Presented by: Dr.-Ing. Dipl.-Inform. Daniel Ewert, Head of Research Group "Engineering Cybernetics," Assoc. Insitute for Management Cybernetics e.V., RWTH Aachen University The Ice moon Enceladus of planet Saturn holds vast amounts of liquid water beneath its solid ice shell which possibly contain simple extraterrestrial life. For further examination an intended space mission by Germany's national space program aims to take probes from subsurface water using an autonomous ice probe. In order to navigate to a designated goal position, this probe must be able to localize itself within the ice. This localization is achieved by utilizing a distributed network of autonomous pinger units (APUs) which serve as external reference for the ice probe. The talk focusses on the technical details and communication and control mechanisms for this network.

1. DDS
Distributed Communication and Control
for a Network of Melting Probes in
Extraterrestrial Ice
Dr.-Ing. Dipl.-Inform. Daniel Ewert
IMA/ZLW&IfU
RWTH Aachen University

2. • Motivation: Project “RANGE”
• Why DDS? Why Connext?
• Implementation/Open Issues
Outline

3. MOTIVATION: PROJECT “RANGE”

4. Aliens!!

5. Aliens!!

6. EnEx Initiative
• Funded by DLR
(German Aerospace
Center)
• Goal: Space Mission
in 2040
 Enhance
Tech Readiness Level
for core technologies

7. EnEx Initiative – IceMole
Dirigible Probe for
retrieving subglacial samples
• Top speed: 4m/h
• Turning radius: ca. 10m

8. EnEx Initiative – IceMole
Open Issue: Autonomy
• Navigation
• Perception
• Localization
• …
?

9. 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

10. EnEx Initiative: RANGE
Sub goals:
• Acoustic world model
• Simulation
Environment
• Hardware
minaturisation &
improvement in
performance

11. RANGE – Development so far

12. RANGE – Development so far

13. RANGE – System architecture

14. APU
AGENT
SKILLS
COMPONENTS
HARDWARE
SUPERVISOR
GLOBAL CONTROL STATION
MONITORING & CONTROL
DATABASE
STATE INFO
COMMANDS
SIGNAL MGMT NEGOTIATIONS
RANGE – Software architecture

15. APU
AGENT
SKILLS
COMPONENTS
HARDWARE
SUPERVISOR
GLOBAL CONTROL STATION
MONITORING & CONTROL
DATABASE
STATE INFO
COMMANDS
SIGNAL MGMT NEGOTIATIONS
RANGE – Languages/Hardware
CLIPS
C
C ++
C++
JAVA/Javascript
SQL
MicroZed/Debian

16. WHY DDS? WHY RTI CONNEXT?

17. Requirements
• Robust  Decentralized, brokerless
• Lightweight
• Easy to Use
• Language support for C/C++, Java, Python

18. 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

19. 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

20. Candidates
• Brokerless
• Lightweight
• Easy to Use
• Language
support





21. Suddenly… Features!!
• Strong Type System
• Distributed Logging
• RTI Record/Replay
• Content-filtered topics

22. IMPLEMENTATION/OPEN ISSUES

23. APU
AGENT
SKILLS
COMPONENTS
HARDWARE
SUPERVISOR
GLOBAL CONTROL STATION
MONITORING & CONTROL
DATABASE
STATE INFO
COMMANDS
SIGNAL MGMT NEGOTIATIONS
Software architecture

24. Domain 0
Topic:
SIGNAL
Topic:
AGENT
Software architecture – external view
Topic:
COMMAND
Topic:
APU_STATE
GLOBAL CONTROL STATION
APU 1 APU 2 APU 2

25. APU
AGENT
SKILLS
COMPONENTS
HARDWARE
SUPERVISOR
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

26. 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

27. Work in Progress/Open Issues
• Permanent Data
Storage – Hack into
RTI Record/Replay
Database?
• Management of
Signals – More than
one DataWriter for
same Object?
• GUI – Web based
frontend needs
ddsjson bridge.

28. 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

29. Thank you for
your attention!
Dr.-Ing. Daniel Ewert
IMA/ZLW&IfU,
RWTH Aachen University
+49 241 80 911 28
Daniel.Ewert@ifu.rwth-
Aachen.de
Project Partners:
Funded by: