Control Structure Constraints Research Articles

Optimal oxygen excess ratio tracking of proton exchange membrane fuel cell with uncertainty based on robust model predictive control strategy

AbstractTo address the challenge of tracking the optimal oxygen excess ratio (OER) in the cell stack cathode of the proton exchange membrane fuel cell (PEMFC), which is subject to norm‐bounded parameter uncertainty and frequent external perturbations, this manuscript provides a novel robust model predictive control strategy with a state feedback control structure and hard constraints. We aim to minimize the tracking error of OER while maximizing the net power under varying operational conditions of the PEMFC. Initially, a control‐oriented model for the air supply system is built and its accuracy is validated by comparing it with experimental results. Next, we construct the discrete state‐space equations for optimal control and employ the linear matrix inequality (LMI) method to transform the problem of difficult min‐max optimization solutions into a convex optimization problem with LMI constraints. Finally, the effectiveness of the proposed control algorithm is validated through simulation. The results demonstrate the strong robustness and superiority of the proposed controller against uncertainties in plant parameters for robust OER trajectory tracking. It improves the transient performance through robust precision tracking applications, which will eventually accelerate PEMFC commercialization.

Local Consistency Reinforcement for Enhancing Web Service Composition

Composing Web services to fulfill a user query remains one of the most challenging research problems due to its importance to the world economy. Several composition techniques have been proposed, but these techniques are becoming more and more expensive due to the tremendous growth of data over the internet, the intensive use of services, and the continuous changes of available services. The workflow-based Web service composition problem is an NP-complete problem, due mainly to the property of the workflow structuring the composition and the diversity of underlying constraints. Reinforcing local consistency is one of the well-known pre-processing techniques to reduce the complexity of most NP-complete problems. These techniques are mainly dedicated to binary constraint satisfaction problems. Therefore, only few researchers devoted their efforts toward reinforcing some level of local consistency on Web service composition problems that can be semantically defined in the Ontology Web Language for Web Services (OWL-S) control structure based constraints. The main goal of this paper is to propose a novel approach for reinforcing a reasonable level of local consistency, node and arc-consistency on any Web service composition problems. It is expected to provide a more up-to-date and realistic representation of any Web service composition problems without any user interactions, but with the ability to cope with any types of user’s query, such as incomplete, ambiguous, and others. This is due to the existence of several novel rules for reinforcing node and arc-consistency on all types of control structure constraints. Experiments were performed on random problems of different levels of complexity to evaluate the performance of the proposed approach.

Robust and adaptive control of three dimensional revolute-jointed cooperative manipulators for handling automation

This paper presents a study of the application of adaptive and robust control methods to a cooperative manipulation system which is developed for handling an object by three dimensional revolute-jointed manipulators. The adaptive control algorithm supports the parameter adaptive law that provides guaranteed stability for uncertain systems. In designing the robust control structure, contact and friction constraints for grasp and bearing conditions, structural flexibility or such similar factors as various unmodeled dynamics are considered as uncertainties that determine available values of control parameters. The novelty of results in the present paper is to define new control inputs using parametric uncertainties and the Lyapunov based theory of guaranteed stability of uncertain systems for handling objects in a spatial workspace.

制御構造制約のある<i>H</i><sub>∞</sub>制御問題に対するPID制御器設計

制御構造制約のある<i>H</i><sub>∞</sub>制御問題に対するPID制御器設計

Application of robust and adaptive control techniques to cooperative manipulation

This paper presents a study on application of adaptive and robust control methods to a cooperative manipulation system, which is developed for handling an object by two-link planar robot manipulators. Adaptive control algorithm ensures a parameter adaptation law satisfying the stability condition of uncertain systems. In designing robust control structure, contact and friction constraints for grasp and bearing conditions, structural flexibility or such similar factors as various unmodeled dynamics are considered as the uncertainties that determine the available values of control parameters. The novelty of results in the present paper is to define new control inputs using the parametric uncertainties and the Lyapunov-based theory of guaranteed stability of uncertain systems.

Gain optimization under control structure and stability region constraints

In this paper we consider the problem of optimizing the Frobenious norm of linear static feedback gains of a system with control structure and stability region constraints. We consider four important control structure constraints. These are: (i) static output feedback; (ii) constant gain feedback for multiple operating conditions; (iii) two-controller feedback; and (iv) decentralized feedback. We obtain a nonlinear programming formulation for the optimization problem and present an effective numerical approach for solving it. We include four examples.

Regional pole placement of multivariable systems under control structure constraints

Many controller realizations are structurally constrained. Some typical examples are static output feedback, constant gain feedback for multiple operating points of a system, two-controller feedback, and decentralized feedback. A general class of problems of regional pole placement of multivariable systems with such control structure constraints is considered and a unified numerical method is given to solve them. First a problem in this class is converted to a problem of solving a system of equalities and inequalities. This system is then solved by using a modified homotopy method. >

A Computational method for optimal L-Q regulation with simultaneous disturbance decoupling

The disturbance decoupling problem with stability (DDPS) and simultaneous infinite-time horizon optimal L-Q regulation, for continuous time-invariant linear systems, is formulated as a parameter optimization problem in L-Q regulators subject to control constraints imposed by the solution of DDPS. For computational solution of DDPS an efficient numerical procedure is proposed which gives the solution directly in the form of constraints on some parameters of the state-feedback matrix. For computational solution of the optimization problem a specialized hybrid descent method is proposed composed by a sequence of steps of modified Newton, Newton's and Quasi-Newton methods, suitable for problems with severe control structural constraints.

A homotopy approach for stabilizing single-input systems with control structure constraints

A linear state feedback gain vector used in the control of a single input dynamical system may be constrained because of the way feedback is realized. Some examples of feedback realizations which impose constraints on the gain vector are: static output feedback, constant gain feedback for several operating points of a system, and two-controller feedback. We consider a general class of problems of stabilization of single input dynamical systems with such structural constraints and give a numerical method to solve them. Each of these problems is cast into a problem of solving a system of equalities and inequalities. In this formulation, the coefficients of the quadratic and linear factors of the closed-loop characteristic polynomial are the variables. To solve the system of equalities and inequalities, a continuous realization of the gradient projection method and a barrier method are used under the homotopy framework. Our method is illustrated with an example for each class of control structure constraint.

A Frequency-Domain Suboptimal Controller Design Methodology for Linear Time-Invariant Systems With Controller Structural Constraints

A general and direct frequency-domain controller design methodology is presented for the design of suboptimal controllers for linear time-invariant systems with controller constraints. The method possesses advantages of simplicity in computer implementation and high efficiency in computation. Compared to previous approaches, this method can deal with both deterministic and stochastic disturbance problems and is applicable to systems with single or multiple control structural constraints

Integrated aeroelastic control optimization of laminated composite lifting surfaces

An integrated design approach for aeroelastic control of laminated composite lifting surfaces is formulated and demonstrated. The design is posed as an optimization problem to determine the optimum ply orientation angles and the control law which maximizes the aeroelastic instability speed of an actively controlled laminated composite lifting surface subject to limited control authority and structural frequency constraints. The lifting surface is simulated by a rectangular symmetric cantilevered composite plate. The formulation incorporates the Rayleigh-Ritz energy method, two-dimensional incompressible unsteady aerodynamic theory, optimum control design, and parameter optimization techniques. The particular control configuration consists of two point-force inputs applied at the leading and trailing edges of the lifting surface. In conjunction with the laminated compositeplate structural model, the control configuration effectively simulates an active flexible lifting surface. The effectiveness of the integrated approach is evaluated by comparing the optimum designs obtained by the method with designs obtained by a design procedure using aeroelastic tailoring and optimum control design as well but in a nonintegrated fashion. The illustrative studies resulted in a design that exhibited 102% higher aeroelastic instability speed with 294.4% lower control cost than designs obtained by a nonintegrated design procedure.

Vibration control of vehicle using the suboptimal output control with frequency-shaped cost functional.

The theory of linear suboptimal output feedback control with a frequency-shaped cost functional is applied to the vibration control of a vehicle model subjected to the input of the roughness of road surface. The feedback control gain is obtained with respect to a quadratic cost functional whose weighting matrices are functions of frequency. In the control using a frequency-shaped cost functional, the vibration frequency components can be reduced over specific bands of frequencies. Janeway and ISO human response curves with respect to acceleration are used to examine the vibration characteristics of a controlled vehicle model. The theory of the suboptimal control problem subjected to control structure constraints is applied to the synthesis of the output feedback control system. The theoretical and simulated results of the suboptimal output feedback control with a frequency-shaped cost functional are compared with those of the optimal control without a frequency-shaped cost functional and with state estimation using a Kalman filter.

Optimal dynamic vibration absorber for multi-degree-of-freedom systems. (Theoretical consideration in the case of random input).

This study deals with the optimization problem of a dynamic vibration absorber (DVA) for multi-degree-of-freedom systems subjected to random input with a dominant frequency. A new design method, which optimizes the parameter of DVA composed of such passive elements as a spring and a damper, is proposed. In this method, a suboptimization method based on the optimal control theory is applied for the optimization problem with control structure constraints due to passive elements. This method can consider the input information and the constraints on the stroke of DVAs. The vibration control performance of this method is investigated and is compared with the previous method, in numerical calculations. As a result, the usefulness of the present method is verified.

An optimal active dynamic vibration absorber for multidegrees-of-freedom systems. (A control using a reduced-order model and output feedback controls).

For the optimal control problem of an active dynamic vibration absorber (active DVA), this paper considers optimal control using a reduced-order model and three kinds of output feedback controls: the acceleration, velocity and displacement feedbacks of a main structure, adding together the displacement and velocity feedbacks of an active DVA. A unified approach for the optimization of the various controls of the active DVA for multidegrees-of-freedom systems is presented by identifying these as an optimization problem with control structure constraints. By carrying out numerical calculations and experiments, the characteristics of those controls were investigated and the usefulness of the present method was demonstrated.

Vibration control of a cylindrical off-shore structure.

In the design of an off-shore tower-like structure, which consists of two pipe sections assembled with universal joints and attached to a buried sinker block on the sea bed, enough buoyancy can be provided to keep the structure vertical. It is desirable to reduce both the structural oscillations due to random wave excitation forces and the reaction forces acting on the sinker block. Assuming that the motion of the structure is two-dimensional in the vertical plane, these design requirements can be effectively satisfied if appropriate restoring and damping coefficients are provided at the joints. In this study, we employed the statistical equivalent linearization technique to linearize a nonlinear fluid drag force, and applied a sub-optimal control theory with control structural constraints to obtain the optima stiffness and damping coefficients required at the joints after a trade-off between the rms values of the top displacement of structure and the rms values of control moments at the joints.

Optimal dynamic vibration absorber for multi-degree-of-freedom systems. Theoretical considerations on the case of random input.

This study deals with the optimization problem of dynamic vibration absorbers (D. V. A.) for multi-degree-of-freedom systems subjected to a random input with a dominant frequency. A new design method is proposed, which optimizes the parameter of D. V. A, composed of such passive elements as a spring and a damper. In this method, a suboptimization method based on the optimal control theory is applied for the optimization problem with the control structure constraints due to passive elements. This method can take into account the information about the input and the constraints on the stroke of D. V. A. The vibration control performance of this method is investigated and is compared to the previous method, in numerical calculations. As a result, the usefulness of the present method is verified.

The role of control processes and structural constraints in models of memory and social judgment

Six experiments examining a recent model of memory and social judgment are reported. In particular, the theoretical concept of a Work Space is examined in terms of both its structural properties and a variety of control processes that govern its operation. In Experiment 1, subjects were given information about a stimulus person and told that they would later be asked to recall it as well as possible. The length of the actual delay before recall and the length of the anticipated delay were factorially varied. Under short delay conditions, subjects anticipating a short delay recalled more of the information than those anticipating a long delay. The reverse was true under actual long delay conditions. Other results suggest that the anticipated length of the delay has an effect on processes related to both encoding and storage/retrieval. Experiments 2 and 3 demonstrate that, relative to no delay conditions, a long actual delay or a long anticipated delay produces polarization in social judgments. Both of these results are predicted by the model. Experiments 4–6 examine the effect of interpolated cognitive activity on memory and social judgment. As predicted by the model, relatively complicated cognitive activity leads to lower levels of recall and a greater polarization of judgments than less complicated intervening cognitive activity. It is argued that all of these results can be accounted for by the concept of a Work Space as a temporary repository devoted to the current information processing activities of the subject. It is thought that such a concept must be kept theoretically distinct from long-term memory. Implications of the results for models of memory and social judgment are discussed.

Stabilization of continuous and discrete linear systems subjected to control structure constraints†

In this paper we present a simple procedure for obtaining stabilization of a class of continuous and discrete linear systems subjected to control structure constraints, giving more attention to the so-called decentralized control. Contrary to the continuous case where much work has been done, the solution presented here for the discrete case is one of the first to be presented. Some examples are treated and, for the continuous case, some comparisons are made with other methods found in the literature.

Design of a Decentralized Load Frequency Controller Using Output Feedback

This paper presents a decentralized load frequency controller design for power systems using output feedback. Decentralization is achieved subject to multiple control structure constraints. Controller in each area is constrained to be a linear time-invariant combination of measurable output variables pertaining to that area only such as frequency deviation and area control error in each area. An iterative technique based on steepest descent gradient method is used for the solution of output feedback problem. Numerical results are obtained for a 2-area identical power systems consisting of thermal plants. It is shown that the decentralized controller implementation results in a system performance quite close to that obtained with centralized controller. Moreover, the system performance is significantly improved compared to that obtained with conventional controller.

Optimum control of an incomplete feedback system subject to control structure constraints (with discussions)

Optimum control of an incomplete feedback system subject to control structure constraints (with discussions)