Introduction: Arm Exoskeleton
Today I'd like to share this exoskeleton project with you.
This is the prototype of the exoskeleton. Now I've only finished the arm part of exoskeleton. The project is still ongoing,and I'll update new goings on time. And I hope I could make a full body exoskeleton in 6 mouths.
So what's exoskeleton?it is basically a kind of wearable robot help the user get more strength than before. The user wears the robot . And the robot moves exactly with the user's movement with much more strength before. This makes it possible to lift, move heavy objects or do other things.
Step 1: Hardware Design
There're mainly two types of hardware design. Some exoskeleton have the joints exactly as human joints. But most of humans joints can not only rotating but also sliding. So the high power of the exoskeleton might hurt the user if we only use one rotating joint to cooperate with user. Then there's another design which uses more joints to compare with a user's joint.
In order to make the control of the exoskeleton easier . We choose the first design .
The frame of Arm exoskeleton was made up with 3 parts. Each part rotates with user's joint.
The exoskeleton also needs drive systems to provide high power on each joint. Electronic ,pneumatic and hydraulic are good choices.
Arm Exoskeleton uses air muscles as the driver which can provide high force in low weight. Each joint has two air muscles to rotate it in two directions.The air muscles works under the pressure of 4 bar. Six telectromagnetic valves were used to control air muscles.
Each part of the joint has a 3 direction force sensor which was made up with 3 Strain gauges to detective the force which user exerts on the joint .
Step 2: Electronic Design
The exoskeleton uses an arduino mega 2560 as the central controller. To drive the telectromagnetic valves, we use the uln2003a chip which works at 24V. The air composer was made up with a composer and an air tank which makes the air source more stayable.
We choose a 12V ,5AH battery to power the whole system. The exoskeleton can work 30 mins with this battery.
Step 3: Control System
The control system of exoskeleton is very important. How could we control it moves exactly as the user?
First we need to talk something about a small game.The game called for Price to be, in effect, the exoskeleton, and his daughter to be the pilot. With her back to her father, she stepped up on his feet, her toes atop his. Then they held hands for balance and she began to walk. Price's job was to stay in step, to keep his feet directly beneath hers. Within a few minutes, they were moving in sync. His daughter made all the high-level decisions—how fast to walk, when to turn—and Price just tried to mimic her, step for step.
So the user acts like the daughter and the exoskeletons is the price. This game prove that it's possible for the exoskeleton to tracking the user with only 4 connections. Unlike humans ,exoskeletons need to use sensor on connections to get the trend of user.
This project uses force sensors. There're 3 sensors on each connections to detective force in different directions. Than the controller will generate the move directions of the user. By using a Pid algorithm, the air muscles can move smoothly with the user. Any way the exoskeleton just try to get the force on those sensors as close to zero as possible.
Which means the user just use a very small strength to drag the whole robot.
After the test. The exoskeleton can work smoothly.
Thanks for watching. Please leave your suggestion.
Step 4: Video
The demo of Arm Exoskeleton