1 3 Microsyst Technol (2016) 22:1189–1197 DOI 10.1007/s00542-016-2863-x TECHNICAL PAPER Investigation of slider out-of-plane and in-plane vibrations during the track-seeking process Wei Hua 1 · Shengkai Yu 1 · Weidong Zhou 1 · Kyaw Sett Myo 1 Received: 10 August 2015 / Accepted: 28 January 2016 / Published online: 23 February 2016 © Springer-Verlag Berlin Heidelberg 2016 track width decreases continually, the requirement on the track seeking process becomes more and more serious. Moreover, just before the unload process, the HSA will normally experience a period of track-seeking move- ment, and the track-seeking performance may directly influence the unload process, especially for emergent cases. Similarly, when a slider is just loaded to the disk, a track-seeking process is also needed to indicate the slider position, and this process may be more serious as the slider is not in a stable state when just leaving a ramp. Therefore, a comprehensive study of the track- seeking process based on the coupled models consider- ing both the air bearing slider and the HAS are essential and important. In the viewpoint of head/disk interface (HDI), the slider position displacements and vibrations may be induced by four factors during the track-seeking pro- cess: (1) The variation of radius and skew angle; (2) The lateral airflow due to the sweeping velocity; (3) The centripetal acceleration caused by the rotation; (4) The sweeping acceleration controlled by the voice coil motor (VCM). As the practical track-seeking process is very complex, numerical quasi-static analysis (Juang et al. 2006; Kim et al. 2009; Cha et al. 1995) is usually used for the simulation, and the suspension is simplified as a simple spring. In such a case, it does not need to solve the complex dynamic air bearing equation and the HSA matrix equation, and a lot of simulation time can be saved. However, the quasi-static method cannot study the slider vibrations, especially the off-track vibrations, which is very important for the track-seeking process. The track-seeking process is studied using the modi- fied Reynolds equation and suspension matrices (Ruiz and Bogy 1990), but the simulation conditions are based on the dog-leg rotary and do not meet the track-seeking Abstract This paper employs the coupled air bear- ing model and modal order reduction (MOR) model of head stack assembly (HSA) to investigate the track- seeking process of a femto slider. Simulations indicate that the flying height and the pitch angle may increase or decrease significantly, depending on the track-seeking directions. For the slider studied in this paper, it is safer for sweeping from OD to ID, than sweeping from ID to OD. The most serious vibration is the off-track vibra- tion, and it is highly related to the sweeping accelera- tion profile. A smooth acceleration profile is crucial to reduce all the vibrations of slider, especially the off- track vibration. 1 Introduction For hard disk drives, in order to cover the whole data zone of a disk surface for read/write operations, the slider has to move between different tracks frequently. To reduce the time of the process, high track-seeking acceleration and velocity are often used, and hence chal- lenges the dynamic performances of the slider and the suspension accordingly. In-plane and out-plane vibra- tions of slider are very important issues for the track- seeking process, since the slider needs not only to locate the correct track, but also to stabilize at the track within the required time. As the track density increases and the * Wei Hua hua_wei@dsi.a-star.edu.sg 1 Data Storage Institute, (A*STAR) Agency for Science, Technology and Research, 5 Engineering Drive 1, Off Kent Ridge Crescent, Singapore 117608, Singapore