Faculty Collaboration Database

An optoelectric plantar "shear" sensing transducer: design, validation, and preliminary subject tests. IEEE Trans Rehabil Eng 1996 Dec;4(4):310-9

Date

12/01/1996

Pubmed ID

8973957

DOI

10.1109/86.547932

Scopus ID

2-s2.0-0030475093 (requires institutional sign-in at Scopus site)   24 Citations

Abstract

A prototype miniature plantar shear sensing transducer was developed, characterized, and tested in this study. Electro-optical components were chosen for the design because of the fast response time, low cost, small size, low power requirements, and adaptability to this application. The optoelectric circuit employed a 660 nm wavelength light source and photodiode solar cell. Signal amplification and sensitivity were adjusted to provide an output voltage proportional to light power. The sensor shell was designed to encapsulate the electro-optical sensing components while providing mechanical resistance to shear through a spring mechanism. A naval bronze was chosen for the shell due to its strength and nonreflective characteristics (alloy of copper and tin). Static and dynamic characteristics of the shear sensor were determined through a series of calibration tests. Mechanical crosstalk sensitivity ranged from 14.34 to 30.51 mV/N. This represented 1% full-scale/Newton sensitivity. Nonlinearity averaged 5.6% in the forward direction and 7.6% in the reverse direction. Overall sensor output hysteresis was 1.1 +/- 3.1% while the natural frequency of the sensor to an input shear transient was approximately 5 Hz. Temperature sensitivity was -7.0 mV/degree C or 3.5% full-scale/degree C. Testing of five adult subjects revealed peak anterior-posterior shear ranging from 6.7 kPa (posterior heel) to 51.4 kPa (great toe) and medial-lateral shear ranging from 5.4 kPa (great toe) to 43.5 kPa (first metatarsal head). Stress-time integral values ranged from 0.78 kPa-sec (posterior shear at the posterior heel) to 37.3 kPa-sec (medial shear at the posterior heel). Contact durations ranged from 0.28 sec (posterior shear at the posterior heel) to 1.25 sec (medial shear at the posterior heel). Further application of the sensor for plantar shear characterization in able-bodied subjects and those with pathology is suggested.

Author List

Lebar AM, Harris GF, Wertsch JJ, Zhu H

Authors

Gerald F. Harris Emeritus Professor in the Orthopaedic Surgery department at Medical College of Wisconsin
Gerald Harris PhD Director in the Orthopaedic Research Engineering Center (OREC) department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adult
Biomechanical Phenomena
Electric Stimulation
Equipment Design
Gait
Humans
Models, Theoretical
Reproducibility of Results
Sensitivity and Specificity
Stress, Mechanical
Transducers
Transducers, Pressure