Petri net-based VR model interactive behaviour specification and control for maintaining training

Virtual reality (VR)-based maintenance training allows the trainee to practice disassembly operations for a maintenance task in a three-dimensional (3D), interactive digital world. To support virtual training, the user interactive behaviour that describes how the trainee interacts with objects in the virtual training environment must be programmed into the VR model. Interactive behaviour programming, however, is usually extensive and complicated, especially when accidental or unexpected events are to be incorporated. In this paper a Petri net (PN)-based approach is proposed to support VR model behaviour programming. The interactive behaviours for the trainee to disassemble a part in the virtual environment are represented by a PN, in which place nodes are used to represent different disassembly states and transition nodes define rules to move a token between places. The PN controls the VR simulation by requiring part disassembly status from the VR model to fire transitions and sending control data to the VR model to modify its behaviour nodes. Several case studies are presented to illustrate how the intuitive, graph-based process description and control language offered by this PN approach to facilitate interactive behaviour programming for VR-based maintenance training.