Slip sensing and force control in robotic grasping

Abstract

In this work we have developed, demonstrated, tested and analysed a new robot fingertip sensor that is able to detect incipient object slip relative to the fingers. The sensor is inspired by its human equivalent, and consists of a finger bone together with a finger skin that is only attached to the bone at specific locations. The sensor is designed in a manner such that, when the fingertip forces are too low, slippage will always occur first between the inside of the skin and the bone. The resulting extension of the skin is detected and this enables the grasping forces to be increased before any gross slip occurs between the object and the skin. The sensor also has the capability to measure the absolute value of the applied grasping force at any time during the grasping process. The work also included a detailed dynamic analysis of the operation of the force/slip sensor during grasping, and the development of a versatile program to simulate the operation of the sensor. The simulation program was validated through experimentation. The model and simulation generated for the one-link analysis and was then extended to a three-fingered gripper. This simulation was used to investigate the behaviour of the incipient and gross slip when the gripper was loaded asymmetrically. Eventually this tool can be used to optimise the features of the three-link gripper prior to construction and interfacing.