System identification and discrete nonlinear control of miniature helicopters using backstepping

This paper deals with the dual problem of system identification and control of small scale unmanned helicopters. Although most controller designs are in continuous time, this paper considers the discrete time dynamics of the helicopter. A simple Recursive Least Square algorithm is used for parameter identification in the time domain, the objective being the derivation of system dynamics that are both minimal in complexity and accurate for control design in discrete time. The helicopter's nonlinear rigid body equations of motion are considered. The necessity to encapsulate the nonlinear terms of the rigid body's motion is very important since it provides a wider dynamical description of the flight envelope. A controller is designed based on a discrete time backstepping technique, for the tracking of predefined position and yaw trajectories. The developed controller provides design freedom in the convergence rate for each state variable of the cascade structure. This is of particular interest since control of the convergence rate in each level of the cascade structure provides better flight results. Both the identification part and control performance are evaluated using a commercial available flight simulator X-Plane ^©.