Master thesis and internship[BR]- Master's thesis : Solutions for robust control algorithm design through gain scheduling for a guided rocket[BR]- Integration Internship : Thales Belgium

Abstract

With the aim to increase the robustness of an already implemented controller, three controllers have been designed: 2-DOF PI (a variant of classical PID), H8, and mu-synthesis controllers. To design them, the system to control had to be linearized and characterised for every flight Mach number since gain scheduling is used. This has been accomplished by the mean of transfer functions. After that, the 2-DOF PI controller has been design using the Control System Toolbox from MATLAB, and both H8 and mu-synthesis controllers have been designed using the Robust Control Toolbox. These controllers have been designed for every flight Mach number, leading to ten controllers expressions per type of controller.

The evolution of the gains of the 2-DOF PI and H8 controllers with respect to the flight Mach number are not intuitive and not physical, in opposition to the mu-synthesis controller. This behaviour reflects in the robustness assessment, where it has been seen that the mu-synthesis controller is the most robust, and the H8 controller is unstable.

In terms of performance, both H8 and mu-synthesis controllers are the best when the Mach number is correctly estimated, followed by the already implemented controller and, lastly, the 2-DOF PI controller. However, when adding uncertainty on the Mach number estimation, the H8 controller becomes unstable and is therefore not robust. On the other hand, the three other controllers are robust to uncertainty, with an important advantage for the mu-synthesis controller. The designed mu-synthesis controller is therefore a strong lead to investigate for possible practical implementation.