Researches On Key Technologies And Related Experiments Of Micro-bionic Robots For Inspecting The Intestines

As one of the promising alternatives to the traditional endoscope,the pill-sized micro-bionic robots which can inspect the intestine actively have attracted a lot of research interest during the past decades.Under the supports of the National Natural Science Foundation of China(No.61673271,No.81601631)and the Program of Shanghai Science and Technology Commision(No.14441902800,No.15441903100),this paper focuses on the research of the key technologies and related experiments of the micro-bionic robots so that a new device for diagnosing the intestinal diseases can be provided.The key technologies involve the compatibility between the robots and the intestine,the design of the locomotion mechanism(LM),and the development of the dedicated wireless power transmission(WPT)system.In the aspect of the compatibility between the micro-bionic robots and the intestine: After considering the particularity of the intestine which is slippery,viscoelastic,and freely suspended,as well as the abilities of two-way locomotion,expanding,and anchoring which are essential for a qualified device for inspecting the intestine,we proposed two locomotion principles of sliding-clamper based and inchworm-like.The sliding-clamper based principle is implemented with a linear motion unit(LMU)and an anchoring unit(AU)which can be actuated by the LMU to move forward and backward.The inchworm-like principle is implemented with a LMU and two AUs which are fixed at both ends of the LMU.The AU is for expanding and anchoring,the LMU is for generating a displacement,and when they cooperates with each other,two-way locomotion can be enabled.The included modules of the micro-bionic robots are introduced,and their axial lengths are served as the design parameters.By analyzing the intestinal deformations induced by the locomotion steps of the robots based on these two locomotion principles,the corresponding continuity models are built,which correlate the locomotion efficiency and the design parameters quantitatively;and the correctness of the models is then validated experimentally.From the continuity models and the related experiments,we find:(1)the locomotion efficiencies of the sliding-clamper based and inchworm-like robots can be improved by increasing the periodic stroke;(2)to minimize the adverse effect exerted by the functional modules that need to be installed at the both ends of the robots,the ratio between the lengths of the functional modules assigned to the front and rear ends should be in a range of 1:(1.5-3)for the sliding-clamper based robot,while for the inchworm-like robot,the functional modules should be installed at the rear end as much as possible but the length should be less than 10-12 mm.In addition,a method of using the long contact devices to improve the locomotion efficiency of the inchworm-like robots has also been proposed and proven effective,which is also beneficial to avoiding intestinal injury relating to excessive expanding.In the aspect of designing the LMs of the micro-bionic robots: arc-shaped leg based expanding mechanism is employed for the AU,which enables an expanding/retracting diameter ratio which exceeds 200%;a pair of lead-screw and nut is employed for the LMU which works reliably and is able to generated a strong thrust.With the AU and LMU,we implemented a sliding-clamper based LM for the small intestine,types I and II of the inchworm-like LMs for the small intestine,and an inchworm-like LM for the colon.Kinetics analysis for the AU and LMU was conducted to select proper motor model and reduction ratio,so that the AU and LMU can perform actions effectively on the premise of not stimulating the intestine.To avoid mechanical and short-circuit faults of the LMs caused by the intestinal mucus,the LMs were sealed with the local and whole strategies,using O-rings,whose design parameters were selected based on the analysis and simulation results to minimize the sealing caused mechanical loss.The two sealing strategies were verified to be feasible and reliable with experiments.In the aspect of WPT technology specific for the micro-bionic robots: two novel distributed and interlaced hollow-cylinder-like 3-D receiving coils were proposed to improve the space utilization of the inchworm-like robots,and they did not increase the robots length as compared to traditional solid 3-D ones.An optimization method for the distributed 3-D coil was proposed with the consideration of the human safety and the limited available space in the robots.This method involves a lot of theoretical formulas and several key electric parameters were measured with experiments,it can be used to select proper copper wire diameter,number of turns,and the resonance frequency.As for the interlaced 3-D coil,we derived a guidance equation for selecting its number of turns,so that the three dimensional coils can output identical electric powers.To handle the voltage drop issue caused by the motor starting and stalling which require short-time high power,a novel power management circuit containing a super-capacitor array(PMC-SCA)was proposed.Design details and working principle of the PMC-SCA were introduced,and its analysis model was build based on deducing the relationships between the input resistances of each two adjacent modules in the PMC-SCA.The analysis model can be used to optimize the series-parallel structure of the SCA and its charging voltage.A PMC-SCA prototype with a size of(37)13mm×4mm has been fabricated,it can make the working voltage of the robot above 3V all the time,thus ensuring performance of the voltage-sensitive modules in the robot.The research of the above three key technologies and related experiments can provide valuable reference and guidance for the design,implementation,and improvement of the micro-bionic robots for inspecting the intestine.