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Signal Coding Choices for Vibration Immunity
By Engineering — Sensing · February 26, 2026 · 6 min read
A vehicle deck vibrates. A sensor that filters vibration too aggressively loses early-stage signal. The middle ground is where the work is.
IR sensor cells on a vehicle deck see two kinds of motion: the slow drift of ambient temperature and the fast modulation of vessel vibration. A naive low-pass filter handles the second at the cost of latency on the first. We treated it as a band-isolation problem instead.
What the bands look like
- 0.05–2 Hz: vessel motion-induced thermal modulation (slow roll, pitch).
- 2–25 Hz: engine and propulsion-induced vibration.
- > 25 Hz: sensor noise floor and electrical pickup.
- Sub-0.01 Hz: the thermal signature of interest.
The filter chain
A cascaded notch at the dominant vibration band of the vessel class, followed by an EWMA at the cell level, followed by the coherence stage at the segment master. Each stage targets a specific band and does not have to cope with the others.
> 40 dB
Vibration-band attenuation at the cell
< 50 ms
Phase delay on the thermal signal of interest
Per-class
Notch centres tuned per vessel class