KR20020016453A - Control algorithm for suppressing vibration of shaft at rolling mill - Google Patents

Abstract

PURPOSE: A control method for suppressing the vibration of a shaft at a rolling roll is provided which improves load response characteristics by compensating the vibration of the shaft during acceleration and deceleration as maintaining characteristics of an existing proportional integration controller. CONSTITUTION: In a vibration control method of a roll shaft in which a vibration of a shaft connecting a motor with a revolution body is controlled through proportional integration control, the method for controlling the vibration of a shaft at a rolling roll comprises the steps of outputting a control torque(Te) according to a standard speed inputted into a speed controller(41); and controlling a motor speed by controlling the control torque(Te) inputted by an observation device(43) with a feedback gain.

Description

Control algorithm for suppressing vibration of shaft at rolling mill}

The present invention relates to a control method for suppressing shaft vibration occurring in a drive motor shaft of a rolling mill, and in particular, to improve speed control performance of a proportional integral controller (hereinafter referred to as a 'PI controller') and to suppress shaft vibration. A rolling roll shaft vibration control method.

1 is a schematic diagram showing a configuration relationship between a motor and a roll shaft of a general two inertial system.

As shown in FIG. 1, a motor drive system for a rolling mill is a multi-inertia system consisting of a motor 1, a gear and a roll 3, and a shaft 4 connecting these three masses. However, this multi-inertial system is itself nonlinear and unstable due to the low stiffness of the shaft 4 and the backlash of the gears.

Conventionally, a PI controller is used as a speed controller of a multi-inertia system connected by such a low rigidity shaft (4).

2 is a conceptual diagram illustrating a PI controller according to the prior art, and FIG. 3 is a control block diagram of the PI controller illustrated in FIG. 2.

As shown in Fig. 2 and Fig. 3, for this PI controller design, control gain is set from the one inertia system, first assuming that the rigidity of the shaft 4 is infinite. Under the assumption that the stiffness of the axis 4 is infinite, the PI controller 10 by the one inertia system performs PI control on the input reference speed ω _ref to output the control torque Te and output the control torque Te. Outputs the motor speed (ω _M ) to which the total inertia (J _S ) of the system is applied after being subtracted from the distortion torque (T _L ).

Here, the total inertia J _S of the system is a value obtained by adding the inertia J _M of the motor 1 and the inertia J _R of the roll 3, as in Equation 1. 1 / Js, K / s, and 1 / Js on the drawings indicate respective loads.

Where J _S is the total inertia of the system, J _M is the inertia of the motor, and J _R is the inertia of the roll.

Such a conventional PI controller has an advantage of easy system installation due to the simple configuration of the controller. However, since the axial vibration occurs when the speed command value changes or load torque is applied, the PI controller lowers the gain or speed command. The disadvantage is that you must choose a method that changes slowly.

On the other hand, Equation 2 is a formula for calculating the motor speed (ω _M ) with respect to the reference speed (ω _ref ) as a transfer function, Equation 3 is a formula for calculating the gain of the PI controller.

In Equations 2 and 3, Kp is a proportionality constant, Ki is an integral constant, and ω _C is a cut-off frequency of the speed controller.

The control torque Te output through the PI controller is calculated as shown in Equation 4.

On the other hand, Figure 4 is a speed difference feedback control block diagram according to the prior art.

Conventional speed difference feedback control compensates torque by multiplying the difference between motor speed and roll speed while maintaining PI control. Since the speed difference feedback control reduces only vibration phenomena above the anti-resonant frequency, it is not a method of suppressing the fundamental vibration, and the speed difference feedback control controls the difference between the motor speed (ω _M ) and the roll speed (ω _R ). because it represents the first derivative of T _Sh), it compensates for the amount of change of the shaft torque (T _Sh). Therefore, it is necessary to know by measuring the roll speed (ω _R ), there is a disadvantage that the control torque Te can be calculated.

On the other hand, the controller input by the speed difference feedback control is calculated through the equation (5).

Where K is a constant that adjusts the feedback gain.

5 is a control block diagram illustrating an RMFC, which is a two-stage control method according to the prior art.

As shown in FIG. 5, Reference Model Following Control (RMFC) is a two-step control method that compensates for the disadvantages of PI control and speed difference feedback control, and includes a first speed controller 21 and a first inertia system model of a mechanical system. It consists of two speed controllers 22, and includes a disturbance meter. The first speed controller 21 is designed to have a low cutoff frequency in order to secure the stability of the entire system, and the second speed controller 22 is designed to control a single inertia system so that the cutoff frequency is set high to provide a quick response characteristic. Have

And, the disturbance measuring device 23 is configured independently of the PI controller described above.

On the other hand, in the RMFC, increasing the I gain (integral gain) of the PI control improves the responsiveness to load disturbance, but damping is worsened, while increasing the P gain (proportional gain) improves damping. Therefore, after adjusting the response speed with I gain (integral gain), the damping is set to P gain (proportional gain) to install the disturbance observer 23.

The characteristics of this RMFC are as follows. Firstly, assuming that the mechanical system's stiffness is large, the mechanical system can be modeled as one inertia system, where the inertia of the mechanical system is expressed as (J _M + J _R ), and the second characteristic is the one inertia system. It has a fast response by the second speed controller 22 for controlling the speed, the third characteristic is that the disturbance estimator is the difference between the actual motor speed (ω _M ) and the model speed by the one inertial system (ω Calculate the load disturbance from _a- ω _M ).

If there is no disturbance measuring device 23 in this RMFC is the same as the two degree of freedom controller of the forward compensation type. However, since the two degree of freedom controller does not improve the response to the load disturbance fundamentally, there is a problem that the response characteristics to the disturbance should be improved by properly configuring the disturbance measuring device 23.

On the other hand, the transfer function of the speed controllers 21 and 22 and the disturbance measuring device 23 is calculated by the equation (6).

Here, Gs1 is a transfer function of the first speed controller, Gs2 is a transfer function of the second speed controller, Gm is a transfer function of the disturbance meter, Kp is a proportional constant, and Ki is an integral constant.

From Equation 6, the transfer function of the motor speed (ω _M ) for the load disturbance is shown in Equation 7.

Such RMFC can make the speed response characteristic faster than the conventional PI controller, but has a disadvantage in that the response characteristic is bad and difficulty in proper design of the disturbance measuring instrument.

The present invention is provided to solve the problems of the prior art as described above, and provides a rolling roll shaft vibration suppression control method for improving the load response characteristics by compensating the axial vibration phenomenon during acceleration and deceleration while maintaining the characteristics of the conventional PI controller. Its purpose is to.

1 is a schematic diagram showing a configuration relationship between a motor and a roll shaft of a general two inertial system,

2 is a conceptual diagram showing a PI controller according to the prior art,

3 is a control block diagram of the PI controller shown in FIG.

Figure 4 is a speed difference feedback control block diagram according to the prior art,

5 is a control block diagram illustrating an RMFC, which is a two-stage control method according to the prior art;

6 is a related two inertial block diagram of the present invention;

7 is an axial vibration control block diagram according to an embodiment of the present invention.

♠ Explanation of symbols on the main parts of the drawing ♠

1: motor 3: roll

4: axis 10: PI controller

21: first speed controller 22: second speed controller

23: disturbance measuring instrument 41: speed controller

43: Observer

According to the present invention for achieving the object as described above, in the roll shaft vibration control method for controlling the vibration of the shaft connecting the motor and the rotor through the proportional integral control, the control torque according to the reference speed input to the speed controller A roll axis vibration control method comprising the step of outputting and controlling the motor speed by adjusting the control torque input to the observer with a feedback gain is provided.

Further, according to the present invention, the control torque is calculated by the equation (10).

In the following, with reference to the accompanying drawings a preferred embodiment of a rolling roll shaft vibration control method according to the present invention will be described in detail.

6 is a related two inertial block diagram of the present invention, and FIG. 7 is an axial vibration control block diagram according to an embodiment of the present invention.

In the axial vibration suppression control method of the present invention, the component of the axial torque T _Sh is observed through the observer 43, and this is added to the speed controller 41 output torque Te, thereby suppressing the vibration suppression effect and the response characteristics of the controller. Improve.

The observer 43 is designed with a two inertial system as shown in FIG. The input control torque T _M and the disturbance torque T _L are added to determine the motor speed ω _R and the load speed ω _L , and the input control torque T _M is modeled under load. Calculated by the equation, the disturbance torque T _L is calculated by the modeling equation of the motor 1, which is then integrated in the integrator 1 / S, and the proportional constant K _sh is applied to the control torque T _M ) and the disturbance torque T _L are added or subtracted.

The state equation of this two inertial system is derived as in Equation (8).

From here, Is the state variable, T _M is the control torque of the motor, T _L is the disturbance torque, ω _M is the motor speed, and ω _L is the load speed.

The output from this two inertial system model is compared with the output from the actual plant.

Where z is an arbitrary variable and H is the time constant that is the gain of the observer.

Therefore, the axial torque is calculated by the arbitrary variable z and the motor speed. The control input of the speed controller of the present invention consists of the sum of the PI controller output and the estimated shaft torque as shown in Equation (10).

Meanwhile, as shown in FIG. 7, the axial vibration control algorithm adds the value of the estimated shaft torque T _sh to the output torque Te of the conventional PI controller to drive the motor. Then, the gain value of the K constant is fed back to have an appropriate controller gain.

As described in detail above, the rolling roll shaft vibration control method of the present invention is a control method of suppressing the phenomenon of shaft vibration during acceleration and deceleration of the rolling roll while maintaining the characteristics of the PI controller. Therefore, there is an advantage that the application is easy and the design is simple.

In addition, the rolling roll shaft vibration control method of the present invention has the advantage that the vibration suppression effect and the response characteristics of the controller is good by applying the output to the input of the plant.

Although the technical idea of the rolling roll shaft vibration control method of the present invention has been described above with the accompanying drawings, this is illustrative of the best embodiments of the present invention and is not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (2)

In the roll shaft vibration control method for controlling the vibration of the shaft connecting the motor and the rotating body through the proportional integral control, Outputting control torque according to the reference speed input to the speed controller; And controlling the motor speed by adjusting the control torque input to the observer as a feedback gain. The method of claim 1, The control torque is calculated by the formula 1, characterized in that the roll axis vibration control method. Equation 1 Where Kp is the proportional constant, Ki is the integral constant, 1 / s is the integrator, ω _ref is the reference speed, ω _M is the motor speed, K is the feedback gain, and T _sh is the axial torque.