A coordination model for agent behaviors using hierarchical finite state machine with inter-level concurrency

Abstract

The hierarchical concurrent finite state machine (HCFSM) model natively supports concurrency, hierarchical decomposition, and event handling, which are essential for robot task executions. Moreover, HCFSM is a user-friendly diagrammatic representation model. The operational semantics of this model is defined under the two fundamental assumptions: synchrony hypothesis and zero-time assumption. This simple and theoretic assumption is suitable for time critical tasks rather than high-level behavior coordination including some operational latency time by detecting events and determining behaviors. In this paper, we propose an extended model of the hierarchical finite state machine (HFSM) using inter-level concurrency (IC), called HFSM-IC, which is focused on the intuitive description with easy-to-use constructs. IC replaces the concurrency in HCFSM assuming synchrony hypothesis and zero-time assumption with the multi-thread concept and enables each threaded HFSM to have its own iteration cycle as constant as resources are available.