JPS6035975A - Speed controller of rotor - Google Patents

Abstract

PURPOSE:To reduce phase delay by detecting the time length between the adjacent preceding edge and the trailing edge of a rotating speed proportional signal and generating a control output in response to the detected result. CONSTITUTION:The first period detector 7a outputs a control output 8a in response to the variation in the time length between adjacent preceding edges and the second period detector 7b outputs a control output 8b in response to the variation in the time length between the adjacent trailing edges. An output selector 11 alternately selects the output 8a of the selector 7a and the output 8b of the selector 7b and outputs 8c. The output 8c is inputted as the output of a speed detector 4 through a filter 9 to a motor drive circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control device for a rotating body that improves the transmission characteristics, particularly the phase delay, of a speed detector that generates a control output according to the rotational speed of the rotating body.

For speed control of rotating bodies that require precise constant speed rotation, such as video tape recorder drums, capstans, etc., a frequency generator is used to generate an AC signal with a frequency proportional to the rotational speed of the rotating body. (hereinafter referred to as FG) and speed detectors that generate a control output according to the frequency of the F'G signal that is the output thereof are widely used.

FIG. 1 is a block diagram showing its basic configuration.
(l) is the motor, (2) is the FG signal, (3) is the FG multiplication signal (4) is the speed detector, (5) is the FG multiplication signal (3), and the speed proportional to the leading and trailing edges. 1d (61), (7) is a period detector that detects the period of the speed proportional signal (6) and generates a corresponding control output (8), (9) is a control output (8). ) filter for the purpose of smoothing or phase compensation, (II is a motor drive circuit. This example shows a so-called direct drive system in which the rotating body and the rotor of the motor are directly connected.

Now, in such an 11-degree control system, it is generally well known that in order to improve the stability of the system and improve the rotational performance, the FG frequency can be set high. This is because, as shown in the explanation below, the higher the FG frequency, the more the phase delay of the speed detector (4) is reduced, and the higher the ripple frequency of the output, the higher the frequency of the filter (9) in the subsequent stage. This is because the time constant can also be small, increasing the phase margin of the control system.

However, in actual systems, FG
The frequency cannot be set unnecessarily high. Therefore, various efforts have been made to obtain sufficient performance even at low FG frequencies, and the most typical method is phase compensation using a filter.

However, this method stabilizes a system that is originally unstable or in a nearly unstable state by changing a part of the gain or phase frequency characteristics of the system, and it is not intended to stabilize the system that is originally unstable or in a state close to it. It is not possible to expect a fundamental performance improvement like that of .

Incidentally, since the overall operation of such a speed control device is already widely known, the following explanation will focus on the speed detector according to the present invention.

First, the operation of the conventional speed detector (4) shown in FIG. 1 will be explained.

If the rotational speed of the motor is Nmo%, and the FG frequency is fO, since both are in a proportional relationship, it can be expressed as fc = -= KG, Nmo - (t)c. Here, Ko is a speed-frequency conversion constant.

Now, consider the case where the rotational speed changes over time.

That is, Nm(4=Nmo+ΔNm(, t) (2). FIG. 2 shows the operation of the speed detector (4) at this time.

When the rotational speed of the motor (1) changes with time, F
The G multiplied signal 3) is frequency modulated (FM), so that the time length between adjacent leading edges of the velocity proportionality 1d (6) changes. The period detector (7) outputs a control voltage according to the amount of change in this time length. That is, as shown in Fig. 2, υ, the control output V'y(i) is 'rn< 7≦Tn+1(n-0,±
1. ±2...), My(4=s Vyo+Δ'Vr(i)=Vν9 +
KV・△Tn 2 Vyo −) Kv−((Tn −Tn−1)−T
o l ·--(3), where Vyo is the rotational speed of the motor in Nm.

is the control output voltage when . Moreover, Kv is a period-one-pressure conversion constant, and here the polarity is negative.

This is because the polarity of △T is opposite to that of ∆Nm, so K
It is merely intended to simplify the explanation by assuming that v has a negative polarity, and the same applies to the embodiments of the present invention to be described later. Here, the leading edge of the speed proportional signal (6) is used to detect the time length, but the same effect can be achieved even if the trailing # is used.

Now, as is clear from Figure 2, this process is
The signal demodulation process itself, that is, by detecting the so-called "zero-crossing time" of the FM modulated carrier wave, the change in the carrier wave period is determined, and by converting it to tl-voltage, the original modulated signal is restored. Therefore, it is easy to imagine that the higher the modulation frequency, the greater the phase delay.

In fact, in equation (2), ΔNm(A)'Ik single sine wave, that is, ΔNm(4=ΔNmos (27cfmi+θm >
-(4) Here, fm + rotational speed fluctuation frequency θms initial phase △Nmo + rotational speed fluctuation amplitude (peak/zero value), and the FG multiplied signal, that is, the carrier wave, is Vo (J)
-hg (2yCfot) ... (5) Where,
f''%θrn, △Nmok are changed variously, the demodulated output at that time is Fourier transformed to extract the fundamental wave component, and the phase delay θv'l is examined. It turns out that there is an inverse relationship.

Here, the expression "approximately equal" in equation 0 means that this speed detection method detects the reciprocal of the frequency, that is, the change in period, and detects the voltage proportional to the amount of change. Since it is an output type, the fluctuation rate (
This is because if ΔNmOAmo ) is large, a slight error will occur. However, according to the calculation, the fluctuation rate? peak·
Even if the zero value is set to a value of 10, which is so large that it is hardly a target in a 1'l system, the error in Ov is less than 1 m. Note that this phase delay has also been confirmed through experiments using an actual motor control system.

Figure 3 shows △Nm(4) and △Vν(i) when expressed in equation (4). Here, the number inside 0 represents the detection time. In this case , phase delay Q, v are given by equation (6), which can be easily confirmed from the waveforms in FIG.

By the way, what becomes immediately clear from such calculations is that if the time length of a half cycle of FGM number (3) is detected and converted to voltage, the phase delay Ov can be reduced to half of equation (6). It means that it will become. This is because this is equivalent to doubling the FG frequency in the demodulation process described above.

However, in this case, unlike the case of detecting the period, the FG multiplied signal 3) is distorted, and if an offset occurs in the waveform shaper (5) as shown in Figure 4, then Even if the rotational speed does not fluctuate, the output of the speed (8) detector ((2) and (c) in Figure 4) is lip/l.
/, and the DC component also changes, resulting in an increase in rotational unevenness f due to ripples and a deviation in the set speed. Furthermore, since the frequency of the ripple fundamental wave component is the FG pigeon wave number, if a filter is added to avoid an increase in rotational unevenness, its time constant must be sufficiently large with respect to the ripple frequency. As a result, the improvement effect of the 10-degree delay caused by speed detection as described above is canceled out, and other countermeasures are also required.
There are many shortcomings.

Therefore, in an actual speed control system, the method of detecting the speed from the half period of the FG multiplied signal 3) has no merit in terms of performance or cost and is hardly used.

On the other hand, in the case of the method of detecting the -period, as is clear from FIG. 4, even if an offset occurs in the waveform shaper (5), no ripples or fluctuations in the DC component occur. However, even with such a -period detection method, as shown in Fig. 3, if there is a speed fluctuation, a rip p in the FG frequency occurs, and as a matter of course, the magnitude of this rip is smaller than the half-period detection method. Since the ripple frequency is larger than that of the conventional method and the ripple frequency is also low, the time constant sound of the filter (9) at the subsequent stage must be set large. Therefore, the aforementioned θV
The synergistic effect between this and the phase delay due to the time constant element of the filter (9) greatly limits the performance of the control system.

As mentioned above, in conventional speed detection, a method of detecting one cycle of the FG multiplied signal is generally used, but if the FG frequency cannot be set to the desired height due to system constraints, In reality, it is rare that we have to lower the specs in anticipation of imperfect performance.

As described above, this invention can reduce performance deterioration even when the FG frequency cannot be set to a sufficiently high level in light of performance standards based on conventional systems. In other words, it is an object of the present invention to provide a speed control device for a rotating body that can obtain higher performance than the conventional system even at the same FG frequency.

Hereinafter, a refreshing example of this invention will be explained with reference to the drawings.

In Fig. 5, (1) is the motor, (2) is F G ,
(3) is the FG signal, (4) is the speed detector, (5) is the FG signal.
Double signal 3) to speed proportional signal (3) with leading and trailing edges (
6) ``II: Waveform shaper to be created (7a) is a first waveform shaper that detects the time length or period between adjacent leading edges of the speed proportional signal (6) and generates a control output (8a) according to the time length or period between adjacent leading edges of the speed proportional signal (6).
The period detector (74) detects the time length, that is, the period between adjacent trailing edges of the speed proportional signal (6), and generates a corresponding control output (the period detector, αυ, of M2 that occurs).
is the output (8a) of the first period detector (7a) and the second period detector (7a).
An output selector that alternately selects and outputs the output (8b) of the period detector (70), (80) is the output of the output selector α9, that is, the output of the speed detector (4), and (9) is , a filter for smoothing the output (8C) or phase compensation of the control system, and a motor drive circuit.

In the following, let us consider a case where the rotational speed changes over time as in equation (2), similar to the conventional example.

The operation of the speed detector (4) at this time is shown in FIG.

When the rotational speed of the motor (11) changes over time, F
The G signal (3) is frequency modulated. Therefore, the time length between adjacent leading edges and the time length between adjacent trailing edges of the waveform-shaped velocity proportional signal (6) change. The first period detector (7a) is controlled according to the change in time length between adjacent leading edges, and the second period detector (7b) is controlled according to the change in time length between adjacent trailing edges. Output (86),
(84) Output e. These first and second period detectors (7
a) and (7b) constitute the same detection method as the conventional one-period detection method described above.

Therefore, the control output (8a)'? V? t, control output (8
From Figure 6, T, A (A≦TIA+C4=0.±1.±2.)
・), Vy, C1) =Vyo -1-ΔVy
t(A)=VFO+KV #ΔT-=Vyo+Kv ((Tri-TmA"t)-
Tc ) ... (9) T, 4+, <1≦T for 10s
('=O, ±1.±2....) 'Vlh (
, t) = Vpo + △VW* (i) = Ypo+
Kv-△Tμ+1 =Vyo-1-KV ((TIJ+l T--t)
'rC)''・(Represented as JQ.

Now, the output selector 00 determines the time T! when the output (8a) of the first period detector (7a) changes! 4, when the output υ (84) of the second period detector (71) changes, the XIT weight'
++ is the output (88) of the first period detector (74) t
, and the time at which the output (86) of the second period detector (74) changes ']4A+1 to the first period detector (7a, )
The output (84) of the second period detector (7k) is selected as the output (8C) of the speed detection i (4) until time TlA+1 when the output (8a) of (8a) changes. Therefore, the output (80)'kVP(A =
0. ±1. ±2. ...) ...(11).

Here, as in the conventional example, fm in equation (4).

It has become clear that θm and ΔNmO are changed to seed 4, the demodulated output Vν at that time is Fourier transformed, the fundamental wave component is extracted, and all the components are examined with a delay of 1,000 degrees. Note that the approximate symbols in the above equation are used for the same reason as in the conventional example. It can be seen that in the speed detector (4) shown in FIG. 5, the phase delay is reduced by about 25% compared to the conventional one-period detection method.

Similarly to the conventional example, FIG. 7 shows ΔNm (z) and ΔVn(i) at the set values shown in equation (7).

The number within 0 represents the detection time. In this case, the phase delay θV becomes 70 0v≠□=33.75° . . . o1 according to equation 0.

As is clear from FIG. 7, the ripple is also reduced and the rip A/frequency is doubled, and in this respect, it has both the advantages of the half-cycle detection described above.

Furthermore, by increasing the rip/l' frequency, the time constant of the filter (9) at the subsequent stage can also be reduced, so it goes without saying that the phase delay of the control loop is synergistically reduced. Furthermore, according to this method, since the time length detection is the same as the conventional one-cycle detection, the disadvantages of half-cycle detection, such as the distortion of FCkM'Pj (3) and the offset of the waveform shaper (5), are avoided. However, in the above embodiment, the speed generator (
A waveform shaper (5) is provided at the first stage of 4), but if F
If the G-multiplied signal 3) has a waveform like the speed proportional signal (6), that is, a waveform with a leading edge and a trailing edge, the waveform shaper (5) can be omitted.

In addition, although the output (80) of the speed detector (4) is shown in a sample-ho/redo format, the so-called pulse width modulation (PV/M) that changes the output duty according to the change in the cycle
) method, it is clear that similar effects can be obtained.

Furthermore, as a method for detecting synchronization, there are methods that achieve the conversion operation, such as a method that utilizes the charging and discharging of an OR circuit that has been commonly used in the past, or a method that counts the period length using a separately obtained clock signal. Any method is fine as long as it is possible.

Furthermore, in the embodiment shown in FIG. 5, two period detectors (7a) and (7D) are installed in parallel, but as shown in FIGS. 8 and 9, The half-cycle of the signal (6), that is, the time length of the adjacent leading edge and trailing edge and the trailing edge and the leading edge, are sequentially detected at the half-cycle detector port, and the detection results are stored in the half-cycle detection result holder (7α ),
If the time length of one cycle is obtained by combining adjacent ones via (7θ), the detection result is completely equivalent to the case of the two cycle detectors (7a) and (71)) shown in the previous example. It is obvious that this can be obtained, and in this case there is an advantage that only one detector is required.

In addition, in FIG. 8, a3 is a half-cycle detection result holder (
This is a control output generator that outputs a control output (so)' based on the outputs (8^) and (1ee) of 7α) and (7θ).

In addition, in the above embodiments, the rotating body was directly driven, but
It goes without saying that similar effects can be obtained with other drive systems such as belt drive. - As described above, according to the present invention, the time length between adjacent leading edges and the trailing edge of the rotation speed inverse proportional signal is detected, and the control output is generated in accordance with the detection result. Therefore, even at the same FG frequency, the phase delay is reduced by about 2 compared to the conventional one-period detector type.
5- can also be reduced. Furthermore, since the output ripple frequency is doubled, the filter time constant at the subsequent stage is also reduced, and it is also possible to reduce the phase delay, so that the speed control performance of the rotating body can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional speed control device for a rotating body, Fig. 2 is a timing diagram for explaining the operation of a conventional speed detector, and Fig. 3 is a concrete diagram based on the conventional speed detector. FIG. 4 is a waveform diagram showing the influence of offset in the half-cycle detection method; FIG. 5 is a block diagram showing an embodiment of the present invention; FIG. 6 is a control output waveform diagram calculated using numerical values. is a timing diagram for explaining the operation of the speed detector in FIG. 5, FIG. 7 is a control output waveform diagram calculated using specific numerical values based on the speed detector of this invention, and FIG. 8 is a diagram of the control output waveform of this invention. FIG. 9 is a timing diagram for explaining the operation of the speed detector in FIG. 8. (υ...Motor 1.2)...Frequency generator, (4)
...Speed detector, (7a), (71)) ...
Period detector, (7C1), (713)...Half cycle detection result holder, Oq...Motor drive circuit, αρ...
・Output selector, @...half cycle detector, al...control output generator. In the drawings, the same reference numerals refer to the same or corresponding parts. Agent Masuo Oiwa Procedural amendment (voluntary) 1. Indication of the case Japanese Patent Application No. 58-138205 2, title of invention Speed control device for rotating body 3, person making amendment representative Hitoshi Katayama Department 4, agent 5, sleeve 11- Subject specification-I “Patent Claims”, “Detailed Description of the Invention”
and [Brief explanation of drawings J columns and drawings. 6. Contents of Supplement 11-A, Description: (1) The scope of claims is amended as shown in the attached sheet. (2) Page 7, line 2, page 13, line 20: Correct "Fourier transform" to "Fourier series expansion". (3) Page 8, line 5; Correct rQVJ to "θV". (4) Page 15, line 18; ``period'' has been corrected to ``cycle J''. (5) wSl Page 5, between lines 7 and 8; add the following. ``Such a feature is due to the detection of two types of time lengths between adjacent leading edges and trailing edges of the rotational speed proportional signal, but these detection results are simply added.'' That is, in Figure 6, from equations (8) and (to), VF (t) = 1/2 (VFI(t) +VF2
(t) )...(14) When the configuration is configured to generate the control output, Ov becomes the same as equation (6), and the 8I calculation reveals that the 1-phase delay is not improved at all. ing. This can be easily inferred from the waveforms of the first and second detector outputs in FIG. As described above, according to the present invention, the above-mentioned two types of time lengths can be detected, and the detection results can be alternately selected and outputted, and furthermore,
In order to achieve this kind of operation, all that is required is to operate conventional period detectors in parallel and provide a switch circuit that switches the output to alternating current.This makes it possible to improve performance with an extremely compact configuration. It is. (6) Page 16, lines 3 to 17; “Furthermore,...
...It is a generator. ” will be deleted. (7) Page 18, 2nd to 4th lines; Delete ", Figure 8...timing diagram." B1 drawing: Figures 8 and 9 will be deleted. Appendix Supplementary II - #'fA'l' Claims [(1) A frequency generator that generates an alternating current (1: a speed detector that generates a control output according to the frequency of a rotational speed proportional signal having a leading edge and a trailing edge equated based on the speed sensor; and a drive circuit that drives the rotating body according to the output of the speed detector. In the speed control device for a rotating body, the speed detector is arranged such that the time difference between adjacent leading edges of the rotational speed proportional signal 1i11 is −4!!−1!1−tiLLΩ−period 1 further”. 1fj-f = Check the time length between the two forks and the adjacent trailing edge (H and standing and detection means and this n, -, m process Lu
The control output according to the detection result of the detection means is +
1. A speed control device for a rotating body, characterized in that it has a "V" or "V" selection means for generating a wave velocity signal according to the rotation speed proportional to the rotation speed. (2) The time period from the leading edge of the rotational speed proportional signal to the first trailing edge following this leading edge is equal to the time length between adjacent leading edges of the rotational speed proportional signal. Nu'
[Do] 2 40,000] - Yukimi 1. . The period from the trailing edge of the rotational speed proportional signal to the first leading edge following this trailing edge is equal to the adjacent trailing edge of the rotational speed proportional signal. MU2 periodic detection 11) is the time length between
5 is configured to generate a control output according to tt
6. A speed control device for a rotating body according to claim 1. ” Procedural amendment (voluntary) 29 Title of invention Speed control device for rotating body 3, Person making the amendment Relationship to the case Patent applicant representative Hitoshi Katayama Department 4, Agent 5, Subject of amendment Mei 1i 111 ancient “ 6. Contents of the amendment (1) Page 3, line 1 to line 3 of the same page of the written procedural amendment submitted on April 28, 1989 [1; In other words, the phrase ``is corrected to ``If added, that is, J.''

Claims (2)

[Claims] (1) A frequency generator that generates an alternating current signal with a frequency proportional to the rotational speed of the rotating body, and a rotational speed proportional generator having a leading edge and a trailing edge obtained based on the output of the frequency generator. In a speed control device for a rotating body, which includes a speed detector that generates a control output according to the frequency of a signal, and a drive circuit that drives the entire rotating body according to the output of the speed detector, the speed detector includes: detection means for detecting both the time length between adjacent leading edges and the time length between adjacent trailing edges of the rotational speed proportional signal; and a control output according to the detection result of the detection means is synchronized with the rotational speed proportional signal. 1. A speed control device for a rotating body, comprising control output generating means for generating a control output. (2) The control output generating means is configured such that the period from the leading edge of the rotational speed proportional signal to the first trailing edge following this m edge is determined according to the time length between adjacent leading edges of the rotational speed proportional signal. control output? The period from the trailing edge of the rotational speed proportional signal to the first leading edge following this trailing edge generates a control output according to the time length between adjacent trailing edges of the rotational speed proportional signal. A speed control device for a rotating body according to claim 1, characterized in that it is configured as follows.