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 f...
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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.
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 sys...
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.
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 int...
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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.
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 ...
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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.
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 sho...
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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 ach...
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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...
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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 s...
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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.
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 sho...
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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.
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 ach...
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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.
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