The Stiffness Analysis Of The Parallel Manipulator

The mechanical design of robotic manipulators is a process in which many criteria, such as the working volume, dexterity, and stiffness, have to be considered. Among these properties of mechanical systems, the latter is particularly important in the context of parallel robotic manipulators. The stiffness of a manipulator is an important element describing the characters of parallel manipulators. The stiffness mapping for a parallel manipulator concerns the transformation of joint stiffness to the stiffness in the Cartesian space. This operation is essential to the stiffness control of the manipulator. The stiffness maps obtained can be used to study the stiffness of manipulators in the Cartesian directions, to explore the stiffness maps and the properties of parallel manipulators, and the influence of the variance in stiffness of manipulators on capability of manipulators, it can own significance on stiffness-controlled of parallel manipulators, structural design and the parameters selecting of manipulators.This paper deduces the analytical stiffness equations of the 6-SPS spatial parallel mechanism and 6-PSS spatial parallel mechanism based on the means of stiffness analysis of the 3-RRR and 3-RPR planar parallel mechanism and new conservation stiffness matrix, analyzes and plots the workspace given of the two mechanisms. Finally, this paper analyzes stiffness characteristics of the two mechanisms based on the above.This paper studies on several aspects, for instance:kinematics equations, stiffness matrix and workspace. The MATLAB software are used in stiffness evaluation, the drafting of workspace and stiffness mapping. The stiffness character of parallel manipulator is analyzed in detail. We find that the stiffness of the 6-SPS spatial parallel mechanism and 6-PSS spatial parallel mechanism are configuration dependent, and proportional to the actuating forces and joint stiffness. The stiffness of the mechanisms not only relates to the size of the actuating forces, but also their direction. And the stiffness has some certain symmetrical relationship for the symmetrical mechanisms.