JPS6058481B2 - Phase adjustment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase adjustment method suitable for use in a servo system of a magnetic reproducing device, so-called a video tape recorder.

The system for driving the rotary head of a video tape recorder is equipped with a servo device.

This servo device is constructed as shown in FIG. That is, the detection pulse from the rotation detector 11 is amplified by the amplifier 12, the amplified detection pulse is time-adjusted by the monostable multivibrator circuit 13, and is input to the first input terminal of the phase comparator 14. At the second input terminal of this phase comparator 14,
A reference signal using a vertical synchronization signal is input, and a direct current direct pressure proportional to the phase difference between the two human power signals is obtained at its output terminal. The rotational phase of the rotary head motor 15 is controlled according to this DC voltage. The rotation detector 11 is composed of a rotating permanent magnet provided on the rotating head substrate, a fixed-side detection coil that detects the passage of the permanent magnet, and the like. In order to maintain tape compatibility between video tape recorders, the signal positions recorded on the tape are usually standardized, and for this reason, the rotating head at the moment when a video signal, for example, a vertical synchronization signal, is generated. The location of will be regulated.

The rotational phase of the rotary head is determined using a detection coil or the like, as described above. This causes variations in the relative position between the rotary head and the detector and in the absolute position of the rotary head itself. In order to correct such variations, a monostable multivibrator circuit 13 is used to adjust the phase of the detection pulse. By controlling the motor 12 as described above, the relative position between the rotary head and the recording track is kept stable.

However, in the conventional servo device described above, a monostable multivibrator circuit 13 is used for phase adjustment of the detection pulse.

For this reason, as the control system becomes more precise, the effects of temporal jitter and drift of the monostable multivibrator circuit will appear on the control output. This invention was made in view of the above circumstances, and it handles the phase data corresponding to the delay time after the fact without directly transmitting the pulse to be position adjusted. The purpose of this invention is to provide a phase adjustment method that eliminates the effects of circuit jitter and drift. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an example in which the present invention is applied to a control system for a rotary head motor of a video tape recorder, where 21 is the rotary head motor and 22 is a rotation detector.

The detection pulse obtained from the rotation detector 22 is transmitted to the amplifier 23
is input. The output of this amplifier 23 is applied to a latch pulse input terminal of a first latch circuit 24. The first latch circuit 24 can latch the data of the cyclic count circuit 27 when a latch pulse from the amplifier 23 is applied, and input its output to the microprocessor 30 .

A reference signal (Ref) using a vertical synchronization signal is applied to the latch pulse input terminal of the second latch circuit 25.
When this reference signal is input, the second latch circuit 25 can latch the data of the cyclic counter circuit 27 and input its output to the microprocessor 30. The latch pulse input terminal of the third latch circuit 26 has
The output from the monostable multivibrator circuit 28 is input. At this time, the third latch circuit 26 can latch the data of the cyclic counter circuit 27 and input its output to the microprocessor 30. The monostable multivibrator circuit 28 can adjust its delay amount by a regulator 29. The cyclic counter circuit 27 includes:
A clock pulse CP is inputted through the input terminal, and this counter circuit always performs a cyclic counting operation.

Further, a trigger pulse obtained when the cyclic counter circuit 27 has zero count data, for example, is input to the monostable multivibrator circuit 28. In the microprocessor 30, arithmetic processing is performed using output data from the first latch circuit 24, the second latch circuit 25, and the third latch circuit 26.

The output data of the first latch circuit 24 is detected as a pulse value,
When the output data of the second latch circuit 25 is referred to as a reference signal value, the following calculation is performed in the microprocessor 30: (reference signal value - detected pulse value + fixed phase difference value).

Here, the fixed phase difference value includes output data from the third latch circuit 26. The calculation result of the microprocessor 30 is converted into an analog quantity by the digital-to-analog converter 31, and is inputted to the drive amplifier 32 of the motor 21 as a control signal.

The present invention is constructed as described above, and the count value of the cyclic counter circuit 27 is read into the first latch circuit 24 using a detection pulse, and the count value is read into the second latch circuit 25 using a reference signal. This is what is read into.

Calculating the data read into the first and second latch circuits 24 and 25 corresponds to calculating the time difference between the detection pulse and the reference signal using binary data. Further, the counter circuit 27 performs a time counting operation using clock pulses. When calculating the time difference, that is, the phase difference, between the above detection pulse and the reference signal, the data on the phase difference indicates the relative positional relationship between the rotating head and the recording track. Since it includes an error in the mechanical relative position with respect to the rotating head, it is necessary to correct the phase difference data.

Since the mechanical relative position error mentioned above is fixed, the purpose can be achieved by creating data corresponding to this error and adding or subtracting it from the phase difference data mentioned above. Can be done.

A portion that generates data for correcting such mechanical relative position errors is comprised of the monostable multivibrator circuit 28 and the third latch circuit 26. In other words, data for correction is created by delaying the trigger pulse obtained by the cyclic counter circuit 27 with all zeros, for example, by the monostable multivibrator circuit 28 and using it as a latch pulse of the third latch circuit 26. It is something. As mentioned above, by calculating the reference signal value and the detected pulse value as well as the above correction data using the microprocessor 30, the standard relative positional relationship between the rotating head and the recording track is obtained. be able to.

The amount of delay of the monostable multivibrator circuit 28 is adjusted by the adjuster 29 according to the error in the mechanical relative position between the rotation detector and the rotary head described above. The phase difference detection circuit using the first and second latch circuits is basically disclosed in Japanese Patent Application No. 52-113864 filed by the applicant.
listed in the number. However, microprocessor 3
0, the calculation is performed as follows: (reference signal value - detected pulse value + fixed phase difference value).

The fixed phase difference is a constant determined by the steady phase difference of the servo system, the range of digital-to-analog conversion, the operating point of the motor, etc., and is determined at the time of design.

Therefore, the fixed phase difference also includes an error in the mechanical relative position between the rotation detector and the rotary head. Furthermore, data indicating the control amount is obtained from the calculation result, and the fixed phase difference also includes a correction amount for determining the center point of the variable range of the data indicating the control amount. In the present invention described above, by varying the delay amount of the monostable multivibrator circuit, the rotational phase of the rotary head (relative to the recording track) can be finely adjusted. In the present invention, the above-mentioned monostable multivibrator circuit 28 is not included in the loop as in the prior art.

Therefore, the monostable multivibrator circuit does not have to respond to high frequency detection pulses as in the conventional case.
According to the method of the invention, the monostable multivibrator circuit only needs to respond to the trigger pulse of the cyclic counter circuit 27. Moreover, the cycle may be longer than that. In other words, this means that the monostable multivibrator circuit 28 is driven with a trigger pulse having a period considerably longer than the period of the detection pulse. Therefore, the design of the monostable multivibrator circuit itself is easier than designing the monostable multivibrator circuit itself to be adapted to short-period detection pulses. Furthermore, compared to the conventional method, the influence of temporal jitter and drift can be reduced. The numerical values actually read by the monostable multivibrator circuit 28 and the third latch circuit 26 are
, the precision of the numerical values read by the second latch circuits 24 and 25 can be much lower.

Therefore, by adding hysteresis to the processing in the microprocessor 30 (to deal with numerical changes in the third latch circuit 26), analog jitter and drift of the monostable multivibrator circuit can be absorbed to some extent. . For example, in order to set the quantization error to several μSec or less, the numerical value based on the rotation detection pulse is set to 12 to 1 MHz clock count value, for example.
Read into the first and second latch circuits with 6-bit precision.
However, for the numerical value read based on the output of the monostable multivibrator circuit 28, a resolution of 10 to 30 μsec intervals is sufficient, and even if the variable width is 1 msec, a capacity of 5 to 7 bits is sufficient. Therefore, even if the monostable multivibrator circuit has jitter within this quantization error range, it will not affect the overall circuit, and at the transition point of quantization, hysteresis can be added in the arithmetic processing to remove jitter. . For example, if the reading value is an integer from 1 to 50, if there is a difference of 2 or more in the comparison result between the current reading value and the previous value, replacing the current value with the previous value will cause the analog value to be less than 1. Jitter can be completely absorbed. By adding lower bits to the numerical value obtained in this way, that is, by adding other fixed numerical elements, the overall precision is the same as that of the first and second latch circuits, and the previous value is By performing calculations, highly accurate control outputs can be obtained. Although the above explanation deals with adjusting the rotational phase of the rotary head, it can also be used in various control units such as a capstan-based servo.

As described above, the present invention does not directly delay the pulse to be phase-adjusted, but handles phase data corresponding to the delay time after the fact, and avoids the effects of jitter and drift of delay circuits such as monostable multivibrator circuits. It is possible to provide a phase adjustment method that can eliminate the

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram showing a conventional servo device, and FIG. 2 is a configuration explanatory diagram showing an embodiment of the present invention. 24, 25, 26...First, second, third latch circuits, 27...Cyclic counter circuit, 28...
・・Simple breaker circuit, 30・・・・Microprocessor.

Claims (1)

[Claims] 1 The numerical value of the counter circuit that performs cyclic counting is latched into the first and second latch circuits by the first pulse (detection pulse) and the second pulse (reference signal). In a phase adjustment method that digitally calculates the reading value of the circuit and obtains a digital output that represents the phase relationship between the first and second pulses, the pulse obtained from the counter circuit is passed through a monostable multivibrator circuit that can vary the amount of delay. means for delaying and causing the content of the counter circuit to be read into a third latch circuit by the delayed output; and adding a fixed numerical value to the output of the third latch circuit;
A phase adjustment system comprising: a microprocessor that performs arithmetic processing on the outputs of the first and second latch circuits to obtain a corrected output for the phase relationship between the first and second pulses.