Vehicle torque method and system based on motor temperature online correction

Abstract

The invention relates to the field of vehicle torque regulation and control, in particular to a vehicle torque method and system based on motor temperature online correction. The method comprises the following steps: firstly, based on measured permanent magnet flux linkages of a motor winding of a to-be-measured vehicle at different temperatures, calculating a current compensation coefficient of each temperature, constructing a mapping relation table, selecting a real-time current compensation coefficient at the current moment from the mapping relation table according to temperature data of the motor winding collected in real time, and calculating the current compensation coefficient at the current moment according to the selected real-time current compensation coefficient. And using the real-time current compensation coefficient to correct the original quadrature-axis current at the current moment received by the controller of the motor winding to obtain the corrected quadrature-axis current at the current moment, and driving the motor winding to output the corrected torque at the current moment based on the corrected quadrature-axis current at the current moment and in combination with an FOC algorithm. The permanent magnet flux linkage attenuation caused by temperature rise can be compensated, so that the torque output by the motor winding is closer to an expected value.

Description

Technical Field

[0001] This invention relates to the field of vehicle torque regulation, and specifically to a vehicle torque method and system based on online correction of motor temperature. Background Technology

[0002] Currently, electric vehicles commonly employ permanent magnet synchronous motors (PMSMs) combined with field-oriented control (FOC) algorithms to achieve high-performance torque and speed control. One of the core principles of FOC is to precisely control motor torque by controlling the direct-axis and quadrature-axis currents. However, in real-world operating conditions, electric vehicles, such as electric forklifts, subjected to harsh conditions like frequent starts and stops and heavy-duty handling, generate significant heat in their motor windings. This leads to a substantial increase in motor temperature, affecting torque output, motor performance, and even potential damage.

[0003] Most existing FOC control systems use fixed-parameter motor models. However, for electric vehicles operating under harsh conditions such as frequent starts and stops and heavy-duty handling, the motor windings generate a large amount of heat, causing the motor temperature to rise significantly. This leads to the drift (e.g., attenuation) of motor model parameters such as permanent magnet flux linkage in the FOC control system with temperature changes. Consequently, the FOC control system using fixed-parameter motor models does not consider the impact of temperature changes, causing the calculated quadrature-axis current to deviate from the actual value. This, in turn, reduces the accuracy of motor torque control, causing the torque output to deviate from the expected value. Summary of the Invention

[0004] To address the technical problem that temperature changes cause permanent magnet flux drift, leading to deviations in the quadrature-axis current calculated by the FOC control system using a fixed-parameter motor model, and consequently, deviations in motor torque output from the expected value, this invention aims to provide a vehicle torque method and system based on online motor temperature correction. The specific technical solution adopted is as follows:

[0005] This invention proposes a vehicle torque method based on online correction of motor temperature, the method comprising:

[0006] Measure the permanent magnet flux linkage of the motor windings of the vehicle under test at different temperatures;

[0007] Based on the permanent magnet flux linkage at each temperature, the current compensation coefficient for each temperature is obtained; and a mapping table containing temperature and current compensation coefficients is constructed.

[0008] The temperature data of the motor winding is acquired in real time. Based on the temperature data at the current moment, the real-time current compensation coefficient at the current moment is selected from the mapping table. The real-time current compensation coefficient is used to correct the original quadrature-axis current received by the controller of the motor winding at the current moment, so as to obtain the corrected quadrature-axis current at the current moment.

[0009] Based on the corrected quadrature-axis current at the current moment, and combined with the FOC algorithm, the drive motor winding outputs the corrected torque at the current moment.

[0010] Furthermore, the current compensation coefficient for each temperature includes:

[0011] The standard value of magnetic flux at the preset standard temperature is used as the numerator, and the magnetic flux of the permanent magnet at each temperature is used as the denominator. The ratio is used as the current compensation coefficient for each temperature.

[0012] Furthermore, the construction of the mapping table containing temperature and current compensation coefficients includes:

[0013] The current compensation coefficients for each temperature are interpolated, and all the interpolated temperatures and their corresponding current compensation coefficients are recorded in a mapping table.

[0014] Furthermore, the mapping table needs to be burned into the controller of the motor windings.

[0015] Furthermore, the controller is an MCU controller.

[0016] Furthermore, selecting the real-time current compensation coefficient from the mapping table includes:

[0017] Select the current compensation coefficient corresponding to the temperature that is the same as the temperature data at the current moment from the mapping table, and use it as the real-time current compensation coefficient at the current moment.

[0018] Furthermore, obtaining the corrected quadrature-axis current at the current moment includes:

[0019] The product of the real-time current compensation coefficient at the current moment and the original quadrature-axis current received by the controller of the motor winding at the current moment is used as the corrected quadrature-axis current at the current moment.

[0020] Furthermore, the corrected torque output by the drive motor winding at the current moment includes:

[0021] The corrected quadrature-axis current at the current moment and the original direct-axis current received by the controller are input into the FOC algorithm, and the controller executes the drive signal generated by the FOC algorithm to drive the motor windings to output the corrected torque at the current moment.

[0022] Furthermore, the original quadrature-axis current is determined by the controller based on motor parameters and a preset motor model.

[0023] The present invention also proposes a vehicle torque system based on online correction of motor temperature. The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of any one of the vehicle torque methods based on online correction of motor temperature.

[0024] The present invention has the following beneficial effects:

[0025] This invention addresses the issue that temperature variations can cause permanent magnet flux drift, leading to deviations in the quadrature-axis current calculated by the FOC control system using a fixed-parameter motor model. This results in unstable motor torque output. Therefore, this invention first measures the permanent magnet flux of the motor windings at different temperatures to provide data support for subsequent current compensation. Then, it calculates the current compensation coefficient for each temperature. This coefficient can then be used to correct the quadrature-axis current affected by temperature rise. A mapping table containing temperature and current compensation coefficients is constructed, allowing for real-time extraction of the current compensation coefficient from the table to correct the quadrature-axis current during online torque correction. Real-time temperature monitoring of the motor windings is performed, and the corresponding real-time current compensation coefficient is extracted from the mapping table based on the current temperature data. This real-time current compensation coefficient is then used to correct the original quadrature-axis current that has deviated from its true value due to permanent magnet flux drift caused by temperature. This compensates for the permanent magnet flux attenuation caused by temperature rise, resulting in a corrected quadrature-axis current closer to the true value. Combined with the FOC algorithm, this drives the motor windings to output torque closer to the desired value. Attached Figure Description

[0026] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart illustrating a vehicle torque method based on online correction of motor temperature, provided as an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structural framework of a vehicle torque method based on online correction of motor temperature, provided in one embodiment of the present invention. Detailed Implementation

[0029] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a vehicle torque method and system based on online motor temperature correction proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0031] The following description, in conjunction with the accompanying drawings, details a specific scheme for a vehicle torque method and system based on online motor temperature correction provided by the present invention.

[0032] Please see Figure 1 The diagram illustrates a flowchart of a vehicle torque method based on online motor temperature correction according to an embodiment of the present invention. The method includes:

[0033] Step S1: Measure the permanent magnet flux linkage of the motor winding of the vehicle under test at different temperatures.

[0034] Electric vehicles commonly employ permanent magnet synchronous motors (PMSMs) in conjunction with field-oriented control (FOC) algorithms to achieve high-performance torque and speed control. In the process of regulating the motor torque using traditional FOC algorithms, the torque command value from a host computer (e.g., speed loop or torque loop) is typically input first. This is then combined with a motor model (e.g., theoretical electromagnetic torque equations) to calculate the quadrature-axis current and direct-axis current that match the current torque command. These currents are then input into the FOC algorithm, which is executed by the controller to generate drive signals, thereby driving the motor windings to output the expected torque. However, for electric vehicles operating under harsh conditions such as frequent starts and stops and heavy-duty handling, the motor windings generate a large amount of heat, leading to a significant increase in motor temperature. This causes the motor model parameters, such as the permanent magnet flux linkage, in the FOC control system to drift (e.g., decay) with temperature changes, resulting in the quadrature-axis current calculated by the motor model deviating from the actual value. Consequently, the final torque output by the motor windings deviates from the expected value.

[0035] In one embodiment of the present invention, the expression for the motor model used is as follows:

[0036]

[0037] in, This indicates the electromagnetic torque of the motor windings; Indicates the number of pole pairs in the motor winding; Represents the original quadrature-axis current; Represents the original direct-axis current; Indicates permanent magnet flux linkage; Indicates quadrature axis inductance; This indicates a direct-axis inductance.

[0038] To avoid such problems, this embodiment of the invention first measures the permanent magnet flux linkage of the motor winding at different temperatures through bench testing during the calibration stage of the motor winding of the vehicle under test, providing data support for subsequent current compensation. In one embodiment of the invention, the temperature measurement range is set to -20 to 150 degrees Celsius, and a measurement is performed every 1 degree Celsius. In other embodiments of the invention, the temperature measurement range and measurement interval can be set by the implementer according to the specific implementation scenario, and are not limited here.

[0039] Step S2: Based on the permanent magnet flux linkage at each temperature, obtain the current compensation coefficient for each temperature; and construct a mapping table containing temperature and current compensation coefficients.

[0040] Because electric vehicles generate a lot of heat in their motor windings under harsh working conditions such as frequent start-stop and heavy-load transport, the temperature rises, causing the magnetic flux of the permanent magnet to decrease. This leads to the cross-axis current calculated by the motor model deviating from the actual value, affecting the accuracy of the torque output from the motor windings. Therefore, this embodiment of the invention first obtains the current compensation coefficient for each temperature based on the magnetic flux of the permanent magnet at each temperature. Subsequently, the cross-axis current affected by the temperature rise can be corrected by the current compensation coefficient.

[0041] Preferably, in one embodiment of the present invention, the method for obtaining the current compensation coefficient for each temperature specifically includes:

[0042] The standard value of magnetic flux at a preset standard temperature is used as the numerator, and the magnetic flux of permanent magnets at each temperature is used as the denominator. The ratio is used as the current compensation coefficient for each temperature. In one embodiment of the present invention, the preset standard temperature is set to 25 degrees Celsius, which is not limited here, and the standard value of magnetic flux is a known fixed value.

[0043] As an example, in one embodiment of the present invention, the expression for the current compensation coefficient at each temperature can be specifically as follows:

[0044]

[0045] in, Indicates the first Current compensation coefficient at each temperature; This indicates the standard value of the magnetic flux linkage of the permanent magnet at a preset standard temperature; Indicates the permanent magnet in the first Permanent magnet flux linkage at a certain temperature.

[0046] Then, a mapping table containing temperature and current compensation coefficients is constructed, which facilitates the direct extraction of current compensation coefficients from the mapping table in real time to correct the quadrature axis current during subsequent online torque correction.

[0047] Preferably, in one embodiment of the present invention, the method for constructing the mapping relationship table specifically includes:

[0048] Since the permanent magnet flux linkage measured at different temperatures is discrete data, in order to distribute the permanent magnet flux linkage over a wider range of temperatures and facilitate more accurate extraction of the current compensation coefficient of the motor winding at the current temperature, the current compensation coefficient of each temperature is first interpolated. All the temperatures obtained after interpolation and their corresponding current compensation coefficients are recorded in a mapping table. That is, the mapping table contains multiple records, each containing a temperature and its corresponding current compensation coefficient. In the embodiments of the present invention, existing methods such as linear interpolation, polynomial interpolation, or spline interpolation can be used for interpolation, which are not limited or elaborated here.

[0049] The obtained mapping table is then burned into the controller of the motor winding. In one embodiment of the present invention, the controller can be a highly integrated, simple system structure and a strong real-time MCU controller, i.e., a microcontroller unit, so that the subsequent controller can quickly extract the required data from the mapping table.

[0050] Step S3: Acquire the temperature data of the motor winding in real time. Based on the temperature data at the current moment, select the real-time current compensation coefficient from the mapping table. Use the real-time current compensation coefficient to correct the original quadrature-axis current received by the controller of the motor winding at the current moment, and obtain the corrected quadrature-axis current at the current moment.

[0051] Since the temperature rise of the motor windings during actual operation will eventually affect the torque output accuracy, this embodiment of the invention first installs a temperature sensor (e.g., PT1000 or KTY84) in the motor windings and uses the temperature sensor to collect the temperature data of the motor windings in real time. Then, based on the temperature data at the current moment, the real-time current compensation coefficient is selected from the mapping table. Subsequently, the real-time current compensation coefficient can be used to correct the quadrature-axis current that deviates from the true value, thereby compensating for the permanent magnet flux attenuation caused by the temperature rise and realizing accurate output of the motor winding torque.

[0052] Preferably, in one embodiment of the present invention, the method for obtaining the real-time current compensation coefficient at the current moment specifically includes:

[0053] Select the current compensation coefficient corresponding to the temperature that is the same as the temperature data at the current moment from the mapping table, and use it as the real-time current compensation coefficient at the current moment.

[0054] It should be noted that since the mapping table contains discrete data, when a temperature that is the same as the temperature data at the current moment cannot be found in the mapping table, the current compensation coefficient corresponding to the temperature that is closest to the temperature data at the current moment can be selected as the real-time current compensation coefficient at the current moment.

[0055] As mentioned above, the motor windings generate a large amount of heat, causing the temperature to rise and the magnetic flux of the permanent magnet to decrease. This leads to the quadrature-axis current calculated by the motor model deviating from the actual value, affecting the accuracy of the torque output from the motor windings. Therefore, this embodiment of the invention uses the real-time current compensation coefficient at the current moment to correct the original quadrature-axis current received by the controller of the motor windings at the current moment, thereby obtaining a corrected quadrature-axis current that is closer to the true value at the current moment. Subsequently, based on the corrected quadrature-axis current, the torque output from the motor windings can be driven to be closer to the expected value.

[0056] Preferably, in one embodiment of the present invention, the method for obtaining the corrected quadrature-axis current at the current moment specifically includes:

[0057] The product of the real-time current compensation coefficient at the current moment and the original quadrature-axis current received by the controller of the motor winding at the current moment is used as the corrected quadrature-axis current at the current moment.

[0058] As an example, in one embodiment of the present invention, the expression for the corrected quadrature-axis current at the current moment can be specifically as follows:

[0059]

[0060] in, This represents the corrected quadrature-axis current at the current moment; This represents the real-time current compensation coefficient at the current moment. This represents the original quadrature-axis current received by the controller of the motor winding at the current moment.

[0061] When the temperature rises, the permanent magnet flux linkage decreases, but the motor model still uses fixed permanent magnet flux linkage parameters to calculate the quadrature-axis current. This causes the controller to receive a lower-than-actual original quadrature-axis current at the current moment. Since the permanent magnet flux linkage has decreased and fallen below the standard value, the real-time current compensation coefficient... The value is greater than 1, thus increasing the real-time current compensation coefficient. The original quadrature-axis current received by the controller at the current moment This is done by increasing its size to compensate for the decrease in permanent magnet flux caused by the increase in temperature.

[0062] Step S4: Based on the corrected quadrature-axis current at the current moment and combined with the FOC algorithm, drive the motor winding output to the corrected torque at the current moment.

[0063] By obtaining a corrected quadrature-axis current that is closer to the true value, the corrected quadrature-axis current at the current moment can be used as a basis, combined with the FOC algorithm, to drive the motor windings to output the corrected torque at the current moment, so that the torque output by the motor windings is closer to the expected value.

[0064] Preferably, in one embodiment of the present invention, the method for outputting a corrected torque at the current moment by the drive motor winding specifically includes:

[0065] The corrected quadrature-axis current at the current moment and the original direct-axis current received by the controller are input into the FOC algorithm, and the controller executes the drive signal generated by the FOC algorithm to drive the motor windings to output the corrected torque at the current moment.

[0066] It should be noted that the original quadrature-axis current and the original direct-axis current mentioned above are both determined by the controller based on the motor parameters and the preset motor model. The motor parameters and the preset motor model are the motor model given in step S1.

[0067] Please see Figure 2 The diagram illustrates a structural framework of a vehicle torque method based on online motor temperature correction according to an embodiment of the present invention.

[0068] One embodiment of the present invention provides a vehicle torque system based on online correction of motor temperature. The system includes a memory, a processor, and a computer program. The memory is used to store the corresponding computer program, and the processor is used to run the corresponding computer program. When the computer program runs in the processor, it can implement the methods described in steps S1 to S4.

[0069] In summary, this embodiment of the invention first measures the permanent magnet flux linkage of the motor winding at different temperatures, then calculates the current compensation coefficient for each temperature. Subsequently, the quadrature-axis current affected by temperature rise can be corrected using the current compensation coefficient. A mapping table containing temperature and current compensation coefficients is constructed, which facilitates the direct extraction of the current compensation coefficient from the mapping table to correct the quadrature-axis current during online torque correction. Then, the motor winding temperature is monitored in real time, and based on the current temperature data, the current compensation coefficient corresponding to the current temperature is extracted from the mapping table in real time. Using the real-time current compensation coefficient, the original quadrature-axis current that deviates from the true value due to permanent magnet flux linkage drift caused by temperature is corrected, compensating for the permanent magnet flux linkage attenuation caused by temperature rise, and obtaining a corrected quadrature-axis current closer to the true value. Combined with the FOC algorithm, the torque output by the drive motor winding is closer to the expected value.

[0070] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0071] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for vehicle torque correction based on online motor temperature, characterized in that, The method includes: Measure the permanent magnet flux linkage of the motor windings of the vehicle under test at different temperatures; Based on the permanent magnet flux linkage at each temperature, the current compensation coefficient for each temperature is obtained; and a mapping table containing temperature and current compensation coefficients is constructed. The temperature data of the motor winding is acquired in real time. Based on the temperature data at the current moment, the real-time current compensation coefficient at the current moment is selected from the mapping table. The real-time current compensation coefficient is used to correct the original quadrature axis current received by the controller of the motor winding at the current moment to obtain the corrected quadrature axis current at the current moment. Based on the corrected quadrature-axis current at the current moment, and combined with the FOC algorithm, the drive motor winding outputs the corrected torque at the current moment.

2. The vehicle torque method based on online correction of motor temperature according to claim 1, characterized in that, The current compensation coefficient for each temperature includes: The standard value of magnetic flux at the preset standard temperature is used as the numerator, and the magnetic flux of the permanent magnet at each temperature is used as the denominator. The ratio is used as the current compensation coefficient for each temperature.

3. The vehicle torque method based on online correction of motor temperature according to claim 1, characterized in that, The construction of the mapping table containing temperature and current compensation coefficients includes: The current compensation coefficients for each temperature are interpolated, and all the interpolated temperatures and their corresponding current compensation coefficients are recorded in a mapping table.

4. The vehicle torque method based on online correction of motor temperature according to claim 1, characterized in that, The mapping table needs to be burned into the controller of the motor winding.

5. A vehicle torque method based on online correction of motor temperature according to claim 4, characterized in that, The controller is an MCU controller.

6. The vehicle torque method based on online correction of motor temperature according to claim 1, characterized in that, The step of selecting the real-time current compensation coefficient from the mapping table includes: Select the current compensation coefficient corresponding to the temperature that is the same as the temperature data at the current moment from the mapping table, and use it as the real-time current compensation coefficient at the current moment.

7. The vehicle torque method based on online correction of motor temperature according to claim 1, characterized in that, The process of obtaining the corrected quadrature-axis current at the current moment includes: The product of the real-time current compensation coefficient at the current moment and the original quadrature-axis current received by the controller of the motor winding at the current moment is used as the corrected quadrature-axis current at the current moment.

8. The vehicle torque method based on online correction of motor temperature according to claim 1, characterized in that, The corrected torque output by the drive motor winding at the current moment includes: The corrected quadrature-axis current at the current moment and the original direct-axis current received by the controller are input into the FOC algorithm, and the controller executes the drive signal generated by the FOC algorithm to drive the motor windings to output the corrected torque at the current moment.

9. A vehicle torque method based on online correction of motor temperature according to claim 1, characterized in that, The original quadrature axis current is determined by the controller based on motor parameters and a preset motor model.

10. A vehicle torque system based on online correction of motor temperature, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 9.

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