Terrain Following for Fixed-Wing Unmanned Aerial Vehicles Using Feedback Equivalence

We present a controller design methodology for unmanned aerial vehicles (UAVs) which is based on feedback equivalence of control affine nonlinear systems. We introduce an arbitrary coordinate transformation of the UAV's physical space, extend it to the entire state space and prove that there exists an input transformation such that the dynamical equations remain invariant. We obtain an explicit expression for this coordinate transformation by parameterizing a reference terrain by a flat surface therefore reducing the problem of terrain following to following a simple plane. Our theoretical contributions are accompanied by simulation results, by which the effectiveness of the method is demonstrated.