Design And Analysis Of The Actuation System Of An Endoscopic Capsule

Current technologies in biomedical engineering focus on minimally invasive surgerywith the features: safety, reliable, painless, and faster recovery, etc. In2000, a new typewireless capsule endoscope (WCE) invented by Given Imaging Ltd, which is able to acquireimages of the gut wall. This allows the exploration of the entire small bowel without pain ordiscomfort. However, the locomotion of the WCE completely depends on the gastrointestinalperistalsis. The posture, location, and speed of those capsules cannot be controlled duringtheir journey inside the GI tract. For the future function expansion, an effective and safelocomotion/actuation mechanism must be developed. Currently, the study on the active driverand post control of the capsule endoscopy has just started. A lot of colleges and researchinstitutes have proposed many kinds of driving principle for the intestinal micro robot.However, none of them is effective and can be used in clinical application.Considering inside of the gastrointestinal tract is a special environment, the designproposal of the screw propelling endoscopic capsule is worth further design and analysis. Andthe practical application in clinical of this capsule should be addressed with the help of furtherexploring.In the design, the actuation system and other supporting design is finish, according to theactual requirements of the safety and feasibility. A safe and reliable working strategy isproposed for the special screw propelling endoscopic capsule, the paper screw promote thecapsule endoscopy. And several prototypes of the screw propelling endoscopic capsule aremade.In the mathematical modeling of the screw driver, previous work was based on theory offluid hydraulic lubrication, without considering the unavoidable contact with the inside wallof the intestinal tract. The mathematical modeling of the driving force is built by three steps.Firstly, the hydrodynamic lubrication theory is applied to build a simplified one dimensionalmodel, and the two dimensional model is solved with the use of finite difference method. Therelation and the rule of influence between the design parameters of endoscopic capsule andthe parameters of environmental impact, and the pressure distribution around the screw, the driving force, the circumferential drag torques and the speed of the capsule are indicated.These connection guides the direction of the optimization design for the screw. Secondly,considering the complexity of the intestinal tract environment, the model when the screw andthe inner wall are in direct contact is analyzed. Finally, a weighted value is introduced tointegrate the two effects and a more complete model of the driving force is built. And becausethe length of the screw is short, similar to a propeller, the theory of propeller is used toanalyze the screw propulsion and drag torque.In the experiment study, the screw propelling endoscopic capsule get the average speedof60mm/s in a water pipe full of water, greatly faster than the other existing actuationmechanism of the capsule endoscopy. And the quantitative comparative and analysisexperiment for the thrust measure, is different from the previous research work. The thrustgenerated by the screw is measured directly, more close to the actual situation, and themeasured data is more scientific and in line with the fact, and more convicting.