Iterative Feedback Tuning (IFT) of Hard Disk Drive Head Positioning Servomechanism

Hard disk drive (HDD) is a mass produced item so are its components including the actuator used for head positioning servomechanism. Transfer characteristics of these actuators vary within a tolerance limit and a nominal model representing the family of actuators is used for controller design. Equally good performance is not possible for all actuators with the designed controller. However, as the demand for performance of the disk drive servomechanism continues to grow higher to meet the requirements for higher storage capacity of HDD, performance of the servo controller becomes more crucial. Furthermore, wear and tear of the components causes degradation of performance over time. These issues demand the use of good on-line tuning of servo controller. This paper explores the possibility of using Iterative Feedback Tuning (IFT) on HDD servomechanism. Enhancement of performance with IFT is demonstrated using simulation and experimental results.