| Under the supports of the National Natural Science Foundation of China and the National High Technology Research and Development Program of China, a miniature robot for intestinal inspection was researched with the purpose of exploring a new way for intestinal inspection and diagnosis with minimal invasion or non-invasion. Wireless powering technique was researched to attack the tethering obstacle, which prevents the robot going further into body.An earth-worm like miniature robot was developed based on the analysis of environment characteristics of human intestinal. The robot gait was realized via linear driver, which was composed of dc motor, gear reducer and screw-nut transfer. The robot may execute instructions including forwards, backwards and halt. Wireless communication subsystem was contributed to information exchanging between inside body and outside body. The designed digital RF communication module was capable of antijamming with baud rate of 50kbps. The imaging module captures images and transmits to outsides with power consumption of 200mW. The image streams at rate of 30 frames per second with high resolution level up to 300,000 pixels. Wireless power subsystem was dedicated to providing electrical energy for the robot. The robot strides forward from"wire"to"wireless"via these three subsystems. The developed prototype is 12mm in outside diameter and 150mm in length. The robot kinematics performance and wireless powering reliability were validated by in vitro experiments.Powering is the bottleneck obstructing the progress of implanted diagnosis and treat systems. The robot wireless powering system using inductive coupling was thoroughly research in this thesis. The coupling coefficient between transmitting coil and receiving coil was analyzed, which is different from that in transcutaneous energy transmission system. The transmission efficiency of four circuit topologies was deduced and concluded the maximizing conditions. The serial resonant circuit and parallel resonant circuit should be used according to the application situation. The essential factors effecting power transmission efficiency, which are coupling coefficient and coils'quality factor, was revealed. A self orientation mechanism was put forward to maintenance the receiving coil orientation, which is internally undetermined, so as to enhance power transmission efficiency. The important conclusion of optimal transmission frequency was drawn from the theoretic and experimental research on coil quality factor, which establishes the foundation of inductive power transmission. In the process of robot working in body, the coupling coefficient of transmitting and receiving coil is always changing, resulting of power transmission efficiency fluctuation. In order to keep efficiency balance and satisfy the maximizing conditions, dual closed loop power transmission system was designed, which consists of receiving voltage feedback based on wireless communication and frequency lock loop. The closed loop improved the stability and reliability of transmission energy.The intestinal inspection robot is powered via wireless power transmission system based on inductive coupling. The patient may suffer from the electromagnetic field produced by transmitting coil. The effects of electromagnetic in human body were researched in this thesis. The electromagnetic field takes effect on human body in the form of thermal effects and non-thermal effects through three basic coupling mechanisms. The long-term effects in human body are currently undetermined because of short of epidemiological reports. However, with the progress of cognition in electromagnetic field, some guidelines and standards have been established for limiting exposure to electromagnetic field by involved organizations in the world. The exposure to electromagnetic filed produced by transmitting coil was evaluated according to ICNIRP (International Commission on Non-Ionizing Radiation Protection) guidelines and IEEE C95.1 standard. Current density and SAR are the primary dosimetric parameters for low-frequency magnetic fields. However, these parameters data can be hardly acquired by experimentation. Numerical electromagnetism provides a new way for biological dosimetry. The effects on human body were obtained by numerical calculation method in this thesis. A high resolution realistic human model, which consists of 56 kinds of tissues or organs, was constructed based on VHP (Visible Human Project) dataset through semiautomatic image segmentation technique. The resolution of the model is 0.33mm in transverse section and 2mm between slices. The dielectric properties of every voxel were described by DPF file. Thus a electromagnetic calculation model was built. The current density and SAR (Specific Absorbtion Rate) in human body caused by transmitting coil electromagnetic field were calculated using finite integral method. The influencing factors were analyzed, such as transmission frequency and transmission current. The results provide biological safety references for the design of wireless power transmission system.
|
PDF Full Text Request