Oil temperature estimation method and device of oil-cooled electric drive system, vehicle and storage medium

Abstract

The present application relates to oil-cooled electric drive system, specifically to oil temperature estimation method, device, vehicle and storage medium of oil-cooled electric drive system, real-time acquisition oil pump speed, when oil pump speed < preset threshold, real-time acquisition motor temperature and oil temperature estimation result of last time and input the acquired motor temperature and oil temperature estimation result of last time into the first estimation model based on heat transfer model, obtain the oil temperature estimation result of oil-cooled electric drive system;When oil pump speed >= preset threshold, real-time acquisition oil pump voltage, oil pump current and oil pump speed to the second estimation model based on the working performance of oil pump and the flow resistance characteristic of oil circuit, obtain the oil temperature estimation result of oil-cooled electric drive system.It can accurately estimate the oil temperature of oil-cooled electric drive system in real time, effectively replace the role of oil temperature sensor, and then reduce the cost of oil-cooled electric drive system.

Description

Technical Field

[0001] This invention relates to oil-cooled electric drive systems, and more specifically to oil temperature estimation methods, devices, vehicles, and storage media for oil-cooled electric drive systems. Background Technology

[0002] For oil-cooled electric drive systems, lubricating oil not only lubricates gears and bearings but also cools heat-generating components inside the drive. If the oil temperature is too low, the oil viscosity will increase significantly, increasing frictional wear on mechanical parts and reducing the efficiency of the oil-cooled electric drive system. If the oil temperature is too high, the cooling effect will decrease, leading to overheating of internal components and, in severe cases, damage. Therefore, to ensure the efficient and reliable operation of oil-cooled electric drive systems, the oil temperature needs to be monitored in real time.

[0003] Existing oil-cooled electric drive systems generally include an oil pump, an oil cooler, and an oil passage structure. The oil pump provides the power for oil flow, the oil cooler cools the lubricating oil, and some systems also include a filter to remove impurities. To monitor oil temperature in real time, existing oil-cooled electric drive systems typically use an oil temperature sensor, but this increases the cost. By using algorithms to estimate oil temperature in real time, the function of an oil temperature sensor can be replaced, making oil-cooled electric drive systems more cost-effective.

[0004] CN202011374193.9 discloses an oil temperature estimation method based on the electrical characteristics of an oil pump motor. The method involves adjusting the output speed of the oil pump motor to its minimum operating speed; adjusting the lubricating oil temperature to its minimum operating temperature and recording the corresponding current; increasing the oil temperature in increments, sequentially acquiring the current corresponding to each oil temperature until the oil temperature reaches the maximum operating temperature, obtaining the mapping relationship between the oil temperature and the oil pump motor current at the minimum operating speed, and obtaining the calculation formula for the oil temperature and oil pump motor current at the minimum operating speed; gradually increasing the output speed in increments until the maximum operating speed, recording the mapping relationship between the oil temperature and motor current at each output speed, and obtaining the calculation formula for the oil temperature and oil pump motor current at each output speed. The advantages are: oil temperature can be obtained using this estimation method, reducing cost and hardware failure rate, and avoiding the inaccurate oil temperature data acquisition caused by oil temperature sensor failure in existing technologies. However, this method has the following problems when used for oil temperature estimation in oil-cooled electric drive systems: ① It does not consider the influence of oil pump voltage. The oil pump in the vehicle is mainly powered by DC-DC converters and batteries, and the normal operating voltage varies between 9 and 16V. Voltage variations will cause changes in the correspondence between oil temperature, oil pump speed, and oil pump current, greatly reducing the accuracy of the estimation. ② The calibration test can only test the correspondence between oil temperature and oil pump motor current at typical oil pump operating speeds. It does not cover oil temperature estimation methods for non-typical oil pump operating speeds. ③ This estimation method can only achieve oil temperature estimation when the oil pump is running normally. If the oil temperature is low, the oil pump cannot operate, and oil temperature estimation cannot be achieved in this case.

[0005] CN202010511132.6 discloses a transmission control method and an automotive transmission. The transmission control method includes an oil temperature estimation working mode, which includes: a-1: controlling the transmission hydraulic system to achieve a preset calculated load and maintaining it for a preset calculation time; a-2: controlling the electronic oil pump to operate at a reference speed, measuring the motor current value of the electronic oil pump at the reference speed, and consulting a current-speed-oil temperature correspondence table to obtain the transmission oil temperature based on the measured motor current value and the reference speed. This addresses the problem of transmission hydraulic control failing due to transmission temperature sensor malfunction, leading to transmission failure. By estimating a more accurate transmission oil temperature signal using the electronic oil pump current, the entire transmission hydraulic system can continue to be precisely controlled, improving the robustness of transmission control. The proposed transmission control method includes an oil temperature estimation working mode, measuring the motor current value of the electronic oil pump at the reference speed, consulting a current-speed-oil temperature correspondence table, and obtaining the transmission oil temperature based on the measured motor current value and the reference speed. This solution is similar to the method used in CN202011374193.9, which estimates oil temperature by looking up a table, but it still has the aforementioned problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method, device, vehicle, and storage medium for estimating the oil temperature of an oil-cooled electric drive system, which can accurately estimate the oil temperature of the oil-cooled electric drive system in real time, effectively replacing the function of an oil temperature sensor, thereby reducing the cost of the oil-cooled electric drive system.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides an oil temperature estimation method for an oil-cooled electric drive system, wherein the oil pump speed is acquired in real time, and when the oil pump speed is less than a preset threshold, the motor temperature and the oil temperature estimation result of the previous moment are acquired in real time and the acquired motor temperature and the oil temperature estimation result of the previous moment are input into a first estimation model constructed based on a heat transfer model to obtain the oil temperature estimation result of the oil-cooled electric drive system.

[0009] When the oil pump speed is greater than or equal to a preset threshold, the oil pump voltage and current are acquired in real time and then fed into the second estimation model based on the working performance of the oil pump and the flow resistance characteristics of the oil circuit to obtain the oil temperature estimation result of the oil-cooled electric drive system.

[0010] Furthermore, the first estimation model is: In the formula, To estimate the oil temperature at the current time t, α is a proportionality coefficient, ranging from 0 to 1; Tmotor Motor temperature; This is the oil temperature estimate from the previous moment. If the previous moment is the initial moment, then the oil temperature estimate from the previous moment is... The ambient temperature.

[0011] Furthermore, the proportionality coefficient α was obtained through experimental calibration.

[0012] Furthermore, the second estimation model is: T oil =f(X1,X2), X1=f(n,n ref X2 = f(n,U,I,β), where T oil For the oil temperature estimation result, X1 is the first input, X2 is the second input, and n is the real-time oil pump speed; n ref The reference speed of the oil pump is set reasonably according to actual needs; U is the oil pump voltage, I is the oil pump current, and β is the calibration correction coefficient.

[0013] Furthermore, the formula for calculating the first input quantity is:

[0014] Furthermore, the formula for calculating the second input quantity is:

[0015] Furthermore, the oil temperature estimation results of the oil-cooled electric drive system are subjected to amplitude limiting and filtering processing; the amplitude limiting coefficient of the amplitude limiting processing is obtained through testing; the filtering processing outputs once every m calculation cycles, and the output value is the average value of the estimation results of m cycles.

[0016] Furthermore, the construction of the first estimation model specifically includes the following steps:

[0017] S11, determine several test conditions for the oil-cooled electric drive system;

[0018] S12, Install an oil temperature sensor in the oil circuit of the oil-cooled electric drive system. The oil-cooled electric drive system is operated according to the test conditions and data is continuously recorded during the process. The data includes the motor temperature, the oil temperature estimation result of the previous moment, and the oil temperature information collected by the oil temperature sensor.

[0019] S13, Repeat step S12 until data recording for all test conditions is completed;

[0020] S14. Using the motor temperature and the oil temperature estimation result of the previous moment as input, and the oil temperature information collected by the oil temperature sensor as output, a fitting regression model is constructed to obtain the first estimation model.

[0021] Furthermore, the construction of the second estimation model specifically includes the following steps:

[0022] S21, determine the minimum oil temperature at which the oil pump of the oil-cooled electric drive system operates, and use it as the starting oil temperature for each test condition;

[0023] S22, Based on the loss of the electric drive system, determine several test conditions of the oil-cooled electric drive system, and at least one of the test conditions includes the maximum loss point of the oil-cooled electric drive system during continuous operation.

[0024] S23, adjust the oil pump power supply voltage to the lowest operating voltage, request the oil pump speed to the preset speed, control the oil-cooled electric drive system to not run, and after the system stabilizes, adjust the oil pump power supply voltage to rise from the lowest voltage to the highest voltage according to the preset gradient. During the process, data is continuously recorded, including oil pump voltage, oil pump current, oil pump speed and oil temperature collected by the oil temperature sensor.

[0025] S24, control the oil-cooled electric drive system to a certain test condition. After the oil-cooled electric drive system stabilizes, adjust the oil pump power supply voltage from the highest voltage to the lowest voltage according to the preset gradient. During the process, data is continuously recorded, including oil pump voltage, oil pump current, oil pump speed and oil temperature collected by the oil temperature sensor.

[0026] S25. Repeat steps S23 and S24 until data recording for all test conditions is completed.

[0027] S26. Using oil pump voltage, oil pump current, and oil pump speed as inputs, and oil temperature information collected by the oil temperature sensor as output, a fitting regression model is constructed to obtain the second estimation model.

[0028] Secondly, the present invention provides an oil temperature estimation device for an oil-cooled electric drive system, capable of executing the steps of the oil temperature estimation method for the oil-cooled electric drive system described in the present invention, including: an information acquisition module for acquiring parameter information, the parameter information including oil pump speed, oil pump voltage, oil pump current, motor temperature and the oil temperature estimation result at the previous moment; and an information processing module for calculating the oil temperature estimation result of the oil-cooled electric drive system based on the parameter information acquired by the information acquisition module according to a preset first estimation model or a second estimation model.

[0029] Thirdly, the present invention provides a vehicle including an oil-cooled electric drive system, wherein the oil-cooled electric drive system includes an oil temperature estimation device for the oil-cooled electric drive system described in the present invention.

[0030] Fourthly, the present invention provides a storage medium storing a computer-readable program, which, when invoked, can execute the steps of the oil temperature estimation method for the oil-cooled electric drive system described in the present invention.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention uses different estimation models based on the real-time acquired oil pump speed. When the oil pump speed is less than a preset threshold, the first estimation model based on the heat transfer model is used to obtain the oil temperature estimation result of the oil-cooled electric drive system. When the oil pump speed is greater than or equal to the preset threshold, the second estimation model based on the working performance of the oil pump and the flow resistance characteristics of the oil circuit is used to obtain the oil temperature estimation result of the oil-cooled electric drive system. This improves the accuracy of the estimation results and has a wider range of applications.

[0033] 2. The data required for oil temperature estimation in this invention are all obtained from existing oil-cooled electric drive systems. The oil temperature estimation algorithm, namely the first estimation model and the second estimation model, replaces the role of the oil temperature sensor, thereby reducing the cost of the oil-cooled electric drive system.

[0034] 3. The present invention constructs a first estimation model based on the motor temperature and the oil temperature estimation result of the previous moment, and constructs a second estimation model based on the oil pump voltage, oil pump current and oil pump speed. Compared with the prior art, the dimension of oil pump voltage is added, and a multi-factor response surface model is constructed. Compared with the single variable interpolation method of the prior art, the interaction between different factors is considered, and the estimation result is more accurate. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in 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.

[0036] Figure 1 This is a schematic diagram of the oil temperature estimation method for the oil-cooled electric drive system described in Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram of the construction method of the first estimation model of the present invention;

[0038] Figure 3 This is a schematic diagram of the construction method of the second estimation model of the present invention;

[0039] Figure 4 This is a schematic diagram of the second estimation model of the present invention;

[0040] Figure 5 This is a schematic diagram of the oil temperature estimation method for the oil-cooled electric drive system described in Embodiment 4 of the present invention. Detailed Implementation

[0041] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0042] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0043] Example 1, see Figure 1 The oil temperature estimation method for the oil-cooled electric drive system illustrated involves real-time acquisition of the oil pump speed. When the oil pump speed is less than a preset threshold, the method acquires the motor temperature and the previous oil temperature estimation result in real time, and inputs these results into a first estimation model based on a heat transfer model to obtain the oil temperature estimation result for the oil-cooled electric drive system. When the oil pump speed is greater than or equal to the preset threshold, the method acquires the oil pump voltage and current in real time, and inputs these parameters into a second estimation model based on the oil pump's operating performance and the flow resistance characteristics of the oil circuit to obtain the oil temperature estimation result for the oil-cooled electric drive system. In this embodiment, the preset threshold is set to 500 rpm.

[0044] This invention uses different estimation models based on the real-time acquired oil pump speed. When the oil pump speed is less than a preset threshold, a first estimation model based on a heat transfer model is used to obtain the oil temperature estimation result of the oil-cooled electric drive system. When the oil pump speed is greater than or equal to the preset threshold, a second estimation model based on the working performance of the oil pump and the flow resistance characteristics of the oil circuit is used to obtain the oil temperature estimation result of the oil-cooled electric drive system. This improves the accuracy of the estimation results and has a wider range of applications.

[0045] The oil temperature estimation required by this invention is obtained from existing oil-cooled electric drive systems. The oil temperature estimation algorithm, namely the first estimation model and the second estimation model, replaces the role of the oil temperature sensor, thereby reducing the cost of the oil-cooled electric drive system.

[0046] This invention constructs a first estimation model based on the motor temperature and the oil temperature estimation result of the previous moment, and constructs a second estimation model based on the oil pump voltage, oil pump current and oil pump speed. Compared with the prior art, it adds the dimension of oil pump voltage and constructs a multi-factor response surface model. Compared with the single variable interpolation method of the prior art, it considers the interaction between different factors and the estimation result is more accurate.

[0047] In the first estimation model, heat transfer theory is used to establish the estimation model. The oil temperature change is related to both the heat exchange capacity between the oil and the motor, and the temperature difference between the motor and the oil. The heat exchange capacity between the oil and the motor is related to the structure of the oil circuit and does not change significantly during the operation of the electric drive system; it can be obtained through experimental calibration. Therefore, a functional relationship between oil temperature and motor temperature can be established.

[0048] In the second estimation model, the estimation model is established based on the electrical and hydraulic characteristics of the electronic oil pump. The input power of the electronic oil pump is related to the input voltage and input current, while the output power is related to the flow rate of the oil medium and the flow resistance of the oil circuit. The input power can be expressed as: P in =U*I, where U is the oil pump input voltage and I is the oil pump input current; the output power can be expressed as: Where Q is the oil flow rate and ΔP is the pressure difference between the inlet and outlet of the oil pump. The oil flow rate is related to the rotational speed of the electronic oil pump and can be expressed as: Q = V t *η v *n, where V t η is the theoretical displacement of the oil pump. v Let n be the volumetric efficiency of the oil pump; and n be the oil pump speed. From this, a functional relationship can be established between oil temperature and oil pump speed, oil pump voltage, and oil pump current.

[0049] As a preferred embodiment of this invention, the first estimation model is: In the formula, To estimate the oil temperature at the current time t, α is a proportionality coefficient, ranging from 0 to 1; T motor Motor temperature; This is the oil temperature estimate from the previous moment. If the previous moment is the initial moment, then the oil temperature estimate from the previous moment is... The ambient temperature.

[0050] In this embodiment, the proportionality coefficient α is determined to be 0.5 through experimental calibration. Therefore, when the oil temperature estimation result from the previous moment is obtained... The temperature is 20℃, and the motor temperature T is... motor At 40℃, the oil temperature of the oil-cooled electric drive system is obtained through the first estimation model as follows:

[0051]

[0052] In a preferred embodiment of this invention, the second estimation model is: T oil =f(X1,X2), X1=f(n,n ref X2 = f(n,U,I,β), where T oil For the oil temperature estimation result, X1 is the first input, X2 is the second input, and n is the real-time oil pump speed; n ref The reference speed for the oil pump is set reasonably according to actual needs; U is the oil pump voltage, I is the oil pump current, and β is the calibration correction coefficient. The formula for calculating the first input quantity is: The formula for calculating the second input quantity is:

[0053] Example 2: A method for estimating the oil temperature of an oil-cooled electric drive system. The method involves real-time acquisition of the oil pump speed. When the oil pump speed is less than a preset threshold, the method acquires the motor temperature and the previous oil temperature estimation result in real time. These results are then input into a first estimation model based on a heat transfer model to obtain the oil temperature estimation result for the oil-cooled electric drive system. When the oil pump speed is greater than or equal to the preset threshold, the method acquires the oil pump voltage and current in real time. These values ​​are then input into a second estimation model based on the oil pump's operating performance and the flow resistance characteristics of the oil circuit to obtain the oil temperature estimation result for the oil-cooled electric drive system. In this example, the preset threshold is set to 500 rpm.

[0054] The first estimation model is: In the formula, T oil The oil temperature is estimated using α, which is a proportionality coefficient ranging from 0 to 1, and its specific value is obtained through experimental calibration; T mor Motor temperature; This is the oil temperature estimate from the previous moment. If the previous moment is the initial moment, then the oil temperature estimate from the previous moment is... The ambient temperature.

[0055] See Figure 2 The construction of the first estimation model specifically includes the following steps:

[0056] S11, determine several test conditions for the oil-cooled electric drive system.

[0057] S12, Install an oil temperature sensor in the oil circuit of the oil-cooled electric drive system, control the electronic oil pump to not run, and run the oil-cooled electric drive system according to the test conditions. During the process, data is continuously recorded, including motor temperature, the oil temperature estimation result of the previous moment, and the oil temperature information collected by the oil temperature sensor.

[0058] S13. Repeat step S12 until data recording for all test conditions is completed.

[0059] S14. Using the motor temperature and the oil temperature estimation result of the previous moment as input, and the oil temperature information collected by the oil temperature sensor as output, a fitting regression model is constructed to obtain the first estimation model.

[0060] For example, three operating conditions are determined for an oil-cooled electric drive system: Condition 1 is the no-load condition, Condition 2 is the rated condition, and Condition 3 is the peak condition. Based on the measured motor temperature, the estimated oil temperature from the previous moment, and the corresponding curve fitting of the oil temperature, the proportional coefficient α is found to be 0.5. Therefore, the first estimation model is as follows: When the oil pump speed is less than the preset threshold, the real-time motor temperature T will be measured. motor Oil temperature estimation results from the previous moment The oil temperature of the oil-cooled electric drive system is accurately and reliably estimated by inputting the data into the first estimation model built on the heat transfer model. Adjusting the oil temperature based on this estimation ensures the system's efficient and reliable operation, effectively preventing excessively low or high temperatures. Low oil temperatures significantly increase oil viscosity, leading to increased frictional wear on mechanical components and reduced system efficiency. Conversely, excessively high oil temperatures reduce cooling effectiveness, causing overheating of internal components and potentially resulting in component damage.

[0061] Example 3: A method for estimating the oil temperature of an oil-cooled electric drive system. The method involves real-time acquisition of the oil pump speed. When the oil pump speed is less than a preset threshold, the method acquires the motor temperature and the previous oil temperature estimation result in real time. These two values ​​are then input into a first estimation model based on a heat transfer model to obtain the oil temperature estimation result for the oil-cooled electric drive system. When the oil pump speed is greater than or equal to the preset threshold, the method acquires the oil pump voltage and current in real time. These values, along with the oil pump speed, are then input into a second estimation model based on the oil pump's performance and the flow resistance characteristics of the oil circuit to obtain the oil temperature estimation result for the oil-cooled electric drive system. In this example, the preset threshold is set to 500 rpm.

[0062] The second estimation model is: T oil =f(X1,X2), X1=f(n,n ref X2 = f(n,U,I,β), where T oil For the oil temperature estimation result, X1 is the first input, X2 is the second input, and n is the real-time oil pump speed; n ref The reference speed for the oil pump is set reasonably according to actual needs; U is the oil pump voltage, I is the oil pump current, and β is the calibration correction coefficient. The formula for calculating the first input quantity is: The formula for calculating the second input quantity is:

[0063] See Figure 3 The construction of the second estimation model specifically includes the following steps:

[0064] S21, determine the minimum oil temperature at which the oil pump of the oil-cooled electric drive system operates, as the starting oil temperature for each test condition. Based on the oil pump's speed control range, set calibration conditions for the oil pump speed, for example, sequentially increasing n0, n1, n2, ..., n... max , n0≥ preset threshold.

[0065] S22, Based on the losses of the electric drive system, determine several test conditions for the oil-cooled electric drive system, wherein at least one of the test conditions includes the maximum loss point of the oil-cooled electric drive system during continuous operation.

[0066] S23, adjust the oil pump power supply voltage to the minimum operating voltage, request the oil pump speed to the minimum operating speed n0, control the oil-cooled electric drive system to not run, and after the system stabilizes, adjust the oil pump power supply voltage to rise from the minimum voltage to the maximum voltage according to the preset gradient. During the process, data is continuously recorded, including oil pump voltage, oil pump current, oil pump speed and oil temperature collected by the oil temperature sensor.

[0067] S24, control the oil-cooled electric drive system to a certain test condition. After the oil-cooled electric drive system stabilizes, adjust the oil pump power supply voltage from the highest voltage to the lowest voltage according to the preset gradient. During the process, data is continuously recorded, including oil pump voltage, oil pump current, oil pump speed and oil temperature collected by the oil temperature sensor.

[0068] S25. Repeat steps S23 and S24 until data recording is completed for all test conditions when the oil pump speed is the minimum operating speed n0.

[0069] Then, let the oil-cooled electric drive system stand still until the oil temperature drops to the initial oil temperature described in S1. Request the oil pump speed to be n1 and repeat steps S23 to S25 until the data recording for all test conditions when the oil pump speed is n1 is completed.

[0070] Repeat the operation until all pump speeds and data records for all test conditions are completed. Table 1 shows the oil temperature data measured under different pump speeds, voltages, and currents under some conditions.

[0071] Table 1. Oil temperature data measured at different pump speeds, pump voltages, and pump currents.

[0072] Serial Number Oil pump speed (rpm) Oil pump voltage (V) Oil pump current (A) Oil temperature (°C) 1 <![CDATA[n0=1000]]> <![CDATA[U0=9]]> 0.8 60 2 <![CDATA[n0=1000]]> <![CDATA[U1=12]]> 0.6 60 3 <![CDATA[n0=1000]]> <![CDATA[U2=16]]> 0.4 60 … … … … … … <![CDATA[n k =3000]]> <![CDATA[U0=9]]> 1.9 80 … <![CDATA[n k =3000]]> <![CDATA[U1=12]]> 1.4 80 … <![CDATA[n k =3000]]> <![CDATA[U2=16]]> 1.1 80 … … … … … … <![CDATA[n max =6500]]> <![CDATA[U2=16]]> 7.0 95 … <![CDATA[n max =6500]]> <![CDATA[U1=12]]> 9.4 95 … <![CDATA[n max =6500]]> <![CDATA[U0=9]]> 12.5 95

[0073] S26, using oil pump voltage, oil pump current, and oil pump speed as inputs, and oil temperature information collected by the oil temperature sensor as output, a fitting regression model is constructed, thus obtaining the second estimation model. Specifically, according to... The first input quantity X1 is calculated, and then... The second input quantity X2 is calculated; see [link / reference]. Figure 4 The regression model is fitted to the obtained X1, X2 and oil temperature data to obtain the second estimation model.

[0074] Example 4, see Figure 5 The oil temperature estimation method for the oil-cooled electric drive system illustrated involves real-time acquisition of the oil pump speed. When the oil pump speed is less than a preset threshold, the method acquires the motor temperature and the previous oil temperature estimation result in real time, and inputs these results into a first estimation model based on a heat transfer model to obtain the oil temperature estimation result for the oil-cooled electric drive system. When the oil pump speed is greater than or equal to the preset threshold, the method acquires the oil pump voltage and current in real time, and inputs these parameters into a second estimation model based on the oil pump's operating performance and the flow resistance characteristics of the oil circuit to obtain the oil temperature estimation result for the oil-cooled electric drive system. In this embodiment, the preset threshold is set to 500 rpm.

[0075] The first estimation model is: In the formula, T oil The oil temperature is estimated using α, which is a proportionality coefficient ranging from 0 to 1, and its specific value is obtained through experimental calibration; T motor Motor temperature; This is the oil temperature estimate from the previous moment. If the previous moment is the initial moment, then the oil temperature estimate from the previous moment is... The ambient temperature.

[0076] The second estimation model is: T oil =f(X1,X2), X1=f(n,n ref X2 = f(n,U,I,β), where T oil For the oil temperature estimation result, X1 is the first input, X2 is the second input, and n is the real-time oil pump speed; n ref The reference speed for the oil pump is set reasonably according to actual needs; U is the oil pump voltage, I is the oil pump current, and β is the calibration correction coefficient. The formula for calculating the first input quantity is: The formula for calculating the second input quantity is:

[0077] To reduce the impact of input signal fluctuations on the estimation results, the oil temperature estimation results of the oil-cooled electric drive system are filtered and limited. The filtering process outputs the value once every m calculation cycles, and the output value is the average of the estimation results over m cycles, specifically expressed as follows:

[0078] In the formula, Y represents the oil temperature estimation result after filtering, Y1 represents the oil temperature estimation result output in the first calculation cycle, and Y2 represents the oil temperature estimation result output in the second calculation cycle. m This is the oil temperature estimation result output in the m-th calculation cycle, where m is the total number of calculation cycles.

[0079] The limiting coefficient for the limiting process was obtained through testing.

[0080] Example 5: An oil temperature estimation device for an oil-cooled electric drive system, capable of executing the steps of the oil temperature estimation method for an oil-cooled electric drive system described in Examples 1, 2, 3, or 4 of this invention, includes: an information acquisition module for acquiring parameter information, the parameter information including oil pump speed, oil pump voltage, oil pump current, motor temperature, and the oil temperature estimation result at the previous moment; and an information processing module for calculating the oil temperature estimation result of the oil-cooled electric drive system based on the parameter information acquired by the information acquisition module, according to a preset first estimation model or a second estimation model.

[0081] Example 6: A vehicle including an oil-cooled electric drive system, wherein the oil-cooled electric drive system includes the oil temperature estimation device for the oil-cooled electric drive system described in Example 5 of the present invention.

[0082] Example 7: A storage medium storing a computer-readable program, which, when invoked, can execute the steps of the oil temperature estimation method for the oil-cooled electric drive system described in Example 1, Example 2, Example 3, or Example 4 of the present invention.

[0083] It should be noted that the storage medium shown can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, optical fiber, portable compact disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this embodiment, the computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying a computer-readable computer program. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media can also be any computer-readable medium other than computer-readable storage media, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The computer program contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to wireless, wired, etc., or any suitable combination thereof.

[0084] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. Each block in a flowchart or block diagram may represent a module, segment, or portion of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0085] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for estimating oil temperature in an oil-cooled electric drive system, characterized in that, The oil pump speed is acquired in real time. When the oil pump speed is less than the preset threshold, the motor temperature and the oil temperature estimation result of the previous moment are acquired in real time and input into the first estimation model based on the heat transfer model to obtain the oil temperature estimation result of the oil-cooled electric drive system. When the oil pump speed is greater than or equal to the preset threshold, the oil pump voltage and oil pump current are acquired in real time and the acquired oil pump voltage, oil pump current and oil pump speed are fed into the second estimation model based on the working performance of the oil pump and the flow resistance characteristics of the oil circuit to obtain the oil temperature estimation result of the oil-cooled electric drive system. The first estimation model is: In the formula, To estimate the oil temperature at the current time t, This is the proportionality coefficient, with a value ranging from 0 to 1; T motor Motor temperature; This is the oil temperature estimate from the previous moment. If the previous moment is the initial moment, then the oil temperature estimate from the previous moment is... Ambient temperature; The second estimation model is: T oil =f(X1, X2), X1=f(n,n ref X2=f(n, U, I, ), In the formula, T oil For the oil temperature estimation result, X1 is the first input, X2 is the second input, and n is the real-time oil pump speed; n ref The reference speed for the oil pump should be set appropriately according to actual needs; U is the oil pump voltage, and I is the oil pump current. For calibration correction factors.

2. The oil temperature estimation method for an oil-cooled electric drive system according to claim 1, characterized in that: proportionality coefficient Obtained through experimental calibration.

3. The oil temperature estimation method for an oil-cooled electric drive system according to claim 1, characterized in that, The formula for calculating the first input quantity is: .

4. The oil temperature estimation method for an oil-cooled electric drive system according to claim 1, characterized in that, The formula for calculating the second input quantity is: .

5. The oil temperature estimation method for an oil-cooled electric drive system according to claim 1, characterized in that: The oil temperature estimation results of the oil-cooled electric drive system are filtered and limited. The filtering process outputs the value once every m calculation cycles, and the output value is the average of the estimation results of m cycles. The limiting coefficient for the limiting process was obtained through testing.

6. The oil temperature estimation method for an oil-cooled electric drive system according to claim 1, characterized in that, The construction of the first estimation model specifically includes the following steps: S11, determine several test conditions for the oil-cooled electric drive system; S12, Install an oil temperature sensor in the oil circuit of the oil-cooled electric drive system. The oil-cooled electric drive system is operated according to the test conditions and data is continuously recorded during the process. The data includes the motor temperature, the oil temperature estimation result of the previous moment, and the oil temperature information collected by the oil temperature sensor. S13, Repeat step S12 until data recording for all test conditions is completed; S14. Using the motor temperature and the oil temperature estimation result of the previous moment as input, and the oil temperature information collected by the oil temperature sensor as output, a fitting regression model is constructed to obtain the first estimation model.

7. The oil temperature estimation method for an oil-cooled electric drive system according to claim 1, characterized in that, The construction of the second estimation model specifically includes the following steps: S21, determine the minimum oil temperature at which the oil pump of the oil-cooled electric drive system operates, and use it as the starting oil temperature for each test condition; S22, Based on the loss of the electric drive system, determine several test conditions of the oil-cooled electric drive system, and at least one of the test conditions includes the maximum loss point of the oil-cooled electric drive system during continuous operation. S23, adjust the oil pump power supply voltage to the lowest operating voltage, request the oil pump speed to the preset speed, control the oil-cooled electric drive system to not run, and after the system stabilizes, adjust the oil pump power supply voltage to rise from the lowest voltage to the highest voltage according to the preset gradient. During the process, data is continuously recorded, including oil pump voltage, oil pump current, oil pump speed and oil temperature collected by the oil temperature sensor. S24, control the oil-cooled electric drive system to a certain test condition. After the oil-cooled electric drive system stabilizes, adjust the oil pump power supply voltage from the highest voltage to the lowest voltage according to the preset gradient. During the process, data is continuously recorded, including oil pump voltage, oil pump current, oil pump speed and oil temperature collected by the oil temperature sensor. S25. Repeat steps S23 and S24 until data recording for all test conditions is completed. S26. Using oil pump voltage, oil pump current, and oil pump speed as inputs, and oil temperature information collected by the oil temperature sensor as output, a fitting regression model is constructed to obtain the second estimation model.

8. An oil temperature estimation device for an oil-cooled electric drive system, characterized in that: The steps for performing the oil temperature estimation method for an oil-cooled electric drive system as described in any one of claims 1 to 7 include: The information acquisition module is used to acquire parameter information, including oil pump speed, oil pump voltage, oil pump current, motor temperature, and the oil temperature estimation result of the previous moment. The information processing module calculates the oil temperature estimation result of the oil-cooled electric drive system based on the parameter information obtained by the information acquisition module, according to the preset first estimation model or second estimation model. The first estimation model is: In the formula, To estimate the oil temperature at the current time t, This is the proportionality coefficient, with a value ranging from 0 to 1; T motor Motor temperature; This is the oil temperature estimate from the previous moment. If the previous moment is the initial moment, then the oil temperature estimate from the previous moment is... Ambient temperature; The second estimation model is: T oil =f(X1, X2), X1=f(n,n ref X2=f(n, U, I, ), In the formula, T oil For the oil temperature estimation result, X1 is the first input, X2 is the second input, and n is the real-time oil pump speed; n ref The reference speed for the oil pump should be set appropriately according to actual needs; U is the oil pump voltage, and I is the oil pump current. For calibration correction factors.

9. A vehicle comprising an oil-cooled electric drive system, characterized in that: The oil-cooled electric drive system includes the oil temperature estimation device of the oil-cooled electric drive system as described in claim 8.

10. A storage medium, characterized in that: It contains a computer-readable program that, when invoked, performs the steps of the oil temperature estimation method for an oil-cooled electric drive system as described in any one of claims 1 to 7.

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