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Towards a Heterogeneous Modular Robotic Team in a Logistic Chain for Extraterrestrial Exploration

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Future exploration of the solar system is calling for robotic missions with increasing complexity. As scientific concepts for the exploration of Moon and Mars ask for advanced instrumentation and experiments for, e.g., sample acquisition and return, these missions may hardly be handled by a common single rover architecture. The planned but abandoned joint ESA/NASA Mars Sample Return (MSR) mission is an example for a multi-landing mission architecture containing two rovers for sample caching and sample fetching respectively. Looking further into the future, robotic systems will be needed to prepare manned missions and possible outposts on extraterrestrial bodies, requiring advanced robotic capabilities.
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Towards a Heterogeneous Modular Robotic Team in a Logistics Chain for
Extended Extraterrestrial Exploration
Roland U. Sonsalla1, Florian Cordes1, Leif Christensen1, Steen Planthaber1, Jan Albiez1, Ingo
Scholz1and Frank Kirchner1,2
1DFKI Robotics Innovation Center Bremen, Germany
e-mail: firstname.lastname@dfki.de
2University of Bremen, Robotics Lab, Germany
Abstract
Future extraterrestrial exploration missions ask for
robotic systems able to handle tasks with increasing com-
plexity. A reference mission within Amundsen crater near
the lunar south pole for volatiles and rogolith analysis is
outlined in this paper. The focus is on implementing a
logistics chain introducing various heterogeneous mobile
and immobile robotic systems. Within this context the
robot cooperation as well as communication architecture
is outlined. The reference mission serves as base line for
later field trials. Furthermore, an overview is given on the
robots to be used within the terrestrial test campaign.
1 Introduction
Future exploration of the solar system is calling for
robotic missions with increasing complexity. Scientific
concepts for the exploration of the Moon and Mars ask for
advanced instrumentation and experiments such as sample
acquisition and return, while pushing into more hostile en-
vironments such as permanently shaded areas at the lunar
poles. These missions get increasingly dicult to han-
dle with common single rover architectures but call for
the combination of multiple, specialized exploration vehi-
cles. A first attempt in this direction is e.g. the proposed
ESA/NASA Mars Sample Return (MSR) mission, includ-
ing one rover for taking samples and a second rover for
fetching these samples and returning them to the sample
return stage [6].
The primary mission objective of the presented
project seeks to extend the exploration capabilities and
handle complex mission tasks in a (semi-)autonomous
manner by introducing a semi-autonomous and heteroge-
neous team of cooperating mobile robots, able to establish
a logistics chain based on stationary modules (so-called
base camps) as well as portable modular payload items.
The general idea of implementing a logistics chain includ-
ing various robotic systems is depicted in Figure 1. An
exploration rover is paired with one or more small sup-
porting rovers (so-called shuttles) building up a logistics
Figure 1. Schematic drawing of the imple-
mentation of a logistics chain using a
heterogeneous team of mobile and sta-
tionary robots
chain between the rover and the lander via the aforemen-
tioned base camps.
In this paper a reference lunar exploration mission is
outlined. First the mission concept is presented, providing
the overall mission design concept as well as the mission
subject and landing site. Furthermore, the mission archi-
tecture is addressed, providing an idea how the dierent
robotic systems are working together. This mission set-up
provides the basis for terrestrial implementations, tests,
and demonstrations of logistics chain applications. The
dierent robotic systems which are used for implement-
ing a logistics chain, referencing to the previously out-
lined mission design, are conceptualized and introduced
In Proceedings of the 12th International Symposium on Artificial Intelligence,
Robotics and Automation in Space (i-SAIRAS 2014), Montreal, Canada,
June/2014.
as well. Finally a conclusion and outlook for further work
is given.
2 Mission Design Concept
The mission design concept is motivated by the need
of robotic systems able to handle exploration tasks with
increasing complexity. This includes e.g. (multi-) sam-
ple return missions as well as tasks in the field of re-
source utilization and even the preparation of (long term)
manned missions. The overall mission concept is oriented
around the implementation of a logistics chain, including
various robotic systems. As shown in Figure 1, this in-
cludes: (1) a team of mobile surface robots, (2) station-
ary elements and (3) portable modular payload items. The
proposed mission concept addresses basically the surface
exploration of the above mentioned elements.
The exploration rover is the primary mobile element
within the mission concept. It serves as main exploration
device, able to conduct the major mission tasks and serves
as transporter for the deployment of base camps.
The exploration rover is paired up with one or more
shuttle rover(s). The shuttle is a compact, highly mo-
bile system and the core element for establishing a supply
chain between stationary infrastructure elements - such
as lander and/or sample return stage, base camps and
the exploration rover. The base camps are stationary el-
ements providing infrastructure to support the logistics
chain. They can serve as junction point as shown in Fig-
ure 1 to exchange, e.g., payload items between the dier-
ent systems. Further functionality for energy harvesting,
communication or scientific instrumentation may also be
provided by base camps depending on the needs of the
mission.
In order to implement a supply chain the shuttles need
to cooperate tightly with the exploration rover. Further
surface elements that may be included in the logistics
chain are potentially the lander and a sample return stage.
Independently of the chosen landing system, a dedicated
home base, i.e. main supply and communication link to
the ground station, is part of the mission concept. The
home base serves as depot for base camps and portable
payload items and may be equipped with additional scien-
tific and/or mission relevant functionality as well.
The mission concept proposes to realize the logistics
chain by including the dierent mobile and stationary sur-
face elements and establish the links using a modular ap-
proach. While each of the surface elements has to sat-
isfy specific needs to execute the mission tasks, a high
interconnectivity between the dierent elements is envis-
aged. An overview of the physical connectivity between
the various elements is shown schematically in Figure 2.
Especially the portable and modular payload items play a
key role for establishing the logistics chain. They serve
Figure 2. Schematic drawing of the modu-
lar interconnectivity of the dierent sur-
face elements
as multipurpose payload containers which can be attached
to several elements. This approach allows to add specific
functionality to the various systems and to handle dier-
ent tasks in a distributed manner. A closer look on the
dierent robotic systems is provided in Section 6.
3 Mission Subject and Landing Site
For the reference mission scenario the robotic systems
are designated to operate inside Amundsen crater, located
close to the lunar south pole. This landing site was cho-
sen based on a trade-obetween dierent scientific goals
for lunar exploration, as identified by [4, 7]. The trade-o
process was conducted to identify an adequate scientific
context and an appropriate landing site for the reference
mission. This was done mainly with respect to which sci-
entific mission concept would benefit the most of the pre-
viously described mission design concept. As most of the
described science goals in [4, 7] require field work, like
sample collection and return to Earth, four high potential
sites are identified which would benefit from a logistics
chain set-up. These are in particular: 1. Amundsen Crater,
2. Tycho Crater, 3. Montes Harbinger and 4. Schr¨
odinger
Basin. The four sites are shown in Figure 3, with poten-
tial landing and exploration sites highlighted as identified
by [4].
The primary scientific objective within Amundsen
crater is to study volatiles and their flux in the lunar pole
regions. Due to its location and crater diameter of approx-
imately 150 km, only some parts of the crater are perma-
nently shadowed regions (PSR) (cf. Figure 3(a)). This
allows to land and deploy the robots directly on the flat
crater floor in a sunlit region such that no descent on a
steep crater wall is required as it would be the case e.g.
at Shackleton crater. Another benefit is the possibility to
send the robots for short exploration excursions into the
thermally and power-wise more challenging PSR environ-
ment.
(a) Amundsen Crater (b) Tycho Crater
(c) Montes Harbinger (d) Schr¨
odinger Basin
Figure 3. The four most favorable lunar
landing sites following the mission de-
sign concept [4]
The main needs which arise from the scientific mis-
sion setup with respect to the mission and system design
are:
Operation in shadowed/dark areas Exploration and
analysis tasks need to be conducted in PSR which
provide continuous low temperatures. These areas
are of main interest to study the accumulation of
volatile materials as well as regolith processes.
Sample analysis The current state of volatile materials
and regolith at very cold spots may need to be an-
alyzed by in-situ measurements. Taking the samples
out of its environment can change the composition
drastically due to temperature change.
Sample return to Earth In order to study regolith com-
position and processes in cold areas in-situ analysis
is needed. However, the science goals ask for the
return of regolith samples allowing a deeper investi-
gation within terrestrial laboratories. As proposed in
[2] returning frozen samples should be considered as
well, calling for sealable sample containers.
The mission needs introduce quite challenging and
complex exploration tasks which would benefit from a lo-
gistics chain e.g. in terms of sample transport, energy and
communication support and assembling special base sta-
tions for keeping-alive support.
Especially the deployment of dierent base camps
can support the mission in terms of, e.g., energy sup-
ply, position tracking, and communications. Furthermore,
they can serve as stationary laboratories for in-situ analy-
sis of samples taken by the exploration rover. Paired with
suitable modular payload items it would be possible to
introduce instrument and/or tool change for the dierent
rover platforms in order to handle a wide range of dier-
ent tasks.
The investigation on establishing and maintaining
a robotic logistics chain provides the possibility of in-
creasing the maturity level and demonstrating the state
of robotic technologies in terms of (1) robotic coop-
eration, (2) multi-robot mission planning and execution,
(3) robotic long-term autonomy, and (4) robotic infras-
tructure setup and maintenance. These robotic technolo-
gies are currently considered to be main issues in prepara-
tion for (long-term) human presence on any celestial body.
The aspired mission definition provides a wide range
of exploration and assembly tasks with the possibility
to prepare In-Situ Resource Utilization (ISRU) and/or
long-term manned missions. Especially the potential of
harvesting volatile materials, e.g., for future long term
manned missions makes the Amundsen crater a quite in-
teresting place.
This concept highly depends on the logistics chain
considering that the base camps will be needed as com-
munication relay stations (cf. Section 5) and potentially
for power supply and sample analysis. Especially for so-
lar powered rover systems the base camps can be used for
energy harvesting. This would allow to extend the PSR
excursions of the exploration rover due to the possibil-
ity to supply recharged energy packages via the logistics
chain. Most likely, however, this concept would not hold
for the surface exploration as described in Section 4. For
extensive PSR traversal an appropriate power supply sys-
tem is needed on the exploration rover which can, e.g., be
based on wireless power transmission techniques or radio
thermal generators. In any case a reliable cooperation be-
tween the robotic systems is required in order to support
exploration and sample analysis in PSR.
4 Surface Exploration
The main scientific and technical focus is on estab-
lishing a logistics chain utilizing a team of robots to sam-
ple regolith and evaluate the presence of volatile material
in dicult to reach areas inside the Amundsen crater. The
chosen landing and exploration site is shown in Figure 4.
The image is a multi-level surface map with a satellite mo-
saic overlay [5], the markers for the science goals refer to
[4]. The paths were chosen to avoid craters on transients
using the tools available in [5].
The rover starts at the landing site Land passes the
Landing Site
b1
base camp 1
b2
b3
b4
b5
base camp 2
b6
b7
Legend
Rover Leg 1
Rover Leg 2
Shuttle
Figure 4. Overview of the surface explo-
ration scenario in Amundsen crater
science sites b1 to b7. The following enumeration gives
more detail on the approach sequence and tasks carried
out at the specific science sites:
1. Following the touchdown of the lander at landing site
B, 83.82S, 87.53E (cf. Figure 3(a)) with crater
floor slopes <5, both, the shuttle as well as the ex-
ploration rover, begin the commissioning phase.
2. After commissioning, the rover, already equipped
with a base camp assembly for communication
and power supply, travels towards the central peak
foothills and then starts approaching point b1 on the
slopes of the central peaks.
3. At point b1 the exploration rover deploys (utilizing
it’s manipulation capabilities) the base camp com-
munication/power assembly. The elevation above the
crater floor will increase visibility both to Earth and
Sun for communication purposes and energy harvest-
ing. The base camp may also be utilized for naviga-
tion purposes by serving as a beacon.
4. A second task at point b1 for the exploration rover is
to take regolith samples, which are of specific interest
due to the potentially layered structure of the central
peak slopes. The gathered samples do not need to be
analyzed in-situ but can be stowed away in a modular
sampling container (payload item) for sample return.
5. Subsequently, the exploration rover descents the cen-
tral peak slopes, heading for point b2 to take further
regolith samples.
6. b2 is also the first rendezvous point for the explo-
ration rover and the shuttle, at which the exploration
rover can reequip itself with fresh battery payload el-
ements brought there by the shuttle, as well as ex-
changing the filled sampling payload elements with
new ones. Additional sample containers are probably
required to take samples at b2 which is proposed for
sensor calibration by [4].
Following the first rendezvous, both robots head for
the lander, the exploration rover in order to fetch the
second base camp assembly (sample drop-off / power
supply type) and the shuttle to deposit the regolith
samples.
7. Thereafter, the exploration rover is approaching and
entering the PSR heading towards point b3 and b4,
taking geological samples in places of utmost scien-
tific interest due to the expected thermally trapped
volatiles.
8. Having sampled at point b3 and b4, the exploration
rover leaves the PSR again in a left side arc toward
b6, deploying the second base camp. At this point
also a rendezvous with the supplying shuttle takes
place again.
9. While the shuttle is returning exchanged sampling
and battery payload elements to the lander, the ex-
ploration rover is entering the PSR again in order to
sample at b6 and b7 subsequently while being resup-
plied by the shuttle.
10. In an extended phase that could follow the mission
procedure stated above, the exploration rover can
continue to climb the Amundsen crater rim sampling
the interesting heavily terraced and layered slopes
looking for ancient regolith.
Following the depicted exploration scenario, the ex-
ploration rover needs to travel a total distance of approxi-
mately 47.75 km with a maximum distance from the land-
ing site of 20 km, and 3915 m of cumulative elevation
gain. In Figure 5(a) a distance profile for the exploration
rover path within Amundsen Crater is plotted. The land-
ing site, scientific exploration points of interest as well
as base camp deployment locations are marked within the
diagram. Accordingly, the travel profiles for the dierent
shuttle legs are given in Figure 5(b). For each shuttle path
the distances to the target and back are plotted since this is
considered a typical shuttle support mission. Specifically
these cover the shuttle traversal from the landing site to b2
and back, again from the landing site to base camp 2 and
back and from base camp 2 to b7 and back.
The travel profiles follow the exploration scenario as
shown in Figure 4 and outlined in the previous descrip-
tions. For compiling the traversal profiles and distance
measurements the data available in [5] were used. For all
measurements the direct path between the depicted points
of interests are taken into account. Hence, no additional
traversal for performing exploration tasks and/or obstacle
(a) Distance profile for the exploration rover path
(b) Distance profile for the shuttle rover paths
Figure 5. Travel distance profiles for the
exploration and shuttle rover
avoidance is considered in the given distance measure-
ments. These need to be included during a detailed mis-
sion design process.
5 Communication Architecture
To allow the implementation of a logistics chain with
various cooperating surface elements a proper communi-
cation architecture needs to be taken into account for op-
erations. A short range communication ability between
the exploration rover and shuttle(s) is necessary to al-
low the handling of cooperative tasks. For longer ranges
base camps can serve as communication relays, e.g. for
transmitting the relative positions of the systems for ren-
dezvous. This implies that the exploration rover as well as
the shuttle need a direct communication link to each other
or at least to one base camp when trying to communicate
with each other. Therefore, each base camp should be able
to link to neighboring base camps to establish a supporting
communication network for the surface elements.
The communication range on the Moon strongly de-
pends on antenna heights and terrain. A direct line of sight
Figure 6. Free line of sight evaluation
for communication within Amundsen
crater
Figure 7. Proposed communication archi-
tecture with optional orbiter displayed.
Dashed lines depict temporary and/or
optional communications and solid lines
mark fixed communication links.
(LoS) is necessary in order to establish communication.
Figure 6 illustrates the communication possibilities over
the terrain between the base camps and the landing unit
representing a cross section of Amundsen crater based on
the data available in [5]. As shown the LoS between the
lander and base camp 2 is blocked by terrain. A commu-
nication between lander and base camp 2 is possible using
base camp 1 as relay.
Using this information, Figure 7 illustrates the pro-
posed communication architecture. As outlined previ-
ously, base camp 1 should be placed on the central peak
of Amundsen crater. This has two main reasons besides
the scientific mission needs: (1) As shown in Figure 6 no
direct LoS can be established between the lander and base
camp 2. Therefore, a relay is needed to set up a commu-
nication network, covering the points of interest b3 to b7.
(2) Due to the landing site at 83.82S, 87.53E the lunar
libration with max. angles of ±7.7longitude and ±6.7
latitude has a major impact on the LoS to Earth (cf. [3]).
Placing a base camp on the central peak reduces the angle
to the crater rim to 2.5while the horizon seen from the
crater floor is at 5. Taking the libration into account
the total time with direct communication ability to Earth
increases by placing the antenna on the central peak. Op-
tionally, communication times with mission control can
be increased by introducing a lunar orbiting satellite or
placing a relay on the outer crater rim of Amundsen. Dur-
ing the traverse of the exploration rover to the deployment
destination of base camp 1 the lander is considered to
serve as communication link to Earth, providing a com-
munication back-up for the later on mission.
For cooperative tasks between the exploration rover
and the shuttle(s) short range communication is required.
For longer ranges base camps serve as communication re-
lays, e.g. for communicating the relative positions of the
systems for rendezvous. This implies that the exploration
rover as well as the shuttle need a communication connec-
tion to each other or at least to one base camp to build up a
communication link. Many aditional types of deployable
units are conceivable when regarding the modular setup
of the overall system. These units are for example surface
deployable scientific experiments. While this modality is
not depicted in Figure 7, such elements need to be con-
nected to the local communication network set up by the
base camps and lander.
6 Robotic Systems Overview
There are several systems involved in the approach of
forming a logistics chain on a celestial body. The systems
include, as mentioned above, mobile units, namely an ex-
ploration rover and one or more supporting shuttle sys-
tems. Immobile units are present in form of base camps
and payload items, extended by the possibility of includ-
ing the landing unit. The main tasks are distributed as
follows.
The exploration rover is responsible for carrying and
deploying base camps and payload items to establish the
basic infrastructure of the logistics chain. By means of the
payload items, the rover can be equipped with additional
tools to fulfill dierent science tasks.
The shuttle rover has to be able to quickly (w.r.t. the
exploration rover) cover rough terrain. Its task is carrying
payload items between stationary nodes to the exploration
rover and back, thus keeping the logistics chain active.
Payload items are containers for scientific instru-
ments, infrastructure elements or tools. They can be con-
nected with other payload items, base camps or mobile
robots via a uniform electro-mechanical interface (EMI).
Connecting dierent payload items into a stack allows to
build up functional units from modular items.
Base camps shall provide stationary points in the lo-
gistics chain. They can be used for energy harvesting,
communication relay, payload storage etc. Base camps
are equipped with EMIs to be able to integrate modu-
lar payload items for extension of functionality or battery
recharging.
Following the previously described reference mis-
sion, it is intended to perform demonstration scenarios
in terrestrial testing facilities. The robotic systems that
Figure 8. Designated systems for terrestrial
proof of concept demonstration of the
described scenarios
are employed in the context of these demonstration sce-
narios are based on already available systems as shown
in Figure 8. The wheeled-leg exploration rover Sherpa
(background), the hybrid legged-wheel shuttle Asguard
(foreground) and some payload items (stack of cubes).
The systems are displayed in their initial state, adaptions
are currently conducted. A brief description of the core
robotic systems and their adaptation to the special needs
for establishing the envisioned logistics chain is given in
the following sections.
6.1 Exploration Rover
The hybrid wheeled-leg system Sherpa is designated
as exploration rover. This system has already demon-
strated its ability to work in a heterogeneous robotic sys-
tem and is capable of transporting modular payload items,
a partner robot, and is equipped with a manipulator for
payload handling [8]. Currently, the main adaption work
for Sherpa is focusing on the suspension system and a new
locomotion control scheme that is being implemented.
A concept study of the Sherpa adaptation as presented
in [1] is shown in Figure 9. The rover is shown with a base
camp attached under its belly and a payload item attached
to the manipulator arm. The main body of the rover holds
four modular payload item bays for reconfiguration pur-
poses or storage of payload containers.
The main dimensions of Sherpa are 2.4×2.4×1.2 m,
with a mass of 160 kg. The adaptation of Sherpa as
shown in Figure 9 is considered to stay within this mass
and size frame.
6.2 Shuttle
The task of a quick and highly mobile shuttle is as-
signed to one of the robots of the Asguard family. These
robots make use of hybrid legged-wheels for propulsion.
Figure 9. Conceptual drawing of the pro-
posed adaptation of Sherpa as explo-
ration rover with attached base camp
and payload item
Figure 10. Conceptual drawing of a shuttle
rover equipped with a manipulator for
payload item handling
The special design of the wheels allows fast movement
in very rough terrain. The system exhibits a generally
low control complexity and a robust design. In its latest
version, Asguard presented high autonomous capabilities
while moving in rough terrain [9].
From the family of Asguard rovers an adaptation of
the Coyote II rover ( cf. [10]) is considered for the ter-
restrial proof of concept trials. A major adaptation of the
rover is to enable the transport and handling of modular
payload items. An initial idea of a possible shuttle concept
is given in Figure 10. The rover concept is equipped with
a payload item bay and a manipulation device to handle
the payload items. While Coyote II has a mass of 9.2kg at
850 ×580 ×410 mm outer dimensions, it is considered
that the adopted rover will have a higher mass due to its
additional mechanisms.
Figure 11. Schematic drawing of the mod-
ularity concept for a general base camp
6.3 Payload Items
The payload items are based on previous develop-
ments as described in [8] and shown in Figure 8. Each
payload item is equipped with an EMI on the top and bot-
tom. The EMI with its accompanying electronics is re-
sponsible for connecting payload items electronically and
mechanically with other payload items or robots that pro-
vide an EMI.
The EMI and the payload items play a key role in es-
tablishing the logistics chain. They provide the modular-
ity and reconfiguration capabilities of the dierent robotic
systems due to a standardized EMI and payload container
shape. The interface as well as the payload items allow to
establish tool and system change for the remaining robotic
systems and can be equipped with dierent tools, instru-
ments, systems or goods. It is foreseen to use the payload
item e.g. for energy supply, sample catching and position-
ing purposes during the planned terrestrial tests. A basic
payload item has a cubical shape with 154 mm edge length
and is designed for an overall mass of 5 kg. The EMI itself
is designed for operation under mechanical loads of up to
300 N in order to support base camp deployment.
6.4 Base Camps
Base camps are considered to either serve as special-
ized base stations designed for a specific task or as mutli-
functional modular base stations providing the main func-
tionality in terms of communication (cf. Section 5) and a
set of EMI, for reconfiguration purposes. The general idea
of modularity for a base camp is outlined in Figure 11.
The base camp, equipped with several EMIs, serves as
multi- functional note within the logistics chain. It can
be equipped with dierent payload items according to the
mission need and progress. This allows to provide a de-
fined assembly point for payload items in order to build
up a supply chain for the mobile robots or to build up a
scientific and/or mission relevant system.
The base camps are carried and deployed by the ex-
ploration rover (cf. Figure 9). It is proposed to connect
them to the bottom of the exploration rover’s main body
using an EMI. Therefore, the dimensions of a base camp
are dependent on the rover body dimensions and are ini-
tially considered at 600 ×600 ×150 mm with a mass of
30 kg.
7 Conclusion and Outlook
In the previous sections a mission design concept is
presented, introducing a heterogeneous modular robotic
team for extended extraterrestrial exploration tasks. In
order to handle tasks with increasing complexity in fu-
ture exploration missions the approach of implementing
a highly modular logistics chain is presented. For this, a
team of mobile robots is accompanied by stationary sur-
face elements as well as portable and modular payload
items.
The analysis of present scientific questions for fu-
ture lunar exploration missions yields a high potential
for multi-robot missions. The proposed approach of im-
plementing a logistics chain promises to gain benefits in
terms of long term exploration, sample transport for sam-
ple analysis and return, energy and communication sup-
port and last but not least providing the ability to han-
dle complex cooperative tasks like setting up infrastruc-
ture elements. Based on the scientific context a reference
mission within Amundsen crater is presented, motivating
the proposed mission design concept. The mission outline
focuses on the implementation of a logistics chain, allow-
ing to analyze volatiles and regolith processes at various
points of interest within Amundsen crater. A set-up in-
cluding one exploration rover and one ore more shuttle
rovers is presented. These mobile robots are accompanied
by stationary base camps which build up a local commu-
nication network to support the logistics chain. Further-
more, base camps are considered to be used for energy
harvesting in order to provide life support within the ther-
mally and power-wise dicult environment of Amundsen
crater.
Based on the lunar reference mission a set of demon-
stration scenarios will be derived for terrestrial proof of
concept trials. The intended robotic systems for the im-
plementation of a logistics chain are presented along with
their proposed functional adaptations. Furthermore, it is
intended to analyze the benefits of all systems proposed
for space exploration purposes within Earth-bound appli-
cations. This includes, e.g., search and rescue, manage-
ment of maritime resources and rehabilitation. It is be-
lieved that the installation of a logistics chain and the co-
operation of a heterogeneous robotic team can add major
benefits to these domains as well.
Acknowledgment
The project TransTerrA is funded by the German
Space Agency (DLR, Grant number: 50RA1301) with
federal funds of the Federal Ministry of Economics and
Technology (BMWi) in accordance with the parliamen-
tary resolution of the German Parliament.
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... Rock is of particular interest for the space community since it follows a model-based software development approach, and is used on a number of space related robotic systems such as SherpaTT [9], Coyote III [9], CREX [8] and ESA's Ex-oMars Test Rover (ExoTeR) [4]. The use of Rock with a variety of single-robotic systems and the use in multirobot scenarios such as TransTerrA [10], RIMRES [8] and VIPE [7] has increased the need and triggered the development of a repeatable and manageable installation and upgrading process. The support of a component database and streamlined, user-friendly development workflow by the project D-Rock [2] added additional requirements for the software packaging solution. ...
... The support of a component database and streamlined, user-friendly development workflow by the project D-Rock [2] added additional requirements for the software packaging solution. The motivation for the development of a binary packaging mechanism originates from the set of application scenarios and user demands which have been identified especially in the context of operating heterogeneous, multi-robot systems for space exploration [7,10]. A large amount of software packages can be shared in a multi-robot system, but in practice this does not necessarily lead to a homogeneous software basis: multiple architectures and distributions have to be supported and in the case of Rock the flexibility of the meta-build system autoproj comes with the risk of an equally heterogeneous landscape of build configurations in a multi-robot system, if not managed with strict user policies. ...
Conference Paper
Full-text available
This paper introduces a binary software packing mechanism for the Robot Construction Kit (Rock). The use of Rock with a variety of single-robotic systems and the use in multi-robot scenarios has triggered the development of a repeatable and manageable installation and upgrading process. The mechanism is based on the widespread De-bian packaging format and takes advantage of the available tooling. The high degree of standardization within the Rock framework, and the application of a meta-build tool have contributed to a build process which allows to automatically package hundreds of associated packages. A transparent integration into the meta-build tool allows to maintain the typical development workflow, and enables users to switch between custom source package variants and binary software packages. This paper will detail the architecture of the packaging approach, illustrate features and show the validation, and lessons learned from daily use.
... For an experimental evaluation of the planning approach we look at a simulated space mission, which has been outlined by Sonsalla et al. [28]. The major goal of the mission is to place scientific payloads in a lunar environment at a predefined set of locations for science goals. ...
Preprint
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While traditional robotic systems come with a monolithic system design, reconfigurable multi-robot systems can share and shift physical resources in an on-demand fashion. Multi-robot operations can benefit from this flexibility by actively managing system redundancies depending on current tasks and having more options to respond to failure events. To support this active exploitation of redundancies in robotic systems, this paper details an organization model as basis for planning with reconfigurable multi-robot systems. The model allows to exploit redundancies when optimizing a multi-robot system's probability of survival with respect to a desired mission. The resulting planning approach trades safety against efficiency in robotic operations and thereby offers a new perspective and tool to design and improve multi-robot missions. We use a simulated multi-robot planetary exploration mission to evaluate this approach and highlight an exemplary performance landscape.
... Multiple tasks require a very precise close-range vehicle localization when approaching structures or other vehicles, for example during handing over probes in sample-and-return missions with a team of cooperative robots [Sonsalla et al., 2014, Sonsalla et al., 2017. Typical examples in maritime applications are docking with a submerged asset infrastructure or with another vehicle, maintenance or georeferencing. ...
Thesis
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This thesis investigates the utilization of magnetic field distortions for the localization and navigation of robotic systems. The work comprehensively illuminates the various aspects that are relevant in this context. Among other things, the characteristics of magnetic field environments areassessed and examined for their usability for robot navigation in various typical mobile robot deployment scenarios. A strong focus of this work lies on the self-induced static and dynamic magnetic field distortions of complex kinematic robots, which could hinder the use of magnetic fields because of their interference with the ambient magnetic field. In addition to the examination of typical distortions in robots of different classes, solutions for compensation and concrete tools are developed both in hardware (distributed magnetometer sensor systems) and in software. In this context, machine learning approaches for learning static and dynamic system distortions are explored and contrasted with classical methods for calibrating magnetic field sensors. In order to extend probabilistic state estimation methods towards the localization in magnetic fields, a measurement model based on Mises-Fisher distributions is developed in this thesis. Finally, the approaches of this work are evaluated in practice inside and outside the laboratory in different environments and domains (e.g. office, subsea, desert, etc.) with different types of robot systems.
... High circular polarization ratios detected by the Mini-RF instrument on the Lunar Reconnaissance Orbiter (LRO) also suggest the presence of large amounts of water ice within the upper 2 m of regolith inside the PSR (Spudis et al., 2013). For these reasons, Amundsen has been recommended as a potential landing site for future human or robotic missions with the potential for high scientific return in the study of lunar volatiles and other regolith properties (Lemelin et al., 2014;Sonsalla et al., 2014). ...
Article
Full-text available
The lunar South Pole crater Amundsen is a prime location to study the effects of space weathering in the far ultraviolet. Amundsen's equator-facing terrace walls are highly illuminated while the northern side of the crater has permanently shaded regions (PSRs). Using data from the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project, we investigate signatures of space weathering in different regions of Amundsen. We find that regions of the surface that receive large amounts of solar illumination and solar wind flux (e.g., the southern terrace walls) display high Lyman-α albedos and blue spectral slopes in the 175–190-nm region, indicative of increased regolith maturity due to solar wind weathering and thermal cycling. Amundsen's PSRs, however, receive no direct solar illumination and very little solar wind flux and have a lower albedo across Lyman Alpha Mapping Project's entire band pass (57–197 nm) than illuminated regions of the crater. We conclude that the low PSR albedos correspond to high regolith porosity in the PSRs. These PSRs are extremely cold regions with very minor thermal cycling. Thermal cycling might be a process that reduces porosity in regions of the crater exposed to a wide range of temperatures, thus increasing their albedos across the entire wavelength range. However, our analysis of the present data set was unable to uniquely identify its role. The low albedos in the PSRs may also result from extreme charging effects inside the PSRs, causing lofting and redeposition of dust, as well as dielectric breakdown, which would act to increase regolith porosity.
... The initial motivation for the planning problem is given by Sonsalla et al. (Sonsalla et al. 2014), where a reconfigurable multi-robot system shall establish a logistics chain operation in order to support sample-return missions as part of extraterrestrial exploration. The robotic team consists of mobile and immobile agents, which can be physically connected via a set of electro-mechanical interfaces. ...
Conference Paper
Recent advances in additive manufacturing (AM) and 3D printing technologies have led to significant growth in the use of additive manufacturing in industry, which allows for the physical realization of previously difficult to manufacture designs. However, in certain cases AM can also involve higher production costs and unique in-process physical complications, motivating the need to solve new optimization challenges. Optimization for additive manufacturing is relevant for and involves multiple fields including mechanical engineering, materials science, operations research, and production engineering, and interdisciplinary interactions must be accounted for in the optimization framework. In this paper we investigate problem where a set of parts with unique configurations and deadlines must be printed by a set of machines while minimizing time and satisfying deadlines, bringing together bin packing, nesting (two-dimensional bin packing), job shop scheduling, and constraints satisfaction. We first describe the real-world industrial motivation for solving the problem. Subsequently, we encapsulate the problem within constraints and graph theory, create a formal model of the problem, discuss nesting as a subproblem, and describe the search algorithm. Finally, we present the datasets, the experimental approach, and the preliminary results.
... Such a scenario was tested in a four week field trial, as described in this paper. For the experiments, the TransTerrA system [6] was deployed in the desert of Utah during October and November 2016. Fig. 1 displays the systems in the test environment. ...
Conference Paper
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This paper presents the evaluation of a heterogeneous robotic team for planetary exploration purposes. An extensive test campaign with a duration of four weeks was conducted in October/November 2016 in the desert of Utah, USA. The employed robotic systems were tested on natural and unstructured Mars analogue terrain and remotely operated from a control station in Bremen, Ger-many. The paper details the performed system tests as well as the conducted cooperative mission sequences in the scope of a sample return mission. Furthermore, the planning and preparation of the field trial campaign as well as the infrastructure setup in Utah and Bremen and the test execution are presented with regard to lessons learned in the field and at the control center in Bremen.
... Within the project TransTerrA a modular robotic system 978-1-5386-2014-4/18/$31.00 c 2018 European Union for semi-autonomous cooperative exploration of planetary surfaces including the installation of a logistics chain was developed [1]. In order to achieve these objectives the robots are designed to be augmented with modular elements for different exploration scenarios, which can be additionally controlled by humans using a man-machine-interface. ...
Conference Paper
This paper presents the design, functionality and evaluation of an end-effector, operating at the end of a 6 degree-offreedom manipulator of the existing planetary rover SherpaTT. The end-effector consists of an active electro-mechanical interface (EMI), which has an active mechanical docking interface, as well as power and data connectors, a camera primary used for visual servoing and LED lights. The ability of the end-effector to grapple different robotic systems and change their configuration is proved under laboratory and field conditions in the framework of a heterogeneous multi-robot system. The end-effector of SherpaTT is an improved version of the previous end-effector of the predecessor project RIMRES. This paper outlines the development process and improvements of the end-effector and describes its the role within different terrestrial test scenarios in more detail. Learned lesson will help to develop the end-effector in the H2020 EU-funded project SIROM(Standard Interface for Robotic Manipulation of Payloads in Future Space Missions), which will be deployed at the manipulator of SherpaTT for experimental verification for future planetary missions.
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With this dissertation, the electromechanic design, implementation, locomotion control, and experimental evaluation of a novel type of hybrid wheeled-leg exploration rover are presented. The actively articulated suspension system of the rover is the basis for advanced locomotive capabilities of a mobile exploration robot. The developed locomotion control system abstracts the complex kinematics of the suspension system and provides platform control inputs usable by autonomous behaviors or human remote control. Design and control of the suspension system as well as experimentation with the resulting rover are in the focus of this thesis. The rover is part of a heterogeneous modular multi-robot exploration system with an aspired sample return mission to the lunar south pole or currently hard-to-access regions on Mars. The multi-robot system pursues a modular and reconfigurable design methodology. It combines heterogeneous robots with different locomotion capabilities for enhanced overall performance. Consequently, the design of the multi-robot system is presented as the frame of the rover developments. The requirements for the rover design originating from the deployment in a modular multi-robot system are accentuated and summarized in this thesis.
Thesis
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With this cumulative dissertation, the electromechanical design, electromechanical implementation, locomotion control, and experimental evaluation of a novel type of hybrid wheeled-leg exploration rover are presented. The actively articulated suspension system of the rover is the basis for advanced locomotive capabilities of a mobile exploration robot. The developed locomotion control system abstracts the complex kinematics of the suspension system and provides platform control inputs usable by autonomous behaviors or human remote control. Design and control of the suspension system as well as experimentation with the resulting rover are in the focus of this thesis. The rover is part of a heterogeneous modular multi-robot exploration system with an aspired sample return mission to the lunar south pole or currently hard-to-access regions on Mars. The multi-robot system pursues a modular and reconfigurable design methodology. It combines heterogeneous robots with different locomotion capabilities for enhanced overall performance. Consequently, the design of themulti-robot system is presented as the frame of the rover developments. The requirements for the rover design originating from the deployment in a modular multi-robot system are accentuated and summarized in this thesis.
Article
Full-text available
This study presents the electromechanical design, the control approach, and the results of a field test campaign with the hybrid wheeled‐leg rover SherpaTT. The rover ranges in the 150 kg class and features an actively articulated suspension system comprising four legs with actively driven and steered wheels at each leg’s end. Five active degrees of freedom are present in each of the legs, resulting in 20 active degrees of freedom for the complete locomotion system. The control approach is based on force measurements at each wheel mounting point and roll–pitch measurements of the rover’s main body, allowing active adaption to sloping terrain, active shifting of the center of gravity within the rover’s support polygon, active roll–pitch influencing, and body‐ground clearance control. Exteroceptive sensors such as camera or laser range finder are not required for ground adaption. A purely reactive approach is used, rendering a planning algorithm for stability control or force distribution unnecessary and thus simplifying the control efforts. The control approach was tested within a 4‐week field deployment in the desert of Utah. The results presented in this paper substantiate the feasibility of the chosen approach: The main power requirement for locomotion is from the drive system, active adaption only plays a minor role in power consumption. Active force distribution between the wheels is successful in different footprints and terrain types and is not influenced by controlling the body’s roll–pitch angle in parallel to the force control. Slope‐climbing capabilities of the system were successfully tested in slopes of up to 28° inclination, covered with loose soil and duricrust. The main contribution of this study is the experimental validation of the actively articulated suspension of SherpaTT in conjunction with a reactive control approach. Consequently, hardware and software design as well as experimentation are part of this study.
Conference Paper
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The importance for small and lightweight rovers providing high mobility and versatility in future exploration missions is increasing. Within this paper the terrestrial test platform Coyote II is presented. The rover is equipped with a novel locomotion concept combining hybrid legged-wheels with spherical helical wheels. This allows to perform side-to-side steering movements and yields high mobility performance in rough terrain as well as on soft soils as shown during various laboratory and real environment tests. The rover is specially designed to act as a scout rover paired up with a primary rover for autonomous long term exploration. The operational concept for the scout rover within the two rover team is addressed with respect to the primary rover.
Conference Paper
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This paper reviews the design of the hybrid wheeled-leg rover Sherpa. Focus is set on the mechanical design of the suspension system that is constituted by four independently controllable legs with a wheel mounted at each leg. Achievements and drawbacks of the current design are outlined and lead together with the new application range to a revised design of the suspension. The new design and its modular actuation components are presented in this paper.
Article
This paper presents the multirobot team RIMRES (Reconfigurable Integrated Multirobot Exploration System), which is comprised of a wheeled rover, a legged scout, and several immobile payload items. The heterogeneous systems are employed to demonstrate the feasibility of reconfigurable and modular systems for lunar polar crater exploration missions. All systems have been designed with a common electromechanical interface, allowing to tightly interconnect all these systems to a single system and also to form new electromechanical units. With the different strengths of the respective subsystems, a robust and flexible overall multirobot system is built up to tackle the, to some extent, contradictory requirements for an exploration mission in a crater environment. In RIMRES, the capability for reconfiguration is explicitly taken into account in the design phase of the system, leading to a high degree of flexibility for restructuring the overall multirobot system. To enable the systems' capabilities, the same distributed control software architecture is applied to rover, scout, and payload items, allowing for semiautonomous cooperative actions as well as full manual control by a mission operator. For validation purposes, the authors present the results of two critical parts of the aspired mission, the deployment of a payload and the autonomous docking procedure between the legged scout robot and the wheeled rover. This allows us to illustrate the feasibility of complex, cooperative, and autonomous reconfiguration maneuvers with the developed reconfigurable team of robots.
Article
Mobile autonomous robots have finally emerged from the confined spaces of structured and controlled indoor environments. To fulfill the promises of ubiquitous robotics in unstructured outdoor environments, robust navigation is a key requirement. The research in the simultaneous localization and mapping (SLAM) community has largely focused on optical sensors to solve this problem, and the fact that the robot is a physical entity has largely been ignored. In this paper, a hierarchical SLAM framework is proposed that takes the interaction of the robot with the environment into account. A sequential Monte Carlo filter is used to generate local map segments with a combination of visual and embodied data associations. Constraints between segments are used to generate globally consistent maps with a focus on suitability for navigation tasks. The proposed method is experimentally verified on two different outdoor robots. The results show that the approach is viable and that the rich modeling of the robot with its environment provides a new modality with the potential for improving existing visual methods and extending the availability of SLAM in domains where visual processing alone is not sufficient.
Article
The interim results of an NRC study, commissioned by NASA to provide scientific guidance for the lunar component of the Vision for Space Exploration, are presented. The study, undertaken by a committee of 15, is designed to examine the scientific challenges and opportunities opened up by a sustained program of robotic and human exploration of the Moon. In particular, the NRC has been asked to undertake two primary tasks--first, to identify a prioritized set of scientific goals that can be addressed in the near term by robotic lunar missions and in the mid term by astronauts on the Moon and, second, to determine which of the identified scientific goals are most amenable to orbital measurements, in situ study, or terrestrial analysis via the return of lunar samples to Earth--and two secondary tasks--first, to comment on those areas where there is a synergistic overlap between measurements addressing scientific goals and measurements required to ensure human survival and, second, to collect and characterize possible scientific goals that might be addressed on or from the Moon in the long term. The scientific scope of the study encompasses the history of the Moon and the Earth-Moon system, the origin and evolution of the Sun and planets, and implications for the origin and evolution of life on Earth and elsewhere in the solar system. The publication of the interim results is designed to promote a broad discussion about lunar science goals and to engage the national and international science and engineering communities in defining an appropriate lunar exploration program. A final report will be issued in the latter half of 2007.
Article
The present status of lunar knowledge based on U.S. and USSR lunar missions and the continuing analysis of lunar samples and data is reviewed. Particular attention given to exploration, samples, and recent concepts of the moon; the lunar environment; lunar surface processes; the lunar minerals, rocks, and regolith; chemical elements in the moon; physical properties of the lunar surface; and global and regional data about the moon.
Mars Sample Return Campaign Status
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Design of a High Mobile Micro Rover within a Dual Rover Configuration for Autonomous Operations Robotics and Automation in Space-i-Sairas 2014
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R.U. Sonsalla et al. "Design of a High Mobile Micro Rover within a Dual Rover Configuration for Autonomous Operations". In: Proc. of the 12th Int. Symp. on Artificial Intelligence, Robotics and Automation in Space-i-Sairas 2014. Montreal, Canada, 2014.
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