Coefficient Adjustment Device of PID Controller Using Fuzzy Expert Device and Its Control Method

摘要

The present invention relates to a coefficient adjusting device of a PID controller using a fuzzy expert device, and a control method thereof. In the conventional device, when a PID controller is applied, the present invention is stable when the following features are present in the process. There was a problem that is difficult to apply.;First, when the process has a large time delay:;If the process is expressed as the first delay factor,;G (s) = ;Where s is the Laplace transformer, and the process system is characterized by the time constant (T), magnitude (K), and delay (L) components shown in the equation above, where the delay time component (L) is large. It is difficult to find the optimal parameters of the PID controller.;Second, when the process shows strong nonlinearity:;The process represented by the first-order delay element like the above equation is a transfer function that simply linearizes the actual system at one operating point, and the actual system has the model characteristics (Dnmodelled Dynamics) that are not taken into account. Tuning of the PID controller is difficult when large non-linearities exist.;Third, when the dynamics of the process change:;The operating point of the process changes according to the change of the set value, and if the dynamic characteristics of the process according to the operating point appear differently, new tuning of control parameters is necessary. At this time, parameter tuning of the PID controller is not allowed.;Fourth, when there are load changes or process disturbances:;Parameter tuning of the PID controller is difficult even when a load variation of a process to be controlled is severe or a disturbance (noise) present in the control output value or the process value is difficult.;Accordingly, the present invention has been devised to solve the above-mentioned conventional problems, and automatically increases the rise time, overshoot, and settling time, which are characteristic values of the system output indicating the property of the system, to the system output of the desired performance index. By providing an apparatus and a control method for adapting the PID coefficient, it has a value smaller than the rise time and the settling time when the Ziegler-Nichols (ZN) method is applied, and is set to '0' in case of overshoot. In the case of [Category 2], since the overshoot is small, the overshoot is set to '0', and at the same time, the rise time and the settling time when the Ziegler-Nichols (ZN) method is applied are improved.