Touch Hand Project

Overview

The AEDG Design team had been brought in to assist with upgrades to the Touch Hand project in preparation for a combined UKZN/NMU team's participation in the Cybathlon event originally intended for Zurich, Switzerland. The CoVid pandemic saw the event changed to an online event which was held in November at the Stopforth Research Lab at UKZN.

Up to this point, this collaborative project has seen an initial hand model designed and 3D printed (Mechatronics Masters: K Setty) with assistance from Rapid3D. This was then iterated by further design upgrades to its 4^th Design iteration, most recently to also include electronics & control systems (Mechatronics Masters: K Purdon) over the last few years.

The Cybathlon event requires the participating team and their amputee team member to carry out 24 predetermined tasks across 6 stations utilizing the Touch Hand-Socket prosthetic to complete these tasks, against other competing teams from across the globe. The UKZN/NMU team are the only African entry, so not only represent South Africa but the entire continent of Africa in this exciting tournament.

The initial task of the AEDG Design team was to further enhance the current design to make the Touch Hand even more proficient at its upcoming tasks as required by the Cybathlon, some of which are as intricate as picking up a matchstick, unbuttoning a jacket and tying a shoelace!...a serious challenge indeed.

As 2020 played out, this blog diary will keep you up to date on the progress of these design enhancements...

Initial Status

The Touch Hand (select link to read more) in its various versions had been in existence over several years now up to the point when the AEDG Team came on board in February 2020 to fast-track the preparation into the Cybathlon, as per the original brief attached to the original Masters outputs.

Previous UKZN iterations have functioned and have been tested as shown in the following photo-montage as tested by Prof Stopforth in his facility, so the basic potential was there...

However, the status of the NMU device as handed over, was that it was in pieces, and it was not functional at all iro its proposed purpose, nor in any remote way was the device ready to complete any of the functions as required by the Cybathlon competition. It had not been tested locally with an amputee, nor could it be in its current state, and furthermore, no-one at NMU could say that they had seen the device operational! This was not what we expected when we came on board, so the challenge immediately had grown into a monster...

Project Diary

As the initial project tasks were to balloon into different areas, we will consider progress in the various sectors as they occurred in parallel per month, so the diary makes a little sense...

2020 February

General

initial meetings to discuss hand functionality, electronics, Cybathlon tasks, acquire existing CAD models & documents, project plan preparation.
meeting with Dr Bryan Theunissen (Orthopaedic Surgeon) to discuss human hand physiology, dynamics & possible limitations in the current model iro carryng out its intended tasks
meeting with CustomWorks' Arno Seyfert to discuss implications & possibilities of introducing composite aspects to the current design iteration to aid lightweighting & stiffness of the structure, as well as the introduction of silicon formed layers to aid functionality.
initial assessment of current CAD models iro integrity and motion limitations.
project timeline and milestones established & tasks diseminated to team members.
the team was divided up into different groups to focus on task completion.

Design Challenges 01

The following design challenges were immediately evident:

the previous Masters projects had been focused on quite specific aspects of the functionality of the hand, and there had been little integration of these aspects into it's actual real-world physical hand or its function
in the existing physical model, there was huge play between the 'fingers' of the hand and the 'palm' so the initial sorting of this would be a priority task.
the 'thumb' on the hand was positioned unnaturally iro orientation and would have to be repositioned to achieve a proper closing effect
the current design needed improvements iro its aesthetics to be considered as a functional 'wearable'
there was no plan iro the connection of the hand to the socket, so a wrist design would have to be conceptualized and manufactured
there were several issues with the existing CAD models, some of which would have to be redrawn from scratch
the motor for the wrist area appeared to have not been spec'd properly which could turn out to be a serious stumbling block
the wrist was unsymmetrical resulting in the operating gear being placed at an offset to the attachment; that made it rotate in more like an arc to the center, this would’ve caused moments about the center, thus making it harder to rotate the wrist
after going through the tasks required by the Cybathlon event, it was found that the current design and finger positioning would mean that none of the required tasks would be achievable by the current design; an entire rethink on the structure of the hand would be needed

Hand Structure

Obvious challenges with the hand structure itself was the play that existed between the digits and the knuckle structure, so, as a first target, this was to be dealt with before any serious modifications could be considered.

Further issues were encountered with the CAD files - some of them were inaccessible, others were full of errors - effectively, Zaahid had to start from scratch with these, which enabled us to attack the redesign of the basic components as part of the process.

The 'index finger' was made thinner, sleeker and pointier, this allowed the finger to be less bulky and ensures a finer grip when completely closed.

The secondary 'ring finger' complex was made to look aesthetically better by becoming two joined fingers and also made less bulky, whilst still being actuated with one linear actuator. Angles between the fingers also had to be readjusted to accommodate proper fitment on closing.

The picture below shows the intermediate assembly of all the components; the thumb has been excluded for the time being while all play issues are sorted, and the thumb orientation angle must be changed and the thumb itself has to be redesigned in the next phase.

Wrist Structure

The wrist structure was thrust upon the team as an unexpected bonus(!) as the design and development of this was not part of the team's original involvement. However, we were able to kill two birds with one stone here, and include it into a project for the Design module, and both Jode Fourie and Daniel Trask were able to take on the challenge and get assessed for it academically as well.

Concepts

The initial challenge was to create concepts with the following global guidelines:

the wrist had to fit seamlessly into both the hand and the socket
it has to have aesthetically pleasing looks
it had to accommodate rotational re-positioning
it had to be modular - ie. it had to accommodate future upgrading capability and multi-level sophistication

with this is mind, the initial concepts produced were as follows:

Concept 1:

A spring loaded pin used to lock the hand and the arm.
The pin could be adjusted and locked in a different position to adjust the position of the hand.

Concept 2:

A multi-splined pin was made to allow for additional locking positions to give the amputee additional positions to move the hand to.
It is still spring loaded.

Concept 3:

A multi-splined cap was made to allow for additional locking positions to give the amputee additional positions to move the hand to.
It is still spring loaded.
The spring has been moved to the inside of the spline system.

Concept 4:

Motor powered wrist, works as a differential.
Two motors turn the top gears in either same or opposite direction, when turning in the same direction the bevel gears turn the whole wrist up or down.
When the motors turn in opposite directions the bevel gears spin the wrist around the rigid bevel gear at the bottom

These concepts would form the basis for decisions moving forward on the wrist.

Electronics & Control

This was to prove the most challenging aspect of the project initially as there was very little available information to our team members, and very little was forthcoming so it was like drawing blood from a stone! Extremely frustrating especially as we were trying to aid the whole process...

What we had was a structure in pieces, with a few dodgy actuators attached and no access to any additional info...co-operation in this regard was also significantly lacking. However, some progress occurred at the end of the month as six additional new actuators were ordered via Prof Stopforth's contacts which would hopefully get things moving along.

At this stage, we were largely restricted to reading up on the electronics on the schematic sheets of the Touch Hand 4.0...

Socket Attachment

The story of the Socket attachment is an entirely separate Design project and can be found at this link.