In light of investigating the interplay between the instantaneous angular speed （IAS） signal and mechanical dynamics of bearings， alongside addressing the vulnerability of rotary arm bearings within industrial robot RV reducers to failure under low speed conditions， this paper presents a novel three-degree-of-freedom dynamics model to explain the IAS perturbations resultant from localized roller bearing failures. The model， rooted in the Hertz line contact theory， dissects the influence mechanism of local ized deformations stemming from roller-raceway interactions on the IAS. A comprehensive approach to computing the coupled tan gential force and torque is outlined. The integration of failure-induced impacts into torque analysis computes torque variations intro duced by the failure zone， thereby augmenting angular degrees of freedom. As a result， a three-degree-of-freedom bearing IAS dis turbance dynamic model， coupling both normal and tangential forces， is established. Employing fourth-order Runge-Kutta numeri cal integration， the model is solved， and its results are meticulously compared and analyzed against experimental approximations under near-approximate conditions. The findings underscore the model’s ability to effectively expound upon the origins of IAS per turbations in cylindrical roller bearings while adeptly reflecting the ramifications of outer ring failures on IAS. This work contributes to the refinement of rolling bearing dynamics theory， advancing the comprehension of intricate mechanical systems.