Microprocessor controlled tape motion

The capstan control system of a high performance digital tape drive starts and stops tape with accelerations of about 500 g's. A microprocessor based control system is now being implemented on STC's 4500 Tape Systems to attain accurate tape speed control with little high frequency variation. Improvements made possible by the processor include controlling rate of change of motor current and drastically reducing start current when a "GO" command is received during a decelerate operation to avoid exciting a torsional resonance. Other improvements are mode-controlled digital error integration for long term accuracy and stop-lock stability enhancement by digital-gain switching.