Development of Hybrid Parallel Mechanism for High Precision Work and Method for Compensating its Work Error

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This research has developed a 5-dof special mechanism for machine tool. As the mechanism is composed of a spatial 3-dof parallel mechanism and a 2-dof planar guide table, it is expected to have a large workspace and high rigidity. The spatial 3-dof parallel mechanism comprises 3-RPS chains and furthermore has board-like links for suppressing bending deformation induced in prismatic pairs and the prismatic pairs are fixed on them at each end. Thus the proposed mechanism will realize higher rigidity and high speed motion. Next, the research has established a method for evaluating output errors of multiple degree-of-freedom mechanisms by forces applied to the output link in arbitrary direction. The output errors evaluated here result from elastic deformations of the driving parts. The evaluation values can be obtained by solving the eigenvalue problem of the matrix introduced from the compliance matrix which reveals the relations between the output error and force applied to mechanism. Th … More e method will facilitate to improve the rigidity of a multiple degree-of-freedom mechanism such as a parallel mechanism in its design. Furthermore, the proposed method can consider elastic deformation induced in the structures as well as the driving parts. Thus, the research analyzed the above mentioned spatial 3-dof parallel mechanism by the proposed method with considering the shape of the board-like links for improving the output errors caused by the translational and rotational deformation in the prismatic pairs. Based on the above results, we designed a 5-dof machine tool and assembled it actually. By the tool machine the research performed multiple degrees of freedom working and confirmed its availability. Next, the research considered the work error caused from the non-linearity relation between the output and input of parallel mechanism, and proposed the method for evaluating it by utilizing differential kinematics that is expressed by the Jacobian matrix. The method can evaluate the maximum value of the ratio of the output to input displacement to the arbitrary direction at each configuration of multiple degrees of freedom mechanism. We actually measured the work error by the assembled machine and confirmed it conforms to the evaluated results. From those results, the research has proposed the method for determining the optimum step size to control machine tool and confirmed its availability. Furthermore, the research considered a method for compensating the various error of the developed mechanism by the response surface methodology. We proposed the method for estimating the distribution of the error induced from the structural error and giving the compensation value for the input displacement. The availability of the proposed method has been confirmed by the numerical simulation of the present mechanism. Less