> fibers. Think about the problem of cables in moving parts breaking over time
I'm not seeing that. Plastic fibers are really flexible. True some Chinese brands might be cheap junk so you would have to know what type plastic fiber optic cable you bought. What are we talking about? Breaks after 10 years??? Maybe longer. No. The utility and super cheap cost outweighs other solutions by more than a order of magnitude. I looked up the cost of plastic fiber optics and saw you could get a hundred meters for under $20 USD! Better fiber can't be too much more.
Wires, well wires have plastic coating so...no better.
Where the utility lies is in the interface. If you use capacitive, magnetic, any other sort of electrical type sensor then you have to add all sorts of parts to the input of a microcontroller. I've been looking at this and MC interfaces are complicated and they cost. You need another board, a bunch of resistors, capacitors (usually) and buffer IC circuits to make this work. You will have to have this for the actuators but adding this complication to the sensors is a whole mass of extra work. Just compensating for stray capacitance,[if you use capacitive sensors], in the pressure senors will be a total pain in the ass and will require constant calibration. Look it up you will see this is true. A lot of design work, more PC boards to make for the interface components. Lots of complication. Lots of cost.
But fibers from all the joints, point it at a $9 ESP32 with camera chip and you are done.
A thought experiment. Don't parse this too tight. It's just a back of the envelope calculation.
Let's say you have 300 actuators of various sorts to be sensed for location. Most you could have 8 bits resolution or 256 units of movement. A few you would need 10 bits. Major limbs. To get 10 bits, I used arm movement. So call the arm movement 2' distance or 609.6mm. Now I say half that to 1218 units of distance so now you have a resolution of 1/2 mm over the whole travel of 609.6mm. Close enough is 10 bits resolution at 1024 units distance for the whole travel of the arm, leg, thigh, forearm. Since the waifu is likely to be smaller this would likely be good enough for 1/2 mm or less resolution in limb, appendage, whatever movement location.
Now I speculate that you could use a gray code wheel picture. The one I uploaded has only three bits. You need more depending on which joint it is.
One fiber lights up the disc, a lens pics up the picture, sends it through the fiber and then it's displayed onto the camera. A ESP32 CAM Camera Module has 1622×1200 pixels or sensor channels. That's 1,946,400 total. Even if you cut that by 4x for alignment troubles it's still 486,600. In fact to get 10-bit resolution on all 300 muscles for a full function waifu you only need 3,000 pixels. So you're way ahead here.
There's a possible glitch in using one fiber to carry the whole picture. "If" moving the fiber screws up the picture, even if the ends are fixed, or changes it as the waifu moves then you can't use one fiber. But that's not really a problem, as we just use one fiber for light and ten fibers to carry the light reflection from the gray code wheel. We have plenty of pixels in the camera to pick this up.
Even better. This would be so fast to put together. You make a standard bracket to hold the wheel and place the fibers. The brackets, wheel holders, etc. could all be the same. You place the fibers in and snap closed. Each limb will have different length fibers. So you do just like car manufacturers make wire looms for cars. They have a big board with channels. They thread the wires, in our case fibers, then cut them to length. Add on connectors and wrap and you have the whole sensor system in one nice package. And even better we don't care what order the fibers for each individual sensor are in. After the waifu is built you give it commands to move one actuator at a time. The various fibers will light up as it moves and the processor then makes a map of each location for each fiber. Saves you a lot of time individually tracing each fiber from one fixed location to another, No need. It calibrates itself in software.
That guy that thought up fibergrids, pure genius. One of the best ideas I've seen in my life.