A control method for a permanent magnet synchronous linear motor

Abstract

The present invention discloses a control method for a permanent magnet synchronous linear motor, comprising: setting a motor system, wherein a PI controller is used in the motor control system to control the permanent magnet synchronous linear motor; obtaining the position of a permanent magnet linear motor rotor through a position sensor, and obtaining the speed of the permanent magnet linear motor rotor based on the position of the permanent magnet linear motor rotor; setting an improved extended state observer to observe the motor system and obtain the total disturbance of the motor system; converting the obtained disturbance into a thrust current compensation value, compensating the thrust current value output by the PI controller, and controlling the permanent magnet synchronous linear motor with the compensated thrust current value. The control method for the permanent magnet synchronous linear motor disclosed by the present invention can more effectively reduce the speed drop when the system is disturbed, and improve the anti-disturbance capability of the system.

Description

Technical Field

[0001] The invention relates to a control method for a permanent magnet synchronous linear motor, and belongs to the field of motor control. Background Art

[0002] Permanent magnet linear synchronous motor (PMLSM) has the performance characteristics of high control accuracy, fast response speed, good repeatability, etc. However, permanent magnet linear synchronous motor also brings new problems compared with traditional motors: the omission of the intermediate transmission mechanism in the linear feed system will make the load act directly on the motor's mover, which will cause the PMLSM to be more sensitive to load changes and it is difficult to establish an accurate mathematical model. The external interference and load changes generated during the operation of the system also increase the uncertainty of the system and affect the high-performance control of the system. This makes it difficult for traditional motor control methods to meet the requirements of high accuracy, strong anti-interference ability and fast response speed of the PMLSM control system.

[0003] The extended state observer (ESO) does not require an accurate mathematical model of the controlled object, and it can approximate the total disturbance of the system as a known quantity for real-time compensation, which can effectively improve the anti-interference ability of the system. Therefore, the extended state observer can be selected and applied to permanent magnet linear synchronous motors to obtain the uncertain disturbance of the system for compensation.

[0004] However, the compensation effect of the expanded state term of the traditional extended state observer is limited. When the system is subjected to external disturbances, it cannot respond quickly to changes in unknown disturbances. Therefore, after compensation, the response speed of the given q-axis current will be slow, making the direct use of the extended state observer for the control of the permanent magnet linear synchronous motor not very good.

[0005] Therefore, it is necessary to conduct in-depth research on the control method of permanent magnet synchronous linear motor to solve the above problems. Summary of the invention

[0006] In order to overcome the above problems, the inventors have conducted in-depth research and proposed a control method for a permanent magnet synchronous linear motor, comprising the following steps:

[0007] Setting up a motor system, wherein a PI controller is used in the motor control system to control the permanent magnet linear synchronous motor;

[0008] The position of the permanent magnet linear motor rotor is obtained by a position sensor, and the speed of the permanent magnet linear motor rotor is obtained based on the position of the permanent magnet linear motor rotor.

[0009] An improved extended state observer is set to observe the motor system to obtain the total disturbance of the motor system;

[0010] The acquired disturbance is converted into a thrust current compensation value, the thrust current value output by the PI controller is compensated, and the compensated thrust current value is used to control the permanent magnet linear synchronous motor.

[0011] In a preferred embodiment, the PI controller outputs a thrust current given value i qref Control the motor.

[0012] In a preferred embodiment, in the motor system, the mathematical model of the permanent magnet synchronous linear motor is expressed as:

[0013]

[0014] Among them, i q is the q-axis current, u q is the q-axis voltage, L is the q-axis inductance, R is the resistance, a and b are the intermediate parameters, N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, τ is the pole pitch, and F(t) is the total disturbance of the motor system.

[0015] In a preferred embodiment, the total disturbance term of the system state equation is expanded into a state variable α2, and the state equation of the motor system is expressed as:

[0016]

[0017] Where v is the permanent magnet linear motor rotor speed, α1 is the permanent magnet linear motor rotor speed, α2 is the total disturbance term of the system, u=i q is the q-axis current, and N(t) is the derivative of the extended state term.

[0018] In a preferred embodiment, the speed information of the mover is obtained by differentiating the position information of the mover.

[0019] In a preferred embodiment, the improved extended state observer is configured as follows:

[0020]

[0021] Among them, z1 is the estimated motor rotor speed, z2 is the estimated total system disturbance, e1 is the estimated error of the motor rotor speed, e2 is the error of the extended state term, β1, β2, β3 are all observer parameters, N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, τ is the pole pitch, u=i q is the q-axis current, is a nonlinear function of the error.

[0022] In a preferred embodiment, the error nonlinear function is set to:

[0023]

[0024] Among them, δ1 and δ2 are filtering factors, and g1 and g2 are nonlinear factors.

[0025] In a preferred embodiment, the total disturbance is converted into a thrust current compensation value by linear transformation.

[0026] In a preferred embodiment, the thrust current value after compensation is expressed as:

[0027]

[0028] Among them, i qref is the thrust current value before compensation, i qref * is the thrust current value after compensation, z2 is the estimated total system disturbance, N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, and τ is the pole pitch.

[0029] The beneficial effects of the present invention include:

[0030] (1) The improved extended state observer permanent magnet linear synchronous motor control method disclosed in the present invention has a faster response speed of the extended state term z2 of the improved extended state observer compared with the traditional extended state observer. The current given by the q-axis after disturbance compensation can respond to the change of disturbance more promptly when the system is subjected to external disturbance. qref Faster response time;

[0031] (2) Compared with the traditional extended state observer, the improved extended state observer permanent magnet linear synchronous motor control method disclosed in the present invention can more effectively reduce the speed drop when the system is disturbed and improve the system's anti-disturbance capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic flow chart of a control method for a permanent magnet linear synchronous motor according to a preferred embodiment of the present invention is shown;

[0033] Figure 2 The curves of the given speed and the actual speed of the linear motor after compensation in Example 1 are shown;

[0034] Figure 3 The curves of the given speed and actual speed of the linear motor after compensation in Comparative Example 1 are shown;

[0035] Figure 4The linear motor speed error curve after compensation obtained in Example 1 is shown;

[0036] Figure 5 The linear motor speed error curve after compensation obtained in Comparative Example 1 is shown;

[0037] Figure 6 The q-axis current given value of the linear motor after compensation in Example 1 is shown;

[0038] Figure 7 Shows Figure 6 Enlarge the image;

[0039] Figure 8 The q-axis current given value of the linear motor after compensation in Comparative Example 1 is shown;

[0040] Fig. 9 Shows Figure 8 Enlarge the image. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0042] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0043] According to a control method of a permanent magnet synchronous linear motor provided by the present invention, Figure 1 As shown, the following steps are included:

[0044] S1. Setting a motor system, wherein a PI controller is used in the motor control system to control the permanent magnet linear synchronous motor.

[0045] S2. Obtain the position of the permanent magnet linear motor rotor through a position sensor, and obtain the speed of the permanent magnet linear motor rotor based on the position of the permanent magnet linear motor rotor;

[0046] S3, setting an improved extended state observer to observe the motor system and obtain the total disturbance of the motor system;

[0047] S4. Convert the acquired disturbance into a thrust current compensation value, compensate the thrust current value output by the PI controller, and use the compensated thrust current value to control the permanent magnet linear synchronous motor.

[0048] In S1, the motor PI controller is a commonly used motor controller. In the present invention, the specific structure and model of the PI controller are not limited, and those skilled in the art can freely select according to actual needs.

[0049] Furthermore, in motor control, the PI controller outputs the thrust current given value i qref Control the motor.

[0050] According to the present invention, in the motor system, the mathematical model of the permanent magnet synchronous linear motor is expressed as:

[0051]

[0052] Among them, i q is the q-axis current, u q is the q-axis voltage, L is the q-axis inductance, R is the resistance, a and b are the intermediate parameters, N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, τ is the pole pitch, and F(t) is the total disturbance of the motor system, where the total disturbance is unknown.

[0053] According to the mathematical model of the permanent magnet synchronous linear motor, the total disturbance term F(t) is a control factor affecting the system. Observing the total disturbance term and giving the q-axis current for compensation can improve the dynamic performance and anti-disturbance ability of the system.

[0054] Traditional PI controllers cannot accurately measure the total disturbance of the motor system, so the control accuracy, anti-interference ability and response speed are all poor. To solve this problem, the inventors proposed to use an extended state observer to observe the total disturbance and compensate it with the total disturbance. The extended state observer (ESO) is a common method for observing unknown disturbances in the system. It can approximate the external disturbance of the system as a known quantity for real-time compensation without the need for an accurate mathematical model of the controlled object.

[0055] Furthermore, by expanding the total disturbance into the state variable α2, the state equation of the motor system can be obtained:

[0056]

[0057] Where v is the permanent magnet linear motor rotor speed, α1 is the permanent magnet linear motor rotor speed, α2 is the total disturbance term of the system, u=i q , N(t) is the derivative of the extended state term.

[0058] In S2, the velocity of the mover is obtained by differentiating the position of the mover, specifically, it is expressed as:

[0059]

[0060] Where v is the velocity of the mover, is the angular velocity of the mover, is the differential value of the mover position, and τ is the pole pitch.

[0061] The traditional extended state observer is generally set as:

[0062]

[0063] Where z1 is the estimated motor rotor speed, z2 is the estimated total system disturbance, e1 is the estimated error of the motor rotor speed, e2 is the error of the extended state term, β1 and β2 are both observer parameters, and both are greater than 0. The function is a nonlinear error function, a is an intermediate parameter in the mathematical model of the permanent magnet synchronous linear motor, u = i q is the q-axis current.

[0064] Error nonlinear function It is expressed as:

[0065]

[0066] Among them, δ is the filter factor, g is the nonlinear factor, δ>0,0 <g<1。

[0067] The z2 in the traditional extended state observer is used as the extended state term of the system for final compensation. However, the inventors have found that the compensation effect of the expanded state term of the traditional extended state observer is limited. When the system is subjected to external disturbances, it cannot respond quickly to changes in unknown disturbances. After compensation, the response speed of the given q-axis current is slow.

[0068] In the present invention, the traditional extended state observer is improved to increase the response speed of the system.

[0069] According to the present invention, in S3, the improved extended state observer is set to:

[0070]

[0071] Among them, z1 is the estimated motor rotor speed, z2 is the estimated total system disturbance, e1 is the estimated error of the motor rotor speed, e2 is the error of the extended state term, β1, β2, β3 are all observer parameters, N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, τ is the pole pitch, u=i q is the q-axis current, fal(e1,g1,δ) and fal(e2,g2,δ) are the error nonlinear functions.

[0072] According to experience, the preferred range of β1 is [100, 400), the preferred range of β2 is [3000, 20000), and the preferred range of β3 is [3500, 45000).

[0073] Furthermore, the error nonlinear function is set as:

[0074]

[0075] Among them, δ1 and δ2 are filtering factors, g1 and g2 are nonlinear factors, and δ1>0,0 <g1<1,δ2> 0,0 <g2<1。

[0076] According to the present invention, in the improved extended state observer, Represents the derivative of the expansion state term, the introduction of β3fal(e2,α,δ) can increase The value of z2 observed by the improved extended state observer can respond to the external disturbance of the system more quickly when the system is subjected to external disturbance. After compensation, the q-axis current setting can have a faster response speed.

[0077] According to the present invention, in S3, the q-axis current u and the speed v of the mover are input into the improved extended state observer, and the improved extended state observer outputs an estimated total disturbance z2 of the motor system, wherein the q-axis current u is the thrust current given value output by the PI controller, and the speed v of the mover is obtained through step S2.

[0078] According to the mathematical model of the permanent magnet synchronous linear motor, it can be known that the total disturbance term F(t) is linearly related to the q-axis current. Based on this, in S4, the total disturbance is converted into a thrust current compensation value through linear transformation.

[0079] Further, in S4, the thrust current value after compensation is expressed as:

[0080]

[0081] Among them, i qref is the thrust current value before compensation, i qref * is the thrust current value after compensation, z2 is the estimated total system disturbance, N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, and τ is the pole pitch.

[0082] Various embodiments of the method described above in the present invention can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include: being implemented in one or more computer programs, which may be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general programmable processor, which may receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0083] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in the present disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document is not limited here.

[0084] Example

[0085] Example 1

[0086] Conduct a permanent magnet synchronous linear motor control experiment, where the core parameters of the permanent magnet synchronous linear motor are as follows:

[0087] Resistance R = 9.7Ω, d-axis inductance L d =43.3mH, q-axis inductance L q =43.3mH, number of motor pole pairs N p =1, permanent magnet flux ψ f =0.1686Wb, mover mass M = 1.1kg, pole pitch τ = 0.0135m.

[0088] The control method comprises the following steps:

[0089] S1. Setting a motor system, wherein a PI controller is used in the motor control system to control the permanent magnet linear synchronous motor.

[0090] S2. Obtain the position of the permanent magnet linear motor rotor through a position sensor, and obtain the speed of the permanent magnet linear motor rotor based on the position of the permanent magnet linear motor rotor;

[0091] S3, setting an improved extended state observer to observe the motor system and obtain the total disturbance of the motor system;

[0092] S4. Convert the acquired disturbance into a thrust current compensation value, compensate the thrust current value output by the PI controller, and use the compensated thrust current value to control the permanent magnet linear synchronous motor.

[0093] In S1, the mathematical model of the permanent magnet synchronous linear motor is expressed as:

[0094]

[0095] Among them, the linear motor speed is given as 0.54m / s, the inverter bus voltage is 311V, and the system is disturbed by 20.5N in 0.8s, then a=53.475, b=0.909.

[0096] In S2, the mover speed is:

[0097]

[0098] In S3, the improved extended state observer is set to:

[0099]

[0100] Among them, β1=125.6, β2=3943.84, β3=4000, δ1=0.01, g1=0.9, δ2=0.005, g2=0.9

[0101] In S4, the thrust current value after compensation is expressed as:

[0102] i qref * =i qref +0.017z2

[0103] Comparative Example 1

[0104] The same experiment as in Example 1 is performed, except that the observer in S2 is a traditional extended state observer, which is designed as:

[0105]

[0106] Where z1 is the estimated speed, z2 is the estimated total disturbance of the system, the preferred range of coefficient β1 is [100, 400), that is, β1 is selected as 125.6; the preferred range of coefficient β2 is [3000, 20000), that is, β2 is selected as 3943.84;

[0107]

[0108] Where δ1=0.01, g1=0.9.

[0109] Comparing the results in Example 1 and Comparative Example 1, Figure 2-8 shown.

[0110] in, Figure 2 The curves of the given speed and actual speed of the linear motor after compensation in Example 1 are shown. Figure 3 The curves of the given speed and actual speed of the linear motor after compensation in Comparative Example 1 are shown;

[0111] Figure 4 shows the linear motor speed error curve after compensation in Example 1, Figure 5 The linear motor speed error curve after compensation obtained in Comparative Example 1 is shown;

[0112] Figure 6 The q-axis current given value of the linear motor after compensation in Example 1 is shown. Figure 7 An enlarged view thereof is shown; Figure 8 The q-axis current given value of the linear motor after compensation in Comparative Example 1 is shown. Fig. 9 An enlarged view thereof is shown.

[0113] It can be seen from the figure that the actual speed drop of the linear motor obtained in Comparative Example 1 when subjected to external disturbance is significantly greater than that in Example 1 ( Figure 2 and Figure 3 ), the speed error of the linear motor obtained in the corresponding comparative example 1 when subjected to external disturbance is significantly larger than the speed error in the embodiment 1 ( Figure 4 and Figure 5 ), and the response speed of the given q-axis current of the linear motor obtained in Example 1 is significantly slower than that of the given q-axis current in Example 1 ( Figure 7 and Fig. 9 ), based on the above, it can be seen that the method in Example 1 has obvious improvements.

[0114] The present invention has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, the present invention may be subjected to a variety of substitutions and improvements, all of which fall within the scope of protection of the present invention.

Claims

1. A control method for a permanent magnet synchronous linear motor, characterized in that: The following steps are involved: Setting a motor control system, in which a PI controller is used to control the permanent magnet linear synchronous motor; The position of the permanent magnet synchronous linear motor rotor is obtained by a position sensor, and the speed of the permanent magnet synchronous linear motor rotor is obtained based on the position of the permanent magnet synchronous linear motor rotor. An improved extended state observer is set to observe the motor control system to obtain the total disturbance of the motor control system; The total disturbance obtained is converted into a thrust current compensation value, the thrust current value output by the PI controller is compensated, and the compensated thrust current value is used to control the permanent magnet linear synchronous motor; The improved extended state observer is set as: in, z1 is the estimated motor rotor speed, z2 is the estimated total system disturbance, e1 is the estimated error of the motor rotor speed, e2 is the error of the expansion state term, β1, β2, and β3 are all observer parameters. N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, τ is the pole pitch, u=i q is the q-axis current, α1 is the rotor speed of the permanent magnet synchronous linear motor, α2 is the total disturbance term of the system, fal(e1,g1,δ1) and fal(e2,g2,δ2) are nonlinear functions of the error, δ1 and δ2 are filtering factors. g1 and g2 are nonlinear factors.

2. The control method of the permanent magnet synchronous linear motor according to claim 1, characterized in that: In the motor control system, the mathematical model of the permanent magnet synchronous linear motor is expressed as: in, i q is the q-axis current, u q is the q-axis voltage, L is the q-axis inductance, R is the resistance, a and b are intermediate parameters. N p is the pole pair number, ψ f is the permanent magnet flux, M is the mass of the mover, τ is the pole distance, F(t) is the total disturbance of the motor control system, v is the rotor speed of the permanent magnet linear synchronous motor.

3. The control method of the permanent magnet linear synchronous motor according to claim 2, characterized in that: The total disturbance term of the system state equation is expanded into the state variable α2, and the state equation of the motor system is expressed as: in, α1 is the rotor speed of the permanent magnet synchronous linear motor, α2 is the total disturbance term of the system, u=i q is the q-axis current, N(t) is the derivative of the extended state term.

4. The control method of the permanent magnet linear synchronous motor according to claim 1, characterized in that: The speed of the mover is obtained by differentiating the position of the mover.

5. The control method of the permanent magnet linear synchronous motor according to claim 1, characterized in that: The error nonlinear function is set as:

6. The control method of the permanent magnet linear synchronous motor according to claim 1, characterized in that: The total disturbance is converted into thrust current compensation value through linear transformation.

7. The control method of the permanent magnet linear synchronous motor according to claim 1, characterized in that: The thrust current value after compensation is expressed as: in, i qref is the thrust current value before compensation, i qref * is the thrust current value after compensation, z2 is the estimated total system disturbance, N p is the pole pair number, ψ f is the permanent magnet flux, M is the mover mass, and τ is the pole pitch.

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