Bearing-free motor suspension current control method based on two-section execution mechanism

Abstract

The invention discloses a bearingless motor suspension current control method based on a two-stage execution mechanism, which aims at the high dynamic response control requirement of the bearingless motor suspension current, combines the high algorithm complexity characteristic of the bearingless motor, is based on the deadbeat thought, and utilizes the symmetry of the duty ratio in one control period of the pulse width modulation technology to control the suspension current of the bearingless motor. Current prediction and model parameter error compensation are completed by sampling the current twice in a control period, meanwhile, complete execution of a control algorithm is guaranteed in cooperation with a two-stage algorithm execution mechanism, and finally high-dynamic-performance accurate control over the suspension current of the bearingless motor is achieved. The method is easy to implement, current prediction and model parameter error identification can be completed without depending on any model parameters, the former can achieve compensation of the digital control delay effect, and the latter can achieve compensation of the model parameter errors. The two-stage algorithm execution mechanism improves the execution efficiency of the control algorithm, guarantees the complete execution of the control algorithm, and is universal.

Description

Technical Field

[0001] The present invention relates to the technical field of bearingless motor driving, and in particular to a bearingless motor suspension current control method based on a two-stage execution mechanism. Background Art

[0002] The advantage of bearingless motors without mechanical wear makes them widely used in aerospace, semiconductor manufacturing, life sciences and chemical processes. The contactless and wear-free characteristics of bearingless motors benefit from the introduction of their additional suspension control system, but this also inevitably greatly increases the algorithm complexity of the bearingless motor control system. In addition, the existence of unknown external disturbances and process non-ideal factors requires the bearingless motor suspension control system to have high dynamic response and strong robustness, especially for the bearingless motor suspension current control link. As a more commonly used high-dynamic performance control scheme, the deadbeat idea is applied to the bearingless motor suspension current control. Its inherent digital control delay and model parameter error problems will seriously affect the suspension control performance. Therefore, for the aforementioned digital control delay and model parameter error problems, real-time targeted compensation measures are required to ensure high-performance suspension control of bearingless motors. In addition, combined with the characteristics of high algorithm complexity of its control system, the compensation measures taken must be simple, reliable and easy to implement. Summary of the invention

[0003] In view of the defects of the above-mentioned prior art, the present invention provides a bearingless motor suspension current control method based on a two-stage execution mechanism. In view of the high dynamic response control requirements of the bearingless motor suspension current, combined with the high algorithm complexity characteristics of the bearingless motor, based on the idea of ​​zero beat, the symmetry of the duty cycle within a control cycle of the pulse width modulation technology is utilized, and the current prediction and model parameter error compensation are completed by double sampling of the current within a control cycle. At the same time, the two-stage algorithm execution mechanism is cooperated to ensure the complete execution of the control algorithm, and finally the high dynamic performance and precise control of the bearingless motor suspension current is realized.

[0004] The present invention adopts the following technical solutions to solve the above technical problems:

[0005] A bearingless motor suspension current control method based on a two-stage execution mechanism, combined with the high algorithm complexity characteristics of bearingless motors, based on the deadbeat idea, completes current prediction and model parameter error compensation by double sampling of current within one control cycle, and cooperates with the two-stage algorithm execution mechanism to ensure the complete execution of the control algorithm, and finally realizes high dynamic performance and precise control of bearingless motor suspension current. The implementation steps of the method are as follows:

[0006] Step S1: at the beginning of the first half of the control cycle, the suspension current i L(k) and other signals required for closed-loop control of the bearingless motor system;

[0007] Step S2, completing the displacement outer loop control and obtaining the suspension current setting value;

[0008] Step S3, completing the torque loop control and obtaining the torque winding terminal voltage setting value;

[0009] Step S4, at the beginning of the second half of the control cycle, the second sampling of the suspension current within a control cycle is performed. L (k+0.5);

[0010] Step S5: Combine the two suspension current sampling values ​​in one control cycle to predict the suspension current at the next moment. Lpre (k+1), the specific formula is: i Lpre (k+1)=2i L (k+0.5)-i L (k);

[0011] Step S6, sampling the actual value of the suspension current i at the initial moment of the current control cycle L (k), combined with the predicted value of the suspension current in the previous control cycle i Lpre (k) Real-time identification and correction of model parameter errors to complete suspension current loop control;

[0012] Step S7, repeating steps S1 to S6 to achieve precise control of the high dynamic performance of the bearingless motor suspension current.

[0013] Furthermore, the signals required for the closed-loop control of the bearingless motor system in step S1 involve a rotor angle signal, a rotor speed signal, a rotor radial displacement signal, and a stator current signal; and signal sampling is completed in the first half of the control cycle.

[0014] Furthermore, the purpose of the displacement outer loop control in step S2 is to obtain the suspension current setting value, using a PID regulator; the displacement outer loop control is completed in the first half of the control cycle.

[0015] Furthermore, the purpose of the torque loop control in step S3 is to obtain a set value of the torque winding terminal voltage, using a PI regulator; the torque loop control is completed in the first half of the control cycle.

[0016] As a bearingless motor suspension current control method based on a two-stage execution mechanism of the present invention, the second sampling of the suspension current in step S4 is completed in the second half of the control cycle.

[0017] As a bearingless motor suspension current control method based on a two-stage execution mechanism of the present invention, the suspension current prediction in step S5 is completed in the second half of the control cycle.

[0018] As a bearingless motor suspension current control method based on a two-stage execution mechanism of the present invention, the suspension current loop control scheme in step S6 is designed based on the zero-beat idea, and the command voltage required at the current moment is obtained through the system model, and the inverter switching signal is obtained through the corresponding modulation link to control the bearingless motor winding voltage and thus realize closed-loop control of the suspension current.

[0019] As a bearingless motor suspension current control method based on a two-stage execution mechanism of the present invention, the real-time identification and correction of the model parameter error and the suspension current loop control in step S6 are completed in the second half of the control cycle.

[0020] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0021] 1. Current prediction can be completed without relying on any model parameters, thus compensating for the delay effect of digital control;

[0022] 2. Model parameter error identification and correction can be completed without relying on any model parameters, thus achieving compensation for model parameter errors;

[0023] 3. The two-stage algorithm execution mechanism improves the execution efficiency of the control algorithm and ensures the complete execution of the control algorithm;

[0024] 4. The algorithm is simple to implement, does not rely on any parameters, and is universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of a bearingless motor suspension current control method based on a two-stage execution mechanism of the present invention;

[0026] Figure 2 This is the current variation law within one control cycle of the pulse width modulation technology of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0028] The present invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Instead, these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0029] The present invention discloses a bearingless motor suspension current control method based on a two-stage execution mechanism. In view of the high dynamic response control requirements of the bearingless motor suspension current, combined with the high algorithm complexity characteristics of the bearingless motor, based on the deadbeat idea, the symmetry of the duty cycle within a control cycle of the pulse width modulation technology is utilized, and the current prediction and model parameter error compensation are completed by double sampling of the current within a control cycle. At the same time, the two-stage algorithm execution mechanism is used to ensure the complete execution of the control algorithm, and finally the high dynamic performance and precise control of the bearingless motor suspension current is realized. The implementation steps of the method are as follows:

[0030] Step S1: at the beginning of the first half of the control cycle, the suspension current i L (k) and other signals required for closed-loop control of the bearingless motor system;

[0031] Step S2, completing the displacement outer loop control and obtaining the suspension current setting value;

[0032] Step S3, completing the torque loop control and obtaining the torque winding terminal voltage setting value;

[0033] Step S4, at the beginning of the second half of the control cycle, the second sampling of the suspension current within a control cycle is performed. L (k+0.5);

[0034] Step S5: Combine the two suspension current sampling values ​​in one control cycle to predict the suspension current at the next moment. Lpre (k+1), the specific formula is: i Lpre (k+1)=2i L (k+0.5)-i L (k);

[0035] Step S6, sampling the actual value of the suspension current i at the initial moment of the current control cycle L (k), combined with the predicted value of the suspension current in the previous control cycle i Lpre (k) Real-time identification and correction of model parameter errors to complete suspension current loop control;

[0036] Step S7, repeating steps S1 to S6 to achieve precise control of the high dynamic performance of the bearingless motor suspension current.

[0037] Furthermore, the signals required for the closed-loop control of the bearingless motor system in step S1 include but are not limited to a rotor angle signal, a rotor speed signal, a rotor radial displacement signal, and a stator current signal.

[0038] Furthermore, the signal sampling in step S1 is completed in the first half of the control cycle.

[0039] Furthermore, the purpose of the displacement outer loop control in step S2 is to obtain a suspension current setting value, which may be achieved by, but not limited to, a PID regulator.

[0040] Furthermore, the displacement outer loop control in step S2 is completed in the first half of the control cycle.

[0041] Furthermore, the purpose of the torque loop control in step S3 is to obtain a set value of the torque winding terminal voltage, which may be achieved by, but not limited to, a PI regulator.

[0042] Furthermore, in step S3, the torque loop control is completed in the first half of the control cycle.

[0043] Furthermore, the second sampling of the suspension current in step S4 is completed in the second half of the control cycle.

[0044] Furthermore, the suspension current prediction in step S5 is completed in the second half of the control cycle.

[0045] Furthermore, the suspension current loop control scheme in step S6 is designed based on the deadbeat concept, and the command voltage required at the current moment is obtained through the system model, and the inverter switching signal is obtained through the corresponding modulation link to control the bearingless motor winding voltage and thus realize closed-loop control of the suspension current.

[0046] Furthermore, in step S6, the real-time identification and correction of the model parameter error and the suspension current loop control are completed in the second half of the control cycle.

[0047] Further, combined with Figure 1 and Figure 2 , a bearingless motor suspension current control method based on a two-stage execution mechanism is described in detail. Currently commonly used pulse width modulation technologies, such as sinusoidal pulse width modulation and space vector pulse width modulation, all use the form of "carrier intersection" to achieve duty cycle control. The carrier is mostly a centrally symmetrical triangular wave, such as Figure 2 The symmetry of the duty cycle of the power device switching signal in a control cycle can be used to predict the current to compensate for the digital control delay. By double sampling the suspension current value at the carrier start point and midpoint, the suspension current value at the carrier start point of the next control cycle is predicted in real time and sent to the current regulator as feedback to compensate for the digital control delay. Figure 2 Taking the three-phase suspension winding as an example, S A , S B , S C are the upper tube switch signals of the three-phase bridge arms A, B, and C, respectively. A is the A-phase current of the suspension winding; the A-phase suspension current i AFor example, the duty cycle of the first half of a control cycle is the same as the duty cycle of the second half of a control cycle. The resistance voltage drop is ignored, and there is no back electromotive force in the suspension winding of the bearingless motor. There is Δi A1 =Δi A2 By double sampling the current in one control cycle, the current at the beginning of the next control cycle can be predicted:

[0048] i A (k+1)=2i A (k+0.5)-i A (k) (1)

[0049] Furthermore, the current prediction scheme based on formula (1) does not need to rely on any model parameters. Compared with the traditional scheme, it eliminates the parameter dependence of the current prediction link and is easy to implement. Based on this, it is only necessary to adopt multi-sampling technology to double sample the suspension current at the midpoint of the carrier, that is, in the middle of the control cycle, to achieve model-independent suspension current prediction. At the same time, combined with the actual value of the suspension current sampled at the initial moment of the current control cycle, i L (k), combined with the predicted value of the suspension current in the previous control cycle i Lpre (k), real-time identification and correction of model parameter errors. Taking the bearingless motor suspension control scheme based on flux oriented control technology as an example, the discretized voltage vector equation of the bearingless motor is:

[0050]

[0051] Among them, T s is the control period, α=R s T s / L s , β=T s / L s , R s With L s is the equivalent resistance and equivalent inductance of the bearingless motor suspension winding, ω e is the motor electrical angular velocity. Formula (2) takes into account the digital control delay effect. The command voltage calculated by sampling the current at time k will act on the bearingless motor at time k+1.

[0052] Furthermore, based on the aforementioned suspension current double sampling current prediction technology, it can be obtained that at the time k+0.5, the deviation between the actual current vector and the estimated current vector is:

[0053]

[0054] in, and Represents the estimated value of the motor winding equivalent resistance and equivalent inductance,

[0055] Furthermore, the model parameter errors can be calculated and identified in real time:

[0056]

[0057] in, Represents the corresponding vector The conjugate value of . It is worth mentioning that since the suspension winding of the bearingless motor has no back electromotive force, there is no need to consider the permanent magnet flux parameter term in the traditional motor, which also allows the real-time model parameter error to be solved and identified. If there are additional permanent magnet flux terms in the traditional permanent magnet motor, the number of unknowns is greater than the number of valid equations, and formula (4) cannot obtain a unique solution.

[0058] Furthermore, the suspension command voltage vector considering the model parameter error identification and correction in the present invention can be expressed as:

[0059]

[0060] in, Represents the reference current vector at time k. The bearingless motor suspension current control real-time model parameter identification and correction scheme in the present invention has a simple structure and is easy to implement.

[0061] At the same time, in order to ensure that the algorithm can be fully executed within one control cycle and have the highest execution efficiency, the proposed control algorithm is divided into two sections, such as Figure 1 As shown. The first half cycle realizes the sampling of the suspension current at time k, and at the same time samples the rotor angle, radial displacement signal and other signals required for the bearingless motor control, and completes the control of the outer displacement loop of the suspension system and the control of the torque system. The second half cycle samples the suspension current at time k+0.5, and predicts the suspension current value at the initial moment of the next control cycle (carrier starting point), and completes the control of the current loop of the suspension system. If the traditional algorithm execution mechanism is adopted, if a double sampling current prediction scheme is to be adopted, it is necessary to ensure that all algorithms must be fully executed within half a cycle. The two-stage algorithm execution mechanism in the present invention cleverly splits the bearingless motor algorithm into two stages for execution. The first half cycle executes the suspension control displacement outer loop and torque control that are unrelated to the double sampling current prediction scheme, and the second half cycle executes the double sampling current prediction scheme and completes the suspension current inner loop control. There is no need to reduce the system control frequency to ensure the complete execution of the algorithm.

[0062] Further, combined with Figure 1 The present invention provides a bearingless motor suspension current control method based on a two-stage execution mechanism as follows:

[0063] First, the suspension current and other signals required for the closed-loop control of the bearingless motor system are sampled at the initial moment of the first half of the control cycle.

[0064] Then, in the first half of the control cycle, the displacement outer loop control and torque loop control are completed to obtain the suspension current and torque current setting values. The first half of the control cycle completes the control part that is not related to the suspension current. At the beginning of the second half of the control cycle, the second sampling of the suspension current in one control cycle is performed, and the two suspension current sampling values ​​in one control cycle are combined to predict the suspension current at the next moment.

[0065] Subsequently, the actual value of the suspension current sampled at the initial moment of the current control cycle is combined with the predicted value of the suspension current in the previous control cycle to identify and correct the model parameter error in real time to complete the suspension current loop control.

[0066] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0067] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A bearingless motor suspension current control method based on a two-stage execution mechanism, characterized in that: Based on the deadbeat idea, the symmetry of the duty cycle in a control cycle of the pulse width modulation technology is utilized, and the current prediction and model parameter error compensation are completed by double sampling of the current in a control cycle. At the same time, the two-stage algorithm execution mechanism is used to ensure the complete execution of the control algorithm, and finally the high dynamic performance and precise control of the suspension current of the bearingless motor is realized; the implementation steps of the method are as follows: Step S1: at the beginning of the first half of the control cycle, the suspension current i L (k) and other signals required for closed-loop control of the bearingless motor system; Step S2, completing the displacement outer loop control and obtaining the suspension current setting value; Step S3, completing the torque loop control and obtaining the torque winding terminal voltage setting value; Step S4, at the beginning of the second half of the control cycle, the second sampling of the suspension current within a control cycle is performed. L (k+0.5); Step S5: Combine the two suspension current sampling values ​​in one control cycle to predict the suspension current at the next moment. Lpre (k+1), the specific formula is: i Lpre (k+1)=2i L (k+0.5)-i L (k); Step S6, sampling the actual value of the suspension current i at the initial moment of the current control cycle L (k), combined with the predicted value of the suspension current in the previous control cycle i Lpre (k) Real-time identification and correction of model parameter errors to complete suspension current loop control; Step S7, repeating steps S1 to S6 to achieve precise control of the high dynamic performance of the bearingless motor suspension current.

2. A bearingless motor suspension current control method based on a two-stage execution mechanism according to claim 1, characterized in that: The signals required for the closed-loop control of the bearingless motor system in step S1 involve a rotor angle signal, a rotor speed signal, a rotor radial displacement signal, and a stator current signal; the sampling of the signals is completed in the first half of the control cycle.

3. The bearingless motor suspension current control method based on a two-stage execution mechanism according to claim 1 is characterized in that: In step S2, the displacement outer loop adopts a PID regulator; the displacement outer loop control is completed in the first half of the control cycle.

4. The bearingless motor suspension current control method based on a two-stage execution mechanism according to claim 1 is characterized in that: In step S3, the torque loop control adopts a PI regulator.

5. The bearingless motor suspension current control method based on a two-stage execution mechanism according to claim 1 is characterized in that: In step S3, the torque loop control is completed in the first half of the control cycle.

6. The bearingless motor suspension current control method based on a two-stage execution mechanism as described in claim 1 is characterized in that: The second sampling of the suspension current in step S4 is completed in the second half of the control cycle.

7. The bearingless motor suspension current control method based on a two-stage execution mechanism as described in claim 1 is characterized in that: The suspension current prediction in step S5 is completed in the second half of the control cycle.

8. The bearingless motor suspension current control method based on a two-stage execution mechanism as described in claim 1 is characterized in that: The suspension current loop control scheme in step S6 is designed based on the deadbeat concept, obtains the command voltage required at the current moment through the system model, and obtains the inverter switching signal through the corresponding modulation link to control the bearingless motor winding voltage and thus realize closed-loop control of the suspension current.

9. The bearingless motor suspension current control method based on a two-stage execution mechanism as described in claim 1 is characterized in that: In step S6, the real-time identification and correction of the model parameter error and the suspension current loop control are completed in the second half of the control cycle.

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