A small startup called K-Scale Labs is in the process of developing an affordable, open-source humanoid robot and Mike Rigsby wanted to build a compatible hand. This three-fingered robot hand is the result, and it makes use of serial bus servos from Waveshare.
Most Arduino users are familiar with full-duplex serial communication, which requires two data lines. The first carries data in one direction, while the second carries data in the other. As such, devices can send and receive data at the same time — they don’t have to wait to until the line is “free” to send data.
But half-duplex serial communication is also possible. Each device just has to wait its turn to send data. That is less common, but it does have some benefits. In this case, Rigsby used Waveshare servo motors that communicate via a half-duplex serial bus. The benefit is that users can daisy-chain multiple servos together, connecting to a single serial pin on the host device. These particular servo motors also have magnetic encoders instead of potentiometers, which are more reliable.
Five of those servos actuate the 3D-printed fingers on Rigsby’s robot hand (the top two fingers have two joints each). He used an Arduino UNO Rev3 board to control them, but couldn’t use the typical RX and TX (0 and 1) pins for communication over the serial bus. For that reason, he included a serial bus module meant specifically for driving servos like these.
This seems to work pretty well and the motors move smoothly — though they currently lack sensors that would enable force/pressure control.
Building a robot is only half the battle, because you also need a way to control it. Something like a rover may work with a simple joystick or even typed commands. But complex robots often have many motors and controlling those all directly becomes a challenge. That’s why Will Cogley chose motion control for his bionic hand.
This is the newest iteration of a project that Cogley first started a few years ago. It is robotic hand meant to mimic a human hand as much as possible. Human fingers do not contain muscles. Instead, muscles in the forearms and palms pull on tendons to move the fingers. Cogley’s bionic hand works in a similar manner by using servo motors in the forearm to pull on cables that actuate the fingers. An Arduino UNO Rev3 moves the servos according to commands from a PC, but Cogley needed a way to streamline those commands.
Cogley chose a Leap Motion Controller for this job. It can track the motion of the user’s hand in near real-time and update a 3D model on the computer to reflect that. It displays that model in Unity, which is a 3D game engine that has the flexibility to perform in applications like this. Unity can determine the angle of each joint and Cogley was able to take advantage of the Uduino plugin to send servo commands to the Arduino based on those angles.
Ivan Miranda has a humble dream: he wants to build a massive 3D-printed robot that he can ride upon. In other words, he wants a mech. But that is obviously a very challenging project that will take an incredible amount of time and money. So he decided to test the waters with one piece of the mech: a huge 3D-printed robotic hand.
Miranda designed this robotic hand at the scale necessary for an enormous rideable mech, but he has only built the one hand at this point. This let him test the idea before jumping into the deep end with the full project. The structure and most of the mechanical components were 3D-printed. It has four fingers and a thumb, each with three joints (like a real human hand). It is mostly rigid PLA, but there are some flexible TPU parts that add grip.
Servos actuate all 15 of those joints. Most of them have 11kg-cm of torque, but the base of each finger has a more powerful servo with 25kg-cm of torque. An Arduino Mega 2560 controls all of the servo motors with pulse-width modulation (PWM) signals. Power, of course, comes directly from the power supply and not the Arduino.
In testing, the hand seems to work quite well. It can move and grip large objects, though the belts do slip and need to be replaced with a type that can’t stretch. We’re not sure if Miranda will complete the entire mech, but we sure hope that he does!
Traditional methods of sending movement commands to prosthetic devices often include electromyography (reading electrical signals from muscles) or simple Bluetooth modules. But in this project, Ex Machina has developed an alternative strategy that enables users to utilize voice commands and perform various gestures accordingly.
The hand itself was made from five SG90 servo motors, with each one moving an individual finger of the larger 3D-printed hand assembly. They are all controlled by a single Arduino Nano 33 BLE Sense, which collects voice data, interprets the gesture, and sends signals to both the servo motors and an RGB LED for communicating the current action.
In order to recognize certain keywords, Ex Machina collected 3.5 hours of audio data split amongst six total labels that covered the words “one,” “two,” “OK,” “rock,” “thumbs up,” and “nothing” — all in Portuguese. From here, the samples were added to a project in the Edge Impulse Studio and sent through an MFCC processing block for better voice extraction. Finally, a Keras model was trained on the resulting features and yielded an accuracy of 95%.
Once deployed to the Arduino, the model is continuously fed new audio data from the built-in microphone so that it can infer the correct label. Finally, a switch statement sets each servo to the correct angle for the gesture. For more details on the voice-controlled bionic hand, you can read Ex Machina’s Hackster.io write-up here.
Designing a modular and ambidextrous four-fingered robot hand
Arduino Team — September 4th, 2019
Gray Eldritch (AKA The Technomanc3r) has been working on a robotic hand for some time now, and has settled (so far) on a design with three independent servo-actuated fingers and a thumb. He’s also implemented a wrist assembly to rotate it back and forth, with an Arduino Uno hidden inside for an entirely self-contained gripper unit.
Each of the three fingers is controlled by a single MG996R servo, as is the wrist, while the thumb adds a second SG90 servo to allow it to move on two axes. The fingers are modular, so they can be swapped out as needed, and you even change the thumb position for ambidextrous operation.
It remains to be seen what Eldritch plans to do with the gripper, but it looks brilliant by itself in the video below.
Researchers from the University of Manchester have developed an extremely affordable 3D printed robotic prosthetic hand. The assistive device enables groundbreaking functionality for amputees, and can be fully customized for the user via an Android app.
A team of designers from the University of Manchester have recently created a robotic hand prosthetic with 3D printing technology. The development could potentially slash production costs for assistive devices, offering a more affordable alternative for amputees.
This new prosthetic can be seen as more than just a cheap alternative, but also as a functional improvement over traditional devices. The joints of the prosthetic hand are fully posable, meaning that each individual finger and thumb can be moved independently. In the real world, the 3D printed hand would provide amputees with an opportunity to handle everyday tasks such as picking up items, using a knife and fork, clicking a mouse, or even playing rock-paper-scissors.
Usually, these expanded functionalities do not come without a hefty price. However, that’s where the prototype really stands out as a groundbreaking device. The engineers from University of Manchester built the hand for just around £307 ($433 USD). On top of that, the creators firmly believe that the production cost can be reduced further. To give you some context, advanced prosthetics like this one usually come with exorbitant price tags, costing anywhere in the range of £25,000 ($35,000 USD) to £60,000 ($85,000).
3D Printing Helps Researchers Develop Prosthetic Hand that is Functional and Fresh
The team 3D printed the robotic prosthetic using stereolithography (SLA) 3D printing. The technique uses resin material, which is solidified into a 3D model using a high-powered laser. The researchers also plan to test out Fused Deposition Modeling (FDM) 3D printing, which could bring the price down even lower.
The UK’s National Health Service (NHS) estimates that there are around 6,000 limb amputations carried out each year in the country. Furthermore, whilst non-robotic limbs are available for cosmetic purpose, robotic ones have the power to transform lives and restore functionality to the user.
But the University of Manchester researchers want to combine functionality and aesthetics, producing a prosthetic that amputees can wear proudly.
“Not only do we want to make it affordable, we want people to actually like the look of it and not be ashamed or embarrassed of using or wearing it. Some traditional prosthetics can both look and feel cumbersome or, those that don’t, are extremely expensive. We think our design really can make a difference and we will be looking to commercialise the project in the future,” said Alex Agboola-Dobson, a Mechanical Engineering Master at the University of Manchester.
And, if that isn’t interesting enough, the prototype also includes a Bluetooth connection and also comes with its own Android app. This enables wearers to control the robotics via muscle sensors on the arm. Additionally, the extent of the prosthetic hand’s functionality is fully customizable through the Android app.
The project was led by mechanical engineer Alex Agboola-Dobson, who received assistance from lead electrical engineer Sebastian Preston-Jensen, lead software engineer Panagiotis Papathanasiou, as well as mechanical and software engineers Maximillian Rimmer and Shao Hian Liew.
Two years ago, Paul McCarthy began searching for an inexpensive yet functional prosthetic hand for his son Leon, who was born without fingers on one of his hands.
McCarthy came across a video online with detailed instruction on how to use a 3-D printer to make a prosthetic hand for his son.
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