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Category: Prosthetic hand

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_1571321010, 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 I may also go history hunting, but the claim that a split hook is old or outdated, and that therefore by inference a prosthetic hand is automatically new or more modern, as an idea, is wrong, particularly technically speaking.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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Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]; published January 4, 2018, 14:29; URL: https://www.swisswuff.ch/tech/?p=8066.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]}}, month = {January},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8066}}


 


This is a blog post of one of the rare focused and well based scientific journal articles that really explains how real work, body powered and myoelectric arms relate and go together for a unilateral right below elbow amputee in a physically demanding work environment.

The prior presentation of this paper [poster at Cybathlon symposium 2016], which had been more pragmatically worded (with me thinking people would know anyway), this was now written up as article and published. During that process, the reviewers clearly made great points of all kinds of aspects I never knew were not sky clear to everyone.

So maybe, writing a ~ 30 page case study with > 210 references does clarify stuff, at least potentially and for those that actually read it. But possibly, it still requires attention to even just read it.

Knowledge does not come easy, Highlander! (Nakano, in: Highlander III The Final Dimension)

 

If you are more interested in visionary posts, read about the gadget features of the prosthetic arm in Kingsmen: The Golden Circle [link]. And technically, myoelectric control did have it coming. That technology remained uncool for four decades [link].

Publication [link]

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Scientific approach taken for implementing a successfully marketable microprocessor-controlled knee - history of Otto Bock C-leg [lessons for prosthetic arms?]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Scientific approach taken for implementing a successfully marketable microprocessor-controlled knee - history of Otto Bock C-leg [lessons for prosthetic arms?]; published January 2, 2018, 15:10; URL: https://www.swisswuff.ch/tech/?p=7790.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Scientific approach taken for implementing a successfully marketable microprocessor-controlled knee - history of Otto Bock C-leg [lessons for prosthetic arms?]}}, month = {January},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=7790}}


This blog post takes a few relevant observations, and assumptions, throws them up in the air and sees if they turn into sunshine.

  • If anything has brought us forward, it is also the ability to find relevant short cuts. We do not always have to invent the wheel when really we just want a variation of it.
  • If there is any acutal success story where academic research was required to leverage consumer market for a prosthetic limb, it is that of Otto Bock's C-leg.
  • If we can understand what the concepts are for getting a C-leg successfuly built, marketed and sold, we should be able to take generalized aspects of it to formulate success elements for prosthetic hands, grippers or arms.

Background

While the idea of a microprocessor controlled knee was created earlier [link], no marketable solution was available in due course. "In the early 1990s, Kelly James, an engineer at the University of Alberta, Edmonton, Canada, developed the C-Leg, the first leg with microprocessor-controlled swing and stance phases. Buying the rights from the university, he traveled around the world to interest prosthetic manufacturers in his invention ("A Leg Up," by Isabelle Gallant, U of A Engineer, Spring 2011). However, he didn't receive any commercial interest until German manufacturer Ottobock bought the patent in 1992 and launched the groundbreaking technology.".

Then, based on work betweeen 1995 and 1998, a doctoral thesis at the ETH Zurich described an intelligently, microprocessor controlled knee for above knee prostheses built from available and affordable materials [1].

That research was performed 1995 to 1998, financially supported by Otto Bock, and Otto Bock presented its first C-Leg in 1997.

The rest is history. If ever there was a leap in performance of prosthetic function, ever, it was the C-Leg. No prosthetic hand ever came close to achieving this level of success.

So this particular doctoral thesis seems to contain some possibly interesting ingredients worthwhile looking at. As any doctoral thesis here is public record, and a copy of it must be made available at the public library, I borrowed a copy for further information.

There are some other prosthetic developments, however, nowhere else is academic research anywhere near that successful as in the instance of the C-leg:

  • Otto Bock Michelangelo hand; the mechanism seems to come from American DARPA or other army research and probably was just built, the first glove was a great design work. So there is no analytical approach comparable to the C-Leg. It is too heavy, it does not work with prosthetic gloves really, it is not sturdy.
  • i-Limb: This cannot possibly have suffered too much analytical thought. The device looks more like it was born out of something else. While it does not always function as maybe intended, it is really lovable. It does not have a reliable precision grip, it is really weak, it tears up its paper thin gloves within minutes.
  • TRS prosthetics: Bob Radocy as end-user himself developed by far the greatest useful solutions. But they are not the result of extensive academic efforts, so they cannot be compared to the C-Leg. They are extremely good though and any analysis must start there.
  • Toughware PRX: These devices are extremely well made, mechanics wise - but we lack an analytical model that precedes the engineering there as well, comparing this to the C-leg approach.
  • Becker Mechanical Hand: Also the Becker hand was clearly built by someone with great practical and pragmatic understanding. No analytical effort of the magnitude of a C-Leg preceded it though.
  • Hosmer hooks: they came out of a practical development, no scholarly work appeared to be prepared for these either.

 

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[1] D. Zlatnik, "Intelligently controlled above knee prosthesis," PhD Thesis, 1998.
[Bibtex]
@phdthesis{zlatnik1998intelligently,
  title={Intelligently controlled above knee prosthesis},
  author={Zlatnik, Daniel},
  year={1998},
 school={ETH Zuerich, Switzerland}
}

Functional failures of prosthetic hands at the Cybathlon 2016 [details]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Functional failures of prosthetic hands at the Cybathlon 2016 [details]; published October 16, 2016, 13:23; URL: https://www.swisswuff.ch/tech/?p=7655.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Functional failures of prosthetic hands at the Cybathlon 2016 [details]}}, month = {October},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=7655}}


The Cybathlon 2016 was accompanied with publically broadcast video documentation of the event.

It is just not just as systematic as one would wish for a comprehensive research and development setting, but then, it was not an academic research event, but a publicity performance. But still, it contains a plethora of technical references.

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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_1571321010, 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 options and Yenga - intricate grip differentiation details [up close grip mechanics]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Prosthetic options and Yenga - intricate grip differentiation details [up close grip mechanics]; published June 14, 2016, 19:30; URL: https://www.swisswuff.ch/tech/?p=6144.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Prosthetic options and Yenga - intricate grip differentiation details [up close grip mechanics]}}, month = {June},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6144}}


Playing Yenga at a prosthetic arm workshop was interesting.

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iLimb glove self destructs (in-storage product suicide) [WTF]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - iLimb glove self destructs (in-storage product suicide) [WTF]; published February 15, 2016, 16:02; URL: https://www.swisswuff.ch/tech/?p=5651.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - iLimb glove self destructs (in-storage product suicide) [WTF]}}, month = {February},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=5651}}


During the last few weeks, I was wearing my "real prosthetic arm" (the one that works for work, the body powered arm) because real work is a bit too much for my "unreal prosthetic arm" (the "iLimb ultra revolution") for some reasons (I pulled weights of up to >100kg a few times, et cetera, I always wear my body powered arm and a Hosmer work hook for that, which however does work like a charm as that real prosthetic arm is geared towards these uses). I then let my skin recover and was not wearing any prosthetic arm for a bit after that.

With the effect that my "unreal prosthetic arm"  sat in the shelf for a few weeks.

There, as I found out when I wanted to put it back to use, it had committed in-storage product suicide. The glove had been put onto the hand on October 30th and the hand, since then, was not used more than a total of maybe 10-20 minutes, doing not much I guess.

Hand and glove all had been in what seemed to be good condition, and not damaged prior to this in-storage damage that the hand had inflicted unto the glove.

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iLimb Ultra Revolution - global news: a fitting work glove has been found [product tip]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - iLimb Ultra Revolution - global news: a fitting work glove has been found [product tip]; published May 25, 2014, 12:38; URL: https://www.swisswuff.ch/tech/?p=3072.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - iLimb Ultra Revolution - global news: a fitting work glove has been found [product tip]}}, month = {May},year = {2014}, url = {https://www.swisswuff.ch/tech/?p=3072}}


(Updated 10/2018)

Durability of iLimb gloves - given the overall iLimb's failure to really assist with hard grips [link] - is a bit of a joke anyway. Even though, prices are high for replacement gloves. Now, a work glove has been found that fits it.

This is global news as several user forums failed to elicit cogent answers. Also, a request to the prosthetist who allegedly had forwarded that problem to Touch Bionics also failed to elicit a useful reply. That means that, again, this website digs into uncharted terrain.

Again!?

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i-Limb ultra revolution [baking apple cake test]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - i-Limb ultra revolution [baking apple cake test]; published February 16, 2014, 19:44; URL: https://www.swisswuff.ch/tech/?p=2783.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - i-Limb ultra revolution [baking apple cake test]}}, month = {February},year = {2014}, url = {https://www.swisswuff.ch/tech/?p=2783}}


Trying to apply an i-Limb ultra revolution to bake an apple cake.

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BeBionic2 - new grip patterns [pictures]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - BeBionic2 - new grip patterns [pictures]; published November 2, 2011, 00:53; URL: https://www.swisswuff.ch/tech/?p=502.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - BeBionic2 - new grip patterns [pictures]}}, month = {November},year = {2011}, url = {https://www.swisswuff.ch/tech/?p=502}}


While the BeBionic and the iLimb shared a number of seemingly similar features the BeBionic2 seems to take things into its own hand. So to say.

Well, finally. Finally a modern prosthetic hand with really useful features. Great stuff. Now all we need are prosthetic sockets and wrists that allow for pin lock mounts and minimal wrist unit dimensions. I have a long stump and so do others. Only once these sockets are really comfortable will they be a real option to body powered arms. But, for now, BeBionic2 - great stuff to look at.

And that's not all. There are some activities that really make overuse symptoms of my left (remaining) hand worse. Using a mouse, using repeated trigger movements when spraying detergents, those sort of things are among the worst. They make my carpal tunnel syndrome come back. This is so far the only prosthetic hand and definitely the first prosthetic hand that seems to specifically look after specific manipulations of people in our society to improve health of my remaining hand.

Ah!!!! Sorry about that. But I was just kidding. But I could not resist ; )

With that, one should probably have a really good look at what the activities really are that strain and overuse the remaining hand and what activities the prosthetic really should be able to do or support.

Other than that, I wonder why no one came up with a simple positioning / click-action USB interface for the prosthetic arm - why using a single finger to operate a mouse, which, to an amputee, are two distinct expensive approximations and go-betweens? I mean, if you can avoid "clumsy", would you?

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Typing and posture [simple functional anatomy]

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Wolf Schweitzer: Technical Below Elbow Amputee Issues - Typing and posture [simple functional anatomy]; published August 25, 2011, 17:26; URL: https://www.swisswuff.ch/tech/?p=476.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Typing and posture [simple functional anatomy]}}, month = {August},year = {2011}, url = {https://www.swisswuff.ch/tech/?p=476}}


It has been alleged that typing is best done using a "bionic" prosthesis using an "extended finger". So I repost this observation [see post dating back to December 2009].

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BECKER Hands have an adaptive grip [what people don't know]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - BECKER Hands have an adaptive grip [what people don't know]; published August 14, 2011, 09:11; URL: https://www.swisswuff.ch/tech/?p=467.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - BECKER Hands have an adaptive grip [what people don't know]}}, month = {August},year = {2011}, url = {https://www.swisswuff.ch/tech/?p=467}}


1 Comment

BECKER Hands have an adaptive grip. This is something people don't know. To wear a Becker hand, all you need is a body powered arm.

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Ironing - one handed, or with prosthetic hook or hand [choice of iron]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Ironing - one handed, or with prosthetic hook or hand [choice of iron]; published July 23, 2011, 13:34; URL: https://www.swisswuff.ch/tech/?p=459.

BibTeX: @MISC{schweitzer_wolf_1571321010, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Ironing - one handed, or with prosthetic hook or hand [choice of iron]}}, month = {July},year = {2011}, url = {https://www.swisswuff.ch/tech/?p=459}}


A while back, I was asked to come up with footage to document how my prosthetic hook would work (or not work) when handling an iron and when ironing shirts [link].

It was then a question whether re-design of an iron would help people with prosthetic hooks. I have no idea why they restricted the research for industrial design to hooks. After all, there are far more people that live with one functioning hand after, say, strokes or paralysis than there are amputees.

Since then I started to trouble shoot the situation myself and found that with my steaming iron (regular plastic body steam iron), (a) the grip that was made of hard plastic also slipped out of my (non-disabled) hand, particularly when I was not paying attention, mostly because using the left hand for me is still awkward, (b) the iron was heavy no matter what hand or hook I was lifting it with, (c) its plastic housing broke when it fell because it was not built to last.

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