Rotorcraft Trajectory Tracking Using the State-Dependent Riccati Equation Controller

Abstract

This paper deals with the State-Dependent Riccati Equation (SDRE) method for designing a rotorcraft flight controller. It focuses on the design of the SDRE controller when a highly complex rotorcraft mathematical model is used. The requirements of the rotorcraft model are investigated to design the SDRE controller and to validate the final designs. Since the SDRE method can be applied to a deterministic system, adequate fidelity in the rotorcraft mathematical model is crucial to guarantee controller performance. However, a complex mathematical model generally prevents us from analytically deriving the State Dependent Coefficient (SDC) form of the system equations, which conforms to the basic structure of the SDRE method. This paper proposes a pure numerical procedure for SDC factorization of the motion equation. The numerical methods available to solve the algebraic Riccati equation are selected to cope with the inherent system instability and are applied to the trajectory tracking problems. The overall feature of the present approach is highlighted through analysis of a bob-up and turn maneuver. The results can be utilized as a guide for appropriate selection of rotorcraft mathematical models and numerical methods in designing a robust SDRE controller.