Nonlinear System Model-free Adaptive Control & Its Application In Process Control

The effect of conventional PID controller is limited if the system shows nonlinear performance and has time delay. Most of the nonlinear processes have too many intermediate states, and their mathematical models are too complicated. System identification of a nonlinear system is a challenge task, so model-based controllers are not well-used in some nonlinear systems. Based on model-free adaptive control theory, a model-free adaptive controller is designed in this paper. Some improved items are also added into this controller, to meet the demands in actual control process. In this paper, the improved controller is used in the electric heating pot to validate the performance of this controller.In this paper, there are two improved items added into model-free adaptive control scheme. There are always some constraints in actual process control problems. Constraints are added into the original model-free control scheme, and the controller is solved by using quadratic programming theory. The other improved item is to add difference control into the model-free adaptive control scheme. By doing so, the control error caused by the time delay decreases and the control performance is greatly improved.To validate the effect of the improved model-free adaptive control scheme, a closed-loop control system of electric heating pot is built by using PLC and MATLAB. This system solve the data exchange problem by using OPC, combined the advantage of MATLAB and that of PLC. The improved model-free adaptive control is then used by the closed-loop system and many experimental data are got.By analyzing the data gotten from the experiment, the control scheme designed by this paper is well suited for the control demands of the electric heating pot, and can be used to the other industrial process.