Digital servo system with second order compensator
View Patent ↗A tracking servo system with a at least one second order digital filter is presented. The servo system calculates an error signal and offsets, amplifies, and filters the error signal before a control signal is calculated. The control signal is then utilized to position an optical pick-up unit which provides signals from which the error signal is calculated. Filters in the servo system can include a low-pass integrator, a phase lead filter, notch filters, or other filters. At least one of the filters is a second order digital filter.
1. A method of controlling the position of an optical pick-up unit, comprising:
calculating an error signal from optical signals received from the optical pick-up unit;
offsetting the error signal to form an offset signal;
amplifying the error signal to form an amplified signal;
filtering a pre-filtered signal related to the amplified signal to form a filtered signal;
calculating a control signal from the filtered signal; and
adjusting a position of the optical pick-up unit in response to the control signal,
wherein filtering the pre-filtered signal includes filtering with at least one second order filter.
2. The method of claim 1 , wherein filtering includes a low frequency integration.
3. The method of claim 1 , wherein filtering includes a phase lead filtering.
4. The method of claim 1 , wherein filtering includes a notch filtering.
5. The method of claim 1 , wherein filtering includes a sample integrity tested filtering.
6. The method of claim 1 , wherein the error signal is a tracking error signal.
7. The method of claim 1 , wherein the error signal is a focus error signal.
8. A servo system, comprising:
an optical pick-up unit;
an analog processor coupled to receive signals from detectors in the optical pick-up unit and provide digital signals;
at least one processor coupled to receive the digital signals, the processor calculating a control signal; and
a driver coupled to control a position of the optical pick-up unit in response to the control signal,
wherein the at least one processor executes an algorithm that
calculates an error signal from the optical signals,
offsets the error signal to form an offset signal;
amplifies the error signal to form an amplified signal;
filters a pre-filtered signal related to the amplified signal to form a filtered signal;
calculates a control signal from the filtered signal; and
adjusts a position of the optical pick-up unit in response to the control signal,
wherein the filters include filtering with at least one second order filter.
9. The system of claim 8 , wherein the filters include a low-frequency integrator.
10. The system of claim 8 , wherein the filters includes a phase lead filter.
11. The system of claim 8 , wherein the filters include a notch filter.
12. The system of claim 8 , wherein the filters includes a sample integrity test filter.
13. The system of claim 8 , wherein the error signal is a tracking error signal.
14. The system of claim 8 , wherein the error signal is a focus error signal.
15. A servo system, comprising:
means for receiving digitized optical signals from an optical pick-up unit;
means for calculating an error signal from the digitized optical signals;
means for offsetting and amplifying the error signal;
means for filtering the error signal to form a filtered signal;
means for calculating a control signal from the filtered signal; and
means for adjusting the position of the optical pick-up unit in response to the control signal.