| 摘要 |
<p>PURPOSE:To stably stop a tape by controlling brake torque in varying a duty ratio of a control bus to a transistor for switching for absorbing counter electromotive force in accordance with moment of inertia of each reel. CONSTITUTION:The moment of inertia is detected from a tension change attending upon a variation in a prescribed tape speed. Then, a tape wound radius is calculated with a capstan FG pulse signal 7a or a timer roller pulse signal 8a and a ratio of reel FG pulse signals 5 and 6 to each other by a control circuit 11, and when this is subtracted from the previous moment of inertia, the moment of inertia of the reel itself is known. Moreover, in the circuit 11, the optimum brake torque is decided with the calculated moment of inertia, so that a duty ratio of the corresponding brake control pulses 14 and 15 to each other is calculated. When a power source is cut off, the pulses 14 and 15 are sent from a backup power source to a motor drive amplifier 10 to drive the transistors 12 and 13. By this method, the brake torque for reel motors 3 and 4 becomes optimum value corresponding to the moment of inertia, thus stopping stably the tape under traveling.</p> |
