Using hierarchical binary Petri nets to build robust mobile robot applications: RoboGraph

Most of the mobile robot control frameworks are based on a middleware layer with several independent modules that implement primitive actions and report events about their state. These modules are usually connected with different interprocess communication mechanisms. Here, we propose to use hierarchical interpreted binary Petri nets to coordinate the activity of these modules. Tasks are described using an interpreted Petri net editor and saved in a xml file. A dispatcher loads these files and executes the different Petri nets under user requests. A monitor that shows the state of all the running nets is very useful for debugging and tracing purposes. The whole system has been applied to a guide robot (vixiabot) that has been guiding users in a public event (XuventudeGalicia.net) for three days in April 2007 and is now extended to a multirobot surveillance application.