Two-Fingered In-Hand Object Handling Based on Force/Tactile Feedback

Abstract

This article describes a set of control algorithms for in-hand object handling using a parallel jaw gripper equipped with force/tactile sensors. The control strategy is model based and relies upon the limit surface concept. The LuGre friction model is combined with the limit surface method to set up a dynamic model of soft contact. The model is exploited to estimate the relative velocity of the object with respect to the fingers, so as to control the grip force to counteract possible slipping events due to external disturbances. Force/tactile feedback, the only perception source used by the algorithms, is suitably exploited not only for safe grasping of a variety of objects with uncertain weight and inertial properties, but also for in-hand manipulation actions, like object pivoting or gripper pivoting. Since the algorithm is based on the control of the object velocity, accuracy of the desired object positioning depends on the initial grasp configuration, as well as on the accuracy of the friction model parameters. Such manipulation skills are evaluated in the execution of various pick and place tasks typical of an in-store logistic scenario.