The present invention relates, in general, to the representation of graphic images on a sur- face of a support.

US 2015/344136 describes an aerial vehicle adapted to perform the painting of the walls of a building, controlled by means of a mobile processing device which may be installed onboard the aerial vehicle or possessed by a user.

US 2015/274294 and US 2016/082460 describe a system based on an unmanned aerial vehicle, arranged to paint a surface of a structure.

DE 10 2015 008086 relates to a system for working on a surface which may comprise two or more drones, of which the one receiving a control device assumes the role of master and the remaining drones assume the role of slaves.

It is the object of the present invention to provide an efficient, fast, accurate and safe system for representing graphic images on a surface of a support, in particular, an extended support surface, such as, for example, a wide panel or vertical wall.

According to the present invention, such object is achieved by virtue of a system for representing a graphic image on a surface of a support by means of at least one autonomous flight aircraft, also known as a drone, and, in particular, by means of the use of at least one autonomous flight aircraft or drone for representing at least one image or a text character on a surface by spraying a coating substance, such as, for example, a paint, towards the surface itself, i.e. without the contact of an instrument with the surface.

Autonomous flight aircraft, commonly known as drones, are a class of aircraft without the presence of a human pilot on-board. They are a component of unmanned aircraft systems, which typically include an unmanned aircraft, a ground controller and a communication system between the two. The flight of an unmanned aircraft may occur with different de- grees of autonomy: either under the remote control by a human operator, or autonomously by means of on-board processing systems.

Unmanned aircrafts, and autonomous flight aircrafts in particular, have been designed, built and used for decades primarily for military use, in repetitive or dangerous missions or in hazardous or contaminated environments, but only recently the scope of use thereof has been expanded to commercial applications. Nowadays, civilian drones are increasingly employed for hobbies, competitions, experimental purposes, for aerial shots of events or for the transport of small objects.

More specifically, the present invention has the features referred to in claim 1.

Particular embodiments are the subject of the dependent claims, the content of which is to be understood as an integral part of the present description.

In summary, the present invention is based on the principle of using autonomous flight aircrafts to create a system for representing images on a surface of a support, adapted to acquire an image to be represented from an image support, such as an electronic file, or a physical carrier provided by at least one user, and to translate it into one or more flight paths of at least one drone by means of a dedicated programming, for example, to represent an artistic work on a surface, in which the drone is equipped with spraying means to direct a coating substance (paint) on the surface of the support during at least some steps of the flight trajectory thereof. To achieve the aforesaid object, a system for positioning the aircraft with respect to the support surface and an aircraft driving system for the autonomous drive of the aircraft along at least one trajectory predetermined with respect to said surface are employed, so as to carry out the deposition desired. Further features and advantages of the invention will be more fully described in the following detailed description of an embodiment thereof, given by way of non-limiting example, with reference to the accompanying drawings, in which: Figure 1 shows a block diagram indicative of the general architecture of the system of the invention;

Figure 2 shows an exemplary representation of an autonomous flight aircraft fleet in front of a support surface with which an aircraft positioning system is associated;

Figure 3 shows a block diagram in which a flow of operations for the management of the system of the invention is represented under a condition of control of the movement of at least one aircraft along at least one spatial flight trajectory including a path of application of the coating substance on the surface of the support shown in Figure 2; and

Figure 4 shows a block diagram in which a flow of operations for the management of the system of the invention is represented under a condition of control of the movement of at least one aircraft along a charging trajectory.

In the Figures, identical or functionally equivalent elements or components have been indicated with the same references.

With reference to Figures 1 and 2, 100 indicates processing means arranged to calculate at least one spatial flight trajectory of at least one autonomous flight aircraft (which may be an aircraft belonging to an aircraft fleet), such as a drone, indicated with 200, adapted to hover at least in one semi-space in front of a surface S of a support (shown in Figure 2), at a distance therefrom, and equipped with spraying means arranged to selectively apply at least one coating substance, such as a paint, on at least one portion of said surface. 300 indicates transceiver means of a positioning system associated with the aforesaid support surface and adapted to detect the position of said at least one aircraft with respect to a predetermined reference system associated with the support surface. 400 indicates an interface for the direct interaction in real time with the system by at least one user; 500 indicates a database of data collected and stored starting from one or more users, for example, information on the positioning of the users themselves or texts and/or graphics voluntarily transmitted by them; 600 indicates any set of pre-existing data, which may be represented in the form of graphic signs.

Processing means 100 are coupled at the input to one or more users U by means of the user interface 400, or a respective user interface for each user, and/or to a database 500 for the collection of data generated by the users U and/or to a set of pre-existing data 600, i.e., not generated in real time, to receive data representative of one or more surface areas or lines on which to apply a coating substance, for example, data indicative of one or more lines, of an image or of one or more text characters (hereinafter overall indicated as graphic image) to be reproduced by applying a paint or a similar coating substance on the support surface S, which may be a wall or a panel, pre-existing or arranged for the purpose.

These data are converted into flight instructions for one or more drones 200 from a flight trajectory calculation module 110. A fleet management module 120 receives one or more trajectories as input from the flight trajectory calculation module 110. If necessary, the fleet management module 120 divides the graphic image to be reproduced in separate portions, for example portions corresponding to the components of a composite image, each of which is provided separately by a user U, by means of a respective interface 400, and assigns the respective reproduction thereof to each drone of a fleet of drones 200, controlling the assignment to each drone of a portion of trajectory, the movement and the speed of flight of the drones to avoid collisions, as well as the activation of the spraying means, advantageously for the entire duration of the power supply battery of the drone. The communication between processing means 100 and drones 200 occurs by means of a wireless data connection. Preferably, a graphical user interface 130 allows to display and control the fleet management module 120 and to configure variables such as the reproduction time and the size of the graphic image.

The graphic images or the components of a composite image preferably include continuous lines or curves, of any shape, closed or open, with an essentially one-dimensional devel- opment, whereby the flight trajectory of a drone follows - for at least one section - the image to be reproduced generated by a user, unlike the case in which a coating substance is to be applied on a surface area whereby the flight trajectory of a drone does not follow the image to be reproduced, and the movement of the drone is controlled to cover an area (for example, by means of a scanning technique) so that it applies a coating substance within a predetermined contour.

The (Each) drone 200 is a highly stable autonomous flight aircraft, equipped with a posi- tioning transmission device 210, on-board processing means 220 and a flight control module 240. The processing means 220 comprise a positioning engine, a trajectory management module, a spraying means management module and a collision control module. Each drone 200 is coupled to a positioning system, for example an ultra-broadband positioning system, comprising at least one mobile transceiver installed on the drone and at least one fixed transceiver, preferably at least three fixed transceivers indicated with 300 and associated with the support surface in positions predetermined with respect to a reference system of the aforesaid surface, each of which is arranged to receive at least one iden- tification signal from the drone, and a positioning engine arranged to determine the position of the drone with respect to the support surface based on the data received from the transceivers, integrated with the on-board processing means 220. Advantageously, the transceivers 300 are associated with the support surface S so as to guarantee the reception of an identification signal by each drone at at least one fixed transceiver when the drone is located close to the surface, for example, they are arranged at the vertices of the surface. Each drone is programmed to irradiate an own identification signal by means of the positioning transmission device 210 according to a predetermined radio signalling packet adapted to be exchanged with the fixed transceivers. The fixed transceivers 300 are adapted to detect the flight time of the signal transmitted by the positioning transmission device 210, i.e., the distance travelled by the signal transmitted by the positioning transmission device 210, and this allows to accurately position the drone in the three dimensions with respect to a predetermined reference system of the support surface, i.e., in the semi-space in front of the support surface itself. A typical positioning accuracy is of the order of twenty centimetres.

Ultra-broadband positioning technology uses an extremely low signal energy level for short-range communications and wide bandwidth over a large portion of the radio spectrum. The short duration of the pulses carrying the positioning signal and the high data transmission speed, in addition to the accuracy of the positioning and the low power con- sumed, make this technology suitable for applications in outdoor positioning systems, within limited spaces, in real time. The drone 200 is equipped with ultrasonic sensors 230 which provide signals indicative of the distance of the drone from obstacles, both moving (other drones) and fixed, including the distance from the support surface, to the collision control module of the on-board processing means 220, so as to detect and keep constant, with an extreme accuracy, the dis- tance of the drone with respect to the support surface and advantageously guarantee the perpendicularity of the spraying means with respect to such surface.

The flight control module 240 - which forms the driving means of the aircraft - is arranged to receive the drone positioning signals processed by means of the positioning module and the trajectory management module of the on-board processing means 220. The flight control module 240 is arranged to follow a flight trajectory communicated by the fleet management module 120. It is - together with the on-board processing means 220 - the automatic pilot of the drone. In particular, it manages the movement of the drone (the engines) based on the current position thereof and on the subsequent coordinates of the intermediate destination of the flight trajectory calculated. The drone is continuously positioned according to the position thereof with respect to the predetermined reference system, and therefore with respect to the support surface, and the flight control module 240 corrects the flight trajectory thereof when it is influenced by external factors, for example, strong wind. According to the position, the trajectory management module controls the spraying means 250 to release or suspend the release of a coating substance towards the surface. This occurs by means of the spraying means management module, arranged to accurately control the release times of the surface coating substance. A set of rules is applied to control the spraying of the coating substance, for example, a paint. For example, different widths of the stroke, i.e., of the curve (and therefore of the surface coating, i.e., of the colouration, in case of coloured paint) may be obtained by varying the spraying distance of the drone with respect to the surface. For the objects of the invention, each drone is equipped with at least one paint tank, accommodated in a designated seat, but additional seats are also possible for additional paint tanks, for example, refills or paints of different colours. Alternatively, multiple drones may be used to reproduce a multi-colour graphic image.

By virtue of the integration of the aforesaid technologies, the system in accordance with the invention may autonomously reproduce one or more graphic images provided by at least one user, in the form of an electronic file or a physical carrier.

Advantageously, the trajectory calculated for each drone is the minimum path calculated within an operating area of the drone for drawing a line or covering a surface area without overlapping and without excessive switching between a condition of active spraying means and deactivated spraying means.

The trajectories of more drones are calculated in an integrated manner so that no intersections of trajectories are provided for at the same time or in a short period of time, which would cause the drones to collide with one another.

In the case of drones reaching spatial positions adjacent within a protection volume, the positioning means would detect the presence thereof by comparison with the respective positioning coordinates and would communicate to the driving means a warning signal as a consequence to which the driving means may stop the movement of a drone, preferably the most discharged one, or move a drone to a predetermined temporary parking position.

In the case in which the fleet management module 120 communicates one or more flight trajectories adapted to allow the creation of a composite image, including lines or areas of images generated by multiple users, the trajectories of said one or more drones are calculated to perform in sequence the lines or areas of image generated by multiple users starting from a first predetermined trajectory followed by subsequent trajectories, in which each subsequent trajectory is selected from the set of trajectories adapted to allow the creation of the composite image, as the trajectory whose initial point is closer to the final point of the prior trajectory.

In a preferred embodiment, a base and parking station for non-operating aircrafts is provided for, provided with processing means, such as, for example, a portable computer, a power and electric charging source and a stock of substances to feed the spraying means, for example, to charge or replace the tanks of substance on-board each aircraft. All these components, together with the positioning means and the drones, may be easily grouped into a transportable kit, for example, in a van, to allow the reproduction of graphic images in al- ways different places.

Figure 3 shows a block diagram in which a flow of operations for the management of the system of the invention is represented under a condition of control of the movement of at least one aircraft along a spatial flight trajectory including a path of application of the coating substance on the surface of the support shown in Figure 2.

Input data representative of a line or area of the surface S on which to spray the coating substance, for example, data of one or more images to be reproduced, are received by the trajectory calculation module 110 in vector form, converted into a set of Cartesian coordinates mapped to the width of the area and translated into one or more target trajectories provided as input to the fleet management module 120. The fleet management module 120 calculates a trajectory from a starting point A to an arrival point B and communicates it to the trajectory management module of the drone which it instructed to follow such trajecto- ry, and the latter consequently controls the flight control module 240. The starting point A is the current positioning point of the drone in the predetermined reference system of the surface S, which is calculated by the positioning engine based on the signal received at the mobile transceiver starting from the detection of the positioning transceivers 300, and transmitted to the trajectory management module.

Figure 4 shows a block diagram in which a flow of operations for the management of the system of the invention is represented under a condition of control of the movement of at least one aircraft along a charging trajectory. In the processing means 100, the flight trajectory calculation module 110 acquires from the fleet management module 120 the current coordinates of the drone and provides the fleet management module 120 with the coordinates of a charging station (or base) R in the predetermined reference system, previously acquired by a transmission device associated with the charging station, analogous to the transmission devices on-board the drones. For exam- pie, the fleet management module 120 requires the coordinates of the charging station R when the flight control module 240 of the drone communicates a state of residual flight autonomy (residual electric charge of the propulsion power batteries) of the drone below a predetermined threshold, or when the spraying means management module on-board the drone communicates a condition of residual quantity of coating substance, below a predetermined threshold. In both cases, the fleet management module 120 calculates the trajectory from the current position to the charging station R and communicates it to the trajectory management module on-board the drone, which provides the coordinates for reaching the charging station to the flight control module 240.

It should be noted that the embodiment proposed for the present invention in the foregoing discussion is given purely by way of explanation and not by way of limitation of the pre- sent invention. A technician skilled in the art may easily implement the present invention in different embodiments which do not depart from the principles outlined herein, and are therefore included in the present patent.

This applies, in particular, to the possibility that the coating substance is a cleaning or pro- tective substance applied to a portion of the surface of a facade of a building, for example the wall portion of the facade.

Naturally, without prejudice to the principle of the invention, the embodiments and the construction details may be widely varied with respect to what has been described and shown purely by way of non-limiting example, without thereby departing from the scope of protection of the invention defined by the appended claims.