Assembly task based on tri-axial tactile data using loose grip

The optical three-axis tactile sensor has attractive characteristics such as three-axis force distribution measurement, resilience against impact force, and flexible contact. In this paper, we demonstrate the usefulness of this tactile sensor in humanrobot collaboration and communication through a simple assembly task. In the task, we include two new skills that cannot be performed without three-axis tactile sensors: one of them is loose grip status; the other is to use an object grasped by a hand as a sensor. To accomplish these skills, we perform a series of basic experiments: one of them is the loose grip test, in which a hand-arm robot grasps a stick horizontally and then releases its grasping force to make the stick attitude vertical; the other is hole search tests, in which the hand-arm robot grasps a stick like a cane to search for a hole on a plate by sliding the stick on the plate and evaluating variation in moment measured by the tactile sensor. In the verification, the hand-arm robot assembles an arch composed of two columns, a top beam and a base through triaxial data obtained from the three-axis tactile sensor.