Geek corner: ATR's amps to accel ratio

background

the idea is to create a onewheel tune that works equally for riders of any weight. PIDs are in Amps so they are providing a fixed amount of current proportional to the degree/duration/speed of tilt. So heavier riders will obviously need more amps than lighter riders. ATR is not only supposed to help you ride steep hills, but also help with equalizing the ride feel across riders of different weights.

My son and I (160lbs vs 100lbs now, used to be 160 vs 80lbs just a 18 months ago…) happily share the same settings.

how does it work

I determine that amps to accel ratio for a given motor (Funhub vs Floathub) by measuring amps/acceleration ratio for a kid. My son (90lbs at the time) was used as the baseline to determine how many amps are needed for 1 unit of acceleration.

So I made him accelerate and brake and I logged how much was needed to accelerate him on a flat smooth road. This was now configured as the amps-accel-ratio

Now if the resistance increases ATR would kick in and thereby supplement the amps to be requested.
The increased resistance could be due to any reason: terrain, rider weight, tire psi, etc

when should the amps/accel ratio be individually adjusted?

if ATR is well implemented and the other parameters are configured correctly then the amps to accel ratio should remain fixed across all boards with a certain motor, unless there's significant variances in the efficiency of those motors

So all Hypercore boards should in theory work with the same amps/accel ratio, and all SuperFlux boards should have the same ratio.

Q: You based this on the weight of your son, doesn't that mean it IS weight dependent??

A: Yes and no. In theory we could pick the weight of any rider as the reference, but then we'd have to change all other parameters too to get that some effect. Also, tunes using different amp/accel ratios will be just really hard to compare - and the holy grail of having simple sliders that change your ride feel will be hard to achieve. So this is why I'm advocating for keeping this ratio fixed an only adjusting it for the selected motor.

what could require adjustments in the amps/accel ratio?

(1) all my settings were created/tuned for a 1000Hz balance loop, yet things like acceleration are affected proportionally to that rate, so a 800Hz balance loop gets you 20 percent less ATR response that explains why the original 14 should have been lowered to 11 right away...

(2) I never formally repeated the measurements for amps/accel ratio using a Hypercore motor, I had simply assumed that due to its similar kv to a Funhub it would also need the same amp-accel ratio

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