or linearly outwardly from said axis/point; and/or the intensity of an optical beam is greater closer to the optical emitting means and decreases with increasing distance from the optical emitting means.

18. The guidance system of claim 1 wherein three optical beams are provided and each optical beam is arranged to be 120 degrees with respect to an adjacent optical beam in use.

19. The guidance system of claim 13 or 18 wherein each optical beam is arranged at 30 degrees to a vertical axis in use.

20. The guidance system of claim 13 or 18 wherein the area the overlap of the optical beams is detected as a central or substantially central position which the aircraft or vehicle attempts to maintain itself when in an operational condition.

21. The guidance system of claim 1 wherein only a single optical divergent beam is emitted by the optical emitting means and this beam is omni-directional.

22. The guidance system of claim 21 wherein the single optical divergent beam is a sinusoidally modulated infra-red beam generated by one or more light emitting diodes (LEDs).

23. The guidance system of claim 21 wherein when only a single optical divergent beam is generated by the optical emitting means, the optical receiving means includes or comprises an incident angle detection means or sensor.

24. The guidance system of claim 23 wherein the incident angle detection means is arranged to measure angles of incidence of +/- 60 degrees.

25. The guidance system of claim 23 wherein the incident angle detection means or sensor comprises two sensors for each horizontal axis, thereby providing four sensors in total for two horizontal axes in a three dimensional space.

26. The guidance system of claims 23 or 25 wherein the incident angle sensors or different parts of the same sensor are arranged at an acute angle to the horizontal and/ or in opposing directions.

27. The guidance system of claims 23, 25 or 26 wherein the incident angle sensor or sensors are flat, planar, substantially flat and/or substantially planar.

28. The guidance system of claims 23 or 25 wherein the incident angle detection means or sensor(s) are mounted on a levelling means, gimbal or actively levelling gimbal on the vehicle or aircraft.

29. The guidance system of claim 1 wherein directional means are provided to allow the direction of movement of the vehicle or aircraft with respect to the first locality to be determined at a point in time.

30. The guidance system of claim 29 wherein the directional means is arranged to emit a further or at least a fourth optical beam and further optical receiving means are provided to receive the further or at least fourth optical beam in use.

31. The guidance system of claim 30 wherein the further or at least fourth optical beam is in the form of at least one polarised light beam and the further optical receiving means are in the form of a polarising light beam receiving means or device.

32. The guidance system of claim 31 wherein the polarising light beam receiving means includes a pair of polarising light beam receiving means, each having filter means associated with the same that are angled at 90 degrees or substantially 90 degrees with respect to each other.

33. The guidance system of claim 1 wherein tethering means or mechanism are provided to allow the vehicle or aircraft to be retained at a fixed or substantially fixed location in a non-operational and/or operational condition.

34. The guidance system of claim 1 wherein inertial sensing means are provided for sensing and/ or measuring tilt or angle of the vehicle or aircraft.

35. A method of using a guidance system for a vehicle or aircraft, said method including the steps of emitting at least one optical beam from optical emitting means; said optical emitting means provided on or associated with one of a first vehicle/aircraft or at a first locality; the first locality being different, separate, independent and/or remote to the first vehicle/aircraft; receiving said at least one optical beam using optical receiving means, said optical receiving means provided on or associated with the other of the first vehicle/ aircraft or first locality; and sensing and/ or calculating an intensity of said at least one received optical beam and/or an incident angle of said at least one received optical beam using processing means to allow positional and/ or orientation information of the vehicle/ aircraft with respect to the first locality to be calculated.