Non-rigid Load Transportation by Multiple Quadrotors

In This paper, the problem of carrying a non-rigid load by multiple quadrotors will be addressed. The load consists of a massless box with three mass points which can move in two directions. Each mass is restricted by four springs and four dampers and can move separately from the other two masses. The box is attached to the quadrotors by cables. Dynamics of the system is derived by Newton's laws. Due to the limited power for flying robot, to carry a massive load more quadrotors would be needed. We use four quadrotors to carry it. To coordinate quadrotors a virtual leader structure is used. This structure helps to arrange quadrotors in a desired shape and also keep this shape along the trajectory. Due to the movable load, a robust controller is employed. To achieve this goal, to control quadrotors robustly, two sliding mode controllers for each quadrotor are designed to guarantee a satisfying tracking performance. To verify the proposed method, a numerical example in Matlab is finally simulated.