Method and apparatus for characterization of voice-coil motor with eddy current effect

Abstract

A method for characterizing a VCM assembly includes measuring a first response of the VCM assembly ( 100 ), removing a first conducting part of the VCM assembly ( 102 ), and measuring a second response of the VCM assembly with the first conducting part removed ( 104 ). Then, the method includes using curve fitting techniques ( 110 ) with the determined VCM compensation parameters to construct a model of the VCM assembly.

1 . A method for characterizing a VCM assembly, comprising: 
 measuring a first response of said VCM assembly;    removing a first conducting part of the VCM assembly;    measuring a second response of said VCM assembly with said first conducting part removed;    and constructing an eddy current model of said VCM assembly from said first and second measured responses.    
     
     
         2 . The method of  claim 1  further comprising verifying that said compensated VCM assembly follows said desired response within a predetermined tolerance.  
     
     
         3 . The method of  claim 1  wherein said first conducting part comprises a first magnet of said VCM assembly.  
     
     
         4 . The method of  claim 1  further comprising determining a Bode plot from said first response, and determining a value for a resistance and an inductance for a VCM coil of said VCM assembly.  
     
     
         5 . The method of  claim 1  wherein said measuring a first response of said VCM assembly comprises measuring a step response of said VCM assembly.  
     
     
         6 . The method of  claim 1  wherein said determining an eddy current characteristic that approximates a desired response approximates a second-order system.  
     
     
         7 . The method of  claim 1  further comprising removing a second conducting part of the VCM assembly, measuring a third response of said VCM assembly, and using said third measured response in determining said eddy current characteristic that approximates a desired response.  
     
     
         8 . The method of  claim 7  wherein said second conducting part comprises a second magnet of said VCM assembly.  
     
     
         9 . The method of  claim 7  wherein said determining an eddy current characteristic that approximates a desired response approximates a third-order system.  
     
     
         10 . The method of  claim 7  wherein said determining an eddy current characteristic that approximates a desired response using said first, second, and third responses approximates a fourth-order system.  
     
     
         11 . A method for characterizing a VCM assembly, comprising: 
 developing a desired VCM characteristic curve;    measuring an actual response of said VCM assembly to a predetermined test drive signal;    and, using curve fitting techniques, determining VCM compensation parameters to construct a model of said VCM assembly.