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Offloading SLAM for Indoor Mobile Robots with Edge-Fog-Cloud Computing

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Indoor mobile robots are widely used in industrial environments such as large logistic warehouses. They are often in charge of collecting or sorting products. For such robots, computation-intensive operations account for a significant percentage of the total energy consumption and consequently affect battery life. Besides, in order to keep both the power consumption and hardware complexity low, simple micro-controllers or single-board computers are used as onboard local control units. This limits the computational capabilities of robots and consequently their performance. Offloading heavy computation to Cloud servers has been a widely used approach to solve this problem for cases where large amounts of sensor data such as real-time video feeds need to be analyzed. More recently, Fog and Edge computing are being leveraged for offloading tasks such as image processing and complex navigation algorithms involving non-linear mathematical operations. In this paper, we present a system architecture for offloading computationally expensive localization and mapping tasks to smart Edge gateways which use Fog services. We show how Edge computing brings computational capabilities of the Cloud to the robot environment without compromising operational reliability due to connection issues. Furthermore, we analyze the power consumption of a prototype robot vehicle in different modes and show how battery life can be significantly improved by moving the processing of data to the Edge layer.
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Offloading SLAM for Indoor Mobile Robots
with Edge-Fog-Cloud Computing
V. K. Sarker1, J. Pe˜
na Queralta1, T. N. Gia1, H. Tenhunen2and T. Westerlund1
1Department of Future Technologies, University of Turku, Turku, Finland
2Department of Electronics, KTH Royal Institute of Technology, Stockholm, Sweden
Email: 1{vikasar, jopequ, tunggi, tovewe}@utu.fi, 2hannu@kth.se
Abstract—Indoor mobile robots are widely used in industrial
environments such as large logistic warehouses. They are often
in charge of collecting or sorting products. For such robots,
computation-intensive operations account for a significant per-
centage of the total energy consumption and consequently affect
battery life. Besides, in order to keep both the power con-
sumption and hardware complexity low, simple micro-controllers
or single-board computers are used as onboard local control
units. This limits the computational capabilities of robots and
consequently their performance. Offloading heavy computation
to Cloud servers has been a widely used approach to solve this
problem for cases where large amounts of sensor data such as
real-time video feeds need to be analyzed. More recently, Fog
and Edge computing are being leveraged for offloading tasks
such as image processing and complex navigation algorithms
involving non-linear mathematical operations. In this paper, we
present a system architecture for offloading computationally
expensive localization and mapping tasks to smart Edge gateways
which use Fog services. We show how Edge computing brings
computational capabilities of the Cloud to the robot environment
without compromising operational reliability due to connection
issues. Furthermore, we analyze the power consumption of a
prototype robot vehicle in different modes and show how battery
life can be significantly improved by moving the processing of
data to the Edge layer.
Index Terms—Edge, Fog, Cloud, SLAM, Efficiency, Computa-
tion, Offloading, Energy, Performance, Mobile, Robots
I. INTRODUCTION
Small indoor robots which work alongside humans have
become ubiquitous in different fields such as home-care,
restaurant business and manufacturing plants. For instance,
lightweight robots are used in exhibitions for guiding visitors
to a desired stall, and are the operational backbone in logistic
warehouses of the world’s top e-commerce companies. In
smart homes, small robots can be used as a pet which can
communicate, watch over or play with children and elderly
people and can notify or trigger alarm when abnormal situation
occurs [1]. Companion robots can remind elderly people to
take medicine on time. However, small robots have limited
resources such as low battery capacity and light processing
capability. In most cases, these robots cannot operate for a long
period of time or cannot make useful decisions in complex
situations due to these limitations.
Internet of Things (IoT) can be defined as a virtual platform
which allows both physical and virtual objects to be inter-
connected and communicate with each other. It consists of
advanced technologies such as sensor fusion, wireless sensor
networks and Cloud computing to help improve the quality of
services [2]–[6]. Besides, global storage allows users to access
data anywhere at any time [7]. Proper utilization of IoT can
help overcome some of the drawbacks of small robots. Partic-
ularly, real-time position of a small robot can be tracked and a
system administrator can send control commands in cases of
complex situations [8]. However, IoT-assisted small robots still
have some disadvantages. For example, traditional gateways in
IoT platform are mainly responsible for collecting data from
robots and forwarding the data to Cloud servers. When the data
volume is tremendous e.g., due to a large number of multi-
sensor equipped robots operating simultaneously, the network
bandwidth may be not adequate or the communication latency
become too high [9]. Hence, an appropriate architecture is
required which can overcome these limitations.
Edge and Fog computing can be described as extra layers
between sensor devices, gateways and Cloud servers for en-
hancing the quality of services. These bring Cloud computing
paradigms to the Edge of the network and help reduce the bur-
den of Cloud providing faster services unsupported by Cloud
computing. Edge and Fog computing help to reduce energy
consumption of sensor nodes and diminish overall latency
[10], [11]. The combination of Edge and Fog computing with
IoT can provide a suitable approach for enhancing overall
performance.
In this paper, we exploit the concept of IoT and Fog
along with Edge gateways to enhance energy efficiency and
operational performance of small indoor robots. We present
a proof of concept for a hybrid Edge-Fog-Cloud architecture
which facilitates use of Fog/Edge and Cloud computing for
offloading computationally expensive tasks from robots with
limited processing power. We discuss related works on how
intensive tasks can be offloaded to Edge, Fog or Cloud
services in Section II. Section III presents the proposed system
architecture applying Edge and Fog computing. Section IV
illustrates the results of different tests and discusses the advan-
tages in terms of power saving and performance boost. Section
V concludes the work and depicts on future improvements.
II. RE LATED WORK
Several works focus on increasing the performance of dif-
ferent algorithms which cannot be fully exploited in resource-
constrained devices. Dey et al. analyzed the advantages of
leveraging Fog and Edge computing to offload computationally
heavy tasks within SLAM algorithms for mobile robots [12].
They provided extensive simulations for different Robot-Edge-
Fog-Cloud computational tasks distribution schemes. The au-
thors concluded that Edge and Fog computing can bring signif-
icant enhancement to computationally intensive tasks such as
localization and positioning tasks. Edge and Fog computing
are shown to provide the same computational performance
than Cloud offloading, with the benefit of reduced bandwidth
and thus faster response time. However, the authors did not
perform real-life tests where the communication layer can play
an important role and become a bottleneck due to the high data
rates between mobile robots and gateways.
Offloading Simultaneous Localization and Mapping
(SLAM) tasks to Edge and Fog layers has only been
considered recently while Cloud-based SLAM has been
studied for the last decade. Benavidez et al. deployed an
instance of the Robot Operating System in the Cloud to
increase the computational capabilities of constraint robots
for Visual SLAM (VSLAM) [13]. They pointed how this
helps to overcome traditional bottlenecks in robots with
limited computational resources with VSLAM performing
feature identification and matching which usually need
large databases. They demonstrated how parallel computing
can be exploited with a multi-node Cloud deployment to
facilitate multi-robot SLAM and with limited impact on
the on-board computers that control the robots. A similar,
more comprehensive work was carried out by Riazuelo et al.
who presented C2TAM, a Cloud framework for cooperative
tracking and mapping [14]. The authors used the unlimited
computational resources available in the Cloud to enable the
implementation of algorithms which fail to run on single
board computers or even more powerful CPUs when the
number of agents increases.
Similarly, Turnbull et al. utilized Cloud servers to enable ad-
vanced neural command for formation control in large groups
of robots [15]. However, the network connection between
robots and Cloud servers is unreliable and cannot be guaran-
teed. Therefore, a trade-off exists between the robustness of the
solution in terms of available computational resources, opera-
tional reliability and performance. This is further explored by
Salmeron-Garcia et al. in their work on Cloud offloading of a
vision-based navigation system [16]. The authors stress in their
paper that processing time can be matched to communication
period with parallel computation in the Cloud and inferred
of a bottleneck due to communication bandwidth and latency.
They concluded that Cloud is necessary if the system needs
to be easily scalable or precise operation is required. This
occurs where the localization or navigation requirements are
such that high quality images need to be processed. Extensive
works exist in this direction by other authors in the field
[17] [18], taking the trade-offs into account both in terms of
communication and computational performance.
Kumar et al. gathered computational offloading techniques
and algorithms into a survey where they accentuate how
shifting of intensive applications will be essential in the future
for battery powered devices [19] and explored the energy-
saving potential of offloading computation to the Cloud.
Extensive work has been carried out on leveraging Cloud
computing for offloading heavy computational tasks. However,
most of this work have been focused on leveraging virtually
unlimited computational resources of the Cloud. Fewer re-
search have targeted the Edge and Fog computing paradigms
as a solution to the high latency and unreliability of Cloud
services. Keeping these in mind, we focus in both energy
efficiency and performance improvement by placing the most
expensive computational tasks in Edge and Fog layers leaving
the Cloud only for monitoring and management and thus not
entirely relying on network link to the Cloud services for
normal operation.
III. SYS TE M ARCHITECTURE
The proposed system architecture consists of 4 layers: Robot
Layer,Edge Layer for data processing and analysis, Fog layer
for distributed storage and Cloud Layer for monitoring and
general mission control. As shown in Fig. 1, we have com-
bined the Edge and Fog layer because the Fog layer consists
of the smart Edge Gateways and they use the same physical
resources. The architecture we present is easily scalable,
modular and distributed by definition. This section thoroughly
describes the role of each layer and the distribution of the
computational load through the network. Energy consumption,
latency and computational power at different layers are the key
factors taken into account when deciding the role of a layer.
In general, data is acquired by robots where minimal anal-
ysis is performed. Real-time decisions are taken at the Edge
gateways to minimize the latency and share the computational
load of different connected robots. The Fog layer provides
additional services such as distributed storage and processing
to enable an efficient handover mechanism with minimal data
loss when a robot switches from one gateway to another.
The handover includes sharing previous map data acquired by
the robot switching gateways so that the result of the SLAM
algorithm remains constant through the connection change.
Edge gateways also play an important role in reducing the
energy consumption at the end nodes or robots by running
the most computational expensive operations. Both Fog and
Edge computing are essential in safety critical situations where
they provide a more robust situational awareness and overall
system control, and robot state knowledge. Finally, the Cloud
layer enables end-users or administrators to control the system
by giving general instructions and monitor the performance at
different layers.
A. Robot Layer
In the robot layer, sensor data is gathered and streamed
in real time to the smart Edge gateways. The control of the
robot is run online and movement instructions are given in
real-time. In the proposed system, the robot can be either
aware or unaware of its current state depending on how
extensively information is analyzed on-board and whether an
Robot Layer Edge-Fog Layer Cloud Layer
Servers
High Computation
Cloud Storage
Analysis
Web Applications
Control Panel
Distributed Storage
Task Coordination
Gateway Management
Motor Control
Proximity Detection
Optional features
Robot 1
Robot 2
Edge / Smart Gateway 1
Edge / Smart Gateway 2
Robot N Edge / Smart Gateway N
Mapping
Positioning
Processing
Compression
Encryption
Intensity
Angle
Length
Speed
Direction
Duration
Fig. 1. Proposed System Architecture
Edge gateway provides enhanced state information to the robot
or only movement instructions.
The robot relies on low power wireless communication tech-
nologies such as Bluetooth or nRF if the bandwidth require-
ments are met, or Wi-Fi for more bandwidth-intensive appli-
cations such as high-quality video transmission. By streaming
sensor data directly to the gateway without being processed by
the MCU, the robot gains in energy efficiency. Furthermore,
low-power techniques can be applied to the MCU in order to
further reduce the overall power requirements.
Compared to a traditional approach where sensing, obsta-
cle detection, path planning and localization are made on-
board the robot, we can significantly reduce the computing
requirements of the robot’s control system and downgrade
them from processor-based to MCU-based. Only the most
basic information is analyzed at the robot itself. This includes,
for instance, wheel odometry or inertial data so that the robot is
aware of its current acceleration, velocity and orientation. This
can be combined with state estimation performed online at the
Edge, Fog or Cloud layers to allow more accurate movement
and simplify the instructions given to the robot.
B. Smart Edge Gateway Layer
Edge gateways receive sensor data from one or multiple
robots in real-time. This includes, for example, images from
on-board cameras or data from range sensors such as Lidars
and radars, which is analyzed at the gateways to perform
obstacle detection and avoidance, path planning, localization
or mapping. Odometry data (e.g. wheel odometry, visual
odometry) and inertial data (e.g. magnetometer, accelerometer
and gyroscope data) is also transmitted from and processed at
the gateway.
Acting as a central element, Edge gateways ensure a low-
latency and robust solution and provide fast decision making
while relocating computationally expensive tasks from the
robots. Moreover, if multiple robots are connected to a single
gateway, data from different sensors and sources is aggre-
gated and analyzed in order to obtain a more comprehensive
understanding of the environment. For instance, two robots
operating in the same environment and connected to the same
gateway are able to obtain information of larger areas through
sensors of other robots and see through other agents if these
are nearby and blocking their field of view.
The role of the Edge layer is of superior importance
in safety-critical situations and scenarios such as industrial
environments where human share operational space with au-
tonomous or semi-autonomous robots. Compared to the more
traditional practice of moving complex tasks to the Cloud,
the Edge layer reduces the latency to the point where safe
operation is achievable even in the case of network connectiv-
ity failure. From an operational point of view, smart Edge
gateways receive information from sensors aboard multiple
robots and are in charge of decision-making in terms of
robot movement and task allocation. These instructions are
transmitted continuously and wirelessly to the robots.
C. Fog Layer
The Fog layer includes the smart Edge gateways as part
of it. Nonetheless, it is defined as a separate layer because
its role in the proposed system architecture differs from the
data analysis and instantaneous control role of the Edge layer.
The Fog layer represents the interconnection of different Edge
gateways, together with other services such as distributed
databases or location services. In particular, the Fog layer takes
care of the handover mechanisms when the robots disconnect
from one gateway and connect to another one together with
the procurement of additional services including distributed
storage, external tracking and monitoring or location services.
Detailed research has been performed to minimize latency
and data-loss during the handover [20] [21]. An alternative for
managing the handover is to deploy Edge gateways just behind
conventional gateways such as Wi-Fi routers so that the gate-
ways can directly store the received information in distributed
storage. Thus, the handover problem would be reduced to the
distribution of the computational load of individual robots into
the set of Edge nodes, since all nodes are able to access robot
data in real-time from the shared storage.
Localization algorithms are mostly run in the Edge layer
in which real-time sensor data is matched with an area of
an existing map. This is crucial in situations where the robot
operates in a partially or totally unknown environment and
simultaneous localization and mapping algorithms are run in
the smart Edge gateways. In these cases, it is required that the
local map stored in one gateway is shared to other gateways
before or during the handover. Accordingly, our proposed
system architecture includes a distributed storage deployment
in the Fog layer. This can be implemented, for instance, in the
form of a decentralized database where the maps and other
essential robot data are stored and available to all nodes in the
Edge/Fog layers at any time.
Other services included in the Fog layer are external sensor
management, collaborative processing and monitoring. For
example, while Edge gateways process the on-board sensor
information from the robots, external monitoring cameras
and other sensors can be used to increase the accuracy of
localization algorithms or assure collision avoidance in cases
of sensor failure or other local problems that might appear
in the robot and go undetected by the Edge gateway. This
results in an enhanced situational awareness [22] where both
externally and internally collected information about a robot is
available in the Fog layer. By introducing additional services
in the Fog layer, we can enhance overall system robustness
and its fault tolerance. For instance, if a gateway abruptly
disconnects or any kind of failure occurs, all the information
that it was handling will be available to other gateways due to
the shared storage resources. This allows the robot to reconnect
to the next available gateway and continue its operation with
minimal data loss, operational interruption and latency.
D. Cloud Services
Time-series data of the robot state, including basic infor-
mation such as position, velocity, acceleration, steering drift
factor, drive torque variation, instantaneous current consump-
tion and battery level is uploaded to the Cloud for monitoring,
control and visualization by users or administrators [23].
Instead of uploading raw sensor data, it is pre-processed
and compressed in the Edge/Fog layers and only sporadic
local map updates or critical information is sent. This can be
implemented in a dynamic way in which, for instance, the map
around a robot or of a given area in the operation environment
is updated and uploaded to the Cloud at different frequencies
depending on whether an end-user is actively monitoring the
operation or not.
The use of Cloud services facilitates generic control in-
structions to the robot and stable operation [24]. For example,
factory managers can easily have an overview of the posi-
tion of different robots around the factory floor, or override
autonomous roaming to involve more robots assigned within
a certain group or to prioritize specific tasks. Besides, the
Cloud allows global access for the administrators and mission
Fig. 2. Prototype car with Lidar running on top, used for the experiment
planners to have a collaborative overview in a cost-effective
way.
However, due to comparatively higher end-to-end latency
between the robot layer and the Cloud, it should not be
used for primary control purpose as it can be subject to
variation in network performance. The Cloud provides access
to pertinently processed data from the robot layer which is
periodically backed up at a reasonable interval. This yields a
conclusive operation and data history which can be analyzed
using high performance computing in the Cloud for machine
learning, better prediction and big data analytics.
IV. IMPLEMENTATION AND EXP ER IME NTA L RES ULTS
In order to test the feasibility and validate the proposed
architecture, we have constructed a car controlled via Blue-
tooth communication to produce a map of the perimeter it is
bounded by. The car shown in Figure 2 incorporates a 360o
Lidar on top of the chassis, two independent motors- one for
steering control and another for driving forward or backward
with appropriate motor control circuitry. The car is connected
to a gateway through a Bluetooth Classic module. An AVR
8-bit MCU is used to control acquisition of raw data from
the Lidar and send to gateway via the serial port profile of
the Bluetooth standard. A prototype is built using the chassis
from an Reely 1:10 Elektro-Monstertruck NEW1 RC car and
replacing the control circuit and motors with lower power
variants with an RPLIDAR A1 M8 on the top, a low cost
360o2D LASER scanner from Slamtec [25].
We have run experimental tests with a minimal setup where
only Lidar is used for both localization and mapping purposes.
Adding inertial sensors would provide more accurate position-
ing and control over the vehicle; however, that is not the main
objective of this work and we focus on the implementation of
the hybrid Edge-Fog-Cloud architecture and its benefits.
The MCU controlling the movement of the car does not
save or analyze the data from the Lidar sensor in any form
and is forwarded directly to the gateway as serial stream over
Bluetooth. The gateway then runs an adapted version of the
BreezySLAM algorithm by S. D. Levy [26]. The algorithm has
been modified to take into account the intermittent nature of
Fig. 3. Mapping and Localization at the Edge. (The position of the car is
marked with a blue pointer)
the connection between the robot and the gateway, and execute
accordingly when processing successive batches of data.
Figure 3 shows the result of applying the mapping and
localization algorithm in the Edge gateway. As we are using
an inexpensive Lidar and the SLAM algorithms run without
any inertial measurement unit such as accelerometer and mag-
netometer, accurate positioning is hard to achieve in complex
environments. However, with more input data from multiple
sensors would suffice for enabling operation in non-trivial
local environments.
The first map in Figure 3 shows the map obtained after
the first few Lidar frames have been analyzed. The RPLIDAR
A1 M8 used in the tests is a low-cost Lidar and therefore
several scans are processed before obtaining a good quality
map. The granularity in the first map is derived from the
relatively low scan speed of the device compared to more
advanced sensors. Also, while the position within the map is
accurate and consistent through the test, noise appears near the
distant walls from the Lidar due to the low accuracy. However,
TABLE I
POWE R CONSUMPTION OF THE PROTO TY PE VE HI CL E AT 5V SU PP LY
Operation Average Current Average Power
/ Approach (mA) (W)
MCU Idle 4 19
MCU + Lidar 339 1695
MCU + Lidar + Streaming 378 1890
R.Pi Idle 301 1503
R.Pi + Lidar 622 3108
R.Pi + Lidar + Edge Processing 829 4152
Car (Drive / Steer) 122 607
Car (Drive + Steer) 184 918
the walls and corners in the local area around the robot are
with little to no noise.
In terms of performance, the recorded path elapsed a total
of 44.3 seconds in which 314 Lidar frames were processed.
This translates into 7 frames/s, which matches with the Lidar
specification for a maximum speed scan of 10 Hz with an
average car speed of 0.3 m/s. This frame rate can be compared
to 1 frame/s processed on a Raspberry Pi 3 Model B running
Ubuntu Mate Desktop with the graphical map display in real-
time. While this can be optimized running a more trimmed,
customized version of Linux on the Raspberry Pi, its compu-
tational capability limits the processing to about 5 frames/s.
Since a MCU is able to handle the vehicle control and
transmission of Lidar data, not only it significantly increases
the system performance by offloading the SLAM tasks to the
Edge gateway, but a considerable amount of energy is saved
by replacing a power-hungry single-board computer such as
the Raspberry Pi with a low-power MCU.
In particular, the specific power consumption and average
current drawn by the prototype in different states are docu-
mented in Table I. In idle state, the Lidar consumes 300 to 350
mA, representing over 90% of the total power consumption.
This can be replaced with low-power cameras or more en-
ergy efficient sensors for a particular SLAM implementation.
However, when the prototype is moving, the Lidar’s share
of the power consumption goes down to around 60%. When
choosing the Lidar, general purpose motors have been used
to show that even with out-of-the-shelf devices, the overall
energy efficiency can be improved by around 40% when a
single-board computer such as a Raspberry Pi in this test is
replaced with a MCU. This yields a significantly longer battery
life and an increase in operational performance due to larger
ratio of active-time with respect to idle or charging time.
V. DISCUSSION
Although Edge computing can bring advantages such as
reduction in latency, bandwidth conservation, improvement in
application robustness and security [11], [27], [28], there are
inherent challenges. As the processing of the data stays near
the Edge, specific data-oriented applications which require
comparatively higher user interaction will have insignificant
performance gain. In the worst case scenario, performance can
deteriorate due to the long path data has to travel.
As multiple robots can connect to the same smart gate-
way, communication latency and inter-unit interference can
be an issue. Depending on the application, an appropriate
communication medium must be chosen to ensure that specific
parameters such as bandwidth, channel spacing, protocol,
sampling frequency and data rate are properly considered for
an interruption-free data transfer. Also, for wireless units,
it is useful to examine the wake-up and sleep time of the
radio communication module so that transmitter and receiver
circuitry is not toggled unnecessarily and sleep modes are
used appropriately. This yields better energy efficiency and
communication at an optimal duty cycle.
Keeping the Edge gateways near the robot layer and a Fog
layer provides distributed and scalable computing. However,
as the number of robots and frequency of data transmission per
node significantly increases, the gateways may not handle all
requests within the highest permitted latency. In such a case,
having more powerful and redundant gateways along with
advanced load-sharing algorithm in the Fog and distributed
data storage can effectively improve performance.
VI. CONCLUSION AND FUTURE WO RK
In this paper, the comparative advantage of using Edge
computing for robots and nodes are discussed keeping the
focus on energy efficiency and operational latency. Instead
of directly transferring a large amount of data from robots
to the Cloud, we proposed an Edge-Fog-Cloud based system
for performance advantages. Run from the mains supply, the
powerful Edge layer can pre-process and analyze data easily,
implement advanced features and ensure data security by
applying complex encryption algorithms. The Fog layer can
intelligently manage the smart gateways of Edge layer.
This approach effectively takes the heavy computational
tasks near the Edge layer and thus reduces the required energy
for operation of the node or robot itself. The shorter path of
data for a complete cycle improves latency and frees up valu-
able network bandwidth, especially when a lot of robots are
connected to the same gateway. In addition, the reduced robot-
to-Cloud transferable data eliminates potential bottleneck in
the network and lowers the chance of system downtime due
to a single point computing failure as in centralized computing
architecture. We demonstrated an example of SLAM showing
how a car in the robot layer can take advantage of the power
of Edge computing for mapping a confined perimeter.
In future, we plan to implement a comprehensive system
consisting of several vehicles, multiple smart Edge computing
gateways constituting a Fog layer and an application for the
Cloud layer. In addition, we plan to develop an autonomous
roaming algorithm for the robot car so as to perform the
mapping operation in shortest possible time. Besides, some
stress tests to estimate the performance of smart gateways
will be evaluated to emulate the scenario when the number
of connected cars is sufficiently high.
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... The MEC and ICC enabled implementations allow the co-location of independent applications on a shared edge/fog node through virtualized abstraction. As illustrated in Ta- ble 1, some of the existing studies where the main focus is on the low-latency and computation offload [9][10][11][12][13][14], [16], [18], [19], [21], [23], [24], [27][28][29] also adapt the concept of virtualization that allows robotic services to reuse the surrounding hardware and deploy applications on demand. ...
... The close proximity of MEC and IIC has been studied in some recent existing experimental studies to offload the location-based robotics services from mobile robots with limited computational and low-energy resources [17], [25], [29][30][31]. Additionally, [12][13][14], [22], [24] elaborate on the reduced network pressure and improved security and privacy of the robot sensor data that can be offered by restricting the access within a trusted private infrastructure. ...
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With the wide penetration of smart robots in multifarious fields, Simultaneous Localization and Mapping (SLAM) technique in robotics has attracted growing attention in the community. Yet collaborating SLAM over multiple robots still remains challenging due to performance contradiction between the intensive graphics computation of SLAM and the limited computing capability of robots. While traditional solutions resort to the powerful cloud servers acting as an external computation provider, we show by real-world measurements that the significant communication overhead in data offloading prevents its practicability to real deployment. To tackle these challenges, this paper promotes the emerging edge computing paradigm into multi-robot SLAM and proposes RecSLAM, a multi-robot laser SLAM system that focuses on accelerating map construction process under the robot-edge-cloud architecture. In contrast to conventional multi-robot SLAM that generates graphic maps on robots and completely merges them on the cloud, RecSLAM develops a hierarchical map fusion technique that directs robots' raw data to edge servers for real-time fusion and then sends to the cloud for global merging. To optimize the overall pipeline, an efficient multi-robot SLAM collaborative processing framework is introduced to adaptively optimize robot-to-edge offloading tailored to heterogeneous edge resource conditions, meanwhile ensuring the workload balancing among the edge servers. Extensive evaluations show RecSLAM can achieve up to 39% processing latency reduction over the state-of-the-art. Besides, a proof-of-concept prototype is developed and deployed in real scenes to demonstrate its effectiveness.
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