Soft sensor for operating shock in a disc drive
View Patent ↗A method of preventing a write operation to a disc in a disc drive during a shock event without the use of a separate shock sensor comprises steps of monitoring an actuator voice coil motor (VCM) control plant output signal, generating an actuator voice coil motor (VCM) plant model module output signal, comparing the VCM plant model module output signal to the VCM control plant module output signal to produce a difference signal, and triggering a write protect gate if the difference signal exceeds a predetermined threshold value. The system comprises a voice coil motor (VCM) control plant module sensitive to a shock event providing a VCM control plant module output, a voice coil motor (VCM) plant model module initially insensitive to the shock event producing a VCM plant model module output, a first comparator module coupled to receive the VCM control plant module output and the VCM plant model module output, operable to generate a difference signal between the model plant module output and the VCM control plant module output, and a triggering module receiving the difference signal for generating a write protect gate signal if the difference signal exceeds a predetermined shock threshold.
1. A control method for controlling a voice coil motor (VCM), the method comprising the steps of:
inputting a common servo control signal to both a VCM plant and a VCM plant model;
summing an output from the VCM plant and a disturbance value to derive an actual position signal;
comparing the actual position signal to an output of the VCM plant model to derive an estimated disturbance signal; and
using the estimated disturbance signal to minimize a shock to the system.
2. The method of claim 1 , wherein the using step comprises the steps of comparing the estimated disturbance signal to a threshold value, and preventing a data transfer operation in relation to said comparison.
3. The method of claim 1 , wherein the using step comprises steps of generating a write protect signal which inhibits a write operation, said write protect signal generated before the VCM moves beyond a threshold distance.
4. The method of claim 3 wherein the estimated disturbance signal is an input to the VCM plant model.
5. The method of claim 1 wherein the using step is responsive to a shock.
6. A method comprising the step of generating a write protect signal in response to an estimated disturbance signal that is derived from comparing a VCM plant model output to an actual position signal that is in turn derived from summing a VCM plant output with a disturbance value, wherein the VCM plant model output and the VCM plant output are results of a common servo control signal.
7. The method of claim 6 wherein the generating step comprises:
comparing the estimated disturbance signal to a threshold value; and
generating the write protect signal if the estimated disturbance signal exceeds the threshold value.
8. The method of claim 7 further comprising the step of filtering the estimated disturbance signal.
9. The method of claim 6 wherein the write protect signal is generated before the VCM moves beyond a threshold distance.
10. The method of claim 6 wherein the write protect signal is generated independent of a position error signal.
11. The method of claim 6 wherein the comparison of actual position signal to estimated position signal is an input to the VCM plant model.
12. A method comprising the step of generating a write protect signal before a positioning device moves beyond a threshold distance from a desired position, in response to an estimated disturbance signal that is derived by comparing an actual position signal derived from summing a positioning device plant output and a disturbance value to an estimated position signal from a positioning device plant model output.
13. The method of claim 12 comprising inputting the results of the comparing the actual position signal to the estimated position signal to the positioning device plant model.
14. The method of claim 12 wherein the generating step is responsive to a shock.
15. The method of claim 12 wherein the generating step comprises:
comparing the estimated disturbance signal to a threshold value; and
generating the write protect signal if the estimated disturbance signal exceeds the threshold value.
16. The method of claim 12 further comprising the step of filtering the estimated disturbance signal.
17. The method of claim 12 wherein the write protect signal is generated independent of a position error signal.
18. The method of claim 12 wherein the write protect signal is usable to control a storage system.
19. The method of claim 12 wherein the positioning device plant output and the positioning device plant model output are results of a common servo control signal.
20. The method of claim 12 wherein the estimated disturbance signal is a result of a common servo control signal to the positioning device plant and the positioning device plant model.
21. A control system comprising:
a positioning device plant model responsive to a servo control module;
a positioning device plant responsive to the servo control module; and
a shock detector configured to generate a write protect gate signal if an estimated disturbance signal exceeds a predetermined threshold, wherein the estimated disturbance signal is derived by comparing an output of the positioning device plant model to an output of the positioning device plant.
22. The control system of claim 21 wherein the positioning device plant is associated with a voice coil motor.
23. The control system of claim 21 further comprising a filter for filtering the estimated disturbance signal.
24. The control system of claim 21 wherein the estimated disturbance signal represents a difference between the positioning device plant model output and a sum of the positioning device plant output and a disturbance value.
25. The control system of claim 21 further comprising a servo control module coupled to the positioning device plant and the positioning device plant model.
26. The control system of claim 25 wherein the servo control module is coupled to receive a reference signal.