A Petri net characterization of a high speed placement machine

A high-speed placement machine for populating printed circuit boards with surface-mounted components is discussed. The operation of these machines requires the user to specify the setup of the workcell and the interrelated sequence of pick-and-place operations. These are complex process-control decisions which, unaided, require extensive engineering overhead. Their effective specification requires a thorough understanding of the machine´s functional operations and also its control logic. Petri nets are used to provide a general framework to develop the characterization of this machine. It is shown that Petri nets provide a sufficiently flexible and yet formal framework in which to describe the concurrency, synchronization, and control of the operations which affect the throughput rate of the workcell. Thus an emulator can be derived and easily updated by coupling the Petri net representation with the MEGAS (Multiple Event Graph Analysis and Simulation) software package and the functional approximations used to model the characteristics of the motors and position servomechanisms.<>