Design Of Hyperthermia Temperature Control System Based On Magnetic Nanoparticles

Temperature control of tumor sites in tumor hyperthermia is the key to killing tumor cells while ensuring the survival of normal cells.Based on the relaxation heat production characteristics of magnetic nanoparticles and the temperature sensitivity of magnetization response intensity of magnetic nanoparticles,a thermal nanometer-based thermotherapy temperature control system was designed to provide a basis for a safer thermotherapy instrument.Firstly,the thesis introduces the composition and operation process of the system,and analyzes the harmonic distortion of the output of the high-frequency alternating magnetic field generating equipment.Due to the presence of harmonic distortion,the temperature measurement model in single-frequency excitation mode cannot accurately acquire temperature information.Therefore,the thesis constructs a harmonic-temperature measurement model based on BP neural network,and establishes a nonlinear mapping between the excitation magnetic field harmonics and the magnetization response harmonics and temperature of the magnetic nanoparticles.The system can obtain magnetic nanoparticles in real time through the model.Temperature information.Then the thesis studies the heat generation principle of magnetic nanoparticles.On this basis,the temperature rise model of magnetic nanoparticles is established,and the PID controller is designed to control the heating process of magnetic nanoparticles.By setting and adjusting the PID parameters,the system can achieve better steady-state accuracy,but it has a long rise time and is prone to overshoot.Since the heating process of magnetic nanoparticles is affected by environmental factors and their own characteristics,the temperature rise model of magnetic nanoparticles is not accurate,so the PID control effect is not very ideal.In order to improve the dynamic performance of the system and obtain better control effect,the thesis proposes to use A fuzzy PID controller that does not require precise modeling controls the heating process.In this thesis,the fuzzy rule table is drafted and revised,and introduced into the fuzzy controller.After several simulation experiments,the steady state accuracy of the heating process under the control of the fuzzy PID controller is improved by about 0.08 K,and the rise time is shortened by about 20 s.There is no overshoot.Comparing the magnetic nanoparticle heating process under PID control and fuzzy PID control,we can see that the dynamic and steady-state performance of the magnetic nanoparticle heating process under the control of fuzzy PID controller is improved.