Intermediate state control of turbofan engine in full envelope based on switched polytopic LPV approach

The parameter range of aeroengine in full flight envelope is so wide that a single controller is difficult to ensure the performance. To avoid this problem, a switched polytopic linear parameter varying (LPV) approach was proposed for the turbofan engine intermediate state control. The full envelope was firstly divided into several locally overlapped sub-regions according to the inlet conditions. The state reset method and the polytopic gain scheduling technique were used to derive the robust stability conditions of this switched LPV system, which was depicted as linear matrix inequality (LMI). Then, the resulting Lyapunov matrices were used to design a family of single LPV controllers which can be applied in the sub-region control combined with the scheduling strategy based on geometric position; Hysteresis switching strategy based on the overlapped sub-regions was used for switching, meanwhile the stability of this closed-loop switching system was also proved. Simulation results with a turbofan engine model show that the steady state error is less than 0.1 percent, and the maximum overshoot is less than 0.5 percent.