Finite Element Investigation of Torque Ripple in Roller-Cycloidal Contact: Examining Gear Ratio, Mesh Density, and Transmitted Power Dependencies

Abstract

The low backlash of cycloidal gearboxes is undoubtedly a distinctive feature. However, due to their architecture, cycloidal drives exhibit torque oscillations, i.e. Torque Ripple (TR), caused by variations in system stiffness as con-tact points change over time. Such oscillations can be critical in position control applications. One of the most common approaches to analyze torque ripple, namely finite element analysis, is exploited and discussed in this paper. Specifically, the aim is to investigate how modeling parameters such as mesh density, in different geometries and operating torques, impact torque ripple estimation. Preliminary results from 12 simulations, conducted at two gear ratios, two levels of transmissible power, and three mesh densities (coarse, medium, fine), demonstrate that with an equal number of elements per cycloidal disk lobe, models with smaller GR exhibit larger TR. It is observed that changes in Mesh density significantly affect TR, without a corresponding significant change in maximum stress levels. Additionally, lower applied torques result in higher TR, though this effect diminishes with denser meshes. These findings highlight the critical need for thorough mesh sensitivity analysis in TR studies and the necessity to establish a contact zone discretization approach that is independent of GR, to accurately assess and mitigate TR in cycloidal drives.