Patent ID: 6272443
Filing Date: 2001-08-07
Classification: B60W,G01P,G08G

Abstract:
A process for accurately measuring the speed of individual test objects that move on a known trajectory, comprising the steps of:detecting passage of a selected point on a test object moving with said trajectory past at least three sensors spaced apart by predetermined distances in sequence along the trajectory path, by generating an analog signal upon passage of said selected point past each sensor;determining the time interval between passage of said selected point on the test object past the first and second sensors in said sequence by measuring the difference between the points in time at which the magnitude of the signals successively generated by the first and second sensor differs from a reference level by a predetermined amount;storing the signal generated when the selected point of the test object passes said second sensor;calculating the value of the cross-correlation function between the signal generated when the selected point of the test object passes the last sensor in said sequence and said stored signal, and calculating further values of said cross-correlation function while varying a delay time which was recorded upon passage of the selected point of the test object past the second sensor and which is related to said time interval according to the ratio of the distances between the first and second sensors and the second and third sensors, respectively;determining the maximum value of the cross-correlation function, and using said maximum value to correct said delay time to obtain an accurate measure of the time taken by the test object to traverse the distance between the second and third sensors, and determining speed of the test object therefrom and from the known value of that distance.