On computational algorithms for pole assignment

A number of computationally reliable direct methods for pole assignment by feedback have recently been developed. These direct procedures do not necessarily produce robust solutions to the problem, however, in the sense that the assigned poles are insensitive to perturbalions in the closed-loop system. This difficulty is illustrated here with results from a recent algorithm presented in this TRANSACTIONS and its causes are examined. A measure of robustness is described, and techniques for testing and improving robustness are indicated.     

Globally convergent algorithms for robust pole assignment by statefeedback

It is observed that an algorithm proposed in 1985 by Kautsky, Nichols, and Van Dooren (KNV) amounts to maximizing, at each iteration, the determinant of the candidate closed-loop eigenvector matrix X with respect to one of its columns (with unit-length constraint), subject to the constraint that it remains an achievable closed-loop eigenvector matrix. This interpretation is used to prove convergence of the KNV algorithm. It is then shown that a more efficient algorithm is obtained if det (X) is concurrently maximized with respect to two columns of X, and such a scheme is easily extended to the case where the eigenvalues to be assigned include complex conjugate pairs. Variations exploiting the availability of multiple processors are suggested. Convergence properties of the proposed algorithms are established. Their superiority is demonstrated numerically     

A framework for and empirical study of algorithms for traffic assignment

Traffic congestion is an issue in most cities worldwide. Transportation engineers and urban planners develop various traffic management projects in order to solve this issue. One way to evaluate such projects is traffic assignment (TA). The goal of TA is to predict the behaviour of road users for a given period of time (morning and evening peaks, for example). Once such a model is created, it can be used to analyse the usage of a road network and to predict the impact of implementing a potential project. The most commonly used TA model is known as user equilibrium, which is based on the assumption that all drivers minimise their travel time or generalised cost. In this study, we consider the static deterministic user equilibrium TA model.The constant growth of road networks and the need of highly precise solutions (required for select link analysis, network design, etc.) motivate researchers to propose numerous methods to solve this problem. Our study aims to provide a recommendation on what methods are more suitable depending on available computational resources, time and requirements on the solution. In order to achieve this goal, we implement a flexible software framework that maximises the usage of common code and, hence, ensures comparison of algorithms on common ground. In order to identify similarities and differences of the methods, we analyse groups of algorithms that are based on common principles. In addition, we implement and compare several different methods for solving sub-problems and discuss issues related to accumulated numerical errors that might occur when highly accurate solutions are required.     

A note on pole assignment

This note gives an alternate proof of Davison's theorem [2] on pole placement and further shows that, for a controllable, observable systemdot{x} = hat{A}x + hat{B}u, y = hat{C}x, the number of poles that can be assigned arbitrarily are equal to max (m,p), wheremRankhat{B}andp= Rankhat{C}. In some cases, more than max (m,p) poles can be assigned arbitrarily.     

A paradigm for robust geometric algorithms

This paper explores a paradigm for producing geometrical algorithms in which logical decisions that depend on finite-precision numerical calculation cannot lead to failure. It applies this paradigm to the task of intersecting two convex polyhedral objects. A key tool in this work is a method of perturbing embedding polyhedra in ways consistent with their topology.Work on this paper was supported in part by NSF Grant DMC-86-17355, NSF Grant DMS-87-02070, ONR Grant N00014-86-0281, ONR Grant N00014-88-0591, and the U.S. Army Research Office through MSI, Cornell University.     

A paradigm for robust geometric algorithms

This paper explores a paradigm for producing geometrical algorithms in which logical decisions that depend on finite-precision numerical calculation cannot lead to failure. It applies this paradigm to the task of intersecting two convex polyhedral objects. A key tool in this work is a method of perturbing embedding polyhedra in ways consistent with their topology.     

Robust pole assignment

This paper presents new theorems on the theory of interval matrix inequalities and the theory of polynomials with interval roots, and applies them to the problem of robust pole-placement. We formulate optimization problems and derive convergent iterative algorithms which allow the designer to find controllers that place closed-loop poles within desired intervals for plants with unknown-but-bounded parameter uncertainties. The algorithms are computationally reasonable and provide a useful addition to currently existing control CAD tools.     

A robust periodic pole assignment algorithm

In this note a robust periodic pole assignment algorithm is proposed for linear, time-invariant, discrete-time systems. The condition numbers of the eigenvector matrices of the closed-loop system are assumed as a robustness measure and a periodic state-feedback law is deduced by the minimization of the condition numbers associated to the eigenvectors of the monodromy matrix of the closed-loop system. The proposed periodic pole assignment algorithm has been tested on a number of examples, giving satisfactory results     

Parameter-insensitive pole assignment

A problem of parameter-insensitive pole assignment for a kind of finite-dimensional linear time-invariant (FDLTI) system is considered. Conditions for the existence of some parameter-insensitive poles are obtained. Further, an approach for constructing the feedback law is suggested.     

A note on robust pole assignment for periodic systems

In this note a robust pole assignment algorithm is proposed for linear periodic discrete-time systems with time-varying dimensions of the state and/or input spaces. The algorithm deduces a periodic state feedback law by the minimization of the condition numbers of the eigenvector matrices of the closed-loop system. Numerical examples are provided to show the performances of the algorithm     

A design procedure for pole assignment using output feedback

A new design procedure is presented for assigning closed-loop eigenvalues of multi-variable, linear systems using output feedback control. Subject to certain mild restrictions, the number of poles which can be assigned to arbitrary, distinct locations is mill [m + r ? 1, n], where m, r and n are the dimensions of the output, control and state vectors, respectively. The design procedure provides an extension of the results of Davison and Chatterjee (1971) and Jameson (1970) but allows a significantly larger number of eigenvalues to be assigned. The simplicity of the design procedure is demonstrated by a numerical example.     

A multishift Hessenberg method for pole assignment of single-inputsystems

A new algorithm is proposed for the pole assignment of single-input linear time-invariant systems. The proposed algorithm belongs to the family of Hessenberg methods and is based on an implicit multishift QR-like technique. The new method compares favourably in many respects (speed, memory usage) with existing numerically stable methods. Its improved vectorizability guarantees good opportunities for parallel implementation on high-performance computers     

Feedback controls for pole subset assignment

A pole assignment problem for multi-input linear systems is discussed. In conventional pole assignment problems, an input is concerned with all poles simultaneously or it assigns only a specified subset of poles. Here we propose a design method which makes each input assign an arbitrary subset of poles. Thus when we replace a pole by using this method, it is enough to reconstruct only the corresponding input.     

A computational algorithm for pole assignment of linear single-input systems

An efficient computational solution of the pole assignment problem of linear single-input systems is presented. It is based on orthogonal reduction of the closed-loop system matrix to upper (quasi-) triangular form whose 1 × 1 or 2 × 2 diagonal blocks correspond to the desired poles. The algorithm proposed is numerically stable and performs equally well with real and complex, distinct, and multiple desired poles. The number of the computational operations is less than6n^{3}, the necessary array storage being2n^{2} + 6nworking precision words, wherenis the order of the system.     

A computational algorithm for pole assignment of linear multiinput systems

An efficient computational algorithm for pole assignment of linear multiinput systems is proposed. A preliminary stage of the algorithm is a reduction of the system matrices into orthogonal canonical form. The gain matrix elements are then found by orthogonal transformation of the closed-loop system matrix into upper quasi-triangular form whose diagonal blocks correspond to the desired poles. The algorithm is numerically stable, the computed gain matrix being exact for a system with slightly perturbed matrices. It works equally well with real and complex, distinct, and multiple poles and is applicable to ill-conditioned and high-order problems.     

A necessary condition for pole assignment by constant output feedback

In this paper we shall investigate the pole assignment problem by constant output feedback using transfer function techniques. In particular, a necessary condition is given for the existence of constant output feedback which assigns the eigenvalues of closed-loop system to any desired positions.     

Robust pole assignment for systems with parameters

In this paper we investigate issues related to the control of linear multivariate systems which contain structured, parametric-type uncertainties. The objective is to construct parameter-independent proper compensators that provide ‘robust control’. Specifically, we consider the question of robust pole assignment. Systems are described by matrix fraction representations which involve a structured parametric form of uncertainty. We suggest conditions for robust pole assignability and demonstrate how to construct the required proper compensators. For the problem considered, we show that the class of systems which satisfy these conditions is quite large and we include results on generic solvability. The method is demonstrated by a physical example.     

Regional pole assignment for uncertain delta-operator systems

The pole assignment in a specified disk by state feedback for uncertain delta-operator systems is studied. By making use of algebra Riccati equations, a sufficient and necessary condition of pole assignment for a kind of parameter uncertain delta-operator system in a specified disk by state feedback is presented. And the design method of state feedback controller is also developed.The proposed method can unify some previous rehted results of continuous and discrete time systems into the delta framework. The efficiency of the design method is illustrated by a numerical example.     

A note on pole assignment in uncertain systems

A new method for full-rank state-feedback pole assignment is introduced. A particular advantage of this method is that no freedom in the design parameters is lost. Hence, further design problems such as robust pole assignment in uncertain systems are alleviated. An application of this feature is shown for a particular linear model of the F16 aircraft. The connections between state feedback and several concepts in the literature such as incomplete input feedback, incomplete state feedback, output feedback and incomplete pole assignment are also given.