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Dual Actuator tuned mass damper pivot bearing Disclosure Number: IPCOM000013589D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue



Described is a method to isolate dual actuators from cross-talk vibration. Traditional dual actuator designs have a dual pivot with a single shaft. This single shaft provides a transmission path for vibrations to travel from the seeking actuator to the track following actuator. A tuned mass damper can be employed in the pivot to attenuate the cross-talk contribution coming from the butterfly mode. A standard dual actuator pivot has a common, hollow shaft on which four ball bearings and two sleeves are positioned. Separating the top and bottom pivots along the shaft is a spacer or bushing that makes contact at the inner bearings. The problem is that the vibrations arising from a seeking actuator have a continuous transmission path to the other actuator. The butterfly mode has the largest gain. During a seek, the actuators coil and arms move in phase resulting in an opposite reaction force at the bearing. Vibrations originating from one actuator first pass through the pivot sleeve, then the ball bearing, then conduct through both the shaft and spacer to the other pivot’s ball bearings, then pass through the sleeve and finally into the second actuator. These vibrations can cause the track following (the second) actuator’s heads to go off track or can increase the settle time if the second actuator is seeking. To minimize the track misregistration from cross-talk the shaft has a tuned mass damper attached to it. The tuned mass damper consists of a mass (of up to 10% of the actuator moving mass) and damping material. The damping material geometry, loss factor and mass are tuned for the mass to be 180 degrees out-of-phase with the frequency of the butterfly mode. When properly tuned the vibrations from a seeking actuator are attenuated by the damper. The figure shows a tuned mass damper having a short cylindrical mass located between the top and bottom pivots at the point of maximum shaft defection from the butterfly mode shape. Separating the mass from the spacer is the damping material. The weight of the mass, damping material loss factor and damping material geometry are all tuned to absorb energy at one specific frequency. 1