Table 3: Comparison of the accuracy of the classifiers between the use of all data, EMG only and FMG only.
Classifier Model Validation
(EMG +FMG)
Test (EMG
+FMG)
Validation
(EMG)
Test
(EMG)
Validation
(FMG)
Test
(FMG)
Linear Discriminant
74,07 75,46 62,96 64,35 50,69 53,24
Quadratic SVM
89,35 87,96 79,28 75 65,16 68,06
Cubic SVM
89,24 87,96 79,4 79,63 70,49 70,37
Narrow NN
79,51 78,7 73,96 74,54 63,19 68,52
Medium NN
85,07 81,02 74,54 75 59,49 60,19
Wide NN
88,43 82,41 78,47 79,17 67,25 68,06
3.3 Bimodal vs EMG vs FMS Efficacy
In this section, we explore the impact of combining
EMG and FMG characteristics on the performance of
classifiers. To this end, the bimodal approach was
contrasted with the more common practice that uses
exclusively EMG characteristics. Table 3 details the
performance of the six classifiers indicated above,
when they use all characteristics, only EMG
characteristics and only FMG characteristics.
4 DISCUSSION
This paper presents preliminary results of the
implementation of a bimodal sys-tem with EMG and
FMG sensors in which two EMG+FMG pairs are
placed in the flexor and extensor muscles. A total of
thirty-six characteristics of these two acquired signals
were used for three healthy individuals, and the
dataset consisted of five different gestures. The main
objective of this study is to evaluate the benefit, in
terms of efficacy in the recognition of the gestures
performed, that is obtained by the acquisition of the
FMG signal simultaneously with the EMG signal,
because this signal when used in isolation has some
limitations that result, for example, from variations in
the impedance of the skin interface.
MATLAB's Classification Learner was used, thirty-
one classifiers were applied and a study was also
made on the possibility of reducing the number of
characteristics, which will be an important point to
reduce the processing time and consequently the
response time of the bionic hand in the execution of
gestures. For this, three different methods of selection
of the characteristics were used, with different
percentages (75%, 50% and 25%) of the total of
thirty-six characteristics.
The preliminary results presented focus on the
most used metric which is accuracy but the results are
also being analyzed with other metrics, namely, F-
score and the area under the ROC curve. It is possible
to verify how different classifiers have very different
behaviors, with those that are more effective but more
sensitive to the reduction of the number of
characteristics and others that are more immune to
this selection of characteristics.
Although this evaluation of the bimodal system is
still ongoing, the results presented here reinforce the
idea, supported by previous research, that the
combination of EMG and FMG allows to improve the
efficiency of machine learning models in gesture
recognition. So, as ultimate conclusion, this study
contributes to the field of myoelectric prostheses by
exploring the implementation and testing the
efficiency of a bimodal EMG/FMG signal acquisition
system for the control of a bionic hand.
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