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The relationship between the concentration of various gas components (CO,NO,HC) at the output of a three-way catalytic converter and the input and output air-fuel ratios (AFRs) is examined. A simple linear-in-the-parameters model is developed and it is assumed that the model parameters in the lean and rich regions are different. The model is fitted to some experimental step response data obtained from fast gas response analysers and UEGO sensors, using a recursive linear least-squares estimation method. A reasonably good fit to the data is obtained, particularly for NO and CO. Results from step tests for different AFR ranges are combined to obtain an overall picture of the dependency of the gas components on measured AFR values. The proposed model provides the possibility of predicting the dynamic performance of catalytic converters from a knowledge of the input and output AFR values.

Conventional ratcheting tools do not work efficiently in confined spaces and they have other limitations when used in space during extravehicular activity (EVA). The National Aeronautics and Space Administration’s (NASA) Goddard Space Flight Center has developed a three-dimensional (3-D) sprag/roller technology that has many benefits over the ratchet mechanism. The Space Systems Laboratory at the University of Maryland is using this technology in the development of EVA tools. The research discussed here describes the testing of an EVA roller wrench aboard NASA’s Reduced-Gravity Flying Laboratory (the KC-135), evaluation by astronauts in NASA/Johnson Space Center’s Neutral Buoyancy Laboratory, and the flight of a 3-D roller mechanism on Space Shuttle Mission STS-95.