FR2865871A1 - Data communication system for e.g. airport ground lighting system, has lamp control module and control unit for module, where bits of data byte are transmitted between unit and module simultaneously, in frequency lines of channel - Google Patents

Abstract

The system has a constant current regulator, an electric line, a number of illuminating lamps, a lamp control module associated to an illuminating lamp and a control unit for the module. The bits (b1-bn) of a byte of data exchanged between the unit and module are transmitted between the unit and the module simultaneously, in the frequency lines (F1-Fn) of a specific frequency channel. An independent claim is also included for a process of communication of data in a lighting system.

Description

Communication system and method

  The present invention relates to a power line data communication system and method in a lighting network having at least one current regulator, a long power supply line. , a plurality of lighting lamps, a lamp control module associated with a lighting lamp and a control unit of this module. More particularly, the invention relates to such a system and method of data communication by carrier current, in an airport beacon network.

  Communication between lights or beacons and control units is increasingly used in airport lighting systems. This communication is done by a dedicated network, by wireless network, or else by a carrier current.

  Powerline communication is well suited for large energy networks, of which markup loops are a part.

  The communication principle commonly used in this field is FSK (Frequency Shift Keying). In FSK communication, each 0 or 1 bit to be transmitted is represented by a distinct frequency. On reception, these distinct frequencies are demodulated by a device of the PLL (Phase Locked Loop) type and decoded in 0 or 1 bits.

  The transmission of information bits is sequential.

  This communication principle imposes high frequencies in front of those of the power signal ranging, in practice, from a few tens to a few hundred kHz. As a result, the data flow of each communicating element is transmitted in a reasonable time.

  Nevertheless, this communication principle has many disadvantages.

  Since the power circuits are not initially designed for transmission of high frequency signals over distances of up to several tens of kilometers, one of the main problems to be solved is line attenuation, which imposes work near the loss of signal and a repetition of transmitted messages, the detection then being done by correlation and likelihood between a number of supposedly identical messages. This is the reason why some manufacturers propose to shunt the parts of loops of a network or the transformers not concerned, thus avoiding their own attenuation.

  In addition, the power line, which is formed alternately of cables and markup transformers, is constantly solicited by strong currents at temperatures that may vary by several tens of degrees. This results in accelerated aging of the line which is accompanied by a change in the electrical characteristics of the marking cable may lead to abnormal heating sometimes leading to fires. To date, no system can measure this aging and unseal an anomaly in cables or transformers before an incident occurs.

  In addition, a fast calculation shows that the signals used have a wavelength of the same order of length as the length of the loops of the network themselves. There are therefore, in some cases, so-called bellies and nodes phenomena corresponding to amplifications or attenuations that depend on the geometry of the loop 2865871 4. The presence of these resonance phenomena sometimes forces some manufacturers to place series or parallel resonant elements forming plugs which come to shunt certain parts of loops. However, it is understood that any modification of a loop, for example, by adding or deleting tags, modifies the state of the resonances of the system and imposes a reconsideration of the problem.

  On the other hand, some sections of the different markup loops coexist for long distances, for example, several kilometers. Under these conditions, the signals radiated by a cable of a loop are likely to be induced in the neighboring cable and this, especially as the working frequencies are important. This phenomenon of crosstalk has two important consequences. First, it requires a sophistication of the coding so that there is no mixing information transmitted in separate loops, resulting in a decrease in the useful information flow transmitted. In practice, it is almost mandatory to use screened cables as soon as you want a reliable transmission over a certain length. This fact eliminates more than half of existing installations in the market.

  When the installation is carried out in screened cables, it is then necessary for it to be properly monitored and to have no faults in the connection of the screens or earth leakage. This state of affairs is contradictory to the philosophy of serial tagging, which is intended to be an extremely earth-fault tolerant distribution system for the markup itself. Moreover, the frequencies used, a few tens of kHz, also do not tolerate a significant value of the reactive part of the impedance of the loop, that is to say the number of lamps failing or non-standard elements. such as fluorescent tube indicating panels or constant current transformers.

  Ultimately, all the aforementioned drawbacks, inherent to existing installations of a certain age or more or less well maintained, result in a lower communication speed, an increased response time of the system and a decrease in the general reliability of the system. .

  The invention aims to overcome the aforementioned drawbacks of the state of the art.

  The solution of the invention firstly relates to a data communication system in a powerline lighting network comprising at least one current regulator, a long power supply line, a plurality of lighting lamps. a lamp control module associated with a lighting lamp and a control unit thereof, characterized in that bits b1,..., bn of a data byte exchanged 2865871 6 between said unit and said module are transmitted, between this unit and this module, simultaneously, in frequency lines F1,..., Fn of a specific frequency channel Ci.

  The second object is a method of data communication in a powerline lighting network comprising a current regulator, a long power supply line, a plurality of lighting lamps, a lamp control module. associated with a lighting lamp, and a control unit of this module, characterized in that bits b1, ..., bn of a multiplet of data exchanged between said unit and said module are transmitted between this unit and this module, simultaneously, in frequency lines F1, Fn of a specific frequency channel Ci.

  The multiplets of data being transmitted simultaneously, and not sequentially, it is possible to communicate a larger amount of information within the system without requiring the use of high frequencies of a few tens to a few hundred. kHz and the aforementioned disadvantages of line attenuation or aging, resonances, crosstalk, fault tolerance or response times are, to a certain extent, solved.

  An additional object of the invention relates to a data communication system in a powerline lighting network comprising a current regulator, a long power supply line, a plurality of lighting lamps, an lamp control module associated with a lighting lamp, and a control unit thereof, characterized in that the frequency channel Ci is in a frequency band from about 1 kHz to about 7 kHz .

  The invention will be better understood on reading the following description of particular and non-limiting embodiments of the invention. This description should be read with reference to the accompanying drawings, in which: FIG. 1 schematically shows a loop of an airport marking system according to the invention; Figure 2 illustrates the principle of the invention; FIG. 3 represents the constituent elements of a beacon control module for a system according to the invention; and FIG. 4 is a diagram showing the different stages of reception of the communication by a module or a control unit of a system according to the invention.

  This is more particularly shown to the lighting network data communication system according to the invention comprises at least one constant current regulator 1, a control unit 2 of lamp modules powered by the regulated current of the regulator 2865871 8 1, a power supply line 3 forming a primary loop, a set of lamps or lighting lights 4 connected in series on the supply line 3 by means of a transformer 5. A control module 6 of the lamps is generally disposed between each transformer 5 and each lamp 4 associated therewith.

  According to the invention, the unit 2 and the modules 6 comprise means for transmitting and receiving data frames on the line 3 by carrier current. Each transmitted data frame is encoded as a succession of bytes, in practice a succession of bytes. Each eight-bit byte bl, b2, ..., b8 is represented by eight distinct and simultaneous frequencies Fi, F2, ..., F8 accompanied by a control frequency F0. The frequency F1 is associated with the bit bi, the frequency F2 is associated with the bit b2 and so on. The frames thus composed transit through a chosen communication channel Ci, each channel Ci being assigned to a markup loop. So we have as many channels as markup loops. Frequency spacing between two Fi Fi + l lines of the same channel is reduced to a few tens of Hertz, which corresponds to a sufficient space to ensure a large number of channels. transmission while allowing their separation. The control frequency is used to ensure bit consistency in the byte. According to the invention, each frequency channel Ci is in a frequency band from about 1 kHz to about 7 kHz, which is well below the frequencies used in the prior art for power line data transmission in a lighting network.

  Two communication channels C1 and C6 are shown in Figure 2. The C1 channel has 9 frequency lines separated by 100 Hz. The first frequency line is located at 1 kHz and the last line is located at 1.8 kHz. We therefore have FO = 1 kHz, F1 = 1.1 kHz, F2 = 1.2 kHz, ..., F8 = 1.8 kHz. Similarly, the C6 channel has 9 frequency lines separated by 100 Hz. However, in the C6 channel, the first frequency line is located at 6 kHz. Between the channels C1 and C6, the channels C2, C3, C4 and C5, not shown in the figure, have likewise 9 frequency lines, the first line of said channels C2, C3, C4 and C5 being located, respectively, at the following frequencies : 2 kHz, 3 kHz, 4 kHz and 5 kHz.

  The frequency lines constituting the communication bytes advantageously all have the same amplitude on transmission. The approximation of these lines as well as the choice of the bandwidth of each communication channel Ci are chosen so as to minimize amplitude differences in the same channel. This makes it possible to correlate the amplitudes of each received line and consequently better eliminate the noise in the useful bandwidth.

  The data of the carrier current communication system according to the invention is transmitted on the power supply line 3, between a control unit 2 for control of the beacon control modules and said modules 6. In said unit 2, as in said modules 6, the received bytes are analyzed by a numerical calculation unit. Such a unit comprises a processor 60 as shown in FIG. 3. This processor 60 constitutes the core of the module 6. It is directly connected to power supply means 61, a communication and filtering interface 62, a current sensor 63 and it controls a switch 64 of the lamp 4. It carries out the analysis of the signals received in the communication band, the analysis of the current passing through the beacon 4 associated with the module 6, the decoding and the execution of the instructions from unit 2 and the coding of instructions or acknowledgments to be transmitted on the transmission line.

  The useful information is extracted from the signals coming from the communication interface 62 shown in FIG. 4. These signals are sampled at 600 and then a digital spectral analysis 601 of said signals is carried out in the frequency band ranging from 1 to 7 kHz. The signals are subsequently filtered 602 and the communication information is extracted 603. They are then decoded at 604 and 605. Thus, using signal processing algorithms, the useful information is extracted from the signals. from the communication interface. It will be noted that redundancy exists at two levels, on the one hand, at the content level of the frame by means of a checksum and on the other hand, at the digital signal processing where the duration of presence useful information on the markup line is significant in front of the occurrence of the noise in this same communication band.

  It is understood that, the remaining low frequencies in the band from 1 kHz to 7 kHz, the clean attenuation of the markup loop and its reactive elements is minimal. The system therefore becomes independent of the length of the beacon circuits and it is not necessary to provide a shunt device, whatever the installation.

  In addition, we have seen that the electrical properties of cables and markup transformers evolve over time. The variation in time of the amplitude and phase shift of the communication frequency lines provides relevant information on the aging of the power line. Previously, replacement of power cables occurred only after an incident or disaster. Thanks to the invention, it is possible to anticipate and locate, in the 2865871 12 module, the interventions on the electric power cables before any incident or disaster, by continuously calculating a coefficient of quality. In fact, after the step of extracting the communication information referenced 603 in FIG. 4, the instantaneous amplitudes and phase shifts of the communication frequencies as well as the minimum and maximum amplitudes and phase shifts of the communication frequencies are stored by the digital processor 60 606 and 607. A comparison of these amplitudes and phase shifts at 608 makes it possible to diagnose the quality of the markup line at the geographical point of the module and consequently to determine the health of the line 610.

  In other words, the monitoring of the amplitude and phase shift of the transmission channels makes it possible, over time, to follow the state of the transmission line by assigning it a quality factor corresponding to its state of degradation and aging.

  It should be noted that the use of all the bandwidth corresponding to all of the communication channels makes it possible to determine the basic attenuation of a markup line to the near module by analyzing the extreme frequency signals contained in the first one. frequency of the first channel and the last frequency of the last channel.

  It is furthermore understood that the low frequencies used place the transmission channels within any resonance of the loop: the system becomes almost independent of the configuration of the installation. In particular, the modifications of the marking circuits, in particular by adding or removing entire portions of the circuit, do not affect the quality of transmission. Similarly, no cap or series circuit is expected to improve the transmission.

  The auto-adaptive system of the emission level makes it possible to transmit on each loop the level of signal just necessary: the noise transmitted by crosstalk is thus reduced to a minimum. Regarding the remaining crosstalk noise, several transmission channels coexist in the bandwidth used. This makes it possible to assign different channels to the neighboring loops and a real differentiation of information between loops. In this way, the elimination of addressing errors or crosstalk collisions associated with the drastic reduction of crosstalk noise level allows communication in unscanned loops.

  Frequencies used, a few kHz, allow reliable operation in all common cases of defects for which the markup must work: earth faults, presence of reactive elements, such as burnt lamps. To a large extent, it can be said that, as long as a lamp is on, the communication within the system is valid, regardless of its state of degradation.

  Finally, the parallelization of the information bits makes it possible to maintain an optimum response time despite the low value of the frequencies constituting the transmission channels. Similarly, the reduction or elimination of the described defects allows the optimization of the communication protocol, without loss of time due to a catch-up or code corrections.

  Of course, the present invention is not limited to networks comprising long series circuits that are found in them in the field of airport lighting. Other networks, in particular networks comprising parallel circuits such as public lighting networks, can serve as a support for the implementation of the invention.

Claims (9)

  A data communication system in a powerline lighting network having at least one current regulator, a long power supply line, a plurality of lighting lamps, a lamp control module associated with a lighting lamp, and a control unit of this module, characterized in that bits b1, b1 of a multiplet of data exchanged between said unit and said module are transmitted between this unit and this module, so that simultaneous, in lines of frequency F1, Fn of a specific frequency channel Ci.   2. System according to claim 1, characterized in that the frequency channel Ci is in a frequency band from about 1 kHz to about 7 kHz.   3. System according to one of claims 1 or 2, characterized in that the frequency spacing between lines Fi and Fi + 1 of a set of lines F1, ..., Fn of the same frequency channel Ci is reduced to a few tens of Hertz.   4. System according to one of claims 1, 2 or 3, characterized in that it comprises a plurality of electrical power lines of great length and in that the data is exchanged in 2865871 16 specific channels, a channel being assigned to a power line.   5. System according to one of the claims   previous, characterized in that the frequency lines of the same channel have the same amplitude.   6. System according to one of the preceding claims, characterized in that the frequency lines Fi, F2, ..., F8 of a channel Ci are accompanied by a control frequency line F0.   7. System according to one of the preceding claims, characterized in that the lamp control module and / or the module control unit comprise a digital calculation unit capable of performing a comparison of the amplitudes and phase shifts of the frequencies of communication to derive information on the state of degradation of the transmission line.   8. System according to one of the preceding claims, characterized in that the lighting network is an airport marking system comprising a plurality of markup loop, the marker lights being mounted in said loops, in series.   A method of data communication in a powerline lighting network having a current regulator, a long power supply line, a plurality of lighting lamps, a lamp control module associated with a lighting lamp, and a control unit of this module, characterized in that bits b1, ..., bn of a multiplet of data exchanged between said unit and said module are transmitted between this unit and this modulates, simultaneously, in frequency lines F1,..., Fn of a specific frequency channel Ci.