The Application Research On Fuzzy PID Control In Hyperthermia Apparatus Flow Velocity Control

In recent years,the malignant tumor has become a serious threat to the main causes of human health,and how to effectively treat cancer has become a difficult problem for research.At present,the method of treating cancer is mainly in the following ways:radiotherapy,chemotherapy and hyperthermia.Hyperthermia apparatus,which can be used to achieve the treatment through the computer controlling the perfusion flow velocity,is a instrument of hyperthermia.Due to the finest human tissues,especially in the case of tumor tissue erosion,the body cavity perfusion speed is neither too large nor too small,or it can damage the normal tissue of the human body and won't produce an effective result for the treatment.Therefore,how to improve the control accuracy of flow velocity is the key to the hyperthermia apparatus.The traditional automatic control is depended on accurate mathematical model to control,but fuzzy control belongs to intelligent control theory,mainly relies on people's thinking,the related knowledge of expert and the experience of the field operator to achieve control.Fuzzy control has advantages of better dynamic characteristics,small overshoot and strong parameter adaptability,but it still has the low control accuracy,the poor steady-state characteristics and easily generating the static errors.While PID control structure is simple,the control effect is more stable,and it can eliminate the steady-state error and has low static error.However,its dynamic characteristics are not good and easy to produce high overshoot in the control process.In order to solve these problems,this paper combines fuzzy control and PID control to design the fuzzy PID control algorithm.Switching method is adopted to the control process,the fuzzy control is used when the relative value of error is large and the PID control is used when the relative value of error is small,which achieve complementary advantages of fuzzy control and PID control,and ensure that the system has a better control effect.Firstly,this paper studies the basic theory of fuzzy control and PID control,introduces the principle and characteristic of the two algorithms,and analyzes their advantages and disadvantages.Secondly,the fuzzy PID control algorithm is proposed,and the fuzzy control and PID control system are detailed design and modeling based on the system transfer function.Then,optimize and select the parameters that have influence on fuzzy control and PID control,and pick the best parameters according to the results of the simulation.Several experiments are carried out to determine the optimal cut-off point of fuzzy PID control system,and the simulation shows its advantages.Finally,the configuration software and PLC are connected to achieve the real-time flow velocity control of hyperthermia apparatus,and further verify the control quality which is much better of the proposed algorithm.The results show that the fuzzy PID control algorithm applied to the flow velocity control of hyperthermia apparatus,which not only can ensure the dynamic characteristics of the system better,but also improves the control accuracy of the system to some extent.What's more,it makes the flow velocity control more precise,and the stability of the system is good,the proposed algorithm is superior to the fuzzy control and PID control algorithm.