A Model-Based Safety Analysis Method for Hybrid Systems Based on Multiple Hazard Factor Categories

Safety issues in hybrid systems increasingly result from a combination of multiple categories of hazard factors. However, current hazard analysis methods mainly focus on just one kind of system hazard. This paper presents a model-based safety analysis method for hybrid system that is based on multiple hazard factor categories. Using a Model-Based Safety Analysis framework, the functional model of a hybrid system is first established. Its logic component is modeled using a state diagram and its continuous component is modeled using a transfer function or a state equation. The safety model of the system is then constructed considering a variety of hazard factors. Improper control and logic inconsistency are established for the logic component. Component deviation and logic inconsistency are established for the continuous component. Finally, the safety of the system is then analyzed and the hazard paths are obtained. As an example, the Wheel Brake System for an aircraft is taken to analyze the safety of the aircraft landing phase. By taking into account multiple hazard factor categories, we are able to identify hazard paths that could not be found using a single hazard factor category.