Model Based Design employed in LMM development

LAND DEFENCE

Model Based Design employed in LMM development

Ronnie Fleming

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LAND DEFENCE

LightweightLightweightLightweightLightweight MultiMultiMultiMulti----rolerolerolerole Missile (LMM)Missile (LMM)Missile (LMM)Missile (LMM)� The LMM opportunity is based upon a requirement for a low cost, precision strike, lightweight weapon for light platforms.

� The LMM System design is derived from Thales experience in previous missile programmes and helicopter/vehicle integration programmes.

� Thales has invested PV funds to advance this opportunity and is now under contract for the FASGW(L) requirement on “WILDCAT”

Introduction - What is LMM ?

•Low Cost

•Multiple Role

�Ground to Air

�Air to Ground/Surface

�Air to Air

�Surface to Surface

•Effective against Static and Moving Targets

•Precision strike, low collateral damage

•Recoil and debris free launch

Max Range >6Km

Min Range <400 m

Guidance LBR (SAL)Max Mach ~1.5 Warhead Weight Blast Fragmentation & Shaped ChargeFuze short range, long range, Impact

Propulsion 2 Stage Solid Propellant(High level of IM compliance)

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What is Model Based Design ?What is Model Based Design ?What is Model Based Design ?What is Model Based Design ?

ModelModelModelModel----Based Design Based Design Based Design Based Design is a mathematical and visual method of

addressing problems associated with designing complex systems1

Key stages in Model Based Design are:� System Modelling� Controller design� Simulation performance assessment� Implementation (auto-code generation)� VALIDATION

Why use Model Based Design ?Why use Model Based Design ?Why use Model Based Design ?Why use Model Based Design ?Model based design tools can allow all of these iterative steps to be performed in a unified visual environment

and can allow engineers to locate and correct errors early in system design, when the time and financial

impact of system modification are minimised. (To summarise: Faster, cheaper, less errors !)

Reduced number of flight trials required for system proving, but use of trials data outputs must be maximised to validate simulations.

While the full model based design cycle is applicable to the overall missile system, it is often also applicable to individual

sub-systems. Even for those sub-systems where, for example, there is no controller design or code generation, significant

advantages can still be had in modelling and simulation assessment.

Warnings !Warnings !Warnings !Warnings ! ----� The risks associated with Model Based Design can on ly be reduced through model validationmodel validationmodel validationmodel validation (ground/flight trials)

� Modelling and simulation may not always be the most cost effective solution. Be pragmatic !Be pragmatic !Be pragmatic !Be pragmatic !

Introduction - What is model based design ?

1. Source - Wikipedia and associated references

iterative process

xPCSIMULINK

TARGET HARDWARE

IMPLEMENTATION

DESKTOP

SystemRequirements

Verify Design

Real TimeValidation

Test Cases

BENCHDEVELOPMENT

VerifyDesign

VerifyTiming

AlgorithmDesign

Modelling

xPCSIMULINK

TARGET HARDWARE

IMPLEMENTATION

DESKTOP

SystemRequirements

Verify Design

Real TimeValidation

Test Cases

BENCHDEVELOPMENT

VerifyDesign

VerifyTiming

AlgorithmDesign

Modelling

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Model Based Design applied to LMM – Key LMM sub-systems

Tail Assembly 2 Stage

Rocket Motor

Ignition Safety and Arming Unit

Guidance

Processing Unit

Laser Proximity Sensor

IMU

Bearing / slip-ring

CAS

warhead

Airframe

Laser Receivers

This presentation will consider those sub-systems having the most influence on missile guidance system design, ie. :

� Lethal Package (warhead + ISAU)� Proximity sensor� Communication link (including laser receivers) � Rocket motor� Airframe� Bearing assembly� Control Actuation System (CAS)� Inertial Measurement Unit (IMU)� Guidance & Control algorithms (within the Guidance Processor Unit (GPU) and CAS control processor)

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While many of the LMM sub-systems are designed, dev eloped and manufactured by Thales Belfast, some niche sub-systems are procured as an entity from ot her suppliers both within, and outside, Thales. Whi le these suppliers may use Model Based Design to varyi ng degrees in the development of their respective su b-systems, it is essential that they can supply suffi cient performance data to inform the design process and, if appropriate, populate sub-system models within the overall missile simulation. The type of data require d for each of these sub-systems would include:

Lethal package:Lethal package:Lethal package:Lethal package:

� Warhead lethality characteristics – informs top leve l lethality performance modelling and thus determines the error budget component attr ibutable to missile guidance

Proximity fuzeProximity fuzeProximity fuzeProximity fuze

� Fuzing capability – again informs top level lethalit y performance modelling and thus determines the error budget component attributable to missile guidance

Rocket motor:Rocket motor:Rocket motor:Rocket motor:

� Thrust vs time characteristics, and associated vari ability, across temperature range

� Thrust misalignment

� Mass, CofG and inertia dependency on motor burn

Bearing assembly: Bearing assembly: Bearing assembly: Bearing assembly:

� Friction variability with axial and lateral loads

Inertial Measurement Unit:Inertial Measurement Unit:Inertial Measurement Unit:Inertial Measurement Unit:

� Statistical error sources for both static and dynam ic environment

LMM sub-system modelling - Supplied sub-systems

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Those sub-systems developed in-house, ie.� Communication link

� Airframe

� Control Actuation System (CAS)

� Guidance & Control algorithms

are critical components of the missile guidance sys tem and detailed simulation models must be developed through collabo ration between the SME’s and modelling engineers.

LMM sub-system modelling - ‘In-house’ sub-systems

Communication link modellingCommunication link modellingCommunication link modellingCommunication link modelling

Communication link modelling is carried out at diff erent levels:�Laser transmission and atmospheric absorption modelling – informs top level missile performance modelling (eg. coverage)

�Detailed system component modelling identifying source and magnitude of noise components

�The communication link model has been validated through ground tests and flight testing of legacy systems (Starburst and Starstreak)

The key communication link features required for mi ssile guidance system modelling are:�Data update rate

�Measurement data resolution

�Noise magnitude

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The LMM missile has been derived from Thales experi ence in previous missile programs, particularly Starburst and Starst reak. In terms of LMM airframe characteristics these have similarities wi th Starburst. Rather than conducting extensive wind tunnel tests to generate LMM aerodynamic data the legacy Starburst aerodynamic data has been used as a starting point from which LMM aerodynamic characteristics have bee n derived.

LMM sub-system modelling - Airframe

Starburst

LMM

•Determine suitability of prediction codes (eg. MISDL, MISL3, CART3d, Fluent) through ‘validation’ comparisons with legacy Starburst wind tunnel data (similar airframe configuration)

•Use the semi-empirical MISL3, and panel based MISDL, codes to generate a full set of LMM aerodynamic coefficient data points (~0.5million)

•Check a limited sub-set of data points using the CFD codes, CART3d and Fluent (<100).

•Employ the generated aerodynamic coefficient data set in the overall missile simulation to assess suitability against requirements.

•Analyse flight data and modify aerodynamic characteristics appropriately

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The full Model Based Design cycle has been applied to the Control Actuation System (CAS)

LMM sub-system modelling - Control Actuation System

xPCSIMULINK

TARGET HARDWARE

IMPLEMENTATION

DESKTOP

SystemRequirements

Verify Design

Real TimeValidation

Test Cases

BENCHDEVELOPMENT

VerifyDesign

VerifyTiming

AlgorithmDesign

Modelling

xPCSIMULINK

TARGET HARDWARE

IMPLEMENTATION

DESKTOP

SystemRequirements

Verify Design

Real TimeValidation

Test Cases

BENCHDEVELOPMENT

VerifyDesign

VerifyTiming

AlgorithmDesign

Modelling

• Design model developed:� DC brushless motors� encoders� mechanical drive system� friction� stiction� expected loads� etc.

• Algorithms developed:� Commutation and current control� Positional control

•Algorithms auto-coded both for FPGA and DSP

•Bench testing

• HWIL testing

• Ground test simulation validation

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LMM sub-system modelling - Guidance and Control algorithms

Design of the Guidance & Control (G&C) algorithms r equires the full missile 6-DOF system simulation model derived from the constituen t components defined previously.

Euler angle reconstruction

Missile aerodynamics

& kinematics

CAS actuator dynamics

CAN Bus

Fin mixing logicRoll shaping

IMU

Laser Information

Field

LMM Guidance shaping

Missile to beam centre error

roll torque demandDemaned fin angles

Achieved Fin angles

missile angular rate measurementsmissile angular rates

Roll Euler angle

acceleration demands

missile position

Roll control angle

Guidance algorithmswithin GPU in rearsection of missile

Control algorithms within CAS controller firmware in forward section of missile

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LMM sub-system modelling - Guidance and Control algorithms

The full Model Based Design cycle is utilised in de velopment of the Guidance & Control algorithms.

xPCSIMULINK

TARGET HARDWARE

IMPLEMENTATION

DESKTOP

SystemRequirements

Verify Design

Real TimeValidation

Test Cases

BENCHDEVELOPMENT

VerifyDesign

VerifyTiming

AlgorithmDesign

Modelling

xPCSIMULINK

TARGET HARDWARE

IMPLEMENTATION

DESKTOP

SystemRequirements

Verify Design

Real TimeValidation

Test Cases

BENCHDEVELOPMENT

VerifyDesign

VerifyTiming

AlgorithmDesign

Modelling

� The full missile 6-DOF system simulation model, derived from the constituent components defined previously, forms the basis for G&C development

� A reduced fidelity (largely linear) design model is derived from the full 6-DOF missile simulation.

� This design model is used for algorithm development

� The algorithms are implemented and assessed within the full 6-DOF simulation

� The algorithms are auto-coded from the 6-DOF simulation, and tested on bench firmware.

� The auto-coded algorithms are implemented in the target hardware and tested in Hardware-in-the-loop (HWIL) simulations and full missile build dynamic tests.

� Flight telemetry data is analysed, the simulation model is updated as appropriate, and a further iteration of the algorithm design loop commences if necessary.

� The auto-coding process, combined with common test cases applied at each stage of algorithm migration, ensures that the algorithms operating within the flight missile are the same as those operating in the 6DOF simulation - reduced opportunity for human error and shortens the design cycle time.

� If the G&C algorithms operate successfully within the 6-DOF simulation (and have appropriate stability margins etc.) then the algorithms are fit for purpose. If the expected performance is not achieved in flight then there is something wrong with the simulation (not the algorithms !).

� Simulation validation is essential.

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LMM validation firing No. 1 (VF01) LMM validation firing No. 1 (VF01) LMM validation firing No. 1 (VF01) LMM validation firing No. 1 (VF01)

� Results from the first LMM validation firing showed very good correlation between simulation model predictions and actual fli ght dynamic response.

Validation of simulation through flight trials data analysis - 1

CAS fin angles vs time from Instant of move

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MODIFIED AERODYNAMIC DATA MODEL

ORIGINAL AERODYNAMIC DATA MODEL

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� Extensive pre-flight ground testing and post-flight trials analysis indicates excellent validation of some sub-system models and indicates that other sub-system models are at a very good baseline level of validation which will be improved upon during future validation firings.

� Given the level of validation associated with each of the individual sub-systems how does the overall guidance system performance compare with ex pectations ?

� Flight trials analysis of the 1 st LMM validation firing indicates an excellent correl ation between expected and achieved guidance performance thus val idating the baseline LMM missile system simulation for use in further refinements of the mi ssile guidance system.

� Detailed analysis of future LMM firings will contin ue to converge on a ‘fully’ validated LMM missile simulation model.



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Zaxis guidance error


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� A model based design approach has been used in LMM missile system development

� The 6-DOF missile simulation model forms the basis for Guidance and Control algorithm development and system performance assessment.

� An auto-coding process has been implemented whereby the code which is used to produce the simulated missile performance is also t he code which is incorporated within the flight missile, thus shortening the design loop time and reducing the likelihood for human error.

� Data from the VF01 validation firing indicates a ve ry good correlation between the 6-DOF simulation and actual flight characteristics. The s imulation characteristics are never-the-less refined based on the flight trials analysis. F urther detailed analysis of all validation firings will be conducted to converge on a ‘fully’ validated LMM missile simulation model.

� Model Based Design can reduce development time and costs.Model Based Design can reduce development time and costs.Model Based Design can reduce development time and costs.Model Based Design can reduce development time and costs.

� Quality of Model Based Design output depends upon quality of simQuality of Model Based Design output depends upon quality of simQuality of Model Based Design output depends upon quality of simQuality of Model Based Design output depends upon quality of simulation ulation ulation ulation

� Simulation validation is essentialSimulation validation is essentialSimulation validation is essentialSimulation validation is essential

Conclusions

Documents

Model Based Design employed in LMM development