Coincidence servosystem

Claim 2

A digital servocontrol system comprising: a basic servocontrol network for controlling a first device to be synchronized with a second device and including having a digital comparator means receiving a first input command signal indicative of the desired operating condition of the first device and a feedback digital signal indicative of the actual condition of said first device, and feedback means providing within a feedback path to said comparator a feedback digital signal train indicative of the actual condition of said first device; and a coincidence servo interrupting said feedback path to said digital comparator, the coincidence servo receiving two input signals including a second input command signal indicative of the actual condition of said second device and a signal indicative of the actual condition of said first device, the coincidence servo generating an error signal adding or subtracting pulses to said feedback digital signal train depending upon the relationship of the input signals to the coincidence servo.

Claim 3

The servosystem of claim 1 including means for locking out the coincidence servo when the error signal generated within the coincidence servo is less than a predetermined value.

Claim 4

The servosystem of claim 2 in which the coincidence servo includes coincidence comparator means receiving the two input signals and generating a responsive digital error signal, pulse add or subtract logic circuitry receiving the digital error signal and including a first means for sensing the polarity of said digital error signal and providing commands the nature of which indicate whether pulses are to be added or subtracted to said feedback train, a second means for sensing the absolute magnitude of said error signal and providing commands to the means for locking out the coincidence servo when the error signal magnitude is less than a predetermined value, and a third means responsive to the error signal And providing commands indicative of the rate the add or subtract pulses are to be provided in said feedback digital train.

Claim 5

The servosystem of claim 3 in which the coincidence servo includes frequency multiplying means receiving said feedback digital signal train and multiplying the frequency a predetermined amount prior to adding or subtracting pulses responsive to the error signal of said coincidence comparator, and frequency dividing means receiving and dividing by the predetermined amount said multiplied frequency signal after the pulse addition or subtraction.

Claim 6

The servosystem of claim 4 in which said first means includes a saturable amplifier adapted to assume saturated or nonsaturated state dependent upon the polarity of the error signal.

Claim 7

The servosystem of claim 4 in which said third means includes a voltage-controlled oscillator, the frequency of which is related to the magnitude of said error signal.

Claim 8

The servosystem of claim 4 in which the second means includes a voltage detector with hysteresis network, the hysteresis level being biases to a predetermined level.

Claim 9

THe servosystem of claim 4 in which: said first means includes a saturable amplifier adapted to assume a saturated or nonsaturated state dependent upon the polarity of the error signal; said second means includes a voltage detector with hysteresis network, the hysteresis level being biases to a predetermined level; and said third means includes a voltage-controlled oscillator, the frequency of which is related to the magnitude of said error signal.

Claim 12

The method of claim 9 further including: generating a once-around signal train related to the actual rotational position of the head; comparing the relationship of the once-around signal train of the head with a train of prestart signals related to the bursts to be recorded and generating an error signal the magnitude and polarity of which is indicative of the actual head position in relationship to the desired position for recording the bursts; and modifying the feedback digital pulse train in response to the error signal with the polarity of the error signal indicating whether pulses are to be added or subtracted and the magnitude of the error signal indicating the rate at which pulses are added or subtracted.

Claim 13

The method of claim 10 further including sensing the magnitude of the error signal and modifying the feedback pulse train only when the absolute value of the error signal exceeds a predetermined value, the predetermined value being selected to provide a synchronizing margin to guard against unstable operation.

Claim 14

The method of claim 11 further including multiplying the frequency of the feedback digital pulse train prior to modification, and then decreasing the frequency of the feedback train after modification.

Claim 15

A digital servocontrol system for synchronizing a rotary-head magnetic tape transport with a transmitter transmitting intermittent bursts of data comprising, in combination: a basic servocontrol network for controlling the rotational operation of the rotary drum of a rotary-head magnetic tape transport and including a digital comparator means receiving a first input command signal indicative of the desired rotational velocity oF said drum and a feedback digital signal train indicative of the actual velocity of said drum, feedback means for generating within a feedback path to said comparator a feedback digital signal train indicative of the actual velocity of said drum; and a coincidence servo interrupting said feedback path, the coincidence servo receiving two input signal including a second input command in the form of intermittent prestart pulses related to bursts of data to be recorded and a signal indicative of the actual position of said drum, the coincidence servo generating an error signal indicative of the phase relationship of the second command and actual position of said drum, and control logic means receiving said error signal and including a controlled oscillator means to provide pulse signals for modifying the feedback digital train, the oscillator frequency being responsive to the magnitude of the error signal, gating means receiving the pulse signals of said oscillator means and responsive to the polarity of the error signal, said gating means controlling whether pulses are added or subtracted to step function the head drum to the desired position when bursts are received.

Claim 16

A digital servocontrol system for synchronizing a rotary-head magnetic tape transport with a transmitter transmitting intermittent bursts of data comprising, in combination: a basic servocontrol network for controlling the rotational operation of the rotary drum of a rotary-head magnetic tape transport and including a digital comparator means receiving a first input command signal indicative of the desired rotational velocity oF said drum and a feedback digital signal train indicative of the actual velocity of said drum, feedback means for generating within a feedback path to said comparator a feedback digital signal train indicative of the actual velocity of said drum; and a coincidence servo interrupting said feedback path, the coincidence servo receiving two input signal including a second input command in the form of intermittent prestart pulses related to bursts of data to be recorded and a signal indicative of the actual position of said drum, the coincidence servo generating an error signal indicative of the phase relationship of the second command and actual position of said drum, and control logic means receiving said error signal and including a controlled oscillator means to provide pulse signals for modifying the feedback digital train, the oscillator frequency being responsive to the magnitude of the error signal, gating means receiving the pulse signals of said oscillator means and responsive to the polarity of the error signal, said gating means controlling whether pulses are added or subtracted to step function the head drum to the desired position when bursts are received.

Claim 17

The system of claim 13 further including: a voltage detector means within the control logic means for sensing the magnitude of said error signal and locking out the coincidence comparator from the feedback path for error signals of a magnitude less than a predetermined value.

Claim 18

The system of claim 14 in which the voltage detector means includes a hysteresis network for providing a synchronizing margin.

Claim 19

A digital servosystem for controlling the operating condition of a rotating device, comprising: a first servo network having a digital comparator controlling such device in response to a first input command signal representing desired rate and phase operating conditions of such device and a feedback pulse signal representing actual rate and phase operating conditions of such device and a feedback pulse signal representing actual rate and phase operating conditions of such device; a feedback path coupled between said device and said comparator and carrying said feedback pulse signal; and a second servo network interposed in said feedback path responsive to a second input command signal to add or subtract pulses from said feedback pulse signal to a step position the phase condition of said device into synchronism with the second input command signal.

Claim 20

A digital servosystem for controlling the operating condition of a rotating device, comprising: a first servo network having a digital comparator controlling such device in response to a first input command signal representing desired rate and phase operating conditions of such device and a feedback pulse signal representing actual rate and phase operating conditions of such device and a feedback pulse signal representing actual rate and phase operating conditions of such device; a feedback path coupled between said device and said comparator and carrying said feedback pulse signal; and a second servo network interposed in said feedback path responsive to a second input command signal to add or subtract pulses from said feedback pulse signal to a step position the phase condition of said device into synchronism with the second input command signal.

Claim 23

The method as defined in claim 17, wherein said control signal is periodic and the phase condition of the rotating member is to be synchronized thereto, and being further characterized by the steps of: comparing the phase difference between the periodic control signal and the phase condition of the rotating member and adding pulses to or subtracting pulses from the feedback signal in accordance with the magnitude and polarity of such compared phase difference.