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## Modal analysis of a manipulator in the whole workspace

#### Abstract

The goal of this work is to perform the modal analysis of the chosen robot manipulator - SCHUNK LWA 4P - in whole of it’s workspace. Described analysis was done using finite element method in Ansys Workbench 14 software. The thesis is divided into a four main sections - preface, theoretical introduction, numeri- cal analysis in ANSYS Workbench and conclusions. In the introduction typical problems connected with vibrations in technics were described, including historical examples. In particular, the topic of vibrations of robots was mentioned. Possible causes and threats were listed. The review of existing scientific works connected with modal analysis in ro- botics, alike experimental, theoretical and numerical was made. It was pointed out that in most of the previous works analysis were made only for few spetial configurations of manipulator but not in the whole modal workspace. In theoretical introduction the concept of modal anlysis and free vibrations was explained. Vibations of systems with one, two and many degrees of freedom were briefly described. The definitions of natural frequencies and mode shapes were given, alongside with me- thods of finding them. Next, the finite element method was described. The way of solving the eigenvalue problem with this method was described on the example of simplified model of described manipulator. The model contained two planar frame elements. The forms of stiffness and mass matrices were given for this type of elements. Then, the de- grees of freedom vector and stiffness and mass matrices were transformed into the global reference system. The boundary conditions were taken into consideration and both the matrices were agregated which allowed to formulate the eigenvalue problem. The problem was solved using the MATLAB software. The first natural frequency and corresponding mode shape were calculated. Then it was pointed out how the attempt to perform such analysis in many points of workspace leads to unacceptable increase of calculation time. In the numerical analysis in Ansys Workbench section two different analysis were de- scribed. In the first one the model of the robot was simplified - it consisted three of line elements. Second one was made using the accurate 3D model of manipulator SCHUNK LWA 4P, based on CAD files. Both analysis were performed in the whole workspace of the robot. The first part is the demonstration of the method. On the example of simple, line body elements the process of modeling bodies and assemblies was described. Also, defini- tion of parameters describing spatial configuration of robot was done. Then, the meshing and contact definiton were performed. Analysis was done for chosen robot position. Then, the parameters defined earlier were used in Goal Driven Optimization module to obtain 2 the response surface and to find the worst case of spatial configuration in whole workspace. In the second part the process of importing 3D geometry of manipulator parts from CAD programs and creating their assembly was described. Then, all the steps listed abo- ve were made for the 3D model. The final analysis results - response surface (plot of the values of first natural frequency dependent on parameters - characteristic angles between robot arms and global reference frame), values of first six natural frequencies in the worst configurtion and corresponding mode shapes were presented. In the last section summary of the work was made. Differences between analysis of most accurate 3D model and approximate models were described. The final conclusion was stated - Goal Driven Optimization module of Ansys Workbench is highly effective and efficient tool for performing modal analysis in the whole workspace of manipulator.
Diploma type
Engineer's / Bachelor of Science
Diploma type
Engineer's thesis
Author
Arkadiusz Łukasiak (FPAE) Arkadiusz Łukasiak,, Faculty of Power and Aeronautical Engineering (FPAE)
Title in Polish
Analiza modalna manipulatora w całej przestrzeni roboczej
Supervisor
Edyta Rola (FPAE/IAAM) Edyta Rola,, The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)Faculty of Power and Aeronautical Engineering (FPAE)
Certifying unit
Faculty of Power and Aeronautical Engineering (FPAE)
Affiliation unit
The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)
Study subject / specialization
, Automatyka i Robotyka (Automation and Robotics)
Language
(pl) Polish
Status
Finished
Defense Date
18-02-2016
Issue date (year)
2016
Pages
52
Internal identifier
MEL; PD-3591
Reviewers
Cezary Rzymkowski (FPAE/IAAM) Cezary Rzymkowski,, The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)Faculty of Power and Aeronautical Engineering (FPAE) Edyta Rola (FPAE/IAAM) Edyta Rola,, The Institute of Aeronautics and Applied Mechanics (FPAE/IAAM)Faculty of Power and Aeronautical Engineering (FPAE)
Keywords in Polish
analiza modalna, drgania, manipulator
Keywords in English
modal analysis, vibrations, manipulator
Abstract in Polish
File
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urn:pw-repo:WUT927212f841394c7786a0faa52d93f2aa