Method for optimizing medium-low speed performance of stepping motor

Abstract

The invention discloses a stepping motor medium and low speed performance optimization method, which is applied to a stepping motor driver, and executes the following steps in each control period of the driver: state acquisition: acquiring the actual operation speed of a motor, the current control mode state of the driver, and the busy / idle state of the motor determined based on instruction pulse activity; cooperative control: based on the actual operation speed and the busy / idle state acquired in the state acquisition, performing the following cooperative control: determining whether to inject a harmonic component to a current instruction, the determination being associated with the actual operation speed, the busy / idle state and the current control mode state; dynamically adjusting control parameters of a current loop according to the actual operation speed; and current instruction synthesis and output: based on the control parameters after cooperative control adjustment, generating a final current loop instruction and outputting the current loop instruction to a motor winding so as to significantly reduce medium and low speed vibration and noise and realize wide speed domain optimal control performance.

Description

Technical Field

[0001] This invention relates to the field of industrial automation technology, and in particular to a method for optimizing the low-speed performance of stepper motors. Background Technology

[0002] In the field of industrial automation, stepper motors are widely used due to their advantages such as simple open-loop control, low cost, and high positioning accuracy. However, when stepper motors operate at medium and low speeds, the following technical problems still urgently need to be solved:

[0003] Low-frequency vibration and noise: Since the working principle of stepper motor is centrifugal stepping motion, its torque pulsation is relatively large. Especially when the motor is near its natural frequency or running at low speed, it will generate obvious vibration and noise, which will affect the accuracy and life of the equipment.

[0004] Wide-speed-range control challenges: Motor parameters (such as inductance) change with speed, and fixed current loop PI parameters are difficult to guarantee both fast system response and stability across the entire speed range. At low speeds, high gain is required to ensure torque, but this can easily lead to oscillations; at high speeds, the gain needs to be reduced to prevent overshoot and loss of synchronization, but this results in slower response and increased tracking error.

[0005] Unsmooth switching of control modes: When switching between traditional open-loop and simple closed-loop (such as lead angle control), if the strategy is singular, shocks or oscillations may occur when the load changes suddenly or when the mechanical limit is near, affecting the smoothness of operation.

[0006] Existing technologies typically employ a single anti-vibration algorithm or fixed control parameters, lacking a comprehensive optimization scheme that can adaptively adjust based on the motor's real-time operating status (speed, direction, and enabling status), making it difficult to fundamentally balance stability, quietness, and rapid response at low and medium speeds. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a method for optimizing the low- and medium-speed performance of stepper motors. It aims to solve the technical problems of high vibration, high noise, performance degradation due to fixed control parameters, and unsmooth switching between different control modes in existing stepper motor drivers operating at low and medium speeds. The invention provides a comprehensive performance optimization method integrating harmonic injection suppression, current loop parameter speed adaptation, and intelligent operating state criteria, thereby systematically improving the operational stability, positioning accuracy, and reliability of stepper motors in the low- and medium-speed range.

[0008] The technical solution adopted by this invention to solve its technical problem is:

[0009] This invention provides a method for optimizing the low-speed performance of a stepper motor, applied to a stepper motor driver, which executes the following steps in each control cycle of the driver:

[0010] S1: Status Acquisition: Acquire the actual running speed of the motor and the current control mode status of the driver, as well as the busy / idle status of the motor based on the activity determination of the command pulse;

[0011] S2: Cooperative Control: Based on the actual operating speed and busy / idle status obtained in S1, the following cooperative control is performed:

[0012] S2.1: Determine whether to inject harmonic components into the current command, the determination is related to the actual operating speed, the busy / idle state and the current control mode state;

[0013] S2.2: Dynamically adjust the control parameters of the current loop according to the actual operating speed;

[0014] S3: Current command synthesis and output: Based on the judgment result of S2.1 and the control parameters adjusted in S2.2, the final current loop command is generated and output to the motor winding.

[0015] Preferably, in the state acquisition step, the acquired operating state information also includes the motor's operating direction, which provides directional information for subsequent harmonic injection phase compensation. This enables dynamic correction of the harmonic phase based on the motor's forward and reverse rotation, ensuring that the vibration suppression effect is independent of the direction of rotation and that the performance optimization effect remains consistent in different operating directions.

[0016] Preferably, the determination of whether to inject harmonic components in S2.1 is specifically achieved by determining whether an enabling condition is met. The enabling condition is that the motor is in a busy state and the absolute value of the actual operating speed falls within at least one preset harmonic enabling speed window. By setting an enabling condition based on the motor's busy state and the preset speed window to determine whether to inject harmonics, invalid energy injection can be avoided when the motor is stationary or idle. Compensation is precisely activated only when vibration suppression is needed in a specific speed range. This achieves the goal of minimizing additional power consumption and potential interference while ensuring performance, thereby improving the system's energy efficiency and intelligence.

[0017] Preferably, the harmonic components include at least two harmonic components for suppressing torque pulsations of different orders; the at least one harmonic enabling speed window includes multiple independent sub-speed windows corresponding to different order harmonic components. This feature defines a speed window containing at least two harmonic components and their respective independent enabling speed windows, which can perform frequency-segmented and differentiated suppression of different order torque pulsations (such as 3rd and 5th harmonics) that cause vibration, and realize refined and targeted compensation for multiple major vibration sources in a wide medium and low speed range, significantly expanding the effective vibration reduction and noise reduction speed range.

[0018] Preferably, the amplitude of the harmonic injection is determined by the product of the peak value of the fundamental current and the preset harmonic amplitude coefficient; the harmonic phase is determined by the current electrical angle of the motor plus a preset phase offset, and the phase is compensated according to the running direction, so that the injected harmonic intensity can adapt to the load (current) and the phase is precisely synchronized with the real-time magnetic field position of the motor, realizing that the amplitude and timing of the compensation torque are precisely matched with the actual operating conditions, which greatly improves the accuracy of harmonic injection and the effectiveness of the suppression effect.

[0019] Preferably, the control parameters of the current loop dynamically adjusted in S2.2 include dividing the speed range into a low-speed zone, a transition zone, and a high-speed zone based on a comparison between the actual operating speed and at least two preset speed thresholds.

[0020] In the low-speed region, a basic proportional gain and a basic anti-saturation compensation gain are used;

[0021] In the transition region, the proportional gain and the anti-saturation compensation gain are linearly interpolated between the base value and the corresponding preset maximum value with respect to the speed.

[0022] In the high-speed region, the maximum proportional gain is adopted, and the anti-saturation compensation gain is set to a predetermined multiple of the basic anti-saturation compensation gain. This feature, through speed division and differentiated configuration and smooth transition of current loop parameters (proportional gain, anti-saturation gain) in different regions, is to adaptively adjust the system performance according to the different requirements of the speed domain (low-speed stability, high-speed response). This achieves a smooth transition and significantly improves the dynamic response speed and anti-load disturbance capability in the medium and high-speed regions while ensuring low-speed smoothness and stability.

[0023] Preferably, the predetermined multiple is 2 times, and the anti-saturation compensation gain in the high-speed region is specifically set to 2 times the base value. This can enhance the motor's anti-integral saturation capability under high speed and large dynamic response, effectively prevent the control performance from deteriorating or becoming unstable due to rapid changes in current command, and achieve the goal of ensuring the robustness and reliability of the control system under large signals while pursuing high bandwidth.

[0024] Preferably, the current control mode states include an open-loop compensation state and a closed-loop tracking state determined based on the magnitude of the position error. In the open-loop compensation state, harmonic injection is enabled; in the closed-loop tracking state, harmonic injection is disabled, and encoder feedback angle is used for control. Linking the enabling / disabling of harmonic injection with the two control mode states of open-loop compensation and closed-loop tracking coordinates the vibration suppression strategy based on feedforward compensation and the closed-loop control strategy based on real-time feedback, avoiding conflicts between the two. This achieves performance improvement through harmonic injection in open-loop mode, while relying on the feedback system itself to ensure performance in closed-loop mode with existing high-precision position feedback, ensuring the optimal synergy of the control architecture under different operating modes.

[0025] Preferably, S3 specifically includes: superimposing the fundamental current given with the harmonic components calculated in S2.1 to obtain the final current loop command, effectively clarifying that the fundamental current given with the calculated harmonic components is superimposed to generate the final current command, thereby realizing the final execution step of the optimization strategy, summarizing the results of all previous analysis and calculation into a control signal that can directly drive the power device, and realizing the transformation of the theoretical vibration suppression and dynamic optimization scheme into the current waveform that actually acts on the motor winding.

[0026] A stepper motor driver includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement a cooperative adaptive control method for the stepper motor driver. By embedding the optimization method into a program executable by the processor and deploying it in specific hardware, the physicalization, productization, and repeatable and reliable operation of the cooperative adaptive control scheme are realized.

[0027] The beneficial effects of this invention are:

[0028] 1. Significantly reduces vibration and noise at low and medium speeds: Through the "intelligent harmonic injection module", precise harmonic current is injected only when the motor is idle and in a specific resonant speed range, which targets and cancels torque pulsation, avoiding the additional losses and potential instability caused by injection at all times, and the vibration reduction effect is significant and efficient.

[0029] 2. Achieve optimal control performance across a wide speed range: Through the "speed adaptive PI adjustment module", the current loop parameters can change smoothly with the speed, maintaining high stiffness in the low-speed range and ensuring fast response in the high-speed range. This solves the contradiction that fixed parameters cannot take into account both high and low speed performance, and improves the dynamic quality and stability across the entire speed range.

[0030] 3. Enhance system intelligence and reliability: Through the "intelligent decision-making module for operating status," harmonic injection, control mode, and the real-time status of the motor (busy / idle, speed, position error) are tightly coupled. This avoids introducing unnecessary interference during dynamic adjustment, ensures smooth switching of control modes, and enhances the system's adaptability and overall reliability under different operating conditions. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. The accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Figure 1 This is one of the flowcharts of the method for optimizing the low-speed performance of the stepper motor according to the present invention;

[0034] Figure 2 This is the second flowchart of the method for optimizing the low-speed performance of the stepper motor according to the present invention;

[0035] Figure 3 This is the third flowchart of the method for optimizing the low-speed performance of the stepper motor according to the present invention. Detailed Implementation

[0036] Reference Figures 1 to 3 A method for optimizing the low-speed performance of a stepper motor, applied to a stepper motor driver, involves performing the following steps within each control cycle of the driver:

[0037] S1: Status Acquisition: Acquire the actual running speed of the motor and the current control mode status of the driver, as well as the busy / idle status of the motor based on the activity determination of the command pulse;

[0038] S2: Cooperative Control: Based on the actual operating speed and busy / idle status obtained in S1, the following cooperative control is performed:

[0039] S2.1: Determine whether to inject harmonic components into the current command, the determination is related to the actual operating speed, the busy / idle state and the current control mode state;

[0040] S2.2: Dynamically adjust the control parameters of the current loop according to the actual operating speed;

[0041] S3: Current command synthesis and output: Based on the judgment result of S2.1 and the control parameters adjusted in S2.2, the final current loop command is generated and output to the motor winding.

[0042] With the above-described structure, during use, the actual speed, busy / idle status, and control mode of the motor are acquired in real time within each control cycle of the stepper motor driver. Based on this information, intelligent harmonic injection judgment and dynamic adjustment of current loop parameters are performed in coordination, and finally, an optimized current command is synthesized. Its function is to adaptively match the motor operating conditions in real time to suppress low- and medium-speed vibration and noise, improve motion smoothness, and achieve the technical effect of significantly improving the operating performance of the stepper motor in the low- and medium-speed range, reducing torque fluctuation and step loss risk, while maintaining high-efficiency response.

[0043] Specifically, in the state acquisition step, the acquired operating state information also includes the motor's operating direction, which provides directional information for subsequent harmonic injection phase compensation. This enables dynamic correction of the harmonic phase based on the motor's forward and reverse rotation, ensuring that the vibration suppression effect is independent of the direction of rotation and that the performance optimization effect remains consistent in different operating directions.

[0044] Specifically, the motor's running direction and actual running speed are calculated via encoder and / or pulse counting feedback.

[0045] Specifically, in S2.1, determining whether to inject harmonic components is achieved by determining whether an enabling condition is met. The enabling condition is that the motor is in a busy state and the absolute value of the actual operating speed falls within at least one preset harmonic enabling speed window. By setting an enabling condition based on the motor's busy state and the preset speed window to determine whether to inject harmonics, invalid energy injection can be avoided when the motor is stationary or idle. Compensation is precisely activated only when vibration suppression is needed in a specific speed range. This achieves the goal of minimizing additional power consumption and potential interference while ensuring performance, thereby improving the system's energy efficiency and intelligence.

[0046] Specifically, the harmonic components include at least two harmonic components used to suppress torque pulsations of different orders; the at least one harmonic enabling speed window includes multiple independent sub-speed windows corresponding to different order harmonic components. This feature defines a speed window containing at least two harmonic components and their respective independent enabling speed windows, which can perform frequency-segmented and differentiated suppression of different order torque pulsations (such as the 3rd and 5th harmonics) that cause vibration, and realize refined and targeted compensation for multiple major vibration sources in a wide medium and low speed range, significantly broadening the speed range of effective vibration reduction and noise reduction.

[0047] Specifically, the at least two harmonic components include a 5th harmonic component and a 3rd harmonic component; the plurality of sub-velocity windows include a first velocity window corresponding to the 5th harmonic component and a second velocity window corresponding to the 3rd harmonic component.

[0048] Specifically, the amplitude of the harmonic injection is determined by the product of the peak value of the fundamental current and the preset harmonic amplitude coefficient; the harmonic phase is determined by the current electrical angle of the motor plus a preset phase offset, and the phase is compensated according to the running direction, which enables the injected harmonic intensity to adapt to the load (current) and the phase to be precisely synchronized with the real-time magnetic field position of the motor. This achieves that the amplitude and timing of the compensation torque are precisely matched with the actual operating conditions, greatly improving the accuracy of harmonic injection and the effectiveness of the suppression effect.

[0049] Specifically, the control parameters of the current loop dynamically adjusted in S2.2 include dividing the speed range into a low-speed zone, a transition zone, and a high-speed zone based on a comparison between the actual operating speed and at least two preset speed thresholds.

[0050] In the low-speed region, a basic proportional gain and a basic anti-saturation compensation gain are used;

[0051] In the transition region, the proportional gain and the anti-saturation compensation gain are linearly interpolated between the base value and the corresponding preset maximum value with respect to the speed.

[0052] In the high-speed region, the maximum proportional gain is adopted, and the anti-saturation compensation gain is set to a predetermined multiple of the basic anti-saturation compensation gain. This feature, through speed division and differentiated configuration and smooth transition of current loop parameters (proportional gain, anti-saturation gain) in different regions, is to adaptively adjust the system performance according to the different requirements of the speed domain (low-speed stability, high-speed response). This achieves a smooth transition and significantly improves the dynamic response speed and anti-load disturbance capability in the medium and high-speed regions while ensuring low-speed smoothness and stability.

[0053] Specifically, the predetermined multiple is 2 times, and the anti-saturation compensation gain in the high-speed region is specifically set to 2 times the base value. This can enhance the motor's anti-integral saturation capability under high speed and large dynamic response, effectively prevent the control performance from deteriorating or becoming unstable due to rapid changes in current command, and achieve the goal of ensuring the robustness and reliability of the control system under large signals while pursuing high bandwidth.

[0054] Specifically, the current control mode states include an open-loop compensation state and a closed-loop tracking state determined based on the magnitude of the position error. In the open-loop compensation state, harmonic injection is enabled; in the closed-loop tracking state, harmonic injection is disabled, and encoder feedback angle is used for control. Linking the enabling / disabling of harmonic injection with the two control mode states of open-loop compensation and closed-loop tracking is to coordinate the vibration suppression strategy based on feedforward compensation and the closed-loop control strategy based on real-time feedback, avoiding conflicts between the two. This achieves performance improvement through harmonic injection in open-loop mode, while relying on the feedback system itself to ensure performance in closed-loop mode with existing high-precision position feedback, ensuring the optimal coordination of the control architecture under different operating modes.

[0055] Specifically, S3 includes: superimposing the fundamental current given with the harmonic components calculated in S2.1 to obtain the final current loop command. This effectively and clearly defines the superposition of the fundamental current given with the calculated harmonic components to generate the final current command, thereby realizing the final execution step of the optimization strategy. The results of all previous analysis and calculation are summarized into a control signal that can directly drive the power device, realizing the transformation of the theoretical vibration suppression and dynamic optimization scheme into the current waveform that actually acts on the motor winding.

[0056] A stepper motor driver includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement a cooperative adaptive control method for the stepper motor driver. By embedding the optimization method into a program executable by the processor and deploying it in specific hardware, the physicalization, productization, and repeatable and reliable operation of the cooperative adaptive control scheme are realized.

[0057] In practical applications, this method is integrated into the driver's interrupt service routine and executed synchronously with core algorithms such as the current loop. Its core lies in three collaborative optimization modules: an intelligent harmonic injection module, a speed-adaptive PI adjustment module, and an intelligent decision-making module for operational status. The following detailed explanation of the solution is provided in conjunction with the implementation flowchart:

[0058] Step 1: Obtain real-time operating status and speed information;

[0059] As attached Figure 1 As shown, in each control cycle, the system calculates the actual operating speed and its absolute value of the motor through encoder or pulse counting feedback. Simultaneously, it determines whether the motor is in a "busy" or "idle" state. This state is determined by the activity of command pulses; if no pulses are emitted for a set time, the motor enters an idle state.

[0060] Step 2: Harmonic Injection Calculation;

[0061] As attached Figure 2As shown, this step dynamically calculates and injects specific harmonic currents based on the current speed and direction of rotation to counteract the inherent torque ripples of the motor. The program has two independent speed thresholds, corresponding to the injection-enabled speed ranges for the 5th and 3rd harmonics, respectively.

[0062] If the current velocity v_fbd2_abs is within the interval (Spd5l,Spd5h), then calculate the 5th harmonic injection quantity AmpCalc1.

[0063] If the current velocity v_fbd2_abs is within the interval (Spd3l,Spd3h), then the 3rd harmonic injection quantity AmpCalc2 is calculated. If it is not within any enabled interval, then the corresponding harmonic injection quantity is zero.

[0064] Harmonic synthesis: The harmonic injection amount is obtained by multiplying the fundamental current peak value (Ipeak) by the user-defined harmonic amplitude coefficients (AmpSet1, AmpSet2). The harmonic phase is composed of the current electrical angle of the motor superimposed with the user-defined phase offset (PhSet1, PhSet2), and the phase addition or subtraction is determined according to the motor running direction.

[0065] Finally, the 5th harmonic current components CurA5, CurB5 and the 3rd harmonic current components CurA3, CurB3 are generated.

[0066] Step 3: Adjust the PI parameters of the speed adaptive current loop;

[0067] As attached Figure 3 As shown, in order to solve the problem of wide-speed-range control, the proportional gain (Kp) and anti-saturation compensation gain (Kc) of the current loop need to be dynamically adjusted according to the speed.

[0068] The program has two speed inflection points: SpeedPoint1 (low speed point) and SpeedPoint2 (medium speed point).

[0069] Low-speed range: Basic PI parameters are used to ensure control stiffness and stability at low speeds.

[0070] Transition zone: The PI parameter is linearly interpolated between its base value and its maximum value.

[0071] Kp=Iloop_KpBase+(v_fbd2_abs-SpeedPoint1)*Iloop_KpDlta;

[0072] Kc=Iloop_KcBase+(v_fbd2_abs-SpeedPoint1)*KcDlta;

[0073] Where Iloop_KpDlta and KcDlta are preset increment coefficients.

[0074] High-speed region: The maximum PI parameters Iloop_KpMax and 2*Iloop_KcBase are used to provide sufficient response speed and resist the back EMF effect at high speeds.

[0075] Step 4: Current setting synthesis and closed-loop mode optimization;

[0076] The fundamental current is combined with the harmonic injection amount to form the final current loop command.

[0077] Open-loop / lead angle mode: The fundamental current is given by Ipeak and sine and cosine functions.

[0078] The harmonic components (CurA5 / B5, CurA3 / B3) calculated in step two are superimposed on the fundamental frequency to obtain the final stepper1A_pi.Ref and stepper1B_pi.Ref.

[0079] In the lead angle closed-loop mode, when the position error is large, the system is in "open-loop compensation" state, in which harmonic suppression and speed adaptive PI are still enabled. When the position error decreases and enters the "closed-loop tracking" state, the encoder feedback angle is used directly for control, and harmonic injection is disabled to avoid interference.

[0080] Compared with existing technologies, the most prominent substantive feature of this invention is that it is not an isolated improvement on problems such as vibration suppression and parameter adjustment, but rather the construction of a "cooperative adaptive control system based on multi-dimensional state perception". This system takes the real-time operating status of the motor (including speed, direction, enable status, and control mode) as input, and organically integrates sub-modules such as harmonic injection, parameter adaptation, and mode switching through the core mechanism of "intelligent decision-making-cooperative execution", thereby systematically and accurately solving the comprehensive performance bottleneck faced by stepper motors in the low-to-medium speed range.

[0081] To achieve this core advantage, the core of the directly impactful solution is:

[0082] A smart enable control method for harmonic injection: characterized in that whether or not harmonic injection is enabled depends simultaneously on whether the motor is in an "idle state" and whether the current actual operating speed falls within a preset specific harmonic enable speed window. Both conditions are indispensable.

[0083] The speed adaptive method for current loop PI parameters is characterized by dividing the operating range into low-speed, transition, and high-speed zones based on a comparison between the motor's real-time speed and a preset speed threshold, and dynamically assigning three different sets of PI parameters. The transition zone parameters are obtained through linear interpolation using preset incremental coefficients. This strategy achieves optimal dynamic performance across the entire speed range.

[0084] The above two methods are coordinated with the running state machine: The harmonic injection and parameter adaptive logic mentioned above do not run independently, but are deeply bound and linked with the driver's control mode state machine and running state machine, ensuring that all optimization actions are triggered in the correct global state, thus guaranteeing the continuity and smoothness of system operation.

[0085] To achieve the same technical objective, the following alternatives may be considered, but none of them are as effective as the present invention:

[0086] Fixed harmonic injection: This method injects harmonics of a fixed amplitude regardless of speed or idle state. This approach may introduce interference during motor acceleration or under load, leading to decreased control performance or even loss of synchronization.

[0087] Speed-zone PI parameter switching: The PI parameter is hard-switched only between high and low speeds, instead of a linear transition. This may cause abrupt changes in control characteristics near the switching point, resulting in shocks or oscillations.

[0088] In practical applications, the load conditions of a motor directly affect its vibration characteristics and dynamic response requirements. To further enhance the depth of collaborative optimization, this embodiment also includes real-time observation of the motor load rate in the state acquisition step.

[0089] Specifically, the load factor can be estimated using one or a combination of the following methods:

[0090] Current-speed observation: During steady-state or uniform acceleration phases, load torque is estimated based on the motor current command (Iq_ref) and back EMF model.

[0091] Disturbance observer: A load torque observer is embedded in the current loop or speed loop to output the load torque observation value in real time.

[0092] Model reference adaptation: The load inertia is identified online by utilizing the deviation between the motor model and the actual response.

[0093] After obtaining the load observation value (T_load) or the normalized load ratio (Load_Ratio, such as 0% to 100%), it is used as a new state variable and input into the cooperative control step.

[0094] The load adaptive cooperative control rules are as follows:

[0095] A. Harmonic injection quantity load adaptive:

[0096] The amplitude of the harmonic injection is determined by the fundamental current peak value (Ipeak) × preset harmonic amplitude coefficient (AmpSet) × load adaptive coefficient (K_load).

[0097] The load adaptation coefficient (K_load) is a function of the load ratio. In a preferred embodiment, this function is set as follows: when the load ratio is below a first threshold (e.g., 30%), K_load takes a smaller value (e.g., 0.5) to reduce unnecessary energy injection under light load; when the load ratio is above a second threshold (e.g., 70%), K_load takes a larger value (e.g., 1.2) to enhance vibration suppression under heavy load; in the intermediate range, K_load increases linearly or non-linearly with the load ratio.

[0098] B. Load fine-tuning of current loop parameters:

[0099] When dynamically adjusting the current loop control parameters, the base values ​​(such as Iloop_KpBase, Iloop_KcBase) can be dynamically biased according to the load characteristics.

[0100] If the load observer detects severe fluctuations in load torque (which can be determined through torque differentiation or spectrum analysis), then Iloop_KpBase is temporarily increased by an increment (e.g., +10%) to enhance the system's disturbance rejection stiffness.

[0101] If the system is in a stable operation under constant heavy load, Iloop_KcBase can be slightly reduced to optimize the steady-state current waveform and reduce losses.

[0102] By introducing load adaptation, the optimization system of this invention is upgraded from relying solely on the internal state of "speed" to simultaneously sensing both "speed" and "load" in a coordinated manner, enabling vibration suppression and dynamic response optimization to accurately match the real-time operating conditions of the motor, achieving a qualitative leap from "open-loop strategy" to "closed-loop adaptation".

[0103] To further enhance the intelligence and precision of vibration suppression, this embodiment can also add a vibration feedback loop to the driver. This feedback does not rely directly on external sensors, but rather indirectly and in real-time obtains motor vibration intensity information by sampling the motor phase current at high frequency and analyzing its ripple spectrum.

[0104] The specific implementation steps are as follows:

[0105] Within each control cycle or specific monitoring cycle:

[0106] Signal acquisition: High-speed ADC samples the instantaneous currents Ia(k) and Ib(k) of two-phase windings of the motor.

[0107] Ripple extraction: The fundamental component is filtered out from the sampled current to obtain the current ripple signal, which mainly contains harmonics and switching noise.

[0108] Spectrum analysis and feature extraction: Perform Fast Fourier Transform (FFT) or apply sliding window filtering on the current ripple signal to extract the energy amplitudes Vib_3rd and Vib_5th of specific frequency bands (such as the electrical frequencies corresponding to the 3rd and 5th mechanical resonances) as quantitative indicators of the current vibration intensity.

[0109] The closed-loop regulation rule based on vibration feedback is as follows:

[0110] A. Closed-loop fine-tuning of harmonic injection parameters:

[0111] The extracted Vib_3rd and Vib_5th values ​​are compared with the set vibration threshold.

[0112] If Vib_5th remains above the threshold, the system automatically fine-tunes the phase offset (PhSet1) of the 5th harmonic injection, for example, by searching in the forward or reverse direction with a minimum step (e.g., 0.1 radians) to find the optimal phase point that minimizes Vib_5th. Simultaneously, the setting value of the 5th harmonic amplitude coefficient (AmpSet1) can be slightly increased until the vibration is suppressed below the threshold.

[0113] Similarly, the third harmonic is independently controlled in a closed loop.

[0114] The adjustment process runs at low speed in the background and does not affect the fast current control in the foreground.

[0115] B. Automatic calibration of the speed window:

[0116] The system records the velocity points corresponding to significant vibrations. If a certain velocity point (e.g., 450 RPM) frequently triggers the closed-loop adjustment of the third harmonic vibration, and this velocity point is not in the center of the originally preset (Spd3l,Spd3h) window, the system can slowly shift or fine-tune the velocity window to better cover the actual mechanical resonance zone.

[0117] This solution evolves the driver's vibration suppression strategy from a preset, open-loop "feedforward compensation" to a real-time, closed-loop "feedback cancellation." This allows it to automatically adapt to individual motor differences, mechanical assembly tolerances, and resonance point drift caused by aging over time, maintaining optimal vibration suppression performance at all times.

[0118] The above descriptions provide one or more embodiments in conjunction with specific content, but do not imply that the specific implementation of the present invention is limited to these descriptions. Any methods or structures that are similar to or identical to those of the present invention, or any technical deductions or substitutions made based on the concept of the present invention, should be considered within the scope of protection of the present invention.

Claims

1. A method for optimizing the low-speed performance of a stepper motor, applied to a stepper motor driver, characterized in that, The following steps are performed during the driver's control cycle: S1: Status Acquisition: Acquire the actual running speed of the motor and the current control mode status of the driver, as well as the busy / idle status of the motor based on the activity determination of the command pulse; S2: Cooperative Control: Based on the actual operating speed and busy / idle status obtained in S1, the following cooperative control is performed: S2.1: Determine whether to inject harmonic components into the current command, the determination is related to the actual operating speed, the busy / idle state and the current control mode state; S2.2: Dynamically adjust the control parameters of the current loop according to the actual operating speed; S3: Current command synthesis and output: Based on the judgment result of S2.1 and the control parameters adjusted in S2.2, the final current loop command is generated and output to the motor winding.

2. The method for optimizing the low-speed performance of a stepper motor according to claim 1, characterized in that: In the state acquisition step, the acquired operating state information also includes the motor's running direction.

3. The method for optimizing the low-speed performance of a stepper motor according to claim 1, characterized in that: In S2.1, the determination of whether to inject harmonic components is specifically achieved by determining whether the enabling condition is met; the enabling condition is: the motor is in a busy state, and the absolute value of the actual running speed falls within at least one preset harmonic enabling speed window.

4. The method for optimizing the low-speed performance of a stepper motor according to claim 3, characterized in that, The harmonic components include at least two harmonic components used to suppress torque pulsations of different orders; the at least one harmonic enabling speed window includes multiple independent sub-speed windows corresponding to different order harmonic components.

5. The method for optimizing the low-speed performance of a stepper motor according to claim 4, characterized in that, The amplitude of the harmonic injection is determined by the product of the peak value of the fundamental current and the preset harmonic amplitude coefficient; the harmonic phase is determined by the current electrical angle of the motor plus a preset phase offset, and the phase is compensated according to the running direction.

6. The method for optimizing the low-speed performance of a stepper motor according to claim 4, characterized in that: The control parameters of the current loop dynamically adjusted in S2.2 include dividing the speed range into a low-speed zone, a transition zone, and a high-speed zone based on a comparison between the actual operating speed and at least two preset speed thresholds. In the low-speed region, a basic proportional gain and a basic anti-saturation compensation gain are used; In the transition region, the proportional gain and the anti-saturation compensation gain are linearly interpolated between the base value and the corresponding preset maximum value with respect to the speed. In the high-speed region, the maximum proportional gain is used, and the anti-saturation compensation gain is set to a predetermined multiple of the base anti-saturation compensation gain.

7. The method for optimizing the low-speed performance of a stepper motor according to claim 6, characterized in that: The predetermined multiple is 2 times.

8. The method for optimizing the low-speed performance of a stepper motor according to claim 1, characterized in that: The current control mode includes an open-loop compensation state and a closed-loop tracking state based on the magnitude of the position error. In the open-loop compensation state, harmonic injection is enabled. In the closed-loop tracking state, harmonic injection is disabled, and the encoder feedback angle is used for control.

9. The method for optimizing the low-speed performance of a stepper motor according to claim 1, characterized in that: Specifically, S3 includes: superimposing the fundamental current given in S2.1 with the harmonic components calculated in S2.1 to obtain the final current loop command.

10. A stepper motor driver, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the cooperative adaptive control method for a stepper motor driver as described in any one of claims 1 to 9.

Images