Constant false alarm resonance detector
View Patent ↗A contact detection system includes a comparator operable to compare a signal derived from a contact sensor with a threshold and to indicate contact when the signal is greater than the threshold, a parameter estimation circuit operable to estimate parameters of a probability density function based on the signal derived from the contact sensor, and a threshold calculator operable to calculate the threshold based at least in part on the parameters of the probability density function.
1. A contact detection system comprising:
a comparator operable to compare a signal derived from a contact sensor with a threshold and to indicate contact when the signal is greater than the threshold;
a parameter estimation circuit operable to estimate parameters of a probability density function based on the signal derived from the contact sensor;
a threshold calculator operable to calculate the threshold based at least in part on the parameters of the probability density function.
2. The contact detection system of claim 1 , wherein the parameter estimation circuit is operable to estimate the parameters of a probability density function based on only a portion of the signal derived from the contact sensor obtained without contact.
3. The contact detection system of claim 1 , wherein the parameter estimation circuit is operable to estimate parameters of the probability density function using a Gaussian fitting.
4. The contact detection system of claim 3 , wherein the parameters comprise a mean and a variance of a modulation density.
5. The contact detection system of claim 1 , wherein the parameter estimation circuit is operable to estimate parameters of the probability density function using a skew normal fitting.
6. The contact detection system of claim 5 , wherein the parameters comprise a mean and a variance and a skewness of a modulation density.
7. The contact detection system of claim 1 , wherein the signal derived from the contact sensor comprises a modulation density.
8. The contact detection system of claim 7 , further comprising a modulation depth calculator operable to calculate the modulation density based on digital samples of an analog signal from the contact sensor.
9. The contact detection system of claim 8 , wherein the modulation depth calculator is operable to calculate the modulation density based on segmented sums of the digital samples.
10. The contact detection system of claim 8 , further comprising a memory, wherein the comparator is operable to store the modulation density in the memory when the modulation density is less than the threshold.
11. The contact detection system of claim 1 , wherein the parameter estimation circuit is further operable to estimate the parameters of the probability density function based on training data from a training data input.
12. The contact detection system of claim 1 , wherein the parameter estimation circuit is further operable to reset the parameters of the probability density function to default values based on a clear input signal.
13. The contact detection system of claim 1 , wherein the threshold calculator is operable to calculate the threshold based at least in part on a false alarm rate request signal.
14. A storage device comprising:
a storage medium;
a read/write head assembly disposed in relation to the storage medium, wherein the read/write head assembly includes a read head to disk interface sensor operable to provide a sensor output indicating contact between the read/write head assembly and the storage medium; and
a contact detector operable to compare a signal derived from the sensor output with a threshold to determine when the read/write head assembly contacts the storage medium, and further operable to calculate a value for the threshold by fitting a distribution to a probability density function of the signal derived from the sensor output.
15. The storage device of claim 14 , wherein the contact detector is operable to compute the signal derived from the sensor output as a modulation density of segmented sums of digital samples of the sensor output.
16. The storage device of claim 14 , wherein the distribution is selected from a group consisting of a Gaussian distribution and a skew normal distribution.
17. A method for detecting contact between a read head and a storage medium, comprising:
comparing a signal derived from a head to disk interface sensor with a threshold and indicating contact between a read head and a disk surface when the signal is greater than the threshold;
estimating parameters of a probability density function of portions of the signal derived from the head to disk interface sensor with no contact between the read head and the disk surface; and
calculating the threshold based at least in part on the parameters.
18. The method of claim 17 , wherein the threshold is calculated based in part on a false alarm rate request signal.
19. The method of claim 17 , wherein the parameters of the probability density function are calculated using a Gaussian fitting of a modulation depth.
20. The method of claim 17 , wherein the parameters of the probability density function are calculated using a skew normal fitting of a modulation depth.