Fuzzy logic techniques to evaluate global dynamic performance of control systems

The paper presents a method to calculate a Global Performance Assessment Index (GPI) for a multiloop control system. The method is based on fuzzy logic techniques because some of the behavioral plant variables, such as energy consumption, product quality and plant trip costs are better expressed by linguistics rather than plain numerical variables. The technique based on fuzzy logic gives results that are close to the human operator evaluation. The method has been applied to a computer simulated model of a Continuous Stirred Tank Reactor (CSTR). Typical simulation results are presented. The performance of a multiloop control scheme applied to a real Interacting Tank System (ITS) has also been assessed by the GPI method. Both simulated and experimental runs demonstrate the potential of the proposed method in assessing control systems performance.