Petri net modelling for robotic assembly and trajectory planning

A new approach to process modelling, task synthesis, motion control and trajectory planning for robotic assembly is presented. Assembly is modelled as a discrete event dynamic system using Petri nets, incorporating both discrete and continuous aspects of the process. A process monitor based on recognizing contact state transitions is presented. A discrete event controller is developed. The controller issues velocity commands that direct the system toward the next desired contact state, while maintaining currently desired contacts and avoiding unwanted transitions. A novel means of trajectory planning which incorporates the system´s ability to both monitor and control the process is given. Experimental results are given for a dual peg-in-the-hole example. The experimental results not only demonstrate highly successful insertion along the desired trajectory, but also demonstrate the ability to detect, recognize, and recover from errors and unwanted situations