Interoperable Models for Dynamics and Shape Tracking of Soft Fingers

A lot of works highlight the soft material properties, used in grasping tasks by soft fingers. However, the kinematics as well as the dynamics of these soft fingers are strongly influenced by the material’s properties along their soft structure. Due to their compliance, the soft grippers are more often used to achieve form closure grasping which is safer than force closure grasping. One main issue related to soft grasping concerns the shape control of the finger, allowing obtaining perfect compliance when attempting a form closure grasping. In this work, we propose interoperable models based on Pythagorean Hodograph and Euler-Bernoulli’s beam dynamics to model both dynamics and shape of Fluidic Elastomeric soft fingers. This makes a relationship between the physical actuators and the virtual control points of the parametric Pythagorean Hodograph (PH) curve which drive the finger shape. The PH curve with its finite control points is used to model and control the kinematics of the shape of the soft fingers, characterized by an infinite degree of freedom (DoF). This modeling will allow controlling the position of the virtual control points of soft fingers. The results of this modeling are validated numerically and experimentally with a soft finger made up of Fluidic Elastomeric Actuators (FEA).

I. INTRODUCTION

In recent years, advances in materials science applied to mechanics and mechanical design have allowed us to propose better alternatives for robotic manipulations [1]. However, identifying and controlling the optimal shape of soft robots present a challenging topic. This requires some form of actuation computation of the soft robot gathering conventional control methods and motion planning.