| Power supply and body safety are two main issues to be considered in micro diagnosis and treatment system for gastrointestinal(GI) tract. The former matters the feasibility of the system, while the latter is the necessary condition for clinical application. With the micro treatment system developing, the power demand increases correspondingly, to increase work time, image quality and diversity of treatment and control movement mode. The first problem can be solved by wireless power transmission technique based on electromagnetic induction. And it also needs to solve the human body safety to realize the clinical application. Supported by national and provincial science project, this paper makes the research and design for micro diagnosis and treatment system based on wireless power transmission and human body safety.According to the working environment of the device, system module is designed to satisfy the requirement of the basic structure, safety, efficiency and authenticity. Judge function containing the induced current density and SAR is derived based on the international electromagnetic safety standard, and the safe operation range of power transmitting system is determined; characteristics of gastrointestinal temperature raising is analyzed with bio-heat transfer equations, and the safety constraint condition is obtained; math model with energy transfer efficiency as the aim function is constructed by solving the electromagnetic coupling equations, and the corresponding parameters of energy emitting and receiving part are separated from each other which makes convenience to upcoming design and research; the authenticity of wireless power transmitting system is analyzed mainly on three aspects, the uniformity of magnetic field, the stability of frequency and posture stability. The above parts make up the design of the wireless micro diagnosis and treatment system, and provide theoretical evidence for later work.To meet the power demand of device, researches on coil structure, radio safety, magnetic field uniformity and frequency stability are studied. Combining the strength of solenoid and Helmholtz coils, the double layer solenoids pair are designed for transmitting coils, which make good compromise between the intensity and uniformity of the transmitting magnetic field; high accuracy body electromagnetic model is built by finite integral method, after its simulation electromagnetic parameters like body tissue current density and SAR are obtained; magnetic field distribution functions of different transmitting coils are obtained from its original definition, and the magnetic field uniformity of the transmitting coils is verified by comparing the theoretical calculation and the experimental measurement result; the resonance of the transmitting circuits minimizes the effect of the frequency drift, and the effect of drift on driving current is evaluated by coil quality factor Q, and the two extreme conditions of coil’s effect on human body are compared. Thus the details of design and reference standard of the wireless power transmitting system are obtained.To satisfy the position stability of the power transmission, the method of the three-dimensional(3D) receiving coils is proposed, and researches on power receiving system are undertaken with the consideration on temperature rise safety, energy transmission efficiency and stability. The temperature rise safety of different kind of coil of litz wire is analyzed, and the safety range of internal resistance of receiving coil related to a load is obtained; material of magnetic core is determined with the initial magnetic conductivity and frequency curve; the geometrical shape of the core is cylinder according to the comparative magnetic conductivity; the number of wire with highest transmission efficiency is obtained from the measurement of the receiving power under coils with different number of wire; the relation between the power of receiving coil and its position is estimated, performance of serial and parallel receiving circuit are simulated, the position stability is analyzed, and all of them are verified by experimental measuring. The research on magnetic core, wound coil geometry and circuit provides design and realization for the wireless power receiving system.To verify the authenticity of the above theory and method, according to the module design of micro diagnosis and treatment system, two devices are constructed: a passive video capsule endoscopy and an active intestinal robot.According to the theories and methods on chapter 2 to 4, a video capsule endoscope and the wearable wireless power transmission system are designed and implemented. According to the safety of human body, the size and packaging requirements of video capsule endoscope are confirmed; working principle of the device and the technique on image capture and process are studied to decide the design plan of video system, and the package dimension is Ф 10 mm×26 mm,power consumption is 63.9 m W. Transmitting coils and circuits are particularly studied, and single layer ellipse-like solenoid pair are selected for the clinic requirements and human body abdomen size, and the weight is 2.1 Kg; the uniformity of magnetic field are evaluated by actual measurement; the parameters of the transmitting coils, like the number of turns(28) and operating frequency(208 KHz), are determined by analyzing the requirements of safety, power and transmitting efficiency; the transmitting circuits are packaged in a control box for portability, and the weight is about 1 Kg. The video capsule endoscope and wireless power transform system, which meet the requirements of wearable capacity, safety, efficiency and feasibility. The prepared system is tested in three environments: air medium, pork medium and living animal. In all of these experiments, the videos are clear and stable, the resolution of the images is 320×240; the frame rate of videos is 30 frames per second, and the wireless power efficiency is 2.8%. The feasibility of system is verified by the experiments, and the proposals for optimization have been offered.Based on inchworm movement mechanism, after study on movement structure and wireless energy transmission system, a gastrointestinal diagnosis and treatment robot comes out. The stress-strain curve is obtained from the tract mechanical character and constitutive equation; the leg-shaped clamp structure based on Archimedean spiral principle ensures the uniformity of expansion movement and safety for the tract; the grain on the top of the ―leg‖ provides addictive clamp force thus accomplish more efficient movement; the scalable leadscrew-nut mechanism can adapt the environment change on the tract well; the unitization design of drive motor saves the internal space; the initial volume of robot is Φ18 mm×41 mm, the axial tensile volume is Φ18mm×63mm, and the maximum radial expansion diameter is 38 mm; the movement performance is analyzed based on the characteristic of the test clamp and the scalable structure, and the anchoring force is 1.49 N, the maximum thrust is 9.67 N, the maximum pull force is 10.89 N. Wireless power transmission device is built according to the module design plan; a novel 3D ring-like receiving coil with less capacity and length is designed under the condition of energy transmission efficiency and stability. In vitro and in vivo experiments on tract robot are undertaken via wireless transmission technique, the power consumption of robot is less than 550 m W, and the wireless power transmitting frequency is 218 KHz. The energy transfer efficiency is 7.98% in vitro and 6.13% in vivo. The result verifies the authenticity of the general plan and indicates much about the upcoming work. |
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