Doctoral Research · Space Robotics Inspection with a Free-Flying Space Manipulator
A Doctoral Research Journal Aerospace Engineering

Near-singular tracking-corruption levers — plan (Jun 19)

Written blind (without the INSIGHTS.md files) on purpose: this is my current intent from the Jun19 campaign evidence alone, to be reconciled against the collected insights before any sim runs.

The reframe (what the 13-stem campaign actually showed)

At the adopted operating point (rs=0.40, corrected base, σ-onset 0.025), the impedance derate is inertretime_only (C/I), coupling (G), and the noise variants (F) are all ≡ incumbent. The Jun18 “derate tax” was an artifact of that study’s wide derived-onset band (σ<0.143). The real problem is not the derate — it is the near-singular tracking corruption: the EE tail error (pe_p99) and the fraction of steps near-singular (fbelow). Two levers move it:

lever pe_p99 cov fbelow profile
incumbent 0.1753 0.995 0.597
E analytic feedforward 0.1590 0.998 0.280 all-rounder, no coverage cost
D/K Tikhonov onset 0.05→0.02 0.1597 0.988 0.027 conditioning specialist, −0.8% cov

D and K are equivalent (onset value robust). K is not a crawl (finishes the helix faster, not slower — k_crawl_diagnostic.py).

Goals now (each is a falsifiable A/B vs incumbent, matched harness, after=90, full helix)

  1. E + D/K combined (new run)analytic_ff=true AND gamma_regularization.floor=0.020. Hypothesis: E holds coverage (feedforward) while D/K drives fbelow down (de-corrupted velocity solve) — they attack the same corruption by different mechanisms, so they may stack. Gate to beat both: pe_p99 ≤ 0.159 AND coverage ≥ 0.99 AND fbelow < 0.10 AND s_min_J min ≥ 0.019.

  2. D/K coverage-gap diagnosis (existing logs first) — why does D/K dip to 0.988 while completing 100% traversal? Hypothesis: the changed solve shifts the camera FOV path → a few missed triangles (benign), not a real hole. Diff coverage(t) and the missed region vs incumbent. Decides whether the 0.8% disqualifies D/K or is cosmetic.

  3. H on the right metric (existing logs) — re-judge base_damping_3.5/5.0 on z_b back_half_pkpk (the slow ~12 s wobble the gate named), not rms. If ptp is also worse → H is genuinely dead; if ptp improves while rms worsens → the wobble was damped and rms saw added lag (different verdict).

  4. rs035 re-run with the footgun fix (new run) — radius_scale=0.35 was inert before (ran as rs040); now valid (db927d6). Get a real small-standoff point. Gate: coverage ≥ 0.99, compare pe_p99 / fbelow / s_min_J to rs040.

  5. Understand the onset→floor shift (analysis) — incumbent here is smin 0.0193 / fbelow 0.60 vs Jun18’s 0.0268 / 0. Confirm this is purely the onset (0.025 vs 0.143) and decide whether the operating onset itself is a lever worth sweeping (σ_high), distinct from the Tikhonov onset (D/K).

Decision criteria (what “done” means)

Objective = smoother COM / Base / EE tracking without losing coverage or the floor. Likely outcome: adopt E (clean win, no coverage cost) as the headline; add D/K only if (2) shows the coverage gap is cosmetic and the combo (1) doesn’t already subsume it. H, C/I, G, F: record as null/negative. Nothing adopted/re-pinned without a full-helix A/B and your sign-off.

Guardrails I’m holding (footgun-aware)

NEXT (with the user)

Reconcile this plan against the central INSIGHTS.md files — confirm none of (1)–(5) re-treads a falsified idea or a known footgun — then run.