Online frequency domain system identification based on a virtualinstrument

System identification is an inherently iterative process. Yet, limited attempts have been made so far to implement the whole identification loop in a single device. This paper discusses the difficulties of the task and presents a solution based on a Matlab toolbox and a set of virtual instruments. During the identification session, the obtained models may call for refinement or validation by new experiments. Using this integrated software-hardware tool, these subsequent experiments can be accomplished online with the identification procedure. As a demonstration, the modeling of a hairdryer is described. The universal applicability of this solution is believed to be guaranteed by the modular architecture of virtual instrumentation and the general definition of the software interface developed. The interface allows combining Matlab-based identification packages with virtual instruments or pure hardware interfaced to Matlab     

Complicated procedures made easy [GUI]

The authors explain how to implement a graphical user interface and automatic procedures for easier identification and modeling.     

How to test graphical user interfaces

An approach for automatically testing GUIs in the MATLAB environment has been proposed. We developed a software tool that tests GUIs by simulating the user through an action recorder. We proposed a heuristic test procedure: providing random input to GUI, but guiding the randomness with predefined weights assigned to the user controls. The weights change during the testing process, as the controls are activated. The errors are collected for later investigation.     

Identification of a furnace from quasi-periodic measurements

Controllers of industrial furnaces operate differently in different temperature ranges. The controller has different parameter sets for each of these ranges. The operation of controllers is switched according to the temperature. It is desirable to change the parameters continuously following the temperature. The continuous change of parameters instead of mode switching may decrease the switching transients and lead to more accurate temperature control. A furnace identification scheme is investigated in this paper. Measurement problems and possible corrections that result in more accurate models after processing the collected data are shown. A possible "interpolation" technique of frequency-domain models is also shown here.     

Bias of mean value and mean square value measurements based onquantized data

This paper investigates the imperfect fulfilment of the validity conditions of the noise model quantization. The general expressions of the deviations of the moments from Sheppard's corrections are derived. Approximate upper and lower bounds of the bias are given for the measurement of first- and second-order moments of sinusoidal, uniformly distributed, and Gaussian signals. It is shown that because of the uncontrollable mean value at the input of the ADC (offset, drift), the worst-case values have to be investigated; it is illustrated how a simple-form envelope function of the errors can be used as an upper bound. Since the worst-case relative positions of the signal and the quantization characteristics are taken into account, the results are valid for both midtread and midrise quantizers, while in the literature results are given for a selected quantizer type only     

Regulating self-organized collaborative learning: the importance of homogeneous problem perception,immediacy and intensity of strategy use

Very often, university students deliberately form self-organized study groups, e.g. to study collaboratively for an upcoming exam. Yet, very little is known about what regulation problems such self-organized study groups encounter during their learning process and how they try to cope with these problems. Therefore, this study investigates how completely self-organized groups (i.e., non-guided groups outside the classroom that form without external impulse) regulate their collaborative learning process when faced with different kinds of regulation problems. More specifically, we tested the hypotheses that members of self-organized study groups are more satisfied with their group learning experience (a) the more homogeneous their problem perceptions are within their group, (b) the more they apply immediate (rather than non-immediate) strategies to remedy their regulation problems, and (c) the more frequently they apply regulation strategies. In a longitudinal study, N?=?122 students, voluntarily studying for their exams in N?=?52 groups, were asked to indicate the types of problems they experienced, the types of strategies they used to tackle those problems, and their satisfaction with their group learning experience after each of their self-organized study meetings. Hierarchical linear modeling confirmed all hypotheses. Qualitative analysis of two selected groups’ self-reported situational data provided additional insights about the mechanisms that may have contributed to the results. Our study provides important directions for future research, including the recommendation to identify the processes by which groups (a) can reach homogeneity of problem perceptions and (b) coordinate the choice of appropriate strategies within the group.

     

Comments, with reply, on `Effect of various dither forms oquantization errors of ideal A/D converters' by M.F. Wagdy

In the above-titled paper (see ibid., vol.38, p.850-5, Aug. 1989), the effect of dithering on correlation (covariance) between the signal and the quantization error and on the spectrum of quantization errors was addressed. The commenter shows that for the evaluation of the correlation (or covariance) more effective methods exist, and the covariance between the signal and the quantization error can be easily made equal to zero with appropriate dithering. It is also pointed out that the mean value of the signal must be taken into account. Some misunderstandable statements on the error spectrum are stated precisely. The author replies that the commenter misunderstood the original paper and further amplifies his work in support of this assertion