RU2030521C1 - Device for combined optimal control of excavator electric drive - Google Patents

Abstract

FIELD: mining machine drives. SUBSTANCE: device for combined optimal control of excavator electric drive has master controller 1, summator 2, thyristor converter 3, first nonlinear element 30, threshold current transducer 31, regulator 15, speed transducer 13 and flexible member transducer, second nonlinear element 16 and switch 17. EFFECT: higher efficiency. 2 cl, 1 dwg

Description

 The invention relates to the management of mining equipment, namely, to control the electric drives of the mechanisms of single-bucket excavators, in which the limitation of currents arising in the modes with control and disturbing influences is required, and can be used to control the electric drives of other mining machines.

 A device for controlling an electric drive of an excavator is known, comprising a command device, an armature, a thyristor converter, as well as a current sensor, an armature current sensor, a speed sensor, a controller for reducing dynamic loads, and a temperature sensor. This device is controlled by two parameters of speed and current [1].

 Closest to the proposed device is a combined control of electric drives of an excavator, comprising a command device connected to the first input of the adder, the output of which through a thyristor converter is connected to an electric drive of the G-D system, a temperature sensor is connected through a threshold element to the first input of the first nonlinear element, to the second input of which a nonlinear element is connected to the second input of the adder, the third input of which is connected to the output of the dynamic voltage reduction controller Nia, the first input of which through normally closed contact of the switching key is connected to the speed sensor output of the second non-linear element is connected to switching key [2]. Known devices do not have sufficient control reliability.

 The aim of the invention is to increase the reliability of control by reducing dynamic loads.

 This is achieved by the fact that an elastic moment sensor is introduced, the output of which is connected to the input of the second nonlinear element and through the make contact of the switching key to the second input of the dynamic voltage reduction regulator.

 The present invention is characterized, firstly, by optimizing the control action by minimizing the quadratic deviations of the engine speed from the steady-state value with a minimum of control energy consumption, and secondly, by optimizing the disturbing action by minimizing the quadratic deviations of the force in the elastic element from the steady-state value with the minimum control energy consumption, thirdly, by switching from one control law when the force in the elastic element of the threshold value is exceeded to another it controls and, fourthly, sequentially corrects the excitation voltage and supply voltage loops with compensation of the time constants of the magnetic amplifier and generator.

 In the drawing, a diagram of an electric drive control system for digging mechanisms of an excavator is presented.

 The device comprises a command device 1, a first adder 2, a system of subordinate regulation of the supply voltage 3, consisting of series-connected regulators of the supply voltage 4, the excitation voltage 5, the summing magnetic amplifier 6 and the generator 7. The output of the first adder 2 is connected to the regulator of the supply voltage 4. Supply sensors voltage 8 and excitation voltage 9 are connected to the second inputs, respectively, of the regulators of the supply voltage 4 and the excitation voltage 5. The generator 7 is connected to the motor 10, p the bucket 1 driving the bucket 1 through the elastic element 11. The speed sensors 13 and the forces in the elastic elements 14 are connected respectively to the first and second inputs of the dynamic load reduction regulator 15. The force sensor in the elastic elements is also connected in series to the load sensor representing the second nonlinear element 16 and switching key 17. The dynamic load reduction regulator 15 consists of two integrators 18, 19, five inverting amplifiers 20-24, two non-inverting amplifiers 25, 26 and a second adder 27. In feedback and the first integrator 18 includes the first inverting amplifier 20, and the output of the integrator 18 is connected to the second inverting amplifier 21. The first input of the dynamic load reduction controller 15 through the NC contact of the switching key 17 and the third inverting amplifier 22 is connected to the first input of the second adder 27. The second input of the controller reduce dynamic loads 15 through the opening contact of the switching key 17 is connected to the first input of the first integrator 19, in the feedback of which is included the first inverting amplifier 23, and the third input through the fourth inverting amplifier 24 is connected to the output of the second integrator 18. The output of the first integrator 19 through the first amplifier 25 is connected to the third input of the second integrator 18 and through the second amplifier 26 to the first input of the second adder 27. The second input of the second adder 27 is connected with the output of the second integrating amplifier 21, and the output of the second adder 27 is connected to the output of the controller for reducing dynamic loads 15. The output of the controller 15 is connected to the third input of the first adder 2. The device also contains sequently connected switch sensor (overheating) 28, the threshold element 29 and the first cut-off type nonlinear element 30, a second input coupled to a current sensor 31, and an output - to a second input of the first adder.

; b =

, где С - конструктивная постоянная двигателя; R_a - активное сопротивление якорной цепи; I_ε- суммарный момент инерции; K_н - коэффициент усиления замкнутого контура питающего напряжения; Х - скорость; U - управляющее воздействие, оптимальное управляющее воздействие, пользуясь модернизированной методикой принципа максимума Л.С. Понтрягина.The device operates as follows. In the event that the load value (the force in the elastic elements) does not exceed the set value obtained by the second nonlinear element 16, the switching key 17 is open, the speed feedback signal is received at the first input of the controller 15, which is fed to the inverting amplifier through a closed opening contact 22 and is amplified by the number of times determined by the coefficient of optimal feedback on engine speed, which is equal to the ratio of the difference of the square root of the sum of squares of the design constant of the engine and oeffitsienta voltage gain of the closed loop and constructive motor constant to the closed loop gain of the supply voltage, and is determined by the following procedure. Under the control action, we neglect the time constant of the anchor chain, which is valid, since it is less than an order of magnitude of the electromechanical time constant. We consider a single-mass system, because from experimental and theoretical studies it is known that when the control action in the digging mechanisms of the throws, the forces in the elastic elements do not even reach the nominal value. Neglecting uncompensated time constants, the mathematical description of a single-mass electromechanical system can be represented as
x = -ax + bu; a =

; b =

where C is the structural constant of the engine; R _a is the active resistance of the anchor chain; I _ε is the total moment of inertia; K _n - gain of the closed loop of the supply voltage; X is the speed; U is the control action, the optimal control action, using the modernized method of the principle of maximum L.S. Pontryagin.

(x²+U²)dt
Т. е. рассматриваем минимизацию квадратичного отклонения скорости от установившегося значения при минимуме энергии управления. Взяв производную функции Гамильтона по управлению и приравняв ее нулю, находим
U^o= b Ψ₁.The optimality criterion has the form
I =

(x ² + U ² ) dt
That is, we consider minimizing the quadratic deviation of the velocity from the steady-state value with a minimum of control energy. Taking the derivative of the Hamilton function of control and equating it to zero, we find
U ^o = b Ψ ₁ .

$\genfrac{}{}{0ex}{}{\text{=}}{\text{=}}$ $\genfrac{}{}{0ex}{}{\text{-ax+}}{\text{aΨ+x}}$ ^bU
Корни характеристического определителя расширенной матрицы
Y_1,2=

Принимаем
Y₁ = -

Предположим, что оптимальное управление является линейной функцией от координаты
U^o= νx,
где ν - коэффициент оптимального управления по скорости. Подставляя U^oв исходное уравнение, получим оптимизированное управление. Приравнивая характеристический многочлен оптимизированного уравнения и характеристический многочлен отрицательных корней расширенной матрицы, получим
ν = -

Представив значения а и b, получим коэффициент отрицательной обратной связи по скорости
ν = -

(1)
В случае, если усилие в упругих элементах превышает заданное, срабатывает коммутирующий ключ 17 и отключается оптимальная обратная связь по скорости. Замыкается размыкающий контакт коммутирующего ключа и подключается сигнал обратной связи по усилию в упругих элементах к аналитически конструируемому оптимальному регулятору, вырабатывающему оптимальное управляющее воздействие по усилию в упругих элементах и построенному на двух интеграторах 18, 19, четырех инвертирующих усилителях 20, 21, 23, 24, двух неинвертирующих усилителях 25, 26 и втором сумматоре 27. Интеграторы 18 и 19 являются форсирующими благодаря наличию в обратных связях соответственно инвертирующих усилителей 20 и 23. На выходе первого интегратора 18 формируется сигнал первой внутренней координаты, а на выходе второго интегратора 19 - сигнал второй внутренней координаты. Сигнал первой внутренней координаты получают в результате формированного интегрирования сигнала второй внутренней координаты, усиленной в усилителе 25 в число раз, равное разности между коэффициентом жесткости и отношением произведения коэффициента вязкого трения на квадрат конструктивной постоянной двигателя к произведению активного сопротивления якорной цепи на приведенный момент инерции двигателя. В обратной связи первого интегратора включен первый инвертирующий усилитель 20 с коэффициентом усиления, равным отношению квадрата конструктивной постоянной к произведению активного сопротивления якорной цепи на приведенный момент инерции двигателя. Сигнал второй внутренней координаты получают в результате форсированного интегрирования сигнала обратной связи по усилию в упругих элементах, который поступает на второй вход регулятора 15 и через замыкающий контакт коммутирующего ключа 17 - на первый вход интегратора 19, и сигнала первой внутренней координаты с интегратора 18, усиленного в четвертом инвертирующем усилителе 24 в число, раз равное величине, обратной приведенному моменту инерции двигателя. В обратной связи интегратора 19 включен первый инвертирующий усилитель 23 с коэффициентом усиления, равным отношению коэффициента вязкого трения к приведенному моменту инерции двигателя. Сигнал первой внутренней координаты с интегратора 18 усиливается в инвертирующем усилителе 21 в число раз, равное отношению коэффициента усиления замкнутого контура питающего напряжения к произведению активного сопротивления якорной цепи на приведенный момент инерции двигателя. Сигнал второй внутренней координаты с интегратора 19 усиливается в усилителе 26 в число раз, равное отношению произведения коэффициента вязкого трения на коэффициент усиления замкнутого контура питающего напряжения к произведению активного сопротивления якорной цепи на приведенный момент инерции двигателя. Усиленные сигналы первой и второй внутренних координат суммируются во втором усилителе. Суммированный сигнал поступает на выход регулятора 15, а затем полученный таким образом оптимальный сигнал по усилию в упругих элементах поступает в первый сумматор 2, где суммируется с сигналом с командоаппарата. Алгоритм оптимального управления по усилию в упругих элементах, реализованный в аналитически конструируемом оптимальном регуляторе, получают следующим образом. При возмущающем воздействии в режиме жесткого стопорения и пренебрежения электромагнитной постоянной времени и некомпенсируемыми постоянными времени математическое описание электромеханической системы можно представить в следующем виде

a₁₁=

; a₁₂=

; b₁₁=

;
a₂₁= C₁₂-β_вт

; a₂₂=

; b₂₂=

, где I₁ - приведенный момент инерции двигателя; С₁₂ - коэффициент жесткости; β_вт - коэффициент вязкого трения; x₁ - скорость двигателя; x₂ - усилие в упругих элементах; U - управляющее воздействие.Extended system of source and conjugate equations

$\genfrac{}{}{0ex}{}{\text{=}}{\text{=}}$ $\genfrac{}{}{0ex}{}{\text{-ax +}}{\text{aΨ + x}}$ ^bU
The roots of the characteristic determinant of the extended matrix
Y _1,2 =

Accept
Y ₁ = -

Assume that the optimal control is a linear function of the coordinate
U ^o = νx,
where ν is the optimal speed control coefficient. Substituting U ^o into the original equation, we obtain optimized control. Equating the characteristic polynomial of the optimized equation and the characteristic polynomial of negative roots of the extended matrix, we obtain
ν = -

Representing the values of a and b, we obtain the coefficient of negative feedback on speed
ν = -

(1)
If the force in the elastic elements exceeds a predetermined one, the switching key 17 is activated and the optimal speed feedback is turned off. The opening contact of the switching key is closed and the feedback signal on the force in the elastic elements is connected to the analytically designed optimal controller that generates the optimal control action on the force in the elastic elements and is built on two integrators 18, 19, four inverting amplifiers 20, 21, 23, 24, two non-inverting amplifiers 25, 26 and the second adder 27. The integrators 18 and 19 are boosting due to the presence of inverting amplifiers 20 and 23 in the feedback, respectively. th integrator 18, a signal is generated first internal coordinates, and the output of the second integrator 19 - second internal signal coordinates. The signal of the first internal coordinate is obtained as a result of the generated integration of the signal of the second internal coordinate, amplified in the amplifier 25 by a factor equal to the difference between the stiffness coefficient and the ratio of the product of the coefficient of viscous friction by the square of the constructive constant of the motor and the product of the active resistance of the armature chain by the reduced moment of inertia of the motor. In the feedback of the first integrator, a first inverting amplifier 20 is included with a gain equal to the ratio of the square of the design constant to the product of the active resistance of the anchor circuit by the reduced moment of inertia of the motor. The signal of the second internal coordinate is obtained as a result of forced integration of the force feedback signal in the elastic elements, which is fed to the second input of the regulator 15 and through the make contact of the switching key 17 to the first input of the integrator 19, and the signal of the first internal coordinate from the integrator 18, amplified in the fourth inverting amplifier 24 in a number times equal to the reciprocal of the reduced moment of inertia of the motor. In the feedback of the integrator 19, a first inverting amplifier 23 is included with a gain equal to the ratio of the viscous friction coefficient to the reduced moment of inertia of the motor. The signal of the first internal coordinate from the integrator 18 is amplified in the inverting amplifier 21 by a number of times equal to the ratio of the gain of the closed loop of the supply voltage to the product of the active resistance of the armature circuit by the reduced moment of inertia of the motor. The second internal coordinate signal from the integrator 19 is amplified in the amplifier 26 by a factor equal to the ratio of the product of the viscous friction coefficient and the gain of the closed loop of the supply voltage to the product of the active resistance of the armature circuit by the reduced moment of inertia of the motor. The amplified signals of the first and second internal coordinates are summed in the second amplifier. The summed signal is fed to the output of the regulator 15, and then the optimal signal thus obtained by the force in the elastic elements is fed to the first adder 2, where it is summed with the signal from the command device. The optimal control algorithm for the force in the elastic elements, implemented in an analytically designed optimal controller, is obtained as follows. With a disturbing action in the hard locking mode and neglecting the electromagnetic time constant and uncompensated time constants, the mathematical description of the electromechanical system can be represented as follows

a ₁₁ =

; a ₁₂ =

; b ₁₁ =

;
a ₂₁ = C ₁₂ -β _W

; a ₂₂ =

; b ₂₂ =

where I ₁ is the reduced moment of inertia of the engine; C ₁₂ - stiffness coefficient; β _W - coefficient of viscous friction; x ₁ - engine speed; x ₂ - force in the elastic elements; U is the control action.

(x $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ +U²)dt
На основании теории оптимального управления оптимальное управляющее воздействие имеет вид
U^o=b₁₁λ₁+b₁₂λ₂.As an optimality criterion, we take the minimization of the quadratic deviation of the force in the elastic elements from its steady-state value with a minimum of control energy consumption
I =

(x $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ + U ² ) dt
Based on the theory of optimal control, the optimal control action has the form
U ^o = b ₁₁ λ ₁ + b ₁₂ λ ₂ .

В том случае, если температура двигателя превышает заданное значение, определяемое пороговым элементом 29, на нелинейном элементе типа отсечки 30 происходит сложение сигналов с выхода порогового элемента 29 и датчика тока 31. Если сумма превышает значение, определяемое нелинейным элементом 30, то сигнал поступает на сумматор 2 и происходит снижение тока. Кроме того, нелинейный элемент типа отсечки 30 формирует необходимый вид экскаваторной характеристики.The optimal controller algorithm, in accordance with which the structure of the analytically constructed optimal controller is implemented, has the following form

In the event that the engine temperature exceeds a predetermined value determined by the threshold element 29, the signals from the output of the threshold element 29 and the current sensor 31 are added to the nonlinear element of the cutoff type 30. If the sum exceeds the value determined by the nonlinear element 30, the signal is fed to the adder 2 and the current decreases. In addition, a nonlinear cut-off element 30 forms the desired kind of excavator characteristic.

(P) =

Т_n1= 2T_μК_муК_онв, где Т_му - постоянная времени магнитного усилителя; T_μ- некомпенсируемые постоянные времени; К_му - коэффициент усиления магнитного усилителя; К_онв - коэффициент передачи датчика напряжения возбуждения.With both control and disturbing influences, a two-loop system of subordinate control of the supply voltage operates. The internal circuit due to the excitation voltage regulator 5 compensates for the time constant of the summing magnetic amplifier 6. The transfer function of the excitation voltage regulator 6 is determined based on the methodology for calculating systems at a technical optimum
W

(P) =

T _n1 = 2T _μ K _mu K _onv, where T _mu is the time constant of the magnetic amplifier; T _μ - uncompensated time constants; To _mu is the gain of the magnetic amplifier; To _onv - the transfer coefficient of the excitation voltage sensor.

T

= 4Tμ

K_гK_он, где Т_г - постоянная времени генератора; К_г - коэффициент усиления генератора; К_он - коэффициент передачи датчика питающего напряжения.In the excitation voltage regulator 5, the signal from the supply voltage regulator 4 and the current value of the excitation voltage from the sensor 6 are summed up. The external circuit, due to the supply voltage regulator 4, compensates for the time constant of the generator 7. In the supply voltage regulator 4, the reference signal from the first adder is summed 2, and the current value of the supply voltage from the sensor 8. The transfer function of the regulator of the supply voltage 4 is determined based on the calculation method for "technical s optimum "
W _rpn (P) =

T

= 4Tμ

K _g K _he where T _g - time constant of the generator; To _g is the gain of the generator; To _he is the transmission coefficient of the supply voltage sensor.

.Transfer function of closed loop power supply
W _sf (P) =

.

.When neglecting uncompensated time constants, the transfer function of the closed supply voltage circuit
W _spn (P) = K _n , K _n =

.

 The advantages of the proposed device especially affect the drives of digging mechanisms. Firstly, in the regime of rigid locking of the bucket, an effective reduction in the coefficient of dynamics of the mechanisms is ensured, dynamic throws are reduced by 40-50%, which leads to an increase in the reliability and, consequently, in the operational performance of the excavator. Secondly, the absence of control signals for the force in the elastic elements and the current of the anchor chain (except for the first nonlinear element such as cut-off 30, formulating an excavator static characteristic) leads to a more complete filling of the time - current diagram, and therefore to an increase in speed and performance . Thirdly, the use of a dual-circuit system of subordinate regulation of the supply voltage allows to reduce the rise time of the supply voltage, i.e. increase speed and productivity by 3-5%.

Claims (2)

 1. DEVICE FOR COMBINED OPTIMAL CONTROL OF EXCAVATOR ELECTRIC DRIVE, containing a command device connected to the first input of the adder, the output of which is connected through the thyristor converter to the electric drive of system G - D, the temperature sensor is connected through the threshold element to the first input of the first nonlinear element, to the second input of which current, the output of the first nonlinear element is connected to the second input of the adder, the third input of which is connected to the output of the dynamic voltage, the first input of which is connected to the speed sensor through the disconnecting contact of the switching key, the output of the second nonlinear element is connected to the switching key, characterized in that in order to increase control reliability by reducing dynamic loads, a force sensor is introduced in the elastic element, the output of which is connected to the input of the second nonlinear element and through the make contact of the switching key is connected to the second input of the dynamic voltage reduction controller.  2. The device according to claim 1, characterized in that the dynamic voltage reduction controller is made on two integrators, two amplifiers, six inverting amplifiers and an adder, while the first input of the first integrator is the second input of the dynamic voltage reduction controller, and the output through the first amplifier is connected to the first input of the second integrator, through the first inverting amplifier to the second input of the first integrator, and through the second amplifier to the first input of the adder, the output of the second integrator through the second invert The driving amplifier is connected to the second input of the adder, and through the third inverting amplifier to the second input of the second integrator, and through the fourth inverting amplifier to the third input of the first integrator, the input of the fifth inverting amplifier is the first input of the dynamic voltage reduction controller, and the output is connected to the third input of the adder, the output of which is the output of the dynamic voltage reduction controller.