Torque characteristic-based asynchronous motor speed band re-throw control method and system
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING JIAOTONG UNIV
- Filing Date
- 2026-03-31
- Publication Date
- 2026-06-19
AI Technical Summary
In asynchronous motor systems without speed sensor control, after the inverter pulse is blocked, existing technology makes it difficult to quickly and accurately obtain the initial speed value, which may cause faults such as overcurrent or torque shock when the speed is restarted.
A torque-based control method is adopted. A full-order state observer model is established by injecting DC current into the asynchronous motor. The frequency characteristics of the torque error signal are calculated to obtain the initial speed, thus avoiding iterative search and dependence on the accuracy requirements of the rotor flux observer.
It achieves rapid and accurate acquisition of the initial rotor speed within 0.2 seconds, ensuring rapid and stable re-start of the asynchronous motor, avoiding the problem of voltage model observation accuracy being affected by parameters and integral drift, and improving the speed and stability of the system.
Smart Images
Figure CN122247280A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of AC motor control technology, and in particular to a control method and device for rapidly and stably achieving belt-speed re-start of asynchronous motors under sensorless control. Background Technology
[0002] Currently, vector control is widely used as the control strategy for asynchronous motors in the rail transit field. To achieve high-precision control, speed sensors are typically installed to monitor motor speed in real time. However, harsh operating environments often lead to speed sensor failures, and speed sensors also cause problems such as increased maintenance costs and reduced system reliability. Adopting sensorless control technology can avoid the problems associated with sensors, not only improving system reliability but also effectively reducing maintenance costs.
[0003] However, in practical applications of rail transit, sensorless control technology faces a challenge: when the system experiences excessive phase splitting or a fault causing the inverter pulses to be blocked, the issue of re-energizing at speed needs to be addressed. Specifically, once the inverter pulses are blocked, the asynchronous motor current drops to zero, and the motor is in an unobservable state, rendering existing speed identification methods ineffective. Forcibly re-energizing without knowing the speed may cause faults such as overcurrent or torque surges. Therefore, accurately obtaining the initial speed value before re-energizing at speed is particularly important.
[0004] The closest prior art is the applicant's earlier application, Chinese Patent Application No. CN201910068954.9, filed on January 24, 2019, entitled "Method for Obtaining the Initial Speed of a Traction Asynchronous Motor, Method and Device for Re-engaging Belt Speed," which discloses a method for obtaining the initial speed of a traction asynchronous motor, a method and device for re-engaging belt speed, and a device for re-engaging belt speed. The method for obtaining the initial speed of the traction asynchronous motor includes: injecting a direct current into the rotating traction asynchronous motor and establishing a state equation for the traction asynchronous motor after the injection of the direct current; solving the state equation to obtain the rotor flux linkage of the traction asynchronous motor; extracting the orthogonal rotor flux linkage signal from the rotor flux linkage; and calculating the initial speed of the traction asynchronous motor based on the orthogonal rotor flux linkage signal. This solution can identify the initial speed of a rail transit traction asynchronous motor under sensorless control, thus solving the problems encountered in re-engaging belt speed.
[0005] Chinese invention patent application No. 2025106404242, published on June 17, 2025, entitled "A Method and System for Belt-Speed Re-starting of a Motor Drive Device," discloses a method and system for belt-speed re-starting of a motor drive device. The method includes: S1, converting the vector control electrical parameters of a three-phase asynchronous motor to the MT coordinate system, where the M-axis component is the excitation current and the T-axis component is the torque current; constructing an adaptive flux linkage model based on the generalized slip relation and adaptive gain coefficient in the MT coordinate system, according to the voltage control model and the current control model; S2, inputting the M-axis and T-axis components into the adaptive flux linkage model to track the real-time motor rotor position; S3, adaptively switching the motor vector control mode to voltage control mode or current control mode according to the real-time motor rotor position parameters. This invention can quickly track the position of the induction motor rotor, switch to a better control mode based on the tracking result, quickly start a high-speed rotating motor, and has very small current surges, high safety, and strong parameter robustness.
[0006] Chinese invention patent application No. 202111563471X, filed on December 20, 2021, entitled "An Initial Speed Identification and Belt Speed Re-start Control Method and Device for an Asynchronous Motor," discloses and specifically discloses an initial speed identification and belt speed re-start control method and device for an asynchronous motor. The method includes: using half of the maximum rotor frequency of the motor as the initial value for the first speed search, and applying a voltage vector based on this rotor frequency value; constructing a stator voltage frequency calculation model for the speed search; plotting the stator current variation curve with rotational speed under a fixed-frequency rotating stator voltage and an extended Heyland circle of the stator current under a fixed-frequency rotating stator voltage, and constructing a criterion function based on this; determining the iteration direction of the stator voltage frequency calculation model according to the criterion function; using the new rotor frequency obtained from the iteration as the stator voltage frequency to be applied in the nth search, repeating the iterative calculation until the search calculation meets the set termination condition, outputting the motor rotor frequency, and assigning this rotor frequency to the speed observer.
[0007] In existing technologies, there are two main methods for obtaining the initial value of rotational speed: one is to give a fixed frequency as the rotor to estimate the initial speed and use an iterative search strategy to gradually approximate the true speed. However, since the method requires continuous iteration, it requires a long search time, which does not meet the speed requirement of belt-driven re-energization. The second method is to use rotor flux linkage to obtain speed information during the DC pre-excitation stage. There are two ways to obtain rotor flux linkage: current model and voltage model. The current model itself requires speed information and therefore cannot be used. The voltage model is affected by the decrease in stator voltage and the increase in stator resistance voltage drop at low speeds. The observation accuracy is greatly affected by changes in stator resistance and inverter dead zone, and the pure integration part is prone to integral drift, which may cause system instability, causing this scheme to fail at low speeds.
[0008] This invention application is filed to address the shortcomings of existing technologies. Summary of the Invention
[0009] In view of the above-mentioned shortcomings of the prior art, the present invention proposes a fast and stable asynchronous motor belt speed re-start control method and device based on torque characteristics, which can solve the problem of initial speed identification when belt speed re-start is performed without speed sensor control.
[0010] To achieve the above-mentioned objectives, the technical solution provided by this invention is as follows: A speed-restart control method for an asynchronous motor based on torque characteristics includes the following steps: Step S1: Establish a full-order observer model during the DC pre-excitation stage; Specifically, this involves injecting DC current into an asynchronous motor in a rotating state and establishing a full-order state observer model of the asynchronous motor after the DC current is injected. The full-order state observer model is specifically represented as follows:
[0011] In the formula, This represents the estimated stator current and estimated rotor flux linkage along the α and β axes at the current moment. This indicates the estimated stator current, actual stator voltage, and estimated rotor flux linkage along the α and β axes at the previous moment. This represents the sum of the estimated currents at the current moment and the previous moment. This indicates the current error at the previous moment. This represents the sum of the current errors between the current time and the previous time. For stator resistance, For rotor resistance, For stator inductance, For rotor inductance, For mutual intuition, The rotor time constant, The total leakage flux coefficient is . To estimate the rotor angular velocity, To control the cycle; Represents the coefficients of the feedback gain matrix. The auxiliary coefficient for flux linkage estimation is expressed as follows:
[0012] In the formula, To estimate the stator angular velocity, it is equal to the sum of the estimated rotor angular velocity and the slip frequency. This refers to the feedback gain amplification factor. Step S2: Solve the full-order state observer model to obtain the estimated rotor flux linkage, estimated stator current, and current error of the asynchronous motor. The current error is obtained by subtracting the estimated stator current from the actual current. Step S3: Calculate the torque error signal; The torque error signal is obtained by multiplying the current error by the estimated rotor flux linkage. Step S4: Determine if the number of zero-crossing points of the torque error signal waveform is greater than 1. If yes, proceed to step S5; otherwise, set the initial value of the estimated speed to 0 and proceed to step S7. Step S5: Extract the time corresponding to two adjacent peak points and valley points of the rotational speed error signal; Step S6: Calculate and estimate the initial value of the rotational speed using the time interval; The initial rotor speed is estimated by taking the reciprocal of the time interval. Step S7: Determine whether the estimated initial speed is less than or equal to the maximum operating speed of the asynchronous motor. If yes, proceed to step S8; otherwise, consider it noise interference and return to step S5. Step S8: The estimated initial speed value is used as the initial speed of the asynchronous motor, and the belt speed is restarted after the pre-excitation stage ends.
[0013] Preferred, In step S1, after injecting DC current into the asynchronous motor in the rotating state, vector control is adopted in the asynchronous motor in the rotating state, and the magnetic field orientation angle of the asynchronous motor using vector control is set to zero.
[0014] Preferred, The specific method of vector control is as follows: A direct current is passed through a rotating asynchronous motor. This represents the q-axis stator current command value, which is set to 0 during the pre-excitation phase. This represents the d-axis stator current command value, which is equal to the DC current during the pre-excitation phase. PI stands for Proportional-Integral Controller. , This indicates the commanded value of the dq-axis stator voltage; During the pre-excitation stage, the synchronous rotation angle is set to 0 and fixed at 0. and The command values of the stator voltages along the α and β axes are obtained after the inverse rotation transformation. and The input is fed into the modulation algorithm and then enters the asynchronous motor via an insulated gate bipolar transistor. This represents the three-phase current output by the asynchronous motor. After coordinate transformation, the actual current values along the dq, α, and β axes are obtained. The actual current value along the dq axis is... , As feedback inputs to the dual current loop, the actual current values along the α and β axes are... , Actual voltage values along the α and β axes , As input to the asynchronous motor fast re-start control method based on torque error characteristics.
[0015] Preferred, In step S1, the rotor speed variable used when solving the full-order state observer model is set to zero.
[0016] Preferred, Step S3 further includes step S31, which removes the DC component of the torque error. The error signal of the torque obtained by multiplying the current error and the estimated rotor flux linkage has a DC bias. The DC bias is suppressed by using a high-order filter, and the AC information of the torque error is retained.
[0017] Preferred, In step S6, before calculating the initial speed of the asynchronous motor based on the characteristics of the torque error signal, a low-pass filter is needed to filter out the noise in the torque error signal.
[0018] Preferred, In step S6, when calculating the initial speed of the asynchronous motor based on the torque error signal characteristics, the torque error signal characteristic used is the frequency of the torque error signal. The frequency of the torque error signal is extracted by recording the time corresponding to two adjacent peaks and valleys of the torque error signal waveform, and taking the reciprocal of twice the time interval to obtain the initial speed of the asynchronous motor. The specific calculation formula is as follows: (1) In equation (1), , These represent the times corresponding to two adjacent peak and valley points of the torque error signal, respectively. This represents the initial speed of the asynchronous motor.
[0019] The present invention also provides an asynchronous motor speed-reset control system based on torque characteristics, comprising: The full-order state observer model building unit (1) is used to inject DC current into the asynchronous motor in the rotating state and build the full-order state observer model of the asynchronous motor after the DC current is injected. The stator current, rotor flux linkage and current error calculation unit (2) is used to solve the full-order state observer model of the asynchronous motor to obtain the estimated stator current, estimated rotor flux linkage and current error; The torque error calculation unit (3) is used to multiply the current error with the estimated rotor flux linkage to obtain the torque error signal, and to perform DC suppression and noise filtering on the torque error; The initial speed calculation unit (4) is used to extract the frequency characteristics in the torque error as the initial value of the rotor speed and to determine whether the initial value is within the maximum operating range of the asynchronous motor speed.
[0020] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the methods described in the above embodiments.
[0021] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the methods described in the above embodiments.
[0022] Beneficial effects: 1. No search iteration is required, and the time required to estimate the initial value of the rotational speed is short, only 0.2s is needed to estimate the rotor speed above 2.5Hz, ensuring that the asynchronous motor can achieve rapid re-start; 2. It does not rely on the observation accuracy of the rotor flux observer. The method of estimating the initial value of the rotational speed using rotor flux requires high observation accuracy of the flux observer. However, the method described in this invention reflects the rotational speed information in the torque error, thus avoiding the problem of the voltage model flux observer being greatly affected by parameters. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 A flowchart of the fast and stable asynchronous motor speed-driven re-start control method based on torque characteristics provided by the present invention; Figure 2 The control block diagram of the fast and stable asynchronous motor speed-driven re-start control method based on torque characteristics provided by the present invention; Figure 3 and Figure 4 This is a waveform diagram of the torque error signal of an asynchronous motor at different speeds during the DC pre-excitation stage, according to an embodiment of the present invention. Figure 5 A schematic diagram of the structure of the high-speed, stable asynchronous motor belt-driven re-switching system based on torque characteristics provided by the present invention. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.
[0025] Figure 1 This is a flowchart of the fast and stable asynchronous motor speed-restart control method based on torque characteristics according to the present invention, including: A speed-restart control method for an asynchronous motor based on torque characteristics includes the following steps: Step S1: Establish a full-order observer model during the DC pre-excitation stage; Specifically, this involves injecting DC current into an asynchronous motor in a rotating state and establishing a full-order state observer model of the asynchronous motor after the DC current is injected. The full-order state observer model is specifically represented as follows:
[0026] In the formula, This represents the estimated stator current and estimated rotor flux linkage along the α and β axes at the current moment. This indicates the estimated stator current, actual stator voltage, and estimated rotor flux linkage along the α and β axes at the previous moment. This represents the sum of the estimated currents at the current moment and the previous moment. This indicates the current error at the previous moment. This represents the sum of the current errors between the current time and the previous time. For stator resistance, For rotor resistance, For stator inductance, For rotor inductance, For mutual intuition, The rotor time constant, The total leakage flux coefficient is . To estimate the rotor angular velocity, To control the cycle; Represents the coefficients of the feedback gain matrix. The auxiliary coefficient for flux linkage estimation is expressed as follows:
[0027] In the formula, To estimate the stator angular velocity, it is equal to the sum of the estimated rotor angular velocity and the slip frequency. This refers to the feedback gain amplification factor. The rotor speed variable used in solving the full-order state observer model is set to zero.
[0028] Step S2: Solve the full-order state observer model to obtain the estimated rotor flux linkage, estimated stator current, and current error of the asynchronous motor. The current error is obtained by subtracting the estimated stator current from the actual current. Step S3: Calculate the torque error signal; The torque error signal is obtained by multiplying the current error by the estimated rotor flux linkage. Step S3 further includes step S31, which removes the DC component of the torque error. The error signal of the torque obtained by multiplying the current error and the estimated rotor flux linkage has a DC bias. The DC bias is suppressed by using a high-order filter, and the AC information of the torque error is retained.
[0029] Step S4: Determine if the number of zero-crossing points of the torque error signal waveform is greater than 1. If yes, proceed to step S5; otherwise, set the initial value of the estimated speed to 0 and proceed to step S7. Step S5: Extract the time corresponding to two adjacent peak points and valley points of the rotational speed error signal; Step S6: Calculate and estimate the initial value of the rotational speed using the time interval; The initial rotor speed is estimated by taking the reciprocal of the time interval. In step S6, before calculating the initial speed of the asynchronous motor based on the characteristics of the torque error signal, a low-pass filter is needed to filter out the noise in the torque error signal.
[0030] In step S6, when calculating the initial speed of the asynchronous motor based on the torque error signal characteristics, the torque error signal characteristic used is the frequency of the torque error signal. The frequency of the torque error signal is extracted by recording the time corresponding to two adjacent peaks and valleys of the torque error signal waveform, and taking the reciprocal of twice the time interval to obtain the initial speed of the asynchronous motor. The specific calculation formula is as follows: (1) In equation (1), , These represent the times corresponding to two adjacent peak and valley points of the torque error signal, respectively. This represents the initial speed of the asynchronous motor.
[0031] Step S7: Determine whether the estimated initial speed is less than or equal to the maximum operating speed of the asynchronous motor. If yes, proceed to step S8; otherwise, consider it noise interference and return to step S5. Step S8: The estimated initial speed value is used as the initial speed of the asynchronous motor, and the belt speed is restarted after the pre-excitation stage ends.
[0032] Figure 2 This is a control block diagram of the fast and stable asynchronous motor speed-restart control method based on torque characteristics of the present invention, combined with... Figure 2 As shown, in step S1, after injecting DC current into the asynchronous motor in the rotating state, vector control is adopted in the asynchronous motor in the rotating state, and the magnetic field orientation angle of the asynchronous motor using vector control is set to zero.
[0033] The specific method of vector control is as follows: A direct current is passed through a rotating asynchronous motor. This represents the q-axis stator current command value, which is set to 0 during the pre-excitation phase. This represents the d-axis stator current command value, which is equal to the DC current during the pre-excitation phase. PI stands for Proportional-Integral Controller. , This indicates the commanded value of the dq-axis stator voltage; During the pre-excitation stage, the synchronous rotation angle is set to 0 and fixed at 0. and The command values of the stator voltages along the α and β axes are obtained after the inverse rotation transformation. and The input is fed into the modulation algorithm and then enters the asynchronous motor via an insulated gate bipolar transistor. This represents the three-phase current output by the asynchronous motor. After coordinate transformation, the actual current values along the dq, α, and β axes are obtained. The actual current value along the dq axis is... , As feedback inputs to the dual current loop, the actual current values along the α and β axes are... , Actual voltage values along the α and β axes , As input to the asynchronous motor fast re-start control method based on torque error characteristics.
[0034] Estimating stator current related variables , And estimating rotor flux linkage related variables , The calculation formula is as follows: (2) (3) In formula (1) , For estimating the stator current along the α and β axes, , The actual voltages along the α and β axes. , For estimating rotor flux linkages along the α and β axes, , For stator and rotor resistance, , For stator and rotor inductance, For mutual intuition, The rotor time constant, The total leakage flux coefficient is . To estimate the rotor angular velocity, it is set to 0 during the pre-excitation stage, i.e.: Therefore, the calculations for estimating rotor flux linkage and current can be simplified to the following formulas: (4) (5) Simplifying equation (5) yields: (6) From equation (6), we can obtain that the expression for estimating the rotor flux linkage at this time is a first-order low-pass filter with a cutoff frequency of Since the value is 1 rad / s, the rotor flux can be considered to be a DC quantity at this time.
[0035] The actual stator current and the estimated rotor flux linkage equations are as follows: (7) (8) in, and for Actual magnetic flux linkage of the shaft rotor Given the actual speed of the motor, solving equation (8) yields: (9) (10) From equations (9) and (10), we can see that the actual rotor flux linkage consists of a DC component and a gradually decaying AC component. The derivative of the actual rotor flux linkage is the gradually decaying AC component, and the frequency of the AC component is the rotor speed. The voltage equation of the motor is: (11) From equation (11), we can see that the voltage equation contains information about the flux linkage derivative. Therefore, the voltage also contains an AC component with a frequency equal to the rotor speed. According to equations (4) and (7), both the estimated current and the actual current formulas contain voltage terms. Therefore, the estimated current and the actual current are AC components with different amplitudes, the same frequency, and both equal to the rotor speed. The current error obtained by subtracting the two is: (12) From equation (12), the stator current error includes two terms: actual flux linkage and flux linkage error. Since the flux linkage error is small and can be ignored, the frequency of the stator current error should be consistent with the actual rotor flux linkage frequency, which is the rotor speed.
[0036] Compare current error with DC flow rate , Torque error component obtained by cross product The frequency is also the rotor speed.
[0037] (13)
[0038] The rotor speed can be obtained by using the method shown in equation (1).
[0039] (1)
[0040] Figure 3 and Figure 4 This is a waveform diagram of the torque error signal of an asynchronous motor at different speeds during the DC pre-excitation stage, according to an embodiment of the present invention. It can be clearly observed from the waveform that during the DC pre-excitation stage at different speeds of the asynchronous motor, the torque error signal consistently exhibits an oscillating waveform with a certain frequency, and this frequency is consistent with the actual rotor speed of the motor. Figure 3 The actual speed and torque error signal frequency of the asynchronous motor are both 20Hz. Figure 4 The actual speed and torque error signal frequency of the asynchronous motor are both 50Hz. This proves that the torque error signal contains the current speed information of the asynchronous motor. Using the method described in this invention, an accurate initial speed value can be obtained within 0.2s, thereby enabling rapid and stable re-energization of the asynchronous motor.
[0041] Figure 5 This invention is a fast and stable asynchronous motor speed-driven re-start device based on torque characteristics. The device includes a full-order state observer model establishment unit (1), a stator current, rotor flux linkage and current error calculation unit (2), a torque error calculation unit (3), and an initial speed calculation unit (4).
[0042] The full-order state observer model building unit (1) is used to inject DC current into the asynchronous motor in the rotating state and build the full-order state observer model of the asynchronous motor after the DC current is injected. The stator current, rotor flux linkage and current error calculation unit (2) is used to solve the full-order state observer model of the asynchronous motor to obtain the estimated stator current, estimated rotor flux linkage and current error; The torque error calculation unit (3) is used to multiply the current error with the estimated rotor flux linkage to obtain the torque error signal, and to perform DC suppression and noise filtering on the torque error; The initial speed calculation unit (4) is used to extract the frequency characteristics in the torque error as the initial value of the rotor speed and to determine whether the initial value is within the maximum operating range of the asynchronous motor speed.
[0043] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.
[0044] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.
[0045] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause an electronic device (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of this application.
[0046] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A torque-characteristics-based asynchronous motor band-slew-restart control method, characterized by, Includes the following steps: Step S1: Establish a full-order observer model during the DC pre-excitation stage; Specifically, this involves injecting DC current into an asynchronous motor in a rotating state and establishing a full-order state observer model of the asynchronous motor after the DC current is injected. The full-order state observer model is specifically represented as follows: In the formula, This represents the estimated stator current and estimated rotor flux linkage along the α and β axes at the current moment. This indicates the estimated stator current, actual stator voltage, and estimated rotor flux linkage along the α and β axes at the previous moment. This represents the sum of the estimated currents at the current moment and the previous moment. This indicates the current error at the previous moment. This represents the sum of the current errors between the current time and the previous time. For stator resistance, For rotor resistance, For stator inductance, For rotor inductance, For mutual intuition, The rotor time constant, The total leakage flux coefficient is . To estimate the rotor angular velocity, To control the cycle; Represents the coefficients of the feedback gain matrix. The auxiliary coefficient for flux linkage estimation is expressed as follows: In the formula, To estimate the stator angular velocity, it is equal to the sum of the estimated rotor angular velocity and the slip frequency. This refers to the feedback gain amplification factor. Step S2: Solve the full-order state observer model to obtain the estimated rotor flux linkage, estimated stator current, and current error of the asynchronous motor. The current error is obtained by subtracting the estimated stator current from the actual current. Step S3: Calculate the torque error signal; The torque error signal is obtained by multiplying the current error by the estimated rotor flux linkage. Step S4: Determine if the number of zero-crossing points of the torque error signal waveform is greater than 1. If yes, proceed to step S5; otherwise, set the initial value of the estimated speed to 0 and proceed to step S7. Step S5: Extract the time corresponding to two adjacent peak points and valley points of the rotational speed error signal; Step S6: Calculate and estimate the initial value of the rotational speed using the time interval; The initial rotor speed is estimated by taking the reciprocal of the time interval. Step S7: Determine whether the estimated initial speed is less than or equal to the maximum operating speed of the asynchronous motor. If yes, proceed to step S8; otherwise, consider it noise interference and return to step S5. Step S8: The estimated initial speed value is used as the initial speed of the asynchronous motor, and the belt speed is restarted after the pre-excitation stage ends.
2. The asynchronous motor speed-restart control method based on torque characteristics according to claim 1, characterized in that, In step S1, after injecting DC current into the asynchronous motor in the rotating state, vector control is adopted in the asynchronous motor in the rotating state, and the magnetic field orientation angle of the asynchronous motor using vector control is set to zero.
3. The asynchronous motor speed-restart control method based on torque characteristics according to claim 2, characterized in that, The specific method of vector control is as follows: A direct current is passed through a rotating asynchronous motor. This represents the q-axis stator current command value, which is set to 0 during the pre-excitation phase. This represents the d-axis stator current command value, which is equal to the DC current during the pre-excitation phase. PI stands for Proportional-Integral Controller. , This indicates the commanded value of the dq-axis stator voltage; During the pre-excitation stage, the synchronous rotation angle is set to 0 and fixed at 0. and The command values of the stator voltages along the α and β axes are obtained after the inverse rotation transformation. and The input is fed into the modulation algorithm and then enters the asynchronous motor via an insulated gate bipolar transistor. This represents the three-phase current output by the asynchronous motor. After coordinate transformation, the actual current values along the dq, α, and β axes are obtained. The actual current value along the dq axis is... , As feedback inputs to the dual current loop, the actual current values along the α and β axes are... , Actual voltage values along the α and β axes , As input to the asynchronous motor fast re-start control method based on torque error characteristics.
4. The asynchronous motor speed-restart control method based on torque characteristics according to claim 1, characterized in that, In step S1, the rotor speed variable used when solving the full-order state observer model is set to zero.
5. The asynchronous motor speed-restart control method based on torque characteristics according to claim 1, characterized in that, Step S3 further includes step S31, which removes the DC component of the torque error. The error signal of the torque obtained by multiplying the current error and the estimated rotor flux linkage has a DC bias. The DC bias is suppressed by using a high-order filter, and the AC information of the torque error is retained.
6. The asynchronous motor speed-restart control method based on torque characteristics according to claim 1, characterized in that, In step S6, before calculating the initial speed of the asynchronous motor based on the characteristics of the torque error signal, a low-pass filter is needed to filter out the noise in the torque error signal.
7. The asynchronous motor speed-restart control method based on torque characteristics according to claim 6, characterized in that, In step S6, when calculating the initial speed of the asynchronous motor based on the torque error signal characteristics, the torque error signal characteristic used is the frequency of the torque error signal. The frequency of the torque error signal is extracted by recording the time corresponding to two adjacent peaks and valleys of the torque error signal waveform, and taking the reciprocal of twice the time interval to obtain the initial speed of the asynchronous motor. The specific calculation formula is as follows: (1) In equation (1), , These represent the times corresponding to two adjacent peak and valley points of the torque error signal, respectively. This represents the initial speed of the asynchronous motor.
8. A speed-reset control system for an asynchronous motor based on torque characteristics, characterized in that, include: The full-order state observer model building unit (1) is used to inject DC current into the asynchronous motor in the rotating state and build the full-order state observer model of the asynchronous motor after the DC current is injected. The stator current, rotor flux linkage and current error calculation unit (2) is used to solve the full-order state observer model of the asynchronous motor to obtain the estimated stator current, estimated rotor flux linkage and current error; The torque error calculation unit (3) is used to multiply the current error with the estimated rotor flux linkage to obtain the torque error signal, and to perform DC suppression and noise filtering on the torque error; The initial speed calculation unit (4) is used to extract the frequency characteristics in the torque error as the initial value of the rotor speed and to determine whether the initial value is within the maximum operating range of the asynchronous motor speed.
9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method described in claims 1 to 8.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method described in claims 1 to 8.