JPH01291683A - Method of controlling speed of motor - Google Patents

Abstract

PURPOSE:To suppress a speed variation width and setting time in the sudden change of disturbance torque by switching a speed regulation loop to a proportional operational action when the rate of change of the disturbance torque outputted from an observer gets to the one of not less than the predetermined value and by returning the speed regulation loop to a proportional plus integral operational action when the speed deviation is reduced within a constant value. CONSTITUTION:A speed regulation circuit 30 performs proportional plus integral operation on the deviation between a speed command value N* and a speed actual value N. A current regulation circuit 9 outputs the deviation between the current command value and the current actual value I to a phase regulation circuit 10. On the other hand, an observer 31 estimates the disturbance torque based on the speed actual value N and the current actual value I and adds it to the output of a speed regulation circuit 6. A switching circuit 34 acts proportional operation and when the speed deviation gets to the one within the constant value, it returns to proportional plus integral operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a speed control method for an electric motor that can control the speed of an electric motor at high speed by using an observer.

[Conventional technology]

FIG. 4 is a control block diagram showing a conventional example of controlling the speed of an electric motor using an observer.

In FIG. 4, electric power for driving an electric motor 1 is supplied from a power source 20 via a power conversion device 2, and a speed adjustment loop is provided to control the speed of this electric motor 1. That is, a speed detector 3 connected to the motor 1 outputs the actual speed value N of this motor 1, while a speed setting device 5 outputs the speed command 4a of this motor 1.
N'' is set, so the deviation between this speed command value N9 and the actual speed 41N is input to the speed adjustment circuit 6, which is composed of a proportional-integral calculator, and the input deviation is made zero. The speed control loop operates.

Furthermore, a current command value is obtained by dividing the output of this speed adjustment circuit 6 by the motor magnetic flux Φ in a divider 7,
The deviation between the actual current value (■) of the motor l detected by the current detector 4 and this current command value is input to the current adjustment circuit 9 which is composed of a proportional-integral calculator, and from this current adjustment circuit 9, This current regulation loop operates to derive a control signal that makes the manual deviation zero. Therefore, the current adjustment circuit 9
The output is supplied to the power conversion device 2 via the phase adjustment circuit 10.

As mentioned above, when controlling the speed of the electric motor 1, it is common to provide a speed adjustment loop and a current adjustment loop as a minor loop inside this speed adjustment loop. If the response time of the speed regulation loop is
It is necessary to set a value several times longer than the response time of this current regulation loop.

For example, in the case of an electric motor that drives a rolling mill, the speed control loop, like the upper body, has a long response time, so it is necessary to quickly respond to speed fluctuations caused by sudden changes in torque when rolling material is bitten into the rolls. This has the disadvantage that speed fluctuations become large.

Therefore, an observer 11 is provided that constantly monitors the actual speed value N and the actual current value I of the motor 1 and estimates the disturbance torque from these two values, and the value obtained by this observer 11 is used to adjust the speed as described above. By adding the output of the circuit 6 (the output of the divider 7 in the conventional circuit shown in FIG. 4) to obtain the current command value, and giving the thus corrected current command value to the current adjustment loop, the disturbance torque can be reduced. The aim is to improve responsiveness to sudden changes and minimize speed fluctuations.

FIG. 5 is a control block diagram showing the inside of the observer 11 shown in the conventional circuit of FIG.

As shown in FIG. 5, the observer 11 is connected to the integrator 1
2 and 16, a multiplier 13, proportional gains 14 and 15, and a divider 17, and inputs the actual speed value N and the actual current value ■ of the electric motor ii. As a result, the signal A corresponding to the current change corresponding to the estimated disturbance torque value output from the observer 11 is added to the current command value given to the current adjustment loop as described above. This compensates for the response delay of the speed control loop.

[Problem to be solved by the invention]

As mentioned above, in a speed control device for an electric motor having a current regulation loop as a minor loop, the response time of the speed regulation loop must be set to a value longer than that of the current regulation loop, and this long response time causes Although large speed fluctuations are covered by the use of the observer 11 that estimates disturbance torque, the torque still exceeds 2. When the actual speed value changes to the same value as the speed command value, the overshoot becomes large and it takes a long time for the speed fluctuation to stabilize.

FIG. 6 is a time cisade showing the speed fluctuation when the disturbance torque suddenly changes in the conventional example circuit (with observer II) shown in FIG. are doing.

As is clear from Fig. 6, in the case of the conventional circuit, there is a large amount of overshoot in which the speed that drops due to a sudden change in disturbance torque jumps in the opposite direction, and it takes until this speed fluctuation stabilizes to zero. .2 seconds is required.

Therefore, an object of the present invention is to suppress overshoot when the motor returns to speed and shorten the speed stabilization time when the torque of an electric motor equipped with a speed control system in which the current adjustment loop is a minor loop suddenly changes. The purpose is to do so.

(Means for Solving the Problems) In order to achieve the above object, the speed control method of the present invention includes a speed control loop that controls the deviation between the speed command value and the actual speed value of the electric motor to zero; The speed of this electric motor is controlled by a current adjustment loop that controls the deviation between the output signal of the speed adjustment loop and the actual current value of the motor to zero, and the actual speed value and the actual current value are input to In the speed control operation of the electric motor, which includes an observer for estimating disturbance torque of the electric motor, and adds a signal output from the observer to an output signal of the speed adjustment loop,
The rate of change signal of the disturbance torque is taken out from the observer, and when this value is greater than a predetermined value, the njl speed change speed adjustment loop example switches from integral calculation operation to proportional calculation operation, and calculates the difference between the speed command value and the actual speed value. If the difference decreases to within a certain value, the speed adjustment loop is returned from proportional calculation operation to proportional integral calculation operation.

[Effect]

In conventional motor speed control devices with an observer, the integral calculator of the speed adjustment circuit used to compensate for speed deviations integrates the speed deviation due to speed fluctuations when the disturbance torque changes. This speeds up the recovery time after the speed fluctuation, but since the integral amount is released after the speed fluctuation has recovered, the speed overshoot in the opposite direction becomes large and the settling time becomes longer. Therefore, this invention focuses on this point, and during normal speed control, the proportional product numerator 4
During the period after the disturbance torque suddenly changes and the motor speed fluctuates, until the speed deviation returns to within a certain value again, the speed adjustment circuit that performs calculations operates only on proportional calculations. By switching in this manner, the speed change width and settling time when the disturbance torque suddenly changes are suppressed.

〔Example〕

FIG. 1 is a control block diagram showing an embodiment of the present invention.

In FIG. 1, electric power from an electric power a20 is passed through a power conversion device 2 to an electric power 1! A1 is applied to drive this electric motor 1, and for speed control, the deviation between the actual speed value N from the speed detector 3 and the speed command value N''' from the speed setter 5 is controlled to zero. A current adjustment circuit 9 that controls the deviation between the output of the speed adjustment circuit 30 and the actual current value from the current detector 4 to zero. The provision of the loop is the same as in the case of the conventional example circuit described in FIG. , and a phase adjustment circuit 10 which receives the output of the current adjustment circuit 9 and outputs a firing phase signal for the power converter 2, as in the case of the conventional circuit shown in FIG.

The fourth feature of the speed adjustment circuit 30 used in the present invention is that it can switch between proportional-integral calculation operation and proportional calculation operation.
This is different from the speed adjustment circuit 6 used in the conventional circuit shown in the figure.

Furthermore, the observer 31 used in the present invention is different from the observer 11 used in the conventional circuit shown in FIG. 4 in that it can output a signal corresponding to the estimated disturbance torque value B.

Furthermore, in the embodiment circuit shown in FIG.
A rate-of-change detection circuit 32 determines whether the rate of change of the estimated disturbance torque signal B outputted by A speed deviation detection circuit 33 that determines whether or not the speed deviation detection circuit 33
A switching circuit 34 is installed which inputs a signal from the controller and instructs the speed adjustment circuit 30 to switch the calculation operation.

FIG. 2 shows a control block diagram showing the inside of the observer 31 used in the embodiment circuit shown in FIG.

The observer 3 shown in FIG. 2 is composed of integrators 12 and 1
6. It is composed of a multiplier 13, proportional gains 14 and 15, and a divider 17, and inputs the actual speed value N of the electric current 'jJ+JAl and the actual current value ■, and generates a signal A corresponding to the current rate of change. This is the same as the observer 11 used in the conventional circuits shown in FIGS. 4 and 5, but this observer 31 outputs the signal B corresponding to the estimated disturbance torque value to the change rate detection circuit 32. What is output to is different from that of the conventional example.

The speed control operation of the present invention using the embodiment circuit shown in FIGS. 1 and 2 is as follows. In other words, when the actual motor speed value N begins to change drastically due to a large disturbance torque, such as when material is caught in a rolling roll, the actual speed value N and the actual current value I are input. The observer 31 changes the output signal B by estimating that the disturbance torque has suddenly changed.

When the change rate detection circuit 32 detects that the change rate of the disturbance torque quasi-plantation exceeds a predetermined value, it outputs a signal C to the switching circuit 34 to set the change rate. The switching circuit 34 maintains this set state and sends E to the speed adjustment circuit 30.
Since the calculation switching signal is sent out, the speed #M node circuit 3
From this point on, the proportional-integral calculation operation is switched to the proportional calculation operation.

After this, these speed 1! Nodal circuit 30 and observer 3
As a result of the speed control operation according to step 1, the speed fluctuation of the electric motor l has recovered, the actual speed value N approaches the speed command value N'', and the speed deviation detection circuit 33 detects that the deviation between the two has become within a certain value. When detected, the aforementioned switching circuit 34 is reset by the signal output from the speed deviation detection circuit 33. By resetting the switching circuit 34, the speed adjustment circuit 30 returns from the proportional calculation operation to the proportional integral calculation operation.

FIG. 3 is a time chart showing speed fluctuations when the disturbance torque changes in the embodiment circuit shown in FIG. 1, in which the horizontal axis represents time (in seconds) and the vertical axis represents speed deviation.

As is clear from FIG. 3, by applying the circuit according to the embodiment of the present invention, the jump in the opposite direction when the speed drops due to a sudden change in disturbance torque recovers is very small, and therefore, this speed fluctuation The time it takes to settle is also 0.1
The time required is approximately 50 seconds, which is half that of the conventional example (see Fig. 6).

Note that in the embodiment circuit shown in FIG. 1, the speed adjustment circuit 30 is switched to the proportional calculation operation according to a change in the rate of change of the disturbance torque, but it is also possible to perform the switching operation according to a change in the level of the disturbance torque. Of course.

(Effects of the Invention) According to the present invention, since the speed control circuit normally controls the motor speed by proportional-integral calculation operation, the responsiveness when changing the speed command value is improved, and the observer's estimation error The speed deviation caused by can be compensated for.

When the disturbance torque changes greatly and the speed fluctuation becomes large, the speed tJ4 node circuit described above switches to proportional calculation operation until the deviation between the speed command value and the actual speed value is reduced to within a certain range. This has the effect of suppressing the speed change range to a small value when recovering the speed in the event of a sudden torque change, and shortening the time until the actual speed value stabilizes (1).

[Brief explanation of the drawing]

FIG. 1 is a control block diagram showing an embodiment of the present invention;
Fig. 2 is a control block diagram showing the configuration of the observer used in the embodiment circuit shown in Fig. 1, and Fig. 3 shows speed fluctuations when disturbance torque suddenly changes in the embodiment circuit shown in Fig. 1. Fig. 4 is a control block diagram showing a conventional example of controlling the speed of an electric motor using an observer, and Fig. 5 shows the configuration of the observer shown in the conventional example circuit of Fig. 4. FIG. 6 is a time chart showing the speed fluctuation when the disturbance torque changes by 2 degrees in the conventional circuit shown in FIG. 4. DESCRIPTION OF SYMBOLS 1... Electric motor, 2... Power converter, 3... Speed detector, 4... Current detector, 5... Speed setter, 6
, 3o... Speed adjustment circuit, 7, 17... Divider, 9...
... Current adjustment circuit, 10... Phase adjustment circuit, II,
31... Observer, 12°16... Integrator, 13
... Multiplier, 14.15 ... Proportional gain, 20...
- Power supply, 32... Rate of change detection circuit, 33... Speed deviation detection circuit, 34... Switching circuit. 3171 Server name 2 Figure b 5 Figure 6

Claims (1)

[Claims] 1) A speed adjustment loop that controls the deviation between the speed command value and the actual speed value of the motor to zero, and a current adjustment loop that controls the deviation between the output signal of this speed adjustment loop and the actual current value of the motor to zero. The speed control loop controls the speed of the electric motor, and includes an observer that inputs the actual speed value and the actual current value to estimate the disturbance torque of the electric motor, and uses the signal output by the observer as the output signal of the speed control loop. In the motor speed control method, a change rate signal of disturbance torque is extracted from the observer, and when this value is equal to or greater than a predetermined value, the speed adjustment loop is switched from proportional-integral calculation operation to proportional calculation operation, and the speed A method for controlling the speed of an electric motor, characterized in that when the difference between the command value and the actual speed value decreases to within a certain value, the speed control loop is returned from proportional calculation operation to proportional integral calculation operation.