Landing aid system

Abstract

Landing aid system This system (10) comprises, on the ground, a beacon (12) and, on board an aircraft (4), a device (14), the beacon comprising: a first unit (26) for transmitting an uplink optical signal (Sm); a unit (22) for pointing the uplink optical signal at the device and measuring angles of the pointing direction; a telemetry unit (24) for measuring a distance (D) between the beacon and the device; a unit (23) for calculating a spatial position of the aircraft from the distance and the angles; and, a first unit (25) for modulating the uplink optical signal as a function of the spatial position of the aircraft, the device comprising: a second reception unit (48) for receiving the uplink optical signal; and a second demodulation unit (47) for extracting the spatial position of the aircraft from the uplink optical signal in order to pilot the latter. Figure for the abstract: Figure 2

Description

Title of the invention: Landing assistance system

[0001] The present invention relates to landing aid systems for an aircraft.

[0002] The landing aid systems of the state of the art are based on the use of radiofrequency means - RF.

[0003] This is particularly the case for ILS systems (Instrument Landing System), which are installed on all aerodromes allowing precision landing, falling under the CAT 3B operating category.

[0004] Such ILS systems generally allow aircraft to approach the runway and, depending on the classification of that aerodrome, to land while being guided from the ground on the runway axis.

[0005] An ILS system comprises, on the ground, two transmitters called respectively "localizer" (or location transmitter) and "glide" (or descent transmitter) to define respectively the axis of the runway and the descent axis.

[0006] An ILS system comprises, on board the aircraft, an ILS receiver for receiving the signals transmitted by the two transmitters on the ground. Preferably, this on-board ILS receiver is supplemented by a radio altimeter for measuring the height between the aircraft and the ground.

[0007] MLS type landing aid systems (“Microwave Landing System”) constitute an evolution of ILS systems.

[0008] However, these ILS and MLS systems, based on the use of RF signals, are likely to be disturbed, for example by cellular communication networks, or even by RF sources causing, involuntarily or not, interference.

[0009] Furthermore, in an urban environment, the reflection of RF signals on buildings is detrimental, for example by creating false runway axes.

[0010] Furthermore, an explosion in the use of autonomous aircraft is expected, particularly in urban environments, such as drones for various applications, such as passenger transport, parcel delivery, and surveillance. Depending on the intended uses, these drones must be able to land outside existing airfields, such as on the roof of a building. It is not feasible to equip such landing zones with ILS systems, which remain complex to deploy and expensive to operate.

[0011] The invention therefore aims to address this problem by proposing in particular a landing assistance system making it possible to dispense with RF signals.

[0012] For this purpose, the invention relates to a landing assistance system comprising, on the ground, a beacon and, on board an aircraft, an onboard device, the landing assistance system being characterized in that: the beacon comprises: a first transmission unit, for transmitting an uplink optical signal from the beacon to the onboard device; a pointing unit, configured to modify a transmission direction of the uplink optical signal to aim at the onboard device and measure at each instant angular parameters of said transmission direction; a telemetry unit for determining at each instant a distance between the beacon and the onboard device, a calculation unit for determining a spatial position of the aircraft from the distance and the angular parameters of the transmission direction, and for developing a first piece of information to be transmitted to the aircraft from the spatial position;and, a first modulation unit for modulating the uplink optical signal according to the first information to transmit it to the onboard device, and the onboard device comprises: a second reception unit for receiving the uplink optical signal; and, a second demodulation unit for extracting from the received uplink optical signal the positioning information in order to transmit it to a piloting system of the aircraft. ;

[0013] According to the particular embodiments, the landing assistance system comprises one or more of the following characteristics taken in isolation or according to all technically possible combinations:

[0014] - the on-board device further comprises: a second transmission unit for transmitting a downlink optical signal to the beacon; a second modulation unit, adapted to modulate the downlink optical signal so that it carries a second piece of information produced by the aircraft piloting system, and the beacon further comprising: a first unit for receiving the downlink optical signal; and, a first demodulation unit for extracting the second piece of information from the received optical signal.

[0015] - the on-board device comprises a cube corner allowing the signal to be emitted downlink optical signal by reflection of the uplink optical signal and modulating the downlink optical signal.

[0016] - the tag includes a module for comparing a phase shift between the signal uplink optical signal and downlink optical signal to determine the distance between the beacon and the on-board device.

[0017] - the uplink optical signal is modulated in a first frequency range and the downlink optical signal is modulated in a second frequency range, the first and second frequency ranges being disjoint.

[0018] - the spatial position corresponds to a latitude, a longitude and a height of the aircraft.

[0019] - the first information is the spatial position of the aircraft, a relative position of the aircraft, a command for piloting the aircraft.

[0020] - the second information is an acknowledgment message of the first information.

[0021] - the pointing unit comprises mechanical signal orientation means optical mounting slaved to a telescope.

[0022] The invention and its advantages will be better understood on reading the detailed description which follows of a particular embodiment, given solely as an illustrative and non-limiting example, this description being made with reference to the appended drawings in which: - [Fig.l] [Fig.l] is a schematic representation of the situation in which the landing aid system according to the invention is implemented; - [Fig.2] [Fig.2] is a schematic representation in the form of functional blocks of the ground and on-board components of the landing assistance system according to the invention; - [Fig.3] [Fig.3] is a representation of a preferred embodiment for optical communication between the ground component and the on-board component of the landing aid system of [Fig.2]; and, - [Fig.4] [Fig.4] is a block representation of a process implementation of the landing system according to the invention.

[0023] Referring to [Fig.l], the landing assistance system 10 according to the invention allows an aircraft 4, in this case a drone, to land inside a landing zone 6, which may be a field airfield, the roof of a building, the deck of a ship, or the equivalent.

[0024] The landing aid system 10 comprises a beacon 12, fixed to the ground, and a device 14 on board the aircraft 4.

[0025] The system 10 is based on bidirectional optical communication between the beacon 12 and the device 14.

[0026] The beacon 12 incorporates a telemetry means making it possible to determine the distance D separating the beacon 12 from the device 14, and consequently from the aircraft 4.

[0027] In addition, the beacon 12 is provided with means allowing the optical beam emitted by the beacon 12 to be aimed at the device 14. The pointing direction A gives the bearing angles a and elevation y.

[0028] From these angles and this distance, the beacon 12 is capable of determining the precise spatial position of the aircraft 4, that is to say the point P (longitude and latitude) above which the aircraft 4 is located at the current time, as well as the current height H relative to the ground.

[0029] By means of uplink communication, from beacon 12 to device 14, beacon 12 communicates its spatial position to aircraft 4.

[0030] The piloting system, autonomous or not, with which the aircraft 4 is equipped then takes this information into account to pilot the aircraft 4 and guide it to zone 6.

[0031] More specifically, as shown in [Fig.2], the system 10 has different functionalities.

[0032] Thus, the beacon 12 comprises a pointing unit 22. These are, for example, mechanical-optical means making it possible to modify the pointing direction A of the optical beam emitted by the beacon 12.

[0033] The pointing unit may comprise an optical camera for locating the aircraft 4 for location within an extended solid angle. Once the target aircraft has been acquired by means of the camera, the intensity of the reflected beam, collected by a telescope (described in more detail below), allows location of the target aircraft within a restricted solid angle.

[0034] Once the beacon 12 is suitably oriented towards the device 14 of the aircraft 4, an optical communication link is established. The pointing unit 22 is then adapted to follow (“tracking”) the target aircraft in order to maintain this link. The pointing unit 22 periodically delivers the angle information a and y relating to the pointing direction A.

[0035] The beacon 12 is provided with a telemetry unit 24 making it possible, once an optical communication link has been established with the device 14 on board the aircraft 4, to determine, at each instant, the distance D separating the beacon 12 from the device 14. Preferably, the telemetry unit 24 is of the Lidar type (“Light Detection and Ranging” or system for detecting and estimating distance by light), using the emitted and reflected beams to determine the distance D.

[0036] The beacon 12 comprises a calculation unit 23 capable, from the information delivered by the pointing unit 22 and that delivered by the telemetry unit 24, of calculating the spatial position of the aircraft 4. The calculation unit 23 thus periodically delivers the instantaneous position P and instantaneous height H of the aircraft 4.

[0037] The beacon 12 comprises a first modulation unit 25 and a first optical signal transmission unit 26. The unit 26 is capable of transmitting an optical signal Sm to the device 14 so as to constitute an uplink channel of the optical communication link, from the beacon 12 to the device 14. The optical beam is modulated by the unit 25 so that the optical signal Sm carries the position P and altitude H information of the aircraft 4, as determined by the calculation unit 23. This modulation is carried out in a first frequency range.

[0038] The beacon 12 comprises a first optical reception unit 28 and a first demodulation unit 27. The optical reception unit 28 is suitable for receiving the optical signal Sd constituting the downlink channel of the optical communication link, from the device 14 to the beacon 12. The unit 27 is suitable for demodulating the signal at the output of the reception unit 28 so as to extract the information contained in the optical signal Sd, coming from the aircraft 4 and incident on the unit 28.

[0039] On the side of the aircraft 4, the on-board device 14 comprises a second reception unit 48 and a second demodulation unit 47. The second unit 48 is suitable for receiving the optical signal Sm coming from the beacon 12. The second demodulation unit 47 is suitable for demodulating the signal delivered at the output of the unit 48 so as to extract from the optical signal Sm the information that it comprises, in particular the position P and the altitude H of the aircraft 4, as calculated by the beacon 12.

[0040] This information is transmitted to a piloting system 16 of the aircraft 4, so as to allow this system to maneuver the aircraft 4 so that it lands.

[0041] The device 14 comprises a second transmission unit 46 and a second modulation unit 45. To transmit information from the aircraft 4 to the ground beacon 12 by means of the optical signal Sd, such as for example an acknowledgment message for position and altitude information, the second modulation unit 45 is capable of modulating the optical beam emitted by the second transmission unit 46. Advantageously, this modulation is carried out in a second frequency range, distinct from the first frequency range.

[0042] Referring now to [Fig. 3], a possible structure of the beacon 12 and the device 14 is presented making it possible to achieve, in practice, some of the functionalities shown in [Fig. 2].

[0043] Thus, the beacon 12 is provided with a laser source 51 delivering a laser beam, for example in the infrared range.

[0044] The beacon 12 comprises an optical modulator 52 making it possible to modulate the intensity of the laser beam leaving the source 51. This modulation is carried out as a function of the information coming from the calculation unit 23, in particular the position and altitude to be transmitted to the aircraft 4. Advantageously, the optical modulator 52 operates in a first frequency range.

[0045] The modulated laser beam exiting the optical modulator 52 falls on a birefringent plate 53.

[0046] A first fraction of this beam, reflected by the blade 53, is applied to the input of a telescope 54.

[0047] A second fraction of this beam, transmitted by the blade 53, is routed towards an optical detector 55, via a first reflecting mirror 56 and a second birefringent blade 57.

[0048] The telescope 54 is capable of emitting, in the medium separating the beacon 12 from the device 14, the modulated laser beam as an uplink signal Sm.

[0049] The device 14 comprises a cube corner 61. This is a set of three semi-reflecting mirrors, mounted at right angles to each other, so as to form a cube corner.

[0050] This cube corner 61 has the physical property of reflecting a fraction of the incident beam exactly at 180°. The reflected laser beam constitutes the descending signal Sd.

[0051] The cube corner 61 also has the property of allowing a fraction of the incident beam to pass through.

[0052] Thus, the transmitted fraction of the uplink signal Sm is applied to the input of an optical demodulator 62. The optical demodulator 62 is capable of generating an electrical signal from the received optical signal, this electrical signal corresponding to the information contained in the uplink signal Sm, namely the position and altitude of the aircraft 4.

[0053] In order for the beam reflected towards the telescope 54 to carry information coming from the aircraft 4, the cube corner 61 is provided with electromechanical means 63, for example piezoelectric, making it possible to vibrate the mirrors constituting the cube corner 61. This vibration makes it possible to modulate the amplitude of the reflected signal and therefore to ensure that the downlink signal Sd carries the information that the aircraft 4 wishes to transmit to the beacon 12. The means 63 are controlled by an electrical modulator 64. The latter generates an electrical signal and applies it to the means 63 according to the information to be coded in the downlink signal Sd. This information comes for example from the piloting system 16.

[0054] On the beacon 12 side, the telescope 54 is adapted to receive the light beam reflected by the device 14, i.e. the descending signal Sd, and to transmit it onto the birefringent plate 53.

[0055] A fraction of this light beam is returned to the source 51 where it is absorbed by a suitable protection system, while the other fraction of this beam, transmitted by the image 53, is sent to the detector 55, via a second mirror 58 and the second birefringent plate 57.

[0056] The detector 55 is an optical detector capable of delivering an electrical signal corresponding to the superposition of the signals Sd and Sm.

[0057] This electrical signal is transmitted to a module 70 on the one hand and to a module 59 on the other hand.

[0058] By comparing the transmitted and received beams, in particular by measuring a phase shift between these two beams, the module 70 is able to determine the distance D between the beacon 12 and the device 14. This is therefore the telemetry function of the beacon 12.

[0059] Furthermore, by filtering the downlink signal around the second frequency range, the module 59 extracts the information transmitted by the aircraft, such as for example the acknowledgment message R transmitted by the aircraft 4.

[0060] In this practical embodiment, it can be seen that a single laser source is used, on the side of the ground station 12. The aircraft equipped with the on-board device 14 do not include a laser source.

[0061] This laser source is used not only for the telemetry function, but also for the communication function, since it can be easily modulated to transport information from the beacon 12 to the aircraft 4 and / or from the aircraft 4 to the beacon 12.

[0062] The advantage of implementing a cube corner is the ease of re-emitting a beam at 180° relative to the incident beam, i.e. if the uplink signal Sm propagates in the direction of axis A, the downlink signal Sd propagates in the opposite direction of axis A. The reception and transmission functions of the device 14 are therefore combined in this single component.

[0063] Furthermore, if the aircraft is to be required to communicate information to the ground, it is easy to modulate the reflected beam.

[0064] For the pointing function of the beacon 12, if the optical camera allows a first coarse pointing towards the aircraft, the telescope 54 is used for a finer pointing. In particular, a telescope 54 is provided with a collimator 72 making it possible to control the mobile head of the beacon 12 for precise pointing towards the aircraft 4.

[0065] As illustrated in [Fig.4], a method 100 of using the landing aid system 10 could be as follows.

[0066] In a step 110, the beacon 12 ensures the optical acquisition of the aircraft 4 by means of the pointing device 22 and maintains this acquisition during the communication.

[0067] Then, in a step 120, the beacon 12 establishes the optical link with the device 14 on board the aircraft 4. The establishment of such a link can begin with an exchange of identifiers between the aircraft and the beacon.

[0068] In step 130, the beacon 12 measures in real time the distance which separates it from the aircraft 4. This information is communicated to the computer of the beacon 12. The beacon 12 also measures in real time the parameters of the pointing direction, namely the bearing angle and the elevation angle and transmitted to the computer of the beacon 12.

[0069] In step 140, at each time step, the beacon calculator 12 determines from the distance and the angles of the pointing direction, the spatial position of the aircraft 4. It derives the spatial position information (latitude, longitude and height) of the aircraft relative to the ground.

[0070] Then in step 150, the beacon 12 transmits, along the uplink channel, this positioning information of the aircraft 4.

[0071] After reception and demodulation of the uplink optical signal Sm, the positioning information is transmitted to the piloting system of the aircraft 4, which performs the piloting actions required for landing.

[0072] Advantageously, following the reception of the positioning information, in a step 160, the aircraft 4 indicates to the beacon 12 the correct reception of this information in the downlink optical signal Sd.

[0073] Steps 110 to 160 are iterated at each time step until the aircraft 4 lands inside the zone 6. Implementation variants

[0074] Alternatively, instead of simply indicating the positioning information to the aircraft, the ground station may indicate transmitting other information.

[0075] For example, instead of an absolute spatial position, a relative spatial position between the aircraft and the landing zone may be transmitted. This relative position is obtained from the absolute spatial position of the aircraft and that of the landing zone.

[0076] For example, the ground station could take control of the piloting of the aircraft in order to carry out the landing phase. This advantageously allows possible human supervision by a ground station controller.

[0077] Alternatively, the aircraft carries a Lidar. While this solution currently remains expensive, it could become more widespread in the near future and could therefore be carried on board the aircraft at a lower cost. This would allow the aircraft to measure the distance separating it from the beacon on the ground.

[0078] Optionally, in addition to the optical bidirectional communication, a radiofrequency communication can be established between the beacon and the aircraft so as, for example, to carry out the first phase of establishing the optical link relating to the identification between the aircraft and the beacon on the ground. Advantages of the invention

[0079] The landing aid system just presented is easily deployable. The ground station does not require any significant infrastructure. It can therefore equip small airfields, helipads or any landing zones suitable for the use of an aircraft, in particular an autonomous aircraft.

[0080] On the aircraft side, the use of a cube corner, which is an inexpensive device, makes it possible to equip a fleet of aircraft at a lower cost, in particular a fleet of drones.

[0081] The proposed solution is robust to electromagnetic disturbances since it is based on optical communication. It is therefore well suited to an urban environment where radiofrequency communication can be disturbed by telecommunication networks, or an environment in which signals from positioning satellites are easily disturbed by reflection.

[0082] We therefore avoid the electromagnetic disturbances which affect the systems of the state of the art.

Claims

Claims

1. Landing assistance system (10), comprising, on the ground, a beacon (12) and, on board an aircraft (4), an onboard device (14), the landing assistance system being characterized in that: - the beacon (12) comprises: - A first transmission unit (26), for transmitting an uplink optical signal (Sm) from the beacon (12) to the onboard device (14); - A pointing unit (22), configured to modify a transmission direction of the uplink optical signal to target the onboard device (14) and measure at each instant angular parameters of said transmission direction;- A telemetry unit (24) for determining at each instant a distance (D) between the beacon (12) and the on-board device (14), - A calculation unit (23) for determining a spatial position of the aircraft from the distance and the angular parameters of the transmission direction, and for developing a first piece of information to be transmitted to the aircraft (4) from the spatial position; and, - A first modulation unit (25) for modulating the uplink optical signal (Sm) as a function of the first piece of information to transmit it to the on-board device, and - the on-board device (14) comprises: - A second reception unit (48) for receiving the uplink optical signal; and, - A second demodulation unit (47) for extracting the positioning information from the received uplink optical signal in order to transmit it to a piloting system of the aircraft.;

2. The system of claim 1, wherein: the on-board device (14) further comprises: - A second transmission unit (46) for transmitting a downlink optical signal (Sd) to the beacon (12); - A second modulation unit (47), adapted to modulate the downlink optical signal so that it carries a second information produced by the aircraft piloting system, the beacon (12) further comprising: - A first unit for receiving the descending optical signal; and, - A first demodulation unit for extracting the second information from the received optical signal.

3. The system of claim 2, wherein the on-board device (14) comprises a cube corner (61) for emitting the downlink optical signal by reflection of the uplink optical signal and for modulating the downlink optical signal.

4. System according to any one of the preceding claims, in which the beacon comprises a module for comparing a phase shift between the uplink optical signal and the downlink optical signal in order to determine the distance between the beacon (12) and the on-board device (14).

5. A system according to any preceding claim, wherein the uplink optical signal is modulated in a first frequency range and the downlink optical signal is modulated in a second frequency range, the first and second frequency ranges being disjoint.

6. A system according to any preceding claim, wherein the spatial position corresponds to a latitude, a longitude and a height of the aircraft (4).

7. System according to any one of the preceding claims, in which the first information is the spatial position of the aircraft (4), a relative position of the aircraft, a piloting command of the aircraft.

8. System according to any one of the preceding claims, in which the second information is an acknowledgment message of the first information.

9. System according to any one of the preceding claims, in which the pointing unit (22) comprises mechanical means for directing an uplink optical signal controlled by a telescope (54).

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