Empirical Study on Characteristics of Angled Spoke-Based Wheels on Granular Media

Abstract

In this study, the optimal shape of angled spoke-based wheels (ASWs) was designed to maximize the driving speed of a mobile robot with ASWs on granular media. As a lightweight search and rescue mobile robot, it is required to have a high driving speed to reach the disaster site quickly. When granular media behave as fluids, slippage occurs, and the mobile robot slows down compared with when the media behave similarly to a solid ground. There are no exact criteria to explain the behavior of granular media. Therefore, the Taguchi method and L9(34) orthogonal array were employed to empirically optimize the shape of the ASW. The design variables evaluated were the motor RPM, width–height proportion of the foot, radius of curvature, and toe angle of the foot. The size of the ocher balls was adopted as the user condition. An orthogonal array and signal–to–noise (S/N) ratio were used to analyze the validity of the design variables. The optimal design variables of the ASW were a motor RPM of 6000, width–height proportion of 3:7, radius of curvature of 1.0×h, and toe angle of 15deg. Verification experiments were performed to evaluate the improved driving speed of the ASW. The angular velocity of the ASW increases by 2.79% for φ1 (mm) and 10.50% for φ6 (mm). Therefore, an optimized ASW design is expected to improve the driving speed of a mobile robot with ASWs.