Two comprehensive indices–based static performance evaluation for the tripod parallel kinematic machine

Abstract

Static performance evaluation is one of the most important issues during the design stage of tripod parallel kinematic machines. Taken the 1T2R tripods as examples, this article proposes two improved static performance indices, namely, local dexterity stiffness index and global dexterity stiffness index. By combining the local dexterity formulation and the eigenstiffness matrix, the two indices can be derived, which considers both the kinematic dexterity and the static rigidity of the tripod parallel kinematic machines. Based on this concept, the indices of local dexterity stiffness index and global dexterity stiffness index are defined for the local and global static performance of the parallel kinematic machines, respectively. With the index of local dexterity stiffness index, the static performance distribution of an Exechon parallel kinematic machine over its entire workspace is predicted, and an optimal workspace is recommended. With the index of global dexterity stiffness index, the effects of design parameters on the global performance are investigated. This study can be further extended to other kinds of tripods, thus provides useful information for structural optimization and rigidity enhancement of the tripod modules.