Storage Technology Corporation

Richard W Van Pelt

Donald F McCarthy

Patrick K Wong

Veda R Huffman

Joseph W Kern

A tape threading arm mechanical linkage undergoes significant variations in mechanical advantage through its motion. In order to compensate for the drastic changes in the mechanical advantage of the tape threading arm, the operation of the tape threading arm is divided up into a plurality of control segments. Each segment represents a portion of the tape threading path wherein the mechanical advantage of the tape threading arm remains fairly constant. A control memory stores data indicative of various control parameters that are required to regulate the operation of the tape threading arm motor to maintain the tape speed throughout this segment of the tape threading path at a constant velocity. In addition, the measured velocity of the magnetic tape as it is removed from the file reel is used to compute the difference between the predicted operation of the tape threading arm and the measured operation of the tape threading arm. The difference between the expected and measured operations is used to generate feedback signals to vary the current in the tape threading arm motor and the file reel motor to maintain a constant tape velocity, tape tension and minimum torque load on the tape threading arm.

Closed loop tape thread/unthread apparatus

An improved H-bridge power amplifier for controllably driving a dc motor is presented. The motor is connected in the center of the H-bridge in conventional manner. The H-bridge includes a current sense resistor placed between the power supply and a common tie point of the upper transistors of the bridge. Free wheeling diodes are connected from the motor directly to the power supply. This arrangement allows current to flow through the current sense resistor only when one of the upper transistors is on. The power amplifier is operated by selecting an appropriate pair of upper and lower transistors on opposite sides of the bridge so as to cause the current to flow through the motor in a desired direction. Both the upper and lower transistors of the selected pair are held ON until the current as sensed in the current sense resistor equals or exceeds a specified value, typically a desired current level. When this occurs, the upper transistor is turned OFF for a fixed off-time period, during which time the lower transistor is maintained ON. The motor current thereby decays through a path comprising the ON lower transistor, one of the free wheeling diodes, and the motor, which decay path significantly reduces the ripple associated with the motor current. At the end of the fixed off-time, the upper transistor is turned ON, and the process repeats itself. If braking is desired to slow the motor down, a plug inhibit mode is enabled wherein the lower transistor is turned off and the upper transistor is alternately turned ON and OFF.

H-bridge power amplifier and method for controlling the same

A control system for controlling the position of tape in a reel to reel tape transport system which includes a loop position responsive generator for generating loop reference signals representing a desired tape position in associated buffers; transducing means for measuring the position of tape loops in the buffers; a plurality of current generators for producing an output signal in response to one of the reference signals and the desired position signal; selector means for selecting an output control signal from one of the current generators selected control signal, and amplifying means for applying current to the reel drive motor. A constant current control mode is used when the tape position error is large, and a linear position control is used when the tape position error is small. Control is switched between the two modes as required for achieving the desired control while using minimal power. The system handles the worst case capstan reversal with a minimum turnaround time. Tape position is sampled at a rate that is a multiple of the mechanical resonance of the tape in the buffers thereby minimizing the effect of the resonance on the measurement. The system further uses a feedforward signal generator during the initial stage of motor control to compensate for the lag in the position transducer means.

Dual mode control system for controlling tape position in a reel to reel

A data clocking and detection system for a digital data storage system includes a common controlled oscillator for the multiple tracks. A phase detector for each track includes a counter and decoding circuitry producing outputs representing the time occurrence of transitions in the data with respect to bit cells defined by multiple clock pulses for each bit cell. Phase errors are used to control the frequency of the VCO, and large phase errors are used to add or subtract a count from the phase counter in each phase detector.

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Boulder, CO, United States of America

Richard W Van Pelt