阅读说明：本技术 非线性柔化与变结构滑模控制永磁同步电机转速稳定的方法 (Method for controlling rotating speed stability of permanent magnet synchronous motor by nonlinear flexible and variable structure sliding mode ) 是由 王新宇 孙卫明 杨咏东 雷军委 于 2019-10-15 设计创作，主要内容包括：本发明公开非线性柔化与变结构滑模控制永磁同步电机转速稳定的方法。该方法测量电机转速与期望转速进行比较得到的转速误差,引入转速误差积分构成变结构滑模面信息,并与非线性柔化函数组合生成定子电流期望值；测量三相电流中的两相电流,坐标变换得到两相旋转坐标系下的定子电流,并与定子电流期望值比较获得电子电流误差信号,生成定子电流误差积分信号形成变结构滑模面信息,再叠加非线性柔化函数,构成两轴电流的跟踪控制器；最终通过电流跟踪实现电机的转速稳定控制。本发明的优点在于具有很强的抗干扰能力,能够消除负载与模型参数变化对控制性能的不良影响,同时柔化函数的引入消除了颤震影响,而且变结构滑模方法具有很好的快速性。(The invention discloses a method for controlling the stable rotating speed of a permanent magnet synchronous motor by a nonlinear flexible and variable-structure sliding mode. The method comprises the steps of measuring a rotating speed error obtained by comparing the rotating speed of a motor with an expected rotating speed, introducing a rotating speed error integral to form variable-structure sliding mode surface information, and combining a nonlinear softening function to generate a stator current expected value; measuring two-phase currents in three-phase currents, performing coordinate transformation to obtain stator currents in a two-phase rotating coordinate system, comparing the stator currents with expected values of the stator currents to obtain electronic current error signals, generating stator current error integral signals to form variable-structure sliding mode surface information, and then superposing nonlinear softening functions to form a tracking controller of the two-axis currents; and finally, the stable control of the rotating speed of the motor is realized through current tracking. The variable-structure sliding mode method has the advantages that the anti-interference capability is high, the adverse effect of load and model parameter change on the control performance can be eliminated, meanwhile, the flutter effect is eliminated by introducing the softening function, and the variable-structure sliding mode method has high rapidity.)

1. The method for controlling the rotating speed stability of the permanent magnet synchronous motor by the nonlinear flexible and variable structure sliding mode is characterized by comprising the following steps:

step S10, measuring the position and the rotating speed of the rotor of the permanent magnet synchronous motor and the two-phase current in the three-phase current, and carrying out coordinate transformation on the two-phase current;

step S20, setting the expectation of the d-axis stator current as 0, and designing a first variable structure sliding mode signal S and a second variable structure sliding mode signal S according to the stator current error signal₁And s₂；

Step S30, aiming at the second variable structure sliding mode signal S₂Designing q-axis stator voltage u based on softening function and nonlinear variable structure method_q；

Step S40, according to the comparison error between the measured rotating speed signal and the expected rotating speed signal, the expected value of the q-axis stator current based on the softening function and the nonlinear variable structure method is designed to be i_qc；

Step S50, according to i obtained after the Park conversion_qValue and desired value i of q-axis stator current_qcComparing to obtain a q-axis stator current error signal, and constructing a variable-structure sliding mode signal;

step S60, according to the sixth variable structure sliding mode signal S₆Designing d-axis stator voltage u based on softening function and nonlinear variable structure method_dAnd the rotation speed is stably controlled by converting the rotation speed to be sent to a motor;

wherein, for step S20, designing the first and second variable structure sliding mode signals S for the stator current error signal₁And s₂The method comprises the following steps:

s₁＝e_id+k₁s_eid，s₂＝s₁+k₂s_s1

wherein k is₁、k₂Can be freely adjusted for controlling parameters, is selected as a positive value,

wherein e_idFor the d-axis current error signal, it is calculated as follows:

e_id＝i_d-0＝i_d

where 0 is the desired value of d-axis stator current, i_dFor d-axis stator current obtained after Park transformation, where s_eidIs the d-axis current error integral signal, which is calculated as follows:

s_eid＝∫e_iddt

where dt represents the integration of the time signal,

wherein s is_s1An integrated signal of the first variable-structure sliding-mode signal is calculated as follows:

s_s1＝∫s₁dt

wherein dt represents the integration of the time signal;

wherein, for step S30, the first and second variable structure sliding mode signals S₁And s₂Designing q-axis stator voltage u based on softening function and nonlinear variable structure method_qThe method comprises the following steps:

wherein k is₃、k₄、k₅、ε₃、ε₄For controlling the parameters, it is freely adjustable and is selected to be positive, where f₁For softening the function signal, epsilon₁、ε₂The coefficient is a softening coefficient, can be freely adjusted, and is selected as a positive value to be used for adjusting the flutter of the system response;

wherein, for step S40, according to the comparison error between the measured rotation speed signal and the expected rotation speed signal, the expected value of the q-axis stator current based on the softening function and the nonlinear variable structure method is designed to be i_qcThe method comprises the following steps:

i_qc＝-k₁₀s₄-f₂

wherein k is₁₀Is a control parameter which can be freely adjusted and is selected to be positive, and

s₃、s₄for the third and fourth variable-structure sliding-mode signals, where k₈、k₉For controlling the parameters, it is freely adjustable and is selected to be a positive value, epsilon₆、ε₇The softening coefficient can be freely adjusted and is selected as a positive value for adjusting the flutter of the system response,

in the above formula s₄Is calculated as follows:

wherein k is₇For controlling the parameters, it is freely adjustable and is selected to be a positive value, epsilon₅The softening coefficient can be freely adjusted and is selected as a positive value for adjusting the flutter of the system response,

in the above formula s₃And s_s3Is calculated as follows:

s₃＝e_ω+k₆s_eω，s_s3＝∫s₃dt

wherein k is₆For controlling the parameters, it is freely adjustable and is selected to be positive, s_s3Is s is₃Wherein dt represents the integration of the time signal,

in the above formula e_ω＝ω_m-ω_mc，s_eω＝∫e_ωdt

Wherein ω is_mAs a measure of the speed of the motor, ω_mcIs the desired speed of the motor, e_ωIs a rotational speed error signal of the motor, s_eωThe dt is a motor rotating speed error integral signal and is used for integrating a time signal;

wherein for step S50, the desired value i for the q-axis stator current_qcComparing the actual value of the q-axis stator current to obtain a current error signal, and constructing a variable-structure sliding mode signal s₅And s₆The method comprises the following steps of;

s₅＝e_iq+k₁₁s_eiq

s₅is a fifth variable structure sliding mode signal, wherein k₁₁For controlling the parameters, it is freely adjustable and is selected to be positive, e_iqFor i obtained after Park transformation_qValue and desired value i of q-axis stator current_qcThe q-axis current error signal obtained after comparison is calculated in the mode of e_iq＝i_q-i_qc，s_eiqIs the integral of the q-axis current error signal, which is calculated as follows:

s_eiq＝∫e_iqdt

dt represents the integral of the time signal and,

s₆the sixth variable structure sliding mode surface signal is calculated as follows:

s₆＝s₅+k₁₂s_s5

wherein k is₁₂Can be freely adjusted for controlling parameters, is selected as a positive value,

wherein s is_s5Is a fifth variable-structure sliding mode signal s₅Is calculated as follows:

s_s5＝∫s₅dt

wherein dt represents the integration of the time signal;

wherein, for the sixth variable structure sliding mode signal in step S60, the d-axis stator voltage u based on the softening function and the nonlinear variable structure method is designed_dThe steps comprise

Wherein k is₁₅、ε₁₀、ε₁₁Can be freely adjusted for controlling parameters, is selected as a positive value,

wherein f is₃To soften the function signal, it is calculated as follows:

wherein k is₁₃、k₁₄For controlling the parameters, it is freely adjustable and is selected to be a positive value, epsilon₈、ε₉The softening coefficient can be freely adjusted, and is selected to be a positive value for adjusting the flutter of the system response.

2. The method of claim 1, wherein for step S10, measuring the position, the rotation speed and two phases of three-phase currents of the rotor of the permanent magnet synchronous motor, and performing coordinate transformation on the currents, the steps comprise:

measuring position and rotating speed signals of the rotor of the permanent magnet synchronous motor, wherein the position of the rotor is recorded as theta_mThe rotational speed is recorded as ω_m(ii) a Three-phase current signals of the permanent magnet synchronous motor are detected through the Hall current sensor and are respectively recorded as i_a、i_b、i_c，

For i in three-phase current_a、i_bPerforming Clarke transformation to obtain stator current i in a two-phase static coordinate system_α、i_βWherein the Clarke transformation is defined as follows:

prak conversion is carried out to obtain stator currents i of d and q axes of a two-phase rotating coordinate system_qAnd i_dWherein the Park transformation is defined as follows:

whereinθ_eFrom measurements of rotor position theta_mThe obtained result is obtained by conversion,

i.e. theta_e＝p_nθ_mWherein p is_nThe number of pole pairs of the motor is shown.

3. The method of claim 1, wherein the q-axis stator voltage u for the design is for step S60_qAnd d-axis stator voltage u_dInverse Park transformation is performed as follows

Wherein u is_α、u_βIs the stator voltage of alpha and beta axes in a two-phase static coordinate system, and then u is calculated_α、u_βThe output is transmitted to a space vector pulse width modulation and three-phase inverter to control the rotating speed of the motor to reach a given speed omega through a permanent magnet synchronous motor_mc。

Technical Field

The invention relates to the field of permanent magnet synchronous motors, in particular to a method for realizing stable control of the rotating speed of a permanent magnet synchronous motor by adopting a nonlinear flexible and variable-structure sliding mode.

Background

Due to the development of the rare earth permanent magnet material industry, the permanent magnet synchronous motor is rapidly developed. And because the permanent magnet synchronous motor can save a mechanical commutator and an electric brush of a common motor, the permanent magnet synchronous motor has high reliability, lighter weight than an asynchronous motor and good control performance, thereby being widely applied to the field of motion control of medium and small power. However, parameters of the permanent magnet synchronous motor model are difficult to accurately measure, or a time-varying problem exists, so that the control effect is not ideal by a method depending on an accurate model. The main problem is that the control performance will be greatly degraded when the motor load parameter or other parameters are changed. Researchers also carry out special parameter online identification on the motor model, but the method can greatly increase the design difficulty, and the identification result still has larger error. The sliding mode variable structure control has good rapidity and robustness, does not need accurate parameters of a model, and often causes a flutter problem.

Namely, because the load change condition of the permanent magnet motor cannot be predicted and the motor model parameters cannot be accurately measured, the control method which depends on the model accurate parameters generally cannot achieve ideal control performance.

It is to be noted that the information invented in the above background section is only for enhancing the understanding of the background of the present invention, and therefore, may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

The invention aims to provide a method for realizing the stable control of the rotating speed of a permanent magnet synchronous motor by adopting a nonlinear flexible and variable-structure sliding mode, and further solves the problems of slow dynamic response of a system or large influence of motor load change on response caused by the limitations and defects of the related technology.

According to one aspect of the invention, a method for realizing stable control of the rotating speed of a permanent magnet synchronous motor by adopting a nonlinear flexible and variable structure sliding mode is provided, which comprises the following steps:

step S10, measuring the position and the rotating speed of the rotor of the permanent magnet synchronous motor and the two-phase current in the three-phase current, and carrying out coordinate transformation on the two-phase current;

step S20, setting the expectation of the d-axis stator current as 0, and designing a first variable-structure sliding mode signal and a second variable-structure sliding mode signal according to the stator current error signal;

step S30, designing the second variable-structure sliding mode signal based onQ-axis stator voltage u of softening function and nonlinear variable structure method_q；

Step S40, according to the comparison error between the measured rotating speed signal and the expected rotating speed signal, the expected value of the q-axis stator current based on the softening function and the nonlinear variable structure method is designed to be i_qc；

Step S50, according to i obtained after the Park conversion_qValue and desired value i of q-axis stator current_qcComparing to obtain a q-axis stator current error signal, and constructing a variable-structure sliding mode signal;

step S60, according to the sixth variable structure sliding mode signal S₆Designing d-axis stator voltage u based on softening function and nonlinear variable structure method_dAnd the rotation speed is stably controlled by converting the rotation speed to be sent to the motor.

In an exemplary embodiment of the present invention, measuring two phases of three-phase currents according to a position, a rotation speed, and a rotor of the motor, and performing the coordinate transformation on the currents includes:

measuring position and rotating speed signals of the rotor of the permanent magnet synchronous motor, wherein the position of the rotor is recorded as theta_mThe rotational speed is recorded as ω_m(ii) a Secondly, three-phase current signals of the permanent magnet synchronous motor are detected through a Hall current sensor and are respectively recorded as i_a、i_b、i_c。

Secondly, for i in three-phase current_a、i_bPerforming Clarke transformation to obtain stator current i in a two-phase static coordinate system_α、i_β. Wherein the Clarke transformation is defined as follows:

the following Prak conversion is carried out again to obtain stator currents i of d and q axes of the two-phase rotating coordinate system_qAnd i_d. Wherein the Park transformation is defined as follows:

wherein theta is_eFrom measurements of rotor position theta_mAnd (5) carrying out transformation to obtain the product. I.e. theta_e＝p_nθ_mWherein p is_nThe number of pole pairs of the motor is shown.

In an exemplary embodiment of the invention, the first and second variable-structure sliding-mode signals s are designed based on the d-axis current error signal₁And s₂The method comprises the following steps:

s₁＝e_id+k₁s_eid，s₂＝s₁+k₂s_s1

wherein k is₁、k₂For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Wherein e_idFor the d-axis current error signal, it is calculated as follows:

e_id＝i_d-0＝i_d

where 0 is the desired value of d-axis stator current, i_dThe d-axis stator current obtained after the Park transformation is obtained. Wherein s is_eidIs the d-axis current error integral signal, which is calculated as follows:

s_eid＝∫e_iddt

where dt represents the integration of the time signal. Wherein s is_s1An integrated signal of the first variable-structure sliding-mode signal is calculated as follows:

s_s1＝∫s₁dt

where dt represents the integration of the time signal.

In an exemplary embodiment of the invention, the first and second variable-structure sliding-mode signals s are based on₁And s₂Designing q-axis stator voltage u based on softening function and nonlinear variable structure method_qThe method comprises the following steps:

wherein k is₃、k₄、k₅、ε₃、ε₄For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Wherein f is₁For softening function informationNumber epsilon₁、ε₂The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response.

In an exemplary embodiment of the invention, the expected value of the q-axis stator current based on the softening function and the nonlinear variable structure method is designed to be i_qcThe method comprises the following steps:

i_qc＝-k₁₀s₄-f₂

wherein k is₁₀Is a control parameter which can be freely adjusted and is generally selected to be a positive value. While

Wherein k is₈、k₉For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Epsilon₆、ε₇The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response. In the above formula s₄Is calculated as follows:

wherein k is₇For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Epsilon₅The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response. In the above formula s₃And s_s3Is calculated as follows:

s₃＝e_ω+k₆s_eω，s_s3＝∫s₃dt

wherein k is₆For controlling the parameters, they can be freely adjusted and are generally selected to be positive. s_s3Is s is₃Wherein dt represents the integration of the time signal. In the above formula

e_ω＝ω_m-ω_mc，s_eω＝∫e_ωdt

Whereinω_mAs a measure of the speed of the motor, ω_mcIs the desired rotational speed of the motor. e.g. of the type_ωIs a rotational speed error signal of the motor, s_eωThe signal is an integral signal of the motor speed error.

In an exemplary embodiment of the present invention, i is obtained according to the Park transformation_qValue and desired value i of q-axis stator current_qcComparing to obtain q-axis stator current error signals, and constructing variable-structure sliding mode signals s₅And s₆Comprises the following steps of;

s₅＝e_iq+k₁₁s_eiq

wherein k is₁₁For controlling the parameters, they can be freely adjusted and are generally selected to be positive. e.g. of the type_iqIs i obtained after the Park transformation_qThe desired value of the q-axis stator current is i_qcAnd the q-axis current error signal obtained after comparison is calculated in a mode of e_iq＝i_q-i_qc。s_eiqIs the integral of the q-axis current error signal, which is calculated as follows:

s_eiq＝∫e_iqdt

dt represents the integration of the time signal.

s₆The sixth variable structure sliding mode surface signal is calculated as follows:

s₆＝s₅+k₁₂s_s5

wherein k is₁₂For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Wherein s is_s5Is a fifth variable-structure sliding mode signal s₅Is calculated as follows:

s_s5＝∫s₅dt

where dt represents the integration of the time signal.

In an exemplary embodiment of the invention, according to the six variable structure sliding mode signals, a d-axis stator voltage u based on a softening function and a nonlinear variable structure method is designed_dComprises that

Wherein k is₁₅、ε₁₀、ε₁₁For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Wherein f is₃To soften the function signal, it is calculated as follows:

wherein k is₁₃、k₁₄For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Epsilon₈、ε₉The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response.

Q-axis stator voltage u for said design_qAnd d-axis stator voltage u_dInverse Park transformation is performed as follows

Wherein u is_α、u_βThe stator voltages of alpha and beta axes in a two-phase static coordinate system are calculated, and finally u is calculated_α、u_βThe output is sent to a space vector pulse width modulation and three-phase inverter and finally sent to a permanent magnet synchronous motor, and the rotating speed of the motor is controlled to reach a given speed omega_mc。

Finally, according to the response condition of the system, all the parameters k are carried out₁To k is₁₅And epsilon₁To epsilon₁₁And (4) debugging, selecting proper control parameters, and finally finishing the control of the rotating speed of the motor.

The method for controlling the rotating speed stability of the permanent magnet synchronous motor by the nonlinear flexible and variable structure sliding mode is characterized in that a rotating speed error is obtained by measuring the rotating speed of the motor and comparing the rotating speed with an expected rotating speed, rotating speed error integral is introduced to form variable structure sliding mode surface information and is combined with a nonlinear flexible function to generate a stator current expected value, meanwhile, two-phase currents in three-phase currents are measured, the stator currents under a two-phase rotating coordinate system are obtained through coordinate transformation and are compared with the stator current expected value to obtain an electronic current error signal, the stator current error integral signal is generated to form variable structure sliding mode surface information, then the nonlinear flexible function is superposed to form a tracking controller of two-axis currents, and finally the rotating speed stability control of the motor is realized through current tracking. Furthermore, the method does not need to accurately know inductance parameters, rotational inertia parameters, load conditions and the like of the motor, can realize stable tracking control of the rotating speed of the permanent magnet synchronous motor through error feedback control, a nonlinear softening function and the design of three layers of six variable-structure sliding modes, has strong anti-jamming capability, and can effectively eliminate adverse effects of load and model parameter changes on control performance.

Has the advantages that:

the invention relates to a method for realizing the stable control of the rotating speed of a permanent magnet synchronous motor by adopting a nonlinear flexible and variable structure sliding mode, which only measures two phases of the angular speed, the angular position and three-phase current of the permanent magnet synchronous motor and better realizes the stable tracking control of the rotating speed of the permanent magnet synchronous motor by error feedback control, a nonlinear flexible function and the design of three layers of six variable structure sliding modes. The method does not need to accurately know inductance parameters, rotational inertia parameters, load conditions and the like of the motor, and has good robustness and rapidity because a variable-structure sliding mode method is adopted. And due to the use of the nonlinear softening function, the motor can run stably under the steady state condition, has small flutter, and can adapt to different changes of the motor load, thereby having high engineering practical value.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

Fig. 1 is a flowchart of a method for realizing stable control of a rotating speed of a permanent magnet synchronous motor by using a sliding mode with a nonlinear flexibility and a variable structure provided by the invention.

Fig. 2 is a first variable configuration sliding surface curve of the method provided by an embodiment of the present invention.

Fig. 3 is a second variable configuration slip-form surface curve of the method provided by an embodiment of the present invention.

Fig. 4 is a graph of a synchronous motor d-axis stator current tracking desired value 0 according to a method provided by an embodiment of the invention.

Fig. 5 is a third variable configuration slip-form surface curve of the method provided by an embodiment of the present invention.

Fig. 6 is a fourth variable configuration sliding surface curve of the method provided by an embodiment of the present invention.

FIG. 7 is a graph of expected values i for q-axis stator current for a method provided by an embodiment of the invention_qcCurve line.

Fig. 8 is a fifth variable configuration sliding surface curve of the method provided by an embodiment of the present invention.

Fig. 9 is a sixth variable configuration sliding surface curve of the method provided by an embodiment of the present invention.

FIG. 10 shows q-axis stator current i for a method provided by an embodiment of the invention_qTracking the actual value of (i) to the expected value i_qcCurve line.

Fig. 11 is a curve of the expected speed tracking value of the permanent magnet synchronous motor according to the method provided by the embodiment of the invention.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, devices, steps, and so forth. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the invention.

The invention provides a method for stably controlling the rotating speed of a permanent magnet synchronous motor by measuring the position and angular speed information of a rotor and the two-phase current information of a stator and combining a variable structure sliding mode with a nonlinear softening function. Meanwhile, the variable-structure sliding mode control method is adopted, so that the method has good anti-interference capability and rapidness, and also has high engineering application value.

The method for realizing the stable control of the rotating speed of the permanent magnet synchronous motor by the non-linear flexible and variable structure sliding mode of the invention is further explained and explained below with reference to the attached drawings. Referring to fig. 1, the method for implementing stable control of the rotating speed of the permanent magnet synchronous motor by the nonlinear flexible and variable structure sliding mode may include the following steps:

step S10, measuring the position and the rotating speed of the rotor of the permanent magnet synchronous motor and the two-phase current in the three-phase current, and carrying out coordinate transformation on the two-phase current;

specifically, firstly, the position and rotation speed signals of the rotor of the permanent magnet synchronous motor are measured through a position/speed detection sensing unit, wherein the position of the rotor is recorded as theta_mThe rotational speed is recorded as ω_m(ii) a Secondly, three-phase current signals of the permanent magnet synchronous motor are detected through a Hall current sensor and are respectively recorded as i_a、i_b、i_c。

Secondly, for i in three-phase current_a、i_bPerforming Clarke transformation to obtain stator current i in a two-phase static coordinate system_α、i_β. Wherein the Clarke transformation is defined as follows:

the following Prak conversion is carried out again to obtain stator currents i of d and q axes of the two-phase rotating coordinate system_qAnd i_d. Wherein the Park transformation is defined as follows:

wherein theta is_eFrom measurements of rotor position theta_mAnd (5) carrying out transformation to obtain the product. I.e. theta_e＝p_nθ_mWherein p is_nThe number of pole pairs of the motor is shown.

Step S20, setting the expectation of the d-axis stator current as 0, and designing a first variable structure sliding mode signal and a second variable structure sliding mode signal aiming at the stator current error signal

Specifically, the expected value of the d-axis stator current is set to 0, and i obtained by the Park conversion is used as the expected value_dValue, d-axis current error signal, defined as e_id＝i_d-0＝i_d。

Secondly, according to the d-axis current error signal e_idDesigning d-axis current error integral signal s_eidIt is calculated as follows:

s_eid＝∫e_iddt

where dt represents the integration of the time signal.

Thirdly, the d-axis current error signal e is used_idAnd d-axis current error integral signal s_eidForming a first variable structure sliding mode surface signal, denoted as s₁It is calculated as follows:

s₁＝e_id+k₁s_eid

wherein k is₁For controlling the parameters, they can be freely adjusted and are generally selected to be positive.

Then according to the first variable structure sliding mode signal s₁Constructing its integral signal, denoted s_s1It is calculated as follows:

s_s1＝∫s₁dt

where dt represents the integration of the time signal.

Finally, according to the first variable-structure sliding mode signal s₁Constructing a second variable structure sliding mode surface signal with the integral signal, and recording the signal as s₂It is calculated as follows:

s₂＝s₁+k₂s_s1

wherein k is₂For controlling the parameters, they can be freely adjusted and are generally selected to be positive.

Step S30, aiming at the second variable structure sliding mode signal, designing a q-axis stator voltage u based on a softening function and a nonlinear variable structure method_q

Firstly, aiming at the first variable structure sliding mode surface signal and the second variable structure sliding mode surface signal, constructing a softening function signal f₁It is calculated as follows:

wherein k is₃、k₄For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Epsilon₁、ε₂The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response.

Secondly, aiming at the softening function signal f₁Combined with variable structure signals s₂Forming a q-axis stator voltage u as follows_qThe calculation method is as follows:

wherein k is₅、ε₃、ε₄For controlling the parameters, they can be freely adjusted and are generally selected to be positive.

Step S40, according to the comparison error between the measured rotating speed signal and the expected rotating speed signal, the expected value of the q-axis stator current based on the softening function and the nonlinear variable structure method is designed to be i_qc。

Specifically, first, the desired rotation speed of the motor is set to ω_mcAccording to the motor speedMeasured value of (a) ("omega")_m(step S10 measurement), comparing to obtain a motor speed error signal, and recording as e_ωThe calculation method is as follows: e.g. of the type_ω＝ω_m-ω_mc。

Secondly, according to the rotating speed error signal e of the motor_ωConstructing a speed error integral signal, denoted as s_eωThe calculation method is as follows: s_eω＝∫e_ωdt, dt represents the integration of the time signal. According to the motor speed error signal e_ωIntegral signal s with rotational speed error_eωConstructing a third variable-structure sliding mode signal s₃It is calculated as follows:

s₃＝e_ω+k₆s_eω

wherein k is₆For controlling the parameters, they can be freely adjusted and are generally selected to be positive.

Thirdly, according to a third variable structure sliding mode signal s₃Constructing its integral signal, denoted s_s3It is calculated as follows:

s_s3＝∫s₃dt

where dt represents the integration of the time signal.

Then according to the third variable structure sliding mode signal s₃Constructing a fourth variable-structure sliding mode surface signal with the integral signal, and recording the fourth variable-structure sliding mode surface signal as s₄It is calculated as follows:

wherein k is₇For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Epsilon₅The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response.

Thereafter, according to the third variable-structure sliding mode signal s₄Constructing a nonlinear softening function signal f₂It is calculated as follows:

wherein k is₈、k₉For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Epsilon₆、ε₇The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response.

Finally, the expected value of the q-axis stator current is designed to be i according to the following formula_qcThe calculation method is as follows:

i_qc＝-k₁₀s₄-f₂

wherein k is₁₀Is a control parameter which can be freely adjusted and is generally selected to be a positive value.

Step S50, according to i obtained after the Park conversion_qValue and desired value i of q-axis stator current_qcComparing to obtain q-axis stator current error signals, and constructing variable-structure sliding mode signals

Specifically, firstly, i is obtained according to the Park transformation_qThe value is compared to obtain a q-axis current error signal, which is recorded as e_iqIn a comparison manner of e_iq＝i_q-i_qc. Designing a q-axis current error signal s according to the q-axis current error signal_eiqIt is calculated as follows:

s_eiq＝∫e_iqdt

dt represents the integration of the time signal.

Next, based on the q-axis current error signal e_iqIntegral signal s with q-axis current error_eiqForming a fifth variable-structure sliding mode surface signal, which is recorded as s₅It is calculated as follows:

s₅＝e_iq+k₁₁s_eiq

wherein k is₁₁For controlling the parameters, they can be freely adjusted and are generally selected to be positive.

Then according to the fifth variable structure sliding mode signal s₅Constructing its integral signal, denoted s_s5It is calculated as follows:

s_s5＝∫s₅dt

where dt represents the integration of the time signal.

Finally, according to the fifth variable structure sliding mode signal s₅And the integral signal s_s5Constructing a sixth variable-structure sliding mode surface signal, which is recorded as s₆It is calculated as follows:

s₆＝s₅+k₁₂s_s5

wherein k is₁₂For controlling the parameters, they can be freely adjusted and are generally selected to be positive.

Step S60, according to the sixth variable structure sliding mode signal S₆Designing d-axis stator voltage u based on softening function and nonlinear variable structure method_dAnd the rotation speed is stably controlled by converting the rotation speed to be sent to the motor

First, for the first to sixth variable-structure sliding-mode surface signals, a softening function signal f is constructed as follows₃It is calculated as follows:

wherein k is₁₃、k₁₄For controlling the parameters, they can be freely adjusted and are generally selected to be positive. Epsilon₈、ε₉The softening coefficient can be freely adjusted, is generally selected to be a positive value and is mainly used for adjusting the flutter of the system response.

Secondly, aiming at the softening function signal f₃Combined with variable structure signals s₆Forming a d-axis stator voltage u as follows_dThe calculation method is as follows:

wherein k is₁₅、ε₁₀、ε₁₁For controlling the parameters, they can be freely adjusted and are generally selected to be positive.

Thirdly, for the designed q-axis stator voltage u_q(obtained in step S30) and d-axis stator voltage u_d(obtained in step S60), inverse Park transformation is performed as follows

Wherein u is_α、u_βThe stator voltages of alpha and beta axes in a two-phase static coordinate system are calculated, and finally u is calculated_α、u_βThe output is sent to a space vector pulse width modulation and three-phase inverter and finally sent to a permanent magnet synchronous motor, and the rotating speed of the motor is controlled to reach a given speed omega_mc. The space vector pulse width modulation and the three-phase inverter are well-known technologies in the art and are not protected by the present invention, and therefore, they will not be described in detail herein.

Finally, according to the response condition of the system, all the parameters k are carried out₁To k is₁₅And epsilon₁To epsilon₁₁And (4) debugging, selecting proper control parameters, and finally finishing the control of the rotating speed of the motor.

Case implementation and computer simulation result analysis:

in the present case, the load torque T of the motor is selected_lIs T_lIn the case of 1 N.m, p is selected as the number of pole pairs of the motor_nPerformed in case 2.

The measurement process and the coordinate transformation process of step S10 are the same as those described above and will not be repeated here.

Setting k in step S20₁＝1，k₂The first and second variable-structure sliding mode surface curves are obtained as shown in fig. 2 and 3, which are equal to 0.1.

Step S30, setting k₃＝100，k₄＝100，ε₁＝2、ε₂＝2、k₅＝200、ε₃＝0.4、ε₄0.5. The resulting d-axis stator current tracks the desired value of 0 as shown in figure 4. It can be seen that the d-axis stator current tracks to the desired value of 0 after approximately 4s, the tracking is good, and the oscillations are small.

Step S40, setting k₆＝1、k₇＝0.1、ε₅＝3、k₈＝50、k₉＝50、ε₆＝1.5、ε₇＝2.5，k₁₀As shown in fig. 5 and 6, the curves of the third and the fourth variable-structure sliding mode surfaces are obtained as 200. Expected value curve of q-axis stator current is i_qcAs shown in fig. 7.

Step S50, setting k₁₁＝1、k₁₂The curves of the third and the fourth variable-structure sliding mode surfaces are obtained as shown in fig. 8 and 9, which are equal to 0.1.

Step S60, setting k₁₃＝2、k₁₄＝2、k₁₅＝20、ε₈＝5、ε₉＝4.5、ε₁₀＝3.5、ε₁₂＝3.5。

Final q-axis stator current i_qTracking the actual value of expected value i_qcAs shown in fig. 10, it can be seen that both can basically track and have partial static error in the steady state, but do not affect the final rotational speed control. The situation that the rotating speed of the permanent magnet synchronous motor tracks the expected value is shown in the figure 11. Therefore, the rotating speed of the final permanent magnet synchronous motor can accurately track the expected rotating speed omega_mc12.6 rad/s. Therefore, the method provided by the invention is reasonable and effective.

On the basis, the parameters can be finely adjusted by considering the changes of the load sizes of different permanent magnet synchronous motors, the change of the flux linkage size of the basic excitation magnetic field chain of the permanent magnet passing through the stator winding and the change of the inductance size of the stator winding, and finally the whole set of parameters of the permanent magnet synchronous motor are determined, so that the design of the method for realizing the stable control of the rotating speed of the permanent magnet synchronous motor by adopting the nonlinear flexible and variable structure sliding mode is completed.

The invention adopts a method of combining a softening function and a sliding mode variable structure to realize the rotating speed control of the permanent magnet synchronous motor, ensures the stability and the accuracy of the system by constructing a plurality of sliding modes with variable structures, and simultaneously introduces the softening function to weaken the flutter problem of the system, and the case implementation and the experiment of computer simulation result analysis show that the method has better robustness, can adapt to the change of load as shown in figures 10 and 11, and can adapt to the change of the q-axis stator current i_qTracking the actual value of expected value i_qcAnd (4) stably tracking, and controlling the rotating speed of the permanent magnet synchronous motor to accurately track the expected rotating speed.

The variable-structure sliding mode method has the advantages that the anti-interference capability is high, the adverse effect of load and model parameter change on the control performance can be eliminated, meanwhile, the flutter effect is eliminated by introducing the softening function, and the variable-structure sliding mode method has high rapidity.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.