Using Unmanned Aerial Vehicles (UAVs) to perform high-altitude manipulation tasks beyond just passive visual application can reduce the time, cost, and risk of human workers. Prior research on aerial manipulation has relied on either ground truth state estimate or GPS/total station with some Simultaneous Localization and Mapping (SLAM) algorithms, which may not be practical for many applications close to infrastructure with degraded GPS signal or featureless environments. Visual servo can avoid the need to estimate robot pose. Existing works on visual servo for aerial manipulation either address solely end-effector position control or rely on precise velocity measurement and pre-defined visual visual marker with known pattern. Furthermore, most of previous work used under-actuated UAVs, resulting in complicated mechanical and hence control design for the end-effector. This paper develops an image-based visual servo control strategy for bridge maintenance using a fully-actuated UAV. The main components are (1) a visual line detection and tracking system, (2) a hybrid impedance force and motion control system. Our approach does not rely on either robot pose/velocity estimation from an external localization system or pre-defined visual markers. The complexity of the mechanical system and controller architecture is also minimized due to the fully-actuated nature. Experiments show that the system can effectively execute motion tracking and force holding using only the visual guidance for the bridge painting. To the best of our knowledge, this is one of the first studies on aerial manipulation using visual servo that is capable of achieving both motion and force control without the need of external pose/velocity information or pre-defined visual guidance.

翻译：使用无人机执行高空操控任务（超越单纯被动视觉应用）可降低人力作业的时间、成本与风险。先前空中操控研究依赖地面真值状态估计或全球定位系统/全站仪结合同时定位与建图算法，但此类方法在靠近基础设施时GPS信号退化或特征缺失环境下实用性不足。视觉伺服可避免估计机器人位姿的需求。现有空中操控视觉伺服研究仅实现末端执行器位置控制，或依赖精确速度测量与预设图案的视觉标记。此外，多数研究采用欠驱动无人机，导致末端执行器机械结构与控制设计复杂。本文提出基于图像的全驱动无人机桥梁维护视觉伺服控制策略，主要包含：(1) 视觉直线检测与跟踪系统，(2) 混合阻抗力与运动控制系统。本方法无需外部定位系统的位姿/速度估计或预设视觉标记，且全驱动特性简化了机械系统与控制器架构。实验表明，该系统仅凭视觉引导即可有效执行桥梁喷涂的运动跟踪与力保持。据我们所知，这是首个无需外部位姿/速度信息或预设视觉引导，即可同时实现运动与力控制的空中操控视觉伺服研究。