Abstract
A near-field readout system using a traditional optical head has been proposed as a technology to increase the storage capacity. However, designing the far-field and the near-field controls so that they both can coordinate in an optimal manner presents challenges to control engineers. In this thesis, we develop a systematic procedure which uses the information on the plant dynamics, hardware limitations and performance specifications to design a far-near field control for optical disc drives. The experiments indicate that the controller designed can move the optical head rapidly from far field to near field without colliding with the optical disc. To further enhance the control performance, a quantization effect reduction (QER) method to reduce output error due to DAC quantization noises is also proposed. The QER technique offers a simple method of reshaping the spectrum of the quantization noise to minimize the output error. The proposed QER method decouples the quantization effect from control system that it does not affect the original control response. The limitation and optimality of the QER method are examined carefully. Experimental results reveal that output error caused from quantization error is reduced by more than a factor of five.