Hydrodynamic Optimization of a Spherical Amphibious Robot's Paddle-Wheel for Effective Water Surface Locomotion
AI summary
Problem
Spherical robots lack effective propulsion mechanisms for agile swimming and struggle with stability during water-land transitions, limiting their use in real-world amphibious applications.
Approach
The authors designed a hybrid differential-drive spherical robot with dual paddle-wheel actuators, optimized four helical paddle geometries using multiphase CFD simulations, and validated performance on a custom testbed with a hierarchical cascade controller.
Key results
- Designed a compact amphibious spherical robot with dual paddle-wheel actuators for forward, turning, and arc maneuvers
- Identified Helix-2 helical paddle geometry as optimal through multiphase CFD simulations
- Achieved 51% higher forward thrust and over 160% greater lateral force compared to straight-blade paddles in experiments
- Implemented a hierarchical cascade controller that suppresses pitch oscillations for stable amphibious operation
Why it matters
Provides a practical, energy-efficient propulsion solution for spherical robots operating in confined water-land transition zones for inspection and rescue missions.
Abstract
This paper presents the design, dynamic modeling, and hydrodynamic optimization of an amphibious hybrid differential-drive spherical robot capable of operating on both land and water. The robot adopts a three-module symmetric structure, where dual paddle-wheel actuators enable forward motion, in-place turning, and arc-turning maneuvers. To address pitch oscillations during operation, a hierarchical cascade controller with current, velocity, and attitude compensation loops is implemented, ensuring stable performance across different environments. Four paddle-wheel designs based on helical screw-thread geometry were systematically analyzed through computational fluid dynamics (CFD) simulations. The Helix-2 configuration exhibited the best balance between thrust and lateral force generation. Experimental validation on a custom-built test-bed confirmed these findings: compared with straight-blade paddles, Helix-2 achieved up to 51% improvement in forward thrust and a maximum lateral force improvement exceeding 160%. The results demonstrate that the proposed spherical robot achieves energy-efficient amphibious locomotion with improved maneuverability, making it suitable for inspection, monitoring, and tasks in confined water–land transition environments.