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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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