Hierarchical Petri Net Representation of Robot Systems

Abstract

The paper presents a holistic robot system specification methodology taking into account both the system structure and its activities. It is based on the concept of an embodied agent. Each agent is decomposed into cooperating subsystems. Previously subsystem activities were defined by a hierarchical finite state machine (HFSM). In that approach communication between subsystems was not specified explicitly. This paper utilises a Hierarchical Petri Net (HPN) with conditions as an alternative modelling tool. HPN can be obtained by transformation of the HFSM into HPN. The resulting HPN consists of consecutive layers: subsystem layer, behaviour layer and communication layer. The proposed methodology not only organizes in a systematic and holistic manner the development of the robot system, but also introduces a comprehensive description of concurrently acting subsystems. The HPN description can be utilised to automatically generate the robot controller code.