DEVELOPING A SYSTEMATIC APPROACH TO DESIGNING A DISCRETE EVENT CONTROL SYSTEM
The study reported in this thesis was aimed at laying a foundation for automating the design process of the discrete event control (DEC) system with the PLC (programmable logic controller) platform. The study had three objectives (in brief): (1) developing a model for technical specification of design requirements of DEC, (2) developing a systematic design process model for DEC, and (3) developing a framework for knowledge repository, in which the knowledge of systematic design of a DEC is stored. The research activity was carried out to achieve the three objectives. First, the current model of the technical specification of design requirements for a functional product called General Design Process Model (GDPM) was revised to the model for a DEC. Second, the general design process model for functional products, such as the open-ended synthesis from a customer’s voice of needs of a DEC to a technical specification of the need, decomposition of functions along with the control functions (both feedback and feedforward), and open-ended synthesis of devices along with their DECs, was combined with the specific design process model for DEC, such as generation of state equation, and generation of the software ladder logic diagram (or generic PLC code). Third, the type of knowledge to support each design step was identified and classified, and the structure of the knowledge was outlined. Last, a case study of designing a DEC for medical ventilator was conducted along with the simulation of the design to validate the efficacy of the design process model and knowledge repository. The research activities lead to the general conclusion that the objectives of this study can be achieved, suggesting that a computer system be feasibly built to conduct design of a DEC in future. The main contribution of the study lies in the field of design automation, including (1) the finding that the entire design process has two parts: open-ended part (first part) and close-ended part (second part), and (2) the demonstration of the feasibility of automating the design process for a DEC, which will have positive impact to designing a DEC more effectively and efficiently.
DEC, Design Process Model, Knowledge Repository Model
Master of Engineering (M.Eng.)