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Input Constraints (input + constraint)
Selected AbstractsStable robust feedback control system design for unstable plants with input constraints using robust right coprime factorizationINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 18 2007Mingcong Deng Abstract A stable robust control system design problem for unstable plants with input constraints is considered using robust right coprime factorization of nonlinear operator. For obtaining strong stability of the closed-loop system of unstable plants with input constraints, a design scheme of robust nonhyphen-linear control system is given based on robust right coprime factorization. Some conditions for the robustness and system output tracking of the unstable plant with input constraints are derived. Numerical examples are given to demonstrate the validity of the theoretical results. Copyright © 2007 John Wiley & Sons, Ltd. [source] Output regulation of discrete-time linear plants subject to state and input constraintsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2003Guoyong Shi Abstract Discrete-time output regulation of linear systems with state and/or input constraints on magnitude is considered. Structural properties of linear plants are identified under which the so-called constrained semi-global and global output regulation problems are solvable. As in the case of continuous-time systems, an important aspect of our development is a taxonomy of constraints showing a clear relationship between the constraint types and the output regulation results. Solvability conditions are developed for semi-global and global output regulation problems. Appropriate regulators are constructed for problems that are solvable. Copyright © 2003 John Wiley & Sons, Ltd. [source] Distributed model predictive control of nonlinear process systemsAICHE JOURNAL, Issue 5 2009Jinfeng Liu Abstract This work focuses on a class of nonlinear control problems that arise when new control systems which may use networked sensors and/or actuators are added to already operating control loops to improve closed-loop performance. In this case, it is desirable to design the pre-existing control system and the new control system in a way such that they coordinate their actions. To address this control problem, a distributed model predictive control method is introduced where both the pre-existing control system and the new control system are designed via Lyapunov-based model predictive control. Working with general nonlinear models of chemical processes and assuming that there exists a Lyapunov-based controller that stabilizes the nominal closed-loop system using only the pre-existing control loops, two separate Lyapunov-based model predictive controllers are designed that coordinate their actions in an efficient fashion. Specifically, the proposed distributed model predictive control design preserves the stability properties of the Lyapunov-based controller, improves the closed-loop performance, and allows handling input constraints. In addition, the proposed distributed control design requires reduced communication between the two distributed controllers since it requires that these controllers communicate only once at each sampling time and is computationally more efficient compared to the corresponding centralized model predictive control design. The theoretical results are illustrated using a chemical process example. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Incorporating a class of constraints into the dynamics of optimal control problemsOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 6 2009K. Graichen Abstract A method is proposed to systematically transform a constrained optimal control problem (OCP) into an unconstrained OCP, which can be treated in the standard calculus of variations. The considered class of constraints comprises up to m input constraints and m state constraints with well-defined relative degree, where m denotes the number of inputs of the given nonlinear system. Starting from an equivalent normal form representation, the constraints are incorporated into a new system dynamics by means of saturation functions and differentiation along the normal form cascade. This procedure leads to a new unconstrained OCP, where an additional penalty term is introduced to avoid the unboundedness of the saturation function arguments if the original constraints are touched. The penalty parameter has to be successively reduced to converge to the original optimal solution. The approach is independent of the method used to solve the new unconstrained OCP. In particular, the constraints cannot be violated during the numerical solution and a successive reduction of the constraints is possible, e.g. to start from an unconstrained solution. Two examples in the single and multiple input case illustrate the potential of the approach. For these examples, a collocation method is used to solve the boundary value problems stemming from the optimality conditions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Potentiel de Productivité et Efficacité Technique du Secteur Agricole en AfriqueCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 3 2006Joachim Binam Nyemeck This study utilizes frontier metaproduction functions to analyze inter-region agricultural productivity differences. Technical efficiency scores are examined through estimation of stochastic frontiers for 16 African countries divided into three different regions (West Africa, East and Southern Africa, and North Africa) from 1970 to 2001. The idea is to explore the differences in efficiency and technological gaps of agricultural sector. Apart of common traits that characterize African agricultural sector, countries exhibit national and regional specificities. These diversities are such that it is difficult to make valuable generalizations. It appears from the results that: in West Africa, the level of technology is relatively good, meaning that there is no problem of input constraints. By contrast, the efficiency with which inputs are used is very low. The situation is very different in the East and Southern Africa, with the level of technology relatively low and appreciable technical level. At least, the North Africa countries make a performing mixture between technology and efficiency. Cette étude utilise les Meta frontières de production pour analyser les différences inter-régionales de la productivité agricole. Les niveaux d'efficacité technique sont examinées par l'estimation des frontières stochastiques de 16 pays africains regroupés en trois régions (l'Afrique de l'Ouest, l'Afrique de l'Est et Australe, et l'Afrique du Nord), sur une période allant de 1970 à 2001. L'idée étant d'explorer les différences d'efficacité et les écarts technologiques du secteur agricole. Au-delà des simples traits communs qui caractérisent le secteur agricole africain, on trouve des expériences nationales et régionales dont il est difficile, du fait de leur grande diversité, de tirer des généralisations valables. Des résultats de l'étude, il ressort que: en Afrique de l'Ouest, le niveau technologique est relativement satisfaisant, traduisant le fait que la présence des inputs ne représente pas une contrainte. Par contre le niveau d'efficacité avec lequel ces intrants sont utilisés est assez faible. La situation est tout autre en Afrique de l'Est et Australe avec un niveau technologique relativement faible et un niveau d'efficacité appréciable. L'Afrique du nord enfin fait un savant dosage entre efficacité et technologie. [source] | ||||||||||