Multivariable Adaptive Control for Turbojet Engines

Integrated flight and propulsion control systems will require propulsion systems to reduce in time to accelerate engine and to improve transient performance for a full flight envelope operation. A multivariate model reference adaptive control (MRAC) scheme is proposed in this paper. Acceleration time is reduced by uptrimming engine pressure ratio in some operating conditions and in parts of the flight envelope where excess stall margin and turbine temperature margin exist. The MRAC scheme is obtained by using Liapunov direct method. Simulation studies are performed for a two-spool turbojet engine. The satisfactory transient responses are obtained at different operating points from idle to maximum dry power in flight envelope which shows good robustness for unmodelled dynamics of nonlinear engine. Simulation results also show the good effectiveness of reducing interaction in multivariable system with significant coupling. Using the Multivariable MRAC controller, the engine acceleration time is reduced about 16 percent in comparison with the conventional engine controller.