Toward image-based visual servoing for cooperative aerial manipulation

This paper proposes a new visual controller to endow flying manipulators with the capability of cooperatively and automatically positioning an assembly part on a visual target. We consider two VToL UAVs each equipped with a robot manipulator and a video camera. The two manipulators are rigidly connected to an assembly part, consisting of bar in this case study, that needs to be automatically placed on its target pose. The control system we propose uses the images relayed from the two onboard cameras to simultaneously control the motions of the UAVs and the manipulators to achieve the task: positioning the bar as well as respecting the closed-chain constraint. The controller evolves in the image space, thus inheriting robustness with respect to calibration errors. It takes into account the under-actuation inherent to rotary-wing aerial vehicles as well as the redundancy of the whole system. Furthermore, by leveraging image moments the 3D relative motion between the carried assembly part and the environment is controlled, thus yielding to natural and practically-relevant movements. Numerical simulations have been carried out to verify the validity of the proposed approach.