Improvement of servo robustness for digital sector servo system (hard disk drives)

In order to improve the servo performance of the digital sector servo, the authors developed initial value compensation for the digital variable structure control system and applied it to a 3.5-in disk drive. This compensation method involves inputting initial values, calculated by minimizing a performance index, into settling servo compensators when the servo mode is switched from seeking to settling. Implementation is quite easy for digital systems. Experimental results show good robust performances for large velocity fluctuations at switching.<
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