Further Results of SoftInplane Tiltrotor Aeromechanics Investigation Using Two Multibody Analyses

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Further Resultsof Soft-Inplane Tiltrotor
Aeromechanics Investigation Using Two Multibody
Analyses

• Pierangelo Masarati
• Assistant Professor
• Dipartimento di Ingegneria Aerospaziale
• Politecnico di Milano (Italy)

AHS International 60th Annual Forum Technology
Display Baltimore, MD - Inner Harbor June 7-10,
2004
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Authors and Contributors

• David J. Piatak NASA Langley Research Center
• Jeffrey D. Singleton Army Research Laboratory
• Giuseppe Quaranta Politecnico di Milano

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Outline

• Objectives and Approach
• Experimental Model Description
• Multibody Dynamics Analyses
• Key Analytical Results
• Isolated Blade Hub Results
• Control System Couplings
• Hover Performance Stability
• Forward Flight Stability
• Selected Nonlinear Analysis Issues
• Concluding Remarks

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Objectives

• Compare multibody analytical techniques
• Develop fundamental understanding of strengths,
  weaknesses, and capabilities of two different
  codes
• Assess prediction capabilities
• Compare response, loads, and aeroelastic
  stability in
• hover forward flight.
• Analysis vs. analysis
• Analysis vs. experiment
• Assess code/user fidelity
• Two different multibody codes
• Two different researchers
• Contrasting two codes helps eliminate errors in
  modeling

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Experimental Model

• Wing Rotor Aeroelastic Test System
  (WRATS)Tested in the Rotorcraft Hover Test
  Facility and the Transonic Dynamics Tunnel at
  NASA Langley Research Center

• Semi-Articulated Soft-Inplane Hub
• (SASIP)
• 4 blades
• articulated
• soft-inplane
• elastomeric lag damper

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Multibody Analyses

• Time domain - analyze via virtual experiments
• Can model components and mechanical effects not
  typically included with comprehensive rotor
  analyses
• Hydraulic components
• Mechanical joints
• Free-play in linkages
• No fixed-hub assumption

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Analytical Models Analysts

• MBDyn - MultiBody Dynamics
• Developed by (a team led by)Prof. Paolo
  Mantegazza, Politecnico di Milano
• WRATS-SASIP analyzed by Pierangelo Masaratiand
  Giuseppe Quaranta
• DYMORE
• Developed by (a team led by)Prof. Olivier
  Bauchau, Georgia Tech
• WRATS-SASIP analyzed by Dave Piatak and Jinwei
  Shen

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MBDyn - Analytical Model

• Analysis includes

• Swashplate mechanics
• Hydraulic actuators
• Blades as composite-ready beams, with blade
  element aerodynamics
• Wing as modal element, with state-space
  aerodynamics

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DYMORE - Analytical Model
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DYMORE Simulation Example
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Blade Modal Analysis
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Control System Couplings

• Typically difficult to model. Elastic
  deformation can have a significant contribution.
• Non-linear modeling - classical analyses
  typically use constant or tabulated lookup
  coefficients.
• Multibody codes capture nonlinear effect.

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Hover Run-up

• Current analytical model is a simple, constant
  stiffness equivalent spring hinge

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HoverPerformance

• Blade elasticity and geometrical cross-couplings
  greatly influence performance predictions

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Hover Dynamics
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Forward Flight Stability
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Forward Flight Stability
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Powered Flight Damping Bucket
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Powered Flight Damping Bucket
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Powered Flight Damping Bucket
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Powered Flight Damping Bucket
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Powered Flight Damping Bucket
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Concluding Remarks

• Multibody codes can
• successfully model complex systems
• improve predictions of rotorcraft dynamic
  behavior
• proficiently address nonlinearity issues
• Next steps are
• Conversion / maneuver simulations
• Hub/blade maneuver loads correlation
• Parametric study of SASIP

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Special Thanks To -

• Giampiero Bindolino (Politecnico di Milano,
  Dipartimento di Ingegneria Aerospaziale)
• Mark W. Nixon (ARL Army Research Laboratory,
  Vehicle Technology Directorate)
• Jinwei Shen (NIA National Institute of
  Aerospace)