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

Abstract

In this study, the optimal design parameters of angled spoke-based wheels(ASWs) was evaluated to maximize the driving speed of a mobile robot with ASWs on granular media. As a search and rescue mobile robot, it is required to locomote various terrains agilely. 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 L-9(3(4)) orthogonal array were employed to empirically optimize the shape of the ASW. Base on the geometry feature of precedent design of ASWs design parameters were selected. The design variables evaluated were the motor input velocity, width-height proportion of the foot, radius of curvature, and toe angle of the foot. Grain size of granular media 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 velocity of 5000 rpm, width-height proportion of 3:7, radius of curvature of 1.0xh, and toe angle of 15 degrees. Verification experiments were performed to evaluate the improved driving speed of the ASW. The angular velocity of the ASW increases by 2.79% for circle divide 1 mm and 10.50% for circle divide 6 mm. Therefore, an optimized ASW design is expected to improve the driving speed of a mobile robot with ASWs.