Modeling And Robust Controller Design Of A Twin Rotor Helicopter System

The Twin Rotor Helicopter System has been used as an experimental setup in many labs to study dynamics of a helicopter flight envelope and functioning of various control techniques in coping with the nonlinearities involved and the coupling effects. This setup is preferred due to its complex nature that is a model of real helicopter. This work examines the robustness of three control methods, the H_∞ controller, the H-infinity loop shaping design procedure and the μsynthesis method. A state feedback design is also used to determine the controllability of the system and a Simulink test conducted with the nonlinear system. Uncertain modeling is done by considering parametric uncertainty with use of LFTs and the sysic function is thereafter used to create the open loop interconnection. The knowledge of the H_∞ norm and singular values is applied to the robust analysis of the systems with the different controllers and represented by graphs. The different robust techniques are compared through Matlab files and presented in figures. The comparisons show that the H_∞ controller is best suited for the design and achieves better results compared to the two other controllers. It is also shown by a comparative design that the H_∞ approach is not always reliable for all designs. The loop shaping procedure fails to satisfy the robust performance tests and has a big overshoot of above 35% despite having a very short settling time of less than 3 seconds. The μ- synthesis controller satisfies all conditions of robust performance, nominal performance and robust stability like the H-infinity controller. It however has an overshoot of over 20% and a settling time of 17 seconds which is not desirable.The H_∞ controller fails to satisfy the nominal performance criterion for the linearized plant at theπ rad working position but achieves all the robustness conditions for the point 0 rad, working position.