RU2358382C2 - Servo drive with asynchronous motor - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to the sphere of electrical engineering and is to find application in servo drives with asynchronous actuating motors. The servo drive with an asynchronous motor consists of the following components: parametrisation unit, integral regulator, proportional regulator, two differentiator units, two multiplier units, two adders, autonomous voltage inverter, asynchronous motor with an actuator, module isolation unit, divider, switching unit, comparator unit and position sensor.

EFFECT: provision for modes of positioning and tracking the actuator travel target position at high response rate and precision determined by the position sensor dimensional resolution and accuracy.

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Description

The invention relates to the field of electrical engineering and can be used in servo drives with asynchronous actuators.

The closest in technical essence is an adjustable AC electric drive (see RF patent No. 2226739, published in BI No. 10, 2004), comprising a parameter setting unit, an integral controller, a proportional controller, a differentiation unit, a multiplication unit, the first and second adders, autonomous voltage inverter, asynchronous electric motor, module allocation unit, division unit, switch, comparison unit and speed sensor.

The disadvantage of the closest in technical essence of the electric drive with an asynchronous electric motor is that it cannot work in the modes of positioning and tracking the given coordinate of movement of the actuator.

The essence of the invention lies in the fact that the servo drive with an induction motor, comprising a parameter setting unit, an integral controller, a proportional controller, a differentiation unit, a multiplication unit, a first and second adder, a stand-alone voltage inverter, an asynchronous electric motor with an actuator, a position sensor, an allocation unit module, division unit, switch and comparison unit, the first output of the parameter setting unit being connected to the first input of the integral controller, the output of which is dined with the first input of the proportional controller, the output of the proportional controller is connected to the input of the differentiation unit and the first input of the first adder, the output of which is connected to the input of the autonomous voltage inverter, the output of the differentiation unit is connected to the first input of the multiplication unit, the output of which is connected to the second input of the first adder, the output the module allocation unit is connected to the first inputs of the comparison unit and the second adder, the output of which is connected to the first input of the division unit, the second output of the task unit the parameters are connected to the second input of the second adder, the third output of the parameter setting unit is connected to the second input of the division unit, the output of which is connected to the first input of the switch, the fourth output of the parameter setting unit is connected to the second input of the switch, the output of which is connected to the second input of the multiplication unit, the fifth output the parameter setting unit is connected to the second input of the comparison unit, the output of which is connected to the third input of the switch, the output of the autonomous voltage inverter is connected to an asynchronous electric motor, kin mathematically connected to an actuator equipped with a position sensor, the output of which is connected to the second inputs of the integral and proportional controllers, is additionally equipped with a second differentiation unit, the output of the position sensor being connected to the input of the differentiation unit, the output of which is connected to the input of the module selection unit.

Significant differences are expressed in a new set of connections between the elements of the device. The specified set of links allows you to ensure the operation of the electric drive with an asynchronous actuator in the positioning and tracking modes for a given coordinate of movement of the actuator.

The drawing shows a functional diagram of a servo drive with an induction motor.

A servo drive with an asynchronous electric motor (drawing) contains a block 1 for setting parameters, an integral regulator 2, a proportional regulator 3, differentiation blocks 4 and 5, a multiplication block 6, adders 7 and 8, an autonomous voltage inverter 9, an asynchronous electric motor 10 with an actuator 11, a module allocation unit 12, a division unit 13, a switch 14, a comparison unit 15, and a position sensor 16.

The first output of the parameter setting unit 1 is connected to the first input of the integral controller 2, the output of which is connected to the first input of the proportional controller 3. The output of the proportional controller is connected to the input of the differentiation unit 4 and the first input of the adder 7, the output of which is connected to the input of the autonomous voltage inverter 9. The output of the differentiation unit 4 is connected to the first input of the multiplication unit 6, the output of which is connected to the second input of the adder 7. The output of the module allocation unit 12 is connected to the first inputs of the comparison unit 15 and the adder 8, the output of which is connected to the first input of the division unit 13. The second output of the parameter setting block 1 is connected to the second input of the adder 8. The third output of the parameter setting block 1 is connected to the second input of the division block 13, the output of which is connected to the first input of the switch 14. The fourth output of the parameter setting block 1 is connected to the second input of the switch 14, output which is connected to the second input of the block 6 multiplication. The fifth output of the parameter setting unit 1 is connected to the second input of the comparison unit 15, the output of which is connected to the third input of the switch 14. The output of the autonomous voltage inverter is connected to an asynchronous electric motor 10 kinematically connected to an actuator 11 equipped with a position sensor 16. The output of the position sensor 16 is connected to the second inputs of the integral 2 and proportional 3 controllers and the input of the differentiation unit 5, the output of which is connected to the input of the module allocation unit 12.

Unit 1 of the parameter setting can be performed, for example, on K555TM8 microcircuits, the bit inputs of which are connected using switches to logical zeros or ones. Integral 2 and proportional 3 regulators and differentiation blocks 4 and 5 can be implemented, for example, according to A.S. USSR No. 1649501, publ. 05/15/91, BI No. 18, and are made, for example, on K555 series microcircuits. The multiplication unit 6 and the division unit 13, for example, are implemented on a K1801BM2 microprocessor having built-in multiplication and division functions. Adders 7 and 8, for example, are made on K555IM6 microcircuits. Autonomous voltage inverter 9, for example, is implemented as a digital modulator according to the patent of the Russian Federation No. 2111608, publ. 05/20/98, BI №14, with a power three-phase transistor bridge at the output. As an asynchronous electric motor 9, any squirrel-cage electric motor manufactured by the industry can be used. The actuator 11, for example, may be a table of a boring machine, connected by a lead screw and a coupling to the shaft of an induction motor. Block 12 allocation module can be implemented in the form of a switch composition, controlled by the sign of the input signal, to one information input of which the input signal is supplied directly, and to the other through inverters. The switch 14, for example, can be implemented on chips K555KP13. Block 15 comparison, for example, is performed on the adders K555IM6. As a position sensor 16, for example, a BE 162 photo-optical ruler with a corresponding device for digitizing its output signal can be used.

It should also be noted that the parameter setting block 1, the integral controller 2, the proportional controller 3, the differentiation blocks 4 and 5, the multiplication block 6, the adders 7 and 8, the module allocation block 12, the division block 13, the switch 14 and the comparison block 15 can be also performed software on a microprocessor controller.

Tracking drive with an asynchronous electric motor operates as follows. In accordance with the magnitude of the driving signal from the first output of the parameter setting unit 1 and the signal of the position sensor 16, the integral controller 2 in conjunction with the proportional controller 3, differentiation blocks 4 and 5, multiplication block 6, adders 7 and 8, module allocation unit 12 , division unit 13, switch 14 and comparison unit 15 form a signal at the input of a stand-alone voltage inverter 9. A stand-alone voltage inverter 8 converts this signal to the frequency and amplitude of the voltage at the stator of the induction motor 10. The shaft of the asynchronous motor starts to rotate and drives the actuator 11, the movement of which is measured by the position sensor 16. The movement continues until the value of the signal from the position sensor 16 is not equal to the value of the reference signal from the first output of the unit 1 of the parameter setting. The integral controller 2 compensates for the effects of all the interference covered by the sensor 16. The proportional controller 3, the differentiation blocks 4 and 5, the multiplication unit 6, the adders 7 and 8, the module allocation unit 12, the division unit 13, the switch 14 and the comparison unit 15 are an internal controller circuit and provide compensation for the basic inertia of the induction motor 10.

In the general case, the dynamic properties of an induction motor are described by a system of nonlinear differential equations (see Mikhailov, OP, Automated Electric Drive of Machine Tools and Industrial Robots. - M.: Mashinostroenie, 1990. P.194). But as a first approximation, when linearizing these equations, it is possible to obtain the transfer function of an asynchronous electric motor with respect to, for example, the control action — magnetic field rotation speed ω ₀ (see Starikov A.V. Linearized mathematical model of an asynchronous electric motor as an object of a frequency control system // Bulletin Samara State Technical University. Series Physics and Mathematics. Issue 16, 2002. S.175-180)

where the following notation is accepted: ω (p) - image of the rotation speed of the shaft of an induction motor;

- коэффициент передачи двигателя по управляющему воздействию;

- gear ratio of the engine for the control action;

,

- электромагнитные постоянные времени цепей статора и ротора; L₁ и R₁ - индуктивность и активное сопротивление цепи статора;

и

- приведенные индуктивность и активное сопротивление цепи ротора;

; L₀ - взаимная индуктивность; ψ_1X0, ψ_1Y0, ψ_2X0 и ψ_2Y0 - значения в определенной рабочей точке проекций векторов потокосцеплений статора и ротора в ортогональной системе координат x-y, вращающейся со скоростью магнитного поля;

,

- electromagnetic time constants of the stator and rotor circuits; L ₁ and R ₁ - inductance and resistance of the stator circuit;

and

- reduced inductance and resistance of the rotor circuit;

; L ₀ is the mutual inductance; ψ _1X0 , ψ _1Y0 , ψ _2X0 and ψ _2Y0 are the values at the specific working point of the projections of the stator and rotor flux link vectors in the orthogonal coordinate system xy rotating with the speed of the magnetic field;

- условное обозначение постоянной времени второго порядка, зависящей от J - приведенного момента инерции ротора; m - числа фаз электродвигателя; Z_П - числа пар полюсов и значений проекций потокосцеплений в выбранной рабочей точке.

- the symbol of the second-order time constant, depending on J - the reduced moment of inertia of the rotor; m is the number of phases of the electric motor; Z _P - the number of pairs of poles and the values of the projections of the flux linkage at the selected operating point.

With a change in the frequency of rotation of the magnetic field ω ₀ and the rotation speed ω of the shaft of the induction motor, the parameters of the operating point, namely, the projection of the flux link vectors and, therefore, the parameters of the transfer function (1) will change. Nevertheless, the calculations show that at any speeds ω, the transfer function (1) can be represented as

where T _f - time constant of the boosting component; T _A is the time constant of the aperiodic component; T _To - the time constant of the oscillatory component; ξ is the damping coefficient.

Choosing the time constant of the regulator of the internal circuit according to the following law

it is possible to achieve stable operation of the servo-driven electric drive with an asynchronous electric motor.

практически не меняется. При скоростях ниже ω_n изменение суммы

происходит по закону, близкому к обратно пропорциональному.Calculations show that the time constant T _{PD of the} controller according to expression (3) should change depending on the speed of rotation of the shaft of the induction motor. Moreover, when changing the speed of the induction motor down from the nominal to a certain speed ω _{n the} sum

practically does not change. At speeds below ω _{n, the} change in the sum

occurs according to a law close to inversely proportional.

The adjustment of the controller is carried out by the differentiation unit 5, the multiplication unit 6, the adder 8, the module allocation unit 12, the division unit 13, the switch 14 and the comparison unit 15. Restructuring is performed in the range from zero speed to the value of speed ω _n specified from the fifth output of parameter setting unit 1. When rotation speeds are greater than ω _n, the input of the multiplication unit 6 from the fourth output of the parameter setting unit 1 is supplied through the switch 14 with some basic predetermined value of the time constant T _{PD0 of the} internal circuit controller. The determination of situations when the speed of the asynchronous electric motor exceeds the value of ω _n in absolute value, and the switch 14 is controlled by the comparison unit 15, the inputs of which receive signals from the module selection unit 12 and from the fifth output of the parameter setting unit 1. At speeds below ω _n , the value of the time constant is supplied to the input of the multiplication unit 6

regulator of the internal circuit. Here, the magnitude of the increment Δω of the speed is set from the second output, and the product T _PD0 ω ₀ from the third output of unit 1 of the parameter setting. Using the differentiation unit 5, the module allocation unit 12, the adder 8 and the division unit 13, the current value of the time constant T _{PD of the} internal loop controller is calculated. The value Δω is introduced in order to limit at a certain level the maximum value of the time constant T _PD . As a result, the dynamics of a servo drive with an induction motor in all operating modes can be approximately described by a transfer function with variable parameters

where x (p) is the image of the output coordinate of the tracking electric drive; x _З (p) - image of the driving signal; k _DP - transfer coefficient of the position sensor; T _And - the time constant of the integral controller; k = k _ПД k _СП k _ДУ k _ИМ k _ДП - transfer coefficient of the inner loop of the servo drive; k _PD - transfer coefficient of the proportional controller; k _SP - transmission coefficient of the power converter (autonomous voltage inverter); k _IM - gear ratio of the actuator.

The selection of the corresponding values of the time constant T _{AND of the} integral controller and the transmission coefficient k _PD of the proportional controller allows you to configure the servo drive with an asynchronous motor to work with high accuracy and speed.

Thus, the proposed electric drive with an asynchronous motor allows you to provide positioning and tracking modes for a given coordinate of the movement of the actuator with high speed and accuracy, determined by the discreteness and accuracy of the position sensor.

Claims (1)

A servo drive with an asynchronous electric motor, comprising a parameter setting unit, an integral controller, a proportional controller, a differentiation unit, a multiplication unit, first and second adders, a stand-alone voltage inverter, an asynchronous electric motor with an actuator, a position sensor, a module selection unit, a division unit, a switch and a comparison unit, the first output of the parameter setting unit being connected to the first input of the integral controller, the output of which is connected to the first input in proportion of the regulator, the output of the proportional controller is connected to the input of the differentiation unit and the first input of the first adder, the output of which is connected to the input of the autonomous voltage inverter, the output of the differentiation unit is connected to the first input of the multiplication unit, the output of which is connected to the second input of the first adder, the output of the module selection unit is connected with the first inputs of the comparison unit and the second adder, the output of which is connected to the first input of the division unit, the second output of the parameter setting unit is connected to the second input of w of the adder, the third output of the parameter setting block is connected to the second input of the division block, the output of which is connected to the first input of the switch, the fourth output of the parameter setting block is connected to the second input of the switch, the output of which is connected to the second input of the multiplication block, the fifth output of the parameter setting block is connected to the second input of the comparison unit, the output of which is connected to the third input of the switch, the output of the autonomous voltage inverter is connected to an asynchronous electric motor kinematically connected with the executive a mechanism equipped with a position sensor, the output of which is connected to the second inputs of the integral and proportional controllers, characterized in that it is additionally equipped with a second differentiation unit, the output of the position sensor being connected to the input of the differentiation unit, the output of which is connected to the input of the module selection unit.