Modeling of Frictional Resistance of a Capsule Robot Moving in the Intestine at a Constant Velocity

Abstract

Capsule robot is the direction for future development of capsule endoscopy. The imperfection of friction model between the capsule robot and the intestine has been one of the biggest obstacles of its development. Uniform motion is the main mode of the capsule robot in the intestine. However, the frictional resistance variation of the capsule robot in this period has not been understood completely until now. This is the research content in the paper. First, some experiments are conducted to measure actual frictional resistance with a homemade experiment platform. Next, the model of the frictional resistance at a constant velocity is established based on the hyperelasticity of the intestinal material and the interactive features between the capsule robot and the intestine. At last, the theoretical result of the model is proved to be reasonable by simulation analysis. The model is efficient to describe the frictional resistance variation at a constant velocity and can be seen as another kind of stick-slip motion. The work is hoped to perfect the friction model between the capsule robot and the intestine and contribute to the development of the capsule robot.

Frictional resistance model for tissue-capsule endoscope sliding contact in the gastrointestinal tract

“…Others have developed models for predicting the resistance force on a capsule in the bowel [22,[24][25][26]29], and they all rely on the assumption that the capsule distends the bowel in the radial direction, allowing for a hoop stress analysis. However, this assumption is not valid for a colonoscopy with insufflation or any other procedure where a cylindrical-shaped device is in one-sided contact with tissue (e.g., insufflated GI or abdominal wall).…”

“…Others have extensively studied the effect of capsule diameter, length, speed, normal force, and velocity, all of which were studied to assess model validity in this work. In summary, literature reports that resistance force is directly proportional to capsule speed [21][22][23][24][25][26][27][28][29], diameter [20-24, 29, 30], length [23,29,30], and normal force [21,23,31].…”

Analytical Friction Model of the Capsule Robot in the Small Intestine

“…My previous work also shows the same result [25,26,27], and we analyzed the friction resistance of CR at stage of start, stop and uniform motion [28]. It is found that the friction exhibits fluctuating change when CR moves at a constant velocity, which has a great significance for the control strategy of CR [29]. But the absence of analytical model results in that it cannot be used directly.…”

“…The COF for the small intestine in contact with another 13 Repetitive experimental data at 10 mm/s [29] surface is highly variable and depends upon the surface material, region of intestine, contact area and animal [33]. The surface material is PDMS, and the experiment object is laboratory pig in my work.…”

“…The whole process can be simplified to a simple physical model, which is shown in Fig. 3 [29]. An infinitely long flat car is placed on a smooth surface.…”