Activity cycle diagram (ACD), which is essentially a timed Petri net, is one of the oldest formal modeling tools for discrete-event systems, and a flexible manufacturing system (FMS) is a highly automated job shop that is used widely in mechanical and electronics industries. Previous FMS modeling studies have indicated that formal modeling of real-life (or industrial) FMSs with classical ACDs (or Petri nets) is almost impossible. This paper presents an incremental modeling procedure for building a formal simulation model of a real-life FMS with parameterized ACD (P-ACD) that was proposed recently. The incremental modeling procedure consists of job flow modeling, job routing modeling, dispatching rule modeling, and refixture operation modeling. In this paper, a P-ACD model of a real-life FMS was constructed and an FMS simulator was implemented from the proposed P-ACD model. A simulation experiment was conducted in order to demonstrate the usefulness of the FMS simulator.

A direct use of activity cycle diagram (ACD) model into a simulation execution has a limitation that it does not maximize the power of the widely adopted three-phase rule in the simulation execution of ACD models. This paper presents a key model specification for the simulation execution of the ACD model, named, activity transition table (ATT). The proposed ATT reduces the gap between the ACD (the flow of state change) and the three-phase rule (activity transition) and maximizes the modularity of the three-phase rule. The presented ATT model and ACD model can be implemented and executed with the help of the visual modeling and simulation toolkit.

In this paper, we propose an extension of classical finite state machine as it called a timer embedded finite state machine (TEFSM) with its formal modeling methods. In the proposed state-based approach, a discrete event system is modeled as a coupled TEFSM. Also presented is a systematic procedure and architecture of developing a simulation executor with a synchronization manager for the coupled TEFSM model. A TEFSM toolkit for modeling and simulation of the proposed TEFSM model has been implemented and a ping pong system was developed as an illustrative example.

In numerically controlled (NC) machining simulation, the Z-map is frequently used to represent the workpiece. Since the Z-map is usually represented by a set of Z-axis aligned vectors, the machining process can be simulated through updating it with the intersection points between the vectors and the tool swept surface. In our previous work (S.R. Maeng et al., 2003), we achieved a fast Z-map update method for linearly moving tools. On the other hand, typical NC simulation codes contain lots of circular tool movements especially for the free-form surface machining. This paper represents how to directly calculate the intersection points for the circularly moving tools. For fast computation, we express each of intersection points with a single-variable nonlinear function and calculate the candidate interval in which the unique intersection point exists. Then, we prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the nonlinear function within a given precision. Due to space limitations, we focus on the filleted-end mills, the most general case of the APT (automatically programmed tool) tools. Since other tools such as ball-end mills and flat-end mills can be regarded as the special cases of the filleted-end mills, our result can be applied to the circular motions of any APT tools. Combining it to our previous result on the linear motion, we can cover most of NC simulation codes. Finally, our implementation and its result show that the new numerical approach is more efficient and reliable, in comparison to the previous methods.

Triangular mesh is one of the most popular shape representations in computer graphics and the CAD/CAM/ CAE area. In this paper we present a memory and time efficient topology construction algorithm from triangle soup, which is a set of triangles without connectivity information. The proposed algorithm consists of the following steps: (1) vertex merging, (2) internal edge linking, (3) multi-disk vertex splitting, and (4) boundary gap stitching. Typical triangle soup comes in the form of an STL file, and topology construction work encounters non-manifold cases for various causes, which should be converted to 2-manifold models for many downstream processes such as rapid prototyping and tool path generation. The proposed algorithm uses a light-weight vertex-based data structure (adapted from a 'corner table' structure), and does not need to construct a full non-manifold topology information. The efficiency of the proposed algorithm is shown by empirical tests on practical examples.