The Research Of A Micro Robot System For Intestinal Diseases Diagnoses And Its Wireless Power Transmission Technology

Being as the most promising alternative of traditional endoscopy,the endoscope micro-robot system can overcome the shortcomings and defects.Supported by the National Natural Science Foundation?NO.6167327,NO.81601631?,this paper foucuses on the endoscope micro-robot system and its wireless power transmission technology,seeking a new diagnostic approach of intestine diseases without invasion.The intestine has a characteristic of non-linear biomedical properties,and the endoscope micro-robot has to deal with its physical environment.Then,based on the locomotion principle of inchworm,which fits best for the intestinal environment,the design and implementation of endoscope micro-robot is conducted.The inchworm endoscope micro-robot consists of three parts:two clamping mechanisms?CM?at either end of the robot and an axial telescoping mechnism?TM?in the middle of robot.The CM should have a wide adjustable range of diameter to suit for the varying diameter of intestine,and therefore adopts the structure of radial expanding mechanism.The diameter of the CM entirelly shrinked is 14mm,and can be maximally expanded to 32mm.As a result,the maximum available ratio of the varying diameter of CM is 2.29.During the delatation of intestine caused by CM,the force of expansion is in the range of 0.9N².55N.Moreover,at run time,the closed curve formed in the radial side of CM effectively avoids the intestinal damage.With its compacted structure,the TM designed saves the space in the middle section of endoscope micro-robot for the receiving coil of wireless power transmission module.Besides,this TM with a push force of2.97N has a designed route of 10.5 mm.Firstly,the force caused by intestine on the endoscope micro-robot is analyzed,and then the robot designed can be divided into two parts:the CM and the robot body.The axial force caused by intestine on the robot body has to be larger than that of the CM to achieve the clampling of the CM and the intestine.Next,two models of the intestine,which has been expanded by the CM and robot body separately,are built,and by the models built,the axial forces on the expanded CM and robot body can be analyzed.At last,the axial force caused by intestine on the CM and robot body are obtained by experiments.The tested results indicates that when the diameter of robot body is set to 14mm,the axial force caused by intestine on the robot body of different length is in a range of 0.1 N to 0.4 N.Meanwhile the expanded diameter of CM has to be larger than 26mm to ensure that the axial force caused by intestine on the CM is far larger than 0.4N,and thereby the clampling of the CM and the intestine is achieved.To provide continuous and sufficient power supply for the endoscope micro-robot,a wireless power transfer system based on the weakly inductive coupling is suitable,which includes a transmitting end and a receiving end.The solenoid pair is utilized in the transmitting end,while the receiving end adopts a thin wall one-dimensional receiving coil,which is installed in the middle section of endoscope micro-robot and thus will not increase the space of robot.Besides,both the video image module and control communication module for intestinal robot are developed.After that,the prototype of endoscope micro-robot is fabricated.The diameter,length and weight of the prototype is 14 mm,45 mm,and 22.43g respectively.Moreover,the mechanical characteristic measured agrees with the theoretic results.Then,the motion properties of the prototype in flexible plastic pipe,rigid pipe and isolated intestinal canal are tested separately.For the prototype in vertical flexible plastic pipe,its ascending and descending operating speed is 2.9mm/s and 3.3mm/s,respectively.While,the operating speed of the prototype in curved rigid PVC pipe reduces to 1.5 mm/s.The horizontal danging isolated intestinal canal can be divided into downward-sloping part,upward-sloping part and horizontal part.The sloped parts of isolated intestinal canal have a great impacte on the operating speed of robot.In the downward and upward sloping parts of isolated intestinal canal,the operating speed of the prototype is 1.2mm/s and 0.3mm/s,separately.For the prototype in the horizontal part of intestine,its operating speed is 0.7mm/s.At last,to deal with the problem of the peak power of prototype system,a capacitor circuit is added into the regulator circuit of control communication module in prototype.With the utilization of the wireless power transmission module,the performances of all modules in the prototype is tested.It can be known from the resutls that the magnetic field generated by wireless power transmission module has little effect on the performance of each module,and thus the wireless power transmission module is compatible with the other modules of prototype.The transmitter of wireless power transfer system?WPT?is optimized with the structure of transmitting coil.To ensure that the performance of WPT system can be effectively improved by the transmitter optimized,firstly,the performance evaluation parameters of WPT,which is only related to the transmitter,is derived;then,for the transmitting coil with different structures,the performance evaluation parameters is calculated through a high-precision analytical model of the transmitting coil built;finally,according to the calculated results and the actual test data,the structure of transmitting coil is optimized,which improves the power efficiency of WPT on the premise of satisfying the power requirement of robot to make sure that the transmitter works stably for a long time.In addition,based on the performance evaluation parameters of transmitter and the analytical model of coil,the optimization process of transmitting coil is summarized and then standardizes.According to the actual clinical requirements,the diameter of transmitting coil grows to 690mm.The performance evaluation parameters of WPT only related to the transmitter derived areH_c² R₁ and the maximum H_c² _d.The optimized transmitting coil is wound with two LITZ wires in both axial and radial directions,and the number of coil turns is 30.The power efficiency of the WPT optimized is enlarged to 7.37%,which is far than the power efficiency of the similar WPT?1.24%?.Moreover,the maximum magnetic field in the center area of transmitting coil can exceed the limits of bio-electromagnetic safety.Thus,the transmitter optimized can be treated as a large launching platform for different intestinal robots.In the case of impedance matching for the receiving circuit,the maximum power transferred of WPT system P_LM is obtained.Thus,duo to its relatively smaller P_LM,a larger equivalent series resistance of receiving coil caused by the influence of robot's parts degrades the performance of WPT system.A loading coil tightly coupled with the receiving coil is added to form a three-coil WPT system that can optimize the receiving end of WPT system,and the coupling factor between loading and receiving coil is adjustable.In accordance with the impedance reflection theory,the three-coil WPT system is theoretically analyzed,and then the applied scope and design criteria are both specified.After that,to introduce the design process of three-coil WPT system,based on the design criteria,the specific receiving end is optimized by simulation,and the performance of the three-coil WPT system designed is consist with that of the corresponded prototype system.In addition,the example optimized illustrates that significantly increases the amount of power transferred and reduces the power losses of receiving end when the robot is in a state of high power consumption.Also,to reduce the power consumption of receiving end when the robot is in a state of low power consumption,the input power of WPT system has to be lowered to control the temperature rise of receiving coil.The three-coil WPT system has a higher design freedom,and can effectively enhance the performance of WPT system.This paper mainly studies the motion module and the inductively power transmission technology of endoscope micro-robot,and the biomechanical property between the endoscope micro-robot and intestine.In addition,the research and discussion on the control and communication technology and the integration technique of the modules of endoscope micro-robot are included as well.All the research work above promotes the clinical application of the endoscope micro-robot.