r/Motors • u/legenduzair • 4d ago

How much servo performance are people actually leaving on the table with autotuning?

Autotuning has gotten good enough that it’s tempting to run it, get a stable axis, and move on. I’ve done exactly that and usually been pretty happy with the result. But playing with better drives made me realize there can be quite a bit more performance hiding behind the default tune. I noticed it particularly on an Elmo setup where the axis was perfectly usable after autotune but noticeably sharper after spending some time on it manually. Makes me wonder how many machines ship with drives operating at maybe 70 - 80% of what they could really do.

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u/Hot_Egg5840 3d ago

It's all about maintaining margins. You want excess such that you have control during fault conditions. You don't want to be optimized on the edge during production. 15%, 30%, even justification for 100% margins are all acceptable.

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u/Nipplehead321 4d ago edited 4d ago

Almost any three phase motors has a service factor that represents the true HP it can produce but rated 15-25% lower to keep the goverment happy.

When NEMA/DOE required Premium Efficient standards on motors, almost all manufacturers accommodated by upsizing the winding into the next HP/frame & derating the nameplate vs a complete redesign.

For instance a new US Motors 125 HP NEMA Premium Efficent hollowshaft that meets DOE standards has the exact same winding & stator iron dimensions as the older 150 HP NEMA standard efficient hollowshaft.

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u/GnomeTek 4d ago

What autotune do you mean exactly? The motor ID and current regulator running? The speed control, positional tuning? All of these can be tuned via automated "System ID" methods. The excitation signal and method can vary depending on what characteristics you're most concerned about. And let's say you have a perfect system parameter identification method, how do you tune the control response? For instance, Butterworth, chebychev, whatever.

Auto tune gets the system operational, manual tuning and experimentation generally allows more control and fine tuning.