Browsing by Subject "Mathematical techniques"

Now showing 1 - 12 of 12

Open Access
An analytical solution to the stance dynamics of passive spring-loaded inverted pendulum with damping
(World Scientific, 2009-09) Ankaralı, M. M.; Arslan, Ömür; Saranlı, Uluç
The Spring-Loaded Inverted Pendulum (SLIP) model has been established both as a very accurate descriptive tool as well as a good basis for the design and control of running robots. In particular, approximate analytic solutions to the otherwise non integrable dynamics of t his model provide principled ways in which gait controllers can be built, yielding invaluable insight into their stability properties. However, most existing work on the SLIP model completely disregards the effects of damping, which often cannot be neglected for physical robot platforms. In this paper, we introduce a new approximate analytical solution to the dynamics of this system that also takes into account viscous damping in the leg. We compare both the predictive performance of our approximation as well as the tracking performance of an associated deadbeat gait controller to similar existing methods in the literature and show t hat it significantly outperforms them in the presence of damping in the leg.
Open Access
Automated web services composition with the event calculus
(Springer, 2007-10) Aydın, Onur; Kesim-Çiçekli, Nihan; Çiçekli, İlyas
As the web services proliferate and complicate it is becoming an overwhelming job to manually prepare the web service compositions which describe the communication and integration between web services. This paper analyzes the usage of the Event Calculus, which is one of the logical action-effect definition languages, for the automated preparation and execution of web service compositions. In this context, abductive planning capabilities of the Event Calculus are utilized. It is shown that composite process definitions in OWL-S can be translated into Event Calculus axioms so that planning with generic process definitions is possible within this framework. © 2008 Springer-Verlag Berlin Heidelberg.
Open Access
Dynamic dispatching algorithm for scheduling machines and automated guided vehicles in a flexible manufacturing system
(Taylor & Francis, 1992) Sabuncuoglu, Ihsan; Hommertzheim, D. L.
In this paper, an on-line dispatching algorithm is proposed for the FMS scheduling problem. The algorithm uses various priority schemes and relevant information concerning the load of the system and the status of jobs in the scheduling process. This information is organized into hierarchical levels. The scheduling decision process is hierarchical in the sense that different decision criteria are applied sequentially to identify the most appropriate part and the machine to be served. The algorithm schedules the jobs on a machine or an automated guided vehicle (AGV) one at a time as the scheduling decision is needed (or as the status of the system changes). Performance of the proposed algorithm is compared with several machine and AGV scheduling rules by using the mean flow-time and the mean tardiness criteria. Simulation results indicate that the proposed algorithm produces significant mean flow-time and mean tardiness improvements over existing scheduling rules for a variety of experimental conditions.
Open Access
Effects of monetary policy on the long memory in interest rates: Evidence from an emerging market
(Elsevier, 2013) Sensoy, A.
We study the presence of long memory in a variety of interest rates in Turkey by time-varying generalized Hurst exponent. We reveal that adopting inflation targeting cause a sudden and considerable decrease in the long memory in interest rates. The improvement lasts till the collapse of Lehman Brothers in 2008 which is followed with an increased persistence in interest rates. Moreover, degree of long memory increases with maturity which is in contrast to economic theory.
Open Access
Fast ray tracing 3D models
(1991) İşler, Veysi; Özgüç, Bülent
In many computer graphics applications such as CAD, realistic displays have very important and positive effects on the users of the system. There are several techniques to generate realistic images with the computer. Ray tracing gives the most effective results by simulating the interaction of light with its environment. However, it may require an excessive amount of time to generate an image. In this article, we present a survey of methods developed to speed up the ray tracing algorithm and introduce a fast ray tracer to process a 3D scene that is defined by interactive 3D modeling software.
Open Access
Generalized scaling reductions and Painlevé hierarchies
(Elsevier, 2013) Gordoa, P. R.; Muğan, U.; Pickering, A.
We give an alternative derivation of two Painlevé hierarchies. This is done by constructing generalized scaling reductions of the Korteweg-de Vries and dispersive water wave hierarchies. We also construct a generalized scaling reduction of Burgers hierarchy. © 2013 Elsevier Inc. All rights reserved.
Open Access
Issues in commonsense set theory
(Springer/Kluwer Academic Publishers, 1994) Pakkan, M.; Akman, V.
The success of set theory as a foundation for mathematics inspires its use in artificial intelligence, particularly in commonsense reasoning. In this survey, we briefly review classical set theory from an AI perspective, and then consider alternative set theories. Desirable properties of a possible commonsense set theory are investigated, treating different aspects like cumulative hierarchy, self-reference, cardinality, etc. Assorted examples from the ground-breaking research on the subject are also given. © 1995 Kluwer Academic Publishers.
Open Access
Multi-dimensional state smoothing in the presence of non-linear interference
(Taylor & Francis, 1989) Demirbas, K.
Component-by-component state smoothing is discussed for multi-dimensional dynamic systems with non-linear random interference such as jamming. Each component of the observation model is a non-linear function of only one state component, arbitrary random interference, and observation noise. Each state component is first approximated by a finite state machine and then, using the Viterbi decoding algorithm of information theory, the state components are sequentially smoothed in parallel. This results in a memory reduction for the implementation of the state smoothing. Simulation results have shown that the proposed scheme performs well, whereas the classical estimation schemes cannot be used, in general, to estimate the states of dynamic models with arbitrary random interference. © 1989 Taylor & Francis Group, LLC.
Open Access
A Note on Robust Stability Bounds
(IEEE, 1989) Sezer, M. E.; Siuak, D. D.
The purpose of this note is to comment on stability robustness bounds for linear systems with multiple uncertain parameters, which were obtained via Lyapunov functions. Simple examples are used to illustrate the effects of the choice of functions and corresponding majorizations. © 1989 IEEE
Open Access
Optimal control for a class of partially observed bilinear stochastic systems
(IEEE, 1990) Dabbous, Tayel E.
An alternative formulation is presented for a class of partially observed bilinear stochastic control problems which is described by three sets of stochastic differential equations: one for the system to be controlled, one for the observer, and one for the control process which is driven by the observation process. With this formulation, the stochastic control problem is converted to an equivalent deterministic identification problem of control gain matrices. Using standard variation arguments, the necessary conditions of optimality on the basis of which the optimal control parameters can be determined are obtained.
Open Access
Representing objects as rays, or how to pile up an octree?
(Elsevier, 1989) Akman, V.; Franklin, Wm. R.
Quadtrees, octrees, and in general k-trees have established themselves as useful hierarchical data structures in computer graphics, image processing, and solid modeling. A fundamental operation in a system based on k-trees is the construction of a k-tree. Here, we review a new way of doing this operation. Basically, we have invented a method to store an object as a set of rays and an algorithm for converting such a set into a k-tree. (For example, in 3D a ray is a thin parallelepiped.) The algorithm is conceptually simple, works for any k, and piles up, using an approach we call stacking, a k-tree from the rays very fast. It produces a minimal k-tree and does not lead to intermediate storage swell. For large-scale realistic objects, which consist of many thousands of rays, the algorithm debunks the "expensive octree creation" myth. © 1989.
Open Access
Set of open-loop block-diagonalizers of transfer matrices
(Taylor & Francis, 1989) Özgüler, A. B.; Eldem, V.
The set of open-loop (right) block-diagonalizers of a given p x m transfer matrix 2, with specified block sizes, is studied. A characterization of this set is obtained in terms of a 'maximal' open-loop block-diagonalizer and a minimal proper basis of the kernel of 2. The relevance of the results to some non-interacting control problems is pointed out. In particular, the results obtained yield a minimum delay solution to the block-decoupling problem using dynamic state feedback. © 1989 Taylor & Francis Group, LLC.