FR2765991A1 - ROAD SIGNALING LIGHT CONTROL EQUIPMENT WITH PRIORITY VEHICLE CONTROL - Google Patents

Abstract

The traffic light control equipment comprises a vehicle detection loop (4), a detector (2, 3) for varying the inductance of the loop (4) and a receiver (1) for signals induced in a loop (4) by a transmitter of a priority vehicle, the detector (2, 3) and the receiver (1) being arranged to be connected to said same loop (4).

Description

Traffic signal control equipment with

  priority vehicle control.

  The crossroads of automobile traffic lanes which have traffic lights regulating traffic are often equipped with vehicle detectors, in order to adapt the cycle of lights to the traffic of the various lanes. The detectors considered here include an inductive loop, embedded in the pavement, which is connected to an oscillator. Any metallic, magnetic mass passing over the loop modifies the inductance and causes a drift of the

oscillator frequency.

  In addition, apart from this evolutionary operation with traffic, we would like priority vehicles to be able to remote control or

telecontrol the fire cycle.

  Up to now, the magnetic mass detection loop has been doubled by another loop which, unlike the first, is an antenna for receiving specific signals emitted by a transmitter on board the priority vehicle. A specific receiver for the lighting control equipment in

then changes the cycle.

  For an equipment treating only one of the two possible loops, the addition of the second loop results in work on the road, which is expensive, and by material

additional equipment.

  The present invention aims to overcome this additional cost.

  To this end, the invention relates to equipment for controlling traffic lights comprising a vehicle detection loop, a detector of variation of the inductance of the loop and a receiver of signals induced in a loop by a transmitter of a priority vehicle, equipment characterized by the fact that the

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  detector and receiver are arranged to be connected to said same loop. Thus, a single sensor is sufficient for the two devices, detector and receiver, so that all civil engineering work is avoided in the case where a second device, detector or receiver, is added to a

equipment installed.

  The arrangement of the detector and the receiver can for example o include an adaptation of input impedance so that they do not

not disturb each other.

  Advantageously, there may also be provided switching means for. switch a connection link of the sensor s alternately on the detector and the receiver. Preferably, the detector and the receiver comprise means

common signal processing.

  The invention will be better understood using the detailed description

  following of a preferred embodiment of the light control equipment of the invention, with reference to the single figure

  which is a very schematic representation.

  The equipment, the electronic part of which is shown limited by a partial frame in dotted line, comprises two reception channels, with respectively a receiver I for priority vehicle signals and a receiver 2 for detecting drift of the impedance of a magnetic sensor, a magnetic loop 4,

common to both receivers 1, 2.

  A switching circuit 5 is here provided for alternately switching the inductive loop 4 on the receiver I and the receiver 2. On the loop side 4, the receiver 2 is connected to an input capacitor 3 to form therewith a variation detector. inductance L of loop 4, which forms, with capacitor 3, a

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  LC circuit, with determined resonant frequency. The circuit

  excitation of the LC circuit has not been shown.

  A common signal processing processor 6, DSP, receives the s signals detected by the receivers 1 and 2 in order to respectively search there for determined frequency signals originating from a transmitter, such as a leakage transformer, from a priority vehicle and for measuring or at least detect a frequency drift

of the LC circuit 3, 4.

  The processor 6, associated with a time base 10, samples the loop 4 through alternately the receivers 1 and 2, by command of the switch 5, to analyze the loop signals, here in time-sharing, and supplies to a controller-sequencer , not shown, for controlling lights, by output links 7 and 8, of the respective priority vehicle detection signals and

detection of any vehicle.

  It could have been planned to permanently connect, in parallel or even in series, the two receivers I and 2 - 3 to loop 4. In all cases, a significantly different oscillation frequency LC (3, 4) is chosen. that of the priority signals (1), in order to be able to separate the signals received by two bandpass switching filters in parallel, at high impedance outside their specific band. In the case of a series connection of the two detectors 1, 2 - 3, the filters in series must then have a low out-of-band impedance for

  avoid attenuating the signal from the other detector 1, 2 - 3.

  In this case too, the processor 6 can operate in timeshare to cyclically sample the output of the filters. The recognition of the frequency of the signals on the two channels can be carried out by a filter bank 9, preferably digital and

integrated into processor 6.

  Provision could also have been made not to physically separate the signals from the two channels 1, 2 - 3 and to apply the composite signal coming from loop 4 to a filter bank 9 corresponding to the

  respective frequency ranges of the two channels (1, 2 - 3).

  In particular, priority transmitters can provide for the transmission of signals of various priority on several frequencies.

  carriers with frequency or phase modulation.

  The DSP processor 6, connected to the two channels, can thus perform all the filtering tasks, the detector (s) (1 and 2) having only a role of amplification annex, if necessary, and of digitization if the DSP 6 does not include an analog / digital converter. As a result, the cost and volume of the equipment remains practically independent of the number of detection channels, only the software being

completed as required.

  As a variant, the detection of metallic mass can be carried out by detecting the variation in amplitude of the oscillation signal of the resonant circuit 3, 4. The LC circuit 3, 4 can be excited at fixed frequency and the variations in amplitude at its terminals linked to the variation in impedance of loop 4. Preferably, for optimal sensitivity, excitation is carried out at the resonance frequency and any reduction in the amplitude of the resonance signal is detected, which

  varies according to the selectivity of the resonant circuit.

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Claims (4)

  1.- Control equipment for traffic lights comprising a vehicle detection loop (4), a detector (2, s 3) of variation of the loop inductance (4) and a signal receiver (1) induced in a loop (4) by a transmitter of a priority vehicle, equipment characterized in that the detector (2, 3) and the receiver (1) are arranged to be connected to said same loop (4). 2.- Equipment according to claim 1, wherein the detector (2, 3) and the receiver (1) comprise common means (6) of signal processing.   is 3.- Equipment according to claim 2, wherein the means for   processing (6) operate on a timeshare basis.   4.- Equipment according to one of claims 2 and 3, wherein the   processing means include a processing processor (6) signal (DSP).   5.- Equipment according to one of claims 2 to 4, wherein the   processing means (6) comprise a bank of digital filters (9).   6.- Equipment according to one of claims I to 5, in which it   switching means (5) are provided for switching a sensor connection link (4) alternately on the   detector (2-3) and receiver (1).