A Discrete Event Controller Using Petri Nets Applied to Robotic Assembly: The Desired Velocity Commands

This paper takes a new approach to robotic assembly, treating assembly as a discrete event system. A discrete event in assembly is defined as a change in contact state reflecting a change in geometric constraint. The discrete event modelling is accomplished with Petri nets. Using the Petri net modelling, the constraint equations for all the states of contact are combined into one compact matrix equation. In addition, a closed form solution for the desired velocity commands is derived. Desired velocity commands insure consistency with geometric constraints, while simultaneously directing the system toward its next desired discrete transition.