A robust control framework for linear, time-invariant (LTI), spatially distributedsystems is outlined in this paper. We adopt an input-output approach which takes account of the spatially distributed nature of the in...
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A robust control framework for linear, time-invariant (LTI), spatially distributedsystems is outlined in this paper. We adopt an input-output approach which takes account of the spatially distributed nature of the input and output signals for such systems. The approach is a generalization of H-infinity control in the sense that the 2-norm (in both time and space) is used to quantify the size of signals. It is shown that a frequency-domain representation, in the form of a graph symbol, exists for every LTI, spatially distributed system under very mild assumptions. The graph symbol gives rise to left and right coprime representations if the system is also stabilizable. We investigate fundamental issues of feedback control such as feedback stability and robust stability to plant and/or controller uncertainty quantified in the gap-metric. This includes a generalization of the Sefton-Ober gap formula to the infinite-dimensional operator case. A design example in which an electrostatically destabilized membrane is feedback-stabilized concludes the paper.
While model-based controllers have been used successfully to control paper machines and other processes dominated by time delay, matching the model to the process gives poor load regulation over lag-dominant processes...
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While model-based controllers have been used successfully to control paper machines and other processes dominated by time delay, matching the model to the process gives poor load regulation over lag-dominant processes. An important class of lag-dominant processes including heat exchangers and distillation columns consists of distributed tags. A PID controller having time-delay compensation, while functionally similar to a model-based controller, is a much better load regulator, and twice as effective as a conventional PID controller on these processes. It is applied in this paper to regulate steam superheat temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.
This paper deals with the controller design for multi-layered piezoelectric structures. From the control point of view piezoelectric materials have the big advantage of making it easy to adjust the actuators and senso...
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This paper deals with the controller design for multi-layered piezoelectric structures. From the control point of view piezoelectric materials have the big advantage of making it easy to adjust the actuators and sensors to the special structural application that is to be controlled. It will be shown that an appropriate spatial shaping of the surface electrode of the piezoelectric actuator and sensor layers simplifies the control synthesis task to a great deal.
The paper deals with using optimal control methods for solving inverse problems of mathematical physics. In many cases this problem can be considered as an optimal control problem in which unknown control functions ar...
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The paper deals with using optimal control methods for solving inverse problems of mathematical physics. In many cases this problem can be considered as an optimal control problem in which unknown control functions are smooth elementsof initial or boundary conditions, coefficients of differential operators or right-hand sides of differential equations. A non-classic optimality condition and numerical algorithm for smooth boundary controls in semi-linear first-order hyperbolic systems are presented. The special feature of the general optimization problem for boundary conditions is non-validity of the classic optimality condition of Pontryagin's type. The suggested approach is based on special variations of admissible continuously differentiable controls. These variations can be applied for controls satisfying either restrictions of inclusion type or integral restrictions.
We derive formulas for normalized doubly coprime factorizations over H-infinity for a class of nonexponentially stabilizable systems. Using these results, we solve the problem of robust stabilization with respect to n...
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We derive formulas for normalized doubly coprime factorizations over H-infinity for a class of nonexponentially stabilizable systems. Using these results, we solve the problem of robust stabilization with respect to normalized coprime factor perturbations for a class of infinite-dimensional systems Sigma(A, B, B*, D), with finite-rank inputs and outputs and dissipative operator A;these systems are not exponentially stabilizable. We give a parameterization of controllers that achieve a given robustness margin. (C) 2000 Elsevier Science Ltd. All rights reserved.
We prove the maximum principle for an optimal control problem governed by the system y'(t) + A(t)y(t) = f (t, y(t), u(t)), u(t) epsilon U(t), with state constraint (y(0),y(T)) epsilon C subset of H x H, under thre...
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We prove the maximum principle for an optimal control problem governed by the system y'(t) + A(t)y(t) = f (t, y(t), u(t)), u(t) epsilon U(t), with state constraint (y(0),y(T)) epsilon C subset of H x H, under three different hypotheses: (H1) C is a convex set with nonempty interior;(H2) C = {y(0)} x C-0, with C-0 a convex set with nonempty interior in H and the evolution system satisfying compactness hypotheses;(H3) the periodic case y(0) = y(T), with the evolution system satisfying compactness hypotheses. We do not assume the controls to be bounded. We give some examples for distributed control problems.
This article proposes an infinite-dimensional state-space realization for linear filters with transfer function C-d(s)corresponds toC(o)((1 + s/omega(b))/ (1 + s/omega(h)))(d), where 0 < omega(b) < omega(h) and ...
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This article proposes an infinite-dimensional state-space realization for linear filters with transfer function C-d(s)corresponds toC(o)((1 + s/omega(b))/ (1 + s/omega(h)))(d), where 0 < omega(b) < omega(h) and 0 < d < 1. This exponentially stable representation is derived from the Taylor expansion at zero of the function (1 - z)(d), and is made up of an infinite number of first-order ordinary differential equations. Finite-dimensional approximations obtained by truncating this representation are shown to converge towards C-d in H-infinity. An example of feedback loop incorporating this approximation of C-d (car suspension) is presented, for which robustness of closed-loop resonance and step response overshoot vis-g-vis a Variation in the vehicle mass is achieved. (C) 2000 Elsevier Science Ltd. All rights reserved.
Rapid prototyping techniques employing thermal material deposition are intended for direct layered fabrication of functional products. This article introduces an analytical geometric model of such material transfer pr...
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Rapid prototyping techniques employing thermal material deposition are intended for direct layered fabrication of functional products. This article introduces an analytical geometric model of such material transfer processes, using superposition of unit deposition distributions, composed of elementary ellipsoidal primitives. The real-time surface geometry model, with its deposition features identified by in-process height measurements, is used for Smith-prediction of the material shape in the deposition region that is inaccessible to sensing. Thus, a distributed-parameter geometry control scheme is established to obtain a desired surface topology, by modulating the feed and motion of a moving mass source. This is obtained by dynamic surface shaping based on minimization of the geometric error-distribution by robust real-time optimization techniques.,A moving constrained polytope and a simulated annealing method at random sampled Surface locations are employed for this purpose. These methodologies are compared experimentally in geometric command following a robotic fused wire deposition plasma-arc welding station, using laser profilometric scanner sensing.
Concurrent engineering requires designers to share information that can be incomplete or contradictory. Information integrity is even more important when this dynamic network crosses company borders to include custome...
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Concurrent engineering requires designers to share information that can be incomplete or contradictory. Information integrity is even more important when this dynamic network crosses company borders to include customers and suppliers. This paper introduces a new modelling view based upon a parameter approach to maintain data validity and to support network dynamics. We then develop a four part implementation of this approach to co-ordination: a parameter checklist to provide engineering transparency, a parameter checklist with integrated processes for simultaneous engineering workflow, a logged parameter network for engineering change support, and a pre-defined parameter network for engineering organisation. The paper describes these four parts.
This paper discusses the boundary stabilization of a beam in free transversal vibration. We consider a nonlinear partial differential equation (PDE) and based on this model construct two linear control laws to stabili...
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This paper discusses the boundary stabilization of a beam in free transversal vibration. We consider a nonlinear partial differential equation (PDE) and based on this model construct two linear control laws to stabilize the system. The first control law guarantees globally convergent of states, while the second control law results into an exponentially stable closed loop. The latter control law is formed by feedbacking slope and velocity of beam’s boundary displacement. Numerical simulations are performed to test each of the control laws. The outcome of simulations are compared and discussed. The novelty of this article is that globally convergece and exponentially stabilization of transversely vibration in a beam is achieved, via boundary control without resorting to truncation of model.
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