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    Vision-based control laws for distributed flocking of nonholonomic agents

    Moshtagh, N. ; Jadbabaie, A. ; Daniilidis, K.
    Robotics and Automation, 2006. ICRA 2006. Proceedings 2006 IEEE International Conference on

    DOI: 10.1109/ROBOT.2006.1642120
    Publication Year: 2006 , Page(s): 2769 - 2774
    Cited by:  Papers (7)

    IEEE Conference Publications

    We study the problem of vision-based flocking and coordination of a group of kinematic agents in 2 and 3 dimensions. It is shown that in the absence of communication among agents, and by using only visual information, a group of mobile agents can align their velocity vectors and move in a formation. A coordinate-free control law is used to develop a vision-based input for each nonholonomic agent. The vision-based input does not rely on heading measurements, but only requires measurements of bearing, optical flow and time-to-collision, all of which can be efficiently measured View full abstract»

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    Distributed Geodesic Control Laws for Flocking of Nonholonomic Agents

    Moshtagh, N. ; Jadbabaie, A. ; Daniilidis, K.
    Decision and Control, 2005 and 2005 European Control Conference. CDC-ECC '05. 44th IEEE Conference on

    DOI: 10.1109/CDC.2005.1582593
    Publication Year: 2005 , Page(s): 2835 - 2840
    Cited by:  Papers (11)

    IEEE Conference Publications

    We study the problem of flocking and coordination of a group of kinematic nonholonomic agents in 2 and 3 dimensions. By analyzing the velocity vectors of agents on a circle (for planar motion) or sphere (for 3D motion), we develop geodesic control laws that minimize a misalignment potential based on graph Laplacians resulting in velocity alignment. The proposed control laws are distributed and will provably result in flocking when the underlying proximity graph which represents the neighborhood relation among agents is connected. Furthermore, we develop a vision based control law that does not rely on heading measurements, but only requires measurement of bearing, optical flow and time-to-collision, all of which can be efficiently measured. View full abstract»

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    Feasibility checks and control laws for reconfigurations of spacecraft clusters

    Moshtagh, N. ; Ahmadi, A.A. ; Mesbahi, M.
    American Control Conference (ACC), 2012

    DOI: 10.1109/ACC.2012.6315644
    Publication Year: 2012 , Page(s): 961 - 966

    IEEE Conference Publications

    A multi-spacecraft system consists of wirelessly-connected spacecraft that share resources in Earth orbit or deep space. One of the enabling technologies of such a fractionated space architecture is cluster flight, which provides the cluster with the capability to perform a cluster scatter and regather maneuvers to rapidly evade debris-like threats or to reconfigure for scientific missions. In this work, we study the cluster reconfiguration problem. First, we propose an algorithm based on semidefinite programming to check for the feasibility of a desired configuration. Next, we provide a control law for cluster reconfiguration that requires only relative state information and the adjacency matrix of the underlying network topology. Stability analysis and simulation results are provided. View full abstract»

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    Topology control of dynamic networks in the presence of local and global constraints

    Moshtagh, N. ; Mehra, R. ; Mesbahi, M.
    Robotics and Automation (ICRA), 2010 IEEE International Conference on

    DOI: 10.1109/ROBOT.2010.5509828
    Publication Year: 2010 , Page(s): 2718 - 2723
    Cited by:  Papers (1)

    IEEE Conference Publications

    Formation flying (FF) is a critical element in NASA's future deep-space missions. Terrestrial Planet Finder (TPF), NASA's first space-based mission to directly observe planets outside our own solar system, will rely on FF to achieve the functionality and benefits of a large instrument using multiple lower cost smaller spacecraft. Many key network design problems for such FF missions can be formulated as optimization problems with local and global constraints. We develop a topology control algorithm that can be used for many network problems in the presence of local constraints, such as collision avoidance, and global constraints, such as network connectivity. The presence of contradictory objectives in topology control problems motivated a game-theoretic approach. We demonstrated that a game-theoretic technique could provide a framework for design and analysis of many topology control problems in dynamic networks. In particular, the problem of motion planning for formation reconfiguration in the presence of constraints on network connectivity and inter-spacecraft collisions is studied. View full abstract»

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    Distributed Geodesic Control Laws for Flocking of Nonholonomic Agents

    Moshtagh, N. ; Jadbabaie, A.
    Automatic Control, IEEE Transactions on

    Volume: 52 , Issue: 4
    DOI: 10.1109/TAC.2007.894528
    Publication Year: 2007 , Page(s): 681 - 686
    Cited by:  Papers (41)

    IEEE Journals & Magazines

    We study the problem of flocking and velocity alignment in a group of kinematic nonholonomic agents in 2 and 3 dimensions. By analyzing the velocity vectors of agents on a circle (for planar motion) or sphere (for 3-D motion), we develop a geodesic control law that minimizes a misalignment potential and results in velocity alignment and flocking. The proposed control laws are distributed and will provably result in flocking when the underlying proximity graph which represents the neighborhood relation among agents is connected. We further show that flocking is possible even when the topology of the proximity graph changes over time, so long as a weaker notion of joint connectivity is preserved View full abstract»

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    Comment on "One-Step Solution for the Multistep Out-of-Sequence-Measurement Problem in Tracking

    Lingji Chen ; Moshtagh, N. ; Mehra, R.K.
    Aerospace and Electronic Systems, IEEE Transactions on

    Volume: 47 , Issue: 3
    DOI: 10.1109/TAES.2011.5937302
    Publication Year: 2011 , Page(s): 2285 - 2288
    Cited by:  Papers (1)

    IEEE Journals & Magazines

    To incorporate out-of-sequence measurements (OOSMs) in a Kalman filter, the cited paper proposed algorithms that reduced the multistep problem into a single-step one, by defining one "equivalent measurement" that has the same dimension as the state vector. However, the authors did not prescribe formulas for the case when such a "full-dimension" equivalent measurement cannot be defined. This correspondence fills the gap by deriving formulas that are always applicable, regardless of the dimension of the equivalent measurement. View full abstract»

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    Vision-Based, Distributed Control Laws for Motion Coordination of Nonholonomic Robots

    Moshtagh, N. ; Michael, Nathan ; Jadbabaie, A. ; Daniilidis, K.
    Robotics, IEEE Transactions on

    Volume: 25 , Issue: 4
    DOI: 10.1109/TRO.2009.2022439
    Publication Year: 2009 , Page(s): 851 - 860
    Cited by:  Papers (45)

    IEEE Journals & Magazines

    In this paper, we study the problem of distributed motion coordination among a group of nonholonomic ground robots. We develop vision-based control laws for parallel and balanced circular formations using a consensus approach. The proposed control laws are distributed in the sense that they require information only from neighboring robots. Furthermore, the control laws are coordinate-free and do not rely on measurement or communication of heading information among neighbors but instead require measurements of bearing, optical flow, and time to collision, all of which can be measured using visual sensors. Collision-avoidance capabilities are added to the team members, and the effectiveness of the control laws are demonstrated on a group of mobile robots. View full abstract»

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    Distributed coordination of dynamic rigid bodies

    Moshtagh, N. ; Jadbabaie, A. ; Daniilidis, K.
    Decision and Control, 2007 46th IEEE Conference on

    DOI: 10.1109/CDC.2007.4434851
    Publication Year: 2007 , Page(s): 1480 - 1485
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper provides a design methodology to construct a set of distributed control laws for a group of rigid bodies moving in 3D space. The motion of the rigid bodies is restricted by a nonholonomic constraint that prohibits the agents from spinning around their velocity vectors. The connections between two seemingly different flocking control laws presented by Tanner et al. [1] and by Justh and Krishnaprasad [2] are studied, and it is shown that they are actually the same laws expressed in different coordinate systems. The former is expressed in the fixed world frame, whereas the latter is expressed in the moving body frame. View full abstract»

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    Steering laws for distributed motion coordination of kinematic agents in three dimensions

    Moshtagh, N. ; Jadbabaie, A.
    Decision and Control, 2008. CDC 2008. 47th IEEE Conference on

    DOI: 10.1109/CDC.2008.4739155
    Publication Year: 2008 , Page(s): 1741 - 1746
    Cited by:  Papers (1)

    IEEE Conference Publications

    We develop a systematic approach to synthesize distributed control laws for motion coordination in a group of constant-speed kinematic rigid bodies. Parallel and balanced circular formations of mobile agents moving in a three dimensional space are studied, and provably correct steering laws are presented. The resulting steering laws have simple geometric intuitions which are based on the structure of each particular formation. View full abstract»

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    Optimal measurement selection for Any-time Kalman Filtering with processing constraints

    Moshtagh, N. ; Lingji Chen ; Mehra, R.
    Decision and Control, 2009 held jointly with the 2009 28th Chinese Control Conference. CDC/CCC 2009. Proceedings of the 48th IEEE Conference on

    DOI: 10.1109/CDC.2009.5400572
    Publication Year: 2009 , Page(s): 5074 - 5079

    IEEE Conference Publications

    In an embedded system with limited processing resources, as the number of tasks grows, they interfere with each other through preemption and blocking while waiting for shared resources such as CPU time and memory. The main task of an Any-Time Kalman Filter (AKF) is real-time state estimation from measurements using available processing resources. Due to limited computational resources, the AKF may have to select only a subset of all the available measurements or use out-of-sequence measurements for processing. This paper addresses the problem of measurement selection needed to implement AKF on systems that can be modeled as double-integrators, such as mobile robots, aircraft, satellites etc. It is shown that a greedy sequential selection algorithm provides the optimal selection of measurements for such systems given the processing constraints. View full abstract»

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    Low resolution face recognition using combination of diverse classifiers

    Ebrahimpour, R. ; Sadeghnejad, N. ; Amiri, A. ; Moshtagh, A.
    Soft Computing and Pattern Recognition (SoCPaR), 2010 International Conference of

    DOI: 10.1109/SOCPAR.2010.5686495
    Publication Year: 2010 , Page(s): 265 - 268
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper presents an appropriate solution for low resolution faces recognition problem, using combination of diverse classifiers. We investigate our model based on extracting important features from low resolution images using three well known feature extractors; PCA, DCT and FFT, assigning MLP classifiers to each feature extractor and combining the votes of MLP classifiers using fusion of experts techniques. The results show that using the combination of three mentioned feature extractors and applying the Stack Generalization as combiner of classifiers for low resolution face recognition task, leads to higher performance than other recognition models. It's worth nothing that using a single feature extractor for low resolution face recognition task was failed in the previously surveys. View full abstract»

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