Robust arm configuration of manipulator mounted on flexible base

We consider the robustness of a manipulator mounted on a flexible base with direct positioning error feedback control. Based on the positive realness of the transfer function matrix, we define the robust arm configuration which is a kind of singular configuration where the system is passive. We show that the system shows good robustness in the neighborhood of this robust arm configuration. We propose a measure which indicates the distance from the robust arm configuration. We also show that the robustness is closely related with the robust stability margin by the normalized coprime factor description. The validity is confirmed by numerical examples. The method is applied to a flexible assembly system consisting of a manipulator and two moving tracks.