Title: REMOTE-CONTROL AIRCRAFT MAINTENANCE SYSTEM

Technical field of the invention

The present invention relates to a remote-control aircraft maintenance system, for example for the cleaning of surfaces difficult to reach or of dangerous environments, and a related maintenance method.

State of the art

Currently, the ordinary maintenance (e.g., cleaning, etc.) and extraordinary maintenance (e.g., painting, surface treatment, etc.) of internal or external surfaces difficult to reach due to the high height from the ground, such as ceilings and/or mezzanines (e.g., of a shed), grates or water drainage channels, under-eaves, eaves, under-roofs, roofs, chimneys, balconies and/or window sills of skyscrapers (e.g., 4-10 floors), monuments, etc., is performed by qualified operators.

For reaching the surface of interest, the operators require appropriate equipment, such as ladders, scaffoldings, mobile elevators and/or frameworks, as well as suitable fall-arrest safe devices.

Once reached the surface, the operators carry out the required operations, such as the removal of dirt from the surfaces (e.g., liquids, dust, debris, etc.) using vacuums, blowers, shredders, mechanical brushes and/or washers, or the lying of a treatment layer (paint, polish, anticorrosive, antirust, etc) or other maintenance operations. Summary of the invention

The Applicant has realized that the known methods for ordinary and extraordinary maintenance of surfaces difficult to reach or of dangerous environments require high costs and/or production times, due to labour costs and/or arrangements costs and times for the necessary equipment, as well as involve risks for the operators, such as risks of falling from heights and/or risks deriving from the dangerous environments, such as chemically and/or radioactively contaminated environments, or deriving from the substances to be removed or used for the maintenance.

Therefore, the Applicant has faced the problem of carrying out a (ordinary or extraordinary) maintenance of surfaces difficult to reach or of dangerous environments, in a safe way for the operators and with limited time and costs. According to the Applicant, the above problem can be solved by a remote-control aircraft maintenance system and a related maintenance method according to the attached claims and/or according to one or more of the following embodiments. According to an aspect the invention relates to a remote-control aircraft maintenance system comprising:

- a main frame and at least four propellers rotatably mounted on the main frame; and

- a first command and control electronic unit programmed and configured for controlling a flight of the maintenance system.

Preferably the maintenance system comprises: a maintenance device and a coupling system for mechanically fixing the maintenance device to the main frame, wherein said coupling system comprises three motorized rotating supports interposed in series between said main frame and said maintenance device, wherein respective rotation axes of each pair of consecutive rotating supports are perpendicular to each other and wherein said coupling system is structured for keeping unchanged a space orientation of said maintenance device in face of a variation of space orientation of said main frame.

Preferably said maintenance device comprises a mechanical arm having a distal end, a fluid pump and a conduit which develops along said mechanical arm to put said fluid pump in fluid communication with a distal end mouth of the conduit placed at said distal end of the mechanical arm.

According to an aspect the invention relates to a maintenance method of a surface comprising:

- flying the aircraft maintenance system according to the former aspect;

- bringing the aircraft maintenance system close to said surface and operating said mechanical arm for placing said distal end in close proximity with said surface;

- operating said fluid pump for sucking fluids from said surface and/or for ejecting fluids onto said surface.

According to the Applicant, the presence of a maintenance device which comprises a mechanical arm having a distal end, a fluid pump and a conduit which develops along the mechanical arm to put the fluid pump in fluid communication with a distal end mouth of the conduit placed at the distal end of the mechanical arm allows carrying out the treatment of the surface of interest, bringing the distal end mouth of the conduit close to the surface so that the fluid pump can carry out some surface treatment operations. Furthermore, according to the Applicant, the fact that the maintenance device is comprised in a remote-control aircraft maintenance system allows carrying out the maintenance in a safe way for the operators, and with low maintenance times and costs, since, by controlling the flight of the maintenance system, it is possible quickly positioning the maintenance device at the surfaces difficult to reach or in the dangerous environments of interest, without the use of equipment and without the operators having to directly carry out the maintenance of the surface.

Finally, according to the Applicant, the presence of a coupling system for mechanically fixing the maintenance device to a main frame of the maintenance system, comprising three motorized rotating supports interposed in series between the main frame and the maintenance device wherein respective rotation axes of each pair of consecutive rotating supports are perpendicular to each other, and wherein the coupling system is structured for keeping unchanged a space orientation of the maintenance device in face of a variation of space orientation of the main frame allows the effective operation of the maintenance system since it is possible keeping the distal end mouth of the conduit fixed in a suitable working position on the surface to be treated, even in face of variations in the space orientation of the main frame (for example due to wind blows or variations in the a flying attitude).

The present invention in one or more of the aforesaid aspects can have one or more of the following preferred features.

It is defined “oriented direction of the conduit” a direction that goes from the distal end mouth of the conduit to the fluid pump.

The terms “upstream” and “downstream” used in the following refer to the flux direction of the fluid considered.

Preferably said fluid pump is structured for sucking fluids along the conduit concordantly with said oriented direction of the conduit and/or for ejecting fluids along the conduit in direction opposite to said oriented direction of the conduit.

In this way it is possible removing solid debris and/or liquids from the surface of interest and/or spraying a fluid (e.g., powders or liquids) on the surface of interest. Preferably said maintenance device comprises a second command and control electronic unit operatively connected to said fluid pump for sending an actuation signal to said fluid pump for sucking fluids and/or for ejecting fluids along said conduit. Preferably said fluid pump comprises a fluid suction unit and a fluid ejection unit distinct from each other. In this way it is also possible performing at the same time the suction and the ejection of fluids.

Preferably said fluid suction unit comprises a rotary pump. Preferably said fluid ejection unit comprises a compressor.

Preferably said second command and control electronic unit is operatively connected to said fluid suction unit and to said fluid ejection unit for sending a respective actuation signal to said fluid suction unit and to said fluid ejection unit for respectively sucking fluids and/or ejecting fluids along said conduit.

Preferably said conduit comprises a suction conduit which develops along said mechanical arm to put said fluid suction unit in fluid communication with a suction mouth of the suction conduit forming part of said distal end mouth of the conduit. Preferably said conduit comprises an ejection conduit which develops along said mechanical arm to put said fluid ejection unit in fluid communication with an ejection mouth of the ejection conduit forming part of said distal end mouth of the conduit.

In this way it is possible providing a separate fluid line for the suction and the ejection of fluids. For example, it is possible ejecting air from the ejection mouth towards the surface for raising debris and/or liquids and at the same time sucking from the suction mouth for removing the raised debris and/or liquids.

Preferably said maintenance device comprises a first tank for a treatment fluid (e.g., air, aqueous cleaning solution, paint, decontaminant and/or anti-radiation solution) in fluid communication with said ejection unit for ejecting said treatment fluid along said ejection conduit.

Preferably said first tank is interposed between said ejection conduit and said fluid ejection unit.

In this way it is possible ejecting the treatment fluid on the surface, for example for cleaning it or covering it with a treating solution.

Preferably said maintenance device comprises an inlet mouth placed upstream of said fluid ejection unit. In this way it is possible allowing the operation of the fluid ejection unit.

Preferably said maintenance device comprises a filter, more preferably an EPA filter, interposed between said suction conduit and said fluid suction unit. In this way it is possible filtering the fluid, typically air, which is sucked through the conduit for separating the solid and/or liquid part suspended in the sucked fluid.

Preferably said maintenance device comprises a second tank in fluid communication with said fluid suction unit for storing a solid and/or liquid part suspended in a fluid sucked by said fluid suction unit.

In one embodiment said second tank coincides with said filter.

In one embodiment said second tank is vertically below said filter. In this way the solid and/or liquid part suspended in the sucked fluid fall by gravity in the second tank.

Preferably said maintenance device comprises an expulsion mouth placed downstream of said fluid suction unit. In this way it is possible expelling the sucked fluid after that it is filtered for avoiding environmental contaminations.

Preferably said maintenance device comprises a secondary frame.

Preferably at least one of, more preferably all, said fluid pump, said first and second tank and said filter are rigidly fixed to said secondary frame. In this way the encumbrance of the maintenance device is reduced.

Preferably said coupling system comprises a gyroscopic sensor integral with said maintenance device, more preferably integral with said secondary frame.

Preferably said coupling system comprises a stabilization electronic unit operatively connected to said gyroscopic sensor for receiving an orientation signal of the maintenance device.

Preferably said stabilization electronic unit is programmed and configured for operating said three motorized rotating supports as a function of said orientation signal for keeping unchanged said space orientation of said maintenance device. Preferably a first rotating support of said three rotating supports is proximal to said main frame and has the respective rotation axis perpendicular to a lying plane of said propellers.

Preferably the coupling system comprises a (adjustable) first L-shaped arm which extends from said first rotating support to a second rotating support of said three rotating supports.

Preferably the coupling system comprises a (adjustable) second L-shaped arm which extends from said second rotating support to a third rotating support of said three rotating supports.

The reference configuration of the maintenance system is defined as the configuration wherein the three rotation axes of the rotating supports are exactly perpendicular to each other. The terms vertical and horizontal and the like refer to an orientation of the maintenance system wherein the lying plane of the propellers is horizontal.

Preferably said mechanical arm is an articulated arm. In this way it is possible placing the distal end mouth of the conduit as desired.

Preferably said mechanical arm comprises a continuous series of (rigid) elements mechanically connected to each other, wherein at least one element of the series has one rotational degree of freedom with respect to an adjacent element. In this way, according to the Applicant, the mechanical arm is able to adjust itself to the actual conformation and/or position of the surface or the environment of interest.

Preferably said series of elements comprises at least three elements and/or no more than six elements, more preferably four elements. The Applicant has in fact noted that this number of elements is sufficient to allow the mechanical arm to reach the surface or the environment of interest, without excessively complicating the maintenance device.

Preferably a first element of said series of elements is rigidly fixed, more preferably directly, to the secondary frame.

Preferably said first element has a main development direction substantially parallel to a lying plane of the propellers.

In this way the mechanical arm protrudes from an encumbrance of the main frame. Preferably a second element of said series of elements, contiguous to the first element, has a respective main development direction perpendicular to the one of the first element, more preferably perpendicular to the lying plane of the propellers. In this way the end part of the mechanical arm protrudes from the lying plane of the propellers.

Preferably the second element has one rotational degree of freedom with respect to the first element with rotation axis perpendicular to the lying plane of the propellers. Preferably the mechanical arm comprises a first rotating actuator interposed between the first and the second element and having said rotation axis.

In this way the end of the mechanical arm rotates on the horizontal plane.

Preferably a third element of said series of elements, contiguous to the second element, has a respective main development direction perpendicular to the one of the second element, more preferably parallel to the main development direction of the first element. In this way the end part of the mechanical arm can protrude beyond the encumbrance of the propellers.

Preferably the third element is integral with the second element.

Preferably a fourth element of said series of elements, contiguous to the third element, has one rotational degree of freedom with respect to the third element with respective rotation axis parallel to the lying plane of the propellers and perpendicular to the respective development direction of the third element.

Preferably the mechanical arm comprises a second rotating actuator interposed between the third and the fourth element and having said respective rotation axis.

In this way the end of the mechanical arm rotates on the horizontal plane.

Preferably said fourth element is telescopic, more preferably comprises two sub elements telescopically coupled.

Preferably the fourth element comprises a linear actuator for adjusting a length of said fourth telescopic element.

Preferably the second command and control unit is operatively connected to one or more of said first and second rotating actuators and said linear actuator for sending a respective command signal.

Preferably one or more of said elements are rectilinear.

Preferably one or more of said elements has a length greater than or equal to 5 cm, more preferably greater than or equal to 10 cm, and/or less than or equal to 50 cm, more preferably less than or equal to 40 cm.

Preferably said maintenance system comprises a further gyroscopic sensor integral with said main frame and operatively connected to said first command and control electronic unit for sending a further orientation signal representative of said space orientation of said main frame.

Preferably said first command and control electronic unit is programmed and configured for actuating said propellers as a function of a further orientation signal for stabilizing the flight of the aircraft maintenance system.

In this way, as known in the art, it is possible stabilizing the flight of the aircraft maintenance system with respect to any external perturbations, for example due to weather conditions and/or to wind.

Preferably said maintenance system comprises a laser sensor structured for detecting a distance from an obstacle by emission of a laser beam and measurement of a respective time of flight and operatively connected to said first command and control electronic unit for sending a first detection signal representative of said distance. In this way, it is possible limiting the collision risks of the maintenance system against any obstacles close to the surface that has to be treated.

Preferably said first command and control electronic unit is programmed and configured for limiting a flight movement of said aircraft maintenance system as a function of said first detection signal.

In this way it is possible preventing the aircraft maintenance system from hitting obstacles close to the surface, even in case of a mistake in the flight command of the maintenance system.

Preferably said maintenance system comprises an altimetric pressure sensor structured for detecting an altitude of said maintenance system by measurement of a pressure difference acting on the altimetric pressure sensor and operatively connected to said first command and control electronic unit for sending a second detection signal representative of said altitude. In fact, the external pressure acting on the altimetric pressure sensor generates a deformation of the sensor membrane proportional to the pressure difference with the internal pressure of the sensor. This deformation of the membrane is subsequently converted (e.g., by a transducer) into an electric signal representative of the detected pressure difference. Depending on altimetric pressure sensor type, the internal pressure of the sensor can be: the vacuum in case of absolute pressure sensors (i.e. , MAP), the atmospheric pressure in case of relative pressure sensors, an arbitrary pressure value that must be measured in case of differential pressure sensors (i.e., MDP).

In one embodiment said maintenance system comprises an ultrasonic sensor structured for detecting an altitude of said maintenance system by emission of an ultrasonic acoustic wave and measurement of a respective return time. In other words, the ultrasonic sensor performs the function of the aforesaid altimetric pressure sensor.

Preferably said first command and control electronic unit is programmed and configured for stabilizing the flight of said aircraft maintenance system keeping the flight of said aircraft maintenance system at a reference altitude as a function of said second detection signal. In this way it is possible to provide the aircraft maintenance system with an instrument capable of measuring the altitude at which the maintenance system is located and in the event of altitude changes due for example to wind gusts and/or other external causes, report the maintenance system at the desired altitude. Preferably said aircraft maintenance system comprises a camera structured for acquiring images during the flight of the aircraft maintenance system and operatively connected to said first command and control electronic unit for transmitting said images to a receiving device (e.g., a computer, a monitor, a tablet).

In this way it is possible to transmit to the receiving device the images acquired by the camera in order to be able to pilot the aircraft maintenance system and/or perform the maintenance of the surface of interest in an accurate manner.

Preferably said camera is rigidly coupled to said mechanical arm, more preferably to said fourth element.

Preferably said camera is rigidly coupled to said mechanical arm near to said distal end.

Typically, said maintenance system comprises an electric energy accumulator, for example for powering the first and second electronic command and control units.

Brief description of the drawings Figure 1 schematically shows a perspective view of a remote-control aircraft maintenance system according to an embodiment of the present invention;

Figure 2 schematically shows a first lateral view of the remote-control aircraft maintenance system of Figure 1 ;

Figure 3 schematically shows a second lateral view, perpendicular to the first lateral view, of the remote-control aircraft maintenance system of Figure 1 ;

Figure 4 shows a flow chart diagram of a maintenance device according to the present invention.

The features and the advantages of the present invention will be further clarified by the following detailed description of some embodiments of the present invention, presented by way of non-limiting example, with reference to the attached figures. Figures 1 , 2 and 3 schematically show a remote-control aircraft maintenance system 100, comprising a main frame 90 having four propellers 40 rotatably mounted thereon and a first command and control electronic unit 70 programmed and configured for controlling a flight of the maintenance system 100.

In the embodiment shown, the main frame 90 consists of a quadcopter drone, i.e. , having four motorized propellers.

In other not shown embodiments, the main frame can consist of different drone types (e.g., hexa-copter and/or octa-copter drone), or other types of remote-control aircraft. Exemplarily the first command and control electronic unit 70 is mounted on the main frame 90. For example, the first command and control electronic unit 70 is an FCB board (Flight Control Board) of the quadcopter drone, i.e., the board which, through the monitoring of the physical parameters associated with the flight thanks to the connection with different sensors, allows the stabilization and adjustment of the flight as a function of the detected parameters, as known in the art.

For example, the following are typically connected to the FCB board:

- a gyroscopic sensor 105 structured for detecting a variation of space orientation of the main frame 90;

- a laser sensor 106, for example of the rotary type, structured for detecting a distance of the maintenance system 100 from an obstacle by emission of a laser beam and measurement of a respective time of flight;

- an altimetric pressure sensor 107 structured for detecting an altitude of the maintenance system 100 by measurement of a pressure difference acting on the altimetric pressure sensor 107.

Preferably the aircraft maintenance system 100 comprises a maintenance device 99 (schematically shown in figure 4) comprising a mechanical arm 1 (schematically shown in figures 1 and 2) having a distal end 25, a fluid pump 3, 4 and a conduit 5, 6 which develops along the mechanical arm 1 to put the fluid pump 3, 4 in fluid communication with a distal end mouth 2 of the conduit 5, 6 placed at the distal end 25 of the mechanical arm 1.

The "oriented direction of the conduit" is defined as a direction that goes from the distal end mouth 2 of the conduit 5, 6 to the fluid pump 3, 4. The oriented direction of the conduit is schematically indicated by the dashed arrows in figure 4.

Exemplarily the fluid pump 3, 4 comprises a fluid suction unit 4 and a fluid ejection unit 3 distinct from each other.

In one not shown embodiment, the fluid suction unit and the fluid ejection unit coincide, for example are made by a single operating unit. Even in this embodiment, through suitable adaptations to the fluid line (such as for example a recirculation conduit for the sucked fluid), it is also possible simultaneously sucking and ejecting fluids.

Exemplarily the conduit comprises a suction conduit 5 which develops along the mechanical arm 1 to put the fluid suction unit 4 in fluid communication with a suction mouth 2a of the suction conduit 5 forming part of the distal end mouth 2 of the conduit.

Exemplarily the conduit comprises an ejection conduit 6 which develops along the mechanical arm 1 to put the fluid ejection unit 3 in fluid communication with an ejection mouth 2b of the ejection conduit 6 forming part of the distal end mouth 2 of the conduit.

As schematically shown in figure 4, the ejection mouth 2b can physically protrude beyond the suction mouth 2a (e.g., the ejection conduit is longer than the suction conduit at the distal end mouth) for favouring the lifting of debris from the surface and their simultaneous suction.

Exemplarily the fluid suction unit 4 comprises a rotary pump. Exemplarily the fluid ejection unit 3 comprises a compressor.

Exemplarily the maintenance device 99 comprises a second command and control electronic unit 18 operatively connected to the fluid suction unit 4 and to the fluid ejection unit 3 for sending a respective actuation signal to the fluid suction unit 4 and to the fluid ejection unit 3 for respectively sucking fluids along the suction conduit 5 (in a direction concordant with the oriented direction of the conduit) and/or for ejecting fluids along the ejection conduit 6 (in a direction discordant with the oriented direction of the conduit).

Exemplarily the second command and control electronic unit 18 is in communication with the aforesaid fluid suction and ejection units by a respective communication line, for example a wire line (schematically shown in figure 4 by the dashed lines). Exemplarily the maintenance device 99 comprises a first tank 7 for a treatment fluid, for example air, aqueous cleaning solution, paint, fixing agent, decontaminating solution and/or anti-radiation solution, in fluid communication with the ejection unit 3 for withdrawing the treatment fluid from the tank, sliding it along the ejection conduit 6 and ejecting it from the ejection mouth 2b.

Exemplarily the first tank 7 is interposed between the ejection conduit 6 and the fluid ejection unit 3 for being pressurized by the compressor 3.

Exemplarily the maintenance device 99 comprises an inlet mouth 19 placed upstream of the fluid ejection unit 3 for allowing the air entry and the compressor operation.

In one not shown embodiment, the fluid ejection unit is interposed between the ejection conduit and the first tank. In this embodiment it is possible operating the fluid ejection unit for generating a vacuum with consequent suction of the treatment fluid towards the ejection conduit, which is then ejected towards the surface of interest. Exemplarily the maintenance device 99 comprises a filter 21, exemplarily an EPA filter, interposed between the suction conduit 5 and the fluid suction unit 4.

Exemplarily the maintenance device 99 comprises a second tank 8 in fluid communication with the suction unit 4 for storing a solid and/or liquid part suspended in a fluid sucked by the suction unit 4 (for example dust, debris or drops of a contaminated liquid suspended in airflow).

Exemplarily the second tank 8 is vertically below the filter 21.

In one not shown embodiment, the second tank coincides with the filter. In this embodiment, the suction line is similarly structured as the one of common household vacuum cleaners.

Exemplarily the second tank 8 is removable by external action (for example a manual unscrewing and/or with a tool) by an operator for allowing an easy elimination of the solid and/or liquid part stored in the second tank following the suction.

Exemplarily the maintenance device 99 comprises an expulsion mouth 20 placed downstream of the fluid suction unit 4, for allowing the escape of the filtered air sucked through the suction conduit 5.

Exemplarily the maintenance device 99 comprises a secondary frame 80.

In the shown embodiment, the secondary frame 80 is a prismatic box-like body for containing the fluid suction unit 4, the fluid ejection unit 3, the second command and control electronic unit 18, the filter 21, the first 7 and the second tank 8 inside a compact volume for reducing the overall encumbrance of the maintenance system 100. Alternatively, the secondary frame (such as the main frame) can have any shape and structure, for example a reticular structure.

Exemplarily both the inlet mouth 19 and the ejection mouth 20 are formed on the body of the secondary frame 80. With reference to figure 2, the structure of the mechanical arm 1 is described below. The mechanical arm can have a tubular structure (as exemplarily shown), or a reticular structure.

Exemplarily the mechanical arm 1 is an articulated arm.

Exemplarily the mechanical arm 1 comprises a continuous series of rigid elements, exemplarily comprising four elements, mechanically connected to each other. Exemplarily a first element 1a of the series of elements is rigidly fixed, for example directly, to the secondary frame 80.

Exemplarily the first element 1a has a main development direction substantially parallel to a lying plane 200 of the propellers.

Exemplarily a second element 1b of the series of elements, contiguous to the first element 1a, has a respective main development direction perpendicular to that of the first element 1 a, for example perpendicular to the lying plane 200 of the propellers. Exemplarily the second element 1b has a rotational degree of freedom with respect to the first element 1a with rotation axis 250 (shown in Figure 2) perpendicular to the lying plane 200 of the propellers.

Exemplarily the mechanical arm 1 comprises a first rotating actuator 11 interposed between the first 1a and the second element 1b, which allows the rotation of the second element 1b with respect to the first element 1a about the rotation axis 250. Exemplarily a third element 1c of the series of elements, contiguous to the second element 1b, has a respective main development direction perpendicular to that of the second element 1b, for example parallel to the development direction of the first element 1a.

Exemplarily the third element 1c is integral with the second element 1b.

In one not shown embodiment, the maintenance device comprises a further rotating actuator interposed between the second and third element.

In this embodiment, a rotation axis of the further rotating actuator is parallel to the lying plane of the propellers and perpendicular to the respective main development direction of the third element. In this way the mechanical arm can even better adapt to the conformation of the surface of interest, allowing the distal end mouth of the conduit to position itself at the surface.

Exemplarily a fourth element 1d of the series of elements (e.g., an end element), contiguous to the third element 1c, has a rotational degree of freedom with respect to the third element 1c with respective rotation axis 251 (shown in figure 3) parallel to the lying plane of 200 of the propellers and perpendicular to the respective development direction of the third element 1c.

Exemplarily the mechanical arm 1 comprises a second rotating actuator 12 interposed between the third 1c and the fourth element 1 d, which allows the fourth element 1d to rotate with respect to the third element 1c about the respective rotation axis 251.

For example, the first 11 and the second rotating actuator 12 (as well as possibly the further rotating actuator) are blade rotating actuators of the type marketed by RS Components S.r.l.

Exemplarily the fourth element 1d is telescopic (not shown), for example it comprises two sub-elements telescopically coupled and a linear actuator (not shown) for adjusting a length of the fourth telescopic element.

Exemplarily the second command and control unit 18 is operatively connected to the first rotating actuator 11, to the second rotating actuator 12 and to the linear actuator for sending a respective command signal for operating the rotation of the first 11 and second rotating actuator 12 and regulating the length of the fourth telescopic element 1d.

Exemplarily the second command and control electronic unit 18 is in communication with the aforesaid first 11 and second rotating actuator 12 and linear actuator by a respective communication line, for example a wires line. Exemplarily the wires of each communication line are placed within a diameter of the mechanical arm 1.

The maintenance system 100 also comprises a coupling system 50 (shown in Figures 1 and 3) comprising three motorized rotating supports 30a, 30b, 30c interposed in series between the main frame 90 and the maintenance device 99. Preferably the coupling system 50 mechanically fixes the maintenance device 99 to the main frame 90.

Preferably the three motorized rotating supports 30a, 30b, 30c have a respective rotation axis 300, 301, 302 (shown in figure 1), wherein the three rotation axes are arranged so that the respective rotation axes of each pair of consecutive rotating supports are perpendicular to each other (i.e. the rotation axis 301 of the second rotating support 30b is always perpendicular to the rotation axes 300 and 302 respectively of the first 30a and third rotating support 30c, while the rotation axes 300 and 302 can also not be perpendicular to each other).

In figures 1, 2 and 3 the remote-control aircraft maintenance system 100 is shown in a so-called "reference" configuration wherein the three rotation axes 300, 301 , 302 of the rotating supports 30a, 30b, 30c are exactly perpendicular to each other. Exemplarily a first rotating support 30a of the three rotating supports is proximal to the main frame 90 and has its respective rotation axis 300 perpendicular to the lying plane 200 of the propellers.

Exemplarily the coupling system 50 comprises a first L-shaped arm which extends from the first rotating support 30a of the three rotating supports to a second rotating support 30b of the three rotating supports.

Exemplarily the coupling system 50 comprises a second L-shaped arm which extends from the second rotating support 30b of the three rotating supports to a third rotating support 30c of the three rotating supports.

In the embodiment shown, both the L-shaped arms are ground adjustable by an operator by adjusting a suited system 400 of screws and grooves schematically shown in figure 3. By adjusting the L-shaped arms it is possible positioning a maintenance device having a secondary frame of variable dimensions according to the maintenance type to be performed on the surface.

Preferably the coupling system 50 is structured keeping unchanged a space orientation of the maintenance device 99 in face of a variation of space orientation of the main frame 90. In other words, the coupling system 50 has the function of releasing the space orientation of the maintenance device 99 from that of the main frame 90.

Exemplarily the coupling system 50 is a known Gimbal stabilizer.

Exemplarily the coupling system 50 comprises a gyroscopic sensor 81 (schematically shown in figure 3) integral with the secondary frame 80 of the maintenance device 99.

Exemplarily the coupling system 50 comprises an stabilization electronic unit 85 operatively connected to the gyroscopic sensor 81 (by a respective communication line, for example a wires line, shown schematically in figure 3 with the two dashed lines) for receiving an orientation signal of the maintenance device 99, the stabilization electronic unit 85 being programmed and configured for operating the three motorized rotating supports 30a, 30b, 30c as a function of the orientation signal for keeping unchanged the space orientation of the maintenance device 99.

In use, the remote-control aircraft maintenance system 100 can implement the surface treatment method according to the present invention.

Exemplarily the method requires the presence of two distinct operators for effectively carrying out the maintenance of the surface of interest.

For example, a first operator is used for controlling the flight of the aircraft maintenance system 100 by a radio-control which sends impulses to the first command and control electronic unit 70 which transforms the received impulses into control signals for regulating the rotation speed and/or the inclination of the propellers, as known. In other words, the first operator controls the flight of the aircraft maintenance system 100.

Furthermore, the first command and control electronic unit 70 being connected to the gyroscopic sensor 105, to the laser sensor 106 and to the altimetric pressure sensor 107 is able to automatically stabilize the orientation of the main frame 90 (i.e. of the drone), according to the detected parameters, to limit the flight movement of the maintenance system 100 in case obstacles close to the maintenance system 100 are detected and to stabilize the altitude at which the maintenance system 100 flies. For example, a second operator is used to control the maintenance device 99, for example by a radio-control that sends impulses to the second command and control electronic unit 18 connected to the fluid suction unit 4, to the fluid ejection unit 3, to the first 11 and second rotating actuator 12 of the mechanical arm 1 and to the linear actuator of the fourth telescopic element, for carrying out the maintenance of the surface of interest and the adaptation of the mechanical arm to the surface of interest.

The operations performed by both operators can be monitored by a computer, a monitor and/or a tablet on which images acquired by a camera 101 (schematically shown in figure 2) are transmitted, exemplarily rigidly coupled close to the distal end 25 of the mechanical arm 1 and operatively connected to the first command and control electronic unit 70.

Typically, the maintenance system comprises an electric energy accumulator, not shown, such as a rechargeable Lithium-Polymer battery (in a single unit or several distinct units), for powering the various active components such as for example the first and the second command and control electronic unit, the fluid pump, the propeller motors, the sensors, the camera, the rotating supports, the rotating actuators, etc.