This paper presents it combined genetic algorithm-fuzzy logic controller (GA-FLC) technique for constrained nonlinear programming problems. In the standard Genetic algorithms, the upper and lower limits of the search ...
详细信息
This paper presents it combined genetic algorithm-fuzzy logic controller (GA-FLC) technique for constrained nonlinear programming problems. In the standard Genetic algorithms, the upper and lower limits of the search regions Should be given by the decision maker in advance to the optimization process. In general it needlessly large search region is used in fear of missing the global Optimum Outside the search region. Therefore, if the search region is able to adapt toward a promising area during the optimization process, the performance of GA will be enhanced greatly. Thus in this work we tried to investigate the influence of the bounding intervals on the final result. The proposed algorithm is made of classical GA Coupled with FLC. This controller monitors the variation of the decision variables during process of the algorithm and modifies the boundary intervals to restart the next round of the algorithm. These characteristics make this approach well suited for finding optimal solutions to the highly NLP problems. Compared to previous works on NLP, our method proved to be more efficient in Computation time and accuracy of the final solution. (c) 2005 Elsevier Inc. All rights reserved.
We treat the sliding mode control problem by formulating it as a two phase problem consisting of reaching and sliding phases. We show that such a problem can be formulated as bicriteria nonlinear programming problem b...
详细信息
We treat the sliding mode control problem by formulating it as a two phase problem consisting of reaching and sliding phases. We show that such a problem can be formulated as bicriteria nonlinear programming problem by associating each of these phases with an appropriate objective function and constraints. We then scalarize this problem by taking weighted sum of these objective functions. We show that by solving a sequence of such formulated nonlinear programming problems it is possible to obtain sliding mode controller feedback coefficients which yield a competitive performance throughout the control. We solve the nonlinear programming problems so constructed by using the modified subgradient method which does not require any convexity and differentiability assumptions. We illustrate validity of our approach by gencrating a sliding mode control input function for stabilization of an inverted pendulum. (c) 2005 Elsevier Inc. All rights reserved.
A closed-form solution for time-optimal detumbling control of a rigid spacecraft with the constraint on maintaining the Euclidean norm of the braking torques below a prescribed value has been reported. The problem of ...
详细信息
A closed-form solution for time-optimal detumbling control of a rigid spacecraft with the constraint on maintaining the Euclidean norm of the braking torques below a prescribed value has been reported. The problem of designing fast detumbling maneuvers for a spacecraft with restricted actuation torques arises in many space applications. The problem of time-optimal detumbling control of rigid spacecraft is formulated as a nonlinear programming and solved numerically by using an iterative procedure. Optimal detumbling of multibody systems has been considered for spacecraft possessing appendages, such as a robotic manipulator, with well-controlled motion relative to the spacecraft to achieve detumbling. The optimal controller can be applied to drive a tumbling axisymmetric spacecraft to a final spin-stabilized state in minimum time given the limitation of an actuator torque.
Line search methods are proposed for nonlinear programming using Fletcher and Leyffer's filter method [ Math. Program., 91 ( 2002), pp. 239 - 269], which replaces the traditional merit function. Their global conve...
详细信息
Line search methods are proposed for nonlinear programming using Fletcher and Leyffer's filter method [ Math. Program., 91 ( 2002), pp. 239 - 269], which replaces the traditional merit function. Their global convergence properties are analyzed. The presented framework is applied to active set sequential quadratic programming (SQP) and barrier interior point algorithms. Under mild assumptions it is shown that every limit point of the sequence of iterates generated by the algorithm is feasible, and that there exists at least one limit point that is a stationary point for the problem under consideration. A new alternative filter approach employing the Lagrangian function instead of the objective function with identical global convergence properties is briefly discussed.
In grids with high wind power penetration, the System Operator may curtail the power injected at critical moments for security reasons. An intermediate operator can optimize this power reduction for a group of wind fa...
详细信息
In grids with high wind power penetration, the System Operator may curtail the power injected at critical moments for security reasons. An intermediate operator can optimize this power reduction for a group of wind farms under its control, attending to their controllability. In this way, resources may be used efficiently, and in cooperation with the system operation. In this paper, an optimization-based procedure is proposed to allocate the power reductions among the wind farms of a region. Application examples based on the Spanish situation are shown, because in that country, these intermediate entities (called Delegated Dispatches) are about to begin their full operation. Copyright (C) 2008 John Wiley g, Sons, Ltd.
In this paper, we discuss the eigenvalue complementarity problem (EiCP) where at least one of its defining matrices is asymmetric. A sufficient condition for the existence of a solution to the EiCP is established. The...
详细信息
In this paper, we discuss the eigenvalue complementarity problem (EiCP) where at least one of its defining matrices is asymmetric. A sufficient condition for the existence of a solution to the EiCP is established. The EiCP is shown to be equivalent to finding a global minimum of an appropriate merit function on a convex set defined by linear constraints. A sufficient condition for a stationary point of this function on to be a solution of the EiCP is presented. A branch-and-bound procedure is developed for finding a global minimum of this merit function on . In addition, a sequential enumerative algorithm for the computation of the minimum and the maximum eigenvalues is also discussed. Computational experience is included to highlight the efficiency and efficacy of the proposed methodologies to solve the asymmetric EiCP.
In this work, the problem of optimization of low-thrust reconfiguration maneuvers for spacecraft flying in formation is addressed. The problem is stated as the solution of an optimal control problem in which an object...
详细信息
In this work, the problem of optimization of low-thrust reconfiguration maneuvers for spacecraft flying in formation is addressed. The problem is stated as the solution of an optimal control problem in which an objective function related to controls is minimized, satisfying a series of constraints on the trajectory that are both differential and algebraic. The problem has been faced by transcribing the differential constraints into a nonlinear programming problem with a parallel multiple-shooting method. The resulting problem has been solved with an interior point method. The method that has been developed is particularly suited for the solution of problems in which the trajectory is constrained with a great number of inequalities on both states and controls. The method has been applied to the design of reconfiguration maneuvers for spacecraft flying in formation;for which the collision avoidance issue leads to the imposition of a large number of inequalities on states derived from the minimum distance constraint.
Future solar sail and solar power satellite missions will consider using centrifugal forces for deployment and stabilization. Some of the main advantages with spin deployment are that the significant forces are in the...
详细信息
Future solar sail and solar power satellite missions will consider using centrifugal forces for deployment and stabilization. Some of the main advantages with spin deployment are that the significant forces are in the plane of rotation, and a relatively simple control can be used and the tension in the membrane or web can be adjusted by the spin rate. Existing control strategies seem to either consume excessive energy or cause oscillations. In this study, control laws are derived from the solution to relevant optimal control problems and existing controls. The derived control laws are used in deployment simulations with both simple analytical three-degree-of-freedom models and a fully-three-dimensional finite element model. The results indicate that the derived control laws can be used to minimize the energy consumption and oscillations as for an optimal control, yet retain the simplicity of previous control laws.
As noted by Wachter and Biegler (Ref. 1), a number of interior-point methods for nonlinear programming based on line-search strategy may generate a sequence converging to an infeasible point. We show that, by adopting...
详细信息
As noted by Wachter and Biegler (Ref. 1), a number of interior-point methods for nonlinear programming based on line-search strategy may generate a sequence converging to an infeasible point. We show that, by adopting a suitable merit function, a modified primal-dual equation, and a proper line-search procedure, a class of interior-point methods of line-search type will generate a sequence such that either all the limit points of the sequence are KKT points, or one of the limit points is a Fritz John point, or one of the limit points is an infeasible point that is a stationary point minimizing a function measuring the extent of violation to the constraint system. The analysis does not depend on the regularity assumptions on the problem. Instead, it uses a set of satisfiable conditions on the algorithm implementation to derive the desired convergence property.
This research investigates strategies to enable a deputy satellite to hover within a defined volume fixed in the vicinity of a chief satellite in a circular orbit for an extended period of time. Previous research deve...
详细信息
This research investigates strategies to enable a deputy satellite to hover within a defined volume fixed in the vicinity of a chief satellite in a circular orbit for an extended period of time. Previous research developed initial methodologies for maintaining restricted teardrop hover orbits that exist in a plane fixed within the chief's local reference frame. These methods use the natural drift of the deputy satellite in the relative frame and impulsive thrust to keep the deputy in a bounded volume relative to the chief, but do not address fuel optimality. This research extends and enhances that work by finding the optimal trajectories produced with discrete thrusts that minimize fuel spent per unit time and stay within the user-defined volume, thus providing a practical hover capability in the vicinity of the chief. The work assumes that the Clohessy-Wiltshire closeness assumption between the deputy and chief is valid. Using the new methodology developed in this work, feasible closed- and nonclosed-relative orbits are found and evaluated based on a fuel criterion and are compared with an easily calculated continuous-thrust baseline. It is shown that in certain scenarios (generally corresponding to a smaller total time of flight) a discrete-thrust solution provides a lower overall fuel cost than a continuous-thrust solution. A simple check is proposed that enables the mission planner to make the correct strategy choice.
暂无评论