Motor and control method, device, storage medium and computer program product thereof

Abstract

The application discloses a motor control method and device, a motor, a storage medium and a computer program product. The method comprises the following steps: in the motor starting stage, a square wave control mode is adopted to drive the motor to operate; in the square wave control operation process, the back electromotive force state of the motor is detected, and the error state of the operation estimation parameter output by the position sensorless observer and the actual operation parameter of the motor is obtained; when the back electromotive force state reaches the preset reliable observation condition, and the error state reaches the preset convergence condition, the control mode of the motor is switched to a sine wave vector control mode. According to the scheme, the operation reliability of the motor in the low-speed starting stage is improved, the switching process jitter and the out-of-step failure probability are reduced, and the motor starting stability and the steady-state operation performance of the sine wave vector control are considered.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a motor control method, device, motor, storage medium, and computer program product, and particularly to a sensorless vector control method, device, motor, storage medium, and computer program product for a permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) have been widely used in many fields, including home appliances, industrial drives, and new energy equipment, due to their advantages such as high efficiency, high power density, and stable operation. Vector control (field-oriented control, FOC), as a high-performance control method for PMSMs, achieves decoupled regulation of magnetic flux current and torque current through coordinate transformation. This effectively reduces torque ripple, improves dynamic response speed, and optimizes system energy efficiency, and has become the mainstream technical solution for PMSM control in the industry.

[0003] To reduce system hardware costs, simplify motor structure, and improve operational adaptability under harsh conditions, sensorless control technology is an important development direction in the field of permanent magnet synchronous motor drives. Current mainstream sensorless vector control schemes are all based on the principle of back EMF observation: the back EMF signal of the motor is estimated in real time through algorithms, and then rotor position and speed information are extracted from the back EMF to form a sensorless closed-loop control system.

[0004] However, existing sensorless vector control technology for permanent magnet synchronous motors based on back EMF observation suffers from a core technical problem: insufficient control reliability during the low-speed start-up phase. Specifically, during the initial start-up phase, the motor speed is extremely low, and the back EMF amplitude decreases synchronously with the speed, resulting in weak signal strength and a poor signal-to-noise ratio. This directly leads to a significant decrease in the accuracy of back EMF observation, making it impossible to provide accurate rotor position and speed feedback to the control system. Consequently, this causes various faults such as start-up failure, running vibration, motor reversal, and loss of synchronization. This makes it difficult for existing solutions to simultaneously guarantee start-up reliability and steady-state performance, thus limiting the application scenarios and operational stability of sensorless vector control technology.

[0005] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a motor control method, device, motor, storage medium, and computer program product to solve the problems of sensorless vector control of permanent magnet synchronous motors based on back EMF observation in related solutions. These problems include inaccurate position and speed estimation due to weak back EMF during low-speed startup, which easily leads to startup failure, jitter, and step loss, and cannot balance startup reliability and steady-state performance. The invention aims to improve the operational reliability of the motor during low-speed startup, reduce the probability of jitter and step loss during switching, and simultaneously balance the startup stability of the motor with the steady-state operation performance of sinusoidal vector control.

[0007] This invention provides a motor control method, comprising: driving the motor to run using a square wave control mode during the motor start-up phase; detecting the back electromotive force state of the motor during the square wave control operation, and obtaining the error state between the estimated operating parameters output by the sensorless observer and the actual operating parameters of the motor; when the back electromotive force state reaches a preset reliable observation condition and the error state reaches a preset convergence condition, switching the motor control mode to a sinusoidal vector control mode.

[0008] In some implementations, the preset reliable observation condition is: the back electromotive force of the motor is greater than a first preset value, and the duration of the state where the back electromotive force is greater than the first preset value is greater than a preset duration.

[0009] In some implementations, the preset duration is dynamically set according to the current operating speed of the motor to cover at least two motor mechanical cycles.

[0010] In some implementations, the estimated operating parameter is the motor speed estimated by a sensorless observer, and the actual operating parameter is the actual motor speed under square wave control; the preset convergence condition is that the error between the estimated motor speed and the actual speed is less than a second preset value.

[0011] In some implementations, the estimated operating parameters are the rotor position estimated by a sensorless observer, and the actual operating parameters are the actual rotor position of the motor under square wave control; the preset convergence condition is that the error between the estimated rotor position and the actual rotor position is less than a third preset value. In conjunction with the above method, another aspect of the present invention provides a motor control device, comprising: a square wave drive unit configured to drive the motor to run using a square wave control mode during the motor start-up phase; a state detection unit configured to detect the back electromotive force state of the motor during square wave control operation and acquire the error state between the estimated operating parameters output by a sensorless observer and the actual operating parameters of the motor; and a mode control unit configured to switch the motor control mode to a sinusoidal vector control mode when the back electromotive force state reaches a preset reliable observation condition and the error state reaches a preset convergence condition. In conjunction with the above-described device, the present invention further provides a motor, comprising: the motor control device described above.

[0012] In conjunction with the above method, the present invention further provides a storage medium comprising a stored program, wherein, when the program is executed, the device on which the storage medium is located executes the motor control method described above.

[0013] In conjunction with the above method, the present invention further provides a computer program product comprising a computer program that, when processed and executed, implements the steps of the above-described motor control method.

[0014] The solution of this invention employs square wave control to drive the motor during the motor startup phase. During square wave operation, the back electromotive force (EMF) of the motor and the error state of the sensorless observation parameters are continuously monitored. Only when the back EMF reaches a reliable observation standard and the parameter estimation error converges to an allowable range is the control switched to sinusoidal vector control. This improves the operational reliability of the motor during low-speed startup, reduces faults such as jitter, step loss, and startup failure during switching, and simultaneously ensures both motor startup stability and the efficient, low-noise steady-state operation performance of sinusoidal vector control.

[0015] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating an embodiment of the motor control method of the present invention; Figure 2 This is a schematic diagram of the structure of an embodiment of the motor control device of the present invention; Figure 3 This is a flowchart illustrating a sensorless vector control method for a permanent magnet synchronous motor.

[0018] Referring to the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows: 101-Square wave drive unit; 102-Status detection unit; 103-Mode control unit. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] According to an embodiment of the present invention, a method for controlling a motor is provided, such as... Figure 1 The flowchart of an embodiment of the method of the present invention is shown. The motor control method may include steps S110 to S130.

[0021] In step S110, the motor is driven by square wave control during the motor start-up phase.

[0022] The startup phase refers to the stage in which the motor's speed increases from zero until it reaches a stable state. The stable state refers to the state in which the motor can run stably and carry a load, which can usually be considered as the lowest speed.

[0023] In step S120, during the square wave control operation, the back electromotive force state of the motor is detected, and the error state between the estimated operating parameters output by the sensorless observer and the actual operating parameters of the motor is obtained.

[0024] During square wave control, only two phase windings are conducting at any given moment, while the third phase winding is in a non-conducting state. The back electromotive force (EMF) signal of the non-conducting phase can be directly acquired, resulting in strong adaptability to low-speed operation. Back EMF is the induced electromotive force generated when the permanent magnet synchronous motor rotor rotates, as the magnetic field of the permanent magnet cuts the stator windings; its amplitude is positively correlated with the motor speed. The sensorless observer is a computational module in the motor control system. Based on measurable signals such as motor voltage and current, it estimates the motor's operating parameters through algorithms, eliminating the need for additional position sensors.

[0025] In step S130, when the back electromotive force state reaches the preset reliable observation condition and the error state reaches the preset convergence condition, the motor control mode is switched to sinusoidal vector control mode.

[0026] Preset reliable observation conditions are used to determine whether the back EMF signal strength is sufficient to support stable operation of the observer. Preset convergence conditions are used to determine whether the deviation between the estimated parameters output by the observer and the true parameters is within an acceptable range.

[0027] Sinusoidal vector control of permanent magnet synchronous motors relies on precise rotor position and speed feedback. In sensorless scenarios, the control system needs to calculate operating parameters by observing the back electromotive force (EMF). During the initial startup phase, the motor speed is extremely low, and the amplitude of the back EMF decreases synchronously with the speed. The signal strength is weak and easily interfered with, leading to severely inaccurate estimations by the sensorless observer, resulting in problems such as startup failure, jitter, reverse rotation, or loss of synchronization. While square wave control mode can directly acquire the back EMF of the non-conducting phase, offering better adaptability for low-speed startup, it suffers from drawbacks such as large torque ripple, high noise, and low efficiency during steady-state operation.

[0028] Therefore, this scheme adopts a segmented control method. During the startup phase, square wave control is used to ensure startup reliability. After the motor speed increases, the back EMF signal is sufficiently stable, and the observer's estimation accuracy meets the standard, it switches to sinusoidal vector control. At the same time, dual judgment conditions are set instead of a single speed threshold to avoid false switching caused by instantaneous interference, ensuring that the observer has reliable computing capabilities at the time of switching and ensuring a smooth switching process.

[0029] Specifically, during the motor startup phase, the motor control system outputs a square wave drive signal to energize the motor windings, driving the motor in square wave control mode. During square wave control operation, the motor control system continuously acquires the motor's electrical signals and monitors the motor's back electromotive force (EMF) state in real time. Simultaneously, the motor control system retrieves the estimated operating parameters output by the sensorless observer and obtains the actual operating parameters of the motor under square wave control mode, calculating the error state between the two types of parameters. The motor control system synchronously determines the back EMF state and the error state. When the back EMF state reaches a preset reliable observation condition, and the error state simultaneously reaches a preset convergence condition, the motor control system performs a control mode switching operation, switching the motor's control mode from square wave control to sinusoidal vector control. If either condition is not met, the motor control system maintains the current square wave control mode, continues operation, and continues monitoring and determining the error state.

[0030] In some implementations, the preset reliable observation condition is: the back electromotive force of the motor is greater than a first preset value, and the duration of the state where the back electromotive force is greater than the first preset value is greater than a preset duration.

[0031] During motor operation, the electrical circuit is susceptible to electromagnetic interference, load fluctuations, and other factors, which may cause momentary spikes or drops in the back EMF sampling signal. If only the amplitude of the back EMF is used as the criterion, the amplitude jump caused by momentary interference can easily trigger misjudgments, causing the control mode to switch prematurely before the observer has stabilized, leading to switching shocks, loss of synchronization, or even start-up failure. Therefore, adding a duration requirement to the amplitude threshold can effectively filter momentary interference signals, ensuring that the back EMF naturally reaches and stabilizes at a reliable level as the motor speed increases. This provides a continuous and stable input signal for the sensorless observer, ensuring that the preconditions for mode switching are true and reliable.

[0032] Specifically, during square wave control operation, the motor control system collects the instantaneous value of the motor's back electromotive force (EMF) in real time and compares the collected back EMF amplitude with a first preset value. When the back EMF amplitude does not reach the first preset value, the motor control system maintains square wave control and continues to detect the back EMF. When the back EMF amplitude is greater than the first preset value, the motor control system starts timing logic and records the cumulative duration for which the back EMF remains above the first preset value. During timing, if the back EMF amplitude is detected to fall below the first preset value, the motor control system will clear the timing data and restart amplitude detection and timing determination. When the duration of the back EMF being greater than the first preset value exceeds the preset duration, the motor control system determines that the preset reliable observation condition has been met. The first preset value can be 0.1 to 0.2 times the highest bus voltage. For example, if the highest bus voltage is 400V, then the first preset value can be selected between 40V and 80V.

[0033] In some implementations, the preset duration is dynamically set according to the current operating speed of the motor to cover at least two motor mechanical cycles.

[0034] Using a fixed preset duration cannot meet the judgment requirements across the entire speed range: when the motor is at a low speed, a single mechanical cycle is relatively long, and the fixed duration may not be sufficient to cover two complete mechanical cycles, resulting in incomplete back EMF waveforms and insufficient effective data for the sensorless observer, leading to unreliable judgment results; when the motor is at a high speed, a single mechanical cycle is relatively short, and the fixed duration will cover too many mechanical cycles, causing switching judgment lag, prolonging the running time of square wave control, and hindering the early realization of the performance advantages of sinusoidal vector control. Setting the preset duration to at least two motor mechanical cycles ensures that the control system can acquire at least two complete back EMF waveforms, fully verifying the stability of the back EMF signal and avoiding the influence of local fluctuations or interference within a single cycle on the judgment results; at the same time, combined with dynamic adjustment of the duration based on speed, both judgment reliability and switching timeliness can be considered at different speeds.

[0035] Specifically, during the operation of square wave control, the motor control system acquires the current operating speed of the motor in real time and calculates the duration corresponding to a single motor mechanical cycle based on the speed value. Using the total duration of at least two mechanical cycles as a benchmark, the motor control system dynamically calculates the preset duration corresponding to the current speed. This duration shortens synchronously as the motor speed increases and lengthens synchronously as the speed decreases. During the duration when the back electromotive force is greater than a first preset value, the motor control system uses the real-time updated preset duration as a judgment threshold. When the cumulative duration exceeds the current corresponding preset duration, the corresponding duration condition is determined to be met.

[0036] Taking a permanent magnet synchronous motor with an operating frequency of 30Hz as an example, the duration of a single mechanical cycle is about 33 milliseconds, and the total duration of at least two mechanical cycles is about 66 milliseconds. At this time, the corresponding preset duration needs to be greater than 66 milliseconds to ensure that two complete back electromotive force waveforms are collected. When the motor speed increases and the operating frequency increases to 60Hz, the duration of a single mechanical cycle is shortened to about 16.7 milliseconds, and the corresponding preset duration will be dynamically adjusted to about 33 milliseconds. There is no need to maintain the 66-millisecond judgment duration anymore, thus avoiding unnecessary switching delays.

[0037] In some implementations, the estimated operating parameter is the motor speed estimated by a sensorless observer, and the actual operating parameter is the actual motor speed under square wave control; the preset convergence condition is that the error between the estimated motor speed and the actual speed is less than a second preset value.

[0038] The smoothness of control mode switching directly depends on the accuracy and reliability of the feedback signal output by the sensorless observer at the moment of switching. Speed ​​is the core regulation parameter of the speed closed loop in the vector control of a permanent magnet synchronous motor. If the speed estimated by the observer deviates significantly from the actual speed at the moment of switching, it will cause a large deviation in the speed closed loop, leading to torque shocks, speed jitter, and in severe cases, motor step loss and switching failure. Square wave control mode can obtain a relatively accurate actual speed. Using this as a benchmark to compare with the observer's estimated speed can intuitively reflect the observer's convergence degree. Only when the error between the estimated and actual speeds is reduced to within the allowable range does it mean that the observer has entered a stable operating state. At this point, switching control modes can ensure a smooth transition of the speed closed loop and avoid switching shocks. Therefore, using a speed error less than a threshold as a convergence condition can ensure the stability of the switching process from the speed feedback dimension.

[0039] Specifically, during square wave control operation, the motor control system reads the estimated motor speed output from the sensorless observer in real time, and obtains the actual motor speed through the square wave control operation status. The motor control system calculates the difference between the estimated and actual speeds to obtain the speed error value, and compares this error value with a second preset value in real time. When the speed error is greater than or equal to the second preset value, the motor control system determines that the observer has not yet converged, maintains the square wave control mode, and continues error detection; when the speed error is less than the second preset value, the motor control system determines that the preset convergence condition has been met and can perform a control mode switching operation. The second preset value can be <0.1.

[0040] In some implementations, the estimated operating parameters are the rotor position estimated by a sensorless observer, and the actual operating parameters are the actual rotor position of the motor under square wave control; the preset convergence condition is that the error between the estimated rotor position and the actual rotor position is less than a third preset value.

[0041] The core of sinusoidal vector control is to achieve decoupling regulation of magnetic flux current and torque current through coordinate transformation. The computational basis of coordinate transformation is accurate rotor position information. If the rotor position estimated by the observer deviates too much from the actual position during control mode switching, it will lead to distortion of the coordinate transformation results, causing current decoupling failure, a sudden increase in torque pulsation, and in severe cases, motor step loss and switching failure. In square wave control mode, the actual rotor position can be obtained with high accuracy through the zero-crossing characteristic of the non-conducting back electromotive force. Using this as a benchmark against the observer's estimated position, the convergence degree of the observer's position estimation can be directly reflected. Only when the error between the estimated rotor position and the actual rotor position is reduced to within the allowable range can the observer's position output be considered to have sufficient accuracy to support the stable operation of sinusoidal vector control. Therefore, using a position error less than a threshold as a convergence condition can directly ensure the computational accuracy and operational stability of vector control after switching from the position feedback dimension.

[0042] Specifically, during square wave control operation, the motor control system reads the estimated rotor position output by the sensorless observer in real time, and obtains the actual rotor position of the motor through the square wave control operation status. The motor control system performs a difference calculation on the estimated rotor position and the actual rotor position to obtain the position error value, and compares this error value with a third preset value in real time. When the position error is greater than or equal to the third preset value, the motor control system determines that the observer has not yet converged, maintains the square wave control mode, and continues to detect errors; when the position error is less than the third preset value, the motor control system determines that the preset convergence condition has been met, and can perform a control mode switching operation.

[0043] Figure 3This is a flowchart illustrating a sensorless vector control method for a permanent magnet synchronous motor. The system first initiates square wave control to drive the motor. After startup, it continuously monitors the motor's back electromotive force (EMF) value and then enters the first judgment stage to determine if the current back EMF is greater than a threshold V1. If the back EMF does not exceed V1, the system maintains square wave control and returns to the back EMF detection step to continuously monitor the motor status. If the back EMF exceeds V1, the system initiates timing logic to accumulate and record the duration the back EMF remains above V1, then enters the second judgment stage to determine if this duration is greater than a threshold t1. If the duration does not exceed t1, the system continues to run the timing logic and accumulate the duration. If the duration exceeds t1, the system enters the third judgment stage to determine if the error between the speed estimated by the sensorless observer and the actual motor speed is less than a threshold K. If the speed error is not less than K, the system returns to maintaining square wave control and re-enters the back EMF detection loop. If the speed error is less than K, the system finally performs a control mode switch, changing the motor's drive method from square wave control to sinusoidal vector control.

[0044] The technical solution adopted in this embodiment relies on square wave control to drive the motor during the startup phase. During square wave operation, the back EMF state of the motor and the error state of parameters observed without position sensors are continuously monitored. Only when the back EMF reaches a reliable observation standard and the estimated parameter error converges synchronously to the allowable range, does the control switch to sinusoidal vector control. This control method improves the operational reliability of the motor during the low-speed startup phase, reduces faults such as jitter, step loss, and startup failure during switching, and simultaneously balances the stability of motor startup with the efficient and low-noise steady-state operation performance of sinusoidal vector control. According to an embodiment of the present invention, a motor control device corresponding to the motor control method is also provided. See also Figure 2 The schematic diagram of an embodiment of the device of the present invention shown indicates that the control device for the motor may include: a square wave drive unit 101, a state detection unit 102, and a mode control unit 103.

[0045] The square wave drive unit 101 is configured to drive the motor using square wave control during the motor start-up phase.

[0046] The startup phase refers to the stage in which the motor's speed increases from zero until it reaches a stable state. The stable state refers to the state in which the motor can run stably and carry a load, which can usually be considered as the lowest speed.

[0047] The state detection unit 102 is configured to detect the back electromotive force state of the motor during square wave control operation and to obtain the error state between the estimated operating parameters output by the sensorless observer and the actual operating parameters of the motor.

[0048] During square wave control, only two phase windings are conducting at any given moment, while the third phase winding is in a non-conducting state. The back electromotive force (EMF) signal of the non-conducting phase can be directly acquired, resulting in strong adaptability to low-speed operation. Back EMF is the induced electromotive force generated when the permanent magnet synchronous motor rotor rotates, as the magnetic field of the permanent magnet cuts the stator windings; its amplitude is positively correlated with the motor speed. The sensorless observer is a computational module in the motor control system. Based on measurable signals such as motor voltage and current, it estimates the motor's operating parameters through algorithms, eliminating the need for additional position sensors.

[0049] The mode control unit 103 is configured to switch the motor control mode to sinusoidal vector control mode when the back electromotive force state reaches a preset reliable observation condition and the error state reaches a preset convergence condition.

[0050] Preset reliable observation conditions are used to determine whether the back EMF signal strength is sufficient to support stable operation of the observer. Preset convergence conditions are used to determine whether the deviation between the estimated parameters output by the observer and the true parameters is within an acceptable range.

[0051] Sinusoidal vector control of permanent magnet synchronous motors relies on precise rotor position and speed feedback. In sensorless scenarios, the control system needs to calculate operating parameters by observing the back electromotive force (EMF). During the initial startup phase, the motor speed is extremely low, and the amplitude of the back EMF decreases synchronously with the speed. The signal strength is weak and easily interfered with, leading to severely inaccurate estimations by the sensorless observer, resulting in problems such as startup failure, jitter, reverse rotation, or loss of synchronization. While square wave control mode can directly acquire the back EMF of the non-conducting phase, offering better adaptability for low-speed startup, it suffers from drawbacks such as large torque ripple, high noise, and low efficiency during steady-state operation.

[0052] Therefore, this scheme adopts a segmented control method. During the startup phase, square wave control is used to ensure startup reliability. After the motor speed increases, the back EMF signal is sufficiently stable, and the observer's estimation accuracy meets the standard, it switches to sinusoidal vector control. At the same time, dual judgment conditions are set instead of a single speed threshold to avoid false switching caused by instantaneous interference, ensuring that the observer has reliable computing capabilities at the time of switching and ensuring a smooth switching process.

[0053] Specifically, during the motor startup phase, the motor control system outputs a square wave drive signal to energize the motor windings, driving the motor in square wave control mode. During square wave control operation, the motor control system continuously acquires the motor's electrical signals and monitors the motor's back electromotive force (EMF) state in real time. Simultaneously, the motor control system retrieves the estimated operating parameters output by the sensorless observer and obtains the actual operating parameters of the motor under square wave control mode, calculating the error state between the two types of parameters. The motor control system synchronously determines the back EMF state and the error state. When the back EMF state reaches a preset reliable observation condition, and the error state simultaneously reaches a preset convergence condition, the motor control system performs a control mode switching operation, switching the motor's control mode from square wave control to sinusoidal vector control. If either condition is not met, the motor control system maintains the current square wave control mode, continues operation, and continues monitoring and determining the error state.

[0054] In some implementations, the preset reliable observation condition is: the back electromotive force of the motor is greater than a first preset value, and the duration of the state where the back electromotive force is greater than the first preset value is greater than a preset duration.

[0055] During motor operation, the electrical circuit is susceptible to electromagnetic interference, load fluctuations, and other factors, which may cause momentary spikes or drops in the back EMF sampling signal. If only the amplitude of the back EMF is used as the criterion, the amplitude jump caused by momentary interference can easily trigger misjudgments, causing the control mode to switch prematurely before the observer has stabilized, leading to switching shocks, loss of synchronization, or even start-up failure. Therefore, adding a duration requirement to the amplitude threshold can effectively filter momentary interference signals, ensuring that the back EMF naturally reaches and stabilizes at a reliable level as the motor speed increases. This provides a continuous and stable input signal for the sensorless observer, ensuring that the preconditions for mode switching are true and reliable.

[0056] Specifically, during square wave control operation, the motor control system collects the instantaneous value of the motor's back electromotive force (EMF) in real time and compares the collected back EMF amplitude with a first preset value. When the back EMF amplitude does not reach the first preset value, the motor control system maintains square wave control and continues to detect the back EMF. When the back EMF amplitude is greater than the first preset value, the motor control system starts timing logic and records the cumulative duration for which the back EMF remains above the first preset value. During timing, if the back EMF amplitude is detected to fall below the first preset value, the motor control system will clear the timing data and restart amplitude detection and timing determination. When the duration of the back EMF being greater than the first preset value exceeds the preset duration, the motor control system determines that the preset reliable observation condition has been met. The first preset value can be 0.1 to 0.2 times the highest bus voltage. For example, if the highest bus voltage is 400V, then the first preset value can be selected between 40V and 80V.

[0057] In some implementations, the preset duration is dynamically set according to the current operating speed of the motor to cover at least two motor mechanical cycles.

[0058] Using a fixed preset duration cannot meet the judgment requirements across the entire speed range: when the motor is at a low speed, a single mechanical cycle is relatively long, and the fixed duration may not be sufficient to cover two complete mechanical cycles, resulting in incomplete back EMF waveforms and insufficient effective data for the sensorless observer, leading to unreliable judgment results; when the motor is at a high speed, a single mechanical cycle is relatively short, and the fixed duration will cover too many mechanical cycles, causing switching judgment lag, prolonging the running time of square wave control, and hindering the early realization of the performance advantages of sinusoidal vector control. Setting the preset duration to at least two motor mechanical cycles ensures that the control system can acquire at least two complete back EMF waveforms, fully verifying the stability of the back EMF signal and avoiding the influence of local fluctuations or interference within a single cycle on the judgment results; at the same time, combined with dynamic adjustment of the duration based on speed, both judgment reliability and switching timeliness can be considered at different speeds.

[0059] Specifically, during the operation of square wave control, the motor control system acquires the current operating speed of the motor in real time and calculates the duration corresponding to a single motor mechanical cycle based on the speed value. Using the total duration of at least two mechanical cycles as a benchmark, the motor control system dynamically calculates the preset duration corresponding to the current speed. This duration shortens synchronously as the motor speed increases and lengthens synchronously as the speed decreases. During the duration when the back electromotive force is greater than a first preset value, the motor control system uses the real-time updated preset duration as a judgment threshold. When the cumulative duration exceeds the current corresponding preset duration, the corresponding duration condition is determined to be met.

[0060] Taking a permanent magnet synchronous motor with an operating frequency of 30Hz as an example, the duration of a single mechanical cycle is about 33 milliseconds, and the total duration of at least two mechanical cycles is about 66 milliseconds. At this time, the corresponding preset duration needs to be greater than 66 milliseconds to ensure that two complete back electromotive force waveforms are collected. When the motor speed increases and the operating frequency increases to 60Hz, the duration of a single mechanical cycle is shortened to about 16.7 milliseconds, and the corresponding preset duration will be dynamically adjusted to about 33 milliseconds. There is no need to maintain the 66-millisecond judgment duration anymore, thus avoiding unnecessary switching delays.

[0061] In some implementations, the estimated operating parameter is the motor speed estimated by a sensorless observer, and the actual operating parameter is the actual motor speed under square wave control; the preset convergence condition is that the error between the estimated motor speed and the actual speed is less than a second preset value.

[0062] The smoothness of control mode switching directly depends on the accuracy and reliability of the feedback signal output by the sensorless observer at the moment of switching. Speed ​​is the core regulation parameter of the speed closed loop in the vector control of a permanent magnet synchronous motor. If the speed estimated by the observer deviates significantly from the actual speed at the moment of switching, it will cause a large deviation in the speed closed loop, leading to torque shocks, speed jitter, and in severe cases, motor step loss and switching failure. Square wave control mode can obtain a relatively accurate actual speed. Using this as a benchmark to compare with the observer's estimated speed can intuitively reflect the observer's convergence degree. Only when the error between the estimated and actual speeds is reduced to within the allowable range does it mean that the observer has entered a stable operating state. At this point, switching control modes can ensure a smooth transition of the speed closed loop and avoid switching shocks. Therefore, using a speed error less than a threshold as a convergence condition can ensure the stability of the switching process from the speed feedback dimension.

[0063] Specifically, during square wave control operation, the motor control system reads the estimated motor speed output from the sensorless observer in real time, and obtains the actual motor speed through the square wave control operation status. The motor control system calculates the difference between the estimated and actual speeds to obtain the speed error value, and compares this error value with a second preset value in real time. When the speed error is greater than or equal to the second preset value, the motor control system determines that the observer has not yet converged, maintains the square wave control mode, and continues error detection; when the speed error is less than the second preset value, the motor control system determines that the preset convergence condition has been met and can perform a control mode switching operation. The second preset value can be <0.1.

[0064] In some implementations, the estimated operating parameters are the rotor position estimated by a sensorless observer, and the actual operating parameters are the actual rotor position of the motor under square wave control; the preset convergence condition is that the error between the estimated rotor position and the actual rotor position is less than a third preset value.

[0065] The core of sinusoidal vector control is to achieve decoupling regulation of magnetic flux current and torque current through coordinate transformation. The computational basis of coordinate transformation is accurate rotor position information. If the rotor position estimated by the observer deviates too much from the actual position during control mode switching, it will lead to distortion of the coordinate transformation results, causing current decoupling failure, a sudden increase in torque pulsation, and in severe cases, motor step loss and switching failure. In square wave control mode, the actual rotor position can be obtained with high accuracy through the zero-crossing characteristic of the non-conducting back electromotive force. Using this as a benchmark against the observer's estimated position, the convergence degree of the observer's position estimation can be directly reflected. Only when the error between the estimated rotor position and the actual rotor position is reduced to within the allowable range can the observer's position output be considered to have sufficient accuracy to support the stable operation of sinusoidal vector control. Therefore, using a position error less than a threshold as a convergence condition can directly ensure the computational accuracy and operational stability of vector control after switching from the position feedback dimension.

[0066] Specifically, during square wave control operation, the motor control system reads the estimated rotor position output by the sensorless observer in real time, and obtains the actual rotor position of the motor through the square wave control operation status. The motor control system performs a difference calculation on the estimated rotor position and the actual rotor position to obtain the position error value, and compares this error value with a third preset value in real time. When the position error is greater than or equal to the third preset value, the motor control system determines that the observer has not yet converged, maintains the square wave control mode, and continues to detect errors; when the position error is less than the third preset value, the motor control system determines that the preset convergence condition has been met, and can perform a control mode switching operation.

[0067] Since the processing and functions implemented by the device in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned methods, any details not covered in the description of this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0068] The technical solution of this invention employs square wave control for motor startup. Throughout the square wave operation, the back electromotive force (EMF) signal of the motor is continuously acquired, and the error between the sensorless observation parameters and the actual operating parameters is compared. When the back EMF meets the observation conditions and the estimated error is within acceptable limits, the system switches to sinusoidal vector control. This control method improves the operational reliability of the motor during low-speed startup, reduces faults such as jitter, step loss, and startup failure during switching, and simultaneously balances motor startup stability with the efficient and low-noise steady-state operation performance of sinusoidal vector control. According to an embodiment of the present invention, a motor corresponding to a control device for a motor is also provided. This motor may include the control device for the motor described above.

[0069] Since the processing and functions implemented by the motor in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned device, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0070] The technical solution of this invention uses square wave control to drive the motor throughout the entire startup process. In square wave mode, the back electromotive force (EMF) index is monitored in real time, and the error between the sensorless estimated parameters and the actual operating parameters is obtained. When the back EMF reaches the reliable observation requirements and the parameter error converges to the allowable range, the motor's drive mode is switched to sinusoidal vector control. This control method improves the operational reliability of the motor during the low-speed startup phase, reduces faults such as jitter, step loss, and startup failure during switching, and simultaneously balances the stability of motor startup with the efficient and low-noise steady-state operation performance of sinusoidal vector control. According to an embodiment of the present invention, a storage medium corresponding to a motor control method is also provided, the storage medium including a stored program, wherein the program controls the device where the storage medium is located to execute the motor control method described above when it is executed.

[0071] Since the processing and functions implemented by the storage medium in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned methods, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0072] The technical solution of this invention employs square wave control during motor startup from zero speed. During the square wave operation phase, the motor's back electromotive force is continuously monitored, and the error between the sensorless observation parameters and the actual operating parameters is calculated. Once both conditions are met, the motor control mode is switched to sinusoidal vector control. This control method improves the operational reliability of the motor during low-speed startup, reduces faults such as jitter, step loss, and startup failure during switching, and simultaneously balances motor startup stability with the efficient and low-noise steady-state operation performance of sinusoidal vector control. According to an embodiment of the present invention, a computer program product corresponding to a motor control method is also provided, the computer program product comprising a computer program that, when processed and executed, implements the steps of the above-described motor control method.

[0073] Since the processing and functions implemented by the computer program product in this embodiment are basically corresponding to the embodiments, principles and examples of the aforementioned methods, any details not covered in the description of this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0074] The technical solution of this invention utilizes square wave control to drive the motor during startup. During square wave operation, the error status of the motor's back electromotive force and the unsensory observation parameters are continuously verified. When both the back electromotive force and parameter error conditions are met simultaneously, the driving mode is switched to sinusoidal vector control. This control method improves the operational reliability of the motor during low-speed startup, reduces faults such as jitter, step loss, and startup failure during switching, and simultaneously balances motor startup stability with the efficient and low-noise steady-state operation performance of sinusoidal vector control.

[0075] In summary, it is readily understood by those skilled in the art that, without conflict, the aforementioned advantageous methods can be freely combined and superimposed.

[0076] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for controlling an electric motor, characterized in that, include: During the motor startup phase, a square wave control method is used to drive the motor. During the square wave control operation, the back electromotive force state of the motor is detected, and the error state between the estimated operating parameters output by the sensorless observer and the actual operating parameters of the motor is obtained. When the back electromotive force state reaches the preset reliable observation condition and the error state reaches the preset convergence condition, the motor control mode is switched to sinusoidal vector control mode.

2. The motor control method according to claim 1, characterized in that, The preset reliable observation condition is: the back electromotive force of the motor is greater than the first preset value, and the duration of the state where the back electromotive force is greater than the first preset value is greater than the preset duration.

3. The motor control method according to claim 2, characterized in that, The preset duration is dynamically set according to the current operating speed of the motor to cover at least two motor mechanical cycles.

4. The motor control method according to claim 1, characterized in that, The estimated operating parameter is the motor speed estimated by the sensorless observer, and the actual operating parameter is the actual motor speed under square wave control; the preset convergence condition is that the error between the estimated motor speed and the actual speed is less than a second preset value.

5. The motor control method according to claim 1, characterized in that, The estimated operating parameters are the rotor positions estimated by the sensorless observer, and the actual operating parameters are the actual rotor positions of the motor under square wave control; the preset convergence condition is that the error between the estimated rotor position and the actual rotor position is less than a third preset value.

6. A control device for an electric motor, characterized in that, include: The square wave drive unit is configured to drive the motor using square wave control during the motor startup phase. The state detection unit is configured to detect the back electromotive force state of the motor during square wave control operation and to obtain the error state between the estimated operating parameters output by the sensorless observer and the actual operating parameters of the motor. The mode control unit is configured to switch the motor control mode to sinusoidal vector control mode when the back electromotive force state reaches a preset reliable observation condition and the error state reaches a preset convergence condition.

7. An electric motor, characterized in that, include: The motor control device as described in claim 6.

8. A storage medium, characterized in that, The storage medium includes a stored program, wherein, when the program is executed, the device containing the storage medium is controlled to perform the motor control method according to any one of claims 1 to 5.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the motor control method according to any one of claims 1 to 5.

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