## An introduction to H-infinity optimisation designs

### Da-Wei Gu, Petko Hr. Petkov and Mihail M. Konstantinov

NICONET Report 1999-4: May 1999.

This NICONET report is prepared for users of the software package SLICOT who are not familiar with the H-infinity optimisation design approach. Together with some previous NICONET reports it is hoped that the reader would have a general idea about the H-infinity method, know how to use the algorithms available in SLICOT to synthesize a controller for a standard H-infinity optimisation problem and, furthermore, be aware of some difficulties such as singularity in the H-infinity controllers design.

## Efficient implementation of subspace method identification algorithms

### Bert Haverkamp

NICONET Report 1999-3: March 1999.

This paper summarises the results of a study to improve existing Subspace Method Identification (SMI) algorithms. Significant improvements in calculation speed can be achieved by combining components from existing algorithms namely N4SID and MOESP. A second improvement can be achieved by more efficient implementation of critical parts of the algorithms.

## SLICOT drives tractors!

### Peter Benner and Heike Fassbender

NICONET Report 1999-2: January 1999.

We describe a successful application of a SLICOT subroutine in a control engineering problem. Based on GPS data it is possible to automatically steer farm vehicles along a prescribed tracjectory. The bottleneck of the successful on-line implementation of a LQG regulator is the numerical solution of a discrete-time algebraic Riccati equation in real time and at high accuracy. This is achieved employing a Fortran-77 subroutine from the Subroutine Library in Control Theory SLICOT.

## A portable subroutine library for solving linear control problems on distributed memory computers

### Peter Benner, Enrique S. Quintana-Orti and Gregorio Quintana-Orti

NICONET Report 1999-1: January 1999.

This paper describes the design of a software library for solving the basic computational problems that arise in analysis and synthesis of linear control systems. The library is intended for use in high performance computing environments based on parallel distributed memory architectures. The portability of the library is ensured by using the BLACS, PBLAS, and ScaLAPACK as the basic layer of communication and computational routines. Preliminary numerical results demonstrate the performance of the developed codes on parallel computers. The suggested library can serve as a basic layer for PSLICOT, a parallel extension of the Subroutine Library in Control Theory (SLICOT).

## DTDSX - a Collection of benchmark examples for state-space realizations of time-invariant discrete-time systems

### Daniel Kressner, Volker Mehrmann and Thilo Penzl

SLICOT Working Note 1998-10: November 1998, revised June 1999.

This paper describes a benchmark collection for state-space realizations of time-invariant discrete-time dynamical systems. The collection is intended to provide a means for testing the correctness, accuracy, and speed of numerical methods for several problems arising in control theory. It has been implemented in FORTRAN and MATLAB.