JPH0564476A - Electric motor speed controller - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a suitable acceleration / deceleration current to the motor according to the state of a certain load so that a constant speed response characteristic can always be secured and stable speed control can be realized. To do. [Structure] A speed controller 2 for controlling the speed of an electric motor 6,
In the electric motor speed control device having the current controller 3 for controlling the electric current of the electric motor 6 and the acceleration / deceleration current calculation unit 24 for controlling the acceleration / deceleration current of the electric motor 6, the magnitude of the inertia moment Jl of the load applied to the electric motor 6 Gain command K ′ according to the gain Kff × acceleration / deceleration current calculation unit 24.
Change K '. As a result, a constant speed response can be obtained even if the load increases. Also, the speed controller 2
The gain of is fixed to a predetermined value. As a result, the stability of the speed control can be maintained without the speed response increasing too much even if the load changes suddenly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an electric motor, and more particularly to a speed control device for an electric motor, which is suitable for speed control of all electric motors including, for example, speed control of rolls in a process line. The present invention relates to a speed control device for an electric motor having speed control means for controlling, current control means for controlling electric current of the electric motor, and acceleration / deceleration current control means for controlling acceleration / deceleration current of the electric motor.

[0002]

2. Description of the Related Art For example, in a steel processing line, an electric motor is usually used as a drive source for rolls. From the viewpoint of stable operation of the process line, the speed of this electric motor needs to be accurately controlled to a desired speed.

Therefore, the speed controller for the electric motor includes a speed controller (hereinafter, ASR; Aut) for controlling the speed of the electric motor.
omatic Speed Regulator) and a current controller that controls the electric current of the electric motor (ACR; Automatic Current)
Regulator) is provided.

Generally, the speed control gain of the ASR is semi-fixed, and the ASR speed control gain is fixed after being adjusted to an appropriate value in advance so that the speed of the motor can be stably controlled regardless of the load. It The adjustment of the speed control gain is performed as follows.

That is, the speed control gain has been adjusted so that the speed control device is trial-operated in the state where there is no actual load on the electric motor and the required response is obtained. It is well known to make such adjustments.

Therefore, when a load is actually applied to the electric motor, the moment of inertia of the load is the cause (since the moment of inertia of the load changes depending on the operating condition), the ASR
In some cases, the speed control device may not be able to obtain the original required response.

On the other hand, various speed control techniques have been proposed in which a response required by the ASR can be obtained even when a load is applied.

As one of the technologies, there is one already disclosed by the applicant in Japanese Patent Application Laid-Open No. 2-307381. This is calculated by paying attention to the change in the load inertia moment during operation, by back-calculating the speed control gain for obtaining the required response from the inertia moment, and using the speed control gain obtained, the speed of the ASR adjusted during the test operation. This is to correct the control gain. FIG. 3 is a block diagram of the disclosed speed control device for an electric motor.

In the speed control device shown in FIG. 3, the speed command is input to the first addition point 9 via the second addition point 10 as a positive signal. Further, the rotation speed of the electric motor 6 is detected by the speed sensor 7 such as a speed pulse generator, and the speed feedback calculation unit 8 detects the speed feedback gain Kf for the detected speed signal.
And is input as a negative signal to the first addition point 9 (speed feedback is performed). The output of the first addition point 9 is input to the ASR2. The ASR 2 outputs a speed control signal, and this output is multiplied by a drooping coefficient Kd in a drooping amount calculation unit 4 to become a drooping amount, which is input to the second addition point 10 as a negative signal.

At the second addition point 10, the drooping amount is subtracted from the speed command, whereby a drooping characteristic is added to the speed command. Then, at the first addition point 9, the speed feedback signal is subtracted from this speed command, whereby the deviation from the actual speed of the speed command S is input to the ASR2.

The ASR 2 outputs a speed control command signal which can eliminate the deviation by multiplying the input deviation by a predetermined gain. The output speed control command signal output is input to the ACR 3 via the third addition point 11, is multiplied by a predetermined gain, and is input to the power conversion unit 5. From this power converter 5, the current value to the electric motor 6 is the third addition point 1
1 and is controlled so that the electric motor current follows the current control command.

In the speed control device described above, the AS for obtaining the required response from the moment of inertia of the load (strip in the process line, etc.) applied to the motor during the load operation by adjusting the gain of the ASR2 during the test operation.
The speed control gain of R2 is calculated backward, and the gain of the ASR2 is corrected to the calculated gain.

Further, in Japanese Patent Application No. 2-235523, there is provided an acceleration / deceleration current (acceleration / deceleration current) control means 1 for obtaining an acceleration / deceleration current value (acceleration / deceleration current value) necessary for accelerating / decelerating the electric motor. As a result, a speed control device for an electric motor is proposed in which drooping amount is prevented from largely changing due to a change in speed command.

This speed control device has a structure as shown in the block diagram of FIG. 4, and is provided with an acceleration / deceleration current calculator (corresponding to acceleration / deceleration current control means) 1. The acceleration / deceleration current calculator 1 inputs a speed command and performs a predetermined calculation on the speed command. Then, the calculation result is input to the fourth addition point 12 and is signaled to the speed control command output from the ASR2. That is, the speed command is fed forward through the acceleration / deceleration current calculator 1.

The calculation time constant of the calculator 1 can be made much larger than the electric time constant of the electric motor 6. Therefore, the drooping amount does not fluctuate even if the speed command changes significantly, so that the stability of the speed control is improved and the speed control can be easily adjusted.

In this speed control device, it may be considered that the gains of the acceleration / deceleration current calculation means 1 and the ASR 2 are automatically changed according to the moment of inertia of the load.

[0017]

However, as disclosed in Japanese Patent Laid-Open No. 2-307381, the speed control means (A
(SR) gain is corrected according to the moment of inertia of the load, or the gain of the speed control means and the acceleration / deceleration current control means (acceleration / deceleration) as in Japanese Patent Application No. 2-235523.
If any of the gains of the deceleration current calculator) is to be corrected according to the moment of inertia of the load, the following problems occur.

That is, in the speed control from the electric motor to the speed control device, the speed control system is connected between the electric motor and the speed control device, between the electric motor and the load, or between the speed control device and the continuous load. There may be destabilizing factors. The factors include, for example, backlash of the speed reducer, elasticity and rigidity of the shaft connecting the electric motor and the roll, or elasticity of the metal ribbon.

For example, due to the backlash, the mechanical edge between the electric motor and the load is momentarily disconnected, and the speed control system becomes unstable at this moment. At this time, if the gain of the speed control means is too large, the response of the closed loop of the speed control means rises too much, which increases the instability of the speed control system and causes a hunting phenomenon, or causes the motor and the roll to move. Torsional vibration may occur due to the rigidity of the connecting shaft.

Therefore, the gain of the speed control means cannot be increased in many cases due to the existence of the destabilizing factor of the speed control system as described above, and the gain is increased according to the moment of inertia of the load as in the prior art. If corrected, the speed control system becomes unstable and stable speed control cannot be realized.

The present invention has been made in order to solve the above-mentioned conventional problems, and can always provide an appropriate acceleration / deceleration current to the electric motor according to the state of any load to ensure a constant response and stable operation. An object of the present invention is to provide a speed control device capable of highly accurate speed control.

[0022]

SUMMARY OF THE INVENTION The present invention is directed to speed control means for controlling the speed of an electric motor, current control means for controlling the electric current of the electric motor, and acceleration / deceleration current control means for controlling the acceleration / deceleration current of the electric motor. And a means for changing the gain of the acceleration / deceleration current control means according to the magnitude of the moment of inertia of the load applied to the electric motor, and the gain of the speed control means is set to a predetermined value. The above-mentioned problem is solved by fixing to the above.

[0023]

In the present invention, the gain of the acceleration / deceleration current control system is changed according to the magnitude of the moment of inertia of the load.
Furthermore, even when the load condition is different, the motor can be accelerated and decelerated in response to moments of inertia under all load conditions.
An appropriate acceleration / deceleration current can always be applied to the electric motor. Therefore, the motor speed can be controlled with the responsiveness that is always required.

Further, the gain of the speed control means is a predetermined value,
For example, since the speed control unit is fixed to the value adjusted during trial operation, the response of the speed control system is not affected by load fluctuations, and therefore the motor speed can be controlled in a stable state, and hunting and motor Also, phenomena such as torsional vibration of the shaft between rolls do not occur.

According to the present invention, an appropriate acceleration / deceleration current is always applied to the electric motor according to the state of any load, a constant response can be always ensured, and stable speed control can be realized with high accuracy.

[0026]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a speed control device for an electric motor according to an embodiment of the present invention.

The speed control device shown in FIG. 1 mainly includes a control stage 20 and a power conversion stage 22.

The speed control device comprises a control stage 20.
The gain of the acceleration / deceleration current calculator (hereinafter referred to as FF) 24 is corrected according to a command from the host controller 26.

The host controller 26 has a structure shown in detail in FIG. 2, and the gain command K'is made in the following procedure.
Is input to the FF 24 and the gain of the FF is changed.

That is, the controller 26 first calculates the moment of inertia Jl of the load (strip or the like in the process line). The moment of inertia of the load can be obtained by, for example, the method already disclosed by the applicant in the specification of Japanese Patent Application Laid-Open No. 2-307381, or by various other methods.

Next, the calculated moment of inertia Jl, the moment of inertia of the electric motor 6 (mainly the moment of inertia of the rotor) Jmo, the load driving means directly connected to the electric motor 6 (pay-off reel for driving a strip, looper roll, etc.)
The gain command K ′ is calculated by the following equation (1) from the inertia moment Jma of the hearth roll, tension reel, etc.

K ′ = (Jmo + Jma + Jl) / (Jmo + Jma) (1)

Next, as shown in the following equation (2), the gain command K'is multiplied by the initially set gain Kff of the FF 24 to change the gain G (s) ff of the FF 24.

G (s) ff = (Kff × K ′) / (1 + TS) (2)

Incidentally, T is a time constant of the FF 24, and S is a Laplace operator.

Further, as in the formula (2), the FF 24 of the embodiment is used.
Has a first-order lag characteristic.

The values of the inertia moment Jmo of the electric motor and the inertia moment Jma of the load driving means can be calculated in advance and input to the host controller 26.

As the host controller 20, for example, a programmable logic controller can be used.

The power conversion stage 22 is a direct current power source (DC).
Alternatively, the AC power supply (AC) is subjected to AC → DC conversion, voltage conversion, frequency conversion, etc. according to the speed control command and the current control command of the control stage 20 to control the electric motor 6.

For the power conversion stage 22, a static power converter (chopper, inverter, converter, etc.) composed of, for example, a thyristor or a transistor can be used.

Further, the electric motor 6 according to this embodiment is applicable to all kinds of electric motors including a DC electric motor, an induction electric motor and a synchronous electric motor.

The structure of the speed control device of the other embodiment is the same as that of the speed control device shown in FIG. 3 or FIG. 4, and therefore, the same components are designated by the same reference numerals and their description is omitted. Is omitted.

The operation of the embodiment will be described below.

In the speed control apparatus of the embodiment, the host controller 26 first obtains the load inertia moment Jl,
Then, the gain command K'is obtained from the equation (1). The gain command K'changes the gain of the FF 24 as shown in the equation (2). In this way, the initially set gain Kff of the FF 24 is corrected by the gain command K'obtained from the load inertia moment Jl and the like.

Therefore, regardless of whether there is no load, there is a load, or the load is different, an appropriate acceleration / deceleration current is always applied to the electric motor 6 in accordance with the moment of inertia of the load in all states. Can be given. Therefore, the speed of the electric motor 6 can be controlled with the required response.

Further, the gain of ASR2 is fixed to the value adjusted at the time of test operation by the speed control device alone. Therefore, speed control can be performed in a stable state even when the moment of inertia of the load suddenly changes, and a phenomenon such as hunting does not occur.

Therefore, appropriate acceleration / deceleration currents are always applied to the electric motor depending on the states of all loads, a constant speed response characteristic can be always secured, and stable speed control can be realized with high accuracy.

For example, when the speed control device embodying the present invention is applied to each drive device (drive motor for payoff reel, looper roll, hearth roll, tension reel, etc.) of continuous annealing equipment, in any motor,
You can keep the ASR response at the desired value,
The final target accuracy was achieved for each motor. From this, the usefulness of the present invention was confirmed.

Although the continuous annealing equipment is exemplified as the process line in the above-mentioned embodiment, the object to which the speed control device according to the present invention is applied is not limited to the electric motor of the continuous annealing equipment. The speed control device according to the present invention can be used for any type of electric motor as long as the electric motor needs to be controlled.

[0051]

As described above, according to the present invention, the gain of the acceleration / deceleration current control unit is made variable according to the magnitude of the moment of inertia of the load applied to the electric motor, so that the magnitude of the moment of inertia changes. Regardless of the condition, always provide the motor with appropriate acceleration / deceleration current according to the state of all loads,
A constant speed response characteristic can be always secured, and stable speed control can be realized with high accuracy.

As a result, in the case of controlling the electric motor by the speed control device according to the present invention, first, when the position control is performed by the electric motor, the position control accuracy is improved.
Further, in the case of equipment that processes a ribbon with a plurality of electric motors, the speed error between the electric motors becomes small and the uniform speed is improved, so that the tension, shape, plate thickness, and width of the ribbon are not changed. It is possible to obtain excellent effects such as the possibility of becoming minute.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a speed control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a logic of a host controller for correcting a gain of an acceleration / deceleration current calculation unit of the speed control device.

FIG. 3 is a block diagram showing an example of a conventional speed control device.

FIG. 4 is a block diagram showing another conventional example of the speed control device.

[Explanation of symbols]

 2 ... Automatic speed controller (ASR), 3 ... Current controller (ACR), 5 ... Power conversion unit, 6 ... Electric motor, 7 ... Speed sensor, 8 ... Speed feedback gain, 9 ... First addition point, 10 ... 2nd addition point, 11 ... 3rd addition point, 12 ... 4th addition point, 20 ... Controller stage, 22 ... Power conversion stage, 24 ... Acceleration / deceleration current calculation part (FF), 26 ... Upper controller.

Claims (1)

[Claims] 1. A speed control means for controlling the speed of an electric motor,
In a speed control device for a motor having current control means for controlling the current of the motor and acceleration / deceleration current control means for controlling the acceleration / deceleration current of the motor, in accordance with the magnitude of the moment of inertia of the load applied to the motor, A speed control device for an electric motor, comprising means for changing the gain of the acceleration / deceleration current control means, wherein the gain of the speed control means is fixed to a predetermined value.