Finite element analysis of torque ripple: Effects of gear ratio, transmitted power, nominal clearance, and mesh density in cycloidal drives

The minimal backlash characteristic of cycloidal gearboxes is widely recognized as a distinctive advantage. However, torque oscillations, referred to Torque Ripple (TR), are induced by variations in system stiffness due to the shifting contact points inherent to their architecture. Such oscillations pose significant challenges, particularly in applications requiring precise position control. This paper examines and discusses the use of Finite Element Analysis (FEA). The focus is placed on analyzing how modeling parameters, including mesh density across various geometries and operating torque levels, influence the estimation of TR. Results derived from 36 simulations, performed at two Gear Ratios (GRs), two levels of transmissible power, three levels of clearance, and three mesh densities, indicate that for an equal number of elements per lobe of the cycloidal disk, smaller GRs lead to larger TR. It is further demonstrated that variations in mesh density significantly impact TR estimation, while maximum stress levels remain largely unaffected. Additionally, higher TR is observed at lower applied torques, although this effect diminishes with finer mesh densities. Eventually, it has been demonstrated that the presence of clearance has a relevant effect on TR, especially for high GRs. These outcomes underscore the importance of conducting detailed mesh sensitivity analyses in TR investigations. Furthermore, the necessity of adopting a contact zone discretization method that remains independent of GR is highlighted to ensure accurate evaluation and mitigation of TR in cycloidal drives.