Abstract-The complexity of present day embedded systems (continuous processes controlled by digital processors), and the increased demands on their reliability motivate the need for monitoring and fault isolation capabilities in the embedded processors. This paper develops monitoring, prediction, and fault isolation methods for abrupt faults in complex dynamic systems. The transient behavior in response to those faults is analyzed in a qualitative framework using parsimonious topological system models. Predicted transient effects of hypothesized faults are captured in the form of signatures that specify future faulty behavior as higher order time-derivatives. The dynamic effects of faults are analyzed by a progressive monitoring scheme till transient analysis mechanisms have to be suspended in favor of steady state analysis. This methodology has been successfully applied to monitoring of the secondary sodium cooling loop of a fast breeder reactor.
This work investigates the efficacy of software simulations of electronic circuits laboratories to support beginning electrical engineering students. Experiment 1 was a formative evaluation of an Electronic Laboratory Simulator (ELS), as an optional add‐on to physical labs for 120 subjects at four universities. All subjects received the same treatment: their normal classes and physical labs, with optional use of simulated labs. Subjects took written tests specific to the lab's content, before and after using each simulated lab. Only subjects who took both pre‐ and post‐tests were included. Pre‐ and post‐test comparisons indicated significant improvement in both theory and lab knowledge when scores for all labs were combined, but inconsistent performance on individual labs. As the treatment included other learning opportunities in addition to simulated labs, the results were not attributed to the simulations, but provided initial indications and qualitative data on subjects' experiences. These helped to improve the labs and the implementation strategies. Experiment 2 used 40 college sophomores in a beginning electronic circuits lab. Physical lab subjects received seven physical labs. Combined lab subjects received a combination of seven simulated labs and two physical labs. The latter repeated two of the simulated labs to provide physical lab practice. Both treatments used the same assignments. Learner outcome measures were: (a) time required to complete a new criterion physical lab; (b) score on written lab and theory tests over all the labs; and (c) comments on the lab experience. The group that used combined simulated and physical labs performed significantly better on the written tests than the group using entirely physical labs. Both groups were equivalent in time to complete the criterion physical lab. Comments about the simulated labs were generally positive, and also provided specific suggestions for changes.
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