Tracking control for 2DOF helicopter via robust LQ control with adaptive law

In this study, a robust LQ control system with Model Reference Adaptive Control (MRAC) law is discussed. By adding MRAC law to the usual robust LQ control system, it is expected that the system output tracks to the reference signal even if there exist larger parameter perturbations that are not guaranteed in the robust LQ controller synthesis process. Through tracking to the reference signal, we expect that proposed system improves the robust control performance. The proposed system is synthesized by two-step approach. It is well known that if a controller is synthesized for a system with parameter perturbations, the tracking performance of the closed loop system is not as good as that of the closed loop with the nominal plant and a controller synthesized for the nominal plant. For this reason, a robust LQ controller is synthesized for a small perturbation, firstly. Then MRAC low is adopted for the closed loop with the plant and the robust LQ controller to improve the tracking performance when there exist large perturbations. LMI based stability analysis method for MIMO system is developed after Yang et al's method[6]. The effectiveness of the proposed method is verified by some experiments using a test-scale 2 Degree-of-Freedom (2DOF) helicopter.