Temperature Tracking Control Based On Smith-Fuzzy PID

Temperature is an important object of control in many fields of industrial production.Most of the physical and chemical changes are influenced by temperature.But the temperature control system usually has the characteristics of large inertia,hysteresis and time variation,which brings some difficulties to the design of controller.Especially for occasions where temperature tracking control is needed,it is very difficult to obtain good tracking results.Therefore,this paper takes the small electric heating kettle as the research object,and studies the modeling and control strategy of the electric heating temperature tracking control system.Specific research contents are as follows:Firstly,the composition and working principle of the electric heating temperature control system are introduced.The experimental platform control system based on SIEMENS S7-1200 PLC as control core,pulse width modulation solid state relay as actuator,and PT100 platinum thermal resistance sensor to collect temperature data of heater is constructed.At the same time,the principle of thermal resistance temperature measurement and pulse width modulation(PWM)principle are introduced briefly.Secondly,the mathematical model of the electric heating kettle is established by analyzing the law of heat flow,and the influence factors of the dynamic characteristics of the controlled object are discussed.In order to obtain the specific parameters of the controlled object,the tangent method is used to identify the off-line parameters of the established mathematical model.Then,the control strategy of the electric heating temperature control system is studied,and the fuzzy PID controller based on Smith estimation is designed.Smith predictor is the role of lag compensation,eliminate the time lag effect on system stability;fuzzy PID controller is mainly to compensate Smith predictor for the controlled object model parameters are very sensitive to this problem.Simulation results show that the Smith-fuzzy PID control strategy adopted in this paper has smaller range of temperature tracking error,better tracking effect and higher temperature tracking performance of the system.Finally,through the development on the experimental platform,completing the control algorithm in the PLC program,making the new version of the man-machine interface,and making communication between the PLC and the man-machine interface,we can conduct the tracking tempetatrue experiment by three control methods of conventional PID,Smith-PID,Smith-fuzzy PID control in the experiment platform.The experimental results show that the variation range of the Smith-fuzzy PID control strategy can effectively reduce the temperature of the tracking error,improve the temperature tracking accuracy,better tracking effect,and improve the overall temperature of the system tracking performance.