Reduction of acoustic noise during VCM open loop control
Original Publication Date: 2001-Dec-01
Included in the Prior Art Database: 2003-Jun-20
Disclosed is a method to reduce acoustic noise of hard disk drive during VCM open loop control. Problem As for the hard disk drive which utilize "Head load/unload function", VCM is driven with open loop control on occasion of confirmation whether the actuator is stopped on the ramp or not, or calibration before loading. In cases of these, the mechanical parts are vibrated because VCM current is changed with rectangle form. It is major cause of acoustic noise during load/unload operation. Solution The cause of acoustic noise when VCM is driven with open loop control, is large change of current with rectangle form. The rectangle form is constituted by many fourier elements, and resonance frequency of mechanical parts is included in them. Therefore the method of driving the VCM is changed in order that VCM is driven with sine curve because it is constituted by only one fourier element. Fig. 1 shows the difference of traditional and new method of driving VCM current when VCM current is changing from Ia to Ib. Amplitude is set as difference of Ia and Ib, and frequency is set as suitable one which is out of resonance of mechanical parts. The RRO table is used for generating sine curve.