Adaptive voltage-mode controller for a voice coil motor
A voltage-mode VCM controller is provided comprising an Infinite Impulse Response (IIR) filter that modifies a servo control voltage signal to a voltage driver in response to an adaptive compensator that configures the IIR filter in relation to an observed VCM velocity and an actual VCM velocity. An associated method is provided comprising modeling a velocity response of a VCM to a voltage input; inputting the observed velocity and an actual VCM velocity to an adaptive compensator that computes a gain and a VCM response pole frequency in relation to the VCM resistance and inductance; configuring an IIR filter in relation to the computed gain and pole frequency values; and using the IIR filter to modify a voltage command from a servo controller to a power driver.
1. A voltage-mode voice coil motor (VCM) controller apparatus comprising an Infinite Impulse Response (IIR) filter that modifies a servo control voltage signal supplied to a voltage mode driver in response to an adaptive compensator that configures coefficients for the IIR filter in relation to an observed VCM velocity and an actual VCM velocity.
2. The apparatus of claim 1 wherein an output of the HR filter is an input to the adaptive compensator.
3. The apparatus of claim 1 wherein the adaptive compensator defines a discrete-time model of the VCM in terms of a second order system.
4. The apparatus of claim 3 wherein the model identifies a gain value and a VCM response pole frequency in configuring the IIR filter.
5. The apparatus of claim 4 wherein the VCM response pole frequency is identified in relation to changes in a VCM inductance and resistance.
6. The apparatus of claim 4 wherein the IIR filter computes a pole conversion for a sampling rate of the adaptive compensator that is different than a sampling rate of the servo control.
7. The apparatus of claim 6 wherein the adaptive compensator is configured for operating in down-sample mode by reconfiguring the IIR filter in relation to the servo control sampling rate.
8. A method comprising:
modeling a response of a VCM to a voltage input;
inputting the modeled velocity and an actual VCM velocity to an adaptive compensator that computes a gain and a VCM response pole frequency in relation to a VCM resistance and inductance;
configuring coefficients for an IIR filter in relation to the computed gain and pole frequency values;
using the IIR filter to modify a voltage command from a servo controller; and supplying the modified voltage command to a voltage mode power driver.
9. The method of claim 8 wherein the configuring an IIR filter step comprises inputting an output signal from the IIR filter to the adaptive compensator.
10. The method of claim 8 wherein the modeling step is characterized by a discrete-time model of the VCM in terms of a second order system.
11. The method of claim 10 wherein the configuring step is characterized by identifying a gain value and a VCM response pole frequency.
12. The method of claim 11 wherein the configuring step is characterized by identifying the VCM response pole frequency in relation to changes in a VCM inductance and resistance.
13. The method of claim 11 wherein the configuring step is characterized by computing a pole conversion for a sampling rate that is different than a sampling rate of the servo controller.
14. The method of claim 13 wherein the using step is characterized by a down-sampling mode by modifying the IIR filter in relation to the servo controller sampling rate.
15. A data storage device, comprising:
a data transfer head in a data storing and retrieving relationship with a data storage medium; and
means for positionally controlling the head by a voltage mode driver supplying a voltage signal to a VCM, the supplied voltage signal is compensated for the VCM resistance and inductance.
16. The device of claim 15 wherein the means for positionally controlling is characterized by modeling a discrete-time VCM response in terms of a second order system.
17. The device of claim 15 wherein the means for positionally controlling is characterized by digitally filtering the voltage signal with an IIR that is computed in relation to an observed velocity and an actual velocity of the VCM.
18. The device of claim 15 wherein the means for positionally controlling is characterized by digitally filtering the voltage signal with an IIR that is computed in relation to a VCM response pole frequency conversion.
19. The device of claim 15 wherein the means for positionally controlling is characterized by a pole conversion related to differences between a filtering calculation sampling time and a servo control sampling time.
20. The device of claim 15 wherein the means for positionally controlling is characterized by down-sampling the compensation to the VCM.