Geometry Optimisation of a Hall-Effect-Based Soft Fingertip for Estimating Orientation of Thin Rectangular Objects.

Rosle Rosle,Hirai Hirai,Wang Wang

doi:10.3390/s19184056

Abstract

Soft tactile sensors have been applied to robotic grippers for assembly. It is a challenging task to obtain contact information and object orientation using tactile sensors during grasping. Currently, the design of Hall-effect-based tactile sensors to perform such tasks is based on trial and error. We present a method of investigating the optimal geometrical design of a cylindrical soft sensor to increase its sensitivity. The finite element model of a soft fingertip was constructed in Abaqus with two design variables, i.e., hollow radius and magnet position. Then, the model was imported into Isight, with the maximisation of magnet displacement as the objective function. We found that the optimal design was at the boundary of the parameter design space. Four fingertips were fabricated with one intuitive, one optimal, and two optional sets of parameters. Experiments were performed, and object orientation was estimated by utilising linear approximation and a machine learning approach. Good agreements were achieved between optimisation and experiments. The results revealed that the estimated average error in object orientation was decreased by the optimised fingertip design. Furthermore, the 3-axis forces could successfully be estimated based on sensor outputs.

Highlights

Tactile sensation plays an important role in providing crucial information about the features of contacted objects for robotic systems that perform assembly tasks in uncertain environments
Research has been conducted on tactile sensors in recent years, such as a flexible tactile sensor that uses a magnetorheological elastomer [1], a tactile sensor for a wire insertion task [2], soft inductive tactile sensors based on the
Robotic gripper needs to grasp at the edge of thin circuit boards since the sensitive and small electronics parts are commonly placed on the board surface

Summary

Introduction

Tactile sensation plays an important role in providing crucial information about the features of contacted objects for robotic systems that perform assembly tasks in uncertain environments. In this rapidly advancing field, the integration of soft tactile sensors with robotic grippers provides a robot system with the advantage of interacting with and perceiving a handled object precisely for successfully performing assembly tasks. A distributed robotic tactile sensor capable of estimating 3-axis applied forces has been introduced in [5]. Designing tactile sensors that can stably grasp and estimate the orientation of thin rectangular objects, such as handling thin circuit boards in the electrical and electronics industry, is a challenging task. The orientation of the objects may vary during the grasping and assembling

Methods

Results

Conclusion