Method for exchanging data between drones of a drone swarm

The present invention relates to a method for exchanging data between drones of a drone swarm comprising at least four drones, the method comprising:

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Entry of International Patent Application No. PCT/EP2019/082284, filed on Nov. 22, 2019, which claims priority to French Application No. 18 71758, filed on Nov. 23, 2018. The disclosures of the priority applications are incorporated in their entirety herein by reference.

The present invention relates to a method for exchanging data between drones of a drone swarm. The present invention also relates to a drone swarm suitable for implementing such a data exchange method.

A drone swarm, also called a drone network, refers to a set of drones flying in close proximity to each other. In order to communicate with each other, the drones of such a swarm are conventionally provided with radio frequency communication devices. In addition, such drones are generally equipped with GPS (Global Positioning System) tracking devices allowing them to locate themselves and to transmit their position to the other drones of the swarm.

However, data exchanges via radio frequency communication are susceptible to being scrambled and are therefore not robust enough for critical applications. Similarly, tracking via a GPS tracking device can easily be jammed.

As such, there is a need for a method of data exchange between drones of a drone swarm allowing for the identification and tracking of drones of the swarm that is robust and does not require the addition of a tracking device on each drone.

To this end, the object of the invention is a method for exchanging data between drones of a drone swarm, the drone swarm comprising at least four drones, each drone being provided with an identifier specific to the drone, each drone comprising at least one transmitter, at least one receiver and a computer, each receiver comprising a pixel matrix configured so that each signal is received on a number of pixels of the pixel matrix that is strictly less than the total number of pixels of the pixel matrix, the method comprising, at each moment:emitting, by the transmitter of each drone, a signal comprising data to be emitted, the data to be emitted comprising the identifier of the drone, as well as the direction and the identifier of each signal received at the previous moment by the receiver of the drone,receiving, by the receiver of at least one drone, called the receiver drone, the signal emitted by at least one other drone of the swarm,determining, by the computer of each receiver drone, the direction of each signal received as a function of the position of the pixel or pixels of the pixel matrix receiving the signal, andif necessary, determining, by the computer of each receiver drone, for each received signal, the relative position of the drone corresponding to the identifier of the received signal as a function of the direction determined for the received signal and of at least two directions obtained at the previous moment by the receiver of the receiver drone and corresponding to the same identifier as the received signal.

According to other advantageous aspects of the invention, the data exchange method comprises one or more of the following features, considered alone or according to all technically possible combinations:the receiver of each drone comprises an event detection sensor, with the pixel matrix being comprised in the event detection sensor;at least one of the drones, referred to as a reference drone, is associated with an absolute position, the data to be emitted by the transmitter of the reference drone comprising the absolute position of the reference drone, the method further comprising the determination, by each receiver drone receiving the signal emitted by the reference drone, of the absolute position of each drone for which a relative position has been determined by the receiver drone as a function of the absolute position of the reference drone and of the relative positions determined by the receiver drone;the or at least one of the reference drones is stationary on the ground;the or at least one of the reference drones is carrying an absolute tracking system;at least one of the drones of the swarm comprises a sensor configured to detect the presence of objects in the field of the sensor, the method comprising, at each moment, for the drone:detecting objects in the field of the sensor, andfor each detected object, classifying the object as being foreign to the drone swarm when no signal is received from the object or when the received signal for the object does not comprise the identifier of a drone in the swarm;each transmitter is a wide field transmitter;each transmitter is configured to transmit signals over a solid angle of at least 2π steradians, each drone preferably comprising at least two diametrically opposed transmitters so as to transmit signals over a solid angle of 4π steradians;the transmitter of each drone is a laser transmitter, preferably in the wavelength range of between 0.7 micrometer and 1.6 micrometer;each receiver is a wide field receiver.

The invention further relates to a drone swarm comprising at least four drones, each drone being provided with an identifier specific to the drone, each drone comprising at least one transmitter, at least one receiver and a computer, each receiver comprising a pixel matrix configured so that each signal is received on a number of pixels of the pixel matrix strictly less than the total number of pixels of the pixel matrix, the drone swarm being suitable for implementing a data exchange method as described above.

A drone swarm10comprising a plurality of drones12is illustrated inFIGS.1and2. A drone is an unmanned aircraft without a human on board that is typically remotely controlled.

In particular, the swarm10of drones12illustrated byFIGS.1and2comprises four drones12A,12B,12C,12D. In a variant, the swarm10of drones12comprises a number of drones12strictly greater than four.

Each drone12is provided with an identifier specific to the drone12. By way of example, an identifier is a number specific to the drone12and which differs from one drone12of the swarm10to another.

Advantageously, at least one of the drones12, called a reference drone, is associated with an absolute position. In this case, the absolute position of the reference drone is, for example, stored in a memory of the reference drone. For example, the reference drone is stationary on a fixed surface, such as the ground.

In a variant, the reference drone carries an absolute tracking system.

For example, the reference drone is equipped with a tracking system, such as a star finder type system, which allows the position of the reference drone to be located at each moment.

Each drone12comprises at least one transmitter14, at least one receiver16, a computer18, and a memory20. Optionally, at least one of the drones12in the swarm10comprises a sensor22.

Each transmitter14is preferably a wide field transmitter. A wide-field transmitter is defined as a transmitter configured to transmit a signal over a solid angle strictly greater than 10° by 10°. As such, a wide field transmitter allows a signal to be emitted in a plurality of directions around the drone12.

Preferably, each transmitter14is configured to transmit signals over a solid angle of at least 2π steradians (hemispheres). In the example shown inFIGS.1and2, each drone12comprises at least two diametrically opposed transmitters14so as to transmit signals over a solid angle of 4π steradians (sphere) around the drone12.

The transmitter14of each drone12is configured to transmit an optical signal. As such, the transmitter14of each drone12does not transmit any radio frequency signal.

Advantageously, the transmitter14of each drone12is a laser transmitter. The wavelength range of the laser transmitter is, for example, between 0.7 micrometers (μm) and 1.6 micrometers.

The receiver16of each drone12is a wide field receiver. A wide field receiver is defined as a receiver configured to receive a signal over a solid angle strictly greater than 10° by 10°. As such, a wide field receiver allows signals to be received from a plurality of directions around the drone12.

For example, each wide field receiver is configured to receive signals over a solid angle of at least 90° by 120°.

Preferably, each drone12comprises at least four receivers14that are orthogonal to a single plane and offset by 90°. As such, this allows for coverage of signals from all four cardinal points around the drone12.

Each receiver16comprises a pixel matrix23configured so that each signal is received on a number of pixels of the pixel matrix23that is strictly less than the total number of pixels of the pixel matrix23. Typically, each pixel in the array is associated with a direction. As such, this allows for determination of the direction of each signal received by the pixel matrix23.

Preferably, each receiver16comprises an event detection sensor, with the pixel matrix23being comprised in the event detection sensor. An event detection sensor is a sensor comprising a pixel matrix whose pixels are autonomous and capable of reacting independently of each other with a response time generally in the order of microseconds. An event detection sensor is capable of capturing and emitting only the changes in events and not the entire scene, as is the case with traditional image sensors. As such, compared to a traditional image sensor, an event detection sensor has reduced latency, data volume to be processed and power consumption. In addition, an event detection sensor has a high bandwidth, typically greater than 1 megabit per second.

The computer18is, for example, a processor.

The sensor22is configured to detect the presence of objects in the field of the sensor22. Such objects are, advantageously, electronic objects. For example, such objects are the other drones12in the swarm10, drones not belonging to the swarm, or aircraft.

The operation of the swarm10of drones12ofFIG.1is now described with reference toFIGS.2and3, which illustrate an example of implementation of a data exchange process according to the invention. The steps of such a process are implemented at each moment, i.e., in real time.

The data exchange method comprises a step100of transmission by the transmitter14of each drone12of a signal comprising data to be emitted. The data to be emitted comprises the identifier of the drone12, as well as the direction and identifier of each signal received at the previous moment by the receiver16of the drone12. Such signals received at the previous moment are signals from other drones12in the swarm10. Advantageously, the signal comprising the data to be emitted also comprises data useful for communication between drones, such as instructions from one drone to another.

When at least one of the drones12, known as the reference drone, is associated with an absolute position, the data to be emitted by the transmitter14of the reference drone also comprises the absolute position of the reference drone.

The direction and the identifier of each signal received by each drone12at the previous moment are, for example, stored in the memory20of the drone12. The memory20of each drone12is updated at each moment, as will be described below.

As such, when initializing a drone12, the data to be emitted comprises only the identifier of the drone12, since the drone12has not received a signal at the preceding moment. When initializing a reference drone, the data to be emitted comprises only the identifier of the reference drone and the absolute position of the reference drone, since the reference drone has not received a signal at the preceding moment.

In the example shown inFIG.2, each of the four drones12A,12B,12C, and12D in the swarm10transmits a signal to the other drones12in the swarm10.

The data exchange method comprises a step110of receiving, by the receiver16of at least one drone12, called the receiver drone, the signal emitted by at least one other drone12of the swarm10.

In the example illustrated inFIG.2, each of the four drones12A to12D of the swarm10receives a signal from each of the other three drones12of the swarm10. Indeed, in the example illustrated inFIG.2, no element, such as a building or vegetation, masks the signals emitted by the various drones12of the swarm10. As such, in this example, each drone12of the swarm10is a receiver drone.

In contrast, if, for example, drone12D were masked by a building, the other drones12A through12C would not receive signals from drone12D and drone12D would not receive signals from the other drones12A through12C.

The data exchange method comprises a step120of determining the direction, by the computer18of each receiver drone, of each received signal as a function of the position of the pixel or pixels of the pixel matrix23receiving the signal. Indeed, each pixel of the pixel matrix23being associated with a direction (in real space), the direction of each received signal is determined as a function of the position, in the pixel matrix23, of the pixel or pixels receiving the signal.

In general, a received signal at the top left, to the right respectively, of the pixel matrix will be considered as coming from a drone to the left, respectively right, of the receiver drone and at a height greater than or equal to that of the receiver drone. A signal received at the bottom left, respectively right, of the pixel matrix will be considered as coming from a drone to the left, respectively right, of the receiver drone and at a height lower than or equal to that of the receiver drone. For example, for drone12A shown inFIG.2, the signal from drone12B is located at the top right of the pixel matrix23of the receiver16of drone12A. The signal from drone12C is located at the bottom left of the pixel matrix23of the receiver16of drone12A, and the received signal from drone12D is located at the bottom right of the pixel matrix23of the receiver16of drone12A.

The direction is determined, for example, in terms of elevation angle and bearing angle. The bearing angle is the angle formed between the longitudinal axis of the receiver drone and the direction of the received signal. The elevation angle, also known as the site angle, is the angle formed between the horizontal plane of the receiver drone and the direction of the received signal.

The data exchange method comprises a step130of determining, by the computer18of each receiver drone, for each received signal, the relative position of the drone12corresponding to the identifier of the received signal.

The relative position of the corresponding drone12is determined as a function of the direction determined for the received signal and at least two directions obtained at the previous moment by the receiver16of the drone12and corresponding to the same identifier as the received signal. As such, a relative position is obtained at the determination step130only when the memory20of the receiver drone comprises the direction of two signals having the same identifier as the received signal.

More specifically, the relative position of the drones12corresponding to each received signal is determined by triangulation. Triangulation is a method of determining the position of a point by measuring the angles between the point and other reference points whose position is known, and this rather than directly measuring the distance between the points. Such a point can be thought of as the third vertex of a triangle where two angles and the length of one side are known.

Upon completion of the determination step130, the memory20of each drone12is, also, updated by replacing the directions and identifiers stored in the memory20with the direction determined for each received signal associated with the identifier of the drone12comprised in the data of each received signal.

When at least one of the drones12, referred to as a reference drone, is associated with an absolute position, the exchange method comprises a step of determining140, by the reference drone, and by each receiver drone receiving the signal emitted by the reference drone, the absolute position of each drone12for which a relative position has been determined by the receiver drone.

The absolute position of the drone12corresponding to the identifier of each received signal is determined as a function of the absolute position of the reference drone and the relative positions determined in the determination step130.

With the matrices providing the site and bearing of the drones seen, the relative position of each drone is deduced in 3 dimensions and absolutely, if one of the drones is referenced absolutely.

Advantageously, for each drone12of the swarm10comprising a sensor22configured to detect the presence of objects in the field of the sensor22, the data exchange method further comprises a step150of detecting objects in the field of the sensor22. The detection step150occurs, for example, at the same time as the receiving step110.

For each detected object, the data exchange method comprises a step160of classifying the object as foreign to the swarm10of drones12when no signal is received from the object or when the signal received for the object does not comprise the identifier of a drone12in the swarm10. Otherwise, the object is considered to be a drone12belonging to the swarm10of drones12.

Advantageously, when an object is classified as foreign to the swarm10of drones12, an alarm is sent to a user piloting or monitoring the drone12remotely.

As such, the data exchange method allows for the identification and tracking, by each drone in a swarm, of other drones in the swarm located in the drone's immediate environment. More generally, the data exchange method allows for communication between drones in a swarm.

The method also makes it possible to avoid the use of radio frequency waves and is therefore more robust to jamming. It also has the advantage of not requiring a GPS tracking device.