A day spent inconclusively tuning horizontal PIDs’ gains, with some integration tweaks to get better accuracy of velocities from the accelerometer, as yet untested, due to a bad beer last night (just 1 pint, guv) which left me after lunch today, staring down a toilet bowl, with undigested lunch staring back up at me.
The PID tuning goes loosely along these lines:
- the P gain is there to maintain a fixed target velocity
- the I gain is there to return Phoebe back to any point she drifts away from
- the D gain is there to apply additional acceleration / braking to stop drift.
It’s visible working, but it is very sensitive – change one gain, and the effect on the others’ change radically – to some extent you can use some structure, but ultimately it’s also a lot of guess work and gut-feel which doesn’t sit well, the way my gut is currently feeling.