Optimization Of Slider Air Bearing Design In Hard Disk Drivers

Hard disk drives continue to increase the data storage density. The flying heights (FH) of air bearing sliders (ABS) should be lower and lower to meet the rapid demands. The FH of current commercial sliders is below 30 nm. The parameters of the slider flying attitude that include flying height, pitch and roll angles must satisfy very strict performance goals. It is possible to achieve the multiple design goals with modern optimization techniques. This paper focuses on the topic of the simulated annealing (SA) algorithm as it applied to the problem of ABS design in hard disk drives. Simulated annealing algorithm is a generalization of a Monte Carlo method for examining the equations of state and frozen states of a multi-body system. Its concept is based on the manner in which liquid freeze or metals recrystallize in the process of annealing. The stochastic global optimization technique can get global optima in the presence of many local optima without the calculation of gradients to determine search directions.In this paper, a sub-ambient pressure tri-pad slider was designed firstly. A new modified Reynolds equation is used to solve the ultra-thin film gas lubrication with the Fukui-Kaneko model considering high Knudsen numbers. SA is proposed to get the optima steady flying attitude of the slider. The results show that rail width, taper length, taper height, preload and its position can be considered as design variables in slider configuration design to obtain a better flying performance. Then, SA is employed for the optimization design of ABS surface. The tri-pad slider mentioned above was taken as the prototype. The straight rail width and length, the taper height and length and the tail rail width and length were taken as design variables respectively with given geometric constrains. Also, the optimization design was done while all the geometric parameters were taken as design variables. Results show that SA is efficient to produce the optimized ABS design with improved flying performance. The FH was lowered significantly with uniform pitch and roll.