JPS6115577A - Speed servo circuit - Google Patents

Abstract

PURPOSE:To suppress an overshoot by providing a differentiation control system in a feedback control system. CONSTITUTION:A rotary signal SM obtained from rotation signal generating means 2 and a reference signal SREF are supplied to speed deviation forming means 4 to obtain a deviation amount of a motor rotating speed for the signal SREF. Means for applying differentiating characteristic of a speed deviation signal such as, digital differentiator is provided in the means 4. This speed deviation signal DELTAV is supplied through a low pass filter 5 to a motor driver 6. Thus, an overshoot at the motor rotation stopping time can be suppressed to shorten the matching time that the rotating speed of the motor arrives at the reference speed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a motor speed servo circuit suitable for application to a motor that drives a floppy disk.

In particular, it relates to speed servo circuits with excellent transient characteristics.

BACKGROUND ART AND PROBLEMS A speed servo circuit used to control the rotational speed of a motor to a reference rotational speed is generally constructed as shown in FIG.

The motor (1) to be controlled is provided with a rotation signal generating means (2) such as a frequency generator (FG) for generating a rotation signal SM proportional to the rotation speed of the motor (1).
M and the reference signal 5REP- supplied to the terminal (3) are supplied to the speed deviation forming means (4), and the reference signal 5REP- is supplied to the speed deviation forming means (4).
The deviation amount (PWM signal) of the motor rotational speed with respect to
By converting the DC control voltage VcTL into a DC control voltage VCTL and supplying the converted DC control voltage VcTL to the motor driver (6), the motor (1) receives the reference signal 5REF.
The rotation speed is controlled to correspond to the

Now, as is well known, such a speed servo circuit a0 has a drawback that the start-up of the rotation of the motor (1), that is, the transient characteristics are poor (overshoot occurs), so that it takes a long settling time.

That is, the feed bank control system of the speed servo circuit 00) shown in FIG. 2 can be expressed as a control block as shown in FIG. In the same figure, ω is the rotational frequency of the motor 11+ after feedback control, ωref is the reference frequency, and the 1:1 bus filter (5) and motor driver (6) are (Since each of 11 is expressed as a -order delay element, the transfer function of this feed bank control system is as follows.

...(1) The denominator of Yama 2 is f fs) = Tt T2 s2+ (T14-T2)
:: 1-AK+ +1... (2) If we express equation (2) using the damping factor ξ·6-, we get equation (3).

f (S) = T I T 2 (s 2+ 2ξ
ω11S'ωn')...() The smaller the damping factor ξ is than 1, the larger the Ebershoot at the rise of the motor rotation speed; conversely, if ξ〉1・Pursuit becomes smaller or can be reduced to zero.

Here, equation (2) can be transformed as follows.

...(4) From the relationship with equation (3), it becomes. In the case of motor rotation speed control, usually T 1 <<
72, equation (5) can be transformed into equation (7).

The amount of overshoot is determined by the ratio of the numerator and denominator in equation (7), and since 1 is usually large enough, ξ<1.0
...(1;) Therefore, in the conventional feedback control system, oversive and -t always occur, as is clear from equation (8).

Note that overshoot can be suppressed by reducing the proportional gain to 1, but 1 to the proportional gain of τ is inversely proportional to the steady deviation of the motor rotation speed, so reducing the proportional gain by 1 will suppress the overshoot. The steady-state deviation becomes large, and therefore, it is generally necessary to reduce the steady-state deviation and cause overshift and to occur. Therefore, the settling time is naturally long.

Figure 4 shows the rise and fall characteristics of the monitor rotation speed in a conventional circuit. In this example, it is a transient characteristic when Kt is -5, and an overage J, -1 is generated, and the target rotation is It can be seen that the settling time until reaching the number is quite long.

Purpose of the Invention Therefore, the present invention suppresses overshoot and improves transient characteristics without deteriorating or reducing steady-state deviation.

Summary of the Invention Therefore, in the present invention, a differential control system is introduced into the feedback control system.

By introducing a differential control system, overshoot can be suppressed for reasons described later. At this time, since the proportional gain is not changed to 1, the steady-state deviation does not become large.

Embodiment Next, a motor speed servo circuit according to the present invention will be explained in detail with reference to FIG. 1 and FIG. 5 onwards.

Figure 1 shows a motor speed servo circuit αO according to the present invention.
This is an example of the conventional circuit shown in FIG. The speed deviation signal forming means (4) has a digital processing configuration.
) is provided with means for imparting differential characteristics to the speed deviation signal, in this example a digital differential circuit (not particularly shown).

Figure 5 shows a feedback control system for determining the transfer function in the speed servo circuit 00) shown in Figure 1. In this case, it can be expressed as a differential element sk added each time a differential circuit is inserted. can.

The transfer function at this time is expressed by equation (8).

...(8) f(S)=T1T2 s2+(Tl +T2 +Ak)
s + AI (month ff3) = Tx T2 (s2+
2ξ6)nS +ωn 2)”= (1
0) Here, .

Now, in equation (12), k represents the differential gain, so if k is increased, the dumbinder factor ξ can be made larger than 1. If ξ>1, the damping effect becomes large, so by setting k to an appropriate value, it is possible to completely eliminate overshoot.

Curve 7!1 in FIG. 6 shows the transient characteristics when Δ=8. In this way, by adding the differential control system, overshoot can be improved and the settling time of the motor (1) can be shortened accordingly. In the illustrated example, the settling time is about 2.0 seconds.

In this case, if the proportional gain is set to 1 larger than before, for example +=20, the steady-state error can be improved, and the curve β
In the case of 1, when the target rotation speed is 40 Orpm, the actual motor rotation speed is 394 rpm.

FIG. 7 shows another example of the speed servo circuit 0111 according to the present invention, and this example is an example in which not only the transient characteristics are improved but also the steady-state deviation is improved.

The rotation signal Sr+ obtained from the rotation signal generating means (2) and the reference signal 5IIEP supplied to the terminal (3) are supplied to the first signal forming means (11), and! & Beni frequency ωt
A first speed deviation signal S1 having a pulse width corresponding to the rotational speed deviation of the motor (11) with respect to el is formed.The first signal forming means (11) includes a differential element. 1 speed deviation amount'; 3S1 is base/1r'.

The signal 5REF is a pulse signal whose pulse width is modulated according to the speed deviation, and corresponds to the speed deviation signal ΔV, which is not shown in FIG.

The first speed deviation signal S1 is transmitted to the second signal forming means (1) together with the reference clock CKa applied to the terminal (12).
3) to form a second speed deviation signal S2 having a polarity corresponding to the polarity of the speed deviation and a pulse width corresponding to the speed deviation amount for each rotation period of the rotation signal SH.

As will be described later, the reference clock CKa is selected to have a higher frequency than the frequency of the rotation signal sM obtained when the motor (1) reaches the reference rotation speed, and the polarity of the speed deviation is set to the base 21 in this example. When the rotation speed is faster than the rotation speed, the polarity is positive, and when it is slower than the rotation speed, the polarity is negative. Therefore, when the rotation speed is faster than the reference rotation speed, the second speed deviation signal S2 is a positive pulse signal having a pulse width corresponding to the amount of speed deviation; Sometimes, a negative second speed deviation signal S2 having a pulse width corresponding to the speed deviation amount is obtained. Further, this pulse of positive or negative polarity is obtained every rotation period of the rotation signal sM.

The second speed deviation signal S2 is further processed by a third signal forming means (
14) is supplied to the motor control voltage Vcvt corresponding to the width and polarity of the second speed deviation signal S2.
The DC level of (DC voltage) is controlled. That is, when the second speed deviation signal s2 is a positive pulse signal, the DC of the motor control voltage vctt.
The level is controlled so that it is lower than the reference value, and vice versa, it is controlled so that it is higher than the reference value.

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 C controller voltage VcTL increases or decreases depending on the second speed deviation signal S2,
Second and third signal forming means (II).

(13) can be regarded as a kind of integrating circuit.

For convenience of explanation, if we exclude the differential element and the -order lag element of the low-pass filter (5) and consider only the steady-state error, the feed hack control system showing the transfer function in this case is integrated as shown in Figure 8. It can be expressed as a zo1 dock whose elements include 2/5 (K2 is the integral gain), and ω
and ωref 1. +M +;I, and at this time, the number of ω at j −* oo is 1, − ωref
...(15), and the deviation Δω is Δ ω −ω. Quantity −ω ref=0
... (16), and the steady deviation Δω becomes zero.

Therefore, in the speed servo circuit α0) shown in FIG. 7, the motor (
1) can be controlled. Therefore, the transient characteristics at this time are as shown by curve β2 in FIG.

FIG. 9 shows the conventional speed servo circuit 00 shown in FIG.
This is a case where the technique shown in the figure is applied, and in this case, the first speed deviation signal S1 becomes the speed deviation signal ΔV shown in FIG. Control voltage (set to V3) and low-pass filter (5
) is superimposed by the mixing circuit (15), and this superimposed control voltage is supplied to the cTL motor driver (6).

This configuration also makes it possible to improve transient characteristics and steady-state deviation.

Next, the present invention will be explained in detail. FIG. 10 shows an embodiment corresponding to FIG. 9, and only the main parts thereof are shown.

In this embodiment, the first and second speed deviation signals <Ell.

In the case where S2 is digitally formed, the first signal forming means (11) is a measurement counter (21).
, bias data memory (or [/ register) (2
2) and a data counter (23) 7, a [Fuchi counter (21) has a rotation signal st1,
t-, bias data (initial data) is loaded,
This rotation signal is sent to the data counter (23)! +t'
At S tl, the measurement data of the measurement counter (21) is read.

Therefore, what is the rotational signal SM (to the [[figure])? (The first multi-output M1 ("3" in the same figure) synchronized with the λγ1 is formed;), and this first multi-output M is further A second multi output M2 (0 in the same figure) synchronized with 1γ and [-4 is formed by the second mono multi output M2 (26).

The second multi-output M2 is an N-bit measurement counter (21
), bias data is loaded during the low level period of the second multi-output M2. The bias data is set to a predetermined value 2M (M<N) such that the target rotational speed is reached at the time when the measurement counter (21) once outputs a carry and reaches the value 2).

The first multi-output M1 is used as a gate pulse to gate the clock CI(b) for the measurement counter (21), so this clock CKb and the first multi-output M1 are supplied to the ant-game-1-(27). If the operation of the a1 measurement counter (21) is illustrated in analog form, the 11th
As shown in the figure, the bias data loaded by the second multi-output M2 starts counting amplifier operation from the time this second multi-output M2 becomes high level, and within one rotation period of the rotation signal sM. After the measurement counter (21) reaches a full count, the count amplifier operation continues again.
The measurement data of the measurement counter (21) is then supplied to the digital differentiation circuit (40) at the time of the first multi-output M1 obtained.

In this example, the first constant device (41) and the measurement counter (
21), and a memory circuit (42) that stores the measurement data of one point before iυ from iυ.
) output from the previous measurement data (・ll'' vs. J
[ma] constant device (second constant device) (43) and the 11th (
The subtracter (44) that subtracts the output of the constant device (2) constitutes j"1. (minute 118 (40). The differential gain (constant) of the first constant device (old) is expressed as k (k is an appropriate lc TK value of 1 or more), the second constant device (43
) is selected to be (k-1).

The measurement data is stored in the memory circuit (42) by the first multi-output M1.

Now, when the differential element sk is interposed, +J, input/, 1(
ωre+−ω) is changed as follows and is supplied to the lie circuit (28) which performs 11 jA;

Now, if the motor rotation frequency at a certain control point is ω11.1 and the motor rotation frequency before the time is ωold, then the differential circuit (40
), the output ω′ (launch circuit (2
8)) is ω'-k(ωref-ωn) (k1)
(ω+am-1kln-x)-ωref-ωn(k-
1) ωI, + (lc-1) ω11-1--ωref-
ωn(k-1)((dr+-1ωn-1)...(1
7) On the other hand, if the differential eye V & (40) is not provided, ω'-
ωrel−ωn (18).

(k-1) (ωn −ω
Since n-t) is equal to dω/dt, the differentiator circuit (4
0), the output ω' is outputted with differential characteristics.

When the differential characteristic is imparted to the output ω' in this manner, the damping effect as described above can be obtained.

The output of the measurement counter (21) whose differential characteristic is JLj, that is, the d1 measurement data, is latched by the latch circuit (28). The latched measurement data is illustrated in analog form as shown in FIG. 11E.

The measurement data at the time when the first multi-output M1 is obtained changes depending on the cycle of the rotation signal sM, that is, the speed of the rotation speed of the motor (). When the motor rotation speed is high, the period of one rotation becomes shorter, so the measurement data that is latched is small.On the other hand, when the rotation speed of the motor is slow, the period of one rotation becomes longer, so the measurement data at this time is becomes larger.

The latched measurement data is loaded into the data counter (23). Therefore, the data counter (
23) is the clock CKa' obtained at the terminal (32).
(which may be the same as or different from CKa) is supplied and also supplied to the frequency divider (33), which converts it to 1/2N
The reference clock CKa shown in FIG. 12B is formed by dividing the frequency into the reference clock CKa, and the d1 measurement data launched in synchronization with the falling timing of this reference clock CKa is loaded.

After loading the data, the measurement data read by the clock CKa' is counted up, and the MSB is shown in the MSB of the counted up count data.
The B pulse PM (FIG. 12A) is supplied to the pulse forming means (30) to form the first speed deviation signal S1.

The MSB pulse pM is the count data of the data counter (23) between θ and 2N-1.
~2N-1 is a 1'' data 1, -te, -50% pulse, and the data counter (23) and frequency divider (33) are driven by the same clock CKa'. Therefore, the reference clock C whose frequency is divided by 1/2N
Ka and the MSB pulse PM have the same pulse period.

However, MSB pulse PM with respect to reference clock CKa
The phase differs depending on the magnitude of the measurement data loaded into the data counter (23). That is, the motor (11
When the rotation speed is high, the measurement data latched by the first multi-output M1 has a value of 2N-1 or less, so
The MSB pulse PM at that time is 0'' and remains at 0'' until the measurement data loaded into the data counter (23) reaches 2N-1 (see FIGS. 12A and 12B).

Note that the data counter (23) is a data counter with a limiter, and if a pollow occurs as a result of an operation, the count data is forcibly set to O, and if a carry occurs, the count data is set to 2N-. 1 is set.

The pulse forming means (30) can be composed of a flip-flop or the like, and is centered at the falling edge of the MSB pulse PM.
If the reference clock (Ja) is reset at the rising edge of the clock, when the phase relationship is as shown in Fig.
The first j1 as shown in C of the same figure! A degree deviation signal Syu is output.

On the other hand, when the rotation speed of the motor (1) is slow, the measurement data loaded into the data counter (23) is 2N-
Since it is 1 or more, if we look at the timing of the reference clock CKa, the M S T3 pulse ph at that time is 1.
' (Figure 12, 1)). Therefore, the first speed deviation signal S1 obtained at this time is as shown in FIG.
A signal having a pulse width corresponding to the speed deviation is obtained.

The MSB pulse Pt1 and the reference clock CKa are further supplied to a second signal forming means (13).

When the motor rotation speed is high, the second signal forming means (13) obtains a negative polarity pulse having a pulse width corresponding to the speed, and when the motor rotation speed is slow, a pulse width of negative polarity is obtained according to the speed. The pulse of positive polarity is iQ, and sometimes L:I:, M S 13 pulse P of measurement data (analog conversion value) as shown in Fig. 13C.
The phase relationship between M and the reference clock CKa is shown in Figure 13 and E.
Therefore, when the phase of the MSB pulse Pr1 is ahead of the reference clock CKa, that is, when the rotation speed is slow, the second speed deviation signal S2 having the negative polarity pulse S2r+ shown in G in the same figure is can get.

Therefore, in the second signal forming means (13), a negative polarity pulse is obtained when the rise of the reference clock CKa is faster than the fall timing of the MSB pulse PM. The pulse width differs depending on the rotation speed. The faster the rotation, the wider the pulse width. Therefore, this negative polarity pulse is MS from the rising timing of the reference clock.
The period up to the falling timing of the B pulse PM can be obtained.

When the rotation speed is slow, the phase relationship between the MSB pulse PM and the reference clock CKa is opposite to that described above, and the rise of the reference clock (Ja) is later than the fall timing of the MSB pulse PM, so the positive polarity pulse 2nd with 32P
A speed deviation signal S2 is obtained, and the pulse width becomes wider IIYi as the rotation speed becomes lower.

In this way, the second speed deviation signal 32 has a polarity corresponding to whether the rotation speed is faster or slower than the reference rotation speed, and
The pulse width is sold according to the amount of deviation, and when the rotation speed is the standard, the MSB pulse width period and the reference clock CKa are the same, so the positive or negative polarity pulse will eventually become t. ) is output.

Note that the second speed deviation signal S y &: l' Ii, i
1 turn (iT S!,; Cleared every cycle at the fall of +1, Y> 5 to r 1j, 11 positive or negative points obtained within one rotation period of -S 2P,
S 211 gets the first pulse (・]reno, :1-)
is self-maintained. Therefore, pulses 32P or 32M are generated at a rate of one pulse G1' per period of the rotation signal S fJ.

Then, pulse 32P, section 1 without S 2+1
+121 are also held at high impedance.

The second speed deviation signal S2 is the DC control f■i 1-IE
a third signal forming means (14) for converting into v, I;
supplied to The third signal forming means (14) can use a charge pump, in which a positive polarity pulse S2P is used to charge for the pulse width period, and a negative polarity pulse 32M is used.
By discharging for that pulse width period, it is possible to obtain a DC control voltage V3 (FIG. 13H) corresponding to the speed deviation of the rotational speed.

As described above, the DC level of the DC control voltage 3 based on the second speed deviation signal S2 is always changed when a speed deviation occurs. Therefore, this DC control voltage V3 is used to control the motor (11). By controlling the rotational speed, it is possible to accurately control the rotational speed to a normal rotational speed without a constant deviation Δ−ω.

Note that the out-of-range detection circuit (35) is connected to the measurement counter (21).
) is a counter that can count the CN+1)th bit and the (N+2)th bit of ``1'' while the ``(N+1) bit l'' remains ``0'' during the period when the first multi-output M1 is at a low level. ”, if the motor [11
It is determined that the rotation is too fast.

At this time, the output of the out-of-range detection circuit (35) forces the pulse forming means (30) and the second signal forming means (13) to generate "■7" and the negative polarity pulse 82N.

On the contrary, (N+2) bit I:81 is “1”6
1″.

Then, if the motor rotation speed is too slow, 11J tlli
In this case, the operation opposite to that described above will be forced into line 2. I get fucked.

In addition, in FIG. 10, the second speed deviation (No. 4 S2
Instead of forming the first speed deviation signal S1, it is also possible to use the first speed deviation signal S1 itself and form the second speed deviation signal S2 based on this and the reference clock CKa4.

As described in detail, according to the present invention, the feed hack control system is provided with a differential characteristic imparting means, so that the transient characteristic at the start-up of motor rotation, A', and overshoot can be suppressed or It can be completely eliminated. Therefore, the settling time for the motor rotation speed to reach the reference rotation speed can be significantly shortened compared to conventional motor rotation speeds.

Moreover, since it is not necessary to reduce the proportional gain by 1 to improve this transient characteristic, the seating deviation 1) is reduced.

Of course, by configuring as shown in FIG. 7 or 9121, it is possible to eliminate the seat deviation, so this invention can be applied to floppy disks that have a quick rise in rotational speed and that need to be driven at a regular rotational speed. It is extremely suitable for application to a morph control system.

[Brief explanation of the drawing]

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 its control operation, and FIGS. FIG. 6 is a transient characteristic diagram of motor rotation, FIG. 5 is a control block diagram of FIG. 1, FIG. 8 is a control block diagram of FIG. 7, FIG. 1O is a system diagram of main parts showing the specific example of FIG. 9, and FIGS. 11 to 13 are waveform diagrams for explaining the operation. (1) is a motor, (2) is a rotation signal generating means, (11)
. (13) and (14) are first to third signal forming means;
St. St represents the first and second speed deviation signals, VCTL represents the control voltage, and (40) represents a digital differential circuit serving as differential characteristic imparting means. ′-(-・-゛Same Hidemori Matsukuma r] ,'1, Figure 9, Figure 9, Figure 12, Figure 11

Claims (1)

[Claims] a rotation signal generating means for obtaining a rotation signal proportional to the rotation speed of the motor to be controlled; a signal forming means for forming a speed deviation signal corresponding to the speed deviation of the motor from this rotation signal and a reference signal; A speed servo circuit comprising a differential characteristic imparting means for imparting a differential characteristic, and a signal forming means for forming a motor control voltage from the speed deviation signal imparted with the differential characteristic.