Examenspresentation av Johan Wallgren

Examiner: Jonas Sjöberg

Opponents: Anton Alinder and Oskar Olsson

Abstract:
Controlling a low bypass aircraft engine is a highly complex problem, partially because the engine characteristics of such an engine are non-linear. The control method used in this thesis is to tie multiple linear controllers together, to cover the operating range of the engine. The operating range, of the engine used in this thesis, ranges from low to high thrust levels with the engine being static at sea level altitude.

For the control design, linear engine models of the low bypass aircraft engine are derived for four different design points, throughout the operating range of the engine. The linear engine models are also scaled and reduced to improve the performance and reduce the order of the resulting controller. The inputs, outputs and control configuration for the control system are selected using methods for Control Structure Design (CSD). The linear engine models are combined with actuator models, sensor models and weighting functions to form the augmented plants for the H-infinity control design. The four multivariable linear H-infinity controllers are tied together using gain scheduling combined with bumpless transfer logic.

For evaluation, the designed control system is implemented and simulated in an existing non-linear engine model, which is a detailed dynamic simulation model based on a low bypass aircraft engine. Various simulations are performed to evaluate the performance of the control system during steady state, disturbances, transients and engine variations. The non-linear engine simulations demonstrate that the designed control system could be implemented in a real low bypass aircraft engine. However, not before all aspects to ensure safe engine operation have been considered.

Welcome!

Johan and Jonas