211 research outputs found
Distributed navigation of multi-robot systems for sensing coverage
A team of coordinating mobile robots equipped with operation specific sensors can
perform different coverage tasks. If the required number of robots in the team is
very large then a centralized control system becomes a complex strategy. There
are also some areas where centralized communication turns into an issue. So, a
team of mobile robots for coverage tasks should have the ability of decentralized or
distributed decision making. This thesis investigates decentralized control of mobile
robots specifically for coverage problems. A decentralized control strategy is ideally
based on local information and it can offer flexibility in case there is an increment
or decrement in the number of mobile robots. We perform a broad survey of the
existing literature for coverage control problems. There are different approaches
associated with decentralized control strategy for coverage control problems. We
perform a comparative review of these approaches and use the approach based on
simple local coordination rules. These locally computed nearest neighbour rules are
used to develop decentralized control algorithms for coverage control problems.
We investigate this extensively used nearest neighbour rule-based approach for
developing coverage control algorithms. In this approach, a mobile robot gives an
equal importance to every neighbour robot coming under its communication range.
We develop our control approach by making some of the mobile robots playing
a more influential role than other members of the team. We develop the control
algorithm based on nearest neighbour rules with weighted average functions. The
approach based on this control strategy becomes efficient in terms of achieving a
consensus on control inputs, say heading angle, velocity, etc.
The decentralized control of mobile robots can also exhibit a cyclic behaviour
under some physical constraints like a quantized orientation of the mobile robot.
We further investigate the cyclic behaviour appearing due to the quantized control
of mobile robots under some conditions. Our nearest neighbour rule-based approach
offers a biased strategy in case of cyclic behaviour appearing in the team of mobile
robots.
We consider a clustering technique inside the team of mobile robots. Our decentralized
control strategy calculates the similarity measure among the neighbours
of a mobile robot. The team of mobile robots with the similarity measure based
approach becomes efficient in achieving a fast consensus like on heading angle or
velocity. We perform a rigorous mathematical analysis of our developed approach.
We also develop a condition based on relaxed criteria for achieving consensus on
velocity or heading angle of the mobile robots. Our validation approach is based on
mathematical arguments and extensive computer simulations
An energy-balanced heuristic for mobile sink scheduling in hybrid WSNs
Wireless sensor networks (WSNs) are integrated
as a pillar of collaborative Internet of Things (IoT)
technologies for the creation of pervasive smart environments.
Generally, IoT end nodes (or WSN sensors) can be
mobile or static. In this kind of hybrid WSNs, mobile sinks
move to predetermined sink locations to gather data
sensed by static sensors. Scheduling mobile sinks energyefficiently
while prolonging the network lifetime is a
challenge. To remedy this issue, we propose a three-phase
energy-balanced heuristic. Specifically, the network region
is first divided into grid cells with the same geo-graphical
size. These grid cells are assigned to clusters through an
algorithm inspired by the k-dimensional tree algorithm,
such that the energy consumption of each clus-ter is
similar when gathering data. These clusters are adjusted
by (de)allocating grid cells contained in these clusters,
while considering the energy consumption of sink
movement. Consequently, the energy to be consumed in
each cluster is approximately balanced considering the
energy consumption of both data gathering and sink movement.
Experimental evaluation shows that this technique
can generate an optimal grid cell division within a limited
time of iterations and prolong the network lifetime.This work was supported in part by the National Natural Science
Foundation of China under Grant 61379126, Grant 61401107, Grant
61572060, and Grant 61170296; in part by the Scientific Research
Foundation for Returned Scholars, Ministry of Education of China; and
in part by the Fundamental Research Funds for the Central Universities.
Paper no. TII-15-0703.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=9424hb2017Electrical, Electronic and Computer Engineerin
Placement, visibility and coverage analysis of dynamic pan/tilt/zoom camera sensor networks
Multi-camera vision systems have important application in a number of fields, including robotics and security. One interesting problem related to multi-camera vision systems is to determine the effect of camera placement on the quality of service provided by a network of Pan/Tilt/Zoom (PTZ) cameras with respect to a specific image processing application. The goal of this work is to investigate how to place a team of PTZ cameras, potentially used for collaborative tasks, such as surveillance, and analyze the dynamic coverage that can be provided by them.
Computational Geometry approaches to various formulations of sensor placement problems have been shown to offer very elegant solutions; however, they often involve unrealistic assumptions about real-world sensors, such as infinite sensing range and infinite rotational speed. Other solutions to camera placement have attempted to account for the constraints of real-world computer vision applications, but offer solutions that are approximations over a discrete problem space.
A contribution of this work is an algorithm for camera placement that leverages Computational Geometry principles over a continuous problem space utilizing a model for dynamic camera coverage that is simple, yet representative. This offers a balance between accounting for real-world application constraints and creating a problem that is tractable
Facilitating Internet of Things on the Edge
The evolution of electronics and wireless technologies has entered a new era, the Internet of Things (IoT). Presently, IoT technologies influence the global market, bringing benefits in many areas, including healthcare, manufacturing, transportation, and entertainment.
Modern IoT devices serve as a thin client with data processing performed in a remote computing node, such as a cloud server or a mobile edge compute unit. These computing units own significant resources that allow prompt data processing. The user experience for such an approach relies drastically on the availability and quality of the internet connection. In this case, if the internet connection is unavailable, the resulting operations of IoT applications can be completely disrupted. It is worth noting that emerging IoT applications are even more throughput demanding and latency-sensitive which makes communication networks a practical bottleneck for the service provisioning. This thesis aims to eliminate the limitations of wireless access, via the improvement of connectivity and throughput between the devices on the edge, as well as their network identification, which is fundamentally important for IoT service management.
The introduction begins with a discussion on the emerging IoT applications and their demands. Subsequent chapters introduce scenarios of interest, describe the proposed solutions and provide selected performance evaluation results. Specifically, we start with research on the use of degraded memory chips for network identification of IoT devices as an alternative to conventional methods, such as IMEI; these methods are not vulnerable to tampering and cloning. Further, we introduce our contributions for improving connectivity and throughput among IoT devices on the edge in a case where the mobile network infrastructure is limited or totally unavailable. Finally, we conclude the introduction with a summary of the results achieved
Applications of wireless sensor technologies in construction
The construction industry is characterised by a number of problems in crucial
fields such as health, safety and logistics. Since these problems affect the progress of
construction projects, the construction industry has attempted to introduce the use of
innovative information and communication technologies on the construction site. Specific
technologies which find applicability on the construction site are wireless sensors, and
especially radio-frequency identification (RFID) technology. RFID tagging is a
technology capable of tracking items. The technology has been applied on the
construction site for various applications, such as asset tracking. There are many
problems related to health, safety and logistics on the construction site which could be
resolved using RFID technology. In the health and safety field, the problems which exist
are the monitoring of dangerous areas on the construction site, such as large excavation
areas, the collisions between workers and vehicles, between vehicles and equipment and
between vehicles, the detection of hazardous substances on the construction site when the
construction work has been completed and the collection of hazard notifications from
specific areas of the construction site as feedback for the prevention of future accidents.
In the logistics field, the tracking of a material during its delivery on the construction site,
its transportation to specific subcontractors and its future utilisation as well as the
monitoring of the rate of use of materials on the construction site, the checking of the
sequence of steel members and the monitoring of the temperature of porous materials are
issues which can be realised using RFID technology. In order to facilitate the use of
RFID technology for the specific health, safety and logistics problems, a system has been
developed. The operation of this system is based on the combined use of hardware and
software elements. The hardware elements of the developed system are a wireless local
area network, RFID readers and tags. Its software elements are a software development
kit based on which, a number of graphical user interfaces have been created for the
interaction of the users with the REID tags, and Notepad files which store data collected
from REID tags through the graphical user interfaces. Each of the graphical user
interfaces is designed in such a way so that it corresponds to the requirements of the
health, safety or logistics situation in which it is used. The proposed system has been
tested on a simulated construction site by a group of experts and a number of findings
have been produced. Specifically, the testing of the proposed system showed that RFID
technology can connect the different stages which characterise the construction supply
chain. In addition, it showed the capability of the technology to be integrated with
construction processes. The testing of the system also revealed the barriers and the
enablers to the use of RFID technology in the construction industry. An example of such
a barrier is the unwillingness of the people of the construction industry to quit traditional
techniques in favour of a new technology. Enablers which enhance the use of RFID
technology in the construction industry are the lack of complexity which characterises the
operation of RFID tagging and the relatively low cost of RFID tags. In general, RFID
technology is an innovative sensor technology which can help the construction industry
through its asset tracking ability. However, further research should be done on the
improvement of RFID technology on specific characteristics, such as its inability to
provide location coordinates and the resilience of the electromagnetic signal emitted by
the RFID reader when there are metallic objects around the reader
Improving Robot Team's performance by Passing Objects between Robots
Department of Computer Science and EngineeringA transport robot system is a robotic system in which robots move objects from one place to another place. Most existing transport robot systems perform three tasks: loading an item, moving to another location, and unloading the item. Traditional mobile robots, which carry objects one at a time, is not suitable for repeatedly transporting objects over a long distance. Therefore, in the factory or warehouse environment, they still use conveyor belts to transport a large number of objects. However, the existing conveyor belts are physically fixed in their environments, and it is difficult to reconfigure the layout of a conveyor network. In this thesis, I presente three new robotic systems that have the ability to pass objects at a distance between mobile robots. These three robotic systems are mobile conveyor belts, dynamic robot chains, and mobile workstations.
First, conveyor belts are commonly used to transport many objects rapidly and effectively. I present a novel conveyor system called a mobile conveyor line that can autonomously organize itself to transport objects to a given location. In this thesis, I analyze the reachability of multiple mobile conveyor belts and present an algorithm to verify the reachability of a specified destination, as well as a way to gen- erate a configuration for connecting conveyor belts to reach the destination. The key results include a complete set of equations describing the reachable set of a mobile conveyor belt on a flat surface, which leads to an effective probabilistic strategy for autonomous configuration. The results of the experiment demonstrated the overlap effect, which states that reachable sets frequently overlap. This system can be suitable for locations where it is difficult to install a conveyor line, such as disaster zones.
Second, I present to use mobile conveyor belts in foraging tasks in environments with obstacles. Foraging robots can form a dynamic robot chain network that can quickly send resources received from other foraging robots to a collecting zone called a depot area. A robot chain is essentially a sequence of mobile robots with the ability to quickly pass resources at a long distance. A dynamic robot chain network is a network of robot chains that allow the branches of the robot chains to connect multiple resource clusters. By allowing branching, the traffic near the end of the robot chain network can be dis- tributed to several branches, and congestion can be avoided. The dynamic robot chain network leverages mobility to relocate, reduce collection time for other robots, and quickly send resources received from other foraging robots to the depot area. The key result is the formation of robot chains capable of over- coming the two major limitations of existing dynamic depot foraging systems: the long travel distance for delivery and congestion near the central collection zone. In the experiments, given the same num- ber of robots, a dynamic robot chain network outperformed existing dynamic depots in multiple-place foraging problems.
Third, I consider the idea of mobile workstations, which integrate mobile platforms with production machinery to improve efficiency by overlapping production time and delivery time. I describe a task planning algorithm for multiple mobile workstations and offer a model of mobile workstations and their jobs. This planning problem for mobile workstations includes the features of both traveling salesman problems (TSP) and job shop scheduling problems (JSP). For planning, I presente two algorithms: a) a complete search algorithm that offers a minimum makespan plan and b) a local search in the space of task graphs to offer suboptimal plans quickly. According to the experiments, the second algorithm can generate near-optimal temporal plans when the number of jobs is small. In addition, the second algorithm can generate noticeably shorter plans than a version of the job shop scheduling algorithm and SGPlan 5 when the number of jobs is large.
This research shows that transport robot systems could work together with other robots or machines in various environments to overcome the limitations of existing systems for the environments. A mobile conveyor line can pass quickly objects at a long distance and can apply to many different environments by overcoming the existing problem of conveyor belts. By using mobile conveyor belts, the robots have the ability to pass objects at a distance between mobile robots to improve the performance of foraging tasks by overcoming the long travel distance for delivery and congestion near the central collection zone. In addition, a mobile workstation can handle the tasks that transport the production of goods to users. By paralleling the production time and the movement, a mobile workstation can substantially shorten the time it takes to deliver products to customers.ope
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