Reconfigurable Straight-Spoke Tri-Wheel Mechanism With Four Bar Linkage for Optimal Stair Climbing

Abstract

In this paper, we propose a new four-bar linkage reconfigurable wheel for stair climbing. Previous works on reconfigurable wheel-based stairclimbers focus on curved-spoke geometries, but we propose a Y-shaped straight-spoke geometry and show why it is superior via a static analysis. Our mechanism adds reconfigurability to the straight-spoke structure, allowing it to both travel smoothly on flat surfaces and climb steep stairs. A four-bar linkage is used for the expansion mechanism, allowing the wheel to mimic a straight-spoke design when fully expanded. We conduct a kinematic study of our mechanism to find the theoretical path during ascent. Then, we simulated our mechanism with PyBullet, finding that the new mechanism achieves stronger results in both ascending and descending stairs when compared to standard curved-spoke designs and similar results when compared to the straight-spoke design. Following this, we analyze and compare the simulated paths of each design. Finally, we investigated boundary failure cases, focusing on the average angular velocity to further compare the ascent capabilities of our design against the curved-spoke design.