Solid State Phenomena Vol. 113

Abstract: FEM is a very important tool for getting the numerical solution of many engineering problems. It has been widely used in solving structural, mechanical, heat transfer, and fluid dynamics’ problems as well as problems of other disciplines such as piezoelectricity. Since the complexity of many problems leads to the formation of models of large dimension, which are described with many degrees of freedom, their numeric solution makes for the highest demands. The number of degrees of freedom is often unnecessarily large to represent the structural response in a limited bandwidth and therefore, in such a case, a reduction should be conducted. The systematic reduction of complex FE models on simple electromechanical equivalent circuit models (with less mechanical degrees of freedom) is the subject of this paper. The aim of the work is to make the reduction in such a way that the characteristics of the systems input/output descriptions are approximated within a pre-selectable frequency range with sufficient accuracy. A transducerwedge- system is used as an example for the method, to extract a state space model of the systems piezoelectric input/output description and to derive the parameters of the electromechanical equivalent circuit directly from the modal finite element analysis. In the present paper we describe the general methodology as well as its application to piezoelectric transducers as used in ultrasonic engineering.

Abstract: The analysis of technological trends nanoelectromechanical systems and processes of self-formation micro- and nanostructures in manufacturing MEMS/NEMS have been made and the requirements have been formulated. The results of modeling geometry nanostructures and the implementation of self-formation processes for creating new technologies of manufacturing MEMS/NEMS have also been presented.

Abstract: This paper presents a two-channel digital control system for the hydraulic stand MZPK 100 designed for fatigue tests of cruciform specimens under biaxial tension-compression. In the past, the fatigue test stand MZPK 100 was provided with unreliable analog control power cubicles. Application of the computer with an analog and digital input-output signal path board, Matlab/Simulink software and a new control box equipped with the necessary electronic subassemblies (responsible for proper switching of the hydraulic supplier, command electrovalves, conditioning of signals from sensors and so on) enables replacement of the old analog system by a new two-channel digital control system. Nowadays, it is easy to modify the control system to different requirements of material tests because the hardware (electronic) solutions have been simplified, and the software has a friendly Simulink interface. Such an approach allows for the implementation of different control algorithms, e.g. PID, adaptive, and fuzzy logic etc. Moreover, this paper presents a description of how to keep the center of the specimen static under a controlled force that is being applied by four independent actuators.

Abstract: A model of the AC induction motor, which allows us to analyze all operation modes of motor supplied by the frequency converter, has been developed. A simulation of the inverter of the frequency converter and the AC induction motor interaction on the basis of the developed motor model, using software MATLAB, was performed and a motor regenerative braking mode was investigated. The results of investigation are used for the development of fault protection of the inverter.

Abstract: An asymmetric PI (aPI) controller based on a control algorithm, which is the modification of the PI control method, has been suggested. The principal characteristic feature of the aPI controller is that different values of proportional and integral constants are used at positive and at negative errors. Contrary to the classical PI controller, the proposed controller allows us to improve the positive disturbance rejection of control systems without sacrificing the unit step response dynamics. Results of the investigation of the concrete control systems based on the aPI controller are also presented. Using the dynamic system simulation program Simulink performed the investigation.

Abstract: The main flaws of electric arc welds and factors determining the quality of the welded seams are considered in this paper. In practice, welding tools and their control systems are affected by some external factors causing deviation of the weld’s quality from the specified values. Currently used control systems of welding tools do not always satisfy the requirements for quality of welded joints. Major principles of developing the adaptive control system of the welding tool are considered here and the developed functional and block diagrams of microprocessor system are presented. General equations describing the welding process are also provided and the obtained transfer function of a closed system is described.

Abstract: The paper considers some problems of calculating major parameters and characteristics of a mechatronic system with a linear induction motor (LIM). It has been shown that LIM operating in the presence of traveling magnetic fields are widely used alongside other actuators. These motors allow for modular design because inductors may be made as independent modules. Then, by choosing the required number of inductors and their arrangement in a mechatronic system, a desired trajectory of transverse motion may be obtained. A theoretical model for LIM calculation, taking into account major assumptions about onedimensional magnetic field, is offered. Complex amplitude is expressed as the exponential function of a longitudinal coordinate of current volumetric density of the inductor. The above inductances as the parameters of dynamic equations may be used in further investigation of dynamics of mechatronic systems. However, in order to create optimal control systems for mechatronic systems with linear actuators, the major parameters and characteristics of a linear motor should be known. Therefore, the present investigation is aimed at developing methods for calculating the parameters of mechatronic systems with linear electric drives.

Abstract: Unreliable and inflexible analog control systems of fatigue test stands applied in laboratories are being replaced by systems enabling easy development and implementation of new test ideas. This paper presents a digital control system applied in the fatigue test stand SHM 250b. It is based on a new electronic system and the I/O board RT-DAQ4/PCI with the software Matlab/Simulink used for communication with the board. The control system for the fatigue test stand SHM 250b gives the possibility of performing fatigue tests under controlled strain ε(t), stress σ(t) and energy parameter W(t) which is calculated from the stress and strain signals. The applied control system is now used, depending on the performed fatigue tests, and can be developed for specific needs of material strength analysis.

Abstract: Analysis into the effects of parametric characteristics of visual aid on the perception level of information transmitted has led to the possibility of examining and determining the quality of the reading level as a function of certain parameters of a digital apparatus (sensor), the distance to the text, the size of letters and the intensity of light. Efforts have been made to evaluate the effect of the specifications of the executor as well as the information transfer (by tactile way) speed onto the sensory organs of the disabled person at the perception level. A choice has been made of rational information transfer speeds and appropriate visual aid characteristics to facilitate an adequate perception level.

Abstract: A laser instrument maintains the course of the positioned gantry module. A laser beam generator emitting a vertical beam is placed at the end of the experimental field. A laser beam catcher with photo diodes is mounted onto a positioned gantry module replaceable support. Course deviations were assessed in two cases: when laser, straight-course maintaining mechanism was mounted at the same end of the spar as positioning trundle; and when it was mounted at the middle of the spar. Furthermore, we estimated how course deviations vary when changing the interaxial distance of laser catcher photodiodes. An electromechanical transmitter was used in the tests. The gantry module is positioned by a special positioning trundle and is run by a 12 V electric motor through a worm self - braking reduction gear.