The Design And Development Of Fuzzy Self-tuning PID Controller

With the rapid development of power industry, expand and improvement of the level of automation unit scale thermal power units, requirements for each system has improved significantly. Simple conventional PID control structure which is easy to implement and robust, thus has been very widely used in industrial process control. But the conventional PID control is not easy to get the ideal control effect in the nonlinear, time-varying, large inertia, large delay control system. Compared with conventional PID control, fuzzy control is easy to express in the form of knowledge processing language, so it is difficult to establish a precise mathematical model and empirically control system. Fuzzy control uses the principle of fuzzy mathematics study of human control activities, ultimate machine language instead of the control subjects of human activity, which is based on the rate of change in their own bias and bias control to adjust the output of the controller can be applied to non-linear, time-varying, large inertia, large delay in the control system.However, the development of fuzzy control is not far-reaching. Fuzzy control system analysis and design do not have effective methods and still need to rely on many occasions trial and error experience. In addition, a fuzzy control strategy inherent flaw exists in the nature of nonlinear variable proportional control, therefore it can’t eliminate the static error and the limit cycle. In fact, a simple fuzzy control strategy can not be applied to the process control system. For this reason, in recent years’ actively exploring fuzzy control and conventional PID control, people proposed numerous intelligent control algorithms such as fuzzy control and predictive control by combining fuzzy control and adaptive control. this paper is to combine research the fuzzy control with conventional PID control combined experience in the use of adjustable parameters to achieve PID parameters itself.In this paper, we propose a practical fuzzy self-tuning PID controllers based on vague criteria. The controller does not rely on accurate mathematical model of controlled object, but just the experience of the operator as the fuzzy rules stored in the computer knowledge. Then the control system uses fuzzy reasoning, the three-line adjustment of the PID controller parameters. It will automatically adjust for optimal PID parameters according to the actual situation. This design of the controller has been implemented in the circulating fluidized bed boiler bed temperature control system MATLAB simulation. The simulation results show that, compared with conventional PID control, fuzzy control enables faster system response, no overshoot. Moreover, in the different operating condition, the controlled object model changes, so there is no need to adjust parameters of the controller which will be able to keep the system stable and better robustness.However, the fuzzy self-tuning PID control is still in the simulation stage in industrial control application. Therefore, this paper mainly studies the fuzzy self-tuning PID control algorithm and its implementation in a distributed control system called LN2000. Through the application in the full simulator proved the fuzzy self-tuning PID control effect than conventional PID control.