SU383491A1 - DEVICE FOR AUTOMATIC REGULATION OF BAND THICKNESS ON ROLLER MILLS - Google Patents

Description

A device for automatically controlling the thickness of a strip in rolling mills is known, comprising a control loop for moving a cutting mechanism with feedback, including a thickness deviation meter, a summing unit with a dead zone, and a feedback control loop with a delay account unit.

To increase the stability of the strip thickness control system with transport delay, it uses the principle of expanding the dead zone by the amount of working by the hydraulic pressure mechanism and maintaining the blocking voltage for a pause time determined by the time delay of the micrometer.

When practicing the deviation of the strip thickness from the wedge-shaped set of small tempo, the discrete regulator, when turned on, creates some processing with respect to the error signal, and the time between its subsequent switching on may be longer than the total pause time.

In this case, the system has a maximum control error, determined by the size of the deadband and the wedge growth rate during the transport lag.

When practicing a wedge-shaped form, deviations of the strip thickness of a greater pace and duration may turn out that the time between subsequent inclusions of the system in one direction will be less than the total

pause time. In this case, the error in adjusting the strip thickness from one inclusion to another increases in proportion to the extended deadband.

Expansion of the dead zone in the above mentioned system is performed in both directions with respect to the disturbing effect, therefore during processing, which may occur if the disturbance sign changes in the rolls, the system will not be able to work it out when measured with a thickness gauge before the next activation, determined by the pause time, which may cause rocking systems and an even greater increase in control error.

The purpose of the invention is to change the dead zone in the direction of deviation testing.

For this, it is proposed to calculate the pause time when the engine is repeatedly turned on.

press the one-way push-up mechanism when first switching on from zero, stop the calculation of the pause time for the controller operation time and then calculate it after turning off the controller in the presence of

feedback signal.

It is proposed to expand the dead zone of the controller in this device in one direction and when changing the mismatch sign, which causes the engine to turn in the opposite direction, reset the previously calculated pause time and extended dead zone.

At the same time, the accuracy of adjusting the crowds and stripes increases while maintaining the stable operation of the system, the device acquires the ability to monitor the processing of the air, without waiting for the end of the calculation of the pause time.

When using in a discrete regulator the principle of extending the dead zone by the amount of processing and the pause time of a thickness gauge with a small constant delay time (0.05 s, it is proposed to introduce a derivative signal over the thickness of the strip, and form it by the first method.

The information about the low-frequency component of the strip thickness variation in the rolls of the stand during detuning from the high-frequency components is only derived from the same sign as the deviation itself.

The deviation from the high-frequency components of the deviation of the strip thickness during the formation of the derivative with respect to the low-frequency coupling is proposed to be performed using an inertial link with a small constant delay time.

When a control signal is generated, taking into account the magnitude of the deviation signal and its derivative of the low-frequency component, the device, if there is a deadband, is put into operation earlier than if the regulator operated only on the deviation signal, which improves the accuracy of the adjustment.

The drawing shows the block diagram of the proposed device for automatic adjustment of the strip thickness.

The thickness of the strip is measured with a thickness gauge 1, which has a small delay time constant.

In the driver unit 2, a signal for deviating the strip thickness from the setpoint is generated. The unit for forming the derivative of the low-frequency component of the thickness deviation includes a series-connected operational amplifier 3, which has a transfer function of the iherm link, two connected in parallel using four diodes 4-7 of the one amplifier 8 and I performing differentiation.

Diodes 4, 5 are included in such a way that differentiation of the low-frequency component of the signal produces variations in band thickness taking into account the sign of the deviation, and diodes 6 and 7 connected to the outputs of operational amplifiers 8, 9 serve to extract the signal of the derivative of the same sign as the deviation ..,

Using a multiplier 10, a signal is generated that is proportional to the product of the derivative signal and a signal proportional to the transport lag time generated by the signal from the tachogenerator 11 using the nonlinearity unit 12.

In summing device 13, a summation control signal, a deviation signal of the strip thickness from the setpoint, a signal received from a multiplier 10, a feedback signal on the engine movement, c-ir deadband, taking into account their signs, are generated. The deadband signal can be set manually or automatically using the gap counting scheme for reversing cold rolling mills.

Two control signals of different polarities are supplied to the contactless device 14 (of the null-organ type), which has the characteristic of a three-position relay with a small deadband.

The signals from the null organs are used to control the keys 15, 16, which serve to turn the engine on one side or the other and control the pause miscalculation unit. When the key 15 or 16 is turned on, rectangular pulses from the generator 17 of the pulses of a constant frequency are fed to the motor control circuit 18, driving the stem of the control spool of the hydraulic pressure mechanism 20.

In addition, rectangular pulses from the frequency generator are also passed to the reversible counter 21, in the initial state of which the initial stroke is recorded. With the help of a code-analog converter 22 and an adder 23 having a reference voltage serving to compensate for the initial stroke, a feedback signal is generated on the displacement of the motor of the required polarity. Using the hardness corrector 24, the feedback signal on the motor movement is fed to the summing device 13. The feedback coefficient on the motor movement can be changed manually using a potentiometer or automatically using a multiplier on reversing cold rolling mills having a skip counting scheme.

For calculating the pause time determined by the transport delay and micrometer delay, a delay miscalculation unit 25 is used, which receives a signal from a pulse sensor 26 mounted on the drive motor shaft 27, a signal from a constant frequency pulse generator 28, signals about the direction of rotation of the engine and a signal for recruited feedback on the movement of the pressure mechanism.

Subject invention

A device for automatically controlling the thickness of a strip in rolling mills, comprising a contour of movement control

a feedback mechanism including a thickness deviation meter, a summing unit with a dead zone and a feedback control loop with a delay counting block, characterized in that, in order to change the dead band in the direction of deviation testing, into a motion control loop

A reversible counter and a three-position relay are inserted in the pressure mechanism, and the summing unit with the dead zone is made phase-sensitive, and a delay-sensitive counting unit is connected to the reversible counter, and a phase-sensitive summing unit is connected to the inputs of the three-position relay.