Decoupled design of controllers for aerial manipulation with quadrotors

In this paper, we model an aerial vehicle, specifically a quadrotor, and a load attached to each other by a rigid link. We assume a torque input at the joint between the aerial vehicle and the rigid link is available. After modeling, we decouple the system dynamics in two separate subsystems, one concerning the position of the center of mass, which we control independently from the chosen torque input; and a second subsystem, concerning the attitude of the rigid link, which we control by appropriately designing a torque control law. Differential flatness is used to show that controlling these two separate systems is equivalent to controlling the complete system. We design control laws for the quadrotor thrust, the quadrotor angular velocity and the torque input, and provide convergence proofs that guarantee that the quadrotor follows asymptotically a desired position trajectory while the manipulator follows a desired orientation. Simulation and experimental works are presented which validate the proposed algorithms.