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Pediatric Independence Project
– Bionic Arm –
Background: The aim of this project was to help Gabriella Fraley, a 7 year old girl born with Arthrogryposis, gain more independence. Arthrogryposis is a congenital condition that causes joint contractures of the upper and lower extremities and severely affects muscle development. Gabriella’s wrists and ankles are severely affected by joint contractures causing them to bend inwards and be limited in movement. Although she has good control of her feet and toes– her hands and fingers are almost completely motionless and lack the strength of her lower extremities. As a result, Gabriella relies on her legs and feet for much of her everyday life. In addition to walking (both with and without her lower limb prosthetic), she uses her feet to write, play, and grasp. Although Gabriella has learned to use her feet in a dexterous way, as most of us use our hands, there are still everyday functions that she requires help with due to the lack of functionality of her hands. This project’s goal is to give Gabriella independence from those tasks that she currently requires help with by giving her a functioning ‘hand’.
Objectives: This project’s goal was to give Gabriella independence from those tasks that she currently requires help with by giving her a functioning ‘hand’. A mostly 3d printed, robotic prosthetic hand that will attach to her forearm.
Final Design: The final design is a lithium polymer (LiPo) battery powered, Adafuit Feather controlled, 3d printed robotic hand and elbow assembly, mounted to a professionally crafted, custom upper limb prosthetic (courtesy of our friends at Hanger Clinic, Thanks Steve!). The design is controlled by Gabriella via a wireless joystick mounted to a bracelet which she wears on her opposite arm which enables her to grasp and move things previously impossible to her.
The main components of the design included: The finger and palm designs which were iterated several times to ensure sufficient and maximum gripping force,
A rotatable wrist which serves a mounting location for the hand-to-forearm and enables gabby to have 2 hand positions for a wider range of possible applications,
An electric motor powered, elbow assembly to aid Gabriella in controlling her arm.
An Adafruit MO featherboard used to control the servo motors thus enabling the opening/closing of the hand and vertical motion of the elbow.
Final Design Related images go here:
Full CAD Assembly vs. Image of Final Product
Below are detailed cad images of each several component's in detail
Above Left: A transparent view of the hand in which the tendon lines and their internal routing are clearly visible
Above Right: An exploded view of the elbow assembly. The left linkage connects to the forearm and the right linkage (with bearings) connects to the bicep.
Above Left: An exploded view of the forearm enclosure which houses the motors and connects the hand to the (via the wrist) rest of the packaging
Above Right: An image (with quarter for relative size) of the onboard Feather MO with LoRa Radio module controller board that is housed inside the bicep.
Overall Performance:
* True max lifting force was not found. 12.77 N was max load tested and is sufficiently higher than what the hand is capable of grasping, including the moment created by the patients arm
** Based on current consumption calculations and assumptions about usage. No endurance test actually performed