Actuability of Underactuated Manipulators

Abstract

In this paper we study underactuated manipulator systems, which are composed of both active and passive joints. The study of underactuated systems is interesting for a variety of applications including space robots, hyperredundant robots, and mobile robots. When one or more joints in a normal manipulator system fail, control techniques for the resulting underactuated system can make use of dynamic coupling within the system for position control. In this paper, we define a performance measure for the motion of these underactuated manipulator systems. We call this performance measure actuability. Actuability is a measure of the ability of the actuators in a robot manipulator to cause acceleration of the end-effector. Based on this concept, we develop sensitivity analysis of the systems performance with respect to geometric and dynamics parameters of the robot. This investigation is significant for the design and control of an underactuated robot system.