Dynamic characteristics and control strategy for airliner cabin humidity

During cruise flight, airliner cabin relative humidity is very low. In order to investigate dynamic characteristics of airliner cabin humidity in flight, a dynamic model was established by means of Lumped Parameter Method with physical analysis and logical simplification. And the flow characteristics equation of humidifying system's regulator valve was derived. According to the model, the control strategy of cabin humidifying system was simulated and analyzed. The results indicate that the value of the cabin relative humidity is lower than the minimal comfort humidity standard value of the American Society of Heating Refrigerating and Airconditioning Engineers that is 20%-30%. It is required to enhance humidity value. The humidifying system with fuzzy controller could satisfy the system design demands. And it is demonstrated that the fuzzy control strategy is more stable and less overshoot than the conventional proportional-integral-differential control strategy.