ABSTRACT

A integrated virtual learning system is being researched and developed to teach students about programmable logic controllers (PLCs). This system, called the Virtual PLC, incorporates intelligent tutoring system, simulation, and animation technologies. This article describes the development and evaluation of modules on PLC timer and counter instructions. These modules were first developed using an intelligent tutoring system (ITS) authoring tool and animation tools. After the concept was proved positively, a Web-based ITS was developed to incorporate both modules. The authoring tool-based ITS timer modules were evaluated with 90 undergraduate manufacturing engineering students in 2002. The Web-based ITS timer and counter modules were evaluated by 38 undergraduate students in 2003. In both cases, students made statistically significant learning gains as a result of taking the modules, and rated the modules positively in terms of ease of use and understanding, clear objectives, amount of interaction, ability to motivate, relevance, and pace.

I. INTRODUCTION

Modern automated manufacturing systems typically use programmable logic controllers (PLCs) to orchestrate and synchronize the process being automated. A PLC is a solid-state control system with a user-programmable memory, used to read input conditions and set output conditions to control a machine or process. Thousands of PLCs have been used for such applications as monitoring security, managing energy consumption, and controlling machines and automatic production lines. PLCs are said to be among the most ingenious devices ever invented to advance the field of manufacturing automation [1]. PLC sales are now about one billion dollars per year and there are more than thirty manufacturers [2]. The world market for programmable logic controllers will continue to grow as units become smaller, more functional, and more able to work in tough environments [3]. Clearly there is a great need for engineers with strong skills and knowledge in this area.

Although PLCs are often covered in undergraduate automation and control-related courses, many educational institutions lack resources to help students to become proficient PLC users due to high faculty-to-student ratios, limited access to labs, and limited equipment to support lab assignments. Needed are technologies that can help instructors to make the most of limited resources. Personal computers hold enormous promise in this regard because they are relatively inexpensive, widely available, and can be used to supplement or replace existing educational methods in a variety of ways.

Intelligent tutoring systems (ITSs), for example, are computer systems that provide individualized instruction, much like that of a human tutor. Although they cannot replace the experience of using actual equipment, they can often be used to teach preliminary information students need to know about equipment before using it, so that lab time can be spent more productively and efficiently. In addition, unlike human instructors, they can be available around the clock, wherever there is a computer. Although ITSs can be very time-consuming to develop, in recent years, there has been increasing interest in the development of authoring tools to make ITS technology more accessible [4]. Examples of such tools include RIDES [5], which can develop sophisticated equipment simulations, and XAIDA [6], which can be used to teach factual information about a subject (e.g., parts of a car, steps in a procedure) and theory of operation. The authors previously used such a tool to develop an intelligent tutoring system to teach students to operate a computer numerical control (CNC) machine [7]. Results indicated that most of the students who participated in this evaluation: (1) learned from the modules, (2) changed their perspectives on learning with computers, and (3) believed that the modules were easy to use, motivating, and relevant to their education.

Gaming approaches utilizing interactive multimedia and/or simulations have also been shown to be effective in improving teaching and learning of various subjects. These subjects include accounting [8], decision maiding skill acquisition [9], and engineering education [10, 11]. Perrone, et al. [12] presents a case study of converting a physical board game (Mr. Roger's Sustainable Neighborhood) into a medium that can be accessed via the World Wide Web. The result was very positive, preserving not only the usefulness of the board game but also increasing its accessibility. Siemer and Angelides [13] argue that gaming-simulation environments have become valuable tools for education and training. They note, however, that for these environments to be maximally pedagogically effective, they should include intelligent tutoring support. In other words, gaming systems should be integrated with intelligent tutoring systems.

The authors have recently undertaken a project to integrate these approaches into a prototype Web-based learning system called the Virtual PLC. The Virtual PLC is intended to be comprehensive in its treatment of PLC topics, motivational, and always available, thereby alleviating current problems arising from low availability of equipment and enabling students and engineers to learn independently. Table 1 lists the modules that have been developed thus far.