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UNH-OE / wave-tow-tank

Configuration files and issue tracking for the UNH wave & tow tank.
MIT License
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Use linear encoder for tow axis feedback #7

Closed petebachant closed 9 years ago

petebachant commented 9 years ago

Currently it is only used for measurement, but could help smooth out the motion a bit.

petebachant commented 9 years ago

Probably going to give this a try soon to eliminate turbine-induced oscillation. I have a feeling the drive will go unstable though.

petebachant commented 9 years ago

Linear encoder is connected to X1 connector. Set lines per rev to 8000. This implies 10 micrometer per line, as one motor rev is 0.08 m. This seems incorrect. Tried to move 0.1 m at 0.1 m/s, and carriage ended up taking off at about 1 m/s. Set EXTPOS to 30, ROD (A QUAD B) Enc 5V (digital).

Positioning seems to be off by a factor of 4. Setting lines per rev to 2000 corrected this, but Kp_p=0.01 caused instability. Kp_p=0.001 fixed instability, but there are still oscillations when moving.

Overall, it looks like the linear encoder may help for positioning accuracy, but not for belt resonance.