This paper proposes a new type of radial expansion mechanism by adopting the scissor type telescopic
design for intestinal robot to meet the requirements of the intestinal robot’s movement and residence in the
intestinal tract. The robot’s maximum expansion radius is up to 25 mm, which can well adapt to the intestinal
tract with different diameters. At first, the mathematical model of the scissors-type telescopic mechanism (STM)
is established to further study its dynamics characteristics by theoretical analysis and simulation. Then, in order
to study the coupling effect between the STM and intestinal wall, the strain-energy function of Fung-type is used
to establish the constitutive model of intestinal wall. Moreover, aimed at solving the non-convergence problem
caused by the selection of material parameters in general Fung-type model, the restrictions for selecting material
parameters were given by using positive definite matrix theory. Furthermore, the motion coupling characteristics
between the mechanism and intestinal wall were analyzed by using the finite element method. The result shows
that if the expansion radius of the STM exceeds a certain value, the intestinal wall may reach its deformation
limit, which means that the maximum rotating angle of the three-claw butterfly disc of STM can be decided based
on the maximum deformation stress of the intestinal wall. Therefore, it provides a design basis for formulating a
reasonable expansion radius in mechanism control to avoid damage to the intestinal wall.
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