Characterization and control of air cell cushion behavior in different environments

Air cell cushions are widely used in wheelchair seating and medical support surfaces to reduce interface pressure and prevent pressure injuries. Their effectiveness depends on maintaining proper internal air pressure, which can fluctuate with environmental changes such as temperature and atmospheric pressure. These fluctuations pose a risk in clinical and transport settings where cushions may be exposed to extreme conditions. This study examines the behavior of air cell cushions made from silicone, polyurethane, and TPU-coated fabric under different environmental conditions. Using a proportional-integral-derivative (PID) control algorithm, we regulated the internal air-cell pressure to remain constant under changing temperature (15-35 °C) and atmospheric pressure (101-75 kPa) conditions. Results indicate that the cushion material significantly influences pressure stability, with TPU-coated fabric being the most sensitive to environmental changes. Applying the closed-loop control algorithm, it is possible to maintain the set pressure within ±0.05 kPa regardless of the cushion material, loading conditions, and environmental variations.