High-order non-singular terminal sliding mode control for dual-stage hard disk drive head positioning systems

A dual-stage actuator system in a hard disk drive will be expected to meet more stringent servo bandwidth requirements for higher recording density in the near future. To simplify the control design, most of the work on the dual-stage actuator track-seeking control is based on the rigid model. However, light-weight materials are used in practice; because of the existence of flexible modes in the system, the challenges involved in designing a reasonable controller need to be addressed. This article proposes a high-order non-singular terminal sliding mode control scheme to suppress undesirable flexural vibrations, while improving the head positioning speed and accuracy. Initially, a model of the system is built and then the flexible dual-stage actuator system is decomposed into input-output and internal sub-systems, to design the high-order non-singular terminal sliding mode controller. Simulation results show that the settling time in track-seeking is reduced and the tracking precision is improved with the proposed method.