Sensor Integrated Load-Bearing Structures: Measuring Axis Extension with DIC-Based Transducers

Nassr Al-Baradoni,Peter Groche

doi:10.3390/s21124104

Abstract

In this paper we present a novel, cost-effective camera-based multi-axis force/torque sensor concept for integration into metallic load-bearing structures. A two-part pattern consisting of a directly incident and mirrored light beam is projected onto the imaging sensor surface. This allows the capturing of 3D displacements, occurring due to structure deformation under load in a single image. The displacement of defined features in size and position can be accurately analyzed and determined through digital image correlation (DIC). Validation on a prototype shows good accuracy of the measurement and a unique identification of all in- and out-of-plane displacement components under multiaxial load. Measurements show a maximum deviation related to the maximum measured values between 2.5% and 4.8% for uniaxial loads ( and between 2.5% and 10.43% for combined bending, torsion and axial load. In the course of the investigations, the measurement inaccuracy was partly attributed to the joint used between the sensor parts and the structure as well as to eccentric load.

Highlights

In the state of the art, traditional strain gauge-based sensors dominate the field of multi-axis force/torque sensors
Considering the increasing research on multifunctional sensory structures, e.g., sensor-integrated metallic load-bearing structures such as in [9,10], the high cost and space requirements for the whole measuring chain seems to hinder the research in the integration of multi-axis force/torque sensors into such structures
In the present study we investigated the principal applicability of a camera-based sensor as a structurally integrated multi-axis force/torque sensor within the framework of a prototype

Summary

Introduction

In the state of the art, traditional strain gauge-based sensors dominate the field of multi-axis force/torque sensors In such measuring techniques, key sensor properties, such as sensitivity, sensor accuracy, measuring range and crosstalk between the measuring axes, depend significantly on the deformation behavior of the spring element and on the sensitive elements [1]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations Such as capacitive [12] or optical transducers, are being investigated primarily with the aim of providing a cost-effective and miniaturizable alternative to conventional strain gauge-based transducers. Optical-based non-contact sensors have gained special attention They stand out due to low-cost, simple design and encourage structural integration by eliminating the spring element as well as miniaturization.

Methods

Results

Conclusion