EP0570755A1 - In a road surface or the like installed induction loop - Google Patents

In a road surface or the like installed induction loop Download PDF

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Publication number
EP0570755A1
EP0570755A1 EP93107192A EP93107192A EP0570755A1 EP 0570755 A1 EP0570755 A1 EP 0570755A1 EP 93107192 A EP93107192 A EP 93107192A EP 93107192 A EP93107192 A EP 93107192A EP 0570755 A1 EP0570755 A1 EP 0570755A1
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EP
European Patent Office
Prior art keywords
loop
induction loop
induction
inductance
detector
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Withdrawn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
EP93107192A
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German (de)
French (fr)
Inventor
Lutz Dipl.-Ing. Breitkreuz
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.)
Airbus Defence and Space GmbH
Original Assignee
Deutsche Aerospace AG
Daimler Benz Aerospace AG
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Filing date
Publication date
Application filed by Deutsche Aerospace AG, Daimler Benz Aerospace AG filed Critical Deutsche Aerospace AG
Publication of EP0570755A1 publication Critical patent/EP0570755A1/en
Withdrawn legal-status Critical Current

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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
    • G08G1/042—Detecting movement of traffic to be counted or controlled using inductive or magnetic detectors

Definitions

  • the invention relates to an induction loop according to the preamble of claim 1.
  • induction loops arranged in lanes are generally known.
  • the operation of such induction loops can be seen from Siemens data sheet 1/91.
  • an inductive loop in the road is traversed by alternating current (approx. 40 ... 100 kHz), which an oscillator generates on the module.
  • the loop inductance L together with the feed line determine the frequency.
  • This loop current results in an alternating magnetic field in the area of perception of the loop, which generates eddy currents in the metal parts of a vehicle located there, which in turn influence the alternating field, so that the loop inductance decreases. This results in an increase in the loop frequency.
  • the change in the loop inductance defined as "loop detuning" dL / L, is used for vehicle detection and is measured by the detector. The sensitivity of the detector is pre-selected in 3 or 2 steps. To record only motor vehicles, the correct response threshold is set automatically by "observing" the passing vehicles (learning effect).
  • a detector module contains two evaluation circuits for one inductive loop each, which are fed by separate loop generators. To avoid mutual interference, different frequencies (channels) are used. They can be selected using rotary switches. The adjustment takes place automatically.
  • the detector works with a specially developed, application-specific circuit (ASIC), which enables a very fast frequency measurement, and a microprocessor, the program of which determines the detector function.
  • ASIC application-specific circuit
  • the detector issues messages about the occupancy of the loop, with double loops also about the direction of travel, vehicle speed and vehicle type, as well as error messages.
  • states or values can also be queried via a serial interface.
  • the length of the supply lines between the induction loop and the detector is limited to approximately 150 m, in the case of a signal which is constantly deteriorating with supply lines becoming longer and longer.
  • a loop detector is also limited to this distance, as described on page 3 of a brochure by Weiss-Electronic GmbH, D-5500 Trier.
  • the invention is therefore based on the object of improving an induction loop of the type mentioned at the outset in such a way that larger distances of, for example, 750 m to 1250 m can be chosen between the induction loop and the detector.
  • the object is achieved in that the capacitor of the resonant circuit in the immediate vicinity the induction loop is arranged, and that for feeding the electrical energy into the resonant circuit, the inductance is arranged spatially distant from the induction loop and is electrically conductively connected to the terminals thereof via long leads.
  • An advantage of the invention lies in particular in the use of a plurality of induction loops one behind the other in the direction of the lane in the saving of a large number of switch cabinets and their energy supply.
  • An advantage can also be seen in a qualitative signal improvement even with longer supply lines than before between the detector and the induction loop.
  • L s shows a three-turn induction loop L s , the inductance of which is approximately 120 ⁇ H.
  • the terminals of this loop are arranged in a sleeve 1 and connected via a two-wire line 2 of a maximum length of 150 m (z. B. Telecommunications cable with about 800 uH / m) to a detector 3, which contains a transmitter and receiver part.
  • the transmitter contains the capacitor C s belonging to the resonant circuit and an inductive transformer, denoted by L u , which is controlled via transistors 4 and 5 with a transmission pattern.
  • the receiver has a reception winding 6, which belongs to L ü , and an evaluation device 7 arranged downstream of this coil.
  • the resonant circuit is excited with a few pulses and then continues to oscillate automatically in its resonance frequency.
  • the reason for the length limitation of the lead 2 lies in its inductance, which acts like a series connection to the induction loop L s .
  • the resonant circuit is thus formed by the inductance of the induction loop L s , by the inductance of the transformer L ü and the capacitor C s , so that the influence of a change in the inductance of the loop L s , that is to say the loop detuning, decreases with the length of the lead 2.
  • the quality of the resonant circuit consisting of C s and L s is also impaired by the transmission losses of the transformer L ü , in particular because the constant reloading of the energy between C s and L s must take place via the transformer.
  • the inventive arrangement shown in Fig. 2 differs from that of FIG. 1 in that the capacitor C s of the resonant circuit is arranged in the immediate vicinity of the induction loop L s , and that for feeding the electrical energy into the induction loop L s, the inductance of Transmitter L ü is used, that is, the resonant circuit of induction loop L s and capacitor C s arranged spatially distant and with their terminals via a long lead 2 of z. B. 750 m to 1250 m is electrically connected.
  • the immediately adjacent arrangement of the induction loop L s and capacitor C s is aimed at an ideal resonant circuit in which the electrical energy is transmitted via the lead 2 to the capacitor C s .
  • the resonant circuit vibrates with high quality. It does not constantly, as after Figure 1, electrical power on the supply line 2 and transmitter L u between the inductive loop L s and are transmitted to the capacitor C s; rather, the supply line 2 mainly acts as a measuring line.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Traffic Control Systems (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

An induction loop, arranged in a roadway or the like, preferably for detecting the road traffic caused by vehicles or the vehicle utilisation of parking spaces or airports. The induction loop is fed via supply leads with an alternating current which is produced by a tuned circuit and produces eddy currents in the metallic parts of a vehicle located above the induction loop, which eddy currents reduce the loop inductance and cause an increase in the loop frequency. The change (which is called the loop mistuning) in the loop inductance is supplied to a detector with a downstream-connected evaluation device. Relatively large distances between the induction coil and the detector can be selected by the capacitor (Cs) of the tuned circuit being arranged in the immediate vicinity of the induction loop (Ls), and by the inductance (Lü) for supplying the electrical energy in the tuned circuit being arranged physically separated from the induction loop (Ls) and being electrically conductively connected to its connecting terminals via long supply leads (2). <IMAGE>

Description

Die Erfindung betrifft eine Induktionsschleife gemäß dem Oberbegriff von Anspruch 1.The invention relates to an induction loop according to the preamble of claim 1.

Beispielsweise in Fahrbahnen angeordnete Induktionsschleifen vorzugsweise zur Erfassung des Straßenverkehrs oder der Fahrzeugbelegung von Parkplätzen sind allgemein bekannt. So ist beispielsweise aus dem Siemens-Datenblatt 1/91 die Arbeitsweise derartiger Induktionsschleifen ersichtlich.For example, induction loops arranged in lanes, preferably for detecting road traffic or the occupancy of parking spaces, are generally known. For example, the operation of such induction loops can be seen from Siemens data sheet 1/91.

Hiernach wird eine Induktivschleife in der Fahrbahn von Wechselstrom (ca. 40...100 kHz) durchflossen, den ein Oszillator auf der Baugruppe erzeugt. Frequenzbestimmend ist die Schleifeninduktivität L zusammen mit der Zuleitung. Dieser Schleifenstrom hat im Wahrnehmungsbereich der Schleife ein magnetisches Wechselfeld zur Folge, das in den Metallteilen eines sich dort aufhaltenden Fahrzeugs Wirbelströme erzeugt, die wiederum das Wechselfeld beeinflussen, so daß die Schleifeninduktivität sinkt. Dies hat ein Ansteigen der Schleifenfrequenz zur Folge. Die Änderung der Schleifeninduktivität, definiert als "Schleifenverstimmung" dL/L, dient zur Fahrzeugerkennung und wird vom Detektor gemessen. Die Empfindlichkeit des Detektors wird in 3 bzw. 2 Stufen vorgewählt. Zur Erfassung von nur Kraftfahrzeugen erfolgt die Einstellung der richtigen Ansprechschwelle automatisch durch "Beobachtung" der vorbeifahrenden Fahrzeuge (Lerneffekt).After that, an inductive loop in the road is traversed by alternating current (approx. 40 ... 100 kHz), which an oscillator generates on the module. The loop inductance L together with the feed line determine the frequency. This loop current results in an alternating magnetic field in the area of perception of the loop, which generates eddy currents in the metal parts of a vehicle located there, which in turn influence the alternating field, so that the loop inductance decreases. This results in an increase in the loop frequency. The change in the loop inductance, defined as "loop detuning" dL / L, is used for vehicle detection and is measured by the detector. The sensitivity of the detector is pre-selected in 3 or 2 steps. To record only motor vehicles, the correct response threshold is set automatically by "observing" the passing vehicles (learning effect).

Eine Detektorbaugruppe enthält zwei Auswerteschaltungen für je eine Induktivschleife, die von getrennten Schleifengeneratoren gespeist werden. Zur Vermeidung gegenseitiger Beeinflussung werden unterschiedliche Frequenzen (Kanäle) benutzt. Sie sind durch Drehschalter wählbar. Der Abgleich erfolgt automatisch. Der Detektor arbeitet mit einem speziell entwickelten, anwendungsspezifischen Schaltkreis (ASIC), der eine sehr schnelle Frequenzmessung ermöglicht, und einem Mikroprozessor, dessen Programm die Detektorfunktion bestimmt. Vom Detektor werden an parallenen elektronischen Ausgängen Meldungen über die Belegung der Schleife, bei Doppelschleifen auch über Fahrtrichtung, Fahrzeuggeschwindigkeit und Fahrzeugart, sowie Fehlermeldungen abgegeben. Zusätzlich können Zustände bzw. Werte auch über eine serielle Schnittstelle abgefragt werden.A detector module contains two evaluation circuits for one inductive loop each, which are fed by separate loop generators. To avoid mutual interference, different frequencies (channels) are used. They can be selected using rotary switches. The adjustment takes place automatically. The detector works with a specially developed, application-specific circuit (ASIC), which enables a very fast frequency measurement, and a microprocessor, the program of which determines the detector function. At the parallel electronic outputs, the detector issues messages about the occupancy of the loop, with double loops also about the direction of travel, vehicle speed and vehicle type, as well as error messages. In addition, states or values can also be queried via a serial interface.

Bei der eingangs beschriebenen Anordnung ist es von Nachteil, daß die Länge der Zuleitungen zwischen Induktionsschleife und Detektor auf ca. 150 m, bei sich ständig verschlechterndem Signal mit länger werdenden Zuleitungen, begrenzt ist. Auf diesen Abstand ist auch ein Loop-Detektor beschränkt, wie in einem Prospektblatt der Fa. Weiss-Electronic GmbH, D-5500 Trier auf Seite 3 beschrieben ist.In the arrangement described at the outset, it is disadvantageous that the length of the supply lines between the induction loop and the detector is limited to approximately 150 m, in the case of a signal which is constantly deteriorating with supply lines becoming longer and longer. A loop detector is also limited to this distance, as described on page 3 of a brochure by Weiss-Electronic GmbH, D-5500 Trier.

Der Erfindung liegt daher die Aufgabe zugrunde, eine Induktionsschleife der eingangs genannten Art derart zu verbessern, daß größere Abstände von beispielsweise 750 m bis 1250 m zwischen Induktionsschleife und Detektor gewählt werden können.The invention is therefore based on the object of improving an induction loop of the type mentioned at the outset in such a way that larger distances of, for example, 750 m to 1250 m can be chosen between the induction loop and the detector.

Die Aufgabe wird erfindungsgemäß dadurch gelöst, daß der Kondensator des Schwingkreises in unmittelbarer Nähe der Induktionsschleife angeordnet ist, und daß zur Einspeisung der elektrischen Energie in den Schwingkreis die Induktivität von der Induktionsschleife räumlich entfernt angeordnet und mit deren Anschlußklemmen über lange Zuleitungen elektrisch leitend verbunden ist.The object is achieved in that the capacitor of the resonant circuit in the immediate vicinity the induction loop is arranged, and that for feeding the electrical energy into the resonant circuit, the inductance is arranged spatially distant from the induction loop and is electrically conductively connected to the terminals thereof via long leads.

Ausgestaltungen der Erfindung sind in den Unteransprüchen 2 und 3 beschreiben.Embodiments of the invention are described in subclaims 2 and 3.

Ein Vorteil der Erfindung liegt insbesondere bei der Anwendung von mehreren, in Fahrbahnrichtung hintereinanderliegenden Induktionsschleifen in der Einsparung einer Vielzahl von Schaltschränken sowie deren Energieversorgung. Ein Vorteil ist auch in einer qualitativen Signalverbesserung selbst bei längeren Zuleitungen als zuvor zwischen Detektor und Induktionsschleife zu sehen.An advantage of the invention lies in particular in the use of a plurality of induction loops one behind the other in the direction of the lane in the saving of a large number of switch cabinets and their energy supply. An advantage can also be seen in a qualitative signal improvement even with longer supply lines than before between the detector and the induction loop.

In der Zeichnung ist ein Ausführungsbeispiel nach der Erfindung dargestellt, und zwar zeigt:

Fig. 1
eine dem Stand der Technik angehörende Schleifen-Detektor-Anordnung, und
Fig. 2
eine erfindungsgemäße Induktionsschleife mit zugehörigem Detektor.
In the drawing, an embodiment according to the invention is shown, namely:
Fig. 1
a prior art loop detector arrangement, and
Fig. 2
an induction loop according to the invention with an associated detector.

In Fig. 1 ist eine drei Windungen aufweisende Induktionsschleife Ls dargestellt, deren Induktivität etwa 120 µH beträgt. Die Anschlußklemmen dieser Schleife sind in einer Muffe 1 angeordnet und über eine zweiadrige Leitung 2 von maximal 150 m Länge (z. B. Fernmeldkabel mit etwa 800 µH/m) an einen Detektor 3 angeschlossen, der einen Sender- und Empfängerteil enthält. Der Sender enthält den zum Schwingkreis gehörenden Kondensator Cs und einen induktiven Übertrager, mit Lü bezeichnet, der über Transistoren 4 und 5 mit einem Sendemuster angesteuert wird. Der Empfänger weist eine Empfangswicklung 6, die zu Lü gehört, und eine dieser Spule nachgeordnete Auswerteeinrichtung 7 auf. Über die Sendetransistoren wird der Schwingkreis mit wenigen Impulsen angeregt und oszilliert dann in seiner Resonanzfrequenz selbsttätig weiter. Bei dieser vorbekannten Anordnung liegt der Grund für die Längenbegrenzung der Zuleitung 2 in ihrer Induktivität, die wie eine Serienschaltung zu der Induktionsschleife Ls wirkt. Der Schwingkreis wird somit durch die Induktivität der Induktionsschleife Ls, durch die Induktivität des Übertragers Lü und den Kondensator Cs gebildet, so daß der Einfluß einer Änderung der Induktivität der Schleife Ls, also die Schleifenverstimmung mit der Länge der Zuleitung 2 abnimmt. Zusätzlich zur Zuleitungsinduktivität wird die Güte des Schwingkreises aus Cs und Ls auch noch durch die Übertragungsverluste des Übertragers Lü verschlechert, insbesondere weil das ständige Umladen der Energie zwischen Cs und Ls über den Übertrager erfolgen muß.1 shows a three-turn induction loop L s , the inductance of which is approximately 120 μH. The terminals of this loop are arranged in a sleeve 1 and connected via a two-wire line 2 of a maximum length of 150 m (z. B. Telecommunications cable with about 800 uH / m) to a detector 3, which contains a transmitter and receiver part. The transmitter contains the capacitor C s belonging to the resonant circuit and an inductive transformer, denoted by L u , which is controlled via transistors 4 and 5 with a transmission pattern. The receiver has a reception winding 6, which belongs to L ü , and an evaluation device 7 arranged downstream of this coil. About the Transmitting transistors, the resonant circuit is excited with a few pulses and then continues to oscillate automatically in its resonance frequency. In this known arrangement, the reason for the length limitation of the lead 2 lies in its inductance, which acts like a series connection to the induction loop L s . The resonant circuit is thus formed by the inductance of the induction loop L s , by the inductance of the transformer L ü and the capacitor C s , so that the influence of a change in the inductance of the loop L s , that is to say the loop detuning, decreases with the length of the lead 2. In addition to the lead inductance, the quality of the resonant circuit consisting of C s and L s is also impaired by the transmission losses of the transformer L ü , in particular because the constant reloading of the energy between C s and L s must take place via the transformer.

Die in Fig. 2 dargestellte erfinderische Anordnung unterscheidet sich von derjenigen gemäß Fig. 1 dadurch, daß der Kondensator Cs des Schwingkreises in unmittelbarer Nähe der Induktionsschleife Ls angeordnet ist, und daß zur Einspeisung der elektrischen Energie in die Induktionsschleife Ls die Induktivität des Übertragers Lü dient, also der Schwingkreis aus Induktionsschleife Ls und Kondensator Cs räumlich entfernt angeordnet und mit deren Anschlußklemmen über eine lange Zuleitung 2 von z. B. 750 m bis 1250 m elektrisch leitend verbunden ist. Durch die unmittelbar benachbarte Anordnung von Induktionsschleife Ls und Kondensator Cs, beispielsweise in der Anschlußmuffe 1 der Induktionsschleife Ls, wird ein idealer Schwingkreis angestrebt, bei dem die elektrische Energie über die Zuleitung 2 in den Kondensator Cs übertragen wird. Der Schwingkreis schwingt mit hoher Güte. Es muß nicht ständig, wie nach Fig.1, elektrische Energie über die Zuleitung 2 und Übertrager Lü zwischen der Induktionsschleife Ls und dem Kondensator Cs übertragen werden; vielmehr wirkt die Zuleitung 2 vorwiegend als Meßleitung.The inventive arrangement shown in Fig. 2 differs from that of FIG. 1 in that the capacitor C s of the resonant circuit is arranged in the immediate vicinity of the induction loop L s , and that for feeding the electrical energy into the induction loop L s, the inductance of Transmitter L ü is used, that is, the resonant circuit of induction loop L s and capacitor C s arranged spatially distant and with their terminals via a long lead 2 of z. B. 750 m to 1250 m is electrically connected. The immediately adjacent arrangement of the induction loop L s and capacitor C s , for example in the connecting sleeve 1 of the induction loop L s , is aimed at an ideal resonant circuit in which the electrical energy is transmitted via the lead 2 to the capacitor C s . The resonant circuit vibrates with high quality. It does not constantly, as after Figure 1, electrical power on the supply line 2 and transmitter L u between the inductive loop L s and are transmitted to the capacitor C s; rather, the supply line 2 mainly acts as a measuring line.

Claims (3)

In einer Fahrbahn oderdergleichen angeordnete Induktionsschleife vorzugweise zur Erfassung des durch Fahrzeuge hervorgerufenen Straßenverkehrs oder der Fahrzeugbelegung von Parkplätzen oder Flughäfen, wobei die Induktionsschleife über Zuleitungen mit einem von einem Schwingkreis erzeugten Wechselstrom gespeist wird, der in den metallischen Teilen eines über der Induktionsschleife befindlichen Fahrzeuges Wirbelströme erzeugt, die ein Absinken der Schleifeninduktivität und einen Anstieg der Schleifenfrequenz bewirken, und wobei die als Schleifenverstimmung bezeichnete Änderung der Schleifeninduktivität einem Detektor mit nachgeschalteter Auswerteeinrichtung zugeführt wird, dadurch gekennzeichnet, daß der Kondensator (Cs) des Schwingkreises in unmittelbarer Nähe der Induktionsschleife (Ls) angeordnet ist, und daß zur Einspeisung der elektrischen Energie in den Schwingkreis die Induktivität (Lü) von der Induktionsschleife (Ls) räumlich entfernt angeordnet und mit deren Anschlußklemmen über lange Zuleitungen (2) elektrisch leitend verbunden ist.An induction loop arranged in a roadway or the like, preferably for detecting the road traffic caused by vehicles or the occupancy of parking spaces or airports, the induction loop being fed via feed lines with an alternating current generated by an oscillating circuit which generates eddy currents in the metallic parts of a vehicle located above the induction loop , which cause a decrease in the loop inductance and an increase in the loop frequency, and wherein the change in the loop inductance referred to as loop detuning is fed to a detector with a downstream evaluation device, characterized in that the capacitor (C s ) of the resonant circuit is in the immediate vicinity of the induction loop (L s ) is arranged, and that for feeding the electrical energy into the resonant circuit, the inductance (L ü ) from the induction loop (L s ) is spatially arranged and with de Ren terminals are electrically connected via long leads (2). Induktionsschleife nach Anspruch 1, dadurch gekennzeichnet, daß der Kondensator (Cs) des Schwingkreises in der Anschlußmuffe (1) der Induktionsschleife (Ls) angeordnet ist.Induction loop according to Claim 1, characterized in that the capacitor (C s ) of the resonant circuit is arranged in the connecting sleeve (1) of the induction loop (L s ). Induktionsschleife nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Induktivität (Lü) des Überträgers im Gehäuse des Detektors (3) angeordnet ist.Induction loop according to Claim 1 or 2, characterized in that the inductance (L ü ) of the transmitter is arranged in the housing of the detector (3).
EP93107192A 1992-05-21 1993-05-04 In a road surface or the like installed induction loop Withdrawn EP0570755A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19924216820 DE4216820A1 (en) 1992-05-21 1992-05-21 Induction loop arranged in a roadway or the like
DE4216820 1992-05-21

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EP0570755A1 true EP0570755A1 (en) 1993-11-24

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EP93107192A Withdrawn EP0570755A1 (en) 1992-05-21 1993-05-04 In a road surface or the like installed induction loop

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3576525A (en) * 1967-07-17 1971-04-27 Singer General Precision Inductive loop vehicle presence detector
GB1513275A (en) * 1974-10-09 1978-06-07 Ericsson Telefon Ab L M Detecting metal-containing objects
FR2469722A1 (en) * 1979-11-12 1981-05-22 Saxby Railway wagon wheel passage detection circuit - employs open gap detector coil in oscillatory circuit excited by oscillator emitting constant energy pulses
FR2494655A1 (en) * 1980-11-27 1982-05-28 Robert Jean Wheel passage detector for railway train - uses trackside inductance changes with passing wheel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3576525A (en) * 1967-07-17 1971-04-27 Singer General Precision Inductive loop vehicle presence detector
GB1513275A (en) * 1974-10-09 1978-06-07 Ericsson Telefon Ab L M Detecting metal-containing objects
FR2469722A1 (en) * 1979-11-12 1981-05-22 Saxby Railway wagon wheel passage detection circuit - employs open gap detector coil in oscillatory circuit excited by oscillator emitting constant energy pulses
FR2494655A1 (en) * 1980-11-27 1982-05-28 Robert Jean Wheel passage detector for railway train - uses trackside inductance changes with passing wheel

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