Abstract A reverse engineering approach to generate a vir- tual plant model is proposed。 The model can be used for programmable logical controller (PLC) simulation。 The virtu- al plant model for the PLC simulation consists of virtual device models and must interact with the input and output signals of a PLC。 The behavior of a virtual device model should be the same as that of real device。 Conventionally, the discrete event system specifications (DEVS) formalism has been used to represent the behavior of a virtual device model。 Modeling using DEVS formalism, however, requires in-depth knowledge of the simulation area, as well as a sig- nificant amount of time and effort。 One of the key ideas of the proposed methodology is to provide a method to generate a virtual plant model using both log data (time-stamped signal history) and a PLC I/O signal table extracted from the existing production system。 The proposed reverse engineering ap- proach provides two major benefits: (1) significant reduction in the time and effort for the construction of a reliable virtual plant model of a current production system, which can be referenced for newly planned production systems, and (2) reduction in the stabilization time of a production system through PLC simulation。 The proposed approach was implemented and applied to an automated production line。85053

Keywords Virtual plant model 。 Virtual device model 。 DEVS 。 PLC simulation

S。 C。 Park : M。 Ko

Department of Industrial Engineering, Ajou University, San 5, Woncheon-dong, Yeongtong-gu, Suwon, South Korea

M。 Chang (*)

Department of Mechanical Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-701, South Korea e-mail: m。chang@solutionix。com

1

Introduction

In the manufacturing industry, there are various concepts and solutions used to reduce the time and costs of product devel- opment [1]。 In the “production ramp-up” trend in the automo- tive industry, a general paradigm shift from cost to time management can be found [2]。 Recently, in order to respond to demands including high productivity and production flex- ibility, the use of the concept of virtual commissioning (VC) has been widely accepted [3–5]。 In the past, VC was applied to small-size (cell) manufacturing system。 However, due to the recent development in computer technology, it is possible to apply VC technology (VCT) to a large-scale manufacturing system (lines and factories)。 As a part of this shift, offline programming for robots and verification of control programs [6–8] along with virtual device models have emerged in various industries。

Generally, a modern production line is a highly integrated system composed of automated workstations such as robots, fixtures, conveyors, and so on。 These are usually controlled by programmable logical controller (PLC) programs for the shop flow。 However, since conventional simulation languages, in- cluding ARENA® and AutoMod®, roughly describe the con- trol logic with independent entity flows between processes, their simulation models are not suitable for utilization in detailed design or for implementation purposes。 To success- fully achieve the implementation of the production line at the control level (sensors and actuators), PLC simulation has been widely accepted both in industry and in academia。 PLC sim- ulation for VC is considered to be an essential tool in the design and analysis of complex control systems that cannot be easily described by analytical or mathematical models。 It is useful for analyzing the control logic in various ways and recognizes hidden errors more intuitively。

Figure 1 shows the procedure for running the PLC simula- tion for the production line。 There are two major design activ- ities: mechanical design and electrical design。 The mechanical

Fig。 1 Virtual commissioning for a manufacturing system (PLC simulation)