Abstract: As human science and technology continue to challenge extremely high precision and bad working conditions, high-end equipment has an increasingly urgent need for ultimate precision and performance. However, traditional assembly theories based on geometric quantity control fall short in addressing the issues of high-precision assembly and maintaining performance under complex working conditions. In response to the above problems, the essential features of precision assembly are first analyzed, and its state-of-the-art is then reviewed. Subsequently, a mesoscale precision-assembly theory and method are proposed, and its technical system is established. Three fundamental issues of precision assembly involving interface, cross-scale, and uncertainty and raised, and the research framework of precision assembly is presented, which covers seven aspects, including assembly joint technology, assembly accuracy analysis, assembly performance stability analysis and control, assembly uncertainty analysis and optimization, assembly process and equipment, assembly digital twin, and assembly measurement and test. Finally, an opinion that precision assembly requires analyzing the formation, evolution, and regulation mechanisms of assembly performance from multiple aspects, such as geometry, materials, assembly, and service, are pointed out, and the future development directions of integration, micro/nano, and intelligence of precision assembly are indicated.

Key words: precision assembly, assembly accuracy, assembly interface, mesoscopic scale, performance stability, uncertainty