Comparison of two approaches to automated PI controller tuning for an industrial weigh belt feeder Yanan Zhao,* Emmanuel G. Collins, Jr. ² Department of Mechanical Engineering, Florida A&M University – Florida State University, Tallahassee, Florida 32310, USA Received 17 September 2003; accepted 27 March 2004 Abstract In this paper, two advanced PI controller tuning methods, unfalsified control and fuzzy control, are applied to an industrial weigh belt feeder that has significant nonlinearities. Both methods do not require an explicit plant model. The advantage of the unfalsified PI control design method is that it is able to directly incorporate multiple performance criteria, while the advantage of fuzzy logic is that it is able to directly incorporate human reasoning in the design process. Experimental results exhibit the effectiveness of both control methods. A detailed comparison of the two approaches is given in the areas of allowed design specifications, process knowledge requirements, computational requirements, controller development effort, transient performance, and the ability to handle motor saturation. © 2004 ISA—The Instrumentation, Systems, and Automation Society. Keywords: Fuzzy logic control; Unfalsified control; PI control; Weigh belt feeder 1. Introduction Automated controller tuning is of significant in- terest to control engineers since it can lead to in- creased performance while saving time and energy 1,2. The original work on tuning focused on the development of procedures and recommendations to be used manually by operators. However, more sophisticated methods of autotuning have since been proposed. For example, automatic tuning is now used extensively in PID control 1,3,4. PID controllers have been the most commonly used controllers in industrial control practice for the past 60 years, even though great progress in control theory has been made over this period. This is because of their simple structure, ease of design and implementation, and transparent inter- pretation. A poorly tuned control system may waste energy and cause excessive and unnecessary wear of actuators 2. High performance is always the design target in industrial control applications and recently many modern control techniques that improve PID tuning have been reported 1,5,6. In this research, automated PI controller tuning tech- niques are studied for an industrial weigh belt feeder. The weigh belt feeder used in this research see Fig. 1 was designed and manufactured by Mer- rick Industries, Inc. of Lynn Haven, Florida. It is a process feeder that is typically used in a food, chemical, or plastics manufacturing process. To ensure a constant feed rate in industrial operation, a PI control law is designed and implemented in the Merrick controller. In current practice the PI tuning process is performed manually by an engi- neering technician. However, for better and more consistent quality, it is desired to use automated PI tuning 7. *E-mail address: yzhao@eng.fsu.edu ² E-mail address: ecollins@eng.fsu.edu ISA TRANSACTIONS ® ISA Transactions 43 2004 611–621 0019-0578/2004/$ - see front matter © 2004 ISA—The Instrumentation, Systems, and Automation Society.