JPS6142286A - Speed controlling method of motor - Google Patents

Abstract

PURPOSE:To prevent the speed of a motor from varying due to load disturbance by presuming the disturbance by the angular velocity in the state of presumed angular velocity and the no load disturbance state, and calculating a compensating current from the presumed result to apply it to a current command. CONSTITUTION:The presumed value omegas of an angular velocity w is calculated in response to an armature current IA on the basis of a similar counterelectromotive force zetaphi' and a similar inertial efficient J'. A load disturbance TD is presumed by the difference between the presumed value omegas and the velocity omega, the counterelectromotive force constant zetaphi' and a current gain are converted by the disturbance TD to calculate the compensating current ID for compensating the variation in the load. The current IA is controlled in response to current base signal IP in response to a deviation between a speed detection signal R and a speed reference signal, and a deviation between a current detection signal I and a compensating current signal I0.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for controlling the speed of an electric motor, and the present invention relates to a method for controlling the speed of an electric motor. The present invention relates to a speed control method suitable for suppressing fluctuations.

[Background of the invention]

In a rolling mill, a DC r motor (hereinafter simply referred to as F1 motor) is used as a driving motor. In order to maintain the rotational speed of this electric motor at a stable value according to a predetermined speed command, so-called feedback control is generally used. The general form of this speed control system! 2! is shown in FIG. 5, and a block diagram expressed by its transfer function is shown in FIG.

I will give a summary without omitting it. The speed sensor 11 extension stem shown in Fig. 5 is detected by the actual rotational speed of the electric motor 2 and the full speed test t1:)3, and the speed detection signal is fed back as a negative feedback, and is controlled in addition to the speed command. It consists of a loop and a minor loop that detects the current given to the thyristor full-wave control rectifier circuit, which is a variable control power source, using a current transformer CT, and controls the current by feeding back the current detection signal ■. Ru.

A more detailed explanation is as follows. The antiparallel three-phase full-wave control rectifier circuit l using thyristors performs full-wave rectification control on the three-phase AC voltage eAc to convert it into a predetermined DC voltage.
The DC voltage is applied to the electric motor 2 to variably control the rotation speed. The current IA flowing through the armature of the motor 2 is instantaneously turned into an equivalent direct current (■) by the current transformer CT and current detector 5 installed on the AC ml side, and becomes a feedback signal for the minor current control system. On the other hand, the actual rotational speed of the motor 2 is detected by a pulse generator, a speed detector 3 such as a lunolva, and a speed detector 7 which are directly connected to the motor 2, accurately and without any time delay (if any, the speed control The deviation, which is compared with the speed command Sp as a speed feedback signal ratio, is input to the speed controller 4, and
Ip corresponding to the above deviation is output. Further ゛'P
The rectifier circuit 1 is controlled to fire by the current control 46 according to the deviation between the PbR command Ip and the equivalent DC current value, and the output DC voltage is controlled so that the target rotational speed is achieved.

FIG. 6 is a block diagram obtained by converting the control system shown in FIG. 5 into a block diagram using a transfer function. Here, the angular velocity ω is represented by the relationship C between the machine precurrent IA and the load torque TD, and if the load disturbance (load torque) To is added and the armature current IA to compensate for it can be given, then the angular velocity It can be seen that ω does not change at all. Should this be compensated for in an uncontrolled system? The IC Isogo flow IA is given as the output of the speed controller G8, and the '1 flow f11+ is determined as the output of the current controller Gc, so it will be greatly influenced by the responses of the speed control system and the current control system. In such a control system, the largest load disturbance To is the jamming of the rolled material between the rolls of the rolling mill.

This reduction in rotational speed that occurs when the rolled material is bitten is called impact drop, and the process that compensates for this is called impact drop compensation. When an impact drop occurs, the above-mentioned controller performs a correction operation due to a major loose and a correction operation due to a minor loose. However, the control system, including the main circuit for driving the electric motor, has mechanical delay elements such as the motor's coefficient of inertia (GD) and friction, and mechanical delay elements such as the inductance component of the control loop. , there is a limit when improving the response speed, and it is extremely difficult to reduce it below a certain value.

An example of control for compensating for a sudden decrease in the load on the electric motor is disclosed in Japanese Patent Publication No. 58875/1983.

[Purpose of the invention]

An object of the present invention is to rapidly and stably suppress speed fluctuations to a minimum when stably controlling the rotational speed of an electric motor without going through the speed controller and current controller in the original control loop. To provide a control method.

[Summary of the invention]

In order to achieve the above object, a method for controlling the speed of a DC motor according to the present invention includes a variable control power supply device that supplies driving power to the motor, a speed detector that detects the actual rotational speed of the motor, and a speed detector that detects the actual rotational speed of the motor. a minor-loose current control circuit that generates a current command from the deviation between a speed detection signal and a speed command signal, and compensates a drive current flowing to the motor using the current command; The load disturbance applied to the motor is estimated based on the speed component in a state where no load disturbance is applied and the speed detection signal obtained from the drive current and torque constant of the motor, and the equivalent drive current of the motor is calculated based on this estimated load disturbance. The minor loose current control circuit is characterized in that it calculates the value and gives the calculated equivalent drive current value to the minor loose current control circuit.

In other words, to summarize, we simulate the back electromotive force constant and inertia factor of the motor, estimate the angular velocity using the simulated results and the current drive current of the motor, and then calculate the estimated angular velocity and the angular velocity in the absence of load disturbance. The load disturbance is estimated using the above estimation, the compensation current is calculated from the estimation result, and the calculated value is added to the current command to perform feedforward compensation control.

[Embodiments of the invention]

Next, a method for controlling the speed of an electric motor according to the present invention will be explained based on the drawings.

FIG. 1 shows a main part of the speed control method according to the present invention in a control block diagram. Note that in this embodiment, the same reference numerals or symbols are given to the parts that overlap with those in FIGS. 5 and 6 and will be explained below.

As mentioned earlier, the angular velocity of the wind motor 20 in Figures CH2 and 6 is given by equation (1), the armature current Ia is given as the output of the speed controller G6, and the current is given as the output of the current controller Gc. In order to determine the ID, it was largely dependent on the responses of the speed control system and the current control system.

Therefore, in the present invention, as shown in FIG. 1, the back electromotive force constant ζφ and the inertia factor J are simulated and given as a simulated back electromotive force constant ζφ' and a simulated inertia rate J', respectively. Estimate the angular velocity ω from the armature current I.
・(2) Now the simulated back electromotive force constant ζφ′ and the simulated inertia rate J′ become J'S.
are simulated accurately, and each J=J
'=J, ζφ−ζφ'=ζφ'.

Subtracting equation (1) from equation (2)...°・TD=JS(ωB-ω)...(
3), and the load disturbance can be estimated accurately. The issues here are the back electromotive force constant ζφ and the inertia factor J
In any case, high speed detection accuracy is required due to the need to detect minute changes in speed. However, the accuracy problems can be solved by using today's developed digital technology, microcontrollers, etc.

When the load disturbance TD is determined, the back electromotive force constant ζφ and current detection gain are converted, and the compensation current In for compensating for load fluctuation is calculated using the following formula. If we directly add this to the flow rate Ip of the 1L flow control system, we get the following without the help of a speed controller:
It is possible to compensate for load disturbances in a kind of feedforward manner.

However, in an actual current control system, the current command Ip
Since there is a response delay from 1'a to the actual armature current 1'a, compensation PatIo is calculated by compensating for the response delay.
Since it is possible to compensate in a faster manner by creating ', In' that compensates for the current response delay is determined by the following formula.

Io' = (1-1-'r: 5) Io
-(5)S Rainbow grass operator 'rc: Current response delay time Adds the compensation Pat, In' obtained by equation (5) to the current command Ip. FIG. 2 shows a block diagram of the speed control system in consideration of the actual transfer function of the current controller Jc and the negative f...f disturbance compensation block. In an actual control system, the speed ω and current IA necessary for load estimation shown in Fig. 1 are detected via a speed detector and a Tlil galvanometer, respectively, so in Fig. 2, the respective feedback signals are is multiplied by the gain H8 and the reciprocal of Fc to obtain the angular velocity ω and the armature current IA.
In general, the current controller dcVi can be separated into an integrator 1/TS and a gain KP (control gain for three-phase full-wave rectification full-wave control) as shown in Figure 2.
Current control systems include damping compensation and current rate control materials, but in either case, the forward-looking element is an integral system. ). It is a very difficult problem to digitally implement the differential elements included in the torque estimation block with high precision and sufficient responsiveness, and this cannot but become an obstacle in implementation. Therefore, in the present invention, we focus on the integrator of the a-flow control system, and by putting the correction pat at the latter stage of the integrator, we can just remove the differentiator of the torque estimation block and respond without using a differentiating circuit. You can make decorative threads.

In Figure 2, the forward transfer function from point 0 to point 1 is as follows. In the above equation, the differentiator in the first term and the integrator in the third term cancel each other out. Therefore, if the compensation pa t is brought to the 0 point after the integrator, it is equivalent to using a differentiating circuit.
Moreover, a control loop can be constructed without impairing the compensation effect.

The output of the conventional speed controller was limited by the limiter, which also served as a stray flow limiting circuit, but according to the present invention, a correction pat is added inside the limiter, so the conventional limiter circuit can be used. In this case, current limiting will not work. Therefore, the actual current ■ should be constantly checked and if it exceeds the overload control, each speed controller
The outputs of the current controller and torque estimation controller are held to serve as a current limiter. Water control system 41 (In any case, it must be configured with a digital control system in order to accurately calculate minute changes, and in digital control systems, it is problematic to hold multiple outputs at the same time under certain conditions. 1 ability.

Next, FIG. 3 shows a block diagram when a current limiter is incorporated into the control system according to the present invention.

Calculate the torque compensation signal without using a differentiator by carefully calculating the current feedback and calculating 9 based on the speed feedback value It /i5, taking into account the characteristics of the current control system and response delay, and calculate the torque compensation signal without using a differentiator. Superimposed on control signal. +1! The current limit is set in accordance with A and B when the DC 1S motor is overloaded, and when the characteristic body is exceeded, the output of the speed controller, current controller, and torque compensation calculation circuit is clamped by the output of the current limiter. . In addition, this control system is entirely a digital control system (
It is preferable to form R.

This control system helps the speed control system especially against load disturbances (variation in load torque), and since the loop gain of minor looseness is approximately 1, it is a completely stable control system with no fear of hunting. It has become. Also, for ζφ' and J', which require accuracy, if they go awry, their evaluation will be degraded as a disturbance element of the speed control system, but ultimately it will be corrected by the response of the speed control system of the major loop. Therefore, there is no concern that the response of the conventional speed control system will deteriorate, and the conventional speed control system can be evaluated as a type of monitor control.

Here, '11!' for load disturbances with and without compensation using the present invention! Figure 4 shows the difference in responsiveness of the machine current and rotational speed ω.

In FIG. 4, the solid line shows the case where the present invention is applied, and the broken line shows the case where the invention is not applied. From this figure, when the present invention is applied, compared to the case where the present invention is not applied, the amount of speed is 3.4
Figure 5 shows that the recovery time is 3.6 times better and the area is 12 times better.

It can be seen that the control system has become something that could never be achieved with a simple feedback control system like the one shown in Figure 6.

Although this embodiment shows the case of a DC motor, it can be said that it can be easily applied to the speed control system of a father-flow forming machine in the same way. [Effects of the Invention] According to the present invention as described above, , the compensation current value is calculated by estimating the load disturbance, and this compensation current value is added to the outflow command value of the aυ1 control loop, so there is no need to intervene with major loop or minor loop control as in the past. The current can be compensated, and as a result of (7), speed fluctuations of the motor due to load disturbance can be rapidly and stably suppressed without being limited by minor looses or major loops.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for load disturbance estimation according to the present invention, FIG. 2 is a block diagram of a speed control system to which load disturbance compensation according to the present invention is applied, and FIG. 3 is a block diagram showing another example.
Fig. 4 is an explanatory diagram showing the difference in characteristics depending on the presence or absence of compensation according to the present invention, Fig. 5 is a block diagram showing a conventional general speed control system, and Fig. 6 is a transfer function representation of the control system of Fig. 5. FIG. 1... Three-phase full-wave control rectifier circuit, 2... DC motor, 3
...Speed detector, 4...Speed controller, -Current detector, 6...Current controller, 几...Speed detection signal, SP
...Speed command, Ip...Current command, In'...Compensation current that compensates for response delay, ω...Angular velocity, ＾...
- Armature current, TD...Load disturbance (torque).

Claims (1)

[Claims] 1. A variable control power supply device that supplies driving power to the electric motor;
A speed detector that detects the actual rotational speed of the electric motor, and a minor that generates a current command from the deviation between the speed detection signal from the speed detector and the speed command signal, and compensates the drive current flowing to the electric motor using this current command. A method for controlling the speed of an electric motor by a loop current control circuit and a load applied to the electric motor based on a speed component in a state where no load disturbance is applied and the speed detection signal obtained from the drive current and torque constant of the electric motor. A speed control method for an electric motor, comprising estimating a disturbance, calculating an equivalent drive current value of the motor based on the estimated load disturbance, and providing the calculated equivalent drive current value to the current control circuit of the minor loop. .