Identification of microactuator resonance at frequencies beyond the Nyquist rate in Dual-Stage Actuator Hard Disk Drives

The output of the Hard Disk Drive (HDD) head positioning control system is inherently restricted to a sampled signal and identification of the plant dynamics embedded in such a closed-loop system requires special considerations to circumvent the aliasing effect. In this study, a non-parametric, off-line algorithm proposed in the literature which employs a continuous-time sinusoidal excitation input is extended to identify the dynamics of the secondary actuator in a Dual-Stage Actuator (DSA) HDD system. The algorithm is then modified to employ a discrete-time sinusoidal input readily available in the on-board digital circuit to eliminates the need of any external instrument required to generate the continuous-time input. Experimental results of the proposed methods are presented.