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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Drill wear monitoring using instantaneous angular speed : a comparison with conventional technologies used in drill monitoring systems

Sambayi, Patrick Mukenyi Kataku January 2012 (has links)
Most drill wear monitoring research found in the literature is based on conventional vibration technologies. However, these conventional approaches still have not attracted real interest from manufacturers for multiples of reasons: some of these techniques are not practical and use complicated Tool Condition Monitoring (TCM) systems with less value in industry. In addition, they are also prone to give spurious drill deterioration warnings in industrial environments. Therefore, drills are normally replaced at estimated preset intervals, sometimes long before they are worn or by expertise judgment. Two of the great problems in the implementation of these systems in drilling are: the poor signal-to-noise ratio and the lack of system-made sensors for drilling, as is prevalent in machining operations with straight edge cutters. In order to overcome the noise problems, many researchers recommend advanced and sophisticated signal processing while the work of Rehorn et al. (2005) advises the following possibilities to deal with the lack of commercial system-made sensors:  Some research should be directed towards developing some form of instrumented tool for drill operations.  Since the use of custom-made sensors is being ignored in drilling operations, effort should be focused on intelligent or innovative use of available sensor technology. It is expected that the latter could minimize implementation problems and allows an optimal drill utilization rate by means of modern and smart sensors. In addition to the accelerometer sensor commonly used in conventional methods, this work has considered two other sensor-based methods to monitor the drill wear indirectly. These methods entail the use of an instrumented drill with strain gauges to measure the torque and the use of an encoder to measure the Instantaneous Angular Speed (IAS). The signals from these sensors were analyzed using signal processing techniques such as, statistical parameters, Fast Fourier Transform (FFT), and a ii preliminary Time-Frequency (TF) analysis. A preliminary investigation has revealed that the use of a Regression Analysis (RA) based on a higher order polynomial function can very well follow and give prognosis of the development of the monitored parameters. The experimental investigation has revealed that all the above monitoring systems are sensitive to the deterioration of the drill condition. This work is however particularly concerned with the use of IAS on the spindle of the drill, compared to conventional monitoring systems for drill condition monitoring. This comparison reveals that the IAS approach can generate diagnostic information similar to vibration and torque measurements, without some of the instrumentation complications. This similitude seems to be logical, as it is well known that the increase of friction between the drill and workpiece due to wear increase the torque and consequently it should reduce or at least affect the spindle rotational speed. However, the use of a drill instrumented with a strain gauge is not practical, because of the inconvenience it causes on production machines. By contrast, the IAS could be measured quite easily by means of an encoder, a tachometer or some other smart rotational speed sensors. Thus, one could take advantage of advanced techniques in digital time interval analysis applied to a carrier signal from a multiple pulse per revolution encoder on the rotating shaft, to improve the analysis of chain pulses. As it will be shown in this dissertation, the encoder resolution does not sensibly affect the analysis. Therefore, one can easily replace encoders by any smart transducers that have become more popular in rotating machinery. Consequently, a non-contact transducer for example could effectively be used in on-line drill condition monitoring such as the use of lasers or time passage encoder-based systems. This work has gained from previous research performed in Tool Condition Monitoring TCM, and presents a sensor that is already available in the arsenal of sensors and could be an open door for a practical and reliable sensor in automated drilling. iii In conclusion, this dissertation strives to answer the following question: Which one of these methods could challenge the need from manufacturers by monitoring and diagnosing drill condition in a practical and reliable manner? Past research has sufficiently proved the weakness of conventional technologies in industry despite good results in the laboratory. In addition, delayed diagnosis due to time-consuming data processing is not beneficial for automated drilling, especially when the drill wears rapidly at the end of its life. No advanced signal processing is required for the proposed technique, as satisfactory results are obtained using common time domain signal processing methods. The recommended monitoring choice will definitely depend on the sensor that is practical and reliable in industry. / Dissertation (MEng)--University of Pretoria, 2012. / gm2013 / Mechanical and Aeronautical Engineering / MEng / Unrestricted
122

Program pro demonstraci kanálového kódování / Programme for channel coding demonstration

Závorka, Radek January 2020 (has links)
The main subject of this thesis is creating a programme, used for channel coding demonstration. This programme will be used for teaching purposes. The programme contains various codes from simple ones, to those which almost reach Shanon’s channel capacity theorem. Specifically these are the Hamming code, cyclic code, convolutional code and LDPC code. These functions are based on theoretical background described in this thesis and have been programed in Matlab. Practical output of this thesis is user interface, where the user is able to input information word, simulate transmission through the transmission channel and observe coding and decoding for each code. This thesis also contains a comparison between individual codes, concerning bit-error rate depending on SNR and various parameters. There is a computer lab with theoretical background, assignment and sheets for convenient accomplishment of each task.
123

Rozvinutí elektroniky a softwaru na robotickém vozidle Car4 / Developement of electronics and software on robotic vehicle Car4

Michal, Mikuláš January 2021 (has links)
Tato diplomová práce se zabývá revizí elektroniky robotického vozidla car4 se zaměřením na měření rychlosti otáčení kol, výkonovou a řídicí elektroniku. Car4 posloužilo jako základ pro již přes 20 diplomových prací od roku 2010. To znamenalo, že některé základní aspekty car4 byly zastaralé. Bylo vytvořeno schéma elektroniky vozidla, které bylo dále využito pro vývoj a výrobu nového hardwaru. Komponenty byly poté otestovány a implementovány na vozidlo. Dále byl vytvořen kinematický model 4WS vozidla za použití Ackermanovy geometrie, který byl implenetován a otestován na car4. Dále by měl sloužit jako základ řídicího algoritmu pro budoucí vývoj car4.
124

Zařízení pro ovládání mikroposuvu / Microposition control device

Kokeš, Ondřej January 2010 (has links)
Presented thesis analyses a function of the particular type of the nanopositioner with aim to suggest and construct an electronic device suitable for control of the nanopositioner slider. In presented material there is a description of the control signals and possibility of their generating in the respect of slider movement accuracy. The main goal of the thesis is to describe electronic units ranging from power supply, control processor unit part to end part that directly joint nanopositioner. There is also programme equipment for microcontroller and computer, communication description, movement measuring and calibration and draft for the close-up of the control loop for additional increase of the movement accuracy.
125

Turbo konvoluční a turbo blokové kódy / Turbo-convolution and turbo-block codes

Šedý, Jakub January 2011 (has links)
The aim is to explain the Turbo convolutional and block turbo codes and decoding the secure message. The practical part focuses on the design of a demonstration program in Matlab. The work is divided into four parts. The first two deal with theoretical analysis of coding and decoding. The third section contains a description created a demonstration program that allows you to navigate the process of encoding and decoding. The fourth is devoted to simulation and performance of turbo codes.
126

Energeticky soběstačný bezdrátový modul pro senzorické aplikace. / Energy Self-sufficient Wireless Module for Sensoric Applications

Jacko, Róbert January 2014 (has links)
Masters thesis deals with design and practical implementation of wireless sensor module. The primary requirement for this module is its energy self-sufficiency. In this context, the work gets to the subject of "energy harvesting". Then, in terms of energy requirements, several wireless communication platforms which are favorable for the selected application, are compared. From mentioned technologies was chosen communication platform IQRF. The next parts deals with initial prototype of sensor module, which will be demonstrated as the application of measuring wind direction. This paper describes the hardware and software solution. Followed by a detailed analysis of its properties in terms of energy requirements. Based on the obtained measurements resource parameters are set.
127

konstrukční návrh stroje pro řezání laserem a plasmou / Design of machines for laser and plasma cutting

Fryčová, Martina January 2012 (has links)
The aim of the thesis is the design machines for laser cutting and plasma workspace 2.0 x1, 8 meters. The work described technology laser cutting and plasma and the resulting demands on the machine. Longer work includes a search of design solutions, then the actual design, including the necessary calculations and drawings.
128

Návrh automatického pohonu kostelních zvonů / Design of automatic drive for church bells

Zajíc, Jiří January 2013 (has links)
The Diploma thesis describes the design, manufacture and testing of a universal automation machine for church bells. The research section summarizes the bell, way of use and properties. The drives and their starting and power switching characteristic are analyzed. The chain drive based on the selected engine and the whole assembly is designed and tested by using PLC. Unique controller based on a modular design was designed. Sensors based on magnetic rotary encoder were also created for this unit. The entire circuit was tested on three evangelical church bells in the town Klobouky u Brna.
129

Návrh systému vertikálního pohonu elevátoru, včetně možností jeho řízení pro skladovací systém LLH / System design vertical drive elevator, including the possibility of control for the storage system LLH

Tichý, Jiří January 2015 (has links)
The aim of this master's thesis are the engineering design of solutions for vertical elevator drive storage systém LLH – Schwerlast. The project is composed of technical report ans drawing documentation. The Technical report deals with storage and handling bar material, methods of control and manipulation of storage systems and structural design. In the structural part are designed draft drive and its main parts. The main parts of drive are checked using structural analysis. The drawing documentation is composed of assembly drawing, manufacturing dravings and welded frame drawing.
130

Implementace metod pro měření rychlosti otáčení rotačních strojů na platformě cRIO / Implementation of methods for measurement of rotational speed using cRIO platform

Fábry, Tomáš January 2016 (has links)
This diploma thesis implements methods for a measurement of rotational speed. It is implemented on the Compact RIO platform from National Instruments. Corresponding SW is implemented using the graphical programming language G in LabView environment. Developed system uses two different sensors – incremental encoder and tacho sensor for measurements of rotational speed. Thesis further analysis and implements a method for an encoder nonlinearity determination and for its on-line correction. For used methods, effects adding errors into the measurements are evaluated and quantified.

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