Dynamic Characteristics of Constrained Manipulators for Contact Force Control Design

Abstract

The authors present the results of eigenstructure analyses of the dy namics of several manipulator and environment configurations and discuss the implications for successful force controller design. The manipulator configurations considered include single rigid link, sin gle flexible link, two rigid links, and two flexible links. In all cases, the tip of the manipulator is in contact with a deformable environ ment. Particular emphasis is placed on the interaction between the structural stiffness of the manipulator link and the stiffnesses of the contacting regions of the manipulator tip and the environ ment. It is shown that, for given link parameters, this interaction results in distinct changes in the modal structure of the manipula tor/environment system as the effective contact stiffness increases. In particular, the contact force response is dominated by a single mode for a given effective contact stiffness, whereas the control inputs excite all modes except those associated with the contact region vibration. The changes in the modal structure of the manip ulator/environment system predicted by the eigenstructure analysis are verified by experiment for the single flexible link configuration.