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Session 3226

A Student Controlled Two-Degree of Freedom Vibration Laboratory S. D’Souza, N.W. Scott & B.J. Stone The University of Western Australia

Abstract student controlled, safe and may be done at any time. Lyons In recent years there has been a significant increase in the use [2] concluded that “a laboratory designed with this in mind of computers in teaching. At the same time there has been a would have the following benefits: corresponding reduction in laboratories undertaken by • The control and prevention of unsafe conditions could be students, especially where large classes are involved. With achieved through the application of safe limits by the increasing student/staff ratios the cost of running well staffed computer. The student would not be able to run the laboratories has become unacceptable. At the same time very experiment outside these limits. few universities reward staff for producing new laboratories. • Large groups could be avoided as students would have the All these factors have led to fewer laboratories. The need for choice to do the laboratory alone and at their own pace. hands-on laboratories is as great as ever, particularly to • The large task of scheduling laboratory classes would be illustrate that the real world does not behave as mathematical reduced or removed as students could do the laboratory at models predict it will. This paper describes a computer the time of their choice. controlled vibration laboratory that is inherently safe and does not need an instructor. The laboratory is controlled through • The real apparatus as opposed to a simulation could the computer which protects both it and the student. Results allow open ended investigation and improved physical are collected and analysed by the computer. Most importantly understanding of the topic.” the laboratory has been designed to behave in a different Lyons developed a single degree of freedom vibration manner from the theoretical models developed in lectures and laboratory to meet these requirements. That laboratory was students are expected to criticise their lecture models. Finally extended by Barrett-Leonard [3] to be a multi-degree of students may leave comments for fellow students so that the freedom laboratory. However it became apparent that there laboratory may slowly evolve in content. was a need for a purpose built two degree of freedom vibration laboratory that would illustrate major concepts. This paper describes the laboratory that was developed. 1 Background The current pressure on teaching resources often means that laboratory classes are removed from the curriculum or at least 2 Design of Rig replaced by virtual laboratories involving simulations. In When the vibration of systems is being taught most course 1994 Stone [1] describing some computer simulations stated, cover the theory for a mass/spring system with viscous “Now a warning, it is possible (inevitable?) that students will damping. This brings out the concepts of damped and believe that the real world behaves exactly the same as undamped natural frequency, transient decaying motion and for depicted by the animation programs. This is a dangerous steady state vibration resonance and vibration isolation. The outcome and it is strongly advised that real laboratories be lab developed by Lyons [2] was such a lab having the benefits used in parallel with the CAL package. We are in the process of computer control described above. of developing self-teach laboratories that have been deliberately designed to not behave as the theoretical models. It is hoped that this will make the students more critically When multi-degree of vibration is considered the important aware of the limits of modelling.” As resources for education concepts to be taught are, multiple natural frequencies, mode are reduced and promotion is rarely affected by any time spent shapes, damped and undamped absorbers etc. Barrett-Leonard on developing laboratories there is the danger that more [3] extended the lab of Lyons to cover multi-degree of freedom simulations will replace laboratories. However the need for vibration. There was a disadvantage with this extended lab in laboratories remains the same, that as it was an extension of the linear vibration rig of Lyons it too involved mainly translation and little rotation. • Students learn best when all their senses are involved. Laboratories use the most senses. • Isolation from the real world is dangerous for engineering It became apparent that an old torsional two-degree of freedom students. They need to know the limits of theory. rig was much my suitable for demonstrating the concepts of multiple natural frequencies, mode shapes and undamped • There is no substitute for hands-on experience of real absorbers. The large and visible low frequency vibration was engineering products. much appreciated by students. It was thus decided to re-design This paper describes the continuing development of a possible this lab to be computer controlled. compromise solution to the need for laboratories and the limitations of staff time. Thus the laboratory is essentially

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1998 ASEE Annual Conference Proceedings EN

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D'Souza, S., & Scott, N., & Stone, B. (1998, June), A Student Controlled Two Degree Of Freedom Vibration Laboratory Paper presented at 1998 Annual Conference, Seattle, Washington. 10.18260/1-2--7429