Hi folks,
Due to a health condition, I've lost some control and strength in my fingers. I'm looking for ways to restore some of what's gone so I can enjoy playing the piano like I was once did.
The trouble I'm having is lifting my fingers once the hand is resting on the keys. Pressing a finger down, even with some resistance (due to the piano key) is mostly fine, but lifting the finger up isn't possible (pressed or not). I tried dynamic finger extension splints but they didn't work well.
I've come up with a basic device using rubber bands and it seems like it has potential. Here's a short video demo.
A rubber band is connected to each finger. The band pulls the finger upwards when I'm not pressing, and is elastic enough that I can push it down to press the key. The main problem I'm having is that most fingers are weak and can't stretch the band enough. I tried a variation of this using constant force springs and it works slightly better but still, I can't push strong enough (I tried using the ones you normally have on employee badges but they weren't "smooth" enough, maybe there are higher quality ones?).
This is where I need your help. I want to build something on the same principles, but have it know when I'm pressing down (so it knows to minimize the resistance as much as possible) and get it to pull my finger when I don't press.
The electronic device I had in mind consists of a ring on each finger (roughly where the band is looped at) that has a string connected to it. On the other end the string is connected to an engine. A sensor measures the tightness of the string (to know whether the finger is being pressed). The engine takes that input to control the string, pulling it up and down (and thus lifting/lowering my finger). Essentially by default the engine keeps the finger lifted, but leaves enough room for me to push down a little, feeding that load into the sensor which tells the engine to release the string a bit, allowing me to press further. Ideally the whole thing has fast response time.
For the sensor I looked around a bit and found out about load cells and strain gauges. I'm not sure how to position these and which one to get (the bridge one looks a bit big since I'll need 10 of these). Remember that the hand needs to have some freedom to move left/right, so the device will probably be attached to some kind of rail (maybe worry about this later).
I'm also not sure which motor to get. It needs to be fast but also sensitive so it can pull in tiny increments so I don't lose too much control.
As far as controlling the motor, I read about PID controller but was told it might be tricky to use because the motor and load cell are connected to the same string and so affect each other. Not sure if that's an issue or not.
I've never built something like this, so have no clue whether this is going to work, or maybe there's a better idea out there (maybe put the sensor underneath the finger?). Any help will be appreciated!
Thank you for your time.