Modelling of a vibro-impact self-propelled capsule in the small intestine

This paper studies the modelling of a vibro-impact self-propelled capsule system in the small intestinal tract. Our studies focus on understanding the dynamic characteristics of the capsule and its performance in terms of the average speed and energy efficiency under various system and control parameters, such as capsule's radius and length, and the frequency and magnitude of sinusoidal excitation. We find that the resistance from the small intestine will become larger once the capsule's size or its instantaneous velocity increases. From our extensive numerical calculations, it is suggested that increasing forcing magnitude or choosing forcing frequency greater than the natural frequency of the inner mass can benefit the average speed of the capsule, and the radius of the capsule should be slightly larger than the radius of the small intestine in order to generate a reasonable resistance for capsule progression. Finally, the locomotion of the capsule along an inclined intestinal tract is tested, and the best radius and forcing magnitude of the capsule are also determined.