| 摘要 |
PURPOSE:To control a servo system to a required resolution in response to a position deviation by selecting a large gain of an A/D conversion section and a D/A conversion section when a detected analog servo signal is small and selecting a small gain when the signal is large conversely. CONSTITUTION:When a magnetic head moves and enters the fixed operation, a position error signal becomes a value as small as 1V or below. The value is detected by a detection section 3 and the gain of an A/D converter 2 is regulated based on the value. Thus, the position of the magnetic head is adjusted minutely and positioned with high accuracy. A digital value representing the shift amount corresponding to a position error signal S is fed to the 2nd gain controller 7 and the gain of a D/A converter 6 is adjusted corresponding to said value. Thus, the digital resolution is increased apparently without increasing the bit number of the A/C converter.
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