CN110620534A - Method for controlling rotating speed stability of permanent magnet synchronous motor by nonlinear flexible and variable structure sliding mode - Google Patents

Abstract

The invention discloses a method for stabilizing the rotation speed of a permanent magnet synchronous motor controlled by nonlinear softening and variable structure sliding mode. This method measures the speed error obtained by comparing the motor speed with the expected speed, introduces the integral of the speed error to form the variable structure sliding mode surface information, and combines it with the nonlinear softening function to generate the expected value of the stator current; measures the two-phase current in the three-phase current, The stator current in the two-phase rotating coordinate system is obtained by coordinate transformation, and compared with the expected value of the stator current to obtain the electronic current error signal, the integral signal of the stator current error is generated to form the variable structure sliding mode surface information, and then the nonlinear softening function is superimposed to form a two-axis Current tracking controller; finally realize the stable control of the motor speed through current tracking. The invention has the advantages of strong anti-interference ability, can eliminate the adverse effects of load and model parameter changes on the control performance, and at the same time, the introduction of the softening function eliminates the influence of chatter, and the variable structure sliding mode method has a good fast sex.

Description

Nonlinear Softening and Variable Structure Sliding Mode Control Method for Speed Stabilization of Permanent Magnet Synchronous Motor

technical field

The invention relates to the field of permanent magnet synchronous motors, in particular to a method for realizing stable control of the rotational speed of permanent magnet synchronous motors by using nonlinear softening and variable structure sliding mode.

Background technique

Due to the development of the rare earth permanent magnet material industry, the permanent magnet synchronous motor has developed rapidly. And because the permanent magnet synchronous motor can save the mechanical commutator and brush of the ordinary motor, it has high reliability, is lighter than the asynchronous motor, and has better control performance, so it is widely used in the field of motion control of small and medium power. However, the parameters of the permanent magnet synchronous motor model are difficult to measure accurately, or there are time-varying problems, so methods that rely on accurate models often have unsatisfactory control effects. The main problem is that when the motor load parameters or other parameters change, the control performance will be greatly reduced. Some researchers also conduct special parameter online identification of motor models, but this method will greatly increase the difficulty of design, and there may still be large errors in the identification results. The sliding mode variable structure control has good rapidity and robustness, and does not require precise parameters of the model, but it often causes chatter problems.

That is, because the load change of the permanent magnet motor cannot be predicted, and the parameters of the motor model cannot be accurately measured, the control method that generally relies on the precise parameters of the model cannot achieve ideal control performance.

It should be noted that the information disclosed in the above background technology section is only used to enhance 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.

Contents of the invention

The purpose of the present invention is to provide a method of using nonlinear softening and variable structure sliding mode to realize the stable control of the permanent magnet synchronous motor speed, and then overcome the slow dynamic response of the system or the response to the motor load caused by the limitations and defects of the related technology Issues with large impacts of change.

According to one aspect of the present invention, there is provided a method for realizing stable control of the speed of a permanent magnet synchronous motor by using nonlinear softening and variable structure sliding mode, comprising the following steps:

Step S10, measuring the position and speed of the rotor of the permanent magnet synchronous motor and the two-phase current in the three-phase current, and performing coordinate transformation on the two-phase current;

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

Step S30, aiming at the above-mentioned second variable structure sliding mode signal, design the q-axis stator voltage u _q based on softening function and nonlinear variable structure method;

Step S40, according to the comparison error between the measured speed signal and the expected speed signal, design the expected value of the q-axis stator current i _qc based on the softening function and the nonlinear variable structure method;

Step S50, comparing the _iq value obtained after the above-mentioned Park transformation with the expected value _iqc of the q-axis stator current to obtain the q-axis stator current error signal, and construct a variable structure sliding mode signal;

Step S60, according to the sixth variable structure sliding mode signal s ₆ , design the d-axis stator voltage u _d based on the softening function and nonlinear variable structure method, and send it to the motor through transformation to realize the stable speed control.

In an example embodiment of the present invention, measuring according to the position and rotational speed of the rotor of the motor and two phases of the three-phase current, and performing coordinate transformation on the current includes:

Measure the position and speed signals of the permanent magnet synchronous motor rotor, where the rotor position is recorded as θ _m , and the rotational speed is recorded as ω _m ; secondly, the three-phase current signals of the permanent magnet synchronous motor are detected by the Hall current sensor, which are respectively recorded as i _a , i _b , i _c .

Secondly, the Clarke transformation is performed on ia and _ib in the three-phase current to obtain the stator current _{i α} and i _β in the two-phase stationary coordinate system. The Clarke transform is defined as follows:

Perform the following Prak transformation again to obtain the stator currents i _q and id of the two-phase rotating coordinate system _d and q axes. The Park transformation is defined as follows:

Among them, θ _e is obtained by transforming the measured value θ _m of the rotor position. That is, θ _e =p _n θ _m , where p _n is the number of pole pairs of the motor.

In an example embodiment of the present invention, designing the first and second variable structure sliding mode signals _s1 and s2 according to the d _- axis current error signal includes:

s ₁ =e _id +k ₁ s _eid , s ₂ =s ₁ +k ₂ s _s1

Among them, k ₁ and k ₂ are control parameters, which can be adjusted freely, and are generally selected as positive values. Where e _id is the d-axis current error signal, which is calculated as follows:

e _id = i _d -0 = i _d

Among them, 0 is the expected value of the stator current of the d-axis, and i _d is the stator current of the d-axis obtained after the above-mentioned Park transformation. Among them, s _eid is the d-axis current error integral signal, which is calculated as follows:

s _eid = ∫e _id dt

where dt represents the integration of the time signal. Wherein s _s1 is the integral signal of described first variable structure sliding mode signal, and its calculation is as follows:

s _s1 = ∫s ₁ dt

where dt represents the integration of the time signal.

In an exemplary embodiment of the present invention, according to the first and second variable structure sliding mode signals s ₁ and s ₂ , designing the q-axis stator voltage u _q based on the softening function and nonlinear variable structure method includes:

Among them, k ₃ , k ₄ , k ₅ , ε ₃ , and ε ₄ are control parameters, which can be adjusted freely, and are generally selected as positive values. Among them, f ₁ is the softening function signal, ε ₁ and ε ₂ are the softening coefficients, which can be adjusted freely, and generally selected as positive values, which are mainly used to adjust the flutter of the system response.

In an exemplary embodiment of the present invention, according to the comparison error between the measured rotational speed signal and the expected rotational speed signal, designing the expected value of the q-axis stator current _iqc based on the softening function and the nonlinear variable structure method includes:

i _qc ＝-k ₁₀ s ₄ -f ₂

Among them, k ₁₀ is a control parameter, which can be adjusted freely, and is generally selected as a positive value. and

Among them, k ₈ and k ₉ are control parameters, which can be adjusted freely, and are generally selected as positive values. ε ₆ and ε ₇ are softening coefficients, which can be adjusted freely. Generally, they are selected as positive values, and are mainly used to adjust the flutter of the system response. The calculation of _s4 in the above formula is as follows:

Among them, k ₇ is a control parameter, which can be adjusted freely, and is generally selected as a positive value. ε ₅ is the softening coefficient, which can be adjusted freely. Generally, it is selected as a positive value, which is mainly used to adjust the flutter of the system response. The calculation of s ₃ and s _s3 in the above formula is as follows:

s ₃ =e _ω +k ₆ s _eω , s _s3 =∫s ₃ dt

Among them, k ₆ is a control parameter, which can be adjusted freely, and is generally selected as a positive value. s _s3 is the integral signal of s ₃ , where dt represents the time signal integration. In the above formula

e _ω =ω _m -ω _mc , s _eω =∫e _ω dt

Among them, ω _m is the measured value of the motor speed, and ω _mc is the expected speed of the motor. e _ω is the speed error signal of the motor, and s _eω is the integral signal of the motor speed error.

In an exemplary embodiment of the present invention, the i _q value obtained after the Park transformation is compared with the expected value i _qc of the q-axis stator current to obtain the q-axis stator current error signal, and construct the variable structure sliding mode signal s ₅ and s ₆ include;

s ₅ =e _iq +k ₁₁ s _eiq

Among them, k ₁₁ is a control parameter, which can be adjusted freely, and is generally selected as a positive value. e _iq is the q-axis current error signal obtained by comparing the i _q value obtained after the above Park transformation with the expected value of the q-axis stator current i _qc , and its calculation method is e _iq =i _q -i _qc . s _eiq is the integral of the q-axis current error signal, which is calculated as follows:

s _eiq =∫e _iq dt

dt means integrating the time signal.

s ₆ is the sixth variable structure sliding mode surface signal, which is calculated as follows:

s ₆ =s ₅ +k ₁₂ s _s5

Among them, k ₁₂ is a control parameter, which can be adjusted freely, and is generally selected as a positive value. Where s _s5 is the integral signal of the fifth variable structure sliding mode signal s ₅ , which is calculated as follows:

s _s5 = ∫s ₅ dt

where dt represents the integration of the time signal.

In an exemplary embodiment of the present invention, according to the six variable structure sliding mode signals, the design of the d-axis stator voltage u _d based on the softening function and the nonlinear variable structure method includes

Among them, k ₁₅ , ε ₁₀ , and ε ₁₁ are control parameters, which can be adjusted freely, and are generally selected as positive values. Where f ₃ is the softening function signal, which is calculated as follows:

Among them, k ₁₃ and k ₁₄ are control parameters, which can be adjusted freely, and are generally selected as positive values. ε ₈ and ε ₉ are softening coefficients, which can be adjusted freely. Generally, they are selected as positive values, and are mainly used to adjust the flutter of the system response.

For the designed q-axis stator voltage u _q and d-axis stator voltage u _d , the inverse Park transformation is performed as follows

Among them, u _α and u _β are the α and β axis stator voltages in the two-phase stationary coordinate system. Finally, u _α and u _β are output to the space vector pulse width modulation and three-phase inverter, and finally output to the permanent magnet synchronous motor. Control the motor speed to a given speed ω _mc .

Finally, according to the response of the system, debug all the parameters _k1 to _k15 and _ε1 to _ε11 , select the appropriate control parameters, and finally complete the motor speed control.

The key to the non-linear softening and variable structure sliding mode control method for permanent magnet synchronous motor speed stability of the present invention is to measure the speed error obtained by comparing the motor speed with the expected speed, introduce the integral of the speed error to form the variable structure sliding mode surface information and Combined with the nonlinear softening function to generate the stator current expected value, at the same time, measure the two-phase current in the three-phase current, coordinate transformation to obtain the stator current in the two-phase rotating coordinate system and compare it with the stator current expected value to obtain the electronic current error signal, and generate the stator current The current error integral signal forms the variable structure sliding mode surface information, and then superimposes the nonlinear softening function to form a two-axis current tracking controller, and finally realizes the stable control of the motor speed through current tracking. Furthermore, this method does not need to accurately know the inductance parameters, moment of inertia parameters, load conditions, etc. of the motor, and can realize the permanent magnet synchronous motor through the design of error feedback control, nonlinear softening function and three-layer six variable structure sliding mode. Speed stable tracking control has strong anti-interference ability, and can effectively eliminate the adverse effects of load and model parameter changes on control performance.

Beneficial effect:

The present invention adopts nonlinear softening and variable structure sliding mode to realize the stable control method of the permanent magnet synchronous motor speed, only measures the angular velocity, angular position and two phases of the three-phase current of the permanent magnet synchronous motor, through error feedback control, The nonlinear softening function and the design of three-layer and six variable-structure sliding modes can better realize the stable speed tracking control of permanent magnet synchronous motor. This method does not need to accurately know the inductance parameters, moment of inertia parameters, load conditions, etc. of the motor. Because it uses a variable structure sliding mode method, this method has good robustness and rapidity. And because of the use of its non-linear softening function, it runs smoothly under steady state conditions, has less flutter, and can also adapt to different changes in motor loads, so it has 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.

Description of 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. Apparently, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other drawings according to these drawings without creative efforts.

Fig. 1 is a flow chart of a method for realizing stable speed control of a permanent magnet synchronous motor by using nonlinear softening and variable structure sliding mode provided by the present invention.

Fig. 2 is the first variable structure sliding mode surface curve of the method provided by the embodiment of the present invention.

Fig. 3 is the second variable structure sliding mode surface curve of the method provided by the embodiment of the present invention.

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

Fig. 5 is the third variable structure sliding mode surface curve of the method provided by the embodiment of the present invention.

Fig. 6 is the fourth variable structure sliding mode surface curve of the method provided by the embodiment of the present invention.

Fig. 7 is a curve of the expected value i _qc of the q-axis stator current according to the method provided by the embodiment of the present invention.

Fig. 8 is the fifth variable structure sliding mode surface curve of the method provided by the embodiment of the present invention.

Fig. 9 is the sixth variable structure sliding mode surface curve of the method provided by the embodiment of the present invention.

Fig. 10 is a curve of the actual value tracking the expected value i _qc of the q-axis stator current i _q according to the method provided by the embodiment of the present invention.

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

Detailed ways

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many 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 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 in order to give a thorough understanding of embodiments of the invention. However, those skilled in the art will appreciate that the technical solution of the present invention may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. 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 of combining variable structure sliding mode and nonlinear softening function by measuring rotor position and angular velocity information, and stator two-phase current information, and realizes the stable control of the speed of permanent magnet synchronous motor. It does not depend on the precise parameters of the model, so the dynamic response is not sensitive to the motor load and has good robustness. At the same time, because it adopts the variable structure sliding mode control method, it has good anti-interference ability and fast type, and also has high engineering application value.

Next, the method for realizing the stable control of the speed of the permanent magnet synchronous motor by nonlinear softening and variable structure sliding mode of the present invention will be further explained and described in conjunction with the accompanying drawings. Referring to Fig. 1, the method for realizing the stable control of the speed of permanent magnet synchronous motor by nonlinear softening and variable structure sliding mode may include the following steps:

Step S10, measuring the position and speed of the rotor of the permanent magnet synchronous motor and the two-phase current in the three-phase current, and performing coordinate transformation on the two-phase current;

Specifically, first, the position and speed signals of the permanent magnet synchronous motor rotor are measured through the position/speed detection sensor unit, where the rotor position is recorded as θ _m and the speed is recorded as ω _m ; secondly, the permanent magnet synchronous motor is detected by the Hall current sensor The three-phase current signals of the synchronous motor are denoted as _ia , _ib and _ic respectively.

Secondly, the Clarke transformation is performed on _{ia and i b in} the three-phase current to obtain the stator current i _α and i _β in the two-phase stationary coordinate system. The Clarke transform is defined as follows:

Perform the following Prak transformation again to obtain the stator currents i _q and id of the two-phase rotating coordinate system _d and q axes. The Park transformation is defined as follows:

Among them, θ _e is obtained by transforming the measured value θ _m of the rotor position. That is, θ _e =p _n θ _m , where p _n is the number of pole pairs of the motor.

Step S20, set the expectation of the d-axis stator current as 0, and design the first and second variable structure sliding mode signals for the stator current error signal

Specifically, firstly, the expected value of the d-axis stator current is set to 0, and the d-axis current error signal is obtained by comparison according to the i _d value obtained after the above Park transformation, which is defined as e _id =i _d -0=i _d .

Secondly, according to the above d-axis current error signal e _id , design the d-axis current error integral signal s _eid , which is calculated as follows:

s _eid = ∫e _id dt

where dt represents the integration of the time signal.

Again, the first variable structure sliding mode surface signal is composed of the d-axis current error signal e _id and the d-axis current error integral signal s _eid , denoted as s ₁ , and its calculation is as follows:

s ₁ =e _id +k ₁ s _eid

Among them, k ₁ is a control parameter, which can be adjusted freely, and is generally selected as a positive value.

Then, according to the above-mentioned first variable structure sliding mode signal s ₁ , construct its integral signal, denoted as s _s1 , and its calculation is as follows:

s _s1 = ∫s ₁ dt

where dt represents the integration of the time signal.

Finally, according to the above-mentioned first variable structure sliding mode signal s ₁ and integral signal, the second variable structure sliding mode surface signal is constructed, denoted as s ₂ , and its calculation is as follows:

s ₂ =s ₁ +k ₂ s _s1

Among them, k ₂ is a control parameter, which can be adjusted freely, and is generally selected as a positive value.

Step S30, for the above second variable structure sliding mode signal, design the q-axis stator voltage u _q based on the softening function and nonlinear variable structure method

Firstly, for the above first and second variable structure sliding mode surface signals, the following softening function signal f ₁ is constructed, and its calculation is as follows:

Among them, k ₃ and k ₄ are control parameters, which can be adjusted freely, and are generally selected as positive values. ε ₁ and ε ₂ are softening coefficients, which can be adjusted freely. Generally, they are selected as positive values, and are mainly used to adjust the flutter of the system response.

Secondly, the above softening function signal f ₁ and the variable structure signal are combined s ₂ to form the following q-axis stator voltage u _q , which is calculated as follows:

Among them, k ₅ , ε ₃ , and ε ₄ are control parameters, which can be adjusted freely and generally selected as positive values.

Step S40 , according to the comparison error between the measured rotational speed signal and the expected rotational speed signal, the expected value of the q-axis stator current i _qc based on the softening function and nonlinear variable structure method is designed.

Concretely, first set the expected rotational speed of the motor as ω _mc , and compare it with the measured value ω _m of the motor rotational speed (measured in step S10) to obtain the motor rotational speed error signal, denoted as e _ω , and its calculation method is as follows: e _ω = ω _m −ω _mc .

Secondly, according to the motor speed error signal e _ω , construct the speed error integral signal, denoted as s _eω , and its calculation method is as follows: s _eω =∫e _ω dt, where dt represents the time signal integration. According to the above motor speed error signal _eω and speed error integral signal s _eω , construct the third variable structure sliding mode signal s ₃ , which is calculated as follows:

s ₃ =e _ω +k ₆ s _eω

Among them, k ₆ is a control parameter, which can be adjusted freely, and is generally selected as a positive value.

Again, according to the third variable structure sliding mode signal s ₃ to construct its integral signal, denoted as s _s3 , its calculation is as follows:

s _s3 = ∫s ₃ dt

where dt represents the integration of the time signal.

Then construct the fourth variable structure sliding mode surface signal based on the above third variable structure sliding mode signal s ₃ and integral signal, denoted as s ₄ , and its calculation is as follows:

Among them, k ₇ is a control parameter, which can be adjusted freely, and is generally selected as a positive value. ε ₅ is the softening coefficient, which can be adjusted freely. Generally, it is selected as a positive value, which is mainly used to adjust the flutter of the system response.

Afterwards, the nonlinear softening function signal f ₂ is constructed according to the above-mentioned third variable structure sliding mode signal s ₄ , and its calculation is as follows:

Among them, k ₈ and k ₉ are control parameters, which can be adjusted freely, and are generally selected as positive values. ε ₆ and ε ₇ are softening coefficients, which can be adjusted freely. Generally, they are selected as positive values, and are mainly used to adjust the flutter of the system response.

Finally, the expected value of the q-axis stator current i _qc is designed according to the following formula, and its calculation method is as follows:

i _qc ＝-k ₁₀ s ₄ -f ₂

Among them, k ₁₀ is a control parameter, which can be adjusted freely, and is generally selected as a positive value.

Step S50, compare the i _q value obtained after the above-mentioned Park transformation with the expected value i _qc of the q-axis stator current, obtain the q-axis stator current error signal, and construct the variable structure sliding mode signal

Specifically, firstly, according to the value of i _q obtained after the above-mentioned Park transformation, the q-axis current error signal is obtained by comparison, denoted as e _iq , and the comparison method is e _iq =i _q -i _qc . According to the above q-axis current error signal, the q-axis current error signal s _eiq is designed, and its calculation is as follows:

s _eiq =∫e _iq dt

dt means integrating the time signal.

Secondly, according to the q-axis current error signal e _iq and the q-axis current error integral signal s _{eiq to} form the fifth variable structure sliding mode surface signal, denoted as s ₅ , its calculation is as follows:

s ₅ =e _iq +k ₁₁ s _eiq

Among them, k ₁₁ is a control parameter, which can be adjusted freely, and is generally selected as a positive value.

Then, according to the above-mentioned fifth variable structure sliding mode signal s ₅ , construct its integral signal, denoted as s _s5 , and its calculation is as follows:

s _s5 = ∫s ₅ dt

where dt represents the integration of the time signal.

Finally, according to the fifth variable structure sliding mode signal s ₅ and the integral signal s _s5 , the sixth variable structure sliding mode surface signal is constructed, denoted as s ₆ , and its calculation is as follows:

s ₆ =s ₅ +k ₁₂ s _s5

Among them, k ₁₂ is a control parameter, which can be adjusted freely, and is generally selected as a positive value.

Step S60, according to the sixth variable structure sliding mode signal s ₆ above, design the d-axis stator voltage u _d based on the softening function and the nonlinear variable structure method, and send it to the motor through transformation to realize the stable speed control

First, for the first to sixth variable-structure sliding mode surface signals above, the following softening function signal f ₃ is constructed, and its calculation is as follows:

Among them, k ₁₃ and k ₁₄ are control parameters, which can be adjusted freely, and are generally selected as positive values. ε ₈ and ε ₉ are softening coefficients, which can be adjusted freely. Generally, they are selected as positive values, and are mainly used to adjust the flutter of the system response.

Secondly, the above softening function signal f ₃ and the variable structure signal are combined s ₆ to form the following d-axis stator voltage u _d , which is calculated as follows:

Among them, k ₁₅ , ε ₁₀ , and ε ₁₁ are control parameters, which can be adjusted freely, and are generally selected as positive values.

Again, for the designed q-axis stator voltage u _q (obtained in step S30) and d-axis stator voltage u _d (obtained in step S60), the inverse Park transformation is performed as follows

Among them, u _α and u _β are the α and β axis stator voltages in the two-phase stationary coordinate system. Finally, u _α and u _β are output to the space vector pulse width modulation and three-phase inverter, and finally output to the permanent magnet synchronous motor. Control the motor speed to a given speed ω _mc . The space vector pulse width modulation and the three-phase inverter are mature technologies in this field and are not protected by the present invention, so they will not be described in detail here.

Finally, according to the response of the system, debug all the parameters _k1 to _k15 and _ε1 to _ε11 , select the appropriate control parameters, and finally complete the motor speed control.

Case implementation and analysis of computer simulation results:

This case is carried out under the condition that the load torque T _l of the motor is selected as T _l =1N·m, and the number of pole pairs of the motor is selected as p _n =2.

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

In step S20, k ₁ =1 and k ₂ =0.1 are set, and the first and second variable structure sliding mode surface curves are obtained as shown in FIGS. 2 and 3 .

Step S30, set k ₃ =100, k ₄ =100, ε ₁ =2, ε ₂ =2, k ₅ =200, ε ₃ =0.4, ε ₄ =0.5. The situation that the final d-axis stator current tracks the expected value 0 is shown in Fig. 4 . It can be seen that the d-axis stator current tracks to the expected value 0 after about 4s, and the tracking is good, and the oscillation is small.

Step S40, set k ₆ =1, k ₇ =0.1, ε ₅ =3, k ₈ =50, k ₉ =50, ε ₆ =1.5, ε ₇ =2.5, k ₁₀ =200, get the third and fourth The sliding mode surface curves of a variable structure are shown in Fig. 5 and Fig. 6. The expected value curve of the q-axis stator current is i _qc as shown in Figure 7.

In step S50, k ₁₁ =1 and k ₁₂ =0.1 are set, and the third and fourth variable structure sliding mode surface curves are obtained as shown in FIGS. 8 and 9 .

Step S60, set k ₁₃ =2, k ₁₄ =2, k ₁₅ =20, ε ₈ =5, ε ₉ =4.5, ε ₁₀ =3.5, ε ₁₂ =3.5.

The actual value of the final q-axis stator current i _q tracks the expected value i _qc as shown in Figure 10. It can be seen that in the steady state, the two can basically track, and there is some static difference, but it does not affect the final speed control. The final rotational speed tracking expectation value of the permanent magnet synchronous motor is shown in Figure 11. It can be seen that the final rotational speed of the permanent magnet synchronous motor can accurately track the desired rotational speed ω _mc =12.6rad/s. Therefore, the method provided by the present invention is reasonable and effective.

On the basis of the above, considering the change of the load of different permanent magnet synchronous motors, the change of the flux linkage of the basic excitation magnetic field chain of the permanent magnet through the stator winding, and the change of the inductance of the stator winding, the above parameters can be fine-tuned to finally determine the permanent magnet synchronous The complete set of parameters of the motor has been completed, so as to complete the design of the method for the stable control of the permanent magnet synchronous motor speed by using nonlinear softening and variable structure sliding mode.

The present invention adopts the method of combining the softening function and the sliding mode variable structure to realize the speed control of the permanent magnet synchronous motor, and ensures the stability and accuracy of the system by constructing multiple variable structure sliding modes, and at the same time introduces the softening function to The chattering problem of the system can be weakened, and the experiment of case implementation and computer simulation simulation results analysis shows that the robustness of this method is relatively good, as shown in Figure 10 and 11, it can adapt to the change of load, and the actual value of the q-axis stator current i _q The value tracks the expected value i _qc to track stably, and the rotational speed of the permanent magnet synchronous motor is controlled to accurately track the expected rotational speed.

The invention has the advantages of strong anti-interference ability, can eliminate the adverse effects of load and model parameter changes on the control performance, and at the same time, the introduction of the softening function eliminates the influence of chatter, and the variable structure sliding mode method has a good fast sex.

Other embodiments of the invention will be readily apparent to those skilled in the art from consideration of the specification and practice of such an invention. This application is intended to cover any modification, use or adaptation of the present invention. These modifications, uses or adaptations follow the general principles of the present invention and include common knowledge or conventional technical means in the technical field not specified in the present invention . The specification and examples are to be considered exemplary only, with the true scope and spirit of the invention indicated by the appended claims.

Claims (3)

1. The method for nonlinear softening and variable structure sliding mode control permanent magnet synchronous motor rotating speed stability, is characterized in that, comprises the following steps: Step S10, measuring the position and speed of the rotor of the permanent magnet synchronous motor and the two-phase current in the three-phase current, and performing coordinate transformation on the two-phase current; Step S20, setting the expectation of the d-axis stator current as 0, and designing the first and second variable structure sliding mode signals s ₁ and s ₂ for the stator current error signal; Step S30, for the above-mentioned second variable structure sliding mode signal s ₂ , design the q-axis stator voltage u _q based on the softening function and nonlinear variable structure method; Step S40, according to the comparison error between the measured speed signal and the expected speed signal, design the expected value of the q-axis stator current i _qc based on the softening function and the nonlinear variable structure method; Step S50, comparing the _iq value obtained after the above-mentioned Park transformation with the expected value _iqc of the q-axis stator current to obtain the q-axis stator current error signal, and construct a variable structure sliding mode signal; Step S60, according to the sixth variable structure sliding mode signal s ₆ , design the d-axis stator voltage u _d based on the softening function and nonlinear variable structure method, and send it to the motor through transformation to realize the stable control of the speed; Wherein, for the step S20, aiming at the stator current error signal, designing the first and second variable structure sliding mode signals s ₁ and s ₂ , the steps include: s ₁ =e _id +k ₁ s _eid , s ₂ =s ₁ +k ₂ s _s1 Among them, k ₁ and k ₂ are control parameters, which can be adjusted freely and are selected as positive values, Where e _id is the d-axis current error signal, which is calculated as follows: e _id = i _d -0 = i _d Where 0 is the expected value of the d-axis stator current, id is the d-axis stator current obtained after Park transformation, and _seid is the _d -axis current error integral signal, which is calculated as follows: s _eid = ∫e _id dt where dt represents the integration of the time signal, Wherein s _s1 is the integral signal of described first variable structure sliding mode signal, and its calculation is as follows: s _s1 = ∫s ₁ dt where dt represents the integration of the time signal; Wherein, for step S30, for the first and second variable structure sliding mode signals s ₁ and s ₂ , designing the q-axis stator voltage u _q based on the softening function and nonlinear variable structure method, the steps include: Among them, k ₃ , k ₄ , k ₅ , ε ₃ , and ε ₄ are control parameters, which can be adjusted freely and are selected as positive values. Among them, f ₁ is the softening function signal, and ε ₁ and ε ₂ are softening coefficients, which can be adjusted freely , selected as a positive value, is used to adjust the flutter of the system response; Wherein, for step S40, according to the comparison error between the measured rotational speed signal and the expected rotational speed signal, the design of the expected value of the q-axis stator current i _qc based on the softening function and the nonlinear variable structure method includes: i _qc ＝-k ₁₀ s ₄ -f ₂ Among them, k ₁₀ is the control parameter, which can be adjusted freely and is selected as a positive value, while s ₃ and s ₄ are the third and fourth variable structure sliding mode signals, among which k ₈ and k ₉ are control parameters, which can be adjusted freely, and they are selected as positive values, and ε ₆ and ε ₇ are softening coefficients, which can be freely adjusted. Adjustment, selected as a positive value, used to adjust the flutter of the system response, The calculation of _s4 in the above formula is as follows: Among them, k ₇ is a control parameter, which can be adjusted freely, and is selected as a positive value; ε ₅ is a softening coefficient, which can be adjusted freely, and is selected as a positive value, which is used to adjust the flutter of the system response. The calculation of s ₃ and s _s3 in the above formula is as follows: s ₃ =e _ω +k ₆ s _eω , s _s3 =∫s ₃ dt Among them, k ₆ is the control parameter, which can be adjusted freely, and is selected as a positive value, s _s3 is the integral signal of s ₃ , where dt represents the integration of the time signal, In the above formula, e _ω ＝ω _m -ω _mc , s _eω ＝∫e _ω dt Among them, ω _m is the measured value of the above-mentioned motor speed, ω _mc is the expected speed of the motor, e _ω is the speed error signal of the motor, s _eω is the integral signal of the motor speed error, and dt represents the integration of the time signal; Wherein, for step S50, comparing the expected value i _qc of the q-axis stator current with the actual value of the q-axis stator current to obtain a current error signal, and constructing variable structure sliding mode signals s ₅ and s ₆ , the steps include; s ₅ =e _iq +k ₁₁ s _eiq s ₅ is the fifth variable structure sliding mode signal, in which k ₁₁ is the control parameter, which can be adjusted freely and is selected as a positive value. e _iq is the value of i _q obtained after Park transformation and compared with the expected value i _qc of the q-axis stator current The q-axis current error signal obtained later is calculated as e _iq =i _q -i _qc , s _eiq is the integral of the q-axis current error signal, and its calculation is as follows: s _eiq =∫e _iq dt dt means integrating the time signal, s ₆ is the sixth variable structure sliding mode surface signal, which is calculated as follows: s ₆ =s ₅ +k ₁₂ s _s5 Among them, k ₁₂ is a control parameter, which can be adjusted freely, and is selected as a positive value, Where s _s5 is the integral signal of the fifth variable structure sliding mode signal s ₅ , which is calculated as follows: s _s5 = ∫s ₅ dt where dt represents the integration of the time signal; Wherein, for the sixth variable structure sliding mode signal in step S60, design the d-axis stator voltage u _d based on the softening function and nonlinear variable structure method, the steps include Among them, k ₁₅ , ε ₁₀ , and ε ₁₁ are control parameters, which can be adjusted freely and are selected as positive values. Where f ₃ is the softening function signal, which is calculated as follows: Among them, k ₁₃ and k ₁₄ are control parameters, which can be adjusted freely, and are selected as positive values. ε ₈ , ε ₉ are softening coefficients, which can be adjusted freely, and are selected as positive values, which are used to adjust the flutter of the system response. 2. The method according to claim 1, characterized in that, for step S10 measuring the position of the rotor of the permanent magnet synchronous motor, the rotating speed and two phases in the three-phase current are measured, and the coordinate transformation is carried out to the current, the steps include : Measure the position and speed signals of the rotor of the permanent magnet synchronous motor, where the rotor position is recorded as θ _m , and the speed is recorded as ω _m ; the three-phase current signals of the permanent magnet synchronous motor are detected by the Hall current sensor, which are respectively recorded as _ia , _ib , i _c , Perform Clarke transformation on i _a and i _b in the three-phase current to obtain the stator current i _α and i _β in the two-phase stationary coordinate system, where the Clarke transformation is defined as follows: Carry out the following Prak transformation to obtain the stator current i _q and i _d of the two-phase rotating coordinate system d, q axis, where the Park transformation is defined as follows: where θ _e is obtained by transforming the measured value θ _m of the rotor position, That is, θ _e =p _n θ _m , where p _n is the number of pole pairs of the motor. 3. The method according to claim 1, characterized in that, for the designed q-axis stator voltage u _q and d-axis stator voltage u _d for step S60, carry out Park inverse transformation as follows where u _α and u _β are the α and β axis stator voltages in the two-phase stationary coordinate system, and then output u _α and u _β to the space vector pulse width modulation and three-phase inverter to control the motor speed through the permanent magnet synchronous motor The given speed ω _mc is reached.