procedure, enables building low-budget and user-
friendly sEMG solutions that may also be useful for
disabled people and amputees.
The main difference in the algorithmic part of
our approach with existing methods based on the
regression techniques (Roche et al., 2014; Hahne et
al., 2014; Fougner et al., 2014) is the use of an
artificial neural network performing the gesture
classification. The ANN is trained at the beginning
by a relatively small set of simple hand gestures:
seven or eleven gestures depending on the method
type. This allows avoiding long lasting tuning
process common for the regression approaches,
which stems from gradual sampling of changes of
muscle tension in different movements and their
combinations. Once the ANN has been trained, it
can detect commands for simulating the right and
left mouse clicks, and for moving cursor on the PC
screen. Using an estimate of the mean muscle effort
we have implemented a proportional control of the
cursor movement. Thus, the user can easily change
the cursor velocity and hence the movement
precision by “applying” more or less effort to the
gesture.
We have tested the method on twelve healthy
subjects of either sex. To do it we implemented two
types of the cursor controlling strategies: “rigid”
classes with four individual gestures for moving
right, left, up, and down; and "fuzzy" classes with
additional compound gestures for diagonal
movements. In both cases all subjects were able to
control cursor. Our experience suggests that the
fuzzy approach is potential preferable (see Fig. 5).
However, the experimental results have shown that
in average the controlling performance decreases for
this approach, despite a theoretically attractive
possibility to move the cursor diagonally.
The subjective evaluation of the user experience
has suggested that, on the one hand, the performance
reduction can be linked with the requirement to
perform unnatural gestures (for example
simultaneous wrist extension and ulnar deviation).
On the other hand, we can anticipate that in the
fuzzy case there may exist a competition in the
output layer of the ANN, which may have negative
influence on the cursor controlling function. Thus,
we can alert the reader on the necessity of future
research involving optimization of the set of gestures
and the ANN architecture.
In the present study specific features of the users
(e.g. the degree of fitness) have been left out due to
small size of the data set. However, the collected
data allow us foreseeing that the type of constitution
may play an important role in the success of the
human-computer interface. For example, Table 1
suggests that hypersthenics may show worst results,
though statistically significant conclusions require
additional experiments.
Another point for discussion is the user readiness
to a specific control of a PC by gestures. It is worth
noting that all subjects had no previous experience
in the use of such type of interfaces, while all of
them used the common mouse interface in their
daily life. Therefore, fair comparison between the
mouse and gesture types of interfaces requires either
special sampling over subjects (for example the use
of elderly, with no experience with PC) or training
subjects to use the MyoCursor system before testing.
An experiment with one user has shown that the user
training may improve significantly the ability to use
the fuzzy sEMG-interface in such a way that its
performance may approach the performance of the
mouse interface (92% vs 100% performance reached
in the test).
ACKNOWLEDGEMENTS
This work was supported by the Russian Ministry of
Education and Science under the Federal Program
(unique identification number RFMEFI58114
X0011).
REFERENCES
Baspinar, U., Varol, H. S., & Senyurek, V. Y. (2013).
Performance comparison of artificial neural network
and Gaussian mixture model in classifying hand
motions by using sEMG signals. Biocybernetics and
Biomedical Engineering, 33(1), 33-45.
Bottomley, A. & Cowell, T. (1964). An artificial hand
controlled by the nerves. New Scientist, 21, 668-71.
Chowdhury, A., Ramadas, R., & Karmakar, S. (2013).
Muscle computer interface: A review. In A.
Chakrabarti & R. V. Prakash (Eds.), ICoRD’13,
Lecture Notes in Mechanical Engineering (pp. 411-
421). Springer India.
Fougner, A., Stavdahl, O., Kyberd, P. J., Losier, Y. G., &
Parker, P. A. (2012). Control of upper limb prostheses:
terminology and proportional myoelectric control – a
review. IEEE Transactions on Neural Systems and
Rehabilitation Engineering, 20(5), 663-667.
Hahne, J. M., Biessmann, F., Jiang, N., Rehbaum, H.,
Farina, D., Meinecke, F. C., Muller, K. R., & Parra, L.
C. (2014). Linear and nonlinear regression techniques
for simultaneous and proportional myoelectric control.
IEEE Transactions on Neural Systems and
Rehabilitation Engineering, 22(2), 269-279.