Student: Dooyong Lee
The shipboard launch and recovery task is one of the most challenging, training intensive, and dangerous of all rotorcraft operations. Pilots must perform the launch and recovery tasks in rough seas and with poor visual cues. The helicopter / ship dynamic interface (DI) is also very difficult to accurately model in flight dynamics simulations. This aircraft interacts with the airwake from the ship and the moving ship deck when landing. Industry and government need better tools for analyzing shipboard operations to reduce the flight test time and cost to establish safe operating envelopes. High-fidelity piloted simulation analysis can also be expensive, and an effective off-line tool for flight dynamics analysis in the DI could reduce cost and increase productivity of flight tests and piloted simulations. Workload requirements could be reduced using task-tailored control system design for shipboard operations. |
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Research Objectives:
• Develop advanced simulation model of the shipboard dynamic interface
• Validate the model using JSHIP flight test data
• Use the model to develop advanced flight control systems to address workload issues in the DI
Approaches:
• Develop a MATLAB/SIMULINK based simulation of the H-60 based on GenHel (will facilitate model improvements and control law development)
• Develop a maneuver controller to simulate pilot control during launch and recovery operations
• Integrate simulation with ship airwake model, investigate relative effects of steady and time-accurate CFD wakes, and stochastic wake models based on CFD and flight test data
• Validate model with available data
• Develop new concepts in AFCS design for shipboard operations
• Develop a real-time simulation facility of shipboard operations (using DURIP funds)
Simulation of the shipboard environment requires us to model the effects of the turbulent airwake of the ship on the helicopter. To model this effect we have been working with Dr. Long and his students. They have provided CFD solutions for various ships in different wind-over-deck or WOD conditions. A sample of thier work is shown in this animation (1.5 MB).
With the CFD solutions it is just a matter of mapping the local air velocities into the simulation as illustrated below:
We have developed an Optimal Control Model of a human pilot in order to automatically simulate approach and departure operations. A schematic of the pilot model is shown in the figure below and a sample simulation video of the pilot model performing an approach (in very difficult 30° / 30 knot WOD conditions) can be seen in this animation (5.8MB). The overall simulation has been checked against JSHIP flight test data as shown in the figure below.
Optimal Control Model of a Human Pilot
Finally, we have developed stochastic disturbance models that replicate the disturbance due to the ship airwake as a random process. We use the CIFER system ID software and a method similar to the approach of Lusardi, Labows, and Tischler at NASA Ames. The equivalent airwake disturbance model is based on traditional von Karmen turbulence model, but with a modified shaping filter as shown below. These filters have been used to optimize the flight control laws in order to improve handling characteristics in approach operations. We use the NASA Ames developed software CONDUIT to optimize the controller.
