Façade Operation Robots on Irregular Buildings: A Survey and Perspective on Mechanism, Perception, Control, and Planning

The increasing adoption of irregular façades in modern architecture has significantly raised the complexity and risks of maintenance tasks, exposing the limitations of conventional human-based approaches. As a result, robotic solutions for façade operations have emerged as a critical alternative to ensure safety, efficiency, and reliability. This paper presents a comprehensive survey of façade operation robots designed for irregular and unstructured environments. The review is organized into four main domains: mechanisms (wheel/track, legged, rope-driven, propeller-based, and hybrid designs), perception (robot localization, surface mapping, and object recognition), control (global path tracking and local stabilization), and planning (coverage and goal-directed methods). By systematically analyzing representative studies in each domain, this survey highlights the current state of the art and identifies key technical challenges. The analysis shows that hybrid locomotion mechanisms and multimodal perception pipelines offer superior adaptability, while robust and optimization-based controllers are effective against irregular surfaces and disturbances. Planning methods increasingly employ 3D models and learning-based techniques, yet scalability remains a limitation. These findings suggest promising research directions in lightweight hybrid designs, perception–control integration, and multi-robot collaboration for future façade operation robots.