This paper aims to develop a nonlinear control algorithm to break the limitations of linear PID controls and improve the transient performance during the short-span track seeking / settling in hard disk drives (HDDs). It is designed based on a baseline PID controller which is well-designed to obtain good track following performance. The control algorithm is a combination of a nonlinear PID controller and a nonlinear turbo controller (NTC): when the position error signal (PES) is large, NTC assists the nonlinear PID controller to rapidly reduce the error; when PES is small, NTC is turned off to avoid possible chattering and ensure good steady state performance. As PES becomes even smaller, the nonlinear PID controller is reduced to the baseline PID controller to keep good steady state performance.

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