| 摘要 |
In accordance with the present invention, a method of operating a magnetic tape drive, a magnetic tape drive and a servo control system are provided for obtaining and maintaining velocity control in a magnetic tape drive. In one embodiment, a method is provided for operating a magnetic tape drive. The tape drive includes a plurality of DC motors, and each DC motor has a plurality of Hall sensors. The DC motors are under the control of a servo system which is configured to read location information from the magnetic tape, and compute a primary tape velocity from the location information, and sense a secondary and tertiary velocity signal and compute a tape velocity based on one of the sensed secondary velocity signal and tertiary velocity. The method includes detecting if the primary velocity location information is available. In response to detecting that the primary velocity location information is available the primary velocity is employed to control the servo system. In response to detecting the primary velocity location information is unavailable then one of a secondary or a tertiary velocity signal is employed. The secondary velocity signal is employed when an absolute value of a term related to tape velocity is less than a predetermined value. The tertiary velocity signal is employed when the absolute value of the term related to tape velocity is greater than the predetermined value.
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