Under-Actuated Systems

Abstract

Techniques for the kinematics, dynamics and control of robotic systems largely focus on fully-actuated manipulators. Every degree of freedom is an active degree of freedom for these manipulators. That is, for each degree of freedom, there is an independent generalized force that can be applied by a control actuator. However, important applications involve manipulators with passive degrees of freedom, i.e., degrees of freedom with no corresponding control actuators. A passive degree of freedom can arise by design, due to actuator failure, during manipulation of artic- ulatable objects or due to modes of operation that avoid the use of some actuators [7]. We refer to manipulators with passive degrees of freedom as under-actuated manipulators, and for these systems the number of available control actuators (or, more specifically, the number of independent generalized forces) is less than the number of degrees of freedom.