Method and arrangement for determining the velocity of a vehicle

Claim 3

A method as claimed in claim 1 including storing the measuring value measured in a measuring time interval for at least one measuring time interval.

Claim 4

A method as claimed in claim 1, characterized in that the interpolation is linear.

Claim 5

A vehicle detection system comprising first and second inductive loops spaced apart a given distance in the direction of vehicle travel, first and second vehicle presence detectors coupled to said first and second inductive loops, respectively, each vehicle presence detector comprising an oscillator circuit including its respective inductive loop wherein the oscillator oscillation frequency is dependent on the position of the vehicle relative to the inductive loop, a clock connected to at least one said oscillator circuit for generating signals defining a sequence of measuring time intervals, means coupling each oscillator circuit to a respective counter for the determination of a measuring value which corresponds to the number of periods of the oscillation frequency during one of the measuring time intervals generated by said clock, means connecting each counter to a first input of a respective storage device for storing the measuring value of the associated counter, means connecting each counter to a cascade connection of a threshold device, a counting device and an interpolation device, means coupling an output at each of the threshold devices, counting devices and interpolation devices to a second input of its respective storage device, means connecting an output of each of the storage devices to respective ones of the interpolation devices, a difference device, means connecting an output of each of the interpolation devices to said difference device to determine the time difference between the instants at which the response thresholds of the first and the second loops are exceeded, means for applying an output of the difference device and a signal determined by said given distance between the first and second inductive loops to a multiplier which derives an output signal which represents the velocity of a passing vehicle.

Claim 6

A vehicle detection system comprising first and second inductive loops spaced apart a given distance in the direction of vehicle travel, first and second vehicle presence detectors coupled to said first and second inductive loops, respectively, each vehicle presence detector comprising an oscillator circuit including its respective inductive loop wherein the oscillator oscillation frequency is dependent on the position of the vehicle relative to the inductive loop, a clock connected to at least one said oscillator circuit for generating signals defining a sequence of measuring time intervals, means coupling each oscillator circuit to a respective counter for the determination of a measuring value which corresponds to the number of periods of the oscillation frequency during one of the measuring time intervals generated by said clock, means connecting each counter to a first input of a respective storage device for storing the measuring value of the associated counter, means connecting each counter to a cascade connection of a threshold device, a counting device and an interpolation device, means coupling an output at each of the threshold devices, counting devices and interpolation devices to a second input of its respective storage device, means connecting an output of each of the storage devices to respective ones of the interpolation devices, a difference device, means connecting an output of each of the interpolation devices to said difference device to determine the time difference between the instants at which the response thresholds of the first and the second loops are exceeded, means for applying an output of the difference device and a signal determined by said given distance between the first and second inductive loops to a multiplier which derives an output signal which represents the velocity of a passing vehicle.

Claim 7

In a vehicle detection system including first and second means for sensing a passing vehicle and spaced apart a given distance in the direction of vehicle travel, the improvement comprising first and second vehicle presence detectors adapted for operation by said first and second sensing means, respectively, and having first and second oscillator circuits, respectively, whose oscillation frequencies are caused to change by a passing vehicle to derive first and second oscillation signals, respectively, means for generating a sequence of control signals that produce a sequence of equal measuring time intervals, means in each of the first and second detectors responsive to the respective first and second oscillation signals and controlled by said signal generating means for deriving first and second measuring signals in successive measuring time intervals, each detector including means for comparing the first and second measuring signals with a reference threshold level to determine the first measuring time interval in which a measuring signal exceeds the reference threshold level, each said detector further including means controlled by said comparing means for interpolating between said first and second measuring signals to derive a third signal that indicates the exact instant within said first measuring time interval that the measuring signal exceeded the reference threshold level, and processing means responsive to the third signal of each detector and to a signal indicative of said given distance between the first and second sensing means for producing an output signal that represents the velocity of a passing vehicle.

Claim 8

In a vehicle detection system including first and second means for sensing a passing vehicle and spaced apart a given distance in the direction of vehicle travel, the improvement comprising first and second vehicle presence detectors adapted for operation by said first and second sensing means, respectively, and having first and second oscillator circuits, respectively, whose oscillation frequencies are caused to change by a passing vehicle to derive first and second oscillation signals, respectively, means for generating a sequence of control signals that produce a sequence of equal measuring time intervals, means in each of the first and second detectors responsive to the respective first and second oscillation signals and controlled by said signal generating means for deriving first and second measuring signals in successive measuring time intervals, each detector including means for comparing the first and second measuring signals with a reference threshold level to determine the first measuring time interval in which a measuring signal exceeds the reference threshold level, each said detector further including means controlled by said comparing means for interpolating between said first and second measuring signals to derive a third signal that indicates the exact instant within said first measuring time interval that the measuring signal exceeded the reference threshold level, and processing means responsive to the third signal of each detector and to a signal indicative of said given distance between the first and second sensing means for producing an output signal that represents the velocity of a passing vehicle.

Claim 9

A vehicle detection system as claimed in claim 5, wherein the control signal generating means includes a clock generator and the means in each detector for deriving a measuring signal comprises a counter whose counting interval is controlled by the clock generator so that in each measuring time interval the counter produces a count determined by the oscillation frequency of its respective oscillator circuit and which is indicative of said first or second measuring signal, said system further comprising a storage device in each detector having first and second storage areas and coupled to its respective counter and its respective comparing means for storing the counts of two successive measuring time intervals.

Claim 10

A vehicle detection system as claimed in claims 5 or 6, wherein the processing means includes in cascade a subtraction device and an arithmetic device that derives a velocity output signal in accordance with the formula, V=S/(t 3 '-t 1 ') where V is the vehicle velocity, S is the given distance between the first and second sensing means and t 3 ' and t 1 ' are the instants in time represented by the third signal derived in said first and second vehicle presence detectors, respectively.

Claim 11

In a vehicle detection system including first and second means for sensing the presence of a passing vehicle and spaced apart a given distance in the direction a vehicle travels and first and second vehicles presence detectors controlled by said first and second sensing means to produce first and second measuring value signals which vary as a function of the vehicle position relative to the respective sensing means, the method of determining vehicle velocity comprising, for each detector, deriving a sequence of equal measuring time intervals, determining two successive measuring time intervals in which measuring value signals are derived that are above and below a given threshold value, respectively, upon determination that two successive measuring time intervals produce measuring value signals above and below said given threshold value, deriving by interpolation a third signal indicative of the instant within a measuring time interval that a measuring value signal equals the given threshold value, and computing the vehicle velocity using as parameters a signal determined by the given distance between the first and second sensing means and the time difference between the third signals derived in each of said detectors.

Claim 12

In a vehicle detection system including first and second means for sensing the presence of a passing vehicle and spaced apart a given distance in the direction a vehicle travels and first and second vehicles presence detectors controlled by said first and second sensing means to produce first and second measuring value signals which vary as a function of the vehicle position relative to the respective sensing means, the method of determining vehicle velocity comprising, for each detector, deriving a sequence of equal measuring time intervals, determining two successive measuring time intervals in which measuring value signals are derived that are above and below a given threshold value, respectively, upon determination that two successive measuring time intervals produce measuring value signals above and below said given threshold value, deriving by interpolation a third signal indicative of the instant within a measuring time interval that a measuring value signal equals the given threshold value, and computing the vehicle velocity using as parameters a signal determined by the given distance between the first and second sensing means and the time difference between the third signals derived in each of said detectors.