A comprehensive study of modal characteristics of a cylindrical manipulator with both link and joint flexibility

A thorough understanding of modal characteristics of vibrating manipulators is essential for improved dynamic positioning accuracy. Presented in this work is an extensive investigation of a cylindrical manipulator, consisting of a revolute and a prismatic joint. In general, for high-speed, flexible manipulators, modal properties depend mainly upon the following factors: (1) physical dimensions and material properties of components (such as arms and joints), which remain unchanged for a chosen manipulator; (2) a manipulator's position (or orientation) as a result of joint actuations; (3) the rigid-elastic coupling effect; and (4) the centrifugal stiffening effect due to the influence of internal axial force on the lateral stiffness. This work is intended to study the effects of each of the above factors on modal characteristics of the manipulator, and gives insight into the susceptibility of the modal parameters to each factor. In addition, joint flexibility has substantial influence on modal properties of a robotic system, depending on the relative importance of joint torsional stiffness to the stiffness of other members, such as the bending stiffness of arms. In the situation where the manipulator moves at a high speed, both rigid-elastic coupling and centrifugal stiffening effects can become important.