Optimization of mecanum wheels for mitigation of AGV vibration

Mecanum wheels (MWs) are valuable components to automated guided vehicles (AGVs) and autonomous mobile robots (AMRs) for their versatile motion capabilities. Such characteristics are associated with the series of rubber-covered rollers obliquely attached around the circumference of the wheel rim. The rollers take turns in contact with the ground while MW is rotating. Even though MWs were designed and appear perfectly circular, vehicles equipped with MWs often exhibit periodic bouncing motion. Such a phenomenon hinders the application of MW in factories, such as panel manufacturing. This article sought the cause of the non-uniform contact stiffness associated with MWs and attempted to improve its design to mitigate the vibration problem. A hard-kill topology optimization scheme was proposed where interfacial elements between the steel core and the rubber layer can switch the material property to steer the contact stiffness toward the desired value. Nonlinear finite element analyses on the detailed 3D geometry of the roller system involving neo-Hookean material and contact simulation were performed for accurate numerical estimation in the optimization process. Due to elastic deformation, dual contacts occur at the transition of adjacent rollers; as a result, the total contact stiffness increases significantly compared to the other regions. The proposed optimization scheme successfully reached a design of uniform contact stiffness for the entire circumference of MW, including transition zones between adjacent rollers. Prototypes of the optimized MW were fabricated. Experiments on the vibration of an AGV with the old and the new MWs were conducted. The new MWs effectively reduced vibration amplitudes by approximately 30%.