Dynamic analysis of a HDD spindle system with FDBs due to the bearing width and asymmetric grooves of journal bearing

Abstract

This paper investigates the dynamic behavior of a HDD spindle system with fluid dynamic bearings (FDBs) by solving the Reynolds equation and the equations of a motion of a HDD spindle system in five degrees of freedom. FEM is used to solve the Reynolds equation in order to calculate the pressure distribution in fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors of a HDD spindle system, such as the whirling and the tilting motion, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This paper also proposes two design methods to improve the dynamic characteristics of a HDD spindle system without increasing friction torque, i.e., optimization of the width of the lower and the upper journal bearings and the journal bearings with asymmetric grooves.

Dynamic Characteristics of a Hard Disk Drive Spindle System Due to Imperfect Shaft Roundness

“…They verified their method by comparing the simulated flying heights with the experimental ones at various speeds. Jang et al calculated the nonlinear equations of motion of a HDD spindle system supported by the coupled journal and thrust bearing due to the effect of the bearing width and asymmetric groove [4]. Jang and Yoon calculated the locus of the rotor with rotating grooves with respect to translational motion and show that it generates a bearing reaction force with the harmonics of rotational speed [5].…”

Investigation of unloading performance for change of FDB transient behavior in low temperature

“…1 and 2 using finite element model. Reaction forces and friction torque is obtained by the following equations [4]. F: = II pR cos BdBdz F y = II pR sin oaBdz (4) Figure 2 shows viscosity of the fluid lubricant as a function of environmental temperature.…”

“…The rotor dynamics of the spindle system are affected by change of friction torque and reaction force at power off condition. Jang et al [4] calculated the rotor dynamics using rigid shaft with five degrees 0 f freedom in operating condition, i.e., two angles in ()x and ()y directions and three translational displacements in X Y and Z directions. A constant angular velocity in ()z was applied to their model and change of the rotating speed was not considered.…”

Whirling, tilting and axial motions of a HDD spindle system due to the manufacturing errors of FDBs

“…Some researchers have solved the equations of motion of rotating parts with the inclusion of nonlinear reaction force of FDBs in order to investigate the dynamic motion, such as the whirling, tilting and axial motions of rotating system supported by FDBs. Li (1999) calculated the orbit of a rotor supported by journal bearing, and Jang et al (2005b) calculated the nonlinear equations of motion of a HDD spindle system supported by the coupled journal and thrust bearing due to the effect of bearing width and asymmetric groove. Prior researchers assumed that FDBs are perfectly manufactured without any machining or assembling error.…”