US 4,003,090 AGranted

Magnetic recording and reproducing system with tape-to-head speed control

AssigneeRCA Corporation

InventorJohn Brewer Beck

Life of this patent

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Abstract

Apparatus is provided for controlling the phase and speed of a motor for driving the rotary magnetic heads of a video tape recorder. An output of a signal generator, for example, a sawtooth wave, having a frequency corresponding to the rotational speed of the motor is compared with an external reference signal, for example, a 60 Hertz power line signal. A difference in frequency generates a varying error voltage whose polarity is indicative of the error direction. Relatively large or prolonged frequency errors result in an error voltage waveform having an abrupt and relatively large change. This error voltage is differentiated to create relatively large pulses of polarity depending on the direction of the error voltage. The relatively large pulses either charge or discharge a capacitor, the output of which changes the current to the motor so as to reduce the relatively large frequency error to a range suitable for handling by a conventional combined position and velocity servo system.

Claims7

Dependent claims

In a magnetic recording and reproducing system in which magnetic recording and reproducing head means are mounted on a wheel driven by rotational driving means for recording and reproducing signals on a transported magnetic tape in successive tracks that are skewed relative to the lengthwise direction of the tape, a control system comprising:

means for producing a substantially square wave having a period determined by the rate of rotation of said wheel for providing a repetitive control signal during each cycle of rotation of said wheel at a rate corresponding to said rate of rotation of said wheel;
monostable multivibrator means for generating a pulse signal in a predetermined time relationship with respect to one edge of said square wave for supplying first controllable reference signals having a repetition rate representative of a desired velocity of said wheel;
a first control means responsive to said control signal and said first reference signals for providing a first velocity error signal;
means for providing second reference signals having a substantially fixed repetition rate;
a second control means responsive to said control signal and to said second reference signals for providing a second error signal indicative of relatively slowly varying deviations in the position of said head means from a predetermined positional relation with respect to said tape;
a third control means responsive to said control signal and to said second reference signals for providing a third error signal in response to errors in velocity of said wheel greater than a predetermined threshold;
means coupling said third error signal to said monostable multivibrator means for varying said predetermined time relationship;
and
means for coupling said first, second and third error signals to said driving means so as to maintain synchronization of said head means with said tracks.

6 more elements

means for providing a repetitive control signal during each cycle of rotation of said wheel at a rate corresponding to the rate of rotation of said wheel;
means for supplying first controllable reference signals having a repetition rate representative of a desired velocity of said wheel;
a first control means responsive to said control signal and said first reference signals for providing a first velocity error signal;
means for providing second reference signals having a substantially fixed repetition rate;
a second control means responsive to said control signal and to said second reference signals for providing a second error signal indicative of relatively slowly varying deviations in the position of said head means from a predetermined positional relation with respect to said tape;
a third control means comprising a sawtooth wave generator responsive to said control signal to provide a sawtooth wave having a relatively slowly sloping portion and a relatively rapidly sloping portion and signal comparison means responsive to said sawtooth wave and said second reference signals for comparing the relative phase therebetween, said third control means providing a third error signal in response to errors in velocity of said wheel greater than a predetermined threshold;
and
means for coupling said first, second and third error signals to said driving means so as to maintain synchronization of said head means with said tracks.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/545,155Filed 29 Jan 1975
Priority: UK 7257/7418 Feb 1974
Granted: 11 Jan 1977
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G11B 27/10
Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel: indexing; Addressing; Timing or synchronising;…
G11B 15/1808
Driving; Starting; Stopping; Arrangements for control or regulation thereof: driving of both record carrier and head
G11B 15/4731
By controlling the speed of the heads: control of headwheel rotation
G11B 15/602
Guiding record carrier: for track selection, acquisition or following