Study Of Active Control Method And Electromagnetic Design Of Micro Capsule Endoscope

Capsule Endoscope, as a new technology involving integrated circuits, MEMS, image processing, radio transmission, and power supply, has made a significant break-through in the GI examination and therapy. Nevertheless, the inaccessibility of any motion control of the capsule makes the inner exploration not accurate enough. As the movement of the capsule depends solely on the peristalsis system, accordingly, their movement, position, and orientation are substantially random. Since it takes 6-8 hours for an examination, a great amount of time is consumed in the inspection and doctors also cannot perform a pinpoint analysis once an irregular vision has been found. All of these drawbacks render capsule endoscopy extremely high in cost but extremely inefficient in terms of time spent and resources used.With the development of pipeline robotics,micro-electro-mechanical systems (MEMS) technology and wireless communication technology, several kinds of mobile micro-machines have been proposed and fabricated for being used in active exploration of the gastrointestinal tract. Active steering of the capsule endoscope suggests a solution to the locomotion control of the self-propelled endoscopic capsule.In this study, we propose a novel solution for the active locomotion of capsule endoscope in the gastrointestinal tract based on the rotating magnetic field technology and magnetic dragging navigation control method and we built the related magnetic analysis model and analyze the viability of this driving method and COMSOL is introduced to simulate the distribution of magnetic field and calculate the driving force and torque. Experiments and measurement are also conducted to prove the results of theoretical analysis and simulation.Chapter 1 reviews the current development of capsule endoscope and some active control methods. Also the existed problems of current capsule endoscope are discussed, and then the author makes an introduction to the whole thesis.Chapter 2 mainly discusses the electromagnetic driving method based on the rotating magnetic field. Magnetic analysis model is established and finite element simulation is performed for obtaining optimized mechanical and control parameters for generating appropriate external magnetic field. The design and optimization of the proposed magnetic propulsion system embody a trade-off among system performance, safety of patients, and cost-effectiveness. The result shows that a large area of rotating magnetic field can be obtained by two groups of Helmholtz coils. Further, by designing the structure, size and number of these two pairs of Helmholtz coils and the magnitude of the energizing current sent in, two harmonic magnetic field with the same magnitude of magnetic flux density can be obtained to synthesize a rotating magnetic field plane when overlaid, whose normal vector is perpendicular to both axes of two coils groups and the direction changed as a function of time. Capsules with outer magnetic shell magnetized in radial direction will be driven under external rotating magnetic field and move in the normal direction of rotating magnetic field plane.Chapter 3 focuses on a novel steering method for active locomotion of a miniaturized endoscopic capsule moving in the gastrointestinal tract based on the magnetic dragging navigation method. We theoretically analyze the viability of this driving method and exploited COMSOL to simulate the distribution of magnetic field for assisting the design of magnetic navigation system. Experiment and measurement are conducted to prove the results of theoretical analysis and simulation. The proposed technique suggests a feasible approach in the field of gastrointestinal endoscopy. Further research is currently in progress for realizing endoscopic capsule's movements in 3D space and visualizing the locomotion control by ways of ultrasonic image.In Chapter 4, based on the magnetic dragging method, we proposed an automated multi-axis magnetic propulsion system for self-controlling endoscopic capsule's location and orientation in the gastrointestinal tract with maximum level of safety and cost-effectiveness. In order to judge the feasibility of the proposed system, experimental tests are carried out and it demonstrats controlled translations, rotations, and rototranslations of the capsule/clay complex under this novel propulsion system.