Model-based observer: a gas turbine engine case study

A model-based control approach to synthesizing a nonlinear controller for a single-spool gas turbine engine is described. Since the main control variable, engine thrust, cannot be directly measured, a model-based observer is considered to provide online estimation of the thrust for feedback control. Both proportional and proportional-integral (PI) observers have been used in the model-based observer design. The latter is intended to provide robust estimation in the event of modeling errors. The controls are the fuel flow and final nozzle area, and the control structure is the PI controller designed using the KQ ( K-matrix compensator, Q-desired response) multivariable design technique. The model-based observer control scheme is studied when the engine is subjected to the disturbance of inlet flow distortion. The results are acceptable in terms of the thrust response and the transient trajectory on the compressor characteristic