Dariusz Buchczik

Comparative study of acceleration transducers for biomedical applications

The results of comparative studies of the metrological parameters of acceleration transducers constructed in Institute of Electronics, Silesian University of Technology is presented in this article. The construction of the transducers is based on commercially available monolithic accelerometers and optimized for biomedical applications. The parameters determined during the tests are similar to the parameters of the monolithic accelerometers declared by their manufacturers. It proofs that both the mechanical and the electronic construction of the transducers are correct.

Evaluation of calibration results using the least median of squares method in the case of linear multivariate models

Robust estimation procedures make it possible to reduce the leverage of outliers on the measurement results. Application of the least median of squares (LMS) method to determine the calibration curves of measuring instruments involves the need to evaluate the obtained results. This paper proposes the method of estimating the variance of the LMS regression coefficients, which allows the evaluation of the quality of the set regression coefficients. The concept of an a priori estimation consists in performing an estimation before the measurement experiment. The a posteriori estimation uses the data from the previously conducted measurement experiment, thus making it possible to obtain much more accurate results compared with the a priori method. Simulation tests were carried out in order to compare the estimation results with the ones obtained in the course of the simulated experiment. The obtained results confirm that the proposed concepts are correct.

RT/FPGA implementation of the IEEE 1451 standard in sensors for machine conditioning systems

IEEE 1451.4 standard introduced the full “plug and play” for sensors and actuators thanks to the Transducer Electronic Datasheet (TEDS). The only requirement for the measuring system is compatibility with 1451.4. The advantage of this standard among all series of IEEE 1451 is that the Network Capable Application Processor (NCAP) is not necessary. This caused the IEEE 1451.4 to become the most popular and widely available on the market. This paper presents the implementation of the IEEE 1451.4 standard in custom made vibration transducers, based on MEMS accelerometers. The transducers were calibrated and the results of calibration are stored in TEDS added to the sensor. Then the transducers with TEDS were utilized in an experimental machine conditioning system based on embedded RT/FPGA platform.

Comparison of baseline estimation algorithms for chromatographic signals

Baseline in signals is a relatively complicated problem in analysis of signals obtained in various analytical techniques such as chromatography and spectroscopy. In this article there are presented results of tests on four algorithms for a baseline estimation in chromatographic signals. Two of them are based on a polynomial fitting in a region of detected peaks. Another two algorithms, i.e. assymetric least squares method and iterative polynomial fitting with the automatic treshold, estimate the baseline under the whole signal and generally does not require peak detection. The tests of the algorithms are performed on both simulated and experimental signals.

Preliminary studies on modelling the drying process in product classification and separation path in an electromagnetic mill installation

The process of loose materials grinding is directly dependent on the type of feed and its physical parameters resulting from presence of water in the material. The grinding process in the electromagnetic mill installation is carried out on dry material, using pneumatic transport and classification system with recycle. Preliminary analyses have shown the possibility to significantly improve the product quality and efficiency of the milling process by appropriate control of the moisture content of the milled material. The main objective of the research is to develop a model describing the changes of moisture content of bulk material in the installation of the electromagnetic mill. This paper presents the results of preliminary studies on models describing the drying process in the path of material classification and its separation from the transport air.

Indirect measurements of milling product quality in the classification system of electromagnetic mill

The article presents results of research on evaluation of the quality of material obtained in the milling and classification installation with the electromagnetic mill. Several methods of indirect on-line measurements in the process of separating the recycle stream from the final product stream were investigated. The methods discussed in the paper are moisture content measurements of the milled material using impedance and near infrared absorption methods as well as vibration-based measurements of granularity and flow rate of the material. The experiments performed on the classification system of electromagnetic mill circuit show that indirect methods of moisture measurements provide satisfactory results, whereas vibration-based method fails in this case. The grains of copper ore examined in the experiments (present in the classification circuit during normal operation of the installation) are too small and lightweight and the signal-to-noise-ratio of the recorded acceleration signal is too low for the vibration method to be used.

Calibration of Accelerometers Using Multisinusoidal Excitation

Vibrational diagnostics of machines is usually based on use of accelerometers. Their calibration is required in order to obtain reliable results. This paper presents method for calibration of accelerometers using a multisinusoidal excitation. There is also proposed a procedure for estimating uncertainty of the obtained characteristics. The routine is based on an analysis of signals in the frequency domain using evaluation of cross power spectral density between the signals from the calibrated and standard accelerometer and evaluation of power spectral density of the signal from the standard accelerometer. The procedure allows to determine the nominal sensitivity, amplitude-frequency characteristics and estimate their uncertainties. The experiments were performed using a piezoelectric sensor PCB 338B35, and a sensor based on ADXL 202 capacitive accelerometer constructed at Silesian University of Technology. Results of this study show that the proposed method can be successfully used. The main advantage of the routine is a very short duration of the measurement experiment. Values of estimated relative uncertainties reach several percent. The procedure can be applied when it is necessary to quickly check the sensor characteristics, for example in the field for periodical maintenance of sensors mounted on the machine.

Rotating Machinery Diagnostics Based on Fusion of Infrared and Vibration Measurements

Systems for on-line vibration diagnostics of rotary machines requires the installation of vibration sensors on practically each bearing. For a typical machine there are at least a couple of bearings to be monitored and for many machines to be monitored it generates considerable costs arising from the price of sensors, diagnostic modules, software and wiring. In this paper we discuss the possibility of reduction in the number of vibration measurement points, with occasional inspection with IR (Infra-Red) camera, which globally could reduce the system costs without compromising the quality of the machine diagnostic. A measurement stand modeling operation of a simple machine driven by an electric motor and a typical industrial vibration diagnostics system together with a thermal imaging camera were used for this purpose. It allows controlled induction of various defects that result in vibrations. Vibrations was measured with properly parameterized system for on-line vibration diagnostic, separately for each bearing. The research involved performing a few experiments, which modeled a typical defect in rotating machines: quasi static unbalance of the shaft, outer race defect of the bearing and cage defect of the bearing. The fusion of obtained IR and vibration information was discussed.