New performance indices for 6R robots

In this paper we introduce four new posture-dependent performance indices for control. Two of them are based on an object-oriented metric in the workspace (end-effector dependent) and the other on a linearized approximation of direct kinematics (end-effector independent). All newly defined indices are invariant under rigid-body motions and similarities, they have a geometric meaning, and they can be computed in real time. We also give a geometric interpretation of the characteristic length.