Tape servo system: Actuator design and modeling
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.
Figure 1. Finite-element model of track-following actuator and flex cable.
Figure 2. A recording head mounted on a piezo-electrically actuated track-following system.
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 tilt the roller in order to steer the tape actively as it is transported through the tape path [2010-6].
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IBM Research Scientist