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Category: Grip testing

Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]; published February 11, 2019, 04:55; URL: https://www.swisswuff.ch/tech/?p=9322.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]}}, month = {February},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9322}}


I had evaluated, subjectively, the grip performance of various prosthetic options that I have. These have been already analysed in the context of grip taxonomy, where so far, research has largely focused on grip geometry as such, using some idiosyncratic logic that I found not too relevant.

Using a more relevant logic, I approached the question of grip mechanic from a different angle, both verbally and proverbially speaking: from a user angle, both actually geometrically and subjectively speaking.

I realized that most of my frequently used grips and grip situations fall into a far more narrow range of angle distributions than I had ever assumed.  So I sat down to add "typical object angles" to my already present grip success statistics over a list of my most frequently or typically used grips. Then I did that in theory and THEN I figured, why not go and video some. Thereby, a prosthetic hook as gripper device appears to be a lot more advanced, design wise, geometrically, in reducing device materials, bulk and design to approximate a really good overall use performance than the iLimb (which I have here also for as much testing as I like) and with that, many current commercial (or other) multi articulated hands.

In fact, prosthetic hands appear to be by far the older (and thus possibly less reflected) geometric design idea of a prosthetic arm's terminal device than the definitely more modern split hook. I may also go history hunting, but the claim that a split hook is old or outdated, and that therefore by inference a prosthetic hand is automatically new or more modern, as an idea, is wrong, particularly technically speaking. But also historically, to replace a hand with a hand is a straightforward design idea, that does not take any imagination, thus it is reportedly old, very old.

The far more elegant reduction, also of angles and controls, to fit into the limited action and option constraints of an arm amputee, is certainly that of a body powered split hook. It boils down the prosthetic needs to a successful sleek elegant reduction of a functional minimum, making it the ideal choice for anyone that wants a maximum of performance from a minimum of failure, cost, decay, bulk, futile grip attempts and total overhead. The subtle distinction is that a "body powered split hook" is an entirely different beast than a passive hook, obviously, which probably no one ever noticed, particularly not the people that assumed that a body powered split hook is best portrayed by installing a "Captain Hook" metaphor.

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Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]; published December 6, 2018, 08:37; URL: https://www.swisswuff.ch/tech/?p=8850.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8850}}


When I mention real work as opposed to work one does in the role of a pansy boy, I certainly mean this both seriously and tongue in cheek.

Only if you spend your days with real work will you ever understand. You will be dripping wet from sweating. Your clothes will be so entirely smelly from external causes. Your materials will be in dire need for cleaning ever so comprehensively. You have worked for many hours. And you will go back to do it all over again. A prosthetic arm that is built to last 3 years dies within 5 seconds, 15 minutes, or 2 months - using stock commercial parts, it burns and dies like paper consumed by a slow fire, component by component.

Welcome to the world of real work.

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How to apply wood screws in series - demonstration, difficulties [bench work]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - How to apply wood screws in series - demonstration, difficulties [bench work]; published October 26, 2018, 14:52; URL: https://www.swisswuff.ch/tech/?p=8717.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - How to apply wood screws in series - demonstration, difficulties [bench work]}}, month = {October},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8717}}


I happily cut and mounted two wooden boards into a pre-existing shelf frame. For that, a series of wood screws were put into place.

If you are interested in mount, assembly, and screws, read these earlier posts, too:

Dismantling, loading, transporting, unloading and reassembling shelf [bimanual, activity] {illustration, a peek into the life of a person with a handicap}

 

Drill a screw [1-handed way]

The ultimate bimanual task - the IKEA Pax wardrobe system with gliding doors [tricks,tips and yeehaw]

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Understanding and informing design issues of a prosthetic arm for below elbow amputation by way of "taxonomy" [literature review, reality check]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Understanding and informing design issues of a prosthetic arm for below elbow amputation by way of "taxonomy" [literature review, reality check]; published July 26, 2018, 21:18; URL: https://www.swisswuff.ch/tech/?p=7651.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Understanding and informing design issues of a prosthetic arm for below elbow amputation by way of "taxonomy" [literature review, reality check]}}, month = {July},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=7651}}


The academic and industrial attempts to approach prosthetic arms so far have been met with less success than the providers must have hoped for. Far less, in fact so little that we wonder what is going on.

Possibly, design issues are the key to this as however vaguely put, some analytic approach needs to inform better design - but how to really inform better design from issues based on analysis? What is a suitable analysis? If we cannot see any better designs anywhere in practice, real life, then what is the analysis worth? Can we analyze analyses to get a better understanding of what might be going on there?

We might best start with what we know to be true.

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TRS Prehensor [grip surface tweaking II]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - TRS Prehensor [grip surface tweaking II]; published May 25, 2017, 13:43; URL: https://www.swisswuff.ch/tech/?p=7381.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - TRS Prehensor [grip surface tweaking II]}}, month = {May},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7381}}


The TRS Adult Grip Prehensor is a bit like an American car. You may want to tune it, even try to tune it well, before you cant take it out  to really shine. Not literally "shine", though. Proverbially! Really I do not need this here to actually shine. It is totally OK if it just makes me look less bad, like, by supporting me, grip wise.

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Fotoserie - Herstellung und Aufbereitung einer Serie von Passteilen für PMCTA-Sets [photos]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Fotoserie - Herstellung und Aufbereitung einer Serie von Passteilen für PMCTA-Sets [photos]; published April 4, 2017, 15:55; URL: https://www.swisswuff.ch/tech/?p=7322.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Fotoserie - Herstellung und Aufbereitung einer Serie von Passteilen für PMCTA-Sets [photos]}}, month = {April},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7322}}


Herstellung von 3D gedrucktem PMCTA Equipment. Alle Teile wurden von mir selbst entworfen und gedruckt. TRS Prehensor im Einsatz.

Fotoserie für die Einreichung zum bgw-Wettbewerb.

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Grip strengths (measured results)

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Grip strengths (measured results); published January 18, 2017, 20:09; URL: https://www.swisswuff.ch/tech/?p=7085.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Grip strengths (measured results)}}, month = {January},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7085}}


Using a Camry EH101 electronic hand dynamometer, I went through a few prosthetic terminal devices for my arm to see just how strong they were. And I added a baseline for my (human) left hand and my (bare) stump.

This certainly provides a base for a range of discussions later. Or previous ones ; )

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Towards Extreme Cyborging (EC) microworks: very small things [grip mechanics theory, parametrization and then testing side by side - Trautman hook, Hosmer Mod 5 hook, TRS Prehensor, Touch Bionics iLimb revolution]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Towards Extreme Cyborging (EC) microworks: very small things [grip mechanics theory, parametrization and then testing side by side - Trautman hook, Hosmer Mod 5 hook, TRS Prehensor, Touch Bionics iLimb revolution]; published December 28, 2016, 17:52; URL: https://www.swisswuff.ch/tech/?p=7010.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Towards Extreme Cyborging (EC) microworks: very small things [grip mechanics theory, parametrization and then testing side by side - Trautman hook, Hosmer Mod 5 hook, TRS Prehensor, Touch Bionics iLimb revolution]}}, month = {December},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=7010}}


Small things to be picked up, side by side demo with other prosthetic devices.

Yes, very small things.

"It is the little things that count", they said. "The little things are important", they said. They all said that. But behold, their "bionic" apparatus cannot handle little things! "Why is a hook not evil", they wondered. And a storm of little demo videos came upon them. Deep into the myriad of grip mechanics this went.

"Get a grip on grips", he said.

This totally bypasses the fact that after laying down real life consequences for what I call Extreme Cyborging, I just finished building my first own steel Trautman hook, and all just with shape information from the internet. Yeah, you read that right. I did not build yet another one of the ubiquitous funny hands that promises to change my life or what it is these 3D printed hands now do - no. I sit on the demand and I sit on the technology and what is it that I do? See? This is what should really disturb you - because given the current signs of the times, it should feel deeply wrong on many levels. To you. But then, we were likely living on different planets all along, and maybe it is time you realize that too ; ) After we knew since years in detail what the Cybathlon showed us yet again, with glory but not with any improvement, it is yet again up to us, the users, to push further into what is, what can be, and what matters. And honestly? We have seen far enough funny hand videos.

What we have not seen is the Rebirth of The Cool. The Rebirth of an absolutely insane gripper. Physically. In 3D printed steel. The Trautman hook is such a device. And I went for it just because I can.
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Grip planning and carrying out [TRS Prehensor vs. iLimb Ultra Revolution - theory and practice]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Grip planning and carrying out [TRS Prehensor vs. iLimb Ultra Revolution - theory and practice]; published October 17, 2016, 17:49; URL: https://www.swisswuff.ch/tech/?p=6764.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Grip planning and carrying out [TRS Prehensor vs. iLimb Ultra Revolution - theory and practice]}}, month = {October},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6764}}


To reliably plan and successfully carry out a grip using a prosthetic hand or gripper, it helps having a few requirements met.

This is obviously not clear at this moment, as recent experiences at the Cybathlon show. All the same, others and myself have addressed various related grip aspects previously so this is something we can come back to.

So let us start by watching the iLimb hand trying to grasp a clothespin.

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TRS Prehensor [grip surface tweaking]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - TRS Prehensor [grip surface tweaking]; published October 16, 2016, 10:58; URL: https://www.swisswuff.ch/tech/?p=6722.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - TRS Prehensor [grip surface tweaking]}}, month = {October},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6722}}


The TRS Prehensor [manufacturer> TRS] is a great gripper, and recently smoked all myoelectric competition (at a prosthetic arm side by side race at the "Cybathlon", a public Circus event that the NCCR Robotics held for reasons that so far are not entirely understood at least from a prosthetic hand/arm user view).

A week has gone by since then, and still no public statement of the NCCR robotics organizers as to why body powered arm technology performed so much better than they anticipated, and worse, still no cogent clever research program drafted to successfully address prosthetic arm issues. Not a single tweet by Professor Riener and his team containing #cybathlon and #trsprehensor - so, in all sports and fairness, we are probably done with assuming this was all about sports. It wasn't, and the communications very clearly show that.

The biggest issue at this moment for robotic researchers now may probably be: why is this possible? What happened? Can we lay down the reasons for that? Because keeping on missing out on any deeper understanding there will likely cause similar problems in the future - and we do not want that again, do we. There are deeply intriguing answers to these pressing questions. It is just that who has time to wait for these people! What takes them so long!

"I waited for 30 years for robot engineers to build me a prosthetic arm so I could finally clean up my house. It became a real mess during all these years. Three decades is a long time, you know." - Anonymous

No peace for the wicked.

And so to clean up the house today, I used the TRS Prehensor. I massively intensified using it for many tasks since then. Now, I always like to use these opportunities to troubleshoot grips and see where I go with the result.

Wowoweewa!

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Der Cybathlon 2016 wurde bei den Armprothesen von einem Mann mit "Hook" gewonnen [#research #surprise #bodypowered]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Der Cybathlon 2016 wurde bei den Armprothesen von einem Mann mit "Hook" gewonnen [#research #surprise #bodypowered]; published October 11, 2016, 18:34; URL: https://www.swisswuff.ch/tech/?p=6670.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Der Cybathlon 2016 wurde bei den Armprothesen von einem Mann mit "Hook" gewonnen [#research #surprise #bodypowered]}}, month = {October},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6670}}


2 Comments

Ich weiss jetzt nicht, ob Sie das mitbekommen haben. Und ob Sie begreifen was da passiert ist.

Aber am Cybathlon 2016 (Cybathlon, ETH, NCCR Robotics), einer Art Behindertenschaulaufen ohne besonderen  wissenschaftlichen aber dafuer sehr publikumswirksamen Hintergrund [wieso/was:link] mit mehrheitlich durch das Patronat der ETH suggerierten "High-Tech-Hintergrund" gewann ein Mann das Armprothesenrennen, der einen "Hook" trug [siehe detaillierte Griffanalyse, link]. Arschcool, mit 67 ein Senior, dort auch klar der älteste.

Fehlerfrei und schnell.

bodypoweredclothespins

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Prosthetic hand and gripper options: grip analysis, grip construction [summary/post list]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Prosthetic hand and gripper options: grip analysis, grip construction [summary/post list]; published October 11, 2016, 12:36; URL: https://www.swisswuff.ch/tech/?p=6663.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Prosthetic hand and gripper options: grip analysis, grip construction [summary/post list]}}, month = {October},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6663}}


This website features a range of posts regarding grips and both analytic and constructive aspects. Here is a short overview of the most relevant.

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ADL learning and body powered prosthesis control [paper review]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - ADL learning and body powered prosthesis control [paper review]; published October 9, 2016, 11:42; URL: https://www.swisswuff.ch/tech/?p=6484.

BibTeX: @MISC{schweitzer_wolf_1569220968, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - ADL learning and body powered prosthesis control [paper review]}}, month = {October},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6484}}


Learning to use a body-powered prosthesis: changes in functionality and kinematics. Laura H. B. Huinink, Hanneke Bouwsema, Dick H. Plettenburg, Corry K. van der Sluis and Raoul M. Bongers. Journal of NeuroEngineering and Rehabilitation 2016 13:90.

Abstract [1]

Background: Little is known about action-perception learning processes underlying prosthetic skills in body-powered prosthesis users. Body-powered prostheses are controlled through a harness connected by a cable that might provide for limited proprioceptive feedback. This study aims to test transfer of training basic tasks to functional tasks and to describe the changes over time in kinematics of basic tasks of novice body-powered prosthesis users. Methods: Thirty able-bodied participants and 17 controls participated in the study, using a body-powered prosthetic simulator. Participants in the training group were divided over four groups and practiced during a 2-week-period either direct grasping, indirect grasping, fixation, or a combination of these tasks. Deformable objects with different compliances had to be manipulated while kinematic variables and grip force control were assessed. Functional performance was measured with the Southampton Hand Assessment Procedure (SHAP) prior to and after the training sessions, and after 2 weeks and 3 months retention. The control group only performed the SHAP tests. Results: All four training groups and the control group improved on the SHAP, also after a period of non-use. Type of training had a small but significant influence on the improvements of the SHAP score. On a kinematic level movement times decreased and hook closing velocities increased over time. The indirect grasping group showed significantly shorter plateau times than the other training groups. Grip force control only improved a little over training. Conclusions: Training action-perception couplings of body-powered prosthesis in basic tasks transferred to functional tasks and this lasted after a period of non-use. During training movement times decreased and the indirect grasping group showed advantages. It is advisable to start body-powered training with indirect grasping tasks but also to practice hook-object orientations. Keywords: Upper-limb prosthesis, Body-powered prosthetic

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[1] [doi] L. H. B. Huinink, H. Bouwsema, D. H. Plettenburg, C. K. van der Sluis, and R. M. Bongers, "Learning to use a body-powered prosthesis: changes in functionality and kinematics," Journal of NeuroEngineering and Rehabilitation, vol. 13, iss. 1, pp. 1-12, 2016.
[Bibtex]
@Article{Huinink2016,
author="Huinink, Laura H. B.
and Bouwsema, Hanneke
and Plettenburg, Dick H.
and van der Sluis, Corry K.
and Bongers, Raoul M.",
title="Learning to use a body-powered prosthesis: changes in functionality and kinematics",
journal="Journal of NeuroEngineering and Rehabilitation",
year="2016",
volume="13",
number="1",
pages="1--12",
abstract="Little is known about action-perception learning processes underlying prosthetic skills in body-powered prosthesis users. Body-powered prostheses are controlled through a harness connected by a cable that might provide for limited proprioceptive feedback. This study aims to test transfer of training basic tasks to functional tasks and to describe the changes over time in kinematics of basic tasks of novice body-powered prosthesis users.",
issn="1743-0003",
doi="10.1186/s12984-016-0197-7",
url="http://dx.doi.org/10.1186/s12984-016-0197-7"
}
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