Explanation: My project is a prosthetic hand that is controlled by glove gestures. Using a Makerbot 3D printer, I printed out the parts of the hand that I would program. Using flex sensors mounted upon a glove (sensors which detect flex and bend movements), a voltage divider, an Arduino microcontroller, and servo motors inside of the 3D printed parts, I assembled a fully functional prosthetic hand that mimics the movements of a glove. When a person bends their fingers inside the glove, the flex sensors send signals to the Arduino, which then signals the prosthetic hand to bend corresponding fingers by a proportional amount. In order to build a system which would allow the flex sensors to communicate signals to the Arduino (which would then control the hand), I conducted research and thought of implementing a voltage divider. The voltage divider proved to be a key solution, because flex sensors are variable resistors, meaning they convert the change in their bend to electrical resistance, so their resistance increases with the amount bent. My goal was to measure the flex sensors’ resistance values using the Arduino’s analog input pins.
However, after discovering that the Arduino is not able to directly interpret resistance values (it can only measure voltage), my challenge was creating a circuit that outputs a voltage value that reflects the flex sensors’ changing resistance. I designed a flex sensor circuit with a voltage divider, in which the 5 volts incoming from the Arduino are divided between the flex sensor resistor and a fixed 22k resistor, so the voltage between the two resistors (the ‘divided voltage’ which is measured by the Arduino) will reflect the changing flex sensor’s resistance. A wire measures the voltage between the flex sensor resistors and fixed resistors, which indicate any variations in the flex sensor’s resistance, and inputs that voltage to the Arduino. To read the flex sensors’ bend, I coded a simple program that prints a 10-bit representation of those voltage values in real time, displaying a number between 1-1023 that reflects the flex sensors’ bend. Lower numbers meant lower voltage, greater resistance, and more bend in the flex sensors.
The next step was programming servo motors (which pull strings that bend and flex the fingers in the hand) to rotate proportionally to the bend of the flex sensors. My code converts the 1-1023 value to a proportional value between 0-180, which can be signaled to the servo, so that it rotates by an amount corresponding to the bend of the flex sensors. I built my own mapping function called findPosition which takes in the current flex value and returns a proportional position between 0-180 to send to the servos. Finally, I assembled all of the parts of my hand and inserted strings which can be pulled to bend and flex the fingers according to the rotation of the servos.
Inspiration: As a coder and computer science enthusiast, I have always been passionate about creative problem-solving, algorithmic thinking, and the innovative realms of technology and engineering. Prior to this project, however, I had mostly only engineered software, and did not have any hands-on experience with hardware (namely, electrical and mechanical engineering). I saw my idea for a prosthetic hand as an incredible opportunity to explore unfamiliar engineering fields, advance my technical abilities, and gain knowledge that allows me to think about novel solutions to real-world problems that integrate all different types of engineering. My self-proposed, self-defined intensive project during the six week Bluestamp Engineering program encompasses these ambitions.
As I first began to define my project, I was certain that I wanted to build something has application potential in the real world. As innovative prosthetic limb technologies are on the rise and more advanced capabilities are being explored every day, I became very interested in building my own 3D printed prosthetic hand that mimics biological, human movement. Furthermore, rather than making a robotic hand that simply does what it’s pre-programmed to do, or is controlled by a remote, I would attach sensors on a glove which interpret one’s human bending movements as they happen and would write code that automatically signals the prosthetic hand to recreate that motion. In the future, I plan on exploring technologies so that the prosthetic hand could be controlled merely by one’s brain, offering even more flexibility to users. I hope to bring the insight I acquired through this engineering experience to future projects as I pursue my interest in engineering, coding, and robotics.
PRIMARY FOCUS
Life Science / Healthcare Robotics and Gadgets Stem or Steam Other Prostheticsa
SCHOOL:
The Brearley School
INFORMATION
Website for the project
VIDEO
Video of the project
PHOTO
Photo of the project