Research On High-Precision Control Technology Of Magnetic Navigation For Capsule Endoscope

Gastrointestinal diseases are a serious threat to human health,causing about 8million deaths worldwide each year.Currently,flexible endoscopy is the gold standard for diagnosing gastrointestinal diseases,but it can be uncomfortable and traumatic if not performed properly.With the development of the capsule endoscopy technology,it is widely used in examining digestive tract diseases because of its userfriendly,painless,no cross-infection and other advantages.At present,passive capsule endoscopy mainly relies on intestinal peristalsis and the gravity of the capsule to move in the intestinal tract.Therefore,there are still problems in clinical application: 1)The movement of the capsule endoscope is not controllable,and it can not stay and observe the intestinal lesions.2)Long inspection cycle.3)The capsule endoscope is easy to stay in the human body.To overcome these problems,researchers have proposed an active capsule endoscope for the diagnosis and examination of the human digestive tract.This paper studies a magnetic navigation capsule endoscope system with active control based on the above considerations.The system is studied from model design,theoretical analysis,modelling and simulation,and experimental verification.A magnetic navigation system for the capsule endoscope based on a 7-DOF manipulator is proposed.Based on the precise positioning and control of the robotic arm,the motion and pose changes of the capsule endoscope in the simulated intestine were realized.The specific research work is as follows:Firstly,to analyze the motion resistance of the capsule endoscope in the intestine,a fluid-structure coupling model of intestinal fluid and intestine was established to simulate the stress conditions of capsules of different shapes under a dynamic intestinal fluid environment.Based on the model,the flow velocity distribution and the stress of the capsule endoscope in horizontal and curved intestinal environments were obtained.The relationship between the stress of capsule endoscope and intestinal diameter,intestinal fluid viscosity coefficient,capsule elevation Angle and capsule head shape was analyzed by orthogonal design.Finally,variance analysis was conducted to obtain the relationship between the capsule endoscope motion and the force on the capsule head,the strength of intestinal fluid flow rate and the maximum stress on the intestine.Secondly,for the use of permanent magnets as the external magnetic field,the capsule endoscope contains permanent magnets as the internal magnetic field to establish a magnetic link between them.According to the control principle of magnetic drive,the magnetic analysis model of driving external magnetic field is established.The spatial distribution of the magnetic field of the permanent external magnet was analyzed by electromagnetic simulation,and the variation of electromagnetic force and torque of internal permanent magnet with distance in external permanent magnet and capsule endoscope was analyzed.Thirdly,aiming at the current application scenario of the magnetic navigation device of capsule endoscope,a magnetically controlled capsule inspection system based on mechanical arm control was designed to control the position and posture of the capsule endoscope in the intestine by controlling the spatial position and posture of a permanent magnet at the end of the mechanical arm.A master-slave control simulation platform for manipulator control was built based on the robot arm’s ability to receive instructions in the space position,to locate the operation at a certain point in space accurately.The forward motion,inverse motion and master-slave control of the manipulator are analyzed.Finally,the performance of the capsule endoscope was tested in PVC pipe and isolated porcine intestinal pipe by the magnetic drive experimental platform.The experimental results show that the proposed magnetically driven capsule endoscope system based on the robotic arm is safe and feasible and can control the motion and lesion examination of the capsule endoscope in the tortuous PVC tube and intestinal tract and improve the diagnostic efficiency.It lays a theoretical foundation and technical verification for the development of active control the capsule endoscopy techonology.