Modeling and verifying the communication and control of a fleet of collaborative autonomous underwater vehicles

This paper presents an application of the formal method to model and verifies the communication and control for a fleet of collaborative autonomous underwater vehicles (AUV) named as Eco-Dolphin. The fleet includes YellowDolphin, BlueDolphin, and RedDolphin, which are designed to collect environmental data and provide surveillance services in littoral water. The system architecture of the fleet is specified by OpCat, a formal modeling tool based on Object-Processing Methodology. The collaborative missions of the fleet are coordinated by a Ground Station (GS) through radio and acoustic dual communication channels. The real-time behaviors and control logic for such a system is complex and error-prone due to the heterogeneous nature of the system and possible faulty communication. A timed state model is built to specify the essential communication and control behaviors. UPPAAL - an open source model-checking tool is used to verify the model against its desired & undesired properties specified in temporal logic queries. Because most of autonomous multi-agent systems depend on asynchronous and distributive controllers with large sets of state variables, the practice of model-checking for such controllers is severely hindered by the state explosion problem. Therefore, innovative heuristics need to be explored to reduce the state spaces of the state model. The major contributions of this paper are: (1) to present a practical software-hardware co-design of a fleet of mission critical AUVs, (2) to demonstrate how software design patterns and architectural styles can be utilized to reduce state spaces, (3) to provide a rare case study for verifying the safety and progress properties of a platform specific model.