Measurement of aerodynamic and acoustic quantities describing flow around a body placed in a wind tunnel

Aerodynamically generated noise affects passenger comfort in cars, high-speed trains, and airplanes, and thus, automobile manufacturers aim for its reduction. Investigation methods of noise and vibration sources can be divided into two groups, i.e. experimental research and mathematical research. Recently, owing to the increase in computing power, research in aerodynamically generated noise (aero-acoustics) is beginning to use modem methods such as computational fluid dynamics or fluid-structure interaction. The mathematical model of turbulent flow is given by the system of partial differential equations, its solution is ambiguous and thus requires verification by physical experiment. The results of numerical methods are affected by the boundary conditions of high quality gained from the actual experiment. This article describes an application of complex measurement methodology in the aerodynamic and acoustic (vibro-acoustic) fields. The first part of the paper is focused on the specification of the experimental equipment, i.e. the wind tunnel, which was significantly upgraded in order to obtain the relevant aerodynamics and vibro-acoustics data. The paper presents specific results from the measurement of the aerodynamic and vibro-acoustic fields.Web of Science191282

Aplikace CAN sběrnice s využitím simulátoru dSPACE

In recent years we can see the increasing of electronic control systems in cars. The reason of this increasing is to ensure better safety, comfort, requirements of users and to bear up against the competitive pressure etc., last but not least the pressure of single governments on all the time reducing of consumption sources and the tendency to lower the emitting of emissions to the atmosphere too. These require to implement new systems to the car. The growing of control systems has the influence on quantity of interconnecting wires, which brings the problems (failure rate, unreliability of connection, disturbance, energy losses, etc.). The right coordination of individual control units have to be ensured e.g. the co-operation of engine, ABS/ASR and automatic gearbox. These systems come through different tests for the ensuring of correct functions. For these purposes the serial communication protocol (Controller Area Network - CAN) by BOSCH company was created. The protocol is designed especially for using in the cars. CAN is used for connection of different device types (drivers, sensors, actuators etc.) through the serial data bus. This protocol is used in different industrial applications too. The reason is above all the lower price, easy access point, reliability, high data rate and easy extensibility.V posledních několika letech jsme svědky nárůstu elektronických řídicích systémů v automobilech. Důvodem tohoto nárůstu je zajištění větší bezpečnosti, komfortu, vzrůstajících nároků uživatelů, konkurenčního tlaku, atd. V neposlední řadě je to také tlak jednotlivých vlád na neustálé snižování spotřeby zdrojů a požadavky vyplývající ze snahy snížit vypouštěné emise do ovzduší. To vyžaduje implementovat nové systémy do vozidla. Při nárůstu řídicích systémů a s nimi řídicích jednotek, musí jednoznačně docházet ke zvyšování propojovacích vodičů, což přináší problémy (poruchovost, nespolehlivost spojení, náchylnost k rušení, energetické ztráty, apod.). Navíc musíme zabezpečit správnou koordinaci samostatných řídicích jednotek, jako například součinnost motoru, ABS/ASR a automatické převodovky. Z tohoto důvodu tyto systémy procházejí různými testy pro zaručení správné funkčnosti. Abychom se vyhnuli problémům a překonali omezení způsobené připojením na konvenční ovládací zařízení, byl vyvinut firmou BOSCH sériový komunikační protokol Controller Area Network (dále jen CAN) speciálně pro použití v automobilech. CAN se používá pro propojení různých druhů zařízení (ovladače, senzory, akční členy) přes sériovou datovou sběrnici, přičemž stále dochází k častějšímu využívání tohoto protokolu i v různých průmyslových aplikacích. Důvodem je především nízká cena, snadné nasazení, spolehlivost, vysoká přenosová rychlost a snadná rozšiřitelnost

SIMULATION STUDY OF THE NON-COLLOCATED CONTROL OF A CANTILEVER BEAM

This article deals with the simulation of the active vibration control of a cantilever beam. For these purposes, a lumped parameter model has been developed and the simplest controller has been designed to ensure the structural stability of the control loop. The controller is of a proportional velocity feedback type. The control loop can also be stable in the case of a very small inherent damping of the cantilever beam. The lumped-parameter model is based on the Euler-Bernoulli beam theory. The developed tools can be used to simulate the collocated and non-collocated active vibration control. Since this article is intended to study the behaviour of a non-collocated control system of the transducer is sensing the vibration of the free end of the beam, while the actuator force acts near the fixed end

The PID and 2DOF control of the integral system-influence of the 2DOF parameters and practical implementation

The article deals with the issue of using the Two Degree of Freedom (2DOF) PID controller to control an integral system and investigates by the simulation and experimental measurement what influence it has on the course of the control process compared to standard PID controller. The controlled plant is represented by the DC electric motor with worm gear and its output shaft rotation angle. The article studies the effect of the added parameters of the 2DOF controller on the dynamics of the closed-loop control. The influence of these parameters is then evaluated using the quality of feedback control criteria ITAE. The paper studies how the overshoot of the controlled variable during the setpoint step is eliminated using 2DOF control theory. The overshoot is caused due to an aggressive tuning of the controller to eliminate the disturbance effect on the controlled variable of the integral plants with dead zones.Web of Science551-21019

Vybrané nástroje a metody z oblasti managementu kvality

Following paper describes selected tools and methods from Quality management field and their practical applications on defined examples. Solved examples were elaborated in the form of electronic support. This in detail elaborated electronic support provides students opportunity to thoroughly practice specific issues, help them to prepare for exams and consequently will lead to education improvement. Especially students of combined study form will appreciate this support. The paper specifies project objectives, subjects that will be covered by mentioned support, target groups, structure and the way of elaboration of electronic exercise book in view. The emphasis is not only on manual solution of selected examples that may help students to understand the principles and relationships, but also on solving and results interpreting of selected examples using software support. Statistic software Statgraphics Plus v 5.0 is used while working support, because it is free to use for all students of the faculty. Exemplary example from the subject Basic Statistical Methods of Quality Management is also part of this paper.Příspěvek popisuje vybrané nástroje a metody z oblasti Managementu kvality a jejich praktické aplikace na definovaných příkladech. Řešené příklady byly zpracovány ve formě elektronické podpory. Tato podrobně zpracovaná elektronická podpora, kterou ocení zejména studenti kombinované formy studia, poskytne studentům možnost více procvičit probíranou problematiku, připravit se na zkoušku a také přispěje ke zkvalitnění výuky. Příspěvek dále specifikuje cíle projektu, oblasti, které budou uvedenou sbírkou pokryty, cílové skupiny, strukturu a způsob zpracování zamýšlené elektronické sbírky příkladů. Při zpracování podpory je kladen důraz jak na ruční zpracování řešených úkolů, které mají studentům pomoci pochopit podstatu problému a souvislosti, tak na zpracování a interpretaci výsledků za použití softwarové podpory v podobě programu Statgraphics Plus v 5.0, který je studentům ve škole volně k dispozici. Součástí příspěvku je také vzorový příklad z předmětu Základní statistické metody managementu jakosti

Design of compact planar monopole UWB MIMO antenna with four orthogonal elements and tapered fed configuration for wireless diversity applications

In this paper, we introduce a four-port self-isolated UWB MIMO antenna for diversity applications. First, we have developed a basic radiating element of the proposed antenna in four stages of design, where patches of geometrically different shapes were added at each stage to arrive at the final radiator form. The antenna was designed on an FR-4 substrate with a compact size of 28 x 28 x 1.6 mm(3). A tapered microstrip feeding was employed to enhance the antenna's impedance matching. An orthogonal arrangement of the four radiators was adopted to mitigate the mutual coupling between them, avoiding the use of a separate isolation structure. A prototype was built and measured with a close agreement between the experimental and simulated results. The MIMO antenna performed well in the entire frequency spectrum of 3.1-10.6 GHz, with an isolation better than 20 dB. The measured envelope correlation coefficient (ECC) was less than 0.001, the diversity gain (DG) was greater than 0.99 dB, and the total active reflection coefficient (TARC) was less than -10 dB. The performance of the proposed antenna design was compared with existing designs. The comparison showed that the proposed quad-element UWB MIMO array is compact, has good isolation and diversity performance compared to existing designs, and is well-suited for wireless diversity applications.Web of Science1119art. no. 308

Actively controlled journal bearing enabling to expand limits of stability

The lecture deals with the stability of the movement of the journal inside the hydrodynamic plain bearings, which limits the operating rotational speed. The purpose of active vibration control using piezoactuators is to increase the limit of the rotor stable rotation speed and control the journal position. Besides theory it will be presented the results of testing the first prototype of this type of the bearings

An efficient chaos-based image encryption technique using bitplane decay and genetic operators

Social networks have greatly expanded in the last ten years the need for sharing multimedia data. However, on open networks such as the Internet, where security is frequently compromised, it is simple for eavesdroppers to approach the actual contents without much difficulty. Researchers have created a variety of encryption methods to strengthen the security of this transmission and make it difficult for eavesdroppers to get genuine data. However, these conventional approaches increase computing costs and communication overhead and do not offer protection against fresh threats. The problems with current algorithms encourage academics to further investigate the subject and suggest new algorithms that are more effective than current methods, that reduce overhead, and which are equipped with features needed by next-generation multimedia networks. In this paper, a genetic operator-based encryption method for multimedia security is proposed. It has been noted that the proposed algorithm produces improved key strength results. The investigations using attacks on data loss, differential assaults, statistical attacks, and brute force attacks show that the encryption technique suggested has improved security performance. It focuses on two techniques, bitplane slicing and followed by block segmentation and scrambling. The suggested method first divides the plaintext picture into several blocks, which is then followed by block swapping done by the genetic operator used to combine the genetic information of two different images to generate new offspring. The key stream is produced from an iterative chaotic map with infinite collapse (ICMIC). Based on a close-loop modulation coupling (CMC) approach, a three-dimensional hyperchaotic ICMIC modulation map is proposed. By using a hybrid model of multidirectional circular permutation with this map, a brand-new colour image encryption algorithm is created. In this approach, a multidirectional circular permutation is used to disrupt the image's pixel placements, and genetic operations are used to replace the pixel values. According to simulation findings and security research, the technique can fend off brute-force, statistical, differential, known-plaintext, and chosen-plaintext assaults, and has a strong key sensitivity.Web of Science2220art. no. 804

Scan time reduction of PLCs by dedicated parallel-execution multiple PID controllers using an FPGA

A programmable logic controller (PLC) executes a ladder diagram (LD) using input and output modules. An LD also has PID controller function blocks. It contains as many PID function blocks as the number of process parameters to be controlled. Adding more process parameters slows down PLC scan time. Process parameters are measured as analog signals. The analog input module in the PLC converts these analog signals into digital signals and forwards them to the PID controller as inputs. In this research work, a field-programmable gate array (FPGA)-based multiple PID controller is proposed to retain PLC scan time at a lower value. Concurrent execution of multiple PID controllers was assured by assigning separate FPGA hardware resources for every PID controller. Digital input to the PID controller is routed by the novel idea of analog to digital conversion (ADC), performed using a digital to analog converter (DAC), comparator, and FPGA. ADC combined with dedicated PID controller logic in an FPGA for every closed-loop control system confirms concurrent execution of multiple PID controllers. The time required to execute two closed-loop controls was identified as 18.96000004 ms. This design can be used either with or without a PLC.Web of Science2212art. no. 458

Actively Controlled Journal Bearings for Machine Tools

The advantage of journal hydrodynamic bearings is high radial load capacity and operation at high speeds. The disadvantage is the excitation of vibrations, called an oil whirl, after crossing a certain threshold of the rotational speed which depends on the radial bearing clearance, the viscosity of lubricating oil, and the rotor mass. A passive way of how to suppress vibrations consists of adjusting the shape of the bearing bushing. Vibrations can be suppressed using the system of active vibration damping with piezoactuators to move the bearing bushing in two directions. The displacement of the bearing bushing is actuated by two piezoactuators, which respond to the position of the bearing journal relative to the bearing housing. Two stacked linear piezoactuators are used to actuate the location of the bearing bushing. A pair of capacitive sensors senses the position of the journal or shaft. The system of the actively controlled journal bearings is the first functional prototype in the known up to now. It works with a cylindrical bushing which does not require special technology of manufacturing and assembly. This new bearing enables not only to damp vibrations but also serves to maintain the desired bearing journal position with an accuracy of micrometers