ADVANCED CONTROL STRATEGIES FOR FLUIDIZED BED DRYERS

ABSTRACT

Generating the best possible control strategy comprises a necessity for industrial processes, by virtue of product quality, cost reduction and design simplicity. Three different control approaches, namely an Input-Output linearizing, a fuzzy logic and a PID controller, are evaluated for the control of a fluidized bed dryer, a typical non-linear drying process of wide applicability. Based on several closed loop characteristics such as settling times, maximum overshoots and dynamic performance criteria such as IAE, ISE and ITAE, it is shown that the Input-Ouput linearizing and the fuzzy logic controller exhibit a better performance compared to the PID controller tuned optimally with respect to the IAE, for a wide range of disturbances; yet, the relevant advantage of the fuzzy logic over the conventional nonlinear controller issues upon its design simplicity. Typical load rejection and set-point tracking examples are given to illustrate the effectiveness of the proposed approach.

Key Words and Phrases:

• non-linear control
• input-output linearization
• fuzzy logic controllers
• fluidized bed dryers