Does a physics-shaped twin of a real buck converter beat plain ARX? Only partly: all models sit at 0.5 to 0.9 V free-run error against a 0.06 V quantisation floor, and the winner flips with which half of the 20 ms record is fitted
research/free-buckreal
Does a physics-shaped twin of a real buck converter beat plain ARX? Only partly: all models sit at 0.5 to 0.9 V free-run error against a 0.06 V quantisation floor, and the winner flips with which half of the 20 ms record is fitted. One 20 ms record; natural frequency fitted, no component values.
What it found
Real buck-converter hardware data (1001 + 999 samples at 10 µs, SysIdentPy data repository, MIT). A 5-parameter twin (static quadratic duty-to-voltage curve into an exactly discretised second-order LC lag, delay chosen on the training half) is compared with ARX 1/1 to 10/10 in free run. Fitting the first 10 ms and testing on the next, the Hammerstein twin has RMSE 0.62 V and ARX 2/2 0.58 V (block-bootstrap interval of the difference −0.28 to +0.26 V); swapping the halves, 0.50 V against 0.82 V (interval +0.22 to +0.49 V). Dropping the curvature costs the twin 0.10 to 0.17 V. Every model stays about nine times above the 0.058 V quantisation floor, so something in the converter (ripple, load, other dynamics) is unmodelled. One 20 ms record, so the two directions are the only replication; the natural frequency is fitted because no component values come with the data.
A figure from its own output
Paper, code and results
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.