European Journal of Scientific Research - EuroJournals

Development of Mechanical Prosthetic Hand System for BCI Application 866
Figure 3: Prosthetic finger
Each phalanx is made from 2-parallel aluminum plate of 1.5mm thickness and join using a
brass spacer bolted with 2mm diameter stainless steel screw. DC motors with the combination of
reduced gear heads are used to actuate finger segments. Process of determining the length of the
phalanx acquired the implementation of the Fibonacci sequence. Fibonacci sequence in application to
the human hand stated that; the difference between the length of the next phalanx and the sum length of
the two prior phalanges must equal to zero. The sum of the distal phalanx and the middle phalanx
should be equal to the length of the proximal phalanx. However, Park et al [6] in his work has showed
that the bone lengths of the finger does not follow the Fibonacci relationship but the motion paths of
the digits still form an equiangular spiral path. Therefore to achieve the equiangular spiral motion path
the respective length that representing each segment should include the absolute bone length and
functional length (radius of the joint). Length of each segment was referred to author’s hand herself
and using the Hamilton’s ratio [7] to verify that the chosen length is sufficient to form an equiangular
spiral motion.
All the fabrication and machining process was done in the mechanical workshop in the
Department of Mechanical Engineering, University of Malaya, Malaysia. The precise machining was
carried out using a CNC (computer numerical control) wire EDM (electrical discharge machining)
machine Sodick, available in the Department of Manufacturing and Design, University of Malaya,
Malaysia.
3.0. Result
A prototype of prosthetic hand was successfully fabricated and tested for functionality, performance
and strength. Figure 4 shows the flow diagram of a BCI system to control prosthetic hand developed by
Biomedical Engineering BCI group, University of Malaya. A fuzzy controller is used to control the
prosthetic hand. Input for controller is fed from the BCI box. EEG signals acquired from subject is
amplified and converted to digital signal. The signal is further process and classified before send to
fuzzy controller.