Navigation method and device for an aircraft, and associated system, aircraft, computer program and data storage medium

Abstract

The present invention relates to a navigation method and device (APP) for an aircraft (AC), and to an associated system (SYS), aircraft (AC), computer program (PROG) and data storage medium (MEM). The proposed method is characterised in that a navigation module (LOC_VIS) determines navigation data (OUT_LOC_VIS) for the aircraft (AC) and in that it comprises: during a landing phase (S50, S70) of the aircraft (AC), a step of determining navigation data (OUT_LOC_VIS) on the basis of data from an inertial measurement unit (IMU) and images acquired by the aircraft (AC); and during a taxiing phase (S90), a step of determining navigation data (OUT_LOC_VIS) on the basis of data from the inertial measurement unit (IMU) and an odometer (ODOM).

Description

Description Title of the invention: NAVIGATION METHOD AND DEVICE FOR AN AIRCRAFT, SYSTEM, AIRCRAFT, COMPUTER PROGRAM AND ASSOCIATED INFORMATION MEDIUM Technical field

[0001] The present invention relates to the fields of navigation and positioning. More particularly, the present invention relates to a navigation method and device for an aircraft, an associated system, aircraft, computer program and information medium. The present invention finds a particularly advantageous, although in no way limiting, application for the implementation of navigation systems for aircraft. State of the prior art

[0002] There are currently, in the state of the art, various navigation systems for aircraft. In particular, it is known to use an inertial unit as a navigation system on board an aircraft. More generally, we hereinafter refer to "inertial navigation" as a navigation solution using data from an inertial measurement unit (i.e. specific force and angular velocity). However, using inertial data to implement a navigation solution requires solving the well-known problem of drift over time of inertial navigation. Indeed, small errors in the measurement of the specific force and angular velocity are integrated over time by inertial navigation and thus lead to increasingly large speed and position errors.

[0003] To limit the drift of inertial navigation, a state-of-the-art approach consists of combining inertial data with data from a satellite positioning module, such as a GPS (Global Positioning System) module. Generally speaking, a navigation solution combining data from several sensors is referred to as a "hybrid navigation" solution. However, existing hybrid inertial-GPS navigation solutions have the following drawbacks. On the one hand, a GPS module can be easily jammed and thus experience a loss of availability. On the other hand, a GPS module is, close to the ground, subject to interference due to multipath propagation, which leads to a loss of satellite positioning accuracy. Ultimately, hybrid inertial-GPS navigation solutions do not do not allow an aircraft to be reliably and precisely located during a landing phase.

[0004] In the state of the art, the navigation system used to assist aircraft during landing is the so-called instrument landing aid system, or more commonly referred to as the ILS system (acronym for the English expression "Instrument Landing System"). The ILS system is a radio navigation system making it possible to provide pilots with position and / or orientation information, relative to the axis of a landing runway and relative to the oblique descent plane towards the landing runway. However, the ILS system requires specific equipment both on the ground and on board aircraft, in particular antennas on the landing runway and specific on-board measuring instruments, which leads to significant complexity in terms of implementation, maintenance, etc.

[0005] There is therefore a need for a navigation solution that can precisely locate an aircraft during a landing phase and requires simple equipment. Statement of the invention

[0006] The present invention aims to remedy all or part of the drawbacks of the prior art, in particular those set out above.

[0007] To this end, according to one aspect of the invention, a navigation method for an aircraft is proposed, in which a first navigation module determines first navigation data of said aircraft, said method comprising: during a landing phase of said aircraft, a step of determining said first navigation data from data originating from an inertial measurement unit and images acquired by said aircraft; and during a taxiing phase following the landing of said aircraft, a step of determining said first navigation data from data originating from the inertial measurement unit and at least one odometer.

[0008] Said first navigation data determined during the taxiing phase are a function of said first navigation data determined during the landing phase.

[0009] By "navigation data" is meant here data relating to the position, and / or movement of the aircraft, such as geographic coordinates (e.g. latitude, longitude, altitude), speed, heading, etc.; and / or to protection radii associated with position / movement data. In the context of the invention, a "position" may designate an absolute position defined in relation to the Earth's reference frame, or a relative position defined in relation to a reference position (e.g. a landing strip).

[0010] In the context of the invention, the "landing phase" includes the approach by said aircraft to a landing runway and the landing of said aircraft on the runway. Also, the "taxi phase" (or "taxi" in English) here designates all movements of the aircraft on the ground. The transition from the landing phase to the taxi phase is detected by a switch called "weight on wheels", more commonly referred to as "Weight on Wheels" in English, this switch indicating whether the weight of the aircraft rests on its wheels.

[0011] By "inertial measurement unit" is meant here a measuring device providing, for a plurality of measurement instants, data relating to the specific force (i.e. the sum of external forces other than gravitational forces divided by the mass) and the angular velocity of the aircraft. In addition, the term "inertial unit" hereinafter means a navigation device integrating over time the specific force and angular velocity data produced by an inertial measurement unit and making it possible to determine navigation data of the aircraft.

[0012] As mentioned previously, the navigation data determined during the taxiing phase are a function of the navigation data determined during the landing phase. Indeed, this property results from the use of data from the inertial measurement unit to obtain the navigation data of the aircraft, which necessarily implies an integration of the inertial data over time. More precisely, the navigation system can continuously integrate the data from the inertial measurement unit over time such that the navigation data determined at one instant are used to determine the navigation data at subsequent instants.It could also be envisaged, within the framework of the invention, that the navigation system integrates the inertial data per flight phase and, to initialize the inertial navigation at the start of a phase, uses navigation data determined during the previous phase.

[0013] The proposed method makes it possible to precisely determine the navigation data of an aircraft during the landing and taxiing phases using simple (i.e. non-specific) equipment. Indeed, the synergy between the different sensors used for navigation (i.e. inertial measurement unit and camera, then inertial measurement unit and wheel odometer) makes it possible to maintain a precise localization chain during the landing and taxiing phases.

[0014] In particular, the use of images makes it possible to overcome inertial navigation drift and improve navigation accuracy during the landing phase. Similarly, the use of data from a wheel odometer makes it possible to overcome inertial navigation drift and improve navigation precision during the rolling phase.

[0015] Furthermore, the synergy between the steps and means implemented by the proposed method should be explained. An odometer measures a distance traveled and, for this reason, locating the aircraft accurately during the taxiing phase from odometry data requires precise positioning at the instant of landing. Also, localization during the taxiing phase from an odometer is all the more accurate as images are used to improve localization during the landing phase. In other words, a navigation solution independently combining: on the one hand, inertial data with images; and, on the other hand, inertial data with odometry data, would be less accurate than the proposed solution.

[0016] Compared to existing solutions, and in particular an ILS navigation system, the proposed method allows an aircraft to be located during the landing phase without requiring complex specific equipment and allows the aircraft to be located more precisely during the taxiing phase.

[0017] According to one embodiment, a second navigation module determines second navigation data. According to this embodiment, the proposed method comprises, during a flight phase of said aircraft preceding the landing phase, a step of determining said second navigation data from data from the inertial measurement unit and a satellite positioning module.

[0018] This embodiment makes it possible, thanks to the use of a satellite positioning module, to precisely locate the aircraft during the flight phase. In particular, the data from the satellite positioning module are precise and reliable in altitude during said flight phase and make it possible to compensate for the drift of inertial navigation.

[0019] According to one embodiment, the proposed method comprises, during a descent phase of said aircraft preceding the landing phase and following the flight phase, a step of determining said first navigation data from data from the inertial measurement unit and an altimeter.

[0020] When approaching the ground, the satellite positioning module is subject to interference due to multipath propagation. Thus, by exploiting the inertial measurement unit and an altimeter (and not the satellite positioning module), this embodiment makes it possible to maintain an accurate location of the aircraft during descent.

[0021] According to one embodiment, a control module provides said navigation data to a guidance module of said aircraft. In particular, during said flight phase, the control module provides the guidance module with said second navigation data determined by the second navigation module; and, during phases subsequent to said flight phase of said aircraft (i.e. during the descent, landing, and taxiing phases), the control module provides the guidance module with said first navigation data determined by the first navigation module.

[0022] This embodiment makes it possible to precisely guide the aircraft during the different phases of an aircraft flight, and in particular during landing and taxiing.

[0023] It should be noted that this embodiment benefits from the technical advantages of the previously described embodiments. Indeed, precise guidance of the aircraft is enabled because the aircraft's navigation data are determined precisely during the different phases. In particular, for one of said phases (i.e. flight, descent, landing, taxiing phases), the control module makes it possible to provide the guidance module with the navigation data produced by the most precise navigation module (i.e. said first or said second) during this phase.

[0024] According to one embodiment, the proposed method further comprises: during a first part of the landing phase, a step of determining said first navigation data from an observed position and a known position of a single terrestrial reference point detected in said acquired images; and during a second part of the landing phase, a step of determining said first navigation data from observed positions and known positions of several terrestrial reference points detected in said acquired images.

[0025] In the context of the invention, a “land reference point” is a land point whose position (e.g. geographic coordinates) is known. Hereinafter, a land reference point is also referred to as a “landmark”.

[0026] By using a first landmark as soon as it is detected, this embodiment makes it possible to quickly compensate for the drift of the inertial navigation. Then, by using several landmarks as soon as they are detected, this embodiment makes it possible to compensate for the drift of the inertial navigation with greater precision. Thus, this embodiment makes it possible to improve the precision of the navigation data determined during the landing phase.

[0027] In combination with the previous embodiments, the proposed navigation solution makes it possible to combine different forms of navigation hybridization during the different phases of an aircraft flight (i.e. inertia-GPS, inertia-altimeter, inertia-imaging with a landmark, inertia-imaging with several landmarks, then inertia-odometry). The proposed sequencing of these different forms of navigation hybridization makes it possible, in a synergistic manner, to accurately determine the navigation data. In comparison, a solution of navigation implementing these different forms of hybridization independently, for example in separate modules, would be less precise.

[0028] More generally, the proposed solution makes it possible to capitalize on the respective advantages of the different sensors to obtain precise navigation information. For each of the different phases, the proposed solution relies on the data emitted by precise and reliable sensors during this phase.

[0029] According to one embodiment, the proposed method comprises: a step of detecting at least one reference terrestrial point in said acquired images; a step of determining an observed relative position of said at least one reference terrestrial point detected with respect to said aircraft from said acquired images; and a step of determining an estimated relative position of said at least one reference terrestrial point detected with respect to said aircraft from a position of said aircraft determined by the first navigation module and a known position of said at least one terrestrial point.

[0030] According to this embodiment, said first navigation data are determined by the first navigation module from the difference between the observed and estimated relative positions of said at least one terrestrial reference point in relation to said aircraft.

[0031] This embodiment makes it possible to compensate for the drift of inertial navigation from images acquired by the aircraft.

[0032] It should also be mentioned that, within the scope of the invention, other embodiments could be envisaged in which navigation data are determined from acquired images, for example using visual odometry techniques, cartographic registration techniques, machine learning algorithms, etc.

[0033] According to one embodiment, at least one said navigation module comprises an inertial unit and a Kalman filter for determining said navigation data. More particularly, the first navigation module comprises a first inertial unit and a first Kalman filter for determining said first navigation data; and the second navigation module comprises a second inertial unit and a second Kalman filter for determining said second navigation data.

[0034] This embodiment allows for multi-sensor data fusion to determine aircraft navigation data.

[0035] In particular, the use of an inertial unit makes it possible to determine navigation data from inertial data; and the use of a Kalman filter makes it possible to correct this navigation data from data from other sensors (i.e. recalibration of the inertial navigation to compensate for drift). Thus, the combination of an inertial unit and a Kalman filter makes it possible to accurately determine the aircraft's navigation data from independent sensors of different types.

[0036] According to another aspect of the invention, there is provided a navigation device for an aircraft comprising a first navigation module configured to determine first navigation data of said aircraft from data from an inertial measurement unit, at least one odometer and images acquired by said aircraft.

[0037] The proposed navigation device has the advantages described above in connection with the proposed navigation method. According to one embodiment, the navigation device implements all or part of the steps of the proposed navigation method.

[0038] According to one embodiment, the navigation device comprises a second navigation module configured to determine second navigation data from data from the inertial measurement unit and a satellite positioning module.

[0039] According to one aspect of the invention, there is provided a navigation system for an aircraft comprising: a navigation device according to the invention; an inertial measurement unit; an image acquisition device; and at least one odometer.

[0040] The proposed navigation system has the advantages described above in connection with the proposed navigation method. According to one embodiment, the proposed navigation system implements all or part of the steps of the proposed navigation method.

[0041] According to one embodiment, the navigation system comprises a satellite positioning module; and / or an altimeter.

[0042] According to one embodiment, the navigation system comprises a computer vision device configured to determine at least one position of the vehicle from the images acquired by said image acquisition device.

[0043] According to one embodiment, the navigation system comprises a guidance module configured to guide said aircraft based on navigation data determined by said navigation device according to the invention.

[0044] According to one aspect of the invention, there is provided an aircraft comprising a navigation system according to the invention.

[0045] According to one aspect of the invention, there is provided a computer program comprising instructions for implementing the steps of a method according to the invention, when the computer program is executed by at least one processor or computer.

[0046] The computer program may consist of one or more subparts stored in the same memory or in separate memories. The program may use any programming language, and may be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0047] According to one aspect of the invention, there is provided a computer-readable information medium comprising a computer program according to the invention.

[0048] The information carrier may be any entity or device capable of storing the program. For example, the carrier may comprise a storage medium, such as a non-volatile memory or ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a hard disk. Furthermore, the storage medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by a telecommunications network or by a computer network or by other means. The program according to the invention may in particular be downloaded onto a computer network. Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question. Brief description of the drawings

[0049] Other features and advantages of the present invention will become apparent from the description provided below of embodiments of the invention. These embodiments are given by way of illustrative example and are not intended to be limiting. The description provided below is illustrated by the attached drawings: [Fig. 1] Figure 1 schematically represents an example of software and hardware architecture of a navigation system according to an embodiment of the invention; [Fig. 2A]-[Fig.2B] Figures 2A and 2B represent, schematically and in the form of a flowchart, steps of a navigation method according to an embodiment of the invention; and [Fig. 3] Figure 3 schematically represents an example of software and hardware architecture of a navigation system according to one embodiment of the invention. Description of the embodiments

[0050] The present invention relates to a navigation method and device for an aircraft, as well as to an associated system, aircraft, computer program and storage medium.

[0051] Figure 1 schematically represents an example of software and hardware architecture of a navigation system according to one embodiment of the invention.

[0052] In the context of the invention, an “aircraft” designates any device capable of rising and moving in the air, such as an airplane, a helicopter, a drone, etc. According to one embodiment, the proposed SYS navigation system is on board an aircraft AC (visible in FIG. 2A).

[0053] As illustrated by FIG. 1, according to one embodiment, the navigation system SYS proposed for an aircraft AC comprises at least the following elements: a set of sensors SENS; a navigation device APP; and a guidance module CMD.

[0054] The APP navigation device is configured to determine, from the data from the SENS sensor set, IN_NAV_CMD navigation data of the AC aircraft.

[0055] The CMD guidance module is configured to guide the AC aircraft based on the IN_NAV_CMD navigation data provided by the APP device.

[0056] In the context of the invention, navigation data of an aircraft designates data relating to the position, and / or the movement of the aircraft and includes, for example, geographical coordinates (e.g. latitude, longitude, altitude), a speed, a heading. The navigation data can be defined absolutely with respect to the terrestrial reference frame, or relatively with respect to a reference position (e.g. a landing runway). For example, a relative position of the aircraft AC at a given instant determined by the navigation device APP can include one or more coordinates from the following set: an azimuth, a vertical distance, a longitudinal distance, and a lateral distance defined with respect to a reference position.

[0057] As illustrated by Figure 1, according to one embodiment, the set of sensors SENS comprises at least one of the following sensors: at least one inertial measurement unit IMU; at least one GPS satellite positioning module; at least one BARO altimeter; a VISION sensor (hereinafter referred to as a computer vision device or sensor); at least one ODOM odometer; a Pitot probe; and a magnetometer.

[0058] The inertial measurement unit IMU provides OUT_IMU data, also called inertial data. According to one embodiment, the inertial data OUT_IMU comprise, for a plurality of measurement instants, data relating to the specific force Fs (i.e. the sum of external forces other than gravitational forces divided by the mass) and the angular velocity of the aircraft AC. Typically, the inertial measurement unit IMU comprises: three gyrometers measuring the three components of the angular velocity (which make it possible to calculate the rates of variation of the roll, pitch and yaw angles); and three accelerometers measuring the three components of the specific force Fs.

[0059] The GPS satellite positioning module provides OUT_GPS navigation data. According to one embodiment, the OUT_GPS navigation data comprise, for a plurality of measurement times, a position Pos and a speed Vel of the aircraft AC. Typically, the GPS satellite positioning module provides an absolute position Pos relative to the terrestrial reference frame comprising one or more coordinates from the following set: latitude, longitude; and altitude. According to one embodiment, the satellite positioning module complies with the “Global Positioning System”, more commonly referred to by the acronym GPS. However, within the scope of the invention, other embodiments could also be envisaged in which all types of GNSS modules (acronym for “Geolocation and Navigation by a Satellite System”) would be used, such as Galileo, Glonass modules, etc.

[0060] The BARO altimeter provides OUT_BARO data as output, called altimetric data. The BARO altimeter is, according to one embodiment, a barometric altimeter. In particular, the OUT_BARO altimetric data are, for a plurality of measurement times, representative of the altitude Alt of the aircraft AC or of variations in altitude of said aircraft AC.

[0061] The computer vision sensor VISION (also referred to as a “computer vision device”) provides OUT_VIS data as output. According to one embodiment, the sensor VISION comprises or is configured to communicate with: a recording medium DB; and an image acquisition device CAM. The recording medium DB, for example a database, comprises the positions (i.e. geographic coordinates) of a plurality of terrestrial reference points AMER_1-AMER_3 (hereinafter referred to as landmarks) as well as information relating to the graphical representations of the terrestrial reference points AMER_1-AMER_3. For example, the terrestrial reference points may be a runway, a navigation light, an approach slope indicator (“Precision Approach Path Indicator”), etc.The CAM image acquisition device comprises at least one camera on board the aircraft AC and having an electromagnetic radiation sensor whose wavelengths belong to the visible light and / or infrared spectrum. According to one embodiment, the CAM image acquisition device. comprises at least one camera from among the following: a visible light camera; a near-infrared camera, a short-wavelength infrared camera, a medium-wavelength infrared camera, and a long-wavelength infrared camera. The CAM image acquisition device is configured to acquire a plurality of images for a plurality of measurement times.

[0062] The computer vision sensor VISION takes as input: the images acquired by the image acquisition device CAM; and the navigation data OUT_LOC_VIS from the navigation module LOC_VISION, in particular the position of the aircraft AC. The sensor VISION is, according to one embodiment, configured to: detect the terrestrial reference points AMER_1-AMER_3 in the acquired images; and determine the observed relative positions of the detected terrestrial reference points AMER_1-AMER_3 relative to the aircraft AC from said acquired images. The sensor VISION is further configured to, according to one embodiment, determine estimated relative positions of the detected terrestrial reference points AMER_1-AMER_3 relative to the aircraft AC from a position of the aircraft AC determined by the navigation module LOC_VISION and known positions of the terrestrial reference points AMER_1-AMER_3.According to one embodiment, the OUT_VIS data provided by the VISION sensor comprises, for a plurality of measurement instants, differences ox,oy between the observed and estimated relative positions of the terrestrial reference points AMER_1-AMER_3 with respect to the aircraft AC. Typically, the relative position (observed or estimated) of a landmark with respect to the aircraft is defined by two angles - a lateral angle and a vertical angle - characterizing the line of sight of the landmark with respect to the longitudinal axis of the aircraft.

[0063] According to one embodiment, to detect a reference terrestrial point in an image, the VISION sensor is configured to select in this image a region of interest (i.e. a portion of this image) and detect the reference terrestrial point in this region of interest. In particular, the coordinates of the region of interest are determined from: the known position of the reference terrestrial point; the position of the aircraft AC determined by the LOC_VISION navigation module; and information provided by the LOC_VISION navigation module relating to the protection radius of the determined position of the aircraft AC (i.e. the probability that the position error is less than the protection radius is greater than a defined value, in particular close to 1). Using a region of interest makes it possible to restrict the portion of the image to be processed to detect a landmark and thus makes it possible to reduce hardware and software resources (e.g.processing time, memory, etc.) required to detect a landmark in acquired images as well as the probability of false detection.

[0064] The ODOM odometer produces as output OUTJDDOM data called odometry data. According to one embodiment, the odometry data OUTJDDOM are, for a plurality of measurement instants, representative of a distance Dist traveled by the aircraft AC or one of the wheels of the aircraft AC between at least two measurement instants during a taxiing phase. The ODOM odometer determines, according to a variant of the invention, a distance traveled by the aircraft AC between two measurement instants from a number of revolutions made by a wheel of the aircraft AC between these two instants and a radius of this wheel.

[0065] According to one embodiment, the set of sensors SENS comprises a plurality of odometers ODOM. This embodiment also makes it possible to obtain information regarding the direction of the aircraft AC during a taxiing phase.

[0066] Obviously, the SYS sensor set may include one or more of each of the IMU, GPS, BARO, VISION, ODOM sensors as described above.

[0067] As illustrated in Figure 1, the navigation device APP comprises, according to one embodiment: a navigation module LOC_GPS (called second navigation module); a navigation module LOC_VISION (called first navigation module); and a control module SWITCH. The navigation modules LOCJ3PS and LOC_VISION respectively provide navigation data OUT_LOC_GPS (called second navigation data) and navigation data OUT_LOC_VIS (called first navigation data). It should be noted that the navigation modules LOCJ3PS and LOC_VISION produce the navigation data OUT_LOC_GPS and OUT_LOC_VIS independently and, more particularly, simultaneously (i.e. in parallel). According to one embodiment, the navigation data OUT_LOC_GPS and OUT_LOC_VIS respectively comprise, for a plurality of measurement instants, a position Pos, a speed Vel and a direction Cap of the aircraft AC.

[0068] It should be noted that the parallel use of the two separate navigation modules LOCJ3PS and LOC_VISION improves the integrity of the SYS navigation system of the AC aircraft and thus the resilience of the SYS system with respect to failures of the sensors used for navigation.

[0069] The LOCJ3PS navigation module determines the OUT_LOC_GPS navigation data from data from the IMU inertial measurement unit, the GPS satellite positioning module, and the BARO altimeter.

[0070] As illustrated in Figure 1, according to one embodiment, the LOCJ3PS navigation module comprises: an inertial unit NAV_IMU_GPS; and a Kalman filter KAL_FLT_GPS. The inertial unit NAV_IMU_GPS is configured to integrate over time the specific force Fs and angular velocity data produced by the measurement unit IMU inertial system and thus determine navigation data Pos, Vel, attitudes including the heading of the aircraft AC. The Kalman filter KAL_FILT_GPS determines, from the data from the GPS and BARO sensors, corrections 5Pos, 5Vel, 5Cap, 5Fs, and 5 to be applied to the inertial unit NAV_IMU_GPS. The navigation data OUT_LOC_GPS provided at output thus correspond, according to one embodiment, to the navigation data determined by the inertial unit NAV_IMU_GPS corrected (i.e. recalibrated) from the data from the Kalman filter KAL_FLT GPS. In other words, the Kalman filter KAL_FLT GPS makes it possible to compensate for the inertial navigation drift (i.e. recalibrate) from the data from the GPS and BARO sensors.

[0071] It should be noted that when the GPS satellite positioning module is not available (e.g. faulty, unusable), the LOCJSPS navigation module continues to output the OUT_LOC_GPS navigation data. However, in this case, the LOCJSPS navigation module cannot use the data from the GPS satellite positioning module to compensate for the drift (i.e. recalibration) of the NAV_IMU_GPS inertial unit. The same applies when the BARO altimeter is not available.

[0072] The LOC_VISION navigation module determines the OUT_LOC_VIS navigation data from the data from the IMU inertial measurement unit, the GPS satellite positioning module, the BARO altimeter, the VISION sensor and the ODOM odometer.

[0073] As illustrated in Figure 1, the LOC_VISION navigation module has, according to one embodiment, an architecture similar to the LOC_GPS navigation module. According to this embodiment, the LOC_VISION navigation module comprises: an inertial unit NAV_IMU_VIS; and a Kalman filter KAL_FLT_VIS. The OUT_LOC_GPS navigation data provided as output thus correspond, according to one embodiment, to the navigation data determined by the inertial unit NAV_IMU_VIS to which the corrections determined by the KAL_FILT_VIS filter are applied from the data from the GPS, BARO, VISION, and ODOM sensors. In other words, the KAL_FLT GPS Kalman filter makes it possible to compensate for the inertial navigation drift (i.e., recalibration) from the data from the GPS, BARO, VISION, and ODOM sensors.

[0074] Within the scope of the invention, other embodiments could also be envisaged in which one or both of the navigation modules respectively use a Kalman filter taking as input the data from the various sensors including the inertial measurement unit and producing the navigation data as output.

[0075] It should be mentioned that the LOC_VISION navigation module uses data from other GPS, BARO, VISION, and ODOM sensors when these data are available to recalibrate the NAV_IMU_VIS inertial unit. For example, when the aircraft AC is in flight, the ODOM odometer is not available and cannot be used by the LOC_VISION navigation module to recalibrate the NAV_IMU_VIS inertial unit. Similarly, the VISION sensor can only be used following the detection of a landmark. In another example, the LOC_VISION navigation module does not use data from the GPS satellite positioning module when the GPS module is faulty or unusable.

[0076] However, it is important to emphasize that the navigation data determined at a given instant are a function of the navigation data determined at previous instants. Indeed, the NAV_IMU_GPS and NAV_IMU_VIS inertial measurement units integrate over time the specific force Fs and angular velocity data produced by the IMU inertial measurement unit to determine OUT_LOC_GPS and OUT_LOC_VIS navigation data. Also, small measurement errors of the specific force Fs and angular velocity are integrated over time by the inertial measurement units and thus lead to speed and position errors that increase over time (i.e. drift of the inertial navigation). Therefore, using a sensor at a given instant to recalibrate an inertial measurement unit improves the accuracy of the navigation data determined at later instants.

[0077] For example, suppose that during a first flight phase of the aircraft AC, the LOC_VISION navigation module uses the data from the GPS module to first recalibrate the position and compensate for the drift of the NAV_IMU_VIS inertial unit. Then, during a second subsequent flight phase, the GPS satellite positioning module is no longer available. During the second phase, although the GPS module is no longer available, the LOC_VISION navigation module determines more accurate OUT_LOC_VIS navigation data than a navigation module that never uses data from a GPS module. Indeed, the LOC_VISION navigation module benefits during the second phase from the recalibration of the inertial unit during the first phase.

[0078] The SWITCH control module receives the navigation data OUT_LOC_GPS and OUT_LOC_VIS respectively produced by the navigation modules LOC_GPS and LOC_VISION and provides the CMD guidance module with IN_NAV_CMD navigation data. According to one embodiment, the SWITCH control module provides the CMD guidance module with either the OUT_LOC_GPS navigation data or the OUT_LOC_VIS navigation data. In particular, the SWITCH control module is configured to select the navigation data to be provided according to the different phases of a flight of the aircraft, this embodiment being detailed below with reference to FIGS. 2A and 2B.More particularly, the SWITCH control module is configured to select the navigation data to be provided depending on the availability of the GPS satellite positioning module: if, and only if, the GPS satellite positioning module is available, the OUT_LOC_GPS navigation data are provided to the guidance module. CMD; otherwise (GPS module being unavailable, faulty or not usable), the OUT_LOC_VIS navigation data is provided to the CMD guidance module.

[0079] However, within the scope of the invention, other embodiments could be envisaged in which either the LOC_GPS navigation module or the LOC_VISION navigation module is activated depending on the different flight phases of the aircraft AC and provides navigation data to the CMD guidance module. For example, when the GPS module is usable, the LOC_GPS navigation module is activated and provides the CMD guidance module with the OUT_LOC_GPS navigation data; and, otherwise, when the GPS module is not usable, the LOC_VISION navigation module is activated and provides the CMD guidance module with the OUT_LOC_VIS navigation data.

[0080] Figures 2A and 2B represent, schematically and in the form of a flowchart, steps of a navigation method according to one embodiment of the invention.

[0081] As illustrated by Figures 2A and 2B, and according to one embodiment of the invention, the proposed navigation method comprises at least one of the following steps S10 to S90 implemented by the proposed navigation system SYS. According to a particular embodiment, steps S10 to S90 are implemented in a chronological order as described below.

[0082] During a flight phase of the aircraft AC, the navigation system SYS implements step S10.

[0083] During step S10, the navigation modules LOC_GPS and LOC_VISION respectively determine navigation data OUT_LOC_GPS and OUT_LOC_VIS from data from the inertial measurement unit IMU and the GPS satellite positioning module; the control module SWITCH provides the guidance module CMD with the navigation data OUT_LOC_GPS determined by the navigation module LOC_GPS. Thus, during this flight phase, the inertial navigation is recalibrated with the data from the GPS satellite positioning module.

[0084] During step S20, the navigation device APP deactivates the use of the OUT_GPS data from the GPS satellite positioning module. Thus, following step S20, and for all the phases and steps described below, the navigation modules LOC_GPS and LOC_VISION no longer use the data from the GPS module; also, the control module SWITCH provides the guidance module CMD exclusively with the OUT_LOC_VIS navigation data determined by the navigation module LOC_VISION. According to a particular embodiment, the navigation device APP deactivates the use of the OUT_GPS data from the GPS satellite positioning module following reception, in from a command module, an instruction to no longer use the GPS satellite positioning module.

[0085] During a so-called descent phase of the aircraft AC, following step S20, the navigation system SYS implements step S30.

[0086] During step S30, the navigation module LOC_VISION determines navigation data OUT_LOC_VIS from the data from the inertial measurement unit IMU. According to one embodiment, the navigation module LOC_VISION further determines navigation data OUT_LOC_VIS from the data from the BARO altimeter.

[0087] During step S40, the computer vision sensor VISION detects a reference terrestrial point AMER_1 (e.g. the landing strip) in images acquired by the acquisition device CAM.

[0088] During a first part of a so-called landing phase of the aircraft AC, and following the detection of a terrestrial reference point in step S40, the navigation system SYS implements step S50. For the purposes of the invention, the landing phase comprises both the approach by the aircraft AC to a landing runway and the landing of the aircraft AC on the runway.

[0089] During step S50, the navigation module LOC_VISION determines navigation data OUT_LOC_VIS from the data from the inertial measurement unit IMU and the VISION sensor. In particular, the navigation module LOC_VISION determines during step S50 navigation data OUT_LOC_VIS using an observed position and a known position of the single terrestrial reference point AMER_1 detected in the acquired images. Thus, during this part of the landing phase, the inertial navigation drift is compensated from a single terrestrial reference point.

[0090] During step S60, the computer vision sensor VISION detects a plurality of reference terrestrial points AMER_2, AMER_3 (eg navigation lights surrounding the landing strip, markings on the landing strip) in images acquired by the acquisition device CAM.

[0091] During a second part of the landing phase of the aircraft AC, and following the detection of several terrestrial reference points in step S60, the navigation system SYS implements step S70.

[0092] During step S70, the navigation module LOC_VISION determines navigation data OUT_LOC_VIS from the data from the inertial measurement unit IMU and the VISION sensor. More precisely, the navigation data OUT_LOC_VIS are determined by the navigation module LOC_VISION from the observed positions and the known positions of the terrestrial reference points AMER_2 detected in the acquired images. Thus, during this second part of the landing phase, the inertial navigation is recalibrated using a plurality of terrestrial reference points.

[0093] According to a particular embodiment, the navigation module LOC_VISION determines during steps S50 and S70 navigation data OUT_LOC_VIS from the differences ox, oy between observed and estimated relative positions of the terrestrial reference points AMER_1-AMER_3 with respect to said aircraft AC. This embodiment is described above with reference to FIG. 1 and the computer vision sensor VISION.

[0094] During step S80, the navigation device APP detects the landing of the aircraft AC via a so-called weight on wheels switch.

[0095] During a so-called taxiing phase, and following the detection of the landing of the aircraft AC in step S80, the navigation system SYS implements step S90.

[0096] During step S90, the navigation module LOC_VISION determines navigation data OUT_LOC_VIS from data from the inertial measurement unit IMU and the odometer ODOM. Thus, during this taxiing phase, the inertial navigation drift is compensated from the odometry data. It should be noted that the navigation data determined during the taxiing phase are a function of the navigation data determined during the previous phases.

[0097] The proposed navigation solution makes it possible to precisely determine navigation data and thus to precisely guide the aircraft during the different phases of a flight, using simple equipment.

[0098] The synergy between the different sensors used for navigation makes it possible to maintain a precise localization chain during the different phases (i.e. IMU-GPS, IMU, IMU-VISION with a landmark, IMU-VISION with several landmarks, and IMU-ODOM). In particular, localization during the taxiing phase from an odometer is all the more precise as images are used to recalibrate the inertial unit during the landing phase. In other words, the use of landmarks during the landing phase makes it possible to precisely initialize the hybrid inertial-odometry navigation for the taxiing phase.

[0099] The proposed navigation solution and phase sequencing make it possible to capitalize on the respective advantages of the different sensors to obtain precise navigation information. For each of the different phases, the proposed navigation solution relies on the data emitted by precise and reliable sensors during this phase.

[0100] Figure 3 schematically represents an example of software and hardware architecture of a navigation system according to one embodiment of the invention.

[0101] As illustrated by Figure 3, according to one embodiment, the proposed APP navigation device comprises: at least one processing unit or processor PROC; and at least one memory MEM.

[0102] The APP device has, according to one embodiment, the hardware architecture of a computer and comprises, as such, a processor PROC, a random access memory, a read-only memory MEM, and a non-volatile memory. The memory MEM associated with the APP device constitutes an information or recording medium in accordance with the invention, readable by a computer and by the processor PROC, on which is recorded a computer program PROG in accordance with the invention. The computer program PROG comprises instructions for carrying out steps of a method in accordance with the invention and implemented by the APP device, when the computer program PROG is executed by the processor PROC.

[0103] As illustrated in Figure 3, according to one embodiment, the APP device has a COM communication module configured to communicate with at least one of the following elements: one or more sensors of the SENS sensor set; and the CMD guidance module. Obviously, no limitation is attached to the nature of the communication interfaces between the proposed APP device and respectively: the sensors of the SENS set; and the CMD guidance module, which may be wired or wireless, and may implement any protocol known to those skilled in the art (Ethernet, Wi-Fi, Bluetooth, 3G, 4G, 5G, 6G, etc.).

[0104] According to one embodiment (not shown), the VISION sensor (also called a computer vision device) has the hardware architecture of a computer and comprises, as such, a processor, a random access memory, a read-only memory, and a non-volatile memory. In the embodiment described here, the memory associated with the VISION sensor constitutes an information medium, readable by a computer and on which a computer program is recorded. This computer program comprises instructions for carrying out steps of a method according to the invention and implemented by the VISION sensor, when this computer program is executed by a processor.

[0105] As illustrated in Figure 3, according to one embodiment, the SENS sensor assembly comprises: a weight on wheels switch configured to indicate whether the weight of the aircraft AC is resting on its wheels and, more particularly, to detect whether the aircraft AC has moved from a landing phase to a taxiing phase.

[0106] The term module can correspond to a software component as well as to a hardware component or a set of hardware and software components, a software component itself corresponding to one or more computer programs or sub-programs or more generally to any element of a program capable of implementing a function or a set of functions as described for the modules concerned. In the same way, a hardware component corresponds to any element of a hardware assembly capable of implementing a function or a set of functions for the module concerned (integrated circuit, smart card, memory card, etc.).

[0107] It should be noted that the order in which the steps of a method according to the invention are carried out, in particular with reference to the attached drawings, constitutes only an example of an embodiment without any limiting character, variants being possible. Furthermore, the reference signs are not limiting of the scope of the protection, their sole function being to facilitate the understanding of the claims.

[0108] A person skilled in the art will understand that the embodiments and variants described above constitute only non-limiting examples of implementation of the invention. In particular, a person skilled in the art may envisage any adaptation or combination of the embodiments and variants described above in order to meet a very specific need.

Claims

Claims Navigation method for an aircraft (AC), in which a first navigation module (LOC_VISION) determines first navigation data (OUT_LOC_VIS) of said aircraft (AC), said method comprising: during a landing phase of said aircraft (AC), a step of determining (S50, S70) said first navigation data (OUT_LOC_VIS) from data (OUT_IMU, OUT_VIS) from an inertial measurement unit (IMU) and images acquired by said aircraft (AC); and during a taxiing phase following the landing of said aircraft (AC), a step of determining said first navigation data (OUT_LOC_VIS) from data (OUT_IMU, OUTJDDOM) from the inertial measurement unit (IMU) and at least one odometer (ODOM), said first navigation data (OUT_LOC_VIS) determined during the taxiing phase (S90) being a function of said first navigation data (OUT_LOC_VIS) determined during the landing phase (S50, S70).Method according to claim 1, in which a second navigation module (LOC_GPS) determines second navigation data (OUT_LOC_GPS), said method comprising: during a flight phase of said aircraft (AC) preceding said landing phase, a step of determining (S10) said second navigation data (OUT_LOC_GPS) from data originating (OUT_IMU, OUT_GPS) from the inertial measurement unit (IMU) and from a satellite positioning module (GPS). Method according to claim 2, comprising: during a descent phase of said aircraft (AC) following said flight phase and preceding said landing phase, a step of determining (S30) said first navigation data (OUT_LOC_VIS) from data originating (OUT_IMU, OUT_BARO) from the inertial measurement unit (IMU) and from an altimeter (BARO).Method according to claim 2 or 3, in which a control module (SWITCH) provides to a guidance module (CMD) of said aircraft (AC): during said flight phase of said aircraft (AC), said second navigation data (OUT_LOC_GPS) determined by the second navigation module (LOC_GPS); and. during said phases subsequent to said flight phase, said first navigation data (OUT_LOC_VIS) determined by the first navigation module (LOC_VISION).

5. Method according to one of claims 1 to 4, comprising: during a first part of said landing phase, a step of determining (S50) said first navigation data (OUT_LOC_VIS) from an observed position and a known position of a single terrestrial reference point (AMER_1) detected in said acquired images; and during a second part of said landing phase, a step of determining (S70) said first navigation data (OUT_LOC_VIS) from observed positions and known positions of several terrestrial reference points (AMER_2, AMER_3) detected in said acquired images.

6. Method according to one of claims 1 to 5, comprising: a step of detecting at least one reference terrestrial point (AMER_1-AMER_3) in said acquired images; a step of determining an observed relative position of said at least one detected reference terrestrial point (AMER_1-AMER_3) with respect to said aircraft (AC) from said acquired images;and a step of determining an estimated relative position of said at least one detected terrestrial reference point (AMER_1-AMER_3) with respect to said aircraft (AC) from a position of said aircraft determined by the first navigation module (LOC_VISION) and from a known position of said at least one terrestrial point (AMER_1-AMER_3), said first navigation data (OUT_LOC_VIS) being determined by the first navigation module (LOV_VISION) from the difference (ox, oy) between said observed and estimated relative positions of said at least one terrestrial reference point (AMER_1-AMER_3) with respect to said aircraft (AC).; 7. Method according to one of claims 1 to 6, in which at least one said navigation module (LOC_VISION, LOC_GPS) comprises an inertial unit (NAV_IMU_VIS, NAV_IMU_GPS) and a Kalman filter (KAL_FLT_VIS, KAL_FLT_GPS) for determining said navigation data (OUT_LOC_GPS, OUT_LOC_VIS).

8. Navigation device (APP) for an aircraft (AC), said device (APP) comprising a first navigation module (LOC_VISION) configured to determine first navigation data (OUT_LOC_VIS) of said aircraft (AC) from data (OUT_IMU, OUT_VIS, OUTJDDOM) from an inertial measurement unit (IMU), from at least one odometer (ODOM) and from images acquired by said aircraft (AC), the first navigation module (LOC_VISION) being configured to: during a landing phase of said aircraft (AC), determine (S50, S70) said first navigation data (OUT_LOC_VIS) from data (OUT_IMU, OUT_VIS) from the inertial measurement unit (IMU) and from the acquired images;and during a taxiing phase following the landing of said aircraft (AC), determining (S90) said first navigation data (OUT_LOC_VIS) from data (OUT_IMU, OUTJDDOM) from the inertial measurement unit (IMU) and said at least one odometer (ODOM), said first navigation data (OUT_LOC_VIS) determined during the taxiing phase (S90) being a function of said first navigation data (OUT_LOC_VIS) determined during the landing phase (S50, S70). Navigation system (SYS) for an aircraft (AC), said system (SYS) comprising: a navigation device (APP) according to claim 8; an inertial measurement unit (IMU); an image acquisition device (CAM);and at least one odometer (ODOM). Navigation system (SYS) according to claim 9, comprising a guidance module (CMD) configured to guide said aircraft (AC) from navigation data (IN_NAV_CMD) determined by said navigation device (APP). Aircraft (AC) comprising a navigation system (SYS) according to claim 9 or 10. Computer program (PROG) comprising instructions for implementing the steps of a method according to any one of claims 1 to 7, when said computer program (PROG) is executed by at least one processor (PROC). Computer-readable information medium (MEM) comprising a computer program (PROG) according to claim 12.;

Images