Fuzzy Adaptive PID Design And Modified Smith Predictor In The Thermal Modified Wood System

As the world population growing, the demand for forest resources is increasing. The renewable capacity of forest resources has been unable to meet the growing needs of humanity. So how to use the limited timber resources effectively and improve the quality of wood production, attracts the attention of governments all over the world. There is a new technology called thermal modified wood, which is free of any chemical agents and it has qualities of anti-corrosion, anti-moth-eaten, environmental protection, durable and so on. So it is an effective measure to increase the service time of wood, reduce environmental pollution and improve the quality of wood production. However the control algorithm used in the production process is not mature, that is the main reason why the production efficiency of it is not high. So it has great significance for the studies of the process control to the thermal modified wood.In this paper, an improved adaptive fuzzy PID-Smith predictor controller is proposed, based on fuzzy PID control, adaptive control and Smith predictor. The program consists of front-end and back-end controller. Fuzzy adaptive PID control is used as a front-end controller, instead of the traditional PID controller. According to the law of regulating the control parameters and the features of the thermal modified wood control process, we design a series of fuzzy rules and applied them to the fuzzy adaptive PID controller to improve the stability of the system. Finally, stability of fuzzy adaptive PID control is verified, based on the Lyapunov theory. In addition, since the thermal modified wood control systems with large delay, this article had done some studies on Smith predictor. For the system which can’t be described by the precise mathematical model but has time-varying parameters and large delay, the PID-based Smith predictor exists poor stability and large overshoot. A feedback loop and an adaptive regulator are imported to ensure the stability of the system and enhance the adaptability of the environmental change, based on the PID-based Smith predictor, and we used it as the back-end controller.In this paper, simulation experiments are done on the Matlab. First, the stability of fuzzy adaptive PID controller, as a front-end controller, is verified. And then the comparative experiments between the fuzzy adaptive PID-Smith control algorithm and the improved one are done on the exact model and model mismatch situation. Simulation results show that: compared to conventional fuzzy adaptive PID-Smith control algorithm, the improved scheme, to some extent, reduce the control system overshoot. In the condition of the model mismatch of 20%, the improved program less affected by changes in the mode, and the value fluctuates around a narrow range in the condition of outside interference signal, so the new method holds a strong stability.In this paper, the modified fuzzy adaptive PID-Smith predictor controller is applied to thermal modified wood control system. A mathematical model of temperature control system of the thermal modified wood is used as an object to the simulation. Simulation results show that:the improved method is a good way to improve the response speed and enhance the stability of the control system, to some extent. So it is a suitable control method to the thermal modified wood control system.