JPS6395874A - Motor controlling method - Google Patents

Abstract

PURPOSE:To prevent current from being fluctuated at the time of switching, by a method wherein speed control bias and forced bias are added to a speed control section prior to change-over from current control to speed control, and wherein the forced bias is reduced at the same time as the control is changed over, and wherein a limit value is slowly increased. CONSTITUTION:When a motor 1 is controlled by means of current control only, then a contact d is ON, and a contact c is OFF, and the input of current command C to a current control section 3 is provided. When the control is changed over to speed control, then contacts X1-X3 are turned ON, and the output of speed control bias v2 is generated. Prior to the time point, a contact(a) is turned ON, and the output of forced bias v1 is kept generated. Then, by limit value signal L, output A=current command C is set. After that, when the contacts a, d are turned OFF and the contact c is turned ON to control speed, then the forced bias v1 is reduced, and the limit value L is slowly increased from the lower to the higher. As a result, current is slowly changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a motor control method that allows switching between current control and speed control of a motor without causing current fluctuations.

(Prior art and its problems) Normally, electric motors are controlled in such a way that speed control and current control are performed individually, or simultaneously in a major loop for the former and a minor loop for the latter.

For example, current control is often used in strip winding machines to maintain a predetermined torque on the electric motor and wind the strip while applying appropriate tension to the strip. However, depending on operating conditions, the speed may vary. There may also be cases where it is desirable to use control more aggressively.

Therefore, it becomes necessary to dynamically switch from independent current control to speed control.

What is shown in FIG. 4 is a general motor control device, in which a power supply section 2 of a motor 1 is connected to a current control section 3. If the speed control unit 4 is connected to the main body and normally open contacts a and c are closed, a major loop of speed control is formed, and by closing only the normally open contact d, a minor loop of current control is formed.

In such a control device, when switching from speed control to current control, setting the current command value C to a value equal to the output from the speed control section 4 will prevent current fluctuations. Can be switched. However, on the contrary, when switching from only current control to speed control, the torque of motor 1 is the control target under current control and has no direct relationship with speed, so the speed command value V
Normally, the control signal output from the speed control section 4 to eliminate the speed deviation between the actual speed Va and the speed bias B does not match the current command value C. Input changes become large. As a result, a significant step is formed in the current value from the power supply section 2 to the motor 1, which causes problems such as loosening of the strip winding state at the time of switching.

For this reason, in the conventional control device, as shown in FIG. 5, a normally open contact X is provided in the major loop.

X2. X, , an arithmetic control unit 5 is provided, and the normally open contacts X, , X2 . With X3 closed, the actual current C immediately before switching
a, the actual speed Va, and the speed command value V, the calculation control unit 5 calculates the optimum speed bias B= (V − Va − Ca/K
v) is calculated and output to reduce current fluctuations after switching. Here, V to the speed control section 4 is
-Va -B = Ca / Kv is output, and the gain of the speed control unit 4 is set to Kv, so the output value is Ca, which is approximately equal to the current command value C, and no current fluctuation occurs. Become.

However, even with such a conventional control device,
As shown in FIG. 2, it has been difficult to completely eliminate current fluctuations due to load fluctuations that occur during time loss during switching or the accuracy of the arithmetic device.

This invention was proposed to solve these problems, and its purpose is to prevent current fluctuations during switching from current control to speed control, even if current fluctuations occur due to load fluctuations. Another object of the present invention is to provide a motor control method that can cause a gentle current change at the time of switching, instead of a sudden current change as in the conventional case.

(Means and effects for solving the problem) The motor control method according to the present invention calculates a speed control bias having the same value as the current control value before switching from current control to speed control, output to the speed control section, apply a forced bias to the speed control section, limit the output value of the speed control section to the same value as the current command value, saturate the speed control value, and simultaneously apply the forced bias. The limit value is gradually expanded to prevent current fluctuations during switching, so that the current changes during switching are gentle.

(Embodiment) The present invention will be described below based on an illustrative embodiment. Note that parts that are the same as or correspond to the conventional ones are given the same reference numerals.

As shown in FIG. 1, in addition to the conventional arithmetic control section 5, a slope signal generator 6 and a variable limiter circuit 7 are provided.

The slope signal generator 6 generates a current command value C via a normally open contact a.
is input, and an integral function determined by the internal capacitor capacity etc. outputs the stepwise input as a slope amount. This slope signal V is a signal as shown in FIG. 3 (8),
It is input to the adder 8 as forced bias v1.

The variable limiter circuit 7 receives the slope signal V, outputs a limit value signal corresponding to the slope signal v1 to the speed control section 4, and saturates the speed control value together with the forced bias V.

In the above configuration, when the motor 1 is controlled by current control alone, the current control section 3 makes the contact d contact and the contact C open, so that the current command value C=actual current Ca. controlled.

In order to switch from this state to speed control, contact points X, , X2. X3 is momentarily connected, a speed correction value (V - Va - Ca /Kv) is calculated, and a speed control bias v2 is output. Prior to this point, contact a is brought into contact and forced bias v1 is output. This forced bias v, is the speed controller 4
It also has the purpose of changing the output A of the circuit, and as shown in Figure 3 (C), after a sufficient period of time has elapsed since the contact a has been connected, the output A is adjusted so that the current command value C becomes the same. There is.

In this state, due to the appropriate bias v2 and the excessive bias v1, the output value ■ of the adder 8 is changed to the actual speed Va
Since the output A of the speed control section 4 tends to become larger (FIG. 3(B)), the output A of the speed control section 4 tends to become a larger value, but A=C due to the limit value signal.

Next, when speed control is performed by opening contacts a and d and contacting C, the forced bias V decreases and the limit value gradually expands from lower to higher. As shown in Figure (C), the current changes gently due to the limit value that gradually rises, and after the crossing, it switches to the normal speed command, and as a result, the actual speed change of the motor 1 changes as shown in Figure 3 (D
) shows a gentle change.

Note that the above control may be performed using a sequence circuit, but
Sequence control by a process control computer is also possible.

(Effects of the Invention) As described above, according to the present invention, a forced bias is applied to the speed control section and the output value of the speed control section is limited to the same value as the current command value to saturate the speed control value. At the same time as switching, the forced bias is reduced and the limit value is gradually expanded, so even if the calculation accuracy decreases or the load fluctuates during switching, it is possible to prevent current fluctuations during switching, and also to increase the limit value. This makes it possible to change the current gently at times, reducing the shock given to the load.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a device for carrying out the control method of the present invention, and FIGS. 2(A) and 2(B). (C) is a graph showing changes in each output value in conventional control, and FIGS. 3 (A), (B), and (C). (D) is a graph showing changes in each output value in the present invention,
FIG. 4 is a block diagram of a general motor control device, and FIG. 5 is a block diagram of a conventional motor control device. 1...Motor, 2...Power source section 3...Current control section, 4...Speed control section 5...Calculation control section 6...Slope signal generator 7...Variable limiter circuit 8...Adder 2nd Figure Strong current control - 1 - Speed control Figure 3 Current control - 1 = Speed control

Claims (1)

[Claims] (1) In a control device having speed control means for controlling the speed of the electric motor based on a speed command value, current control means for controlling the current of the electric motor based on the current command value, and means for switching between current control and speed control, When switching from current control to speed control, before switching, calculate a speed control bias that is the same value as the current control value, output it to the speed control section, apply forced bias to the speed control section, and adjust the output of the speed control section. An electric motor control method characterized in that the speed control value is saturated by limiting it to the same value as the current command value, and at the same time as switching, the forced bias is decreased and the limit value is gradually expanded.