JP5223470B2 - Electric motor control device - Google Patents

Description

  The present invention relates to a load following control device that performs electric motor control.

In general, motor control is performed by a drive control device having a speed control function for controlling the speed of a motor and a current control function for controlling a motor current. An electric motor used for strip rolling and threading in steel rolling and process equipment needs to be accurately controlled to a desired speed by this drive control device from the viewpoint of stable operation.
In the conventional motor control by the drive control device, the control gain is set at a fixed value so that stable operation is possible regardless of the load. On the other hand, recently, several speed control techniques that can obtain a requested speed response even when the load fluctuates have been proposed.

  For example, as a prior art, there is one described in Patent Document 1 below. In the device described in Patent Document 1, paying attention to the change in the inertia moment of the mechanical load during operation, the speed control gain for obtaining the required response is calculated from this inertia moment by back calculation. And the speed control gain adjusted at the time of trial operation is correct | amended with the calculated | required speed control gain. FIG. 4 is a configuration diagram showing a conventional motor control device, and shows a specific configuration described in Patent Document 1. In FIG. Details will be described below with reference to FIG.

A torque signal τ ₁ output from a speed controller (ASR: Automatic Speed Regulator) 17 includes a speed command (SP_Ref) from an external controller and a motor speed ω ₁ output from a speed detector (SS: Speed Sensor) 6. It is generated based on the deviation. The ASR 17 multiplies the input deviation by a predetermined gain setting value, and outputs a torque signal τ ₁ so that the deviation can be eliminated.

Reference numeral 5 denotes a current detector that detects a current value flowing through the electric motor 1. The torque signal τ ₁ output from the _{ASR 17} is subtracted from the current feedback τ _IFbk from the current detector 5, and is input to a current controller (ACR: Automatic Current Regulator) 18 as an output τ _T. The output τ _T is processed by the ACR 18 and input to a power conversion circuit 19 such as an IGBT (Insulated Gate Bipolar Transistor). The ACR 18 normally constitutes a current feedback loop in order to improve the speed control response and improve the stability of the speed control system.

  In the ASR 17, gain adjustment is performed during a trial operation, and a speed control gain for obtaining a response to be requested from an inertia moment such as a load applied to the electric motor 1 during load operation is calculated backward. Then, the gain of the ASR 17 is corrected so as to become the gain calculated in reverse.

  However, in the case where only the gain of the ASR 17 is corrected according to the moment of inertia such as a load, as in the case of the patent document 1, in this speed control system, the speed control gain may not be increased beyond a certain value. . The reason for this is as follows.

  In general, for the purpose of making the speed ratio between the electric motor 1 and the load machine 3 variable, a speed reducer is often employed as the torque transmission mechanism 4 that couples the two. Since this reduction gear usually has backlash, the mechanical characteristics differ between when the gear is in contact and when the gear is away. In particular, when the gear is disengaged, the electric motor 1 and the load machine 3 are insulated from each other, so that the speed control system becomes unstable. Further, if the speed control gain is too large, the response of the speed control closed loop will increase too much, so the instability of the speed control system will increase, causing a hunting phenomenon, or connecting the electric motor 1 and the load machine 3. If the shaft rigidity is low, torsional vibration may occur.

  As a conventional technique for solving such a problem, for example, a technique described in Patent Document 2 below has been proposed. In the device described in Patent Document 2, the gain of the acceleration and deceleration current control system is changed according to the magnitude of the inertia moment of the load. Therefore, in any case of no load, load, or load change, the acceleration and deceleration currents are always appropriate when accelerating and decelerating the motor, corresponding to the moment of inertia of all load conditions. Can be given to the electric motor. Therefore, the electric motor can always be controlled with the required responsiveness.

FIG. 5 is a block diagram showing a conventional motor control device, and shows a specific configuration described in Patent Document 2. In FIG. That is, in FIG. 5, an acceleration / deceleration current calculator (FF) 20 is added to the configuration shown in FIG. 4, and the gain of the acceleration / deceleration current calculator 20 can be corrected by a gain setting value from an external controller. It is configured as follows.
In addition to the method shown in FIG. 5, the configuration shown in FIG. 6 is generally known as a method using an external controller. That is, the torque τ _acc required for acceleration and deceleration is calculated by an external controller and added to the output τ ₁ of the ASR 17.

On the other hand, the configuration described in Patent Document 3 below employs the configuration shown in FIG. 7 in order to solve the problem that the speed control gain cannot be increased. That is, the model ASR 21 and the mechanical system model 22 are added in the drive control device 23, and control is performed so that the ideal speed ω ₀ that is the output of the mechanical system model 22 follows the speed command from the outside.

Specifically, in the example shown in FIG. 7, the torque signal τ ₀ output from the model ASR 21 is an output of the mechanical system model 22 to which an external speed command (SP_Ref) and the torque signal τ ₀ are input. It is generated based on the deviation from the speed ω ₀ .
The mechanical system model 22 is composed of one integrator, and the ideal speed ω ₀ that is the output corresponds to the speed when the electric motor 1 and the load machine 3 are regarded as one mass point. In the model ASR21, P control is performed. Since there is no load torque in this closed loop, there is no problem because the speed command matches the actual speed.

The torque signal τ ₁ output from the ASR 17 is generated based on the deviation between the speed command SP_Ref and the motor speed ω ₁ output from the speed detector 6. In the ASR 17, PI control is performed. This is because the speed reduction in the presence of load torque can be compensated by integrating the deviation between the speed command and the actual speed. Further, since the output τ _{0 of the} model ASR 21 does not change with the motor speed ω ₁ , the stability of the speed control is maintained regardless of the state of the mechanical system. Thereby, the responsiveness of the speed control due to the change of the external speed command at the time of acceleration and deceleration can be maintained constant, and the circuit for that purpose can be achieved only within the drive control device 23 that controls the electric motor 1. become able to.

Japanese Patent Laid-Open No. 2-303781 JP-A-5-64476 Japanese Patent No. 2552719

In the conventional control device as described above, when the moment of inertia of the mechanical load is constant, the speed response can be set at the initial speed. However, when the inertia moment of the mechanical load changes, the speed control response of the motor speed ω ₁ changes unless the control gain of the model ASR 21 is adjusted. The load disturbance can be dealt with by increasing the control response of the ASR 17, but the control gain of the ASR 17 may not be increased due to stability problems.

  For example, when a looper carriage moves up and down in a steel process line, the moment of inertia of the mechanical load is located on the short end side when the strip is discharged and on the long end side when the strip is accumulated. It shows a different value from the case where That is, there is a problem that the response of the speed control system changes depending on the position of the carriage. As a result, the occurrence of tension fluctuation due to changes in speed control becomes a problem. For example, if the process section is an annealing furnace, the tension fluctuation from the looper propagates to cause tension fluctuation in the furnace, causing the strip to meander. There is a risk that production may be hindered by generating heat buckles.

Conventionally, as a countermeasure, a method of changing a torque command from an external controller or the like in accordance with a continuously changing load has been adopted, but the control cycle of the external controller and the control cycle in the drive control device are Since the control period of the external controller is not always synchronized and the external controller is slow, a delay in torque compensation has occurred.
In recent years, the required level of quality for products has increased, and the looper capacity has increased with the increase in line speed. In addition, the demand for control accuracy of the carriage is increasing. For this reason, appropriate improvements are required.

  The present invention has been made to solve the above-described problems, and its purpose is to make the speed control response variable even when the inertial moment of the load machine changes, or to perform torque compensation by an external controller. Therefore, it is an object of the present invention to provide an electric motor control device that can keep the response of the speed control system constant and simplify the drive adjustment contents.

The motor control apparatus according to the present invention approximates a motor, a load machine, a torque transmission mechanism that mechanically connects the motor and the load machine as one integral element, and flows to the motor , a mechanical system model that outputs an ideal speed. Based on the current detector that detects the current value, the speed command from the external controller and the deviation of the ideal speed output from the mechanical system model, the ideal speed output from the mechanical system model is compared to the speed command from the external controller. The motor speed is output from the mechanical system model based on the first speed control means for outputting the torque signal so as to have a predetermined response and the deviation of the motor speed and the ideal speed output from the mechanical system model. The second speed control means for outputting the first compensation torque signal so as to follow the ideal speed, and the torque when the inertia moment of the load machine changes. Without changing the speed control gain to output a speed control gain and the first compensation torque signal for outputting the item, and a control means for performing torque compensated to load following, control means, first An output obtained by subtracting the current feedback from the current detector from the sum of the torque signal output from the first speed control means and the first compensation torque signal output from the second speed control means is input to the current controller. The output of the current controller is multiplied by the speed ratio between the speed and the ideal speed output from the mechanical system model .

  According to the present invention, even when the moment of inertia of the load machine changes, the speed control response can be kept constant without making the speed control response variable or performing torque compensation by an external controller. The drive adjustment contents can be simplified.

  In order to explain the present invention in more detail, it will be described with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an electric motor control apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes an electric motor used for strip rolling and threading in steel rolling and process equipment, and 2 denotes a drive control device that drives and controls the electric motor 1. 3 is a load machine driven by the electric motor 1, and 4 is a torque transmission mechanism that mechanically connects the electric motor 1 and the load machine 3. The torque transmission mechanism 4 is installed for the purpose of making the speed ratio between the electric motor 1 and the load machine 3 variable, and is configured by, for example, a speed reducer.
The current detector 5 detects the value of the current flowing through the electric motor 1 and the speed detector (SS) 6 detects the speed of the electric motor 1.

Next, a specific configuration of the drive control device 2 will be described.
The drive control device 2 includes, for example, a mechanical system model 7, a model ASR 8, a speed controller (ASR) 9, an LFC (Load Flowing Control) 10, a current controller (ACR) 11, and a power conversion circuit 12.
Mechanical system model 7 approximates the electric motor 1 and the load machine 3 and the torque transmission mechanism of the reduction gear 4 as one integral element, and outputs the ideal speed omega _0. That is, the ideal speed ω ₀ is a speed when the electric motor 1, the load machine 3, and the torque transmission mechanism 4 are regarded as one mass point.

The model ASR (first speed control means) 8 receives the deviation between the speed command (SP_Ref) from an external controller (not shown) and the ideal speed ω ₀ output from the mechanical system model 7 as an input. The torque signal τ ₀ is output so that ω ₀ has a desired response to the speed command SP_Ref from the external controller. The torque signal τ ₀ that is the output of the model ASR ₈ is an input of the mechanical system model 7. In the model ASR8, P control is performed.

The ASR (second speed control means) 9 receives a deviation between the motor speed ω ₁ detected by the speed detector 6 and the ideal speed ω ₀ output from the mechanical system model 7, and the motor speed ω ₁ is A compensation torque signal τ ₁ is output so as to follow the ideal speed ω ₀ . In the ASR 9, PI control is performed. This is because a decrease in speed when there is a load torque can be compensated by integrating the deviation between the speed command and the actual speed.

The drive control device 2 includes a speed control gain for outputting the torque signal τ ₀ and a speed control gain for outputting the compensation torque signal τ ₁ when the inertia moment of the load machine 3 changes. A function of performing torque compensation so as to follow the load without changing is provided.
A specific configuration (control means) for realizing the above function will be described below.

The LFC 10 receives the deviation between the motor speed ω ₁ detected by the speed detector 6 and the ideal speed ω ₀ output from the mechanical system model 7 so that the load follows the load even when the moment of inertia of the load machine 3 changes. A compensation torque signal τ ₂ is output. The compensation torque signal τ ₂ output from the LFC ₁₀ is added to the sum of the torque signal τ ₀ output from the model ASR ₈ and the compensation torque signal τ ₁ output from the ASR 9. In the LFC 10, P control is performed.

For example, when the moment of inertia of the load machine 3 becomes larger than the moment of inertia when the speed control response is adjusted, the motor speed ω ₁ is delayed from the ideal speed ω ₀ , so that the positive compensation torque signal τ from the LFC 10. ₂ is output. As a result, the positive compensation torque signal τ ₂ is added to the sum of the torque signal τ ₀ and the compensation torque signal τ ₁ so that the motor speed ω ₁ can follow the ideal speed ω ₀ . Note that the torque signal τ ₀ cannot increase the speed control gain as described above. For this reason, when the LFC 10 is not provided, a delay occurs until the motor speed ω ₁ follows the ideal speed ω ₀ .

Then, the current feedback τ _IFbk from the current detector 5 is further subtracted from the sum of the torque signal τ ₀ and the compensation torque signal τ ₁ added to the compensation torque signal τ ₂ , and the output τ _T is input to the ACR 11. Is done. Thereafter, the output τ _T is processed by the ACR 11 and input to the power conversion circuit 12 such as an IGBT.

  According to the first embodiment of the present invention, even when the inertia moment of the load machine 3 changes, the response of the speed control system is kept constant without making the speed control response variable or performing torque compensation by an external controller. The drive adjustment contents can be simplified.

Embodiment 2. FIG.
2 is a block diagram showing an electric motor control apparatus according to Embodiment 2 of the present invention. In the drive control device 2 shown in FIG. 2, the same function as that of the first embodiment is ensured by including the divider 13, the multiplier 14, and the circuit changeover switch 15.

Specifically, the divider 13 outputs a speed ratio τ ₃ between the motor speed ω ₁ detected by the speed detector 6 and the ideal speed ω ₀ output from the mechanical system model 7. Then, the speed ratio τ ₃ output from the divider 13 is multiplied by the value processed by the ACR 16 by the multiplier 14. The ACR 16 receives an output τ _{T obtained} by subtracting the current feedback τ _IFbk from the sum of the torque signal τ ₀ output from the model ASR ₈ and the compensation torque signal τ ₁ output from the _{ASR 9} , and this output τ _T Processed by ACR16.

For example, when the inertia moment of the load machine 3 becomes larger than the inertia moment when the speed control response is adjusted, the motor speed ω ₁ is delayed with respect to the ideal speed ω ₀ , and thus the speed ratio output from the divider 13. τ ₃ becomes larger than 1. Then, by multiplying the speed ratio τ ₃ by the value processed by the ACR 16, the motor speed ω ₁ can follow the ideal speed ω ₀ .

In the divider 13, when the motor speed ω ₁ is used as the denominator, 0 is input to the denominator when the motor 1 is stopped, and thus the value processed by the ACR 16 is multiplied by infinity. The circuit change-over switch 15 is provided to solve such a problem. FIG. 3 is a diagram showing an operation flow of the circuit changeover switch shown in FIG. 2, and shows a function of adjusting the value of the speed ratio τ ₃ output from the divider 13 according to the value of the input motor speed ω _1. Yes. That is, when the motor speed ω ₁ is less than the predetermined speed, the speed ratio τ ₃ = 1 is output, and when the motor speed ω ₁ is equal to or higher than the predetermined speed, the speed ratio τ ₃ = ω ₀ / ω ₁ is output. In such a case, control for amplifying the torque is performed according to the state of the motor speed ω ₁ .

It is a block diagram which shows the control apparatus of the electric motor in Embodiment 1 of this invention. It is a block diagram which shows the control apparatus of the electric motor in Embodiment 2 of this invention. It is a figure which shows the operation | movement flow of the circuit changeover switch shown in FIG. It is a block diagram which shows the control apparatus of the conventional electric motor. It is a block diagram which shows the control apparatus of the conventional electric motor. It is a block diagram which shows the control apparatus of the conventional electric motor. It is a block diagram which shows the control apparatus of the conventional electric motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 2, 23 Drive control apparatus 3 Load machine 4 Torque transmission mechanism 5 Current detector 6 Speed detector (SS)
7, 22 Mechanical system model 8, 21 Model ASR
9, 17 Speed controller (ASR)
10 LFC
11, 16, 18 Current controller (ACR)
12, 19 Power conversion circuit 13 Divider 14 Multiplier 15 Circuit switch 20 Acceleration / deceleration current calculator (FF)

Claims (2)

A mechanical system model that approximates an electric motor, a load machine, a torque transmission mechanism that mechanically connects the electric motor and the load machine as one integral element, and outputs an ideal speed;
A current detector for detecting a current value flowing through the electric motor;
Based on the speed command from the external controller and the deviation of the ideal speed output from the mechanical system model, the ideal speed output from the mechanical system model has a predetermined response to the speed command from the external controller. First speed control means for outputting a torque signal,
Based on the speed of the motor and the deviation of the ideal speed output from the mechanical system model, a first compensation torque signal is output so that the speed of the motor follows the ideal speed output from the mechanical system model. Two speed control means;
Torque to follow the load without changing the speed control gain for outputting the torque signal and the speed control gain for outputting the first compensation torque signal when the moment of inertia of the load machine changes. Control means for performing compensation;
Equipped with a,
The control means outputs an output obtained by subtracting the current feedback from the current detector from the sum of the torque signal output from the first speed control means and the first compensation torque signal output from the second speed control means. An electric motor control apparatus, wherein the electric motor controller is inputted to a current controller, and an output of the current controller is multiplied by a speed ratio between the speed of the electric motor and an ideal speed outputted from the mechanical system model . The control means obtains the speed ratio using the speed of the motor as a denominator, and when the speed of the motor is less than a predetermined speed, the speed ratio is set to 1 and the output of the current controller is multiplied. The motor control device according to claim 1.

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