UAV Sky-Y flight loads:a Multi-Disciplinary approach

Daniele Catelani (MSC)

G.M. Carossa, E. Baldassin, R. Digo, E. Marinone, O. Valtingojer(Alenia Aeronautica)

© 2010 Alenia Aeronautica S.p.A.

The contents of this document are the intellectual property of Alenia Aeronautica S.p.A.. Apart from those contractually-agreed user rights, any copying or communication of this document in any form is forbidden without the written authorisation of Alenia Aeronautica S.p.A..

2 Target of the study

- Integration of various disciplines (flight mechanics, aerodynamics, structures, loads) simulation models

- Benchmark on flight simulation using Multi-Disciplinaryapproach

- Air Vehicle Methodology improvement: the goal is toachieve the result through an “unique simulation”

3 Unmanned Air Vehicle (UAV)

Alenia Aeronautica major achievements in UAV domain:• 2005 - Sky-X (1°flight May ’05), the first in its c lass to have flown in Europe• 2007 - Sky-Y (1°flight June ’07), operating demonst rator to gain experience both in civil and

military domains, aimed to Medium Altitude – Long Endurance (MALE) missions.

From surveillance to reconnaissance, from patrol to the most risky defence operations, the new frontier of aeronautics lies in the UAV (Unmanned Air Vehicle) domain development.Alenia Aeronautica, thanks to its effort in dealing with the various aspects of this new environment, is today the European leader in the UAV technology.

4 Sky-Y

Dimensions

Length 9.725 m

Span 9.937 m

Weights

MTOW 1200 kg

OEW 850 kg

Fuel 200 kg

Payload 150 kg

Performances

LOS Radius 50 nm

Range 500 nm

Altitude 25.000 ft

Endurance 12 h

Engine1 Diesel 160 HP

Dimensions

Length 9.725 m

Span 9.937 m

Weights

MTOW 1200 kg

OEW 850 kg

Fuel 200 kg

Payload 150 kg

Performances

LOS Radius 50 nm

Range 500 nm

Altitude 25.000 ft

Endurance 12 h

Engine1 Diesel 160 HP

Conceived as technology demonstrator for a MALE surveillance UAV. Its purpose is to develop enabling technologies that increase the aircraft’s autonomous flight and data collection and distribution capabilities.Sky-Y has an all-composite structure, all-electric systems and a diesel engine of automotive derivation giving it up to 12 hours endurance.

5 Sky-Y - SMATThe SMAT (Sistema di Monitoraggio Avanzato del Territorio – Advanced Monitoring System of Territory), lead by Alenia Aeronautica and Selex Galileo, is a research project mainly based on Sky-Y UAV.It is financed by Regione Piemonte and Distretto Aerospaziale Piemontese.

Sensors Coordinationcenter

Ground Control Station

Ground Network

Sky-Y

Aim of SMAT is to study and demonstrate the feasibility of an automated surveillance system for environmental and civil security, traffic surveillance, pollution control, etc…It will integrate three different UAV platforms with the existing ground infrastructures.

6 Multi-Disciplinary (MD) simulation

ADAMSPilot input FCS model

Aerodynamicdata set

FEM Model with

Inertial data

MB Data (Control surfaces)

Flight Loads Time History

Dynamic model of UAV flight:� coupling aerodynamic data set, structural models, FCS (Flight Control System)

� flexible structural model (including control surfaces)

� control surfaces actuator models

� aerodynamic and inertial loads due to flight manoeuvres

7

Structure Technologies Domain

FEM+

pressuredistribution

MB controlledmodel

Matching aerod/FEM

Action 1

Aerodata set

FEM +

inertia data

Createmodal data

Action 2

Loads on structure

ManoeuvreanalysisAction 4

Modaldata

Create MBmodel

Action 3

MBdata:

controlsurfaces

Actuatorsloads and position

Manoeuvreresponse

data

Requirements

CAD & FEM &MB & CFD

Preprocessing

Action 0

Genericmanoeuvreresponse

Data

Extracting specific

responsesAction 5

System Technologies Domain

Flight Tecnologies Domain

Pilot Input

MD processFCS

model

8 Aerodynamic data setThe aerodynamic analysis is accomplished by using various analytical techniques such as Vortex Lattice or Euler formulation methods (CFD - Computational Fluid Dynamics).These analytical techniques allow to generate an aerodynamic model starting from the external shape of the air vehicle.

For a set of flight parameters (αααα, ββββ, δδδδ, Mach), relevant aero-coefficients on predefined grids of the aerodynamic mesh are calculated. These coefficients are assembled into the aerodynamic data set.

Macropanel

MacropanelPanels

9

-- Original FEM model: Original FEM model: full A/C NASTRAN model used for aeroelastic analyis

-- Modification of FEM model:Modification of FEM model:modifications have been applied to take into account static and dynamic analysis

differences and MultiBody needs:

- separation of FlexBodies from assembled FEM model

- master nodes definition

- number of modes definition

- ADAMS MNF cards

Airframe

Elevator

Aileron

Rudder

FEM model

10 Structural/Aerodynamic coupling

Aerodynamic model mesh Structural model (FEM)

Models coupling

CFD aero coefficent data set are transferred on the structural mesh(not coincident with the aerodynamic one) using RBE3 element

11 Structural/Aerodynamic coupling

Aerodynamic model mesh Structural model (FEM)

Models coupling

CFD aero coefficent data set are transferred on the structural mesh(not coincident with the aerodynamic one) using RBE3 element

12 Flight Control System (FCS) model

A Flight Control System has been developed, using General State Equation(GSE) element (which allows discrete integration time step)

Input data time history of pilot commands (aileron, elevator, rudder, throttle) are transferred through FCS model (Alenia Fortran routine – black box) and GSE to control surfaces

Output are controlled surfaces rotations

13 Assembly of MD model – 1Aerodynamic Forces in Adams

CFD / Aerodynamic data

FORCE 97 3059 0 1.06412 .0165988.0667837-.997629FORCE* 97 3060 0 1.25965* -.00241019 .0635587 -.997975FORCE* 97 3074 0 9.1782* -.00184328 .0636041 -.997974FORCE* 97 3075 0 9.61135* -.00534181 .0623677 -.998039FORCE* 97 3076 0 1.90042* -3.79548-4 .0633518 -.997991FORCE* 97 3078 0 5.7019* -.0163088 .050371 -.998597FORCE 97 3079 0 12.9511 .0182413.0660599-.997649FORCE* 97 3080 0 11.2832* -.0110068 .0644774 -.997859FORCE* 97 3094 0 18.1014* .00230714 .0638071 -.99796

From aero mesh tostructural mesh

From structuralmesh to Adamsinput: Fortran routine

Grid ForceLoads

Nodal forcesVFORCE

Modal forcesMFORCE

Case: L_201 -0.09137785412 133.71724567233 9746.45928377814 -4481.21750821565 -49437.21069326076 778.08342811117 -24.1865506319

14 Assembly of MD model – 1Aerodynamic Forces in Adams

CFD / Aerodynamic data

FORCE 97 3059 0 1.06412 .0165988.0667837-.997629FORCE* 97 3060 0 1.25965* -.00241019 .0635587 -.997975FORCE* 97 3074 0 9.1782* -.00184328 .0636041 -.997974FORCE* 97 3075 0 9.61135* -.00534181 .0623677 -.998039FORCE* 97 3076 0 1.90042* -3.79548-4 .0633518 -.997991FORCE* 97 3078 0 5.7019* -.0163088 .050371 -.998597FORCE 97 3079 0 12.9511 .0182413.0660599-.997649FORCE* 97 3080 0 11.2832* -.0110068 .0644774 -.997859FORCE* 97 3094 0 18.1014* .00230714 .0638071 -.99796

From aero mesh tostructural mesh

From structuralmesh to Adamsinput: Fortran routine

Grid ForceLoads

Nodal forcesVFORCE

Modal forcesMFORCE

Case: L_201 -0.09137785412 133.71724567233 9746.45928377814 -4481.21750821565 -49437.21069326076 778.08342811117 -24.1865506319

15 Assembly of MD model – 2Structural elements in Adams

Aeroelastic model

•Separated

FE bodies

•Master nodes

•MNF statements

Flex Bodies

FULL

MultiBody model

MNF

files

Connections

16 Assembly of MD model – 2Structural elements in Adams

Aeroelastic model

•Separated

FE bodies

•Master nodes

•MNF statements

Flex Bodies

FULL

MultiBody model

MNF

files

Connections

17

• read pilot input

• link FCS to pilot input at sampled time

• get FCS output

• Aileron rotation

• Rudder rotation

• Elevator rotation

• Throttle

• link output to actuators

Assembly of MD model – 3FCS in Adams

GSE subroutine

� GSE

• array

• state variablesPilot Input

• mobile surfacesrotation

• thrust

18 Assembly of MD model – 4Full Adams model

Graphics

Simulationcommand

Solver parameters

Forces• aerodynamic

• thrust

• drag

• damping moment

Connections• fixed

• rev

• sph

• bushingMeasures• disp

• vel

• acc

• loads

Data• splines

• matrices

• array

• vars

33 rigid bodies

7 flex bodies

47 joints

15 bushings

1550 aerodynamic forces (vector forces) or 27 modal forces

2 vector torques

1 single component force

34 requests

19

The manoeuvre simulation is splitted in two phases:

1. Trim analysis defining the first instanct of the dynamic response. At the required speed, altitude, load factor (Nz), the equilibrium aircraft condition is found with angular acceleration = 0.

2. Dynamic analysis starting from trimmed position imposing pilot commands

Three kind of trimming have been considered:

pull out (Nz ≥ 1 ) steady turn (Nz > 1) inverted flight (Nz = -1)

Manoeuvres description

20 MD simulation – Trim AnalysisImplemented Strategy for trimming the aircraft:

� pin the aircraft to the aggregate mass node (C++ feature) through revolute and bushing allowing pitchrotation

� define the required A/C condition in term of speed, altitude, load factor and trim type (GUI)

� apply a sequence of static analysis reducing bushingKt to 0

� apply methods to obtain “robust” trim solution:

• run rigid model first, then flexible one

• increment number of iterations and KT values

• find intermediate (not trimmed but closer) configuration and then restart

• reduce error tolerance

GUI

21 MD simulation – Trim AnalysisImplemented Strategy for trimming the aircraft:

� pin the aircraft to the aggregate mass node (C++ feature) through revolute and bushing allowing pitchrotation

� define the required A/C condition in term of speed, altitude, load factor and trim type (GUI)

� apply a sequence of static analysis reducing bushingKt to 0

� apply methods to obtain “robust” trim solution:

• run rigid model first, then flexible one

• increment number of iterations and KT values

• find intermediate (not trimmed but closer) configuration and then restart

• reduce error tolerance

GUI

22 MD simulation – Trim Analysis results

Results in tabular form and in GUI

23

Implemented strategy for Dynamic Analysis:

� start from trimmed analysis results or from position imposed by user (GUI)

� define pilot inputs in terms of longitudinal, lateral, directional and handle commands in the bulk data file

� define time for balancing and simulation

� run rigid or flexible model

MD simulation – Dynamic Analysis

GUI

24 MD simulation – Dynamic Analysis

Implemented strategy for Dynamic Analysis:

� start from trimmed analysis results or from position imposed by user (GUI)

� define pilot inputs in terms of longitudinal, lateral, directional and handle commands in the bulk data file

� define time for balancing and simulation

� run rigid or flexible model GUI

25 MD simulation - results 1

PULL OUT

26 MD simulation - results 2

Alpha

Elevator

Drag

PUSH DOWN

27 MD simulation - results 3

STEADY TURN

28 From Adams to FE: Nodal Loads(GPFORCES)

� Adams/Durability module exports Adams analysis as a modaldeformation file (mdf) file

� Nastran Restart analysis is performed including GPFORCE/ALL

� The Nastran output (f06 file) contains GPFORCES informationson each structural node for each time step

� Patran is used for graphical visualisation

� A reading/writing Fortran (C++) routine could be developed forextracting hotspot informations (max forces, monitoring stationsloads, etc.)

29 Nodal Loads: GPFORCES

Example of output

TIME = 2.120000E+00

G R I D P O I N T F O R C E B A L A N C E

POINT-ID ELEMENT-ID SOURCE T1 T2 T3 R1 R2 R313120 13312 BEAM -2.755696E+03 -2.819249E+04 1.426504E+03 4.351999E+00 -2.657374E+00 -3.209920E+0113120 13313 BEAM 2.960352E+03 3.174499E+04 -1.292652E+03 -4.313663E+00 1.043627E+00 3.121524E+0113120 13149 QUAD4 3.952978E+02 -2.408490E+03 7.174867E+01 9.150950E-02 6.318014E-01 -2.617756E-0213120 13161 QUAD4 -4.564485E+02 7.612727E+02 4.015422E+01 -1.273894E-01 7.018989E-01 -1.694177E-0313120 13508 QUAD4 -1.397564E+02 -1.369168E+03 8.041031E+02 3.546397E-02 4.387868E-01 2.068550E-0113120 13510 QUAD4 -4.971187E+01 -5.222424E+02 -1.524998E+03 -3.230371E-02 -1.815095E-01 -6.307498E-0213120 13517 QUAD4 1.470395E+02 -5.599373E+00 4.537404E+02 -7.230631E-02 2.103570E-02 1.150132E-0113120 13702 ROD 0.0 0.0 1.100292E+01 0.0 0.0 6.949344E-0513120 *TOTALS* 1.709518E-07 4.396483E-08 4.000717E-07 -9.861861E-11 -1.026633E-09 2.421182E-11

0 13121 13305 BEAM 2.579122E+03 2.470907E+04 -1.986231E+03 2.452257E+00 7.972231E-01 -2.371344E+0113121 13306 BEAM -3.192366E+03 -2.892795E+04 2.296607E+03 -2.716814E+00 -4.582419E-01 2.383611E+0113121 13160 QUAD4 -3.231614E+02 1.796923E+03 -1.525345E+02 6.193042E-02 -8.084043E-02 1.519091E-0313121 13172 QUAD4 6.732228E+02 -2.212344E+02 2.058180E+01 2.989256E-01 3.210797E-02 -5.509890E-0313121 13510 QUAD4 1.673334E+02 1.608403E+03 1.488966E+03 5.392670E-03 2.683917E-01 3.503260E-0213121 13512 QUAD4 9.584893E+01 1.034791E+03 -1.667389E+03 -1.016917E-01 -5.586404E-01 -1.537168E-0113121 *TOTALS* 1.604205E-07 1.072726E-08 3.533314E-07 1.305214E-10 1.339109E-09 -7.649933E-11

30 Nodal Loads: GPFORCES

Example of output

TIME = 2.120000E+00

G R I D P O I N T F O R C E B A L A N C E

POINT-ID ELEMENT-ID SOURCE T1 T2 T3 R1 R2 R313120 13312 BEAM -2.755696E+03 -2.819249E+04 1.426504E+03 4.351999E+00 -2.657374E+00 -3.209920E+0113120 13313 BEAM 2.960352E+03 3.174499E+04 -1.292652E+03 -4.313663E+00 1.043627E+00 3.121524E+0113120 13149 QUAD4 3.952978E+02 -2.408490E+03 7.174867E+01 9.150950E-02 6.318014E-01 -2.617756E-0213120 13161 QUAD4 -4.564485E+02 7.612727E+02 4.015422E+01 -1.273894E-01 7.018989E-01 -1.694177E-0313120 13508 QUAD4 -1.397564E+02 -1.369168E+03 8.041031E+02 3.546397E-02 4.387868E-01 2.068550E-0113120 13510 QUAD4 -4.971187E+01 -5.222424E+02 -1.524998E+03 -3.230371E-02 -1.815095E-01 -6.307498E-0213120 13517 QUAD4 1.470395E+02 -5.599373E+00 4.537404E+02 -7.230631E-02 2.103570E-02 1.150132E-0113120 13702 ROD 0.0 0.0 1.100292E+01 0.0 0.0 6.949344E-0513120 *TOTALS* 1.709518E-07 4.396483E-08 4.000717E-07 -9.861861E-11 -1.026633E-09 2.421182E-11

0 13121 13305 BEAM 2.579122E+03 2.470907E+04 -1.986231E+03 2.452257E+00 7.972231E-01 -2.371344E+0113121 13306 BEAM -3.192366E+03 -2.892795E+04 2.296607E+03 -2.716814E+00 -4.582419E-01 2.383611E+0113121 13160 QUAD4 -3.231614E+02 1.796923E+03 -1.525345E+02 6.193042E-02 -8.084043E-02 1.519091E-0313121 13172 QUAD4 6.732228E+02 -2.212344E+02 2.058180E+01 2.989256E-01 3.210797E-02 -5.509890E-0313121 13510 QUAD4 1.673334E+02 1.608403E+03 1.488966E+03 5.392670E-03 2.683917E-01 3.503260E-0213121 13512 QUAD4 9.584893E+01 1.034791E+03 -1.667389E+03 -1.016917E-01 -5.586404E-01 -1.537168E-0113121 *TOTALS* 1.604205E-07 1.072726E-08 3.533314E-07 1.305214E-10 1.339109E-09 -7.649933E-11

31 Conclusions

ADVANTAGES:

- the results are in agreement with the outputs of currently used method

- integration of simulation models of different disciplines

- easy I/O management by use of GUI

DISADVANTAGES:

- aerodynamics/structural modal simulation quite complex

- requirements of high computing power (possibly HPC)

Performed test simulating various types of manoeuvres evidence:

32 Way forward

- extension of the module to generic airframe: generic number of mobile surfaces, different aerodynamic data set, different FCS

- Introduction of aeroelastcity

- implementation of hydraulic/electric systems (co-simulation)

- simulation of landing / taxing introducing landing gear model in the airframemultibody model

- improvement of output results

33

Questions?

Thank You