In this article, a concurrent design procedure of a production system is presented, which supports the virtual commissioning between a real controller and a virtual plant consisting of virtual devices. To achieve the concurrency, we split a virtual device model into two parts, a physical device model (a geometric model with kinematics for the motion programming of tasks) and a logical device model (a behavioral model to interact with a real controller). The whole design procedure consists of four major steps: (1) process design, (2) physical device modeling, (3) logical device modeling, and (4) system control modeling. First, the process design step identifies effective manufacturing processes and produces the sequence of operations. Once the sequence of operations is obtained at Step 1, then the other three steps can be performed concurrently without interfering each other. All the three concurrent steps start from the sequence of operations, and a detailed procedure for each of the step has been developed. The concurrent attribute of the proposed design procedure significantly contributes to the saving of the delays in time to market. The proposed design procedure has been implemented and tested for various examples.

This article presents a template-based modeling methodology for the effective construction of a virtual plant that can be used for the virtual commissioning of a programmable logic controller. For virtual commissioning, the corresponding virtual plant, consisting of virtual devices, is required to interact with the input and output symbols of a programmable logic controller. In other words, the behavior of a virtual device should be the same as that of the real device. Conventionally, discrete event systems specifications formalism has been used to represent the behavior of a virtual device. However, modeling using discrete event systems specifications formalism requires in-depth knowledge of simulation as well as significant amounts of time and effort. One of the key ideas of the proposed methodology is to provide a device template model representing the relations between the tasks of a device. The proposed template is very intuitive and can be used to generate a comprehensive behavior model of a virtual device. The proposed approach has been implemented and demonstrated for a robotic cell.

A manufacturing system consists of various manufacturing devices, and each device has a set of tasks which are triggered by specific commands. Traditionally, simulation has been considered as an essential technology for the evaluation and analysis of manufacturing systems. Although discrete event system specification formalism has been a popular modeling tool for manufacturing systems, it has limitations in describing situations such as sudden cancelation of tasks. Proposed in this article is an extended discrete event system specification formalism for the effective description of a smart factory which requires the intelligence to handle turbulences in real-time production. The extended discrete event system specification formalism incorporates the configuration space concept, which is well-known in classical mechanics. While the conventional discrete event system specification formalism uses only the logical states set to represent the device states, the proposed formalism employs the combination of two sets: a logical states set (sequential states set) and a physical states set (configuration space of the device). As a result, the extended formalism enables the effective description of nondeterministic tasks which may occur frequently in a smart factory.

Conventional simulators have focused on the abstract aspects of an automatic storage and retrieval system, which mainly deals with design verification, alternative comparison, and system diagnosis. Although such simulators can provide overall system visibility by monitoring how well the process works, the simulation models are not sufficiently realistic for detailed design and implementation purposes. To address this problem, we propose a method of control level simulation of an automatic storage and retrieval system in an automobile plant. The proposed method involves four major steps:(1) designing the process and layout for effective storage and retrieval; (2) abstract simulation of the automatic storage and retrieval system; (3) preparing the mechanical design to obtain three-dimensional kinematic models and the electrical design to produce a control program and a plant model; and (4) control level simulation of the automatic storage and retrieval system, including both manual mode and automode simulations via a human-machine interface. The major benefit of the proposed method is the reduction of the construction time and effort required to validate the programmable logic controller program of a real automatic storage and retrieval system, since potential errors can be detected and fixed before actual implementation.

Make-to-order wafer Fabrications (FABs) have to deal with two different types of lots: high priority and normal. Highpriority lots have shorter cycle times, tighter target due dates, and higher margins than normal lots. This article presents a dispatching rule for on-time delivery of high-priority lots with low tardiness for normal lots. The proposed dispatching rule uses the concept of reservation, which refers to the provisional allocation of capacity for high-priority lots. The reservation policy has been applied to ensure capacity for high-priority lots in real FABs. The reservations of highpriority lots may cause considerable tardiness of normal lots. To cope with the problem, the proposed dispatching rule considers tool utilization as well as the on-time delivery of high-priority lots. Also, we introduce the concept of reservation depth to control the influence level of the reservation. The proposed dispatching rule has been implemented and outperforms conventional dispatching rules and conventional reservation policy.