Integrated Virtual Learning System for Programmable Logic Controller*

Journal of Engineering Education, Apr 2004 by Hsieh, Sheng-Jen (Tony), Hsieh, Patricia Yee

After initial evaluations of the instructional effectiveness of XAIDA lessons proved successful (to be described in next section), we developed a Web-based ITS that duplicates some of XAIDA's student modeling and pedagogical strategies. The Web-based version of the ITS is written in Visual Basic and implemented using Microsoft's Internet Information System (US). The system includes three tiers-client, business logic, and database-and records facts about PLC instructions in a database in the form {instruction, attribute, value}. So for example, the fact that the Counter Up (CTU) instruction counts up by one from the accumulated value (AC) each time it counts would be stored in the database as {CTU, counts, up by one from AC every time it counts}.

Instructional algorithms and templates are used to present information from the fact table and to formulate practice questions and feedback. Student knowledge is modeled by marking individual facts as known or unknown based on practice question performance. In addition, a separate table is used to record misconceptions exhibited during the practice sessions. The misconception table has the same {instruction, attribute, value} structure as the fact table, but contains a student's misconceptions rather than facts. Thus, for example, if a student is asked how the CTU instruction counts and incorrectly replies that it counts down by one, the misconception {CTU, counts, down by one from AC every time it counts} is added to the misconception table. The misconception table is part of the student model and is used by the system in determining what to ask during practice. A misconception is removed if a student has the opportunity to exhibit it again but fails to do so.

Questions are generated by applying instructional algorithms and templates to the information in the database. Topics are selected based on the information in the student model. The system can ask three types of questions:

* Given an instruction and a characteristic, select the applicable value(s), e.g., What does CTU stand for?

* Given a characteristic and a value, select the applicable instruction(s), e.g., The instruction that stands for counter up is...

* True-false questions, e.g., True or false. CTU stands for Counter Up.

Note that in some cases, there may be more than one correct answer. Based on a student's responses to a practice question, the system marks the responses (blue check mark for correct answers, red "X" for incorrect answers, and red "O" for omitted correct answers), provides explanatory feedback, and updates the student model. When there are no more unknown facts and no more misconceptions, the system stops asking questions. Figure 3 shows a practice question that has been answered and evaluated using the Web-based ITS.

V. MODULE EVALUATION

Results from two rounds of evaluations are reported in this section. In the first round, only the module on timer instructions was evaluated, and XAIDA provided the ITS function. In the second round, the modules on timer and counter instructions were evaluated, and the Web-based ITS was used.