InMoov is a project made by French Sculptor and designer Gael Langevin. It was initiated in January 2012 as the first Open Source prosthetic hand, it has lead to projects like Bionico, E-Nable, and many others. One of its many benefits is that it is replicable on any home 3D printer with a 12x12x12cm area.
Due to its versatility, it can be used to create prosthetics, robotic arms, or even bionic arms for remote work. The designs provided are compatible with Arduino microcontrollers and specific servo motors that can be viewed on the website.
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An interesting mechanical design I found extremely significant was the design of the pinky and ring finger. An important note is that the movement and degrees of freedom of those two fingers are different from the middle and index finger. The ring and pinky fingers move on a different plane/axis than the other two fingers to simulate the movement and flexibility of the metacarpals.
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Here you can purchase the full right hand for an InMoov robotic hand.
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The InMoov robotic hand provides users with a plethora of avenues to achieve their goals, customize their experiences, and tailor the device to their needs. You can use InMooov's open-source design to create animatronics, robotics, and prosthetics. It all depends on how you code the device to respond to certain signals. This also extends to the motors, microcontrollers, and screws. The InMoov hand is essentially a template on which you can build your project off of.
Step 1A: Finger Starter
As you can see here I’m starting to work on my own prosthetic hand using the InMoov Robot design. This here is the starter finger. As of now, I have assembled it I just need to get proper servos to actuate it. My plan is to assemble this first to get a basic understanding of how the hand will function. By the end of the summer, I should have a fully assembled forearm controlled via EMG signals (Myoelectric Prosthesis).
Step 1B: Finger Starter
I completed the InMoov starter finger. I replaced the clear fishing line with a blue braided line because I wouldn’t have to worry about the line deforming plastically and also it’s easier to see😂.
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I used the preset code on the InMoov website which features a loop to initialize the finger.
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Step 1C: Alternative Control Scheme
This is an alternative control scheme for the robotic fingers. In my research, I noticed a lot of commercially available externally powered prosthetic hands have preset grips that can be accessed via a button. This shows a future addition I could make to my device.
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I developed the code myself, and derived it from a program I had made earlier in which I controlled LEDs through the use of a button.
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Although the servo code can be found on the InMoov website, an important lesson learned from the Cybertruck competition was how to set up scenarios in the Arduino IDE and implement them into different projects.
Step 2A: Basic hand components
Step 2 Progress:​
In this step, I began the development and construction of the InMoov hand. I printed out the finger and palm components. Unfortunately, I had to print out the ring finger twice because I had ruined one of the pieces by gluing the phalange joint restricting its movement.
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In this step, I learned the ability of my printer. At first, I printed the palm components with supports in fear that the overhang and hollow pathways (for artificial tendons) would cause failure. The supports, however, were too intricate and hard to remove from the interior so I opted to reprint the components without prints and it came out perfectly. ​
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Next, I used the 0.75mm PLA filaments and placed them in between each phalange joint to act as a wheel and axle. I then used leftover screws from my IR car project to combine the cover parts on the palm components.
Step 2B: Basic hand components assembled
Step 2 Progress:​
In this step, I began the development and construction of the InMoov hand. After I printed out all the pieces I assembled them and utilized Zap-A-Glue for the pieces that must be fused.
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For the bolts, they were a bit too thick so I had to sand them down with a rotary sander to allows them to fit.
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The bolts were also very brittle so I had to reinforce them with an outer shell of dried glue to hold them together.
Step 2C: Basic hand components assembled and strings embedded
Step 2 Progress:​
I have successfully printed and fused the forearm components together and installed the strings that will serve as a way to move the fingers.
In this step, I have essentially completed the mechanical portion of this project. I just need to secure the wrist components and attach the pulleys. After that, it’s just wiring and programming next.
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This step will take me the longest because not only do I have to snuggly place the pulleys on the servos I also have to acquire correct screws to properly secure each component. This will require me to take a trip to the hardware store to hold down the servos and the pulleys.
Step 3: Basic Arduino Codes and Assembled Hand
I fitted all the pulleys and installed all the cables so this was my first test run that didn’t go so well. The servos and pulleys were displaced so they did not all have the same starting position which explains why the fingers are all moving differently. Also, the cables didn’t have enough tension so I have to work on a way to increase the tension and better fit the pulleys so that the cables don’t go limp.