Research in the area of hauling loads using an Unmanned Aerial Ve hicle (UAV) has been very restricted. The main obstacle is that the model for the vehicle and the load together is not yet established and available. The next hurdle faced is while designing a controller for an underactuated UAY. Finally, the last obstacle is the control of the load swing during hauling. These challenges make it a very intriguing area of research. The aim of this work is to propose a model for the UAV with a slung load. A feedback linearization controller which helps in trajectory tracking of the UAV and a time-delayed feedback controller to stabilize the load swing angles are also proposed which work together to make the overall system stable.
II. INTRODUCTIONUnmanned Aerial Ve hicles (UAVs) are being de ployed for many appliations in security, monitoring of natural risks of environment, intervention in hos tile environments, management of ground installa tions, agriculture and military. Deployment of UAVs helps to gather information in hostile environments without posing risk to flight crews and humans. In UAV's, rotary wing types are superior to the fixed wing type, because the rotary wing type UAVs are capable of Ve rtical Take Off and Landing (VTOL), omni-directional flying and hovering performances. VTOL is very important as runway space is not readily available for modern missions and tasks. Hovering is also important to do monitoring and surveillance. Rotary-wing type UAVs can be divided into quad-rotor and helicopter based on their shapes and structure. The advantages that the quad-rotor possesses over its counterparts is that it does not 978-1-4799-3866-7/14/$31.00 ©2014 IEEE 1 require mechanical linkages to vary rotor angle of attack as they spin. The use of four rotors allows each individual rotor to have a smaller diameter than the equivalent helicopter rotor allowing them to store less kinetic energy during flight and this reduces the damage caused by the rotors hitting any objects. They are very miniature, cost-effective, easily maneuverable and have low maintenance cost. In addition, by enclosing the rotors within a frame, the rotors can be protected during collisions. The control structure for the quad-rotor is one of the most important desing as it determines the operation and performance of the overall mission. The quad rotor being an under-actuated vehicle makes the control design challenging. A lot of research has been done in the area of stabilization of quad rotor angles and trajectory tracking. Different con trol methods have been developed and designed for stabilization and tracking. Tayebi (2008) proposed a quaternion based dynamic output feedback control scheme without the need of velocity measurements for attitude tracking. Bourquardez and Mahony et al. (2009) proposed an image based visual servo controller for regulation of the quadrotor. Raffo, G. Y., M. G. Ortega, et al. (2010) proposed a integral model predictive based nonlinear H infinity controller for the quadrotor. Dierks and Jagannathan (2010) p...