Research On Driving Characteristics Of Petal Shaped Capsule Robot

Micro medical robot can be used to navigate autonomously inside human body in places such as, digestive system, arteries, and spinal canal, and perform some delicate tasks, for example, drug delivery, tumor detection, and even minimally invasive microsurgery. It features safe, painless and efficient, and has great significance in medical applications.This paper presents a rigid petal-shaped capsule robot based on the principle of multiple wedge effects. It is greatly simplified in structure comparing with previous generation robot with radical clearance compensation; What’s more, its unique petal shape can produce multiple wedge effects together with the pipe wall, significantly increasing the average fluid hydrodynamic pressure, thereby improving the driving performance of capsule robot in viscous liquid environment.Firstly, introduce the structural features of the petal-shaped robot and the control theory of rotating magnetic vector, conduct dynamic analysis of the capsule robot, and solve the fluid Reynolds equation on the surface of the robot using finite difference method. Hydrodynamic pressure model is established to satisfy the actual boundary conditions of the petal-shaped tile, and numerical integration method is used to solve the shear force of the robot. The force balance equations on the axial and circumferential directions can be built based on this.Then, analyze the impacts of the structural parameters on driving characteristics of the petal-shaped robot. Genetic algorithm is used to optimize the structure of the petal robot, taking the steady state swimming speed and the viscous liquid friction moment of the capsule robot as objective functions.For realizing wireless driving of capsule robot, an innovative driving theory of rotating magnetic vector is proposed. To get the relationship between current, structure parameters of the coils and the magnetic field strength, electromagnetic model of the three-axis square Helmholtz coils is built. Combined with the equivalent circuit model of the three-axis square coils, we can deduce the universal voltage formula for generating the rotating magnetic field, which is verified by simulation, and then analyze the dynamic characteristics of the square coils as well as the quality of the superimposed magnetic field, mainly include the dynamic response of current, uniformity, and stability of the magnetic field. To validate the driving performance of the petal-shaped capsule robot and the feasibility of the control theory about rotating magnetic vector, prototype of the petal capsule robot and the magnetic field generator have been developed. And we conduct a series of demonstration experiments about robot prototype in plexiglas tubes with variety of shapes, such as, straight pipe, spiral pipe, and so on. Finally, the success of the driving experiment of robot in isolated pig intestine proves the practicability of rotating magnetic vector control of petal-shaped capsule robot further.