The Discrete Event Control of Robotic Assembly Tasks

A new approach to process modeling, task synthesis, and motion control for robotic assembly is presented. Assembly is modeled as a discrete event dynamic system using Petri nets, incorporating both discrete and continuous aspects of the process. The discrete event modelling facilitates a new, task-level approach to the control of robotic assembly. To accomplish a desired trajectory 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. Experimental results are given for a dual peg-in-the-hole example. The experimental results not only demonstrate highly successful insertion along the optimal trajectory, but also demonstrate the ability to detect, recognize and recover from errors and unwanted situations.