JPH0510032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a motor speed control device.

2. Description of the Related Art A motor speed control device that detects the rotational speed of a motor using a speed detector and controls the power supplied to the motor based on the detected signal is used in capstan motors, cylinder motors, etc. of video tape recorders. It is widely used (see, for example, Japanese Patent Application No. 142,724/1989 proposed by the present applicant). However, such speed control devices only perform proportional, integral, and differential control that has been used in the past, and have not been able to sufficiently suppress fluctuations in rotational speed due to fluctuations in load torque. below,
This will be explained with reference to the drawings.

The configuration of a conventional motor speed control device is shown in FIG. A rotation sensor 2 directly connected to the DC motor 1 generates an AC signal as the motor 1 rotates. The speed detector 3 generates a DC-like voltage according to the period of the AC signal from the rotation sensor 2, and inputs it to the proportional compensator 9. The signal amplified by a predetermined factor by the proportional compensator 9 is input to the power amplifier 8 . The power amplifier 8 amplifies the power of the input signal to supply power to the motor, increases or decreases the torque generated by the motor 1, and applies the power to the load 1.
Controls the rotation speed of 0.

Problems to be Solved by the Invention A control block diagram of this conventional speed control device is shown in FIG. In Fig. 9, the value obtained by subtracting the load torque TI from the generated torque Tm of the motor 1 (Tm -
TI) becomes the net driving torque (addition point 41), which rotationally drives the combined moment of inertia Jm of the motor 1 and the load 10. The driving torque is the moment of inertia Jm
(block 42) and converted into the rotational speed ωm of the motor 1. In addition, s in block 42
is the Laplace operator. After the rotational speed ωm is multiplied by Kv and detected by the rotation sensor 2 and the speed detector 3 (block 43), it is compared with the reference signal Sref (addition point 44) to obtain an equivalent speed error e.
The speed error e is amplified by a factor of R by the proportional compensator 9 (block 45), and is further amplified by the power amplifier 8
The current is doubled (block 46) and motor 1
supplied to The motor 1 generates a torque Tm that is a torque constant kt times the current supplied to the power amplifier 8 (block 47).

The transfer function from load torque TI to rotational speed ωm is: G(s) = ωm/TI = -1/(Jm s)/1+(KvRBaKt)/(Jm s
)...(1) becomes. A boat-gain diagram of the frequency transfer function G(jω) is shown in FIG. Within the control range below the corner frequency fc, it can be approximated as G(jω)≈−1/(KvRaBaKt) (2).

From equation (2), it can be seen that if the gain R of the proportional compensator 9 is increased, the fluctuation in the rotational speed ωm of the motor 1 due to the fluctuation in the load torque TI is reduced. However, in practice, since there is a time delay in the speed detection operations of the rotation sensor 2 and the speed detector 3, if the gain R of the proportional compensator 9 is made too large, the control system becomes unstable. . That is, there is a limit to the gain R of the proportional compensator 9. As a result, the rotational speed of the motor 1 fluctuated greatly due to torque fluctuations caused by the load 10.

In consideration of these points, the present invention has been devised to significantly reduce fluctuations in the rotational speed of the motor due to fluctuations in load torque.

Means for Solving the Problems The present invention includes a rotation sensor that generates an AC signal with a period corresponding to the rotation speed of a motor, and a speed detection that performs detection multiple times per rotation of the motor based on the AC signal of the rotation sensor. means, compensating means for calculating and storing a control signal based on the detection signal of the speed detecting means, and power amplifying means for supplying electric power to the motor according to the control signal of the compensating means, The compensation means includes a rotation error detection means for obtaining a rotation error in response to the detection signal of the speed detection means, and an ordered number of NxL (herein,
a memory means for storing digital values M[0] to M[NxL-1] (Nx is an integer of 2 or more, and L is an integer of 4 or more); and Nx digital values spaced apart by L intervals in the memory means. a composite value calculation means for substantially calculating a composite value calculated using the
update storage means for substantially sequentially updating and storing digital values in the memory means with update values corresponding to a value obtained by calculating and combining the composite value of the composite value calculation means and the rotation error of the rotation error detection means; The above-mentioned problem is solved by comprising a control signal generating means for calculating and combining the composite value of the composite value calculating means and the rotation error of the rotation error detecting means to generate the control signal. It is something.

Effects In the present invention, by having the above configuration, the frequency transfer function from fluctuations in load torque to fluctuations in rotational speed becomes 0 or extremely small at a specific frequency, and also at other frequencies, it has the same characteristics as the conventional one. It turned out that it was about the same amount.
That is, the influence of fluctuations in a specific frequency of load torque was significantly reduced, and the effect of suppressing fluctuations in other frequencies as well as that of the conventional technology could be obtained. As a result, the composite value of rotational speed fluctuations was significantly reduced, and a high-performance motor speed control device was realized.

Embodiment FIG. 2 shows a configuration diagram representing an embodiment of the present invention.
In FIG. 2, a DC motor 1 directly drives a rotation sensor 2 and a load 10 to rotate. As the motor 1 rotates, the rotation sensor 2 generates an alternating current signal a Zq times per rotation (Zq is an integer of 4 or more; in a capstan motor of a video tape recorder, usually Zq=100). The alternating current signal a of the rotation sensor 2 is input to the speed detector 3, and a digital signal b corresponding to the period of the alternating current signal a is obtained.

A specific example of the configuration of the speed detector 3 is shown in FIG. The AC signal a is waveform-shaped by a waveform shaping circuit 31 to obtain a shaped signal g. The shaping signal g is input to an AND circuit 33 and a flip-flop 35. The clock pulse p of the oscillation circuit 32 and the overflow output signal w of the counter 34 are also input to the input side of the AND circuit 33. The oscillation circuit 32 is composed of a crystal oscillator, a frequency divider, etc., and generates a clock pulse p (approximately 500 kHz) which has a considerably higher frequency than the frequency of the shaped signal g. The counter 34 is a 12-bit up counter that counts up its contents every time the output pulse h of the AND circuit 33 arrives. Further, the overflow output signal w is "H" when the count content of the counter 34 is below a predetermined value,
When the count of the counter 34 exceeds a predetermined value, w changes to "L" (here, "H" represents a high potential state, and "L" represents a low potential state). The data input type flip-flop 35 takes in the "H" input to the data input terminal using the falling edge of the shaping signal g as a trigger signal.
The output Q is set to "H"(q="H"). Also,
When the reset signal r from the compensator 4 becomes "H", the internal states of the counter 34 and flip-flop 35 are reset (b=
“LLLLLLLLLLLL”, w = “H”, q = “L”).

Next, the operation of the speed detector 3 shown in FIG. 3 will be explained. Assume that the counter 34 and flip-flop 35 have been reset by the reset signal r. When the output signal g of the waveform shaping circuit 31 changes from "L" to "H", the clock pulse p of the oscillation circuit 32 is outputted as the output signal h of the AND circuit 33. The counter 34 counts the output signal h and changes its internal state. When the output signal g of the waveform shaping circuit 31 changes from "H" to "L", the output signal h of the AND circuit 33 changes to "L".
, and the counter 34 holds its internal state. Furthermore, the flip-flop 35 takes in data "H" at the falling edge of the signal g.
The output signal q is changed from "L" to "H". The digital signal b of the counter 34 has a value proportional to the (half) cycle length of the alternating current signal a of the rotation sensor 2, and is inversely proportional to the rotation speed of the motor 1.
A compensator 4, which will be described later, looks at the output signal q of the flip-flop 35, and when q becomes "H", it outputs a signal from the counter 34.
After that, the reset signal r is set to "H" for a predetermined short period of time to reset the counter 34 and flip-flop 35 to their initial states in preparation for the next speed detection operation. In addition,
When the rotational speed of the motor 1 is too slow, the period of the output signal g of the waveform shaping circuit 31 is long, so the internal state of the counter 34 exceeds a predetermined value, and the overflow output signal w changes from "H" to "L". ,
The output signal h of the AND circuit 33 may become "L" and the counter 34 may hold a predetermined large value.

The compensator 4 in FIG. 2 is composed of an arithmetic unit 5, a memory 6 and a D/A converter 7,
A digital signal b is calculated and processed by a built-in program to be described later, and a control signal c is output. The control signal c of the compensator 4 is input to the power amplifier 8,
A power amplified drive signal d (a current proportional to the control signal c) is supplied to the motor 1. Therefore, the motor 1, the rotation sensor 2, the speed detector 3, the compensator 4, and the power amplifier 8 constitute a speed control system, and the rotation speed of the motor 1 is controlled to a predetermined value.

The memory 6 of the compensator 4 is divided into a ROM area (ROM: read-only memory) in which predetermined programs and constants are stored, and a RAM area (RAM: random access memory) in which necessary values are stored. The arithmetic unit 5 performs predetermined operations and calculations according to a program in the ROM area. FIG. 1 shows a specific example of the program. Next, the operation will be explained in detail.

<Rotation error detection section 1A> (1) First, the arithmetic unit 5 inputs the output signal q of the flip-flop 35 of the speed detector 3, and waits for the signal q to become "H". That is, the speed detector 3 detects the (half) period of the AC signal a,
The output of a new digital signal b is monitored.

(2) When q becomes "H", read the digital signal b of the speed detector 3, convert it to the speed detection value S (digital value) corresponding to the digital signal b, and set the reset signal r to "H" for a predetermined period of time. Then, the counter 34 and flip-flop 35 of the speed detector 3 are reset.

(3) Subtract the speed detection value S from the predetermined reference value Sref (Eo = Sref - S), and multiply that value Eo by R (E =
R・Eo), and calculate the current rotational error E of the motor 1.

<Count section 1B> (4) Nx・L (here, Nx is an integer of 2 or more,
L is an integer multiple of Zq that is 2 or more) mod
As, every time a new speed detection value S is obtained, the variable I
count up. That is, I=I
After setting it to +1 (I+1 becomes a new I),
If I=NxL, set I=0. If such an operation is performed, I will be an integer between 0 and NxL-1. Note that the initial value of I is NxL-1.

<Control Signal Creation Unit 1C> (5) A control signal value Y is calculated by adding and combining a composite value V obtained by a composite value calculating unit 1E, which will be described later, and a current rotational error E. That is, Y=E+V.

(6) Output the control signal value Y to the D/A converter 7, and
Converts to a DC voltage (control signal) corresponding to the value of .

<Update storage unit 1D> (7) Calculates an updated value by adding and combining a composite value V produced by a composite value calculation unit 1E, which will be described later, and a current rotation error E, and calculates an updated value by adding and combining a composite value V produced by a composite value calculation unit 1E, which will be described later, and a rotation error E at the current time, and calculates an updated value by adding and combining a composite value V produced by a composite value calculation unit 1E, which will be described later, and a rotation error E at the current time. The digital value M[I] is updated (M[I]=E+V) and stored until the next update.

<Composite value calculation unit 1E> (8) Calculate the integer J by adding 1 to I with NxL as mod [J = I + 1 (mod NxL)], and calculate a group of Nx digital values separated by L intervals in the RAM area. M[J-nL (mod NxL)] (n=1, 2,...,
Nx), calculate the composite value V by the following formula,
After that, the operation returns to (1).

V= _Nx 〓 ⁿ⁼¹ Wn・M [J−nL (mod NxL)] ...(3) Here, the value of the ratio Wn is 0<Wn<2/Nx (n=1, 2,..., Nx )
...(4) _Nx 〓 ⁿ⁼¹ Wn=1 ...(5) shall be satisfied. Specifically, if Wn=1/Nx (n=1, 2,...,Nx) (6), favorable characteristics are likely to be obtained. In addition,
This composite value V is obtained after the next speed detection value S is obtained and the counting section 1B increments the count value I (after I and J become substantially equal).
It is used in the control signal generation section 1C and update storage section 1D.

If configured in this way, the load 10 in FIG.
It is extremely resistant to fluctuations in load torque that occur. This will be explained. A control block diagram of this embodiment is shown in FIG. Note that the same elements as those shown in FIG. 9 are given the same numbers and symbols, and their explanation will be omitted. The operation of the compensator 4 is shown in the dashed line 50.
corresponds to The reference value Sref and the detected value S are compared at an addition point 44 to obtain a rotation error E multiplied by a gain R (block 45). The control signal value Y is obtained by adding and combining the composite value V and the rotational error E (addition point 53). Further, the composite value V and the rotation error E are added and combined to obtain an updated value, which is updated and stored as a new digital value M[I] (addition point 51). Furthermore, the next new composite value V is calculated from the digital value group in the RAM area according to equation (3), so the relationship between the digital value M[I] and the composite value V is expressed as block 52. . Here, z in the block 52 is z=exp(sTx) (7), and Tx corresponds to one sampling period of the speed detector 3.

Calculating the transfer function from load torque T1 to rotational speed ωm of the control block in Fig. 4, Gx (s) =
-1/(Jms)/1+(KvRBaKt)/{Jms・H(s)}
...(8) H(s)=1- _Nx 〓 ⁿ⁼¹ Wn・z ^-nL ...(9) Within the control range below the corner frequency fc, it can be approximated as Gx(jω)≒−{1/(KvRBaKt)}·H(jω)≒G(jω)·H(jω) (10). Equation (10) is the control characteristic Gx of this embodiment
This means that (jω) is equal to the conventional control characteristic G(jω) multiplied by H(jω).

FIG. 5 shows an example of the amplitude characteristics of the frequency transfer function H(jω). In Figure 5, Nx=2, W1=1/2, W
This is the case where 2=1/2, and Nx=3, W1=
This is the case where 1/3, W2=1/3, and W3=1/3.
Further, fr is fr=1/(L·Tx) (11), and H(jω) is a periodic function of fr.
As shown in Figure 5 (in general, Nx
≧2), the frequency transfer function becomes −H(jω)−=0 at frequencies fr, 2fr, 3fr, …, and −H(jω)− is approximately equal to 1 at other frequencies as well. I found out. That is,
The frequency transfer function Gx (jω) in this example is the frequency
-Gx(jω)-=0 at fr, 2fr, 3fr, . . . and approximately equal to the conventional frequency transfer function G(jω) at other frequencies. As a result, a very good control characteristic Gx (jω) can be obtained, and the composite value of the fluctuations in the rotational speed ωm of the motor 1 due to the fluctuations in the load torque T1 can be reliably made smaller than the conventional control performance value. It became possible.

Also, if L is set equal to an integer multiple of 2 or more of Zq (if L is set to a value corresponding to an integer multiple of 2 or more of one rotation period of motor 1), the load torque T
This has the effect of greatly suppressing overall fluctuations in the rotational speed ωm due to fluctuations in the rotational speed ωm. Next, this will be explained using the capstan motor of a video tape recorder as an example. Since the load of the capstan motor is a magnetic tape or a pinch roller, the load fluctuation generated by the load 10 is a component that is synchronized with the rotation of the motor 1 (periodic load fluctuation with the rotation of the motor 1 as the basic cycle). In addition, load fluctuation components with a frequency lower than the rotational frequency of the motor 1 often occur.
Such load fluctuations cause fluctuations in the rotational speed of the capstan motor, causing wow and flutter in the tape speed. By the way, such load fluctuations are often periodic fluctuations that have a period that is an integral multiple of the period of one rotation of the motor 1, and conventional fluctuations in the rotational speed of the motor 1 also have a period that is an integral multiple of the period of one rotation. It was found that many periodic fluctuations occur in low frequencies. Therefore, L is 2 of one rotation period of motor 1.
If the value corresponds to an integer multiple of the above, fr will be an integer divided by 2 or more of the rotational frequency fm of the motor 1, and the low frequency fluctuation of the rotational speed ωm of the motor 1 due to the load torque T1 will be effective. can be reduced.

Such an effect cannot be obtained by increasing the gain of the proportional compensator 9 of the conventional motor speed control device shown in FIG. 8, or by adding an integral or differential compensator after the proportional compensator 9. do not have. It should be noted that the larger the value of L, the more effective it is against long-cycle load fluctuations, but the size of the ram area becomes larger, so there is a limit in practice. Usually, L is 6 of the motor rotation period.
It is preferable to double the amount from the following point of view. In other words, 6 has many divisors such as 1, 2, 3, and 6, so 1, 2, 3, and 6 of one rotation period of motor 1
It can be expected to completely suppress fluctuations in rotational speed due to load fluctuations of twice the period.

FIG. 6 shows an example of a program for the compensator 4 that takes into consideration the stability of the entire control system. Here, improvements have been made in the way update values are calculated in the update storage section, the number of composite values prepared in the composite value calculation section, and the way the composite value calculation section uses the composite values in the control signal creation section. Next, its operation will be explained in detail (the overall configuration is the same as that in FIG. 2, so the explanation will be omitted).

<Rotation error detection section 6A> (11) First, the arithmetic unit 5 inputs the output signal q of the flip-flop 35 of the speed detector 3, and waits for the signal q to become "H". That is, the speed detector 3 detects the (half) period of the AC signal a,
The output of a new digital signal b is monitored.

(12) When q becomes "H", read the digital signal b of the speed detector 3, convert it to the speed detection value S (digital value) corresponding to the digital signal b, and set the reset signal r to "H" for a predetermined period of time. Then, the counter 34 and flip-flop 35 of the speed detector 3 are reset.

(13) Subtract the speed detection value S from the predetermined reference value Sref (Eo = Sref - S), and multiply that value Eo by R (E =
R・Eo), and calculate the current rotational error E of the motor 1.

<Count unit 6B> (14) Using Nx·L as a modulus, the variable I is counted up every time a new speed detection value S is obtained.

<Control signal generation unit 6C> (15) The latest composite value V [Px] calculated by the composite value calculation unit 6E, which will be described later, and the current rotation error E
are added and combined to calculate the control signal value Y. That is, Y=E+V[Px].

(16) Output the control signal value Y to the D/A converter 7, and
Converts to a DC voltage (control signal) corresponding to the value of .

<Update storage unit 6D> (17) Obtain the added value M0 by adding and combining the old composite value V [0] calculated by the composite value calculation unit 6E (described later) and the current rotation error E (M0 = E + V
[0]). From count variable I with NxL as mod
Calculate the integer K by subtracting Qf (Qf is an integer greater than or equal to 2, preferably Qf = 3) [K = I - Qf
(mod NxL)].

Transfer the contents of register variable X[m+1] to X[m] in order (m=0, 1, 2,..., 2Qf-
1), put M0 into X[2Qf]. That is, X
From [2Qf], 2Qf+1 consecutive added values (added value of the composite value and rotation error) are obtained from X[0]. Next, a predetermined positive ratio Cm (m=0,
1,...,2Qf) is added and combined to obtain a new updated value, and the digital value M in the RAM area is
It is stored as [K] until the next update. Here, the ratio Cm has the following relationship.

Cm=C2Qf−m(m=0,1,...,Qf) ...(12) _2Qf 〓 ^m=0 Cm=1 ...(13) <Composite value calculation unit 6E> (18) Count variable I with NxL as mod 1+Px
(Px is an integer greater than or equal to 1 and less than or equal to 5, and Px = 3
(preferably)) [J=
I+1+Px (mod NxL)]. Register variable V[m
+1] to V[m] (m=0, 1,..., Px-1), the digital value group M[J-nL (mod NxL)] (n=
1, 2,..., Nx) and enter the latest composite value calculated by the following formula into V[Px]. After that, the operation returns to (11).

V[Px] = _Nx 〓 ⁿ⁼¹ Wn・M[J−nL (mod NxL)] ...(14) Here, the value of Wn satisfies equations (4), (5), and (6). ing. That is, Px+1 consecutive composite values from V[Px] to V[0] are obtained. At this time,
Let J1 be the integer J in formula (14) when calculating V[Px], and let J2 be the integer J in formula (14) when calculating V[0].
Then, there is a relationship of J1 = J2 + Px. That is,
There is a gap between V[Px] and V[0] corresponding to the integer Px. As already explained, after obtaining the next speed detection value S and incrementing the count value I of the counting section 6B, V[Px] is used in the control signal generation section 6C, and V[0] is used in the update storage section 6.
Used in D.

As in this embodiment, an operation for taking a weighted average may be inserted into the update storage section 6D, or a combination of the first composite value of the composite value calculation section 6E used in the control signal generation section 6C and the composite value used in the update storage section 6D. It has been confirmed that if a predetermined deviation is provided between the second composite values of the value calculation unit 6E, good control characteristics as described above can be obtained within the control range, and the operation of the entire control system can also be stabilized. (Satisfies Nyquist stability condition). In particular, in order to simplify the calculation while ensuring the stability of the control system, Qf = 3, Px = 3,
I also learned that it is good to make L>Qf+Px.

FIG. 7 shows another example of a program for the compensator 4 that takes into consideration the stability of the entire control system. Here, the method of calculating the composite value in the composite value calculating section and the number of preparations, and the method of using the composite value of the composite value calculating section in the control signal generating section are improved. next,
The operation will be explained in detail (the overall configuration is the same as that in FIG. 2, so the explanation will be omitted).

<Rotation error detection section 7A> (21) First, the arithmetic unit 5 inputs the output signal q of the flip-flop 35 of the speed detector 3, and waits for the signal q to become "H". That is, the speed detector 3 detects the (half) period of the AC signal a,
The output of a new digital signal b is monitored.

(22) When q becomes “H”, read the digital signal b of the speed detector 3, and
At the same time, the counter 34 and flip-flop 35 of the speed detector 3 are reset by setting the reset signal r to "H" for a predetermined period of time.

(23) Subtract the speed detection value S from the predetermined reference value Sref (Eo = Sref - S), and multiply that value Eo by R (E =
R・Eo), and calculate the current rotational error E of the motor 1.

<Counting unit 7B> (24) Using Nx·L as a modulus, the variable I is counted up every time a new speed detection value S is obtained.

<Control signal creation unit 7C> (25) The latest composite value V [Px] calculated by the composite value calculation means described later and the current rotation error E
are added and combined to calculate the control signal value Y. That is, Y=E+V[Px].

(26) Output the control signal value Y to the D/A converter 7,
Convert to a DC voltage (control signal) corresponding to the value of Y.

<Update storage unit 7D> (27) Calculate an updated value by adding and combining the old composite value V [0] calculated by the composite value calculation means to be described later and the current rotation error E, and calculate the updated value as the count value of the counting means. Update the digital value M[I] in the RAM area corresponding to I (M[I]=E+V[0]),
Stored until the next update.

<Composite value calculation unit 7E> (28) Set NxL as mod and add 1 to count variable I
PxQf (Px is an integer greater than or equal to 1 and less than or equal to 5, and Qf
is an integer greater than or equal to 2) [J = I + 1 + Px + Qx (mod NxL)]. The contents of the register variable
(mod NxL)] (n = 1, 2,..., Nx) calculated using the following formula and enter it into X[2Qf].

X[2Qf] = _Nx 〓 ⁿ⁼¹ Wn・M[J−nL (mod NxL)] ...(15) Here, the value of Wn satisfies equations (4), (5), and (6). ing. In other words, consecutive 2Qf+1 addition values from X[2Qf] to X[0] (separated by L intervals)
The sum value obtained from Nx digital values is obtained. Next, after sequentially transferring the contents of register variable V[m+1] to V[m] (m=0, 1,...,
Px-1), the latest composite value obtained by adding and combining the values obtained by multiplying X[m] (m = 0, 1, ..., 2Qf) by a predetermined positive ratio Cm (m = 0, 1, ..., 2Qf) Get V[Px]
Put it in. That is, Px+1 consecutive composite values from V[Px] to V[0] are obtained. Here,
The ratio Cm has the relationship shown in equations (12) and (13). After that,
The operation returns to (21).

At this time, when actually calculating V[Px], (15)
Let J1 be the integer J in the formula, and let J2 be the integer J in formula (15) when actually calculating V[0], then J1=J2+Px
There is a relationship between That is, there is a difference between V[Px] and V[0] corresponding to the integer Px. As already explained, after obtaining a new speed detection value S and incrementing the count value I of the counting section 7B, V[Px] is used in the control signal generation section 7C, and V[0] is used in the update storage section 7D. used.

As in this embodiment, the calculation for taking a weighted average and the calculation for preparing a plurality of composite values are inserted into the composite value calculation unit 7E, and the first composite value of the composite value calculation unit 7E used in the control signal generation unit 7C is By providing a predetermined gap between the value and the second composite value of the composite value calculation unit 7E used in the update storage unit 7D, good control characteristics as described above can be obtained, and the operation of the entire control system can also be improved. Becomes stable (satisfies Nyquist stability condition). In this case as well, in order to simplify the calculation while ensuring the stability of the control system, Qf=3, Px
It is better to set = 3, L > Qf + Px.

It should be noted that the calculations using the ratios Wn and Cm are not limited to the above-mentioned forms, but may be any form that realizes the content of the above-mentioned program, and it goes without saying that various equivalent expression transformations are possible. Also,
When a new rotation error is obtained, the control signal generation means first outputs a new control signal, and then the composite value calculation means calculates a composite value to be used at the next sampling point. In this case, the computation time of the composite value calculation means can be lengthened, and the time delay until the control signal is output can be shortened, so that the stability of the control system can be easily ensured.

In each of the above-mentioned embodiments, only the rotational speed of the motor is detected by the speed detector, but in addition to this, the rotational phase of the motor is detected by a well-known phase detector, and the two are combined. It goes without saying that this may be considered a rotation error and is included in the present invention. Also, the output of the compensator can be converted into a digital signal or
A PWM signal (pulse width modulation signal) may be used, or the output signal of a power amplifier may be used as a PWM signal. Further, a brushless DC motor may be used as the motor. Furthermore, the compensator may be constructed entirely in hardware and perform the same operations as the program described above. In addition, various modifications can be made without changing the gist of the present invention.

Effects of the Invention The motor speed control device of the present invention has extremely good control characteristics at a specific frequency, and is almost the same as the conventional control characteristics at other frequencies, and the overall load torque is reduced. Fluctuations in rotational speed due to fluctuations are significantly reduced. Therefore,
If the capstan motor of a video tape recorder is configured based on the present invention, the running speed of the magnetic tape can be controlled extremely accurately, and a high performance video tape recorder with less wow and flutter can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing an example of the built-in program of the compensator shown in FIG. 2, FIG. 2 is a block diagram showing the overall configuration of the embodiment of the present invention, and FIG. FIG. 4 is a block diagram showing a control block of an embodiment of the present invention;
Fig. 5 is a characteristic diagram showing an example of the characteristics of the frequency transfer function - H (jω) - Fig. 6 is a flow diagram showing another example of the built-in program of the compensator of the present invention, and Fig. 7 is a compensation diagram of the present invention. 8 is a flowchart showing another example of the built-in program of the device, FIG. 8 is a block diagram showing the configuration of the conventional example, FIG. 9 is a block diagram showing the control block of the conventional example, and FIG.
FIG. 0 is a characteristic diagram showing the control characteristic of the conventional example - G(jω). DESCRIPTION OF SYMBOLS 1... Motor, 2... Rotation sensor, 3... Speed detector, 4... Compensator, 5... Arithmetic unit, 6... Memory, 7... D/A converter, 8... Power amplifier,
10...Load.

Claims (1)

[Scope of Claims] 1. A rotation sensor 2 that generates an AC signal with a period corresponding to the rotation speed of the motor 1, and a speed detection means that performs detection multiple times per rotation of the motor 1 based on the AC signal of the rotation sensor 2. 3, a compensating means 4 that calculates and stores a control signal based on the detection signal of the speed detecting means 3, and a power amplifying means 8 that supplies the motor 1 with electric power according to the control signal of the compensating means 4. The compensation means 4 includes rotation error detection means 1A, 6A, 7A for obtaining rotation errors in response to the detection signal of the speed detection means 4, and NxL ordered rotation error detection means 1A, 6A, 7A (where Nx is 2 or more). digital value M[0] (integer, L is an integer greater than or equal to 4)
a memory means 6 for storing M[NxL−1] from
Composite value calculating means 1E, 6E, 7E for substantially calculating a composite value that is compositely calculated using Nx digital values spaced apart by L intervals in the memory means 6;
Then, the digital value of the memory means 6 is updated by an updated value corresponding to the value obtained by calculating and combining the composite value of the composite value calculating means 1E, 6E, 7E and the rotation error of the rotation error detecting means 1A, 6A, 7A. Update storage means 1D, 6D, 7D that update and save substantially in order
and control signal generating means 1C, 6C, 7C which generates the control signal by calculating and combining the composite value of the composite value calculating means 1E, 6E, 7E and the rotation error of the rotation error detecting means 1A, 6A, 7A . A motor speed control device comprising: 2. The composite value calculation means 1E, 6E, 7E calculate the digital value M[J-nL (mod NxL)] of the memory means 6.
(n = 1, 2, ..., Nx) (here, J is an integer) to calculate a composite value that substantially corresponds to the additive composite value. The speed control device for the motor described in Section 1. 3. Claim 1, characterized in that L is set to a value corresponding to an integral multiple of one rotation period of the motor 1.
The speed control device for the motor described in Section 1. 4. The update storage means 6D obtains an added value by adding the combined value of the combined value calculating means 6E and the rotational error of the rotational error detection means 6A , and multiplies each of the consecutive added values by a predetermined positive ratio. 2. The motor speed control device according to claim 1, wherein the value obtained by adding and combining the values is stored as a new updated value in the digital value of the memory means 6. 5 The first composite value of the composite value calculating means 6E, 7E used in the control signal generating means 6C, 7C is substantially the Nx digital values M of the memory means 6.
[J1−nL (mod NxL)] (n=1, 2,..., Nx)
(here, J1 is an integer) and used in the update storage means 6D, 7D, the second composite value of the composite value calculation means 6E, 7E is substantially the other Nx of the memory means 6 digital values M[J2
−nL(mod NxL)] (n=1, 2,...,Nx) (where J2 is an integer), and the integer J1
and J2 between J1=J2+Px(mod NxL) (here,
2. The motor speed control device according to claim 1, wherein Px is an integer greater than or equal to 1 and less than or equal to 5. 6 The composite value calculation means 7E calculates Nx digital values M[J−nL
(mod NxL)] (n=1,2,...,Nx) (here,
J is an integer) to obtain an added value, and further, a plurality of consecutive added values with respect to the integer J are multiplied by a predetermined positive ratio, respectively, and then added and combined to obtain a composite value. A motor speed control device according to claim 1.