Nonlinear And Optimization Methods To Aircraft Engine Control

An aircraft engine is a complicated thermomechanical system with strong nonlinear dynamic characteristic. As the complicated working condition of high temperature and high pressure, the rate of the operating of traditional FADEC can't meet the requirement with advanced control law or algorithm. Gain scheduling has always been the method to solve the control problem of the aircraft engine. With the development of the nonlinear control theory having improved, it needs the study of the nonlinear control techniques for the aero-engine control system design.At first, the future development trend of the aircraft engine and its control technology is stated,and then identified model approaches of the aircraft engine, nonlinear control theory, transition optimization control of the aircraft engine are done.Furthermore, the nonlinear model structure of NARX, a nonlinear and nonmathematical model is identified by the data of the operation of model that based on some component level turbofan model.An optimal identified model is selected by referring to the evaluation of AIC and Best Fit and then an error comparative analysis is performed, and the results show that the identified model is suitable for further research.Also, with the nonlinear and nonmathematical model identified, a nonlinear controller is designed by the approach of Nonlinear Generalized Minimum Variance. With this approach we design the reference signal model, the sensor model and the time delay link and then build the control system. A PID controller is designed also to set up a comparative analysis. The results show that both performances of the outputs have almost the simliar affect. But the input variables of control show different effect, the NGMV controller shows better results than the PID controller. To verify the robustness of the controller, some noise signal is introduced into the system and the system shows that it is capable of suppressing interference.To consider the real condition there are many limits during the aircraft engine operation. In view of optimization, with the algorithm of Active Set Method, the input control variables, fuel flow and nozzle area are optimized. The simulation results show that the optimized control law can achieve the engine operating condition change.Finally, the approach with Nonlinear Generalized Minimum Variance and the approach with optimization algorithm are compared to get the better way to design the control system of the aircraft engine. The results show the two approaches have their own superiority with different points. TheNGMV concerns the integrity of the whole control system, and the ASM concerns more other important parameters of the engine. The NGMV gets more convenience and efficiency than the ASM.But the ASM gets less error and less fuel flow than the NGMV.