Showing 1 to 10 of 3742 matching Articles
Results per page:
By
Sevastyanov, S. V.; Sitters, R. A.; Fishkin, A. V.
3 Citations
We present hardness and approximation results for the problem of preemptive scheduling of n independent jobs on m identical parallel machines subject to a migration delay d with the objective to minimize the makespan. We give a sharp threshold on the value of d for which the complexity of the problem changes from polynomial time solvable to NPhard. Next, we give initial results supporting a conjecture that there always exists an optimal schedule with at most m − 1 job migrations. Finally, we provide a O(n) time (1 + 1/log_{2}n)approximation algorithm for m = 2.
more …
By
Grigor’ev, I. S.; Danilina, I. A.
2 Citations
Problems of threedimensional trajectory optimization of transfers for stage spacecraft and spacecraft with auxiliary fuel tank (AFT) from the low circuit orbit of the Earth’s artificial satellite (EAS) into the geostationary orbit and optimization problems of fuel distribution in stages or tanks are solved. Control of spacecraft motion is conducted by jet engines of bounded thrust; stage engines can have different characteristics, i.e., thrusttoweight ratio and specific thrust. The used stage or auxiliary fuel tank is detached on the passive segment. Detachment is considered to be instantaneous, if the spacecraft position and velocity do not change at the detachment instant and the mass decreases in jumping mode. The mass of detached tanks is considered proportionate to the mass of consumed fuel; the mass of engine and auxiliary constructions, to thrusttoweight ratio. The useful mass of the spacecraft with the limited time of transfer is maximized. The considered problems are intricate nonlinear optimal control problems with discontinuous phase variables. They are formalized as optimal control problems by a union of dynamic systems and are solved on the basis of the corresponding principle of the maximum. In this paper, boundaryvalue problems of the principle of the maximum are numerically solved by the shooting method. The choice of computing schemes of the shooting method and solution to systems of nonlinear equations is conducted by using a series of auxiliary problems.
more …
By
Tsykunov, A. M.
A dynamic controller for controlling linear systems under a priori uncertainty of their parameters when only scalar inputsoutputs are measurable is designed.
By
Stetsyura, G. G.
1 Citations
Fractal lines and grouped operations are considered for the use in multiprocessor computers with a rearrangeable structure of lines, which execute evolutionary algorithms. The regularity of fractal lines facilitates the subdivision of the common structure into portions and the performance of grouped operations. Grouped operations enable many processors to interact within one operation for obtaining the common result, which simplifies and accelerates the elaboration of collective decisions.
more …
By
Furtat, I. B.
We design a control algorithm for objects under parametric uncertainty, external bounded disturbances, and saturation of the controlled signal. We assume that the object model is described by a linear dynamical system with arbitrary relative degree and several inputs and outputs. The developed algorithm provides approximate tracking of the output of the control object for a reference signal. We obtain sufficient stability conditions for the closed system that depend on object parameters, reference model, and the controller. We show modeling results that illustrate the operation of the developed scheme.
more …
By
Lukin, D. V.; Lyakhov, A. I.
In the wireless networks controlled by the IEEE 802.16 protocol, the subscriber stations reserve the common channel using the mechanism of competitive access. Developed was an analytical model for studying the efficiency of transmission of the upward traffic in IEEE 802.16 network including the processes of channel reservation by the algorithm of multiple random access and packet transmission.
more …
By
Dombrovskii, V. V.; Lyashenko, E. A.
12 Citations
A quadratic control for discrete stochastic systems with random parameters and additive and multiplicative noises dependent on state and controls is studied. Equations for the optimal linear static and dynamic output controllers are derived. The controllers are robust to the type of the distribution of the vector of random parameters. The results are applied to dynamic investment portfolio optimization.
more …
By
Grigoriev, I. S.; Zapletin, M. P.
4 Citations
We consider the problem of constructing Pontryagin extremals for the optimal control task of asteroid flyby. This problem is a part of a large optimization problem posed on the Third Global Trajectory Optimization Competition. Information about the competition and problem details can be found at
http://www2.polito.it/eventi/gtoc3
.
more …
By
Pyrkin, A. A.; Aranovskiy, S. V.; Bobtsov, A. A.; Kolyubin, S. A.; Nikolaev, N. A.
Show all (5)
1 Citations
Consideration was given to the problem of adaptive output control of the class of MIMO (Multiple Input Multiple Output) systems that are functionally and parametrically uncertain. An approach to the design of the control law ensuring stabilization of the MIMO nonlinear Lurie system, that is, a system consisting of the linear part (strictly minimumphase unit) and nonlinear static feedback unit, was proposed on the basis of the Fradkov theorem on feedback passification of linear systems.
more …
