Experimental Testing of a Prototype of an Active Elbow Orthosis Based on in vivo Investigation of Elbow Flexion/Extension of Healthy Subjects

Abstract

Many people have problems with elbow joint driving because of different diseases, sport trauma, road traffic injuries, etc. A good way for restoring elbow motions is a self-rehabilitation using an active orthosis. It has to be light, convenient for daily use, active, easy to control by patients, and safe. The paper presents a prototype of an active elbow orthosis. The plastic details were designed using a CAD system and were 3D printed. The joint was driven by a Dynamixel actuator. To increase the joint moment, a reduction gear-belt drive was constructed and applied. Experiments with six healthy subjects were performed using a Noraxon measuring system, aiming to investigate elbow joint angles in natural movements with four different velocities of elbow flexion and extension without and with a load of 0.5 kg in the hand. The four velocities (from very slow to very fast) were controlled by a specialized PC application. In order to achieve similar motions of the orthosis, the angle profiles were approximated so that the motion was between 10° and 120° because of electro/mechanical and software safety stoppers. Experiments were performed with the orthosis following the given angle profile without load and with a load of 0.5 kg. The results show that the orthosis’ forearm performs the given angle and angular speed profiles with enough precision.