Method for locking the screwdown motor shaft after the screwdown motor of a plate mill has been stopped

Abstract

The application discloses a method for locking the shaft of a screwdown motor after the screwdown motor of a middle plate rolling mill stops, and relates to the technical field of rolling mills, which comprises the following steps: when the screwdown motor is in the state of starting, speed increasing, stable running and speed decreasing, and the absolute value of the rotating speed of the screwdown motor is greater than a preset value, setting the rotating speed regulator of the screwdown motor on the main side as a proportional-integral regulator; when the screwdown motor is in the state of speed decreasing, and the absolute value of the rotating speed of the screwdown motor is less than or equal to the preset value, and the screwdown motor stops, setting the rotating speed regulator of the screwdown motor on the main side as a proportional regulator. The application effectively avoids the phenomenon that the shafts of the screwdown motors on both sides rotate in a small amplitude in the clockwise and counterclockwise directions alternately after the screwdown motors stop, and the roll gap data on the roll gap instrument fluctuate in a small amplitude around the target roll gap value, and achieves the purpose of locking the shafts of the screwdown motors on both sides.

Description

Technical Field

[0001] This invention relates to the field of rolling mill technology, and in particular to a method for locking the shaft of a rolling mill after the rolling mill has stopped. Background Technology

[0002] The electrical control system for the electric roll cutter in the medium plate rolling mill consists of an operating-side roll cutter motor, a speed encoder for the operating-side roll cutter motor, a speed control device for the operating-side roll cutter motor, and a drive-side roll cutter motor, a speed encoder for the drive-side roll cutter motor, and a speed control device for the drive-side roll cutter motor. An electromagnetic clutch is installed between the operating-side and drive-side roll cutter motor shafts. When the electromagnetic clutch is engaged, a rigid shaft connection between the operating-side and drive-side roll cutter motor shafts is achieved, as well as linkage between the operating-side and drive-side roll cutter motors, synchronously adjusting the roll gap on both sides. When the electromagnetic clutch is disengaged, only one roll cutter motor is activated, while the other roll cutter motor remains stationary, achieving leveling of the roll gap on both sides, i.e., single-action leveling of the roll cutter motor. Since the roll cutter motor is a separately excited DC motor, and the speed control device for the roll cutter motor is also a DC motor speed control device, the outer loop of the roll cutter motor speed control system is a speed loop, and the inner loop is an armature current loop. The control of the operating side pressing motor and the transmission side pressing motor adopts master / slave control. If the operating side is set as the master side, the transmission side should be set as the slave side; if the transmission side is set as the master side, the operating side should be set as the slave side. When the electromagnetic clutch engages and the two pressing motors move in tandem, the armature current input from the main pressing motor speed regulator in the main pressing motor speed control device is simultaneously sent to the input terminals of the main pressing motor armature current regulator in the main pressing motor speed control device and the input terminals of the slave pressing motor armature current regulator in the slave pressing motor speed control device. This ensures that the shaft torque of the two pressing motors remains consistent, enabling them to move in tandem and synchronously adjust the roll gap on both sides. When the electromagnetic clutch disengages and the main pressing motors are leveled individually, the enable signal of the slave pressing motor speed control device is temporarily canceled, prohibiting the slave pressing motor from operating and allowing only the main pressing motor to operate to level the roll gap on both sides. After leveling is completed, the enable signal of the slave pressing motor speed control device is restored, and the two pressing motors immediately return to the tandem state.

[0003] After the pressing motors on both sides of a medium plate rolling mill stop, mechanical brakes are typically used to lock the motor shafts of both pressing motors to ensure the accuracy of the roll gap. However, due to the frequent operation of the mechanical brakes and the frequent operation of the mechanical contacts in the relays and contactors in the control circuit, these easily malfunction and vulnerable parts require frequent replacement. Furthermore, in medium plate rolling mills, due to limitations in the installation location of the mechanical brakes, neither of the pressing motors on either side is equipped with mechanical brakes. Therefore, a more reliable electrical method is needed to lock the pressing motor shafts after the pressing motors stop. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for locking the shaft of the pressing motor after the pressing motor of the medium plate rolling mill stops.

[0005] To solve the above technical problems, the technical solution of the present invention is as follows: A method for locking the shaft of a plate rolling mill pressing motor after it stops includes: When the pressing motor is in the starting, speed-up, stable operation, or deceleration phase and the absolute value of the speed is greater than the preset value, the speed regulator of the main pressing motor is set to a proportional-integral regulator; when the pressing motor is decelerating and the absolute value of the speed is less than or equal to the preset value, or when the pressing motor stops, the speed regulator of the main pressing motor is set to a proportional regulator.

[0006] As a preferred embodiment of the method for locking the shaft of the pressing motor after it stops in the medium plate rolling mill according to the present invention, the method further includes: setting the speed regulator of the main pressing motor to a proportional-integral regulator when the pressing motor is in the starting, speed-up, stable operation, and deceleration stages and the absolute value of the speed is greater than a preset value; and setting the speed regulator of the main pressing motor to a proportional regulator when the pressing motor is decelerating and the absolute value of the speed is less than or equal to the preset value and the pressing motor stops. Obtain the operating status and speed of the pressing motor.

[0007] As a preferred embodiment of the method for locking the shaft of the pressing motor after the pressing motor of the medium plate rolling mill stops according to the present invention, wherein: the input of the speed regulator of the main pressing motor is the difference between the speed setpoint provided by the main pressing motor setpoint integrator and the actual speed value of the main pressing motor.

[0008] In a preferred embodiment of the method for locking the shaft of the pressing motor after the pressing motor of the medium plate rolling mill stops according to the present invention, the preset value is 5 r / min.

[0009] The beneficial effects of this invention are: This invention sets the speed regulator of the main pressing motor to a proportional-integral regulator when the pressing motor is in the starting, acceleration, stable operation, and deceleration stages and the absolute value of the speed is greater than a preset value. When the pressing motor is decelerating and the absolute value of the speed is less than or equal to the preset value, or when the pressing motor stops, the speed regulator of the main pressing motor is set to a proportional regulator. The speed regulator of the main pressing motor in the two stages switches between the proportional-integral regulator and the proportional regulator. This effectively avoids the phenomenon that the motor shafts of the two pressing motors rotate slightly clockwise and counterclockwise after the pressing motors stop, and that the roll gap data on the roll gap meter fluctuates slightly around the target roll gap value. This achieves the purpose of locking the shafts of the two pressing motors. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a flowchart illustrating the method for locking the shaft of the pressing motor after it stops in a medium plate rolling mill, as provided by the present invention. Figure 2 A schematic diagram of a proportional-integral regulator for the main-side pressurized motor. Figure 3 This is a schematic diagram of a proportional regulator for the main-side pressurized motor. Detailed Implementation

[0012] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0013] Figure 1 This is a flowchart illustrating a method for locking the shaft of a medium plate rolling mill after the pressing motor stops, as provided in an embodiment of this application. The method includes the following steps: Step S101: Obtain the operating status and speed of the pressing motor.

[0014] Specifically, the operating states of the pressing motor include starting state, acceleration state, stable operation state, and deceleration state. Among them, the stable operation state means that the pressing motor runs continuously at a fixed speed.

[0015] Step S102: When the pressing motor is in the starting, speed-up, stable operation, and deceleration stages and the absolute value of the speed is greater than the preset value, set the speed regulator of the main pressing motor to a proportional-integral regulator; when the pressing motor is decelerating and the absolute value of the speed is less than or equal to the preset value, and when the pressing motor stops, set the speed regulator of the main pressing motor to a proportional regulator.

[0016] Specifically, when the pressing motor is in the starting, speed-up, stable operation, or deceleration phase and the absolute value of the speed is greater than the preset value, the speed regulator of the main pressing motor is set to a proportional-integral regulator.

[0017] Figure 2 This is a schematic diagram of a proportional-integral (PI) controller for the main-side down-pressure motor speed regulator. In the diagram, Kp is the proportional gain of the main-side down-pressure motor speed regulator, and Tn is the integral time constant of the main-side down-pressure motor speed regulator. The input to the main-side down-pressure motor speed regulator is the difference between the speed setpoint provided by the main-side down-pressure motor speed setpoint integrator and the actual speed value of the main-side down-pressure motor, i.e., the speed deviation.

[0018] Since the two pressing motors adopt master / slave control, when the two pressing motors are linked, the armature current given by the speed regulator of the master pressing motor in the speed control device of the master pressing motor is simultaneously sent to the given input terminal of the armature current regulator of the master pressing motor in the speed control device of the master pressing motor and the given input terminal of the armature current regulator of the slave pressing motor in the speed control device of the slave pressing motor.

[0019] Understandably, when the two pressing motors are linked, after they stop, the speed input from the integrator of the main pressing motor becomes 0, and the actual speed of the main pressing motor should also be 0, meaning the input speed deviation of the main pressing motor speed regulator should be 0. At this time, the shafts of the two pressing motors should not be moving. However, in actual steel rolling, due to pressure fluctuations in the mill balance cylinder, the motor shafts of the two pressing motors rotate slightly clockwise and counterclockwise after stopping. Specifically, this manifests on the roll gap meter as the roll gap data fluctuating slightly up and down around the target roll gap value. The reason for this phenomenon is that when the two pressing motors stop briefly, the enable signal of the speed control device for the two pressing motors is not canceled; the enable signal of the speed control device for the two pressing motors is valid at this time, meaning the speed control device for the two pressing motors is open. At this time, although the speed command from the integrator of the main-side pressing motor becomes 0, the actual speed value of the main-side pressing motor is a small non-zero value. That is, the input speed deviation of the main-side pressing motor speed regulator in the speed control device of the main-side pressing motor is a small non-zero value, so that the input speed deviation of the main-side pressing motor speed regulator in the speed control device of the main-side pressing motor is not 0 at this time.

[0020] To restore the speed deviation to zero, the speed regulator of the main-side pressing motor in the speed control device is a proportional-integral regulator, containing both proportional and integral components. The regulator's output includes the amplified portion of the speed deviation via the proportional component and the accumulated portion via the integral component. This regulator's adjustment causes the motor shafts of both pressing motors to rotate slightly clockwise and counterclockwise several times, thus restoring the input speed deviation of the main-side pressing motor speed regulator to zero. However, this process causes the roll gap data on the roll gap meter to fluctuate slightly around the target roll gap value, affecting the accuracy of the roll gap data. Therefore, improvements are needed.

[0021] Therefore, when the pressing motor is decelerating and the absolute value of its speed is less than or equal to the preset value, and when the pressing motor stops, the speed regulator of the main pressing motor is set to a proportional regulator. Figure 3 This is a schematic diagram showing the speed regulator of the main pressing motor set as a proportional regulator. When the two pressing motors are linked, when the pressing motor decelerates and its speed approaches 0 (i.e., the absolute value of the speed is less than or equal to the preset value) and when the pressing motor stops, the speed regulator of the main pressing motor in the speed control device is switched from a proportional-integral regulator to a proportional regulator.

[0022] Because it only has a proportional element, when the enable signal of the speed control device for the two pressing motors is valid, the two pressing motors can smoothly decelerate to 0 speed without overshoot. After the two pressing motors stop, the speed input from the integrator of the main pressing motor becomes 0. If the actual speed of the main pressing motor shows a slight change that is not zero, that is, if the input speed deviation of the main pressing motor speed regulator in the speed control device of the main pressing motor shows a slight change that is not zero, since the main pressing motor speed regulator in the speed control device of the main pressing motor is a proportional regulator at this time, its output is only the amplified part of the speed deviation through the proportional element. This allows the main pressing motor speed regulator in the speed control device of the main pressing motor, which is a proportional regulator at this time, to immediately eliminate its input speed deviation, without causing the shafts of the two pressing motors to rotate slightly clockwise and counterclockwise. This avoids the phenomenon that the roll gap data on the roll gap meter fluctuates slightly around the target roll gap value, thus achieving the purpose of locking the shafts of the two pressing motors.

[0023] In this embodiment, the preset speed of the pressing motor is 5 r / min. When the pressing motor decelerates and the speed approaches 0, it is 5(r / min)≥n≥0(r / min), or -5(r / min)≤n≤0(r / min), where n is the motor speed, r / min is the unit of speed: revolutions per minute, and the positive and negative signs indicate the two directions of the speed. For example, if a positive number represents the speed in the clockwise direction, then a negative number represents the speed in the counterclockwise direction; that is, 5(r / min)≥|n|≥0(r / min).

[0024] It should be noted that when the two pressing motors are linked, when the pressing motor is not decelerating and its speed is close to 0, and when the motor stops, the speed regulator of the main pressing motor in the speed control device of the main pressing motor needs to be switched from the proportional regulator back to the proportional-integral regulator.

[0025] Similarly, during single-action adjustment of the main-side pressing motor, in order to lock the main-side pressing motor shaft when the main-side pressing motor stops, the speed regulator of the main-side pressing motor in the speed control device should also use a proportional-integral regulator during the starting, acceleration, smooth operation, and deceleration at higher speeds of the main-side pressing motor. When the main-side pressing motor decelerates and its speed approaches 0, and when the pressing motor stops, the speed regulator of the main-side pressing motor in the speed control device should use a proportional regulator, and the speed regulator of the main-side pressing motor in the speed control device should switch between a proportional-integral regulator and a proportional regulator during these two stages.

[0026] After the above improvements, the medium plate rolling mill no longer experienced the phenomenon of the motor shafts of the two pressing motors rotating slightly clockwise and counterclockwise alternately after the pressing motors on both sides stopped, or the roll gap data on the roll gap meter fluctuating slightly up and down around the target roll gap value.

[0027] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for locking the shaft of a pressing motor after it stops in a medium plate rolling mill employing master / slave control, wherein, The armature current input of the main-side pressed motor speed regulator in the speed control device of the main-side pressed motor is simultaneously sent to the input terminal of the armature current regulator of the main-side pressed motor in the speed control device of the main-side pressed motor and the input terminal of the armature current regulator of the slave-side pressed motor in the speed control device of the slave-side pressed motor, characterized in that the method includes: Obtain the operating status and speed of the pressing motor; The input of the speed regulator of the main-side pressing motor is the difference between the speed setpoint provided by the main-side pressing motor setpoint integrator and the actual speed value of the main-side pressing motor. When the pressing motor is in the starting, speed-up, stable operation, or deceleration phase and the absolute value of the speed is greater than the preset value, the speed regulator of the main pressing motor is set to a proportional-integral regulator; when the pressing motor is decelerating and the absolute value of the speed is less than or equal to the preset value, or when the pressing motor stops, the speed regulator of the main pressing motor is set to a proportional regulator.

2. The method for locking the pressing motor shaft after the pressing motor of the medium plate rolling mill stops, as described in claim 1, is characterized in that: The preset value is 5 r / min.

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