Configuration-Dependent Vibration Controllability of Flexible Arm Manipulators

Abstract

In some spatial flexible arm manipulators, the structural vibration controllability is configuration-dependent. Therefore, the flexible arm manipulator might have some vibration uncontrollable configurations. In order to understand the physical interpretation of vibration uncontrollable configurations, we propose the “modal accessibility” concept which indicates how well the actuators can affect the structural vibration modes. The configuration in which all actuators cannot affect at least one of the vibration modes of the manipulator is vibration uncontrollable. Main contributions of the paper are the following two points: First, interesting structural vibration uncontrollable configurations are found within the 2-link 3-joint type manipulator's workspace. Some of these vibration uncontrollable configurations are shown with experimental results. Secondly, the modal accessibility index is introduced to indicate how well the corresponding vibration mode is controllable. Experimental results show that even in the controllable configurations, it becomes difficult to suppress some vibration modes if their modal accessibility indices are small.