Question 5.5: Use the Petri net to model the testbed for gearbox assembly ...
Use the Petri net to model the testbed for gearbox assembly in Fig. 5.31;
the testbed was developed at the National Institute of Standards and Technology (NIST) to evaluate the grasping capabilities of end-effectors (Falco et al. 2015; Kootbally et al. 2016). Aseries of operations are to (1) open a gearbox kit, (2) move around parts, and (3) assemble them together as a functional gearbox. The testbed consisted of robots A and B, vision systems A and B, force sensors, trays and the assembling platform. Note that opening the gearbox kit and place parts on the platform are done manually. robot A was equipped with a force sensor to assemble parts; while robot B was equipped with a vision system only to move and hold a part (Bi et al. 2020).
Table 5.18 shows the possible events which can be classified into three basic types, i.e., (1) an event initialized by human, (2) an event performed by a robot and a vision, (3) an event performed by a robot, a vision, and a force sensor.
Figures 5.32, 5.33, and 5.34 show the Petri net examples of three event types, respectively.
The sub-Petri net models for different events can be selected and assembled as a testing plan. In executing the testing plan, the states of resources and transitions are tracked to evaluate the performance of the assembly system.
