We are currently using cotton belts that were made by a dressmaker. Unfortunately it's impossible to single handedly fasten them because they lack the proper mechanism. They are also not elastic with makes the problem even worse. 

One of the biggest challenge will be to figure out a way for proper mounting, without the exoarm slipping down or rotating when it shouldn't.

The red part is X711 module for straing gauge. 

The motor driver that I'm using is way overpowered for this motor. The window motor will draw ardoun 1.5A at no load and 4A at stall torque. I'm saying this because this motordriver is pretty expensive and you could get away with weaker and cheaper one.

We created animation showing the range of motion of exoskeleton arm. Range of motion is 105° from vertical. While designing we had to take human anatomy into account. Range of motion has to be limited both ways to avoid overextension and correlated joint injury.

Few comments:

- This design is far from finished, however we are using this to get some sense of curvatures and best way to mount it.

- Red gears are used because I had to move potentiometer (elbow angle sensor) away from the center of rotation due to practical constraints. So now it's excentric and thankfuly still in the range of movement (gear ratio) .

- There is still no power window motor 3D model, so the only way for you to see how it's mounted is to look at the last picture and try to see the motor sketch. 

Here is a little test with PID control. As you can see it can hold a position pretty well. The PID is not tuned. That's why you can hear that beeping sound coming from the motor. 

Now all I have to do is to join PID control with intuitive movement, so that I can actually lift something. 

This video is without any regulator/power:

Here you can see PID regulator in action. It is designed so that it holds a setpoint (angle), and tries to do that no matter whether there is a force on it or not)

I tried using it and it did not work as I thought it will. Not even a bit. See the problem is that when you put the electrode on your biceps, you can trigger it just by stretching your skin. it causes so much electricity that it false triggers and device thinks that you send a muscle signal. So when the Exo-Arm is fastened to your arm, the belt will stretch your skin, especially at the biceps. What happens? Exo-Arm flexes, but does not let go, because it thinks you're still sending signals to the biceps when the only signal is your stretched skin, if that makes any sense.

Will stick to load cells (the same part that is used in weights to read weight). Will require some adaptations however.