# Concept, Design, Initial Tests and Prototype of Customized Upper Limb Prosthesis
## 4 Discussion  
The research results presented in this paper are focused on the concept and design of a prosthesis for the upper limb.  
Customization of this prosthesis is an important issue. Due to the reverse engineering technique, size, dimensions, and other geometric characteristics of a real upper limb would  
Figure 26: Components of the 2-FPRINT prototype.  
Figure 25: Checking the geometric precision of the DLP printed parts. (**a**) Printed parts, (**b**) plug gauge check, (**c**) correct gear assembly for motion transmission, (**d**) bearings mounted.  
be achievable with this prosthesis. The 3D scan of the upper limb was performed for one of the authors of this paper. The reverse engineering technique enabled determining the value for any dimension, both in the transversal and horizontal planes. The design of this prosthesis would match, as much as possible, these dimensions, which are the ones of the scanned upper limb. This poses a real challenge for the concept and design of the mechanical components, as there is limited available space when considering the reverse engineered contour characteristics.  
The finger mechanism was studied from the point of view of kinematic and kinetostatic analyses. The matrix-vector method, aided by Matlab software, was used to determine the joint and fingertip trajectories. Simulation results for the finger mechanism evidenced correct motions.  
The command and control system is embedded and designed for customized applied mechatronics applications. The novelty of this concept is that for each of the five fingers, there are three micro-motors to generate motion (and not servomotors, as in most available myoelectric prostheses). The combination of software and hardware (the mechatronic system included) is specific to this prosthesis. It enables the accurate trajectory of the fingertips and different set rules (gripping pressure, object temperature, acceleration toward the object). The ROM of each joint will be defined once all the tests are completed, and the validation of the results will be performed.  
Preliminary testing of the sensors and micro-motors on a small platform, Arduino, was performed for the prototype (two fingers, 2-FPRINT). The conclusion from testing the resistive sensors pointed out the need for the careful selection of the base material, specifically the one for the fingers' surface. The upper limb prosthesis (whole product) will have its PCB, or micro-computer; will be versatile; and will be of small dimensions.  
The concept of this upper limb prosthesis is aimed at becoming a high-versatility hardware platform. Optionally, for example, a system for sound or vibration warning could be integrated if a visually impaired person was to need the prosthesis.  
Prototyping the mechanical components has been a challenge because of the high accuracy needed for the geometric precision of parts. Several techniques of rapid prototyping have been considered, out of which the DLP (Digital Light Processing) proved to be the right one.  
As, for the moment, only obtaining the prototype is intended, there is no ethical approval asked from any authorities. Later in time, after the prototype manufacturing is completed and all tests are correct, validation and, perhaps, IRB approval would be required.