User-centric assembly planning and instruction development – a systematic literature review and conceptual framework for integrating digital and assistive technologies

Assembly planning and the creation of assembly instructions are central in manufacturing, yet they are challenged by the digital transformation of industrial environments. While automation and cyber-physical integration have advanced under Industry 4.0, the transition toward Industry 5.0 emphasises human-centred, flexible, and context-sensitive production. This shift calls for a renewed examination of how planning processes, assistance systems, and instruction development interact within manual assembly contexts. To address this, a systematic literature review over the last two decades was conducted. The analysis examined thematic categories, keywords, temporal and geographic distributions, citations, and methodological approaches. A taxonomy of assistance and instruction types was developed to reveal conceptual relationships between traditional planning and emerging digital technologies, including augmented and virtual reality, digital twins, and cyber-physical systems. The findings highlight a shift from algorithmic and rule-based assembly planning toward digitally integrated, user-centred approaches. Visual and model-based assistance dominates current research, while data-driven and adaptive systems remain underrepresented. Despite this, the analysis reveals persistent fragmentation among assembly planning, assistance systems, and instruction development. To address this, the paper proposes a literature-derived conceptual framework that integrates the analysed adaptive technology into the production process and links planning decisions to user-centred instruction design.