Floor heating system for passenger trains Description Field of the art The present invention operates in the context of heating systems. More in detail it regards systems for controlling the temperature for passenger transport vehicles. Still more in detail, the present invention regards a new and innovative system for heating trains for transporting people. Prior art Presently, the heating systems used on trains for transporting people provide for heating the air and generating convective air motions within the train car: once generated, the hot air tends to rise towards the ceiling and a hot air circulation is created; however such hot air is distributed in a non-uniform manner within the room. The result is a slow, poorly distributed heating that in particular leaves a rather low temperature close to the floor and thus close to the feet of the passengers. These systems are particularly inefficient since they are subjected to loss of energy due to air motion. Known are systems for ambient heating of infrared irradiation capable of converting the heat coming from the combustion of a burner into an infrared radiation which is emitted outward from the external surface by a hollow cylindrical case, as in the patent ITBS20100098 (A1). It is evident that the abovementioned patent, as with other technologies for controlling the temperature in use up to now, do not resolve the above-described problems; nor do the other presently valid patents solve such problems. Therefore, the object of the present patent application is that of describing and claiming a system capable of increasing the effectiveness of the heating of train cars, increasing the possibility for controlling the temperature and increasing the comfort of the passengers, filling the present detected technological void. Description of the invention According to the present invention, a floor heating system for passenger transport trains is attained which effectively solves the abovementioned problems. The present finding is an infrared heating system which operates in the field of heating systems for train cars. Object of the present invention is to provide a heating system for passenger trains which exploits the infrared technology in order to uniformly heat the train car environment, directly heating the objects and the human bodies present in the train car and preventing the generation of convective air motions, thus providing a more pleasant sensation of warmth for the user, with respect to that offered by conventional systems, since it is felt by the passengers in a uniform manner, over the entire body. The infrared heating involves an increase of the overall efficiency of the heating system, which is capable of preventing energy dissipation, which is verified after the air motion, and a greater control of the desired temperature, due to the uniformity of the same within the train car. According to the present invention, the floor heating system for passenger trains is composed of at least three lines of panels, connected as three branches of a triangular three-phase load, each line independent and hence separately controllable in its temperature values. Each panel is composed of an infrared mesh inserted between two glass fiber insulating layers GFRP, all this inserted between two aluminum layers, the honeycomb-like lower layer and the upper layer constituted by a thin plate fixed on the lower part by means of a high-performance fireproof bicomponent epoxy adhesive, especially formulated for gluing of large-size surface and which provides excellent mechanical strength and aging resistance. Alternatively, it is possible to use an acrylic adhesive film having analogous performance and certifications. Within the panels, also a fireproof foam layer is present with polyethylene terephthalate base (to improve the acoustic and thermal performances), and they can be coated in their upper part, that in direct contact with the outside environment, with a washable and removable fabric layer glued thereto by means of an acrylic adhesive. Each panel is provided with a temperature sensor and the temperature of the floor is maintained at the established level by means of integrated thermocouples and connected to a Temperature Data Hub (TDH) which supplies the measurement data to the central HVAC system by means of CAN protocol. The panels are supported by a pair of aluminum guides and by different elastomers made of anti-vibration polyurethane, suitably calibrated, in rigidity in order to ensure a dynamic behavior of the floor aimed to achieve maximum comfort for the passengers. The guides also have the function of fixing the seats of the passengers and are provided with a plastic lid with the function of hiding the groove used for fixing the seats. The guides are also supported and connected to the lower shell of the body by means of elastic bearings provided with an anti- vibration material in order to increase the comfort of the seated passengers. Said panels generate a temperature difference between the floor and the roof of the train car and directly heat the bodies and objects close by, not the air within the train car, then the objects in turn release heat into the environment, creating a uniform increase of temperature within the environment and preventing the generation of unpleasant air currents at its interior. The system carries out two control types: an operating control and a safety control. In order to carry out the operating control on the system, the lines of panels can be controlled through three independent control algorithms or combined strategies for energy savings or balancing; it can be carried out by means of a simple ON/OFF system, or by means of a Proportional Integral Derivative “PID” system. The object of the operating control is that of supplying energy to the heating elements and monitoring the detected temperature of the panels. The safety control instead has the objective of preventing the actual temperatures of the panels from exceeding the admissible maximum temperatures. This is implemented in the temperature data management unit “THD” and is based on a two-level protection algorithm: the first level safety protection will intervene when the temperature of the panel exceeds the limits of a defined temperature range. This protection is automatically restored if the temperature of the panel returns within the temperature range. The second level safety protection will intervene when the temperature of the panel exceeds the limits of a defined temperature range, wider than the first level. This protection is only restored with the supply cycle “TDH”. The temperature data management unit “THD” is also responsible for the acquisition, calibration and sending of the temperatures of each single panel. The advantages offered by the present invention are evident in light of the description set forth up to now and will be even clearer due to the enclosed figures and to the relative detailed description. Description of the figures The invention will be described hereinbelow in at least a preferred embodiment by way of a non-limiting example with the aid of the enclosed figures, in which: - FIGURE 1 shows the composition of each single panel 1, showing: the honeycomb-like aluminum layer 2, the infrared mesh 3, the thin aluminum plate 4, the washable fabric with adhesive 5, the fireproof bicomponent epoxy adhesive 6, the foam with polyurethane terephthalate base 7, the glass fiber layers GFRP 8. - FIGURE 2 shows a bottom view of the panel 1, showing anti-noise strips 9 and anti-noise bearings 10. - FIGURE 3 shows a housing of the electronic and electrical interfaces in the panel 1, showing the cover 11, the integrated thermocouple 12, the connector of the thermocouple 16, the cable sleeves 17 and the power supply connector 18. - FIGURE 4 shows a “3x3” configuration of assembled panels 1. - FIGURE 5 shows the temperature data management unit “TDH” 14. - FIGURE 6 shows the flow diagram which describes the algorithm of operating control on a single line of panels 1. - FIGURE 7 shows the flow diagram which describes the safety control cycle of the system. - FIGURE 8 shows a layer of the panel, showing the infrared mesh 3 and the copper strip 13. Detailed description of the invention The present invention will now be illustrated as a merely non-limiting or non-binding example, with reference to the figures which illustrate several embodiments relative to the present inventive concept. With reference to FIG. 6, the algorithm of operating control on a single line of panels 1 is shown, wherein: - T is the feedback element for the control cycle. With reference to a single line composed of 3 or 4 panels, T can be any combination of temperatures read by the TDH; - T_ON is the lowest reference for the hysteresis cycle; - T_OFF is the upper reference for the hysteresis cycle; - T_ON and T_OFF can be any value satisfying the following condition: T_ON < T_OFF < T1_MAX; - T1_MAX is the upper limit of the temperature range of first-level safety. With reference to FIG. 7, the algorithm of safety control is shown, wherein: - ‘T is valid?’ verifies that the value T is within a range of electrical plausibility; - T2_MAX is the upper limit of the second-level safety threshold. With reference to Fig. 4, we observe a particular configuration of three lines, each formed by three panels 1; each line of this configuration is independent and therefore allows a dedicated control of the temperature values. With reference to Fig.2, we can observe a particular arrangement of the anti-noise strips 9 and anti-noise bearings 10, adapted to soften impact and noises deriving from the pressure exerted on the panel 1. With reference to Fig.3 and to Fig.9, we observe that all the electronic and electrical interfaces of the panel 1 are situated in specific housings provided with cover 11 adapted to prevent the infiltration of water or dust in housing and hence preserve the integrity of the electrical and electronic components. Finally, it is clear that modifications, additions or variations that are obvious for a man skilled in the art can be made to the invention described up to now, without departing from the protective scope that is provided by the enclosed claims.