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Author

Rajnikant Sharma

Bio: Rajnikant Sharma is an academic researcher from University of Cincinnati. The author has contributed to research in topics: Global Positioning System & Extended Kalman filter. The author has an hindex of 18, co-authored 104 publications receiving 1092 citations. Previous affiliations of Rajnikant Sharma include Indian Institute of Technology Roorkee & University at Buffalo.


Papers
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Proceedings ArticleDOI
14 Apr 2015
TL;DR: It is shown that a single, maliciously controlled vehicle can destabilize a vehicular platoon, to catastrophic effect, through local modifications to the prevailing control law, by combining changes to the gains of the associated law with the appropriate vehicle movements.
Abstract: In this paper, we show that a single, maliciously controlled vehicle can destabilize a vehicular platoon, to catastrophic effect, through local modifications to the prevailing control law. Specifically, by combining changes to the gains of the associated law with the appropriate vehicle movements, the attacker can cause the platoon to oscillate at a resonant frequency, causing accidents that could result in serious injury or death. We determine the range of gains, and their corresponding frequencies, that allow an attacker to violate the string stability and stability criteria at different positions in the platoon. Furthermore, we prove that the attack can be successful at any position in the platoon and at frequencies that can be realized by the other vehicles in the platoon. Our work implies that neither the string stability nor stability conditions, when used singly, ensure proper platoon operation, and that neither can be used to ensure the other. Finally, we show that an attacker is theoretically capable of gaining control over the individual position and velocity (states) of other vehicles in the platoon; two attacks are demonstrated for this vulnerability.

107 citations

Journal ArticleDOI
TL;DR: This paper establishes a link between observability and a graph that represents measurements and communication between the robots and shows that for complete observability, all of the nodes in the graph must have a path to at least two different landmarks of known location.
Abstract: In this paper, we investigate the nonlinear observability properties of bearing-only cooperative localization. We establish a link between observability and a graph that represents measurements and communication between the robots. It is shown that graph theoretic properties like the connectivity and the existence of a path between two nodes can be used to explain the observability of the system. We obtain the maximum rank of the observability matrix without global information and derive conditions under which the maximum rank can be achieved. Furthermore, we show that for complete observability, all of the nodes in the graph must have a path to at least two different landmarks of known location.

88 citations

Journal ArticleDOI
TL;DR: It is shown that when cohesion rule is applied an equilibrium condition is reached in which all the UAVs settle at the same altitude on a circle of constant radius, and it is proved analytically that this equilibrium conditions is stable for all values of velocity and acceleration.
Abstract: In this article, several basic swarming laws for Unmanned Aerial Vehicles (UAVs) are developed for both two-dimensional (2D) plane and three-dimensional (3D) space. Effects of these basic laws on the group behaviour of swarms of UAVs are studied. It is shown that when cohesion rule is applied an equilibrium condition is reached in which all the UAVs settle at the same altitude on a circle of constant radius. It is also proved analytically that this equilibrium condition is stable for all values of velocity and acceleration. A decentralised autonomous decision-making approach that achieves collision avoidance without any central authority is also proposed in this article. Algorithms are developed with the help of these swarming laws for two types of collision avoidance, Group-wise and Individual, in 2D plane and 3D space. Effect of various parameters are studied on both types of collision avoidance schemes through extensive simulations.

75 citations

Journal ArticleDOI
29 Jul 2010
TL;DR: It is shown that if at least one vehicle in a group has target information with some uncertainty and the corresponding communication graph is connected, then a target-centric formation can be maintained and the combined strategy enforces each of the vehicles to maintain its respective position in the formation.
Abstract: This paper presents distributed formation control of a multi-agent system to encircle a maneuvering target using Lyapunov and graph theories with emphasis on consensus and cooperation. The proposed approach embeds a consensus algorithm into a robust controller to capture a target whose information is partially known. To address this issue, a cooperative strategy in conjunction with a controller is proposed to enable a fleet of UAVs either to escort a target to a desired destination or to keep the target movement restricted in a certain set in order to gain superiority. We have employed a sliding mode controller to achieve a target centered formation whose information is partially available to the capturing vehicles. Simulation results are presented to validate the proposed approach.

73 citations

Journal ArticleDOI
TL;DR: Assessment of the function of A1S_1331 suggests that efflux is an important mechanism of fosfomycin resistance and AbaF is involved in fosFomycin Resistance in A. baumannii.
Abstract: Objectives To decipher the function of A1S_1331, named AbaF (Acinetobacter baumannii Fosfomycin efflux), one of the primary targets of AbsR25, a small RNA of A. baumannii. Methods abaF was cloned in a multicopy plasmid and expressed from its native promoter in an efflux-deficient strain-Escherichia coli KAM32. Drug susceptibility, accumulation and efflux of ethidium bromide (EtBr) were determined in this strain. abaF was disrupted in A. baumannii using homologous recombination and its effect on drug susceptibility, biofilm formation and virulence was studied. Expression of abaF was followed by quantitative PCR in fosfomycin-challenged A. baumannii and fosfomycin-resistant mutants of A. baumannii. Expression of abaF in clinical strains of A. baumannii was determined by RT-PCR. Results Expression of abaF in E. coli KAM32 resulted in increased resistance to fosfomycin. Lower accumulation and higher efflux of EtBr from this strain confirmed the role of AbaF as an efflux pump. Disruption of abaF in A. baumannii caused an increase in fosfomycin susceptibility and a decrease in biofilm formation and virulence. The expression of abaF was higher in A. baumannii cells exposed to fosfomycin and in cells resistant to higher concentrations of fosfomycin. The clinically relevant strains of A. baumannii also tested positive for the expression of abaF. Conclusions The results of this study suggest that efflux is an important mechanism of fosfomycin resistance and AbaF is involved in fosfomycin resistance in A. baumannii. AbaF also seems to play a role in biofilm formation and virulence of A. baumannii.

63 citations


Cited by
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Journal ArticleDOI
TL;DR: The increasing resistance of microorganisms to conventional chemicals and drugs is a serious and evident worldwide problem that has prompted research into the identification of new biocides with broad activity.
Abstract: The increasing resistance of microorganisms to conventional chemicals and drugs is a serious and evident worldwide problem that has prompted research into the identification of new biocides with broad activity. Plants and their derivatives, such as essential oils, are often used in folk medicine. In nature, essential oils play an important role in the protection of plants. Essential oils contain a wide variety of secondary metabolites that are capable of inhibiting or slowing the growth of bacteria, yeasts and moulds. Essential oils and their components have activity against a variety of targets, particularly the membrane and cytoplasm, and in some cases, they completely change the morphology of the cells. This brief review describes the activity of essential oils against pathogenic bacteria.

1,281 citations

Journal ArticleDOI
TL;DR: To achieve predefined time-varying formations, formation protocols are presented for UAV swarm systems first, where the velocities of UAVs can be different when achieving formations, and consensus-based approaches are applied to deal with the time-Varying formation control problems.
Abstract: Formation control analysis and design problems for unmanned aerial vehicle (UAV) swarm systems to achieve time-varying formations are investigated. To achieve predefined time-varying formations, formation protocols are presented for UAV swarm systems first, where the velocities of UAVs can be different when achieving formations. Then, consensus-based approaches are applied to deal with the time-varying formation control problems for UAV swarm systems. Necessary and sufficient conditions for UAV swarm systems to achieve time-varying formations are proposed. An explicit expression of the time-varying formation center function is derived. In addition, a procedure to design the protocol for UAV swarm systems to achieve time-varying formations is given. Finally, a quadrotor formation platform, which consists of five quadrotors is introduced. Theoretical results obtained in this brief are validated on the quardrotor formation platform, and outdoor experimental results are presented.

705 citations

Journal ArticleDOI
TL;DR: A comprehensive survey on the UAVs and the related issues will be introduced, the envisioned UAV-based architecture for the delivery of Uav-based value-added IoT services from the sky will be introduction, and the relevant key challenges and requirements will be presented.
Abstract: Recently, unmanned aerial vehicles (UAVs), or drones, have attracted a lot of attention, since they represent a new potential market. Along with the maturity of the technology and relevant regulations, a worldwide deployment of these UAVs is expected. Thanks to the high mobility of drones, they can be used to provide a lot of applications, such as service delivery, pollution mitigation, farming, and in the rescue operations. Due to its ubiquitous usability, the UAV will play an important role in the Internet of Things (IoT) vision, and it may become the main key enabler of this vision. While these UAVs would be deployed for specific objectives (e.g., service delivery), they can be, at the same time, used to offer new IoT value-added services when they are equipped with suitable and remotely controllable machine type communications (MTCs) devices (i.e., sensors, cameras, and actuators). However, deploying UAVs for the envisioned purposes cannot be done before overcoming the relevant challenging issues. These challenges comprise not only technical issues, such as physical collision, but also regulation issues as this nascent technology could be associated with problems like breaking the privacy of people or even use it for illegal operations like drug smuggling. Providing the communication to UAVs is another challenging issue facing the deployment of this technology. In this paper, a comprehensive survey on the UAVs and the related issues will be introduced. In addition, our envisioned UAV-based architecture for the delivery of UAV-based value-added IoT services from the sky will be introduced, and the relevant key challenges and requirements will be presented.

693 citations