My 3 main questions are:
• Is an absolute rotary encoder suitable for these purposes?
• What specs (resolution, etc.) should the absolute rotary encoder have?
• Is there a better or cheaper alternative type of sensor setup to close the loop?
Right now I am looking at a few absolute rotary encoders on AliExpress, but I would also appreciate any suggestions for U.S. vendors as long as the sensor is comparably affordable.
About the prosthesis:
The motors are Bimba pneumatic cylinders. The valves are 5/3-way solenoid valves. The microcontroller is an ESP32. The battery is 18v LiPo. The air supply is up to 100psi from a portable tank.
The system works great so far but I need to "close the loop" for the next stages ahead. I plan on adding some IMUs and giving the prosthesis instructions on "when" and "how fast" to bend the knee and ankle based on walking speed and orientation.
The cylinders I have didn't come with magnetic wipers for position sensing or anything like that. So, I figured I'd get rotary encoders and attach them to the point of rotation for the knee and ankle. Make sense?
Alternatively,
I guess I could instead try to use some type of linear potentiometer mounted parallel on the cylinder with the moving part attached to the rod end.
Would this be a suitable alternative to the rotary encoder for my purposes?
I am not sure how fast or accurately the linear potentiometer would be able to relate it's position so hopefully someone here with more experience than I have could chime in on this.
I plan on walking and eventually running on the prosthesis so I'll need something that's reasonably fast and somewhat accurate. The absolute encoders seem like a good choice because the device won't need to "home" when powered on and I can use fixed points in the software as soft "end stops".
Any assistance is much appreciated, thank you for taking the time to read this post, and have a great week!