Generalized Cascaded Control Technology for a Twin-Rotor MIMO System with State Estimation

This article explores the design of a generalized feedback control operator coupled with state estimation for a twin-rotor MIMO system (TRMS) intended to regulate its predefined configurations (i.e., pitch and yaw) or follow time-varying reference configurations in a unified manner. Designing a generalized controller subject to the process and measurement uncertainties of a TRMS is a difficult task to undertake due to the coupling effects between its rigid body structure and the propeller dynamics associated with it. Many techniques have been proposed in the literature to control the output trajectory of a TRMS. However, they are either focused on addressing the regulator problem or do not take into account the process and measurement uncertainties in controlling the motion of the TRMS's output (i.e., pitch and yaw). The proposed control technology mainly addresses the regulator problem of a TRMS in two cascaded phases. In the first phase, a nominal optimal feedback operator is obtained based on the reference output trajectory of a TRMS. The nominal operator is then used to determine the nominal state and input trajectories of a TRMS platform. In the second phase, the dynamics of a TRMS platform is linearized around its nominal trajectories. The linearized model is then used to find the optimal input signals for tracking/regulating the reference pitch and yaw angles of the TRMS platform subject to its process and measurement uncertainties. The proposed control law is also proven to be stable in the sense of Lyapunov. Theoretical results are validated through a set of computer simulations, and their performance is compared against a conventional proportional-integral-derivative scheme to demonstrate the superiority of the generalized cascaded control technology.