JPH07111790A - Control method for optimal speed in variable speed control equipment - Google Patents

Abstract

PURPOSE:To accelerate speed settling time and improve speed control accuracy in a method for controlling optimal speed in a variable speed control equipment provided with a speed control arithmetic unit that obtains a speed command based on the deviation between speed setting for a motor load and detected speed. CONSTITUTION:The title method involves a speed increase/decrease detector 21 that judges increase and decrease in speed and load based on detected speed, speed deviation and detected current; and a gain and time constant arithmetic unit 22 that calculates an optimal gain and time constant based on speed deviation and speed setting. When the detector 21 detects rapid change in load, the gain and time constant on the arithmetic unit 22 are used in speed control arithmetic operation. While the detector does not detect rapid change, the gain and time constant set on a gain and time constant setter 23 are used. When the detector 21 detects light load, a reduced set speed obtained by multiplying a set speed by a coefficient for the purpose, is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed control device for controlling the speed of an electric motor load by means of an inverter or the like, and more particularly to an optimum control method for speed control.

[0002]

2. Description of the Related Art A speed control method generally used in a current variable speed control device is shown in FIG. In FIG. 2, 1 is an AC power supply, 2 is an inverter, 3 is an induction motor, 4
Is a pulse pickup and 5 is a speed detection device. The detected speed of the speed detecting device 5 is compared with the signal passed through the input limiting circuit 8 in the matching section 6 with the setting signal of the speed setter 7 to obtain the deviation.

Reference numeral 9 is a speed control arithmetic unit for obtaining a speed command from the output of the gain / time constant setting unit 10 and the deviation output of the matching unit 6. The speed command signal from the speed control arithmetic unit 9 is sent via the switch 11 to the matching section 1
At 2, it is matched with the inverter output current detection signal of the current transformer 13. The output of the matching section 12 is supplied to the current control arithmetic unit 14. The output signal of the current control arithmetic unit 14 is subjected to predetermined pulse shaping and used for controlling the inverter 2.

In the circuit of FIG. 2, the speed command is determined by the deviation between speed setting and speed detection. The time (response time) required for the speed command to be reflected in the actual speed is determined by the gain and time constant of the speed control computing device 9.

[0005]

In the conventional general speed control as shown in FIG. 2, the speed setting value and the speed detection value are compared, and the deviation is amplified by the speed control calculation to keep the speed at the reference value. To control. However, the speed control by the apparatus of FIG. 2 has the following problems.

(1) When the load is large at the time of starting, it takes time to reach the set speed. (2) The speed increases when the load suddenly decreases during load operation. (3) When the speed setting changes during load operation, the time until settling to the set speed is not constant depending on the load amount. (4) When the load suddenly increases during load operation, it takes time for the speed to decrease and to return to the original speed. It is important for control that the speed is the same for the setting in any state.

The present invention has been made in view of the above points, and an object thereof is to provide an optimum speed control method for a variable speed control device, which speeds up the speed settling time and improves speed control accuracy. is there.

[0008]

SUMMARY OF THE INVENTION The present invention provides an optimum speed control method for a variable speed control device equipped with an inverter for converting electric power of an AC power supply to supply electric power to a load such as an electric motor. A signal, a speed deviation signal of the signal and the speed setting signal, and a judgment unit for judging increase / decrease of speed and increase / decrease of load based on the current detection signal of the load, and the speed deviation signal and the speed setting signal. Based on the optimum gain, a calculation unit for calculating the time constant, when the determination unit determines a sudden change in load, perform the speed control calculation to obtain the speed command using the gain of the calculation unit, the time constant, When the sudden change is not determined, the speed control calculation is performed using a predetermined gain and a time constant, and when the determination unit determines a sudden decrease in load, the speed set value obtained by multiplying the speed set value by a predetermined coefficient is used. for It is characterized by performing the speed control calculation Te.

[0009]

When the load suddenly changes, the speed control calculation is performed by the optimum gain and time constant calculated by the calculation unit. Therefore, the speed settling time is accelerated, and the speed control is performed in real time. Although the speed may increase when the load suddenly decreases, the speed increase is suppressed because the original speed setting value is multiplied by, for example, a coefficient for decreasing the setting value.
This improves the speed control accuracy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1, the same parts as those in FIG. 2 are indicated by the same reference numerals. In FIG. 1, 21 is a speed detection signal,
It is a speed increase / decrease detection device that determines speed increase / decrease and load increase / decrease based on the speed deviation signal and the current detection signal of the current transformer 13. Reference numeral 22 is a gain / time constant calculation device that calculates optimum gain and time constant based on the speed deviation and speed setting (speed setter 7, not shown).

Reference numeral 23 is a gain / time constant setting device for setting constant gain and time constant. One of the set value of the setter 23 and the calculated value of the gain / time constant calculation device 22 is selected by the changeover switch 24 controlled by the judgment output of the speed increase / decrease detection device 21, and the speed control calculation device is selected. 9 is input.

Reference numeral 25 is a speed setting coefficient calculation device for obtaining a coefficient for decreasing the speed setting when the load is suddenly reduced, based on the determination output of the speed increase / decrease detection device 21. Reference numeral 26 is a multiplier for multiplying the speed setting signal (output signal of the speed setting device 7) by the output signal of the speed setting coefficient computing device 25.

Reference numeral 27 is a changeover switch for switching between the speed setting signal and the output signal of the multiplier 26 according to the judgment output of the speed rising / falling detecting device 21.

In the apparatus constructed as described above, normally, the changeover switch 27 is changed over to the speed setting side (the speed setting device 7 side not shown) and the changeover switch 24 is changed over to the gain / time constant setting device 23 side. Has been. For this reason, the speed control arithmetic unit 9 determines the deviation between the speed setting and the speed detection signal (the output of the matching unit 6) and the gain / time constant setting unit 2
The speed command signal is calculated based on the set value of 3 and output.

Here, when the speed increase / decrease detection device 21 determines a sudden change in load, the changeover switch 24 is changed over to the gain / time constant calculation device 22 side. Therefore, the speed control calculation device 9 calculates and outputs the speed command signal based on the output of the matching unit 6 and the calculated value of the gain / time constant calculation device 22.

When the speed increase / decrease detector 21 detects a sudden decrease in load, the changeover switch 27 causes the multiplier 26 to operate.
Can be switched to the output side of. Therefore, the speed control computing device 9 causes the deviation between the speed detection signal and the output signal of the multiplier 26 in which the speed setting signal (the output signal of the speed setting device 7 not shown) is multiplied by the coefficient for reducing the set value. The speed command signal is calculated and output based on the minute and the calculated value of the gain / time constant calculation device 22. The above control keeps the actual speed constant with respect to the speed setting.

[0017]

As described above, according to the present invention, the speed increase / decrease and the speed decrease based on the speed detection signal of the load, the speed deviation signal of the signal and the speed setting signal, and the current detection signal of the load are performed. A determination unit that determines whether the load increases or decreases, and an operation unit that calculates the optimum gain and time constant based on the speed deviation signal and the speed setting signal are provided. When the determination unit determines a sudden change in the load, the calculation operation is performed. The speed control calculation for obtaining the speed command is performed using the gain and time constant of the section, and when the sudden change is not determined, the speed control calculation is performed using the predetermined gain and the time constant, and the determination section determines the sudden decrease of the load. When the determination is made, the speed control value is calculated by using the speed setting value obtained by multiplying the speed setting value by a predetermined coefficient, so that the following excellent effects can be obtained.

(1) It has become possible to speed up the speed settling time by changing the load. (2) Real-time speed control can be achieved. (3) Speed control accuracy can be improved.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing an example of a conventional speed control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... Inverter 3 ... Induction motor 4 ... Pulse pickup 5 ... Speed detection device 6, 12 ... Matching part 7 ... Speed setting device 9 ... Speed control calculation device 21 ... Speed rise / fall detection device 22 ... Gain Time constant calculation device 23 ... Gain / time constant setting device 24, 27 ... Changeover switch 25 ... Speed setting coefficient calculation device 26 ... Multiplier

Claims (1)

[Claims] 1. An optimum speed control method for a variable speed control device comprising an inverter for converting electric power of an AC power supply to supply electric power to a load such as an electric motor, comprising: a speed detection signal of the load, the signal and the speed setting. A speed deviation signal of the signal, a determination unit that determines the increase or decrease of the speed and the increase or decrease of the load based on the current detection signal of the load, the optimum gain and time constant based on the speed deviation signal and the speed setting signal When the determination unit determines a sudden change in load, a speed control calculation for obtaining a speed command using the gain and time constant of the calculation unit is performed, and a predetermined value is determined when the sudden change is not determined. Gain of
The speed control calculation is performed using a time constant, and when the determination unit determines a sudden decrease in load, the speed control calculation is performed using the speed setting value obtained by multiplying the speed setting value by a predetermined coefficient. Optimal speed control method for variable speed control device.