JPS648544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a motor that has several set rotational speeds or is used by continuously changing the rotational speed. The aim is to maximize the control performance of the motor by automatically varying the loop gain, always obtaining the maximum possible loop gain at the set rotation speed, and obtaining the optimum tapping.

Generally, when designing a motor control system, the gain of the control loop is designed to be as large as possible in order to reduce the rotation speed fluctuation rate and speed up the response time to motor disturbances.
Usually, the maximum value of the gain of the control loop, or in other words, the maximum value of the possible cut-off frequency of the control system, is limited by the value of the output frequency of the frequency generator, which outputs a frequency proportional to the rotational speed of the motor. Ru. For example, in a motor control system that generally uses a sample-and-hold type speed discriminator, the maximum response frequency of the control system is approximately 1/12 to 1/20 of the output frequency of the frequency generator. It is considered to be a value.

For the above reasons, in order to always obtain the best control characteristics, it is necessary to vary the reference frequency, and each time the motor rotation speed setting is changed, the control loop gain corresponding to each rotation speed is adjusted. It is necessary to set the loop gain to a high control loop gain during high-speed rotation, and in order to switch the control loop gain at the same time as switching the reference frequency, and to maintain optimal damping, a filter is used to determine the phase margin at the gain intersection. It was also necessary to switch the corner frequency of the high frequency compensation filter (in the case of the present invention).

The present invention aims to provide a motor control device that eliminates the above-mentioned drawbacks, and when the reference frequency is varied to change the rotation speed of the motor, the loop gain of the control system is automatically adjusted according to the rotation speed. The aim is to always obtain the best control performance.

FIG. 1 is a main part block diagram showing one embodiment of the present invention. In the figure, 1 is a frequency signal that rotates disk 2 and is proportional to the number of rotations.
a motor equipped with a frequency generator 3 that generates _FG ;
A frequency dividing circuit 4 divides the output frequency of the oscillation circuit 5, and its output frequency _R becomes a reference frequency for the rotation of the motor 1. 6 is a phase comparison circuit that compares the reference frequency _R and the output frequency _FG of the frequency generator 3 to generate a phase error signal of the rotation of the motor 1; 7 is a phase comparison circuit that enhances the high-frequency component of the phase error signal (high-frequency phase ) This is a high-frequency compensation circuit for adding damping to the entire control system, and its corner frequency ₁ (the frequency at which the amplification degree begins to increase or the phase begins to advance) is equal to the output frequency _c of the oscillation circuit 5. It is varied proportionally, and at the same time, its amplification degree is also varied. That is, when the value of the output frequency _c of the oscillation circuit 5 is doubled, the corner frequency ₁ of the high-frequency compensation circuit 7 is doubled, and the amplification degree is also doubled.

8 is a low-pass filter for removing noise and ripple components contained in the output of the high-frequency compensation circuit 7, and its cutoff frequency _r is also varied in proportion to the reference frequency _c of the oscillation circuit 5. Reference numeral 9 denotes a drive circuit for amplifying the output voltage of the low-pass filter 8 and supplying current to the motor 1.

The motor 1, frequency generator 3, phase comparison circuit 6, high-frequency compensation circuit 7, and low-pass filter 8 described above
and the drive circuit 9 constitute a phase control loop, and the rotation of the motor 1 is controlled in proportion to the reference frequency _R.

Figures 2 and 3 show changes in the transfer characteristics of the high-frequency compensation circuit 7 when the reference frequency _R is varied and the rotational speed of the motor 1 is set to 1/2, and the control characteristics of the motor (rotation FIG.

In FIGS. 2 and 3, a corresponds to A and b corresponds to B. ₁ and ₁ ' are the corner frequencies of the high-frequency compensation circuit 7, and ₂ and ₂ ' are the cutoff frequencies of the system that occur when the loop of the control system is closed, and the geometric mean of ₁ and ₂ or ₁ ' and ₂ ' is indicates the response frequency (natural frequency) of the system.

In state A in Figure 3, in order to improve the control characteristics of the motor, the response frequency of the system, that is, the loop gain, is raised to a value close to its upper limit, for example, ₂ = _FG /12. Assuming that when you try to reduce the rotational speed of motor 1 to 1/2 by setting reference frequency _R to 1/2, if the loop gain is constant and does not change, the output frequency of frequency generator 3 and the control system cut-off The frequency ratio becomes six times half the limit value, and the operation of the control system becomes unstable.

Therefore, as shown in FIG. 2, by setting the characteristics of the high-frequency compensation circuit 7, that is, the gain of the slope portion and the corner frequency, both to 1/2, the cutoff frequency of the control system can be adjusted to B in FIG. 3. As shown, it can be lowered to 1/2. As a result, the ratio of the output frequency _FG ' of the frequency generator 3 to the cut-off frequency ₂ ' of the control system becomes 12 times, and the stability of the control system is maintained.

FIG. 4 is a diagram showing an example of the configuration of the high frequency compensation circuit 7 in which the amplification degree and the corner frequency are controlled depending on the frequency. In the figure, 11 is an electronic switch 11a composed of a field effect transistor (FET),
11b and capacitor 11c, the capacitance of capacitor 11c is
When C _p and the switching period are T, the equivalent resistance value R _p is expressed as R _p =T/C _p . Reference numeral 12 designates a switching pulse generating circuit which uses the output frequency _c of the oscillation circuit 5 as an input and causes the electronic switches 11a and 11b to alternately and repeatedly perform switching operations at a period T (T=1/2π _c ). Figure 5 shows a time chart of the output pulses φ ₁ and φ ₂ .

13 is an operational amplifier, which has a feedback resistor 1 with a resistance value R _f.
Since it has 4, switched capacitor 1
1. The amplification degree G _p of the inverting amplifier circuit composed of the resistor 14 and the operational amplifier 13 is as follows: G _p = R _f /R _p = C _p・R _f /T=2π・_c・C _p・R _f It can be seen that the output frequency _c of the oscillation circuit 5 changes in proportion to the output frequency c.

15 is the same as the switched capacitor 11,
Electronic switches 15a, 15b and capacitor 15c
When the capacitance of the capacitor 15c is _C1 , the equivalent resistance value _R1 is expressed as _R1 =T/ _C1 . 16 is capacity
The differential capacitor 17 of C ₂ is an operational amplifier having an oscillation prevention capacitor 18 and a resistor 19 with a resistance value R _d as feedback elements.

Switched capacitor 15, capacitor 1
6, 18, resistor 19, and operational amplifier 17 constitute a high-frequency enhancement circuit (phase lead circuit), and if the influence of capacitor 18 is ignored, its transfer function (S)
is (S)=R _d /R ₁ (1+C ₂・R ₁・S) =C ₁・R _d /T (1+C ₂ /C ₁ +S), and the corner frequency ₁ of this circuit is ₁ =C ₁ /C ₂ ·T×1/2π= _c ·C ₁ /C ₂ The corner frequency ₁ also changes in proportion to the output frequency _c of the oscillation circuit 5.

FIG. 6 is a diagram showing the characteristics of the high-frequency compensation circuit 7 shown in FIG. 4. When the output frequency _c of the oscillation circuit 5 is set to 1/2, the corner frequency varies from ₁ to ₁ ' (= _1/2 ). An example is shown in which the value is changed to 1/2. _H is the frequency determined by the anti-oscillation capacitor 18, typically ₁
It is set far away from

As explained above, the high frequency compensation circuit 7 in FIG.
is composed of an inverting amplifier circuit controlled by frequency and a high-frequency amplification circuit, so its overall characteristics are as shown in Figure 2, where the amplification degree of the slope part and the corner frequency are It can be seen that they are controlled simultaneously.

FIG. 7 is a diagram showing another configuration example of the high-frequency compensation circuit 7, in which the oscillation prevention capacitor 18 in FIG. 4 is removed and a resistor 21 is inserted in series with the differential capacitor 16 instead. With this, characteristics similar to those shown in FIG. 6 can be obtained.

In FIG. 8, the resistor 21 in FIG. 7 is replaced with a switched capacitor 31 consisting of electronic switches 31a, 31b and a capacitor 31c, and the switched capacitors 15 and 31 can be driven with the same switching pulse. Therefore, the frequency _H , which was fixed in the explanation of FIG. 6, can also be controlled at the same time. As a result, the corner frequency can be varied while keeping the ratio of ₁ and _H constant. By setting the ratio of ₁ and _H to about 10 times, high-frequency oscillation can be achieved. Of course, prevention is
More stable control can be achieved by suppressing the high-frequency loop gain to an appropriate value (lowering the high-frequency gain while maintaining the amount of phase advance that provides appropriate damping).

FIG. 9a shows an example of the configuration of a low-pass filter 8 whose cutoff frequency is controlled by frequency. In the figure, 41 is an electronic switch 41
42 is a switched capacitor composed of electronic switches 42a, 42b and a capacitor 42c;
3 and 44 and the operational amplifier 45 constitute a second-order positive feedback filter. Switched Capacitor 4
1 and 42 are switched by the switching pulse generation circuit 12 used in the explanation of FIG. 4, and have an equivalent resistance value proportional to the switching period. 9th
Figure b is an equivalent circuit of figure a. Since the equivalent resistances 41' and 42' of the switched capacitors are inversely proportional to the switching frequency, the cutoff frequency of this secondary low-pass filter is varied in proportion to the switching frequency.

As described above, the motor control device of the present invention has
The gain of the control loop, the corner frequency of the high-frequency compensation filter, and the cut-off frequency of the low-pass filter can all be changed simultaneously in proportion to the motor reference frequency, that is, the rotational speed.

In other words, at any set rotation speed,
Since the relationship (frequency ratio) among the output frequency of the frequency generator, the gain intersection frequency of the control loop, the corner frequency of the high-frequency compensation filter, and the cut-off frequency of the low-pass filter can be kept constant, the control loop's The phase margin at the gain intersection can be set to a constant value, so that the optimum damping value is always maintained and stable performance can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of main parts showing an embodiment of the present invention, Fig. 2 is a characteristic diagram of the high frequency compensation circuit, Fig. 3 is a diagram showing the control characteristics of the motor, and Fig. 4 is a diagram of the high frequency compensation circuit. Figure 5 is a time chart of the output pulse of the switching pulse generation circuit, Figure 6 is a characteristic diagram of the high frequency compensation circuit of Figure 4, and Figures 7 and 8 are diagrams of the high frequency compensation circuit. Other configuration example diagrams, Figure 9a,
b is a configuration example of a low-pass filter and its equivalent circuit diagram. 1... Motor, 3... Frequency generator, 4... Frequency dividing circuit, 5... Oscillation circuit, 6... Phase comparison circuit,
7...High frequency compensation circuit, 8...Low pass filter,
9... Drive circuit, 11, 15, 31, 41, 42
...Switched Capacita.

Claims (1)

[Claims] 1. A motor equipped with a frequency generator that generates a frequency signal according to the number of rotations, and a phase comparison that compares a reference frequency signal with an output frequency signal of the frequency generator and outputs a phase error signal. means, high-frequency compensation means for amplifying the output signal of the phase comparison means and advancing the phase of high frequency components included in the output signal, and ripples included in the output signal of the high-frequency compensation means. a motor phase control loop including a filter means for removing the component, and a drive means for amplifying the output voltage of the filter means and supplying a drive current to the motor, and the high frequency compensation The means includes a variable amplifier whose amplification degree is controlled by an external control signal, and a high-pass filter whose corner frequency is controlled by an external control signal, and the high-frequency compensation means A motor control device characterized in that control is performed using a frequency signal proportional to the number of rotations of the motor. 2. According to claim 1, the corner frequency and amplification degree of the high-frequency compensation means are controlled by a frequency signal having a frequency that is an integral multiple of the reference frequency signal. Motor control device. 3. In the statement of claim 1 or 2, the reference frequency signal is obtained by dividing the output frequency signal of an oscillator, and the output frequency signal of the oscillator is used to obtain the reference frequency signal of the high frequency compensation means. A motor control device characterized by controlling a corner frequency and amplification degree. 4. In the statement of claim 1 or 2, the reference frequency signal is obtained by dividing an output frequency signal of an oscillator, and the output frequency signal of the oscillator is used to obtain the reference frequency signal of the high frequency compensation means. A motor control device characterized in that the cut-off frequency of the filter means is controlled as well as the corner frequency and the amplification degree. 5. In the statement of claim 1 or 2, the high-frequency compensation means comprises an inverting amplifier whose input element is an equivalent resistance formed by a switched capacitor, and an equivalent resistance formed by the switched capacitor. 1. A motor control device comprising an inverting amplifier whose input element is a parallel element of a capacitor and a capacitor. 6. In the statement of claim 1 or 2, the high frequency compensation means is an inverting amplifier whose input element is an equivalent resistance composed of a switched capacitor, and a series element of a capacitor and a resistor is composed of a switched amplifier. 1. A motor control device comprising: an inverting amplifier whose input element is a composite element configured in parallel with an equivalent resistance constituted by a capacitor. 7. In the statement of claim 1 or 2, the high-frequency compensation means is an inverting amplifier whose input element is an equivalent resistance made of a switched capacitor, and an equivalent resistance made of a switched capacitor. A motor control device comprising an inverting amplifier whose input element is a composite element constructed by connecting a series element of a capacitor and a capacitor in parallel with an equivalent resistance composed of another switched capacitor. 8. A motor control device according to claim 1 or 2, characterized in that the resistor constituting the filter means is an equivalent resistor composed of a switched capacitor.