A COMPREHENSIVE STUDY OF MODAL CHARACTERISTICS OF A CYLINDRICAL MANIPULATOR WITH BOTH LINK AND JOINT FLEXIBILITY

A thorough understanding of modal characteristics of vibrating manipul ators is essential for improved dynamic positioning accuracy. Presente d in this work is an extensive investigation of a cylindrical manipula tor, consisting of a revolute and a prismatic joint. In general, for h igh-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; a nd (4) the centrifugal stiffening effect due to the influence of inter nal axial force on the lateral stiffness. This work is intended to stu dy the effects of each of the above factors on modal characteristics o f the manipulator, and gives insight into the susceptibility of the mo dal parameters to each factor. In addition, joint flexibility has subs tantial influence on modal properties of a robotic system, depending o n the relative importance of joint torsional stiffness to the stiffnes s of other members, such as the bending stiffness of arms. In the situ ation where the manipulator moves at a high speed, both rigid-elastic coupling and centrifugal stiffening effects can become important. (C) 1997 Elsevier Science Ltd.