Fuzzy adaptive control system of a non-stationary plant with closed-loop passive identifier

Abstract Typically chemical processes have significant nonlinear dynamics, but despite this, industry is conventionally still using PID-based regulatory control systems. Moreover, process units are interconnected, in terms of inlet and outlet material/energy flows, to other neighboring units, thus their dynamic behavior is strongly influenced by these connections and, as a consequence, conventional control systems performance often proves to be poor. This paper proposes a hybrid fuzzy PID control logic, whose tuning parameters are provided in real time. The fuzzy controller tuning is made on the basis of Mamdani controller, also exploiting the results coming from an identification procedure that is carried on when an unmeasured step disturbance of any shape affects the process behavior. In addition, this paper compares a fuzzy logic based PID with PID regulators whose tuning is performed by standard and well-known methods. In some cases the proposed tuning methodology ensures a control performance that is comparable to that guaranteed by simpler and more common tuning methods. However, in case of dynamic changes in the parameters of the controlled system, conventionally tuned PID controllers do not show to be robust enough, thus suggesting that fuzzy logic based PIDs are definitively more reliable and effective

Development of the frequency PID tuning method with filter

In the previous research authors developed tunable method for PID controllers to achieve the desired phase margin. Crossover frequency is used as a parameter that allows correcting time response of closed-loop system. The aim of the research is to find proportional, integral, derivative and filter coefficients of PID controller that will provide desired characteristics (phase margin and crossover frequency) in the system. The analytical approach of proposed PID tuning method is presented. The comparison proposed method with conventional was done. Practical approach contains developing the control system of extraction process. This system is a part of Russian Federation large project - closed-loop nuclear fuel cycle. The plant was linearized and digital control system was developed