JPH0589569A - Software servo device - Google Patents

Abstract

PURPOSE:To decide the feed of tape in accordance with a frequency change of a phase difference data X and to suppress generation of noise at an intermittent slow time. CONSTITUTION:A phase differential data X between an RFSW and an ATFLOCK is read out by a timer 20 of a mechanical controller 12. The phase difference data X is passed to a low pass filter 24 included in a slow control part 22 of the mechanical controller 12 and a data X' having a frequency characteristic is obtained. A phase relation between the head at the time of tape stop and a recording track, namely a tape position is detected by the data X' and a desired count value A, namely the feed of tape is decided by A=C-X'XN and the intermittent slow is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a software servo device, and more particularly, it detects a tape position based on phase difference data between a head switching pulse and a tracking state signal and changes the tape feed amount, for example, 8 mm VTR.
The present invention relates to a software servo device that controls an intermittent throw in the.

[0002]

2. Description of the Related Art As shown in FIG. 8, in an intermittent slow mode of 8 mm VTR, frame feeding is repeated at a cycle of 10 fields, each field is counted down to 9 to 0, and a field counter (hereinafter referred to as "FCNT").
Stored in RAM for use. Then, as shown in FIG. 9, it is determined in step S1 whether or not FCNT = 5. If FCNT = 5, the timer is reset in step S2, and 2.5 V of the ATF error signal is cut out in step S3. It is determined whether or not the level (tracking state signal: hereinafter referred to as "ATFLOCK") has been reached. If the level has been reached, the timer data, that is, the phase difference data X is read in step S4. In FIG. 8, the time from the edge of FCNT = 5 to ATFLOCK, that is, the phase difference data (X0 or X1) is measured by the timer. Then, in step S5, FCNT
= 3, and if FCNT = 3, after delay of FCNT = 3 for a fixed time a in step S6, in step S7, the F of the capstan motor is changed.
After resetting the G counter, the capstan motor is turned on in step S8. The on-time of the capstan motor is calculated by counting the FG pulse of the capstan motor with the FG counter, and the desired count value A of the FG pulse is determined by the equation 1.

[0003]

## EQU1 ## A = C-X.times.N (C and N are constants) Then, in step S9, the capstan motor is operated until the count value of the FG counter reaches the desired count value A of the FG pulse determined by the expression 1. When the count value of the FG counter reaches the count value A, the capstan motor is turned off in step S10. In FIG. 8, (C−X0 × N) and (C−X1 ×)
N) corresponds to the on-time of the capstan motor.

Then, the process returns to step S1 and these operations are repeated at a cycle of 10 fields. As described above, in the conventional method, the phase relationship between the head and the recording track when the tape is stopped is detected by the phase difference data X between the RF switching pulse (head switching signal: hereinafter referred to as “RFSW”) and ATFLOCK. According to 1, the next tape feed amount, that is, the count value A is determined.

[0005]

However, in the conventional method, as shown in the equation 1, the count value A and the phase difference data X
Was in inverse proportion to. So, for example, 12
The load applied to the capstan differs greatly between the top and the end of the 0-minute tape, and the load applied to the capstan fluctuates in synchronization with the rotation of the reel. However, in such a case, the conventional method causes a problem. .. That is, if the tracking adjustment is adjusted to be noiseless at the tape top only with the proportional control as shown in Formula 1 as in the prior art, noise appears at the top or bottom of the screen at the tape end. There is also a problem that noise may appear on the screen in synchronization with the rotation of the reel.

Therefore, a main object of the present invention is to provide a software servo device capable of suppressing the generation of noise during intermittent throw.

[0007]

SUMMARY OF THE INVENTION The present invention is a software servo device for controlling an intermittent throw by detecting a tape position based on phase difference data between a head switching pulse and a tracking state signal and changing a tape feed amount. In the above, the software servo device is characterized in that the tape position is detected by data obtained by low-pass filtering the phase difference data.

[0008]

The frequency characteristic is given to the phase difference data between RFSW and ATFLOCK by low-pass filtering. When the change frequency of the phase difference data is low, the change amount of the tape feed amount with respect to the phase difference data is made larger than when the change frequency of the phase difference data is high.

[0009]

According to the present invention, since the tape feed amount can be determined according to the changing frequency of the phase difference data, the stability of the intermittent slow motion can be ensured in the intermittent slow motion of the 8 mm VTR, and the tape top and end can be secured. Alternatively, the amount of feedback can be increased with respect to the extremely low frequency fluctuation such as the reel rotation synchronization, and the generation of noise can be suppressed. Further, since control data in the time axis direction such as phase difference data is low-pass filtered, it is difficult to realize with a control circuit having a hardware configuration, but it can be easily realized by using a software servo as in the present invention.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 2, a software servo apparatus 10 of this embodiment is, for example, a camera integrated type 8 mm VTR.
8 mm VTR in this embodiment.
The servo system based on the pilot signal will be described.
The software servo device 10 includes a microcomputer (hereinafter, simply referred to as “mechancon”) 12 that shares a mechanical controller and a microcomputer (hereinafter, simply referred to as “syscon”) 14 that shares a system controller. The mechanical control 12 operates in response to a command from the system control 14, and the mechanical control 12 includes an FG counter 18 and a timer 20 for the capstan motor 16. The mechanical control unit 12 includes a slow control unit 22 that controls an intermittent throw, and the slow control unit 22 includes a low-pass filter 24 including, for example, a lag filter. Further, the mechanical controller 12 has a built-in RAM 26 for FCNT. A PWM signal for controlling the capstan motor 16 is output from such a mechanical controller 12. The driver 28 outputs a motor voltage according to the PWM signal and supplies it to the capstan motor 16. Then, the FG signal from the capstan motor 16 is amplified by the FG amplifier 30 to generate F
It is input to the mechanical controller 12 as a G pulse.

The intermittent throwing operation of the software servo device 10 thus configured will be described. First, as described in the related art with reference to FIG. 8, frame feeding is repeated at a cycle of 10 fields to set each field to 9 to 0.
And count down to and store in RAM 26. Then, as in the conventional case, FCNT = 5 in step S11.
If FCNT = 5, the timer 20 is reset in step S13, and step S1
It is judged whether or not ATFLOCK is reached in 5, and A
If TFLOCK has been reached, the data of the timer 18 at that time, that is, the phase difference data X is read in S17. And, it should be noted that in step S19,
The phase difference data X is converted into the data X ′ by passing through the low pass filter 24. Here, the data X ′ is obtained by the equation 2.

[0013]

X ′ = X ′ ₋₁ + a (X−X ′ ₋₁ ) + b (X−X ₋₁ ) X ′ = filter output at the current sampling time point X′− ₁ = 1 at the previous sampling time point Filter output X = filter input at the current sampling time X _-1 = filter input at the previous sampling time Further, the low pass filter 24 has frequency characteristics as shown in FIG. The amount of change of the output data X ′ is changed according to the changing frequency of.

In FIG. 3, f ₁ = a / {π (2b +
a) t}, f ₂ = a / {π (2-a) t}, t: sampling period. It should be noted that this frequency characteristic is determined by a control system including a mechanism, and in the case of 8 mm VTR, it is 1/5 slow operation, and generally f ₁ = 0.1 Hz and f ₂ = 0.01 Hz.

As described above, when the data X'has frequency characteristics and the change frequency of the phase difference data X is high as shown in FIG. 4, the change amount ΔX of the phase difference data X is changed as shown in FIG. On the other hand, the correction amount ΔA (= ΔX ×
N) is controlled. On the other hand, when the change frequency of the phase difference data X is low as shown in FIG. 6, the correction amount ΔA (= ΔX × N) of the count value A with respect to the change amount ΔX of the phase difference data X as shown in FIG. ) Is controlled to be larger than that at the high frequency shown in FIG.

Thereafter, as in the conventional case, it is determined in step S21 whether or not FCNT = 3, and FCNT = 3.
If so, FCNT = 3 is delayed for a certain period of time in step S23, the FG counter 18 is reset in step S25, and then the capstan motor 16 is turned on in step S27. And step S
In 29, it is judged whether or not the count value of the FG counter 18 becomes the count value A = (C−X ′ × N) calculated by the equation 1, and if the count value of the counter 18 becomes the count value A, step In S31, the capstan motor 16 is turned off. That is, the tape feed amount by the capstan motor 16 is determined by substituting the data X ′ obtained by passing through the low pass filter 24 into Equation 1.

Software servo apparatus 10 of this embodiment
According to the 8 mm VTR, in the intermittent throw,
The fluctuation of the slow noise position due to load fluctuations due to the winding position of the tape and the rotation phase of the reel can be greatly suppressed. Further, in this embodiment, the servo system using the pilot signal of 8 mm VTR is explained, but it is 1/2
It can be easily applied to the CTL system of the inch VTR.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention.

FIG. 2 is a block diagram showing this embodiment.

FIG. 3 is a graph showing frequency characteristics of a low pass filter.

FIG. 4 is a waveform diagram showing a case where the change frequency of the phase difference data is high.

5 is a waveform diagram showing a control state of a correction amount of a count value in the case of FIG.

FIG. 6 is a waveform diagram showing a case where the change frequency of the phase difference data is low.

FIG. 7 is a waveform diagram showing a control state of the correction amount of the count value in the case of FIG.

FIG. 8 is a waveform diagram showing an intermittent throw method.

FIG. 9 is a flowchart showing a conventional technique.

[Explanation of symbols]

 10 ... Software servo device 12 ... Mechanical controller 16 ... Capstan motor 18 ... FG counter 20 ... Timer 24 ... Low-pass filter

Claims (1)

[Claims] 1. A software servo apparatus for controlling an intermittent throw by detecting a tape position based on phase difference data between a head switching pulse and a tracking state signal and changing a tape feed amount, wherein the phase difference data is low-passed. A software servo device, characterized in that the tape position is detected based on filtered data.