Abstract: Copulas enabling to characterize the joint distributions of random vectors by means of the corresponding one-dimensional marginal distributions are presented and discussed. Some properties of copulas and several construction methods, especially when a partial knowledge is available, are included. Possible applications are indicated.
Keywords: random variable, random vector, dependence, copula, aggregation function
Abstract: A further step towards a novel approach to adaptive nonlinear control developed at Budapest Tech in the past few years is reported. This approach obviates the use of the complicated Lyapunov function technique that normally provides global stability of convergence at the costs of both formal and essential restrictions, by applying Cauchy sequences of local, bounded basin of attraction in an iterative control that is free of such restrictions. Its main point is the creation of a robust iterative sequence that only slightly depends on the features of the controlled system and mainly is determined be the control parameters applied. It is shown that as far as its operation is considered the proposed method can be located between the robust Variable Structure / Sliding Mode and the adaptive Slotine-Li control in the case of robots or other Classical Mechanical Systems. The operation of these method is comparatively analyzed for a wheel + connected mass system in which this latter component is “stabilized” along one of the spokes of the wheel in the radial direction by an elastic spring. The robustness of these methods is also investigated againts unknown external disturbances of quite significant amplitudes. The numerical simulations substantiate the superiority of the robust fixed point transformations in the terms of accuracy, simplicity, and smoothness of the control signals applied.
Keywords: Adaptive Slotine-Li Robot Control, Variable Structure / Sliding Mode Controller, Fixed Point Transformations, Cauchy Sequences, Banach Spaces
Abstract: During a day, moving in an unstructured environment, man is realizing different types of walk, requiring from him on-line trajectory planning and permanent changes of gait parameters (turning, stopping, speeding up and slowing down, switching from the walk on a flat ground to the walk on inclined surfaces or staircases, etc.). Besides, apart from realizing the motion, there appears frequently the need to perform some additional tasks, e.g. manipulation. In view of the expectation that the future robots will share with humans their living and working environment, it is expected from them to be endowed with similar capabilities of motion. We think that a necessary prerequisite for fulfilling all these tasks is a permanent maintenance of dynamic balance, which may be achieved by the realization of a regular gait. Therefore, one of the basic characteristics of regular bipedal walk of humanoid robots is the maintenance of their dynamic balance during the walk, whereby a decisive role is played by the unpowered degrees of freedom arising at the foot-ground contact. Hence, the role of Zero-Moment Point (ZMP) as an indicator of dynamic balance is indispensable. On the other hand, we are witnesses of the diverse realizations of locomotion systems, from those with human-like feet, aiming to mimic in full the human gait, passive walkers, which practically roll on specially profiled feet, to the footless locomotion systems. It is quite clear that any of these systems can realize a gait (very often such gait is not dynamically balanced), but our present study shows that the performances of such walking systems are essentially different and inapt to meet the requirements that are put before the humanoids in a human environment. The work points out the indispensability of the regular, fully dynamically balanced gait for the simultaneous realization of locomotion-manipulation activities, as well as for the walk in an unstructured environment.
Keywords: humanoid robot, regular gait, irregular gait, stability, dynamic balance, ZMP
Abstract: With the appearance of micromachined mechanical elements and nanotechnology, increased demand can be observed for coordinate measuring systems having submicron accuracy. Probes are major components of such a coordinate measuring machine. They contribute to a large extend to measurement uncertainty of the CMM. In this paper a new low cost design is presented. The moving element of the probe head consists of the stylus and a cross form intermediate body with a small aluminum enhanced mirror at each ends and at the center. The intermediate body is suspended on four springs made of beryllium-copper foils. The displacement of the probe tip is calculated from the displacement and the rotations of the mirrors measured by modified optical pick-ups.
Abstract: There is given a short overview of the monograph ”Aggregation Functions” (M. Grabisch, J. L. Marichal, R. Mesiar, E. Pap), Cambridge University Press (in press) with more details from introductory Chapters 1 and 2.
Keywords: aggregation function, continuity, absolute continuity, Lipschitz condition, conjunction, disjunction, internality
Abstract: Surface morphology of GaAs (001) surface after electrochemical layer removal with the help of image processing was investigated. The surface pattern of GaAs shown fractal behaviour under non-selective etching conditions. The morphological surface study was carried out using digital image processing of scanning electron microscope data. The surface patterns were segmented by the so called grade of membership method. Fractal behaviour of the surface morphology was established using the box counting method.
Keywords: GaAs, surface morphology, electrochemistry, grade of membership fractal
Abstract: This paper proposes that pathfinding for mobile robots, in unknown environment, be based on extracting 3D features of an object using 2D image edge detection and infrared (IR) distance measuring sensor. Standard VGA color camera gives very good results only in environment that is very well illuminated. Our solution is based on IR camera which enables robot to navigate between obstacles even in complete darkness.
Keywords: path finding, edge detection, Sobel
Abstract: This article presents a simple method on how to implement a super-resolution based video enhancement technique in .NET using the functions of the OpenCV library. First, we outline the goal of this project and after that, a short review of the steps of superresolution technique is given. As a part of the discussion about the implementation itself, the general design aspects are detailed in short. Then, the different optical flow algorithms are analyzed and the super-resolution calculation of omnidirectional image sequences is discussed. After all that, the achieved results can be seen and finally, a short general conclusion can be read. This paper is a revision of our previous work . In this edition, we focus on the super-resolution of omnidirectional image sequences rather than the technological issues that were discussed in our previous article. Further information about the implementation and wrapper development can be found in [1 and 12].
Keywords: super-resolution, optical flow, omnidirectional vision, OpenCV wrapper
Abstract: This paper describes fuzzy logic control of induction generator speed in wind turbine application. The aim of fuzzy controller is to establishe maximum power delivery to the grid from available wind power. Fully-controlled wind turbine which consists of induction generator and back-to-back converter is under estimate. This configuration has full control over the electrical torque, full control of the speed, and also supports reactive power compensation and operation under grid disturbances. Fuzzy logic control alorithm has been aplied and validated by detailed simulation in MATLAB/Simulink. All system components have been described in detail.
Abstract: Our present work is to examine and offer an automatic electronic circuit construction solution which – using electronic devices and Field Programmable Analog Arrays (FPAA) – enables us to form analogue circuits. The automatic computer-assisted construction is an old endeavor in the electronic development of electronic circuit constructional tasks. The currently used constructional systems are integrated devices which contain simulation modules based on circuit drawings and component parameters. It is relevant in printed circuit construction as well, where wiring geometry can be modified depending on the examined (EMC, thermo-technical, transmission\ldots, etc.) parameters. To achieve this goal, new simulation and circuit generation processes are required, which select the most appropriate solutions regarding the parametrical description of electronic topology.
Keywords: symmetric pseudo-operations, non-monotonic set function, general fuzzy integral, asymmetric Choquet integral
Abstract: In the case of using content-based image retrieval algorithms is very important that the image database let be classified in certain sense. One possible way of classification is the face detection based classification.
In this paper a face detection algorithm is presesented which was used in color images, and some classification methods and these usage for the classification of image database are reviewed.
Keywords: face detection, image classification, image retrieval