Design and Flight Testing of a Two DOF Decoupled Pantograph Aerial Manipulator for Commercial UAVs

Aerial manipulation devices have been increasingly tailored to use at the limit of unmanned aerial vehicle (UAV) technology. The utility value of affordable off-the shelf UAVs for aerial manipulation is relatively unexplored as they often do not meet the performance requirements of coupled manipulator design systems. This paper presents the design and validation of a balanced pantograph manipulator prototype for decoupled use, evaluated with bench tests and and flight tests on a quadrotor UAV. The design exhibits two degrees of freedom (DOF) with a larger range of motion than most preceding decoupled manipulators. The paper also discusses an analytical model which maps the centre of gravity (CG) of all the links of the device in its operational range, allowing fine-tuning of a compact counter mass assembly which operates mechanically to achieve a net-zero stability impact on the UAV. This primary function is ideal for close quarters inspection and contact sensing tasks which engage passively with the environment. Results show that the decoupled pantograph manipulator has no measurable stability impact on the UAV, is appropriate for the use cases described and shows promise for development into a coupled design platform.