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<!DOCTYPE html>
<html lang="en"><head><meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Force-Informed Actions — React Dataset</title>
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</style></head><body><div class="wrap">

<header>
<div class="kicker">React dataset · action processing</div>
<h1>The missing half of the action:<br>putting force back into pose-only demonstrations</h1>
<p class="sub">React's actions are computed from OptiTrack sensor poses — like all
UMI-style data, the demonstrated pose <i>is</i> the achieved pose. A stiffness
controller exerts <span class="mono">F&nbsp;=&nbsp;k·(target&nbsp;&nbsp;actual)</span>,
so replaying these actions reproduces the motion but presses with <b>zero
intended force</b>. This page shows how each action is transformed, on real
episode data, and what the transformation is worth.</p>
<span class="pill">36 episodes · 72 sensor-sides</span>
<span class="pill">no F/T sensor involved</span>
<span class="pill"><a href="index.html" style="color:inherit;text-decoration:none">↖ full methods &amp; validation</a></span>
<span class="pill"><a href="actions_zh.html" style="color:inherit;text-decoration:none">中文版</a></span>
</header>

<h2>How an action is processed</h2>
<div class="card">
<div class="flow">
<div class="fstep">pose p<sub>t</sub><small>OptiTrack, 30 Hz</small></div>
<div class="farr">+</div>
<div class="fstep">GelSight frame<small>640×480 RGB</small></div>
<div class="farr"></div>
<div class="fstep"><sub>n</sub><small>LUT depth → force,<br>GlowTact-calibrated</small></div>
<div class="farr"></div>
<div class="fstep">n̂ = R<sub>t</sub>·a<sub>gel</sub><small>dual-ball calibrated axis</small></div>
<div class="farr"></div>
<div class="fstep" style="border-color:var(--target)">action target<small>virtual, past the surface</small></div>
</div>
<div class="formula">p<sub><b>target</b></sub> = p<sub>observed</sub> + ( F̂<sub>n</sub> / k ) · n̂
&nbsp;&nbsp;&nbsp;k = 1500 N/m</div>
<p>The action stays a pose. In free space F̂<sub>n</sub>&nbsp;=&nbsp;0 and the target
<i>is</i> the observed pose — nothing changes. In contact, the target moves past
the surface along the gel normal by exactly the displacement an impedance
controller at stiffness k needs to exert the demonstrated force. No new action
dimension, no force interface at deployment — a DexForce-style transform
(arXiv:2501.10356) driven by tactile-estimated rather than measured force.</p>
</div>

<h2>Live on real data — drag across the trace</h2>
<div class="card">
<p style="margin-top:0">90 s of <span class="mono">motherboard/2026-05-10/episode_000</span>
(left sensor), centred on the strongest press. Top: estimated normal force.
Bottom: the transform's entire effect on the action — the target's offset from
the observed pose along the gel normal. The cyan zero-line <i>is</i> the
original action; the sensor itself sweeps ±170 mm through this window, which
is why the offset is drawn on its own millimetre scale.</p>
<div id="chartbox"></div>
<div class="legend"><span class="l-force">F̂ normal [N]</span>
<span class="l-pose">observed pose = zero offset (action before)</span>
<span class="l-tgt">target offset F̂/k along n̂ (action after)</span></div>
<div id="readout">
<div class="r"><div class="k">t</div><div class="v" id="ro-t"></div></div>
<div class="r"><div class="k">F̂ normal</div><div class="v" id="ro-f" style="color:var(--force)"></div></div>
<div class="r"><div class="k">target offset F̂/k</div><div class="v" id="ro-p" style="color:var(--target)"></div></div>
<div class="r"><div class="k">state</div><div class="v" id="ro-s"></div></div>
</div>
<p class="hint">drag / hover to scrub · data is the actual per-row output, not a mock-up</p>
</div>

<h2>The effect, measured</h2>
<div class="stat-row">
<div class="stat"><div class="lbl">free-space invariance</div>
<div class="val ok">0.0e+00 m</div>
<div class="lbl" style="margin-top:6px">max |target − pose| when F̂=0, all 72 sides</div></div>
<div class="stat"><div class="lbl">round-trip error</div>
<div class="val ok">9e-14 N</div>
<div class="lbl" style="margin-top:6px">k·‖target−pose‖ vs F̂ — machine precision</div></div>
<div class="stat"><div class="lbl">penetration in contact</div>
<div class="val">0.9 mm <span style="font-size:.9rem;color:var(--dim)">median</span></div>
<div class="lbl" style="margin-top:6px">max 15.2 mm at the hardest ~23 N press</div></div>
</div>
<div class="card">
<p style="margin-top:0"><b>Why this matters for training.</b> Policies trained on
raw poses learn "touch the surface and stop": the label says the fingertip halts
at the contact plane, so at deployment the controller exerts whatever residual
force tracking error happens to produce. With force-informed targets the label
itself encodes <i>how hard</i> — DexForce measured near-zero task success without
this correction and 76% with it, on kinesthetic demonstrations with measured
forces; here the same transform runs from tactile-estimated force, with the
estimator validated against FEA ground truth (ρ=0.70 pooled, 0.85 on unseen
indenter shapes — see the <a href="index.html">main page</a>).</p>
<img src="assets/dexforce_motherboard_episode_000_left.png" alt="virtual target offsets">
<video controls muted loop playsinline preload="metadata" src="assets/clip_motherboard_episode_000_left.mp4"></video>
<p class="hint">the force signal driving the action transform, live under the tactile stream</p>
</div>

<h2>Using it</h2>
<div class="card">
<pre><code># per-episode force estimates ship as npz next to the release
import numpy as np
from force_recovery.dexforce import force_informed_targets, gel_axis
from force_recovery.evaluate import median3_fresh

z = np.load("force_recovery/motherboard/2026-05-10/episode_000_left.npz")
force = median3_fresh(z["force_normal_n"], is_new)      # de-spike on fresh frames
act = force_informed_targets(pose, force, gel_axis("motherboard", "left"))
train_targets = act.target_pos                          # (T,3) — drop-in pose labels</code></pre>
<p>Caveats, stated plainly: absolute newtons carry the GlowTact-calibration
uncertainty (cross-sensor scale drifts 2–4×; within-episode relative force is
the reliable part), shear-dominant contact is a blind spot of the normal-force
estimator, and legacy recordings update tactile at ~8.5 fps — the
<code>tactile_*_is_new</code> flags mark which rows carry fresh force evidence.</p>
</div>

<footer>React force recovery · data <a href="https://huggingface.co/datasets/yxma/React">yxma/React</a>
· methods &amp; external validation on the <a href="index.html">main page</a>
· transform: DexForce (2501.10356) · force: per-sensor RGB-LUT photometric calibration + Poisson (LUT-v2), GlowTact-calibrated</footer>
</div>

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