An action-chain model for the design of hazard-control systems for robots

The authors establish a hazard-control design methodology based on a categorization of action changes and the dissociation of action chains. In this methodology, the damage process is modeled by propagation of actions among system elements, the actions are put into two groups (state-failure and function-failure), the concept of action-linkage dissociation is developed for damage prevention, application rules for information-processing systems are defined, and a systematic procedure to identify hazards and to conceptualize hazard-control systems is developed. It is postulated that dissociations involving paths or sources lead to fail-safe systems, while those involving substitution-of-function lead to fault-tolerant systems. Examples involving robot systems are given to demonstrate the new technology