JP2584435B2 - Speed servo circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed servo circuit for a motor suitable for application to a motor for driving a floppy disk, and more particularly to a speed servo circuit having no steady-state deviation.

2. Description of the Related Art A speed servo circuit used to control the rotation speed of a motor to a reference rotation speed is generally configured as shown in FIG.

Rotation signal generating means such as a control object serving as the motor (1) obtaining a rotation signal S _M which is proportional to the rotational speed of the motor (1) is a frequency generator (FG) (2) is provided, and the rotation signal S _M The reference signal S _REF supplied to the terminal (3) is supplied to the speed deviation forming means (4) to determine a deviation amount (PWM signal) of the motor rotation speed with respect to the reference signal S _REF . Is the DC control voltage by the low-pass filter (5)
The DC control voltage V _CTL is converted to V _CTL and the converted DC control voltage V _CTL is supplied to the motor driver (6), whereby the motor (1) is controlled to a rotation speed corresponding to the reference signal S _REF .

Now, in such a speed servo circuit (10), as is well known, the motor (1) cannot be controlled to a rotational speed completely corresponding to the reference signal S _REF, and a steady-state deviation always occurs.

In other words, the feedback control system, which is a frequent feedback servo circuit (10) shown in FIG. 2, can be represented as a control block as shown in FIG. In the figure, ω is the rotation frequency of the motor (1) after the feedback control, ω _ref is the reference frequency, and the motor (1) and the motor driver (6) are expressed as first-order lag elements.
The relationship with _ref is From the Laplace transform formula, the value of ω at t → ∞ is Becomes Therefore, the actual motor rotation speed ω with respect to the target rotation frequency ω _ref is Only the deviation Δω occurs. This deviation Δω is a steady-state deviation, and the motor (1) is always in a stable state at a rotational speed slightly lower than the target rotational speed. Therefore, in the conventional are selected rotation frequency omega _ref goal slightly larger value in consideration of this steady-state deviation [Delta] [omega.

However, if the steady-state deviation Δω can be eliminated by the feedback control system shown in FIG. 2, it is not necessary to change the target rotation frequency ω _ref , so that the target rotation frequency ω _ref can be set more accurately.

SUMMARY OF THE INVENTION In view of the above, the present invention proposes a speed servo circuit that suppresses the oscillation of a measured value and does not generate a steady-state deviation.

SUMMARY OF THE INVENTION Therefore, in a speed servo circuit according to the present invention which employs the above-described feedback control system, for example, as shown in FIGS. 1 and 13, the rotational speed is proportional to the rotational speed of a motor (1) to be controlled. A rotation signal generating means (2) for obtaining a signal, a measurement counter (21) for acquiring initial bias data in synchronization with the rotation signal of the motor and measuring data converted from the rotation signal, and a measurement counter (21). A circuit (40) which adds a differential characteristic to the measured value and subtracts the measured value and the measured value one time before the measured value by a predetermined constant after subtracting them, thereby suppressing the vibration of the measured value. ), A data counter (23) for loading the output value of the differentiating circuit, and a speed with respect to a reference speed based on the measured value loaded in the data counter (23). The deviation for each cycle of the measured value (P _M),
First control signal generating means (30) for generating a _first speed deviation signal (S ₁ ) having a pulse width corresponding to the speed deviation amount, and the measured value loaded in the data counter (23) (P _M ), a speed deviation with respect to the reference speed is determined for each rotation cycle of the rotation signal (S _M ) by a second having a polarity corresponding to the direction of the speed deviation and a pulse width corresponding to the speed deviation amount. _Second generated as speed deviation signal (S ₂ )
And a second speed deviation signal (S ₂ ) from the control signal generating means as a DC control voltage via a charge pump (14). The rotation speed control of the motor is performed by adding to the _first speed deviation signal (S ₁ ) from the means.

Embodiment Next, a speed servo circuit for a motor according to the present invention will be described in detail with reference to FIGS.

FIG. 1 shows a motor speed servo circuit (1) according to the present invention.
Shows an example of a 0), the rotation signal generating means (2) from the obtained rotation signal S _M and the supplied reference signal to the terminal (3)
S _REF is supplied to the first signal forming means (11), a first speed deviation signals S ₁ having a pulse width corresponding to the rotational speed deviation of the motor (1) with respect to the reference frequency omega _ref is formed. The first speed deviation signals S ₁ is a pulse-width modulated signal in response to the reference signal S _REF is speed deviation, corresponding to the speed deviation signal ΔV shown in Figure 2.

With the reference clock CKa made to the first speed deviation signals S ₁ terminal (12), it is supplied to the second signal forming means (13) for each rotation cycle of the rotation signal S _M, the speed deviation polarity second speed deviation signal S ₂ is formed to have a pulse width corresponding to the polarity and the speed deviation amount corresponding to.

Reference clocks CKa, as described below, is selected to be a frequency higher than the frequency of the rotation signal S _M obtained when the motor (1) reaches the reference rotational speed, also a polarity of the speed deviation, the reference in this example When the rotation speed is higher than the rotation speed, the polarity is positive, and when the rotation speed is lower, the polarity is negative. Therefore, when higher than the reference rotational speed, a second speed deviation signal S ₂ is negative pulse signal is obtained having a pulse width corresponding to the speed deviation amount, which the than the reference rotational speed conversely when slow, the second speed deviation signal S ₂ of the positive polarity is obtained having a pulse width corresponding to the speed deviation. The pulse of the positive or negative GokuTadashi is obtained for each rotation cycle of the rotation signal S _M.

Second speed deviation signal S ₂ is further third signal forming means (14) and supplied to a second speed deviation signal corresponding to the pulse width and polarity of S ₂ motor control voltage V _CTL (DC voltage)
DC level is controlled. That is, when the second speed deviation signal S ₂ is a positive polarity pulse signal is controlled so that the DC level of the motor control voltage V _CTL is lower than the reference value, than the reference value in the opposite case Controlled to be high.

Therefore, the motor driver (6) is driven by the motor control voltage _VCTL , and the motor (1) is controlled to the reference rotation speed.

Now, since the DC level of the control voltage V _CTL by a second speed deviation signal S ₂ is intended to increase or decrease, the second and third signal forming means (11), (13) should be regarded as a kind of integration circuit Can be. Therefore, the feedback control system of FIG. 1 can be represented as a block including the integral element K ₂ / s as shown in FIG. 4, and the relationship between ω and ω _ref is At this time, the value of ω at t → ∞ is Next, deviation Δω is, become a _{Δω = ω ref -ω ref = 0} ...... (6), steady-state error Δω is zero.

For this reason, the speed servo circuit (10) shown in FIG. 1 can control the motor (1) to the reference rotation speed completely proportional to the reference signal S _REF .

Figure 5 is a case of applying the invention to the conventional velocity servo circuit (10) shown in FIG. 2, the speed deviation signal ΔV of the first speed deviation signal S ₁ is the second view in this case from becoming, third (and V ₁₎ signal forming means (4) (a V ₃₎ control voltage is the output of the control voltage which is smoothed by a low pass filter (5) is mixed circuit (15)
The control voltage VCTL, which is superimposed on the control voltage _VCTL, is supplied to the motor driver (6).

As shown in FIG. 6, the feedback control system shown in FIG. The relationship between ω and ω _{ref at} this time is Therefore, the value of ω when t → ∞ is In this case as well, the steady-state deviation Δω can be made zero.

By the way, in the equation (8), when the real root when the denominator on the right side is zero is large, the vibration amplitude is small, so that the settling time until reaching the reference rotation speed is shortened, and the system is more resistant to disturbance.

Next, an embodiment of the present invention will be described. FIG. 7 shows the fifth
This is an embodiment corresponding to the figure, and only the main part is shown.

In this embodiment, the first and second speed deviation signals S ₁ and S ₂ are digitally formed. The first signal forming means (11) includes a measurement counter (21), a bias data Memory (or register) (22) and a data counter (23). The measurement counter (21) is loaded with bias data (initial data) in synchronization with the rotation signal _SM, and is loaded into the data counter (23). is also measured data of the rotation signal S _M in synchronization with measurement counter (21) is loaded.

Therefore, the rotation signal S _M (FIG. 8A) is supplied to the first mono-multi (25) to form a first multi-output M ₁ (B in FIG. 8) synchronized with the fall of the signal. the first multi-output M ₁ further second monostable multivibrator (26) and supplied to a second multi-output M ₂ synchronized with the rise (FIG. C) is formed. Second multi-output M ₂ is used as a load pulse for the N-bit measurement counter (21), bias data is loaded during the second low-level multi-output M _2. The bias data is set to a predetermined value 2 ^M (M <N) such that the target rotation speed is reached when the value of 2 ^N-1 is reached after the measurement counter (21) once outputs the carry.

First multi-output M ₁ is used as a gate pulse to gate the clock CKb for measuring counter (21),
Therefore multi-output M ₁ of the clock CKb and the first is supplied to an AND gate (27). It becomes the operation of the measurement counter (21) as shown in FIG. 8 D if analog manner shown, biased data loaded in the second multi-output M ₂ is turned multiple output M ₂ of the second to the high level When the count-up operation starts, the measurement counter (21) reaches a full count within one rotation cycle of the rotation signal S _M and reaches the maximum value of 2 ^N −1.
It continues the count-up operation again after it becomes, the measurement data of the next resultant first multi output M ₁ falling measured at counter (21) is latched. FIG. 8E shows analogously the measurement data latched by the latch circuit (28).

Period of measurement data rotation signal S _M at the time the first multi-output M ₁ is obtained, i.e. changes in accordance with the rotational speed of the speed of the motor (1). When the motor rotation speed is high, the one rotation cycle becomes shorter, so the measurement data to be latched is small. Conversely, when the motor rotation speed is low, the one rotation cycle becomes longer, so the measurement data at this time is increased. Becomes larger.

The latched measurement data is loaded into an N-bit data counter (23). Therefore, the data counter (2
3) is supplied with a clock CKa '(which may be the same as or different from CKa) obtained at a terminal (32) and is also supplied to a frequency divider (33), which divides the frequency into 1 / ^2N. FIG. 9B
The reference clock CKa shown in FIG.
The latched measurement data is loaded in synchronization with the fall timing of Ka.

After data loading is measured data counted up loaded by a clock CKa ', MSB pulse P _M that indicates the MSB bit of the count-up count data
(FIG. 9 A) and the clock CKa is supplied to the pulse forming means (30), a first speed deviation signal S ₁ is formed.

MSB pulse P _M is the count data of the data counter (23) is at "0" between 0 to 2 ^N-1, between the ^{2 N-1 ~2 N -1 "} 1"
And the data counter (23) and the frequency divider (33) have the same clock CK
since it is intended to be driven by a ', 1/2 and the divided reference clock CKa and MSB pulse P _M to ^N that the pulse period is matched.

However, MSB pulse P _M of the phase with respect to the reference clock CKa is different depending on the magnitude of the measured data to be loaded into the data counter (23). That is, when the number of revolutions of the motor (1) is high, the measurement data latched by the _first multi-output M1 is a value of 2 ^N-1 or less.
Pulse P _M is "0", to the measurement data to be loaded into the data counter (23) is 2 ^N-1 remains "0" (FIG. 9 A, see B).

As the data counter (23), a data counter with a limiter is used. If a borrow occurs as a result of the operation, the count data is forcibly set to 0. If a carry occurs, 2 ^{N -1} is set.

Pulse forming means (30) may be constituted by a flip-flop or the like, is set at the falling edge of the MSB pulse P _M, if as to reset at the falling edge of the reference clock CKa, FIG. 9 A, the B when in the phase relationship, the first speed deviation signals S ₁ such as shown in C in the drawing is outputted.

On the other hand, when the rotation speed of the motor (1) is low, the measured data loaded into the data counter (23) is 2 ^N-1 or more. pulse P _M is set to "1" (FIG. 9 D). Accordingly, the first speed deviation signals S ₁ obtained at this time is as shown in FIG E, a signal having a pulse width corresponding to the speed deviation is obtained.

MSB pulse P _M and the reference clock CKa is further supplied to the second signal forming means (13).

The second signal forming means (13) obtains a negative pulse having a pulse width corresponding to the speed when the motor rotation speed is high, and a positive pulse having a pulse width corresponding to the speed when the motor rotation speed is low. be one pulse is to be obtained, when the measurement data as shown in FIG. 10 C (analog converted value), the phase relation between the MSB pulse P _M and the reference clock CKa is in Figure 10 D, E The reference clock CKa
If advances the phase of the MSB pulse P _M to: a pulse S _2M in when the rotation speed is slow, the negative polarity shown in the drawing G
A second speed deviation signal S ₂ having obtained.

Therefore, in the second signal forming means (13), the reference clock is used.
When faster than the falling timing of the rising MSB pulse P _M of CKa, so that the negative pulse is obtained. The pulse width differs depending on the number of rotations. The faster the rotation, the wider the pulse width. Therefore, MSB pulse P _M from the rising timing of the negative pulse is the reference clock
Is obtained until the fall timing.

MSB pulse when the rotation speed is slow, P _M and the reference clock CKa
The phase relationship between the turned above opposite, MSB pulse P since the rise of the reference clock CKa than the falling timing of _M is delayed, the second speed deviation signal S having a positive pulse S _2P
2 is obtained, and the pulse width becomes wider as the rotation speed becomes slower.

As described above, the second speed deviation signal S ₂ has a polarity corresponding to whether the rotation speed is faster or slower than the reference rotation speed, and
The deviation amount are those having a pulse width corresponding, the reference when the rotational speed of and the MSB pulse P _M and the reference clock CKa in phase, either positive or negative pulse is not output.

The second speed deviation signal S ₂ together with cleared for each cycle on the falling edge of the rotation signal S _M, pulses S _2P positive or negative polarity obtained in this one rotation cycle, S _2M first After the pulse is obtained, it is self-held. Therefore, the rotation signal
One pulse S _2P or S _2M is generated in one period of S _M. Then, the sections without the pulses S _2P and S _2M are both kept at high impedance.

Second speed deviation signal S ₂ is supplied to the third signal forming means for converting to a DC control voltage V ₃ (14). Third signal forming means (14) can be used a charge pump, only the pulse width period in positive pulse S _2P charge, if only discharge the pulse width period in negative pulse S _2M, rotation A DC control voltage V ₃ (FIG. 10H) corresponding to the number speed deviation can be obtained.

As described above, the DC control voltage V ₃ based on the second speed deviation signal S ₂ is a sure that the DC level is changed when the speed deviation occurs, therefore, the DC control voltage
By controlling the rotational speed of the motor (1) with V _3, the steady-state deviation Δω
Can be correctly controlled to the normal rotation speed in the absence of the rotation.

The out-of-range detection circuit (35) is a measurement counter (21)
And (N + 1) th bit, while the (N + 2) A counter can count bit, the period of the first low-level multi-output M _1, (N + 1) th bit is "0",
If it is not "1", it is determined that the rotation of the motor (1) is too fast. At this time, the output of the out-of-range detection circuit (35) is used as the pulse forming means (30) and the second signal forming means (1).
3) Forcibly generate "L" and a negative pulse _S2M .

Conversely, when the (N + 2) th bit becomes “1”,
It is determined that the motor speed is too slow, and in this case, the operation opposite to the above is forcibly performed.

FIG. 11 shows another example of the present invention. Instead of forming the second speed deviation signal S ₂ on the basis of the MSB pulse P _M and the reference clock CKa in this example, by using the first speed deviation signals S ₁ itself, based on which the reference clock CKa This is the case in which it is formed. In this case, it is clear that the same operation as described above can be obtained.

By the way, as shown in FIG. 12, the rising characteristic of the motor rotation speed in the above-described embodiment, particularly the embodiment shown in FIG. 1, vibrates. Therefore, in this case, there is a disadvantage that it takes time (settling time) to reach a stable rotation speed (target value).

Such a vibration phenomenon can be prevented by providing a differentiating circuit in the first signal forming means (11).

FIG. 13 shows an example thereof. The same reference numerals are given to the portions corresponding to those in the above-mentioned drawings, and the description thereof will be omitted. In this embodiment, however, between the measurement counter (21) and the latch circuit (28). Is provided with a digital differentiating circuit (40).

In this example, a first constant unit (41), a memory circuit (42) for storing measurement data of one time before obtained by the measurement counter (21), and a memory circuit of one time before output from the memory circuit (42). Constant device (second constant device) for the measured data of
A differentiation circuit (40) is composed of (43) and a subtracter (44) for subtracting the first and second constant device outputs. Assuming that the constant of the first constant unit (41) is k (k is an appropriate integer value of 1 or more), the constant of the second constant unit (43) is selected to be (k-1).

Store the measurement data to the memory circuit (42) is performed by the first multi-output M _1.

Now, when such a digital differentiating circuit (40) is provided, in FIG. 4, before the element K ₂ / s, in FIG. 6, before the element (K ₁ + K ₂ / s). This means that the differential element sk has been inserted. When the differential element sk is interposed, the input (ω _ref −
ω) is changed as follows so that each element K ₂ / s or (K ₁ +
K ₂ / s).

Assuming now that the motor rotation frequency at a certain control time is ω _n and the motor rotation frequency one time before is ω _n−1 , the differentiation circuit (4
0), the output ω ′ is given by: ω ′ = k (ω _ref −ω _n ) − (k−1) (ω _ref −ω _n−1 ) = ω _ref −ω _n − (k−1) ω _n + (k−1) ω _n−1 = ω _ref −ω _n − (k−1) (ω _n −ω _n−1 ) (9) On the other hand, when the differentiating circuit (40) is not provided, Is ω ′ = ω _ref −ω _n (10)

Since the third term (k−1) (ω _n −ω _n−1 ) in the third term on the right side of the equation (9) is equal to dω / dt, the output ω ′ has a differential characteristic by providing the differentiating circuit (40). It will be output in the state given.

In the case where a differential characteristic is given to the output ω ′ in this way,
Since the vibration of the rotation speed ω is suppressed, the motor rotation speed ω
As shown in FIG. 14, the rise characteristics of the first embodiment do not cause overshoot, vibration can be almost completely suppressed, and the settling time can be shortened accordingly. When k = 8, the settling time can be reduced to about 2 seconds. Conventionally, the settling time is almost twice as long.

Effect of the Invention As described above, according to the present invention, the steady-state deviation can be eliminated, so that the rotation speed of the motor (1) can always be controlled to the target rotation speed. Moreover,
It is not necessary to select the target rotation frequency _ωref to a slightly larger value in consideration of the steady-state deviation Δω as in the related art. Therefore,
The feature is that the target rotation frequency ω _ref can be set accurately.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a speed servo circuit according to the present invention, FIG. 2 is a system diagram of a conventional speed servo circuit, FIG. 3 is a control block diagram for explaining the control operation thereof, and FIG. 1 is a control block diagram, FIG. 5 is a system diagram showing another example of a speed servo circuit according to the present invention, FIG. 6 is a control block diagram thereof, and FIG. 7 is a diagram showing a specific example of FIG. 8 to 10 are waveform diagrams for explaining the operation thereof, FIG. 11 is a system diagram of a main part showing a specific example of FIG. 5, and FIG.
FIG. 14 and FIG. 14 are diagrams showing the rise characteristics of the motor rotation speed, respectively, and FIG. 13 is a system diagram showing still another example of the speed servo circuit according to the present invention. (1) is a motor, (2) is a rotation signal generating means, (11),
(13) and (14) are first to third signal forming means, S ₁ and S ₂ are first and second speed deviation signals, and _VCTL is a control voltage.

Claims (1)

(57) [Claims] 1. A rotation signal generating means for obtaining a rotation signal proportional to the rotation speed of a motor to be controlled, and data converted from the rotation signal by receiving initial bias data in synchronization with the rotation signal of the motor. A measurement counter for measuring the measurement value, and subtracting the measurement value obtained from the measurement counter and the measurement value one time before the measurement value by a predetermined constant after subtraction, thereby giving a differential characteristic to the measurement value. A circuit for suppressing the oscillation of the measured value; a data counter for loading the output value of the differentiating circuit; and a speed deviation from a measured value loaded in the data counter with respect to a reference speed, for each cycle of the measured value. First control signal generating means for generating a first speed deviation signal having a pulse width corresponding to the speed deviation amount, and the data counter The speed deviation with respect to the reference speed from the measured value loaded to the second speed having a polarity corresponding to the direction of the speed deviation and a pulse width corresponding to the speed deviation amount for each rotation cycle of the rotation signal. A second control signal generating means for generating a deviation signal, wherein the second speed deviation signal from the second control signal generating means is supplied as a DC control voltage via a charge pump to the first control signal. A speed servo circuit for controlling the rotation speed of the motor by adding to a first speed deviation signal from the generating means;