JP2993679B2 - Motor rotation phase control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a video tape recorder (hereinafter referred to as a VTR).
The present invention relates to a capstan motor for driving a tape and a rotary phase control device for a motor effective as a servo device for a drum motor for driving a rotary head.

(Prior Art) A home VTR is provided with a drum servo device for controlling the rotation speed and phase of a rotary head. In addition, a capstan servo device is provided to control the traveling speed and phase of the magnetic tape. These servo circuits control the rotation speed and phase of the drum motor or the capstan motor, thereby controlling the speed and phase of the rotary head and the magnetic tape, respectively.

By the way, usually, the servo device has a rotation frequency detection signal (hereinafter referred to as FG signal) generating means for detecting the rotation speed of the motor and a rotation phase detection signal (hereinafter referred to as FG signal) generating means. The FG or PG signal generating means is built around the rotating shaft of the motor and around it.

In the capstan control system, during VTR recording, by controlling the frequency of the FG signal, feedback is applied to the drive signal of the capstan motor, and a stable rotation speed and phase can be obtained. On the other hand, when playing a VTR,
A control signal recorded in advance on a magnetic tape driven and driven by the capstan is also used as control information. That is, the phase of the reproduced control signal is
The phase control of the capstan motor is performed so that the same reference signal as the phase control system of the drum servo device has a predetermined phase.

Here, the control signal is recorded on a magnetic tape at the time of recording, and is recorded corresponding to the vertical synchronization signal for each frame of the video signal (two periods of the vertical synchronization signal). In the case of NTSC system, the control signal is 29.9
7 Hz. Therefore, the control characteristic of the rotational phase of the capstan motor is determined by the frequency of the control signal determined by the standard, and the control accuracy cannot be further improved.

On the other hand, there is a similar problem in the drum control system. For example, at the time of VTR recording, if the rotation phase of the rotary head is controlled by synchronizing the phase with the vertical synchronization signal, the accuracy is determined by the frequency of the vertical synchronization signal (59.9 Hz).

(Problems to be Solved by the Invention) As described above, in the conventional capstan servo device, the phase control accuracy at the time of reproduction is determined by the accuracy of the reproduced control signal, and higher accuracy can be desired. Did not. For this reason, for example, in a magnetic tape (commercially available soft tape) recorded by another model, if the control signal has a steady offset, that is, the control signal when the magnetic tape is run at a predetermined speed. Frequency of 29.97Hz (NTS
If it deviates steadily from C), the capstan servo device operates so that the control signal becomes 29.97 Hz, so that an error corresponding to the offset occurs in the speed control system.
That is, the running speed of the tape deviates from the target speed.

On the other hand, there is a similar problem in the drum control system. For example, during VTR recording, the rotation phase of the rotary head is controlled in phase with the vertical synchronization signal (59.9 Hz), but if there is a steady deviation in the frequency of the vertical synchronization signal,
An error corresponding to the offset occurs in the speed control system, and the rotation speed of the drum motor deviates from the target rotation speed.

Therefore, according to the present invention, it is possible to improve the rotational phase control accuracy of the servo motor, and to prevent the offset from being caused even if an offset due to a steady deviation of the input signal from the outside of the loop serving as the control information of the motor occurs. It is an object of the present invention to provide a motor rotation phase control device.

[Means for Solving the Problems] The present invention shows a measurement counter that cyclically counts a clock of a predetermined frequency, a reference signal serving as a reference of a rotation phase of the motor, and a rotation frequency of the motor. A first feedback signal obtained from the signal detecting means, and a second feedback signal generated at a longer period than the first feedback signal and obtained from the signal detecting the signal indicating the rotational phase of the motor. A latch means for latching the count value of the measurement counter each time the signal arrives, a means for setting and storing reference data based on latch data obtained in correspondence with the reference signal, and a step of generating the first feedback signal Means for setting and storing rotation frequency data based on the latch data obtained in response to the above, and latch data obtained in response to the generation of the second feedback signal. Means for setting and storing rotation phase data, means for obtaining phase control data of the motor based on a difference between the reference phase data and the rotation phase data, and setting and storing predetermined speed control target data. Means, means for obtaining the difference between the previous and current values of the rotation frequency data to create cycle data of the motor, and means for obtaining speed control data by subtracting the speed control target data from the cycle data. High-pass filter means for removing a DC component from the speed control data; and means for obtaining control data for controlling the rotation of the motor based on the phase control data and the output of the high-pass filter means.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Reference numeral 11 denotes a counter that counts high-speed clocks cyclically. The count data of the counter 11 is supplied to the latch circuit 12.
The latch circuit 12 includes a rotation frequency detection signal (D-FG), a rotation phase detection signal (D-PG), and a reference signal (vertical synchronization signal = V-SY) from the drum motor frequency rotation detection means.
Is supplied. The rotation frequency detection signal (D-FG) and the rotation phase detection signal (D-PG) are signals that are fed back from the rotation detection signal generator of the motor that is driven and controlled by this servo device, and (D-FG)
Has a sufficiently higher frequency than the rotation phase detection signal (D-PG). For example, the rotation frequency detection signal (D-FG) is eight times the rotation phase detection signal (D-PG). Reference signal (V-
SY) is a signal serving as a reference for the rotation phase of the motor, and is a signal created based on a vertical synchronization signal separated from a video signal to be recorded.

The latch circuit 12 outputs signals (D-FG), (D-PG), (V-
SY), and each section latches count data each time these signals arrive.

The data latched by the signal (D-FG) is sequentially sent to the frequency discriminator 13 as rotational frequency data. The frequency discriminator 13 includes a delay unit 131 and a subtraction unit 132, and obtains a difference between previous data and current data. This difference is cycle data representing the cycle of the drum.

On the other hand, the data latched by the reference signal is supplied to the speed target circuit 14 as reference data. Also in this circuit, the difference between the previous reference data and the current reference data is obtained by using the delay unit 141 and the subtraction unit 142, and the difference value is further divided by the division unit 143 to derive the difference data as target data.
N (numerator) in the division unit 143 is the number of D-FG pulses per rotation of the drum motor.

The target data is supplied to the subtraction unit 15 and becomes a subtraction element of the frequency discrimination output. Thereby, the difference between the actually obtained drum rotation period and the period of the reference signal is obtained, which becomes the rotation frequency control information of the motor. However, if there is a steady frequency shift of the reference signal, the servo loop attempts to pull the rotation of the motor to a predetermined rotation, so that a difference (DC offset) always occurs. If this is left as it is, a synchronization shift occurs, and recording is performed in a state where the original relationship between the video signal and the synchronization signal is not maintained. Therefore, in this embodiment, the output of the subtracting unit 15 is supplied to the high-pass filter 16 to remove the offset, thereby obtaining speed control data, and supplying this to the amplifier 17.

The high-pass filter 16 includes a subtraction unit 161, an addition unit 162, a delay unit 163, and a coefficient unit 164. The adder 162 accumulates the offset, and the subtractor 161 removes the offset from the speed control data. Coefficient unit
K in 164 satisfies 0 <k <1, and by selecting this coefficient to be sufficiently smaller than 1, high Q characteristics can be obtained. On the other hand, when the coefficient k is reduced, the response corresponding to the offset becomes slow. Therefore, it is preferable to select the coefficient according to the target device.

FIG. 2 shows the frequency characteristics of the high-pass filter.

Next, the reference data and the rotation phase data obtained from the latch circuit 12 are supplied to the phase comparator 20. In the phase comparator 20, the subtractor 201 subtracts the reference data from the rotational phase data to obtain the difference. This corresponds to detecting a deviation of the rotation phase of the motor from the reference phase. The phase control target data is subtracted from the phase difference data in the subtraction unit 202. This results in a subtraction 202
, Phase control data is obtained. The phase control data is
It is preset in a delay unit 32 described later.

The speed control data from which the offset is removed is added to the adder
Supplied to 31. The output of the adder 31 is supplied to the amplifier 21 and amplified, and is also supplied to the delay unit 32 where the phase control data from the subtraction unit 202 is preset. This preset is performed every time phase control data arrives (for example, 1/30
Every second). The output of the delay unit 32 is input to the adder 31. The output of the adder 31 eventually becomes phase error data in which the phase control data from the subtraction unit 202 also incorporates a minute variation (phase variation) of the speed control signal that changes during the rotation phase pulse period. The phase control data from the amplifier 21 and the speed control data from the amplifier 17 are
It is added at 18 and output as drive data for the drum motor.

Although the above embodiment has been described as a rotation phase control system of a drum motor, the present invention is not limited to this, and can be similarly applied to a rotation phase control system of a capstan motor.
In this case, information input to the latch circuit 12 is a capstan frequency detection signal, a capstan phase detection signal, and a control pulse.

[Effects of the Invention] As described above, the present invention can improve the rotational phase control accuracy of a servomotor, and moreover, an offset occurs due to a steady deviation of an input signal from outside the loop, which is motor control information. Even if they are not affected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing frequency characteristics of the high-pass filter of FIG. 11 ... Counter, 12 ... Latch circuit, 13 ... Frequency discrimination circuit, 14 ... Speed target circuit, 15 ... Adder, 16 ... High-pass filter, 17,22 ... Amplifier, 20 ... Phase comparator , 2
1 ... Adder.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 5/00

Claims (1)

(57) [Claims] A first counter obtained from a measurement counter for cyclically counting a clock of a predetermined frequency, a reference signal serving as a reference for a rotation phase of the motor, and a signal indicating a rotation frequency of the motor.
Every time a second feedback signal, which is generated at a period longer than that of the first feedback signal and is obtained from a signal detecting a rotation phase of the motor, arrives, the count of the measurement counter is counted. Latch means for respectively latching values; means for setting and storing reference data based on latch data obtained corresponding to the reference signal; based on latch data obtained corresponding to the generation of the first feedback signal Means for setting and storing rotational frequency data; means for setting and storing rotational phase data based on latch data obtained in response to the generation of the second feedback signal; Means for obtaining phase control data of the motor based on a difference from the data; means for setting and storing predetermined speed control target data; Means for generating the cycle data of the motor by obtaining the difference between the previous and current values; means for obtaining speed control data by subtracting the speed control target data from the cycle data; and DC from the speed control data. A high-pass filter unit for removing components; and a unit for obtaining control data for controlling rotation of the motor based on the phase control data and an output of the high-pass filter unit. .