Magnetic-based Soft Tactile Sensors with Deformable Continuous Force Transfer Medium for Resolving Contact Locations in Robotic Grasping and Manipulation.

Alireza Mohammadi,Denny Oetomo,Peter Choong,Ying Tan,Yangmengfei Xu

doi:10.3390/s19224925

Abstract

The resolution of contact location is important in many applications in robotics and automation. This is generally done by using an array of contact or tactile receptors, which increases cost and complexity as the required resolution or area is increased. Tactile sensors have also been developed using a continuous deformable medium between the contact and the receptors, which allows few receptors to interpolate the information among them, avoiding the weakness highlighted in the former approach. The latter is generally used to measure contact force intensity or magnitude but rarely used to identify the contact locations. This paper presents a systematic design and characterisation procedure for magnetic-based soft tactile sensors (utilizing the latter approach with the deformable contact medium) with the goal of locating the contact force location. This systematic procedure provides conditions under which design parameters can be selected, supported by a selected machine learning algorithm, to achieve the desired performance of the tactile sensor in identifying the contact location. An illustrative example, which combines a particular sensor configuration (magnetic hall effect sensor as the receptor, a selected continuous medium and a selected sensing resolution) and a specific data-driven algorithm, is used to illustrate the proposed design procedure. The results of the illustrative example design demonstrates the efficacy of the proposed design procedure and the proposed sensing strategy in identifying a contact location. The resulting sensor is also tested on a robotic hand (Allegro Hand, SimLab Co) to demonstrate its application in real-world scenarios.

Highlights

The resolution of contact locations is an important feature required in many robotics applications involving grasping and manipulation [1,2]
In the context of robotic grasping and manipulation, the knowledge of the location of contact with the object is very important in validating the grip configuration, evaluating the satisfaction of wrench closure condition, allowing the robot to adjust its grip on an object to reject
This paper focuses on the systematic design and characterisation procedure when the location of the contact force is needed for a large class of magnetic-based tactile sensors with a continuous force-transfer deformation medium

Summary

Introduction

The resolution of contact locations is an important feature required in many robotics applications involving grasping and manipulation [1,2]. In the context of robotic grasping and manipulation, the knowledge of the location of contact with the object (i.e., where contact force is applied by the object to the robotic hand/gripper) is very important in validating the grip configuration, evaluating the satisfaction of wrench closure condition, allowing the robot to adjust its grip on an object to reject. Due to the complexity of the manipulation tasks, model-based methods utilising force/torque sensors to detect the location of the applied contact force have not been shown to be robust [10,11]. It is, necessary for tactile sensors to be developed to identify locally the contact locations of the object with the robot/gripper. In terms of the medium of detection mechanism for contact localisation, tactile sensing methods may be classified into two main approaches: (1) using an array of discrete individual tactile receptors, where the contact location is identified by which individual receptor is triggered, and (2)

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Conclusion