JPS61231887A - Speed controller of motor - Google Patents

Abstract

PURPOSE:To reduce the variation in the speed at a load abruptly varying time by calculating a load torque from the variation in a speed at the prescribed period and the integrated value of the torque generated in a motor in the period, and adding it to the torque command of the speed control calculating result. CONSTITUTION:A microcomputer 2 inputs the outputs of a speed command generator 1 at every prescribed period Ts and a counter 10 for counting the output of an encoder 7 to calculate an ASR of controlling the speed. The microcomputer 2 further inputs the value of a current detector 8 at every prescribed period Tc to perform a current control calculation ACR, thereby obtaining the first current command Ir1. The variation in the speed during the period Ts is subtracted from the value added with the current feedback value over the period Ts to obtain the second current command Ir2. The second current commands Ir1, Ir2 are added, and output of a gate pulse generator 3.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a control device suitable for digitally controlling the speed of an electric motor, and particularly to a speed control device of an electric motor suitable for improving control response during sudden changes in load. get involved.

- [Background of the Invention] In speed control devices for electric motors used to drive rolling mills, it is desired to minimize speed fluctuations in response to rapid changes in load. As a method to deal with this problem, a method was proposed in JP-A-55-16 in which an estimated value equivalent to the load torque is obtained using a state observation device using the speed and current of the motor.
It is described in Publication No. 2894. This method gradually estimates the estimated value of the load torque from the deviation between the model speed and the actual speed, and has the advantage that a relatively accurate estimated value can be obtained in a steady state. However, if the load has a vibration component and the frequency of vibration is relatively fast, it becomes difficult to stabilize the control system because there is a delay in the state observer. Furthermore, recently, digital arithmetic circuits such as micropin computers have been increasingly used as speed control circuits, and in this case, using a closed-loop state observer would complicate processing.

[Purpose of the invention]

) An object of the invention is to provide a speed control device for an electric motor that minimizes speed fluctuations when the load suddenly changes even when the speed of the electric motor is digitally controlled.

[Summary of the invention]

A motor speed control device using a microcomputer detects the speed of the motor at regular intervals and performs speed control calculations. The present invention focuses on this speed detection at regular intervals,
Calculate the load torque from the change from the detected value in the previous cycle and the integral value of the motor generated torque within that cycle,
This value is used to control the motor torque in addition to the first torque of the speed control calculation result7. In this way, the latest load torque can be calculated for each cycle, so the load It can be controlled with good response even in sudden changes.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows an example in which the present invention is applied to a speed control device for a DC motor. The embodiment shown in FIG. 1 is a speed command generation circuit 1. Microcomputer 2. Gate pulse generation circuit 3. AC power supply 4
．． Thyristor converter 5, DC motor 6. encoder 7,
Current detector 8° A/D converter 9. It is composed of a counter 10.

The microcomputer 2 takes in the values of the speed command generation circuit 1 and the counter 10 every cycle T shown in FIG. 2 and performs speed control calculation ASR. At each time, the output of the current detector 8 is converted into a digital value by the A/D converter 9, and current control calculation ACR is executed using the value as a feedback signal. The result of the current control calculation ACH is set to the gate pulse generation circuit 3. The gate pulse generation circuit 3 generates a pulse with a set phase, operates the thyristor converter 5, and rotates the DC motor 6. As a result, an encoder 7 mechanically coupled to the electric motor 6 generates a pulse train with a shoulder wave number proportional to the speed of the electric motor. Since the output pulses of the encoder 7 are counted by the counter 10,
The counted value indicates the rotational position of the electric motor.

The features of the present invention in the embodiment shown in FIG. 1 are the speed control calculation ASR and the current control calculation ACH, and these characteristics will be explained below with reference to flowcharts shown in cylinders 3 and 4.

The microcomputer 2 performs processing A in FIG. 3 every T8 cycle.
Execute SR. First, in step 20, the output rti, (i) of the speed command generation circuit 1 is input.

Hereinafter, (i) means the i-th sampling point.

Next, the value P (i) of the counter 10 is taken in. Since the value P (i) of the counter 10 counts the output pulses of the encoder 7, the counted value indicates the rotational position. Therefore, the current detected value P(i) and the previous detected value P(i−
1), the velocity feedback amount N, (i) is calculated by the following equation.

N, (i)=(P(i)-P(i-1))/T,...
(1) Next, the speed command N, (i) and the speed feedback amount N, (i
) is used to perform speed control calculation, and the first current command Ll
(i) Calculate. If, for example, proportional compensation is used in the speed control calculation and its gain is , then the first current command I, 1(i) can be found by the following equation.

l-1ax) = Ka(N-(x)-Nt(x
)) ...(2) This first current command Ul, □(i
) has the role of flowing a current (proportional to torque in a DC machine) to the motor that makes the speed deviation zero. That is, it generates torque for accelerating and decelerating the electric motor.

On the other hand, in step 28, the second current command L2(i) is calculated using the following equation.

l-1b)=S(iy J) Kf(Nr(i)Nt
(i 1))...(3) Here, S (iy J)
is a value obtained by the current control calculation ACR as described later, and is the execution period T of ACH. Current feedback amount detected every time,
(i, j) over 16 cycles of ASR and is proportional to the torque generated by the motor in the previous cycle.

The second term in equation (3) is the speed change during T1 multiplied by a coefficient, and means the torque required to accelerate or decelerate the motor.From this result, the second current command 2
(i) is the torque generated by the electric motor minus the torque required for acceleration/deceleration, and is a value proportional to the load torque.

The first and second current commands Ire (
i) By adding t L3 (i), the current command I, (i
) get.

I, (i): I, 1 (i) + Iri (i) ...
(4) Then, in step 32, j is set to 1 as preprocessing for the current control calculation, and in step 34, the current P(i) is set for the next speed control calculation.

N, (i) is memorized. These values are the following AS
In the cycle in which R is executed, P (i
-1), N, (i-1). 'The process of current control calculation ACR has a cycle T shorter than that of speed control calculation ASR. (See FIG. 2), and its contents are shown in the flowchart of FIG.

First, in step 36, it is determined that j=1.

When j=1, it is immediately after executing the speed control calculation ASR, and S (l r j-1) is set to O. Furthermore, this j
means the number of times current control is performed within the calculation period T of speed control.

Next, in step 40, the current detector 8. 'Input the current feedback amount In(xt j) via the A/D converter 9. Using this current feedback amount Iz (iyj) and the current commands I, (i) obtained by the speed control process ASR, step 42
A current control calculation is performed at , and the ignition phase α(i, j) is calculated. If, for example, proportional compensation is used as the current control calculation and the proportional constant is Ka, then the ignition phase α(i, j) is determined by the following equation.

α(it j)=180-Kc+('I,(i)-If
(it, i)) (5) Furthermore, in step 44, the following equation is calculated and the current feedback amount rt(xt J) is added.

5(it j)=KaIt(iy j)+s(i, j
-1)...(6) In step 46, the firing phase αCip J) obtained in step 42 is set to the gate pulse generation circuit 3. Then, in step 48, j is incremented by 1, and the process ends.

Such speed control processing ASR and current control processing ACR
By executing these two processes, the microcomputer 2 controls the current flowing through the DC motor 6 and its speed.

As described above, according to the embodiment shown in FIG. 1, it is possible to obtain the current commands x, z(i) corresponding to the load torque using equation (3) every cycle when the speed control process ASR is performed.
Moreover, since this value is used as a command for the current control system, it is possible to quickly compensate for speed fluctuations when the load suddenly changes. In addition, since the microcomputer 2 can detect the current equivalent to the load torque using only the detected value counter 10 and the output of the A/D converter 9, which are necessary for normal speed control and current control, the hardware Can be easily configured without any increase.

Furthermore, in detection for each ASR processing cycle, even a small error has a large influence, so in order to reduce the influence, it is also possible to easily average the detected values of the number of times by applying this embodiment. For example, to obtain the second current command in a time corresponding to three cycles of ASR, calculate the following equation after equation (3) to obtain Irz-+(1), and combine that value with the first The current command IJi) may be calculated by the sum of the current command I, 1(i).

1rzzx) = (工ri(i z>+xtzCx
1) +I, □(i)]...(7) Engineering, (i) = Engineering,
,(i)+x,! , (i)...(8) In this way, even if a small error occurs in one calculation, it will not have a negative effect. Furthermore, since the current corresponding to the load can be estimated in fewer times (shorter time) than in the method of taking feedback and averaging, it has the effect of quickly compensating for speed fluctuations when the load suddenly changes. Furthermore, since the calculation can be performed using only the detected values used by the microcomputer 2 for control calculations, the configuration can be simplified without increasing hardware.

〔Effect of the invention〕

As explained above, according to the present invention, only the detected values of the speed and current used to control the speed of the electric motor with a digital processing device such as a microcomputer are used.
Furthermore, since the load can be estimated for each speed control cycle and the estimated value can be given as a load command, speed fluctuations when the load suddenly changes can be reduced.

In addition, although the above-mentioned embodiment explained the case where a DC motor is used, it is possible to estimate the load torque of the electric motor and add that value as a torque command in the same way when an AC motor is used.

[Brief explanation of drawings]

FIG. 1 is a block configuration I' diagram showing one embodiment of the present invention, FIG. 2 is a time chart showing the operation of the microcomputer 2 shown in FIG. 1, and FIGS. It is a flowchart which shows the processing content. 2...Microcomputer, 9...A/D converter. 10...Counter, 7...Encoder.

Claims (1)

[Claims] 1. An electric motor, a digital position detector mechanically coupled to the electric motor, and a speed detection circuit that calculates the speed of the electric motor from the amount of change in the output of the digital position detector every predetermined constant cycle; an electric motor torque detection circuit that outputs a value corresponding to the torque generated by the electric motor; an electric motor torque control circuit that controls the torque generated by the electric motor using the output of the electric motor torque detection circuit as a feedback signal; and outputs a speed command. a speed command generation circuit and a digital calculation circuit, the digital calculation circuit calculates the first motor torque command using the outputs of the speed command generation circuit and the speed detection circuit at regular intervals; A second electric motor torque command is calculated using a change in the speed detection circuit output from the previous cycle output and an integral value of the motor torque detection circuit output within the previous cycle, and further the first and second electric motors are A speed control device for a motor that obtains an added value of a torque command and uses the added value as a command for the motor torque control circuit.