← Physical
Jean held an underwater vehicle at depth within ±0.5 m for three times the required duration — three runs agreeing within 1%, every constant measured on the plant, not assumed.
The exit criterion was to hold depth within ±0.5 m for 120 continuous seconds across three settled runs, no saturation, every constant traceable. Here's what happened.
"The three runs agreeing to within 1% is itself the finding. Earlier in this programme, identical configurations produced 354% spread in the same measurement. The bench is now an instrument."
| Run | Samples | Median error | Within ±0.5 m | Continuous hold |
|---|---|---|---|---|
| Run 1 | 10,621 | 0.216 m | 94.3% | 376.7 s |
| Run 2 | 10,606 | 0.212 m | 94.0% | 355.2 s |
| Run 3 | 10,643 | 0.216 m | 92.0% | 352.6 s |
No saturation in any run. KD = 0 because the water itself supplies the damping — at 0.2 m/s the quadratic drag term alone opposes motion with nearly 12,000 N. No gain was chosen to make a test pass.
The first version of our Phase 0 test harness printed "PHASE 0 PASSED." It was wrong. The vehicle had reportedly risen under downward force, and the total response across a 1,200 N swing was a rounding error — but the monotonicity check passed on noise that happened to be ordered.
"A gate that passes when it should not is a more serious defect than the bug it was built to catch."
Three defects: no minimum effect size, a detection threshold below the natural variation in the vehicle's buoyant drift, and a baseline measured at a different depth than the test. None of it was caught by the test. It was caught by a person reading the numbers and asking why a vehicle rose when pushed down.
We record this because it is the whole discipline: an instrument that has never been caught failing has not yet been tested. The constants this program now runs on superseded the earlier assumed values by factors of 55×, 26×, and 1,500×. Every one of those corrections came from refusing to trust a green checkmark.
The controller holds depth because the forces acting on the vehicle were measured, not estimated — buoyancy by bisection, drag fitted to net force across a 65,000 N range with a 3% residual.
The proportional gain follows directly from that measured drag curve: a 1 m error commands ~3,000 N and closes at 0.1 m/s. The derivative gain is zero — the water damps the system better than any tuning could.
One constant, the effective heave mass, could not be separately identified at the achievable sample rate. We say so plainly rather than report the number the optimizer returned when it hit its bound — and the controller doesn't need it, because this plant is governed by drag.
Station-keeping and depth-hold derived from the vehicle's own measured drag and buoyancy — not a policy trained in a pool that may not match your hull.
Every control decision traces to a measured constant. Three runs within 1% means the behavior is repeatable — the precondition for trust in an environment you can't observe directly.
We publish what we couldn't measure and why, the harness that lied, and the corrections that followed. The record is built to survive a hostile reader.
A second physical domain proven by the same small team, the same architecture — evidence that each new domain costs less than the last.
Both phase records — actuation verification, plant characterization, the false pass, and the depth loop — are documented in full. If you want to verify the constants or the methodology, write to us.
Tell us your vehicle and your environment. We respond personally — no sales process, no auto-responder.
Write to us →contactus@myasolutions.org · full phase records available on request