STEP Protocol Development and Converter Implementation Processes at ESA Hans Peter de Koning - ESA/ESTEC - The Netherlands [email protected]

STEP Protocol Development and Converter Implementation Processes

at ESA

Hans Peter de Koning - ESA/ESTEC - The [email protected]

Sandrine Fagot - Simulog - [email protected]

STEP for Aerospace Workshop, NASA-JPL, 16-19 January 2001

Sheet 216-19 Jan 2001 STEP for Aerospace Workshop - NASA-JPL

Topics

• What is Europe doing w.r.t. standardisation of product data exchange & archival for space applications?

• How did we develop STEP based solutions?• What successes?• What lessons learned?• Road ahead


What is Europe doing?

• ECSS E-10-07 WG “Exchange of Product Data”– European Cooperation for Space Standardization– High level ‘meta-standard’ like NASA-STD-2817

• www.estec.esa.int/ecss

• ftp://ftp.estec.esa.nl/pub/ecss-e-10-07-wg/index.html

• Specific standards– STEP-TAS “Thermal Analysis for Space” (ESA)– STEP-NRF “Network-model Results Format” (ESA)– STEP-PRP “Propulsion” (CNES) (CNES = French Space Agency)– Active role AP232 “Technical Data Package” (CNES + Industry)– Active role AP233 “System Engineering” (Aerospace Industry)

w.r.t. standardisation of product data exchange & archival for space applicationsw.r.t. standardisation of product data exchange & archival for space applications


Focus of this presentation

• Development process of STEP-TAS and STEP-NRF• Achievements, some metrics and lessons learned• Objective:

To provide useful feedback for others contemplating to develop similar ‘niche’/specific purpose standards


Main characteristics NRF (1)Network-model Results Format

• Targets engineering-discipline independent exchange of bulk results data from analysis, test or operation– Representation of engineering objects by network models

consisting of discrete nodes and node-relationships– Hierarchical tree of network models / submodels– Definition of properties

• Quantitative, descriptive and functional properties

• Scalar, vector and tensor property values

• Property values only at discrete locations / discrete states

– Full annotation of analysis / test / operation context• Campaign, case, phase, run

• Facility/tool, environment, date and time, organisation, person, ...


Main characteristics NRF (2)NRF dataspace

abscissa_property

mod

el_c

ompo

nent

(mod

el,

node

, no

de_r

elat

ions

hip)

stat

e

prop

erty

_cla

ss

Each gridpoint in the 3D dataspace is a property value

Each can be scalar, vector, tensor

Data model and implementation designed to handle sparsely populated dataspace efficiently


Main characteristics NRF (3)Proposed NRF/HDF architecture

STEP-NRFprotocol

(discipline- independent)

NRFDictionaryStructural

NRFDictionaryThermal

NRFDictionaryElectrical

NRFDictionary

...

STEP-NRF SDAIprogramming library

HDF 5programming library

NRF – HDF mapping

HDF5binary

results file

User Application(Reading or Writing

Results Data)

AP203STEP file AP209

STEP file(future)

reference to product (-part),shape, location

reference to FEM / FE

COTS or PDData Analysis / Visualisation

Application with HDF i/f(also via WWW)

discipline-specific dictionaries

HDF5 = Hierachical Data Format v5- Public domain from NCSA- Efficient portable binary storage format- Full C, Fortran, Java libraries on >10 platforms- Standard for all NASA EOS missions and some ESA earth observation- Info/downloads at hdf.ncsa.uiuc.edu- Many COTS / PD tools with HDF interfaceHDF5 as an

efficient alternative for Part21for large amounts of similar data


Main characteristics TAS (1)Thermal Analysis for Space

• Self contained, complete Application Protocol– AAM, ARM, Mapping Table, AIM, Express-G– Conforms to TC184/SC4 methods and guidelines– Geometry defined conform AP203 CC4 surface model– Thermal-radiative model faces added as associated features

• Including possibility to support hierarchical submodel tree

• Associated notional thickness, surface material and bulk material

• Thermo-optical, thermo-physical properties for named material

• Concept of material property environment (Part 45)

– Kinematic model conform STEP Part 105• For articulated rigid bodies (e.g. rotating solar arrays, ...)


Main characteristics TAS (2)

– Space mission aspects• orbit arc (Keplerian and discrete ephemeris)

• space co-ordinate system, celestial bodies

• orientation, general and named pointing, spinning, linear rotation rates

• space thermal environment, including constant or lat/long dependent albedo / planetshine tables

– Boolean construction surfaces available for advanced tools– STEP-TAS CC1 Abstract Test Suite

• conform STEP Part 3xx series

• test suite used in validation of TAS processors


Main characteristics TAS (3)STEP-TAS Conformance Classes

thermal-radiative model with basic geometry

kinematic model

constructivegeometry

space missionaspects

CC-1

CC-2

CC-3

CC-4

CC-5

CC-6


Brief history TAS and NRF developments

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

SET-ATS precursor (French standard, CNES)

ESA R&D project “Thermal neutral formats”

TAS protocol (pure extension of NRF)

Space IR and NRF protocol

Programming libraries v1 with C & F77 API / porting 5 platforms

Abstract test suite TAS-CC1 / roundtrip ESARAD/STEP-TAS

Prototype NASA-JPL, import in TSS, export from TRASYS

Editorial update protocol to TC184/SC4 MS-Word format

Production release ESARAD/STEP-TAS-CC1 converter

Porting F77 API 5 platforms; Thermica/STEP-TAS-CC1 converter (Astrium)

US STEP-TAS pilot (JPL, 5 thermal tool vendors)

Thermal Desktop/STEP-TAS-CC1 converter (C&R, NASA-LaRC)

Large model cross validation ESARAD & Thermica; update architecture and libraries


Challenge

• Find an effective development process– Within modest budget constraints– TAS for a ‘niche’ market

• Between 20 to ~300 real users per space thermal analysis tool

– Make sure that user requirements are well captured– Ensure implementations can be, and are, validated– Facilitate efficient and maintainable converters– Attempt to obtain global consensus

• Ensure robustness and ease of use for end-users


Incremental development scheme

Define / Refine / Extend Protocol

(ARM, AIM, Express)

Develop / UpgradeLibraries

Develop / UpgradeConverters

& Test Suites

ValidateConverters

with Test Suites


Stable Team with Clear Roles

• Simulog (F, software engineering services)– lead since 1998, implementation libraries and some converters

• Fokker Space (NL, space subsystems contractor)– initial lead, user requirements, ARM, ATS

• GOSET (F, STEP standardisation experts)– mapping table, AIM, EXPRESS/p21 verification

• Epsilon Ingénierie (F, thermal analysis services)– check user requirements, converter implementation

• ALSTOM Power (UK, thermal tool vendor)– converter implementation, distribution to end-user

• CNES (F, French Space Agency)– Review requirements and model, generation of test suites


Approach to Developing with STEP

• Be as precise as possible on semantics– Regular feedback between protocol editor and implementors

• Minimise ARM - AIM mapping need as much as possible– Use IR contructs where possible direct in ARM

• Automate generation of library APIs as much as possible– Directly from EXPRESS model

• Design for simplicity, implementability and testability– E.g. do not use EXPRESS ANDOR

• Use a high level programming interface to build converters• Use an SDAI toolkit for low level interface


STEP-TAS High Level Libraries Toolkit

• High-level API to support efficient converter development– Use ARM constructs - close to thermal developer’s data model– Hide STEP complexity– Full set of reading / writing functions in ANSI-C and F77– Associated documentation, examples and test suite

• BagheraView (CNES) included to perform independent visual inspection and model reporting on PC/Windows

• Distribute toolkit at nominal cost to attract tool vendors

API = Application Programming Interface


BagheraView Screenshot


Benefits of High Level Libraries Approach

• Already ported and tested with target compilers– PC/Windows, Sun/Solaris, HP/HP-UX, Compaq/Tru64, SGI/Irix

• Enables to jumpstart converter implementation• Reduces converter validation / verification effort• All converters share reading/writing interface

– implementation mismatch is minimised– increased reliability

• Extensibility at affordable cost– e.g. to add HDF or XML encoding


STEP-TAS

EXPRESS

data model

STEP-TAS

EXPRESS

data model STEP-TAS

physical

file

(ISO 10303-21)

STEP-TAS

physical

file

(ISO 10303-21)

Thermal Analysis Tool(ESARAD, THERMICA, TRASYS, …)

Thermal Analysis Tool(ESARAD, THERMICA, TRASYS, …)

STEP-TAS High Level LibrariesC and Fortran API(Simulog, France)

STEP-TAS High Level LibrariesC and Fortran API(Simulog, France)

SDAI C Library (ISO 10303-24)ST-Developer

(STEP Tools Inc., USA)

SDAI C Library (ISO 10303-24)ST-Developer

(STEP Tools Inc., USA)

STEP-TAS Converter Architecture

Native

Tool

Format

Native

Tool

Format


Successes …

• Full implementation of converters at reasonable cost– ESARAD/STEP-TAS-CC1 since mid 1999– Thermica/STEP-TAS-CC1 since Dec 2000

• Broad awareness and (prototype) implementation in US– JPL STEP-TAS demonstrator in 5 US thermal tools– Full bi-directional implementation STEP-TAS-CC1 in Thermal

Desktop 3.3Beta (Cullimore & Ring sponsored by NASA-LaRC)

• Reached almost 100% of space thermal tool vendors• Very close to robust and reliable quality exchange for

STEP-TAS-CC1 in production tools


… Problems with STEP

• Bulkiness and incomprehensibility for humans of AIM• Makes validation cumbersome and costly

• Causes large overheads

• Additional in-core storage

• Addition interface layer in library

• Part21 files much larger than really really necessary

• ARM to AIM mapping is not computer interpretable• EXPRESS-X was not available for TAS: a lot of handwork for high

level library interface mapping

• Conformance checking / Abstract Test Suite (Parts 3x)• Very cumbersome and costly to develop and maintain

• Not well designed for automation of regression testing


Lessons Learned

• Iterative, incremental development necessary– Can not get things right in one go …

• High level programming library very useful– Greatly reduces converter development effort– Speeds up standard penetration & increases exchange reliability– Chosen API close to old SET-ATS interface needs reconsideration

• Continuous resource / funding level is needed– To meet vendor expectations by providing timely support

and library updates resolving SPRs

• Communication must be improved– Start a ‘STEP-TAS implementors forum’ ?


Metrics

• STEP-TAS took ~5 years from conception to CC1 industrial converter release

• Up to now funded with roughly 1 million Euro / USD– Excluding US converter developments– Appears to be a quite good price/performance ratio

• Approximately 20 different people have worked on different parts of STEP-TAS and STEP-NRF


Why was STEP-TAS not yet submitted as an ISO TC184/SC4 work item?

• Valid question• Started as a European effort to follow up SET-ATS• Limited resources prevented us to bear the additional

effort of formal ISO standardisation - no added value yet• With the good co-operation with NASA in place,

nearly 100% of the space thermal tool vendors in the world were reached

• However it is agreed that a formal way of publishing and maintaining the standard is now needed imminently


Road Ahead (1)

• Web-based collaboration on further development– ftp://ftp.estec.esa.nl/step-tas/index.html as a start– Publication of protocol, SPR list, test suite– FTP distribution of STEP-TAS toolkit releases– E-mail tech support

• Take European / US collaboration to a next stage– Action ESA and NASA together with Simulog– Clarify/establish intellectual property rights and support


Road Ahead (2)

• Currently trade-off for ‘Return on Investment’ next 5 years– Appropriate level of formal publishing (ISO?, ECSS?, NASA?)– Select AIM or ARM based exchange?– Upgrade high level API to support all STEP-TAS constructs

• e.g. submodelling, non-uniform meshing and node numbering

• Upgrade libraries to resolve all reported issues (SPRs)• Upgrade converter options

– Consistently support length unit selection / conversion– Meta data entry


Road Ahead (3)

• TRASYS/STEP-TAS-CC1 bi-directional converter– Stand-alone tool by Simulog on ESA funding

– Will be made available at nominal cost or preferrably free

• Upgrade BagheraView capabilities– By Simulog sponsored by CNES

• PATRAN/STEP-TAS-CC1 interface– By MSC sponsored by NASA-LaRC

• Continue NRF developments– HDF5 binding (co-operation with EDF, NCSA and others)

– Assess links with Engineering Analysis modules, ISO 10303-50

– Pilot web-based remote consultation of structural test results


Acknowledgements

• STEP-TAS and STEP-NRF were developed under ESA contract by an industrial consortium, consisting of:– Simulog (F, prime)– Fokker Space (NL)– Association GOSET (F)– Epsilon Ingénierie (F)– Alstom Power (UK)

and supported by CNES (F)

• Special thanks to Georg Siebes (NASA-JPL) who is and has been the driving force for the development and acceptance of STEP-TAS in the US

• Also acknowledgements to Ruth Amundsen (NASA-LaRC)for actively promoting STEP-TAS implementations

Documents

STEP Protocol Development and Converter Implementation Processes at ESA Hans Peter de Koning - ESA/ESTEC - The Netherlands [email protected]