Function analysis diagram

A function analysis diagram (FAD) is an engineering design method that models and visualizes the functions and interactions within a system or product. It uses blocks to represent physical components, users, or environmental resources, with labeled arrows indicating functional interactions. FAD was first proposed in 1997 by Invention Machine Corporation as part of their TRIZ-based software tools and has since been developed through academic-industry collaborations.

FAD is considered more intuitive than traditional methods like function trees because it incorporates the physical structure of a product, capturing richer networks of functional relationships. The layout can mirror the spatial arrangement of components, providing additional insight. By mapping interactions, FAD helps understand design rationale and identify areas for improvement, including harmful functions.

The diagrams can be hierarchical, linking different system states or levels of detail. Labels are often in natural language but may use shorthands for recurring relation types. Benefits include simple notation, ease of use due to product structure representation, capturing complex systems, and reflecting spatial arrangements. FAD supports design decisions, adaptive tasks, knowledge reuse, and quality improvement.

Applications span aerospace, manufacturing, and power systems. Tools like Decision Rationale Editor (DRed), TechOptimizer, and DesignVUE provide specific support for FAD creation, though general drawing tools can also be used. This method aids in sharing functional knowledge and enhancing design discussions.