further results on morgan s problem this paper deals with the row by row decoupling problem known as the morgan problem with static state feedback the solution of this problem is well known when some artificial constraints on the feedback laws are imposed such as regular input transformations or restricted state feedbacks however in its most general setting the problem remains unsolved we provide here a new sufficient condition of its solvability the fact that this condition turns out to be also necessary in the particular case of systems having 2 outputs and 3 inputs enforces its interest

minimal completion problem for quasi regular matrix pencils abstract in this paper we study the problem of completion of an arbitrary matrix pencil by rows and columns in order to obtain a quasi regular matrix pencil in the case when the number of added columns or rows is the minimal possible to obtain a quasi regular matrix pencil in the solution we use combinatorial methods involving lr coefficients a solution of the carlson problem and localization techniques the result is given over algebraically closed fields

structured squaring down and zero assignment the problem of zero assignment by squaring down is considered for a system of p inputs n outputs and n states m p where not all outputs are free variables for design we consider the case where a k subset of outputs is preserved in the new output set and the rest are recombined to produce a total new set of p outputs new invariants for the problem are introduced which include a new class of fixed zeros and the methodology of the global linearization developed originally for the output feedback pole assignment problem is applied to this restricted form of the squaring down problem it is shown that the problem can be solved generically if p k m p where k k p is the number of fixed outputs and is a system and compensation scheme invariant which is defined as the restricted forney degree

on a special case of model matching a special case of model matching a generalized version of the feedback simulation problem is considered and a necessary condition of its solvability is established this condition is also a new necessary and sufficient condition of solvability for the feedback simulation problem

feedback invariants of matrices with prescribed rows abstract let a f n n b f n m where f is an arbitrary field in this paper we solve the problem of the existence of the matrix a b when its feedback invariants and some rows are prescribed

assignment of complete structural properties of linear systems via sensor selection for x ax bu the problem of structural assignment via sensor selection is to find an output equation y cx du such that the resulting system a b c d has the pre specified structural properties such as the finite and infinite zero structures as well as the invertibility properties in this paper we establish a set of necessary and sufficient conditions under which a complete set of system structural properties can be assigned and an explicit algorithm for constructing the required matrix pair c d

inverse and direct airfoil design using a multiobjective genetic algorithm some of the advantages and drawbacks of genetic algorithms applications to aerodynamic design are demonstrated a numerical procedure for the aerodynamic design of transonic airfoils by means of genetic algorithms with single point multipoint and multiobjective optimization capabilities is presented in the rst part an investigation on the relative ef ciency of different genetic operators combinations is carried out on an aerodynamic inverse design problem it is shown how an appropriate tuning of the algorithm can provide improved performances better adaption to design space size and topology and variables cross correlation in the second part the multiobjective approach to design is introduced the problem of the optimization of the drag rise characteristics of a transonic airfoil is addressed and dealt with using a single point a multipoint and a multiobjective approach a comparison between the results obtained using the three different strategies is nally established showing the advantages of multiobjective optimization

automatic design of wing body nacelle configurations for minimum drag a computational fluid dynamics driven robust and accurate method for aerodynamic shape optimization previously developed by the authors is further enhanced by extending it to automatic multipoint design of wing body nacelle configurations the shape is optimized for minimum drag at fixed lift subject to numerous geometrical and aerodynamical constraints the method which is driven by genetic algorithms and full navier stokes computations combined with reduced order models approach is supported by massive multilevel parallelization the applications include single and multipoint aerodynamic designs for a transport type aircraft configuration for the considered class of shape optimizations significant drag reduction in on and off design conditions has been achieved it was also shown that the optimizations which start from markedly different initial shapes ultimately converge to optimum shapes very close one to one another the paper demonstrates how automated techniques based on the developed met

fundamental theorem of state feedback for singular systems abstract the limits of state feedback in altering the dynamics of singular systems are studied a necessary and sufficient condition is given for a list of polynomials to be invariant polynomials of a proper system obtained by state feedback from the singular system the condition consists of inequalities which involve the controllability indices of the singular system and the degrees of the invariant polynomials the development is based on the properties of polynomial matrices a procedure is given for the calculation of a feedback gain which achieves the desired dynamics

a one dimensional reaction diffusion system with a fast reaction abstract we consider a system of second order ordinary differential equations describing steady state for a three component chemical system with diffusion in the case when one of the reactions is fast we discuss the existence of solutions and the existence uniqueness and characterization of a limit as the rate of the fast reaction approaches infinity

on the structure at infinity of linear square decoupled systems the purpose of this note is to demonstrate that a square invertible linear system c a b is decouplable by static state feedback if and only if its infinite zero orders are respectively equal to the infinite zero orders of the subsystems c i a b where c i denotes the i th row of c until now only the necessity of this condition has been established 1

interlacing inequalities and control theory abstract given a p by p matrix a we solve the problem of the existence of a p by q matrix b such that a b has prescribed controllability indices and i p a b has prescribed invariant polynomials the solution of this problem together with an earlier theorem of the author s is used to provide a new proof of the sa thompson interlacing inequalities for invariant polynomials

interlacing inequalities for regular pencils abstract we solve the problem of finding a necessary and sufficient condition for the existence of a regular pencil when its invariant homogeneous factors and a subpencil are prescribed the solution obtained is an extension of the well known sa thompson interlacing inequalities for invariant factors of characteristic matrices

infinite structure and exact model matching problem a geometric approach we first generalize to a b c d quadruples the geometric characterization of the infinite zero structure we then give a new geometric proof for a solvability condition of the exact model matching problem expressed in terms of this concept and previously established in the polynomial context by morse verghese and pernebo this emphasizes the approach independent character of the infinite zero structure

interlacing and majorization in invariant factor assignment problems this paper shows some connections between pole assignment in control theory and assignment of invariant factors on matrices with some prescribed submatrices the majorization in the hardy littlewood polya sense and the interlacing inequalities for invariant factors play a fundamental role in the solution of some problems common to both theories

on the modification of a structure at infinity by a return of static state le bouclage d un systeme lineaire par un retour d etat statique non regulier c est a dire du type u fx gv avec g non inversible modifie en general sa structure et en particulier sa structure a l infini qui joue un role cle daps les problemes de commande l objet de cet article est d etudier ces modifications nous donnons une condition structurelle necessaire et sufsante pour qu une lists donnee soft la lists des ordres des zeros infinis du systeme boucle par un retour d etat statique nous calculons alors explicitement un retour d etat f g qui produit cette modification de structure a l infini

completion up to a matrix pencil with column minimal indices as the only nontrivial kronecker invariants abstract in this paper we give explicit necessary and sufficient conditions for a completion of an arbitrary matrix pencil up to a pencil with a prescribed set of kronecker invariants in the case when the only nontrivial invariants of the resulting pencil are its column row minimal indices the result is given over arbitrary fields

assigning the kronecker invariants of a matrix pencil by row or column completions abstract the challenge consists in describing the relationships between the kronecker invariants of a matrix pencil and one of its subpencils for a given subpencil an algorithm for constructing a matrix pencil with prescribed kronecker invariants should also be proposed

effect of artificial viscosity on three dimensional flow solutions artificial viscosity is added either implicitly or explicitly in practically every numerical scheme for suppressing spurious oscillations in the solution of fluid dynamics equations in the present central difference scheme artificial viscosity is added explicitly for suppressing high frequency oscillations and achieving good convergence properties the amount of artificial viscosity added is controlled through the use of preselected coefficients in the standard scheme scalar coefficients based on the spectral radii of the jacobian of the convective fluxes are used however this can add too much viscosity to the slower waves hence the use of matrix valued coefficients which give appropriate viscosity for each wave component is suggested with the matrix valued coefficients the central difference scheme produces more accurate solutions on a given grid particularly in the vicinity of shocks and boundary layers while still maintaining good convergence properties

constrained aerodynamic optimization of three dimensional wings driven by navier stokes computations ar obust and efficient approach to the multiobjective constrained design previously developed by the authors is extended to optimization of three dimensional aerodynamic wings the objective is to minimize the total drag at fixed lift subject to various geometrical and aerodynamical constraints the approach employs genetic algorithms gas as an optimization tool in combination with a reduced order models rom method based on linked local databases obtained by full navier stokes computations the work focuses on the following issues geometrical representation of three dimensional shapes handling of sensitive nonlinear constraints such as pitching moment and the influence of flight conditions on the results of optimization the method implemented in the computer code optimas optimization of aerodynamic shapes was applied to the problem of multipoint transonic threedimensional wing optimization with nonlinear constraints the results include a variety of optimization cases for two wings a classical test case of onera m6 wing and a generic cranked transport type wing for the investigated class of problems significant aerodynamic gains have been obtained nomenclature c d total drag coefficient cl total lift coefficient c m total pitching moment coefficient c p pressure coefficient m freestream mach number n d dimension of the search space nws number of sectional airfoils q objective function r c relative radius of the airfoil leading edge re freestream reynolds number t c relative thickness of airfoil angle of attack trailing edge angle of airfoil

robust hybrid approach to multiobjective constrained optimization in aerodynamics a new approach to the multiobjective constrained design of aerodynamic shapes is suggested the approach employs genetic algorithms ga as an optimization tool in combination with a reduced order models method based on linked local databases obtained by full navier stokes computations the method was applied to the problem of multiobjective transonic profile optimization with nonlinear constraints the results demonstrated that the method retains high robustness of conventional gas while keeping computational fluid dynamics computational volume to an acceptable level as a result of a limited use of full navier stokes computations a significant computational time saving in comparison with optimization tools fully based on navier stokes computations allowed the algorithm to be used in a demanding engineering environment