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This work addresses the application of discrete event dynamic systems (DEDS) for autonomous sensing and inspection as part of the reverse engineering process. A dynamic recursive context for DEDS is presented and its usage for managing a complex hybrid system which has continuous, discrete and symbolic aspects is illustrated. We suggest that the dynamic recursive context is aptly suited to controlling and observing the active inspection of machined parts using such a hybrid system.
Reverse engineering is the process of constructing an accurate representation from sensed data. It can be represented by a closed loop system that consists of four main modules:
This closed loop system is the framework we used to develop an integrated CAD/CAM/sensing system for inspection and reverse engineering. The process starts by constructing an initial CAD model using 2-d and 3-d vision, then the inspection module uses this model to drive a coordinate measuring machine (CMM). The results are used to increase the accuracy of the model. Additional sensing iterations could be made until the desired accuracy is obtained. Figure 15 shows this closed loop system.
Most research in reverse engineering ([10][9][14][13][12][21][24]) concentrates on the sensing and fitting techniques required. Hsieh[16] describes a system which does sculptured surface reconstruction with a CMM. The focus of the work is on path planning and surface fitting. If errors occur while gathering data, the system aborts and must be restarted. Van Thiel [35] describes an interactive CMM inspection system. The user is included as part of the control loop, and can abort inspections and call for explorations of particular features. Our work describes an approach that automatically gathers the sense data, processes it, and makes decisions based upon it for reverse engineering.
We use a recursive dynamic strategy for exploring machine parts. A discrete event dynamic system (DEDS) framework is designed for modeling and structuring the sensing and control problems. The dynamic recursive context for finite state machines (DRFSM) is a DEDS representation tailored to the recursive nature of the mechanical parts under consideration.
DRFSM is particularly useful for controlling the inspection module, and this has been an important aspect of our research.
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