Change search
ReferencesLink to record
Permanent link

Direct link
Active control of vibration and analysis of dynamic properties concerning machine tools
Responsible organisation
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Vibration in internal turning is a problem in the manufacturing industry. Vibrations appear under the excitation applied by the material deformation process during the machining of a workpiece. In order for a lathe to perform an internal turning or boring operation, for example, in a pre-drilled hole in a workpiece, it is generally required that the boring bar should be long and slender; therefore extra sensitive to vibrations. These vibrations will affect the result of machining, in particular the surface finish, also the tool life may be reduced. As a result of tool vibration, severe acoustic noise frequently occurs in the working environment. This thesis comprises three parts and the first part presents a method for active control of boring bar vibration. This method consists of an active boring bar controlled by, for example, an analog controller. The focus lies on the analog controller and the advantages that may be obtained from working in the analog domain. The controller is a lead-lag compensator with digitally controlled parameters, such as gain and phase. However, signals remain in the analog domain. In addition, the analog controller is compared with a digital adaptive controller and it is found that both controllers yield an attenuation of the vibration by up to 50 dB. The second part of this thesis concerns the dynamic properties of a clamped boring bar used by the industry. In order to design a robust controller for a certain system, knowledge about the system's dynamic properties is required. On the workshop floor, a boring bar is dismounted and remounted, and reconfiguration of boring bars will alter the dynamic properties of the clamped boring bar. The dynamic properties of a standard boring bar and an active boring bar for a number of possible clamping conditions, as well as for a linearized clamping have been investigated based on an experimental approach. Also simple Euler-Bernoulli modeling of clamped boring bars incorporating simple non-rigid models of the boring bar clamping are investigated. Initial simulations of nonlinear SDOF systems have been carried out: one with a signed squared stiffness and one with a cubic stiffness. The purpose of these simulations was to identify a nonlinearity that introduces a similar behavior in the SDOF system dynamics as the nonlinear behavior observed in the dynamic properties of a clamped boring bar. The third and final part of this thesis focuses on vibration analysis methods in engineering education. A signal analyzer (which is a commonly used instrument in signal processing and vibration analysis) was made accessible via the Internet. Assignments were developed for students to learn and practice vibration analysis on real signals from a real setup of a relevant structure; a clamped boring bar. Whilst the experimental setup was fixed, the instrument and sensor configuration nonetheless enable a variety of experiment, for example: excitation signal analysis, spectrum analysis and experimental modal analysis.

Place, publisher, year, edition, pages
Karlskrona: Blekinge Institute of Technology , 2007. , 208 p.
Blekinge Institute of Technology Licentiate Dissertation Series, ISSN 1650-2140 ; 4
Keyword [en]
Active Control, Modal Analysis, Analog Controller
National Category
Signal Processing Applied Mechanics
URN: urn:nbn:se:bth-00360Local ID: 978-91-7295-112-9OAI: diva2:837060
Available from: 2012-09-18 Created: 2007-04-04 Last updated: 2015-06-30Bibliographically approved

Open Access in DiVA

fulltext(6181 kB)318 downloads
File information
File name FULLTEXT01.pdfFile size 6181 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Signal ProcessingApplied Mechanics

Search outside of DiVA

GoogleGoogle Scholar
Total: 318 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 50 hits
ReferencesLink to record
Permanent link

Direct link