JPH0340784A - Rotating phase controller for motor - Google Patents

Abstract

PURPOSE:To improve rotating phase control accuracy by obtaining speed control data by dividing the difference between reference data at a previous time and reference data at this time by a predetermined value and subtracting target data from period data, and removing a DC component from the speed control data as the final speed control data. CONSTITUTION:Data latched by a reference signal V-SY is supplied to a speed target circuit 14 as reference data, difference between reference data at previous time and reference data at this time is obtained by a delay unit 141 of the circuit 14 and a subtracter 142, the difference value is divided by a divider 143, and led as target data. The target data is supplied to a calculator 15 to become a subtracting factor of frequency discrimination output. Then, the output of the subtracter 15 is supplied to a high pass filter 16 to remove DC offset, thereby obtaining speed control data.

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) This invention is applicable to, for example, a video tape recorder (hereinafter referred to as VTR).
The present invention relates to a rotational phase control device for a motor that is effective as a servo device for a capstan motor that drives a tape (denoted as ) and a drum motor that drives a rotary head.

(Prior Art) A household VTR is provided with a drum servo device for controlling the rotational speed and phase of a rotary head. A capstan servo device is also provided to control the running speed and phase of the magnetic tape. These servo circuits control the speed and phase of the rotary head and magnetic tape by controlling the rotational speed and phase of the drum motor or capstan motor, respectively.

Incidentally, a servo device usually has a rotation frequency detection signal (hereinafter referred to as FG signal) generation means and a rotation phase detection signal (hereinafter referred to as PG multiplied signal) generation means for detecting the rotation speed of the motor. This FC or PG signal generating means is constructed around the rotating shaft of the motor.

In the capstan control system, when recording on a VTR, the FG
By controlling the double signal frequency, feedback is applied to the drive signal of the capstan motor, and a stable rotational speed and phase can be obtained. On the other hand, during reproduction by a VTR, control signals prerecorded on a magnetic tape driven by a capstan are also used as control information. That is, the phase of the capstan motor is controlled so that the phase of the reproduced control signal becomes a predetermined phase with respect to the same reference signal as the phase control system of the drum servo device.

Here, the control signal is recorded on the magnetic tape during recording, and is recorded in correspondence with the vertical synchronizing signal every frame of the video signal (two cycles of the vertical synchronizing signal). In the case of NTSC system, the control signal is 2
It is 9.97Hz.

Therefore, the control characteristics of the rotational phase of the capstan motor are:
This is determined by the frequency of the control signal determined by the standard, and it is not possible to increase the control accuracy any further.

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

(Problem 8 to be solved by the invention) As mentioned above, in the conventional capstan servo device, the phase control accuracy during reproduction is determined by the accuracy of the reproduced control signal, and higher accuracy is not desired. I could not do it. For this reason, for example, when a magnetic tape (commercially available soft tape) recorded by another model has a constant offset in the control signal, that is, when the magnetic tape is run at a predetermined speed, the control signal The frequency is the specified 29.97Hz
If there is a constant deviation from (NTSC), the capstan servo device works so that the control signal becomes 29.97 Hz, and an error corresponding to the offset occurs in the speed control system.

In other words, the running speed of the tape deviates from the target speed.

On the other hand, a similar problem exists in the drum control system. For example, when recording on a VTR, the vertical synchronization signal (59.9Hz)
The rotational phase of the rotary head is controlled in phase synchronization with the vertical synchronization signal, but if there is a steady deviation in the frequency of the vertical synchronization signal, an error corresponding to the offset will occur in the speed control system, and the rotational speed of the drum motor will decrease. will deviate from the target rotation speed.

Therefore, in this invention, it is possible to improve the rotational phase control accuracy of the servo motor, and to avoid being affected by offsets caused by steady deviations in human input signals from outside the loop that serve as motor control information. An object of the present invention is to provide a rotational phase control device for a motor.

[Structure of the Invention] (Means for Solving the Problems) This invention provides a reference signal that serves as a reference for the rotational phase of a motor;
a first feedback signal obtained from means for detecting a signal indicative of the rotational frequency of the motor; and a first feedback signal generated at a longer period than the first feedback signal from the means for detecting a signal indicative of the rotational phase of the motor. Every time the second feedback signal arrives,
a measurement counter capable of obtaining latch data, a means for setting and storing reference data based on the latch data obtained in response to the generation of the reference signal, and a means corresponding to the generation of the first feedback signal. means for setting and storing rotational frequency data based on latch data obtained in response to generation of the second feedback signal; means for setting and storing rotational phase data based on latch data obtained in response to generation of the second feedback signal; means for obtaining the difference between the previous and current values of rotational frequency data to create cycle data of the motor; and dividing the difference between the previous and current values of the reference data by a predetermined value to obtain speed control target data. means for obtaining speed control data by subtracting the target data from the periodic data; and means for removing a DC component from the speed control data to obtain final speed control data. be.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Reference numeral 11 denotes a counter that cyclically counts a high-speed clock, and count data of this counter 11 is supplied to a latch circuit 12. This latch circuit 12 receives a rotation frequency detection signal (D-FG) from a frequency rotation detection means from the drum motor.
, a rotational phase detection signal (D-PG), and a reference signal (vertical synchronization signal -v-sy) are supplied. Rotation frequency detection signal (
D - F G) and rotational phase detection signal (D - P G)
is a signal fed back from the rotation detection signal generator of the motor whose drive is controlled by this servo device,
The rotational frequency detection signal (D-FG) has a sufficiently higher frequency than the rotational phase detection signal (D-PG'). For example, the rotational phase detection signal (D-FG) is 24 Hz%
The rotational frequency detection signal (D-PG) is 30Hz. The reference signal (V-SY) is a signal that serves as a reference for the rotational 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 is connected to each signal (D-FC)CD-PC)(
It has a latch section corresponding to V-3Y), and each section latches count data every time these signals arrive.

The data latched by the signal (D-F G) is sequentially sent to the frequency discriminator 13 as rotation frequency data. This frequency discriminator 13 includes a delay section 131 and a subtraction section 13.
2 to obtain the difference between the previous data and the 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. In this circuit as well, a delay section 141 and a subtraction section 142 are used to obtain the difference between the previous reference data and the current reference data, and this difference value is further divided by a division section 143 to derive target data. N (numerator) in the divider 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. As a result, the difference between the actually obtained drum rotation period and the period of the reference signal is obtained, which becomes motor rotation frequency control information.

However, if there is a constant frequency shift in the reference signal, the servo loop tries to pull the motor rotation to a predetermined rotation, so a difference (DC offset) always occurs. If this is left as is, a synchronization error 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 subtraction section 15 is supplied to a bypass filter 16 to remove offsets to obtain speed control data, which is then supplied to an amplifier 17.

The bypass filter 16 includes a subtraction section 161 and an addition section 162.
, a delay section 163, and a coefficient unit 164.

The adder 162 accumulates the offset, and the subtracter 16
1, the offset is removed from the speed control data. k in the coefficient multiplier 164 satisfies 0<k<1, and by selecting this coefficient sufficiently smaller than 1, a high Q characteristic can be obtained. On the other hand, if the coefficient k is made small, the response to the offset becomes slow, so it is preferable to select it according to the target device.

FIG. 2 shows the frequency characteristics of the bypass filter.

Next, the reference data, ', and rotational phase data obtained from the latch circuit 12 are supplied to the phase comparator 2o. In the phase comparator 20, the subtraction unit 201 subtracts the reference data from the rotational phase data to obtain the difference. This corresponds to detecting a shift in the rotational phase of the motor with respect to the reference phase. The phase control target data is subtracted from this phase difference data in the subtraction unit 202. This results in
Phase control data is obtained from the subtraction unit 202. The phase control data is preset in a delay section 32, which will be described later.

The speed control data from which the offset has been removed is sent to adder 3.
1. The output of this adder 31 is transmitted to the amplifier 21
The phase control data from the subtraction section 202 is supplied to the delay section 32 where it is preset. This presetting is performed every time phase control data arrives (for example, every 1730 seconds). Delay section 32
The output of is input to the adder 31. The output of the adder 31 ultimately becomes phase error data in which minute fluctuations (phase fluctuations) of the speed control signal that change during the rotational phase pulse period are also incorporated into the phase control data from the subtraction section 202. The phase control data from the amplifier 21 and the speed control data from the amplifier 17 are added by an adder 18 and output as drum motor drive data.

Although the above embodiment has been described as a rotational phase control system for a drum motor, the present invention is not limited thereto, and can be similarly applied to a rotational phase control system for a capstan motor. In this case, the 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 explained above, the present invention can improve the rotational phase control accuracy of a servo motor, and also eliminates offsets caused by steady deviations of input signals from outside the loop that serve as motor control information. However, you can avoid being affected by it.

[Brief explanation of 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 bypass filter shown in FIG. 11...Counter, 12...Latch circuit, 13...
・Frequency discrimination circuit, 14...Speed target circuit, 15...
・Adder, 16... Bypass filter, 17.22・
...Amplifier, 20...Phase comparator, 21...Adder.

Claims (1)

[Claims] A reference signal serving as a reference for the rotational phase of the motor, a first signal obtained from means for detecting a signal indicating the rotational frequency of the motor.
Latch data is obtained each time a feedback signal of the motor and a second feedback signal generated at a longer cycle than the first feedback signal from the means for detecting a signal indicating the rotational phase of the motor arrive. means for setting and storing reference data based on the latch data obtained in response to the generation of the reference signal; and means for setting and storing reference data based on the latch data obtained in response 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 generation of the second feedback signal; and previous and current rotational frequency data. means for obtaining periodic data of the motor by obtaining a difference between the values of the reference data; and means for obtaining speed control target data by dividing the difference between the previous and current values of the reference data by a predetermined value; and the periodic data. A rotation of a motor characterized by comprising means for obtaining speed control data by subtracting said target data from said speed control data, and means for removing a DC component from said speed control data to obtain final speed control data. Phase control device.