INTERACTIVE COMPUTER AIDED LEARNING COURSEWARE FOR ENGINEERING MECHANICS M.A. McCarthy, K.M. Pearse, J. Bourke
Abstract: CAL courseware for Engineering Statics, Engineering Dynamics and Mechanical Vibrations has been developed with the aid of high-level programming tools. The programs are designed not to be standalone teaching resources, replacing functions that lecturers and textbooks do well, but to address the particular problem of providing interactive help in an environment of high student/staff ratios. Their main function is to interactively solve problems with the student, but additionally, various means are used to reinforce the theory presented in lectures. The aim is to integrate tightly with the other elements of the course, and not add to the burden on the student by introducing new material. Keywords: computer-based learning, computer-aided learning, teaching, engineering, mechanics, statics, dynamics, vibrations, trusses, Visual Basic, Toolbook.
1. Introduction In this paper, we describe our experiences with the development of CAL courseware for third-level Engineering Mechanics. The specific topics covered are Statics, Dynamics and Vibrations, and the tools used are Microsoft Visual Basic, Asymetrix Multimedia Toolbook and the C programming language. The projects arose out of specific perceived problems with the methods of teaching these subjects. The traditional approach has provided three sources of information: lectures, tutorials and a textbook. Within the time constraints that students face, it is important that all sources integrate and reinforce each other. Lectures provide focus thereby saving valuable time, textbooks provide reinforcement and fill in gaps, while tutorials should provide interactive help. In general, the delivery of tutorials presents the most difficulties, particularly with student numbers continually rising. The nature of these subjects requires the theory to be applied to concrete problems before it is fully understood. Sample problems are covered in lectures and texts, but it is only by tackling problems themselves that students learn, so a large number of problems are assigned for self-study. The ideal use of tutorials in such subjects would be to provide timely help to students who have made serious attempts at the problems, but have become stuck. A number of factors make this hard to achieve. Typically only a small percentage of students will have made serious attempts and many are there only to copy down solutions. Providing solutions only encourages this passive approach. Nowadays even "small" tutorial groups can be quite large, so it is difficult to find a level that will benefit everyone, and in the time allotted only a small number of problems can be covered in an interactive fashion. The level of skill required of the tutor for such interactive group teaching is also quite high.
An approach that has recently been tried is not to address the class as a group, but for the lecturer and teaching assistants to circulate around and answer queries from individuals or small groups. This has the advantage of putting the onus back onto students to solve problems for themselves. This has received positive feedback, but with the major complaint that not enough time could be spent with each student. Ultimately the tutorial problem is one of resources. It is simply not possible with present staff/student ratios to provide timely help to all students. The CAL programs described here, have been designed to address this specific problem. We did not seek to replace the lecture or textbook, which we feel are performing their functions well. Indeed for study of large quantities of theory, the printed page is still superior in terms of ergonomics and availability, compared to the computer. Rather we sought to embellish the tutorial system by providing an additional source of help in solving assigned problems. The advantages include constant availability, and the provision of help when the student is ready to receive it. The novelty of using a computerised system should also encourage students to make a start on the problems and improve the overall standard coming into tutorials. Aware of the time constraints facing students, it was desired that any theory provided served to reinforce rather than add to the information elsewhere. 2. Methods The work was not funded, so we used available resources, which were Microsoft Visual Basic 3.0 Professional Edition, Asymetrix Multimedia Toolbook Version 1.53 for Windows, and Borland's Turbo C for DOS. The programmers were final year engineering students who undertook the work as part of their final year project work. The students learned considerable programming skills and greatly improved their understanding of the subject matter, while the advantages to the lecturer were obviously low cost, and the fact that the students were semi-experts having already taken the subjects. From the start, it was intended that when a product of sufficient quality was created, it would be placed on the university network, so that it would be accessible from every IBM compatible PC on campus. Since the range of PC available is wide, from the occasional 386 to the now common Pentium, an early decision was made to design for the most basic machine. Thus the use of sound for example was deferred. Apart from this, the programs were allowed to develop independently, with each programmer generating their own ideas. This has enabled us to quickly build up expertise. We expect to standardise more in the near future. So far, over two years, programs have been written on Statics and Dynamics in Visual Basic, on Vibrations in Toolbook and on Trusses in C. 3. Statics and Dynamics Programs in Visual Basic Both the Statics and Dynamics programs are now in their second versions and have recently been placed on the university network. All problems covered are from the textbook [4] used in the course, which is taught to first year engineering students. Figs. 1 and 2 show the opening screens for both programs. The Dynamics program uses standard pull-down Windows menus, while the Statics program uses a hierarchical system of button menus. Either is probably acceptable given the few options available, but the pull-down menus are more standard and lead to less layers. Some of the more significant features of the programs are as follows:
Fig. 1: Opening screen of Statics Program
Fig. 2: Opening screen of Dynamics Program Backtrack and Show Question: Both programs allow the user to backtrack to previous screens, and to view the question at any time. The backtracking feature allows viewing of progress to date, which user surveys indicated was essential. Having the question statement available at all times, eliminates any requirement for the student to have the textbook available. Calculator: To further reduce the materials a student needs to have at hand, the standard Microsoft Windows Calculator is available at all times (Fig. 3). This was implemented by means of the VB Shell Function and the AppActivate command. The Shell Function allows the activation of any windows application from within an application, while AppActivate allows the focus to be shifted to any currently loaded application. To avoid multiple openings of the
Fig. 3 Progression of a problem in the Dynamics program, illustrating the provision of Background Theory and the Windows Calculator, with ability to paste results.
Calculator, AppActivate is called first. If an error is returned (because the Calculator is not currently loaded) then the Shell Function is called, otherwise it is not. To improve convenience further, Copy/Paste options were implemented in one of the programs which allows pasting of the calculator result into a question box in the program. Automatic Resizing: An important issue for placing the software on the network is that it run on all screen resolutions. One of the Version 1 programs was developed on an 800× 600 screen and of course partly disappeared off the side of 640× 480 screens. A program developed on 640× 480 will work on higher resolutions, but is not optimal. In the second versions, two quite different but equally effective solutions were devised. In the first solution, instead of the usual practice of drawing screen elements (e.g. buttons etc.) on screen, their dimensions were all defined in code as ratios of the overall screen height and width. Hence when the program is run, the page fills the screen no matter what the resolution, and controls and images resize accordingly. To improve display speed, all controls were made invisible, resized and then made visible again. The second solution made use of third party software, VSVBX 4.0, the Videosoft Custom Control Library. The "elastic control" from this library is a "container", the properties of which can be set, such that it automatically resizes its elastic child controls proportionally. Some problems existed with child controls set to invisible on loading of the form, which were not resized automatically, and so were incorrectly placed when they later became visible. These were solved however by workarounds and the method worked equally satisfactorily. Figs 4 and 5 illustrate the appearance of the software at high and low resolutions respectively. Interaction and Context Sensitive Help: The programs attempt to interact with the student in the same way as a tutor in the classroom, i.e., the problem is broken into manageable steps and the student is prompted for what to do next. Input is by means of checkboxes, and symbolic or numeric text. Context-Sensitive help is implemented through message boxes. For example, Figs 4 and 5 refer to the vital concept of Free Body Diagrams (FBDs). Fig. 4 addresses the problem of what part of the structure to isolate for the FBD, which students often have difficulty with. The question has asked for the tension in the cable attached at B and the reaction force at the hinge O, and the student must pick one of the numbered parts of the structure. If the F1 key is pressed a hint is provided, i.e. since only external forces go on a FBD, and can subsequently be solved for, the body must be chosen such that the desired forces are external to it. The correct body to use is the boom OA (part #3 in the figure). Fig. 5 deals with what forces should be shown on the FBD. Feedback for wrong answers is shown here. Fig. 6 shows numeric and symbolic input by means of textboxes (partially filled in). Symbolic input must allow for mixed-case input, while numeric input must allow for round-off, and so accept answers within a certain percentage of the target correct answer. Subject Help using Winhelp: Both programs implemented general subject help using the familiar Microsoft Windows Winhelp facility, which is only possible with the Professional Edition of Visual Basic 3.0. The first feature of the help system, illustrated in Fig. 7, is the on-line availability of the lecturer's notes. This helps to provide reinforcement of the lecture material and may even subtly raise its credibility by being available from a second source. Other features include Definitions, a Nomenclature section and a "How to.." section which covers topics like how to find the resultant of a number of forces. All material is based on the notes and text and so integrates well with the rest of the course. Help on using the program itself is also available. The Winhelp facility is powerful, easy to use, and is familiar to a wide
audience. Indeed it has been suggested [1] as an alternative in its own right for development of CAL software.
Fig. 4 Example of interaction with context-sensitive help. The appearance on high resolution screens is also illustrated here.
Fig. 5 Further example of interaction with feedback for wrong answers. The appearance on low resolution screens is also illustrated here.
Fig. 6 Interaction with numerical and symbolic input
Fig. 7 Subject Help using Winhelp Background Theory: A further source of help in the Dynamics program is the provision of Background Theory (directly from lecture notes) for each question, illustrated in Fig. 3. This may be a particularly effective vehicle for reinforcement, as within a certain class of questions, the same pieces of essential information are repeatedly presented. It helps very much to tie the theory to the problem solving process. Other Features: A very crude effort at matching user capabilities is the setting of three different levels in the Dynamics program. Presently this simply controls the amount of background theory that is presented with each question. User surveys after the first versions showed a strong desire to be able to obtain printouts, which further illustrates the preference for the printed page for study purposes. Standard Windows print facilities were thus implemented. The Dynamics program will give the correct answer if three wrong answers are input. On reflection this is a very debatable feature. In the overall context of the course, it is probably better if students bring problems they cannot surmount to the tutorials. 4. Vibrations Program in Multimedia Toolbook The Vibrations program is in its first version and is not yet as well developed as the above programs, so we only deal briefly with it here. The problems covered are from the primary text [5] and three supplementary texts [3,6,7], and the course is delivered to third year aeronautical engineering students. Many of the features in the Statics and Dynamics programs are also implemented here. The lecturer's notes are available on-line as is the Windows Calculator. Navigation tools for backtracking and showing the Question are present. Resizing has not been addressed as yet, so the current program displays properly only on high resolution screens. In general, Toolbook results in an attractive interface. The availability of widgets as illustrated by the Review Question function and the Show Free Body Diagram option in Fig. 8 allow more elaborate navigation control, while additional means of user interaction
Fig. 8 Sample screens from Vibrations program using Toolbook such as the use of scroll boxes (Fig. 8) are easily implemented. Feedback from the programmers indicates that it is easier to get started with Visual Basic than with Toolbook, but after the initial learning period, progress with Toolbook is quite rapid. 5. Incorporation of Equations One difficulty we encountered with Visual Basic and Toolbook was the incorporation of complex equations, which is clearly a necessity for presenting these subjects. With Visual Basic, we were able to paste in equations created by the Equation Editor in Microsoft Word for Windows, but very often they did not appear as desired, with the positioning being incorrect, or elements such as dots (representing differentiation) disappearing. In Toolbook, the creation of equations involved the tortuous process of positioning superscripts manually on screen - it is
highly unlikely that an automated resizing method will be found which preserves the correct positioning of these equations. These problems may be due to our lack of knowledge, but the availability of a tool like the Equation Editor within these products, would be very useful. 6. Structural Truss Program in C The Truss program is different from the above programs in that it is intended to be able to solve problems which are not pre-defined. The program should be able to accept input of any two-dimensional, statically determinate truss, and interactively guide the user through the solution by the Method of Joints. The purpose is to teach this method and the idea is not new [2]. It is our intention to identify other areas of Mechanics in which problems which are not pre-defined could be solved by a computer. This type of problem has a requirement to create diagrams "on the fly". Since Visual Basic's drawing capabilities are quite limited, we decided to use the C programming language, for which advanced graphics libraries are available. Fig. 9 illustrates output from the program. Joint co-ordinates, member connectivities, constraints and forces are input, and the program draws the truss. Analysis is done in the same way as it would be by hand. The user determines the joint to be analysed, and the program draws a Free Body Diagram of the joint. The user is then asked to solve the equilibrium equations. Feedback concerning correct signs for compressive and tensile stresses (the most common source of error) is provided. The current program is rudimentary, in that the general standard of the graphics and user interface are poor. This reflects a steep learning curve and generally longer development time for C, compared to Visual Basic and Toolbook.
Fig. 9 Sample screen from Truss program 7. Evaluation A number of limited surveys with small student groups have been carried out for the Statics and Dynamics programs. A more extensive survey will be possible now that the software has been placed on the network. In general the feedback has been positive with close to 100% indicating they would use the programs as supplements to standard tutorials, though only 30% would use them as alternatives. Some of the advantages listed related to constant availability, being able to work at their own pace, and being able to obtain help without the trauma of
asking questions in tutorials. Disadvantages included the lack of possibility for discussion, and the assumption of a certain level of knowledge. Suggestions for improvements include animation, sound, greater interactivity and greater feedback for wrong answers. 8. Conclusions In this paper, courseware for Engineering Mechanics has been described. The courseware is intended to integrate with, rather than replace, existing teaching methods, and efforts have been made to provide reinforcement of lecture material, wherever possible. These programs should lead to better use of tutorial time, and an improved level of interactive help available to the student, which is seen as the primary deficiency in present teaching methods. Ultimately, it is hoped this will lead to improved ability on the part of students to apply complex theory to concrete problems. Tools such as Visual Basic and Toolbook make the programming aspect of creating courseware relatively easy as is demonstrated by the programs presented here. Developing for Microsoft Windows ensures a professional appearance and a wide audience. However improved facilities for drawing and incorporating equations would be desirable. Our aims for the future include increased interactivity, extension of the idea of addressing students at different levels, and use of animation and sound.
References [1]
Davison, L.R., Poritt, N, Whitlow, R., "Using Winhelp for CAL in Engineering", Proceedings of Conference on Computer Aided Learning in Engineering, University of Sheffield, 5-7 September, 1994.
[2]
Hommel, G., "Courseware for the Analysis of Plane Trusses", Proceedings of the International Conference on Computer Aided Learning and Instruction in Science and Engineering, EPFL, Lausanne, Switzerland, 9-11 September, 1991.
[3]
Inman, D., "Engineering Vibration", Prentice Hall, 1994.
[4]
Meriam, J.L., Kraige, L.G., "Engineering Mechanics, Volumes 1 and 2", 3rd Edition, John Wiley & Sons Inc., 1993
[5]
Rao, S.S., "Mechanical Vibrations", 2nd Edition, Addison-Wesley, 1990.
[6]
Scanlan, R.H., Rosenbaum, R., "Introduction to the Study of Aircraft Vibration and Flutter", Dover Publications Inc., 1968.
[7]
Thomson, W.T., "Theory of Vibrations with Applications", 4th Edition. Prentice Hall, 1993.
Michael A. McCarthy, Kieran M. Pearse, Jonathan Bourke Department of Mechanical and Aeronautical Engineering University of Limerick Limerick Ireland
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