P7.11 A computer system requires a high-performance magnetic tape transport system [17]. The environmen

tal conditions imposed on the system result in a se

vere test of control engineering design. A direct-drive DC motor system for the magnetic tape reel system is shown in Figure P7.11, where r equals the reel radius, and J equals the reel and rotor inertia. A complete re

versal of the tape reel direction is required in 6 ms, and the tape reel must follow a step command in 3 ms or less.

The tape is normally operating at a speed of 100 in/s.

FIGURE P7.11 (a) Tape control system. (b) Block diagram. Tape reels and motors Capstans Photocells Vacuum (a) Photocell transducer Amplifier Motor R(s) Desired position 0.5K + Kr/L s+R/L -15 Motor back emf Tachometer K K Kp (b) Reel Y(s) Tape position