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Journal ArticleDOI

Theory and applications of optimal control problems with multiple time-delays

01 Oct 2013-Journal of Industrial and Management Optimization (American Institute of Mathematical Sciences)-Vol. 10, Iss: 2, pp 413-441
TL;DR: In this article, a discretization method is presented by which the delayed control problem is transformed into a nonlinear programming problem, and the associated Lagrange multipliers provide a consistent numerical approximation for the adjoint variables of the delayed optimal control problem.
Abstract: In this paper we study optimal control problems with multiple time delays in control and state and mixed type control-state constraints. We derive necessary optimality conditions in the form of a Pontryagin type Minimum Principle. A discretization method is presented by which the delayed control problem is transformed into a nonlinear programming problem. It is shown that the associated Lagrange multipliers provide a consistent numerical approximation for the adjoint variables of the delayed optimal control problem. We illustrate the theory and numerical approach on an analytical example and an optimal control model from immunology.
Citations
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Journal ArticleDOI
TL;DR: This work seems to be the first to consider such time-delays for TB and apply time-delay optimal control to carry out the optimality analysis.
Abstract: We introduce delays in a tuberculosis (TB) model, representing the time delay on the diagnosis and commencement of treatment of individuals with active TB infection. The stability of the disease free and endemic equilibriums is investigated for any time delay. Corresponding optimal control problems, with time delays in both state and control variables, are formulated and studied. Although it is well-known that there is a delay between two to eight weeks between TB infection and reaction of body's immune system to tuberculin, delays for the active infected to be detected and treated, and delays on the treatment of persistent latent individuals due to clinical and patient reasons, which clearly justifies the introduction of time delays on state and control measures, our work seems to be the first to consider such time-delays for TB and apply time-delay optimal control to carry out the optimality analysis.

64 citations


Cites background or methods from "Theory and applications of optimal ..."

  • ...], λ˙L 1(t) = −HL1[t], λ˙L 2(t) = −HL2[t], and λ˙I(t) = −HI[t]+χ[0,T−d I]Hy3[t+dI], where subscripts denote partial derivatives and χ[0,T−d I] is the characteristic function in the interval [0,T −dI] [10]. Note that only the equation for λ˙ I(t) contains the advanced time t+ dI. Since the terminal state x(T) is free, the transversality conditions are λS(T) = λL1(T) = λI(T) = λL2(T) = 0. (20) To charac...

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  • ...owerful optimization solvers. We use the Interior-Point optimization solver IPOPT developed by Wachter and Biegler [30]. Details of discretization methods for delayed control problems may be found in [10]. The subsequent computations for the terminal time tf = 5 have been performed with N = 2500 to N = 5000 grid points using the trapezoidal rule as integration method. Choosing the error tolerance tol ...

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  • ...15), initial conditions (16) and control constraints (17). Necessary optimality conditions for optimal control problems with multiple time delays in control and state variables may be found, e.g., in [10]. Here, we discuss the Maximum Principle in order to display the controls and the switching functions in a convenient way. To define the Hamiltonian forthe delayedcontrolproblem, we introduce the delay...

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Journal ArticleDOI
TL;DR: The numerical simulations show that the combination of immuno-chemotherapy protocol reduces the tumour load in few months of therapy.

51 citations

Journal ArticleDOI
TL;DR: In this article, the authors formulated an alcohol quitting model in which they considered the impact of distributed time delay between contact and infection process by characterizing dynamic nature of alcoholism behaviours, and they generalized the infection rate to the general case, simultaneously, they considered two different control strategies.
Abstract: In this paper, we formulate an alcohol quitting model in which we consider the impact of distributed time delay between contact and infection process by characterizing dynamic nature of alcoholism behaviours, and we generalize the infection rate to the general case, simultaneously, we consider two different control strategies. Next, we discuss the qualities on the model, the existence and boundedness as well as positivity of the equilibrium are involved. Then, under certain proper conditions, we construct appropriate Lyapunov functionals to prove the global stability of alcohol free equilibrium point $E_{0}$ and alcoholism equilibrium $E^{*}$ respectively. Furthermore, the optimal control strategies are derived by proposing an objective functional and using classic Pontryagin's Maximum Principle. Numerical simulations are conducted to support our theoretical results derived in optimal control.

39 citations


Cites background or methods from "Theory and applications of optimal ..."

  • ...A necessary condition for optimal control problems can be found in [13] and it’s applications [11, 12]....

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  • ...Then, we consider a range of issues related to the delay optimal control with the method of Pontryagin’s Maximum Principle similar to the way as what the documents [11, 12] did....

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Journal ArticleDOI
TL;DR: A new computational approach is proposed, which combines the control parameterization technique with a hybrid time-scaling strategy, for solving a class of nonlinear time-delay optimal control problems with canonical equality and inequality constraints.
Abstract: In this paper, we consider a class of nonlinear time-delay optimal control problems with canonical equality and inequality constraints. We propose a new computational approach, which combines the control parameterization technique with a hybrid time-scaling strategy, for solving this class of optimal control problems. The proposed approach involves approximating the control variables by piecewise constant functions, whose heights and switching times are decision variables to be optimized. Then, the resulting problem with varying switching times is transformed, via a new hybrid time-scaling strategy, into an equivalent problem with fixed switching times, which is much preferred for numerical computation. Our new time-scaling strategy is hybrid in the sense that it is related to two coupled time-delay systems--one defined on the original time scale, in which the switching times are variable, the other defined on the new time scale, in which the switching times are fixed. This is different from the conventional time-scaling transformation widely used in the literature, which is not applicable to systems with time-delays. To demonstrate the effectiveness of the proposed approach, we solve four numerical examples. The results show that the costs obtained by our new approach are lower, when compared with those obtained by existing optimal control methods.

39 citations


Cites background from "Theory and applications of optimal ..."

  • ...In particular, Many theoretical results are now available in the literature, which include necessary optimality conditions for time-delay optimal control problems [5,7]....

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Journal ArticleDOI
TL;DR: A novel transformation procedure is developed that converts a given time-delay system into an equivalent system – defined on a new time horizon – in which the control switching times are fixed, but the dynamic system contains multiple variable time delays expressed in terms of the durations between the switching times for each of the approximate control functions in the original time horizon.

39 citations

References
More filters
Journal ArticleDOI
TL;DR: A comprehensive description of the primal-dual interior-point algorithm with a filter line-search method for nonlinear programming is provided, including the feasibility restoration phase for the filter method, second-order corrections, and inertia correction of the KKT matrix.
Abstract: We present a primal-dual interior-point algorithm with a filter line-search method for nonlinear programming. Local and global convergence properties of this method were analyzed in previous work. Here we provide a comprehensive description of the algorithm, including the feasibility restoration phase for the filter method, second-order corrections, and inertia correction of the KKT matrix. Heuristics are also considered that allow faster performance. This method has been implemented in the IPOPT code, which we demonstrate in a detailed numerical study based on 954 problems from the CUTEr test set. An evaluation is made of several line-search options, and a comparison is provided with two state-of-the-art interior-point codes for nonlinear programming.

7,966 citations


Additional excerpts

  • ...[33, 34]....

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Book
01 Dec 1962
TL;DR: The fourth and final volume in this comprehensive set presents the maximum principle as a wide ranging solution to nonclassical, variational problems as discussed by the authors, which can be applied in a variety of situations, including linear equations with variable coefficients.
Abstract: The fourth and final volume in this comprehensive set presents the maximum principle as a wide ranging solution to nonclassical, variational problems. This one mathematical method can be applied in a variety of situations, including linear equations with variable coefficients, optimal processes with delay, and the jump condition. As with the three preceding volumes, all the material contained with the 42 sections of this volume is made easily accessible by way of numerous examples, both concrete and abstract in nature.

6,056 citations


Additional excerpts

  • ...[14, 20, 22, 25] assures the existence of a adjoint (costate) function Λ̂ ∈W 1,∞([0, h],R ·n), a multiplier λ0 ≥ 0, a multiplier function M̂ ∈ L∞([0, h],R ·p) and a vector ν̂ ∈ R(N−1)·n+q, ν̂ = (ν̂∗ 0 , ....

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Book
01 Jan 1993
TL;DR: An efficient translator is implemented that takes as input a linear AMPL model and associated data, and produces output suitable for standard linear programming optimizers.
Abstract: Practical large-scale mathematical programming involves more than just the application of an algorithm to minimize or maximize an objective function. Before any optimizing routine can be invoked, considerable effort must be expended to formulate the underlying model and to generate the requisite computational data structures. AMPL is a new language designed to make these steps easier and less error-prone. AMPL closely resembles the symbolic algebraic notation that many modelers use to describe mathematical programs, yet it is regular and formal enough to be processed by a computer system; it is particularly notable for the generality of its syntax and for the variety of its indexing operations. We have implemented an efficient translator that takes as input a linear AMPL model and associated data, and produces output suitable for standard linear programming optimizers. Both the language and the translator admit straightforward extensions to more general mathematical programs that incorporate nonlinear expressions or discrete variables.

3,176 citations


"Theory and applications of optimal ..." refers methods in this paper

  • ...To solve the optimization problem (NLP) in (40) – (43) numerically, we employ the programming language AMPL developed by Fourer, Gay and Kernighan [9] in conjunction with the optimization solvers LOQO by Vanderbei [31, 32] or IPOPT by Wächter et al....

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Book
01 Jan 1972

1,127 citations


"Theory and applications of optimal ..." refers background in this paper

  • ...[1, 3, 6, 7, 11, 13, 15, 16, 17, 21, 23, 26, 27, 28, 35]....

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  • ...In particular, Warga [35] presents a general approach for deriving necessary optimality conditions which is based on optimization theory in function spaces....

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  • ...We must admit that we could not translate the necessary conditions of Warga [35] in the presence of a practical example like the one in Section 6....

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Book
01 Jan 1966

1,021 citations


Additional excerpts

  • ...[14, 20, 22, 25] assures the existence of a adjoint (costate) function Λ̂ ∈W 1,∞([0, h],R ·n), a multiplier λ0 ≥ 0, a multiplier function M̂ ∈ L∞([0, h],R ·p) and a vector ν̂ ∈ R(N−1)·n+q, ν̂ = (ν̂∗ 0 , ....

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