EP0410878A1 - Verfahren zur Übertragung mittels Kabel eines analogen Sollwertes und System zur Durchführung des Verfahrens - Google Patents

Verfahren zur Übertragung mittels Kabel eines analogen Sollwertes und System zur Durchführung des Verfahrens Download PDF

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Publication number
EP0410878A1
EP0410878A1 EP90402136A EP90402136A EP0410878A1 EP 0410878 A1 EP0410878 A1 EP 0410878A1 EP 90402136 A EP90402136 A EP 90402136A EP 90402136 A EP90402136 A EP 90402136A EP 0410878 A1 EP0410878 A1 EP 0410878A1
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EP
European Patent Office
Prior art keywords
signal
square
transmission
predetermined
reception
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90402136A
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English (en)
French (fr)
Inventor
Claude Foltzer
Philippe Aubin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Faiveley Transport SA
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Faiveley Transport SA
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Filing date
Publication date
Application filed by Faiveley Transport SA filed Critical Faiveley Transport SA
Publication of EP0410878A1 publication Critical patent/EP0410878A1/de
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
    • G08C25/00—Arrangements for preventing or correcting errors; Monitoring arrangements
    • G—PHYSICS
    • G08—SIGNALLING
    • G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
    • G08C19/00—Electric signal transmission systems
    • G08C19/16—Electric signal transmission systems in which transmission is by pulses
    • G08C19/22—Electric signal transmission systems in which transmission is by pulses by varying the duration of individual pulses

Definitions

  • the present invention relates to a method of transmitting an analog setpoint by cable.
  • the invention also relates to a system for its implementation.
  • the invention relates in particular, but not limited to the application of the above method and system to the electrical control of the braking of railway vehicles.
  • the aforementioned system aims to replace the current pneumatic control systems which have the drawbacks of being heavy, of posing maintenance problems and of having relatively long reaction times.
  • This type of method does not, however, make it possible to envisage effective filtering over a narrow frequency band, a condition required in the practical situations concerned in the present application, and cannot lead to high immunity to disturbances.
  • the object of the present invention is to remedy these drawbacks by proposing a method of transmitting an analog setpoint from a transmission site to one or more reception sites connected to said transmission site by transmission cable, comprising, at emission site level: a step of generating a square-shaped signal at a predetermined reference frequency and with an emission duty cycle varying as a function of said analog setpoint according to a predetermined variation law, a step of modulation by said square signal of a signal at a first predetermined frequency during the upper part of said square signal, and at a second predetermined frequency during the lower part of said square signal, followed - a step of transmitting said modulated signal, and at a reception site, - a step of receiving the transmitted modulated signal, - A demodulation step thereof to extract a demodulated setpoint signal corresponding to said analog setpoint.
  • the first and second predetermined frequencies are chosen so that their difference is very small compared to their average value.
  • the aforementioned steps are carried out in a redundant manner, so that at least two modulated signals are transmitted respectively on at least two separate outgoing lines and the corresponding reception steps are followed by a step of indicating discrepancy and of a step of choosing a demodulated set signal from the demodulated signals, according to a predetermined availability criterion.
  • the system is given better reliability by increasing its level of availability.
  • the simultaneous failure of two channels for a time less than the repair time has such a low probability that it is not considered in practice.
  • the demodulation step comprises the following steps: - a step of filtering the modulated signal, - a shaping stage, a step of processing the modulated, filtered and shaped signal, in order to extract therefrom a signal resulting from a square shape and a reception duty cycle substantially equal to said emission duty cycle, and followed by a step of conversion of the duty cycle to receive the demodulated setpoint signal.
  • the system for transmitting an analog setpoint implementing the method according to the invention and comprising: at the emission site, - means for generating a shape signal square at a predetermined reference frequency and emission duty cycle varying as a function of said analog setpoint according to a predetermined variation law, means for modulating by said square signal a signal at a first predetermined frequency, during the upper part of said square signal, and at a second predetermined frequency during the lower part of said square signal, - Means for transmitting said modulated signal on a so-called forward line, is characterized in that it comprises at the reception site: means for receiving the modulated signal transmitted on a return line connected to the outgoing line, and means for demodulating the latter with a view to extracting therefrom a demodulated setpoint signal corresponding to said analog setpoint, said demodulation means being adapted for processing signals over a narrow frequency band including said first and second predetermined frequencies whose difference is very small compared to the average value.
  • the transmission system 1 shown in FIG. 1 comprises a receiver assembly R connected to the transmitter assembly E by transmission lines LA, LB.
  • This system is made up of two transmitter-receiver sub-assemblies or channels 1A, 1B which guarantee high reliability by redundancy.
  • Each channel 1A, 1B comprises a transmitter EA, EB receiving as input an analog reference signal CONS, with a value for example between 0 and 10 volts and delivering an output signal sA, sB, and a receiver RA, RB connected to its corresponding transmitter EA, EB by a line LA, LB of length D and delivering an output signal SA, SB.
  • the two output signals SA, SB are applied at the input of a discrepancy indication circuit ID and of a channel selection circuit CS which selects between the output signals SA, SB, the output signal EXP guaranteeing a good availability of the set. Any failure of one of the channels 1A, 1B is detected by the discrepancy indication circuit ID.
  • the coding of the reference signal CONS is carried out so as to guarantee good immunity to disturbances, in particular electromagnetic, and its principle is presented. in figure 2.
  • the transmission system 10 comprises, at the transmission level, a voltage / duty cycle converter module 11 receiving as input the analog setpoint to be transmitted CONS and delivering a square signal v c with a duty cycle P proportional to the analog setpoint CONS.
  • the square signal v c is then applied to the input of a voltage controlled oscillator 12 which generates a frequency modulated signal v s .
  • Galvanic isolation between the oscillator 12 and the transmission lines is provided by a transformer 13.
  • the modulated signal is applied to a forward line LA.
  • Each receiver RA1, ..., RAn is connected to a return line LR connected to the forward line LA.
  • a common line LC ensures the common point between the transmitter and the receivers RA1, ..., RAn.
  • the modulated output signal v s applied to the line LA has a wave form v s (t) illustrated in FIG. 3.
  • This signal is periodic with frequency Fo (period T) and comprises in each period two parts.
  • the modulated signal v s is sinusoidal at a predetermined frequency F2, while in the second part of duration PT, the signal v s is of frequency F1.
  • the second predetermined frequency F2 is greater than the first predetermined frequency F1, these two modulation frequencies being much greater than the frequency Fo of the square signal v c and close to each other, so that their difference is very small compared to their average.
  • is less than a tenth of the average (F1 + F2) / 2.
  • the frequency spectrum G (f) corresponding to the modulated output signal v s is represented in FIG. 4. It has two relative maxima corresponding respectively to the first predetermined frequency F1 and to the second predetermined frequency F2 relatively close to F1, the half width of the bump of the spectrum G (f) corresponding to F1 being equal to 1 / PT while the half-width of the other bump corresponding to F2 is equal to 1 / (1 - P). This curve indicates the maximum frequency congestion of the signal around the neighboring frequencies F1 and F2.
  • the sensitivity S (f) of the transmission system as a function of the frequency is represented in FIG. 5. It is noted that it is advantageous to bring the two frequencies F1, F2 together, without however making the information carried by the modulated signal confused .
  • a transmitter 20 preferably includes a module 11 for generating the square signal v c , a voltage-controlled oscillation module 12, a sinusoidal shaping circuit 25 and an isolation transformer 13, with reference to FIG. 6.
  • the generation module 11 comprises a comparator 21 at the negative input of which the analog reference signal to be transmitted CONS is applied and receiving at its positive input a signal v o of triangular shape and of predetermined frequency Fo from an appropriate generator 22
  • the comparator 21 delivers a square signal v c of duty cycle P directly linked to the setpoint level analog CONS. This square signal v c is then applied to the input of a switch 23 comprising for example an amplifier 23a and a transistor 23b of the MOSFET type.
  • This transistor 23b is placed in series with a secondary resistance r and ensures the selective paralleling of this secondary resistance r with the main resistance R of a time constant circuit [R, C] of a voltage controlled oscillator 24
  • This oscillator generates a triangular signal Ve which, like the signal Vs represented in FIG. 2, presents sequences at frequency F1 alternating with sequences at frequency F2.
  • a clipping circuit 25 makes it possible to obtain from the triangular signal v e a pseudo-sinusoidal signal v s which is sent in the line LA via an isolation transformer 13 ensuring the galvanic isolation between the emitter 20 and the line.
  • the distortion of the signal v s isssue from the clipper 25 is less than 5%.
  • FIG. 7 A particular embodiment of the receiver for a transmission system according to the invention is shown in FIG. 7.
  • the receiver 30 is connected to a return line LR and to a common line LC via an adaptation circuit, comprising a resistor 32 and a capacitor 31, and an isolation transformer 33.
  • the receiver 30 includes a demodulation unit 60 associated with a given transmission channel, for example channel 1A.
  • the receiver 30 then includes a channel selection circuit CS in order to determine the channel that can actually be used.
  • the demodulation unit 60 firstly comprises a bandpass filter 34 connected to the output of the transformer 33.
  • the filter 34 has a relatively narrow passband providing a favorable signal / noise ratio. It of course lets the signals of frequencies F1 and F2 to be interpreted whose frequencies F1 and F2 are reconciled as explained above.
  • This filter 34 used to guarantee immunity to parasites, is preferably a filter of order 2 with a quality coefficient greater than 4, for example equal to 6.
  • the filtered signal is shaped by means of a rocker 35 of RS type, the output of which is connected, on the one hand, to a monostable 36 and, on the other hand, to a branch circuit consisting of a resistor 41 and a capacitor 40.
  • the output of the monostable circuit 36 is connected to the input of an integrator-type circuit, comprising a resistor 37 and a capacitor 38, and the output of which is connected to the input of a sampler / blocker circuit 39 controlled by the pulses supplied by the differentiator 40, 41.
  • the signal delivered by the sampler / blocker 39 is then applied to a circuit 42 to extract the ripple which is then amplified by the amplifier circuit 43 and shaped by the circuit 44.
  • This signal is also applied to a comparator with window comprising of ux comparators 47, 49, the first comparator 47 having its positive input at an intermediate point of a divider bridge 45, 46, 48 and its negative input connected to the output of the sampler / blocker 39, while the second comparator 49 has its positive input connected to said output and its negative input connected to another intermediate point of the divider bridge 45, 46, 48.
  • this window comparator 47, 49 makes it possible to ensure that the DC component of the output signal of the sampler / blocker 39 is well between two predetermined values, which corresponds to a rejection of the frequencies outside of the useful band F1-F2.
  • the demodulated signal having a square waveform is applied to a duty cycle / voltage conversion circuit 50, consisting of a filter of order 4 to have a short delay time while having good suppression of the ripple on the SA setpoint signal.
  • the setpoint signal obtained is finally applied at the input of the channel selection circuit CS to be delivered as an exploitable signal EXP.
  • the signal SB originating from channel 1B which is taken into account as an exploitable signal, the failure of said channel being detected by the discrepancy indicator ID.
  • the waveform (a) is that of the modulated signal after shaping in the circuit 35. It is observed at this stage that the duty cycle in the part at the frequency F1 is equal to 1/2, which is also true in the part of the signal at frequency F2 (not shown).
  • the signal is then applied at the input of a monostable 36 which will deliver a signal having synchronous rising edges but a constant duration of slots whatever the frequency (F1 or F2).
  • the signal from the monostable 36 is then subjected to the integrator type circuit 37, 38.
  • the monostable 36 has imposed a constant high level duration while the low level duration depends on the frequency (F1 or F2)
  • the low value of the signal (b) at the output of the integrator 37, 38 will depend on the instantaneous frequency of the signal.
  • the duration of decrease of the signal (b) is necessarily less than the duration of decrease when the frequency is F1.
  • the low value of the signal (b) in the frequency sequence F1 is necessarily lower than the low value of the signal (b) in the frequency sequence F2.
  • the signal (b) is applied at the input of the sampler / blocker 39.
  • the latter being synchronized by the pulses (d) coming from the differentiator circuit 40, 41, it therefore outputs a signal (c) of square wave form and having a direct component directly linked to the frequencies of the modulated signal. If this DC component is found to be less than or greater than a predetermined value band, this means that the frequencies of the modulated signal do not correspond to the predetermined transmission frequencies.
  • the window comparator 45-49 performs this function of rejection of parasitic frequencies. From the signal (c), it is easy to extract an amplified and shaped square signal, which, after conversion by filtering in the circuit 50, will lead to the analog reference signal SA.
  • This principle of non-linear demodulation has the advantage of having a very short response time.
  • the system which has just been described is used as "general driving" for the transmission of the braking setpoint in a train.
  • the electrical control system advantageously replaces the current system with pneumatic control which has the drawbacks of being heavy, of posing sealing problems, of maintenance, of having relatively long reaction times, etc. All of these drawbacks are eliminated by the system according to the invention which has compared to known electrical systems (but which are not currently used) the advantages of being reliable and insensitive to electromagnetic disturbances.
  • the transmission technique which has just been presented can be applied in fields other than the railway field, when immunity to disturbances and reliability are important criteria in transmissions of analog quantities.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)
  • Transmitters (AREA)
EP90402136A 1989-07-26 1990-07-25 Verfahren zur Übertragung mittels Kabel eines analogen Sollwertes und System zur Durchführung des Verfahrens Withdrawn EP0410878A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8910077 1989-07-26
FR8910077A FR2650422B1 (fr) 1989-07-26 1989-07-26 Procede de transmission d'une consigne analogique par cable et systeme pour sa mise en oeuvre

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EP0410878A1 true EP0410878A1 (de) 1991-01-30

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EP90402136A Withdrawn EP0410878A1 (de) 1989-07-26 1990-07-25 Verfahren zur Übertragung mittels Kabel eines analogen Sollwertes und System zur Durchführung des Verfahrens

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EP (1) EP0410878A1 (de)
DE (1) DE410878T1 (de)
ES (1) ES2021570A4 (de)
FR (1) FR2650422B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996022125A1 (en) * 1995-01-19 1996-07-25 Medtronic, Inc. Method and apparatus for heart transplant monitoring and analog telemetry calibration

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3651765A (en) * 1970-04-14 1972-03-28 Westinghouse Air Brake Co Train line communication and control stem
FR2210311A5 (de) * 1972-12-13 1974-07-05 Arnoult Jean

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3651765A (en) * 1970-04-14 1972-03-28 Westinghouse Air Brake Co Train line communication and control stem
FR2210311A5 (de) * 1972-12-13 1974-07-05 Arnoult Jean

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
INSTRUMENTS AND EXPERIMENTAL TECHNIQUES. vol. 30, no. 1, janvier 1987, NEW YORK US pages 148 - 151; E.P.BOCHKAR et al: "Analog-digital optical telemetry line" *
PROCEEDINGS OF THE NATIONAL ELECTRONICS CONFERENCE. vol. 21, 1965, OAK BROOK, ILLINOIS pages 180 - 185; A.L.PACHYNSKI: "Journal temperature data transmission system using pulse duration modulation" *
RADIO FERNSEHEN ELEKTRONIK. vol. 30, no. 4, 1981, BERLIN DD pages 249 - 251; H.JULITZ: "10-Kanal-Telemetrieanlage" *
SIEMENS COMPONENTS. vol. XXII, no. 1, 1987, MUNCHEN DE pages 8 - 11; M.JUNG: "Potential-Free Transmission of DC Voltage Signals Using Pulse-Width Modulation" *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996022125A1 (en) * 1995-01-19 1996-07-25 Medtronic, Inc. Method and apparatus for heart transplant monitoring and analog telemetry calibration

Also Published As

Publication number Publication date
DE410878T1 (de) 1991-08-14
FR2650422A1 (fr) 1991-02-01
ES2021570A4 (es) 1991-11-16
FR2650422B1 (fr) 1994-10-21

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