Janusz Kwaśniewski

Selected Applications of the Wavelet Transform

The wavelet transform is used to analyze: (1) the strain respons e signal in a resonant mechanical spectrometer, (2) the signal from a magnetic inspec tion of wire ropes, and (3) the Barkhausen noise signal. The wavelet transform of the analyzed signal yields a three-dimensional representation (the time-scale joint representation), that is, s pace (time), frequency (scale), and amplitude. The time-dependent strain signals measured by a mecha nical spectrometer, represented in the time-scale joint representation, are called “Identifie d Strain Response Signal” (ISRS) to emphasize that not only frequency content of the strain response signal but lso time is clearly revealed. The wavelet transform is applied to on-line analysis of the strain signal during mechanical loss measurements. The wavelet transform of the strain response s ig al can also be used to identify fine irregularities in a very low frequency strain response sig nal and to denoise this signal in order to obtain better signal to noise ratio of the strain signal recor d d in a subresonant mechanical spectrometer. For these reasons the wavelet analysis has proved t o b a useful tool to analyze the strain and the stress signals and thereby to improve the quali ty of oscillations in both a resonant and a subresonant mechanical spectrometer. It is concluded that the wave let transform can be successfully used in spectroscopic techniques. Nonstationary Barkhausen noi (BN) signals and signals obtained during magnetic inspection of twisted and lay ropes are also investigated by the wavelet analysis. The wavelet transform is used in the magnet ic i spection of wire ropes and in the decomposition of signals from induction sensors, that is, in non-destructive testing (NDT) techniques of wire ropes. Appropriate levels of signal decomposition provi de both reliable detection of various forms of rope wear and supplementary information about wear-of f forms in twisted and lay ropes. The wavelet transform of nonstationary magnetic signal is a promising and powerful tool for wire rope inspection and investigation of ferromagnetic materials. Introduction This paper reports results on the application of wavelet analysis: (1) to nearly stationary harmonic signals recorded in a mechanical spectrometer, (2) to nonstationary signals obtained in the investigation of the magnetic Barkhausen noise (BN), and (3) to nonstationa ry signals obtained in the non-destructive magnetic inspection of wire ropes. Solid State Phenomena Online: 2003-02-13 ISSN: 1662-9779, Vol. 89, pp 355-0 doi:10.4028/www.scientific.net/SSP.89.355

The SMA Wires Application in the Braille Monitor

The main aim of the research was to establish whether SMA wires are suitable to build a Braille tactile display. The particular goals were to design, fabricate and programme a device, which would be cheap, convenient and easy to use, and would work independently from the PC. The prototype was to have one letter at least and be ready to add more letters in the future. In the article the conception of the prototype design is presented. The single pin was designed in the shape of a vertical cylinder of 3 mm in diameter. A significant disadvantage of modern Braille monitors is the length of the piezo crystals that prevents engineers from building large matrices. Thanks to SMA wires the possibility to build a large matrix is unlimited. Having built a Braille letter prototype the research on the selection of an appropriate control method was launched. Eventually, it was decided that all of the control tasks would be covered by one single chip – the PIC18F4455 processor. This unit had all the necessary peripherals, such as USB, timers, as well as enough speed to run the software. The designed device has proved that SMA wires can be used for this kind of application [2]. It has also demonstrated that graphic Braille monitors can be built. In the current stage of research, this design is not ready for mass production, but additional research can lead to the improvement of this device.

Self-Tuning Controller for Nonlinear Object

The main subject matter of the paper is the application of adaptive control systems. This type of control is particularly useful for processes and machines with variable parameters. Classic controllers in this case are not satisfactory. Therefore a research work was initiated on advanced algorithms of control. The paper analyzes algorithms based on fuzzy logic. It should be noted that parameters of fuzzy controllers require adjustment to changeable process (machine) parameters for which an adaptive mechanism is required. The proposed algorithm has been tested on a laboratory stand with a hydrostatic transmission, which is a non-linear and a non-stationary object.

Application of the Ionic Polymer-Metal Composite Sensor Array Indisplacement Measurement

An Ionic Polymer-Metal Composite (abbr. IPMC) is a type of a smart materialconsisting of two layers of noble metal and an ion-conducting layer between them. Smart ma-terials are generally capable of actuating and sensing. Mechanical deformation of the IPMCbeam produces an electric potential di erence (in the order of mV) proportional to the tipdisplacement on the electrodes. In this paper, the sensing capabilities of IPMC samples will beinvestigated. The composites are manufactured in a form of a thin (0.3 mm) plate, which arecut into rectangular samples. Tests will be performed on separate samples and two electricallyconnected samples. Response to various frequencies will be tested for each sample and for twomechanically and electrically coupled samples, creating a simple sensor array.

Laboratory Research on Energy Harvesting of Ionic Polymer Metal Composite

The aim of this paper is to present the results of laboratory research on Ionic Polymer-Metal Composite (IPMC), in context of energy harvesting applications. IPMC is a novel type of material, a smart polymer, which can work as a sensor or an actuator. One of its biggest advantages is low actuating voltage of about 4V (with 120mA current), what makes it very energy-efficient. Step response for various input amplitudes of two IPMC samples is shown. Also, a voltage generated in response to mechanical deformation of the composite is measured, and a hysteresis loop is plotted. Lastly, the changes of properties of the IPMC caused by long-term actuation are researched. These results are necessary to build an energy harvesting system utilizing IPMC. A simple gripper built with IPMC is also presented.

Fuzzy Logic Controller for Position Actuator SMA

Shape Memory Alloys SMA attracts more and more interest and nowadays many research centers are working on developing more accurate and applicable actuators. A tangible effect of using SMA materials is considerable simplification of the constructions used so far, which entails obvious economic benefits. Along with the increase in the volume of production and decrease in the cost of production, SMA materials become increasingly available on the consumer market. In the article the use of SMA wire to build and control linear position actuators was presented. The SMA actuator is characterized by one of the highest in technology weight ratios, which describes the ratio of maximum external load to its own weight. It allows for building miniature devices which are extremely efficient. Generally SMA wires are applied as on-off objects. After initial research and building several prototypes the gear transmission was chosen. It was decided to realize an actuator which can work in both directions of displacement, and so allow for the elimination of a return spring, which is a unique solution.

Piezoelectric Self-Excited System in Mining Roof Anchor Stress Change Measurement

The paper presents the application of a new type of a measurement system called Self-excited Acoustical System (SAS). It was applied for stress change monitoring of anchors which are used to secure roofs and walls in mines and in hollowed tunnels. The knowledge about the state of anchors can indirectly indicate the state of rock masses which is crucial for mining safety. One of the main problems so far has been reliable sensor mounting, especially in difficult mining conditions. The SAS system overcomes this problem because it can be mounted easily at the anchors end or even on the anchors flange. The laboratory tests were conducted on a hydraulic tensile testing machine. The mining roof anchor was placed in the machine and then stretched. The changes of the resonance frequency caused by the increase of the tensile strength were observed during the research.

Modelling Coupled Electric Field and Motion of Beam of Ionic Polymer-Metal Composite

Abstract In this paper, a mathematical model of electromechanical transduction of Ionic Polymer-Metal Composites is presented. The aim of the research was to create a physics-based, geometrically scalable model to use in control systems. The relation between actuating voltage and the tip displacement was described with a transfer function. The model is derived from the basic physical properties of researched materials. To calculate the final transfer function, two impedance models are considered - with and without neglecting the resistance of the metal electrodes. In this paper, the model with non-zero electrode resistance is calculated. Later, the model is simplified (taking the physical properties into account) and the numerical values based on the parameters of the samples are calculated. The simplifications allow the model to predict the response to low-frequency sine wave actuation. The frequency-domain characteristics of the samples were created experimentally and compared to the model. The results have proven the accuracy of the model.

Harmonic Analysis of Self-Excited Acoustical System for Stress Changes Measurement in Compressed Steel Structural Section

This paper presents the application of the Self-exited Acoustical System (SAS) for monitoring stress changes in steel. The change of the speed of wave propagation, which is associated with the change of the resonance frequency in the system is caused by the deformation of the examined material. The SAS system is based on this phenomenon and can be used for an indirectly measurement of the stresses changes in the steel. Preliminary calculations such as static analysis and dynamic simulation of the system were carried out. The results of calculations were compared with the experimental data of the steel beam.

Analysis of Dependence between Stress Change and Resonance Frequency for Self-Excited Acoustical System

Continuous supervision of mechanical endurance is very important in the time of the advance constructions. The Self-excited Acoustical System (SAS) is a kind of a self-oscillating system, which uses the auto-resonance phenomena for measurement of construction stress changes. The advantage of this solution is the ability to apply it to a wide spectrum of materials from elastoplasts to brittle ones where the conventional techniques cannot be used. The Self-excited Acoustical System is characterized by its great sensitivity in comparison with the traditional techniques. This paper presents the results of the research carried out on a metal bar expanded by variable force. The dependence between the relative elongation of the sample and the transition time of the wave was elaborated. The delay occurring during a wave transition has a direct impact on the value of self-oscillation frequency. The influence of the coupling force between a metal sample and the wave receiver was also analysed.