END OF VALVE MOTION DETECTION FOR A SPOOL CONTROL VALVE

摘要

A fuel injector system 10 calculates a first derivative filtered signal and a second derivative filtered signal from an unpowered spool valve coil signal. When the spool valve 16 reaches the end of travel, either open or closed position, a flat slope f is genrated on the falling edged of the bell shaped signal. The second derivative provides a readily apparent determination of when the steep slope occurs. A comparator 62 thereby need only determine when the second derivative is zero to identify that the spool valve has reached the end of travel.