Professor Steven Weller

This paper addresses two important aspects of anti-windup (AW) designs, namely the parametrization of linear AW compensators, and the role of artificial nonlinearity (AN) in the design of AW compensators for multivariable systems. For the first issue, a simple parametrization is given using the classical feedback structure in the framework of constrained unity feedback multivariable control system. Conditions for controller implementability and closed-loop stability are stated in terms of this parametrization. For the second issue, two existing AN designs for coordinate plant inputs whenever one plant input enters saturation are reviewed. The first design is the widely used input direction preserving technique, and the second is an optimal AN design. A comparative simulation study illustrates that the conditioning technique, enhanced by optimal AN design, gives the best tracking performance among different existing methods.

There has recently been interest in the use of orthonormal bases for the purposes of SISO system identification. Concurrently, but separately, there has also been vigorous work on estimation of MIMO systems by computationally cheap and reliable schemes. These latter ideas have collectively become known as '4SID' methods. This paper is a contribution overlapping these two schools of thought by showing how general orthonomal bases may be generated to form model structure suitable for identification of MIMO systems using only simple calculations. In contrast to general prediction error methods and in common with 4SID schemes the estimation algorithms involved are computationally simple. However, a distinguishing feature of the orthonormal basis approach described here is that significant prior knowledge about system poles may be included in the estimation problem.

In order to maintain reliable communications with low-earth and inclined orbit geostationary satellites, ground based antenna systems must use tracking systems. Two approaches to tracking, passive and active tracking systems, are described in this paper including a tutorial style introduction to optimal filtering applications. We show that the design of antenna control and tracking systems is a multidiscipline problem that encompasses computer engineering, structural and mechanical engineering and signal processing. Finally we describe a low earth orbit tracking system being built at the University of Melbourne.