A method and device for reverse start control of a sensorless motor

Abstract

The application discloses a kind of reverse starting control method and device of position sensorless motor, method includes: the three-phase current signal and three-phase voltage signal of position sensorless motor are collected, and the voltage signal under α-β coordinate system is obtained by Clarke conversion to the signal collected;Based on the voltage signal under α-β coordinate system, the original phase is calculated, the continuous phase is obtained by executing phase unpacking processing to original phase, the continuous phase is operated differentially, and the electrical angular velocity estimation value of position sensorless motor is obtained;Combined with preset reverse trigger condition, whether position sensorless motor exists unexpected high-speed reverse phenomenon is judged;If yes, linear deceleration trajectory is generated to linear deceleration by executing linear deceleration of real-time monitored electrical angular velocity measured value generation, and linear deceleration trajectory is mapped as limited torque current;After electrical angular velocity measured value meets zero speed stability criterion, enter initial position detection and standard starting process, and finally closed-loop operation.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a method and apparatus for reverse start control of a sensorless motor. Background Technology

[0002] In applications such as fans and pumps driven by loads, motors may reverse due to external forces such as wind or water flow; this is known as "tailwind" or "headwind" reversal. Existing motor starting solutions typically suffer from the following problems and drawbacks:

[0003] 1. Start-up shock and overcurrent: When the motor controller fails to detect the motor's reverse state, or starts the motor directly in the normal way, it will violently conflict with the actual rotation direction of the motor, generating huge current shocks and mechanical stress, which may cause overcurrent protection of the driver and damage to mechanical transmission components.

[0004] 2. Inability to decelerate smoothly: Traditional methods lack effective identification and targeted handling strategies for reversal states, making it impossible to achieve a smooth transition from high-speed reversal to a stop, resulting in a rough braking process.

[0005] 3. Low system reliability: Repeated impacts will significantly reduce the service life of motors, drives and mechanical structures, affecting the reliability and stability of the entire system. Summary of the Invention

[0006] This invention provides a method and device for controlling the reverse start of a sensorless motor, which can effectively avoid the current surge and mechanical stress caused by direct start, achieve a smooth transition from high-speed reverse state to stop, and improve the reliability of system operation.

[0007] According to one aspect of the present invention, a method for controlling the reverse start of a sensorless motor is provided, comprising:

[0008] The three-phase current signal and three-phase voltage signal of the sensorless motor are acquired, and the Clarke transform is performed on the three-phase current signal and the three-phase voltage signal to obtain the voltage signal in the α-β coordinate system;

[0009] Based on the voltage signal in the α-β coordinate system, the Atan2 algorithm is used to calculate the original phase, the phase unpacking process is performed on the original phase to obtain the continuous phase, the differential operation is performed on the continuous phase, and / or the observed angular velocity output by the motor speed observer is selected to obtain the estimated value of the electric angular velocity of the sensorless motor.

[0010] Based on the preset reversal trigger conditions, determine whether there is an unexpected high-speed reversal phenomenon in the sensorless motor;

[0011] When it is determined that the sensorless motor has an unexpected high-speed reverse phenomenon, the measured value of the real-time monitored electric angular velocity is linearly decelerated to generate a linear deceleration trajectory, and the linear deceleration trajectory is mapped to a constrained torque current.

[0012] Once the measured electric angular velocity value meets the zero-speed stability criterion, the initial position detection and standard start-up process begins, ultimately resulting in closed-loop operation.

[0013] Optionally, based on preset reversal trigger conditions, determining whether a sensorless motor exhibits unexpected high-speed reversal includes:

[0014] Determine whether the composite condition of "historical command speed is approximately zero, current command speed is positive, measured electrical angular velocity is negative and the measured electrical angular velocity exceeds the preset reversal threshold" is met. If it is met, it is determined that the sensorless motor has an unexpected high-speed reversal phenomenon.

[0015] Optionally, after the actual value of the electric angular velocity meets the zero-velocity stability criterion, the initial position detection and standard start-up process is initiated, and the final closed-loop operation includes:

[0016] Real-time monitoring of the actual electrical angular velocity of a sensorless motor;

[0017] The braking state ends when the zero-speed stability criterion of "the absolute value of the actual value of the electric angular velocity is less than the preset zero-speed threshold, the variance of the velocity short window is less than the preset variance threshold, and the preset number of samples is maintained" is met.

[0018] Perform initial position detection of the motor, and after the initial position detection is completed, enter the standard start-up process, and finally run in a closed loop.

[0019] Optionally, after mapping the linear deceleration trajectory to a constrained torque current, the method further includes:

[0020] The braking process is coupled with DC bus overvoltage protection and driver temperature rise protection strategies.

[0021] If the DC bus voltage reaches the preset derating voltage threshold, the braking torque will be reduced; if the DC bus voltage exceeds the preset voltage threshold, a fault state will be entered.

[0022] If the driver temperature reaches the preset derating temperature threshold, it will be linearly drated; if the driver temperature reaches the preset temperature threshold, it will enter a fault state.

[0023] Optionally, the reverse start control method for the sensorless motor further includes: only when the composite condition is satisfied for N consecutive FOC cycles is it finally determined that the sensorless motor has an unexpected high-speed reverse phenomenon; and the preset reverse threshold is set to max(300erpm,0.5%・MTR_MAX_SPD), where MTR_MAX_SPD is the rated maximum speed of the motor, and N is an integer ≥3.

[0024] Optionally, the preset derating voltage threshold is set to 0.95 × OVP, where OVP is the rated overvoltage protection threshold of the DC bus.

[0025] Optionally, the reverse start control method for the sensorless motor further includes:

[0026] When the zero-speed stability criterion of "the absolute value of the actual value of the electric angular velocity is less than the preset zero-speed threshold, the variance of the speed short window is less than the preset variance threshold, and the preset number of samples is continuously met" is not satisfied, the braking duration is monitored.

[0027] If the braking duration exceeds the preset braking timeout threshold and the zero-speed stability criterion is still not met, then a fault state is entered.

[0028] Optionally, the specific implementation of phase unpacking is as follows: record the original phase of the previous cycle, calculate the difference between the original phase of the current cycle and the original phase of the previous cycle, and if the difference exceeds the range of ±π, then add ±2π compensation to the original phase of the current cycle, and accumulate the compensated phase into the continuous phase to eliminate the phase jump caused by the Atan2 algorithm.

[0029] Optionally, the specific process of the initial position detection is as follows: apply a preset alignment current to the motor to align the motor rotor magnetic poles with the stator winding magnetic flux, and complete the electrical angle zero point calibration; after calibration, switch to OPEN / IF_SWITCH mode, gradually build up the stator current, and after the stator current stabilizes, switch to CLOSE mode, start SVPWM FOC control, and enter closed-loop operation.

[0030] According to another aspect of the present invention, a reverse start control device for a sensorless motor is provided, comprising:

[0031] The acquisition and coordinate transformation module is used to acquire the three-phase current signal and the three-phase voltage signal of the sensorless motor, and to perform Clarke transformation on the three-phase current signal and the three-phase voltage signal to obtain the voltage signal in the α-β coordinate system.

[0032] The phase and electric angular velocity calculation module is used to calculate the original phase based on the voltage signal in the α-β coordinate system using the Atan2 algorithm, perform phase unpacking processing on the original phase to obtain a continuous phase, perform differential operation on the continuous phase, and / or select the observed angular velocity output by the motor speed observer to obtain the estimated value of the electric angular velocity of the sensorless motor.

[0033] A reversal detection module is used to determine whether a sensorless motor exhibits unexpected high-speed reversal by combining preset reversal trigger conditions.

[0034] The braking control module is used to generate a linear deceleration trajectory by performing linear deceleration on the real-time monitored measured value of the electric angular velocity when it is determined that the sensorless motor has an unexpected high-speed reverse phenomenon, and to map the linear deceleration trajectory as a constrained torque current.

[0035] The zero-velocity determination and startup module is used to enter the initial position detection and standard startup process after the measured value of the electric angular velocity meets the zero-velocity stability criterion, and finally to operate in a closed loop.

[0036] This invention provides a method and apparatus for reversing start control of a sensorless motor. The method includes: acquiring three-phase current signals and three-phase voltage signals of the sensorless motor, and performing Clarke transformation on the three-phase current signals and three-phase voltage signals to obtain voltage signals in the α-β coordinate system; based on the voltage signals in the α-β coordinate system, calculating the original phase using the Atan2 algorithm, performing phase unpacking processing on the original phase to obtain continuous phases, performing differential operations on the continuous phases, and / or selecting the observed angular velocity output by a motor speed observer to obtain an estimated value of the electric angular velocity of the sensorless motor; determining whether there is an unexpected high-speed reversal phenomenon in the sensorless motor by combining a preset reversal trigger condition; when it is determined that there is an unexpected high-speed reversal phenomenon in the sensorless motor, performing linear deceleration on the real-time monitored measured value of the electric angular velocity to generate a linear deceleration trajectory, and mapping the linear deceleration trajectory to a constrained torque current; after the measured value of the electric angular velocity meets the zero-speed stability criterion, entering the initial position detection and standard start process, and finally operating in a closed loop. The technical solution provided by this invention realizes a smooth transition of the motor from high-speed reverse to stop, completely avoiding the electrical and mechanical shocks caused by direct start. Through current limiting and state reset mechanisms, it ensures that the entire braking and restart process is always carried out within the safe operating range of the system, protecting power devices and mechanical structures, improving system reliability, and significantly improving product performance without increasing hardware costs.

[0037] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0038] 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. Obviously, 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.

[0039] Figure 1 A flowchart of a sensorless motor reverse start control method provided in an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the signal flow of a sensorless motor reverse start control method provided in an embodiment of the present invention;

[0041] Figure 3 This is a state transition diagram of a state machine for a sensorless motor reversal start control method provided in an embodiment of the present invention.

[0042] Figure 4 A timing diagram of the braking phase of a reverse start control method for a sensorless motor provided in an embodiment of the present invention;

[0043] Figure 5 A speed estimation path diagram for a sensorless motor reverse start control method provided in an embodiment of the present invention;

[0044] Figure 6 A schematic diagram of the structure of a sensorless motor reverse start control device provided in this embodiment of the invention;

[0045] Figure 7 This is a schematic diagram of the electronic device used in an embodiment of the present invention to provide a method for controlling the reverse start of a sensorless motor. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] Figure 1 This is a flowchart illustrating a sensorless motor reverse start control method according to an embodiment of the present invention. This embodiment is applicable to the control of motor reverse start. The method can be executed by a sensorless motor reverse start control device, which can be implemented in hardware and / or software. This device can be configured in any electronic device with communication capabilities. See also... Figure 1 The method includes:

[0049] S110. Acquire the three-phase current signal and three-phase voltage signal of the sensorless motor, and perform Clarke transformation on the three-phase current signal and three-phase voltage signal to obtain the voltage signal in the α-β coordinate system.

[0050] Specifically, sensorless motors, lacking additional position sensors, cannot directly obtain the rotor's position and speed. Therefore, they must inversely calculate the rotor's phase and speed by acquiring the three-phase current / voltage signals from the stator—this is the raw data source for subsequent reverse detection, braking control, and stable starting. An analog-to-digital converter (ADC) acquires the three-phase current and voltage signals of the sensorless motor. The Clarke transform is a mathematical transformation from a three-phase coordinate system to a two-phase stationary coordinate system, aiming to simplify the computational complexity of motor control. The motor's three-phase windings (U, V, W) are symmetrical, but their current / voltage signals are three AC signals with a 120° phase difference. Directly calculating the motor's phase and speed using these three signals requires handling three coupled variables, resulting in a complex mathematical model and a large computational load. The Clarke transform can convert the signals from these three three-phase coordinate systems into signals from two mutually perpendicular two-phase stationary coordinate systems (α-β coordinate system). That is, the Clarke transform of the three-phase current signal and the three-phase voltage signal yields the voltage signals Uα and Uβ in the α-β coordinate system, making subsequent phase and electric angular velocity calculations simpler and more efficient.

[0051] S120. Based on the voltage signal in the α-β coordinate system, the Atan2 algorithm is used to calculate the original phase. The original phase is unpacked to obtain the continuous phase. The continuous phase is differentially calculated, and / or the observed angular velocity output by the motor speed observer is selected to obtain the estimated value of the electric angular velocity of the sensorless motor.

[0052] Specifically, Atan2 is a mathematical function that can directly calculate the original phase θraw based on the voltage signals Uα and Uβ in the α-β coordinate system. However, since the output range of Atan2 is fixed at -π to π, as the motor continues to rotate, the original phase θraw will gradually increase from π to π+Δθ, but Atan2 will directly jump from π+Δθ to -π+Δθ; similarly, when decreasing from -π to -π-Δθ, it will jump to π-Δθ. This jump will cause the original phase θraw to be discontinuous. Therefore, it is necessary to unpack the original phase θraw to eliminate the phase jump and make the phase continuous. Differential operation is performed on the continuous phase to obtain the estimated value of the electric angular velocity of the sensorless motor. At the same time, it can be combined with the observed electric angular velocity output by the motor speed observer. The two methods can be combined or one of them can be selected to finally obtain a reliable estimated value of electric angular velocity.

[0053] S130. Based on the preset reversal trigger conditions, determine whether there is an unexpected high-speed reversal phenomenon in the sensorless motor.

[0054] Specifically, it is determined whether the following composite conditions are met: "the historical command speed is approximately zero, the current command speed is positive, the measured electrical angular velocity is negative, and the measured electrical angular velocity exceeds a preset reversal threshold." If these conditions are met, it is determined that the sensorless motor exhibits an unexpected high-speed reversal phenomenon. The sensorless motor is only determined to have an unexpected high-speed reversal phenomenon if the composite conditions are met consecutively for N Field-Oriented Control (FOC) cycles. The preset reversal threshold is set to max(300erpm, 0.5%・MTR_MAX_SPD), where MTR_MAX_SPD is the motor's rated maximum speed, and N is an integer ≥ 3.

[0055] S140. When it is determined that the motor without a position sensor has an unexpected high-speed reverse phenomenon, the measured value of the real-time monitored electrical angular velocity is used to generate a linear deceleration trajectory, and the linear deceleration trajectory is mapped to a restricted torque current.

[0056] Specifically, when it is determined that the sensorless motor is experiencing unexpected high-speed reverse rotation, the braking state machine (BRAKE) is activated to generate a linear deceleration trajectory v(t) = v0 + a・t (where v(t) is the estimated electrical angular velocity, v0 is the initial electrical angular velocity of the reverse rotation, a is the deceleration, a>0 indicates a linear rise from a negative value to 0, and t is time). This trajectory is mapped to a restricted torque current IqRef, and amplitude and slope limits are applied to the restricted torque current IqRef. Simultaneously, the braking process is coupled with DC bus overvoltage protection and driver temperature rise protection strategies. If the DC bus voltage reaches a preset derating voltage threshold, the braking torque is reduced; if the DC bus voltage exceeds the preset voltage threshold, a fault state is entered. If the driver temperature reaches a preset derating temperature threshold, linear derating is performed; if the driver temperature reaches a preset temperature threshold, a fault state is entered.

[0057] The purpose of generating a linear deceleration trajectory is to avoid directly using maximum torque to brake to a stop, which would cause a huge current surge when the speed drops to 0 instantly, leading to overcurrent in the driver and damage to mechanical components.

[0058] Braking is essentially about applying reverse torque to the motor to prevent it from reversing. The magnitude of the motor's torque is directly determined by the q-axis current Iq, so it is necessary to convert the speed trajectory into the required torque current.

[0059] Mapping logic: Based on the relationship between speed and torque (the higher the motor speed, the greater the braking torque required to ensure linear deceleration), the estimated electrical angular velocity v(t) is proportionally converted into a restricted torque current IqRef (the negative sign represents reverse torque, opposite to the motor's reverse direction, serving as a braking effect); amplitude and slope limits are applied because directly mapping IqRef based on speed may exceed the hardware's capacity, thus requiring double constraints.

[0060] Amplitude limiting: The absolute value of the limited torque current IqRef cannot exceed the preset maximum braking current—to prevent excessive current from burning out the driver power devices; wherein, the preset maximum braking current can be preset according to 0.6×rated Iq.

[0061] Slope limiting: The rate of change of the torque current IqRef must not be too fast—to avoid sudden changes in current that could cause a sudden change in motor torque and generate mechanical shock.

[0062] In summary, mapping is used to accurately calculate the required braking force, while limiting is used to ensure that the braking force does not exceed the hardware's capacity limit.

[0063] Braking process coupled with overvoltage / temperature rise protection:

[0064] New risks may arise during braking (e.g., the motor reverses and acts as a generator, charging the DC bus and causing overvoltage; excessive braking torque causes the driver to overheat), therefore, braking control must be linked to hardware protection in real time—this is the core of safe braking, and it is divided into two types of protection:

[0065] 1. DC bus overvoltage protection: Prevents components from burning out due to excessive bus voltage.

[0066] The DC bus is the main circuit supplying power to the driver. When the motor reverses for braking, the rotor cutting the stator magnetic field generates a back electromotive force, which is equivalent to charging the bus, causing the bus voltage to spike. Therefore, two levels of protection are implemented:

[0067] Level 1: When the bus voltage reaches the preset derating voltage threshold, it means that the voltage is about to reach the upper limit. At this time, the braking torque is immediately reduced, that is, the restricted torque current IqRef is reduced to reduce the generator effect of the motor and prevent the voltage from continuing to rise. (The preset derating voltage threshold can be preset according to 0.95×OVP, where OVP is the rated overvoltage protection value of the bus.)

[0068] Level 2: If the voltage continues to rise and exceeds the preset derating voltage threshold, it means that the overvoltage risk can no longer be mitigated by derating. At this point, stop braking immediately and allow the system to enter a fault state.

[0069] 2. Driver temperature rise protection: Prevents driver overheating and damage.

[0070] During braking, the limited torque current IqRef is relatively large, and the power devices in the driver will generate a lot of heat due to current loss. Excessive temperature can lead to device failure. Therefore, two levels of protection are also set up:

[0071] Level 1: When the driver temperature reaches the preset derating temperature threshold, it indicates that the heat generation is close to the upper limit. At this time, linear derating is performed to reduce current loss and thus reduce the rate of heat generation. The preset derating temperature threshold can be set in advance according to device characteristics or empirical values.

[0072] Level 2: If the temperature continues to rise and exceeds the preset derating temperature threshold, it means that the device is approaching its tolerance limit. At this point, it immediately enters a fault state, stops all outputs, and prevents the driver from burning out.

[0073] In summary, when a sensorless motor experiences unexpected high-speed reverse rotation, a smooth braking is achieved through linear deceleration trajectory, torque current mapping, and current limiting. At the same time, the DC bus voltage and driver temperature are monitored in real time—preemptive derating is implemented to prevent risks, and emergency shutdown is triggered if limits are exceeded. Ultimately, a balance is found between smooth braking and hardware safety, thereby improving the reliability of system operation.

[0074] After the measured value of the standby angular velocity S150 meets the zero-speed stability criterion, it enters the initial position detection and standard start-up process, and finally operates in a closed loop.

[0075] Specifically, the zero-velocity stability criterion typically includes two core conditions (which must be met simultaneously and sustained for a certain period of time before the initial position detection and standard startup process can begin):

[0076] Speed ​​amplitude condition: The absolute value of the measured electric angular velocity is less than the preset zero speed threshold - ensuring that the motor speed is close to zero and there is no obvious rotation trend; where the preset zero speed threshold can be preset according to the test calibration value, for example, the preset zero speed threshold = 200erpm.

[0077] Speed ​​stability condition: The speed variance within a short time window is less than the preset variance threshold - excluding situations where the speed fluctuates around 0 (for example, the speed jumps between ±100 erpm due to sampling noise, which seems close to zero, but the motor has not truly stopped); The preset variance threshold can be preset according to the experimental calibration value, for example, preset variance threshold = (150 erpm)².

[0078] The above two conditions must be met continuously for N sampling cycles—to further reduce jitter and avoid misjudging zero-speed stability due to instantaneous noise; N is an integer ≥ 3. Only when both of the above requirements are met simultaneously can the motor be determined to have truly stopped, and only then can the initial position detection and standard start-up process be entered—if not met, the braking state will continue until a timeout occurs and the fault state is entered.

[0079] In summary, once the sensorless motor meets the zero-speed stability criterion through braking, the rotor starting point is first accurately located through initial position detection. Then, a stable speed is gradually established through the standard process of open-loop acceleration → closed-loop transition. Finally, it enters dual-loop control based on real-time feedback to achieve stable operation of the motor.

[0080] Figure 2 This is a schematic diagram of the signal flow of a sensorless motor reverse start control method provided in an embodiment of the present invention. The overall signal flow process of the method is as follows:

[0081] ADC sampling:

[0082] Input the three-phase current signal and three-phase voltage signal of the sensorless motor: ia, ib, ic, va, vb, vc or Vbus, temperature T. After synchronous sampling and zero bias correction by ADC, output: ia, ib, ic, va, vb, vc or Vbus; Traw.

[0083] Clarke transform:

[0084] Input: ia, ib, ic, va, vb, vc or Vbus, processed by Clarke transform, output current signal and voltage signal Iα, Iβ, Uα, Uβ in α-β coordinate system.

[0085] Phase calculation & unpacking (based on the output of the previous step):

[0086] Input: Uα, Uβ; Processing: Original phase θraw = atan2(Uβ, Uα) → Phase unwrapping → Continuous phase θcont → Differential / low-pass; Output: Estimated electric angular velocity we_adc; Application: Used as the primary reference during low speed, restart, and when the observer has not converged.

[0087] Velocity estimation (with hysteresis):

[0088] Normally, we_obs is the primary data source; in low-speed regions or when the variance of we_obs increases, we switch to we_adc. Hysteresis and one-time bias alignment are configured to avoid "jittering switching." Two scenarios are provided as examples:

[0089] Scenario A (Normal): The motor operates in a positive closed-loop manner at 4000 erpm. The variance of we_obs is extremely low, and the difference between we_adc and it is within ±1%. In this case, we_obs is used for speed loop and direction determination, while we_adc is only used for monitoring.

[0090] Scenario B (abnormal / boundary): The external wind blows the motor in the opposite direction to −1500 erpm. The controller has just been powered on, and the observer has not yet fully converged. we_adc relies on the geometric phase of unwrap to stably give the negative velocity, which serves as the main basis for inversion detection and zero velocity criterion. We will switch back to we_obs after the variance of we_obs decreases.

[0091] Reversal Detection (Debouncing):

[0092] Determine if the inversion trigger condition is met: lastCmd≈0 and cmd>0 and we_sel_slow < −reverseThreshold. After meeting the condition, debouncing is performed: for N consecutive FOC cycles, output: reverse_detected ∈ {0,1}.

[0093] Braking control:

[0094] Determine if the zero-speed stability criterion is met: |we_sel_slow| < zeroSpeedEps and var(we_sel_slow, window W) < VarEps. Continue for N samples, and after passing the test, detect the state INI_POS from the braking state BRAKE to the initial position.

[0095] INI_POS alignment and restart:

[0096] Alignment: Apply alignment current to complete electrical angle alignment; Transition: OPEN / IF_SWITCH → CLOSE closed loop; Normal regression: we_obs as the main controller, geometric link monitoring.

[0097] state machine

[0098] Process: IDLE → BRAKE → INI_POS → OPEN / IF_SWITCH → CLOSE (Exception → ERR), Timing: t_state timer for each state.

[0099] Target trajectory and IqRef generation:

[0100] Input: v0 = we_adc(T1), trajectory: v(t) = v0 + a·T1, a>0, mapping: IqRef0 = kq ·(v(t) − we_adc(T1)), constraints: |IqRef0| ≤ brakeIqMax; |ΔIqRef| ≤ brakeIqSlew / period, output: IqRef_cmd.

[0101] Overvoltage / temperature rise protection coupling:

[0102] Voltage: If Vbus ≥ 0.95·OVP → Derating IqRef_cmd; if Vbus > OVP → ERR. Temperature: Exceeding the derating temperature → Torque limit; Exceeding the cut-off temperature → ERR. Output: IqRef_safe; derate_flag / err_flag.

[0103] Current / voltage loop and modulation:

[0104] Inputs: IqRef_safe, IdRef, Iα / Iβ, θ (θobs or θcont), which are processed by SVPWM modulation and output: PWM duty cycle, which is used to control the DC bus and motor.

[0105] The technical solution provided by this invention realizes a smooth transition of the motor from high-speed reverse to stop, completely avoiding the electrical and mechanical shocks caused by direct start. Through current limiting and state reset mechanisms, it ensures that the entire braking and restart process is always carried out within the safe operating range of the system, protecting power devices and mechanical structures, improving system reliability, and significantly improving product performance without increasing hardware costs.

[0106] In some other embodiments, optionally, step S150 specifically includes:

[0107] The actual electrical angular velocity of the sensorless motor is monitored in real time. When the zero-speed stability criterion is met that "the absolute value of the actual electrical angular velocity is less than the preset zero-speed threshold, the variance of the speed short window is less than the preset variance threshold, and the preset number of samples is continuously met", the braking state ends. The initial position detection of the motor is performed. After the initial position detection is completed, the standard start-up process is entered, and finally the closed-loop operation is completed.

[0108] Initial Position Detection (INI_POS) – The core of this process is finding the rotor's starting point: Sensorless motors lack encoders and cannot directly read the rotor's physical position. When the motor starts, the stator windings need to apply current in the correct direction based on the rotor's magnetic pole position to generate positive torque. Therefore, the core purpose of initial position detection is to accurately locate the rotor's initial magnetic pole position using algorithms, calibrate the electrical angle zero point, and provide a directional reference for subsequent startup.

[0109] Optionally, the initial position detection process is as follows: apply a preset alignment current to the motor to align the motor rotor magnetic poles with the stator winding magnetic flux, and complete the electrical angle zero point calibration; after calibration, switch to OPEN / IF_SWITCH mode, gradually build up the stator current, and after the stator current stabilizes, switch to CLOSE mode, start SVPWM FOC control, and enter closed-loop operation.

[0110] Specifically, a constant alignment current is applied to specific windings of the motor stator (such as the U phase and V phase)—this current generates a magnetic field in a fixed direction in the stator; the permanent magnets of the rotor will automatically rotate to the position where the stator magnetic field aligns with the rotor magnetic poles under the magnetic pull of the stator magnetic field; at this time, the current electrical angle is recorded and calibrated as the electrical angle zero point (i.e., the electrical angle corresponding to the initial position of the rotor = 0)—which is equivalent to setting the starting point for the motor.

[0111] The key role of initial position detection: If initial position detection is skipped, the direction of stator current and rotor magnetic pole direction will randomly match, which may result in the stator magnetic field pushing the rotor, but the rotor cannot rotate due to the opposite direction or rotates in the opposite direction during startup, leading to startup failure or burnout of power devices.

[0112] Standard startup process – from static and smooth transition to dynamic:

[0113] After the initial position detection is completed, although the motor has located the rotor position, it is still in a static state. The speed needs to be gradually built up through a standard starting procedure to avoid the current surge caused by direct starting. (See also...) Figure 3 , Figure 3 This is a state transition diagram of a state machine for a sensorless motor reverse start control method provided in an embodiment of the present invention, combined with... Figure 3 As can be seen, the standard startup process typically consists of two key stages:

[0114] Phase 1: OPEN / IF_SWITCH (Open-loop startup / current switching)

[0115] OPEN (open loop): At this time, speed feedback is not relied upon. Instead, the corresponding stator current command is calculated according to the preset speed curve, and the voltage is output to the stator through SVPWM to make the motor start to rotate slowly from a standstill.

[0116] IF_SWITCH (current switching): If constant current startup is used in the initial stage, this stage completes the smooth switching from alignment current to startup current, avoiding sudden current changes.

[0117] Core objective: When the motor is first started, the speed feedback signal is weak and the noise is high, making closed-loop control unstable; open-loop start-up can smoothly accelerate through a preset curve, providing a stable speed feedback basis for subsequent closed-loop control.

[0118] Phase Two: CLOSE (Closed-Loop Preparation)

[0119] When the measured electrical angular velocity rises to the estimated electrical angular velocity, it indicates that the velocity feedback signal is sufficiently stable. At this point, the system is ready to switch from open-loop control to closed-loop control.

[0120] The controller begins to receive the measured value of the electric angular velocity as feedback, compares it with the estimated value of the electric angular velocity, and calculates the velocity error.

[0121] The limited torque current IqRef is adjusted according to the speed error (increase IqRef if the error is large, decrease IqRef if the error is small), and the stator current is precisely tracked by controlling the current loop.

[0122] The key to this stage is a smooth transition: the transition from open-loop to closed-loop requires slow adjustment of control parameters to avoid sudden changes in current or speed due to feedback intervention.

[0123] Closed-loop operation is the final working state of the motor. Its core principle is to continuously adjust control commands based on real-time feedback to ensure stable motor speed and torque. Its core logic is dual-loop control:

[0124] Velocity loop: The estimated electrical angular velocity is taken as input, compared with the measured electrical angular velocity, and the constrained torque current IqRef is output.

[0125] Current loop: Taking the constrained torque current IqRef output by the speed loop as input, it compares it with the actual stator current sampled by the ADC and outputs voltage commands Uα and Uβ;

[0126] SVPWM modulation: Converts voltage commands Uα and Uβ into switching signals for the inverter, controls the on / off state of power devices, outputs precise voltage to the stator, and drives the motor to rotate stably.

[0127] See also Figure 3 The state transition process of the state machine provided in this embodiment of the invention is as follows:

[0128] Entry requirements:

[0129] IDLE → BRAKE: Satisfies the compound inversion condition of "lastCmd≈0 and cmd>0 and meas<−Thr" and is debouncing.

[0130] BRAKE → INI_POS: Zero-rate stability holds (|we| < threshold and short-window variance is below threshold, keep N samples).

[0131] INI_POS → OPEN / IF_SWITCH: Alignment of current and electrical angle is completed.

[0132] OPEN / IF_SWITCH → CLOSE: The open-loop / current feedforward switching closed-loop condition is met.

[0133] Exit and Errors:

[0134] If OVP or temperature exceeds the limit at any stage, it will enter ERR; if BRAKE times out, it will enter ERR or return to IDLE.

[0135] Figure 4 The timing diagram for the braking phase of a sensorless motor reversal start control method provided in this embodiment of the invention is shown below. Figure 4 The timing sequence of the braking phase in this method is as follows:

[0136] T0: The conditions are met, debouncing passes → proceed to BRAKE.

[0137] T1: Set v(t) to linear deceleration; map IqRef0 and apply amplitude and slope limits → obtain IqRef_cmd.

[0138] T2: Vbus / T protection linkage is activated, and derating or ERR may be necessary if required.

[0139] T3: Enter the zero-speed window: |we| < threshold;

[0140] T4: N consecutive samples within the window are valid → BRAKE ends → Enter INI_POS.

[0141] T5: Alignment complete → OPEN / IF_SWITCH → CLOSE, reverting to normal we_obs dominance.

[0142] Ttimeout: If BRAKE exceeds the timeout period and still has not reached zero speed → ERR or return to IDLE.

[0143] Figure 5 The speed estimation path diagram for a sensorless motor reverse start control method provided in this embodiment of the invention is shown below. Figure 5 The specific process of velocity estimation using this method is as follows:

[0144] Two speed channels:

[0145] AD acquisition channels: Uα, Uβ → atan2 to get θraw → unwrap to get θcont → differential / filtering → we_ad.

[0146] Observer channel: based on the observer output we_obs (which can be combined with the back potential Ebmf).

[0147] Integration and Switching:

[0148] Normally, we_obs is the primary data source; in low-speed regions or when the variance of we_obs increases, we switch to we_ad. Hysteresis and one-time bias alignment are configured to avoid "jittering switching." Two scenarios are provided as examples:

[0149] Scenario A (Normal): The motor operates in a positive closed-loop manner at 4000 erpm. The variance of we_obs is extremely low, and the difference between we_geom and it is within ±1%. In this case, we_obs is used for speed loop and direction determination, while we_geom is only used for monitoring.

[0150] Scenario B (abnormal / boundary): The external wind blows the motor in the opposite direction to −1500 erpm. The controller has just been powered on, and the observer has not yet fully converged. we_ad relies on the geometric phase of unwrap to stably give the negative velocity, which serves as the main basis for inversion detection and zero velocity criterion. We switch back to we_obs after the variance of we_obs decreases.

[0151] Dual-bandwidth low-pass: The we direction and zero-rate criteria use a lower bandwidth (e.g., 60 Hz) to enhance stability; fast quantities such as Ebmf or switching boundaries use a higher bandwidth (e.g., 200 Hz) to preserve response.

[0152] Core function: Unwrap eliminates the "page-turning jump" of atan2 in ±π, ensuring that the geometric channel does not generate false high-velocity pulses when crossing quadrants, thus providing a stable and reliable reference for direction and zero velocity determination.

[0153] In some other embodiments, the optional reverse start control method for a sensorless motor further includes:

[0154] When the zero-speed stability criterion of "the absolute value of the actual value of the electric angular velocity is less than the preset zero-speed threshold, the variance of the speed short window is less than the preset variance threshold, and the preset number of samples is continuously met" is not satisfied, the braking duration is monitored; if the braking duration exceeds the preset braking timeout threshold and the zero-speed stability criterion is still not met, the system enters a fault state.

[0155] The preset braking timeout threshold can be pre-set according to the experimental calibration value. For example, the preset braking timeout threshold is 1000ms.

[0156] Optionally, the specific implementation of phase unpacking is as follows: record the original phase of the previous cycle, calculate the difference between the original phase of the current cycle and the original phase of the previous cycle, and if the difference exceeds the range of ±π, then add ±2π compensation to the original phase of the current cycle, and accumulate the compensated phase into the continuous phase to eliminate the phase jump caused by the Atan2 algorithm.

[0157] The technical solution provided by this invention achieves a smooth transition of the motor from high-speed reverse rotation to a complete stop, completely avoiding the electrical and mechanical shocks caused by direct starting. Current limiting and state reset mechanisms ensure that the entire braking and restart process always occurs within the system's safe operating range, protecting power devices and mechanical structures and improving system reliability. Software parameters allow for flexible configuration of preset reverse thresholds, deceleration, and holding time, enabling this technical solution to quickly adapt to motors with different power and inertia, and various application scenarios. This significantly improves product performance without increasing hardware costs.

[0158] Figure 6 This is a schematic diagram of a sensorless motor reversing start control device provided in an embodiment of the present invention. (See attached diagram.) Figure 6 The device includes a data acquisition and coordinate transformation module 610, a phase and electric angular velocity calculation module 620, a reversal detection module 630, a braking control module 640, and a zero-speed determination and start-up module 650.

[0159] The acquisition and coordinate transformation module 610 is used to acquire the three-phase current signal and three-phase voltage signal of the sensorless motor, and to perform Clarke transformation on the three-phase current signal and three-phase voltage signal to obtain the voltage signal in the α-β coordinate system.

[0160] The phase and electrical angular velocity calculation module 620 is used to calculate the original phase based on the voltage signal in the α-β coordinate system. It uses the Atan2 algorithm to calculate the original phase, performs phase unpacking processing on the original phase to obtain the continuous phase, performs differential operation on the continuous phase, and / or selects the observed angular velocity output by the motor speed observer to obtain the estimated value of the electrical angular velocity of the sensorless motor.

[0161] The reverse detection module 630 is used to determine whether there is an unexpected high-speed reverse phenomenon in a sensorless motor by combining preset reverse trigger conditions.

[0162] When the braking control module 640 determines that there is an unexpected high-speed reverse phenomenon in the sensorless motor, it performs linear deceleration on the real-time monitored measured value of the electric angular velocity to generate a linear deceleration trajectory and maps the linear deceleration trajectory to a constrained torque current.

[0163] The zero-speed determination and startup module 650 is used to enter the initial position detection and standard startup process after the measured value of the standby angular velocity meets the zero-speed stability criterion, and finally to achieve closed-loop operation.

[0164] The reverse start control device for a sensorless motor provided in this embodiment of the invention can execute the reverse start control method for a sensorless motor provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the method.

[0165] Figure 7 This is a schematic diagram of an electronic device for a sensorless motor reversing start control method provided in an embodiment of the present invention. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices (such as helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the invention described and / or claimed herein.

[0166] like Figure 7 As shown, the electronic device 10 includes at least one processor 11 and a memory, such as a read-only memory (ROM) 12 or a random access memory (RAM) 13, communicatively connected to the at least one processor 11. The memory stores computer programs executable by the at least one processor. The processor 11 can perform various appropriate actions and processes based on the computer program stored in the ROM 12 or loaded from storage unit 18 into the RAM 13. The RAM 13 can also store various programs and data required for the operation of the electronic device 10. The processor 11, ROM 12, and RAM 13 are interconnected via a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0167] Multiple components in electronic device 10 are connected to I / O interface 15, including: input unit 16, such as keyboard, mouse, etc.; output unit 17, such as various types of displays, speakers, etc.; storage unit 18, such as disk, optical disk, etc.; and communication unit 19, such as network card, modem, wireless transceiver, etc. Communication unit 19 allows electronic device 10 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0168] Processor 11 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. Processor 11 performs the various methods and processes described above, such as a reverse start control method for a sensorless motor.

[0169] In some embodiments, the reverse start control method for a sensorless motor can be implemented as a computer program tangibly contained in a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program can be loaded and / or installed on electronic device 10 via ROM 12 and / or communication unit 19. When the computer program is loaded into RAM 13 and executed by processor 11, one or more steps of the reverse start control method for a sensorless motor described above can be performed. Alternatively, in other embodiments, processor 11 can be configured to perform the reverse start control method for a sensorless motor by any other suitable means (e.g., by means of firmware).

[0170] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), payload-programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0171] Computer programs used to implement the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0172] In the context of this invention, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0173] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the electronic device. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0174] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as data servers), or middleware components (e.g., application servers), or frontend components (e.g., user computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., communication networks). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0175] A computing system can include clients and servers. Clients and servers are generally located far apart and typically interact through communication networks. The client-server relationship is created by computer programs running on the respective computers and having a client-server relationship with each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a hosting product within the cloud computing service system to address the shortcomings of traditional physical hosts and VPS services, such as high management difficulty and weak business scalability.

[0176] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0177] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for controlling the reverse start of a sensorless motor, characterized in that, include: The three-phase current signal and three-phase voltage signal of the sensorless motor are acquired, and the Clarke transform is performed on the three-phase current signal and the three-phase voltage signal to obtain the voltage signal in the α-β coordinate system; Based on the voltage signal in the α-β coordinate system, the Atan2 algorithm is used to calculate the original phase, the phase unpacking process is performed on the original phase to obtain the continuous phase, the differential operation is performed on the continuous phase, and / or the observed angular velocity output by the motor speed observer is selected to obtain the estimated value of the electric angular velocity of the sensorless motor. Based on the preset reversal trigger conditions, determine whether there is an unexpected high-speed reversal phenomenon in the sensorless motor; When it is determined that the sensorless motor has an unexpected high-speed reverse phenomenon, the measured value of the real-time monitored electric angular velocity is linearly decelerated to generate a linear deceleration trajectory, and the linear deceleration trajectory is mapped to a restricted torque current, and amplitude and slope limits are applied to the restricted torque current. Once the measured electric angular velocity value meets the zero-speed stability criterion, the initial position detection and standard start-up process begins, ultimately resulting in closed-loop operation.

2. The reverse start control method for a sensorless motor according to claim 1, characterized in that, Based on preset reversal trigger conditions, determining whether a sensorless motor exhibits unexpected high-speed reversal includes: Determine whether the composite condition of "historical command speed is approximately zero, current command speed is positive, measured electrical angular velocity is negative and the measured electrical angular velocity exceeds the preset reversal threshold" is met. If it is met, it is determined that the sensorless motor has an unexpected high-speed reversal phenomenon.

3. The reverse start control method for a sensorless motor according to claim 1, characterized in that, Once the actual value of the electric angular velocity meets the zero-velocity stability criterion, the initial position detection and standard start-up process begins, and the final closed-loop operation includes: Real-time monitoring of the actual electrical angular velocity of a sensorless motor; When the zero-speed stability criterion of "the absolute value of the actual value of the electric angular velocity is less than the preset zero-speed threshold, the variance of the velocity short window is less than the preset variance threshold, and the preset number of samples is maintained" is met, the braking state ends. Perform initial position detection of the motor, and after the initial position detection is completed, enter the standard start-up process, and finally run in a closed loop.

4. The reverse start control method for a sensorless motor according to claim 1, characterized in that, The process of mapping the linear deceleration trajectory to a constrained torque current also includes: The braking process is coupled with DC bus overvoltage protection and driver temperature rise protection strategies. If the DC bus voltage reaches the preset derating voltage threshold, the braking torque will be reduced; if the DC bus voltage exceeds the preset voltage threshold, a fault state will be entered. If the driver temperature reaches the preset derating temperature threshold, it will be linearly drated; if the driver temperature reaches the preset temperature threshold, it will enter a fault state.

5. The reverse start control method for a sensorless motor according to claim 2, characterized in that, Also includes: Only when the composite condition is met for N consecutive FOC cycles is it finally determined that the sensorless motor has an unexpected high-speed reverse phenomenon; and the preset reverse threshold is set to max(300erpm,0.5%・MTR_MAX_SPD), where MTR_MAX_SPD is the rated maximum speed of the motor, and N is an integer ≥3.

6. The reverse start control method for a sensorless motor according to claim 4, characterized in that, The preset derating voltage threshold is set to 0.95 × OVP, where OVP is the rated overvoltage protection threshold of the DC bus.

7. The reverse start control method for a sensorless motor according to claim 3, characterized in that, Also includes: When the zero-speed stability criterion of "the absolute value of the actual value of the electric angular velocity is less than the preset zero-speed threshold, the variance of the speed short window is less than the preset variance threshold, and the preset number of samples is continuously met" is not satisfied, the braking duration is monitored. If the braking duration exceeds the preset braking timeout threshold and the zero-speed stability criterion is still not met, the system enters a fault state.

8. The reverse start control method for a sensorless motor according to claim 1, characterized in that, The specific implementation of phase unpacking is as follows: record the original phase of the previous cycle, calculate the difference between the original phase of the current cycle and the original phase of the previous cycle, and if the difference exceeds the range of ±π, then add ±2π compensation to the original phase of the current cycle, and accumulate the compensated phase into the continuous phase to eliminate the phase jump caused by the Atan2 algorithm.

9. The reverse start control method for a sensorless motor according to claim 1, characterized in that, The specific process of initial position detection is as follows: apply a preset alignment current to the motor to align the motor rotor magnetic poles with the stator winding magnetic flux, and complete the electrical angle zero point calibration; after calibration, switch to OPEN / IF_SWITCH mode, gradually build up the stator current, and after the stator current stabilizes, switch to CLOSE mode, start SVPWM FOC control, and enter closed-loop operation.

10. A reverse start control device for a sensorless motor, characterized in that, include: The acquisition and coordinate transformation module is used to acquire the three-phase current signal and the three-phase voltage signal of the sensorless motor, and to perform Clarke transformation on the three-phase current signal and the three-phase voltage signal to obtain the voltage signal in the α-β coordinate system. The phase and electric angular velocity calculation module is used to calculate the original phase based on the voltage signal in the α-β coordinate system using the Atan2 algorithm, perform phase unpacking processing on the original phase to obtain a continuous phase, perform differential operation on the continuous phase, and / or select the observed angular velocity output by the motor speed observer to obtain the estimated value of the electric angular velocity of the sensorless motor. A reversal detection module is used to determine whether a sensorless motor exhibits unexpected high-speed reversal by combining preset reversal trigger conditions. The braking control module is used to generate a linear deceleration trajectory by performing linear deceleration on the real-time monitored measured value of the electric angular velocity when it is determined that the sensorless motor has an unexpected high-speed reverse phenomenon, and to map the linear deceleration trajectory into a restricted torque current, and to apply amplitude limiting and slope limiting to the restricted torque current. The zero-velocity determination and startup module is used to enter the initial position detection and standard startup process after the measured value of the electric angular velocity meets the zero-velocity stability criterion, and finally to operate in a closed loop.

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