Simulator for single stage and dual stage hard disk drives

We describe a simulator for the evaluation of the performance of different control algorithms and strategies, applied to hard disk drives (HDD) with single stage (SSA) and dual stage actuators (DSA). In order to perform realistic simulations, each part of the HDD must be described with high level of detail. As for the mechanics, the usual inertia plus resonance model of the voice coil motor (VCM) has been enriched with non-linear friction modeling and, in case of DSA, with the dynamic coupling between primary and secondary actuator. The non-linear friction model has been tuned on experimental data, using an experimental system presented in the paper. As for the electronics, the VCM driver model is included and quantizations in position error signal (PES) measurement and computation (i.e. finite wordlength calculations) are explicitly considered. Finally, in order to evaluate the tracking performance of different servo-controllers, repetitive and non-repetitive run outs are included, their values obtained from commercial HDDs, with a procedure that is detailed in the paper