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Data Exchange and MBSE Developments for Space

Hans Peter de Koning (ESA/ESTEC, Noordwijk, The Netherlands)

Harald Eisenmann (EADS/Astrium Satellites, Friedrichshafen, Germany)

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European Space Agency

• Intergovernmental organisation– 18 member states– Annual budget around 3 billion €– Approximately 2000 staff

• http://www.esa.int

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Topics

• Moving towards Model Based Systems Engineering– Standardization

• INCOSE & OMG: SysML• ECSS: "Engineering Database" ...

– R & D• Studies to validate standardization approach• Virtual Spacecraft Design

• Space Thermal Analysis Model Exchange– Status STEP-TAS implementations

• Geometrical models and space mission apects• Thermal test results

– New development• Conversion between ESATAN, SINDA/FLUINT, SINDA/G

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What is Model Based Systems Engineering?(INCOSE definition)

• Model-based systems engineering (MBSE) is the formalized application of modeling to support system requirements, design, analysis, verification and validation activities beginning in the conceptual design phase and continuing throughout development and later life cycle phases

"INCOSE SE Vision 2020"INCOSE-TP-2004-004-02

Sep 2007

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European space industryCurrent approach and status

• Space system development process– Overall system engineering process well established – applied on all ESA projects

• Standard: ECSS-E-ST-10-1C "System engineering general requirements"– All domain (discipline-specific) processes are well established – applied on all ESA projects

• Avionics, power, structures, mechanisms, thermal control, propulsion, optics, software (on-board, groundstation), communication, control (orbit & attitude, robotics),

• Project management, cost, risk, logistics, product assurance, …• Each with own ECSS standard

• Tools– Domain disciplines are well supported in terms of engineering and analysis tools – For some disciplines there is excellent integration of design and analysis tools– Lack of support for system engineering: System level design is typically defined with office tools– System level design is “scattered” in different tools – with little traceability

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Industrial PracticeLimited Model Based Capabilities

• Current industrial practice:– Many elaborated tools (analysis) and databases in use– Pragmatic bottom-up integration of particular tool chains– Many ad hoc databases

• System level design status – by system modeling– Very good representation in phase 0/A (parametric models – standardized set of properties)– Requirements specifications partly in databases (RE Tools), partly in documents, some traceability– Very good representation for some disciplines (e.g. MCAD)– Phase B representation often kept in MS-Office products

• System modeling is often driven bottom-up (e.g. flight software or simulation)

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Mission Need

Phase A

Phase B

Phase C

Phase D

Phase EFeasibility Study

Conceptual Design

System / PreliminaryDesign

Detailed Design

Manufacturing

Assembly

Integration

Verification

Deployment

Validation

Top-DownDesign

Bottom-UpProduction, V&V

(Development &Qualification)

Trend: System Engineering "V"with Model-based Validation & Verification

Early

V&

V

Early

V&

V

Executable Model-basedValidation & Verification

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Model Based (System) EngineeringExpected benefits

• Systematic application of models for specification, design, verification and validation– Both for structure and behavior of the system– Managed traceability between all aspects and integrated version/configuration control

• Expected benefits of consistent application of models– As much as possible single source data – generate/transform where possible– Allows computer aided completeness, consistency and quality checking– Improved collaboration between disciplines and organisations

• Multidisciplinary teams• Efficient and reliable communication through supply chain

– Eases development iterations and change impact analysis– Enables and promotes knowledge capture and (re-)use– Enables multiple, concurrent views (subsets, presentations) on same data– Reduced “manual” work and thus improve cost, schedule and quality / reduce risk

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Ultimate Goal – MBSE

• Comprehensive system level design representation• Seamless data traceability from system level design into domain engineering design• Consistent “transformation” from system design model into analysis (executable) model

– For domain analysis models – System simulators

• Consistent representation of the decision making process (analysis design verification)• Continuous verification / validation based on consistent application of virtual models

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Enabling Technologies

• Overall Integration Framework required– For efficient tool integration– For data exchange and sharing– To ensure common and mappable semantics

• Specification of the required data– In a formal way on a conceptual level – ref. OMG/MDA PIM (Platform Independent Model)– Enabling subsequent “generation” of required implementation technology

• System level design editors– Definition, modification and presentation of engineering data– Capturing properties and values

• Supported by open standards– Cannot and want not standardize on tools

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Supporting standardization and R&D

• ECSS-E-TM-10-23 "Engineering Database"– Technical Memorandum evolving to a future standard – Conceptual data model defining precise common semantics– MBSE reference architecture – using OMG/MDA principles– Re-use from STEP-NRF: formalized representation of quantities, units, dimensions, …– As much as possible aligned with SysML

• ESA funded R&D– Space System Reference Model

• Prototyping of centralized services as integration platform – validation of E-TM-10-23– Virtual Spacecraft Design

• Demonstration of a space system engineering process relying on a virtual representation– Design Resource Center

• Design data library to ease access

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ECSS =European Cooperation for Space Standardization

• Initiative started in 1995 to produce a coherent, single set of user-friendly standards for use in all European space activities

• Previously there were different ESA and national space standards

• Partners are space industry (via the Eurospace association), ESA and national space agencies

• Published standards freely available from http://www.ecss.nl in PDF(after a simple registration procedure)

• Complete update per March 2009

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ECSS E-TM-10-23 "Engineering database"

• Conceptual data model standard• Purpose: to provide common semantic

reference for all engineering data repositories needed to develop and operate a space system through the whole life cycle

• Defined using UML2 (class diagram)– Looking at simultaneous specification in

ontology language (OWL, ORM) and EXPRESS

• First release imminent– Expected May/June 2009– Will be published in hyperlinked wiki form to

allow efficient review and evolution (generated from OpenAMEOS UML tool)

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ECSS E-TM-10-23 "Engineering database"

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ECSS E-TM-10-23Adoption of the ECSS global conceptual data model for a project

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ECSS E-TM-10-25

• Technical Memorandum to agree the exchange of conceptual design models (Phase 0 / A) between concurrent design facilities

• Aligned with E-TM-10-23 (subset)• Agreed list of reference data

– List of design parameters with responsible discipline (~600 parameters)

– List of recognised disciplines– Basic system decomposition

• First release expected May/June 2009• Supported by OCDS (Open Concurrent

Design Server) replacing Excel based infrastructure

ESTEC CDF

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Space System Reference Model

Integration Platform

SSRM Tool Connectors

SSRDB Connector

SSRM Database

SSRM Tools

ATV ToolsATV

SSRM

Control WS

Engineering WS

Business Logic

Basic WS

Sys

tem

En

gin

eeri

ng

Co

ntr

ol G

UI

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Space System Reference Model

• Objective– Prototype physical and semantic integration platform– Validation of draft E-TM-10-23 data model w.r.t. STEP, MDA compatibility– Demonstration based on real industrial scenarios

• Result– Centralized webserver hosts shared applications like: adaptors, core application, version control, …– Persistent storage of data in RDBMS– Control applications – MDA based development framework

• Status– Study successfully finished in May 2008– Results will be evolved in Virtual Spacecraft Design

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Design Resource Center

• Objective– Development of design data library – Definition of equipment properties (used for

design)

• Result– Web-server application for the core

application– HTML front-end integrated in ESA portal– Underlying relational database– Linkage to ESA DMS

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Virtual Spacecraft Design

• Objectives– Demonstration of a model-based system engineering process using a full virtual representation of

the space system• Status - End phase 1 Requirements analysis and conceptual design

– Overall process analysis performed– Use case analysis and user requirements specification performed– Overall architecture defined lower level elements identified for prototyping

• Next step – Phase 2 realization and demonstration (2009 – 2010)– Space System Design Editor– Space System Reference Database– Space System Visualization Tool– Builds further on E-TM-10-23, SSRM centralized integration platform, MDA for design editors,

STEP-NRF

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Virtual Spacecraft Engineering Environment

Space System Design Editor

VSEE Application Server

RDE

SSDE Services

Space System Design Browser

Wiki Service

Space System Reference Database

SSRDB

SSRDB Services

Space System Virtual Model

Space System Visualization Tool

Space System Functional Simulator

Space System Virtual Model Integration Bus

SSVM Services

FDE ODE PDE AITDE OADE VDE

Virtual Spacecraft Design

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ASTRIUM

AIT SDB

Overview Data Bases

S/C Eng. ReferenceSupplierCustomer

El.Test Tool

Tool: IDAS

IDAS DBEGSE DB

OBSWSDE

AOCSOSE

Tool: Matlab/Simulink

FDDB

CC DB = SCC DB

Input by domainAdministrators

Handling of Datavia Eng. Tool

SRDB

Parts/ Struct./Harness

Manufact.

Control Console

Tool: SimOps/OpenCenter

EGSE DB

MCADTool: CATIA

SimDBTool: SimDB

SCOE TM/TC DB AP DBTool: MOIS

SDB(TM/TC)

SEDB

MDVE Simulator

ECADTool: Eng. Base

EPPDEquip.

Physical Props.

MCAD DB(CAD

Model)

Unit/ Equipment-

SDB

Development & Verification Tools

Space System Engineering Repository

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Example validation of E-TM-10-23 in prototype space system design editor

Eclipse (Ganymede) based toolUsing GMF and EMFCode generated from E-TM-10-23 data model using MDA approachDeveloped by ScopeSET (Germany)

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Example validation of E-TM-10-23 in prototype space system design editor

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Support to SysML

• Support SysML RTF 1.2 and 2.0 work through INCOSE/OMG– Upgrade of Quantities, Units and Dimensions – foundation for SysML "value properties"

• Now based on International Vocabulary of Metrology by BIPM• Combined concepts and lessons learned from ISO 10303-41, STEP-NRF, MARTE, ontologies• Fully supports multiple quantities and units systems• Using new ISO/IEC 80000 standard (harmonised replacement of SI) as main reference

– Integration of SysML Parametrics and Modelica• Modelica is a neutral language to define object oriented non-causal simulation models

see http://www.modelica.org • Powerful definition of executable (high level to detailed) system models

– Mathematical equations relating properties at ports of blocks– With or without predefined causality (order of variable assignment or expression evaluation)

• Fits well with SysML contraint blocks

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STEP-TAS progress

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STEP-TAS Activities in 2008

• IITAS – Industrial Implementation of STEP-TAS – in progress– ESA completed full test suite with automation tools

• TASverter by ESA TEC-MTV (Thermal analysis and verification section)– Now more than 150 different users (2~5 downloads per week)– Routine use in many projects– Under maintenance – but very few bugs reported

• Evolution of Expressik to support code generators STEP EXPRESS to C++ and Python• Evolution mapping STEP data into HDF5 format• Completed ESATAP v1 thermal analysis post-processor using STEP-TAS in HDF5 format• First validation of STEP-TAS Kinematics and Mission Aspects (CC2, CC4, CC5, CC6)

– Implementation in TASverter for ESARAD• Proof of concept implementation in DynaWorks® for import of STEP-TAS analysis predictions

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In progress 2009

• Started IITAS-TMG activity with Maya (Canada)– Implementation of STEP-TAS import/export into TMG

• Completion of IITAS and IITAS-TMG– Emphasis on testing and obtaining robustness of imports/exports

• Full validation of STEP-TAS Kinematics and Mission Aspects• Implementation of full ESATAN / SINDA conversion in STEP-TAS and TASverter• Formalisation of STEP-NRF/TAS under ISO TC184/SC4

– Was planned for 2008 but put on-hold due to lack of resources – shifted to 2009• R&D "Innovative methods for improved thermal testing"

– o.a. using STEP-TAS to interface between analysis prediction and test results• Consolidate support software and test suites as true open source software

– Depending on ESA open source software policy that is currently being finalised

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ESATAN / SINDA conversion using STEP-TAS

• ESATAN, SINDA/FLUINT, SINDA/G are major space thermal analysis tools• Old style FORTRAN finite difference / lumped parameter solvers

– Common heritage to CINDA which was developed in 1960s• Used on many space projects worldwide• Model defined in two parts: DATA and OPERATION blocks

– DATA blocks define model structure: nodes, conductors, boundary and initial conditions, ...– OPERATION blocks define behaviour simulation: user defined logic and solver calls

• Quite sophisticated modelling capabilities for active thermal control: thermostats, PID controllers, heatpipes, fluid loops, evaporators/condensors, Peltier elements, mission (power) mode switching, model parameterization, non-linear material properties, ...

• Exchange of DATA blocks is supported by existing tool-to-tool converters– But incomplete and not reliable

• Exchange of OPERATION blocks is manual: very complicated and time consuming

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Data exchange implementationESATAN / SINDA OPERATION blocks

• Use ANTLR to parse ESATAN or SINDA MORTRAN language• Store resulting abstract syntax tree in prefix notation using JSON

– For expressions we use the Content MathML approach• Only not in XML but JSON encoding• e.g. "X = 4.0 * (2.0 + 3.5)" → ["assign", "X", ["times", 4.0, ["plus", 2.0, 3.5]]]

– For algorithms (sequence of statements, if-elseif-else blocks, loops, etc.) we use simple keywords• e.g. ["loop_for", loop_var, start_expression, end_expression, step_expression, statement_block]

• Integrated into STEP-TAS through EXPRESS ENTITY instances– nrf_algorithmic_language, nrf_algorithmic_expression, nrf_algorithmic_statement– Both in neutral JSON language and original ESATAN or SINDA language

• Prototypes work very well• Perhaps interesting light approach also for other algorithm conversion need• Upgrade of TASverter expected later this year• Development contracted to DOREA (France)

ANTLR (http://www.antlr.org) is avery powerful OSS lexer/parser package.JSON (http://www.json.org) is JavaScript Object Notation, a very powerful but simple serialization format supported by OSS in almost all programming languages.

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References

• European Space Agencyhttp://www.esa.int

• Astrium Satelliteshttp://www.astrium.eads.net

• European Cooperation for Space Standardizationhttp://www.ecss.nl

• SysML – Systems Modeling Languagehttp://www.omg.sysml.org

• STEP-NRF and STEP-TAShttp://www.esa.int/thermalcontrolLook for "Standards”

• TASverterhttps://exchange.esa.int Look for "TASverter“

• ISO TC184 / SC4 standardization committee (a.o. STEP standards)http://www.tc184-sc4.org