Desenvolvimento de um dedo robótico acionado por atuador de liga com memória de forma.

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.