JPH01117675A - Rotation controller - Google Patents

Abstract

PURPOSE:To effectively remove the irregular component of rotation of a motor irrespective of the setting speed of the motor by so setting the constant of a pectinated filter to which a rotating speed control signal is supplied as to have a gain near 0Hz. CONSTITUTION:A counter 21 is reset by the rise of a speed pulse FG to count a clock pulse CK, and samples a counted value at the fall of the pulse FG. On the other hand, a counter 22 is reset by the rise of a vertical synchronizing signal VP to start counting and samples a counted value at the rise of a phase pulse VP. The output of the counter 21 is supplied through a pectinated filter 4 to a differentiator 24 and an integrator 26, and the output of the counter 22 is supplied to a multiplier 27 and an integrator 29. Here, the constant of the filter 4 is so set to a predetermined value as to provide a gain near 0Hz.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation control device suitable for application to a servo circuit of a motor used in a VTR or the like.

[Summary of the invention]

The present invention achieves a predetermined servo operation function while controlling the motor by setting the constant of a comb filter to which a control signal for controlling the rotational speed of the motor to be substantially constant is set to have a gain near 0 Hz. This is to remove the influence of certain rotational fluctuation components such as rotational unevenness.

(Prior art) In the drum speed servo circuit of a VTR, the rotational speed of the drum motor is detected by an FC (frequency generator) to generate an FC pulse having a frequency corresponding to the rotational speed as shown in Fig. 4. In a servo circuit that performs digital control, as shown in Fig. 4, the counter is reset and starts counting at the rising edge of the FC pulse, and the count values Nt and N are obtained at the falling edge of the FC pulse.
2, N3, etc. are sampled.

These sampled count values N1, N2, N3・
The data consisting of .

In such a motor servo circuit, installation errors of the drum, FG, etc., such as uneven rotation due to eccentricity, pose a serious problem. Such rotational unevenness is always superimposed on the speed detection signal at a constant period. In the case of the above-mentioned servo circuit which obtains speed error data from the FG pulse, a component of the rotation period of the drum, for example, 30 Hz, which causes rotational unevenness, and its harmonic components are superimposed on the FG pulse. Therefore,
The speed error data obtained based on this FC pulse is
The 0 Hz component is mixed in, which causes distortion etc. on the playback screen.

In order to eliminate the influence of such rotational unevenness, the servo system has conventionally been designed to have a gain of 30 Hz as low as possible. However, when the gain is set low, a new problem arises in that it becomes susceptible to torque fluctuations.

Another method is to provide an analog notch filter to attenuate the 30 Hz gain. However, in a VTR, in a speed change mode such as picture search, the set speed of the drum is changed in order to correct the horizontal frequency, so the component of rotational unevenness also changes from 30H2. Therefore, it is not possible to use a notch filter with a high Q characteristic that attenuates steeply at 30 Hz, and it is necessary to use a notch filter with a low Q characteristic. If a filter with such flat characteristics is used, the 30 Hz component cannot be sufficiently removed, and screen distortion etc. cannot be sufficiently improved.

Therefore, it is conceivable to use a digital feedback comb filter as shown in FIG. 5 to remove the 30 Hz component and its harmonic components.

In FIG. 5, speed error data DS consisting of the sampling values Nl, N2, . . . of FIG. 4 is applied to the input terminal (1). This data DS is applied to the adder (2) and to the movable contact of the switch (3). This switch (3) is N1 in Fig. 4,
In synchronization with the time when the data of N2...... is obtained, the six fixed contacts a, b,...
...It is configured so that f can be switched. Digital feedback comb filters (41), (42)...
...(46) is connected. <S-shaped filter (41), (42)... (46)
) is the fixed contact a of switch (5).

b, ......... are added to f, respectively. This switch (5) synchronizes with switch (3) and contacts a,
b,......f can be switched, and the output data DS4 obtained at the movable contact is sent to the adder (
2) and subtracted from the error data DS.

Now, assuming that the input error data DS consists of each sampling value of N1, N2, N3, etc. as shown in Fig. 6A, in Fig. 5 ( Error data DS1 shown in FIG. 6B consisting of N1, N7, N13, . DS! is added to the limiter (8) through the adders (61, (71) constituting the comb filter (41) to limit the dynamic range, and then the delay circuit (9
) is delayed by 6 sampling periods, ie, the rotation period of the motor. The output DS2 of the delay circuit (9) is fed back to the adder (7) and added to the data from the adder (6), and is also multiplied by (K×1) by the multiplier (10). The multiplied data is added to the adder (6) and subtracted from the original data DSt.

In the adder (7), data corresponding to, for example, N1 obtained from the delay circuit (9) is added to data corresponding to N7 obtained in the next sampling.

This addition output passes through the limiter (8) to the delay circuit (9).
This delayed output DS2 is returned to the adder (7) again. As a result, an integrating circuit is formed by the adder (7), limiter (8), and delay circuit (9), and the output DS2 of the delay circuit (9) represents the average value of the data DS1. After this output DS2 is multiplied by a multiplier (10), it is added to an adder (6) and subtracted from the original data DS1 to prevent the loop from oscillating.

Therefore, the output data DSI obtained from the multiplier (10)
As shown in FIG. 6C, Nl, r of the input data DS
'LL? , N13, . . . , the error from the center value (zero level) in each phase is shown. That is, this comb filter (41) is a filter substantially equivalent to a first-order RCC co-pass filter for analog signals.

The other comb filters (42) to (48) are constructed in the same way as the comb filter (41), and have the same phase obtained from the contacts b.......f of the switch (3). The sampling value of is input, and the same processing as described above is performed. The outputs of these comb filters (41) to (48) are sequentially taken out from the switch (5). This extracted data DS4 is 30H from the original data DS.
z and its harmonic components are the extracted data, and this data DS4 is added to the adder (2) and subtracted from the corresponding sampled value of the input data DS.

As a result, it is possible to obtain output data DSo from the output terminal (11) having a comb-shaped characteristic in which 30 Hz and its harmonic components, which cause rotational unevenness, as shown in FIG. 6 and FIG. 7 are removed. Also, this comb filter characteristic is 301
(The attenuation portions of z, 60 Hz, and 90 Hz follow the set speed of the motor. Therefore, components of rotational unevenness can be effectively removed regardless of the set speed of the motor.

[Problem that the invention seeks to solve]

By the way, in the circuit using the comb filter shown in FIG. 5, even when the DC level of the input data DS is not zero, the data DS4 obtained from the switch (5) has a DC
Since the level is included, the output data DSo has a DC level of zero. That is, the DC gain of the circuit shown in FIG. 5 is zero. Since the DC level in the servo loop represents the set speed of the motor, if the DC level cannot be transmitted, servo operation will not be possible.

In order to enable the transmission of DC level in FIG.
It is necessary to separately provide a circuit configuration for subtracting from 4, which makes the circuit configuration extremely complicated.

The present invention has been made in view of these points, and it is an object of the present invention to provide a rotation control device that enables DC level transmission using the comb filter circuit shown in FIG. 5 without complicating the circuit configuration. .

[Means for solving problems]

The rotation control device according to the present invention includes detection means (16, 18) for detecting the rotation speed of the motor (15), and signal processing means for generating a control signal for controlling the rotation speed of the motor to be substantially constant based on the rotation speed. (19, 21), a comb filter for removing the motor rotation period component and its harmonic components from the control signal, and a drive means (4) for supplying the output signal of the comb filter to the motor. 26,30~
32), and the constant K of the comb filter means is 0Hz.
The configuration is set so that there is a gain nearby.

[Effect]

The detection means (16, 18) detects the rotational speed of the motor (15) and generates FC pulses. In the signal processing means (19, 21), the counter (21) is reset and started counting at the rising edge of the FG pulse, and the count values N1, N2, N3 are set at the falling edge of the FG pulse.
........., and the sampled count values Nz, N2, N3...
The data consisting of ... is the speed error data,
By processing this speed error data, a control signal for controlling the speed of the motor to be constant is obtained. The comb filter means (4) removes motor rotation period components and harmonic components from the control signal. At this time, the constant K of this comb filter means is set so that the gain is near 0 Hz. With this setting, as described above, it is possible to remove the rotation period component and harmonic component of the motor, and also to transmit a component approximately close to the DC level that performs the servo operation.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 shows an example in which the present invention is applied to a drum servo circuit of a VTR, and this drum servo circuit has a speed servo loop and a phase servo loop.

In FIG. 1, the rotation of a drum motor (15) is detected by a rotation detector (16) provided on this motor (15). This rotation detector (16) includes an FG and a pulse generator (PG), and its speed detection head °
From (17), an FG pulse having a period corresponding to the speed as shown in FIG. 4 described above can be obtained. Further, a PG pulse corresponding to the rotational phase of the motor (15) as shown in FIG. 3 is obtained from the phase detection head (18) at a rate of one per rotation of the motor (15).

The FG pulse is applied to the control signal generator (technique 9), and the PC
The pulses are applied to a control signal generator (20).

The control signal generator (19) is a speed error counter (21)
The data Ns, N2, N3, . . . are sampled as described with reference to FIG. This N1, N2, N3...
The data consisting of... is speed error data DS
The signal is sent to the digital feedback comb filter circuit (4).

The control signal generation circuit (20) also generates a phase error counter (20) along with a vertical synchronization signal VP applied from a terminal (23).
22). rg, as shown in Fig. 3, the counter (22) is reset and started counting at the rising edge of the vertical synchronizing signal vP, and the count values M1, N2, etc. are set at the rising edge of the PG pulse.・It is designed to sample. The data consisting of the sampled count values M1, N2...
) and the integrating circuit (29). In addition, the counter (2
1) and (22) are given, for example, an I MHz clock CK.

The comb filter circuit (4) uses the circuit shown in FIG. 5 as it is, except that the constant K is set to a predetermined value as described later, and the input terminal (1) is connected to the circuit shown in FIG. 6A. Speed error data DS is input.

The transfer function of the comb filter circuit (4) is expressed as follows.

1-e″″ST 1- (1-K) e-8 is a constant (multiplication coefficient of multiplier (10)), and T is 1/30 second here.

By the way, if the accuracy of FC etc. is poor, the counter (21)
Since the speed error data DS obtained on the output side of the counter (21) contains a large amount of information on rotational irregularities, in this embodiment, a comb filter circuit (4) is provided on the output side of the counter (21). Since the comb filter circuit (4) has a simple configuration as described above, the DC gain is 0 (see FIG. 2).Normally, in a servo system, when the DC gain is 00, the speed is not determined.

However, the definition of DC (0■2) is physically unclear, and it is difficult to determine whether O,0OIH2, O,0OOIHz is DC or not, and the only way to confirm this is through experiment. This comb filter circuit (4) has Q
Since the constant K is set to a predetermined value such that the gain is near QHz, for example, =2-5 as shown in FIG. 2, the motor (15) rotates at a normal speed. This means that D at 0Hz in a mathematical sense
C/gain is O, but since it has a gain near 0 Hz, the actual motor (5) rotates at a specified speed. However, it will not rotate at the exact speed, but will rotate near it, but the difference is measured by the counter (2
Since the dynamic range of the phase servo loop such as 2) is much wider than that of a normal digital servo, sufficient phase locking is possible.In this state, the DC gain is taken care of by the phase servo loop, so the motor (15) It rotates with the same performance as the conventional system and completely eliminates rotational irregularities.

Furthermore, Figure 2 shows the gain characteristics of the comb filter circuit (4) when the constant K is changed; the smaller the value of the constant, the larger the gain near 0 Hz, and the higher the Q. I know that there is. However, if the constant K is made too small, the time constant becomes large and there is a problem that the time at which the filter starts operating is delayed.

Therefore, in this embodiment, the value of the constant of the comb filter circuit (4) is set to K -2-'. However, this value is the most desirable value, and if the time required for the filter circuit to start operating is allowed, then K It may be set to -2-6 or less.

In this way, the value of the constant of the comb filter circuit (4) is set to 0.
) By setting the gain to a predetermined value in the vicinity of 1z, it is possible to obtain data in which 30Hz and its harmonic components, which cause uneven rotation, as shown in Figure 7 are removed, and also to perform servo operation. Transmission of components close to the required DC level is substantially possible, and the motor (15) can be started within the lock range of the phase servo loop.

The data from the comb filter circuit (4) with 30 Hz and its harmonic components removed is supplied to a differentiator circuit (24) and a multiplier (26). The differentiation circuit (24) differentiates the supplied data and converts it into angular acceleration data, and this angular acceleration data is sent to the multiplier (25). Furthermore, the integrating circuit (29) integrates the phase error data DP and sends this integrated data to the multiplier (28), thereby increasing the low-frequency gain of the phase servo loop.

The multiplier (25) multiplies the angular acceleration data by Ko, and the multiplier (25) multiplies the angular acceleration data by Ko.
26) multiplies the data by 1, and the multiplier (27) multiplies the data D
P is multiplied by 2, and the multiplier (28) multiplies the integral data by 3. In this embodiment, the multiplication coefficients Ko SKs, 2 and 3 are selected in the relationship Ko > K1 > K2 > K3. Weight each data by
It determines the magnitude of the effect of servo operation.

That is, the data obtained by differentiating the data from the comb filter circuit (4) and converting it into acceleration is multiplied by the largest Ko to obtain the effect of adaptability to the speed error. 1 and K2 to obtain the effect of speed error and phase error in that order, and further multiply the integral data by 3 to obtain the effect of increasing the low-frequency gain.

Further, since the differentiating circuit (Se4) differentiates data having components approximately close to the DC level, the differentiated data has components approximately close to the DC level removed. Note that the loop (acceleration loop) of the differentiating circuit (24) and the multiplier (25) can be omitted if necessary.

Each data obtained from the multipliers (25), C2B), (27) and (28) is added to the adder (30).

The added data obtained from this adder (30) is D
/A converter (31) converts it into an analog control signal,
This control signal controls the speed and phase of the motor (15) through the drive amplifier (32).

In this way, in this embodiment, since the data DS is added to the comb filter circuit (4), only the true rotational unevenness component can be removed. In addition, a comb filter circuit (4
) is set so that the gain is near 0Hz, so it is practically possible to transmit components close to the DC level necessary for servo operation, and the lock range of the phase servo loop is The motor (15) can be started up and rotated at a normal speed.

Incidentally, the comb filter circuit (4) is the differentiator circuit (2).
4) and a multiplier (25), the rotational unevenness component is mostly caused by the multiplier ( 26), this rotational unevenness component is not a problem with the accuracy of normal FG, etc., but when considering cost reduction by lowering the accuracy of FC, etc., a large amount of rotational unevenness component is transmitted from the speed loop, causing jitter. It may cause deterioration. However, in this embodiment, the comb filter circuit (4) is inserted immediately after the counter (21), so even if the accuracy of the FG etc. is lowered, the rotational unevenness component can be reliably removed. no problem.

In the above-described embodiments, the present invention has been described for the case where it is applied to a digital servo circuit, but it can also be applied to an analog servo circuit. In that case, a COD element or the like may be used for the delay circuit (9) in FIG. 5.

〔Effect of the invention〕

As described above, according to the present invention, with a simple circuit configuration,
Errors based on the rotation period component and its harmonic components depending on the set speed of the motor can be effectively removed. Also Q
Since it is possible to use a comb-shaped filter with a high frequency, signal processing can be performed only on the rotation period component and its harmonic components. Therefore, there is no phase shift in the low frequency range, and stable high performance is always achieved. It becomes possible to control the Furthermore, even if the accuracy of the FG is lowered, the rotation period component and its harmonic components can be reliably removed, and the cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a characteristic diagram of a comb filter when the constant K is changed, FIG. 3 is a timing chart explaining the principle of obtaining phase error data, and FIG. Figure 4 is a timing chart explaining the principle of obtaining speed error data, Figure a is a block diagram of a digital feedback comb filter circuit that can be applied to this invention, Figure 6 is a timing chart of Figure 5, and Figure 7. FIG. 3 is a characteristic diagram of a comb filter. (4) is a digital feedback comb filter circuit, (15
) is the drum motor, (16) is the rotation detector, (9) is the control signal generation circuit, (21) is the speed error counter, (
26) is a multiplier, (30) is an adder, (31) is a D/A
It is a converter.

Claims (1)

[Scope of Claims] Detection means for detecting the rotational speed of the motor; signal processing means for generating a control signal for controlling the rotational speed of the motor to be substantially constant based on the rotational speed; comb-shaped filter means for removing rotational periodic components and harmonic components thereof; and driving means for supplying an output signal of the comb-shaped filter means to the motor, the gain of which is set to a constant of the comb-shaped filter means near 0 Hz. A rotation control device characterized in that the rotation control device is set so that