Design and development of low-cost exoskeleton hand robot structure

Number of people with traumatic injury related to hand amputation is rising up day by day and it causes them to experience a lot of problems, especially in performing their daily life activities. There are many prosthetic hands that have been developed to assist people to do the activities like a normal person. The feature of the hand robot structure is the main issues to be studied in order to construct a user-friendly and highperformance device. There are various considerations must be taken in order to identify the best type of material of the hand robot structure such as material durability, size, weight and fabrication cost. The objective is to present the static analysis of exoskeleton robotic hand structure for the evaluation on the selected material used such as aluminum and acrylonitrile butadiene styrene (ABS). From this, the effect of the material to the strength of the structure is observed. The 3D drawing and the static analysis of the hand robot structural design are performed by using Autodesk Inventor Professional software. The static analysis is focused on the safety factor evaluation of the structure by referring the ratio between the strength of the finger structure and the force (load) with a direction exerted on the tip of it. Hence, the maximum load withstood by the structure with the respective material can be determined. The results have shown that the maximum force that can be withstood by aluminum hand robot structure is much higher than ABS hand robot structure. The findings have shown that aluminum finger structure is able to withstand less than 3KG of load for no damage on the structure. Thus, the strength of robot structure is effected by the type of the material used and aluminum is more durable than ABS.

I. Introduction

There are over 350,000 numbers of registered disabled people under the Social Welfare Department and 34% of this number were registered under handicapped people which is physical disabilities such as upper limb amputees and paralysed [1]. Some of them experienced the upper limb amputees that caused by warfare, accidents or birth defects. These people went through a lot of problems in their daily life activities which involved the uses of hand such as grasping and lifting an object. Hence, several prosthetic hands have been developed that is similar to the actual human hand that can be controlled by myoelectric, kinematic and cosmetic prosthetic hand to sweep over this issue. In order to fulfil the characteristics, some aspects need to be considered such as material weight, material strength, material durability, and the cost of material. Metal is the most material used for the application due to its characteristics [2]. The strength of the material used in the structure can be determined by measuring the safety factor of the structure when a specific amount of force is exerted on it. A safety factor of the structure can be obtained by doing static analysis that is available in Autodesk Inventor Professional software. Thus, the most suitable material used in this application and the maximum force that can be withstood by the structure are obtained. In the robotic hand development field, ABS and aluminum are usually used for the robot structure and there are several robotic hands that use the ABS material for its structure such as HEXOES (Hand Exoskeleton with Embedded Synergies) and Cyber Hand [3], [4]. For Touch Bionics's i-LIMB aluminum is used [5].