SILVA, A. F. C.; http://lattes.cnpq.br/0668602006899114; SILVA, André Fellipe Cavalcante.
Abstract:
This work is based on studies that demonstrate the high rate of
rejection by amputees to use prosthetic upper limbs due to various problems,
such as weight, high noise and lack of anthropomorphism. In this context, this
paper presents the development of a robotic finger whose activation is
performed by non-conventional actuators, which consist of Shape Memory Alloy
(SMA) wires. The mechanical structure of the robotic finger was designed using
a CAD computer program and then manufactured in ABS polymer through the
technique of rapid prototyping. The project was entirely based on physiological
characteristics of the human finger, and the proportions and the angles formed
by the phalanges. The activation of the finger is realized by inserting a Ni-Ti
SMA thin wire arranged at the bottom of the structure of the finger. When
activated by resistive heating through Joule effect, the SMA wire contract and
realize the flexion movement. It was developed a mechanical system so that the
SMA wires stay compact at the base of the finger, thus there was no need for
the creation of a forearm to accommodate the actuators. Orthodontic rubber
bands were used on the top of the finger to hold the extension movement. In
other words, the return of the finger occurs passively. To monitor the angles
formed by each phalanx, a system of image acquisition and processing was
implemented. This system was able to calculate the angles without the need for
installation of rotation sensors, leading to weight and volume reduction of the
prototype. This artificial vision system, that uses a simple camera with a control
technique based on fuzzy logic, proved to be extremely efficient in monitoring
the position of the robotic finger.