Vibration-based Full State In-Hand Manipulation of Thin Objects

TL;DR

This paper introduces a vibration-based method for full in-hand manipulation of thin objects using simple parallel grippers, enabling control over the entire object state through cyclic motion and duty cycle modulation.

Contribution

It presents a novel cyclic excitation technique and an algorithm for manipulating the full object state, including orientation, with analytical validation and experimental demonstration.

Findings

Successful manipulation of object position and orientation

Validation through finite element analysis and experiments

Enhanced control accuracy via duty cycle modulation

Abstract

Robotic hands offer advanced manipulation capabilities, while their complexity and cost often limit their real-world applications. In contrast, simple parallel grippers, though affordable, are restricted to basic tasks like pick-and-place. Recently, a vibration-based mechanism was proposed to augment parallel grippers and enable in-hand manipulation capabilities for thin objects. By utilizing the stick-slip phenomenon, a simple controller was able to drive a grasped object to a desired position. However, due to the underactuated nature of the mechanism, direct control of the object's orientation was not possible. In this letter, we address the challenge of manipulating the entire state of the object. Hence, we present the excitation of a cyclic phenomenon where the object's center-of-mass rotates in a constant radius about the grasping point. With this cyclic motion, we propose an algorithm for manipulating the object to desired states. In addition to a full analytical analysis of the cyclic phenomenon, we propose the use of duty cycle modulation in operating the vibration actuator to provide more accurate manipulation. Finite element analysis, experiments and task demonstrations validate the proposed algorithm.