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International Joint Conference on Neural Networks

作者： T. Guthier V. Willert A. Schnall K. Kreuter J. Eggert Control Theory and Robotics Department Technische Universitaet Darmstadt Germany Honda Research Institute Europe Germany

ISBN: (纸本)9781467361279

Visual motion is a rich source of information that is directly coupled to the underlying shape of a moving object. One way to describe motion is to use optical flow fields. Due to the aperture problem, dense optical flow estimation is an ill-constraint problem, while sparse optical flow estimation looses the shape information of moving objects. Current estimation algorithms based on regularization or segmentation fail at surface deformations or when the relevant motion is less dominant then its sourrounding movements. Both is e.g. true for face movements, where small movement patterns, so called action units, need to be preserved for further image analysis. We present a novel approach to capture the characteristics of local motion patterns that is based on the brightness constancy equation of optical flow estimation in combination with feature extraction using translation invariant non-negative sparse coding. Our approach simultaneously learns basic motion patterns and estimates the flow field without requiring pretrained motion patterns from ground truth optical flow data. We show on a face expression dataset how this method can preserve weak movements even in the presence of large head movements.

关键词： Motion Extraction underlying shape flow field without requiring pretrained

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Stability of longitudinal bunch length feedback for heavy-ion synchrotrons

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Physical Review Special Topics - Accelerators and Beams 2013年第3期16卷 032801-032801页

作者： D. Lens H. Klingbeil []Institute of Automatic Control Control Theory and Robotics Laboratory Technische Universit?t Darmstadt Landgraf-Georg-Stra?e 4 D-64283 Darmstadt Germany

In heavy-ion synchrotrons such as the SIS18 at Helmholtzzentrum für Schwerionenforschung, Helmholtz Centre for Heavy Ion Research (GSI), coherent oscillations of the particle bunches are damped by rf feedback systems to increase the stability and to improve the beam quality. In the longitudinal direction, important modes are the coherent longitudinal dipole and quadrupole oscillation. In this paper we present a new and rigorous approach to analyze the longitudinal feedback to damp these modes. The results are applied to the rf feedback loop at GSI that damps the quadrupole mode. The stability analysis is compared with simulations and is in good agreement with results of a beam experiment. Finally, we summarize practical implications for the operation of the feedback system regarding performance and stability.

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From Grid Maps to Parametric Free Space Maps - A Highly Compact, Generic Environment Representation for ADAS

From Grid Maps to Parametric Free Space Maps - A Highly Comp...

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IEEE Intelligent Vehicles Symposium

作者： Matthias Schreier Volker Willert Jüren Adamy Institute of Automatic Control and Mechatronics Control Theory and Robotics Lab TU Darmstadt Landgraf-Georg-Str. 4 64283 Darmstadt Germany

ISBN: (纸本)9781467327534

We propose a highly compact, generic representation of the driving environment, so-called Parametric Free Space (PFS) maps, specifically suitable for future Advanced Driver Assistance Systems (ADAS) and bring them into line with existing metric representations known from mobile robotics. PFS maps combine a closed contour description of arbitrarily shaped outer free space boundaries with a representation of inner free space boundaries, respectively objects, by geometric primitives. A real-time capable algorithm is presented that obtains the representation by building upon an inermediate occupancy grid map-based environment representation generated from an automotive radar and a stereo camera. The proposed representation preserves all relevant information contained in a grid map - thus remaining function-independent - in a much more compact way, which is considered particularly important for the transmission via low data-rte automotive communication interfaces. Examples are shown in real traffic scenarios.

关键词： Grid Maps Parametric Free Space Maps Generic Environment Representation for ADAS

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Efficient trajectory optimization using a sparse model

Efficient trajectory optimization using a sparse model

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European Conference on Mobile Robots (ECMR)

作者： Christoph Rösmann Wendelin Feiten Thomas Wösch Frank Hoffmann Torsten Bertram Institute of Control Theory and Systems Engineering Technische Universität Dortmund Germany Siemens Corporate Technology Research Group Robotics Germany

The “timed elastic band” approach optimizes robot trajectories by subsequent modification of an initial trajectory generated by a global planner. The objectives considered in the trajectory optimization include but are not limited to the overall path length, trajectory execution time, separation from obstacles, passing through intermediate way points and compliance with the robots dynamic, kinematic and geometric constraints. “Timed elastic bands” explicitly consider spatial-temporal aspects of the motion in terms of dynamic constraints such as limited robot velocities and accelerations. The trajectory planning operates in real time such that “timed elastic bands” cope with dynamic obstacles and motion constraints. The “timed elastic band problem” is formulated as a scalarized multi-objective optimization problem. Most objectives are local and relate to only a small subset of parameters as they only depend on a few consecutive robot states. This local structure results in a sparse system matrix, which allows the utilization of fast and efficient optimization techniques such as the open-source framework “g2o” for solving “timed elastic band” problems. The “g2o” sparse system solvers have been successfully applied to VSLAM problems. This contribution describes the application and adaptation of the g2o-framework in the context of trajectory modification with the “timed elastic band”. Results from simulations and experiments with a real robot demonstrate that the implementation is robust and computationally efficient.

关键词： Trajectory Optimization Robots Linear programming Acceleration Collision avoidance Modeling

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Robust observer-based fault detection and isolation in the standard control problem framework

Robust observer-based fault detection and isolation in the s...

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7th IFAC Symposium on Robust control Design, ROCOND'12

作者： Wahrburg, Arne Khodaverdian, Saman Adamy, Jürgen Institute of Automatic Control Control Theory and Robotics Lab. Technische Universität Darmstadt Germany

ISBN: (纸本)9783902823038

This paper deals with the design of robust fault detection and isolation observers where only a single observer is employed to isolate different faults. To this end, the problem of parameterizing such observers is shown to be equivalent to designing a structurally constrained controller in the standard control problem framework. Thereby, the problem is reformulated as a well known classical control problem, which enables the use of existing tools to optimize robustness with respect to arbitrary exogenous disturbances. To account for parametric uncertainties, an approximate model matching approach is used. © 2012 IFAC.

关键词： Fault detection

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Robust fault isolation observers for non-square systems - A parametric approach

Robust fault isolation observers for non-square systems - A ...

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8th IFAC Symposium on Fault Detection, Supervision and Safety of Technical Processes, SAFEPROCESS 2012

作者： Wahrburg, Arne Adamy, Jürgen Institute of Automatic Control Control Theory and Robotics Lab. Technische Universität Darmstadt Germany

ISBN: (纸本)9783902823090

In this article, a linear matrix inequality (LMI)-based design for robust fault isolation observers (FIOs) for linear systems with arbitrary fault detectability indices is presented. A parametric design is used to achieve stable fault isolation in square systems as well as non-square systems. Based on this design, the influence of arbitrary disturbances is attenuated by a proper optimization of the observer gain matrices. The applicability of the proposed design is verified in simulations of a helicopter model. © 2012 IFAC.

关键词： Linear matrix inequalities

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Modeling and adaptive control of a quadrotor

Modeling and adaptive control of a quadrotor

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2012 9th IEEE International Conference on Mechatronics and Automation, ICMA 2012

作者： Schreier, Matthias Institute of Automatic Control and Mechatronics Control Theory and Robotics Lab. TU Darmstadt Landgraf-Georg-Str. 4 64283 Darmstadt Germany

ISBN: (纸本)9781467312776

In this paper, we propose two variants of adaptive state space controllers for attitude stabilization and self-tuning of a four-rotor aerial robot, a quadrotor. First of all, the use of a Model Identification Adaptive controller (MIAC) is proposed in terms of combining a recursive least-squares estimator with exponential forgetting with an integral discrete-time state space controller. Furthermore, a continuous-time Model Reference Adaptive control (MRAC) scheme based on Lyapunov theory is applied to the simplified dynamics of a quadrotor, which guarantees global asymptotic stability for at least linear overall systems. The effectiveness of the suggested adaptive methods is demonstrated in simulations with a quaternion-based nonlinear dynamic model of a quadrotor derived in this work. The results are compared to a designed nonadaptive integral state space controller. © 2012 IEEE.

关键词： Unmanned aerial vehicles (UAV)

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Finding a tradeoff between compression and loss in motion compensated video coding

Finding a tradeoff between compression and loss in motion co...

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International Conference on Signal Processing and Multimedia Applications, SIGMAP 2012 and International Conference on Wireless Information Networks and Systems, WINSYS 2012

作者： Guthier, Thomas Sosic, Adrian Willert, Volker Eggert, Julian Control Theory and Robotics TU Darmstadt Landgraf-Georg Strasse Darmstadt Germany Honda Research Institute Europe Offenbach Germany

ISBN: (纸本)9789898565259

In video coding, affine motion models combined with a quadtree decomposition have often been suggested as an extension to the mostly used translational models combined with a blockwise decomposition. What is missing so far is a thorough analysis to judge the tradeoff between using more complex motion models or more elaborate decomposition methods in terms of data compression and information loss. In this paper, we compare different polynomial motion models with a quadtree decomposition concerning motion model complexity and granularity of decomposition. We provide a statistical evaluation based on optical flow databases to quantitatively find a tradeoff between bitrate and reconstruction error.

关键词： Image coding

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Robust observer-based fault detection and isolation in the standard control problem framework

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IFAC Proceedings Volumes 2012年第13期45卷 473-478页

作者： Arne Wahrburg Saman Khodaverdian Jürgen Adamy Institute of Automatic Control Control Theory & Robotics Lab Technische Universität Darmstadt Germany

关键词： robust fault diagnosis observer-based fault detection isolation standard control problem structurally constrained control model matching

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Robust fault isolation observers for non-square systems - a parametric approach

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IFAC Proceedings Volumes 2012年第20期45卷 1275-1280页

作者： Arne Wahrburg Jürgen Adamy Institute of Automatic Control Control Theory & Robotics Lab Technische Universität Darmstadt Germany

关键词： robust fault isolation observer-based fault isolation LMIs parametric design

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