6 DOF manipulator design for maneuvering autonomous aerial mobile robot

A considerate amount of literature has been published on small and low altitude aerial mobile robot navigation. The autonomous tasks include trajectory tracking, hovering, goal seeking, object approach, formation keeping and landing etc. Many algorithms have been proposed to navigate the aerial robot in the uncertain, unstructured and dynamic environment. However, how to emulate the actual aerodynamic environment to evaluate those algorithms has not received much attention. The direct test of the navigation system in low altitude easily leads the small aerial mobile robot to stall, flip over and crash upon unexpected disturbances. This paper proposed a novel aerodynamic emulation system for the small and low altitude rotorcraft vehicles. A 6 DOF mechanical manipulator is designed to withhold 3 types of rotorcraft aerial locomotion. The stress analysis of the CAD/CAM model is conducted to obtain the optimal design parameters prior to the fabrication. The D-H matrix transformation is applied to derive the analytical trajectory model of the end effector motion and then further simulated through ADAMS software. The proposed aluminum manipulator is tested in an emulated subsonic wind tunnel to investigate the actual flight scenario and analyze the aerodynamic effect (e.g. forces and moments) over the aerial robot. Data analysis results show the proposed aerodynamic emulation system can successfully validate the trajectory error compensation algorithm developed under a turbulence of varies winds levels up to 13.8m/s (Level 6). The 6 degrees of freedom in the manipulator, translation and rotation in xyz axis, constrain the aerial mobile robot to fly in a safe altitude of 0.2 m within a radius of 1.9 m. The manipulator is robust and stable in the flight test with the payload up to 20N, the maximum velocity as 30 km/h, and the maximum tolerable stress as 68.9 GPa.