Active Sensing of Static Friction Coefficient ^|^mu; for Controlling Grasping Force

摘要

There have been a number of slip sensors proposed and developed for controlling the grasping force of robot hands in order not to drop objects. However, detecting only slips is insufficient for control since it may be too late to increase the grasping force after detecting the object's slips and the friction system of the contact part changes to be dynamic. In the paper, we stress the necessity of detecting the static friction coefficient of the contact surface between an object and a robot hand, and describe the development of a sensor and an algorithm to detect the coefficient: The sensor mounted on the hand detects three-axis contact force components and acquires slip information due to stick-slip vibration at the contact surface. The algorithm to integrate the contact force and the slip information enables the robot to detect the static friction coefficient in the active motion of lifting the object with the hand. Further experiments verify that the proposed method in the study allows a two-fingered parallel hand to detect the static friction coefficient for various surfaces and demonstrate adaptive grasping force control of the hand in response to changes in the weight of the grasped object by using the detected static friction coefficient.