Mechanical Designs of Active Upper-Limb Exoskeleton Robots

Introduction


This report will explain the article written by Kazuo Kiguchi about the state of art and different difficulties on the designs of upper-limb exoskeleton robots. This document called Mechanical Designs of Active Upper-Limb Exoskeleton Robots and published at the IEEE \(11^{t}{}^{h}\) International Conference on Rehabilitation Robotics in 2009, explains the anatomy analysis necessary to develop this type of exoskeleton, their requirements and characteristics to be useful and the design obstacles at the moment of the conception. Also it explains the methods used to evaluate the performance of the exoskeleton and makes a review of different designs of active upper-limb exoskeleton robots developed.

Kazuo Kiguchi, professor in Systems and Control at Kyushu University, Doctor of Engineering specialized on Robotics and Biorobotics.

Context of the work


The upper-body driving system of a person makes him possible to manipulate objects and do the most part of the different tasks that an individual effectuates. Due to different reasons, as a physical disability or a lack of capacity, upper-limb exoskeleton robots have been subject of research from 1960s.

At the beginning the principal fields where this type of robots were studied to be applied were on industry and medical applications. The size and weight required to make them work properly limited their use as a structure where necessary to hold the complete system. The development and miniaturization made possible to create lighter systems without loosing the strength capable of transmitting to the user, this change the point of view of their uses and conceived the idea of adapting it to be carried by a human and make it portable.

Right now, research continues to provide more sophisticated systems with better features increasing their uses (industry, military, medical, rehabilitation,…) and approaching the line to the frontier of a complete useful upper-limb exoskeleton robot.

Positioning and contributions


Upper-limb anatomy


Before starting to construct any type of robot or prototype, it is necessary to analyze the behavior and characteristics of the upper-limbs of a human being. The main parts that shape the upper-limbs, as can be seen in the left part of Figure 1, are shoulder complex, elbow complex, wrist joint and fingers.

Shown in the center of Figure 1, it is possible to determine the different bones that are part of the shoulder complex that use the thorax as a base to stabilize [2]. The joints involved in this structure are the glenohumeral, connects the scapula and the humerus; the acromioclavicular, connects the clavicle and the scapula; the sternoclavicular, connects the shoulder to the axial skeleton; and scapulothoracic, a bone-muscle-bone articulation that connects the scapula to the thorax.

In the left part of Figure 1, it is shown the structure of the elbow complex. This system also includes the humeroradial joint, placed in between capitulum and radial head; and the humeroulnal joint, placed between trochlea and ulna. Also in the same part of Figure 1, the composition of the wrist and fingers can be studied. The wrist is formed by a group of eight small bones called carpals, it connects the hand with the forearm using multiple joints between the ulna and radius, and the carpal bones. This particular structure makes the wrist motions be considered to be around a instantaneous center.