Vehicle permanent magnet synchronous motor rotor initial position identification method, terminal and medium

Abstract

The invention discloses a method for identifying the initial position of a rotor of a permanent magnet synchronous motor for a vehicle, a terminal and a medium. The method comprises a rough identification stage and a fine identification stage. During rough identification, fixed duty ratio PWM voltage of U-phase input and VW-phase output is applied to a three-phase winding of the no-load motor, and a filtering value fed back by a rotary transformer is read as a rough initial position angle after a rotor is locked; and during fine identification, constructing a search interval by taking the rough angle as the center, generating a test angle through iteration under the condition that the D-axis current is 0 and the Q-axis current is fixed, recording the steady-state rotating speed, and updating the interval at the angle corresponding to the maximum rotating speed until the interval reaches the preset precision. The method does not need extra hardware, is suitable for the surface-mounted motor, is high in precision, and is easy for engineering realization.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor technology, and in particular to a method, terminal and medium for identifying the initial rotor position of a permanent magnet synchronous motor for vehicles. Background Technology

[0002] High-precision, high-performance vector control of automotive permanent magnet synchronous motor (PMSM) drive systems relies heavily on accurate acquisition of the rotor's initial position. The industry commonly uses a rotary transformer to detect the rotor position of the PMSM. However, an unavoidable angular deviation exists between the motor's stator zero position and the rotary transformer's stator zero position, and this deviation is random. Ignoring this angular deviation during startup can lead to motor start-up failure, low efficiency, insufficient output torque, and other problems. Therefore, controllers for automotive PMSMs must possess the ability to identify the rotor's initial position.

[0003] Currently, existing technologies for identifying the initial position of permanent magnet synchronous motor (PMSM) rotors mainly include back EMF detection, rotor positioning, and high-frequency signal injection. Back EMF detection is further divided into offline and online methods: offline detection requires additional equipment and is only suitable for research and development scenarios; online identification requires an additional back EMF detection circuit, increasing hardware costs. The rotor positioning method stops the rotor at a predetermined position by supplying DC current to the motor windings, but this method requires rotor rotation, and is affected by factors such as rotor inertia, resulting in a deviation between the final locked position and the actual initial zero position. The high-frequency signal injection method detects rotor position based on salient pole characteristics, but it requires polarity determination; incorrect determination can lead to a 180° deviation between the estimated and actual positions, and this method is not suitable for surface-mounted PMSMs with insignificant salient pole characteristics. These issues limit the practicality and reliability of initial position identification for automotive PMSM rotors. Summary of the Invention

[0004] To address the above problems, this invention provides a method for identifying the initial rotor position of a permanent magnet synchronous motor for vehicles. This method is compatible with the rotor initial position identification requirements of surface-mounted motors and improves identification accuracy by utilizing the motor's own rotational resistance and open-loop speed control testing.

[0005] In a first aspect, the present invention provides a method for identifying the initial rotor position of a permanent magnet synchronous motor for vehicles, comprising the following steps: S1, Coarse Identification Stage: Apply a PWM voltage waveform with a fixed duty cycle to the three-phase windings of the unloaded motor, where the U phase is the input and the VW phase is the output. After locking the rotor, read the filter value fed back by the rotary transformer as the coarse initial position angle. S2, Fine Identification Stage: Construct a fine search range centered on the rough initial position angle. Under the condition that the D-axis current is 0 and the Q-axis current is a preset fixed current value, iteratively search for the rotor position angle corresponding to the maximum steady-state speed until the preset accuracy is achieved.

[0006] Furthermore, the fine search interval is [AngleMin, AngleMax], where AngleMin = Angle0 – DTheta, AngleMax = Angle0 + DTheta, DTheta is the maximum error value of the coarse identification, and Angle0 is the coarse initial position angle.

[0007] By clearly defining a fine search range [AngleMin, AngleMax] centered on the coarse initial position angle Angle0 and covering the maximum coarse identification error DThet, it is possible to ensure that the fine identification search range accurately covers the possible initial position error range. This avoids both the inefficiency caused by an excessively large search range and the omission of the true initial position due to an excessively small range. This lays the foundation for subsequent efficient and accurate iterative searches and improves the stability and reliability of rotor initial position identification.

[0008] Furthermore, the step of iteratively searching for the rotor position angle corresponding to the maximum steady-state rotational speed until a preset accuracy is achieved specifically includes: S21, generate 5 test angles with a step size of (AngleMax–AngleMin) / 4, and run the motor to steady state at each test angle, and record the speed value; S22, Select the angle corresponding to the maximum rotational speed, and update the search interval with this angle and its two adjacent test angles; S23, repeat S21-S22 until the step size is less than the preset accuracy threshold. At this point, the angle corresponding to the maximum rotational speed is the initial position of the rotor.

[0009] Through the above steps, the initial position angle is gradually and accurately locked. This iterative search method utilizes the correlation between motor rotational resistance and speed (the maximum speed corresponds to the optimal initial position). By using a fixed step size and interval update rules, it can quickly narrow the search range (focusing on a smaller interval with each iteration) while ensuring that the final identification accuracy meets the preset requirements. The operation logic is clear and the engineering implementation is simple, solving the problems of insufficient accuracy or low search efficiency of existing methods. It is also applicable to surface-mounted permanent magnet synchronous motors, thus broadening the application scenarios.

[0010] Furthermore, the value of DTheta is 10°, which is determined based on the statistical results of the maximum coarse identification deviation caused by the mechanical installation error of the motor and the rotor inertia, and is applicable to surface-mounted permanent magnet synchronous motors.

[0011] The value of DTheta is set to 10°, determined based on statistical results of the maximum coarse identification deviation caused by motor mechanical installation errors and rotor inertia. This value is specifically applicable to surface-mounted permanent magnet synchronous motors, effectively covering the typical error range of surface-mounted motors in the coarse identification stage. This value avoids missing the true initial position due to an excessively small range, while also preventing iterative redundancy caused by an excessively large range, significantly improving the adaptability and stability for identifying the initial rotor position of surface-mounted motors.

[0012] Furthermore, the preset fixed current value must be such that, at any rotor position angle within the fine search range, this current value can drive the unloaded motor rotor to rotate.

[0013] The aforementioned limitations explicitly pre-set a fixed current value to ensure that the rotor can be rotated at any position within the fine search range, guaranteeing stable operation of the motor and output of a detectable steady-state speed at each test angle. This setting avoids situations where the rotor cannot rotate or its speed is unstable due to insufficient current, ensuring the validity and comparability of speed data at each test point. It provides reliable data support for determining the optimal initial position through the maximum speed, further improving the accuracy of the identification results and the reliability of the testing process.

[0014] Furthermore, the step of reading the filtered value fed back from the rotary transformer as a coarse initial position angle includes: The rotor position data output from the rotary transformer is continuously collected and processed by median filtering to eliminate instantaneous interference errors. The median value is then taken as the rough initial position angle.

[0015] By continuously acquiring the output data of the rotary transformer and performing median filtering (taking the median value), outliers caused by transient interference (such as mechanical vibration, signal noise, etc.) can be effectively eliminated, reducing the measurement error of the coarse initial position angle. This provides a more reliable initial reference for the subsequent fine identification stage, reducing the cumulative error from the source and improving the accuracy and stability of the entire rotor initial position identification process.

[0016] Secondly, the present invention also provides a computer terminal, comprising: Memory, which stores executable programs; A processor is configured to run the program, wherein the program executes the rotor initial position identification method for a vehicle permanent magnet synchronous motor during runtime.

[0017] Thirdly, the present invention also provides a computer-readable storage medium comprising a stored executable program, wherein, when the executable program is executed, it controls the device where the computer-readable storage medium is located to execute the rotor initial position identification method for a vehicle permanent magnet synchronous motor.

[0018] Fourthly, the present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the rotor initial position identification method for a vehicle permanent magnet synchronous motor.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This method achieves coarse identification by applying a PWM voltage with a fixed duty cycle to the unloaded motor, without the need for additional hardware equipment or detection circuits, reducing costs and making the algorithm simple and easy to implement; In the fine identification stage, an interval is constructed with the coarse angle as the center, and the position corresponding to the maximum steady-state speed is iteratively searched under zero current on the D-axis and fixed current on the Q-axis. It does not depend on the salient pole characteristics of the motor and is suitable for surface-mounted permanent magnet synchronous motors, solving the application limitations of the high-frequency signal injection method. At the same time, the accuracy is gradually improved through iterative search, avoiding the deviation caused by rotational inertia and other factors in the rotor positioning method, thus improving the identification accuracy and stability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0023] This invention provides a method for identifying the initial rotor position of a permanent magnet synchronous motor for vehicles, such as... Figure 1 As shown, the specific steps include the following: S1, Coarse Identification Stage: Apply a PWM voltage waveform with a fixed duty cycle to the three-phase windings of the unloaded motor, with U-phase input and VW-phase output. After locking the rotor, read the filter value fed back from the rotary transformer as the coarse initial position angle.

[0024] Specifically, the motor controller applies a PWM voltage with a certain duty cycle to the motor via the U-phase input and the VW-phase output to lock the motor rotor instead of the DC voltage. This duty cycle value can be determined during the initial calibration based on the actual output current. It varies slightly depending on the motor, but can generally be set to 5%. After the motor rotor comes to a stop, the rotor position data output from the rotary transformer is continuously collected. The collected data is then processed by median filtering to eliminate instantaneous interference errors. The processed median value is taken as the initial position angle Angle0 for rough identification.

[0025] S2, Fine Identification Stage: Construct a fine search range centered on the rough initial position angle. Under the condition that the D-axis current is 0 and the Q-axis current is a preset fixed current value, iteratively search for the rotor position angle corresponding to the maximum steady-state speed until the preset accuracy is achieved.

[0026] Specifically, a fine search interval [AngleMin, AngleMax] is constructed with the rough initial position angle Angle0 as the center, where AngleMin = Angle0 – DTheta, AngleMax = Angle0 + DTheta, and DTheta is the maximum error value of the rough identification, which is generally converted into an angle value of 10°. This value is determined based on the statistical results of the maximum rough identification deviation caused by the mechanical installation error of the motor and the rotor inertia, and is applicable to surface-mounted permanent magnet synchronous motors.

[0027] The step of iteratively searching for the rotor position angle corresponding to the maximum steady-state rotational speed until a preset accuracy is achieved specifically includes: S21, generate 5 test angles with a step size of (AngleMax–AngleMin) / 4, and run the motor to steady state at each test angle, recording the speed value.

[0028] Specifically, within the fine search range [AngleMin, AngleMax], five corresponding initial search position values ​​are generated with a step size of (AngleMax–AngleMin) / 4, which are five test angles. The operation test is carried out based on these five test angles, and the corresponding rotor steady-state speed is recorded during the test.

[0029] During this test, the D-axis current needs to be set to 0, and the Q-axis current needs to be set to a preset fixed current value IqSet0. IqSet0 satisfies the requirement that this current value can drive the unloaded motor rotor to rotate at any rotor position angle within the fine search range.

[0030] S22, select the angle corresponding to the maximum rotational speed, and update the search interval with this angle and its two adjacent test angles.

[0031] Specifically, a new search interval is formed by selecting the test angle corresponding to the maximum steady-state rotational speed from the five test angles, along with the two test angles closest to that value. The maximum value is used as the reference value. The minimum value is used as ,by Two new test angles were inserted on both sides of the middle value for the step size interval, and the corresponding data were recorded.

[0032] S23, repeat S21-S22 until the step size is less than the preset accuracy threshold. At this point, the angle corresponding to the maximum rotational speed is the initial position of the rotor.

[0033] Specifically, when If the value is less than the preset accuracy threshold, the rotor initial position identification is determined to be complete. The rotor initial position test angle corresponding to the maximum steady-state speed is taken as the rotor initial position identification value based on the 5 test angles tested.

[0034] The principle of the above method is described as follows: When testing under the condition of no motor shaft, firstly, the motor rotor is fixed to the zero position MotAngle=MotAngle1 by a voltage vector with a fixed duty cycle (001, i.e., positive voltage output of U phase, negative voltage output of VW phase or zero voltage can be used, and zero voltage is directly set here). (In reality, due to mechanical and inertial reasons, the motor rotor can only be pulled to a range of approximately ±10° of the rotor zero position). However, the motor zero position obtained under this condition is sufficient to drive the motor to run when the motor shaft is empty.

[0035] Based on the coarse zero-point value MotAngle1, a fixed value is applied to the torque current, such as 3% of the rated current, which can generally drive the motor to a certain steady-state speed. Then, based on MotAngle1, an angle search is performed within the range of MotAngle1±10°. Only when the searched angle value MotAngle2∈[MotAngle1-10°, MotAngle1+10°] matches the actual motor rotor angle value, the given 3% current is a complete torque current component. This allows the motor speed to reach its maximum value under steady-state operation based on the 3% current. The value obtained at this moment is the actual initial angle of the motor rotor.

[0036] In this embodiment, the specific implementation process of the method is as follows: Step 1: First, obtain the initial position angle value Angle0 = 1.0 rad through rough identification.

[0037] Step 2: Search within a range of ±10° (corresponding to ±0.175 rad) to determine the search angle range as [AngleMin, AngleMax] = [0.825, 1.175] rad.

[0038] Step 3: Divide the above angle range [0.825, 1.175] rad into four segments, or five points, namely [0.825, 0.9125, 1.0, 1.0875, 1.175] rad; where DTheta = 0.0875 rad.

[0039] Step 4: Using the above values ​​as zero points respectively, drive the motor shaft to run with 3% of the current as the torque current (Q-axis current).

[0040] Step 5: If the speeds corresponding to the above values ​​are [1000, 1050, 1060, 1070, 1050] RPM, then the search zero-point value corresponding to the maximum speed of 1070 RPM is closest to the true zero-point value. Taking the search zero-point value corresponding to this value as the center, the search zero-point values ​​corresponding to speeds of 1060 RPM and 1050 RPM on both sides are the boundaries. After the average calculation, the next zero-point value to be searched is inserted to form a new search interval, specifically [1.0, 1.04375, 1.0875, 1.13125, 1.175] rad; here DTheta = 0.04375 rad.

[0041] Step Six: Repeat Steps Four and Five. This time, the speed to be tested only requires the two newly inserted search zero values, namely 1.04375 rad and 1.13125 rad, which correspond to the steady-state speeds of the motor running with the idle shaft driven by 3% current as torque current.

[0042] Step 7: If the search rotational speeds corresponding to the search zero points [1.0, 1.04375, 1.0875, 1.13125, 1.175] rad in Step 6 are [1060, 1075, 1070, 1060, 1050] RPM, then the actual initial angle after further search is in the range [1.0, 1.0875] rad; repeat Step 5 to divide this range equally, i.e., [1.0, 1.021875, 1.04375, 1.065625, 1.0875] rad; here DTheta = 0.021875 rad.

[0043] Step 8: Repeat the above search steps until DTheta < 0.01745 rad. That is, the angle deviation range found at this time has reached ±1°. The search zero angle corresponding to the highest speed during the search process is the initial rotor zero angle value that needs to be obtained.

[0044] Step 9: If a more precise angle identification is required, the lower limit of DTheta can be increased in the search loop to further accurately search and identify the rotor zero-position angle.

[0045] Furthermore, based on the above method, a real-time correction stage is added during operation: during the operation of the motor after startup, a preset time T is used to correct the error. C Initial position angle verification is triggered. By calculating the Q-axis current error, it is input into the PID controller to generate the angle correction, dynamically updating the rotor's initial position angle. This mechanism can eliminate the cumulative error of the initial angle caused by temperature drift or mechanical stress during operation, improving the long-term stability of the system.

[0046] Specifically, after the motor starts, every preset time T C Trigger initial position angle verification; Get the current Q-axis current error ,in This is the Q-axis current command value. This is the Q-axis current feedback value; Will Input to PID controller, output angle correction. ; Where Kp is the proportional coefficient, used to amplify the current error; Ki is the integral coefficient, used to accumulate historical errors and eliminate steady-state deviations; and Kd is the differential coefficient, used to predict error trends and suppress oscillations.

[0047] Update rotor initial position angle θ t =θ t-1 + , where θ t-1 This is the initial position angle of the rotor before the update.

[0048] During the real-time correction phase, the initial position angle is dynamically calibrated by periodically monitoring the Q-axis current error and combining it with PID adjustment, which solves the angle drift problem caused by long-term operation, significantly improving the robustness and control accuracy of the system, and is especially suitable for temperature changes and vibration conditions in vehicle environments.

[0049] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for identifying the initial rotor position of a vehicle permanent magnet synchronous motor, characterized in that, Includes the following steps: S1, Coarse Identification Stage: Apply a PWM voltage waveform with a fixed duty cycle to the three-phase windings of the unloaded motor, where the U phase is the input and the VW phase is the output. After locking the rotor, read the filter value fed back by the rotary transformer as the coarse initial position angle. S2, Fine Identification Stage: Construct a fine search range centered on the rough initial position angle. Under the condition that the D-axis current is 0 and the Q-axis current is a preset fixed current value, iteratively search for the rotor position angle corresponding to the maximum steady-state speed until the preset accuracy is achieved.

2. The rotor initial position identification method for a vehicle permanent magnet synchronous motor as described in claim 1, characterized in that, The fine search interval is [AngleMin, AngleMax], where AngleMin = Angle0 – DTheta, AngleMax = Angle0 + DTheta, DTheta is the maximum error value of the coarse identification, and Angle0 is the coarse initial position angle.

3. The rotor initial position identification method for a vehicle permanent magnet synchronous motor as described in claim 2, characterized in that, The step of iteratively searching for the rotor position angle corresponding to the maximum steady-state rotational speed until a preset accuracy is achieved specifically includes: S21, generate 5 test angles with a step size of (AngleMax–AngleMin) / 4, and run the motor to steady state at each test angle, and record the speed value; S22, Select the angle corresponding to the maximum rotational speed, and update the search interval with this angle and its two adjacent test angles; S23, repeat S21-S22 until the step size is less than the preset accuracy threshold. At this point, the angle corresponding to the maximum rotational speed is the initial position of the rotor.

4. The method for identifying the initial rotor position of a vehicle permanent magnet synchronous motor as described in claim 2, characterized in that, The value of DTheta is 10°. This value is determined based on the statistical results of the maximum coarse identification deviation caused by the mechanical installation error of the motor and the rotor inertia, and is applicable to surface-mounted permanent magnet synchronous motors.

5. The rotor initial position identification method for a vehicle permanent magnet synchronous motor as described in claim 1, characterized in that, The preset fixed current value must be such that, within any rotor position angle within the fine search range, this current value can drive the unloaded motor rotor to rotate.

6. The rotor initial position identification method for a vehicle permanent magnet synchronous motor as described in claim 1, characterized in that, The step of reading the filtered value fed back from the rotary transformer as a coarse initial position angle includes: The rotor position data output from the rotary transformer is continuously collected and processed by median filtering to eliminate instantaneous interference errors. The median value is then taken as the rough initial position angle.

7. A computer terminal, characterized in that, include: Memory, which stores executable programs; A processor for running the program, wherein the program, when running, performs the method according to any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored executable program, wherein, when the executable program is executed, it controls the device on which the computer-readable storage medium is located to perform the method according to any one of claims 1 to 6.

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