What does a quadratic thrust curve do to a controller designed in a linear-thrust twin?

research/thrust-twin

A controller that inverts a linear-thrust twin meets a quadratic thrust curve: realised acceleration is a+a²/(4g), so climbs overshoot more (0.046→0.095) and descents less, and steps below p≈0.5 hardly notice.

8 tests

What it found

A throttle controller inverts a twin whose thrust is linear around hover; the real thrust is quadratic. The realised acceleration is exactly a_cmd+a_cmd²/(4g): climbs over-deliver, descents under-deliver, and the throttle floor is reached at a_cmd=−2g. At ζ=0.7 the climb overshoot rises from 0.046 to 0.095 while the descent falls to 0.027 for a step of p=ω_n²|x₀|/g=4; gentle steps (p≤0.5) change overshoot by under 1.1 points. Stylised: 1-D, static thrust map, assumed throttle ceiling, no field data.

A figure from its own output

Figure produced by research/thrust-twin: accel — thrust-twin/experiments/accel.svg, written by the project's own experiment code.

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.