Hybrid State Machines with Timed Synchronization for Multi-Robot System Specification

In multi-robot systems, the need for precise modeling or specification of agent behaviors arises due to the high complexity of the robot agent interactions and the dynamics of the environment. Since the behavior of agents usually can be understood as driven by external events and internal states, it is obvious to model multiagent systems by state transition diagrams. The corresponding formalisms come equipped with a formal semantics which is advantageous. In this paper, a combination of UML statecharts and hybrid automata is proposed, allowing formal system specification on different levels on abstraction on the one hand, and expressing real-time system behavior with continuous variables on the other hand. One important aspect of multi-robot systems is the need of coordination and hence synchronization of behavior. For both, statecharts and hybrid automata, it is assumed that synchronization takes zero time. This is sometimes unrealistic. Therefore, a new notation and implementation of synchronization is proposed here, which overcomes this problem. The proposed method is illustrated with a case study from the robotic soccer domain