Linear Electric Motor Applied to a Finger of Upper Limb Prosthesis

Resumo

This work puts forward the use of an electromechanical device in the linear motors category. Its application is in the finger of upper limb prosthesis as a translational actuator. This linear motor can substitute systems that use electric rotational motors, with planetary gears and lead screw transmission, to convert the rotational movement into linear. The main advantages of this scheme are the reduction in noise and the implementation complexity because of the small amount of moving components. Hybrid mechanisms like electro-pneumatic and electro-hydraulic actuators, which need energy sources different from electrical, can also be changed for linear electric machines. This paper describes linear electric motors focused on upper limb prosthesis applications and presents their advantages and disadvantages. Based on this study, the best option in the electric motor universe is selected and prototyped. Experimental measurements provided the motor's technical characteristics. They were according to the theoretical calculations. Then, the actuator was connected to the artificial finger to observe the closing movement in open-loop operation. The permanent magnet synchronous machine is the best choice for the studied application. It has high electromagnetic force with few oscillations, non-complex electric control to slow speed, and high efficiency. The experimental results are coherent with the calculated values. Besides, they show that the linear motor can attend to the force requirement and drive the artificial finger.