阅读说明：本技术 一种永磁游标直线电机的控制方法及系统 (Control method and system of permanent magnet vernier linear motor ) 是由 孔武斌 陈智 曲荣海 周游 于 2019-09-24 设计创作，主要内容包括：本发明公开了一种永磁游标直线电机的控制方法及系统,方法包括根据电机的反电势特性以及速度控制器的输出信号,计算dq坐标系下的参考电流正序分量和参考电流负序分量；将所述dq坐标系下的参考电流正序分量和参考电流负序分量进行Park反变换到两相静止αβ坐标系下；所述αβ坐标系下的参考电流正序分量和参考电流负序分量与电机电流作差产生的电流误差信号,经过VPI控制器输出,通过SVPWM产生逆变器开关的开关信号。系统包括速度控制器、电流正负序分量参考值计算模块、第一Park反变换模块、第二Park反变换模块、电流VPI控制器和SVPWM模块。本发明能够有效地降低电机输出电磁推力的波动,提高电流控制精度,从而获得更为理想的控制性能。(The invention discloses a control method and a system of a permanent magnet vernier linear motor, wherein the method comprises the steps of calculating a reference current positive sequence component and a reference current negative sequence component under a dq coordinate system according to the back electromotive force characteristic of the motor and the output signal of a speed controller; carrying out Park inverse transformation on the reference current positive sequence component and the reference current negative sequence component in the dq coordinate system to a two-phase static alpha beta coordinate system; and current error signals generated by the difference between the reference current positive sequence component and the reference current negative sequence component in the alpha beta coordinate system and the motor current are output through a VPI controller, and switching signals of the inverter switch are generated through SVPWM. The system comprises a speed controller, a current positive and negative sequence component reference value calculating module, a first Park inverse transformation module, a second Park inverse transformation module, a current VPI controller and an SVPWM module. The invention can effectively reduce the fluctuation of the electromagnetic thrust output by the motor and improve the current control precision, thereby obtaining more ideal control performance.)

1. A control method of a permanent magnet vernier linear motor is characterized by comprising the following steps:

calculating a reference current positive sequence component and a reference current negative sequence component under a dq coordinate system according to the back emf characteristic of the motor and an output signal of the speed controller;

carrying out Park inverse transformation on the reference current positive sequence component and the reference current negative sequence component in the dq coordinate system to a two-phase static alpha beta coordinate system;

and current error signals generated by the difference between the reference current positive sequence component and the reference current negative sequence component in the alpha beta coordinate system and the motor current are output through a VPI controller, and switching signals of the inverter switch are generated through SVPWM.

2. The method of claim 1, wherein the reference current positive sequence component and the reference current negative sequence component in the dq coordinate system are based on the output signal of the speed controllerCalculating opposite potentials to respectively obtain reference current positive and negative sequence component reference values i_q ^p、i_d ^p、i_d ^p、i_d ^pIs formulated as:

i_q ^P＝i_q ^*

wherein i_q ^*Is the output current of the speed controller, E_q ^p、E_q ⁿ、E_d ^p、E_d ⁿThe counter potential positive and negative sequence component amplitudes in the dq coordinate system are shown, p represents the positive sequence, and n represents the negative sequence.

3. The method of claim 2, wherein the inverse Park transformation of the positive and negative sequence components of the reference current is formulated as:

wherein i_q ^p、i_d ^p、i_q ^p、i_d ^pIs a reference value of a positive and negative sequence component of a reference current in dq coordinate system, i_α ^p、i_β ^p、i_α ⁿ、i_β ⁿThe reference value of the positive and negative sequence components of the reference current in the two-phase static alpha beta coordinate system is shown, and theta is the electrical angle of the motor.

4. The method of claim 1, wherein the transfer function of the VPI current controller is:

wherein K_p、K_i、K_pr、K_ir、ω_c、ω₀Is a preset VPI controller parameter.

5. A control system of a permanent magnet vernier linear motor is characterized by comprising a speed controller, a current positive and negative sequence component reference value calculating module, a first Park inverse transformation module, a second Park inverse transformation module, a current VPI controller and an SVPWM module; the output of the speed controller is used as the input of a current positive and negative sequence component reference value calculating module, the output of the current positive and negative sequence component reference value calculating module is respectively input into a first Park inverse transformation module and a second Park inverse transformation module, the output of the first Park inverse transformation module and the output of the second Park inverse transformation module are used as the input of a VPI controller, the VPI controller calculates a reference voltage signal according to the difference value of the output of the first Park inverse transformation module and the output of the second Park inverse transformation module and a current signal of a motor acquired by a current detecting unit, the reference voltage signal is input into an SVPWM module, and the SVPWM module generates a switching signal of an inverter switch;

the first Park inverse transformation module and the second Park inverse transformation module are used for carrying out Park inverse transformation on a reference current positive sequence component and a reference current negative sequence component in a dq coordinate system to a two-phase static alpha beta coordinate system;

the VPI controller is used for calculating a reference voltage signal according to the output of the first Park inverse transformation module and the second Park inverse transformation module and the difference value of the current signals of the motor acquired by the current detection unit, and inputting the reference voltage signal into the SVPWM module;

the SVPWM module is used for generating switching signals of the inverter switches.

6. The permanent magnet vernier linear motor control system according to claim 5, wherein the reference current positive sequence component and the reference current negative sequence component in the dq coordinate system are respectively calculated according to three opposite potentials of the motor by utilizing an output signal of the speed controller to obtain a reference current positive and negative sequence component reference value i_q ^p、i_d ^p、i_q ^p、i_d ^pIs formulated as:

i_q ^p＝i_q ^*

wherein i_q ^*Is the output current of the speed controller, E_q ^p、E_q ⁿ、E_d ^p、E_d ⁿThe counter potential positive and negative sequence component amplitudes in the dq coordinate system are shown, p represents the positive sequence, and n represents the negative sequence.

7. The permanent magnet vernier linear motor control system of claim 6 wherein the inverse Park transformation of the positive and negative sequence components of the reference current is formulated as:

wherein i_p ^q、i_d ^p、i_q ^p、i_d ^pIs a reference value of a positive and negative sequence component of a reference current in dq coordinate system, i_α ^p、i_β ^p、i_α ⁿ、i_β ⁿThe reference value of the positive and negative sequence components of the reference current in a two-phase static alpha beta coordinate system is shown, and theta is an electrical angle.

8. The permanent magnet vernier linear motor control system of claim 5 wherein the transfer function of the VPI current controller is:

wherein K_p、K_i、K_pr、K_ir、ω_c、ω₀Is a preset VPI controller parameter.

Technical Field

The invention belongs to the field of motor servo and control, and particularly relates to a control method and a control system of a permanent magnet vernier linear motor.

Background

With the rapid development of a series of advanced machining and manufacturing technologies such as ultra-high-speed cutting, ultra-precision machining, multi-axis linkage and the like, the performance requirements of machining on a machine tool are higher and higher. Compared with the traditional transmission mode of 'a rotating motor and a ball screw', the linear motor cancels a mechanical mechanism of a motor and a workbench, thereby realizing high-speed response of direct drive, reducing mechanical friction and improving the precision of a machine tool. The trend has been for high performance machine tools to be driven by linear motors.

In order to ensure the control precision requirement and the performance requirement, a double-ring control system is commonly adopted in a control system of the linear motor, and comprises a current inner ring and a speed outer ring, so that the decoupling of excitation and thrust can be realized, the vector control is carried out, the fluctuation of current can be inhibited, and the rapid tracking of speed can be realized.

The permanent magnet vernier linear motor has the characteristic of high thrust density, but because of the existence of a special structure that two ends of the linear motor are disconnected, the end effect and three phases of the motor are asymmetric, the fluctuation of the electromagnetic thrust of the motor can be caused by adopting a traditional three-phase current symmetric control method, and a controller is difficult to achieve the accurate control requirement. Due to the three-phase asymmetry problem, in order to output stable thrust, positive sequence current and negative sequence current need to be injected into the three-phase current of the motor, so that the effect of eliminating the electromagnetic thrust fluctuation of the motor is realized. The existing positive and negative sequence current control technology is widely applied to a power grid, a filter is required to be added for extracting positive and negative sequence currents under a dq coordinate system, and the current control bandwidth is reduced.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a control method and a control system of a permanent magnet vernier linear motor, and aims to solve the problems that the traditional three-phase symmetric control method is applied to a three-phase asymmetric system of a linear motor winding, the output electromagnetic thrust fluctuates, and the control system is low in precision.

To achieve the above object, according to an aspect of the present invention, there is provided a method for controlling a permanent magnet vernier linear motor, including:

calculating a reference current positive sequence component and a reference current negative sequence component under a dq coordinate system according to the back emf characteristic of the motor and an output signal of the speed controller;

carrying out Park inverse transformation on a reference current positive sequence component and a reference current negative sequence component in the dq coordinate system to a two-phase static alpha beta coordinate system;

and current error signals generated by the difference between the reference current positive sequence component and the reference current negative sequence component in the alpha beta coordinate system and the motor current are output through a VPI controller, and switching signals of the inverter switch are generated through SVPWM.

Preferably, the reference current positive sequence component and the reference current negative sequence component in the dq coordinate system are respectively calculated according to three opposite potentials of the motor by utilizing an output signal of the speed controller to obtain reference current positive and negative sequence component reference values i_q ^p、i_d ^p、i_q ^p、i_d ^pIs formulated as:

i_q ^P＝i_q ^*

wherein i_q ^*Is the output current of the speed controller, E_q ^p、E_q ⁿ、E_d ^p、E_d ⁿThe reference current in dq coordinate system has positive and negative sequence component amplitude, p represents positive sequence, and n represents negative sequence.

Preferably, the inverse Park transformation of the positive and negative sequence components of the reference current is formulated as:

wherein i_q ^p、i_d ^p、i_q ^p、i_d ^pIs a reference value of a positive and negative sequence component of a reference current in dq coordinate system, i_α ^p、i_β ^p、i_α ⁿ、i_β ⁿThe reference value of the positive and negative sequence components of the reference current in the two-phase static alpha beta coordinate system is shown, and theta is the electrical angle of the motor.

Preferably, the transfer function of the VPI current controller is:

wherein K_p、K_i、K_pr、K_ir、ω_c、ω₀Is a preset VPI controller parameter.

According to another aspect of the invention, a control system of a permanent magnet vernier linear motor is provided, which comprises a speed controller, a current positive and negative sequence component reference value calculation module, a first Park inverse transformation module, a second Park inverse transformation module, a current VPI controller and an SVPWM module; the output of the speed controller is used as the input of a current positive and negative sequence component reference value calculating module, the output of the current positive and negative sequence component reference value calculating module is respectively input into a first Park inverse transformation module and a second Park inverse transformation module, the output of the first Park inverse transformation module and the output of the second Park inverse transformation module are used as the input of a VPI controller, the VPI controller calculates a reference voltage signal according to the difference value of the output of the first Park inverse transformation module and the output of the second Park inverse transformation module and a current signal of the motor obtained by a current detection unit, the reference voltage signal is input into an SVPWM module, and the SVPWM module generates a switching signal of an inverter switch;

the first Park inverse transformation module and the second Park inverse transformation module are used for carrying out Park inverse transformation on a reference current positive sequence component and a reference current negative sequence component in a dq coordinate system to a two-phase static alpha beta coordinate system;

the VPI controller is used for calculating a reference voltage signal according to the output of the first Park inverse transformation module and the second Park inverse transformation module and the difference value of the current signals of the motor acquired by the current detection unit, and inputting the reference voltage signal into the SVPWM module;

the SVPWM module is used for generating switching signals of the inverter switches.

Preferably, the input of the current positive and negative sequence component reference value calculation module is the output i of the speed controller_q ^*Outputting a positive sequence current reference value i in a dq coordinate system according to the three-phase back electromotive force characteristic of the motor_q ^p、i_d ^pAnd a negative sequence current reference value i_q ⁿ、i_d ⁿ. Measuring three-phase voltage of the motor under the condition that the motor is in no-load (three-phase current is equal to 0), converting the measured three-phase back electromotive force into a dq coordinate system of a positive sequence and a negative sequence to obtain a dq positive-negative sequence amplitude E of the back electromotive force_q ^p、E_q ⁿ、E_d ^p、E_d ⁿ。i_q ^p、i_d ^p、i_q ⁿ、i_d ⁿAccording to E_q ^p、E_q ⁿ、E_d ^p、E_d ⁿAnd output i of the speed controller_q ^*And (4) calculating.

Preferably, the input of the first Park inverse transformation module is a current reference value i in a positive sequence dq coordinate system_q ^p、i_d ^pThe output is a reference value i of positive sequence current under a two-phase static alpha beta coordinate system_α ^p、i_β ^p(ii) a The input of the second Park inverse transformation module is a current reference value i under a negative sequence dq coordinate system_q ⁿ、i_d ⁿThe output is a reference value i of positive sequence current under a two-phase static alpha beta coordinate system_α ⁿ、i_β ⁿ。

Preferably, the current VPI controller is based on a closed loop stability criterion that the amplitude response of the open loop transfer function is sufficiently large, i.e. greater than 35dB, with a phase margin of about 45 °, at a resonance frequency ω with different resonance bandwidths₀And keeping constant gain, selecting parameters of a current VPI controller, and realizing high-performance control of the controller on the alternating current under the two-phase static alpha beta coordinate system.

Aiming at the given problem of positive and negative sequence currents of the motor, a current positive and negative sequence component reference value calculation module based on the back electromotive force characteristic of the motor is provided; aiming at the problem of reduction of current control bandwidth caused by sampling positive and negative sequence currents into a filter in a dq coordinate system, a first Park inverse transformation module and a second Park inverse transformation module are provided, and the currents are transformed into a two-phase static alpha beta coordinate system to be controlled; the current VPI controller is introduced for the alternating behavior exhibited by the current in a two-phase stationary α β coordinate system. The control system is composed of the current positive and negative sequence component reference value calculation module, the first Park inverse transformation module, the second Park inverse transformation module, the current VPI controller and the SVPWM module, fluctuation of electromagnetic thrust output by the motor can be effectively reduced, current control precision is improved, and therefore more ideal control performance is obtained.

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. compared with the traditional three-phase current symmetrical control method, the positive sequence current and the negative sequence current are injected into the three-phase winding of the linear motor with the end effect, so that the fluctuation of the electromagnetic thrust output by the motor is reduced, and the control precision of the thrust output of the permanent magnet vernier linear motor is improved;

2. the introduction of the Park inverse transformation module realizes the control of the current under the two-phase static alpha beta coordinate system, eliminates a filter which needs to be added for controlling the current under the dq coordinate system, does not influence the bandwidth of the current control, and also does not influence the stability of a control system;

3. aiming at the alternating current characteristic presented by the current under the two-phase static alpha beta coordinate system, the current VPI controller is adopted, and the control capability of the current controller on harmonic current is improved.

Drawings

FIG. 1 is a block diagram of a permanent magnet vernier linear motor drive according to an embodiment of the present invention;

fig. 2 is a block diagram of a control system of the motor of the embodiment of the present invention;

FIG. 3 is a schematic diagram of the structure of the current positive and negative sequence component reference value calculation module 61;

FIG. 4 is a schematic diagram of the structure of the VPI current controller 62;

FIG. 5 is a comparison of the current VPI controller 62 and the current PI controller Bode plot optimized for a particular frequency;

the attached drawings are marked as follows:

10. the device comprises a main circuit power circuit, 11, a direct current power supply, 12, an inverter, 13, a direct current filter capacitor, 20, a control unit, 22, a position detection unit, 24, a current detection unit, 26, a main controller, 28, a driving unit, 30, a permanent magnet vernier linear motor, 50, a first Park inverse transformation module, 52, an SVPWM module, 55, a second Park inverse transformation module, 60, a speed controller, 61, a current positive and negative sequence component reference value calculation module, 62 and a VPI controller.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, which are provided for reference and illustration only and are not intended to limit the present invention. The dimensions shown in the figures are for clarity of description only and are not to be taken in a limiting sense.

It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Referring to fig. 1, fig. 1 is a block diagram illustrating a driving system of a permanent magnet vernier linear motor according to an embodiment of the present invention. The electric permanent magnet vernier linear motor driving system mainly comprises a main circuit power circuit 10, a control circuit 20 and a permanent magnet vernier linear motor 30. The main circuit power circuit 10 includes a dc power supply 11 for supplying power to the permanent magnet vernier linear motor 30, an inverter 12, and a dc filter capacitor 13. The control circuit 20 comprises a position detection unit 22, a current detection unit 24, a drive circuit 28 and a main controller 26, wherein the main controller 26 controls the operation of a permanent magnet vernier linear motor 30. The position detection unit 22 includes a linear grating. The current detection unit 24 includes a current sensor and a Clark transformation algorithm. The signals output by the current detection unit 24 and the position detection unit 22 are output to the main controller 26. The main controller 26 outputs a driving signal for driving the permanent magnet cursor linear motor 30 according to the received current signal, the motor mover position signal and the preset speed, and the driving signal is output to the inverter 12 through the driving unit 28 to control the switching device in the inverter 12 and drive the permanent magnet cursor linear motor 30 to operate. The design process of each controller is explained in detail below.

Fig. 2 is a block diagram of a control system of the motor of the present invention. The motor control system includes a position detection unit 22,The device comprises a current VPI controller 62, a first Park inverse converter 50, a second Park converter 55, an SVPWM module 52, an inverter 12, a speed controller 60, a current positive and negative sequence component reference value calculation module 61, a current detection unit 24, a direct current power supply 11 and a direct current filter capacitor 13. The motor control block diagram comprises a rotating speed ring and a current ring, wherein the rotating speed ring is an outer ring, and the current ring is an inner ring, so that the functions of frequency conversion, speed regulation and the like are realized. Given rotating speed is calculated by a speed controller to obtain given q-axis current i_q ^*The positive and negative sequence current reference value i under the dq coordinate system is obtained by calculation through the current positive and negative sequence component reference value calculation module 61_q ^p、i_d ^p、i_q ⁿ、i_d ⁿ。i_q ^p、i_d ^p、i_q ⁿ、i_d ⁿConverted to i under a two-phase static alpha beta coordinate system by a first Park inverse converter 50 and a second Park converter 55_α ^p、i_β ^p、i_α ⁿ、i_β ⁿ。i_α ^p、i_β ^p、i_α ⁿ、i_β ⁿThe current VPI controller 62 calculates the alpha beta reference voltage U in the two-phase stationary alpha beta coordinate system_α ^*、U_β ^*. Reference voltage U_α ^*、U_β ^*The driving signal is obtained by the SVPWM module 52. The driving signal controls the operation of the switching tube of the inverter 12 through the driving unit 28, and controls the permanent magnet vernier linear motor 30. It will be appreciated by those skilled in the art that the Clark conversion part of the current detection unit 24, the position detection unit 22, the current VPI controller 62, the first Park inverse converter 50, the second Park converter 55, the SVPWM module 52, the speed controller 60, the current positive and negative sequence component reference value calculation module 61, etc. may be a series of computer program segments that can be executed by the main controller 26 and that can perform a fixed function.

As shown in FIG. 3, the input of the current positive and negative sequence component reference value calculation module 61 is the output i of the speed controller_q ^*From the measured back electromotive force characteristics of the motorObtaining the positive and negative sequence component amplitude E of the dq coordinate system_q ^p、E_q ⁿ、E_d ^p、E_d ⁿ：

I_q ^P＝i_q ^*

Calculating and outputting a current positive and negative sequence component reference value i_q ^p、i_d ^p、i_q ⁿ、i_d ⁿ。

The mathematical model of the first Park inverse transformer 50 is:

the mathematical model of the second Park inverse transformer 55 is:

as shown in FIG. 4, the current controller employs a current VPI controller 62 with inputs of a given α β axis positive and negative sequence current i_q ^p、i_d ^p、i_q ⁿ、i_d ⁿAnd the actual α β axis current i_α、i_βOutput is a control quantity U_α、U_β. The transfer function of current VPI controller 62 is:

wherein K_p、K_i、K_pr、K_ir、ω_c、ω₀Controller parameters are to be designed.

As shown in fig. 5, the ac characteristic of the α β current reference value in the two-phase stationary α β coordinate system is shown at ω₀Setting a resonance point at the frequency of the electrical angular velocity omega, and raising the controller at omega₀The amplitude response of (c). Compared with a PI controller, the phase margin of the controller is improved by the current VPI control. The magnitude response according to the open loop transfer function should be large enough, i.e. larger than 35dB, with a phase margin of about 45 °, at the resonance frequency ω with different resonance bandwidths_cThe constant gain is maintained, and the current VPI controller 62 parameters are selected to maintain closed loop stability of the control system.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.