Robust control of a laboratory circuit thermal plant

Abstract

At the Faculty of Applied Informatics, Tomas Bata University in Zlín, a laboratory circuit heating plant containing internal (state) delays was assembled. It provides unordinary step responses, which makes it difficult to be modeled, identified and controlled in general. This contribution aims controller design and its verification for the appliance by algebraic means in a robust sense. A simple negative control feedback is utilized. The ring of quasipolynomial meromorphic functions (RMS), which has been recently revised and extended, is briefly presented and serves as a primary algebraic tool for controller design. A mathematical model of the plant derived in our previous works based on the anisochronic principle is introduced. A free (selectable) controller parameter is set such that requirements of robust stability and robust performance are satisfied. The final controller is verified by simulations in Matlab- Simulink. Because of the plant is controlled via a discrete-time program in a PC, a simple controller discretization based on delta models is proposed. A simple user-program interface has been programmed. Finally, the controller structure and setting is verified on a real process and compared with simulations. The obtained results show the applicability of the controller design methodology. In the future research, we intent to utilize other control system structures and/or to perform an optimization procedure for robust controller tuning.