Continuous Caster - Nonlinear Issues
Summary
This virtual laboratory is a sequel to Laboratory 4 (Continuous Caster - Classical Control Design).
The laboratory accurately reflects a real life control system design exercise carried out on a continuous caster. This phase of the design focuses on real world smooth and non-smooth nonlinearities.
Figure 5.1: Screenshot of Program
The Physical Apparatus
You may read the introduction to Virtual Laboratory 4 to get an overview of the physical apparatus.
This virtual laboratory is a sequel to the Continuous Caster 4 laboratory, hence it is strongly recommended that students review the previous laboratory before commencing this one. The laboratory again allows students to gain exposure to a real world control problem. Students are advised to refer to Continuous Caster 4 for a more detailed overview of the system.
The laboratory accurately reflects a real life control system design exercise carried out on a continuous caster at BHP’s Newcastle steel works see reference [1]. The application of control was motivated by a desire to improve the quality attributes of the cast material.
In the previous laboratory we successfully designed a PI controller that provided excellent performance. However in practice, an oscillation of about +/-10mm was found to spontaneously develop and required operator intervention to stop. This slow oscillation in the mould level causes a degradation in the quality of the cast steel, hence it is desirable to remove the oscillation from the system. Investigation into the cause of this problem and the solution actually implemented on the real plant are the subject of the current virtual laboratory.
Prerequisites
This virtual laboratory involves a simple approach to dealing with a stiction nonlinearity in a valve. Thus students should have some familiarity with describing function methods.
Learning Objectives
The learning objectives of this virtual laboratory are:
- Modelling of nonlinearities and nonideal characteristics
- Describing function methods
- Analysis of nonlinear/nonideal closed loop systems
- Dealing with nonlinear/nonideal effects
References
- S.F. Graebe, G.C. Goodwin and G. Elsley, “Control Design and Implementation in Continuous Steel Casting”, IEEE Control Systems Magazine, Vol 15, No. 4, August 1995.
