JPS6217952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor control device that connects a motor and a load and eliminates shaft resonance.

First, FIG. 1, which is an example of a conventional speed control system, will be described.

The basic device is a device that performs speed control of 10 by converting the power source power into the power necessary to control the electric motor 10 using a converter 8.

1 is a speed setting adjustment resistor, and a speed reference voltage is input to the next stage via resistor 2. 5 is an operational amplifier for speed control. 3 is a calculation capacitor, and 4 is a calculation resistor. The difference between the speed reference signal input through 2 and the speed feedback signal input through resistor 6 is amplified by 5, and the output is used as a current reference (or torque reference) in the current control circuit of the next stage. 7 is input. The difference between the current reference signal and the current feedback signal inputted from the current detection circuit 12 is amplified by 7, and the output thereof is inputted to 8. The speed of 10 is controlled by 8, but a current detector 9 is inserted between them, and the output of 9 is input to 12. A tachometer generator 11 is directly connected to 10, the output of which is input to a speed detection circuit 13, and the output of 13 is input to 5 via 6.

In the conventional speed control device as shown in FIG. 1, the frequency response characteristic of the open loop transfer function for speed control is designed as shown in FIG. In the figure, ω _C is the response frequency of speed control. When the capacitance of the capacitor 3 is C ₃ and the value of the resistor 4 is R ₄ , ω _N =1/C ₃ R ₄ , and ω is the response frequency of the minor current control loop.

However, when driving a load with the device shown in Figure 1,
Shaft resonance frequency ω due to motor inertia and load inertia
When the values of _r and antiresonance frequency ω _ar are close, the gain of speed control increases at a rate of 40 db/dec between ω _ar and ω _r , so the frequency response characteristic of the open-loop transfer function of speed control becomes It may look like the one shown in Figure 3. Third
The speed control system as shown in the figure is in a state of vibration, and it is difficult to stabilize it just by adjusting the gain.

In order to stabilize the conventional speed control system as shown in Fig. 3, C ₃ is increased, the ω _N point is shifted to the lower frequency side, and the speed control loop gain is greatly reduced to increase the speed. The frequency response of the control system was as shown in Figure 4. However, the system shown in FIG. 4 has drawbacks such as a slower speed response and the occurrence of overshoot than the system shown in FIG.

Therefore, an object of the present invention is to provide a variable speed control device for an electric motor, in which the original response frequency of the speed control system is prevented from changing due to the influence of the resonance frequency of the load drive shaft, and a response frequency according to the designed value can be obtained. The goal is to provide equipment.

FIG. 5 shows an example of the configuration of the present invention.

A calculation capacitor 21, a calculation resistor 22, feedback circuit resistors 23, 24, and a feedback circuit capacitor 25 are added to FIG. All additional items are for reducing the speed control loop gain between the anti-resonant and resonant frequencies between the motor and the load.

The operation of the present invention will be explained below.

In Figure 2, the capacitance of capacitors 21 and 25 is C ₂₁ ,
C ₂₅ , the values of resistors 6, 22, 23, 24 are R ₆ ,
Let R ₂₂ , R ₂₃ , and R ₂₄ .

21,2 so that the first and second equations are satisfied.
Select values 2, 23, 24, and 25 to construct Figure 2.

ω _ar =C ₃ +C ₂₁ /C ₃・C ₂₁・R ₄ +C ₃・C
₂₁・R ₂₂ =1/C ₃₅・R ₂₄ …(1) ω _r =1/C ₂₁・R ₂₂ =R ₆ +R ₂₃ /C ₂₅・
R ₂₃・R ₂₄ ...(2) From the above, the round transfer function of speed control is ω _ar and ω
The gain is reduced at a rate of 40db/dec between _r and corrects the effects of axial resonance. Therefore, the frequency response of the open loop transfer function of speed control becomes as shown in FIGS. 3 to 6, and the response of speed control can be stabilized.

If the shaft resonance frequency between the motor and the load is low and approaches the response frequency of minor current control,
After the correction circuit shown in FIG. 5 is activated, the frequency response of the speed control loop transfer function is as shown in FIG. 7. 7th
The response of the speed control system in the figure is still oscillatory.

In this case, if the response frequency of the minor current control shown in FIG. 5 is increased, the frequency response of the open loop transfer function of the speed control becomes as shown in FIG. 8. The response of the speed control system in FIG. 8 is stable.

In addition, the speed control loop gain is set between ω _ar and ω _r .
The correction circuit that reduces the power at a rate of 40 db/dec is not limited to the above-mentioned embodiment, and can be implemented with various modifications.

As described above, when a speed control system becomes unstable, it has conventionally been attempted to stabilize it by changing the response frequency of the speed control, but according to the present invention, the response of the speed control can be reduced. Further stabilization can be achieved without

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional motor control device.
Figure 2 is an ideal frequency response characteristic diagram of the speed control loop open-loop transfer function in the device shown in Figure 1;
Figure 1 is a frequency response characteristic diagram when the device is affected by axial resonance, Figure 4 is a conventional characteristic diagram that is an improvement over the frequency response diagram in Figure 3, and Figure 5 is a characteristic diagram of the present invention. A block diagram showing an embodiment and FIGS. 6 to 8 are frequency response characteristic diagrams for explaining the present invention. 1... Adjustment resistor, 2, 4, 6, 22, 23, 2
4...Resistor, 3,21,25...Capacitor, 5...
Operational amplifier, 7... Current control circuit, 8... Converter, 9
...Current detector, 10...Electric motor, 11...Tachometer generator, 12...Current detection circuit, 13...Speed detection circuit.

Claims (1)

[Scope of Claims] 1. In a motor control device having a current control loop in a minor loop of the speed control loop, a series circuit including a capacitor and a resistor is provided in parallel to the speed control circuit provided in the speed control loop, and By providing a speed feedback signal to be fed back to the speed control circuit through a feedback impedance connected in parallel with a delay circuit, a speed control loop is created between the anti-resonance frequency and the resonant frequency of the shaft connecting the motor and the load. A motor control device characterized by being able to reduce gain at a rate of 40db/dec. 2. In a motor control device having a current control loop in a minor loop of the speed control loop, a series circuit consisting of a capacitor and a resistor is provided in parallel to the speed control circuit provided in the speed control loop, and the circuit is fed back to the speed control circuit. By giving the speed feedback signal through the feedback impedance connected in parallel with the delay circuit, the speed control loop gain is set at a rate of 40 db/dec from the anti-resonant frequency to the resonant frequency of the shaft connecting the motor and the load. and increase the current control response when the response frequency of the current control loop is equal to or lower than the resonance frequency of the load drive shaft in the current control circuit provided in the current control loop. A motor control device characterized in that it is provided with a current control response frequency variable circuit that can perform the following.