Design and tuning of standard additive model based fuzzy PID controllers for multi-variable process systems

This paper describes a two-level tuning method for fuzzy PID controllers for multi-variable control system. The fuzzy PID system is designed using the inference of standard additive model (SAM). In the two-level tuning scheme the tuning follows two steps, low-level tuning followed by high-level tuning. The low-level tuning adjust the linear gain parameters. The high-level tuning changes the nonlinearity in the normalized fuzzy output. For that purpose a nonlinearity diagram is defined to choose membership parameters of the fuzzy system. The controller performance is verified through real-time multi-zone soil temperature control problem having a 3 times 3 process system. The proposed method can be used for any n times n dimensional multi-input-multi-output (MIMO) process system.