Abstract: A system for determining the angular position of a rotating element such as an engine crankshaft. An encoder wheel is divided into a plurality of equal-angle segments, each comprising a peripheral tooth extending radially over a central angle representing an angular percentage of each segment. The total angle in each segment is a tooth dwell angle and a gap dwell angle. The ratio of the tooth dwell angle to the total segment angle is the duty cycle. A prime segment is given a first tooth dwell angle. Each segment has a unique tooth dwell angle. As the wheel rotates, a sensor begins timing at a first tooth rise and determines the time to the first tooth fall and the time to the second tooth rise. Since each duty cycle is unique, for a wheel having 45 degree segments the system can determine the segment being interrogated within 90 rotational degrees.

Abstract: An exhaust emissions control system includes a valve in an exhaust stream portion of a mainstream exhaust ahead of an aftertreatment element such as a catalytic converter. The valve controls the amount of exhaust flowing into a hydrocarbon reformer. A bi-directional acoustical air meter in the exhaust stream portion ahead of the reformer measures the velocity of the exhaust stream portion, and a computer determines the amount of combustion needed in the converter at all times, adjusts the amount of hydrocarbon fuel provided to the reformer, and adjusts the position of the valve to provide the optimum amount of exhaust gas flow into the reformer to achieve a desired temperature in the converter.