Vibration compensation in tape drive track following using multiple accelerometers

Reliable operation of tape storage devices requires high positioning accuracy of the servo control system under vibration conditions. The demand for increased storage density makes it increasingly more challenging to meet the track-following performance requirements especially in the presence of external vibration disturbances. In the recently introduced flangeless tape drives, the head positioning system has translational and rotational capabilities to be able to compensate for both the lateral tape motion and the head-to-tape skew arising from large tape excursions. In this paper, vibration measurements from two accelerometers are utilized to enhance the closed-loop track-follow accuracy of the two-degree-of-freedom actuator system. Specifically, the accelerometers are placed on the tape drive frame and on the actuator system providing measurements of the vibration of the drive frame and the track-follow actuator, respectively. Vibration coupling effects from the rotational degree-of-freedom are estimated by combining the measurements from the two accelerometers. A feedforward control scheme is proposed that utilizes the acceleration measurement of the applied vibration and the estimated acceleration due to coupling effects. Experimental results demonstrate that the combined feedforward scheme provides substantial improvement in the track-follow performance under vibration conditions.