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  • Market-Based Solution to the Allocation of Tasks to Agents

    Article thumbnail: Market-Based Solution to the Allocation of Tasks to Agents
    Type:
    Article
    Description/Abstract:
    Tasks allocation is a fundamental problem in multiagent systems. We formulate the problem as a multiple traveling salesmen problem (MTSP), which is an extension to the well known traveling salesman problem (TSP), both considered to be NP-hard combinatorial optimization problems. We propose a solution in which agents interact in an economic market to win tasks situated in an environment. The agents strive to minimize required costs, defined as either the total distance traveled by all agents or the maximum distance traveled by any agent. Using a set of simple market operations, the agents come up with a solution for task allocation. In this work we examine the processing speed of the market-based solution (MBS), as well as the quality vs. optimal solutions achieved using enumeration for a 3 agents by 8 tasks scenario. We show that the MBS is both quick and close to optimal. We then show that the MBS can be scaled to more complicated problems, by comparing its results with results from genetic algorithm (GA) and clustering. We also show the robustness of the MBS to changes in the scenario, e.g. the addition and removal of tasks or agents.
    Creator/Author:
    Cohen, Kelly; Kumar, Manish, and Kivelevitch, Elad
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/13/2017
    Date Modified:
    04/05/2017
    Date Created:
    2011-10
    License:
    All rights reserved

  • Filtered POD-based low-dimensional modeling of the 3D turbulent flow behind a circular cylinder

    Article thumbnail: Filtered POD-based low-dimensional modeling of the 3D turbulent flow behind a circular cylinder
    Type:
    Article
    Description/Abstract:
    Low-dimensional models have proven essential for feedback control and estimation of flow fields. While feedback control based on global flow estimation can be very efficient, it is often difficult to estimate the flow state if structures of very different length scales are present in the flow. The conventional snapshot-based proper orthogonal decomposition (POD), a popular method for low-order modeling, does not separate the structures according to size, since it optimizes modes based on energy. Two methods are developed in this study to separate the structures in the flow based on size. One of them is Hybrid Filtered POD method and the second one is 3D FFT-based Filtered POD approach performed using a fast Fourier transform (FFT)-based spatial filtering. In both the methods, a spatial low-pass filter is employed to precondition snapshot sets before deriving POD modes. Three-dimensional flow data from the simulation of turbulent flow over a circular cylinder wake at Re=20000 is used to evaluate the performance of the two methods. Results show that both the FFT-based 3D Filtered POD and Hybrid Filtered POD are able to capture the large-scale features of the flow, such as the von Karman vortex street, while not being contaminated by small-scale turbulent structures present in the flow.
    Creator/Author:
    Cohen, Kelly; Seidel, Jurgen; Siegel, Stefan; McLaughlin, Thomas, and Aradag, Selin
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/13/2017
    Date Modified:
    04/05/2017
    Date Created:
    2011-05
    License:
    All rights reserved

  • Cooperative Control of Multiple Uninhabited Aerial Vehicles for Monitoring and FightingWildfires

    Article thumbnail: Cooperative Control of Multiple Uninhabited Aerial Vehicles for Monitoring and FightingWildfires
    Type:
    Article
    Description/Abstract:
    Uninhabited aerial vehicles provide numerous advantages in fighting wildland fires that include persistent operation and elimination of humans from performing what can be dull, dangerous, and dirty work. Multiple cooperating uninhabited aerial vehicles can potentially bring about a paradigm shift in the way we fight complex wildland fires. This paper investigates algorithmic development for cooperative control of a number of uninhabited aerial vehicles engaged in fighting a wildland fire. The paper considers two tasks to be performed by a group of uninhabited aerial vehicles: 1) Cooperative tracking of a fire front for accurate situational awareness, and 2) cooperative, autonomous fire fighting using fire suppressant fluid. The scenario considered in this paper makes the following assumptions: information regarding the location of the fire and position of all uninhabited aerial vehicles is made available to each uninhabited aerial vehicle; and each uninhabited aerial vehicle is equipped with unlimited fire suppressant fluid which extinguishes fire in a circle of specified area directly beneath it. This paper formulates these two tasks of fire fighting based upon optimization of respective utility functions, develops a decentralized control method for the cooperative uninhabited aerial vehicles, and analyzes the system for its stability and its ability to carry out the tasks. The proposed strategies have been verified with the help of extensive simulations. Although simplifying assumptions have been made, this preliminary study presents a framework for path planning and cooperative control of multiple uninhabited aerial vehicles engaged in gathering data and actively fighting forest fires.
    Creator/Author:
    Cohen, Kelly; KomChaudhuri, Baisravan, and Kumar, Manish
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/13/2017
    Date Modified:
    04/05/2017
    Date Created:
    2011-01
    License:
    All rights reserved

  • Multi-Agent Maze Exploration

    Article thumbnail: Multi-Agent Maze Exploration
    Type:
    Article
    Description/Abstract:
    Mazes have intrigued the human mind for thousands of years, and have been used to measure cognitive abilities of laboratory animals. In recent years, mazes have been used to examine the artificial intelligence of robots by observing their ability to traverse mazes using algorithm for maze exploration and exploitation.A simulation of a multi-agent system is used to demonstrate the benefits of utilizing a group of several robots in maze exploration. Using a behavioral algorithm based on Tarry’s algorithm, it is shown that the group performance improves and becomes more robust as the number of robots increases. In addition, the amount of data transfer required for group coordination can be minimized to a small set of data items, which is independent of either the number of robots in the group or the maze size.As a result, the above multi-agent approach can be scaled up to mazes or groups of any size, as indicated by the results of the MATLAB-based simulation.
    Creator/Author:
    Cohen, Kelly and Kivelvitch, Elad H.
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/13/2017
    Date Modified:
    04/05/2017
    Date Created:
    2010-12
    License:
    All rights reserved

  • Spatially Distributed Forcing and Jet Vectoring with a Plasma Actuator

    Article thumbnail: Spatially Distributed Forcing and Jet Vectoring with a Plasma Actuator
    Type:
    Article
    Description/Abstract:
    The ability to spatially alter both the amount of body force along the span of a plasma actuator and the angle of the resulting jet relative to the surface has been demonstrated. A dielectric barrier discharge plasma actuator consists of two electrodes separated by a dielectric barrier, which imparts momentum to the surrounding fluid parallel to the dielectric. To investigate a technique to shape the spanwise body force created by the plasma actuator, a control volume momentum balance was used. By shaping the buried electrode along the span of the actuator, the local volume of plasma generated can be controlled, which is related to the local body force. Pressure measurements were taken in the boundary layer behind the actuator to calculate the momentum imparted to the flow at various spanwise locations corresponding to different electrode widths. Particle image velocimetry data were then used to show that spatially varying, steady jets could be created with the use of only one actuator by varying the width of the buried electrode in a quiescent flow. The angle of the jet created, relative to the dielectric, by a plasma synthetic jet is also investigated. By pointing two plasma actuators at each other, an inverted impinging jet can be created as a result of the two independent jets colliding. By altering the strength of one of the jets relative to the other, the angle of separation can be changed. Particle image velocimetry data were taken to show the effects of altering the voltage (strength) applied to one of the actuators relative to the other. It was found that, with this method, jet vectoring could be achieved. The angle of the jet could be controlled a full 180 deg through small changes in the voltage applied to the electrodes, also in a quiescent flow.
    Creator/Author:
    Enloe, C. L.; Cohen, Kelly; Porter, C.; McLaughlin, T., and Abbas, A.
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/13/2017
    Date Modified:
    04/05/2017
    Date Created:
    2009-06
    License:
    All rights reserved

  • Introduction: Enhancing Intelligence in Aerospace Systems

    Article thumbnail: Introduction: Enhancing Intelligence in Aerospace Systems
    Type:
    Article
    Description/Abstract:
    Not available.
    Creator/Author:
    Gregory, Irene; Figueroa, Fernando; Cohen, Kelly; Ingham, Michel; Atkins, Ella; Obayashi, Shigeru; Truszkowski, Walt; Garg, Sanjay; Blackmore, Lars; Doyle, Richard, and Nguyen, Nhan
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/10/2017
    Date Modified:
    04/05/2017
    Date Created:
    2009-03
    License:
    All rights reserved

  • Low-dimensional modelling of a transient cylinder wake using double proper orthogonal decomposition

    Article thumbnail: Low-dimensional modelling of a transient cylinder wake using double proper orthogonal decomposition
    Type:
    Article
    Description/Abstract:
    For the systematic development of feedback flow controllers, a numerical model that captures the dynamic behaviour of the flow field to be controlled is required. This poses a particular challenge for flow fields where the dynamic behaviour is nonlinear, and the governing equations cannot easily be solved in closed form. This has led to many versions of low-dimensional modelling techniques, which we extend in this work to represent better the impact of actuation on the flow. For the benchmark problem of a circular cylinder wake in the laminar regime, we introduce a novel extension to the proper orthogonal decomposition (POD) procedure that facilitates mode construction from transient data sets. We demonstrate the performance of this new decomposition by applying it to a data set from the development of the limit cycle oscillation of a circular cylinder wake simulation as well as an ensemble of transient forced simulation results. The modes obtained from this decomposition, which we refer to as the double POD (DPOD) method, correctly track the changes of the spatial modes both during the evolution of the limit cycle and when forcing is applied by transverse translation of the cylinder. The mode amplitudes, which are obtained by projecting the original data sets onto the truncated DPOD modes, can be used to construct a dynamic mathematical model of the wake that accurately predicts the wake flow dynamics within the lock-in region at low forcing amplitudes. This low dimensional model, derived using nonlinear artificial neural network based system identification methods, is robust and accurate and can be used to simulate the dynamic behaviour of the wake flow. We demonstrate this ability not just for unforced and open-loop forced data, but also for a feedback-controlled simulation that leads to a 90% reduction in lift fluctuations. This indicates the possibility of constructing accurate dynamic low-dimensional models for feedback control by using unforced and transient forced data only.
    Creator/Author:
    Luchtenburg, D. M.; Cohen, Kelly; Seidel, Jurgen; Fagley, Casey, and Siegel, Stefan G.
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/10/2017
    Date Modified:
    04/05/2017
    Date Created:
    2008-09
    License:
    All rights reserved

  • Experimental estimation of a D-shaped cylinder wake using body-mounted sensors

    Article thumbnail: Experimental estimation of a D-shaped cylinder wake using body-mounted sensors
    Type:
    Article
    Description/Abstract:
    The effectiveness of a small array of body-mounted sensors, for estimation and eventually feedback flow control of a D-shaped cylinder wake is investigated experimentally. The research is aimed at suppressing unsteady loads resulting from the von-Kármán vortex shedding in the wake of bluff-bodies at a Reynolds number range of 100–1,000. A low-dimensional proper orthogonal decomposition (POD) procedure was applied to the stream-wise and cross-stream velocities in the near wake flow field, with steady-state vortex shedding, obtained using particle image velocimetry (PIV). Data were collected in the unforced condition, which served as a baseline, as well as during influence of forcing within the “lock-in” region. The design of sensor number and placement was based on data from a laminar direct numerical simulation of the Navier-Stokes equations. A linear stochastic estimator (LSE) was employed to map the surface-mounted hot-film sensor signals to the temporal coefficients of the reduced order model of the wake flow field in order to provide accurate yet compact estimates of the low-dimensional states. For a three-sensor configuration, results show that the estimation error of the first two cross-stream modes is within 20–40% of the PIV-generated POD time coefficients. Based on previous investigations, this level of error is acceptable for a moderately robust controller required for feedback flow control.
    Creator/Author:
    Cohen, Kelly; Stalnov, Oksana; Fono, Ilan; Seifert, Avi, and Palei, Vitali
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/10/2017
    Date Modified:
    04/05/2017
    Date Created:
    2007-02
    License:
    All rights reserved

  • Numerical Simulations of a Feedback-Controlled Circular CylinderWake

    Article thumbnail: Numerical Simulations of a Feedback-Controlled Circular CylinderWake
    Type:
    Article
    Description/Abstract:
    The effect of feedback flow control on the wake of a circular cylinder at a Reynolds number of 100 is investigated in direct numerical simulation. The control approach uses a low-dimensional model based on proper orthogonal decomposition (POD). The controller applies linear proportional and differential feedback to the estimate of the first POD mode. The range of validity of the POD model is explored in detail. Actuation is implemented as displacement of the cylinder normal to the flow. It is demonstrated that the threshold peak amplitude below which the control actuation ceases to be effective is in the order of 5% of the cylinder diameter. The closed-loop feedback simulations explore the effect of both fixed-phase and variable-phase feedback on the wake. Whereas fixed-phase feedback is effective in reducing drag and unsteady lift, it fails to stabilize this state once the low drag state has been reached. Variable-phase feedback, however, achieves the same drag and unsteady lift reductions while being able to stabilize the flow in the low drag state. In the low drag state, the near wake is entirely steady, whereas the far wake exhibits vortex shedding at a reduced intensity. A drag reduction of 15% of the drag was achieved, and the unsteady lift force was lowered by 90%.
    Creator/Author:
    Cohen, Kelly; Siegel, Stefan, and McLaughlin, Thomas
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/10/2017
    Date Modified:
    04/05/2017
    Date Created:
    2006-06
    License:
    All rights reserved

  • A heuristic approach to effective sensor placement for modeling of a cylinder wake

    Article thumbnail: A heuristic approach to effective sensor placement for modeling of a cylinder wake
    Type:
    Article
    Description/Abstract:
    The effectiveness of a sensor configuration for feedback flow control on the wake of a circular cylinder is investigated in both direct numerical simulation as well as in a water tunnel experiment. The research program is aimed at suppressing the von Kármán vortex street in the wake of a cylinder at a Reynolds number of 100. The design of sensor number and placement was based on data from a laminar two-dimensional simulation of the Navier–Stokes equations for the unforced condition. A low-dimensional proper orthogonal decomposition (POD) was applied to the vorticity calculated from the flow field and sensor placement was based on the intensity of the resulting spatial eigenfunctions. The numerically generated data was comprised of 70 snapshots taken over three cycles from the steady state regime. A linear stochastic estimator (LSE) was employed to map the velocity data to the temporal coefficients of the reduced order model. The capability of the sensor configuration to provide accurate estimates of the four low-dimensional states was validated experimentally in a water tunnel at a Reynolds number of 108. For the experimental wake, a sample of 200 particle image velocimetry (PIV) measurements was used. Results show that for experimental data, the root mean square estimation error of the estimates of the first two modes was within 6% of the desired values and for the next two modes was within 20% of the desired values. This level of error is acceptable for a moderately robust controller.
    Creator/Author:
    Cohen, Kelly; Siegel, Stefan, and McLaughlin, Thomas
    Submitter:
    Kelly Cohen
    Date Uploaded:
    02/10/2017
    Date Modified:
    04/05/2017
    Date Created:
    2006-01
    License:
    All rights reserved