Planning and distributed control for cooperative transportation of a non-uniform slung-load by multiple quadrotors

This paper presents a novel control and planning algorithm for cooperative slung-load transportation using multiple quadrotors. Each aerial robot modeled as a quadrotor is connected to a non-uniform payload by the cables. Udwadia-Kalaba equations are used for calculating the forces on the cables acting on each robot. A novel leaderless distributed adaptive control algorithm is presented which not only ensures the safe transport of payload in the generated path in the presence of external disturbances but also manages to solve the problems related to the interaction of payload with the aerial robots. Moreover, the payload dynamics is not considered in the design of the controller which facilitates the load transportation in any size, shape, or weight by the robotic team without compromising performance. Then, an improved rapidly exploring random tree star (RRT*) algorithm is developed to generate desired path for each aerial robot in order to avoid known obstacles for cooperative payload transportation problem. The proposed path planning algorithm is capable of finding a free collision path in any situation, specially where high maneuverability is crucial to avoid collision of the payload with obstacles. Three numerical simulations are conducted to verify the proposed planning and control scheme. Additionally, in the distributed control algorithm simulation, two indexes including ISE and IADU demonstrate the improved performance of the distributed control over independent control of robots. The superior performance of the proposed controller in terms of reduced tracking errors in presence of external disturbances is also shown in comparison with a distributed nonlinear H∞ design.