DAC quantization noise reduction for servo control systems in hard disk drives

In hard disk drive (HDD) servo control systems, quantization noises due to the finite precision of the D/A converter (DAC) driving the VCM contribute a significant portion of the total track mis-registration (TMR). In this paper, a quantization error feedback (QEF) technique to reduce TMR due to DAC quantization noises is introduced. The QEF technique offers a simple method of reshaping the spectrum of this noise to minimize its contribution to TMR. Despite the name, QEF is an effectively feed-forward technique that means that it does not affect or degrade the servo loop response. In addition, the limitation and optimality of different QEF schemes are examined in detail. Simulations reveal that contribution to TMR on an HDD is reduced by more than a factor often. Tests have verified the improvement.