Bell + Howell Company

F Nicholaas Spanhak

Thomas E Hainsworth

Richard R Paske, Jr

A self-adapting signal detector is adapted to be used with a plurality of guidepath sensors for controlling an automatically guided vehicle. The circuitry detects the presence of a valid guidepath signal over a large dynamic range without the need to make threshold or gain adjustments. A background noise signal is detected as well as a signal from each of the guidepath sensors. The background noise signal is substracted from each sensor signal to define a plurality of difference signals. A maximum remainder signal is defined as the maximum difference signal. Each difference signal is then compared with a predetermined percentage of the maximum remainder signal. Those sensors whose signal level exceeds the predetermined percentage of the maximum remainder signal by a predetermined amount are defined to be a valid guide path signal. The maximum remainder signal is also compared with a predetermined percentage of the background noise signal to determine the signal-to-noise ratio. If the signal-to-noise ratio signal falls below a predetermined value, a signal is provided to stop the vehicle. In an alternate embodiment, the lesser of a predetermined percentage of the maximum remainder signal and a predetermined percentage of the background level is selected to define a reference signal. Those sensors whose signals exceeds the reference signal are defined to be a valid guidepath signal.

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Jennison, MI, United States of America

F Nicholaas Spanhak