Journal: IFAC Proceedings Volumes

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Elsevier

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1474-6670

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Publications 1 - 10 of 115
  • Experimental validation of patrolling strategies in an automated surveillance environment
    Item type: Conference Paper
    Huck, Stephan M.; Kariotoglou, Nikolaos; Dahinden, Michael; et al. (2014)
    IFAC Proceedings Volumes ~ 19th IFAC World Congress, IFAC 2014. Proceedings
    The Autonomous Robotic Patrolling and Surveillance environment (AuRoPaS) is a testbed at the Automatic Control Laboratory of ETH Zurich to experimentally validate tracking, observation, and monitoring strategies for security systems. The setup comprises two high performance closed-circuit television (CCTV) cameras and mobile robots to simulate different types of surveillance scenarios. We propose a velocity based model predictive control scheme for the camera movements, which allows us to generate smooth trajectories and acquire stable images from targets. Experimental results demonstrate the successful reference tracking of the camera controller. We illustrate the integration of high level algorithms into the testbed by applying two stochastic patrolling strategies. The patrolling performances are evaluated on a scenario with moving targets visiting prioritized regions.
  • Performance bounds for min-max uncertain constrained systems
    Item type: Conference Paper
    Van Parys, Bart P.G.; Goulart, Paul; Morari, Manfred (2012)
    IFAC Proceedings Volumes ~ 4th IFAC Conference on Nonlinear Model Predictive Control
    We present a method to bound the performance of causal controllers for uncertain linear systems with mixed state and input constraints. The performance is measured by the worst-case value (over all possible disturbance inputs) of a convex piecewise linear cost function over a finite horizon. Our method computes a causal affine control policy that satisfies the constraints robustly, while simultaneously providing a lower bound on the achievable performance of this, or any other causal control policy constructed by any other method. The controller and performance guarantee can be found by solving a number of convex conic optimization problems which are closely connected.
  • Using controllable thermal household appliances for wind forecast error reduction
    Item type: Conference Paper
    Koch, Stephan; Soto Barcenas, Fernando; Andersson, Göran (2010)
    IFAC Proceedings Volumes ~ 1st IFAC Conference on Control Methodologies and Technology for Energy Efficiency
    This paper deals with the utilization of a large cluster of thermal household appliances, which are enabled to participate in active power control through a two-way communication system, for reducing the infeed prediction error of a wind generator. A recently developed coordination algorithm for thermostat-controlled appliances provides the basis for shaping the consumption profile of a multitude of dispersed heating and cooling devices. In the present approach, a Model Predictive Control strategy is used to operate the controllable thermal appliances together with a controllable generation unit in such a way that the financial penalties for external balancing are reduced.
  • Distributed collision avoidance for interacting vehicles: A command governor approach
    Item type: Conference Paper
    Tedesco, Francesco; Raimondo, Davide M.; Casavola, Alessandro; et al. (2010)
    IFAC Proceedings Volumes ~ 2nd IFAC Workshop on Distributed Estimation and Control in Networked Systems
    This paper deals with a distributed coordination problem including collision avoidance. The problem is solved by using a Command Governor strategy based on mixed integer optimization. First, we present an algorithm to find an appropriate command in the centralized case, then a distributed sequential procedure is described. Simulations are reported for comparisons.
  • Fast range image segmentation for indoor 3D-slam
    Item type: Conference Paper
    Harati, Ahad; Gächter, Stefan; Siegwart, Roland (2007)
    IFAC Proceedings Volumes ~ 6th IFAC Symposium on Intelligent Autonomous Vehicles, IAV 2007. Proceedings
    Real-time 3D localization and mapping is eventually needed in many service robotic applications. Toward a light and practical SLAM algorithm, we focus on feature extraction via segmentation of range images. Using horizontal and vertical traces of the range matrix, 2D observed polygons are considered for calculation of a one-dimensional measure of direction, called Bearing Angle (BA). BA is the incident angle between the laser beam and edges of the observed polygon by the scanner in the selected direction. Based on this measure, two different approaches to range image segmentation, region- and edge-based, are proposed and evaluated through a set of standard analysis. It is experimentally shown that for navigation applications, edge based approaches are more efficient. Extensive tests on real robots prove BA-based segmentation is successful for SLAM.
  • Closed Loop Relay Estimation of Uncertainty Bounds for Robust Control Models
    Item type: Conference Paper
    Smith, Roy; Doyle, John C. (1993)
    IFAC Proceedings Volumes ~ 12th Triennal World Congress of the International Federation of Automatic control. Volume 5 Associated Technologies and Recent Developments, Sydney, Australia, 18-23 July
    This paper describes an ad-hoc technique for the closed loop experimental estimation of perturbation bounds for robust control models. The approach is based on the closed loop relay identification method proposed by Åström and Hägglund. A series of lead compensators is designed such that the closed loop system limit cycles at progressively higher frequencies. Beyond a certain frequency, consistent limit cycling no longer occurs. The heuristic is that at this frequency uncertainty (or perturbations) should dominate the model. The idea is illustrated by application to a process control experiment.
  • Optimization methodology for tuning fuzzy logic controllers
    Item type: Conference Paper
    Koulocheris, Dimitris V.; Vrazopoulos, Harry; Dertimanis, Vasilis K. (2002)
    IFAC Proceedings Volumes ~ Proceedings of the 15th IFAC World Congress
    The scope of this paper is to present an optimization methodology for tuning fuzzy logic controllers used in suspension system for ground vehicles. The proposed optimization method combines the advantages of two categories of optimization algorithms, deterministic and stochastic. Numerical experiments show the improvement in efficiency and reliability of the search for the optimum. The fuzzy logic membership functions are optimized such that the maximum value of vertical and rotational acceleration of vehicle body at the passengers seats are minimized from the view point of ride comfort under the geometrical constraints of the car. The simulation results of the proposed fuzzy logic controller show significant improvement regarding the vehicle ride comfort.
  • Active coordination of thermal household appliances for load management purposes
    Item type: Conference Paper
    Koch, Stephan; Zima, Marek; Andersson, Göran (2009)
    IFAC Proceedings Volumes ~ 6th IFAC Symposium on Power Plants and Power Systems Control
    In this paper, a coordination approach for thermostat-controlled household appliances is developed. Under consideration are heating and cooling devices such as refrigerators, freezers, water boilers and heat pumps, which are usually characterized by an intermittent (duty cycle) operation. Without influence from the outside, an internal hysteresis switching controller toggles the “on/off” state of a device when its temperature boundary is reached. In order to realize the approach proposed here, the devices are connected to a central control entity by two-way communication. The coordination consists of a step-wise heuristic solution of a binary optimization problem, which serves to select a number of devices in each time step that are subject to compulsory switching, i.e. toggling the “on/off” state. It allows a large group of devices to track a setpoint trajectory with its aggregated power consumption, acting like a distributed virtual energy storage, while the individual temperature bounds of the appliances are not violated. This behavior can be used for grid-control purposes, such as the provision of active power reserves. It will be shown that the group of appliances can be characterized by an approximate aggregated dynamical model consisting of a first-order differential equation together with an approximate aggregated nonlinear cost function penalizing the control actions. The developed methodology is evaluated in a numerical simulation with a small appliance cluster corresponding to a residential housing area.
  • Revisiting the viability algorithm for hybrid systems using optimal control
    Item type: Conference Paper
    Margellos, Kostas; Lygeros, John (2012)
    IFAC Proceedings Volumes ~ Proceedings of the 4th IFAC Conference on Analysis and Design of Hybrid Systems (ADHS 2012)
    In this paper, we revisit the problem of approximating viability sets for hybrid systems with nonlinear continuous dynamics and competing inputs. As usual in the literature, an iterative algorithm, based on the alternating application of a continuous and a discrete operator, is employed. Three different cases, based on whether the continuous evolution and the number of discrete transitions are finite or infinite, are considered. A complete characterization of the reach-avoid computation (involved in the continuous time calculation) is provided based entirely on optimal control. Moreover, we show convergence of the iterative process by using a constructive version of Tarski's fixed point theorem, to determine the maximal fixed point of a monotone operator on a complete lattice of closed sets. To illustrate its performance, the viability algorithm is applied to investigate voltage stability for a single machine-load system in case of a line fault.
  • Distributed control of antenna array with formation of UAVs
    Item type: Conference Paper
    Tonetti, Stefania; Hehn, Markus; Lupashin, Sergei; et al. (2011)
    IFAC Proceedings Volumes ~ Proceedings of the 18th World Congress
    This paper studies the feasibility and the advantages of a distributed control strategy for a linear end-fire antenna array formation with UAVs. We first analyze the sensitivity of different interaction topologies to a low frequency sinusoidal disturbance affecting just one single vehicle, for antenna array sizes of up to 30 elements. The ETH Zurich Flying Machine Arena (FMA) is used as a test case. Then we consider a more realistic case of wind gust acting on all of the antennas. We show that under such conditions the simplified analysis does well at predicting the formation behavior under different distributed and decentralized control strategies.
Publications 1 - 10 of 115