# Dynamic Simulation of a 5 Degrees of Freedom Rotor Dropping on a Protective Bearing
## 1 Introduction  
In the active magnetic bearing (AMB) system [1], as a key component of the AMB protection system, the protection bearing [2] plays a role [3] in temporarily supporting the rotor and protecting the whole system from damage after the failure of the AMB [4, 5]. However, in actual working conditions, the traditional protective bearing is often unable to support the high-speed rotation of the rotor [6, 7, 8], and the huge vibration and impact caused by the drop will affect the reliability and safety [9, 10] of the whole magnetic levitation system.  
The technical problems of the five-degree-of-freedom rotor-protective bearing system are focused on the rotor dynamic response under the coupling influence of multiple complex working conditions and structural parameters in the dynamic process of rotor dropping to the protection bearing, and the processes of rotating speed fluctuation, rotor dropping track, protection bearing damage, and the like in the normal operation of the rotor are affected by the coupling influence [3, 11] of multiple factors such as working conditions, structures, and the like. And as the internal structure of the protective bearing is complex, the dynamic modeling sometimes cannot facilitate the deep analysis of the motion state of the ball of the protective bearing, but it simplifies the rotor-protective bearing as a spring-damper system [12, 13, 14], which cannot truly reflect the internal motion of the actual bearing.  
Therefore, this paper mainly uses the multi-body dynamics software to model the five-degree-of-freedom rotor-protective bearing system and simulate the rotor drop process [15], relying on the advantages of multi-body dynamics software [16], to establish a more realistic five-degree-of-freedom rotor-protective bearing system simulation model, to obtain more intuitive model and data, and to better summarize the law. At the same time, the future research trends and directions of rolling bearing slippage are prospected. On the other hand, the potentiality contribution of the article could be used in collaborative robotics [17]. The dynamic characteristics of rotor fall are analyzed theoretically through dynamic modelingand multi-body dynamic simulation method, and the corresponding rules and conclusions are drawn, and then the optimization scheme is provided for the design and reliability of protective bearings.  
In the second chapter, the dynamics simulation model of the five-degree-of-freedom rotor-protective bearing system is established. Firstly, several possible results of rotor drop in actual working conditions are introduced, and the mathematical model is established. Secondly, the five-degree-of-freedom rotor-protective bearing system model is established by the ADAMS multi-body dynamics software package (ADAMS VIEW 2020). The third chapter uses multi-body dynamics software to study the drop characteristics of the five-degree-of-freedom rotor, changes the initial drop speed of the rotor and the friction coefficient between the rotor and the protection bearing, summarizes the dynamic characteristics of the five-degree-of-freedom rotor falling on the protection bearing through the rotor speed and the inner ring speed of the protection bearing, and studies the performance of the contact force between the rotor and the bearing inner ring. The fourth chapter summarizes the findings of the article, so as to better play a guiding role in practical application.