Estimation of Object Orientation Using Conductive Ink and Fabric Based Multilayered Tactile Sensor

Robots, either made from hard or soft materials, are being used increasingly for unknown object manipulation tasks in unstructured environments. To hold an object firmly and do the required task, the orientation of the object with respect to the robotic hand gripper is one of the necessary key information. Humans can sense the orientation of an object based on vision, kinesthetic sensation, or touch sensation. Similarly, robots shall also be able to estimate grasped object orientation just based on tactile sensing without knowing manipulator kinesthetic or kinematics. Existing sensors are mostly based on vision or rigid inertial measurement units (such as accelerometers, gyroscopes, magnetometers), which require additional setup and are typically not compliant with the arbitrary surfaces of the unknown obj ects. This paper discusses a new approach for object orientation estimation from a multilayered tactile sensor based on conductive silver ink and conductive fabric. Fabric based sensors are flexible and can confer to both hard and soft surfaces. Experimental results show that the tactile sensor developed is able to estimate the tilt angle without any information about manipulator kinematics.

I. Introduction

In robotic object handling tasks, the orientation of the object being handled is one of the important information required to plan and perform the task effectively. It helps in handling the object with a better grasp and in a more stable manner. Conventional methods to estimate object orientation use manipulator kinematics, vision based estimation [1], [2], gyroscopic sensors or inertial measurement units [3], which require additional setup and typically are not compliant with the arbitrary surfaces of the unknown objects. This paper proposes a human-like touch sensation based methodology to estimate the orientation of an object being manipulated using tactile information, without the need of manipulator kinematics. This is especially useful when it is difficult to get accurate manipulator kinematics (e.g., soft robots), to incorporate inertial measurement units or to utilize vision (e.g., cluttered underwater manipulations). Fig. 1

Conductive ink & fabric based multilayered tactile sensor - layered architecture