Design and development of a fiber bragg grating-based technique for interface pressure measurement inside below-knee prosthetic sockets / Ebrahim Ali Ahmed Al-Fakih
Limb amputation is a surgical procedure performed to remove a whole or a part of a limb in an attempt to save the residual limb from any further damage. Amputees typically use artificial limbs (also called “prostheses”) as rehabilitation tools to restore their daily activities and cosmetic appear...
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| Format: | Thesis |
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2015
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| Online Access: | http://studentsrepo.um.edu.my/7193/ http://studentsrepo.um.edu.my/7193/4/All.pdf http://studentsrepo.um.edu.my/7193/1/PhD_Thesis_(Ebrahim_Al%2DFakih)%2D_KHA110090.pdf |
| Summary: | Limb amputation is a surgical procedure performed to remove a whole or a part of a
limb in an attempt to save the residual limb from any further damage. Amputees typically
use artificial limbs (also called “prostheses”) as rehabilitation tools to restore their daily
activities and cosmetic appearance. Unfortunately, almost all amputees are dissatisfied
with their existing prostheses because of the poor fitting of prosthetic sockets. Despite the
considerable advances in the pressure measurement techniques employed over the past
five decades to map pressure distribution within prosthetic sockets, these techniques still
exhibit several limitations, including their bulkiness (i.e., strain gauge transducers) and
vulnerability to hysteresis, drift, and creases (i.e., piezoresistive and capacitive
transducers). Therefore, developing a new technique that offers valid and reliable pressure
measurement within prosthetic sockets is deemed necessary to help prosthetic
professionals fabricate better-designed sockets that provide a good fit and amputee’s
satisfaction. This research aims to investigate the feasibility of optical fiber Bragg grating
(FBG) sensors as a potential alternative to the aforementioned techniques to spot peak
pressures within prosthetic sockets. First, a single FBG flexible sensing pad was designed
and evaluated at the anterior proximal region of the residual limb to assess its performance
in dynamic conditions. This sensor was tested in real time by inserting a heavy-duty
balloon into the socket and inflating/deflating it using an air compressor to mimic the
actual amputee’s gait. Promising results in terms of sensitivity, accuracy, and hysteresis
were obtained. These findings encouraged me to fabricate a series of FBG sensing pads
with full consideration of three key fabrication parameters: different FBG embedding
depth, sensing pad thickness, and host material hardness. Results revealed that the FBGs
embedded in the neutral layer of hard and thick sensing pads exhibited the highest
sensitivity and excellent accuracy. This concept was subsequently employed to fabricate
four new expandable sensing pads with at least two sensing sites each to cover the proximal and distal sub-regions of each socket aspect. An amputee was involved to
evaluate the in situ performance of this technique. The results were compared with the
pressure measurements obtained using the commercially available F-socket sensors to
validate the findings. The results revealed the advantages of the new sensor design as it
could successfully detect all the events of an amputee’s gait. Higher pressure values were
logged by the FBG sensors compared with the F-socket, which was attributed to the
thickness of the sensor. However, the trend on pressure changes was similar for both
sensor types. Eliminating the thickness drawback was achieved by embedding an array
of FBGs within a custom fabricated silicone liner that is typically inserted in prosthetic
sockets to cushion the transfer of loads from the socket to the residual limb. This FBG instrumented
liner was designed so it could function both as a cushioning material and a
sensing tool. No previous studies have implemented such a technique in prosthetic
applications. Therefore, this research was the first investigation into the potential use of
such a technique in prosthetic applications. |
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