EP0369373A1 - Initialization information transmitting system between fixed installations and trains - Google Patents

Abstract

Initialisation information transmitting system, between fixed installations and trains. It comprises, an initialisation loop (bi), physically constituted as a speed monitoring loop, a speed monitoring coil (cd), also used for receiving initialisation messages, a source of initialisation messages (si) connected to the initialising loop and delivering a message in the form of an initialisation carrier wave, having an initialisation frequency modulated by frequency jumps, the level of which is markedly greater than the level of the speed monitoring carrier wave, and initialisation information detecting circuits (di) connected to the speed monitoring coil and detecting the modulation by frequency jumps in order to deliver a received initialisation message, subordinate to a switching device (ad, dp, sd, ri) responding only upon receiving the initialisation frequency, when the latter possesses a level exceeding a specified threshold. <IMAGE>

Description

The present invention relates to railway signaling systems and, more particularly, information transmission systems between fixed installations and trains.

The object of the invention is an information transmission system of this type used for what is called the "initialization" of trains.

There is in fact known a system for driving and / or supervising trains, called SACEM (for "Driving, Operation and Maintenance Aid System"), comprising fixed installations along the tracks and a control equipment in each train. The control equipment of any train in the network under the control of SACEM receives fixed installations messages describing the part of the network, by "sections" of several cantons, which it will encounter while continuing its journey. The train control system thus receives "invariants", indications of a permanent nature, on the locations of switches, lights, sections at limited speed, slopes, etc., and "variant" indications which change over time, in particular on the position of the switches and lights. In addition, the train receives similar indications from the track when it crosses switches, lights and signs. By comparison, between these indications and integration of internal running data, the system is thus capable of locating the train in relation to the network and of adjusting the running of the train accordingly.

Such a system - and any similar system - obviously supposes an initialization of the control equipment of each train, on its entry into the network under the control of SACEM, so that this equipment receives, while the train is still outside the network. control, one or more messages describing sufficiently the section in which the train will enter upon entering the network, so that this control equipment allows the train to run - and prohibits it if the track is not clear. Likewise, an initialization is necessary in the case where a train is subject, for example, to a reversal or uncoupling.

Such initialization needs to be done under the strictest safety conditions, an error on initialization can cause an unexpected intrusion of the train into the controlled network.

The problem of message transmission from fixed installations to the train has received many solutions. In the SACEM system, for example, the message is transmitted by induction of a current on the rails. Security with regard to the falsification of a message is obtained by the redundancy contained in the messages received; the information contained in each message is subject to a compliance check of the message with respect to the environment, as already established in the train control system, from messages received previously and accepted . A message contradicting this environment is rejected.

In the case of initialization, such a measure is not applicable, since the environment is not yet established. This led, in the SACEM system, to provide specific initialization means. These take the form of an initialization loop arranged between the rails at each entry of the controlled network. This loop is supplied by an alternating current and in places includes crossings of wires such that the detection of this alternating current by a coil mounted on the train brings up phase inversions constituting coded information. Another loop arranged between the rails parallel to the first and read by another coil provides reference information allowing the interpretation of the coded information.

Such a system is satisfactory from the point of view of security. The signals coming from the two loops are not likely to be detected separately by the two initialization coils of a train located on a neighboring track and to communicate an erroneous initialization to it. However, there are two constraints: specific equipment must be mounted on the train and the train must be in motion for the initialization message to reach it.

A system for transmitting messages from fixed installations to trains is also known, used outside any controlled network, for controlling the speed of trains. At each transmission location, this system comprises an elongated loop arranged on either side of a rail, on the base of the rail, supplied by a frequency-modulated speed control carrier. This wave is detected by a speed control coil placed on the train opposite the rail. In fact two loops are arranged in parallel, one on each rail, and the train carries two speed control coils, one per rail. Such a system, used only for controlling the speed of the train, therefore not having a direct influence on the running of the train, need not offer great security. It presents in particular a risk of crosstalk, as will be seen, and therefore cannot be used for the secure transmission of initialization messages.

The present invention therefore relates to an initialization system which borrows from the second system mentioned, but by providing it with the necessary security, and allows initialization without the constraints stated in connection with the first system mentioned.

This results in significant material savings, means of transmission being used for two purposes, and, in operation, significant time savings, a train can be initialized when stopped, just before being authorized to move in the controlled network.

The transmission system of the invention comprises an initialization loop physically constituted as a speed control loop, a speed control coil, also used for the reception of initialization messages, a source of initialization messages connected to the initialization loop and providing a message in the form of an initialization carrier wave, having an initialization frequency modulated by frequency hopping, the level of which is clearly higher than the level of the control carrier wave speed, as well as initialization information detection circuits connected to the speed control coil and detecting frequency hopping modulation to provide a received initialization message, dependent on a switching device responding only upon receipt of the initialization frequency, when the latter has a level exceeding a predetermined threshold.

According to another characteristic of the invention, said switching device comprises, after the speed control coil, at least one linear amplifier and a circuit for detecting the level of the carrier wave, which drives a circuit provided with said predetermined threshold and provides a tilt signal when the level of the carrier wave exceeds this threshold.

According to another characteristic of the invention, said amplifier also controls two demodulators in parallel, one for detecting the frequency modulation of an initialization message and the other for detecting the frequency modulation of a control message speed, the output of one or the other of these demodulators only being active according to said switching signal.

According to another characteristic of the invention, said switching device comprises a control relay by said switching signal, this relay carrying at least one contact making active the output of one or the other of the two said demodulators.

According to another characteristic of the invention, said switching device also controls the output of a second modulator detecting the frequency modulation of a second speed control message that can be received by a second coil, so as to render the latter output inactive during reception of an initialization message.

According to another characteristic of the invention, the output of said level detection circuit of the carrier wave is connected, by a switching element controlled by said switching device, to a safe signaling circuit allowing the exploitation of the message d initialization as provided by the output of said demodulator detecting the frequency modulation of an initialization message.

According to another characteristic of the invention, said demodulator detecting the frequency modulation of an initialization message is a circuit evaluating the duration of the periods of the received modulated carrier wave and providing an output signal of a first level when this duration is on average greater than a predetermined duration and providing an output signal of a second level when this duration is on average less than this same duration or another predetermined duration.

We will now describe an example of an embodiment of the invention with reference to the appended figure which represents a system for transmitting initialization messages also including the reception of speed control messages.

The figure represents a rail r1, for example the rail must of a track, at the location of this track where a bi initialization loop is arranged. Parts bi1 and bi2 of this loop extend over the parts sm1 and sm2 of the sole of the rail, to the left, in the figure and, after a length of a few meters, they meet below the rail. On the right, in the figure, the conductors bi1 and bi2 are connected to a source of initialization messages si. This source of messages if is part of the fixed installations of a train control and / or supervision system of the type of the SACEM system already mentioned. It generates a carrier wave modulated by frequency hopping which is transmitted in the bi loop. The frequency of the carrier wave is for example 125 kHz, the current in the loop of 145 mA peak, the frequency jumps move the frequency +/- 10%, the frequency of the frequency jumps corresponding to a transmission speed of 250 Bauds. It should be emphasized at this stage that the current in the loop is deliberately chosen to be much higher than that which can be induced anywhere in the network for whatever reason under similar conditions.

A train to be initialized present above the loop carries a right sensor cd just above the rail r1. This sensor comprises an induction coil at the terminals of which appears a signal representative of the modulated carrier wave applied in the bi loop. The train may be stopped or in motion.

The signal from the sensor is transmitted through a fd filter, of the bandpass type, to a linear amplifier (in the level range provided) ad. This amplifier must be of the safe type, that is to say it must in no case amplify the signal at its input more than the maximum expected gain. A known type of amplifier of this type essentially comprises a common collector transistor amplifier followed by a step-up transformer. The amplifier provides a current gain, but its voltage gain is at most 1. The amplification in input signal voltage is therefore at most equal to the transformer transformation ratio.

The amplified signal is then supplied to a level detection circuit of the carrier wave dp which can be a simple peak rectifier.

The level of the carrier wave is communicated to a threshold circuit sd. This circuit can be a comparator which supplies a tilting signal exciting an initialization relay ri when the level of the carrier wave exceeds a predetermined threshold. The contacts ri1, ri2 and ri3 of this relay, represented in their rest position, then assume their working position.

The signal from the amplifier ad is also applied in parallel to two demodulators di and dv. The contact ri1 switches on the output sti only of the demodulator di, the output stv of the demodulator dv being made inactive.

The demodulator di, for secure transmission, will preferably be a period demodulator, that is to say a circuit evaluating the duration of periods (or half-periods) of the received modulated carrier wave and supplying an output signal d a first level when this duration is on average greater than a predetermined duration and providing an output signal of a second level when this duration is on average less than this same duration or another other predetermined duration. The start of each period of the received wave can thus trigger several time constant circuits, two of them, for example, delimiting time intervals the end of which frames the time scheduled for the end of the period, when the carrier wave frequency is increased by frequency hopping, while two others frame the end of the period when the frequency is decreased by frequency hopping. A logical combination of the outputs of these circuits thus provides, via an integration circuit, a signal having at least two states, one of them corresponding to a frequency increased by frequency hopping and the other state to any other frequency. It is also possible to provide an output with three states, corresponding respectively to an unmodulated frequency, an increased frequency and a decreased frequency. This signal supplied on the output sti is transmitted by the contact ri1 to the train control equipment, on a miv link.

The signal supplied by the carrier wave level detection circuit, when this threshold exceeds the predetermined threshold at the circuit sd, is transmitted by the contact ri2, on a link ei, in the direction of the train control equipment. There, to increase safety, the signal transmission can include a DC to DC converter providing safety decoupling. Indeed, the presence of this signal characterizes for the control equipment an initialization request and must in no case be able to be falsified, as a result of a component failure for example.

The initialization message transmitted by the source if, repeatedly, on the bi loop, is thus detected by a train which can come to a stop on the bi loop, and it is transmitted to the control equipment of this train,. The train control equipment can thus be initialized.

It will be noted that the contact ri3, which is open, isolates the left transmission chain, which will be described later, so that a disturbance on this chain cannot interfere with the initialization process.

The level of the message carrier wave being higher than any other signal likely to be induced along the right rail of the track, anywhere in the network, detection by exceeding a predetermined threshold puts the system safe from accidental imitation of an initialization message by another regular signal rement induced. This also resolves the case of the improper transmission of a true initialization message to a train not on the track on which this message is transmitted; its reception level is too low for the threshold to be reached. There remains the case where the amplifier ad enters into oscillation. The threshold of the sd circuit would obviously be reached. The probability that this oscillation occurs at the frequency of the initialization carrier is low, but because of nonlinear phenomena always present in such a case, a conventional frequency demodulator could provide demodulated signals capable of being accepted by the control equipment. However, the use of a period demodulator, in this case, with a response which can be closely centered on the two modulation frequencies, makes it possible in practice to avoid the risk of an incorrect response from the system d 'initialization.

We will now examine how the same equipment also allows the reception of speed control messages and how these can in no case be taken for initialization messages. It will therefore be assumed that the train is in line with a speed control loop which occupies the place of the bi loop in the figure.

A speed control message transmission loop is similar to the bi loop. However, the level of the signals transmitted on this loop is lower than the level of the initialization signals. The frequency of these signals is the same as that of the initialization signals. The modulation conditions are different. The modulation speed is in particular higher.

Such signals pass through the filter fd and the amplifier ad. The level detected by the dp circuit is too low to reach the threshold included in the sd circuit. The relay ri therefore remains at rest and its contacts in the position illustrated in the figure. No signal is not provided on the ei link. The received message cannot therefore be interpreted as an initialization message. The frequency demodulator dv, of conventional type, receives the signal present at the output of the amplifier ad, at the same time as the demodulator di. It demodulates it and provides the demodulated message on its stv output. As the contact ri1 is at rest, this output is active and the speed control message is transmitted to the train control equipment, via the miv link. The output of the demodulator di is inactive during this time. There is therefore no risk that the received message will be mistaken for an initialization message.

It is important to underline that all the elements contributing to the reception of this message also allow the reception of initialization messages, which brings a significant saving of material.

At the same time, the other rail of the track being equipped with a similar loop, a CG sensor, not shown, feeds a bandpass filter fg, an amplifier ag, a demodulator dg, the output of which is coupled by contact ri3 to a link. ed, which constitutes a left chain similar to the right chain which we have just described, which allows the transmission of a second speed control message to the train control equipment.

It will be noted that, in the case where the track equipped with the initialization loop is taken in the opposite direction by a train, the left chain and this train receives the signal from the bi loop. However, the right chain does not receive any signal capable of causing excitation of the ri relay. With the ri2 contact remaining open, the control equipment cannot accept an initialization message. Since the miv link does not receive any messages, the one provided on the left chain will be ignored.

Claims (7)

1. System for transmitting initialization information, between fixed installations and trains, characterized in that it comprises, an initialization loop (bi) physically constituted as a speed control loop, a control coil speed (cd), also used for receiving initialization messages, a source of initialization messages (si) connected to the initialization loop and supplying a message in the form of an initialization carrier wave, having an initialization frequency modulated by frequency hopping, the level of which is significantly higher than the level of the speed control carrier wave, as well as initialization information detection circuits (di) connected to the speed control and detecting frequency hopping modulation to provide a received initialization message, dependent on a switching device (ad, dp, sd, ri) responding only to the reception of the initialization frequency, when it has a level exceeding a predetermined threshold. 2. Initialization information transmission system according to claim 1, characterized in that said switching device comprises, after the speed control coil, at least one linear amplifier (ad) and a level detection circuit of the carrier wave (dp), which attacks a circuit (sd) provided with said predetermined threshold providing a tilt signal when the level of the carrier wave exceeds this threshold. 3. Initialization information transmission system according to claim 2, characterized in that said amplifier (ad) also controls two demodulators in parallel (di, dv), one (di) for detecting frequency modulation an initialization message and the other (dv) for detecting the frequency modulation of a speed control message, the output of one (sti) or the other (stv) of these demodulators only being active according to said switching signal. 4. Initialization information transmission system according to claim 2 or 3, characterized in that said switching device comprises a relay (ri) controlled by said switching signal, this relay carrying at least one contact (ri1) making the output of one or other of the two so-called demodulators active. 5. An initialization information transmission system according to claim 2 or 4, characterized in that said switching device also controls the output (sg) of a second modulator (dg) detecting the frequency modulation of a second speed control message can be received by a second coil, so as to make this last output inactive during the reception of an initialization message. 6. Initialization information transmission system according to claim 2 or 4, characterized in that the output of said level detection circuit of the carrier wave is connected, by a switching element (ri2) controlled by said switching device, to a secure signaling circuit (ei) allowing the exploitation of the initialization message as it is provided by the output of said demodulator (di) detecting the frequency modulation of an initialization message. 7. Initialization information transmission system according to claim 3, characterized in that said demodulator (di) detecting the frequency modulation of an initialization message is a circuit evaluating the duration of the periods of the wave modulated carrier received and providing an output signal of a first level when this duration is on average greater than a predetermined duration and providing an output signal of a second level when this duration is on average less than this same duration or another predetermined duration.

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