FUZZY BASED VARIABLE STEP APPROACHING DIGITAL-CONTROL FOR PLANTS WITHTIME-DELAY

A simple digital controller named Variable Step Approaching Digital Co ntroller (VSADC) based on fuzzy concept is proposed for plants with ti me delay. The proposed controller is basically a modified Takagi-Sugen o Type Fuzzy Controller and can be represented by a compact analytical equation with only several adjustable parameters. The tuning rule and self tuning scheme in constant value control are developed. Detailed simulation investigation is carried out. Verification experiment using Process Trainer PT326 heating system as testbed is conducted. The pro posed controller is compared with PID controller tuned by well-known Z iegler and Nicliols's ultimate cycle method. Both simulation and exper imental results show that the proposed VSADC is effective in suppressi ng overshoot and in attenuating decaying oscillation cycles. It is als o superior to PID controller in the control of plants with dominant ti me delay. (C) 1998 Elsevier Science Ltd. All rights reserved.