2.0 2. System Architecture

Pneumatic System

[PUMP]
   ↓
[MANIFOLD]
   ↓
[PLENUM]
   ↓
[SPLIT LEFT / RIGHT]

ZONE:
Fill Valve → Check Valve → Tee → Mattress
                             ↓
                       Pressure Sensor
                             ↓
                         Vent Valve

Pneumatic Specifications

• main tubing: 8–10 mm ID
• sensor tubing: 4–6 mm ID
• tee: matched to tubing size
• plenum: small sealed air chamber

Why a plenum is used

Diaphragm pumps produce pulsating airflow rather than steady flow.

The plenum acts as a buffer volume that:

• reduces pressure ripple
• stabilizes airflow
• improves measurement consistency
• reduces control instability during fill operations

Pressure Model (Critical Concept)

The system maintains two stored pressures:

• empty-bed pressure (preload condition)
• occupied pressure (user-defined reference)

The internal pressure of the mattress is determined by:

• the amount of air in the system
• the volume available to that air

When a user lies down, the mattress deforms and its internal volume decreases.

Because the amount of air remains constant while the volume decreases, the internal pressure increases.

This is a direct result of gas compression.

When properly calibrated, the empty-bed pressure is set such that when the mattress is compressed by a user, the resulting pressure matches the user-defined comfort setting.