A key component of the track-following system is the track-following actuator. IBM’s tape drives use voice coil actuators to position the head relative to the tape. Electrical connectivity is provided to the head by means of flex cables that route signals to and from the drive electronics for reading and writing data.
In order to increase the data rate in future tape systems, the number of parallel channels will have to be increased, resulting in larger and stiffer flex cables. Increased mass and stiffness of the flex cables may degrade the performance of the track-follow actuator.
To minimize such effects, we use finite element modeling (FEM) to optimize the design of the head, cable and actuator assembly. Higher-order resonances in the actuator can limit the bandwidth and track-following performance of the actuator.
FEM modeling is used to identify the origin of such resonances and test strategies to minimize their effects. An example of an FEM simulation of a track-following actuator is shown in Figure 1.
In the future, the performance of the track-following system can be improved by increasing the bandwidth of the track follow actuator [1-2].
Figure 2 shows an example of a prototype actuator using aluminum flexures and a piezo-electric stack to achieve a first resonance of about 5 kHz, compared to around 100 Hz for a typical voice coil actuator.
Another area of active research is the use miniature actuators built into the tape guide rollers to actively tilt the roller in order to actively steer the tape as it transported through the tape path [3].
Figure 3 shows a photograph of a prototype tilting roller for active tape steering. The basic concept is illustrated in Figure 4 and involves using optical sensors to measure the position of the edge of tape. This information is used by a feedback controller to drive the tilting rollers to compensate for lateral tape motion and or tape skew.
- Figure 1. (a) Finite element model of track follow actuator and flex cable (b) Visualization of 1st and (c) 2nd resonance modes.
Figure 3. Photograph of a grooved roller tape guide with built in voice coil actuation for tape steering.
- Figure 4. Schematic of a tape path with an active tape guiding system comprising two tilting rollers (R1 & R4) and two optical edge sensors.
References
[1] High Bandwidth Track Following for Moving Media, V. Kartik, A. Pantazi, M.A. Lantz, Proc. 20th ASME Annual Conf. on Information Storage & Processing Systems "ASME ISPS 2010," Santa Clara, CA June 2010) 265-267.
[2] Piezo-electrically actuated high band width vibration compensation for moving media, V. Kartik, M.A. Lantz and E. Eleftheriou, 2009 JSME-IIP/ASME-ISPS Joint Conference on Micromechatronics for Information and Precision Equipment (MIPE 2009) June 17-20, 2009, Tsukuba, Japan.
[3] Active Tape Guiding, A. Pantazi, M. A. Lantz, W. Haeberle, W. Imaino, J. Jelitto, E. Eleftheriou, Proc. 20th ASME Annual Conf. on Information Storage & Processing Systems 2010 "ISPS," Santa Clara, CA, (June 2010) 304-306.