WO2009090276A1

WO2009090276A1 - Stand-alone laser-based flight system

Info

Publication number: WO2009090276A1
Application number: PCT/ES2008/000356
Authority: WO
Inventors: Jesús POZO CAMPOS; Koldo BIDAURRAZAGA EREÑO; Galder BENGOA ENDEMAÑO
Original assignee: Oberon Space, S.L.L.
Priority date: 2008-01-16
Filing date: 2008-05-22
Publication date: 2009-07-23
Also published as: ES2335632A1; ES2335632B1

Abstract

The invention relates to a stand-alone laser-based flight system including a land device (ST) and an air device (SA) which are very different from one another. The land device (ST) is provided with means for powering the air device (SA) and for communicating with same in a fully wireless manner, using laser (L) to transmit the necessary power and information. The air device (SA) is provided with means for collecting data and power from the land device (ST) and sending experimental data to the land device (ST).

Description

"AUTONOMOUS FLIGHT WITH LASER SYSTEM"

D E S C R I P C I Ó N

In the current state of the art systems for transferring energy without wires are already known; Today there are basically two types of technologies for the transfer of the same:

- Microwave transmission, preferred by Japanese researchers.

- Laser transmission, preferred by the European Space Agency (ESA).

Also known, and widely used, are systems for transferring telecommunications signals without the need for cables (some of which is described in, for example, the

Patents EP071 1476, GB2O82995, EP1031242 and EP1232579, among others).

Although no previous applications have been found that perform wireless transmission of power and data simultaneously, evidence has been found that technology is being investigated. Wireless power transmission can be achieved by microwave or laser. Below are some known applications that have been developed for each of them and that can be included within the field of power and data transmission.

• MICROWAVE TRANSMISSION: - Project "SHARP" (CANADA): The Sharp Project was first conceived in 1 980. In September 1 982 the Department of Communications of the Government of Canada approved a development and research program that used the concept of electric power transmission by microwave. The wave front was directed from an antenna on the ground, feeding an aircraft that was capable of flying at a height of 21 km with a radius of 1 km.

On September 17, 1 987, at the Center for Communications and Research, the first flight of the Sharp project took place with a 4.5 m model of wingspan.

On October 7, 1 987, the first public demonstration of the Sharp project took place before the Canadian Minister of Communications and the press. The International Aeronautical Federation recognized it as the first flight of this class.

- Project "MILAX", Mlcrowave Lifted Airplane Experiment (JAPAN): In this project, driven by the Japanese, the same concept was used as in the SHARP project, that is, microwave energy transmission. The prototype was introduced in 1 992.

• LASER TRANSMISSION:

- Project "Power in the space illumination from a ground station Ia" presented by NASA Ia Ia Ia 26 edition of Energy Intersociety.

Conversion Engineering Conference (USA): This system will reduce the mass of the power equipment that is taken to space, because in periods of eclipse or lunar night the cells Photovoltaic would be illuminated by a laser from a station located on the ground. This project is under study

- Project "Coded Optical Power System", Technology Service Corporation (USA): In March 2004 a demonstration was carried out in the "Air Force Space and Missile Systems Center" of the ability to propel and transmit data by laser. The project is still under study today.

- "SPI" Project, Solar Power Initiative (Germany): This project was presented in September 2003 by EADS Space. There was a demonstration of feeding a small robot using a laser beam. The project is still under study today.

The object of the invention is to apply this technology to achieve an autonomous system that flies without the need for any type of energy or antenna other than that emitted by laser from a platform located on the ground.

The most important feature of this system is that you can fly continuously without needing to land on the ground to recharge your power system, since the system will be fully powered from the ground.

A preferred, but not limited to, application of the autonomous laser flight system object of the invention is the aerospace sector.

The autonomous laser flight system according to the invention is characterized in that it consists of a well-differentiated ground equipment and aerial equipment; going: -TO-

a) said ground equipment provided with means to feed the aerial equipment in addition to communicating with it, laser transmitting the necessary power and information;

b) said aerial equipment provided with means to collect the energy and data from the terrestrial equipment, and in turn the collection of experimental data to send them to the terrestrial equipment.

Both the ground equipment and the aerial equipment used include subsystems to achieve the specific purposes proposed; varying, where appropriate, the components of these subsystems for better achievement of the proposed purposes, without altering the essence of the invention.

The number of applications of this technology is infinite both in the Aerospace sector and in the land sector.

Preferred, but not limited to, applications of the system object of the invention are, for example and among others:

- Geostationary Generator. This innovative technology would serve to supply energy and communicate anywhere on earth, even those that are inaccessible due to its geographical location.

The minimum number of energy transmitting satellites to cover all the earth would be three. With this number it would be possible to cover the entire globe. Therefore, any user in need of energy or information anywhere in the world would have direct access to it. - Power between satellites: The system could provide energy or send information to any satellite that needs it. One might even consider that in the future satellites will not carry solar panels, since they could be supplied by this system.

This would greatly reduce the cost of satellites and, above all, greatly reduce the failure rate in the satellites, since one of the most critical systems when putting the satellite into orbit is the correct deployment of the panels. It should be noted that if the deployment of the panels is unsuccessful, the entire mission could fail.

- Supply from the Moon. The idea could also be to place a power plant on the moon, although in this case the energy would be subject to the situation of the moon with respect to the earth, and in addition it would be an enormous cost to launch the panels to the same .

The reason why it might be interesting is that in the polar regions of the Moon, both in its northern hemisphere and in the South, the sun's rays do not reach all areas, therefore it is not possible to generate electricity through solar cells in all desirable places. This mostly affects craters, whose edges prevent the sun's rays from reaching the bottom of their cavity.

The use of wireless energy transmission by means of

The laser radiation allows the use of lunar research robots to search for ice and, therefore, water in those regions. This is a fundamental condition for humans to live there in the future. But also the search for other riches of the subsoil and the In situ sample analysis are activities of the utmost importance.

The use of batteries causes serious inconveniences due to their size and weight, since their transport to the Moon causes high costs. On the other hand, the use of atomic energy sources in the form of small nuclear power plants poses major security problems. In turn, the teletransmission of energy by means of laser beams allows prolonging the duration of the missions, since it is not necessary to return to the base to recharge the batteries.

- Interplanetary Missions: You can also consider the possibility of using the system for interplanetary missions (mission to Pluto), where the energy of the sun is very tenuous. In this way, the probe that was sent could be supplied by a satellite that was in a high orbit of the Earth, sending the necessary power to the probe via Laser. In addition to that the Laser would allow a much faster communication than the transmission via antenna.

- Rovers. The system can be very useful when a vehicle is inserted in the planet (Rover). In this case, the Rover would also not need any type of energy plant since it could be supplied by the satellite that orbited around that planet (Orbiter), thus also reducing the failure rate in the solar panels, cost and complexity thereof.

It may also be imaginable to work with more than one of these research vehicles. Two or three of them could form a "swarm." The vehicles in a swarm would then be interconnected in a power grid. This means that every Rover at least one neighbor is supplied by means of the laser energy transmitter.

Space-base telescopes: Large modular telescopes in heliocentric orbits and several astronomical units of the Sun offer benefits to astronomers, impossible to achieve within the solar interior system (for example, absence of zodiacal dust, which interferes with infrared exams). Such telescopes could use wireless energy to obtain the necessary energy on board and the care of the station of the modular elements of the telescope.

- Sensor systems connected to a network: Hundreds of tiny sensors receiving power from a "mother" satellite equipped with wireless power transmission capability, can allow detailed revisions of interplanetary and spatial regions.

- Military Satellites: There could be great military interest since less visible spy satellites can be built. If satellites are not required to carry large solar panels (for example 30 meters), they could be more difficult to discover from the ground or by interceptors.

- Commercial satellites. Small commercial satellites could be powered by batteries, periodically recharging from remote sources of energy.

- Satellite robots: Satellite maintenance could be done using robots supplied by lasers.

- Satellite launch. Future small satellites can be launched using wireless power. This would greatly reduce the expenses of any space mission. - Autonomous sensors: With this technology you can build sensors totally independent of your power supply, being able to operate without wires indefinitely. A very useful example can be its use in wind sensors of wind turbines, where carrying cables inside the blades can generate serious problems in case of storms.

- Surveillance robots. The technology will allow robots to explore enclosures continuously, recharging their batteries when passing in front of the wireless power source.

- Sending energy and data to mobiles. Currently does not exist

The possibility of transferring energy wirelessly to mobile phones. This capacity could eliminate their cumbersome adapters, since it would be a universal system that, when exposed to the wireless power source, would allow it to be recharged automatically. You could even transfer the excess energy from one mobile to another.

- Recharge laptops. As in the case of mobile phones, the user could recharge his laptop simply by placing it in front of the wireless power.

- Surveillance Systems: With this system you can have drones above our homes that acquire images and data of any anomaly that occurs in our vicinity, recharging the aircraft wirelessly.

- Traffic control systems. Airplanes can be available continuously in areas where you want to control the traffic and driver infractions. Currently helicopters are used whose hourly expense is huge.

- Coastal control system. The coasts will be swept by drones continuously, controlling the entry of vessels to the port, infractions, or boats.

- System for aerial photographs. A high precision camera may be included in the system to be able to take aerial photographs of houses, mountains, rivers, etc.

To better understand the object of the present invention, a preferred form of practical embodiment is shown in the drawings, susceptible to accessory changes that do not distort its foundation.

Figure 1 schematically represents the autonomous laser flight system object of the invention, with its ground equipment (ST) and aerial equipment (SA) interconnected by laser (L).

Figure 2 represents a block diagram with the main components that make up the different subsystems (21), (22), (23), (24), (25) and (26) of the ground equipment (ST).

Figure 2a represents the movement (N) in azimuth (A) and elevation (E).

Figure 2b represents an example of the mechanical subsystem design (21). Figure 2c represents the way in which the energy affects the receiver of the aerial equipment (SA) to effect the transmission of power and necessary data from the terrestrial equipment (ST).

Figures 2d, 2e, 2f and 2g represent operation diagrams of the control subsystem (22).

Figure 2h represents the frequency modulation (FSK).

Figure 2i represents the phase modulation (PSK).

Figure 2j represents regions 3C1, where the laser beam (L) does not diverge (near field) and part 3C2 where the laser beam (L) diverges (far field).

Figure 2k represents the necessary diameter of the receiver with respect to three different wavelengths: 400, 700 and 1000 nm.

Figure 21 represents an exemplary embodiment, with low power lasers (Li).

Figure 3 represents a block diagram with the main components that make up the different subsystems (31), (32), (33), (34), (35) and (36) of the aerial equipment (SA)

Figure 3a schematically represents the block diagram of the control software (321 a).

An example of practical, non-limiting embodiment of the present invention is described below. The Ground Equipment (ST) will be responsible for feeding the Air Equipment (SA) using the laser beam (L), in addition to communicating with it. The structure of the Ground Equipment (ST) is shown in Figure 2 and consists of the following subsystems:

- Mechanical subsystem (21), in which the mechanical parts necessary to build the two-axis follower platform (21 1) will be found.

- Control subsystem (22), which contains all the software (221) and hardware (222) necessary to control the two-axis tracker (21 1).

- Reception Subsystem (23), which consists of the hardware (232) and software (231) necessary for the reception of all information from the Air Team (SA).

- Transmission Subsystem (24), consisting of the hardware (242) and software (241) necessary to transmit power and information to the Air Team (SA) (aircraft).

- User Interface Subsystem (25), which consists of the software (251) necessary to allow the user to easily and intuitively communicate the position, speed and attitude of reference to the Air Team (SA). It also allows to visualize the data coming from the Aerial Equipment (SA).

- Power Subsystem (26), which provides the power (261) of necessary energy to the Ground Equipment (ST).

According to the embodiment shown, in the Mechanical Subsystem (21) of the Ground Equipment (ST) the mechanical parts necessary to build the two-axis follower platform (21 1). The mechanical subsystem (21) will have two degrees of freedom (it can move in two axes), azimuth and elevation, so that it can be oriented in the direction of the Aerial Equipment (SA), provided it is in its field of view and after Let this last report grounded your position and speed. The movement (N) in azimuth (A) and elevation (E) will be carried out by means of two motors, one for each degree of freedom as shown in Figure 2a.

An example of the design of the mechanical subsystem (21) can be that of the structure used in two-axis solar trackers (see figure 2b). Automatic trackers have a central metal mast (21 a) that supports a mobile support (21 b), whose position varies.

The preliminary characteristics of the mechanical subsystem (21) for this exemplary embodiment are:

- The central mast (21 a) and the mobile support (21 b) will withstand the adverse climatic conditions of the geographical area where the Ground Equipment (ST) is installed.

- They must have perforations that allow the use of screws to anchor the necessary systems for the transmission of energy and data with the Aerial Equipment (SA).

- The base where the systems are supported for the transmission of energy and data must be adjustable.

- The structure, metal surface and tortilleria will have a special treatment to avoid galvanic corrosion and oxidation. - The weight of the total follower assembly must be balanced for better operation.

Although the possibility of using other mechanical subsystems (21) that vary these characteristics is being considered, without altering the essence of the invention.

According to the embodiment shown, the control subsystem (22) of the Ground Equipment (ST) will direct the mechanical subsystem (21) towards the Air Equipment (SA). In the example described, this subsystem has been divided into two sets detailed below.

- Platform Control Software

As described in the previous section, the Ground Platform Control Software (221) will orient a laser (L) located in the mobile support (21 b) of the mechanical subsystem (21), so that its energy It affects the receiver of the Aerial Equipment (SA) and thus the transmission of power and necessary data can be carried out (according to the form represented in Figure 2c.

This Control software of the ground platform (221) will have as input the position of the Aerial Equipment (SA) in the reference system of the follower platform itself. Depending on the position of the aircraft, the software will demand the appropriate position instructions to the engines of the Ground Equipment platform (ST) so that they are oriented until the error between the laser direction (L) and the receiver address ( aircraft) be null.

The steps to follow to ensure that the mechanical subsystem (21) points to the Aerial Equipment (SA) are the following: one . Set the azimuth (A) and elevation (E) angles of the follower (see Figure 2a).

2. Transform the position of the Aerial Equipment (SA) in axes linked to the platform (azimuth and elevation).

3. Calculate the error angle between the position of the aircraft b and

The normal ñ of the follower.

4. Perform a check of the motors so that they reach the required azimuth and elevation, making the error angles zero.

The output of the control system will be the torque or intensity that needs to be supplied to the motors to reach the proper position. The control system consists of a PID, where its equation can be expressed as:

T = -k D engine # _ERR ^"k," k P θ _err

Where T _mo t _or is the torque that is supplied to the engines, θ _err is the angle of error between the position of the aircraft and the normal ñ, θ _err is its derivative, and [θ _err is its integral.

The control system has been simulated in Simulink to check its proper functioning (see Figure 2d).

With this model it is verified that for a simulation of

1 000 seconds, the system achieves very fine control. Of course, both Azimuth and Elevation angles are varied over time (see figures 2e, 2f, 2g).

- Platform Control Hardware (222) In order to control the mechanical subsystem (21), it is necessary to have a Control Hardware of the Ground Platform (222) that interprets the control signal generated by the Control Software of the ground platform (221) and Ia transform into a physical signal (voltage, intensity) that causes the mechanical orientation of the system.

This control hardware of the ground platform (222) will consist of the following components:

- Motors to mechanically orient the two-axis system to the required position.

- Positioning sensors to know the exact position of the motors at every moment. To control the two-axis follower platform, it is necessary to know the position of the motors at all times. The position of the motors will be obtained using encoders, which can be installed on the azimuth or elevation axes of the mechanical subsystem (21) or on the motors themselves.

- Control Electronics. To carry out the control in position of the motors, additional hardware may be necessary to control them (for example, a PWM signal generator).

- Microcontroller. The control software of the ground platform (221) will be implemented within a microcontroller. A possible microcontroller to use is the Softect indart-HSC12.

According to the embodiment shown, the transmission subsystem (24) of the Ground Equipment (ST) will be responsible for transmitting

The power and to communicate the data to the Air Team (SA) through a High power laser (L). This subsystem has been divided into two sets that are detailed below.

- Transmission Software (241)

Once the transmitting laser (L) of the Ground Equipment (ST) is aligned ("hooked") with the photovoltaic panels (receiver) of the Aerial Equipment (SA), the transmission of power and data can begin.

The Transmission Software (241) of the Ground Equipment (ST) will be responsible for making the two desired transmissions (power and data).

- For the transmission of power, it will be enough to place a laser with the adequate output power (Watts / m ² ), so that the necessary power reaches the surface of the photovoltaic panels of the Aerial Equipment (SA), taking into account losses and deviations that may exist along the way. During the transmission of energy, it will be necessary to take into account the losses produced by the absorption of energy from the atmosphere, the dispersion of energy produced by the collisions between particles and other factors that will be studied during the realization of the project.

- For data transmission, there are several possibilities.

The output light of a laser, known as the laser beam, is usually represented by a continuous beam that has constant energy. But in the case of laser communications, the beam can be modulated in a suitable way to transmit information. This modulation can take the form of an amplitude modulation (AM), which alters the force or energy of the beam, or a frequency modulation (FM), which alters the frequency or color of the beam, or a phase modulation that does not alter either the energy or the color of the beam.

The modulation adds information to the laser beam so that it can be transported by the beam and transmitted to a distant place, where it can be extracted and used. For example, a telephone conversation can be encoded in a modulated laser beam and sent to the other side of the US or, under the sea, to Europe or Asia, where it can be decoded and heard in voice form.

Modulation is a process in which a "modulator" changes some attributes of a "carrier signal" of higher frequency in relation to the frequency of the "message signal".

The "carrier signal" can be represented by the equation:

Where Ac = AMPLITUDE h = FREQUENCY φ = PHASE

A change in the signal will produce the corresponding change in amplitude, frequency or phase of the carrier depending on the modulation performed. In the analog modulation, a transmitter can send this carrier signal through the communication means more efficiently than if we send the message signal alone. When the signal reaches its destination, a receiver will demodulate the signal obtaining the original message.

In the analog amplitude modulation (AM) the amplitude of the carrier changes depending on the amplitude of the message to be transmitted.

The signal with the message is mounted above the carrier since the amplitudes of the two vary with time. However, the frequency of the carrier is much greater than the frequency of the message.

The digital modulation is very similar to the analog modulation, but instead of changing to continuous values of the amplitude (ASK), frequency (FSK) or phase (PSK) it is changed only to discrete values of these attributes that correspond to the digital codes . There are a few common digital modulation schemes, each varying separately set of parameters.

The simplest mode is called "On-Off Keying (OOK)" (Modulation of all or nothing), where the amplitude of the carrier corresponds to two digital states. A nozero amplitude represents a digital one, while an amplitude of zero a digital zero. An application of OOK is the morse code.

The ASK is a form of modulation whereby the amplitude of the signal is given by the equation

, Asen (ωot) O ≤ t ≤ T. φ - (- U - -; in _ other _ case>

ASK can then be described as the multiplication of the input signal f (t) = A (valid in digital systems) by the carrier signal. In addition, this technique is very similar to modulation in AM amplitude.

In the case of frequency modulation (FM) what is varied is the frequency of the carrier. The frequency modulation (FSK) is represented in Figure 2h, where it can be observed that a certain frequency represents a binary value. On the contrary, in the phase modulation (PSK) what is modified is the phase of the carrier as shown in Figure 2i.

The combination of the modulation in phase, amplitude and frequency gives rise to different types of modulation. Throughout this project it will be studied which of them is the optimum to use when transmitting data and power.

By way of redundancy, the communication with the Aerial Equipment (SA) will be carried out additionally using a radio modem, encoding the information analogously to the laser.

- Transmission Hardware (242)

The Transmission Hardware (242) of the Ground Equipment (ST)

Io will form the physical systems through which the Transmission Software (241) sends the power and data to the Aerial Equipment (SA). The Transmission Hardware (242) will form the following components.

- An amplitude, frequency or phase modulator to transform the information and send it together with the power transmission.

- A high power laser (L) to transmit energy and data.

It should be noted that a radio modem and an antenna will be used as a redundant data transmission system with the Air Equipment. It should also be noted that the laser beam does not continue without diverging indefinitely. Even in the case of an ideal laser there is a divergence of the beam.

As shown in Figure 2j there is a region (3c 1) where the beam does not diverge, (near field) and a part (3c2) where it diverges (far field). For long distances you can consider the

(3c 1) negligible, considering that the diameter that would be obtained in the receiver would be:

Z) = 21 tan0

Where θ is the angle of divergence, L is the distance to the receiver and D is the diameter obtained in the receiver.

The angle θ depends on the wavelength λ and the radius of the ray when "lightning" does not diverge. Such that:

_{0 =0 =} ^λλ

Tt ^• rrayo

If we consider these equations we will have the figure 2k using a beam diameter of 0.6 mm and wavelengths of 400, 700 and 1000 nm.

It can be seen in this figure 2k that for large distances of the receiver, distances of 500 km, and wavelengths of 1000 nm, the effect can be considerable, since the diameter of the energy incident in the receiver will be more than 1 km. In the case of the system that proposes this effect it will not have great consequences since we are talking about small distances, but it is convenient to take it into account when considering the transmission of energy from space to earth.

In the design of our system it is also necessary to know the amount of energy that affects our receiver (Watts / m ² ) This energy is very simple to calculate, since if we consider that the effect of the atmosphere is negligible it can be obtained as Ia laser power used between the Area in which the energy is distributed.

Of all the existing lasers, different industrial lasers will be considered for the experiment, since they are those that are used for the powers that are required (> 300 W) and that can be used in a test laboratory. Each of them works with light of a certain wavelength, according to the following table:

Laser technology Wavelength λ (nm)

Diode laser 808-940 Solid state laser 1064 CO2 laser 10600 Among the three options, the Laser option of

CO2, because the wavelength is not usable by commercial cells, and the diode laser is chosen. In general, they have a useful life of about 15,000 hours and a yield of 35%, superior to other technologies.

Because the current legislation does not allow radiation of excessive magnitude per square meter in open places, it has been considered to use instead of a single high power laser (L), a numerous set of low power lasers (Li). Each laser unit (Li) will not exceed by itself the energy allowed by the legislation and therefore will be totally harmless to the human being. In this project of realization the beams will converge in a point (LP) of the space so that thanks to the sum of the energies the required levels are reached. The convergence of the energy will be carried out by placing the low power lasers (Li) with the appropriate inclination on a base (Bi) (see figure 21)

For the embodiment shown, the receiving subsystem (23) of the Ground Equipment (ST) will be responsible for receiving and demodulating the information coming from the Air Equipment (SA), obtaining the experimental data sent by means of a radio modem. This subsystem (23) has been divided into two sets detailed below:

The Receiving Software (231) of the Ground Equipment (ST) will be responsible for decoding the information transmitted by the Air Equipment (SA) to obtain the original message. As in the transmission subsystem, the radio modem signal will be modulated in amplitude, frequency or phase and will have to be decoded to convert it into valid information. The type of demodulation will depend on the modulation chosen to transmit the information from the Aerial Equipment (SA) to the Ground Equipment (ST).

Once the original message has been obtained, the data will be presented in the user interface for further analysis.

The Receiving Hardware (232) of the Ground Equipment (ST) will be responsible for converting the information from the radio modem of the Air Equipment (SA) into electrical signals (voltage, intensity), so that they can be interpreted by the Receiving Software (231) explained in the previous point.

The receiving Hardware (232) is very simple, since it will form a radio modem and a conventional antenna that will connect directly to the Microcontroller.

It is included in the object of the invention to use photovoltaic cells of different materials to take advantage of the energy transmitted by the earth transmission system, depending on the wavelengths that they can take advantage of.

The most common materials used in the photovoltaic technology for the manufacture of the cells are those detailed in the following table:

Material Forbidden band Eg Long. Maximum wave λmá _*

Crystalline silicon 1 .12 eV 1 .107 nm

GaAs 1,424 eV 871 nm

InP 1.35 eV 918 nm

Amorphous Silicon 1 .8 eV 689 nm

CdTe 1 .45-1.5 eV 855 nm

CulnSe2 0.96-1 .04 eV 1 .292 nm

CdS 2.42 eV 512 nm

ZnS 3.58 eV 346 nm

ZnO 3.3 eV 375 nm

Of all the incident photons, only those that have an Efoton energy> E _g of the material will be able to generate a pair electron-hollow, and therefore contribute to the generation of the electric current.

h and Efoton = - ^ -> Eg

TO

h being the Planck constant, c the speed of light and λ the wavelength of the incident photon.

In view of the results, it is concluded that by means of a suitable combination of laser and solar cell, electrical energy can be generated from the incident beam of laser light. The most appropriate option, or the one that offers greater ease for the acquisition of the materials, is a priori Ia of the binomial crystalline silicon solar cell and diode laser.

Since the solar cells will be mounted on the aircraft that is developed for the demonstration project, and that it is important not to exceed the payload of the same, it has been considered as initial idea of the experiment to use silicon concentration cells.

These cells, in their commercial version, are small in size, not exceeding ² cm. In addition, they have a higher conversion efficiency than normal crystalline silicon (efficiencies of up to 27% versus 15-17%), and allow incident light concentrations of up to 100 soles, equivalent to 10 W / cm ² , compared to at 0.1 W / cm ² of sunlight.

Once the energy transmission and reception technology has been chosen, two possible solutions are contemplated: one . Use concentration silicon cells (commercial), and mount them on a structure that would be housed in the aircraft.

2. Use commercial optics for the laser, achieving the desired light concentration.

The option of the concentration cells requires a greater technical development to solve the problems of dissipation, positioning of the small cells, development of the support structure, etc. For example, to achieve a concentration of 100 soles, a density is necessary of power of 1 0 W / cm ² . If the area occupied by the photovoltaic cells were 0.1 m ² , an incident power of 1000 W. would be necessary.

For the exemplary embodiment shown, the user interface subsystem (25) will be the software in charge of allowing the communication between the user and the transmitting and receiving subsystems of the Ground Equipment (ST). The GUI will be designed so that the communication with the user is easy and intuitive, so that the user can transmit the new coordinates of position, speed and attitude to the Air Team (SA), and at the same time view the data received in time real.

The GUI is divided into two parts, one will be responsible for transmitting the position, speed and attitude guidance of the new point or trajectory that the Air Team (SA) must follow and another part will be responsible for receiving the position, speed and real attitude as well as the experimental data obtained.

For the embodiment shown, the Power Subsystem (26) of the Ground Equipment (ST) will be responsible for power all the Earth Equipment (ST) providing enough energy to power all the subsystems, in addition to supplying the energy necessary to use the laser and thus power the Air Equipment (SA).

Therefore, the power subsystem (26) is a fundamental system that is integrated into the Ground Equipment (ST) but actually feeds both the Ground Equipment (ST) and the Air Equipment (SA).

The power subsystem (26) can be the electricity grid itself, power generators, batteries or solar panels. Depending on the necessary power consumption, one system or another will be used.

The Aerial Equipment (SA) (aircraft model aircraft) will be responsible for collecting all experimental data (pressure, temperature, humidity ...) and sending them to the Ground Equipment (ST) for analysis.

The structure of the Aerial Equipment (SA) represented in the following figure 3 consists of the following subsystems:

- Mechanical Subsystem (31). In this subsystem is included the prototype to fly (31 1).

- Control Subsystem (32). In this subsystem is all the software (321) and hardware (322) necessary to control the aircraft.

- Reception Subsystem (33). In this subsystem you will find all the software (331) and the hardware (332) necessary to receive the energy and information from the laser (L) of the Ground Equipment (ST).

- Transmission Subsystem (34). In this subsystem you will find all the software (341) and hardware (342) necessary to transmit the experimental and navigation data to the Ground Equipment (ST).

- Navigation Subsystem (35). In this subsystem is the navigation software (351) and hardware (352) necessary to determine the status vector of the Air Equipment (SA) (position, speed and attitude).

- Power Subsystem (36). In this subsystem is the auxiliary hardware (362) necessary to supply the aircraft, if at any time it could not be radiated by the laser.

The Aircraft Mechanical Subsystem (31 1) of the Air Equipment (SA) will be the prototype to be flown and, in this case, will be an aircraft model aircraft. The Aircraft Mechanical Subsystem (31 1) of the Aerial Equipment (SA) will be powered by the energy transmitted by the Earth Equipment (ST) laser, therefore the structure of this set will be covered by solar cells (a priori concentration cells ) that will transform that radiation into electrical energy to provide the necessary power to the electronic systems of

The aircraft

These cells will not only serve to receive power but also to receive the information sent from the Ground Equipment (ST). Therefore, the aircraft will have to be modified with respect to a conventional aircraft model aircraft. For the embodiment shown, the control subsystem (32) of the Aerial Equipment (SA) will be responsible for controlling the mechanical subsystem (31) of the Aerial Equipment (SA).

The Control Software (321 a) of the Air Equipment Aircraft (SA) will be in charge of controlling the aircraft by means of the data coming from the Ground Equipment (ST) (trajectory and attitude of reference) and the data coming from the navigation (trajectory and real attitude). The complete control system, in schematic form, is the one represented in Figure 3a, in which:

- The dynamics (3a 1) of the Aircraft will be subject to the forces of:

• Gravitational Acceleration

• Push due to the motor propeller

• Aerodynamic Resistance

- Guidance (3a6) will be provided from the Ground Team (ST), sending the reference path (3a4) to follow to the aircraft and the necessary orientation of the aircraft.

- Navigation (3a2) provides real information to the system where it is located and how it is oriented (3a7) with respect to an inertial system.

- The control system (3a5) calculates the actions that must be followed by the actuators (3a3) so that the reference path (3a4) can be followed as precisely as possible. - The actuators are composed of the control surfaces that guide the aircraft.

The Control hardware (322a) of the Aircraft Equipment Aircraft (SA) will be responsible for executing the control signals generated by the Control Software (321 a). The control of the aircraft is done through a series of servos that transmit movement to the aerodynamic surfaces of the model. The following components will therefore be needed:

- Servos for control of the aircraft

- Electronics needed for control

- Encoders to know the position of the servos

- Microcontroller

For the embodiment shown, the transmission subsystem (34) of the Aerial Equipment (SA) will be responsible for transmitting the data to the Ground Equipment (ST) via a radio modem. This subsystem has been divided into the two sets detailed below.

The Transmission Software (341) of the Air Team (SA) will be responsible for making the desired transmissions. The form of transmission of the data to the Ground Equipment (ST) will be exactly the same as explained in the corresponding section of the Ground Equipment (ST),

The data to be transmitted will be the experimental data collected, in addition to the position, speed and attitude data collected by the hardware of the navigation subsystem that will be explained in the corresponding section.

The Transmission Hardware (342) of the Aerial Equipment (SA) shall be formed by the physical systems through which the transmission subsystem (34) sends the data to the Ground Equipment (ST).

The Data Transmission Hardware (342) will be able to transform the information that is to be sent in the form of radio frequency pulses.

The Data Transmission Hardware (342) will form a radio modem.

The Receiving Software (331) of the Aerial Equipment (SA) will be responsible for decoding the information transmitted by the Ground Equipment (ST) to obtain the original message. As in the transmission subsystem, the signal will be modulated in amplitude, frequency or phase, and will have to be decoded to convert it into valid information. The type of demodulation will depend on the modulation chosen to transmit the information from the Ground Equipment (ST) to the Air Equipment (SA).

The Receiving Software (331) will be a specific software whose task will be to extract the reference trajectory and attitude and present the new input data to the Control Software (321 a) of the Air Team (SA).

The Reception Hardware (332) of the Aerial Equipment (SA) will be in charge of converting the radiation coming from the laser of the Ground Equipment (ST) into electrical signals (voltage, intensity) so that they can be interpreted by the Reception Software ( 331) In addition to using the incident power to power the Aerial Equipment (SA). The Receiving Hardware (332) is very simple and will form solar cells (a priori concentration cells). It is important to note that the solar cells located in the Aerial Equipment (SA) will not only act as power receivers but also as information receivers.

The reception of data is also carried out by radiomodem link (as a redundant device) to ensure that in case the reception with the solar cells did not work correctly, the aircraft continues to contact the ground equipment

(ST).

The Air Equipment (SA) will be fed by placing solar cells attached to the aircraft that will transform the radiation received from the Earth Equipment (ST) into energy to power the Air Equipment (SA).

It should also be noted that solar cells will have a much greater efficiency when they are irradiated with laser than when they are with solar energy, since in this case it is possible to choose that the laser wavelength is optimal for those cells. An example of the energy generated with respect to the wavelength is that known for GaAs cells, frequently used in space applications.

The solar cells will be arranged in the aircraft in such a way that when the night is done the aircraft can be powered entirely by the energy of the laser, and that when it is done by day use both the energy of the sun and that of the laser (being able to reach increase the efficiency of the cells to double). For the exemplary embodiment shown, the Navigation Subsystem (35) of the Aerial Equipment (SA) will be responsible for providing the aircraft with the actual position, speed and rotation with respect to an inertial system. The aircraft will need to know these data to be able to go to the desired reference. For this you can use different sensors or systems.

It has been proven that the Navigation Hardware (352) that makes the aircraft as autonomous as possible is the INS (Inertial Navigation System), since they not only provide the position and speed of the system but also its attitude. The problem that generally exists with these systems is that they usually need an additional system (Global Position GPS System) to avoid drifts over time. For the precise calculation of the height and the speed of the aircraft with respect to the wind, static and dynamic pressure sensors have been used respectively.

The integration of all GPS, INS and static and dynamic pressure sensors data has been carried out in the Navigation Software (351) by means of a Kalman filter.

For the embodiment shown, the Power Subsystem (36) of the Aerial Equipment (SA) will be a safety system that will be in charge of feeding the aforementioned systems in case due to any misfortune the laser does not fully affect the apparatus.

This system will consist of a battery and a power regulator, and can be additionally charged when the aircraft is under solar radiation.

Claims

REIVINPICATIONS

1 .- Autonomous laser flight system, characterized in that it consists of a well-differentiated ground equipment (ST) and aerial equipment (SA); going:

a) said ground equipment (ST) provided with means to power the aerial equipment (SA) in addition to communicating with it in a completely wireless manner, transmitting with laser (L) the necessary power and information;

b) said aerial equipment (SA) provided with means to collect the data and energy of the ground equipment (ST), and send experimental data to the ground equipment (ST).

2. Autonomous laser flight system according to claim 1, characterized in that the ground equipment (ST) includes at least:

a) a terrestrial mechanical subsystem (21) with the mechanical parts necessary to constitute a two-axis follower platform (21 1);

b) a ground control subsystem (22) with all the software (221) and hardware (222) necessary to control said two-axis follower platform (21 1);

c) a ground reception subsystem (23); with all the software (231) and hardware (232) necessary for the reception of all the information coming from the aircraft (SA); d) a terrestrial transmission subsystem (24), with all the software (241) and hardware (242) necessary to transmit power and information to the aircraft (SA);

e) a terrestrial terrestrial subsystem (25), with all the software (251) necessary to allow the user, easily and intuitively, to communicate the position, speed and attitude of reference to the aircraft (SA), as well as visualize the data coming from her;

f) a terrestrial power subsystem (26) with at least one power supply (261) that provides the energy necessary for at least one laser (L) that transmits (n) to the aircraft (SA) the power and necessary information.

3. Autonomous laser flight system according to claim 1, characterized in that the aerial equipment (SA) includes at least:

a) an aerial mechanical subsystem (31) that encompasses an aircraft (31 1)

b) an air control subsystem (32) with all the software (321 a) and hardware (322a) necessary to control, said aircraft (31 1).

c) an air reception subsystem (33), with all the software (331) and hardware (332) necessary to receive the energy and information coming from the laser (L), with all the necessary hardware to communicate the ship in case in some moment I could not communicate with the laser (L); d) an air transmission subsystem (34), with all the software (341) and hardware (342) necessary to transmit the experimental and navigation data to the ground equipment (ST);

e) an air navigation subsystem (35), with all the hardware (352) and software (351) necessary to determine the status vector of the aerial equipment (SA) (position, speed and attitude);

f) an air supply subsystem (36), with all the hardware (362) necessary to supply the aircraft (31 1) if at any time it could not be radiated directly from the laser (L).

4. Autonomous laser flight system according to claim 3, characterized in that, in particular, said data transmission hardware is a radio modem.

5. Autonomous laser flight system according to claim 1, characterized in that, in particular, said aerial equipment (SA) is an aircraft model aircraft.

6. Autonomous laser flight system, according to claim 2, characterized in that, particularly, the ground feeding subsystem (26) consists of a plurality of low power lasers (Li) arranged in a base (Bi) with the appropriate inclination so that its beams converge in a point (LP) of the space so that the sum of energies reaches the required levels.

7. Autonomous laser flight system according to claim 3, characterized in that said reception hardware (332) is formed by solar cells (particularly concentration cells), and an auxiliary system formed by a radio modem.