Research On Aero-engine Nonlinear Parameter Estimation Methods

Direct thrust control becomes an important research project in aero-engine control field because it can reduce the design margin and can excavate aero-engine's performance potential. This method needs information about thrust. And stall margin provides important information for aircraft's safe fly. But they both can't be directly measured during flight. This paper studied two methods in order to find the best evaluation of them.One is to design a Constant Gain Extend Kalman Filter (CGEKF). The CGEKF is developed by combining an on-board engine model and a single Kalman gain matrix. It can estimate aero-engine's performance parameters indirectly through estimating the efficiencies and flow capacities (health parameters) of it's components. Only a subset of health parameters can be estimated because the number of available sensors, in general, is less than the number of health parameters, and also because of the converge condition of Kalman Filter technology. Therefore, those estimated health parameters not only represent themselves but also the change of other health parameters, they become tuning parameters to make the on-board engine model adaptive to the real engine's performance variations due to the degradation or anomalies. Performance of the CGEKF is evaluated in many simulation conditions. The simulation results show that the CGEKF is able to estimate the parameters with high accuracy.The other method uses nonlinear equations which include health parameters as the way to estimate performance parameters. According to the number of the equations and health parameters selected, there are three different ways in which nonlinear optimizing is the most important to solve equations. The simulation results show that they are suitable.