| According to the World Cancer Report 2020 released by the World Health Organization(WHO),the incidence of gastrointestinal malignancies(colorectal cancer and stomach cancer)is among the top five in China.Physical examination screening plays an important role to realize early detection and treatment,and improve the cure rate of gastrointestinal diseases.At present,traditional gastroscope and capsule endoscope can be applied to human gastrointestinal examination.Traditional gastroscopy has accurate results and biopsy functon,but it is easy to bring the risk of pain and infection.Capsule endoscope can provide a comfortable and clear view of the small intestine,but there is no drive mechanism,and it is easy to miss the stomach.As an active control of gastrointestinal examination equipment,capsule robot integrates multiple fields such as electromagnetic control,wireless communication,biological materials and intelligent manufacturing,and can safely and effectively carry out noninvasive diagnosis and treatment of gastrointestinal diseases,becoming an important milestone in the development of micro-medical robot.However,due to the complex environment of human gastrointestinal tract and the increasing demand for diagnosis and treatment,capsule robot with soft surface and medical function is still in the stage of theoretical research.There are many problems in mechanical structure,positioning methods and control strategies,which greatly limit the application of capsule robot in clinical practice.In view of the problems existing in the current capsule robot,this thesis carries out research in the following aspects:(1)Based on the rheological and magnetization characteristics,a driving method combined magnetorheological fluid and Nd Fe B material is proposed,and a structural model of magnetorheological soft capsule robot is designed.Symmetric turning motion mode of magnetic controlled capsule robot is studied in gradient magnetic field.Compared with three different design schemes of composite shells,the magnetorheological soft capsule robot has better driving and compliant characteristics.The distribution of coupled magnetic field is studied inside the capsule robot,and an oscillation mechanism with high compatibility is designed to realize the targeted drug delivery function.(2)Multi-magnetic dipole model is derived,and the near field error of which is corrected based on the magnetorheological soft capsule robot.The dynamic relationship of magnetorheological soft capsule robot on horizontal and slope surface is studied,where the dynamic models of the capsule robot are constructed,and the co-simulation analysis of magnetic field and gravity field is carried out.The motion characteristics of the oscillating plate in the oscillating mechanism are studied,the numerical analysis of which is carried out,and the feasibility of targeted drug delivery function of the capsule robot is verified by simulation.(3)The interaction between the capsule robot and the external drive magnetic field is studied in this thesis,and a magnetic field location algorithm model is deduced based on magnetic sensor array.In order to reduce the calculation error of magnetic field,an arrangement method of double-layer symmetric sensor array is proposed.According to the principle of vector superposition of magnetic field,the numerical simulation analysis of external drive permanent magnet is carried out,and the validity of the positioning method is verified based on double-layer symmetric sensor array.Furthermore,the positioning device of the capsule robot is built.The LevenbergMarquardt algorithm is optimized by using BP neural network model,and the inverse model of magnetic field for the capsule robot is solved to achieve precise positioning.(4)The motion characteristics of magnetorheological soft capsule robot in stomach is studied,and a ‘detour route’ motion mode based on space planarization is proposed to simplify the control steps of the capsule robot.The magnetic field platform of manipulator-permanent magnet is built,and a combined motion control system is designed,including the main motion subsystem based on fuzzy controller and the auxiliary motion subsystem based on PID controller.A wolf parallel hunting strategy is adopted to improve the traditional gray wolf optimization algorithm,calculation accuracy of which is enhanced.The improved gray wolf optimization algorithm is utilized to adjust the controller parameters in the combined motion control system,where the control performance of the system is optimized.(5)Prototype of the magnetorheological soft capsule robot is made,and a corresponding PC system is designed based on the platform of magnetic field and positioning device.The motion tests of the magnetorheological soft capsule robot in the experimental platform and simulated stomach environment are carried out to verify the effective control strategy and accurate positioning method,respectively.The targeted drug delivery tests of magnetorheological soft capsule robot are carried out,and the feasibility of targeted drug delivery function is verified by experiments.The dissertation has 109 figures,21 tables and 140 references. |
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