Closed-Loop Control Strategy for Simulated Smoke Concentration in Aircraft Cargo Compartment Mock-Up

In airworthiness verification flight test on fire smoke detection systems in aircraft cargo compartments, simulated smoke from a smoke generator that can replicate the characteristics of actual fire smoke should be used. In current studies, most of the boundary conditions of smoke generators are adjusted by open-loop control to fulfill the equivalence of the actual fire smoke. However, this method consumes a large amount of resources and has difficulty achieving optimal results from the complex turbulent flow field of smoke in an aircraft cargo compartment. To solve this problem, a computational fluid dynamics (CFD) model was first established to simulate smoke in the full-scale cargo compartment mock-up. Then, a state-space model with the exit parameters of the smoke generator as the input and the smoke concentration in the full-scale cargo compartment mock-up as the state variable was constructed using the data generated by the CFD model. Subsequently, a closed-loop simulated smoke concentration control strategy is proposed. In this strategy, the sensor in the full-scale cargo compartment mock-up collects the simulated smoke concentration signal and feeds it back to the controller. The controller processes the control target and feedback signal in real time. It realizes the automatic closed-loop control of the simulated smoke concentration by automatically adjusting the boundary condition parameters of the smoke generator. In the control law design, the control input constraint and the error between the linear state-space model and the real flow are considered, making the linear state-space model a nonlinear model. Finally, we prove the stability of the control system. The simulation shows that the designed control law can realize the closed-loop control of smoke concentration. The findings of this study can expand the control of simulated smoke flow field in airworthiness verification flight test from open loop to closed loop, and offer a new theoretical approach for smoke simulation technology.