Design, Sensing, and Control of a Novel UAV Platform for Aerial Drilling and Screwing

Abstract

Hole drilling and bolt screwing are frequently performed tasks in construction, decoration, and maintenance. Traditionally, sending human workers to perform these tasks in hard-to-reach locations is both dangerous and costly. In this letter, we present an aerial manipulation platform that allows a human user to remotely conduct omnidirectional drilling and screwing. The design of the platform features a quadrotor UAV with each pair of rotors independently tilted by a servo, forming an “H” configuration, on which a 1-DOF manipulator carrying a motorized drill or screw driver is mounted. With such a design, the end-effector can face any direction on the longitudinal plane and exert a big enough contact force for drilling and screwing without the need of changing the vehicle body's orientation. Compared to previous UAVs that can only drill holes vertically into the ground, the proposed design also allows horizonal drilling/screwing into a wall or a cliff, making it suitable for a vast range of real applications. Based on the dynamic equations of the system, a dual-level control law is proposed. The low-level attitude controller uses an adaptive robust control (ARC) to accurately regulate the attitude angles in the presence of force/torque uncertainties that may occur during the drilling and screwing process, while a selective impedance controller is implemented at high level to indirectly control the contact force commanded by the user. In addition, a vision-based real-time target identification and tracking method integrating a YOLO v3 real-time object detector with feature tracking, and morphological operations is developed to identify and track the target point for drilling and screwing specified by the user. Various in-lab experiments on a self-made prototype demonstrate the feasibility and effectiveness of the proposed approach for aerial drilling and screwing.