利用間隙電容伺服控制近場光碟機之飛行高度

Abstract

為了突破傳統光學技術的繞射極限瓶頸，近場光碟機採用飛行讀寫頭，在碟片上方以穩定的高度飛行，藉以大幅提昇光學儲存容量與密度，故光學讀寫機構的性能要求也相對提昇。本研究在控制實驗中量測讀寫頭與碟片表面間的間隙電容變化，利用解調變轉換成電壓訊號，從而獲得讀寫頭飛行高度的變化。順滑模態控制對模型之不確定性及外界干擾具有強健性。因此本研究為了順應近場光碟片瞬間的振動變形，使用DSP卡執行順滑模態控制的運算，即時調整讀寫頭的飛行高度，達成穩定的飛行高度。

In order to overcome the diffraction limit of conventional optical disk drives, the flying pickup head in near-field optical disk drives enables the slider to fly at a stable spacing above the disk surface, thereby substantially increasing storage capacity and density. Hence, enhancing control performance to improve focusing speed and accuracy is required. To sense flying height in control experiments, a gap capacitance servo measures capacitance variation between the pickup head and disk surface and process voltage signals out of the capacitor by demodulation. Sliding mode control inherited with robust properties can deal with model uncertainty and disturbances. Therefore, a DSP control card executes a sliding mode control algorithm to compensate the vibration of the optical disk surface and achieve a stable flying height for the pickup head.