Influência do comportamento estrutural no erro de posicionamento de uma máquina de cinemática paralela. / Influence of the structural behavior in the error of positioning of a parallel kinematic machine.

AUTOR(ES)

João Gustavo Hermanson Rosa

DATA DE PUBLICAÇÃO

2007

RESUMO

In spite of the effort spent by the academic and industrial communities (goods, patents and laboratory prototypes), the Parallel Kinematics Machines - PKMs - they still present an inexpressive participation in the market of machine-tools and robots. One of the reasons for this fact is their low indexes of accuracy and precision, in comparison with the machines of conventional milling. This work presents the evaluation of the compliance mapping (kinetostatic analysis) and natural frequency about the positioning of the work piece and milling preferential directions, inside the available workspace of a parallel kinematics machine tool. At present this analysis has been accomplished in parallel kinematics machine using the virtual work principle or partially involving this method and the finite element method, with the overlap of the results of both. This work presents a compliance analysis just using the finite element method in parallel kinematics machine of type 2PRS+2PUS with 4 degrees of freedom (two moves - Y and Z - and two rotations - tetax e tetaYG), denominated Tetraglide. In all of the done analyses the degree of freedom tetaYG was maintained constant, tetaYG = 0°. This way all of the analyses occurred on the plan YZ. Starting from the compliance analysis the axial loads are evaluated in the bars, which connect the actuators to the movable platform along the workspace, determining where the buckling occurs. After this, with the finite element method, 1st natural frequency is obtained along each constant-orientation workspace, once the knowledge of this frequency is important factor in the evaluation of the dynamic structural behavior of machine-tools. After these analyses, structural parameters are analyzed in sensibility analyses seeking to maximize to smallest 1st natural frequency observed in each constant-orientation workspace.

ASSUNTO(S)

máquinas de cinemática paralela erro de posicionamento positioning error structural rigidity rigidez estrutural parallel kinematics machines

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