US 4,065,074 AGranted

Reel servo control system

AssigneeSperry Rand Corporation

InventorsDavid Robert Anderson, Wilbert Cleon Anderson, Vaughn Junior Jenkins

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Abstract

A tape reel servo control system for use with a tape transport system wherein tape loop position within vacuum loop boxes is maintained by digital techniques as opposed to analog techniques. In normal operation when the tape loop deviates from an equilibrium position in one direction within a loop box, its associated reel is accelerated to move it back to its equilibrium position by means of a series of motor drive pulses whose pulse lengths are determined by the count registered in a counter wherein the count is varied in accordance with the difference between actual and required acceleration of the reel. When the tape loop deviates from the equilibrium position in the other direction, the reel drive motor is braked by electronically shorting its terminals until the tape loop moves back to its equilibrium position. When the direction of tape movement is changed, means are provided which override the normal control of the system and prevents tape damage by overrun into or removal of the tape from its associated loop box by applying a combination of motor braking and plugging current to the motor drive.

Claims20

Dependent claims

A tape reel servo control system for use in a tape transport system comprising in combination:

a supply reel;
a take-up reel;
a tape drive capstan;
a first vacuum loop box for receiving a tape loop between said supply reel and said capstan;
a second vacuum loop box for receiving a tape loop between said capstan and said take-up reel;
a motor responsive to drive pulses for driving each of said supply and take-up reels;
first means for controlling the acceleration of each of said motors in accordance with the position of a tape loop within its associated loop box;
said first means for each of said motors, comprising:
a tape loop sensor means for providing an output indicative of the position of a tape loop within its associated loop box;
current programmer means connected to said tape loop sensor means for providing one of several discrete current levels as an output dependent on the position of said tape loop in its associated loop box;
current comparator means connected to said current programmer means;
feedback means for connecting a feedback signal from the associated motor to said current comparator means;
digital means comprising:
an up-down counter;
a hold circuit connected between said current comparator means and said up-down counter;
a pulse width counter connected to said up-down counter for receiving the counter in said up-down counter at the end of each of said drive pulses;
a clock pulse source connected to said pulse width counter;
said hold circuit causing said up-down counter to count up one or down one at the end of each motor drive pulse depending on whether the current from said current programmer means is greater or lesser than said feedback signal provided by said feedback means;
and
said pulse width counter counting down to zero at the end of each motor drive pulse from the adjusted count registered therein.

17 more elements

A tape reel servo control system for use in a tape transport system of the type employing a vacuum loop box disposed to receive a tape loop between a supply reel and a tape drive capstan and a vacuum loop box between the capstan and a take-up reel, comprising in combination:

motor means for driving each of the supply and take-up reels,
first means for controlling the acceleration and direction of rotation for each of said motor means in accordance with the position of a tape loop in its associated loop box, said first means, for each of said motor means comprising:
current programmer means providing discrete current levels as outputs dependent on the position of the tape loop in its associated loop box;
current comparator means connected for receiving the outputs of said current programmer means;
feedback means for connecting feedback signals from the associated motor means to said current comparator means;
digital means connected to said current comparator means and comprised of a pulse width counter, an up-down counter, a hold circuit and a clock pulse source for generating motor drive pulses having time intervals indicative of the difference between the signals applied to said current comparator means;
second means connecting said digital means to said associated motor means whereby said motor means is driven by said motor drive pulses.

4 more elements

Dependencies are inferred from the claim text.