Minsuk Ko

A concurrent design methodology of a production system for virtual commissioning

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.

Fixture modelling for an automotive assembly line

This paper proposes an efficient fixture modelling procedure for automotive body assembly lines. A fixture model consists of two sub-models; a geometric model and a kinetic model that should be remodelled frequently whenever design changes occur. We develop an algorithm extracting the kinetic model from the geometric model of a fixture to reduce the fixture modelling time and effort. Although the geometric models of fixtures used in automotive assembly lines vary, most follow the same kinetic mechanism, the so-called slider-crank mechanism; this is a four-axis system of three revolute and one prismatic joint. The prismatic axis of a fixture represents a pneumatic actuator involving a piston and a cylinder. It is very important to identify the prismatic axis from a given geometric model to extract the kinetic model of a fixture. We use the concept of the ‘moment of inertia’, which is a measure of an objects resistance to changes in its rotation rate, to identify the prismatic axis. Since the exact computation of the moment of inertia for an arbitrary solid model requires complicated computations, we introduce an approximating method for the moment of inertia. The proposed procedure has been implemented and tested with various examples.

New modelling formalism for control programs of flexible manufacturing systems

Proposed in this paper is a modelling formalism, called the FMS control model, which is able to provide a detailed guideline for the implementation of the FMS control program (PLC program). Although, there are numerous simulation models for FMSs describing the system dynamics at the level of discrete event simulation, they cannot be fully utilised for the generation of a real control program involving sensors and actuators. Due to this, PLC programs for FMSs are usually done by the repetitive method of code writing, testing, and debugging until the control objectives are achieved. This is an error-prone and time-consuming task. The proposed FMS control model is described at the level of sensors and actuators. It can support the PLC program generation from the model. Since the FMS control model has been developed by expanding the DEVS formalism, it has a well-defined formalism. The proposed methodology has been implemented and test runs were made.

Control level simulation of an automatic storage and retrieval system in the automotive industry

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.

Template-based modeling methodology of a virtual plant for virtual commissioning:

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.

Machine control level simulation of an as/rs in the automotive industry

This paper illustrates a case study of a PLC (Programmable Logical Controller) logic simulation in the car manufacturing industry. The case study is developed in order to simulate and verify the PLC control program for an automobile panel AS/RS. Because of increasing demand, the complexity of the supply system is rising in this industry. To cope with this problem, companies use AS (automated storage) and RS (retrieval system) systems, despite inherent logical complexities. Industrial automated processes use PLC code to control the AS/RS; however, control information and the control code (PLC code) are difficult to understand. Therefore, this paper suggests a PLC simulation environment, using 3D models and PLC code, which consists of real automobile manufacturing data. Data used in this simulation is based on 3D and logical models, using actual size and PLC signals, respectively. The environment resembles a real factory; users can verify and test the PLC code using the simulation prior to implementation of AS/RS. The developed simulation environment can be used to run AS/RS systems to reduce time and cost.

A Method for Generating a Plant Model Based on Log Data for Control Level Simulation

Presented in the paper is a log data based modeling method for effective construction of a virtual plant model which can be used for the virtual PLC (Programmable Logic Controller) simulation. For the PLC simulation, the corresponding virtual plant, consisting of virtual devices, is required to interact with the input and output symbols of a PLC. In other words, the behavior of a virtual device should be the same as that of the real device. Conventionally, the DEVS (Discrete Event Systems Specifications) formalism has been used to represent the behavior a virtual device. The modeling using DEVS formalism, however, requires in-depth knowledge in the simulation area, as well as the significant amount of time and efforts. One of the key ideas of the proposed method is to generate a plant model based on the log data obtained from the production system. The proposed method is very intuitive, and it can be used to generate the full behavior model of a virtual device. The proposed approach was applied to an AGV (Automated Guided Vehicle).

A Proposal of Scenario Generation Process for Small Scale Engagement

Computer-based modeling and simulation (M&S) techniques have become an essential component in the development of new weapons systems. M&S techniques provide a means to simulate military training, strategies, military doctrines, and weapons acquisition processes. This paper proposes a small scale engagement scenario generation method. This work also includes a process for scenario generation and visualization. The proposed scenario generation methodology employs the Timed-FSA (finite state automata) and DFS (depth first search) algorithms. The proposed scenario generation method is verified using a one-on-one combat engagement scenario between two submarines. In addition, we suggest a scenario generation process including whole scenario generation and scenario visualization.

Seed Point Detection of Multiple Cancers Based on Empirical Domain Knowledge and K-means in Ultrasound Breast Image

The objective of this paper is to remove noises of image based on the heuristic noises filter and to automatically detect seed points of tumor region by using K-MEANS in breast ultrasound. The proposed method is to use 4 different kinds of process. First process is the pixel value which indicates the light and shade of image is acquired as matrix type. Second process is an image preprocessing phase that is aimed to maximize a contrast of image and to prevent a leak of personal information. The next process is the heuristic noise filter which is based on the opinion of medical specialist and it is applied to remove noises. The last process is to detect a seed point automatically by applying K-MEANS algorithm. As a result, the noise is effectively eliminated in all images and an automated detection is possible by determining seed points on each tumor.

A Study of PLC Simulation for Transport System in Virtual Environment

Received 10 February 2012; received in revised form 22 June 2012; accepted 27 June 2012ABSTRACTThis paper proposed a control simulation method for design and verification of the transportsystem in an automobile assembly line based on digital manufacturing system. The design ofthe transport system involves two major activities: mechanical design (device specification) andelectrical design (device behavior and system control). Conventionally, the simulation and emu-lation system of the transport system focuses on the abstract level, which mainly deals withdesign verification, alternative comparison, and system diagnosis. Although it can provide over-all system visibility in monitoring how well it works in the process and view, its simulationmodels are not sufficiently realistic to be used for a detailed design or for implementation pur-poses. In this paper, a digital simulation model for a transport system in an automotive assem-bly line is constructed by adapting a digital manufacturing methodology. We use the concept ofthe “Virtual Probe”, which transport a carrier instead of the belt of the conveyor. In conclusion,the proposed method is valuable in the process of test run in the shop floor. This method wouldreduce the time and effort for validating the manufacturing system and improve the productiv-ity and integrity of the control program.Key words: Control simulation, Digital environment, Transport system, Virtual manufacturing