Sounds like you want a strain gauge. I would consider trying to estimate the relative load, indirectly, by way of motor current consumption.
Thanks for the term also OM222O thanks.
I will certainly look into that. The motor current could also be a good parameter, it is 230VAC but with a small current clamp around the phase or something like that it is easy to measure
Far too complicated.
Just let the "pulling" tubemotor run and disengage the other (let it run free or lightly braked).
Have to investigate this because I think the Somfy motors brake the shaft when power is off and I never noticed that they can be disengaged.
They are usually used for window blinds, you know those heavy aluminium bars, and you don't want to have the whole blinds tumble down if you stop halfway.
I do not know the particulars but it sounds like a bad design to begin with. In principle you do not need two motors at all as you can have one rolling up the screen and working against a constant tension provided by weight, spring or whatever. Having to control two motors to achieve the correct tension seems unnecessarily complex IMHO.
At this moment it works with a heavy spring, so heavy that the metal wires can be used to play piano
Twice already the past ten years the spring has disengaged, a lot of noise and even damage. So I would like to replace this since it is too heavy for the application. Since I want to go to a new wider screen I am looking for alternatives. But thanks for bringing it up, valid point.