GB1601147A - Vehicle speed detection systems - Google Patents

Vehicle speed detection systems Download PDF

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Publication number
GB1601147A
GB1601147A GB1754378A GB1754378A GB1601147A GB 1601147 A GB1601147 A GB 1601147A GB 1754378 A GB1754378 A GB 1754378A GB 1754378 A GB1754378 A GB 1754378A GB 1601147 A GB1601147 A GB 1601147A
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United Kingdom
Prior art keywords
voltage
waveform
instant
envelope
excursion
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GB1754378A
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Koninklijke Philips NV
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Philips Gloeilampenfabrieken NV
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Publication of GB1601147A publication Critical patent/GB1601147A/en
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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/50—Devices characterised by the use of electric or magnetic means for measuring linear speed
    • G01P3/52—Devices characterised by the use of electric or magnetic means for measuring linear speed by measuring amplitude of generated current or voltage
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
    • G01P3/66—Devices characterised by the determination of the time taken to traverse a fixed distance using electric or magnetic means

Description

(54) VEHICLE SPEED DETECTION SYSTEMS (71) We, N.V. PHILIPS' GLOEILAMPEN- FABREKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands, dd hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to vehicle speed detection systems wherein a transmitter supplying a continuous wave signal is coupled to a receiver via sensing means so that the approach of a sensed vehicle produces an amplitude increasing excursion of the envelope of the received signal.
In one known system, the sensing means comprise a transmitting coil forming part of the transmitter and inductively coupled to a receiving coil forming part of the receiver, the sensing means being located beneath the road surface. As a vehicle enters the zone of influence, the inductive coupling between the transmitting coil and the receiving coil is influenced and causes a corresponding change in the level of the received signal.
An object of the present invention is to provide a system for detecting the speed of a sensed vehicle.
According to the invention, there is provided a vehicle speed detection system wherein a transmitter supplying a continuous wave signal is coupled to a receiver via vehicle presence sensing means so that the passage of a sensed vehicle through the vicinity of said sensing means produces an amplitude increasing excursion of the envelope of the signal at the receiver, characterized in that at the receiver, in response to each said excursion, electrical quan tities representative of (V2 - ) and Vp are respectively derived from the received signal, and a further quantity representative of the expression (V2 - V1 )/Vp is formed from said electrical quantities, where VP is the envelope voltage of the received signal at an instant Ip during the leading edge portion of the corresponding said excursion at which the firstoccurring marked decrease of slope of the leading edge occurs less the envelope voltage prior to the excursion, V1 is the envelope voltage of the received signal at an instant I, at which the slope of the leading edge of the corresponding said excursion is substantially at its maximum prior to preceding the instant Ip, and V2 is the envelope voltage of the received signal at an instant 12 occurring a fixed time later than the instant Ii and prior to the instant Ip, said further quantity representing the vehicle speed.
Preferably, the envelope voltage of the received signal is sampled at the instants Ip, I and 12 during the leading edge portion of the corresponding said excursion to obtain the said voltages Vp, V1 and V2, the instants Ip, I1 and 12 being determined by the characteristics of a derived signal corresponding with the differential of the envelope of the received signal.
In one form, the system comprises sampling means for deriving a sample voltage corresponding with the voltage V1 of each said amplitude increasing excursion by sampling the envelope voltage of the received signal under the control of a peak detection means fed by a differentiating means forming a differential signal corresponding with the differential of the envelope of the received signal, the peak detection means detecting differential signal peaks to initiate sampling at the instant I1 of each said amplitude increasing excursion and sampling means for deriving sample voltages corresponding with the voltage Vp of each said amplitude increasing excursion by sampling the envelope voltage of the received signal under the control of a zero crossover detection means fed by a differentiating means forming a differential signal corresponding with the differential of the envelope of the received signal, the zero crossover detection means detecting zero crossover points of the differential signal to initiate sampling at the instant Ip of each said amplitude increasing excursion.
In another form, the system comprises sampling means for deriving sample voltages corresponding with the said voltages V1 and Vp of each said excursion by sampling the envelope voltage of the received signal under the control of a zero crossover detection means fed by a double differentiating means forming a double differential signal corresponding with the differential of the differential of the envelope of the received signal, the zero cross-over detection means detecting zero crossover point of the double differential signal to initiate sampling at the respective instants I1 and Ip of each said excursion.
In vehicle detection systems of the kind to which the invention relates, the aforementioned amplitude increasing excursion of the envelope of the received signal may be regarded as an amplitude modulation of the continuous wave signal, the slope of the excursion being determined by the characteristics of the particular sensed vehicle. The shape of the excursion of the envelope so formed can be referred to as the "signature waveform" of the vehicle in question.
The present invention is based upon the observation that the initial portion of the "signature waveform" is predictable within narrow limits for all vehicles whereas subsequent to the initial period the signature waveform is unpredictable and depends upon the characteristics of the individual vehicle. The invention is also based upon the further observation that the voltage reached (Vp) as the "signature waveform" levels off at the end of its initial portion when divided by the slope of the initial portion is relatively constant despite the characteristics of the sensed vehicle.
The invention will now be further described with reference to the accompanying drawings, of which Figure 1 is a block schematic diagram of a system according to the invention and Figures 2 to 4 show various waveforms in the system.
The system of Figure 1 comprises a transmitting apparatus denoted by the letters TX and a receiving apparatus denoted by the letters RX. The transmitter coil L1 of the transmitting apparatus TX and the receiving coil L2 of the receiving apparatus RX are each located just beneath the surface of a roadway or traffic lane and spaced apart from each other with their respective coil axes substantially in align- ment and orthogonal to the roadway or traffic lane so that the inductive coupling between the coil L1 and the coil L2 is influenced by the presence of a vehicle in the roadway or lane.
The generator G of the transmitter TX produces in known manner a continuous wave signal of constant frequency (e.g. 100 khz) which is fed to the coil L1 and radiated thereby.
Signals received by the receiving coil L2 are fed to the input of the receiving stage RR which selects and amplifies in a known manner incoming signals within a predetermined bandwidth including the frequency of the signal radiated by the coil L1. Thus, the output signal of the stage RR is a continuous wave signal which is amplitude modulated whenever a vehicle approaches and/or passes over the sensing means formed by the coils L1 and L2.
The stage M, following the receiving stage RR, processes the received signal by demodulation or otherwise so that a signal is produced at its output corresponding with the envelope of the received signal.
The stage I, following the stage M, further processes the output signal of the stage M by identifying the occurrence of an amplitude increasing excursion of the envelope of the received signal due to the approach of a vehicle as distinct from an excursion due to other causes such as a changed environmental condition. Such identification systems are described in the applicant's co-pending United Kingdom Patent Application No. 17545/78 (Serial No. 1573673). The stage I identifies amplitude increasing excursions of the envelope of the received signal having a sharply rising leading edge produced by the approach of a vehicle and without such recognition produces no output but upon such recognition produces an output signal coinciding with the difference between a stored sample voltage and the envelope voltage, the stored sample voltage being a voltage corresponding with that of the envelope voltage itself at an initial portion of the sharply rising leading edge.
Figure 2 is a graphical indication of a signal produced at the output of the stage RR. Between the instants TI and T2 there is no vehicle within the zone of influence and between the instants T2 and T4 a vehicle is approaching and passing over the sensing means formed by the coils Ll and L2.
Figure 3a is a graphical indication of the resultant signal waveform W1 produced at the output of the stage M, there being an amplitude increasing excursion between the instants T2 and T4 due to the passage of a vehicle.
Figure 3b is a graphical illustration of the resultant signal produced at the output of the stage I. The waveform W2 illustrated in Figure 3b is the difference between the waveform W1 of Figure 3a and the stored voltage indicated by the dotted line V of Figure 3a.
Figure 4a shows graphically by means of the voltage waveform Al the change in level of the envelope of the received signal approximately between the instants TT1 and TT2 i.e.
during the leading edge portion of the signal of Figure 3a.
Figure 4b shows graphically by means of the waveform B1 a voltage representing the differential of the voltage of the waveform A1.
Figure 4c shows graphically by means of the waveform C1 a voltage representing the differential of the waveform of the voltage of the waveform B1.
Figure 4d shows graphically by means of the waveform D1 a derived pulse, the timing of which may be controlled by the voltage waveform B1 or which may alternatively be controlled by the voltage waveform C1.
Figure 4e shows graphically by means of the waveform El another derived pulse, the timing of which may be controlled by the voltage waveform of B1 or which may alternatively be controlled by the voltage waveform Cl.
Figure 4f shows graphically by means of the waveform F1 a pulse of fixed duration, the timing of which is controlled by the pulse of waveform D1.
Referring once more to Figure 1, the output signal by way of example as indicated by the voltage waveform W2 of Figure 3b, the leading edge portion between the instants TT1 and TT2 thus coinciding with the waveform of Figure 4a, is produced at the output of the stage I and is fed to the stages STV1, STV2 and STVP and also to the timing generator TG. The stages STV1, STV2 and STVP will, upon command by timing pulses, store at their respective outputs in known manner the voltage present at their respective inputs at the occurrence of the respective timing pulses until occurrence of the next timing pulse applied thereto.
The timing generator TG, under the control of the waveform W2 produces timing pulses coinciding with the instants 11,12 and IP and the timing pulses are applied respectively to the stages STV1, STV2 and STVP to command storage at these instants. Thus, the stage STV1 stores the voltage V1 ,the stage STV2 stores the voltage V2 and the stage STVP stores the voltage VP in response to passage of a vehicle. The outputs of the stages STV1 and STV2 are applied to the subtractor SUB producing at its output (V2 - V1).
The output of the subtractor stage SUB is applied to the dividing stage DIV to which the voltage VP from the store STVP is also applied.
The divider operates in known manner to divide the voltage (V2 - V1) by the voltage VP.
Accordingly, the output voltage of the dividing stage DIV is representative of (V2 V1 )/Vp, this voltage being substantially proportional to the speed of the sensed vehicle from which the waveform W2 has resulted.
The output of the divider stage DIV is fed via an amplifier having an amplification equivalent to a constant K thus producing at the output terminal OP a voltage also proportional to the speed of the said sensed vehicle and in terms of kilometers per hour.
The timing pulse generator TG may take any one of several different forms. In one form, the waveform Al is differentiated to produce the waveform Bl and by peak detection the instant at which the waveform B1 reaches its maximum is determined for producing a timing pulse coinciding with the instant I1 as indicated by the waveform D1. In addition, by means of known zerocrossover detection techniques, the instant of zerocrossover of the waveform B1 is determined for producing a timing pulse coinciding with the instant IP as indicated by the waveform El.
In another form, the waveform Al is differentiated to produce the waveform B1 and the waveform B1 is also differentiated to produce the waveform C1. By zero-crossover detector techniques the instants I1 and IP are determined to produce timing pulses as indicated by the respective waveforms D1 and El.
A monostable multivibrator or equivalent device may be employed to determine the instant I2 and produce a timing pulse at the instant I2 at a fixed instant following 11. The trailing edge of the pulse of the waveform F1 of Figure 4f may be employed for this purpose.
The present invention has been described loosely in terms of analogue techniques but lends itself particularly to the application of digital techniques throughout and the necessary modifications to achieve operation employing digital techniques will be apparent to persons skilled in the art.
The invention is by no means limited to the embodiments of the invention schematically described in relation to Figures 1, 2, 3 and 4 of the accompanying drawings.
Many variations and modifications to the embodiment of the invention disclosed herein but employing the principles of the invention will be readily apparent to persons skilled in the art and it is intended to include such variations within the scope of the present invention.
WHAT WE CLAIM IS:- 1. A vehicle speed detection system wherein a transmitter supplying a continuous wave signal is coupled to a receiver via vehicle presence sensing means so that the passage of a sensed vehicle through the vicinity of said sensing means produces an amplitude increasing excursion of the envelope of the signal at the receiver, characterized in that at the receiver, in response to each said excursion, electrical quan tities representative of (V2 - V1) and Vp are respectively derived from the received signal, and a further quantity representative of the expression (V2V1 )/Vp is formed from said electrical quantities, where Vp is the envelope voltage of the received signal at an instant Ip during the leading edge portion of-the corresponding said excursion at which the firstoccurring marked decrease of slope of the leading edge occurs less the envelope voltage prior to the excursion, V1 is the envelope voltage of the received signal at an instant II at which the slope of the leading edge of the corresponding said excursion is substantially at its maximum prior to the instant Ip, and V2 is the envelope voltage of the received signal at an instant 12 occurring a fixed time later than the instant Il and prior to the instant Ip, said further quantity representing the vehicle speed.
2. A vehicle speed detection system according to Claim 1, characterized in that the system comprises sampling means for deriving a sample voltage corresponding with the voltage V1 of each said amplitude increasing excursion by sampling the envelope voltage of the received signal under the control of a peak detection means fed by a differentiating means forming a differential signal corresponding with the differential of the envelope of the received signal, the peak detection means detecting differential signal peaks to initiate sampling at the instant I1 of each said amplitude increasing excursion and
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. timing of which is controlled by the pulse of waveform D1. Referring once more to Figure 1, the output signal by way of example as indicated by the voltage waveform W2 of Figure 3b, the leading edge portion between the instants TT1 and TT2 thus coinciding with the waveform of Figure 4a, is produced at the output of the stage I and is fed to the stages STV1, STV2 and STVP and also to the timing generator TG. The stages STV1, STV2 and STVP will, upon command by timing pulses, store at their respective outputs in known manner the voltage present at their respective inputs at the occurrence of the respective timing pulses until occurrence of the next timing pulse applied thereto. The timing generator TG, under the control of the waveform W2 produces timing pulses coinciding with the instants 11,12 and IP and the timing pulses are applied respectively to the stages STV1, STV2 and STVP to command storage at these instants. Thus, the stage STV1 stores the voltage V1 ,the stage STV2 stores the voltage V2 and the stage STVP stores the voltage VP in response to passage of a vehicle. The outputs of the stages STV1 and STV2 are applied to the subtractor SUB producing at its output (V2 - V1). The output of the subtractor stage SUB is applied to the dividing stage DIV to which the voltage VP from the store STVP is also applied. The divider operates in known manner to divide the voltage (V2 - V1) by the voltage VP. Accordingly, the output voltage of the dividing stage DIV is representative of (V2 V1 )/Vp, this voltage being substantially proportional to the speed of the sensed vehicle from which the waveform W2 has resulted. The output of the divider stage DIV is fed via an amplifier having an amplification equivalent to a constant K thus producing at the output terminal OP a voltage also proportional to the speed of the said sensed vehicle and in terms of kilometers per hour. The timing pulse generator TG may take any one of several different forms. In one form, the waveform Al is differentiated to produce the waveform Bl and by peak detection the instant at which the waveform B1 reaches its maximum is determined for producing a timing pulse coinciding with the instant I1 as indicated by the waveform D1. In addition, by means of known zerocrossover detection techniques, the instant of zerocrossover of the waveform B1 is determined for producing a timing pulse coinciding with the instant IP as indicated by the waveform El. In another form, the waveform Al is differentiated to produce the waveform B1 and the waveform B1 is also differentiated to produce the waveform C1. By zero-crossover detector techniques the instants I1 and IP are determined to produce timing pulses as indicated by the respective waveforms D1 and El. A monostable multivibrator or equivalent device may be employed to determine the instant I2 and produce a timing pulse at the instant I2 at a fixed instant following 11. The trailing edge of the pulse of the waveform F1 of Figure 4f may be employed for this purpose. The present invention has been described loosely in terms of analogue techniques but lends itself particularly to the application of digital techniques throughout and the necessary modifications to achieve operation employing digital techniques will be apparent to persons skilled in the art. The invention is by no means limited to the embodiments of the invention schematically described in relation to Figures 1, 2, 3 and 4 of the accompanying drawings. Many variations and modifications to the embodiment of the invention disclosed herein but employing the principles of the invention will be readily apparent to persons skilled in the art and it is intended to include such variations within the scope of the present invention. WHAT WE CLAIM IS:-
1. A vehicle speed detection system wherein a transmitter supplying a continuous wave signal is coupled to a receiver via vehicle presence sensing means so that the passage of a sensed vehicle through the vicinity of said sensing means produces an amplitude increasing excursion of the envelope of the signal at the receiver, characterized in that at the receiver, in response to each said excursion, electrical quan tities representative of (V2 - V1) and Vp are respectively derived from the received signal, and a further quantity representative of the expression (V2V1 )/Vp is formed from said electrical quantities, where Vp is the envelope voltage of the received signal at an instant Ip during the leading edge portion of-the corresponding said excursion at which the firstoccurring marked decrease of slope of the leading edge occurs less the envelope voltage prior to the excursion, V1 is the envelope voltage of the received signal at an instant II at which the slope of the leading edge of the corresponding said excursion is substantially at its maximum prior to the instant Ip, and V2 is the envelope voltage of the received signal at an instant 12 occurring a fixed time later than the instant Il and prior to the instant Ip, said further quantity representing the vehicle speed.
2. A vehicle speed detection system according to Claim 1, characterized in that the system comprises sampling means for deriving a sample voltage corresponding with the voltage V1 of each said amplitude increasing excursion by sampling the envelope voltage of the received signal under the control of a peak detection means fed by a differentiating means forming a differential signal corresponding with the differential of the envelope of the received signal, the peak detection means detecting differential signal peaks to initiate sampling at the instant I1 of each said amplitude increasing excursion and
sampling means for deriving sample voltages corresponding with the voltage Vp of each said amplitude increasing excursion by sampling the envelope voltage of the received signal under the control of a zero crossover detection means fed by a differentiating means forming a differential signal corresponding with the differential of the envelope of the received signal, the zero crossover detection means detecting zero crossover points of the differential signal to initiate sampling at the instant Ip of each said amplitude increasing excursion.
3. A vehicle speed detection system according to Claim 1, characterized in that the system comprises sampling means for deriving sample voltages corresponding with the said voltages Vl and Vp of each said amplitude increasing excursion by sampling the envelope voltage of the received signal under the control of a zero crossover detection means fed by a double differentiating means forming a double differential signal corresponding with the differential of the differential of the envelope of the received signal, the zero crossover detection means detecting zero crossover point of the double differential signal to initated sampling at the respective instants 11 and Ip of each said excursion.
4. A vehicle speed detection system substantially as herein described with reference to the accompanying drawings.
GB1754378A 1977-05-06 1978-05-03 Vehicle speed detection systems Expired GB1601147A (en)

Applications Claiming Priority (1)

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AUPD000877 1977-05-06

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GB1601147A true GB1601147A (en) 1981-10-28

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JP (1) JPS549678A (en)
DE (1) DE2819566A1 (en)
FR (1) FR2389893A1 (en)
GB (1) GB1601147A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5742235U (en) * 1980-08-21 1982-03-08
JPS5742234U (en) * 1980-08-21 1982-03-08

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2999999A (en) * 1955-02-08 1961-09-12 Everhard H B Bartelink Highway traffic control system
US3626413A (en) * 1970-02-02 1971-12-07 Howard C Zachmann Traffic surveillance and control system
US3721821A (en) * 1970-12-14 1973-03-20 Abex Corp Railway wheel sensor
IT1013280B (en) * 1974-05-28 1977-03-30 Autostrade Concess Const PERFECTED SYSTEM FOR ELECTRONIC CONTROL OF TRAFFIC IN REAL TIME AND FOR BIDIRECTIONAL TRANSMISSIONS IN CODE AND PHONY BETWEEN OPERATION CENTER AND MOBILE VEHICLES

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DE2819566A1 (en) 1978-11-16
FR2389893A1 (en) 1978-12-01
JPS549678A (en) 1979-01-24

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