Optimal adaptive control of an ash stabilization batch mixing process using change detection

• Published in: 2000 IEEE International Conference on Control Applications pp. 109 - 114
• Main Authors: Svantesson, T., Olsson, G.
• Format: Conference Proceeding Book Chapter
• Language: English
• Published: IEEE 2000
• Subjects: Adaptive control; adaptive control batch processing (industrial) closed loop systems least squares approximations mixing predictive control process control recursive estimation tuning; Annan elektroteknik och elektronik; Ash; Chemical processes; Electrical Engineering, Electronic Engineering, Information Engineering; Elektroteknik och elektronik; Engineering and Technology; Least squares approximation; Optimal control; Other Electrical Engineering, Electronic Engineering, Information Engineering; Process control; Programmable control; Recursive estimation; Resonance light scattering; Teknik; Viscosity
• ISBN: 9780780365629; 0780365623
• DOI: 10.1109/CCA.2000.897408

We present an optimal adaptive controller that is used to regulate the chemical process of wood ash stabilization (WAS). The model parameters of the time-varying process dynamics are estimated using recursive least squares (RLS). At each batch an auto-tuning sequence produced with the controller disabled is carried through in order to obtain a good estimate of the process dynamics. After the auto-tuning sequence is completed, a generalized predictive controller is enabled to control the WAS process. The control objective is to regulate the normalized effective power P/sub e/(t) to the level P/sub e//sup crit/ that represents the critical rate of useful work being performed by the three-phase asynchronous machine used for the stirrer drive. Hence, P/sub e//sup crit/ also represents the desired mixture viscosity. If more water is added to the stabilization process after P/sub e//sup crit/ has been reached, one will obtain a mixture useless for granular material. To cope with this problem, change detection is used to reach the desired level P/sub e//sup crit/ without any pre-determined set-point. Two methods are evaluated; a probing strategy and the geometric moving average test, both adequate for successful implementation. The used control strategies are presented and off-line simulations with a model of the physical process evaluate the control performance.