Method and apparatus for testing runout velocity and acceleration on a surface

Claim 1

A method for testing a surface for the largest acceleration associated with an irregularity on the surface from a signal representing the displacement between a fixed probe and the surface passing beneath the probe, said method comprising the steps of: producing a plurality of data points representative of substantially instantaneous acceleration of the displacement over time between the fixed probe, and the surface passing under the probe; transforming said plurality of data points into an exponential distribution curve; determining the largest acceleration associated with an irregularity on the surface from said exponential distribution curve; and comparing the determined largest acceleration associated with an irregularity on a surface to a selected level of acceleration.

Claim 2

A method for testing a surface for the largest acceleration associated with an irregularity on the surface from a signal representing the displacement between a fixed probe and the surface passing beneath the probe, said method comprising the steps of: producing a plurality of data points representative of substantially instantaneous acceleration of the displacement over time between the fixed probe, and the surface passing under the probe; transforming said plurality of data points into an exponential distribution curve; determining the largest acceleration associated with an irregularity on the surface from said exponential distribution curve; and comparing the determined largest acceleration associated with an irregularity on a surface to a selected level of acceleration.

Claim 7

A method for determining the largest acceleration associated with an irregularity on a surface of a disk used in a computer memory device, said computer memory device including a head which flies at an essentially fixed altitude over the disk, said head capable of a certain maximum acceleration, said method comprising the steps of: detecting the distance between a sensor and the surface as it is passed underneath the sensor to produce an analog signal representative of the distance between the sensor and the surface with respect to time; twice differentiating said analog signal representative of the distance with respect to time to produce an analog signal representative of the acceleration associated with the change in distance between the disk surface and the sensor with respect to time; digitizing the analog acceleration signal into digitized data bits each having a value of acceleration; setting up a plurality of registers, each register having a unique threshold value of acceleration; comparing the absolute value of acceleration of each digitized data bit with the threshold value of acceleration associated with each register; incrementing a count in each register which has a threshold value of acceleration greater than the absolute value of acceleration for each digitized data bit; fitting the number of counts in each register versus the threshold value of each register to a curve to produce a distribution function; determining the largest acceleration associated with an irregularity on the surface of the disk from the distribution function; and comparing the largest acceleration associate with an irregularity on the surface of the disk with the maximum acceleration the head is capable of to determine if the head will be capable of flying at a substantially constant height over the disk.

Claim 8

A method for determining the largest acceleration associated with an irregularity on a surface of a disk used in a computer memory device, said computer memory device including a head which flies at an essentially fixed altitude over the disk, said head capable of a certain maximum acceleration, said method comprising the steps of: detecting the distance between a sensor and the surface as it is passed underneath the sensor to produce an analog signal representative of the distance between the sensor and the surface with respect to time; twice differentiating said analog signal representative of the distance with respect to time to produce an analog signal representative of the acceleration associated with the change in distance between the disk surface and the sensor with respect to time; digitizing the analog acceleration signal into digitized data bits each having a value of acceleration; setting up a plurality of registers, each register having a unique threshold value of acceleration; comparing the absolute value of acceleration of each digitized data bit with the threshold value of acceleration associated with each register; incrementing a count in each register which has a threshold value of acceleration greater than the absolute value of acceleration for each digitized data bit; fitting the number of counts in each register versus the threshold value of each register to a curve to produce a distribution function; determining the largest acceleration associated with an irregularity on the surface of the disk from the distribution function; and comparing the largest acceleration associate with an irregularity on the surface of the disk with the maximum acceleration the head is capable of to determine if the head will be capable of flying at a substantially constant height over the disk.

Claim 10

An apparatus for comparing the maximum acceleration associated with an object passed over a surface to the maximum acceleration to which the object will be subjected to maintain an essentially uniform height while passed over the surface comprising: means for projecting a signal representing distance between a fixed probe and the surface with respect to time; means for passing the probe over the surface; means for twice differentiating the signal representing the distance between a fixed probe and the surface with respect to time; an analog to digital converter for digitizing the signal representing the twice differentiated signal of the distance between a fixed probe and the surface with respect to time, to produce a plurality of digital acceleration values; a plurality of registers each having a threshold value associated with each register; means for comparing the absolute value of each of the plurality of digital acceleration values to the threshold value associated with each register; means for placing a count in a register in response to the particular absolute value of digital acceleration being greater than the threshold value associated with the register so as to produce distribution data of the number of counts versus the threshold value of the registers; means for fitting the distribution data to a curve approximating the functional relationship between the number of counts and the threshold value of the registers; means for determining the highest absolute value of digital acceleration from the curve approximating the functional relationship between the number of counts and the unique value of the registers, said highest absolute value of digital acceleration being equal to the maximum acceleration to which the object will be subjected if the object maintains an essentially uniform height while being passed over the surface; and means for comparing the maximum acceleration associated with an object to the maximum acceleration to which the object will be subjected to determine if the object is capable of maintaining an essentially constant height while passed over the surface.

Claim 11

An apparatus for comparing the maximum acceleration associated with an object passed over a surface to the maximum acceleration to which the object will be subjected to maintain an essentially uniform height while passed over the surface comprising: means for projecting a signal representing distance between a fixed probe and the surface with respect to time; means for passing the probe over the surface; means for twice differentiating the signal representing the distance between a fixed probe and the surface with respect to time; an analog to digital converter for digitizing the signal representing the twice differentiated signal of the distance between a fixed probe and the surface with respect to time, to produce a plurality of digital acceleration values; a plurality of registers each having a threshold value associated with each register; means for comparing the absolute value of each of the plurality of digital acceleration values to the threshold value associated with each register; means for placing a count in a register in response to the particular absolute value of digital acceleration being greater than the threshold value associated with the register so as to produce distribution data of the number of counts versus the threshold value of the registers; means for fitting the distribution data to a curve approximating the functional relationship between the number of counts and the threshold value of the registers; means for determining the highest absolute value of digital acceleration from the curve approximating the functional relationship between the number of counts and the unique value of the registers, said highest absolute value of digital acceleration being equal to the maximum acceleration to which the object will be subjected if the object maintains an essentially uniform height while being passed over the surface; and means for comparing the maximum acceleration associated with an object to the maximum acceleration to which the object will be subjected to determine if the object is capable of maintaining an essentially constant height while passed over the surface.