Web Speed Control
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Cutter, JT: AUTHOR [+1]
The web speed adjacent a variable-radius reel is maintained at a controlled value by measuring the speed of the reel, and comparing this speed to a read-only memory whose contents are addressed by a digital reel tachometer as a function of the reel's variable radius.
Web Speed Control
The web speed adjacent a variable-radius reel is maintained at a controlled value by measuring the speed of the reel, and comparing this speed to a read- only memory whose contents are addressed by a digital reel tachometer as a function of the reel's variable radius.
Reel 10 contains a variable web quantity, such as magnetic recording tape
11. The reel's web quantity or radius varies between a full reel, represented as BOT (beginning-of-tape) or "R max" and an empty reel, represented as EOT (end-of-tape) or "R min". The reel speed is servo controlled, in order to maintain the web speed adjacent the reel at a constant or programmed-variable value.
Variable-speed motor 12 is directly connected to the reel and to digital tachometer 13. This tachometer provides an output pulse on conductor 14 for each unit of motor rotation. For example, the tachometer may provide 500 to 1,000 pulses for one reel revolution.
The tachometer pulses are divided by digital divider network 15 to provide one output pulse on conductor 16 for each revolution of reel 10. The pulses on conductor 16 are continuously accumulated in counter 17. This counter is initialized for the R max or the R min condition and its content at any given time is, therefore, a measure of exactly how much of the web has been taken from or added to the reel, that is, the reel's variable radius.
The tachometer pulses are also connected to period measuring network 18. This network measures the time interval between adjacent tachometer pulses, as by making reference to constant-frequency clock 19. The measured period appears on conductor 20 and is converted to rotational speed by period-to-speed converter 21. This converter supplies a sampled-data calculation of actual reel speed t...