Fail of the Week: Good Prosthetic Hand Design Goes Bad

Is this a case of a good design gone wrong in the build phase? Or is this DIY prosthetic arm a poor design from the get-go? Either way, [Will Donaldson] needs some feedback, and Hackaday is just the right place for that.

Up front, we’ll say kudos to [Will] for having the guts to post a build that’s less than successful. And we’ll stipulate that when it comes to fully articulated prosthetic hands, it’s easy to fail. His design is ambitious, with an opposable thumb, fingers with three phalanges each, a ball and socket wrist, and internal servos driving everything. It’s also aesthetically pleasing, with a little bit of an I, Robot meets Stormtrooper look.

But [Will]’s build was plagued with print problems from the start, possibly due to the complex nature of the bosses and guides within the palm for all the finger servos. Bad prints led to creaky joints and broken servos. The servos themselves were a source of consternation, modified as they were for continuous rotation and broken apart for remotely mounting their pots in the hand’s knuckles. The video below relates the tale of woe.

There’s a lot to admire with [Will]’s build, but it certainly still has its issues. He’s almost to the point of other more successful DIY hand builds but just needs a little help. What say you in the comments line? Continue reading “Fail of the Week: Good Prosthetic Hand Design Goes Bad”

Three Thumbs, Way, Way Up!

At least one in their lives — or several times a day — everyone has wished they had a third hand to help them with a given task. Adding a mechanical extra arm to one’s outfit is a big step, so it might make sense to smart small, and first add an extra thumb to your hand.

This is not a prosthetic in the traditional sense, but a wearable human augmentation envisioned by [Dani Clode], a master’s student at London’s Royal College of Art. The thumb is 3D-printed out of Ninjaflex and mounted to a printed brace which slides over the hand. One servo rotates the thumb, and a second pulls it closed using a bowden cable system — not unlike that of a bicycle brake. Control of the thumb is achieved by pressure sensors in the wearer’s shoes, linked via Bluetooth to a wristband hosting the servos and the electronics. We already use our hands and feet in conjunction, so why not capitalize on this intuitive link?

Continue reading “Three Thumbs, Way, Way Up!”

Hackaday Prize Entry: Open-Source Myoelectric Hand Prosthesis

Hands can grab things, build things, communicate, and we control them intuitively with nothing more than a thought. To those who miss a hand, a prosthesis can be a life-changing tool for carrying out daily tasks. We are delighted to see that [Alvaro Villoslada] joined the Hackaday Prize with his contribution to advanced prosthesis technology: Dextra, the open-source myoelectric hand prosthesis.

dextra_handDextra is an advanced robotic hand, with 4 independently actuated fingers and a thumb with an additional degree of freedom. Because Dextra is designed as a self-contained unit, all actuators had to be embedded into the hand. [Alvaro] achieved the necessary level of miniaturization with five tiny winches, driven by micro gear motors. Each of them pulls a tendon that actuates the corresponding finger. Magnetic encoders on the motor shafts provide position feedback to a Teensy 3.1, which orchestrates all the fingers. The rotational axis of the thumb is actuated by a small RC servo.

mumai_boardIn addition to the robotic hand, [Alvaro] is developing his own electromyographic (EMG) interface, the Mumai, which allows a user to control a robotic prosthesis through tiny muscle contractions in the residual limb. Just like Dextra, Mumai is open-source. It consists of a pair of skin electrodes and an acquisition board. The electrodes are attached to the muscle, and the acquisition board translates the electrical activity of the muscle into an analog voltage. This raw EMG signal is then sampled and analyzed by a microcontroller, such as the ESP8266. The microcontroller then determines the intent of the user based on pattern recognition. Eventually this control data is used to control a robotic prosthesis, such as the Dextra. The current progress of both projects is impressive. You can check out a video of Dextra below.

Continue reading “Hackaday Prize Entry: Open-Source Myoelectric Hand Prosthesis”

Cyborg Olympics is Coming this Fall

You heard right. There’s a team of scientists in Europe who are arranging the world’s first Cyborg Olympics, called the Cybathlon. Hosted in Zurich this October, it aims to help gauge the performance and advancement in the latest developments of prosthesis and other devices that can augment human ability beyond what is considered normal or baseline.

The best example of this is [Oscar Pistorius] — the man with fiberglass spring legs. He’s a double amputee who can run at an Olympic level — or maybe even faster. With the Cybathlon, his prosthesis would not only be accepted, but encouraged to help demonstrate and further the technology by adding a competitive angle to the companies manufacturing them.  Continue reading “Cyborg Olympics is Coming this Fall”

Hackaday Prize Entry: OpenBionics

For the last few years now, the 3D printing community has been searching for a groundbreaking application for out little boxes of plastic squirting goodness. On of the most interesting applications the community has stumbled upon is prosthetics.

There have been a lot of people warming up their 3D printers and laser cutters to make prosthetic limbs in recent years. For [OpenBionics]’ entry for The Hackaday Prize, they’re building a prosthetic hand that costs less than $200, weighs less than 300 grams, and can be easily fabricated with 3D printers and laser cutters.

The human hand is the most complex end-effector on the planet, and emulating its range of motion is a difficult task. Still, the [OpenBionics] team is working hard to properly emulate a thumb with three degrees of freedom, putting 144 different grasps on the hand, and making their hand useful with soft fingertips.

Even with all this capability, [OpenBionic]’s robotic hand – motors and all – is about the same size as a normal human hand. That’s incredible, especially when you consider the motors for your hand – muscles – are all in your arm.

The team has put together a video demoing the capabilities of their hand. It’s somewhat remarkable, and able to do everything from lift a coffee cup to holding a pen. You can check that video out below.


The 2015 Hackaday Prize is sponsored by:

Continue reading “Hackaday Prize Entry: OpenBionics”

[Bil’s] Quest for a Lost Finger: Episode I

A little over a year ago I had a semi-gruesome accident; I stepped off of a ladder and I caught my wedding ring on a nail head. It literally stripped the finger off the bone. This was in spite of me being a safety-freak and having lived a whole second life doing emergency medicine and working in trauma centers and the like. I do have trauma center mentality which means, among other things, that I know you can’t wind the clock back.

hand9A few seconds make an incredible differences in people’s lives. Knowing that it couldn’t be undone, I stayed relaxed and in the end I have to say I had a good time that day as I worked my way through the system (I ended  up in a Philadelphia trauma center with a nearby hand specialist) as I was usually the funniest guy in the room. Truth be told they ask incredibly straight questions like”are you right handed?”  “Well I am NOW”.

So now I could really use a bit of a body hack, having seen the X-Finger on Hackaday long before I knew that I would one day work with them, I was hoping that we could get one to work for me. In speaking with a couple of the mechanical engineers on the Hackaday staff we decided to get [James Hobson] and [Rich Bremer] involved and that the best way to do it was to get a casting of my injured hand out to them.

 

Continue reading “[Bil’s] Quest for a Lost Finger: Episode I”

Artificial Leg Comes with a Normal Gait!

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Did you know over 50% of amputees take at least one fall per year due to limited prosthetic mobility? That compares to only about a third of all elderly people over the age of 65!

[Professor Mo Rastgaar] and his PhD student [Evandro Ficanha] set out to fix that problem, and they have come up with a microprocessor controlled prosthetic foot capable of well, to put it bluntly, walking normally.

Working with a scientist from the Mayo Clinic, the pair have created a prosthesis that uses sensors to actively adjust the ankle to create a normal stride. Commercially available prosthetics can do this as well, but can only adjust the foot in an up-down motion, which is fine — if you only plan on walking in a straight line. In addition to having an ankle that can also roll side-to-side and front-to-back based on sensor feedback, they have also moved the control mechanism up the leg using a cable-driven system, which lightens the foot making it easier to use.

We find the test apparatus almost as interesting as the prosthesis itself. The researchers had to come up with a way to measure the performance of the prosthesis when used to walk in an arc. The solution was the turn-table treadmill seen above.

If you have time, check out the video demonstration on the main article’s page which covers the leg and the treadmill build.

[via Reddit]