Runtime Safety Monitor 2D: Anomaly Detection & Fallback Switch

Fault Injection

Perception drift 30%

Monitor Tuning

Detection threshold 1.20

Debounce window 10 frames

Monitor Status

NOMINAL

score 0.00trip 1.20

Hazard intrusions

Fallback trips

Divergence

0.00 m

Run time

0.0 s

How it works

Two controllers steer identical dynamics from the same potential field, seen here from directly above: a reference ("ghost") policy always keeps full repulsion from the restricted zone, while the primary policy's hazard-repulsion gain is degraded by the drift slider — a stand-in for a mis-calibrated perception stack that under-estimates risk. Neither policy is watched directly; the runtime monitor only watches how far apart they drift:

residual_t = ‖ x_primary(t) − x_reference(t) ‖
score_t = (1−λ)·score_(t−1) + λ·residual_t      (EWMA, λ = 0.12)

trip:    score_t > threshold_hi for `debounce` consecutive frames
release: score_t < threshold_lo = 0.5·threshold_hi, held for a cooldown

While tripped, control authority is handed to the reference policy's own commanded force each frame — a hard, verified-safe fallback, not a gentle blend. Raise the threshold and the monitor tolerates more divergence before intervening (fewer false trips, later catches); raise the debounce window and a single noisy spike can't trigger a trip, at the cost of detection latency. Turn the monitor off to see how often the degraded policy alone would have entered the restricted zone. The strip below the top-down view plots the live EWMA score against the trip threshold over the last run, with fallback windows shaded red.

Perception drift — how much the primary policy's hazard-avoidance gain is reduced (0% = identical to reference, 100% = ignores the hazard entirely).
Fault burst — a temporary spike in drift, simulating a transient sensor glitch rather than a steady bias.
Threshold / debounce — the monitor's own tuning: same idea as a chi-squared alarm limit and a persistence counter in real runtime-verification stacks.
View — drag the top-down view to pan, scroll/pinch to zoom; double-click to recentre.

Primary robot Reference (ghost) Restricted zone

drag to pan · scroll to zoom

EWMA score vs. trip threshold