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Dynamic Analysis and VI Bration Control of a Precision Machine Subjected to Moving Dynamic Loads
|Contributors: ||NTOU:Department of Mechanical and Mechatronic Engineering|
|Keywords: ||moving dynamic loads;precision positioning;dynamic analysis|
|Issue Date: ||2012-04-13T01:18:33Z
This project aims to explore dynamic characteristics and vibration control of a precision machine subjected to moving dynamic loads. Opposed to the traditional consideration of moving load problems for civil structures, such as bridges or railroads, the subject matter studied in this work is related to the design and analysis of precision machines, such as high speed precision drilling machines or precision positioning platforms. Consequently, special attention must be paid on the dynamic behavior of the moving dynamic system. In this project, a moving dynamic system with two degrees of freedom traveling on a flexible support structure will be considered. The finite element model of the integrated system will first be formulated to facilitate the treatment of a system with complex boundary conditions. Unlike the traditional moving load analysis considering a constant moving speed or acceleration, the moving dynamic system considered in this work travels with a general movement profile. From a stationary condition, it rapidly moves to the next operation position while still remaining stationary. The operation usually incorporates a minimal traveling time strategy for maximal production efficiency. The movement profile involves three motion stages, i.e. rapid acceleration, rapid deceleration, and settling for subsequent operation. To provide such a movement profile, the moving dynamic system is subjected to sudden applications of external excitation to accelerate and to decelerate, which can easily result in severe vibration and may reduce the production efficiency and the product quality. We shall examine the dynamic characteristics of the entire system to pinpoint the crucial parameters, such as support conditions of the moving dynamic system, forcing function characteristics, and flexible base support characteristics, on the performance of the precision machine. Structural modification by changing the sensitive parameters and passive vibration control will be studied subsequently for improvement of system performance. This strategy provides quality enhancement without considerable cost. No additional external energy is required and little effort is needed for system maintenance. Finally, to further enhance the performance of the precision machine, active vibration control strategy will be examined, which provides appreciable vibration control capability by external excitation mechanisms orchestrated by a closed loop feedback controller. The application of the active vibration suppression strategy can be crucial if strict requirements on accuracy and efficiency are imposed for today’s ultra precision high speed machines.
|Appears in Collections:||[機械與機電工程學系] 研究計畫|
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