Reconfigurable Multi-Rotor for High-Precision Physical Interaction

Unmanned aerial vehicles (UAVs) for contact-based tasks at height can greatly improve the safety of the human workers involved. However, performing contact-based tasks with typical under-actuated UAVs is non-trivial. Due to their coupled translational and rotational dynamics and their limited station-keeping performance under physical disturbances, it is difficult to maintain precise and consistent contact. We address these problems in the context of physical interaction with vertical, cylindrical target objects, such as trees. We present a novel UAV design with a pair of tilt-rotors and a landing gear that can reconfigure into a front-mounted, two-fingered gripper. While the tilt-rotors provide horizontal force toward the target object without pitching the UAV forward, the reconfigurable landing gear enables the UAV to obtain support from the target object. Such support results in an approximately 80% improvement in position- and heading-keeping performance. Moreover, the landing gear is designed as a cable-driven under-actuated system, which requires only one actuator to control both the reconfiguration and the grasping (i.e., five degrees of freedom in total). Such a minimalist design helps keep the UAV power consumption for interactions low. This marks progress towards safe, high-precision physical interaction against vertical, cylindrical target objects. Our UAV in action: https://youtu.be/D-65vldox_A.