Development of a new mechanism to change velocity in a helical swimmer robot at low Reynolds number

Abstract

In this paper, a new mechanism with unique and prominent feature for helical swimmer robot has been presented. “Double Helices Propulsion Mechanism", consists of two parallel helices with single axis which rotate in the same direction. The outer helix acts as the main propulsion component and the inner helix, which is made of a shape memory alloy (SMA), controls the forward velocity during swimming. This mechanism by varying the geometrical parameters of its helical tail can change the forward velocity of the helical swimmer robot that is required by its predefined missions. In order to study the effects of geometric parameters on the forward velocity in the single helical swimmer, a hydrodynamic model based on Slender Body Theory (SBT) are implemented. Moreover, in order to validate the predicted results, a scaled-up macro-dimension prototype with a single helical tail and Reynolds number of less than one, is built. Finally the performance of the double helices system is estimated by modeling the dynamics of the motion in different tail lengths. This comparison indicates that, this mechanism increases the forward velocity and the efficiency of swimmer robot and it can be produce the variable forward velocities at each frequency.