Variable Stiffness Robotic Hand for Stable Grasp and Flexible Handling

Saber Mahboubi,Samia Nefti-Meziani,Steven Davis

doi:10.1109/access.2018.2879633

Saber Mahboubi, Samia Nefti-Meziani + Show 1 more

Open Access

https://doi.org/10.1109/access.2018.2879633

Copy DOI

Journal: IEEE Access	Publication Date: Jan 1, 2018
Citations: 45	License type: CC BY 3.0

Affiliation: University of Salford

Abstract

Robotic grasping is a challenging area in the field of robotics. When interacting with an object, the dynamic properties of the object will play an important role where a gripper (as a system), which has been shown to be stable as per appropriate stability criteria, can become unstable when coupled to an object. However, including a sufficiently compliant element within the actuation system of the robotic hand can increase the stability of the grasp in the presence of uncertainties. This paper deals with an innovative robotic variable stiffness hand design, VSH1, for industrial applications. The main objective of this paper is to realize an affordable, as well as durable, adaptable, and compliant gripper for industrial environments with a larger interval of stiffness variability than similar existing systems. The driving system for the proposed hand consists of two servo motors and one linear spring arranged in a relatively simple fashion. Having just a single spring in the actuation system helps us to achieve a very small hysteresis band and represents a means by which to rapidly control the stiffness. We prove, both mathematically and experimentally, that the proposed model is characterized by a broad range of stiffness. To control the grasp, a first-order sliding mode controller is designed and presented. The experimental results provided will show how, despite the relatively simple implementation of our first prototype, the hand performs extremely well in terms of both stiffness variability and force controllability.

Highlights

The uncertainty associated with miscalculated grasp models and/or objects with unknown mechanical parameters create difficulties in performing a stable grasp
This is true in the human hand, as it has been demonstrated that the passive nonlinear dynamics of the joints in the human hand play a vital role in providing a stable grasp [1]-[7]
VARIABLE STIFFNESS HAND (VSH1) we introduce the design of a novel variable stiffness hand (VSH1) for industrial robotic manipulators, which can be used for stable grasps with unknown objects to be grasped, as well as to control the applied grip force in the absence of any accurate force sensor

Summary

Introduction

The uncertainty associated with miscalculated grasp models and/or objects with unknown mechanical parameters create difficulties in performing a stable grasp. Including a sufficiently compliant element within the actuation system of the robotic hand can provide an alternative solution to this challenge. Integrating such a passive component into a robotic system will increase the stability of the grasp in the presence of uncertainties. In-depth discussions about human hand grasping and human body impedance modulation can be found in [1]-[8], to mention but a few Following these and other similar studies, a plethora of variable stiffness/compliance designs have been proposed for robotic systems over the last decade [9]-[18]

Objectives

Results

Conclusion