US2622140A - High-frequency control system for traffic signals - Google Patents

High-frequency control system for traffic signals Download PDF

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Publication number
US2622140A
US2622140A US11464A US1146448A US2622140A US 2622140 A US2622140 A US 2622140A US 11464 A US11464 A US 11464A US 1146448 A US1146448 A US 1146448A US 2622140 A US2622140 A US 2622140A
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United States
Prior art keywords
radiator
frequency
radiation
impedance
amplifier
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Expired - Lifetime
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US11464A
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English (en)
Inventor
Muller Josef
Patry Jean
Baumberger Willy
Klein Albert
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.)
Siemens Schweiz AG
Albiswerk Zuerich AG
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Siemens Albis AG
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G1/00—Traffic control systems for road vehicles
    • G08G1/01—Detecting movement of traffic to be counted or controlled
    • G08G1/04—Detecting movement of traffic to be counted or controlled using optical or ultrasonic detectors
    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G1/00—Traffic control systems for road vehicles
    • G08G1/01—Detecting movement of traffic to be counted or controlled

Definitions

  • Treadle contacts built into the different traffic lanes of a street crossing and actuated by each vehicle to release a control impulse.
  • Treadle contacts of this kind require extensive ground installations that are apt to be affected by water and inoperative when covered by snow and ice.
  • transmitter-receiver systems operating with visible or invisible-optical radiation, or with sound waves of very high frequency, or with electromagnetic waves.
  • transmitter-receiver systems for radiation of various kinds avoid the shortcomings of a treadle-actuated installation, they are deficient in other respects.
  • the control equipment for the signal must not respond to pedestrians, nor to trolleys and other vehicle of the other traveling direction. This precludes installations in which a transmitter, located at one side of the street, directs a horizontal beam of radiation onto a receiver at the other side of the street.
  • Transmitter and receiver must be disposed close to each other above the road section under supervision. The radiation, directed from the transmitter onto the traffic lane should be reflected, from an object to be responded to, toward the receiver.
  • transmitter-receiver systems for high-frequency radiation fail to guarantee a satisfactory control.
  • Other objects of the invention are to readily permit confining the radiation beam of a radiation-type traffic detector to a desired area of a traffic lane so as to safely exclude interference due to trafiic on adjacent lanes or areas, and to provide a traffic detector of greatly improved sensitivity and selectivity.
  • the invention is based upon the recognition that the input impedance of an antenna varies in dependence upon conditions within the radiation field or space.
  • the radiation space With a radiator for highfrequency Waves, the radiation space, due to its total reflection and absorption phenomena, reacts back on the radiator as a complex load.
  • the impedance (radiation resistance) of the radiator i. e. the ratio of the applied voltage to the current taken up by the radiator, varies together with variations within the radiation space.
  • This dependence of directional radiation impedance upon the field conditions in the radiation space is utilized, according to the invention, for controlling a trafiic signal.
  • the impedance-responsive impulse producing devices with discriminator means so that a signal controlling impulse is issued only when the intensity and duration of the impedance variation exceed given minimum values.
  • the high-frequency radiator as a broadside array of dipoles and. operate it at a frequency whose wave length is not appreciably larger than the linear dimensions of the traiilc objects to be responded to.
  • the dipoles are designed and energized to operate in parallel resonance and have a length substantially equal to the wave length of the frequency radiation, these length magnitudes being preferably in the same order of magnitude as the averagelinear dimensions of the traffic objects.
  • FIG. l is a schematic illustration of a traffic detector and signal control system according to the invention
  • Figs. 2 to 5 show diagrammatically four respective embodiments of the variation-sensing and impulse controlling section of such a system.
  • a directional radiator 3 consisting of an array of five parallel dipole antennas, lying in a common plane, is energized from a high-frequency generator I.
  • the radiator emits a laterally limited beam of radiation toward the ground area 4 under supervision, for instance, a trafiic lane at a street crossing.
  • several, at least three, dipoles are required.
  • the operating point of the individual dipoles and the reflecting properties of the radiated ground area determine a definite normal impedance (radiation resistance) of the directional radiator, i. e. a given ratio of high-frequency current and high-frequency voltage at the input circuit of the directional radiator or at any other point of the transmission line between generator and radiator.
  • an object such as the vehicle 5, traversing the radiation beam and having linear dimensions approximately equal to the wave length of the radiated frequency, causes a variation in impedance of the radiator.
  • a detector device 2 is provided which senses these impedance changes and converts them into electric impulses.
  • a direct impedance gauge circuit may be used for this purpose, e. g. an impedancemeasuring bridge circuit.
  • the changes in radiation impedance may also be determined as current or voltage changes by means of a high-frequency current or voltage indicator. Of course, in all these cases a corresponding matching member between the high-frequency transmission and the radiator will be necessary.
  • the circuit tap points for current and voltage measurements must be properly selected.
  • the generator and couple it to the directional radiator in such a manner that the impedance variation of the radiator directly influences a characteristic operating quantity, e. g. the grid current, of the generator.
  • a characteristic operating quantity e. g. the grid current
  • the indicative impulses issuing from the de tector 2 depend, as to amplitude and time curve, upon the kind and velocity of the object responded to. They are, therefore, passed through a frequency-dependent discriminating device 6 whose time constant and sensitivity are adjusted so that only impulses of a desired amplitude and duration are released to a relay unit I for the control of the signallin device 8.
  • the discriminating device 6 is preferably designed as an impulse amplifier of adjustable time constant.
  • the operating point for the dipoles lies, preferably, within the range of parallel resonance because then the impedance curve is very steep so that small variations in field conditions cause large variations in impedance.
  • the length of the dipoles must be ap roximately equal to half the wave length of the radiated frequency.
  • a reflector 9 may be mounted above the dipoles 4 in order to secure a better utilization of the high-frequency energy.
  • the reflector may consist of sheet metal or wire mesh, or of an arrangement of reflector dipoles.
  • two or more directional radiators may be disposed above the respective lane areas, each having its own detector device for changes in radiation impedance, the indicating impulses from these detectors being diiferently responded to by a single discriminating device depending upon the timely sequence of the impulses.
  • the various directional radiators may be fed from a, single generator.
  • the traflic-responsive'variations of radiation impedance may be determined in various ways, in particular as changes in radiator input voltage or current, as changes in voltage to current ratio, or as changes in an electric operating magnitude of the generator. These possibilities are elucidated by the embodiments shown in Figs. 2 to 4 and described presently.
  • the array 3 of dipoles is connected to the transmission line by an impedance matching coupling comprising capacitors II and an inductive coupling member [2.
  • the voltage across the transmission line is applied to an amplifier from tap points located away from voltage nodes.
  • the signal from the amplifier is applied to'an electronic trigger unit [4 which issues its trigger impulses to the grid circuit of a thyratron IS.
  • the plate circuit of the thyratron is shown to be connected to the coil I6 of an electromagnetic relay in series with plate-current supply terminals I1.
  • the'detector, amplifier, trigger and other units may be integrated or built together in any suitable manner, for instance, to a single electronic tube arrangement and that the desired impulse producing, filtering or discrimin'atin functions may be assigned to any suitable unit or tube circuit section.
  • thetrigger circuit may consist of an impulseamplifier of" such characteristic that a firing impulse is issued to the thyratron only if the voltage across the input terminals of amplifier [3 drops below iven magnitude, and either amplifier l3 or unit I 4 may contain a timing circuit so that a iven duration of the voltage reduction isalso necessary for triggering the tube l 5.
  • the relay l6 represents the impulse responsive relay of a signal control device which need not depart from those known for treadle-aotuated or electromagnetically controlled signal systems.
  • the detector unit 2 If the detector unit 2 is to respond to'cha'nges in current, its amplifier, according to Fig. 3,- may be input-connected across a resistoror' any other available series impedance of the transmission line so that the voltage applied to theiampli-fier I3 is substantially proportional to the load current of the radiator, the rest of the system being otherwise similar to that of Fig. 2. It is obvious, that voltage response according to Fig. 2 ancl current response according to Fig. 3 may be combined by applying the two respective voltages to a ratio measuring circuit so that the control intelligence derived from the two voltages is more strictly a measure of the radiation resistance of the dipole array.
  • the highfrequency generator is composed of an oscillator I9 and a power amplifier 28 interconnected by a suitable coupling 2
  • Oscillator and amplifier are of customary design, except that the grid circuit of the amplifier tube 22 is coupled to an amplifier 23, for instance, across a resistor or other series impedance 24 of the grid circuit.
  • the grid current of tube 22 varies in dependence upo'n variations of the antenna input impedance and causes a corresponding voltage variation to occur across the input terminals of amplifier 23.
  • the amplified signals are applied to dis criminator and impulse transmitter sections as described in. the foregoing.
  • the coupling between high-frequency generator l and dipole array 3 is designed as a Lecher wire to facilitate matching of the antenna and transmission line impedances.
  • the shorting bar 32 and the feed points of a terminal bar 33 are preferably displaceable, as is indicated by arrows. By properly positioning the bars 32 and 33 relative to each other, the points of attachment to the detector unit 2 can readily be kept away frornvoltage nodes.
  • the detector unit 2 consists essentially of an electronic voltmeter with two symmetrically arranged diodes 3d and 35. Such high-frequency voltmeters are known as such so that details of unit 2 need, not be further described.
  • the output voltage of the detector is applied across the resistor of a potentiometric rheostat 36 in series with a source 3'! of directcurrent voltage.
  • Source 31 imposes a polarizing bias on the tube voltmeter so that the impulse amplifier 6, of which the rhetostat 36 forms part, is not afiected by the normal voltage impressed on the detector 2, but responds only to variations of that voltage.
  • the amplifier 6 comprises two tubes 38, as whose circuits include resistors, of which one is denoted by id, and capacitors of which one is denoted by 4!.
  • the amplifier circuits are essentially conventional, except that the output circuit includes in series the two coils 42, 43 of a difierential relay 44 and a capacitor is in parallel connection to only one of the two coils.
  • Relay 45 corresponds to relay It in Fig. 2, i. e. its contact 46 controls the operation of the traffic signal devices proper.
  • the sensitivity of the amplifier 6 can be adjusted by correspondingly adjusting the slide contact of rheostat 36 so that only voltage variations above a given minimum amplitude are ef- 3t flows through both windings 42, 43 of relay 44 whose fields cancel each other so that contact 46 remains open.
  • a sudden increase in plate current as caused by a detected voltage change of sufiicient magnitude and duration, is temporarily only effective in coil 43 but not in coil 42 because the capacitor 55, due to the sudden increase in voltage drop across coil 42, is charged and hence absorbs the current increase.
  • a sudden decrease in plate current of tube 39 is likewise temporarily effective in coil 53 only, while the current in coil 42 remains at first at the previous value due to the fact that capacitor 35 now discharges through coil Consequently, any sudden change in output current of amplifier 6 results in an unbalanced excitation of the two coils of the differential relay so that contact 46 is actuated and issues a control impulse to the trafllc signal devices.
  • a trafiic signal installation comprising a directional high-frequency radiator disposed above a surface area of the road lane and having a beam directed downwardly onto said area and laterally substantially limited to said area, a high-frequency generator connected to said radiator to provide energization therefor and having a frequency corresponding to a wave length in the order of magnitude of the average vehicle length, detector means connected with said radiator and responsive to input-impedance variations of said radiator due to vehicles passing through said beam, and trafiic signal means connected to said detector means to be controlled by said impulses.
  • a vehicle-controlled trafiic signal system comprising a high-frequency generator having a wave length in the order of magnitude of the average vehicle dimensions, a broadside array of antennas connected to said generator and being, when installed, horizontally disposed above a traffic lane area under supervision to direct a laterally confined beam downwardly toward said area, said antennas having a horizontal length substantially equal to said wave length, detector means connected to said array and responsive to variations in input impedance of said array due to vehicles passing through said beam, and signal control means connected to said detector means to be controlled by said variations.
  • a traffic-controlled signal system comprising a high-frequency generator having a wave length in the order of magnitude of the average vehicle length, a directional radiator disposed above a surface area under supervision for beaming high-frequency radiation toward said area, said radiator being composed of at least three dipoles disposed substantially in a common horizontal plane and having each a length substantially equal to said wave length to operate in parallel resonance, detector means responsive to variations in input impedance of said radiator due to vehicles passing through said beam, and signal control means connected to said detector means to be controlled in dependence upon given minimum conditions of said variations.
  • a traflic si nal syst m ac ordinet laim 2 comprising a reflective surface member disposed above said array and having a substantially horizontal reflective surface extending substantially over the entire length and width of Said, array.
  • a trafiic signal installation comprising a directional high-frequency radiator disposed above. a surface area of the roadlane and having a beam directed downwardly onto said area and laterally substantially limited to said area, a highfrequency generator connected to said radiator to provide energization therefor, said surface area having a surface layer whose dielectric constant has an average value of at least four, detector means connected with said radiator and responslve to input-impedance variations of said radiator due to vehicles passing through said beam, and traffic signal means connected to said detector .means to be controlled by said impulses.
  • a trafiic signal installation comprising a directional high-frequency radiator disposed above a surface area of the road lane and having a beam directed downwardly onto said area and laterally substantially limited to said area, a highfrequency generator connected to said radiator to provide energization therefor, metallic reflection means embedded in said area of said lane, detector-means connected with said radiator and responsive to input-impedance variations of said radiator due to vehicles passing through said beam, and traffic signal means connected to said detector means to be controlled by said impulses.
  • a trafiic signal system comprising a transmission line connecting said generator to said array, said detector means having a circuit member connected in said transmission line and responsive to the current flowing through said line from said generator to said array.
  • traific signal stem nr neio claim 2 comprising a frequency-dependent discriminator means of adjustable time constantbeing connected between said detector means and said signal control means for releasing control-pulses .to said signal means when said variationsexceed given intensity and duration values.
  • a traffic-responsive signal control system comprising a directional highs-frequency radiator to be disposed above a surface area so -as to direct a beam toward said area, a high-frequency generator connected to said radiatorto provide energization therefor, detector means responsive to variations in input impedance of said radiator due to objects passing through said beam, frequencyedependent discriminator means of adjustable time constant comprising an impulse amplifier andbeing connected with said detector means forreleasing control impulses in dependence upon given intensity. and duration ofsaid variations, and signal control means connected to saiddiscriminatormeans to be controlledby said impulses.

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  • General Physics & Mathematics (AREA)
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US11464A 1946-09-05 1948-02-27 High-frequency control system for traffic signals Expired - Lifetime US2622140A (en)

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GB (1) GB655876A (ja)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2965893A (en) * 1955-05-31 1960-12-20 Eastern Ind Inc Vehicle detector
US3042899A (en) * 1959-06-16 1962-07-03 Gen Railway Signal Co Ultrasonic vehicle detection system
US3042303A (en) * 1959-04-24 1962-07-03 Gen Railway Signal Co Object or vehicle detection system
US3045909A (en) * 1959-06-15 1962-07-24 Gen Railway Signal Co Pulsed ultrasonic detector
US3046519A (en) * 1959-10-28 1962-07-24 Gen Railway Signal Co Ultrasonic vehicle detection system
US3056106A (en) * 1958-07-14 1962-09-25 Gamewell Co Infrared detectors
US3063179A (en) * 1959-10-16 1962-11-13 Gen Railway Signal Co Vehicle parking area gate control system
US3105953A (en) * 1960-01-25 1963-10-01 Gen Signal Corp Directional sonic vehicle detector
US3109157A (en) * 1959-06-15 1963-10-29 Gen Signal Corp Directional traffic control system
US3110007A (en) * 1959-10-14 1963-11-05 Gen Signal Corp Ultrasonic vehicle detector
US3110008A (en) * 1960-05-09 1963-11-05 Gen Signal Corp Vehicle detection apparatus
US3152315A (en) * 1961-01-27 1964-10-06 Lab For Electronics Inc Aircraft tracking and indicating system
US3176266A (en) * 1960-08-12 1965-03-30 Gen Signal Corp Vehicular traffic detection system
US3278922A (en) * 1963-11-14 1966-10-11 Gen Electric Position and motion detector
US3663937A (en) * 1970-06-08 1972-05-16 Thiokol Chemical Corp Intersection ingress-egress automatic electronic traffic monitoring equipment
US5339081A (en) * 1991-04-09 1994-08-16 Peek Traffic Limited Vehicle detection systems
ITMI20091625A1 (it) * 2009-09-24 2011-03-25 Agla Elettronica S R L Sistema per rilevare automaticamente la presenza o assenza di oggetti in una predeterminata porzione di spazio da controllare, per esempio per rilevare i posti auto liberi o occupati in un parcheggio

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2358269A (en) * 2000-01-11 2001-07-18 Roke Manor Research Vehicle detection

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1658953A (en) * 1924-12-11 1928-02-14 Firm Of M J Goldberg Signaling apparatus
US1898432A (en) * 1929-10-02 1933-02-21 Paul S Edwards Reactance controlled relay
US1917243A (en) * 1929-09-13 1933-07-11 Paul S Edwards Ultra sensitive relay
US2031951A (en) * 1932-02-25 1936-02-25 Bell Telephone Labor Inc Burglar alarm system
US2238041A (en) * 1939-03-03 1941-04-15 Dickens Harry Power control system
US2290771A (en) * 1939-04-25 1942-07-21 Rca Corp Relay system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1658953A (en) * 1924-12-11 1928-02-14 Firm Of M J Goldberg Signaling apparatus
US1917243A (en) * 1929-09-13 1933-07-11 Paul S Edwards Ultra sensitive relay
US1898432A (en) * 1929-10-02 1933-02-21 Paul S Edwards Reactance controlled relay
US2031951A (en) * 1932-02-25 1936-02-25 Bell Telephone Labor Inc Burglar alarm system
US2238041A (en) * 1939-03-03 1941-04-15 Dickens Harry Power control system
US2290771A (en) * 1939-04-25 1942-07-21 Rca Corp Relay system

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2965893A (en) * 1955-05-31 1960-12-20 Eastern Ind Inc Vehicle detector
US3056106A (en) * 1958-07-14 1962-09-25 Gamewell Co Infrared detectors
US3042303A (en) * 1959-04-24 1962-07-03 Gen Railway Signal Co Object or vehicle detection system
US3109157A (en) * 1959-06-15 1963-10-29 Gen Signal Corp Directional traffic control system
US3045909A (en) * 1959-06-15 1962-07-24 Gen Railway Signal Co Pulsed ultrasonic detector
US3042899A (en) * 1959-06-16 1962-07-03 Gen Railway Signal Co Ultrasonic vehicle detection system
US3110007A (en) * 1959-10-14 1963-11-05 Gen Signal Corp Ultrasonic vehicle detector
US3063179A (en) * 1959-10-16 1962-11-13 Gen Railway Signal Co Vehicle parking area gate control system
US3046519A (en) * 1959-10-28 1962-07-24 Gen Railway Signal Co Ultrasonic vehicle detection system
US3105953A (en) * 1960-01-25 1963-10-01 Gen Signal Corp Directional sonic vehicle detector
US3110008A (en) * 1960-05-09 1963-11-05 Gen Signal Corp Vehicle detection apparatus
US3176266A (en) * 1960-08-12 1965-03-30 Gen Signal Corp Vehicular traffic detection system
US3152315A (en) * 1961-01-27 1964-10-06 Lab For Electronics Inc Aircraft tracking and indicating system
US3278922A (en) * 1963-11-14 1966-10-11 Gen Electric Position and motion detector
US3663937A (en) * 1970-06-08 1972-05-16 Thiokol Chemical Corp Intersection ingress-egress automatic electronic traffic monitoring equipment
US5339081A (en) * 1991-04-09 1994-08-16 Peek Traffic Limited Vehicle detection systems
ITMI20091625A1 (it) * 2009-09-24 2011-03-25 Agla Elettronica S R L Sistema per rilevare automaticamente la presenza o assenza di oggetti in una predeterminata porzione di spazio da controllare, per esempio per rilevare i posti auto liberi o occupati in un parcheggio
EP2302410A1 (en) * 2009-09-24 2011-03-30 Agla Elettronica S.R.L. System for automatically detecting the presence or absence of objects in a predetermined portion of space to be monitored, for example for detecting free or occupied parking spaces in a car park

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BE478044A (ja) 1948-01-31
GB655876A (en) 1951-08-08
FR956864A (ja) 1950-02-09
CH270146A (de) 1950-08-15

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