The Unmanned Systems Research (USR) Group at the Chinese University of Hong Kong (CUHK) devotes to the development of advanced unmanned systems platforms and technologies for industrial applications. One of our current research focuses is to develop an innovative collaborative task assignment of multi-agent unmanned systems for general infrastructure inspection. It aims to design the best task assignment strategy and the most efficient paths that enable a team of drones to automatically collect high-quality data. Compared with single-agent methods, our approach has the advantages of being more efficient and effective. It can also resolve task complexity, enhance the overall system reliability, and more significantly, bring the research on multi-agent systems to real industrial applications. The result can be further integrated with advanced AI and DT (digital twin) techniques to develop an information management system within a smart city framework.