Seigo Sasaki

A convex characterization of analysis and synthesis for nonlinear systems via extended quadratic Lyapunov function

Using an extended quadratic Lyapunov function of the form V(x)=x/sup T/P(x)x, we consider L/sub 2/-gain analysis and state feedback control synthesis for input-affine polynomial type nonlinear systems, and derive Riccati type matrix inequality conditions that depend on x. We show that the solution P(x) can be given by solving linear matrix inequalities as a polynomial type matrix. We also determine the domain of internal stability. We finally show that the proposed method is effective through a numerical example of bilinear systems.

Systematic approach to robust nonlinear voltage control of buck/boost converter

Nonlinear state feedback controllers are systematically derived to achieve output voltage control of a buck/boost converter behind variations of input voltage and resistive load. The controller design is carried out on the basis of a state averaged model of the converter, which is a bilinear system. The control problems are treated as nonlinear H/sup /spl infin// state feedback control problems for the bilinear system, and are solved via the Lyapunov-based game theory approach. Convex programming technique gives concrete controllers solving the problems via considering a domain of voltage and current in the converter circuit. Computer simulations show efficiency of the control system and the control system design approach.

Nonlinear H∞ Control System Design via Extended Quadratic Lyapunov Function

Abstract Using extended quadratic Lyapunov functions, we consider H ∞ control synthesis problems for input-affine polynomial type nonlinear systems, and characterize nonlinear H ∞ controllers, in the state feedback case and the output feedback case, via Riccati type matrix inequality conditions. The controllers can be given by solving linear matrix inequalities which are given at vertices of a convex hull enclosing a domain of states. We also detennine a domain of internal stability. We finally show that the proposed method is effective through a numerical example for output feedback control problem of bilinear system.

Quadratic cost output feedback control for bilinear systems

This paper considers output feedback control problems for bilinear systems with a quadratic cost function and develops a robust control theory approach. A key point of the approach is to regard once the bilinear term as a term with unknown parameters and then use some robust control synthesis methods. This approach derives two types of nonlinear output feedback controller that guarantee an upper bound for the cost function. Efficiencies of the proposed approach are also demonstrated through a numerical example.

Syntheses of H/sub /spl infin// output feedback control for bilinear systems

In this paper, we consider H/sub /spl infin// output feedback control synthesis problems for bilinear systems. We develop two types of approach to the problem. The first approach is based on a differential game theory. The second approach uses linear fractional representations. We derive sufficient conditions for feasibility of the problems and propose controller synthesis algorithms corresponding to the conditions. We also discuss computer simulations for continuous stirred tank reactors by using the two developed approaches.

System clarification through systematic controller design for a forward converter with power factor corrector

A nonlinear controller is systematically designed on the basis of nonlinear model for a forward converter with power factor corrector. The systematic controller design clearly analyzes the behavior of a nonlinear system to improve the performance. It is clarified that a nominal load resistance characterizes the controller performance. Finally, computer simulations demonstrate efficiencies of the approach.

SYSTEMATIC NONLINEAR CONTROLLER DESIGN FOR A POWER FACTOR CORRECTOR

Abstract A nonlinear controller for a power factor corrector is systematically constructed via Lyapunov-based controller design approach for the bilinear state averaged model. First, a nonlinear gain of the controller is derived to shape the source current and the output voltage be desired form respectively via nonlinear H ∞ control system design approach. Second, a source current reference generator is constructed, which consists of a feedforward loop given by steady state analysis and a feedback loop with output voltage error amplifier. This paper, finally, shows efficiencies of the approach through computer simulations.

H∞ Output Feedback Control Problems for Bilinear Systems

In this paper, we consider H ∞ output feedback control problems for bilinear systems, and present a design example of artifical rubber muscle actuator control system. First we derive two types of H ∞ output feedback controller via the differential game approach. The controllers are characterized in terms of the solutions satisfying two Riccati inequalities depending on the state of generalized plant or controller. Second, we propose algorithms to solve the Riccati inequalities via specifying a domain of the state and solving constant coefficient Riccati inequalities. The proposed algorithms include an evaluation method for the domain of internal stability. Finally, we demonstrate efficiency of the proposed algorithm through a numerical example.