EP0387092A2 - Strassenverkehr-Überwachungsanlage - Google Patents

Strassenverkehr-Überwachungsanlage Download PDF

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Publication number
EP0387092A2
EP0387092A2 EP90302553A EP90302553A EP0387092A2 EP 0387092 A2 EP0387092 A2 EP 0387092A2 EP 90302553 A EP90302553 A EP 90302553A EP 90302553 A EP90302553 A EP 90302553A EP 0387092 A2 EP0387092 A2 EP 0387092A2
Authority
EP
European Patent Office
Prior art keywords
signal
equipment
cable
validation
speed detection
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.)
Granted
Application number
EP90302553A
Other languages
English (en)
French (fr)
Other versions
EP0387092A3 (de
EP0387092B1 (de
Inventor
Franz Josef Gebert
Rudiger Heinz Gebert
Ralf Dieter Heinrich Gebert
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.)
Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0387092A2 publication Critical patent/EP0387092A2/de
Publication of EP0387092A3 publication Critical patent/EP0387092A3/de
Application granted granted Critical
Publication of EP0387092B1 publication Critical patent/EP0387092B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • G08G1/052—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed
    • 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
    • G08G1/02—Detecting movement of traffic to be counted or controlled using treadles built into the road

Definitions

  • This invention relates to validation checks applied to traffic monitoring equipment including traffic speed detection equipment.
  • the invention is, however, in principle applicable to any traffic data collection equipment subject to what will be said herein below.
  • An area of primary application which is envisaged, for example, is traffic monitoring equipment based on a cable or cables extending across a road or other surface and providing electrical signals.
  • electrical signals can have one or more of several physical origins including piezo-electric effects whether resistive and/or generative piezo-electric effects, capacitive effects and tribo-electric effects, for example.
  • the validation checks or security checks are to be provided to enhance the reliability, accuracy and convenience of operating such equipment. In the use of such equipment for law enforcement this can have favourable legal implications. Generally less reliance may be placed on the operator of the equipment to ensure the integrity of the equipment and the security of the measurements it takes.
  • the apparatus may be adapted to check the correct sequence of impulses derived from several cables a single cable and/or a sensor pad or other sensor according to the set up of the equipment. This can be a security against swopping errors, for example, connection of cables incorrectly to the equipment after the cables have been set out in a suitable array with or without sensors or the like on a road surface, for example in the case of a duplicated pair of cables extended across the full width of a road in a spaced parallel array for speed law enforcement.
  • the correct sequence of pulses will be from start cable 1, then start cable 2 followed by stop cable 1 and then stop cable 2 or, the reverse sequence for traffic in the opposite direction on the other side of the road being stop cable 2 then stop cable 1, then start cable 2 and then start cable 2.
  • instrument 1 function measures the time from start 1 to stop 1 independently of the instrument 2 function which measures from start 2 to stop 1, each on either the front or the back axles or any other axles in physical contact with the road.
  • instrument 2 function measures from start 2 to stop 1, each on either the front or the back axles or any other axles in physical contact with the road.
  • cables can also be used and the verification can have application in measurement of deceleration and acceleration.
  • This sequence checking verification can be generalised as stated to any desired or required arrays of cable, cables and/or detector pads, magnetic loop detectors or others.
  • a RFI radio frequency interference check can be implemented in the instrument to monitor any radio interference during and in between measurements in order to ensure interference free measurements.
  • the cables act as antennas for electro-magnetic energy and provide radio signals any risk of this causing measurement errors can be excluded by such radio interference checks and validations provided in the instrument.
  • a EMI (Electromagnetic Interference) check from sources such as two-­way radios, high frequency communication, high tension cables or lighting, can be implemented in the instrument to monitor any RFI (Radio Frequency Interference) or other EMI interference during and in between measurements in order to ensure interference free measurements.
  • RFI Radio Frequency Interference
  • the cables act as antennas for electro-magnetic energy fields and any risk of this causing measurement errors can be excluded.
  • Further validation can be provided by ongoing checking of the level of insulation resistance between conductors in a particular cable and monitoring for low impedance, that is below the prescribed threshold value.
  • the instrument will memorise the initial impedance of the cable and/or be set to a prescribed minimum limit impedance for monitoring the degrading of cable insulation resistance by means of impedance measurements.
  • the gradual or abrupt deterioration of a cable in service conditions leading to degrading of the insulation resistance and which can lead to erroneous measurements and degraded accuracy or reliability can be monitored for and the equipment rendered inoperative and/or warning signals displayed when the cable deteriorates below a certain prescribed state.
  • the degrading of the impedance of insulation material between conductors of the cable can seriously degrade the signal strength to be generated between the conductors, for example, such as is generated by piezo-electric effects in such material.
  • low impedance may arise due to physical contact of the conductors due to mechanical damage of the insulating material between them.
  • Low impedance can also result due to moisture and water becoming present in the cable which, for example, can arise during rainy weather where the outside sheath of the cable has become pervious to water, for example, due to mechanical damage again or water has access to the interior of the cable via its ends or in other ways.
  • Degradation of the cable insulation can also occur under conditions of service due to heat, solar radiation, mechanical impulses of the vehicles and other conditions of use.
  • the instrument can be provided with further validation by means of a facility for signal strength monitoring.
  • each individual pulse be it piezo-electric or tribo-electric or both in origin (for example, refer to South African patent number 66/0493) must pass through a minimal signal level before being detected as a valid trigger for time pulses. There is thus a minimum threshold level below which signals will be ignored, in order to avoid rise time error due to weak signals.
  • the instrument is given this validation facility designed to prescribe that the minimum signal strength must arise within a certain minimum time measured from a starting threshold in order to be validated for time measurement.
  • the first pulse (be it positive or negative) must have a minimum steepness, i.e.
  • the minimum rise time to the prescribed minimum signal level may be of the order of 1 ms to 20 ms depending on the application and the features required in various circumstances.
  • this validation test will be applied typically to both positive and negative going signals, whichever occurs first.
  • preference is made to South African patent No. 76/4959 whose content is incorporated herein by reference. The discovery and observation of this phenomenon and the design of suitable circuitry to provide accurate measurement in its context is described in this patent. The addition of the signal strength monitoring or validation features described will thus further enhance the security, reliability and convenience of use of the apparatus.
  • the instrumentation will be so designed that if the time measurement start signal has triggered positive the validation signal must be of the same polarity, i.e. positive and vice versa if the start signal has triggered negative. Failing this check again the start signal will not be accepted.
  • Degradation of the inner coaxial conductor or the screen in the case of a coaxial conductor by means of capacitance checking can be a further validation of checking features supplied to an instrument.
  • the instrument will be designed to monitor frequency changes, phase changes, changes in natural frequency, for example, in particular ringing of the cable and any other means of detecting changes in capacitances can be employed.
  • any particular cable will be detected to have a certain capacitance per metre length and should a break occur of course the capacitance will change and an error signal can be produced indicating a faulty cable.
  • the integrity of the inner core conductor and/or of the coaxial screen conductor can be monitored in this way again to provide more reliable operation of the instrument without dependance upon the operator.
  • the instrument can also be designed to monitor for any spurious signal which is not in accordance with the typical signal produced by the cable under normal circumstances and required for detection of traffic and/or speed measurements.
  • parameters describing a category of signal within which the signal must fall can be prescribed and every signal produced by the cable can be checked against these parameters. If such a spurious signal should occur, for example, more than a prescribed number of times the cable can be flagged by means of a suitable error message displayed by the instrument for checking.
  • the instrument can be made "fail safe" in this or any of the other aspects by being adapted to stop functioning and to await correction if any prescribed threshold is exceeded.
  • the monitoring of cables as described can be adapted to coaxial cables, triaxial cables, screened pair cables or any other cable construction or array.
  • the coaxial cables referred to herein have been referred to merely by way of example.
  • a vehicle wheel 1 is rotating as shown by the arrow 2 and moving forward as shown by the arrow 3 over a road surface 4 which has laid on it a cable 5 of piezo-electric shielded cable type.
  • the wheel 1 thus moves to the position fully over the cable as shown at 1′ and then to the position where it is just leaving the cable as shown at 1 ⁇ .
  • the graph 6 below shows the voltage pulse produced in the piezo-­electric cable 5 by the passage of the wheel and the three positions shown above the broken line 7, 8 and 9 indicating correspondence between the successive positions on the graph 6 and the successive positions of the wheel 1.
  • the pulse begins to rise from the zero line 10 at "V b ".
  • the pulse reaches the peak at the position of the wheel 1′ as indicated by the broken line 8 at "V p ".
  • the pulse then declines to a voltage of zero at the position of the wheel 1 ⁇ indicated by the broken line where the pulse crosses the zero line 10 and then moves into a negative pulse portion or "under shoot "U” followed by an atenuating oscillation 11.
  • a concentric shielded cable 12 is shown, the central core 13 carrying the signal and the outer shield 14 being earthed.
  • the electrical equivalent of the cable is shown as a capacitance 15 which can be located in an equivalent circuit comprising a series connection of the capacitor 15 with a piezo-electrical or tribo-electrical generator 16 to provide the output voltage at V out as shown.
  • This is the equivalent circuit for the generative type of piezo-electrical or tribo-electrical ponomo which is used in the insulating material 17 between the core 13 and shield 14.
  • the minimum threshold level detection with polarity verification is an important validation check in accordance with this invention.
  • the graph 18 shows the normal pulse of the kind shown in figure 1 as compared with a weak signal 18′.
  • the broken lines 19 show the trigger level and the broken lines 20 the verification level to which the instrument is set in accordance with this invention.
  • the broken lines 21 show the commencement of the pulse 18 and the broken lines 22 the commencement of the trigger signal 23 which follows after a time delay t d from the commencement of the signal.
  • the verification signal 24 commences at the instant indicated by the broken lines 25. By contrast in the case of a weak signal no verification signal as indicated at 26 occurs and the measurement is aborted.
  • Minimum threshold verification can be applied using another criteria, namely that the verification signal must occur within a minimum specified time, e.g. 1 ms or an adjustable delay being calculated once the speed of the vehicle has been established, e.g. 3 ms if 30 km/h or 0,3 ms at 160 km/h - this allows a maximum constant signal error over the whole speed range (e.g. 1%).
  • a minimum specified time e.g. 1 ms or an adjustable delay being calculated once the speed of the vehicle has been established, e.g. 3 ms if 30 km/h or 0,3 ms at 160 km/h - this allows a maximum constant signal error over the whole speed range (e.g. 1%).
  • FIG. 4 illustrates techniques used in radio frequency interference and electro-magnetic interference checking.
  • the graph 27 shows a normal pulse and the graph 28 a pulse which has been degraded by RFI or EMI intereference.
  • this interference can produce a trigger signal 29 which is premature as compared with the correct trigger signal as indicated at 30.
  • This type of interference can arise with deteriorating sensors making them prone to external signals.
  • RFI and EMI signals receiving components in the instrument can then provide a necessary instruction to disallow measurement where interference on these sources is detected.
  • Figure 5 shows an example graph of a pulse arising where insulation resistance results in a weaker signal which leads to greater triggering uncertainty.
  • the triggering pulse 33 only occurs at the instant indicated by the broken lines 44 when it should have occured at the instant indicated by the broken lines 35 implying the delay period shown.
  • the insulation resistance check will be carried out as described above.
  • the capacitance check implies monitoring breakage of the inner or outer conductors of the coaxial cable which could lead to false triggering by vehicles moving across or in close proximity of the cable. This occurs as a result of compression or tension waves which move the cables and cause the broken cable ends to make and break contact thus causing an impulse which cannot be reliably related to the occurance of physical contact with the tyre of a vehicle. In general spurious signal monitoring will be resorted to as described above.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Traffic Control Systems (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Road Signs Or Road Markings (AREA)
  • Devices For Checking Fares Or Tickets At Control Points (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Alarm Systems (AREA)
EP90302553A 1989-03-10 1990-03-09 Strassenverkehr-Überwachungsanlage Expired - Lifetime EP0387092B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA8901830 1989-03-10
ZA891830 1989-03-10

Publications (3)

Publication Number Publication Date
EP0387092A2 true EP0387092A2 (de) 1990-09-12
EP0387092A3 EP0387092A3 (de) 1991-05-15
EP0387092B1 EP0387092B1 (de) 1996-06-12

Family

ID=25579626

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90302553A Expired - Lifetime EP0387092B1 (de) 1989-03-10 1990-03-09 Strassenverkehr-Überwachungsanlage

Country Status (8)

Country Link
EP (1) EP0387092B1 (de)
AT (1) ATE139359T1 (de)
DE (1) DE69027351T2 (de)
DK (1) DK0387092T3 (de)
ES (1) ES2087889T3 (de)
HU (2) HU213827B (de)
PT (1) PT93397B (de)
ZA (1) ZA901905B (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993022756A1 (de) * 1992-04-30 1993-11-11 Robot Foto Und Electronic Gmbh & Co Kg Vorrichtung zur überprüfung der funktionsfähigkeit von geschwindigkeits-messeinrichtungen für die verkehrsüberwachung
WO1998052008A1 (en) * 1997-05-14 1998-11-19 Snap-On Equipment Limited Tyre pressure determination

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102163369A (zh) * 2010-02-24 2011-08-24 交通运输部公路科学研究所 公路运行速度采集***
CN103617736B (zh) * 2013-12-17 2016-04-13 南宁光波科技有限公司 一种道路监测装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4276539A (en) * 1978-06-22 1981-06-30 U.S. Philips Corporation Vehicle detection systems
US4368428A (en) * 1979-08-09 1983-01-11 U.S. Philips Corporation Method and arrangement for determining the velocity of a vehicle

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4276539A (en) * 1978-06-22 1981-06-30 U.S. Philips Corporation Vehicle detection systems
US4368428A (en) * 1979-08-09 1983-01-11 U.S. Philips Corporation Method and arrangement for determining the velocity of a vehicle

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
SIEMENS ZEITSCHRIFT, vol. 44, no. 2, February 1970, pages 61-66, Munich, DE; P. LINGENFELSER et al.: "Schleifendetektoren zum Messen des Strassenverkehrs" *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993022756A1 (de) * 1992-04-30 1993-11-11 Robot Foto Und Electronic Gmbh & Co Kg Vorrichtung zur überprüfung der funktionsfähigkeit von geschwindigkeits-messeinrichtungen für die verkehrsüberwachung
WO1998052008A1 (en) * 1997-05-14 1998-11-19 Snap-On Equipment Limited Tyre pressure determination
AU733735B2 (en) * 1997-05-14 2001-05-24 Snap-On Equipment Limited Tyre pressure determination

Also Published As

Publication number Publication date
PT93397A (pt) 1991-10-31
ES2087889T3 (es) 1996-08-01
ATE139359T1 (de) 1996-06-15
HU901598D0 (en) 1990-06-28
DE69027351D1 (de) 1996-07-18
HU213827B (en) 1997-10-28
DE69027351T2 (de) 1996-10-10
PT93397B (pt) 1996-01-31
EP0387092A3 (de) 1991-05-15
EP0387092B1 (de) 1996-06-12
DK0387092T3 (da) 1996-07-01
ZA901905B (en) 1991-01-30

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