LAG DAMPER RESEARCHBrano Titurus, Nick Lieven & Peter Bunniss

Lag damper research

Lag damper research

Passive damper design

Passive damper design

Active damper design

Active damper design

Model refinement

Model refinement for improved correlation with experimental validation datasets.

Data for validation

Experiments designed for model validation, parameter ID etc.

Test rig for validation

Test rig design for model validation, refinement and substructuring.

Control performance

Control performance studies for a range of cost functions, response quantities and flight conditions.

R150 implement.

Algorithmic and software implementation of HHC/IBC concept and new damper models into rotor performance prediction code R150.

Evaluation & concept

(Semi)active damper concept and initial evaluation (damping capacity etc.) Model selection and further use (e.g. in R150).

Research evolution

Nominal damper model

Evaluation & validation

Smart damper

Nominal damper model

Parametric studies

Passive damper

Previous research (PhD)

Passive damper design

{Brano.Titurus,Nick.Lieven,Peter.Bunniss}@bristol.ac.uk

Displacement-Force profile for sine excitation: 20.46 mm; 3.5 Hz.

Velocity-Force profile for sine excitation: 20.46 mm; 3.5 Hz.

Characteristic lines for 3.5 Hz.

Model validationLag damper on EH101

Active damper designR150 implementation

Analysis blocks

Comparison of the damper forces and piston velocities for nominal and decoupled cases.

Decoupled trimming

Damper response change due to 5/rev COS harmonic change of the orifice diameter on rotor trim.

Standard trim (constant parameter) ‘Harmonic’ trim

Resp

onse

chang

e

Periodic parameter variations

Nominal damper model

, , , , ,

,0 0

1, ,

iV i V i i V i i C i V i

P o j V j j

d x tA p b x t k x t X m

dtd p

A y sign p Q p p x Q p xdt V

D

,

0

P PP CD m y sign yA p fF

Basis of the model – relief valve dynamics, fluid compressibility equation:

Force generated by the damper:

Refined damper model

, , , , , ,

*,

( )

1, ,

, ,

iV i V i i V i i V i i C i V i

P O j V j jE P C

d x tA p R x b x t k x t X m

dtd p

A y sign p Q p p x Q p xdt p k k V

D

D PF A p

Refined damper model (relief valve losses, by-pass tube losses, finite flexibility, effective compressibility):

Force generated by the damper (massless piston):

Test rig for validation Actuator+LVDT Load cell Lag damper

0 0,V

Vp

pLp Ep

y t

0Pm

Relief valves

Orifice

Attachment flexibility

( )

V p

p

Vp

pLp Ep

Py t

,E Vp

V p

Pk Ck

y t

0Pm

y t

( )

V p

p

O Op d ,E Op

V p

Pk Ck

Od

0Pm

Single variable orifice

Modified passive design

e.g. single variable orifice instead of a pair of mechanical

relief valves

1

,, , P O O O O

E P C

d pA y sign p Q p d d d

dt p k k V

D PF A p

Active damper model concept

cos sinO O j jj

d d A j t B j t Variable orifice (diameter) for trimmed flight:

Force generated by the damper (massless piston):

Basis of the model – pressure difference evolution:

Modified R150

• decoupled rotor-damper integration (FOH/ZOH Z-transform vs Runge-Kutta),• continuation between trimmed states (on-line trimming) for fast evaluations, • periodic variations of damper parameters to implement HHC/IBC schemes.

Evaluation, analysis & modificationDamper with variable orifice, 1/rev harmonic perturbation:

Damper with variable orifice, 4/rev harmonic perturbation:

0.1 cos 1 0.2 sin 1O O O Od d d t d t

0.7 sin 4O O Od d d t

Dcpl. logic

isNext

isID

1

0

10

Model ID

Controller

(Damper) HHC/IBC controller

Con

trol

log

ic

Mod

al &

tri

m

con

verg

en

ceIn

itia

lisati

on

s,

data

in

pu

tPost

-pro

c.,

stru

ct.r

esp

. etc

.

R150

Aero-elasticity Hydro-mechanics Control logic

Z-transform Runge-Kutta HHC/IBC

ROTOR DAMPER CONTROL & ID

, ;t x f x

Damper v.X.X

Higher-Harmonic/Individual Blade Control (HHC/IBC) schemes assuming sequences of trimmed states.

,y t y t

DF t

A library of damper models for different design options and configurations.

Interactive parameter change (orifice diameter) after nominal trim.

Standard (thrust & flapping) trim 12x 12x 12x

do=1.0 (normalised orifice diameter) do=0.2 do=1.6 do=1.0

. i jcomp z p

On-line trimming

Nom

inal tr

im