Central Engineering / ASG 74 Data Processing Advanced Studies Sev Gunes-Lasnet, Olivier Notebaert...

Central Engineering / ASG 74Data Processing Advanced Studies

Sev Gunes-Lasnet, Olivier Notebaert

2008, November 5th

Prototype implementation of a routing policy using FlexRay frames concept over a SpaceWire Network

International SpaceWire conference 2008, Nara, Japan

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Central Engineering (ASG74)Data Processing Advanced Studies


Presentation outlineOn-board data links optimisationSpaceWire networksConcepts from automotive industryPrototype implementationConclusions and way further

On-board data links optimisation

SpaceWire networks

Concepts from automotive industry

Prototype implementation

Conclusions and way further

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On-Board Data links optimisation

Payload Data processing trends: P/L Science data cannot be downlinked at acquisition

rate Increasing need for high performance on-board data processing

(e.g. compression, formatting, filtering…) Increasing need for high capacity on board data storage

Several independent instruments on a same spacecraft

With high rate data links Growing need for on-board intelligence (AOCS,

camera, radar, robotics, navigation…) resulting in data rate increase


SpaceWire networks




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Architecture trade-offs In parallel, critical trade-offs are made in the implementation of

space systems, due to: Technologies adaptation to environmental constraints On-board processing performance Redundancies of elements and data links Power consumption, Overall Weight/length of cables Overall cost …

Efficiency of the data links solutions depends on the systems priorities and on the nature of the transmitted data

This results in several types of data links: Command and control buses (OBDH, 1553, Can) Point to point serial data links (RS232, RS422, 1355,

SpaceWire,…) Discrete dedicated interfaces (Direct commands, sensor

acquisition…)


SpaceWire networks




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Typical data processing architecture Typical resulting on-board data processing architecture

Independent instruments data processing units Direct interfaces to Mass Memory for high rate data storage Instrument control through system bus and Remote Terminal

Units (RTU) Several types of data links adapted to communication needs

Low rateDigital I/F

-DiscreteInterface

High rateDigital I/F

Low rateDigital I/F

-DiscreteInterface

Control &Monitoring

drivers

Sensors

Mechanisms

Thermal

InstrumentData

ProcessingUnit

Instrument electronics

Mass MemoryUnit

RTUelectronics

System bus


Low rateDigital I/F

-DiscreteInterface

OBMU

TFG

Spacecraft DataProcessing

Unit

Low rateDigital I/F

-DiscreteInterface


Low rateDigital I/F

-DiscreteInterface


Low rateDigital I/F

-DiscreteInterface

Control &Monitoring

drivers

Sensors

Mechanisms

Thermal

InstrumentData

ProcessingUnit

Instrument electronics

Mass MemoryUnit

RTUelectronics

System bus


Low rateDigital I/F

-DiscreteInterface


Low rateDigital I/F

-DiscreteInterface

OBMU

TFG

Spacecraft DataProcessing

Unit


SpaceWire networks




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Alternate data processing architecture: SpaceWire networks

Dedicated to improve the system budget issues:

Lower number of nodes and links variants

Share of common functions/resources

Budgets optimisation

LR Instrument

LR Instrument

MR Instrument

LR Instrument

PSU Router

OBC

VeryHigh-RateInstrument

Mass MemoryEquipment

LR Instrument

LR Instrument

MR Instrument

LR Instrument

PSU Router

OBC

VeryHigh-RateInstrument

Mass MemoryEquipment

Spacewire as payloaddata handling network

SpaceWire Networks are an element for improvement of future on-board data processing architecture and overall budgets


SpaceWire networks




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SpaceWire networks as Payload data handling building blocks Development of

SpaceWire networks Determinism studies are

necessary to guarantee the respect of timing and reliability constraints of spacecrafts

Development of standard protocols ensuring time deterministic packet delivery will enable the use of SpaceWire networks

SpaceWire networks development can benefit from the automotive spin-ins:

Safety/highly critical applications requirements

Availability of tools/products Large user data base Low cost Thorough products

validation

On-Board network

Benchmarking the automotive industry concepts and products is of high interest in the context of the development of standardised protocols over

SpaceWire networks


SpaceWire networks




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Benchmarking concepts from automotive industry: Proposed strategy

Prefer a standard Avoid monopolistic Supplier Implement an obsolescence management plan Market might not provide a solution on its own


SpaceWire networks




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Benchmarking concepts from automotive industry Trends in automotive

industry: Synchronous &

Asynchronous communication supported

Fault-tolereance, guaranteed latency, high speed capabilities are supported to target X-by-Wire applications (steer-by-wire & brake-by-wire)

Existing consortiums FlexRay, TTP…

FlexRay consortium situation

Initially, the consortium was only open to automotive industry players

semiconductor manufacturers, equipment and system suppliers, tools and services suppliers and

manufacturers In late 2006, the consortium agreed

the membership to EADS CCR Germany as a move to non-automotive companies

Technology use and licensing is still not cleared for non-automotive applications


SpaceWire networks




A customised pilote implementation has been chosen rather than the direct evaluation of automotive products

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SpaceWire network protocol prototyping activity Principle: Higher level protocols

could be implemented over SpaceWire to ensure the respect of timing constraints, while respecting the SpaceWire standard

Prototyping of a higher level

protocol using concepts from

the automotive protocol

FlexRay Pilote implementation over a

SpaceWire network allowing

further analysis of the

concept and performance

assessment


SpaceWire networks




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Prototyping configuration A time master on the

network distributes a global time reference

Modules use this time reference for sending packets over the network

The configuration implements a priority based bandwidth reservation:

Packets with high priority are transmitted first during the static part of the cycle

Time master

Packets analysis

Rosetta modules


SpaceWire networks




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Prototyping activity Definition of a communication model over a SpaceWire network,

with the following caracteristics: Priority based packet transmission using bandwidth reservation

slots during first part of the cycle Cycle allows asynchronous communication during second half on

the cycle


SpaceWire networks




Time zone number 2 : 800 ms

Reception of messages

A B C D E F

Transmission of messages

ABC D EF

Packet treatment

Storage of messages

G H I J K

G H I ﾉ

temp

temp

A B C D E F

Bandwidth reservationUsing priorities assignment No priority based arbitration

Time zone number 1 : 100 ms

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Prototyping activity During first part of cycle

The router analyses and treats the incoming packets

Messages are sent using bandwidth reservation (slots) based on priority allocation

During second part of cycle, incoming packets are not reorganised by the router.

Reorganisation of packets during the first part of the communication cycle has been monitored


SpaceWire networks




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Prototyping further improvements Increase the traffic between the modules. Synchronisation method between the different

modules Precise attribution of communication slots to each node

connected to the SpaceWire network.

Optimisation of the communication cycle Length of the packets and of the communication cycle can

be adapted.

Specification of dedicated router capabilities Slots reservation for each user on the network, Control of the packets transmission to prevent babbling idiot

errors, Further capabilities.


SpaceWire networks




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Future perpectives The prototype allows

Investigations such as the measurement of the sensitivity of the latency wrt the length of packets transmitted over the network

The optimal dimensioning of the network elements: Size of an internal router buffer (hardware complexity factor), Optimal length of the communication cycle…

The platform used for this pilote implementation Can be used for the evaluation of a further concept of real

time protocol over a SpaceWire network


SpaceWire networks




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Conclusions and way forward

First implementation of concepts developed in the automotive industry over a SpaceWire networks

Communication cycle model defined allows both bandwidth static allocation and dynamic allocation

Router in charge of arbitration and bandwidth attribution Existing SpaceWire sensors and actuators can be used without

modifications due to specific RT requirements

Further prototype use Optimal dimensioning of network elements Evaluation of further concepts of real time protocols over

SpaceWire networks


SpaceWire networks




Central Engineering / ASG 74 Data Processing Advanced Studies Sev Gunes-Lasnet, Olivier Notebaert...

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Transcript of Central Engineering / ASG 74 Data Processing Advanced Studies Sev Gunes-Lasnet, Olivier Notebaert...