A method for suppressing speed fluctuation of a direct-current brushless motor

Abstract

The application discloses a method for suppressing speed fluctuation of a direct-current brushless motor, and relates to the technical field of motor control. The method collects three-phase current, bus voltage, rotor position signal and actual speed signal during operation of the direct-current brushless motor, and performs synchronous separation on a speed error signal. A speed fluctuation mapping model is established according to a preset electric angle interval, and corresponding compensation coefficients are configured for different electric angle intervals. A disturbance feedforward compensation amount is generated based on a disturbance component, and a commutation suppression amount is generated based on a periodic fluctuation component. The speed loop control parameters and the current loop control parameters are adjusted according to the current speed fluctuation amplitude and the current ripple level. The disturbance feedforward compensation amount, the commutation suppression amount and the adjusted speed loop control parameters and current loop control parameters are combined into a final control amount, which is output to an inverter driver. The method can take into account load disturbance suppression and commutation ripple suppression, and improve the speed stability and long-term operation disturbance resistance under low-speed heavy-load working conditions.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, specifically to a method for suppressing speed fluctuations in a brushless DC motor. Background Technology

[0002] Brushless DC motors are widely used in industrial automation, home appliances, robot actuators, power tools, and precision drive systems due to their high efficiency, long lifespan, low maintenance, and good control precision. However, in actual operation, brushless DC motors are susceptible to factors such as commutation processes, sudden load changes, bus voltage fluctuations, parameter drift, and sampling errors, resulting in varying degrees of speed fluctuations, especially under low-speed, heavy-load, and frequent start-stop conditions. Existing technologies typically employ traditional closed-loop speed control to regulate motor speed. However, this approach primarily focuses on uniformly compensating for overall speed errors, making it difficult to distinguish between commutation pulsations and external load disturbances, and also struggling to implement differentiated control based on the fluctuation characteristics of different electrical angle ranges. Therefore, it often suffers from insufficient suppression precision, response lag, significant overshoot, and long-term operational mismatch. Thus, there is an urgent need for a brushless DC motor speed fluctuation suppression method that can decompose and identify the sources of speed fluctuations and combine interval modeling and adaptive compensation mechanisms to improve the stability and disturbance rejection performance of the motor under complex operating conditions. Summary of the Invention

[0003] The purpose of this invention is to provide a method for suppressing speed fluctuations in a brushless DC motor, in order to solve the problems mentioned in the background art, such as the difficulty in distinguishing between commutation pulsation and external load disturbance, and the difficulty in implementing differentiated control techniques for fluctuation characteristics in different electrical angle ranges.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for suppressing speed fluctuations in a brushless DC motor, the method comprising the following steps: Collect three-phase current, bus voltage, rotor position signal and actual speed signal during the operation of the brushless DC motor; A speed error signal is constructed based on the target speed and the actual speed signals; The speed error signal is synchronously separated to obtain the periodic fluctuation component corresponding to the change in electrical angle and the disturbance component caused by the change in load. A speed fluctuation mapping model is established according to the preset electrical angle range, and corresponding compensation coefficients are configured for different electrical angle ranges. The perturbation feedforward compensation is generated based on the perturbation component, and the commutation suppression is generated based on the periodic fluctuation component. Adjust the speed loop control parameters and current loop control parameters according to the current speed fluctuation amplitude and current ripple level. The disturbance feedforward compensation, commutation suppression, and adjusted speed loop and current loop control parameters are combined into the final control quantity and output to the inverter driver to suppress the speed fluctuation of the brushless DC motor.

[0005] Preferably, the synchronous separation of the speed error signal includes: Within a set sliding window, the speed error signal is smoothed and combined with the electrical angle information corresponding to the rotor position signal for bandpass filtering and synchronous extraction. This decomposes the speed error signal into a low-frequency disturbance component, a periodic fluctuation component synchronized with the electrical angle, and a high-frequency noise component. The low-frequency disturbance component is used to characterize changes in external load, the periodic fluctuation component is used to characterize torque pulsation during commutation, and the high-frequency noise component is used to eliminate sampling jitter and electromagnetic interference.

[0006] Preferably, the speed fluctuation mapping model is based on dividing one electrical cycle into multiple electrical angle intervals, and establishing a correspondence between speed fluctuation characteristic values, load level values ​​and compensation coefficient values ​​for each electrical angle interval; different compensation weights are set in the commutation start zone, commutation transition zone and commutation end zone, and a compensation weight mainly for load disturbance correction is set in the non-commutation zone, so that the control strategy corresponding to different segments matches the fluctuation source of that segment.

[0007] Preferably, the disturbance feedforward compensation amount is obtained through a disturbance observer. The disturbance observer constructs an equivalent disturbance estimation model based on the motor's moment of inertia, the actual rate of change of angular velocity, the rate of change of target speed, and the speed error signal, and outputs an equivalent disturbance torque or an equivalent disturbance current. The disturbance feedforward compensation is calculated from the equivalent disturbance torque using a preset compensation coefficient and is added to the control reference quantity before the speed loop output.

[0008] Preferably, the commutation suppression amount is obtained by harmonic analysis of the historical speed waveform within the commutation interval. The harmonic analysis includes extracting the amplitude and phase of the fundamental component and the first and second characteristic harmonic components. A compensation signal with the opposite phase to the characteristic harmonic component is generated according to the current electrical angle position, and after being corrected according to a preset amplitude ratio, it is superimposed on at least one of the q-axis current setpoint, PWM duty cycle correction amount, or commutation timing correction amount to form reverse cancellation during the commutation stage.

[0009] Preferably, the speed loop control parameters and current loop control parameters are adjusted according to the current speed fluctuation amplitude and current ripple level, including: The operating condition discrimination quantity is calculated based on the current speed fluctuation amplitude, speed error change rate, current ripple level, bus voltage fluctuation amplitude and disturbance estimate, and the speed loop proportional coefficient, integral coefficient and current loop proportional coefficient are dynamically adjusted based on the operating condition discrimination quantity. Increase the suppression gain when low-speed heavy load, sudden load change or frequent commutation conditions are detected. When steady-state operation is detected and the fluctuation amplitude decreases, the compensation intensity is reduced.

[0010] Preferably, the final control quantity is generated by the disturbance feedforward compensation quantity, the commutation suppression quantity, and the adjusted speed loop control parameters and current loop control parameters according to the weighted fusion rule, and the weighted fusion rule is at least related to the current electrical angle range, load level, and speed fluctuation amplitude. The final control quantity includes one or more of the following: speed setpoint correction quantity, q-axis current setpoint correction quantity, PWM duty cycle correction quantity, and commutation timing fine-tuning quantity.

[0011] Preferably, the method further includes an online update step: after completing one or more control cycles, the actual speed fluctuation results, load disturbance estimation results, and commutation suppression effect are fed back to the speed fluctuation mapping model, and the compensation coefficients for different electrical angle ranges are iteratively corrected; during the update process, a forgetting factor is introduced to weight the current operating condition data and historical operating condition data, so that the recent operating condition samples have higher weights.

[0012] Preferably, the rotor position signal is output from any one of a Hall sensor, an encoder, or a position-sensorless estimation module, and the actual rotational speed signal is obtained from the rotor position signal through period counting, differential calculation, or estimation by an observer; and during the acquisition process, the rotor position signal is subjected to jitter removal and time synchronization correction to reduce the impact of position sampling error on electrical angle interval division, synchronization separation, and commutation suppression amount generation.

[0013] Preferably, the method is applied to at least one of the following conditions: low-speed heavy-load operation, frequent commutation operation, bus voltage fluctuation operation, or parameter drift operation. Under the above conditions, through coordinated control of electrical angle interval compensation, disturbance feedforward compensation, commutation suppression superposition, and adaptive parameter correction, the speed fluctuation caused by external load changes, commutation torque pulsation, and power supply fluctuation is reduced, and the stability and disturbance rejection of the brushless DC motor under long-term operating conditions are improved.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention decomposes speed error into different components according to its source, corresponding to load disturbance and commutation pulsation respectively. This solves the problem that traditional methods treat all errors uniformly, which easily mixes up fluctuations from different sources, leading to inaccurate compensation direction. It improves the accuracy of fluctuation identification, makes subsequent compensation more targeted, and avoids insufficient or over-compensation caused by single closed-loop regulation. 2. This invention configures different compensation coefficients and control weights for different electrical angle intervals within one electrical cycle, solving the problem that the fluctuation mechanism of the commutation zone and the non-commutation zone is different, and that traditional fixed parameter control cannot adapt to this spatiotemporal difference. This enables the control strategy to change dynamically with the electrical angle position, enhances the ability to suppress fluctuations in the commutation start, commutation transition and commutation end stages, and improves the stability of operation. 3. This invention uses feedforward cancellation for load disturbances and harmonic reverse suppression for commutation pulsation, solving the problem that existing solutions mostly rely on single-path control and cannot simultaneously take into account external load changes and commutation torque pulsation. It forms a "dual-channel compensation" mechanism, which shortens the recovery time after load changes and reduces periodic speed fluctuations caused by commutation, thereby improving the overall speed control quality. 4. This invention dynamically corrects control parameters based on the amplitude of speed fluctuation, current ripple, and bus voltage status, solving the problem that fixed parameters are prone to mismatch under different loads, speeds, and power supply conditions, which can lead to oscillations or slow response. It enhances the adaptability of the control system to changes in operating conditions, enabling the motor to maintain good stability and robustness under low speed, heavy load, power supply fluctuation, and long-term operation conditions. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall process of the rotational speed fluctuation suppression method of the present invention; Figure 2 This is a schematic diagram of the structure for constructing the speed error signal synchronization separation and speed fluctuation mapping model of the present invention; Figure 3 The logic block diagram for generating the disturbance feedforward compensation and commutation suppression amounts of the present invention; Figure 4 This is a control block diagram for the adaptive adjustment of speed loop control parameters and current loop control parameters of the present invention; Figure 5 This is a schematic diagram of the iterative process of the online updating speed fluctuation mapping model of the present invention. Detailed Implementation

[0016] 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.

[0017] Please see Figure 1 The present invention provides an embodiment of a method for suppressing speed fluctuations in a brushless DC motor, a basic speed fluctuation suppression embodiment based on Hall signals: In this embodiment, the brushless DC motor includes a three-phase winding, an inverter driver, a Hall sensor, a bus voltage sampling unit, and a controller. The controller acquires the three-phase current, bus voltage, Hall position signal, and actual speed signal converted from the Hall position signal in real time with a control cycle of 1ms.

[0018] The controller constructs a speed error signal based on the target speed and the actual speed signals. This speed error signal is then smoothed using a sliding window of 32 control cycles. Synchronous separation is performed based on the electrical angle information corresponding to the Hall commutation signal, yielding the periodic fluctuation component corresponding to the electrical angle change and the disturbance component caused by load changes. Specifically, the speed error signal is low-pass filtered to extract the low-frequency disturbance component, and the pulsation term that occurs synchronously with the commutation node is retained as the periodic fluctuation component.

[0019] Subsequently, the controller divides one electrical cycle into six electrical angle intervals, with each interval being 60°, and presets a corresponding compensation coefficient table for each electrical angle interval. The controller inputs the disturbance component into the disturbance observer, constructs an equivalent disturbance estimation model based on the motor's moment of inertia J, the actual rate of change of angular velocity dω / dt, and the target rate of change of speed, obtains the equivalent disturbance torque Teq, and then calculates the disturbance feedforward compensation amount If according to the compensation coefficient. At the same time, the controller performs harmonic analysis on the historical speed waveform within the commutation interval, obtains the fundamental component and the second harmonic component, and generates a commutation suppression amount Ic with opposite phase.

[0020] When the detected speed fluctuation amplitude exceeds a preset threshold, the controller increases the proportional and integral coefficients of the speed loop; when the current ripple decreases, the controller reduces the compensation gain to avoid overshoot. The final control quantity is generated by weighted fusion of If, Ic, and the adjusted speed loop and current loop parameters, and output to the inverter driver. This embodiment is suitable for drive scenarios with simple structures and high cost, and can significantly improve speed fluctuations during low-speed operation.

[0021] Please see Figure 2 The present invention provides an embodiment of a method for suppressing speed fluctuations in a brushless DC motor, based on an embodiment of high-precision position feedback from an encoder: In this embodiment, the motor is equipped with an incremental encoder, and the controller executes a fluctuation suppression algorithm with a control cycle of 500μs. The pulse signal output by the encoder is differentially calculated to obtain the actual speed signal, and the encoder signal is subjected to jitter removal and time synchronization correction to reduce the impact of position jitter on the division of electrical angle intervals.

[0022] The controller first generates a speed error signal based on the target speed and the actual speed signals. Then, within each control cycle, it performs a short-time Fourier analysis on the speed error signal to identify characteristic frequency points in its spectrum that are synchronized with the electrical angle. Spectral lines with frequencies consistent with the commutation frequency are defined as periodic fluctuation components, and the low-frequency energy concentration portion is defined as disturbance components. Compared to using only time-domain filtering, this embodiment can more accurately distinguish between commutation pulsations and external load disturbances.

[0023] The controller divides one electrical cycle into twelve 30° electrical angle intervals and sets different compensation weights for the commutation start, commutation middle, and commutation end regions. For the commutation start region, commutation suppression is prioritized; for the commutation middle region, fundamental frequency reverse compensation is prioritized; and for the commutation end region, the q-axis current setpoint is corrected first. The disturbance feedforward compensation is updated in real time by the observer based on the rate of change of the velocity error signal.

[0024] During steady-state operation, the controller employs a small integral coefficient to avoid error accumulation. In the event of sudden load changes, the controller rapidly increases the integral action based on the disturbance estimate and simultaneously adds feedforward compensation. After the final control output, the peak speed fluctuation is significantly compressed, making it suitable for precision actuators requiring high speed stability.

[0025] Please see Figure 3 The present invention provides an embodiment of a method for suppressing speed fluctuations in a brushless DC motor, specifically an enhanced suppression embodiment for low-speed, heavy-load operating conditions. In this embodiment, the brushless DC motor operates under low-speed, heavy-load conditions for extended periods, such as when the speed is less than 20% of the rated speed and the output load is close to the rated load. In this situation, torque ripple is more easily transmitted to the speed range; therefore, the controller incorporates a dedicated low-speed compensation strategy into its basic control structure.

[0026] The controller first acquires three-phase current, bus voltage, rotor position signal, and actual speed signal, and performs sliding window integration processing on the speed error signal for 40 control cycles to improve the signal-to-noise ratio under low-speed conditions. Subsequently, the controller estimates the equivalent disturbance torque under low-speed heavy load using a disturbance observer and converts it into a disturbance feedforward compensation amount. Compared to normal operating conditions, the feedforward compensation amount in this embodiment has a higher coefficient and a faster response speed.

[0027] Meanwhile, the controller establishes a dedicated speed fluctuation mapping model for the commutation interval. This model does not use a uniform compensation weight, but instead sets different compensation parameters for the 20° before, 20° during, and 20° after commutation to adapt to the characteristics of slow commutation current build-up and delayed torque recovery at low speeds. For continuous speed dips caused by low-speed heavy loads, the controller adds an additional correction to the q-axis current setpoint to maintain continuous output torque during commutation.

[0028] Furthermore, when the speed fluctuation amplitude is detected to be higher than the preset threshold for three consecutive control cycles, the controller automatically increases the speed loop proportional coefficient and the current loop proportional coefficient; when the fluctuation amplitude returns to below the threshold, the gain is gradually reduced to avoid control oscillation. This embodiment can significantly improve crawling instability, jitter, and speed fluctuation under low-speed heavy-load conditions.

[0029] Please see Figure 4 The present invention provides an embodiment of a method for suppressing speed fluctuations in a brushless DC motor, specifically an adaptive compensation embodiment for bus voltage fluctuation conditions. In this embodiment, the bus voltage of the motor drive power supply experiences periodic fluctuations or transient drops. For example, in a scenario where multiple loads share a power supply, the bus voltage may change due to the startup of other loads. To suppress speed fluctuations caused by power supply fluctuations, the controller introduces a bus voltage correction step into the original control algorithm.

[0030] The controller samples the bus voltage in real time and uses the bus voltage fluctuation amplitude as one of the operating condition discrimination parameters. When the bus voltage deviates from the rated value, the controller first corrects the reference current output by the speed loop, and then calculates the duty cycle compensation term based on the voltage deviation. At the same time, the speed error signal is still separated into periodic fluctuation components and disturbance components according to the synchronous separation method. The disturbance component not only reflects the change in mechanical load, but also comprehensively reflects the decrease in effective torque on the power supply side.

[0031] In this embodiment, the speed fluctuation mapping model is divided into three levels: "normal voltage region, slight undervoltage region, and significant undervoltage region," with different compensation coefficients set for each level. When the bus voltage enters the significant undervoltage region, the controller prioritizes increasing the weight of the feedforward compensation while reducing the proportion of excessively high-frequency components in the commutation suppression to prevent additional oscillations caused by insufficient drive margin. If the bus voltage stabilizes, it gradually returns to the standard parameter table.

[0032] This embodiment is particularly suitable for battery-powered devices, vehicle auxiliary devices, and power supply parallel scenarios, and can effectively reduce speed collapse, slow recovery, and speed pulsation caused by power supply fluctuations.

[0033] Please see Figure 5 The present invention provides an embodiment of a method for suppressing speed fluctuations in a brushless DC motor, specifically an embodiment for harmonic-oriented suppression under frequent commutation conditions. In this embodiment, the motor operates under conditions of frequent starts and stops, frequent acceleration and deceleration, or high commutation frequency. In this case, speed fluctuations mainly arise from insufficient continuity of electromagnetic torque during commutation. Therefore, this embodiment focuses on enhancing the accuracy of commutation suppression generation.

[0034] The controller performs fluctuation analysis with a short control cycle. First, it performs harmonic decomposition on the historical speed waveform within the commutation interval, extracting the fundamental, second, and third harmonic components, and recording the amplitude and phase of each harmonic component in different electrical angle intervals. Subsequently, the controller generates a compensation signal with the opposite phase to the characteristic harmonic component based on the current electrical angle position, and then trims the amplitude of the compensation signal to ensure that it does not exceed the current safety limit.

[0035] In this embodiment, the commutation suppression amount is not directly and fixedly applied to a single control node, but is dynamically selected from the q-axis current setpoint correction amount, PWM duty cycle correction amount, and commutation timing fine-tuning amount according to the current operating conditions. If the motor is in the low-speed commutation stage, the q-axis current setpoint correction amount is used first; if the motor is in the medium-to-high-speed commutation stage, the PWM duty cycle correction amount is used first; if the commutation boundary error is large, the commutation timing fine-tuning amount is used.

[0036] To enhance adaptability, the controller feeds back the commutation effect to the speed fluctuation mapping model after completing several commutation cycles, updating the weight parameters of each characteristic harmonic. This embodiment can reduce torque surges during commutation and improve the smoothness of acceleration and deceleration, making it particularly suitable for servo drives and fast-response loads.

[0037] Please see Figure 5 The present invention provides an embodiment of a method for suppressing speed fluctuations in a brushless DC motor, with a long-term stable operation embodiment featuring an online learning and update mechanism: In this embodiment, in addition to performing the aforementioned synchronization separation, disturbance feedforward compensation, and commutation suppression, the controller also introduces an online update mechanism to adapt to parameter drift, temperature rise changes, and mechanical wear that may occur after the motor has been running for a long time.

[0038] The controller archives operating data at fixed intervals, including actual speed fluctuation results, load disturbance estimation results, commutation suppression effect, bus voltage fluctuation amplitude, and current ripple level. Whenever an update window is accumulated, the controller inputs the current sample and historical samples into the speed fluctuation mapping model, and uses a forgetting factor to weight the samples, with recent operating condition samples having a higher weight than historical operating condition samples.

[0039] During the update process, the controller focuses on correcting the compensation coefficients for different electrical angle ranges. If the periodic fluctuation component in a certain electrical angle range continues to increase, the commutation suppression weight for that range is increased; if the disturbance component is significantly enhanced, the disturbance feedforward compensation coefficient is increased; if the current ripple is consistently large, the proportional and integral coefficients of the current loop are reduced or reset. In this way, the controller can maintain good speed stability without recalibrating the overall machine parameters.

[0040] This embodiment is applicable to industrial equipment, fan and pump equipment, and automated production line actuators that operate continuously for long periods of time, and can significantly improve control consistency and resistance to parameter drift throughout the system's life cycle.

[0041] The "synchronous separation of speed error signals," "establishment of speed fluctuation mapping model," "generation of disturbance feedforward compensation," "generation of commutation suppression," and "adaptive adjustment of speed loop control parameters and current loop control parameters" in this invention are not abstract functional descriptions, but correspond to specific executable control processes. Specifically, the synchronous separation of speed error signals is based on the error signal formed by the actual speed signal and the target speed, combined with the electrical angle information determined by the rotor position signal. This error signal is then smoothed using a sliding window, bandpass filtered, and synchronously extracted to distinguish between low-frequency disturbance components and periodic fluctuation components. Speed ​​fluctuation mapping... The model divides an electrical cycle into multiple electrical angle intervals and presets different compensation coefficients in each interval to adapt to the different fluctuation characteristics of the commutation start region, commutation transition region, commutation end region, and non-commutation region. The disturbance feedforward compensation is obtained by combining the disturbance observer with the motor's moment of inertia, actual angular velocity change rate, and speed error signal to perform equivalent disturbance estimation. The commutation suppression is obtained by performing harmonic analysis on the historical speed waveform within the commutation interval and generating a compensation signal with opposite phase. The adaptive adjustment dynamically corrects the speed loop and current loop control parameters based on the current speed fluctuation amplitude, current ripple level, bus voltage fluctuation amplitude, and disturbance estimate. Working principle: The system collects three-phase current, bus voltage, rotor position signal, and actual speed signal in real time during motor operation, and constructs a speed error signal based on the difference between the target speed and the actual speed. Subsequently, the controller combines the electrical angle information corresponding to the rotor position signal to perform synchronous separation processing on the speed error signal, distinguishing between the low-frequency disturbance component caused by load changes and the periodic fluctuation component caused by the commutation process, thereby avoiding mixing fluctuations from different sources.

[0042] Based on this, the present invention establishes a speed fluctuation mapping model according to a preset electrical angle range, and configures the fluctuation characteristics, compensation coefficients, and control weights at different positions within one electrical cycle accordingly, so that different compensation strategies are adopted for the commutation start region, commutation transition region, commutation end region, and non-commutation region. For disturbance components, the controller generates disturbance feedforward compensation amount through a disturbance observer; for periodic fluctuation components, the controller performs harmonic analysis on the historical speed waveform of the commutation range to generate a commutation suppression amount with opposite phase, thereby corresponding to the two main sources of fluctuation: load disturbance and commutation pulsation.

[0043] Finally, the controller adaptively adjusts the speed loop control parameters and current loop control parameters based on the current speed fluctuation amplitude, current ripple level, and bus voltage fluctuation. It then synthesizes the disturbance feedforward compensation, commutation suppression, and adjusted control parameters into a final control output to the inverter driver. Through a coordinated control chain of "synchronous separation—interval modeling—feedforward compensation—commutation cancellation—adaptive parameter tuning," continuous suppression of speed fluctuations in the brushless DC motor is achieved, enabling the motor to maintain a more stable operating state under conditions such as low speed, heavy load, frequent commutation, and power supply fluctuations.

[0044] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method of suppressing speed fluctuation of a direct current brushless motor, characterized by: The method includes the following steps: Collect three-phase current, bus voltage, rotor position signal and actual speed signal during the operation of the brushless DC motor; A speed error signal is constructed based on the target speed and the actual speed signals; The speed error signal is synchronously separated to obtain the periodic fluctuation component corresponding to the change in electrical angle and the disturbance component caused by the change in load. A speed fluctuation mapping model is established according to the preset electrical angle range, and corresponding compensation coefficients are configured for different electrical angle ranges. The perturbation feedforward compensation is generated based on the perturbation component, and the commutation suppression is generated based on the periodic fluctuation component. Adjust the speed loop control parameters and current loop control parameters according to the current speed fluctuation amplitude and current ripple level; The disturbance feedforward compensation, commutation suppression, and adjusted speed loop and current loop control parameters are combined into the final control quantity and output to the inverter driver to suppress the speed fluctuation of the brushless DC motor.

2. The method of claim 1, wherein: The synchronous separation of the speed error signal includes: Within a set sliding window, the speed error signal is smoothed and combined with the electrical angle information corresponding to the rotor position signal for bandpass filtering and synchronous extraction. This decomposes the speed error signal into a low-frequency disturbance component, a periodic fluctuation component synchronized with the electrical angle, and a high-frequency noise component. The low-frequency disturbance component is used to characterize changes in external load, the periodic fluctuation component is used to characterize torque pulsation during commutation, and the high-frequency noise component is used to eliminate sampling jitter and electromagnetic interference.

3. The method of claim 1, wherein the method comprises: The speed fluctuation mapping model is based on an electrical cycle divided into multiple electrical angle intervals, and establishes a correspondence between speed fluctuation characteristic values, load level values ​​and compensation coefficient values ​​for each electrical angle interval. Different compensation weights are set in the commutation start zone, commutation transition zone and commutation end zone, and a compensation weight mainly based on load disturbance correction is set in the non-commutation zone, so that the control strategy corresponding to different segments matches the fluctuation source of that segment.

4. The method of claim 1, wherein the method comprises: The disturbance feedforward compensation amount is obtained through a disturbance observer. The disturbance observer constructs an equivalent disturbance estimation model based on the motor's moment of inertia, the actual rate of change of angular velocity, the rate of change of target speed, and the speed error signal, and outputs an equivalent disturbance torque or an equivalent disturbance current. The disturbance feedforward compensation is calculated from the equivalent disturbance torque using a preset compensation coefficient and is added to the control reference quantity before the speed loop output.

5. The method of claim 1, wherein the method comprises: The commutation suppression amount is obtained by harmonic analysis of the historical speed waveform within the commutation interval. The harmonic analysis includes extracting the amplitude and phase of the fundamental component and the first and second characteristic harmonic components. A compensation signal with the opposite phase to the characteristic harmonic component is generated according to the current electrical angle position, and after being corrected according to a preset amplitude ratio, it is superimposed on at least one of the q-axis current setpoint, PWM duty cycle correction amount, or commutation timing correction amount to form reverse cancellation during the commutation stage.

6. The method of claim 1, wherein: Adjust the speed loop control parameters and current loop control parameters according to the current speed fluctuation amplitude and current ripple level, including: The operating condition discrimination quantity is calculated based on the current speed fluctuation amplitude, speed error change rate, current ripple level, bus voltage fluctuation amplitude and disturbance estimate, and the speed loop proportional coefficient, integral coefficient and current loop proportional coefficient are dynamically adjusted based on the operating condition discrimination quantity. Increase the suppression gain when low-speed heavy load, sudden load change or frequent commutation conditions are detected. When steady-state operation is detected and the fluctuation amplitude decreases, the compensation intensity is reduced.

7. The method of claim 1, wherein the method comprises: The final control quantity is generated by the disturbance feedforward compensation quantity, the commutation suppression quantity, and the adjusted speed loop control parameters and current loop control parameters according to the weighted fusion rule, and the weighted fusion rule is at least related to the current electrical angle range, load level and speed fluctuation amplitude. The final control quantity includes one or more of the following: speed setpoint correction quantity, q-axis current setpoint correction quantity, PWM duty cycle correction quantity, and commutation timing fine-tuning quantity.

8. The method of claim 1, wherein: The method also includes an online update step: after completing one or more control cycles, the actual speed fluctuation results, load disturbance estimation results, and commutation suppression effect are fed back to the speed fluctuation mapping model, and the compensation coefficients for different electrical angle ranges are iteratively corrected. During the update process, a forgetting factor is introduced to weight the current operating condition data and historical operating condition data, giving recent operating condition samples a higher weight.

9. The method of claim 1, wherein: The rotor position signal is output from any of the Hall sensor, encoder, or position-sensorless estimation module. The actual rotational speed signal is obtained from the rotor position signal through period counting, differential calculation, or estimation by an observer. Furthermore, during the acquisition process, the rotor position signal is subjected to jitter removal and time synchronization correction to reduce the impact of position sampling error on electrical angle interval division, synchronization separation, and commutation suppression generation.

10. The method of claim 1, wherein: The method is applied to at least one of the following conditions: low-speed heavy-load operation, frequent commutation operation, bus voltage fluctuation operation, or parameter drift operation. Under the above conditions, through coordinated control of electrical angle interval compensation, disturbance feedforward compensation, commutation suppression superposition, and adaptive parameter correction, the speed fluctuation caused by external load changes, commutation torque pulsation, and power supply fluctuation is reduced, and the stability and disturbance rejection of the brushless DC motor under long-term operating conditions are improved.

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