PI : Asst. Prof. Joseph F. Horn Tel: (814) 865 6434 Email: joehorn@psu

1. Project PS 5.2Simulation and Control of Shipboard Launch and Recovery Operations PI: Asst. Prof. Joseph F. Horn Tel: (814) 865 6434 Email: joehorn@psu.edu Graduate Student: Dooyong Lee, PhD Candidate 2002 RCOE Program Review April 3, 2003

2. Tailwinds from astern Poor field-of-view High vibrations Starboard side winds Local flow acceleration High vibrations Port side winds Main rotor vortex ingestion Uncommanded right yaw Background / Problem Statement • The shipboard launch and recovery task is one of the most challenging, training intensive, and dangerous of all rotorcraft operations • The helicopter / ship dynamic interface (DI) is difficult to accurately model • Industry and government could use better tools for analyzing shipboard operations to reduce the flight test time and cost to establish safe operating envelopes • Workload requirements could be reduced using task-tailored control systems for shipboard operations Technical Barriers • Accurate models require the integration of the time-varying ship airwake and the flight dynamics of the helicopter • Currently pilot workload requirements and HQ analysis must be assessed using expensive flight tests and piloted simulation • A practical fully autonomous or piloted assisted landing AFCS has not yet been developed, need to assess requirements and potential benefits

3. Task Objectives: • Develop advanced simulation model of the shipboard dynamic interface • Validate the model using available 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 models, 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) Expected Results: • A simulation tool for analyzing handling qualities in the DI and predicting safe landing envelopes • A methodology for designing a task-tailored AFCS for shipboard operations • A conceptual design of an autonomous landing systems and assessment of the system requirements for such a system (possible UAV applications)

4. MATLAB/SIMULINK based DI Program • Based on GENHEL • Updated : Higher order Peter-He inflow model, Gust penetration model • Maneuver controller model

5. Time-Accurate Ship Airwake • Established CFD solutions of ship wake(Sezer-Uzol , Dr. Long) • Parallel flow solver PUMA2 is used to calculate the flow • Time-varying, inviscid CFD solutions of the airwake of an LHA class ship • 3-D, internal and external, non-reacting, compressible, unsteady solutions of problems for complex geometries

6. Data load 0.0 0.1 0.2 0.3 19.8 19.9 20.0 19.9 … … Interpolation Application of Time-Accurate Ship Airwake • Time step of base dynamic model is 0.01 sec • Time varying solutions are stored at every 0.1sec(total 20 sec) • Start from the pseudo steady state solution • Airwake data is loaded at every 0.1 sec • Linear interpolation method is used for ( ~ 0.01 sec) Reverse

7. Gust Penetration Account for Local Velocities at Blade Elements, Fuselage, Empennage, Tail Rotor Time-Accurate Ship Wake Gust Velocities from CFD Linear look-up algorithm 3-D uniform grid

8. Maneuver Controller UH-60 Flight Dynamic Model Desired Output Model Compensator Command u + - Command Stick input K Desired Target Model Online Compensator Maneuver Controller

9. PID Type Maneuver Controller Nonlinear Dynamic model Longitudinal control Lateral control Linearized 29 state model Heave axis control Reduced 9 state model Decoupled dynamic model Find the gains for PID controller

10. Shipboard Departure • Shipboard departure sequences • Phase I : From the stationkeeping location accelerating to a desired climb rate and a desired horizontal acceleration • Phase II : Keeping a constant climb rate and horizontal acceleration • Phase III: Reducing the climb rate and horizontal acceleration to zero, and ending in a steady level flight Phase III Phase II Phase I

11. Simulation Results of Shipboard Departure • Helicopter position w.r.t LHA coordinate system Y(ft) Escape time is 46.5 sec DI mesh Z(ft) X(ft) LHA ship Z(ft) Y(ft) X(ft) X(ft)

12. No wake Steady wake Time-varying wake Simulation Results of Shipboard Departure • Helicopter angular rate and Attitude angle • High oscillatory motion is cause by time-varying ship airwake - Angular rate(deg/sec) - Attitude angle(deg) Roll Phi Escape from DI mesh Theta Pitch Psi Yaw Time(sec) Time(sec)

13. No wake Steady wake Time-varying wake Simulation Results of Shipboard Departure • Stick inputs(%) • Lateral cyclic input : Left  0%, Right  100% • Longitudinal cyclic input : Forward  0% , Aft 100% • Collective input : Down  0%, Up  100% • Pedal input : Left  0%, Right  100% Escape from DI mesh Lateral Lateral Hover Longitudinal Longitudinal Collective Collective Pedal Pedal Time(sec) Time(sec)

14. Shipboard Approach • Shipboard approach sequences • Phase I : From the steady level flight, accelerating to a desired decent rate and a desired horizontal deceleration • Phase II : Keeping a constant descent rate and horizontal deceleration • Phase III: Reducing the decent rate and horizontal deceleration to zero, and ending in a station keeping

15. Simulation Results of Shipboard Approach • Helicopter position w.r.t. LHA coordinate system Entering time is 38.7 sec Y(ft) Z(ft) X(ft) Z(ft) Y(ft) X(ft) X(ft)

16. No wake Steady wake Time-varying wake Simulation Results of Shipboard Approach • Helicopter angular rate and Attitude angle - Angular rate(deg/sec) - Attitude angle(deg) Enter the DI mesh Roll Phi Theta Pitch Psi Yaw Time(sec) Time(sec)

17. No wake Steady wake Time-varying wake Simulation Results of Shipboard Approach • Stick inputs(%) • Later cyclic input : Left  0%, Right  100% • Longitudinal cyclic input : Forward  0% , Aft 100% • Collective input : Down  0%, Up  100% • Pedal input : Left  0%, Right  100% Enter the DI mesh Lateral Lateral Longitudinal Longitudinal Collective Collective Pedal Pedal Time(sec) Time(sec)

18. Stochastic wake Time-varying wake Correlated airwake model White Noise Transfer function : turbulence intensity : scale length of turbulence : speed of the mean wind field : PSD temporal break frequency Stochastic ship airwake model • Correlated airwake is determined by • passing through spectral filter with • desired transfer function • (ref.Clement, Labows et al.) • Modeling parameters were obtained • from flight test data(temporal data) • Need parameters that describe both • the temporal and the spatial • characteristics Lateral Longitudinal Collective Pedal

19. Conclusions • Dynamic interface simulation model • MATLAB based simulation model for UH-60(based on GenHel) • Gust penetration model • Integrated with time-varying, inviscid CFD solutions of the airwake for an LHA ship • using 3-D look-up algorithm • Maneuver controller • Develop a PID controller to simulate pilot control for launch and recovery operations • - Investigate pilot workload during launch and recovery, use to develop improved control laws • Shipboard approach and departure operations • The time-varying airwake effects on the helicopter appear to be significant for pilot workload when operating in the helicopter/ship dynamic interface • Potential areas for improvement • -Data storage requirements for time varying are extensive, might make real-time implementation difficult. • -A stochastic airwake implementation should be investigated.

20. Future Work • Update the dynamic interface simulation model • Aerodynamic effects of moving ship deck currently in development (Peters-He inflow model with moving ground effect) • Model of Ship Deck Motion, use Navy SMP software • Improve maneuver controller to handle a variety of shipboard operations • Develop a stochastic time-varying wake model based on the statistical properties of the temporal and spatial variations of the CFD airwake • Still pursuing validation data. JSHIP flight test data may be most promising, matches the current configuration that we are simulating – LHA + UH-60A. • Task-tailored control systems for shipboard operations • Optimized stability augmentation • TRC / position hold over flight deck • Autonomous landing

21. Completed Short Term Long Term Schedule and Milestones 2001 2002 2005 2003 2004 Tasks • Update GenHel Simulation for shipboard simulation • Develop simplified MATLAB Sim for control design • Interface GenHel with ship air wake solutions and ship motion • Develop maneuver controller • Validation of DI simulation • Investigate relative fidelity of time-accurate and stochastic wakes • Develop low-fidelity real-time simulation capability at PSU • Piloted simulation of DI simulation (cooperative effort with industry) and analyze HQ requirements • Task tailored control design • Piloted simulation of task-tailored control • Lee PhD Degree

22. 2002 Accomplishments • Improved Dynamic Interface Simulation • Integration of time varying CFD solutions of LHA airwake • Integration with simple stochastic time-varying gust field • Peters-He inflow model, currently developing with moving ground effect • Developed Maneuver Controller to simulate pilot control inputs during launch and recovery operations • Analysis of effects of time varying wake on flight dynamics • Developing real-time simulation facility for piloted simulation and visualization tool • Presented results at AHS Flight Controls Specialists’ Meeting Planned Accomplishments for 2003 • Will present newest results at 2003 AHS Forum and AIAA Atmospheric Flight Mechanics Conference, submit AHS Forum paper as journal article • Continue to update and improve model • Developing advanced stochastic time-varying airwake model with temporal and spatial variations in gust field, based on statistical properties of CFD airwake solutions. • Start development of task-tailored control laws / autonomous landing systems • Continue development of real-time simulation

23. Technology Transfer Activities: • Collaboration with Lyle Long, used latest LHA airwake solutions • Horn and Long briefed U.S. Navy Advanced Aerodynamics Group at Pax River. Continue to interact with this group. • Presented work at AHS Flight Controls Technical Specialists’ Meeting • Paper to be presented at 2003 AHS Forum / AIAA AFM Conference. Leveraging or Attracting Other Resources or Programs: • DURIP equipment grant supporting helicopter simulator project, being used for this project • Currently pursuing data from JSHIP program to help validate model. Recommendations at the Kickoff Meeting: Actions Taken: • Interacting with U.S. Navy Advanced Aerodynamics Group (Dave Findlay, Colin Wilkinson, Susan Polsky) • No formal interaction with DERA (now QinetiQ?) at this time. • Need collaboration with U.S. Navy and possibly DERA