Nonlinear control of small scale rotary wing unmanned aerial vehicle (R-UAV) using backstepping

Abstract

This thesis demonstrates the application of Backstepping Algorithm for the control of Small Scale Rotary wing Unmanned Aerial Vehicle (R-UAV).The Backstepping method eventually includes the derivation of Lyapunov function guaranteeing Global Stability. Rotorcraft flight control design is traditionally based on linear control theory, due to the existing wealth of tools for linear design and analysis. However, in order to achieve tactical advantages, Rotorcrafts tend to perform maneuvers outside the region where the dynamics of flight are barely linear, and the need for nonlinear tools arises. In this thesis work Backstepping is proposed as a possible framework for nonlinear flight control design. Backstepping is a design tool for constructing globally stabilizing control laws for a certain class of nonlinear dynamic systems whose state equations can be manipulated in a strictly feedback form. Backstepping has advantages over the nonlinear technique of feedback linearization in many aspects. Feedback linearization, as the name implies, aims at canceling the nonlinear system behavior. By using nonlinear feedback. the closed loop system is rendered linear. A major demerit of this approach is that for the cancellation to be possible, all the nonlinearities involved must be known exactly. In aircraft flight control, the aerodynamic forces and moments acting on the aircraft are important sources of nonlinearity to be dealt with. In practice these can not be modeled exactly and hence, perfect cancellation is not possible. Backstepping offers a more flexible way of dealing with nonlinearities compared to feedback linearization. Nonlinearities that act stabilizing may be kept in the closed loop system while destabilizing nonlinearities may be can-celled. Using this merit controller for the Rotorcraft is derived. The control law for general maneuver case and control of Flight path angle is obtained here. The aspect of general maneuver includes the control of Angle of Atta...