Control of the radial motion of a self-propelled microboat through a side rudder

Similar to macroboats, microboats can be potentially employed to transport a target from one place to another in a small area for the purposes of delivery and detection. In previous work, we developed a type of self-propelled microboat which is capable of having straight motion at speeds of order 0.1 m/s. In this work, using a combination of theoretical, numerical and experimental investigations, we explored another type of self-propelled microboat that could have radial motions. This type of microboat has side rudders. The side rudder induced an additional drag on one side, creating a moment to set the boat into an approximately circular motion. The radii of this motion could be controlled by varying the length of the side rudder. In this work, we designed, fabricated and tested eight microboats, whose rudders ranged from 0 to 10 mm in length. The speeds of these microboats were also in the order of 0.1 m/s. Depending on the rudder lengths, their moving paths had radii varying from infinity to 20 mm. According to moving trajectories, the radius of motion and the travel distance both decreased with the increase in the rudder length. We further built a theoretical model to predict the radius of the first loop of the moving path. By comparing experimental results with numerical solutions to the theoretical model, we found: (i) the numerical results had reasonably good agreement with the experimental results, and (ii) the mismatch between numerical and experimental results increased with an increase in the rudder length due to the simplified consideration in the simulation. (C) 2012 Elsevier B.V. All rights reserved.