Permanent magnet synchronous motor torque control method and system

Abstract

This invention relates to a torque control method and system for a permanent magnet synchronous motor (PMSM), belonging to the field of PMSM control. This technical solution uses a linear Hall sensor to acquire the air gap magnetic flux density signal online, and combines it with an offline-calibrated flux linkage conversion coefficient to calculate the actual electromagnetic torque in real time. This dynamically compensates for rotor flux linkage attenuation caused by temperature, effectively improving the torque control accuracy of the motor over a wide temperature range. Simultaneously, an adaptive vector filter is introduced to effectively filter out harmonic interference caused by Hall element temperature drift and installation errors, ensuring the quality of the flux linkage signal. In terms of control architecture, a flux linkage compensation torque outer loop and a torque-current mapping feedforward work in tandem. The torque outer loop PI regulation corrects the current command in real time, and the mapping table, combined with temperature, provides the optimal reference current, ensuring stable motor torque output under temperature variation conditions. Furthermore, this method establishes a relevant lookup table through offline calibration, eliminating the need for complex online parameter identification, reducing computational load, and facilitating engineering implementation.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor control technology, and in particular to a torque control method and system for a permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs), with their significant advantages of high efficiency and high power density, have been widely used in fields with high power performance requirements, such as industrial servo systems and new energy vehicles. In high-performance PMSM control systems, precise torque control highly depends on accurate rotor flux linkage parameters; the accuracy of the rotor flux linkage directly determines the precision of torque control and the stability of system operation. However, the magnetism of permanent magnets is significantly temperature-sensitive. During motor operation, stator winding heating and rotor losses lead to an increase in internal motor temperature, which in turn causes rotor flux linkage decay. If effective temperature compensation measures are not taken, torque estimation errors will inevitably occur, significantly affecting the system's control accuracy and making it difficult to meet the demands of high-performance applications.

[0003] Linear Hall sensors have been widely used in rotor position detection of permanent magnet synchronous motors due to their outstanding advantages such as low cost, fast response speed, and simple structure. However, existing control methods based on linear Hall sensors mostly only use them for coarse sensing of rotor position, which has many limitations: on the one hand, the temperature drift characteristics of the Hall element itself and deviations generated during installation can affect the accuracy of the acquired signal; on the other hand, existing methods fail to fully exploit the rotor flux linkage information contained in the Hall signal, and cannot use this information to compensate for the temperature parameters of the rotor flux linkage, making it difficult to achieve high-precision torque closed-loop control. Therefore, developing a torque control method based on linear Hall sensors that can effectively compensate for changes in rotor flux linkage temperature, and overcoming the shortcomings of existing technologies, has significant engineering application value and practical promotion significance. Summary of the Invention

[0004] The purpose of this invention is to provide a torque control method and system for permanent magnet synchronous motors to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a torque control method for a permanent magnet synchronous motor, the method comprising: Three linear Hall sensors are installed at 120° electrical angle intervals at the center of the stator slot of the permanent magnet synchronous motor, and the three-phase air gap magnetic flux density signal of the motor is acquired online through the linear Hall sensors. The three-phase air gap magnetic flux density signal is sequentially subjected to Clarke transform and adaptive vector filtering to obtain the filtered two-phase stationary α-β coordinate system air gap magnetic flux density; The filtered air gap magnetic flux density in the two-phase stationary α-β coordinate system is converted into the air gap magnetic flux density in the rotor synchronously rotating dq coordinate system by performing the Park transformation. An offline experimental calibration method was used to obtain a lookup table of temperature-related flux conversion coefficients and a torque-current mapping table. The actual output electromagnetic torque of the motor is calculated based on the flux linkage conversion coefficient lookup table and the real-time collected air gap magnetic flux density in the dq coordinate system. The feedforward reference current is obtained by querying the torque-current mapping table based on the set torque and real-time temperature. The torque error is obtained by subtracting the actual output electromagnetic torque from the set torque, and then the current correction is generated by PI regulation. The feedforward reference current is superimposed with the current correction amount to obtain the final current command. Based on the final current command, current closed-loop field-oriented control is executed to achieve torque closed-loop compensation under rotor flux temperature changes.

[0006] In some embodiments, the step of sequentially performing Clarke transform and adaptive vector filtering on the three-phase air gap magnetic flux density signal to obtain the filtered two-phase stationary α-β coordinate system air gap magnetic flux density includes: The three-phase air gap magnetic flux density signal is converted from the ABC three-phase coordinate system to the air gap magnetic flux density in the two-phase stationary α-β coordinate system by the constant amplitude Clarke transform. The constant amplitude Clarke transform formula is expressed as: ; In the formula, B a B b B c The air gap magnetic flux density in the ABC three-phase coordinate system is measured using a linear Hall sensor; B α B β The air gap magnetic flux density is given in the α-β coordinate system at two-phase stationary conditions. The air gap magnetic flux density B obtained by Clarke transform in the two-phase stationary α-β coordinate system α B β Constructed as a complex vector form B1=B α +jB β ; The complex vector B1 is input into an adaptive vector filter, and the transfer function of the adaptive vector filter is: ; In the formula, b is the filter bandwidth parameter. To track the frequency and equal to the current rotor electrical angular velocity; The optimal filter bandwidth parameter b at different temperatures was calibrated through offline frequency sweep experiments. A filter parameter lookup table b(T) indexed by temperature was established. During real-time operation, the current bandwidth parameter b was obtained by looking up the table based on the real-time temperature of the motor. The filter output is , and The filtered air gap magnetic flux density is shown in the two-phase stationary α-β coordinate system.

[0007] In some embodiments, the step of obtaining a temperature-related flux linkage lookup table includes: Obtaining the magnetic flux linkage Ψ of a permanent magnet using the back electromotive force method f The pulse voltage injection method was used to identify the dq axis inductance L of the motor offline. d L q ; According to the stator flux linkage formula , Calculate the stator flux linkage Ψ on the dq axis under different current conditions. d Ψ q ; Synchronously acquire the air gap magnetic flux density B in the dq coordinate system obtained by coordinate transformation under the corresponding operating conditions. d B q Calculate the flux linkage conversion factor: , ; The calibration process was repeated at multiple preset temperature points to establish a two-dimensional flux linkage conversion coefficient lookup table C, indexed by both current amplitude and temperature. d (i s ,T)C q (i s ,T); For operating points not marked in the two-dimensional flux linkage conversion coefficient lookup table, the corresponding flux linkage conversion coefficient C is obtained using a linear interpolation method. d C q .

[0008] In some implementations, the step of obtaining a temperature-dependent torque-current mapping table includes: At multiple preset temperature points, the current output by the motor controller is gradually increased from the minimum current to the maximum current according to a preset gradient; At each current amplitude, the current vector angle is gradually adjusted from 0° to 90° in preset steps, and the dq-axis current i corresponding to each operating point is recorded. d i q And the actual output torque of the motor; By fitting the data from all calibrated operating points using linear interpolation, a three-dimensional torque-current mapping table i is generated, indexed by both set torque and temperature. dref (T ref ,T) i qref (T ref ,T).

[0009] In some embodiments, the step of calculating the actual output electromagnetic torque of the motor based on the flux linkage transformation coefficient lookup table and the real-time acquired air gap magnetic flux density in the dq coordinate system includes: ; In the formula, T is the actual electromagnetic torque output by the motor; P is the number of pole pairs of the motor; Ψ d The stator flux linkage along the d-axis in the dq coordinate system during synchronous rotor rotation; Ψ q The stator flux linkage along the q-axis in the dq coordinate system for synchronous rotor rotation; i d i represents the d-axis stator current in the dq coordinate system under synchronous rotor rotation; q C represents the q-axis stator current in the dq coordinate system under synchronous rotor rotation. d The d-axis flux linkage conversion coefficient is obtained through an offline calibrated two-dimensional lookup table C. d (i s ,T) to obtain; C q The q-axis flux linkage conversion coefficient is obtained through an offline calibrated two-dimensional lookup table C. q (i s T) to obtain; B d B is the air gap magnetic flux density along the d-axis in the dq coordinate system under synchronous rotor rotation; q The air gap magnetic flux density is the q-axis air gap magnetic flux density in the dq coordinate system under synchronous rotor rotation.

[0010] In some embodiments, the step of superimposing the feedforward reference current with the current correction amount to obtain the final current command includes: The final d-axis current command is directly taken from the d-axis feedforward reference current output from the torque-current mapping table, i.e. ; The final q-axis current command is the sum of the q-axis feedforward reference current and the q-axis current correction amount generated by PI regulation of the torque error, i.e. ; in, , For the final current command, , For the feedforward reference current, This is the q-axis current correction amount.

[0011] In some implementations, the step of superimposing the feedforward reference current and the current correction amount to obtain the final current command, and performing current closed-loop field-oriented control based on the final current command to achieve torque closed-loop compensation under rotor flux temperature changes, employs a composite control strategy of feedforward and feedback to achieve torque closed-loop control. The torque-current mapping table provides a feedforward reference current corresponding to the optimal operating point of MTPA, which is used to ensure the steady-state torque response speed and operating efficiency of the motor. The actual output electromagnetic torque calculated based on the flux linkage conversion coefficient forms a feedback closed loop, which is used to compensate for the steady-state torque error caused by the rotor flux linkage decay due to temperature changes.

[0012] In some embodiments, the formula for the Park transformation in converting the filtered two-phase stationary α-β coordinate system air gap magnetic flux density into the air gap magnetic flux density in the rotor synchronously rotating dq coordinate system is expressed as: ; In the formula, and B is the air gap magnetic flux density in the two-phase stationary α-β coordinate system after filtering; d B is the air gap magnetic flux density along the d-axis in the dq coordinate system under synchronous rotor rotation; q θ is the air gap magnetic flux density along the q-axis in the dq coordinate system under synchronous rotor rotation; θ is the electrical angle between the rotor d-axis and the α-axis of the two-phase stationary coordinate system.

[0013] In some embodiments, the magnetic sensing surface of the linear Hall sensor faces the surface of the motor rotor, and the three linear Hall sensors respectively collect the air gap magnetic flux density signals at the three phases A, B, and C of the motor. The flux linkage conversion coefficient lookup table and torque-current mapping table were both calibrated offline on the dynamometer testing platform.

[0014] Secondly, the present invention provides a torque control system for a permanent magnet synchronous motor, the system being applied in the aforementioned torque control method for a permanent magnet synchronous motor, the system comprising: The linear Hall sensor group consists of three linear Hall sensors, which are installed at the center of the stator slot of the permanent magnet synchronous motor at 120° electrical angle intervals to collect the three-phase air gap magnetic flux density signal of the motor. Temperature sensors are installed on the stator windings or housing of the motor to collect real-time temperature signals of the motor. A current sensor array is used to collect the three-phase stator current signals of the motor. A speed sensor is used to acquire the real-time electrical angular velocity signal of the motor rotor; The motor controller has a built-in offline calibrated flux linkage conversion coefficient lookup table and torque-current mapping table. It integrates a linear Hall signal processing module, an adaptive vector filtering module, a flux linkage conversion and torque calculation module, a torque closed-loop regulation module, an MTPA feedforward lookup table module, and a current inner-loop FOC control module. The motor controller receives the air gap magnetic flux density signal, temperature signal, stator current signal, and electric angular velocity signal, and sequentially executes Clarke transformation, adaptive vector filtering, Park transformation, flux linkage conversion and torque calculation, torque closed-loop regulation, MTPA feedforward lookup table, and current inner-loop FOC control to finally generate an SVPWM modulated inverter drive signal. A three-phase inverter is used to receive the inverter drive signal and output three-phase AC power to drive the permanent magnet synchronous motor.

[0015] The beneficial effects of the technical solution provided by this invention include at least the following: This technical solution uses a linear Hall sensor to acquire the air gap magnetic flux density signal online, and combines it with the offline calibrated flux linkage conversion coefficient to calculate the actual electromagnetic torque in real time. This dynamically compensates for rotor flux linkage attenuation caused by temperature, effectively improving the torque control accuracy of the motor over a wide temperature range. Simultaneously, an adaptive vector filter is introduced to effectively filter out harmonic interference caused by Hall element temperature drift and installation errors, ensuring the quality of the flux linkage signal. In terms of control architecture, a flux linkage compensation torque outer loop and a torque-current mapping feedforward work in tandem. The torque outer loop PI regulation corrects the current command in real time, and the mapping table, combined with temperature, provides the optimal reference current, ensuring stable motor torque output under temperature variation conditions. Furthermore, this method establishes a relevant lookup table through offline calibration, eliminating the need for complex online parameter identification. It has low computational load, is easy to implement in engineering, and can be widely applied in cost-sensitive fields with high torque accuracy requirements, such as electric vehicles and industrial servos. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0017] Figure 1 The diagram shows a flowchart of a torque control method for a permanent magnet synchronous motor provided by an exemplary embodiment of the present invention.

[0018] Figure 2 The diagram shows a linear Hall sensor arrangement for a torque control method for a permanent magnet synchronous motor provided by an exemplary embodiment of the present invention.

[0019] Figure 3 An adaptive vector filter block diagram of a torque control method for a permanent magnet synchronous motor provided by an exemplary embodiment of the present invention is shown.

[0020] Figure 4 The diagram illustrates the control principle of a torque control system for a permanent magnet synchronous motor according to an exemplary embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 The diagram illustrates a flowchart of a torque control method for a permanent magnet synchronous motor according to an exemplary embodiment of the present invention. The torque control method includes the following steps: Step 101: Install three linear Hall sensors at 120° electrical angle intervals at the center of the stator slot of the permanent magnet synchronous motor, and collect the three-phase air gap magnetic flux density signal of the motor online through the linear Hall sensors.

[0024] Understandable, please refer to Figure 2 The magnetic sensing surface of the linear Hall sensor faces the surface of the motor rotor, and the three linear Hall sensors respectively collect the air gap magnetic flux density signals at the A, B and C phase positions of the motor.

[0025] In this embodiment, three linear Hall sensors are arranged at 120° electrical angle intervals at the center of the stator slots, with their magnetic sensitive surfaces facing the rotor. This arrangement minimizes interference from the stator core magnetic field and accurately captures magnetic field changes in the air gap, ensuring a stable spatial phase difference in the acquired A, B, and C phase air gap magnetic flux density signals. This arrangement creates a symmetrical spatial distribution of the three-phase signals, providing theoretically sound input for subsequent Clarke and Park coordinate transformations, avoiding distortion caused by signal phase deviations, and thus ensuring the accuracy of flux linkage conversion and torque calculation.

[0026] Step 102: Perform Clarke transform and adaptive vector filtering on the three-phase air gap magnetic flux density signal in sequence to obtain the filtered two-phase stationary α-β coordinate system air gap magnetic flux density.

[0027] In some embodiments, the steps of sequentially performing Clarke transform and adaptive vector filtering on the three-phase air gap magnetic flux density signal to obtain the filtered two-phase stationary α-β coordinate system air gap magnetic flux density include: The three-phase air gap magnetic flux density signal is converted from the ABC three-phase coordinate system to the air gap magnetic flux density in the two-phase stationary α-β coordinate system by the constant amplitude Clarke transform. The constant amplitude Clarke transform formula is expressed as: ; In the formula, B a B b B c The air gap magnetic flux density in the ABC three-phase coordinate system is measured using a linear Hall sensor; B α B β The air gap magnetic flux density is given in the α-β coordinate system at two-phase stationary conditions. To eliminate harmonic interference introduced by temperature drift and installation errors in linear Hall sensors, the air gap magnetic flux density B obtained by Clarke transformation in the two-phase stationary α-β coordinate system is... α B β Constructed as a complex vector form B1=B α +jB β ; See Figure 3 The complex vector B1 is input into the adaptive vector filter, and the transfer function of the adaptive vector filter is: ; In the formula, b is the filter bandwidth parameter. To track the frequency and equal to the current rotor electrical angular velocity, it is provided in real time by a speed sensor; b and This determines the amplitude-frequency and phase-frequency characteristics of the filter; The optimal filter bandwidth parameter b at different temperatures was calibrated through offline frequency sweep experiments. A filter parameter lookup table b(T) indexed by temperature was established. During real-time operation, the current bandwidth parameter b was obtained by looking up the table based on the real-time temperature of the motor. The filter output is , and The filtered air gap magnetic flux density is obtained in the two-phase stationary α-β coordinate system. The filtered output is used for subsequent Park transformation.

[0028] In this embodiment, the spatially symmetrical three-phase magnetic flux density signal is converted into a two-phase orthogonal form, completing the decoupling of the three-phase spatial signals and providing a suitable signal form for synchronous filtering. Furthermore, to address the asynchronous interference introduced by the inherent bias of the Hall sensor and temperature changes, a tracking filtering mechanism synchronized with the rotor speed is adopted to extract the effective magnetic flux density component synchronized with the motor's fundamental magnetic field, while suppressing clutter interference. Combined with pre-calibrated temperature-correlated filtering parameters, the filtering characteristics are dynamically adjusted according to operating conditions, avoiding the filtering failure problem of fixed parameters in a wide temperature range.

[0029] Step 103: Perform Park transformation on the filtered two-phase stationary α-β coordinate system air gap magnetic flux density to convert it into the air gap magnetic flux density in the rotor synchronously rotating dq coordinate system.

[0030] In this embodiment, the filtered α-β coordinate system magnetic flux density signal belongs to a stationary coordinate system, and its amplitude varies periodically with rotor rotation, making it unsuitable for direct use in flux linkage parameter calculation and current control. By converting it to a dq coordinate system where the rotor rotates synchronously using the Park transformation, the time-varying magnetic flux density signal is transformed into a constant DC quantity, significantly simplifying the calculation of the flux linkage conversion coefficient and avoiding control lag caused by the time-varying signal. Simultaneously, the dq coordinate system is aligned with the rotor flux linkage direction, allowing the d-axis magnetic flux density to directly reflect the rotor permanent magnet flux linkage state, and the q-axis magnetic flux density to correspond to the magnetic field component required for torque control. This provides parameter support for subsequent calculation of the actual electromagnetic torque and implementation of rotor flux linkage temperature compensation using offline calibrated flux linkage conversion coefficients.

[0031] Step 104: Using an offline experimental calibration method, obtain a lookup table of temperature-related flux conversion coefficients and a torque-current mapping table.

[0032] In one example, both the flux linkage conversion coefficient lookup table and the torque-current mapping table were calibrated offline on a dynamometer test platform.

[0033] In some embodiments, the step of obtaining the temperature-related flux linkage conversion coefficient lookup table includes: Obtaining the magnetic flux linkage Ψ of a permanent magnet using the back electromotive force method f The pulse voltage injection method was used to identify the dq axis inductance L of the motor offline. d L q ; According to the stator flux linkage formula , Calculate the stator flux linkage Ψ on the dq axis under different current conditions. d Ψ q ; Synchronously acquire the air gap magnetic flux density B in the dq coordinate system obtained by coordinate transformation under the corresponding operating conditions. d B q Calculate the flux linkage conversion factor: , ; The calibration process was repeated at multiple preset temperature points to establish a two-dimensional flux linkage conversion coefficient lookup table C, indexed by both current amplitude and temperature. d (i s ,T)C q (i s ,T); For operating points not marked in the two-dimensional flux linkage conversion coefficient lookup table, the corresponding flux linkage conversion coefficient C is obtained using a linear interpolation method. d C q .

[0034] In some embodiments, the step of obtaining the temperature-related torque-current mapping table described above includes: At multiple preset temperature points, the current output by the motor controller is gradually increased from the minimum current to the maximum current according to a preset gradient; At each current amplitude, the current vector angle is gradually adjusted from 0° to 90° in preset steps, and the dq-axis current i corresponding to each operating point is recorded. d i q And the actual output torque of the motor; By fitting the data of all calibrated operating points using linear interpolation, a torque T is generated to set the torque. ref A three-dimensional torque-current mapping table with temperature as a dual index. dref (T ref ,T) i qref (T ref ,T).

[0035] In this embodiment, the flux linkage conversion coefficient lookup table establishes a quantitative mapping relationship between the Hall-measurable air gap magnetic flux density and the stator flux linkage, which cannot be directly measured. Through a dual-index design of current amplitude and temperature, it fully covers the flux linkage variation patterns under all motor operating conditions. This not only pre-defines the temperature-induced attenuation characteristics of the permanent magnet flux linkage into the controller but also fills the gaps between discrete calibration points using a linear interpolation algorithm. The torque-current mapping table pre-calibrates the current command for the optimal operating point of the MTPA at different temperatures, providing a reliable benchmark for feedforward control.

[0036] Step 105: Calculate the actual output electromagnetic torque of the motor based on the flux linkage conversion coefficient lookup table and the real-time collected air gap magnetic flux density in the dq coordinate system.

[0037] In some embodiments, the step of calculating the actual output electromagnetic torque of the motor based on the flux linkage transformation coefficient lookup table and the real-time acquired air gap magnetic flux density in the dq coordinate system includes: ; In the formula, T is the actual electromagnetic torque output by the motor; P is the number of pole pairs of the motor; Ψ d The stator flux linkage along the d-axis in the dq coordinate system during synchronous rotor rotation; Ψ q The stator flux linkage along the q-axis in the dq coordinate system for synchronous rotor rotation; i d i represents the d-axis stator current in the dq coordinate system under synchronous rotor rotation; q C represents the q-axis stator current in the dq coordinate system under synchronous rotor rotation.d The d-axis flux linkage conversion coefficient is obtained through an offline calibrated two-dimensional lookup table C. d (i s ,T) to obtain; C q The q-axis flux linkage conversion coefficient is obtained through an offline calibrated two-dimensional lookup table C. q (i s T) to obtain; B d B is the air gap magnetic flux density along the d-axis in the dq coordinate system under synchronous rotor rotation; q The air gap magnetic flux density is the q-axis air gap magnetic flux density in the dq coordinate system under synchronous rotor rotation.

[0038] In this embodiment, unlike traditional methods that rely on offline solidified flux linkage parameters for torque estimation, this step uses the air gap magnetic flux density directly collected by the linear Hall sensor as the basis for calculation. Combined with the offline calibrated temperature-related flux linkage conversion coefficient, the attenuation characteristics of temperature on permanent magnet flux linkage are integrated into the torque calculation process in real time. The accurate actual torque value across the entire temperature range can be obtained without complex online parameter identification. The pure algebraic operation method used has a very small computational load and fully meets the real-time requirements of motor control.

[0039] Step 106, according to the set torque T ref Query the torque-current mapping table with real-time temperature to obtain the feedforward reference current.

[0040] In this embodiment of the application, by setting the torque T ref With just two parameters, namely the real-time temperature, the feedforward reference current adapted to the current operating conditions can be quickly obtained. At the same time, the mapping table incorporates the optimal operating point characteristics of MTPA at different temperatures. The reference current obtained can not only adapt to the flux decay caused by temperature changes, but also ensure that the motor always operates in the high-efficiency range, taking into account both torque accuracy and energy consumption optimization.

[0041] Step 107: Compare the actual output electromagnetic torque with the set torque T. ref The torque error is obtained by subtraction, and the current correction is generated by PI regulation.

[0042] In this embodiment of the application, the actual output electromagnetic torque and the set torque T ref The difference is essentially a comprehensive deviation caused by factors such as temperature drift, load fluctuation, and sensor error, which directly affects the accuracy of torque control. By performing proportional-integral calculations on this error through PI regulation, the instantaneous torque deviation can be converted into a correction quantity that can be directly applied to the current command, achieving a rapid response to the deviation and eliminating steady-state error, thus avoiding the accumulation of deviation.

[0043] Step 108: The feedforward reference current and the current correction amount are superimposed to obtain the final current command. Based on the final current command, the current closed-loop field-oriented control is executed to realize the torque closed-loop compensation under the change of rotor flux temperature.

[0044] In some embodiments, the step of superimposing the feedforward reference current and the current correction amount to obtain the final current command includes: The final d-axis current command is directly taken from the d-axis feedforward reference current output from the torque-current mapping table, i.e. ; The final q-axis current command is the sum of the q-axis feedforward reference current and the q-axis current correction amount generated by PI regulation of the torque error, i.e. ; in, , For the final current command, , For the feedforward reference current, This is the q-axis current correction amount.

[0045] In some embodiments, the steps described above—superimposing the feedforward reference current with the current correction to obtain the final current command, and executing current-closed-loop field-oriented control based on the final current command to achieve torque closed-loop compensation under rotor flux temperature changes—employ a composite control strategy of feedforward and feedback to achieve torque closed-loop control: the feedforward reference current provided by the torque-current mapping table corresponds to the optimal operating point of MTPA, used to ensure the steady-state torque response speed and operating efficiency of the motor; the actual output electromagnetic torque calculated based on the flux conversion coefficient constitutes the feedback closed loop, used to compensate for the torque steady-state error caused by rotor flux attenuation due to temperature changes. The two work together to both quickly respond to torque commands and suppress steady-state errors caused by parameter changes.

[0046] It is understandable that the final current command is input into the inner loop PI regulator, and the inverter drive signal is generated through Park inverse transformation and SVPWM modulation to achieve field-oriented control, thereby realizing torque closed-loop control and compensating for the impact of temperature changes on flux attenuation on torque accuracy.

[0047] In this embodiment, a differentiated current synthesis method with d-axis direct pass-through and q-axis superposition is adopted, which fully utilizes the decoupling characteristics of the dq coordinate system. That is, the d-axis current directly uses the feedforward optimal value, avoiding the interference of feedback regulation on flux stability and ensuring that the motor always operates in the MTPA high-efficiency range. The q-axis current integrates the feedforward reference and feedback correction, retaining the fast response capability of feedforward control, and eliminating torque steady-state errors caused by uncalibrated factors such as temperature drift and load fluctuation through closed-loop regulation. Finally, the synthesized current command is converted into an inverter-executable drive signal through current inner loop regulation, coordinate inverse transformation and SVPWM modulation, completing the conversion from digital control quantity to physical torque output.

[0048] Figure 4 This diagram illustrates the control principle of a permanent magnet synchronous motor torque control system according to an exemplary embodiment of the present invention. This torque control system is applied to the aforementioned permanent magnet synchronous motor torque control method. The system includes: a linear Hall sensor group consisting of three linear Hall sensors, installed at 120° electrical angle intervals at the center of the stator slot of the permanent magnet synchronous motor, for acquiring the three-phase air gap magnetic flux density signal of the motor; a temperature sensor installed on the stator winding or housing of the motor for acquiring the real-time temperature signal of the motor; a current sensor group for acquiring the three-phase stator current signal of the motor; a speed sensor for acquiring the real-time electrical angular velocity signal of the motor rotor; and a motor controller with a built-in offline calibrated flux linkage conversion system. The system integrates a lookup table and a torque-current mapping table, and internally incorporates a linear Hall signal processing module, an adaptive vector filtering module, a flux linkage conversion and torque calculation module, a torque closed-loop regulation module, an MTPA feedforward lookup table module, and a current inner-loop FOC control module. The motor controller receives the air gap magnetic flux density signal, temperature signal, stator current signal, and electric angular velocity signal, and sequentially executes Clarke transformation, adaptive vector filtering, Park transformation, flux linkage conversion and torque calculation, torque closed-loop regulation, MTPA feedforward lookup table, and current inner-loop FOC control to ultimately generate an SVPWM modulated inverter drive signal. The three-phase inverter receives the inverter drive signal and outputs three-phase AC power to drive the permanent magnet synchronous motor.

[0049] In this embodiment, a feedforward and feedback composite control architecture is adopted. Real-time torque observation and temperature adaptive compensation are achieved by directly acquiring the air gap magnetic flux density using linear Hall sensors. This solves the industry pain point of torque accuracy degradation caused by the demagnetization of permanent magnets due to temperature rise in traditional control methods. After system power-on, the controller parameters are first initialized, and the offline calibrated flux linkage conversion coefficient lookup table and torque-current mapping table are loaded. During operation, the linear Hall sensor group acquires the three-phase air gap magnetic flux density signal B in real time. a B b B cAfter undergoing constant-amplitude Clarke transform by the linear Hall signal processing module, the air gap magnetic flux density B is converted into a two-phase stationary α−β coordinate system. α B β The signal is then fed into an adaptive vector filter module to filter out harmonic interference introduced by Hall element temperature drift and installation errors, outputting a clean, filtered air gap magnetic flux density signal. This signal is then converted by Park transformation into an air gap magnetic flux density B in a dq coordinate system that rotates synchronously with the rotor. d and B q Meanwhile, a temperature sensor collects the real-time temperature of the motor, and a current sensor collects the three-phase stator current i. a i b i c The dq-axis feedback current i is obtained through coordinate transformation. d-back i q-back The flux conversion and torque calculation module obtains the flux conversion coefficient C by looking up a table based on the current current amplitude and temperature. d and C q Combined with B d and B q The real-time stator flux linkage Ψ was calculated. d Ψ q Substituting these values ​​into the electromagnetic torque formula yields the actual output torque T of the motor. The torque closed-loop regulation module then compares the actual torque with the set torque T. ref The torque error is obtained by subtraction, and the q-axis current correction is output by the PI regulator. The MTPA feedforward lookup module synchronously queries the torque-current mapping table based on the set torque and real-time temperature, and outputs the feedforward reference current i corresponding to the optimal operating point of the MTPA. dref i qref Furthermore, the system employs a differentiated current synthesis strategy of d-axis direct current and q-axis superposition: the final current command on the d-axis... Directly take the feedforward reference current i dref To ensure magnetic flux stability and operating efficiency; q-axis final current command For the feedforward reference current i qref With feedback correction amount The sum of these factors balances command response speed and steady-state control accuracy. The final current command is sent to the inner current loop FOC control module, and the inner current loop PI regulator outputs the dq-axis voltage command U. d U q Then, through the inverse Park transformation, it is converted into a two-phase stationary coordinate system voltage, combined with the DC bus voltage U. dc SVPWM modulation is completed to generate six inverter drive signals, which drive the three-phase inverter to output AC power to control the permanent magnet synchronous motor. The system executes the above process cyclically to achieve high-precision real-time closed-loop control of torque over a wide temperature range.

[0050] It should be noted that the permanent magnet synchronous motor torque control system provided in the above embodiments is only an example of the division of the above functional units. In actual applications, the above functions can be assigned to different functional units as needed, that is, the internal structure of the equipment can be divided into different functional units to complete all or part of the functions described above.

[0051] It is understood that the specific examples in this document are only intended to help those skilled in the art better understand this disclosure, and are not intended to limit the scope of the invention.

[0052] It is understood that in the various embodiments of this specification, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this disclosure.

[0053] It is understood that the various implementation methods described in this specification can be implemented individually or in combination, and this disclosure does not limit them.

[0054] Unless otherwise stated, all technical and scientific terms used in this disclosure have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this specification. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0055] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this specification.

[0056] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems and units described above can be referred to the corresponding processes in the aforementioned method implementations, and will not be repeated here.

[0057] In the several embodiments provided in this specification, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the embodiments of the systems described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between systems or units may be electrical, mechanical, or other forms.

[0058] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0059] In addition, the functional units in the various embodiments of this specification can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0060] The above description is merely a specific embodiment of this specification, but the scope of protection of this 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 this specification should be included within the scope of protection of this specification. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A torque control method for a permanent magnet synchronous motor, characterized in that, The method includes: Three linear Hall sensors are installed at 120° electrical angle intervals at the center of the stator slot of the permanent magnet synchronous motor, and the three-phase air gap magnetic flux density signal of the motor is acquired online through the linear Hall sensors. The three-phase air gap magnetic flux density signal is sequentially subjected to Clarke transform and adaptive vector filtering to obtain the filtered two-phase stationary α-β coordinate system air gap magnetic flux density; The filtered air gap magnetic flux density in the two-phase stationary α-β coordinate system is converted into the air gap magnetic flux density in the rotor synchronously rotating dq coordinate system by performing the Park transformation. An offline experimental calibration method was used to obtain a lookup table of temperature-related flux conversion coefficients and a torque-current mapping table. The actual output electromagnetic torque of the motor is calculated based on the flux linkage conversion coefficient lookup table and the real-time collected air gap magnetic flux density in the dq coordinate system. The feedforward reference current is obtained by querying the torque-current mapping table based on the set torque and real-time temperature. The torque error is obtained by subtracting the actual output electromagnetic torque from the set torque, and then the current correction is generated by PI regulation. The feedforward reference current is superimposed with the current correction amount to obtain the final current command. Based on the final current command, current closed-loop field-oriented control is executed to achieve torque closed-loop compensation under rotor flux temperature changes.

2. The torque control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The step of sequentially performing Clarke transform and adaptive vector filtering on the three-phase air gap magnetic flux density signal to obtain the filtered two-phase stationary α-β coordinate system air gap magnetic flux density includes: The three-phase air gap magnetic flux density signal is converted from the ABC three-phase coordinate system to the air gap magnetic flux density in the two-phase stationary α-β coordinate system by the constant amplitude Clarke transform. The constant amplitude Clarke transform formula is expressed as: ； In the formula, B a B b B c The air gap magnetic flux density in the ABC three-phase coordinate system is measured using a linear Hall sensor; B α B β The air gap magnetic flux density is given in the α-β coordinate system at two-phase stationary conditions. The air gap magnetic flux density B obtained by Clarke transform in the two-phase stationary α-β coordinate system α B β Constructed as a complex vector form B1=B α +jB β ; The complex vector B1 is input into an adaptive vector filter, and the transfer function of the adaptive vector filter is: ； In the formula, b is the filter bandwidth parameter. To track the frequency and equal to the current rotor electrical angular velocity; The optimal filter bandwidth parameter b at different temperatures was calibrated through offline frequency sweep experiments. A filter parameter lookup table b(T) indexed by temperature was established. During real-time operation, the current bandwidth parameter b was obtained by looking up the table based on the real-time temperature of the motor. The filter output is , and The filtered air gap magnetic flux density is shown in the two-phase stationary α-β coordinate system.

3. The torque control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The step of obtaining the temperature-related flux linkage conversion coefficient lookup table includes: Obtaining the magnetic flux linkage Ψ of a permanent magnet using the back electromotive force method f The pulse voltage injection method was used to identify the dq axis inductance L of the motor offline. d L q ; According to the stator flux linkage formula , Calculate the stator flux linkage Ψ on the dq axis under different current conditions. d Ψ q ; Synchronously acquire the air gap magnetic flux density B in the dq coordinate system obtained by coordinate transformation under the corresponding operating conditions. d B q Calculate the flux linkage conversion factor: ， ； The calibration process was repeated at multiple preset temperature points to establish a two-dimensional flux linkage conversion coefficient lookup table C, indexed by both current amplitude and temperature. d (i s ,T)C q (i s ,T); For operating points not marked in the two-dimensional flux linkage conversion coefficient lookup table, the corresponding flux linkage conversion coefficient C is obtained using a linear interpolation method. d C q .

4. The torque control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The step of obtaining the temperature-related torque-current mapping table includes: At multiple preset temperature points, the current output by the motor controller is gradually increased from the minimum current to the maximum current according to a preset gradient; At each current amplitude, the current vector angle is gradually adjusted from 0° to 90° in preset steps, and the dq-axis current i corresponding to each operating point is recorded. d i q And the actual output torque of the motor; By fitting the data from all calibrated operating points using linear interpolation, a three-dimensional torque-current mapping table i is generated, indexed by both set torque and temperature. dref (T ref ,T) i qref (T ref ,T).

5. The torque control method for a permanent magnet synchronous motor according to claim 3, characterized in that, The step of calculating the actual output electromagnetic torque of the motor based on the flux linkage conversion coefficient lookup table and the real-time acquired air gap magnetic flux density in the dq coordinate system includes: ； In the formula, T is the actual electromagnetic torque output by the motor; P is the number of pole pairs of the motor; Ψ d The stator flux linkage along the d-axis in the dq coordinate system during synchronous rotor rotation; Ψ q The stator flux linkage along the q-axis in the dq coordinate system for synchronous rotor rotation; i d i represents the d-axis stator current in the dq coordinate system under synchronous rotor rotation; q C represents the q-axis stator current in the dq coordinate system under synchronous rotor rotation. d The d-axis flux linkage conversion coefficient is obtained through an offline calibrated two-dimensional lookup table C. d (i s ,T) to obtain; C q The q-axis flux linkage conversion coefficient is obtained through an offline calibrated two-dimensional lookup table C. q (i s T) to obtain; B d B is the air gap magnetic flux density along the d-axis in the dq coordinate system under synchronous rotor rotation; q The air gap magnetic flux density is the q-axis air gap magnetic flux density in the dq coordinate system under synchronous rotor rotation.

6. The torque control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The step of superimposing the feedforward reference current and the current correction amount to obtain the final current command includes: The final d-axis current command is directly taken from the d-axis feedforward reference current output from the torque-current mapping table, i.e. ; The final q-axis current command is the sum of the q-axis feedforward reference current and the q-axis current correction amount generated by PI regulation of the torque error, i.e. ; in, , For the final current command, , For the feedforward reference current, This is the q-axis current correction amount.

7. The torque control method for a permanent magnet synchronous motor according to claim 6, characterized in that, The step of superimposing the feedforward reference current and the current correction amount to obtain the final current command, and executing current closed-loop field-oriented control based on the final current command to achieve torque closed-loop compensation under rotor flux temperature changes, employs a composite control strategy of feedforward and feedback to achieve torque closed-loop control. The torque-current mapping table provides a feedforward reference current corresponding to the optimal operating point of MTPA, which is used to ensure the steady-state torque response speed and operating efficiency of the motor. The actual output electromagnetic torque calculated based on the flux linkage conversion coefficient forms a feedback closed loop, which is used to compensate for the steady-state torque error caused by the rotor flux linkage decay due to temperature changes.

8. The torque control method for a permanent magnet synchronous motor according to claim 1, characterized in that, In the step of performing a Park transformation on the filtered two-phase stationary α-β coordinate system air gap magnetic flux density to convert it into the air gap magnetic flux density in the rotor synchronously rotating dq coordinate system, the formula for the Park transformation is expressed as: ； In the formula, and B is the air gap magnetic flux density in the two-phase stationary α-β coordinate system after filtering; d B is the air gap magnetic flux density along the d-axis in the dq coordinate system under synchronous rotor rotation; q θ is the air gap magnetic flux density along the q-axis in the dq coordinate system under synchronous rotor rotation; θ is the electrical angle between the rotor d-axis and the α-axis of the two-phase stationary coordinate system.

9. The torque control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The magnetic sensing surface of the linear Hall sensor faces the surface of the motor rotor, and the three linear Hall sensors respectively collect the air gap magnetic flux density signals at the three phases A, B and C of the motor. The flux linkage conversion coefficient lookup table and torque-current mapping table were both calibrated offline on the dynamometer testing platform.

10. A torque control system for a permanent magnet synchronous motor, characterized in that, The system is applied in the torque control method for a permanent magnet synchronous motor according to any one of claims 1 to 9, and the system includes: The linear Hall sensor group consists of three linear Hall sensors, which are installed at the center of the stator slot of the permanent magnet synchronous motor at 120° electrical angle intervals to collect the three-phase air gap magnetic flux density signal of the motor. Temperature sensors are installed on the stator windings or housing of the motor to collect real-time temperature signals of the motor. A current sensor array is used to collect the three-phase stator current signals of the motor. A speed sensor is used to acquire the real-time electrical angular velocity signal of the motor rotor; The motor controller has a built-in offline calibrated flux linkage conversion coefficient lookup table and torque-current mapping table. It integrates a linear Hall signal processing module, an adaptive vector filtering module, a flux linkage conversion and torque calculation module, a torque closed-loop regulation module, an MTPA feedforward lookup table module, and a current inner-loop FOC control module. The motor controller receives the air gap magnetic flux density signal, temperature signal, stator current signal, and electric angular velocity signal, and sequentially executes Clarke transformation, adaptive vector filtering, Park transformation, flux linkage conversion and torque calculation, torque closed-loop regulation, MTPA feedforward lookup table, and current inner-loop FOC control to finally generate an SVPWM modulated inverter drive signal. A three-phase inverter is used to receive the inverter drive signal and output three-phase AC power to drive the permanent magnet synchronous motor.

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