Showing papers presented at "Mediterranean Conference on Control and Automation in 2004"

On Load balancing in distributed systems with large time delays: Theory and experiment

Abstract: In a distributed computing environment with a high communication cost, limiting the number of balancing instants results in a better performance than the case where load balancing is executed continuously. Therefore, finding the optimal number of balancing instants and optimizing the performance over the interbalancing time and over the load-balancing gain becomes an important problem. In this paper we discuss the performance of a previously reported, control-theoretic motivated single load-balancing strategy on a distributed physical system and the performance is compared to our simulation predictions. Based on the concept of regeneration, we also present a mathematical model for the distributed system with two nodes where a one-shot balancing is done. We obtain a system of four difference-differential equations characterizing the mean of the overall completion time. and compare its predictive capabilities via simulation to the physical system.

On output feedback robustified anti-windup compensators

Abstract: Conditions are given under which it is possible to implement a compensator solving a weakened anti-windup problem without full state measurements. The effectiveness of unknown input observers is also shown for the cases when the above conditions are not satisfied.

Effective computations with 2-variable polynomial matrices in MATHEMATICA

Abstract: This report describes our joint work on implementation of effective numerical routines for two-variable polynomial matrices in the MATHEMATICA software. New functions are connected to the already created program package, being developed at the Czech Technical University in Prague, which calculates only with polynomial matrices in one variable. As the first step, new polynomial object for 2-D polynomial matrix was created in the MATHEMATICA programming language. This was essential for good integration with the polynomial package mentioned above. Implementation of a bunch of efficient and reliable numerical routines followed.

Non quadratic stabilization of multiple models

Abstract: This paper deals with the stabilization of Takagi-Sugeno models (T-S) using state feedback controllers. New sufficient stability conditions are given for both continuous and discrete T-S models. The stability conditions, formulated in term of bilinear matrix inequalities (BMIs), are based on a piecewise quadratic Lyapunov function and the use of the so-called S-procedure. A method of linearisation, applied on the obtained BMIs conditions, is presented.

A Robust Anti-Windup Scheme for Manual Flight Control of an Unstable Aircraft

Abstract: A result on robust in the large, anti-windup compensation obtained for the case of asymptotically stable systems is extended to deal with an unstable fighter aircraft model. Simulations show the effectiveness of the proposed techniq ue.

Stabilization of a Class of Autonomous Unstable Switching Systems

Abstract: In this paper we present a switching law for the asymptotic stabilization of continuous LTI switching systems. We introduce a suitable state space partition based on the locally contractive behaviour of the continuous subsystems. We use gauge functions (more general than norm) to measure trajectory's contractions and expansions. This partition allows us to build a switching strategy which produces a sequence of monotonically decreasing points (with respect to the xed gauge function) and which is capable to asymptotically stabilize the switching system.