Acceleration feedforware control for head positioning in magnetic disk drives.

We have developed a new control method for head positioning which improves positioning accuracy in magnetic disk drives. In the new faster and lighter head disk assemblies (HDAs), the base cannot be regarded as stationary. We analyzed the control characteristic of a conventional feedback controller exposed to different types of vibration using a model that includes disk and HDA motion. The results show that the conventional feedback controller does not have enough resistance against disturbances produced by mechanical resonances the HDA base or spindle. To improve controllability, we developed "acceleration feedforward control", which comepensates for disk motion by detecting an acceleration signal at the HDA base. Theoretically, this feedfefward can completely compensate for seek reaction and any other disturbance. Examination of the mechanical interaction between the dual actuators shows the effectiveness of this control method.