Research On Helicopter Shipboard Wind-Over-deck Envelope And Pilot Workload

Theoretical prediction of helicopter shipboard Wind-over-Deck(WOD)envelope and pilot workload are the key technologies to affect the flight safety of helicopter shipboard operations.They are always the hot and difficult points in the research area of helicopter flight dynamics and control.This article conducts a research on the flight dynamics modeling and pilot workload analysis of helicopter shipboard operations.A numerical simulation method of helicopter shipboard flight is established.On this basis,a theoretical method is developed for prediction of helicopter shipboard WOD envelope and a flight control system is proposed for alleviation of pilot workload.The main work includes the following aspects:Based on the temporal and spatial characteristics of ship airwake by unsteady Computational Fluid Dynamics(CFD)method,an order reduction and reconstruction method of time-varying ship airwake is developed with Proper Orthogonal Decomposition(POD)theory.On this basis,an accurate and efficient ship airwake model is established.The spatial and spectral distribution characteristics of the POD reconstructed ship airwake are validated.The result shows that the POD reconstructed ship airwake model can significantly reduce the vast data while retain the accuracy of CFD method.Based on the POD reconstructed model of ship airwake,a dynamic coupling method of unsteady ship airwake with helicopter flight dynamics model is established to form a flight dynamics model of helicopter shipboard operations.The model is validated against the flight test data in calm atmospheric environment.The effect of the spatial variation of ship airwake caused by shipboard superstructure on the helicopter trimmed characteristics is analyzed.The result shows that the flight dynamics model of helicopter shipboard operations has the capability to capture the effects of both the uniform and nonuniform ship airwake on the helicopter equilibrium states.Based on the flight dynamics model of helicopter shipboard operations,a pilot model is developed for simulation of helicopter shipboard flight.Mathematical description and generation algorithm of helicopter shipboard flight trajectory are developed.Therefore,a numerical simulation method of helicopter shipboard flight is formed and validated against the flight test data.On this basis,a theoretical method for prediction of helicopter WOD envelope is developed.The effect of the temporal and spatial variations of ship airwake on helicopter shipboard WOD envelope is analyzed.The results show that the proposed method has the capability to capture the effect of the temporal and spatial variations of ship airwake on the helicopter shipboard WOD envelope.Based on the numerical simulation of helicopter shipboard flight and predicted WOD envelope,the pilot workload for helicopter shipboard operations is analyzed.On this basis,a flight control system integrating with Rotor-State Feedback(RSF)is developed.The control system optimizes the rotor/body dynamic stability and helicopter turbulence rejection comprehensively by designing body and rotor state feedback gains together.Meanwhile,feedforward compensation and command model optimization are used to further improve the response bandwidth and attitude quickness.The result shows that in comparison to the baseline control system,the integrated RSF control system has higher response bandwidth and attitude quickness as well as better turbulence rejection,and therefore can effectively reduce the pilot workload for both the moderate-amplitude attitude control and low-amplitude highfrequency attitude compensation.