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Multibody simulation of the power boosted
control section of a medium sized helicopter EHTC, November 2011, Bonn
Felix Blume, Eurocopter Deutschland GmbH
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Outline
Introduction and basis information
Motivation for Multibody Simulation
Development of Rigid Body Model
Loads
Validation
First Results
Status/Open Actions
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Introduction
Presenter information:
Felix Blume, Development Engineer, Stress Department Analysis Rotors and Blades
• Blades
• Rotors
• Flight Control (power boosted and not power boosted)
• Hydraulics
• Gearboxes
• Drive Train
Company information:
• Eurocopter Deutschland GmbH, EADS Group
• 4300 Employees
• Mainsite Donauwörth
• EC135, EC145, BO105, Tiger, NH90
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Basis Information
Pitch Link
Hub
Control
Cuff
Lead-lag damper
Flexbeam
(flexible in torsion and
flapwise / lead-lag direction)
Basis Information
• Rotor without
mechanical flapping and
lead-lag hinge
• Feathering with flexible
composite element
Bearingless Main Rotor EC135
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5
Mast
Pitch Link
Basis Information
• Pilot input force amplified by
3 hydraulic actuators (1 for
each axis)
• Limit Load on Pitch Link
8500 N
• Limit load on collective
booster axis 16500 N
• Scissor transfers rotating
motion to bearing ring
Power Boosted Control Section
Three Booster
Axis
Scissor
Swashplate
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Motivation for Multibody Simulation
External loads (blade loads) are calculated from the aerodynamic
department based on flight test results, scaling and CFD
Interface loads measured during flight test
In early phase of new design, no new flight test data available
Current Status:
• Linear scaling of all interface loads for certain swashplate positions
• Exact load distribution is difficult to calculate for all swashplate
positions
Consequence: Calculated loads are conservative
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Motivation for Multibody Simulation
Interface loads to be determined by stress department based on blade
loads and different swashplate positions by using advanced
tools/methods
Decision of introducing a Multibody Simulation Tool:
Software : Altair MotionView (included already in Hyperworks)
First two models created with support of Altair
Building up competences for Multibody Simulation
We are just at the beginning
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Development of Rigid Body Model
• Geometrical Data Imported
from Catia V5
• 37 solid bodies
• Meshed with Hypermesh
• Assignment of Properties
(Aluminium and Titanium)
• Calculation of mass and inertia
(Mass= 53kg)
• Length of mast 918 mm
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• 37 Rigid Bodies
• 12 revolute joints
• 14 ball joints
• 5 inline joints
• 7 constant velocity joints
• 4 cylindrical joints
• Some joints are statically
overdetermined, but in reality there
is an existing play, i.e. not fully
blocked)
Development of Rigid Body Model
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Development of Rigid Body Model
Defined motions:
• Rotation rotormast: 415 RPM
• Max. translational movement of the
3 control axis:
Longitudinal: +/- 32.2 mm
Lateral: +20.0 mm/ -22.8 mm
Collective: +/- 21 mm
Max. blade angle: 17°
Fwd
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Development of Rigid Body Model
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Loads
External loads calculated by aerodynamic department
• Blade loads (flapping, leadlag and torsional moments, centrifugal force)
• Resulting control force in the rotating pitch link
Loads calculation based on existing flight test data
• Harmonic analysis
• Scaled to different RPM values and geometrical blade data
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Loads
Limit Load curve
• Load on pitch link 1 for
one full rotation (360 °)
• Rotation Angle = 0 °
when blade number one
above tailboom
• Load is shifted with 72 °
phases between each
pitch link
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Loads
Load introduction
FPL1
FPL2
• Limit Load curve is
applied on each Pitch
Link
• Load shifted with 72°
phase clockwise
• Rotor is turning counter
clockwise
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Loads
• Limit Load Manoeuvre:
• Turning Flight with VNE (Velocity
Never Exceed) and max. bank angle
• Control inputs:
Longitudinal: -17.4 mm
Lateral : 2.5 mm
Collective: 18.7 mm
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Loads
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Check of correct kinematic behaviour without external loads
• Clearance
• Reactive forces
• Gravity check
Check of force sign convention with external load
• Comparison with flight test data (with similar rotor system)
Comparison with analytically calculated forces for selected swashplate positions
Final validation when flight test data is available
Validation
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Force Interface Bearing Ring / Pitch Link
First Results
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Booster forces vs. rotation angle
First Results
Lateral Axis
Longitudinal
Axis
Collective Axis
Status / Open Actions
Status
• First Validation performed
• Booster loads calculated
Open Actions
• Interface loads for the remaining parts
• Stress calculation of the parts (FEM and Analytical)
• Introduction of Flexbodies for some parts (Booster Levers)
Conclusion
• Multibody Simulation has raising importance for stress
calculation of dynamic systems
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Status / Open Actions
Thank you for your attention.
Questions?
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