JPS5854594B2 - direct drive motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in direct drive motors used in audio equipment.

More specifically, the present invention relates to improvements in direct drive motors whose speed is controlled by a speed proportional-integral control loop.

The object of the present invention is to provide a direct drive motor that uses a direct drive motor whose speed is controlled by a speed proportional-integral control loop and which improves hazyness in the low frequency range of sound reproduced by audio equipment and ambiguity in sound image localization. It is to provide.

According to the invention, this purpose is achieved by a direct drive motor (hereinafter referred to as
When the moment of inertia of a rotated object (referred to as DD motor in this specification), such as the turntable of a record player, is J, the gain of the speed integral control loop is Gl, and the gain of the speed proportional control loop is G2, - This is achieved by setting the detection limit below the 2π flutter frequency at which the detection limit is the lowest.

The present invention will be explained below.

As shown in the configuration diagram shown in FIG. 1, the DD motor includes a speed detector 1, a speed voltage conversion circuit 2, a comparator 3, an amplifier 4,
The speed is controlled by a servo system consisting of a speed proportional control loop consisting of a motor drive circuit 5 and a speed integral control loop consisting of a phase difference detection circuit 6 and a mixer 7.

Note that Sp is a reference signal, Sv is a reference voltage, and 8 is a DD motor.

The block diagram of the servo system shown in FIG. 1 is as shown in FIG. 2.

In Figure 2 S = jω JT=DD motor load torque V = Angular velocity of DD motor Kv=speed-voltage conversion gain φ = velocity-phase conversion gain τ = phase difference - voltage conversion gain Kt=Driving torque constant of DD motor A - gain of amplifier J = Moment of inertia of the rotated body ω〇−Reference angular frequency of reference signal It is.

The transfer function from load torque fluctuation to angular velocity fluctuation in this servo system is expressed by:

becomes.

This angular frequency ωp is a resonant angular frequency. Moreover, the Q value representing the sharpness of resonance is .

In addition, a servo system using a frequency difference detection circuit 9 and an integrator 10 as a speed integration control loop as shown in FIG. 3 instead of the speed integration loop consisting of the phase difference detection circuit 6 shown in FIG. It is used.

The block diagram of the servo system shown in Figure 3 is shown in Figure 4.
It will look like the figure.

In FIG. 4, Kf = speed-frequency conversion gain KD = frequency difference-voltage conversion gain τ = time constant of the integrating circuit, and S, J, Kt, Kv, and A are the second
The same elements as in the figure are shown.

In the block diagram shown in FIG. 4, the transfer function from the load torque fluctuation to the angular velocity fluctuation of this servo system is expressed as follows.

becomes.

This angular frequency ωp is a resonant angular frequency. Moreover, the Q value representing the sharpness of resonance is .

Generally, in a DD motor whose angular velocity is controlled by two types of closed loops, a velocity proportional control loop and a velocity integral control loop, between the load torque input and the angular velocity output, the transfer function from the load torque JT to the angular velocity fluctuation is It is shown in the form of

Therefore, it represents the angular frequency ωp and the sharpness of resonance.

Here, X, Y and Z are expressed by algebraic expressions including electrical and mechanical constants of the servo system, and x>o, y>o
, z>o.

■ Therefore, if we express the transfer function -1 angular frequency ωp by the gain G+ 'h of the speed integral control loop of the servo T system and the gain G of the speed proportional control loop, then in the servo system shown in Figure 2, G1- is τ・Kψ・K [・A ・・・・・・・・・
(10) Gt = Kv-Kt-A ・”
"""α1), and in the servo system shown in Figure 4, Gl = Kt-KD-K t・A/τ ・・・・・・・・・
... (12) G2 = Kv-K [・A ...
. . . (13), (1) Therefore, the transfer function - (T in equation 7), and the angular frequency ωp shown in equation (8) becomes.

Since ωp is the resonant angular frequency, the resonant frequency fp is becomes.

On the other hand, α and β are If you put it From equation (7), the transfer function is It is expressed as ■ , T+7) The absolute value is becomes.

(2) Therefore, if - is called the variation in angular velocity with respect to load, the angular frequency characteristic of T will be as shown in FIG. 5, which shows equation (22) as a curve.

As is clear from equation (22) and Figure 5, the maximum variation in angular velocity with respect to load occurs when ω = /aγ, and its value is -
, and when ω-α and ω=β, its value is σ=X/%
/2(α2+β2).

The condition that α and β are each real numbers is Y2-4Z≧0.
・(23), and if this condition is expressed in terms of control loop gains G1 and G2, it becomes 2 (-)2- 1 4-≧O (2), and control loop gain G1 The relationship between G and G2 is as follows: G; 4G, ≦-... (25).

Therefore, since Q≦0.5, the DD motor will not be under-braked, and the rotated body will not overshoot even in a step load transient response.

Here, the value on the left side of equation (25) may be smaller than or approximately equal to the value on the right side.

The above means that the coordinates rotating at a specified speed can be regarded as an inertial frame with respect to rotation, but the angular frequency characteristics shown in Figure 5 above are D
This shows that the D motor has a natural frequency due to the restoring force in the sense of a vibrating sieve, even if it is not under-braked.

Also, since the fluctuation of the load torque excites minute vibrations of rotation regarding the DD motor shaft in this inertial system,
Equation (22), that is, the characteristic shown in FIG. 5 represents the maximum angular velocity of this minute vibration.

Now, if the energy of vibration is W, then W = -J (angular velocity) 2 + (position energy)...
...(26), and the angular velocity is maximum when the positional energy is zero, and since it is expressed by the maximum angular velocity force equation 2, the vibrational energy is, and the vibrational energy W is the The result will be as shown in Figure 6.

Therefore, in a DD motor that adopts a speed proportional integral control loop, even if mechanical machining accuracy and other technical matters are ideally handled, a resonant frequency exists in the servo system and various frequency components are When a load torque is applied, among these frequency components, the frequency that matches the resonant frequency resonates, and angular velocity fluctuations are concentrated at this resonant frequency, and the vibration energy is also concentrated, eliminating angular velocity fluctuations. That is impossible.

By the way, the sound frequency of an audio device, for example, the signal frequency that is recorded as a signal on a recording medium when recording sound in a recording/playback device, and the signal frequency that is reproduced as sound during playback, is the same as that of a DD motor. Therefore, in an audio device using a DD motor whose speed is controlled by an angular velocity proportional-integral control loop, this variation in angular velocity with respect to the load is 7 easy.

Therefore, the amount of wah 7 rack has an angular frequency characteristic that is the same as or similar to the formulas (22) and (27), that is, FIGS. 5 and 6.

On the other hand, the detection limit for wow and flutter, that is, the amount of variation that humans can detect in the frequency variation of sound, is based on conventional measurement results.The horizontal axis represents the flutter frequency, and the vertical axis represents the detection limit % (Jf
/f) as shown in FIG.

(Journal of the Acoustical Society of Japan Vol. 29, No. 12, p. 766) In Figure 7, curves A, B, and C show the measurement results by different measurers, and a 1000 Hz pure tone was selected as the reference signal, and a sine wave fluctuation was selected as the fluctuation. It has been measured and the trends are almost the same.

Concerning the detection limit, (a), the wow 7 easy detection limit must have frequency characteristics.

(b) When the wow and flutter frequency is 1 to 5 Hz, it is detected with the smallest amount of variation.

←→, the value of (b) is a change of 0.1%, that is, 1000H
Even if the z signal changes in IHz, it can be detected.

), when the wow and flutter frequency approaches the signal frequency, the detection limit decreases rapidly.

The matters shown in (a), (b), ←→ and ii) regarding this detection limit are generally accepted.

Therefore, for the present invention, the resonant frequency of the DD motor is ``E''. The flutter frequency at which the detection limit is the lowest is 2π Set below the wave number.

For this reason, even when a load torque having a frequency component that resonates with the resonance frequency of the DD motor is applied, the frequency fluctuation of the reproduced sound caused by the speed fluctuation with respect to the load will not be detected.

Therefore, hazyness in the bass range and unclear sound image localization are improved.

Furthermore, for example, even if the amount of variation in wow and flutter in audio equipment is suppressed to 0.03%, when listening to the playback sound through the audio equipment, it will be affected by wow and flutter at least twice: during recording and during playback. Become.

When playing a record, it is affected by wow and flak at least four times: during recording, during cutting (twice), and during playback.

Therefore, the total wow and fluff characteristic is 0612% at the peak value (
1,00034).

This value is on the order of enough to be detected in terms of the detection limit characteristics shown in FIG.

Also, if the mixing work is repeated before cutting during record production, the peak value will be added to the amount of fluctuation by the number of times it has passed through the recording/playback machine, s, r.

The smaller the car, the heavier it will be.

In addition, in the measurement shown in Fig. 7, the reference signal was set at 1000Hz,
I chose a pure tone and a sine wave fluctuation for the fluctuation.

However, from the section (regarding the detection limit), for example, 100
If a sound with a frequency of Hz is selected as a reference signal and the detection limit is measured, the frequency characteristics shown in FIG. 7 may not necessarily be obtained.

If the reference signal is 100Hz and the signal receives a 0.05% fluctuation at a flutter frequency of 10Hz, it will be at point P shown by X in Figure 7 and should not be detected because it is below the detection limit. , regarding the detection limit).

However, human perception generally has the property that the slower the change, the less it can be detected, and if the resonant frequency of the DD motor is set to, for example, IHz2π or less, the amount of wow and flutter fluctuation will be around 0.1%. However, it is well below the detection limit and will not be detected.

As explained above, according to the present invention, when the moment of inertia of the rotated body of the DD motor is J, the gain G1 of the speed integral control loop of the speed control system, and the gain G of the speed proportional control loop 4.f', - - is set below the flutter frequency at which the detection limit is the lowest value of J, so that frequency fluctuations in the reproduced sound are not detected, and hazyness in the bass range and unclearness of the sound image are improved.

In addition, 4 is related to the gain of the speed integral control 2π J loop in the speed control system, that is, in a phase-locked loop, and setting the -1 layer below the frequency at which the detection limit is the lowest, 2π, is the phase-locked loop. This means that the gain may be small enough to suppress drift, which also has the effect of facilitating the design and manufacture of the phase-locked loop.

02' Furthermore, by setting 4G≦-, the DD motor will not be underbraked and the rotated body will not overshoot.

Note that the above explanation has been made assuming that the DD motor is a DC motor.

Even if the DD motor is an AC motor, as long as the speed control system is configured with a speed proportional integral control loop, the transfer function from load torque to angular velocity fluctuation is the same as in the case of a DC motor. It doesn't matter if there is.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a speed control system of a DD motor,
FIG. 2 is a block diagram of the speed control system shown in FIG. 1. FIG. 3 is a configuration diagram showing another example of a speed control system for a DD motor. FIG. 4 is a block diagram of the speed control system shown in FIG. 3. Figure 5 shows a DD having the speed control system of Figures 1 and 3.
Angular frequency characteristics of the motor's angular velocity variation with respect to load. Figure 6 shows a DD with the speed control system of Figures 1 and 3.
Angular frequency characteristics of motor vibration energy. Figure 7 shows the characteristics of flutter frequency versus detection limit. 1...Speed detector, 2...Speed voltage conversion circuit, 3.
...Comparator, 4...Amplifier, 5...Motor drive circuit, 6...Phase difference detection circuit, 7...Mixer, 8...
DD motor, 9... frequency difference detection circuit, 10... integrator.

Claims (1)

[Claims] Controlled by a speed proportional integral control system consisting of a speed integral control loop with a gain of 1 and a speed proportional control loop with a gain of G2,
3. A direct drive motor for driving a rotated body having a moment of inertia) J, the direct drive motor being characterized in that at least K is set to a flutter frequency of 2π or less at which the detection limit is the lowest. 2. The direct drive motor according to claim 1, characterized in that the flutter frequency at which the detection limit is the lowest is 1. 3. A speed integral control loop with a gain G1 and a speed proportional control loop with a gain G2. It is controlled by a speed proportional integral control system consisting of
In a direct drive type motor that drives a rotated object having a moment of inertia) J, -2π is set below the flutter frequency at which the detection limit is the lowest, and 4G, ≦-. 4. The direct drive motor according to claim 3, wherein the flutter frequency at which the detection limit is the lowest is 1.