RU2523032C1 - Rolling mill drive - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: electric drive of a roll mill includes angular velocity setter (1) of independent-excitation DC motor (13), scaling amplifier (2), two comparator elements (3, 4), two nonlinear functional converters (5, 6) performing functions listed in the invention, controller switch element (7), limiting unit (8), speed and current controllers (9, 10), power amplifier (11), current and voltage sensors (12, 14), motor angular velocity and rolling speed sensors (15, 16); result is achieved by damping of oscillation caused by nonlinear dependency of rolling momentum from angular velocity of electric drive, and operating point shift in the electric drive to stable operation zone, which is performed by connection of constant signal U₀ to input signal of current controller at critical angular velocity of motor rotation when oscillation evolves, in order to ensure controlled speed change and respective shift of operating point to stable zone.

EFFECT: improved quality of speed regulation in electric drive.

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Description

The invention relates to an automated electric drive and is intended for use as part of industrial technological complexes of rolling production.

Known electric drives of rolling mills containing a direct current electric motor of independent excitation, the anchor winding of which is connected through a current sensor to the output of a power amplifier, the input of which is connected to the output of a current regulator connected by a summing input to the output of the speed controller, and by a subtracting input to the output of the current sensor, the master and engine angular velocity sensor, the outputs of which are connected respectively to the summing and subtracting inputs of the comparison element, the output of which is connected to the input speed, and a voltage sensor connected to the armature winding of the motor (RF patent No. 2065660. Publ. 20.08.96, Bull. No. 23, IPC H02P 5/06; Thyristor DC drives / A. G. Ivanov et al. - Electrical Engineering , 2001, No. 2, pp. 10-15, Fig. 3; Pivnyak G.G., Beshta O.S., Filkin M.P. Automation of an electric drive in a rolling virobnosti. - Dnipropetrovsk, National University. - 2008, p. .121, Fig. 4.11).

In the known electric drives of rolling mills, speed control and subordinate regulation of the motor current are carried out. During operation of the electric drive as part of the rolling mill as a result of plastic deformation of the metal, a change in load occurs, leading to a violation of the stable operation of the electric drive and the occurrence of vibrations.

Therefore, a disadvantage of the known technical solutions is the low quality of speed control during rolling of metals.

Of the known technical solutions, the closest to the proposed result is an electric drive of a rolling mill containing an independent excitation DC motor, the anchor winding of which is connected through a current sensor to the output of the power amplifier, the input of which is connected to the output of the current regulator, connected by the first summing input to the output of the regulator speed, and subtracting the input to the output of the current sensor, the outputs of the master and the sensor of the angular velocity of the motor are connected respectively to the summing to it and the subtracting inputs of the first comparison element, the output of which through the restriction unit is connected to the first summing input of the speed controller and is directly connected to the first input of the nonlinear functional converter that implements the function

where ε, u ₂ - the first and second input signals; U _e is the voltage corresponding to the level of a logical unit, the second input of which is connected through a scaling amplifier to the output of the speed controller, and the output is connected to the control input of the controlled key connected between the summing input of the speed controller and the output of the second comparison element, the summing input of which is connected to the output of the controller speed, and the subtracting input is connected to the output of the voltage sensor connected to the armature winding of the motor (RF patent No. 2254665, IPC 02P 5/06. - Publish. 20.06.2005, Bull. No. 17).

In the known electric drive, speed and voltage are regulated on the anchor winding and subordinate regulation of the motor current. During operation of the electric drive as part of the rolling mill as a result of plastic deformation of the metal, a change in load occurs, leading to a violation of the stable operation of the electric drive and the occurrence of vibrations.

Therefore, a disadvantage of the known technical solution is the low quality of speed control during rolling of metals.

The purpose of the invention is to improve the quality of regulation of the speed of the electric drive by increasing stability and damping oscillations during rolling of metals.

This goal is achieved by the fact that in the known electric drive of a rolling mill containing a DC motor of independent excitation, the anchor winding of which is connected through a current sensor to the output of the power amplifier, the input of which is connected to the output of the current regulator connected by a summing input to the output of the speed controller, and subtracting input to the output of the current sensor, the outputs of the master and the sensor of the angular velocity of the motor are connected respectively to the summing and subtracting inputs of the first element of comparison, the output to it is connected to the combined input of the restriction unit and the first input of a nonlinear functional converter, the second input of which is connected through a scaling amplifier to the output of the master, summing and subtracting the inputs of the second comparison element are connected to the outputs of the speed master and voltage sensor, respectively, and the output through the controlled key is connected to one from the inputs of the adder, the other input of which is connected to the output of the limiting unit, and the output is connected to the input of the speed controller, the control input is controlled th key connected to the output of the nonlinear function converter; the input of the voltage sensor is connected to the armature winding of the motor, an additional rolling speed sensor and a second non-linear functional converter that implements the function are introduced

where Ω is the input signal of the speed sensor; Ω ₀ and Ω ₁ are the boundaries of the range of critical angular velocities at which oscillations occur, U ₀ is the bias voltage, V _p is the rolling speed, and the current controller is equipped with a second summing input, while the first and second inputs of the nonlinear functional converter are connected to the outputs, respectively engine angular velocity sensor and rolling speed sensor, and the output is connected to the second summing input of the current regulator.

Compared with the closest similar technical solution, the proposed electric rolling mill has the following new features:

- rolling speed sensor.

- the second nonlinear functional converter that implements the function

- the current controller is equipped with a second summing input.

Therefore, the claimed technical solution meets the requirement of "novelty."

When implementing the invention, it is possible to improve the quality of speed regulation by damping oscillations caused by the nonlinear dependence of the rolling moment on the angular speed of the electric drive, by shifting the operating point of the electric drive to the area of stable operation. The shift of the operating point at critical angular rotational speeds of the engine, at which the oscillations appear, is carried out by connecting to the input signal of the current controller a constant signal U ₀ providing a controlled change in speed and, thus, transferring the corresponding operating point to a stable section.

Therefore, the claimed technical solution meets the requirement of "positive effect".

For each distinguishing feature, a search is made for well-known technical solutions in the field of electrical engineering, automation, and electric drive.

Known current regulators equipped with several inputs (summing and subtracting) in electric drives (Handbook of an automated electric drive / Edited by V.A. Eliseev and A.V.Shinyansky. - M .: Energoatomizdat, 1983, p. 246-247, fig. .7.34; Thyristor DC electric drives / A.G. Ivanov et al. - Electrical Engineering, 2001, No. 2, pp. 10-15, Fig. 3).

In known technical solutions and the proposed device, regulators with several inputs perform similar functions.

Rolling speed sensors and non-linear functional converters that implement the function

$$F\left(\Omega \right)=\{\begin{array}{l}{U}_{0}PR\mathrm{and}|\; |\; |\Omega |\; |\; |\in \left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right];\\ 0PR\mathrm{and}|\; |\; |\Omega |\; |\; |\notin \left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right],\end{array}$$

in known devices of similar purpose are not found.

Thus, these features provide the claimed technical solution according to the requirement of "significant differences".

The essence of the alleged invention is illustrated by drawings. Figure 1 shows the functional diagram of the electric drive, figure 2 shows a diagram of the relative relative moment of rolling from the linear speed of the rolls, figure 3 shows the processes during rolling of metals in the proposed drive with correction and without corrective action.

The electric drive of the rolling mill (Fig. 1) contains a motor angular speed adjuster 1, a scaling amplifier 2, first 3 and second 4 comparison elements, a first non-linear functional converter 5 that implements the function

$$F\left(\epsilon ,u_2\right)=\{\begin{array}{l}{U}_{e}PR\mathrm{and}|\; |\; |\epsilon |\; |\; |\ge |\; |\; |u_2|\; |\; |;\\ 0PR\mathrm{and}|\; |\; |\epsilon |\; |\; |<|\; |\; |u_2|\; |\; |,\end{array}$$

second nonlinear functional Converter 6 that implements the function

$$F\left(\Omega \right)=\{\begin{array}{l}{U}_{0}PR\mathrm{and}|\; |\; |\Omega |\; |\; |\in \left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right];\\ 0PR\mathrm{and}|\; |\; |\Omega |\; |\; |\notin \left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right],\end{array}$$

controlled key 7, restriction unit 8, speed controller 9, current controller 10, power amplifier 11, current sensor 12, independent excitation DC motor 13, voltage sensor 14, angular speed sensor of the engine 15, rolling speed sensor 16.

In the proposed electric drive, the anchor winding of the independent excitation DC motor 13 through a current sensor 12 is connected to the output of the power amplifier 11, the input of which is connected to the output of the current regulator 10, connected by the first summing input to the output of the speed controller 9 and the second summing input to the output of the second nonlinear functional converter 6, and by subtracting the input to the output of the current sensor 12, the outputs of the engine angular speed adjuster 1 and the engine angular speed sensor 15 are connected respectively to the sums to the subtracting and subtracting inputs of the first comparison element 3, the output of which through the restriction block 8 is connected to the first summing input of the speed controller 9 and is directly connected to the first input of the nonlinear functional converter 5, the second input of which is connected through the scaling amplifier 2 to the output of the angular speed adjuster 1, and the output is connected to the control input of the controlled key 7 connected between the summing input of the speed controller 9 and the output of the second comparison element 4, summing the input which is connected to the output of the engine angular speed adjuster 1, and the subtracting input is connected to the output of the voltage sensor 14 connected to the armature winding of the independent excitation DC motor 13, the output of the second nonlinear functional converter 6 by the first and second input is connected to the outputs of the engine angular speed sensor 15 and the rolling speed sensor 16, and the output is connected to the second summing input of the current regulator 10.

The electric rolling mill operates as follows. The armature winding of the independent excitation DC motor 13 is connected to the output of the power amplifier 11. The motor speed Ω is regulated by changing the voltage across the armature winding. The angular velocity of the engine 13 is measured by a sensor 15 of the angular velocity of the engine, for example a tachogenerator. The current of the motor 13 is measured using a current sensor 12, for example a shunt. The voltage measurement at the armature winding of the motor 13 is made by the voltage sensor 14.

The signal u ₃ proportional to the required value of the engine speed 13 is input to the summing input of the first comparison element 3 from the output of the engine angular speed setter 1. The subtracting input of the first comparison element 3 receives the output signal u _{15 of the} engine angular speed sensor 15 proportional to the rotor speed Ω of the motor rotor 13. In the comparison element, the calculation of the regulatory error ε = u ₁ -u ₁₅ . The signal ε from the output of the comparison element 3 is fed to the combined first input of the nonlinear functional converter 5 and the input of the restriction unit 8. At the second input of the nonlinear functional converter 5, the signal u ₂ from the output of the scaling amplifier 2 is proportional to the reference signal u ₃ . At the output of the nonlinear functional converter 5, a signal is formed

$$F\left(\epsilon ,u_2\right)=\{\begin{array}{l}{U}_{e}PR\mathrm{and}|\; |\; |\epsilon |\; |\; |\ge |\; |\; |u_2|\; |\; |;\\ 0PR\mathrm{and}|\; |\; |\epsilon |\; |\; |<|\; |\; |u_2|\; |\; |,\end{array}$$

where ε, u ₂ - the first and second input signals;

U _e is the voltage corresponding to the level of a logical unit.

The output of block 8 is

$$u_8=\{\begin{array}{l}\epsilon PR\mathrm{and}|\; |\; |\epsilon |\; |\; |<{\epsilon }_m;\\ \pm |\; |\; |{\epsilon }_m|\; |\; |PR\mathrm{and}|\; |\; |\epsilon |\; |\; |\ge {\epsilon }_m\end{array}(5)$$

where ε _m is the maximum value of the output signal of the restriction block.

The second comparison element 4, to the summing and subtracting inputs of which the signals from the outputs of the engine speed sensor 1 and the voltage sensor 14 respectively, calculates the mismatch u ₄ = γ = u ₁ -u ₁₄ . In a DC electric drive, the motor speed is directly proportional to the voltage u on the armature winding and the moment of load resistance M _c :

; $${\Omega }_c=\frac{U}{c}-\frac{r{\mathrm{<figure-callout\; id="2"\; label="M\; c\; c"\; filenames="00000023.png"\; state="\{\{state\}\}">M\; </figure-callout>}}_c}{c^{}}$$

;

where c is the structural constant of the engine,

r is the resistance of the armature winding.

therefore

, $$\gamma =\epsilon +\frac{r{\mathrm{<figure-callout\; id="2"\; label="M\; c\; c"\; filenames="00000023.png"\; state="\{\{state\}\}">M\; </figure-callout>}}_c}{c^{}}$$

,

therefore, the voltage mismatch in the electric drive system differs from the speed mismatch by an amount proportional to the load moment M _c .

и разомкнут при $$\epsilon |<|u_2|$$

. Это означает, что при большой ошибке системы электропривода по скорости ε, величина этой ошибки на первом суммирующем входе регулятора скорости 9 ограничивается значением ε_M, а на другом суммирующем входе регулятора скорости 9 действует сигнал, пропорциональный рассогласованию по напряжению. Регулятор скорости 9 преобразует входной сигнал в соответствии с законом регулирования, например пропорционально-интегральным, и формирует сигнал задания для подчиненного контура регулирования тока 10, который в свою очередь формирует сигнал управления для усилителя мощности 11. Работа системы управления происходит таким образом, что величина суммарной ошибки u₄+u₈ уменьшается, а следовательно, уменьшаются ε и γ. При достижении рассогласованием системы по скорости ε значения u₂ происходит изменение выходного сигнала нелинейного функционального преобразователя 5 и размыкание управляемого ключа 7. Далее электропривод функционирует как двухконтурная система регулирования скорости с подчиненным контуром регулирования тока. Рассогласование ε электропривода при этом достигает значения, величина которого определяется структурой электропривода и погрешностью датчика скорости.The signal u ₄ from the output of the second comparison element 4 through the controlled key 7 is fed to one of the inputs of the adder, the second input of which is the output signal of the restriction unit 8. The controlled key 7 in accordance with the algorithm (1) of the nonlinear functional converter 5 is closed when $$|\; |\; |\epsilon |\; |\; |\ge |\; |\; |{\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="00000023.png"\; state="\{\{state\}\}">u</figure-callout>}}_2|\; |\; |$$

and open when $$\epsilon |\; |\; |<|\; |\; |{\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="00000023.png"\; state="\{\{state\}\}">u</figure-callout>}}_2|\; |\; |$$

. This means that with a large error of the electric drive system with respect to speed ε, the value of this error at the first summing input of the speed controller 9 is limited to ε _M , and a signal proportional to the voltage mismatch acts on the other summing input of the speed controller 9. The speed controller 9 converts the input signal in accordance with the regulation law, for example, proportional-integral, and generates a reference signal for the slave current control loop 10, which in turn generates a control signal for the power amplifier 11. The control system operates in such a way that the total errors u ₄ + u ₈ decreases, and consequently, ε and γ decrease. When the mismatch of the system in speed ε reaches the value u ₂ , the output signal of the nonlinear functional converter 5 changes and the controlled key 7 opens. Next, the electric drive functions as a two-loop speed control system with a slave current control loop. In this case, the mismatch ε of the electric drive reaches a value whose value is determined by the structure of the electric drive and the error of the speed sensor.

момент прокатки уменьшается при увеличении скорости. Это означает, что в электроприводе действует положительная обратная связь по скорости. Действие этой связи вызывает колебания скорости и нарушение устойчивой работы электропривода. Диапазоны критических скоростей $$\left[{\Omega }_0\left(V_{П}\right);{\Omega }_1\left(V_{П}\right)\right]$$

при различных скоростях прокатки V_П на фиг.2 показаны штриховкой. Устойчивость электропривода может быть достигнута исключением его работы в диапазоне указанных критических скоростей. При возникновении колебаний в электроприводе прокатного стана, происходящих на частотах вращения $$\left[{\Omega }_0\left(V_{П}\right);{\Omega }_1\left(V_{П}\right)\right]$$

, требуется либо уменьшение скорости ниже Ω₀, либо ее увеличение выше Ω₁,. Увеличение сигнала задания для главных контуров скорости и напряжения воздействием на задатчик скорости 1, во-первых, не обеспечивает требуемого быстродействия, а во-вторых, при большой амплитуде колебаний в электроприводе возникают дополнительные переключения порогового элемента 5 и управляемого ключа 7.When rolling metals, the load moment on the motor shaft non-linearly depends on the speed of the rolls and the rolling speed. Figure 2 shows a typical dependence of the rolling moment on the speed of the rolls. In ranges of linear speeds of rolls $$\left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right]$$

rolling moment decreases with increasing speed. This means that the actuator has positive speed feedback. The action of this connection causes fluctuations in speed and a violation of the stable operation of the electric drive. Critical Velocity Ranges $$\left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right]$$

at different rolling speeds V _P in figure 2 are shown by hatching. The stability of the electric drive can be achieved by excluding its operation in the range of critical speeds indicated. When oscillations occur in the electric drive of the rolling mill occurring at rotational speeds $$\left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right]$$

, either a decrease in speed below Ω ₀ or its increase above Ω ₁ , is required. An increase in the reference signal for the main circuits of speed and voltage by acting on the speed controller 1, firstly, does not provide the required speed, and secondly, with a large amplitude of oscillations in the electric drive, additional switching of the threshold element 5 and the controlled key 7 occur.

, на выходе нелинейного функционального преобразователя 6 формируется сигнал U₀, который действует на суммирующем входе регулятора тока 10. Это приводит к росту сигнала задания для подчиненного контура регулирования тока 10 и, таким образом, возрастанию угловой скорости вращения двигателя.In the proposed electric drive at critical angular speeds of rotation of the electric motor 13, which are in the range $$\left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right]$$

, at the output of the nonlinear functional converter 6, a signal U ₀ is generated, which acts on the summing input of the current controller 10. This leads to an increase in the reference signal for the slave current control loop 10 and, thus, an increase in the angular speed of rotation of the motor.

, на выходе нелинейного функционального преобразователя 6 формируется сигнал U₀, который действует на суммирующем входе регулятора тока 10. Это приводит к росту сигнала задания для подчиненного контура регулирования тока 10 и, таким образом, увеличению угловой скорости вращения двигателя.Thus, in the proposed electric drive, the speed is controlled using two main feedbacks - by voltage, which provides coarse speed control with an error depending on the load moment, and by speed, providing accurate speed control. If oscillations occur in the electric drive of the rolling mill, at angular speeds of rotation $$\left[{\Omega }_0\left(V_P\right);{\Omega }_{\mathrm{one}}\left(V_P\right)\right]$$

, at the output of the nonlinear functional converter 6, a signal U ₀ is generated, which acts on the summing input of the current controller 10. This leads to an increase in the reference signal for the slave current control loop 10 and, thus, an increase in the angular speed of rotation of the motor.

Thanks to the introduction of the bias signal, which acts on the reference signal of the slave current loop, stable operation of the electric drive of the rolling mill without emergency stops is ensured.

In order to confirm the positive effect achieved by using the proposed technical solution, computer simulation of the electric drive was carried out, implemented according to the scheme depicted in figure 1. System parameters had the following meanings.

DC motor: armature resistance r = 0.0244 Ohm; anchor chain inductance L = 0.0046 H; design constant c = 1 V · s / rad; reduced moment of inertia J = 130 kg · m ² ; power amplifier: transmission coefficient k _y = 132; PI current regulator: transmission coefficient k _rt = 0.0244; time constant T _rt = 5.3043 s; PI speed controller: gear ratio of the controller k _pc = 80; time constant T _pc = 0.7 s; a scaling amplifier with a transmission coefficient k = 2.

The results of simulation are shown in figure 2 and figure 3. Figure 2 shows the dependence of the relative load moment (with respect to the nominal value) on the linear speed of the rolls. The relationship between the linear speed of the rolls and the angular speed of the engine

where Ω is the angular speed of the engine, rad / s, V is the linear speed of the rolls, m / s, R is the radius of the rolls, m. When a working point hits a section with a negative slope (Fig. 2), fluctuations in the electric drive of the rolling mill occur .3. Diagrams of processes in the electric drive without correction and when using the proposed correction are presented in figure 3.

Thus, the use in a known electric drive of a rolling mill containing a DC motor, the anchor winding of which is connected through a current sensor to the output of a power amplifier, the input of which is connected to the output of the current regulator, connected by the first summing input to the output of the speed controller, and by subtracting the input to the output of the sensor current, the outputs of the master and the engine angular velocity sensor are connected respectively to the summing and subtracting inputs of the first comparison element, the output of which is through the block niya is connected to the first summing input of the speed controller and is directly connected to the first input of a nonlinear functional converter that implements the function

where ε, u ₂ - the first and second input signals; U _e is the voltage corresponding to the level of a logical unit,

the second input of which is connected through a scaling amplifier to the output of the angular speed adjuster of the engine, and the output is connected to the control input of the controlled key connected between the summing input of the speed controller and the output of the second comparison element, the summing input of which is connected to the output of the angular speed adjuster of the engine, and the subtracting input is connected with the output of a voltage sensor connected to the armature winding of the motor, additionally a rolling speed sensor and a second non-linear functional conversion ovatelya realizing the function

where Ω is the input signal of the speed sensor; Ω ₀ and Ω ₁ are the boundaries of the range of critical angular velocities at which oscillations occur, U ₀ is the bias voltage, V _p is the rolling speed, and the current controller is equipped with a second summing input, while the first and second inputs of the second nonlinear functional converter are connected to the outputs respectively, the engine angular speed sensor and the rolling speed sensor, and the output is connected to the second summing input of the current regulator, improves the quality of regulation of the speed of the electric drive by increasing stability and vibration damping during metal rolling.

The use of the proposed device in industrial control systems for rolling metals will improve the technical level of equipment and the quality of the process.

Claims (1)

An electric drive of a rolling mill containing a DC motor, the anchor winding of which is connected through a current sensor to the output of a power amplifier, the input of which is connected to the output of a current regulator connected by the first summing input to the output of the angular speed controller of the motor, and by the subtracting input to the output of the current sensor, the outputs of the master and the engine angular velocity sensor are connected respectively to the summing and subtracting inputs of the first comparison element, the output of which through the restriction unit is connected to the first to the summing input of the speed controller and is directly connected to the first input of the nonlinear functional converter that implements the function

where ε, u ₂ - the first and second input signals; U _e is the voltage corresponding to the level of a logical unit,
the second input of which is connected to the output of the speed controller through a scaling amplifier, and the output is connected to the control input of a controlled key connected between the summing input of the speed controller and the output of the second comparison element, the summing input of which is connected to the output of the speed controller, and the subtracting input is connected to the output of the voltage sensor connected to the armature winding of the motor, characterized in that it additionally includes a rolling speed sensor and a second non-linear functional converter spruce that implements the function

where Ω is the input signal of the speed sensor; Ω ₀ and Ω ₁ are the boundaries of the range of critical angular velocities at which oscillations occur, U ₀ is the bias voltage, V _p is the rolling speed, and the current controller is equipped with a second summing input, while the first and second inputs of the nonlinear functional converter are connected to the outputs, respectively engine angular velocity sensor and rolling speed sensor, and the output is connected to the second summing input of the current regulator.

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