Eitaku Nobuyama

A new algorithm for finite spectrum assignment of single-input systems with time delay

Finite spectrum assignment for time-delay systems is the elimination of delay operators from the characteristic function of the closed-loop system and the arbitrary assignment of poles. The control consists of polynomials in the delay operator and finite Laplace transforms. An algorithm for computing the control matrix is presented. In particular, the control matrix over rational functions of a delay operator is computed and expanded to partial fractions. Partial fractions are systematically transformed to finite Laplace transforms. >

Iterative method for designing an observer-based mixed H2/D-stability controller

This paper treats the output feedback H2 control with regional pole placement condition. In general, this problem is a BMI problem which is difficult to be solved theoretically. The purpose of this paper is to propose an iterative method for obtaining a sub-optimal solution of the H2 control problem with regional pole placement condition. The key idea of this paper is to employ a full-order observer-based controller. The proposed method produces a sequence of controllers which approaches to the unconstrained globally optimal H2 controller while it satisfies the D-stability constraint. A numerical example shows the effectiveness of our method

Minimax polynomial optimization by using sum of squares relaxation and its application to robust stability analysis of parameter-dependent systems

This paper gives a sufficient condition for a robust control problem in terms of minimax polynomial optimization. A minimax problem is investigated by using sum of squares relaxation of parametric polynomial optimization problems. The sufficient condition can be exact from the Positivstellensatx. The minimax approach is adopted for robust stability analysis of parameter-dependent systems and an equivalent stability condition is also given from quadratic version of distinguished representation of positive polynomials. Finally, a numerical example is shown.

Parametrization of all ripple-free deadbeat controllers

Abstract This paper is concerned with deadbeat control in sampled-data systems. Deadbeat control achieves finite-time settling (deadbeat settling) at sampling instants, but there may exist error called ripple “between” sampling instants even after the response is settled “at” sampling instants. The objective of this paper is to give a parametrization of all ripple-free deadbeat controllers (controllers which achieve deadbeat settling without ripple) in sampled-data systems. It is also shown that the following holds in general: minimum-time deadbeat control causes ripple when the pulse transfer function to be controlled has stable zeros.

Robust stabilization of time-delay systems via reduction to delay-free model matching problems

The authors considers four types of model uncertainty for time-delay systems and shows that the robust stabilization problems can be reduced to delay-free model matching problems by using doubly Bezout factorizations based on predictive controllers. As a result, the robust stabilization problems of time-delay systems can be solved using the usual Nevanlinna-Pick interpolation technique.<<ETX>>

L2-Gain Analysis and Control Design of Linear Systems with Input Saturation using Matrix Sum of Squares Relaxation

In this paper, matrix sum of squares (SOS) relaxation is used for analysis of linear systems with input saturation. On the basis of a polytopic type saturation model, we consider a polynomial type saturation model which leads less conservative analysis of Lscr2 -gain performance. The idea is also applicable to design problems. Both the analysis and the design problems are reduced to robust linear matrix inequality problems that can be solved by using a matrix SOS technique. A structural reduction for the relaxation is also discussed. Finally, numerical examples are shown

Deadbeat control of continuous-time systems: MIMO case

This paper is concerned with a deadbeat tracking problem of continuous-time systems. The control objective is to achieve complete (or deadbeat) tracking in finite time. The purpose of this paper is to give a design method for achieving deadbeat tracking in multivariable continuous-time systems. A special feature of the method is to use delay elements in the controller (instead of sample-and-hold devices).

A Gradient Method for the Static Output Feedback Mixed H2/H∞ Control

This paper is concerned with the mixed H2/H∞ control problem via static output feedback control. The main purpose of this paper is to give an iterative method for finding a sub-optimal static output-feedback controller for the mixed H2/H∞ control problem. The contribution of this paper is to derive a gradient of the H2 cost function. Using this gradient, we propose a gradient method for H2 and mixed H2/H∞ control problems. Numerical examples show the efficiency of our methods.

A generalization in mixed H 2 / H ∞ control with state feedback

Abstract In this note, we consider a mixed H 2 / H ∞ control problem with a performance cost which combines the H 2 norm cost and the so-called auxiliary cost. The main result is to give a formula for the optimal cost and a nearly optimal controller. It is assumed that the state of the plant is available for feedback.

Multiobjective control for continuous time MIMO systems via deadbeat regulation

We extend the framework of continuous time deadbeat control, which is given by Nobuyama et al. to multi-constraints control in time and frequency domains for continuous time MIMO systems. Two conditions for the free parameter of H/sub /spl infin// suboptimal controllers are shown, which correspond to a deadbeat control interpolation condition and H/sub /spl infin// norm constraint. By restricting modified free parameters of H/sub /spl infin// controllers to commensurate time delay functions, we give all controllers which satisfy the two conditions simultaneously. Moreover, we show that time domain constraints of L/sub 2/ or L/sub 1/ norms are also reduced to finite dimensional convex problems and these mixed problems can be solved numerically.