Data storage device concurrently controlling and sensing a secondary actuator for actuating a head over a disk

Abstract

A data storage device is disclosed comprising a voice coil motor (VCM) and a secondary actuator configured to actuate a head over a disk. A control signal is applied to the secondary actuator while processing a sensor signal generated by the secondary actuator. A vibration signal is generated based on the sensor signal, wherein the vibration signal has a cut-off frequency between ten percent and ninety percent of a bandwidth of a control loop for controlling the secondary actuator.

What is claimed is: 
     
         1 . A method of operating a data storage device, the method comprising:
 actuating a head over a disk using a voice coil motor (VCM) and a secondary actuator;   applying a control signal to the secondary actuator and concurrently process a sensor signal generated by the secondary actuator; and   generating a vibration signal based on the sensor signal and a sensor capacitor, wherein a capacitance of the sensor capacitor is at least two times less than a capacitance of the secondary actuator.   
     
     
         2 . The method as recited in  claim 1 , wherein the vibration signal has a cut-off frequency between ten percent and ninety percent of a bandwidth of a control loop for controlling the secondary actuator. 
     
     
         3 . The method as recited in  claim 1 , wherein:
 a control loop for controlling the secondary actuator has a high-pass response; and   the vibration signal has a cut-off frequency above a cut-off frequency of the high-pass response of the control loop for the secondary actuator.   
     
     
         4 . The method as recited in  claim 1 , wherein the vibration signal has a cut-off frequency higher than a cut-off frequency of a response of a control loop for controlling the VCM. 
     
     
         5 . The method as recited in  claim 1 , further comprising:
 generating a sensor current proportional to a current applied to the secondary actuator due to the control signal;   estimating a capacitive voltage of the secondary actuator based on the sensor current; and   generating the vibration signal based on a difference between the sensor signal and the estimated capacitive voltage.   
     
     
         6 . The method as recited in  claim 5 , further comprising estimating the capacitive voltage of the secondary actuator by applying the sensor current to the sensor capacitor. 
     
     
         7 . The method as recited in  claim 5 , further comprising adapting a gain of the sensor capacitor based on the sensor signal and the estimated capacitive voltage. 
     
     
         8 . The method as recited in  claim 7 , further comprising:
 low pass filtering a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and   adapting the gain of the sensor capacitor based on the low-pass signal.   
     
     
         9 . The method as recited in  claim 1 , further comprising generating a feed-forward compensation signal applied to the secondary actuator based on the vibration signal. 
     
     
         10 . Control circuitry configured to control a voice coil motor (VCM) and a secondary actuator to actuate a head over a disk, the control circuitry configured to:
 apply a control signal to the secondary actuator and concurrently process a sensor signal generated by the secondary actuator; and   generate a vibration signal based on the sensor signal and a sensor capacitor, wherein a capacitance of the sensor capacitor is at least two times less than a capacitance of the secondary actuator.   
     
     
         11 . The control circuitry as recited in  claim 10 , wherein the vibration signal has a cut-off frequency between ten percent and ninety percent of a bandwidth of a control loop for controlling the secondary actuator. 
     
     
         12 . The control circuitry as recited in  claim 10 , wherein:
 a control loop for controlling the secondary actuator has a high-pass response; and   the vibration signal has a cut-off frequency above a cut-off frequency of the high-pass response of the secondary actuator.   
     
     
         13 . The control circuitry as recited in  claim 10 , wherein the vibration signal has a cut-off frequency higher than a cut-off frequency of a response of a control loop for controlling the VCM. 
     
     
         14 . The control circuitry as recited in  claim 10 , further configured to:
 generate a sensor current proportional to a current applied to the secondary actuator due to the control signal;   estimate a capacitive voltage of the secondary actuator based on the sensor current; and   generate the vibration signal based on a difference between the sensor signal and the estimated capacitive voltage.   
     
     
         15 . The control circuitry as recited in  claim 14 , further configured to estimate the capacitive voltage of the secondary actuator by applying the sensor current to the sensor capacitor that is proportional to a capacitance of the secondary actuator. 
     
     
         16 . The control circuitry as recited in  claim 14 , further configured to adapt a gain of the sensor capacitor based on the sensor signal and the estimated capacitive voltage. 
     
     
         17 . The control circuitry as recited in  claim 16 , further configured to:
 low pass filter a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and   adapt the gain of the sensor capacitor based on the low-pass signal.   
     
     
         18 . The control circuitry as recited in  claim 10 , further configured to generate a feed-forward compensation signal applied to the secondary actuator based on the vibration signal. 
     
     
         19 . A data storage device comprising:
 a disk;   a head;   a voice coil motor (VCM) and a secondary actuator configured to actuate the head over the disk; and   control circuitry configured to:
 apply a control signal to the secondary actuator and concurrently process a sensor signal generated by the secondary actuator; and 
 generate a vibration signal based on the sensor signal, wherein the vibration signal has a cut-off frequency between ten percent and ninety percent of a bandwidth of a control loop for controlling the secondary actuator. 
   
     
     
         20 . The data storage device as recited in  claim 19 , wherein:
 the control loop for controlling the secondary actuator has a high-pass response; and   the vibration signal has a cut-off frequency above a cut-off frequency of the high-pass response of the control loop for the secondary actuator.   
     
     
         21 . The data storage device as recited in  claim 19 , wherein the vibration signal has a cut-off frequency higher than a cut-off frequency of a response of a control loop for controlling the VCM. 
     
     
         22 . The data storage device as recited in  claim 19 , wherein the control circuitry is further configured to:
 generate a sensor current proportional to a current applied to the secondary actuator due to the control signal;   estimate a capacitive voltage of the secondary actuator based on the sensor current; and   generate the vibration signal based on a difference between the sensor signal and the estimated capacitive voltage.   
     
     
         23 . The data storage device as recited in  claim 22 , wherein the control circuitry is further configured to estimate the capacitive voltage of the secondary actuator by applying the sensor current to a sensor capacitor that is proportional to a capacitance of the secondary actuator. 
     
     
         24 . The data storage device as recited in  claim 23 , wherein the control circuitry is further configured to adapt a gain of the sensor capacitor based on the sensor signal and the estimated capacitive voltage. 
     
     
         25 . The data storage device as recited in  claim 24 , wherein the control circuitry is further configured to:
 low pass filter a difference between the sensor signal and the estimated capacitive voltage to generate a low-pass signal; and   adapt the gain of the sensor capacitor based on the low-pass signal.   
     
     
         26 . The data storage device as recited in  claim 23 , wherein a capacitance of the sensor capacitor is at least two times less than the capacitance of the secondary actuator. 
     
     
         27 . The data storage device as recited in  claim 19 , wherein the control circuitry is further configured to generate a feed-forward compensation signal applied to the secondary actuator based on the vibration signal.