Alain Pierre Garassino

An Advanced Control System for Turbofan Engine: Multivariable Control and Fuzzy Logic (Application to the M88-2 Engine)

The search for better performance of present and future turbofan engine involves an increase on the number of variable geometries and thus of control loops.As we can not or do not want to disregard the interaction between loops any more, the future control systems will therefore be multivariable. The aim of the architecture of multivariable control presented here is to optimize a performance index during transients.This architecture consists of an inner loop which optimizes the performance index taking in account the limitations, an outer loop which brings the nominal steady-state offsets to zero and a trajectory which allows to take into account the topping schedule limitation.This basic architecture can be improved by fuzzy supervisor.Indeed, two control outputs are generated according to the description above:- the first one optimizes the thrust and does not care very much about LP stall margin limitation,- the second one optimizes again the thrust and strongly takes low pressure stall margin limitation into account.The fuzzy logic then allows to do a compromise between these two control outputs according to the engine state.Simulation results showing the efficiency of the method are given.Copyright