Stabilization of unmanned helicopter with suspended payload in presence of wind gusts and rotor downwash

Helicopters utilization is not limited to military and surveillance applications but they are also used for transporting heavy loads from one place to another because of their vertical takeoff and landing (VTOL) capabilities. However slung load is drastically affected by disturbances around the system making difficult for helicopter to regain control. Tip vortices at the blades induce velocity which not only effect blades but also degrade performance of the whole system by creating vibrations. This paper proposes control technique based on sliding mode control utilizing linear matrix inequality to keep payload unaffected in the presence of rotor downwash and time varying air disturbances during hovering. With the help of proposed controller desired trajectory is achieved due to its robustness and variable control structure.