i want to build an exoskeleton arm at home. I looked up a few examples on youtube that i found interesting.

1. example:

Here i can clearly see that they attached a force sensor (like this one: https://www.flintec.com/weight-sensors/force-sensors/miniature/mk ) to the structure and the user's forearm is resting on it (putting a load on the force sensor).

My assumptions here: they need to know the base load (forearm), so if the load is bigger than the base load then it means the user wants to push down, and if the load is lighter than the base load then it means the user wants to pull up (also the base load is dependent on the elbow's angle).

My question here: are my assumptions correct? do they need to determine the base load before every start? Later in the video they can also make it work with a plus load on the end of the arm, so does that mean they have to calculate how much more load does it put on the force sensor?
Isn't there a more convenient method to do it (which can work with different loads in a simpler way).

2. example:

In the beginning of the video he says that he uses 2 dimensional force sensors, but i couldn't figure out where the sensors are and what kind of sensor they are. In the end of the video (

) he shows that he can move freely the exoskeleton arm, but when he stops to hold it then it is capable of holding itself in the current position (i would be more than happy to achieve this).

My question here is the same: do they need to determine the base load before every start (he also does it with a bottle of water attached to the end)? What kind of force sensors is he using (and where, and how)?

 

I saw a video about an exoskeleton arm on Youtube. In the beginning of the video they say that they use 2 motors to move the joints and a 2 dimensions force sensor. but i can't figure out what kind of force sensor exactly (and where do they use it and how?).

The interesting part comes in the end of the video at 3mins 30secs :

If the guy moves the arm then the arm keeps up with the movement, but the moment when he stops to hold it then the arm stays in that position.
My assumption here: he needs to determine the arm's weight to know how much load is on the force sensor, so the system can know what is the acceptable measured load by the force sensor in the given position (but where is the force sensor and what type is it?).

Are my assumptions correct? Isn't there a more convenient method to do it? Because if i want to do it with different weights then everytime i have to determine the new load and recalculate the system.