Supervisory fuzzy control of an exhaust measuring system

The main element of an exhaust measuring system is a Venturi tube where exhaust gas is diluted by pure air. Samples of the diluted gas are taken from a probe and analyzed with a special analyzing device. The control task is to keep a constant volume ratio of exhaust gas and air despite high external disturbances and parameter fluctuations. This is done by means of a discrete sliding mode fuzzy controller (SMFC). To avoid oscillations, the variation of the exhaust/air ratio is monitored by a fuzzy supervisor where the overall gain is reduced until the oscillations disappear. In the paper a simplified model of the system is presented and the control design of a conventional controller and a SMFC is discussed. Furthermore, the use of a supervisor is motivated, and the fuzzy supervisor is introduced. Finally, simulation results are shown and the implementation of the system under control is presented