FR3139653A1 - Navigation method and device for a vehicle, system, vehicle, computer program and associated information carrier - Google Patents

Abstract

The present invention relates to a navigation method and device (APP) for a vehicle (AC), a system (SYS), a vehicle, a computer program (PROG) and an associated information medium (MEM). The method comprises steps of: determination (S10) by a first navigation module (LOC_GPS) of first navigation data of said vehicle (OUT_LOC_GPS) from data (OUT_IMU, OUT_GPS) from an inertial measurement unit (IMU) and a satellite positioning module (GPS); anddetermination (S20) by a second navigation module (LOC_VISION) of second navigation data of said vehicle (OUT_LOC_VIS) from: data (OUT_IMU, OUT_VIS) from the inertial measurement unit (IMU) and images acquired by said vehicle; and furthermore from data (OUT_GPS, OUT_BARO) from said satellite positioning module (GPS) and/or an altimeter (BARO). Figure for abstract: Fig. 1

Description

Navigation method and device for a vehicle, system, vehicle, computer program and associated information carrier

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

State of the prior art

There are today, in the state of the art, different navigation systems for vehicles. In particular, it is known to use an inertial unit on board a vehicle as a navigation system. 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 speed). However, using inertial data to implement a navigation solution requires solving the well-known problem of drift over time in inertial navigation. Indeed, small errors in measuring the specific force and angular velocity are integrated over time by inertial navigation and thus lead to increasingly larger errors in velocity and position.

To limit the drift of inertial navigation, a prior art approach consists of combining inertial data with data from a satellite positioning module, such as a GPS module (acronym of the expression English “Global Positioning System”). Generally speaking, a navigation solution combining data from several sensors is referred to as a “hybrid navigation” solution. Existing hybrid inertia-GPS navigation solutions, however, have the following disadvantage: a GPS module can be easily jammed and thus experience a loss of availability. Ultimately, hybrid inertia-GPS navigation solutions do not make it possible to reliably and precisely locate a vehicle while guaranteeing a high level of integrity. Integrity is defined as the ability to provide, in addition to an estimated quantity (e.g. the position, speed, heading of a vehicle), a protection radius associated with this quantity, i.e. a bound increasing the estimation error with a defined probability, in particular very close to 1.

It can also be considered to use computer vision techniques to compensate for the drift of inertial navigation from images acquired by a vehicle. However, existing computer vision devices – both cameras and image processing algorithms – have a low level of maturity such that the reliability of these devices is low. In particular, such devices present a high hourly integrity risk. The hourly integrity risk for a navigation system is defined as the hourly risk of obtaining erroneous information, that is to say an estimated quantity whose error is greater than the protection radius. In this sense, using a computer vision device to implement a navigation solution does not achieve a sufficient level of integrity for critical applications, such as aeronautics.

There is therefore a need for a navigation solution to improve the level of integrity and availability of existing navigation systems.

The present invention aims to remedy all or part of the disadvantages of the prior art, in particular those explained above.

• détermination par un premier module de navigation de premières données de navigation dudit véhicule à partir de données issues d’une unité de mesure inertielle et d’un module de positionnement par satellites ; et de détermination par un deuxième module de navigation de deuxièmes données de navigation dudit véhicule à partir de : données issues de l’unité de mesure inertielle et d’images acquises par ledit véhicule ; et en outre à partir de données issues dudit module de positionnement par satellites et/ou d’un altimètre.

To this end, according to one aspect of the invention, a navigation method is proposed for a vehicle, said method comprising steps of:

• determination by a first navigation module of first navigation data of said vehicle from data from an inertial measurement unit and a satellite positioning module; and determination by a second navigation module of second navigation data of said vehicle from: data from the inertial measurement unit and images acquired by said vehicle; and furthermore from data from said satellite positioning module and/or an altimeter.

By “navigation data”, we refer here to: data relating to the position, and/or movement of the vehicle – such as geographical coordinates (e.g. latitude, longitude, altitude), speed, heading, etc. ; and/or protection radii associated with position/displacement data. In the context of the invention, a “position” can designate an absolute position defined in relation to the terrestrial reference frame, or a relative position defined in relation to a reference position.

In the context of the invention, by “inertial measurement unit”, reference is made to 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 divided by the mass) and the angular speed of the vehicle. In addition, the term "inertial unit" hereinafter designates 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 vehicle navigation data.

The proposed method makes it possible to precisely determine the navigation data of a vehicle (e.g. the position and movement data of the vehicle as well as the associated protection radii) while guaranteeing a high level of integrity and availability of the system. navigation.

According to one embodiment, the step of determining navigation data by the first navigation module and the step of determining navigation data by the second navigation module are carried out concomitantly (i.e. in parallel, or simultaneously) . Thus, the parallel use of two distinct navigation modules (i.e. said first and second navigation modules) makes it possible to improve the resilience of the vehicle's navigation system with regard to failures of the sensors used for navigation (e.g. satellite positioning module, image acquisition device), such as a failure of the satellite positioning module, a failure of the image acquisition device, or unavailability of another sensor, etc.

In addition, the use of a satellite positioning and image module makes it possible to compensate for inertial navigation drift and thus accurately determine the vehicle's navigation data.

Compared to existing navigation solutions, the proposed navigation solution, by exploiting a plurality of navigation modules, makes it possible to improve the level of integrity and availability of the vehicle's navigation system while accurately determining the navigation data of the vehicle.

More precisely, the proposed navigation solution presents: a higher level of availability than existing hybrid inertia-GPS navigation systems; and a higher level of integrity than existing hybrid inertia-vision navigation systems.

• si ledit module de positionnement par satellites est fonctionnel, fourniture desdites premières données de navigation à un module de guidage dudit véhicule ; et
• sinon, fourniture desdites deuxièmes données de navigation audit module de guidage dudit véhicule.

According to one embodiment, the proposed method comprises steps of:

• if said satellite positioning module is functional, supplying said first navigation data to a guidance module of said vehicle; And
• otherwise, supplying said second navigation data to said guidance module of said vehicle.

This embodiment makes it possible to precisely guide a vehicle. It should be noted that this embodiment benefits from the technical advantages of the proposed navigation solution. Indeed, precise guidance of the vehicle is enabled because the navigation data is precisely determined.

As mentioned previously, the proposed solution exploits images for navigation to compensate for inertial navigation drift. According to this embodiment, the use of navigation data determined from images by the second navigation module for vehicle guidance is conditioned on unavailability of the satellite positioning module (e.g. faulty module, or unusable ). Thus, this embodiment makes it possible to significantly relax the constraints on the reliability (i.e. the hourly risk of integrity) of the image acquisition device and the associated image processing algorithms. Thus, the proposed navigation solution makes it possible to precisely determine the navigation data of a vehicle while guaranteeing a high level of integrity, even for an image acquisition device and image processing algorithms. associated images of low maturity.

Indeed, the second navigation module uses, according to this embodiment, data from the satellite positioning module or the altimeter in addition to the acquired images. This makes it possible to compensate with better precision the inertial navigation drift of the second navigation module when the satellite positioning module or the altimeter are usable. Thus, this embodiment makes it possible to maintain a precise location chain by exploiting the different sensors when they are available.

For example, suppose that during a first period, the second navigation module uses data from the satellite positioning module to compensate for inertial navigation drift. Then, during a second subsequent period, the satellite positioning module is no longer available. So, although the satellite positioning module is no longer available, the second navigation module benefits during the second period from the adjustment of the inertial navigation during the first period.

According to one embodiment, the first and second navigation modules respectively comprise an inertial unit and a Kalman filter to determine said first and second navigation data. More particularly, the first navigation module comprises a first inertial unit and a first Kalman filter to determine 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.

This embodiment makes it possible to exploit data from independent sensors of different types to determine the vehicle's navigation data in an efficient manner, particularly in terms of precision of the navigation data obtained and the necessary hardware and software resources (e.g. resources processing, memory resources, etc.).

More specifically, this embodiment makes it possible to implement multi-sensor data fusion to determine vehicle navigation data. 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 using data from other sensors (i.e. realignment of the inertial navigation to compensate for the drift). Thus, the combination of an inertial unit and a Kalman filter makes it possible to implement multi-sensor data fusion to precisely determine the vehicle's navigation data from independent sensors of different types.

• détection d’au moins un point terrestre de référence dans lesdites images acquises ;
• détermination d’une position relative observée dudit au moins un point terrestre de référence détecté par rapport audit véhicule à partir desdites images acquises ;
• détermination d’une position relative estimée dudit au moins un point terrestre de référence détecté par rapport audit véhicule à partir d’une position dudit véhicule déterminée par le deuxième module de navigation et d’une position connue dudit au moins un point terrestre de référence ; et
• détermination de dites deuxièmes données de navigation à partir de la différence entre les positions relatives observée et estimée dudit au moins un point terrestre de référence par rapport audit véhicule.

According to one embodiment, the proposed method comprises steps of:

• detection of at least one terrestrial reference point in said acquired images;
• determination of an observed relative position of said at least one terrestrial reference point detected relative to said vehicle from said acquired images;
• determination of an estimated relative position of said at least one terrestrial reference point detected relative to said vehicle from a position of said vehicle determined by the second navigation module and a known position of said at least one terrestrial reference point; And
• determination of said second navigation data from the difference between the observed and estimated relative positions of said at least one terrestrial reference point relative to said vehicle.

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

This embodiment makes it possible to compensate for the drift of the inertial navigation of the second navigation module from images acquired by the vehicle.

It should also be mentioned that, in the context 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.

• sélection d’une portion d’au moins une image acquise, les coordonnées de ladite portion étant déterminées à partir d’une position connue dudit au moins un point terrestre de référence, d’une position dudit véhicule déterminée par le deuxième module de navigation et d’une information relative à la précision de ladite position déterminée dudit véhicule fournie par le deuxième module de navigation ; et
• détection dudit au moins un point terrestre de référence dans ladite portion de ladite au moins une image acquise.

According to one embodiment, said step of detecting at least one terrestrial reference point in the acquired images comprises steps of:

• selection of a portion of at least one acquired image, the coordinates of said portion being determined from a known position of said at least one terrestrial reference point, from a position of said vehicle determined by the second navigation module and information relating to the precision of said determined position of said vehicle provided by the second navigation module; And
• detection of said at least one terrestrial reference point in said portion of said at least one acquired image.

This embodiment is advantageous in that it makes it possible to use only a portion of the image (i.e. a region of interest) to detect a terrestrial reference point and thus to restrict the portion of the image to be processed. More generally, this embodiment makes it possible to reduce the hardware and software resources (e.g. processing resources, memory resources, etc.) necessary for the detection of a terrestrial reference point in acquired images and therefore for the determination of data of navigation from acquired images.

• un premier module de navigation configuré pour déterminer des premières données de navigation dudit véhicule à partir de données issues d’une unité de mesure inertielle et d’un module de positionnement par satellites ; et
• un deuxième module de navigation configuré pour déterminer des deuxièmes données de navigation dudit véhicule à partir de données issues de l’unité de mesure inertielle et d’images acquises par ledit véhicule ; et en outre à partir de données issues dudit module de positionnement par satellites et/ou d’un altimètre.

According to another aspect of the invention, a navigation device is proposed for a vehicle comprising:

• a first navigation module configured to determine first navigation data of said vehicle from data coming from an inertial measurement unit and a satellite positioning module; And
• a second navigation module configured to determine second navigation data of said vehicle from data from the inertial measurement unit and images acquired by said vehicle; and furthermore from data from said satellite positioning module and/or an altimeter.

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.

• si ledit module de positionnement par satellites est fonctionnel, fournir desdites premières données de navigation à un module de guidage dudit véhicule ; et
• sinon, fournir desdites deuxièmes données de navigation audit module de guidage dudit véhicule

According to one embodiment, the proposed device comprises a control module configured to:

• if said satellite positioning module is functional, providing said first navigation data to a guidance module of said vehicle; And
• otherwise, providing said second navigation data to said guidance module of said vehicle

According to one aspect of the invention, there is proposed a navigation system for a vehicle comprising: a navigation device according to the invention; an inertial measurement unit; a satellite positioning module; and an image acquisition device.

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.

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.

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

According to one aspect of the invention, a vehicle is proposed comprising a navigation system according to the invention.

According to one aspect of the invention, a computer program is proposed 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 a computer.

The computer program may be made up of one or more sub-parts stored in the same memory or in separate memories. The program may use any programming language, and 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 shape.

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

The information carrier can be any entity or device capable of storing the program. For example, the support may comprise a storage means, such as a non-volatile memory or ROM, for example a CD-ROM or a microelectronic circuit ROM, or even a magnetic recording means, for example a floppy disk or a hard disc. On the other hand, 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 can 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 executing the method in question.

Other characteristics and advantages of the present invention will emerge from the description provided below of embodiments of the invention. These embodiments are given by way of illustrative example and are devoid of any limiting nature. The description provided below is illustrated by the attached drawings:

There schematically represents an example of software and hardware architecture of a navigation system according to one embodiment of the invention;

- Figures 2A and 2B represent, schematically and in flowchart form, steps of a navigation method according to one embodiment of the invention; And

There schematically represents an example of software and hardware architecture of a navigation system according to one embodiment of the invention.

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

There schematically represents an example of software and hardware architecture of a navigation system according to one embodiment of the invention.

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

The APP navigation device is configured to determine, from the data from the set of SENS sensors, IN_NAV_CMD navigation data of the vehicle.

The CMD guidance module is configured to guide the vehicle based on the IN_NAV_CMD navigation data provided by the APP device.

According to one embodiment, the SYS system is on board a vehicle, for example in a land vehicle: car, truck, train, etc., or in a marine vehicle: boat, frigate, or even in an air vehicle: an aircraft, a helicopter, a plane, a drone, etc. In particular, the SYS system is, according to an alternative embodiment, on board an aircraft.

In the context of the invention, navigation data of a vehicle designates data relating to the position, and/or movement of the vehicle and includes, for example, geographical coordinates (e.g. latitude, longitude, altitude), a speed, a heading. Navigation data can be defined absolutely in relation to the terrestrial reference frame, or relatively in relation to a reference position (e.g. a landing strip). For example, a relative position of the vehicle at a given moment determined by the navigation device APP may include one or more coordinates of the following set: an azimuth, a vertical distance, a longitudinal distance, and a defined lateral distance relative to a reference position.

As illustrated by the , according to one embodiment, the set of SENS sensors 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 odometer; a Pitot probe; and a magnetometer.

The IMU inertial measurement unit 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 divided by the mass) and the angular speed Ω of the vehicle. Typically, the IMU inertial measurement unit includes: three gyrometers measuring the three components of the angular speed Ω (speeds of variation of the roll, pitch and yaw angles); and three accelerometers measuring the three components of the specific force Fs.

The GPS satellite positioning module provides OUT_GPS navigation data. According to one embodiment, the OUT_GPS navigation data includes, for a plurality of measurement instants, a position Pos and a speed Vel of the vehicle. Typically, the GPS satellite positioning module provides an absolute Pos position 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 framework 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 modules. , Glonass, etc.

The BARO altimeter provides OUT_BARO so-called altimeter data as output. The BARO altimeter is, according to one embodiment, a barometric altimeter. In particular, the altimeter data OUT_BARO are, for a plurality of measurement instants, representative of the altitude Alt of the vehicle or variations in altitude of said vehicle.

The VISION computer vision sensor (also referred to as a “computer vision device”) outputs OUT_VIS data. According to one embodiment, the VISION sensor comprises or is configured to communicate with: a DB recording medium; and a CAM image acquisition device. The recording medium DB, for example a database, includes the positions (i.e. geographical coordinates) of a plurality of terrestrial reference points AMER (hereinafter called bitters) as well as information relating to the graphic representations of the terrestrial points reference AMER. For example, the terrestrial reference points can be a landing strip, a navigation light, a Precision Approach Path Indicator, etc. The CAM image acquisition device comprises at least one camera embedded in the vehicle and having an electromagnetic radiation sensor whose wavelengths belong to the spectrum of visible light and/or infrared. According to one embodiment, the CAM image acquisition device comprises at least one camera among the following: a visible light camera; a near-infrared camera (or “Near-Infrared” in English), a short infrared camera (“Short Wavelength InfraRed” in English), a medium infrared camera (“Medium Wavelength InfraRed” in English), and a far infrared camera (“ Long Wavelength InfraRed” in English). The CAM image acquisition device is configured to acquire a plurality of images for a plurality of measurement times.

The VISION computer vision sensor takes as input: images acquired by the CAM image acquisition device; and the OUT_LOC_VIS navigation data from the LOC_VISION navigation module, in particular the position of the vehicle. The VISION sensor is, according to one embodiment, configured to: detect the AMER terrestrial reference points in the acquired images; and determining the observed relative positions of the AMER detected terrestrial reference points relative to the vehicle from said acquired images. The VISION sensor is further configured to, according to one embodiment, determine estimated relative positions of the detected terrestrial reference points AMER relative to the vehicle from a position of the vehicle determined by the navigation module LOC_VISION and known positions AMER terrestrial reference points. According to one embodiment, the OUT_VIS data provided by the VISION sensor include, for a plurality of measurement instants, differences αx, αy between the observed and estimated relative positions of the AMER terrestrial reference points relative to the vehicle. Typically, the relative position (observed or estimated) of a landmark relative to the vehicle is defined by two angles – a lateral angle and a vertical angle – characterizing the axis of sight of the landmark relative to the longitudinal axis of the landmark. vehicle.

According to one embodiment, to detect a terrestrial reference 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 terrestrial reference point in this region of interest. In particular, the coordinates of the region of interest are determined from: the known position of the terrestrial reference point; the position of the vehicle 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 vehicle (i.e. the probability that the position error is less than the protection radius is greater than a defined value, in particular very close to 1). The fact of 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 the hardware and software resources (e.g. processing time, memory, etc.) necessary for the detection of a landmark. 'a bitter in acquired images.

Obviously, the set of SYS sensors can include one or more of each of the IMU, GPS, BARO, VISION sensors as described above.

As illustrated by the , the APP navigation device comprises, according to one embodiment: a LOC_ GPS navigation module (called first navigation module); a LOC_VISION navigation module (called second navigation module); and a SWITCH control module. The LOC_GPS and LOC_VISION navigation modules respectively provide OUT_LOC_GPS navigation data (called first navigation data) and OUT_LOC_VIS navigation data (called second navigation data). It should be noted that the navigation modules LOC_GPS and LOC_VISION produce the navigation data OUT_LOC_GPS and OUT_LOC_VIS independently and, more particularly, simultaneously (ie 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 heading direction of the vehicle and associated protection radii PL.

It should be noted that the parallel use of the two distinct navigation modules LOC_GPS and LOC_VISION makes it possible to improve the integrity of the vehicle's SYS navigation system and thus the resilience of the SYS system with regard to failures of the sensors used. for navigation.

The LOC_GPS 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.

As illustrated by the , according to one embodiment, the LOC_GPS navigation module comprises: a NAV_IMU_GPS inertial unit; and a Kalman filter KAL_FLT_GPS. The NAV_IMU_GPS inertial unit is configured to integrate over time the specific force Fs and angular speed Ω data produced by the inertial measurement unit IMU and thus determine navigation data Pos, Vel, Heading of the vehicle. The Kalman filter KAL_FILT_GPS determines, from data from the GPS and BARO sensors, corrections δPos, δVel, δCap, δFs, and δΩ to be applied to the NAV_IMU_GPS inertial unit. The OUT_LOC_GPS navigation data provided as output thus correspond, according to one embodiment, to the navigation data determined by the NAV_IMU_GPS inertial unit corrected (ie realigned) 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 inertial navigation drift (ie realign) from data from the GPS and BARO sensors.

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

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

As illustrated by the , 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 NAV_IMU_VIS inertial unit to which the corrections determined by the KAL_FILT_VIS filter are applied from the data from the GPS, BARO and VISION sensors. In other words, the Kalman filter KAL_FLT_GPS makes it possible to compensate for inertial navigation drift (ie readjust) using data from GPS, BARO and VISION sensors.

In the context of the invention, it could also be envisaged other embodiments according to which one or both of the navigation modules LOC_GPS and LOC_VISION respectively use a Kalman filter (e.g. an extended Kalman filter) taking as input the data coming from all or part of the sensors of the SENS assembly and producing said navigation data as output.

It should be mentioned that the LOC_VISION navigation module uses, to realign the NAV_IMU_VIS inertial unit, data from other GPS, BARO, VISION sensors when this data is available. According to one example, the VISION sensor can only be used by the LOC_VISION navigation module to realign the NAV_IMU_VIS inertial unit following the detection of a landmark. According to another example, the LOC_VISION navigation module does not use the data from the GPS satellite positioning module, when the GPS module is faulty or unusable.

However, it is important to emphasize that the navigation data determined at a given time is a function of the navigation data determined at previous times. Indeed, the NAV_IMU_GPS and NAV_IMU_VIS inertial units integrate over time the data of specific force Fs and angular speed Ω produced by the inertial measurement unit IMU to determine navigation data OUT_LOC_GPS and OUT_LOC_VIS. Also, small errors in measuring the specific force Fs and the angular speed Ω are integrated over time by the inertial units and thus lead to errors in speed and position increasing over time (i.e. drift of inertial navigation ). Consequently, the fact of using a sensor at a given moment to realign an inertial unit makes it possible to improve the precision of the navigation data determined at subsequent moments.

Let us assume for example that during a first period, the navigation module LOC_VISION uses data from the GPS module to compensate for the drift of the inertial unit NAV_IMU_VIS. Then, during a second subsequent period, the GPS satellite positioning module is no longer available. During the second period, although the GPS module is no longer available, the LOC_VISION navigation module determines OUT_LOC_VIS navigation data that is more precise than a navigation module that never uses the data from a GPS module. Indeed, the LOC_VISION navigation module benefits during the second period from the alignment of the inertial unit during the first period.

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 guidance module CMD with navigation data IN_NAV_CMD. 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 depending on the availability (i.e. functional or non-functional) of the GPS satellite positioning module, this embodiment being detailed below with reference in Figures 2A and 2B.

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

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 S50 implemented by the proposed navigation system SYS. According to a particular embodiment, steps S10 to S50 are implemented in chronological order as described below.

During step S10, the LOC_GPS navigation module determines OUT_LOC_GPS navigation data of the vehicle from data from the inertial measurement unit IMU, the GPS satellite positioning module, and the BARO altimeter.

During step S20, the navigation module LOC_VISION determines navigation data OUT_LOC_VISION of the vehicle from data from the inertial measurement unit IMU, the GPS satellite positioning module, the BARO altimeter, and of the VISION computer vision sensor. According to one embodiment, step S20 comprises sub-steps S21 to S24 detailed below with reference to the .

Steps S10 and S20 can be carried out simultaneously, one before the other or vice versa. According to a particular embodiment, steps S10 and S20 are carried out in parallel.

As mentioned previously, if one of the GPS, BARO, or VISION sensors is not functional (e.g. unavailable, broken, faulty, unusable), the LOC_GPS and LOC_VISION navigation modules continue to produce navigation data as output. OUT_LOC_GPS and OUT_LOC_VIS. However, in this case, the LOC_GPS and LOC_VISION navigation modules cannot use the data from the non-functional sensor to compensate for the drift (i.e. readjust) of the NAV_IMU_GPS and NAV_IMU_VIS inertial units.

During step S30, the SWITCH control module determines whether the GPS satellite positioning module is functional (i.e. available and usable). As an indication, the GPS satellite positioning module may not be functional (i.e. faulty, broken down) due to a failure of one of the satellites in the GPS constellation, or a failure of the on-board GPS module itself. even. During step S30, the SWITCH control module implements, according to one embodiment, a fault detection step (i.e. failure) of the GPS satellite positioning module to determine whether the satellite positioning module GPS is functional.

During step S40, if and only if it has been determined in step S30 that the GPS satellite positioning module is functional, the SWITCH control module provides the OUT_LOC_GPS navigation data to the CMD guidance module of the vehicle.

During step S50, if it has been determined in step S30 that the GPS satellite positioning module is not functional (the GPS module being unavailable, faulty, broken down or not usable), the module SWITCH control module provides OUT_LOC_VIS navigation data to the vehicle's CMD guidance module.

Following step S50, the navigation system implements, according to one embodiment, the steps S10 and S20 previously detailed. Thus, the proposed navigation method comprises, according to this embodiment, several iterations of steps S10 to S50 described above.

As illustrated by the , step S20 comprises, according to one embodiment, at least one of the steps S21 to S24 detailed below with reference to the and implemented by the proposed SYS navigation system.

During step S21, the VISION sensor detects at least one terrestrial reference point AMER in images acquired by the image acquisition device CAM.

According to a particular embodiment, to detect an AMER terrestrial reference point in an image, the VISION sensor implements the following steps. The VISION sensor selects a portion of this image (i.e. a region of interest), the coordinates of the portion of the image being determined from: the known position (e.g. geographic coordinates) of the terrestrial reference point AMER; the position of the vehicle determined by the LOC_VISION navigation module; and information relating to the precision of the vehicle position provided by the LOC_VISION navigation system (i.e. the protection radius). Following the selection of the image portion, the VISION sensor detects the terrestrial reference point AMER in the image portion.

During step S22, the VISION sensor determines an observed relative position POS_AMER_OBS of the detected terrestrial reference point AMER relative to the vehicle from the acquired images.

During step S23, the VISION sensor determines an estimated relative position POS_AMER_EST of the detected terrestrial reference point AMER relative to the vehicle from a position of the vehicle provided by the navigation module LOC_VISION and a known position of the AMER terrestrial reference point.

During step S24, the VISION sensor provides the navigation module LOC_VISION with the difference αx, αy between the observed relative position POS_AMER_OBS and the estimated relative position POS_AMER_EST of the terrestrial reference point AMER relative to the vehicle; and the navigation module LOV_VISION determines navigation data OUT_LOC_VIS in particular from this difference αx, αy.

There schematically represents an example of software and hardware architecture of a navigation system according to one embodiment of the invention.

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

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

As illustrated by the , 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 from the set of SENS sensors; 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 assembly; and the CMD guidance module, which can be wired or non-wired, and can implement any protocol known to those skilled in the art (Ethernet, Wi-Fi, Bluetooth, 3G, 4G, 5G, 6G, etc.).

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

The proposed SYS navigation system can accurately determine a vehicle's navigation data while ensuring a high level of integrity, allowing the SYS navigation system to be integrated into a critical system such as an aircraft.

In particular, the proposed SYS navigation system ensures a high level of integrity while significantly relaxing the hourly integrity risk constraints on the VISION computer vision sensor. In other words, the proposed SYS navigation system ensures a high level of integrity, even with a low maturity VISION computer vision sensor.

Let's take for example a reference navigation system comprising a single navigation module using data from an inertial measurement unit, a satellite positioning module and a computer vision sensor. Such a navigation system does not ensure a high level of integrity and could not be integrated into a critical system. Indeed, the hourly integrity risk conditions to be verified for the computer vision sensor are not achievable with this reference system, due to the lack of maturity of the computer vision sensor and computer vision techniques.

In comparison to the aforementioned reference system, the proposed navigation system SYS has two navigation modules LOC_GPS and LOC_VISION and conditions the use of the computer vision sensor VISION to situations for which the GPS satellite positioning module is not available. Thus, the proposed SYS navigation system and, more particularly, the architecture of the APP navigation device make it possible to significantly relax the constraints on the hourly integrity risk to be verified for the VISION computer vision sensor.

The term module can correspond as well to a software component 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 subprograms 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. .).

It should be noted that the order in which the steps of a process according to the invention are linked, in particular with reference to the attached drawings, constitutes only an example of an embodiment devoid of any limiting character, variants being possible.

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, those skilled in the art may consider any adaptation or combination of the embodiments and variants described above in order to meet a very specific need.

Claims (12)

Navigation method for a vehicle, said method comprising steps of:

• determination (S10) by a first navigation module (LOC_GPS) of first navigation data of said vehicle (OUT_LOC_GPS) from data (OUT_IMU, OUT_GPS) coming from an inertial measurement unit (IMU) and a positioning module by satellite (GPS); And
• determination (S20) by a second navigation module (LOC_VISION) of second navigation data of said vehicle (OUT_LOC_VIS) from: data from (OUT_IMU, OUT_VIS) of the inertial measurement unit (IMU), and acquired images by said vehicle; and furthermore from data (OUT_GPS, OUT_BARO) from said satellite positioning module (GPS) and/or an altimeter (BARO).

Method according to claim 1, comprising steps of:

• if said satellite positioning module (GPS) is functional (S30), supply (S40) of said first navigation data (OUT_LOC_GPS) to a guidance module (CMD) of said vehicle; And
• otherwise, supply (S50) of said second navigation data (OUT_LOC_VIS) to said guidance module (CMD) of said vehicle.

Method according to claim 1 or 2, in which the first (LOC_GPS) and second navigation modules (LOC_VISION) respectively comprise an inertial unit (NAV_IMU_VIS, NAV_IMU_GPS) and a Kalman filter (KAL_FILT_GPS, KAL_FILT_VIS) for determining (S10, S20) said first and second navigation data (OUT_LOC_GPS, OUT_LOC_VIS). Method according to one of claims 1 to 3, comprising steps of:

• detection (S21) of at least one terrestrial reference point (AMER) in said acquired images;
• determination (S22) of an observed relative position (POS_AMER_OBS) of said at least one detected terrestrial reference point (AMER) relative to said vehicle from said acquired images;
• determination (S23) of an estimated relative position (POS_AMER_EST) of said at least one detected terrestrial reference point (AMER) relative to said vehicle from a position of said vehicle determined by the second navigation module (LOC_VISION) and a known position of said at least one terrestrial reference point (AMER); and of
• determination (S24) of said second navigation data (OUT_LOC_VIS) from the difference (αx, αy) between the observed (POS_AMER_OBS) and estimated (POS_AMER_EST) relative positions of said at least one terrestrial reference point (AMER) with respect to said vehicle.

Method according to claim 4, wherein said step of detecting (S21) at least one terrestrial reference point (AMER) in the acquired images comprises steps of:

• selection of a portion of at least one acquired image, the coordinates of said portion being determined from a known position of said at least one terrestrial reference point (AMER), of a position of said vehicle determined by the second module navigation (LOC_VISION) and information relating to the precision of said determined position of said vehicle provided by the second navigation module (LOC_VISION); and of
• detection of said at least one terrestrial reference point (AMER) in said portion of said at least one acquired image.

Navigation device (APP) for a vehicle, said device (APP) comprising:

• a first navigation module (LOC_GPS) configured to determine (S10) first navigation data of said vehicle (OUT_LOC_GPS) from data (OUT_IMU, OUT_GPS) coming from an inertial measurement unit (IMU) and a monitoring module satellite positioning (GPS); And
• a second navigation module (LOC_VISION) configured to determine (S20) second navigation data of said vehicle (OUT_LOC_VIS) from: data (OUT_IMU, OUT_VIS) from the inertial measurement unit (IMU) and acquired images by said vehicle; and furthermore from data (OUT_GPS, OUT_BARO) coming from said satellite positioning module (GPS) and/or an altimeter (BARO).

Navigation system (SYS) for a vehicle, said system (SYS) comprising:

• a navigation device (APP) according to claim 6;
• an inertial measurement unit (IMU);
• a satellite positioning module (GPS); And
• an image acquisition device (CAM).

Navigation system (SYS) according to claim 7, comprising a computer vision device (VISION) configured to determine at least one position of the vehicle from the images acquired by the image acquisition device (CAM). Navigation system (SYS) according to claim 7 or 8, comprising a guidance module (CMD) configured to guide said vehicle from navigation data (IN_NAV_CMD) determined by said navigation device (APP). Vehicle comprising a navigation system (SYS) according to one of claims 7 to 9. Computer program (PROG) comprising instructions for implementing the steps of a method according to any one of claims 1 to 5, when said computer program (PROG) is executed by at least one processor (PROC ). Computer-readable information carrier (MEM) comprising a computer program (PROG) according to claim 11.