JPH02219485A - Rotational speed controller for motor - Google Patents

Abstract

PURPOSE:To reduce the impact drop of a rotational speed by obtaining a speed difference on the basis of a rotational speed signal, by obtaining an estimated load torque on the basis of said speed difference and by controlling an armature current corresponding to a load torque on the basis of said estimated load torque and a rotational speed detection signal. CONSTITUTION:A speed difference is calculated within a digital Ward-Leonard circuit 12. Also, the high frequency of a speed difference signal is cut by the low-pass filter 13 of an analog load torque estimation circuit 10A and further a load torque is estimated and operated by a second generated torque computer part 1b, a rotational inertia computer part 5 and a second adder-subtracter part 2b. Moreover, when an armature current corresponding to an estimated load torque obtained from said load torque estimation circuit 10A is caused to flow excessively through a current control minor loop 16 composed of a current computer part 14 inputting said estimated load torque and a current gain regulator part 15, the effect of a load torque TL as a disturbance can be made smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a control device for an electric motor, and particularly to a rotational speed control device for an electric motor that reduces sudden decreases in the rotational speed (impact drop) of the electric motor. Regarding.

B0 Summary of the Invention The present invention obtains the generated torque of an electric motor based on the armature current and torque constant, obtains the acceleration torque based on the generated torque and load torque, and generates a rotation speed signal based on the acceleration torque and rotational inertia. and the rotation speed is controlled by estimating the load torque based on the rotation speed signal and the generated torque, the rotation speed signal is detected, and the rotation speed detection signal and the rotation speed command signal are By providing a major loop that obtains an armature current command signal based on the above-mentioned load torque, and a minor loop that obtains a current signal based on the estimated load torque and adds or subtracts this current signal to the armature current command signal, the rotation speed can be adjusted. To obtain a rotation speed control device for an electric motor that can significantly reduce impact drop.

C1 Conventional Technology In a control system including an electric motor that can be controlled at variable speed, when the rotational speed of the electric motor is held constant, fluctuations in load torque become a disturbance. Therefore, various proposals have been made for a rotational speed control device for an electric motor that estimates the load torque and performs predetermined control processing based on this estimated value to reduce the impact drop in the rotational speed.

D1 Problems to be Solved by the Invention Fig. 4 shows an example of the position of the load torque estimating means in a conventional motor rotation speed control device, where la is the armature current 1a.
Input the torque constant K. Based on the motor generated torque τ
8 is the generated torque calculation unit, 2a is the generated torque calculation unit! A first addition/subtraction unit adds and subtracts the motor generated torque τ14S load torque τ calculated by a to obtain the acceleration torque τ6, and 3a inputs the acceleration torque τa and calculates the rotational inertia TM.
and the differential element S, the reciprocal of the product Tm・S 1/T M・S
a speed calculation unit that calculates a speed signal N using the transfer function;
is an accelerometer that differentiates the velocity signal N and outputs an acceleration signal N−S. 5 is a rotational inertia calculation unit that receives the acceleration signal N-S as an input and calculates the signal TM・S-N using the rotational inertia T as a transfer function, and tb is an electric motor that receives the armature current ■a as an input and uses the torque constant KT as a transfer function. A second generated torque calculation unit that obtains the generated torque τ8, 2b is the generated torque signal τ9
and a second subtraction section that adds and subtracts the output signal 71'M/S-N of the rotational inertia calculation section 5, which includes the second generated torque calculation section 1b, the second addition/subtraction section 2b, and the rotational inertia calculation section. 5 constitutes a load torque estimating circuit 6.

Here, the measurable quantities are only the armature current 1a and the rotational speed N, and the following equation is used to calculate the load torque from these armature current 1a and rotational speed N.

* r L-rs-r a-KT-1a-TM・S
-N In other words, if the torque constant TH and rotational inertia TM are known, the load can be calculated from the armature current 1a and the rotational speed N.
* It is possible to find the ruku τ. Here, L is the estimated torque.

To estimate the negative torque, an accelerometer 4 is attached to the motor shaft to directly detect the speed. However, at present,
Accelerometer 4 is unsatisfactory in terms of performance and price.

Furthermore, as shown in FIG. 5, the load torque can be estimated as described above by adding a differentiator 7 to the load torque estimating circuit 6 and differentiating the speed signal.
It is difficult to provide the differentiator 7 with an appropriate high frequency range.

Furthermore, as shown in FIG. 6, it is also conceivable to calculate the estimated load torque τ 1 using the observer circuit * and feed back this estimated load torque to reduce the impact drop in the rotational speed. That is, as shown in FIG. 6, the generated torque calculation section 1b, the second addition/subtraction section 2b, the third addition/subtraction section 2c, the first gain adjustment section 8, and the second gain adjustment section 9 in FIG. An observer circuit IO is configured to adjust the load torque. However, when considering that the observer circuit is constructed with analog circuits such as operational amplifiers, the gains gr and gt in the figure are extremely large (several 10
(about 0 is required), which is not realistic.

The present invention has been made in view of the above-mentioned problems, and its purpose is to obtain a speed difference based on a rotational speed signal, use this speed difference to obtain an estimated load torque, and combine this estimated load torque with the rotational speed. An object of the present invention is to provide a high-performance motor rotation speed control device that can reduce impact drop by controlling an armature current corresponding to load torque based on a detection signal.

81 Means for Solving the Problems In order to achieve the above-mentioned object, the present invention takes the armature current of the motor as input, calculates the generated torque of the electric motor using the torque constant as a transfer function, and calculates the generated torque and the load torque. A rotation speed signal calculation means for adding and subtracting to obtain acceleration torque and calculating a rotation speed signal of the electric motor by using the acceleration torque as a transfer function of rotational inertia; speed difference calculation means for calculating a speed difference signal as a digital value based on the speed detection value; load torque estimating means for calculating an estimated load torque of the electric motor by adding and subtracting the generated torque signal;
a measure loop means for obtaining an armature current command signal based on the speed detection signal and the motor speed command signal, which is obtained by inputting the speed signal obtained by the rotational speed calculation means; and the load torque A rotation speed control device is constructed in which an impact drop in rotation speed is reduced by a minor loop means that obtains a current signal by using an estimated torque signal obtained by an estimation means as a transfer function of a torque constant, and adds or subtracts this current signal to an electric machine current command signal. do.

The speed difference is calculated digitally by calculating ((current scan speed detection value) - (previous scan speed detection value)) using the F1 action gain Tal Leonard circuit.

Further, an analog load torque estimating circuit performs a high frequency cut of the speed difference signal and performs a load torque estimation calculation to calculate the estimated load torque. Further, a major loop detects the rotation speed of the motor to obtain a rotation speed detection signal, a motor current command signal is obtained based on the rotation speed detection signal and the rotation speed command signal, and a minor loop generates a current based on the estimated torque. A signal is obtained, and an armature current commensurate with the load torque is obtained based on this current signal and the armature current command signal, thereby significantly reducing the impact drop in rotational speed.

G. Examples Examples of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows a rotation speed control device for an electric motor according to an embodiment of the present invention, and 2 shows a speed signal N as an input and a transfer function ΔN/
A digital Leonard circuit 12 is formed by a speed difference calculating section that calculates a digital signal of the speed difference based on Δt. 1
3 is a low-pass filter (LPF) which receives the output signal of the speed difference calculation section 11; and a rotational inertia calculation section 5.3. A load torque estimating circuit 1OA is configured together with the second generated torque calculation section 1b and the second addition/subtraction section 1b.

Reference numeral 14 denotes a current calculation unit which inputs the estimated load torque *torque signal of the load torque estimation circuit 10A and uses l/KT as the transfer function. Reference numeral 15 designates a current gain adjustment unit, which includes the current calculation unit 14 and the current gain adjustment unit. 15 forms a minor current control loop 16.

2c is the third addition/subtraction unit, 2d is the fourth addition/subtraction unit, 17 is the speed control amplifier gain consisting of 1 and the speed control amplifier 1+T+S integral time constant T1, transmitting T,
The speed control signal amplification section 18 is a speed control signal amplification section that uses a current minor loop gain KACR and a current minor loop-next feed time constant TACR.
) is the current amplification unit with the transfer function. Reference numeral 19 denotes a speed detection section having a speed detection gain KNd5t as a transfer function, forming a major loop 2o for speed control.

In the rotational speed control device having the above configuration, in the digital Leonard circuit 12, ((current scan speed detection value) = (
The speed difference is calculated by calculating the curve scan speed detection value)). Also, low pass filter of analog load torque estimation circuit 10A! 3 performs high-frequency cut of the speed difference signal, and further performs load torque estimation calculation by the second generated torque calculation section 1b, rotational inertia calculation section 5, and second addition/subtraction section. Therefore, since the speed detection is digital, there is almost no detection delay, and an analog circuit can be easily constructed.

In addition, through a minor current control loop 16 consisting of a current calculation unit 14 and a current gain adjustment unit 15 that input the estimated load torque, the armature current corresponding to the estimated load torque obtained from the load torque estimation circuit 10A is increased. If it is allowed to flow, the influence of the load torque τ1 as a disturbance can be reduced.

Further, the speed detection section 19 detects the speed by inputting the speed signal N, and inputs this detection signal to the third addition/subtraction section 2c. The third addition/subtraction section 2c inputs a deviation signal between the speed command signal Nrat and the speed detection signal to the speed amplification section 17.

The output signal of the speed signal amplifier 17 is the armature current command signal 1
arm (obtained by closing this armature current command signal 1
□, t, and the feedback current signal from the current control minor loop 16 are added by the fourth addition/subtraction unit 2d. The output of the fourth addition/subtraction unit 2d is amplified by the current amplification unit 18, and the armature current [a is set to the first generated torque calculation unit 1
a and the second generated torque calculation unit 1b. Here, the output signal Ia of the current amplifying section 18 is first-order delayed and approximates the armature current command signal 1 arsf.

As a result of a simulation study of the armature rotational speed control device having the above configuration, characteristics as shown in FIGS. 2 and 3 were obtained.

That is, FIG. 2 shows the speed characteristics of the apparatus not equipped with the impact drop reduction means, and FIG. 3 shows the speed characteristics of the above embodiment equipped with the impact drop reduction means. As is clear from Fig. 2, when impact drop reduction means is not provided, when 100% load is applied at time T=O, the rotational speed N of the motor rapidly decreases in approximately 0.0 seconds, and the It took 0.5 seconds to recover to speed. On the other hand, in the case of the above-mentioned embodiment equipped with an impact drop reduction means, as is clear from FIG. It takes about 0.8 seconds to recover,
Taking into consideration the delay and saturation of the amplifier, the speed was completely restored to the set speed in 0.2 seconds.

1 (Effects of the Invention The present invention is as described above, and in a control system for an electric motor capable of variable speed control, an armature current command signal is obtained based on a rotational speed detection signal and a rotational speed command signal of the electric motor, and
An estimated load torque obtained based on the speed difference signal of the rotational speed is obtained, a current signal is obtained based on this estimated load torque, and an electric machine corresponding to the load torque is obtained using this current signal and the indicated armature current command signal. Since the secondary current is obtained, it is possible to obtain a motor rotation speed control device that has a simple circuit configuration, has high response speed, and can significantly reduce the impact drop of the rotation speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a rotational speed control device for an electric motor according to an embodiment of the present invention, FIGS. 2 and 3 show characteristics based on simulation, and FIG. 2 is a rotational speed characteristic diagram of a general rotational speed control device. , FIG. 3 is a rotational speed characteristic diagram of the rotational speed control device according to the embodiment of the present invention, FIG. 4 is a block connection diagram of the load torque estimating means of the conventional rotational speed control device, and FIG. 5 is a diagram of other conventional loads. Block diagram of torque estimating means FIG. 6 is a block diagram of yet another conventional load torque estimating means. 1a...first generated torque calculation section, tb...second generated torque calculation section, 2a...first addition/subtraction section, 2b.
・Second addition/subtraction unit, 2c...Third addition/subtraction unit, 2d・
4th addition/subtraction unit, 3a... rotational speed calculation unit, 5th rotation inertia calculation unit, IOA... load torque estimation circuit, 11...
Speed difference calculation unit, 12...Digital Leonard circuit,
13... Low pass filter, 14... Current signal calculation section, 15... Current gain adjustment section, 16... Minor loop, 17... Speed signal amplification section, 18... Current amplification section, 19. ...Speed detection section, 20... Menoyar loop. 2 other people Figure 5 Figure 5 Figure 6 L

Claims (1)

[Claims] (1) Using the armature current of the motor as input, calculate the generated torque of the electric motor using the torque constant as a transfer function, add and subtract this generated torque and load torque to obtain acceleration torque, and
a rotational speed signal calculation means for calculating a rotational speed signal of the electric motor using the acceleration torque as a transfer function of rotational inertia; and a speed difference based on the current speed detection value and the previous speed detection value using the rotational speed signal as an input. A speed difference calculation means that calculates the signal as a digital value, and a speed difference signal of the speed difference calculation means is input to calculate a rotational inertia signal, and the rotational inertia signal and the generated torque signal of the electric motor are added and subtracted to calculate the electric motor. load torque estimating means for calculating an estimated load torque city center number; and a speed detection signal obtained by inputting the speed signal obtained by the rotational speed calculating means, based on this speed detection signal and a speed command signal of the electric motor. Major loop means for obtaining an armature current command signal, and minor loop means for obtaining a current signal from the estimated torque signal obtained by the load torque estimating means using a torque constant as a transfer function, and adding or subtracting this current signal from the electric machine current command signal. A rotational speed control device for an electric motor, characterized by comprising: