Global Planning for Dexterous Reorientation of Rigid Objects: Finger Tracking with Rolling and Sliding

We address global motion planning for quasi-static reorientation of convex objects (polyhedral and smooth objects) with a four-fingertip grasp. We make use of a simple humanlike manipulation strategy in which a single finger is moved at each instant while the other three are maintained fixed (with regard to the palm)—an extended version of the original finger-tracking scheme of Rus. This new version es sentially incorporates frictional rolling and sliding at the fingertips and deals with the related contact kinematics and quasi-static mo tion/force prediction issues. Our contribution is twofold. First, we describe an analysis showing that this extended scheme is suitable for reducing the space of the object motions, thereby making motion planning easier and operating on a search space of low dimension. Our second contribution is a planner that exploits such a search space reduction and applies the extended finger tracking at the core of a multilevel hierarchical framework to search for global reorien tation trajectories. The planner has been implemented and used for achieving several nontrivial frictional reorientation tasks that show the capabilities and the promise of our approach.