Patent ID: 7174269
Filing Date: 2007-02-06
Classification: G01P

Abstract:
1. A speed sensing system for measuring the speed of a target object, comprising: a first differential speed sensor unit operatively disposed adjacent a surface of said target object, said first differential speed sensor unit configured to generate a first differential signal responsive to the passage of at least one random feature of said target object; a second differential speed sensor unit operatively disposed adjacent a surface of said target object and displaced at a predetermined distance from said first differential speed sensor unit substantially in a direction of motion of the target object, said second differential speed sensor unit configured to generate a second differential signal responsive to the passage of said at least one random feature of said target object; a signal processor configured to receive said first and second differential signals, said signal processor further configured to apply a cross correlation analysis to determine a phase shift between said first and second differential signals, said phase shift inversely proportional to a speed of said target object; and wherein said signal processor is configured utilize a Fast Fourier Transform-based algorithm to determine a cross correlation function between said generated differential signals, said cross correlation function defined by: where x x t is a signal time; and τ is a time delay between said generated differential signals.