Kinematic and Dynamic Modeling and Simulation-Based Performance Evaluation of a Novel Central-Actuated Transformable Wheel Design for Mobile Robots

Abstract

This paper presents the design, kinematic modeling, and dynamic simulation of a novel conical-slider-based transformable wheel with five deployable wheel-leg elements for mobile robotic systems. The proposed wheel can operate in a closed-wheel configuration for regular terrain and in an open wheel-leg configuration for enhanced interaction with rough terrain and obstacle profiles. The transformation motion is generated through a central linear actuation input transmitted by a conical slider mechanism integrated into the wheel hub. A CAD-supported mechanical design was developed to examine the geometric feasibility of the proposed wheel structure and to verify the radial deployment motion of the wheel-leg elements. The kinematic formulation was revised in a compact indexed form by consistently considering the angular offsets of all five wheel-leg elements. In addition, a dynamic model including the six-wheel vehicle body, suspension elements, wheel-ground contact, wheel-leg-ground contact, and wheel driving inputs was formulated. A unilateral contact model was used to represent contact, loss of contact, and re-contact events while preventing non-physical tensile normal forces. The proposed wheel concept was evaluated using a MATLAB-based representative mixed-terrain simulation scenario that combines rough-terrain locomotion and traversal of a 0.35 m single obstacle. The simulation results show that the fully deployed wheel-leg configuration successfully traverses the tested 0.35 m obstacle, whereas the closed-wheel configuration fails under the same terrain condition. Because the conical slider is continuously adjustable, an intermediate deployment state was also evaluated: it traverses a 0.30 m obstacle that the closed configuration cannot, yet fails against the 0.35 m obstacle, so that the traversal threshold varies monotonically with the deployment stroke. The comparison demonstrates that the deployed wheel-leg elements improve obstacle traversal capability by increasing the effective contact geometry and providing additional interaction with the obstacle surface. The results indicate that the proposed conical-slider-based transformable wheel has the potential to improve the terrain adaptability and obstacle traversal performance of six-wheel mobile robotic systems. Since the present study is limited to CAD-supported design verification and MATLAB-based dynamic simulation, future work will focus on prototype manufacturing, actuator design, structural analysis, and experimental validation under real terrain conditions.