June 20, 2010
June 20, 2010
June 23, 2010
15.82.1 - 15.82.10
A Review of Programmable Logic Controllers in Control Systems Education
A Programmable Logic Controller (PLC) is a standard industrial control device that provides a simple, yet robust, method of controlling manufacturing and dynamic processes. As a result of their low cost, adaptability, and reliability, PLCs are by far the most common control mechanism used by manufacturing businesses of all sizes for environment control, food processing, motion control, and automated test equipment. Yet even though PLCs are heavily used by industry, their use in teaching control theory concepts is uncommon for mechanical engineering programs. Traditional control systems engineering courses focus on the theory and mathematics of continuous-based control systems and rarely involve the use of PLCs, which provide an excellent platform to teach feedback control. Only a few programs have included a speciﬁc focus on non-continuous (on/off) control commonly used in industrial environments. In addition, learning ladder logic, a programming language for PLCs, can be difﬁcult and seem unnecessary for those with a traditional programming background, such as C++. Recognizing the appropriate ways of how and when to use PLCs is a key factor in applying control theory effectively in an industrial or even a research environment
This paper reviews the literature devoted to control systems education. It shows how academia is using PLCs in education and how it can complement the traditional focus on continuous-based control. A key objective of this paper is to review the PLC use in mechanical engineering education, which traditionally takes place in a control systems engineering course. This paper will also address a proposal by the authors that implementing PLCs into a control systems course for mechanical engineering students can enable a natural integration of continuous and non-continuous control theory.
Engineering control problems can generally be categorized solely or as a combination of the following three ways: 14
1. Continuous Linear — these systems can be described by linear differential equations, and exact equations can be used to design controllers. 2. Continuous Non-linear — these systems can be described with differential equations that are non-linear, and the controllers can be designed with some effort. In some systems differential equations are not available, forcing reliance on other methods, such as heuristic rules. 3. Non-continuous — these systems have discrete states and are characterized with on/off transitions of inputs and outputs. Logical decisions are required to control the system.
Control Systems Engineering is traditionally seen as a “dry” course by students with a mechanical concentration. The popular textbooks on the subject 7,20,21 are meant for a more general engineering student audience, cover the theory that is typically associated with the subject, and
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