Tracking control of quad-rotor helicopters suspended a power supply cable with on-line estimation of disturbances

In this paper, we propose a tracking controller for quad-rotor suspended a flexible cable. The first contribution is to present a new disturbance observer to estimate online both the tension of the cable and unknown disturbances applied to dynamics. The second one is to propose a new exact linearization method which reduces the nonlinear closed-loop system to a linear controllable state equation by changing coordinates in the state-space. By using the linearization, a new tracking controller based on disturbance observer is presented for obtaining asymptotically rejection against unknown constant disturbance.