R. Dennis Irwin

Optimization of Microstructure Development: Application to Hot Metal Extrusion

A new process design method for controlling microstructure development during hot metal deformation processes is presented. This approach is based on modern control theory and involves state- space models for describing the material behavior and the mechanics of the process. The challenge of effectively controlling the values and distribution of important microstructural features can now be systematically formulated and solved in terms of an optimal control problem. This method has been applied to the optimization of grain size and certain process parameters such as die geometry profile and ram velocity during extrusion of plain carbon steel. Various case studies have been investigated, and experimental results show good agreement with those predicted in the design stage.

Hybrid System Identification for MIMO Control-System Design

Abstract Herein a method of hybrid frequency domain and state space system identification is developed, tested and implemented. A frequency domain least squares system identification algorithm, along with a coherence function technique for eliminating noisy data is used to sequentially develop discrete single-input, multiple-output (SIMO) transfer function models between each input and the outputs. From the transfer function models, difference equations are obtained. Using the difference equations, discrete impulse responses between each input and each output are computed. These impulse responses are then processed by a state space system identification technique to create a minimum order state space multiple-input, multiple-output (MIMO) model. This process is illustrated on a controls-structures interaction platform called Flexlab.

Characterization of an infra-red multi-position sensor system

The results of calibrating an infrared multiposition sensor system are presented. The system is characterized from both a spatial position accuracy and frequency domain point of view. Data are presented to support the conclusions drawn from these results.

Parametrizations of internal stability and performance applications to sub-optimal controller design

The use of a known controller parameterization to effect control system designs oriented toward classical frequency domain objectives is described. Although the approach is similar to the preliminary steps of certain H/sup infinity / optimal control approaches, the actual optimization step is omitted, leading to considerable simplification. The complete method, with examples of its use, is given for the single-output case.<<ETX>>