| 摘要 |
Servo loop gain is automatically adjusted for control loops of precision tracking and focusing servos in an optical or magneto optical storage device (114). To adjust servo loop gain during operation, the servo loop (100) is modelled as a series of simple gain components (KPA, KACT, KOPT, KPRE A, KADC, KC, KDAC), with the total servo loop gain being the product of the gain components. A controller gain components (KC) is adjusted based on measured servo loop gain to keep the total servo loop gain constant. To measure the servo loop gain during operation, a sinusoidal signal (104) is injected into the servo loop (100) by addition to the normal servo control signal for a period of n cycles of the sinusoidal signal. The servo loop (100) response is measured for the last n-1 cycles of this injection period, with the Fourier Transform excitation frequency component of the measured response being computed to determine the response amplitude. The servo loop gain may then be computed from measured response amplitude and the known amplitude of the injected signal (104). If the computed gain value is within a range of expected values, the controller gain (KC) is adjusted to keep the total servo loop gain constant. Otherwise, a default gain value is employed to adjust the servo loop gain. In an alternative embodiment, the servo loop gain excluding the controller gain component (KC) is determined from two measurements of the system response to the injected sine wave (104). |
