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DDS
Distributed Communication and Control for a Network of Melting Probes in Extraterrestrial Ice
Dr.-Ing. Dipl.-Inform. Daniel EwertIMA/ZLW&IfU
RWTH Aachen University
• Motivation: Project “RANGE”
• Why DDS? Why Connext?
• Implementation/Open Issues
Outline
MOTIVATION: PROJECT “RANGE”
Aliens!!
Aliens!!
EnEx Initiative
• Funded by DLR (German Aerospace Center)
• Goal: Space Missionin 2040 EnhanceTech Readiness Level for core technologies
EnEx Initiative – IceMole
Dirigible Probe forretrieving subglacial samples
• Top speed: 4m/h
• Turning radius: ca. 10m
EnEx Initiative – IceMole
Open Issue: Autonomy
• Navigation
• Perception
• Localization
• …
?
EnEx Initiative: RANGE
Goal: Develop network of autonomous pinger units (APU)• Self-localization via acoustic-
based multilateration
• Autonomous optimization of melting depth Maximize coverage
• Adaptation to • APU failures
• Changes in ice quality
• Environment
EnEx Initiative: RANGE
Sub goals:
• Acoustic world model
• Simulation Environment
• Hardware minaturisation & improvement in performance
RANGE – Development so far
RANGE – Development so far
RANGE – System architecture
APU
AGENT
SKILLS
COMPONENTS
HARDWARESU
PER
VISO
R
GLOBAL CONTROL STATION
MONITORING & CONTROL
DATABASE
STATE INFO
COMMANDS
SIGNAL MGMT NEGOTIATIONS
RANGE – Software architecture
APU
AGENT
SKILLS
COMPONENTS
HARDWARESU
PER
VISO
R
GLOBAL CONTROL STATION
MONITORING & CONTROL
DATABASE
STATE INFO
COMMANDS
SIGNAL MGMT NEGOTIATIONS
RANGE – Languages/Hardware
CLIPS
C
C ++ C+
+
JAVA/Javascript
SQL
MicroZed/Debian
WHY DDS? WHY RTI CONNEXT?
Requirements
• Robust Decentralized, brokerless
• Lightweight
• Easy to Use
• Language support for C/C++, Java, Python
Candidates
• Brokerless
• Lightweight
• Easy to Use
• Language support
”…a flexible framework for writing robot software.”
ros.org
“…a publish/subscribe, extremely simple and
lightweight messaging protocol, designed for
constrained devices and low-bandwidth, high-latency or unreliable
networks”mqtt.org
Candidates
• Brokerless
• Lightweight
• Easy to Use
• Language support
”It’s sockets on steroids.” zeromq.org
“… is a socket library that provides several common communication patterns”
nanomsg.org
Candidates
• Brokerless
• Lightweight
• Easy to Use
• Language support
Suddenly… Features!!
• Strong Type System
• Distributed Logging
• RTI Record/Replay
• Content-filtered topics
IMPLEMENTATION/OPEN ISSUES
APU
AGENT
SKILLS
COMPONENTS
HARDWARESU
PER
VISO
R
GLOBAL CONTROL STATION
MONITORING & CONTROL
DATABASE
STATE INFO
COMMANDS
SIGNAL MGMT NEGOTIATIONS
Software architecture
Domain 0
Topic:SIGNAL
Topic:AGENT
Software architecture – external view
Topic: COMMAND
Topic:APU_STATE
GLOBAL CONTROL STATION
APU 1 APU 2 APU 2
APU
AGENT
SKILLS
COMPONENTS
HARDWARE
SUP
ERV
ISOR
Topic: HEATER
Topic: LOCAL.
Topic: IMU
Topic: ACOUST.
Topic: COMMAND
Domain i
Domain 0
Topic:SIGNAL
Topic:AGENT
Software architecture – internal view
Topic: COMMAND
Topic:APU_STATE
Resulting Benefits
Core functionality
• Robust decentralized system
• One single communication framework
• Isolation of systems through different domains
• Loose coupling of components
Free gifts on top
• IDL-Specifications in central repository Ease of collaboration
• Content-filtered topics one channel, dedicated recipients
• Decentralized logging
• Replay of experiments with RTI Record/Replay
Work in Progress/Open Issues
• Permanent Data Storage – Hack intoRTI Record/Replay Database?
• Management ofSignals – More thanone DataWriter forsame Object?
• GUI – Web basedfrontend needsddsjson bridge.
Summary/Outlook
• 2040 Mission to find extraterrestrial life on Saturn’s moon Enceladus
• Acoustics based autonomous network allows for in-ice localization
• RTI DDS allows brokerless, decentralized communication
• Unexpected features satisfy unknown requirements
Thank you for your attention!Dr.-Ing. Daniel Ewert
IMA/ZLW&IfU,RWTH Aachen University
+49 241 80 911 28
Project Partners:
Funded by:
