Method for detecting an airport including a landing area, and associated method for automatic takeoff or landing
The method uses polarization-rotating reflectors to enable precise airport landing zone detection and automatic guidance, addressing infrastructure and precision issues of existing systems, ensuring reliable and cost-effective automatic landings.
Patent Information
- Application Number
- FR2024008883
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-08-13
- Publication Date
- 2026-02-20
AI Technical Summary
Existing airport landing systems, such as Category III ILS, Ground Based Augmentation System (GBAS), and Satellite-Based Augmentation System (SBAS), require significant infrastructure and are not sufficiently precise or available for automatic landings, especially in dense environments.
A method using reflectors configured to rotate the polarization of incident electromagnetic waves, allowing aircraft to detect and locate the landing zone with high precision by measuring polarization changes, enabling automatic guidance without extensive infrastructure.
Enables precise detection of landing zones and automatic aircraft guidance with minimal equipment on the aircraft and airport, suitable for various environments, including dense areas, while being cost-effective and robust against interference.
Smart Images
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Abstract
Description
Title of the invention: Method for detecting an airport comprising a landing zone, and associated method for automatic takeoff or landing
[0001] The present invention relates to a method for detecting an airport comprising a landing area, and an associated method for automatic takeoff or landing.
[0002] Herein, airport means the facilities for enabling the landing, takeoff and ground maneuvers of an aircraft.
[0003] A system in the context of an automatic landing until touchdown is the Category III instrument landing system, or ILS CAT II, according to the IACI Convention - Annex 10 in force in June 2024.
[0004] This system includes important airport installations, including a location set, such as a runway alignment radio beacon, to provide the aircraft's deviation from the runway centerline, and a so-called glide path set, or descent path set, to provide the aircraft's deviation from the nominal approach slope.
[0005] This presents a very high installation cost for the airport, as well as for its operation, so that such a system is limited to large airports, which are able to make such investments.
[0006] Alternatively, another system includes a ground-based augmentation system or Ground Based Augmentation System (GBAS).
[0007] Such a system also requires significant installations, and presents the same disadvantages as the CAT III ILS.
[0008] Other systems, such as the satellite-based augmentation system (SBAS), are not sufficient both in terms of positioning accuracy and especially availability (particularly due to sensitivity to jamming, and the effects of multipathing which become increasingly important as one approaches the ground) to assist in the context of an automatic landing up to wheel touchdown.
[0009] The aim of the invention is therefore to propose a method for locating an aircraft, without requiring significant infrastructure, with sufficient precision, in particular to allow automatic guidance of the aircraft until it touches down.
[0010] To this end, the invention relates to a method for detecting an airport comprising a landing zone, the airport being equipped with a plurality of reflectors, each reflector being configured to reflect a wave electromagnetic field incident on said reflector and having an incident polarization, each reflector having a polarization rotation property, such that the reflected field predominantly has a polarization orthogonal to the incident polarization, the process comprising the following steps:
[0011] - approach to the airport by an aircraft or presence of the aircraft at the airport, the aircraft being equipped with at least one radar,
[0012] - emission by at least one radar of a signal having an initial polarization,
[0013] - reception by at least one radar of a reflected signal, the at least one radar being capable of receiving waves with a polarization orthogonal to the initial polarization, and
[0014] - determination of the presence and, where applicable, the respective location of reflectors based on the polarization of the reflected signal.
[0015] The port installation includes the reflectors, which represents limited equipment, and therefore allows for the global deployment of this solution. The equipment on board the aircraft is also limited and does not add significant extra weight. This method also allows the aircraft to precisely detect the reflectors, and thus deduce the aircraft's position relative to the airport, and for example, to the landing zone.
[0016] According to other advantageous aspects of the invention, the method comprises one or more of the following features, taken individually or in all technically possible combinations:
[0017] - the method further comprises a step of determining the location of the landing area in relation to the aircraft from the determined location of the reflectors, in the event that the presence of reflectors is determined;
[0018] - the determination of presence includes a measurement of the power of the component of the reflected signal exhibiting orthogonal polarization;
[0019] - at least one radar is capable of receiving waves of the initial polarization and of waves of the polarization orthogonal to the initial polarization;
[0020] - the determination of presence includes a measurement of a parameter of the component of the reflected signal exhibiting orthogonal polarization, a measurement of a parameter of the component of the reflected signal exhibiting the initial polarization, a calculation of the ratio of the parameter of the component of the reflected signal exhibiting orthogonal polarization to the parameter of the component of the reflected signal exhibiting the initial polarization, and a comparison of the ratio with a threshold;
[0021] - at least one radar is further capable of emitting waves exhibiting a second initial polarization, the second initial polarization corresponding to the orthogonal polarization of the initial polarization, the process comprising a step of emission by at least one radar of a signal having the second initial polarization;
[0022] - the determination of presence includes a measurement of the power of the component of the reflected signal exhibiting the initial polarization from the signal exhibiting the second initial polarization, a measurement of the power of the component of the reflected signal exhibiting the orthogonal polarization from the signal exhibiting the second initial polarization, a calculation of a second ratio of said power for the component exhibiting the initial polarization to said power of the component of the reflected signal exhibiting the second initial polarization, and a comparison of the ratio with the threshold, a reflector being detected only when the ratio and the second ratio are greater than the threshold;
[0023] - at least one radar comprises a frequency-modulated continuous wave radar;
[0024] - each reflector has a radar cross-sectional area such that each reflector is distinguishable from the rest of the airport; and / or
[0025] - reflectors surround the landing area.
[0026] The invention also relates to a method for the automatic takeoff or landing of an aircraft from or on a landing area of an airport, the airport being provided with a plurality of reflectors, each reflector being configured to reflect an electromagnetic wave incident on said reflector and having an incident polarization, each reflector having a polarization rotation property, so that the reflected wave predominantly has a polarization orthogonal to the incident polarization, the automatic takeoff or landing method comprising an airport detection step according to the method described above.
[0027] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:
[0028] [Fig-1] [Fig. 1] is a schematic partial top view of an airport according to a first example of an embodiment,
[0029] [Fig.2] [Fig.2] is a schematic top view of an airport according to a second example of a method of implementation,
[0030] [Fig.3] [Fig.3] is a schematic view of the steps of the detection process according to a method of embodiment of the invention, and
[0031] [Fig.4] [Fig.4] is a schematic view of certain elements of an aircraft according to a example of a method of implementation.
[0032] The invention relates to a method for detecting an airport comprising a landing area.
[0033] Examples of airports according to the method of the invention are shown in Figures 1 and 2.
[0034] Similar or identical elements are numbered on [Fig.2] with the same numerical reference as on [Fig.1], incremented by 100.
[0035] Airport 10, 110 includes a landing area 12, 112.
[0036] Landing zone 12, 112 allows for the landing and takeoff of aircraft.
[0037] The landing area 12 includes, for example, a landing strip, as shown in [Fig.1], extending along a longitudinal direction X.
[0038] The runway 12 then presents, for example, a wheel touchdown spot 13, said spot being an area in which an aircraft is expected to touch the ground at wheel level during its landing.
[0039] The airport is then adapted for airplanes.
[0040] The track includes, for example, at least one identifiable region.
[0041] More specifically, the track here comprises a start region D, a central region C, and an end region, the start region D and the end region being identifiable regions.
[0042] The starting region D, the central region C and the ending region F are aligned in that order along the longitudinal direction X.
[0043] The track is here symmetrical, with respect to a median plane P, perpendicular to the longitudinal direction X.
[0044] Thus, the track is capable of being used in two directions.
[0045] Alternatively, airport 110 includes, for example, a vertiport.
[0046] The vertiport is suitable for helicopters.
[0047] The landing zone 112 then has, for example, the shape of a disc.
[0048] Alternatively, the landing zone 112 has, for example, the shape of a regular polygon.
[0049] Airport 10, 110 is equipped with a plurality of reflectors 14, 114.
[0050] In the case of a runway, the airport 10 is, for example, equipped with at least one pair of reflectors 14. In the case of a vertiport, the airport 110 is, for example, equipped with at least three reflectors 114.
[0051] Each reflector 14, 114 is configured to reflect an electromagnetic wave incident on said reflector and having an initial polarization.
[0052] Each reflector 14, 114 has a polarization rotation property, so that the reflected wave predominantly has a polarization orthogonal to the initial polarization of the incident wave, that is to say that the polarization of at least 50% of the incident wave is transformed into orthogonal polarization by reflection on said reflector 14, 114.
[0053] More particularly here, each reflector 14, 114 is such that the polarization of at least 80%, here at least 90%, of the incident wave is transformed into polarization orthogonal to the polarization of the incident wave, by reflection on said reflector 14, 114.
[0054] Each reflector is adapted to be distinguishable from the rest of the airport by radar.
[0055] Each reflector has a radar cross-section (RCS).
[0056] The radar cross-sectional area is such that each reflector is distinguishable from the rest of the airport by radar, in particular from the ground including tar and / or vegetation of the airport.
[0057] The radar cross-sectional area is, for example, greater than or equal to 10 times the radar cross-sectional area of the other elements of the airport, and in particular of the clutter formed by the ground.
[0058] The reflectors 14, 114 here surround the landing area 12, 112.
[0059] More specifically, the reflectors 14, 114 are arranged outside the landing area 12, 112.
[0060] The landing zone 12, 112 here presents two sides with respect to a transverse direction Y.
[0061] The airport 10, 110 is equipped with reflectors 14, 114 on each side of the landing area 12, 112.
[0062] In the case of a landing strip, the sides correspond to the lateral sides of the runway.
[0063] The reflectors 14 are, for example, arranged symmetrically on either side of the track, more particularly according to an orthogonal symmetry with respect to a central axis of the track.
[0064] The reflectors 14 are, for example, further distributed along a longitudinal direction X of the track, more particularly of at least one identifiable region.
[0065] Reflectors 14 are, for example, arranged on either side of the track along the transverse direction Y at location 13.
[0066] The reflectors 14 form, for example, at least one pattern 16, more particularly of a plurality of reflectors 14.
[0067] Each motif 16 includes, for example, at least two reflectors 14.
[0068] In one embodiment, more particularly here in the case of a landing strip, each pattern 16 is formed of four reflectors arranged on two lines, the lines being along the transverse direction Y. The reflectors of the two lines are arranged in a staggered pattern.
[0069] Here, the reflectors 14 form a plurality of identical patterns, distributed along the runway in the longitudinal direction X, more particularly in at least one identifiable region, and on either side of the runway in the transverse direction Y.
[0070] More particularly here, the patterns are distributed along at least one identifiable region at regular intervals along the longitudinal direction X, on either side of the track along the transverse direction Y.
[0071] The patterns are set far apart from the runway side, so that the distance between the patterns and the longitudinal centerline is constant, for example between 25 m and 100 m.
[0072] In the case of a vertiport, the reflectors 114 are, for example, arranged in the form of two lines, each line extending from one side of the vertiport along the transverse direction Y.
[0073] Each line of reflectors comprises, for example, at least three reflectors, here at least four, more particularly four, reflectors 114.
[0074] The reflector lines are equidistant with respect to a central line.
[0075] The reflector lines are, for example, in the example shown, arranged symmetrically on either side of landing zone 112, more particularly with respect to a plane of symmetry.
[0076] Alternatively, the reflectors of the reflector lines are, for example, arranged in a staggered pattern.
[0077] The median line is here called the line connecting the midpoint of the two reflector lines.
[0078] The reflectors are arranged so that the center of the landing zone 112 corresponds to the intersection between the central line and the median line.
[0079] The detection method will now be described with reference to [Fig.3].
[0080] The detection method includes the approach 210 of the airport 10, 110 by an aircraft 18, 118, in particular for a landing on the landing area, or the presence of the aircraft 18, 118 in the airport 10, 110, in particular for a takeoff from the landing area.
[0081] An example of certain elements of an aircraft according to an embodiment of the invention is shown schematically in [Fig.4].
[0082] The aircraft is equipped with at least one 310 radar.
[0083] At least one radar 310 includes, for example, a frequency-modulated continuous wave radar.
[0084] The radar 310 here includes at least one antenna, here two antennas 312, 314, more particularly a transmitting antenna 312 and a receiving antenna 314.
[0085] Alternatively, the radar comprises a single antenna capable of emitting and receiving electromagnetic waves.
[0086] The radar 310 is capable of emitting a signal having an initial polarization.
[0087] The radar 310 is capable of receiving waves of a polarization orthogonal to the initial polarization.
[0088] In a particular embodiment, the radar 310 is further capable of receiving waves of orthogonal polarization and waves of initial polarization.
[0089] In this particular embodiment, the radar 310 is, for example, also capable of emitting waves having a second initial polarization, the second initial polarization corresponding to the orthogonal polarization.
[0090] The radar 310 has a frequency band, between the X and W bands, for example between 10 GHz and 100 GHz.
[0091] The 310 radar, for example, has a radial range resolution between 60 cm and 3 m.
[0092] The radar 310 has, for example, an angular resolution of less than 3°, more particularly between 1° and 2°.
[0093] The 310 radar, for example, has a range of between 350 m and 5 km.
[0094] In the example of [Fig.4], the aircraft includes an information processing unit formed for example of a memory 312 and a processor 314 associated with the memory 312.
[0095] The aircraft further comprises herein, for example, a measurement module 316, the measurement module 316 being capable of measuring at least one parameter of the orthogonal polarization component of a wave received by the radar, and, where appropriate, of the initial polarization component of a wave received by the radar.
[0096] At least one parameter includes, for example, power.
[0097] The aircraft further comprises here a determination module 318.
[0098] The determination module is capable of determining the presence and, where applicable, the relative location of reflector(s) with respect to the aircraft from the polarization of the signal received by the radar 310, as will be described below.
[0099] The determination module is, for example, also capable of determining the location of the landing zone 12 in relation to the aircraft 18.
[0100] In the example of [Fig. 4], the determination module 318, and optionally the measurement module 316, are each implemented as a software program, or a software component, executable by the processor 314. The memory 312 of the processor is then capable of storing a determination software program, and optionally a measurement software program. The processor is then capable of executing each of the software programs.
[0101] In an alternative not shown, the determination module, as well as the optional measurement module, are each implemented as a programmable logic component, such as an FPGA (Field Programmable Gate Array) or an integrated circuit, such as an ASIC (Application Specified Integrated Circuit).
[0102] When the modules are implemented in the form of one or more software programs, that is, in the form of a computer program, also called a computer program product, it is further capable of being stored on a computer-readable medium, not shown. A computer-readable medium is, for example, a medium capable of storing electronic instructions and being connected to a bus of a computer system. By way of example, a readable medium is an optical disc, a magneto-optical disc, ROM, RAM, any type of non-volatile memory (for example, FLASH or NVRAM), or a magnetic card. A computer program comprising software instructions is then stored on the readable medium.
[0103] The process further comprises the following steps:
[0104] - emission 212 by at least one radar 310, more particularly via the antenna emit 312, of a signal exhibiting an initial polarization,
[0105] - reception 214 by at least one radar 310, more particularly via the antenna receiver 314, of a reflected signal, and
[0106] - determination of the presence 216 and, where applicable, of the respective location reflectors based on the polarization of the reflected signal, more specifically by the determination module 318.
[0107] The presence determination step 216 includes, for example, a measurement substep 218 and an application substep 220 of at least one criterion.
[0108] The method includes, for example, in addition a step of determining the location 222 of the landing zone 12, 112 relative to the aircraft 18, 118, in the event of determination of the presence of reflectors, more particularly by the determination module 318.
[0109] In a first embodiment of the method, the signal emitted by at least one radar 310 has only the initial polarization.
[0110] When the signal reaches a reflector 14, 114, the reflector reflects the signal, so that the polarization of at least 50%, more particularly at least 80%, more particularly at least 90%, of the wave incident on said reflector is transformed into orthogonal polarization by reflection on said reflector 14, 114.
[0111] The rest of the airport also reflects the incident wave, but does not exhibit polarization rotation properties or polarization rotation properties strictly less important than reflectors 14, 114.
[0112] During reception 214, radar 310 receives waves reflected by the airport, including reflectors.
[0113] Here, in the first embodiment, the radar 310 is capable of receiving waves of the polarization orthogonal to the initial polarization.
[0114] The determination of the presence and, where applicable, the respective location of the reflectors, here in relation to the aircraft, is carried out by distinguishing the elements which have particularly reflected by crossing the polarization, that is to say by transforming the initial polarization into a polarization orthogonal to said initial polarization, which is here received by the radar 310.
[0115] The measure 218 includes the measurement of at least one parameter, here the reflected power, or in other words the amplitude of the received signal, of the orthogonal polarization component of the signal received by the radar 310.
[0116] Alternatively, the at least one parameter includes, more particularly, the Doppler velocity equal to the projection of the carrier velocity vector onto a radar-reflector axis.
[0117] The application 220 of at least one criterion includes, for example, comparing the measured parameter, here the power, with a predetermined threshold. Here, if the measured power is greater than or equal to the predetermined threshold, then a reflector is detected at the corresponding location. If the measured reflected power is strictly less than the predetermined threshold, then it is determined that no reflector is detected at the location.
[0118] The threshold is, for example, linked to the power contrast with the ambient medium, for example equal to the average power reflected by the ambient medium multiplied by a given number.
[0119] Alternatively, the threshold is, for example, a given portion of the power of the signal emitted by the radar 310.
[0120] In case of detection of the reflectors 14, 114, the step of determining the location 222 of the landing zone 12, 112, here relative to the aircraft, is carried out from the respective location determined of the reflectors 14, 114.
[0121] For example, one or more reflector location configurations relative to a landing area are previously recorded in the aircraft, more particularly in memory 312.
[0122] The location determination step 222 includes comparing the determined locations of the reflectors with the previously recorded configuration(s).
[0123] When the determined locations correspond to a previously recorded configuration, then the location of the landing zone determined during the determination of location 222 corresponds to the location of the landing zone in the corresponding configuration.
[0124] Alternatively, the location of the landing area 12, 112 is determined as the area delimited by the reflectors 14, 114 by removing a given margin, for example of a given distance.
[0125] Alternatively, in the case of a vertiport, the center of the landing area 112 is calculated as the intersection between the center line between the reflector lines and the median line, as described previously.
[0126] The location of the landing zone is, for example, determined as the circle having as its center the calculated center and having a given diameter.
[0127] Alternatively, in the case of a vertiport, the center of the landing area 112 is calculated as the isobarycenter of the respective locations of the reflectors 114.
[0128] If the presence of the reflectors is not determined during step 216, then the process is, for example, repeated from emission step 212.
[0129] This first embodiment allows a very good level of confidence in the detection of reflectors, and thus of the landing zone, for different types of landing zone.
[0130] This is particularly advantageous in dense environments, improving robustness to saturation, for example, while increasing contrasts and identification.
[0131] Such a solution is also economical in size, weight and power to be carried in the aircraft.
[0132] In a second embodiment of the method, the signal emitted by at least one radar 310 has only the initial polarization.
[0133] When the signal reaches a reflector 14, 114, the reflector reflects the signal, so that the polarization of at least 50%, more particularly at least 80%, more particularly at least 90%, of the wave incident on said reflector is transformed into a polarization orthogonal to the initial polarization by reflection on said reflector 14, 114.
[0134] The rest of the airport also reflects the incident wave, but does not exhibit polarization rotation properties or polarization rotation properties strictly less important than reflectors 14, 114.
[0135] During reception 214, radar 310 receives waves reflected by the airport, including reflectors 14, 114.
[0136] Here, in the second embodiment, the radar 310 is capable of receiving waves of the initial polarization and of the polarization orthogonal to the initial polarization.
[0137] The determination of the presence and, where applicable, the respective location of the reflectors, here in relation to the aircraft, is carried out by distinguishing the elements which have particularly reflected by crossing the polarization with respect to the reflection without change of polarization, which are here received by the radar 310.
[0138] Measure 218 includes the measurement of at least one parameter, here the reflected power, of the orthogonal polarization component of the signal received by the radar 310 and of the initial polarization component of the signal received by the radar 310.
[0139] The application 220 of at least one criterion includes, for example, a calculation of the ratio r of the parameter of the component of the reflected signal having the orthogonal polarization to the parameter of the component of the reflected signal having the initial polarization, and a comparison of the ratio with a threshold.
[0140] The ratio r is thus equal to , with Scross poi the parameter of the component of the reflected signal exhibiting orthogonal polarization and Sco.poi the parameter of the component of the reflected signal exhibiting the initial polarization.
[0141] Here, if the ratio is greater than or equal to the threshold, then a reflector is detected at the corresponding location. If the ratio is strictly less than the threshold, then no reflector is detected at the location.
[0142] The threshold is, for example, strictly greater than 1, for example strictly greater than 5, for example equal to 10.
[0143] The threshold is, for example, predetermined.
[0144] In the event of detection of the reflectors, the step of determining the location 222 of the landing zone 12, 112, here in relation to the aircraft, is, for example, carried out similarly as in the first embodiment of the method of the invention.
[0145] The method further includes, for example, the detection of at least one obstacle on the landing area.
[0146] More particularly, the method includes, for example, the detection of an object from the signal received by the radar 310, more particularly the object being detected in the determined landing area, the ratio for the object being less than the above threshold.
[0147] The object is then detected as an obstacle.
[0148] If the presence of reflectors is not determined during step 216, then the process is, for example, repeated from emission step 212.
[0149] This second embodiment allows for a very high level of confidence in the detection of reflectors, and thus of the landing zone, particularly for different types of landing zones. This is especially advantageous in dense environments, as mentioned previously. Furthermore, compared to the first embodiment, it allows for the detection of obstacles in the landing zone.
[0150] In a third embodiment of the method, the signal emitted by at least one radar 310 has the initial polarization, referred to as the first initial polarization hereafter, and a second initial polarization, corresponding to the polarization orthogonal to the first initial polarization.
[0151] The signal comprises, for example, a first portion exhibiting the first initial polarization and a second portion exhibiting the second initial polarization.
[0152] The first portion and the second portion are, for example, emitted successively in time.
[0153] Alternatively, they are emitted simultaneously. The first and second portions of the signal are then distinguishable, for example by their frequency or orthogonal phase codings.
[0154] When the signal reaches a reflector 14, 114, the reflector reflects the signal, so that the polarization of at least 50%, more particularly at least 80%, more particularly at least 90%, of the wave incident on said reflector is transformed by reflection on said reflector 14, 114, more particularly from the first initial polarization to the second orthogonal polarization and from the second initial polarization to the first initial polarization.
[0155] The rest of the airport also reflects the incident wave, but does not exhibit polarization rotation properties or polarization rotation properties strictly less important than reflectors 14, 114.
[0156] During reception 214, radar 310 receives waves reflected by the airport, including reflectors.
[0157] Here, in the third embodiment, the radar 310 is capable of receiving waves of the first initial polarization and of the polarization orthogonal to the first initial polarization, that is to say here the second initial polarization.
[0158] The determination of the presence and, where applicable, the respective location of the reflectors, here in relation to the aircraft, is carried out by distinguishing the elements which have particularly reflected by crossing the polarization with respect to the reflection without change of polarization, which are here received by the radar 310.
[0159] Measure 218 includes the measurement of at least one parameter, here the reflected power, of the orthogonal polarization component of the signal received by the radar 310 and of the initial polarization component of the signal received by the radar 310.
[0160] More specifically, the first signal portion and the second signal portion are distinguished from each other.
[0161] Measure 218 includes the measurement of at least one parameter, here reflected power, for each of the following components:
[0162] - the orthogonal polarization component, i.e. presenting the second polarization initial, of the signal received by radar 310 corresponding to the reflection of the first portion,
[0163] - the initial polarization component, i.e. exhibiting the first polarization initial, of the signal received by radar 310 corresponding to the reflection of the first portion,
[0164] - the orthogonal polarization component, i.e. presenting the second polarization initial, of the signal received by radar 310 corresponding to the reflection of the second portion, and
[0165] - the initial polarization component, i.e. exhibiting the first polarization initial, of the signal received by radar 310 corresponding to the reflection of the second portion.
[0166] The application 220 of at least one criterion includes, for example, a calculation of two ratios and a comparison of the ratios with a threshold.
[0167] The first ratio rl is equal to the ratio of the parameter of the component of the reflected signal exhibiting the orthogonal polarization corresponding to the reflection of the first portion to the parameter of the component of the reflected signal exhibiting the initial polarization corresponding to the reflection of the first portion.
[0168] The second ratio r2 is equal to the ratio of the parameter of the component of the reflected signal having the initial polarization corresponding to the reflection of the second portion to the parameter of the component of the reflected signal having the orthogonal polarization corresponding to the reflection of the second portion.
[0169] The ratio rl is thus equal to -^.^i, with Scross poi i the parameter of the ^co-poll component of the reflected signal exhibiting the orthogonal polarization corresponding to the reflection of the first portion, which therefore corresponds to the signal having a cross polarization with respect to the incident polarization of the first portion, and Sco poi i the parameter of the component of the reflected signal exhibiting the initial polarization corresponding to the reflection of the first portion, which therefore corresponds to the signal having a copolarization with respect to the incident polarization of the first portion.
[0170] The ratio r2 is equal to <^^2, with Scross poi 2 the parameter of the component of the ç reflected signal exhibiting the initial polarization corresponding to the reflection of the second portion, which therefore corresponds to the signal having a cross polarization with respect to the incident polarization of the second portion, and Sco poi 2 the parameter of the component of the reflected signal exhibiting the orthogonal polarization corresponding to the reflection of the second portion, which therefore corresponds to the signal having a copolarization with respect to the incident polarization of the second portion.
[0171] Here, if each of the ratios is greater than or equal to the threshold, then a reflector is detected at the corresponding location.
[0172] If both ratios are strictly below the threshold, then no reflector is detected at the location.
[0173] If one ratio is greater than or equal to the threshold, and the other ratio is strictly less than the threshold, then no reflector is detected at the location.
[0174] The threshold is, for example, greater than 1, for example strictly greater than 5, for example equal to 10.
[0175] The threshold is, for example, predetermined.
[0176] In the event of detection of the reflectors, the step of determining the location 222 of the landing zone 12, 112, here in relation to the aircraft, is, for example, carried out similarly as in the first embodiment of the method of the invention.
[0177] The method further includes, for example, the detection of at least one obstacle on the landing area.
[0178] More particularly, the method includes, for example, the detection of an object from the signal received by the radar 310, one of the reports for the object being below the above threshold.
[0179] The object is then detected as an obstacle.
[0180] This third embodiment provides a form of redundancy with respect to the second embodiment, and allows for an excellent level of confidence in distinguishing reflectors, and thus the landing zone, for different types of landing zone. This is particularly advantageous in dense environments.
[0181] The invention further relates to a method of automatic takeoff or landing of an aircraft from or on a landing area of an airport as described above.
[0182] In the case of a landing, the aircraft approaches the airport.
[0183] In the case of a takeoff, the aircraft is present in the airport, on the ground.
[0184] The automatic takeoff or landing method includes an airport detection step according to the method as described above.
[0185] The aircraft thus detects the location of the reflectors, and thus of the landing zone.
[0186] The method then includes, for example, a takeoff step from the landing area, the aircraft being automatically controlled from the determined location of the landing area.
[0187] Alternatively, the method then includes a landing step on the landing area, the aircraft being automatically controlled from the determined location of the landing area, in particular until the wheels of the aircraft touch the landing area.
[0188] Reflector detection makes it possible to know the location of the aircraft relative to the landing area, in particular the distances along the longitudinal, transverse and vertical directions, or the distance, the angle of slope, and the alignment along the transverse Y direction for an aircraft.
Claims
Demands
1. A method for detecting an airport (10; 110) comprising a landing area (12; 112), the airport (10; 110) being provided with a plurality of reflectors (14; 114), each reflector (14; 114) being configured to reflect an electromagnetic wave incident on said reflector (14; 114) and having an incident polarization, each reflector (14; 114) having a polarization rotation property such that the reflected wave predominantly has a polarization orthogonal to the incident polarization, the method comprising the following steps: - approach (210) of the airport (10; 110) by an aircraft (18; 118) or presence of the aircraft (18; 118) in the airport (10; 110), the aircraft (18;118) being equipped with at least one radar (310), - emission (212) by the at least one radar (310) of a signal having an initial polarization, - reception (214) by the at least one radar (310) of a reflected signal, the at least one radar (310) being capable of receiving waves of a polarization orthogonal to the initial polarization, and - determination of the presence (216) and, where applicable, the respective location of the reflectors (14; 114) from the polarization of the reflected signal.
2. A method according to claim 1, further comprising a step of determining the location (222) of the landing zone (12; 112) relative to the aircraft (18; 118) from the determined location of the reflectors (14; 114), in the event of determination of the presence of reflectors.
3. A method according to claim 1 or 2, wherein the determination of the presence (216) includes a measurement (218) of the power of the component of the reflected signal exhibiting orthogonal polarization.
4. A method according to any one of claims 1 to 3, wherein at least one radar (310) is capable of receiving waves of the initial polarization and waves of the polarization orthogonal to the initial polarization.
5. A method according to claim 4, wherein the determination of the presence (216) comprises a measurement of a parameter of the component of the reflected signal having the orthogonal polarization, a measurement of a parameter of the component of the reflected signal having the initial polarization, a calculation of the ratio of the parameter of the component of the reflected signal having the orthogonal polarization to the parameter of the component of the reflected signal having the initial polarization, and a comparison of the ratio with a threshold.
6. A method according to claim 4 or 5, wherein at least one radar (310) is further capable of emitting waves having a second initial polarization, the second initial polarization corresponding to the orthogonal polarization of the initial polarization, the method comprising a step of emitting by at least one radar (310) a signal having the second initial polarization.
7. A method according to claims 5 and 6, wherein the determination of the presence (216) comprises a measurement of the power of the component of the reflected signal having the initial polarization from the signal having the second initial polarization, a measurement of the power of the component of the reflected signal having the orthogonal polarization from the signal having the second initial polarization, a calculation of a second ratio of said power for the component having the initial polarization to said power of the component of the reflected signal having the second initial polarization, and a comparison of the ratio with the threshold, a reflector (14; 114) being detected only when the ratio and the second ratio are greater than the threshold.
8. A method according to any one of claims 1 to 7, wherein at least one radar (310) comprises a frequency-modulated continuous wave radar.
9. A method according to any one of claims 1 to 8, wherein each reflector (14; 114) has a radar cross-sectional area such that each reflector is distinguishable from the rest of the airport.
10. A method according to any one of claims 1 to 9, wherein the reflectors (14; 114) surround the landing area (12; 112).
11. A method for the automatic takeoff or landing of an aircraft (18; 118) from or on a landing area (12; 112) of an airport (10; 110), the airport (10; 110) being equipped with a plurality of reflectors (14; 114), each reflector (14; 114) being configured to reflect an electromagnetic wave incident on said reflector (14; 114) and having an incident polarization, each reflector (14; 114) having a polarization rotation property, such that the reflected wave predominantly has a polarization orthogonal to the incident polarization, the automatic takeoff or landing method comprising an airport detection step (10; 110) according to the method according to any one of claims 1 to 10.
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