A method and system for verifying the efficiency of a hydraulic mechanical transmission of a vehicle

Abstract

The application provides a kind of automobile hydraulic mechanical transmission efficiency verification method and system, the method includes obtaining the input speed, input torque, output speed, output torque and hydraulic oil temperature of hydraulic mechanical transmission system;Establish transmission system theoretical leakage loss and mechanical friction loss model, build full working condition efficiency atlas;The partial derivative of efficiency value at any working point on efficiency atlas along torque and speed coordinate axis is calculated, and the efficiency sensitive area is determined;Calculate additional loss, when the working point falls into the efficiency sensitive area, the sensitive area compensates the loss;Theoretical leakage loss, mechanical friction loss and additional loss are superimposed to obtain comprehensive theoretical loss;The deviation between theoretical output power and measured output power is used to verify the efficiency of the transmission system.The application solves the problem that the existing model ignores the small change of working point, leading to the amplification of theoretical calculation error in key area.

Description

Technical Field

[0001] This invention belongs to the field of transmission efficiency verification, and in particular relates to a method and system for verifying the transmission efficiency of automotive hydraulic machinery. Background Technology

[0002] As a core component of hybrid electric vehicles, the energy transmission efficiency of the automotive hydraulic-mechanical transmission system determines the fuel economy and power performance of the entire vehicle. Currently, the industry generally adopts a combination of theoretical modeling and test bench testing to verify transmission efficiency. Conventional theoretical modeling methods establish a theoretical loss model of the transmission system by analyzing the internal energy loss mechanism, mainly considering the volumetric loss of the hydraulic system and the mechanical friction loss of the transmission system. By constructing a theoretical efficiency map covering all operating conditions and comparing it with bench test data, the efficiency characteristics are verified. Traditional models are mostly based on steady-state assumptions and fail to consider the additional transient energy losses generated by changes in the transmission system's speed and torque operating parameters. This causes the model's prediction accuracy to decrease when facing frequent start-stop and acceleration / deceleration transient conditions. In specific operating regions with low speed and low torque and low efficiency, the transmission system's efficiency is not only numerically low but also highly sensitive to small changes in the operating point. Existing models do not specifically identify and compensate for the loss patterns in the "efficiency-sensitive region," leading to amplified theoretical calculation errors in critical areas and affecting the reliability of efficiency verification. Summary of the Invention

[0003] This invention proposes a method for verifying the efficiency of automotive hydraulic mechanical transmission, which addresses the problem that existing models neglect minute variations in the operating point, leading to amplified theoretical calculation errors in critical regions. The method includes:

[0004] The input speed, input torque, output speed, output torque, and hydraulic oil temperature of the hydraulic mechanical transmission system under preset working conditions are obtained. Based on the working parameters and hydraulic oil temperature, a theoretical leakage loss and mechanical friction loss model of the transmission system taking into account the viscosity-temperature characteristics of the oil is established, and an efficiency spectrum for all working conditions is constructed.

[0005] Calculate the partial derivatives of the efficiency value along the torque and speed axes at any operating point on the efficiency graph, and define the region where the efficiency value is lower than a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold as the efficiency sensitive region;

[0006] Calculate additional losses, which include: additional transient losses calculated based on the time-domain rate of change of the input speed and input torque, and sensitive area compensation losses calculated based on a compensation function with the magnitude of the partial derivative of the efficiency at the operating point as the independent variable when the operating point falls into the efficiency sensitive area.

[0007] The theoretical leakage loss, mechanical friction loss, and additional loss are superimposed to obtain the comprehensive theoretical loss; the theoretical output power of the transmission system is calculated based on the comprehensive theoretical loss, and the efficiency of the transmission system is verified by using the deviation between the theoretical output power and the measured output power.

[0008] Furthermore, the present invention also relates to an automotive hydraulic mechanical transmission efficiency verification system, comprising the following modules:

[0009] A construction module is used to obtain the input speed, input torque, output speed, output torque and hydraulic oil temperature of the hydraulic mechanical transmission system under preset working conditions; based on the working parameters and hydraulic oil temperature, a theoretical leakage loss and mechanical friction loss model of the transmission system taking into account the viscosity-temperature characteristics of the oil is established, and a full-condition efficiency map is constructed.

[0010] The definition module is used to calculate the partial derivatives of the efficiency value along the torque and speed coordinate axes at any operating point on the efficiency graph, and to define the region where the efficiency value is lower than a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold as the efficiency sensitive region.

[0011] The calculation module is used to calculate additional losses, which include: additional transient losses calculated based on the time-domain change rate of the input speed and input torque, and sensitive area compensation losses calculated based on a compensation function with the magnitude of the partial derivative of the efficiency at the operating point as the independent variable when the operating point falls into the efficiency sensitive area.

[0012] The verification module is used to superimpose the theoretical leakage loss, mechanical friction loss and the additional loss to obtain the comprehensive theoretical loss; calculate the theoretical output power of the transmission system based on the comprehensive theoretical loss, and use the deviation between the theoretical output power and the measured output power to complete the verification of the transmission system efficiency.

[0013] Compared with existing technologies, this invention improves the reliability of efficiency verification for automotive hydraulic mechanical transmission systems by utilizing additional transient losses and sensitive zone compensation losses. A conventional theoretical loss model considering the viscosity-temperature characteristics of the oil is established, representing the additional energy loss during rapid changes in operating parameters by calculating the time-domain rate of change of input speed and torque. Simultaneously, this invention defines the concept of an efficiency-sensitive zone; for specific operating areas with low efficiency values ​​and sensitivity to changes in operating conditions, compensation losses are calculated using a compensation function, correcting the significant theoretical errors present in existing models within these areas. By superimposing the conventional losses with the two additional losses, a comprehensive theoretical loss model is constructed, ensuring that the theoretically calculated output power matches the measured results, thus providing reliable data support for transmission system optimization and control strategy development. Attached Figure Description

[0014] Figure 1A flowchart of the first embodiment;

[0015] Figure 2 This is a schematic diagram of the synchronous acquisition of multiple physical quantities in a transmission system.

[0016] Figure 3 This is a schematic diagram for verifying the efficiency model and analyzing the error of the transmission system. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use, and processing of related data must comply with relevant laws, regulations, and standards, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0018] In the first embodiment, the present invention proposes a method for verifying the efficiency of automotive hydraulic mechanical transmission, such as... Figure 1 ,include:

[0019] S1, obtain the input speed, input torque, output speed, output torque and hydraulic oil temperature of the hydraulic mechanical transmission system under preset working conditions; based on the working parameters and hydraulic oil temperature, establish a theoretical leakage loss and mechanical friction loss model of the transmission system that takes into account the viscosity-temperature characteristics of the oil, and construct an efficiency spectrum for all working conditions;

[0020] Specifically, a hydraulic-mechanical transmission system was built on a test bench, and speed sensors, torque sensors, and temperature sensors were installed. A preset vehicle driving cycle, such as the WLTC cycle, was run. Input shaft speed, input shaft torque, output shaft speed, output shaft torque, and hydraulic oil temperature at key components were synchronously collected and recorded at a sampling frequency of 10Hz throughout the entire operating cycle, forming multiple sets of time-series data, such as... Figure 2 .

[0021] Based on the collected hydraulic oil temperature, the kinematic viscosity of the hydraulic oil at the current temperature is calculated using the Roland viscosity-temperature equation or the Vogel viscosity-temperature equation. A theoretical leakage loss model is established, which expresses the leakage flow rate as a function of pressure difference (torque-related term) and speed-oil viscosity-related term. Simultaneously, a mechanical friction loss model is established, typically using the extended Stribeck model, which fits the friction torque as the sum of speed-related viscous friction, load-related Coulomb friction, and static friction terms. On a two-dimensional speed-torque coordinate grid covering the operating range, for each grid point, the theoretical leakage loss power and mechanical friction loss power are calculated using the above models; the sum of these two is the theoretical total loss. The theoretical output power is obtained by subtracting the theoretical total loss from the input power, and then divided by the input power to obtain the theoretical efficiency at that point. After traversing all grid points, a full-condition efficiency map is formed.

[0022] S2, calculate the partial derivatives of the efficiency value along the torque and speed axes at any operating point on the efficiency graph, and define the region where the efficiency value is lower than the first threshold and the magnitude of the partial derivative of the efficiency value is greater than the second threshold as the efficiency sensitive region;

[0023] Specifically, for each grid point on the efficiency graph, numerical methods such as the central difference method are used to calculate the partial derivatives of the efficiency value η with respect to torque T and speed n. and Calculate the magnitude of the efficiency gradient vector at that point, i.e. Set an efficiency threshold as the first threshold, for example, 85%, and then set a gradient magnitude threshold as the second threshold, for example, 0.05. When the efficiency value of a certain operating point is less than 85% and the efficiency gradient magnitude is greater than 0.05, then that point and its neighboring area are marked as an efficiency-sensitive region.

[0024] S3, Calculate additional losses, which include: additional transient losses calculated based on the time-domain change rate of the input speed and input torque, and sensitive area compensation losses calculated based on a compensation function with the magnitude of the partial derivative of the efficiency at the operating point as the independent variable when the operating point falls into the efficiency sensitive area;

[0025] Specifically, the additional transient loss is calculated by differentiating the acquired input speed and input torque time series data to obtain the speed change rate dn / dt and the torque change rate dT / dt. The additional transient loss power is modeled as a function of these two rates of change, for example... ,in and These are the calibration coefficients for the experiment. The calculation of the sensitive area compensation loss involves determining at each sampling time whether the current operating point is within the defined efficiency sensitive area. If so, the magnitude of the efficiency partial derivative at that point is used as the independent variable and substituted into a preset compensation function, such as a third-order polynomial function. , where x is the modulus of the efficiency partial derivative, and a, b, and c are calibration coefficients, thus calculating the compensation loss; if the operating point is not within the sensitive region, the compensation loss is zero.

[0026] S4. The theoretical leakage loss, mechanical friction loss and additional loss are superimposed to obtain the comprehensive theoretical loss; the theoretical output power of the transmission system is calculated based on the comprehensive theoretical loss, and the efficiency of the transmission system is verified by using the deviation between the theoretical output power and the measured output power.

[0027] Specifically, at each time sampling point of the operating condition data, the corresponding theoretical leakage loss and mechanical friction loss are calculated based on the input speed, input torque, and oil temperature at that moment. Simultaneously, additional transient losses are calculated based on the rate of change of speed and torque at that moment, and the operating point location at that moment is determined to determine whether sensitive area compensation losses need to be calculated and included. The power values ​​of the four or three of these losses are directly added together to obtain the comprehensive theoretical loss power at that moment.

[0028] At each time sampling point of the operating condition data, the measured input power at that moment (i.e., the product of input speed and input torque) is subtracted from the calculated comprehensive theoretical power loss to obtain the time series of the theoretical output power. Simultaneously, the measured output speed and output torque are multiplied to obtain the time series of the measured output power. By calculating the root mean square error or mean absolute percentage error of the two power curves throughout the entire operating condition period, if the error value is less than a preset target, such as less than 5%, the efficiency verification of the transmission system is passed. Figure 3 .

[0029] In an optional embodiment, establishing a theoretical leakage loss and mechanical friction loss model for the transmission system that takes into account the viscosity-temperature characteristics of the oil includes:

[0030] Based on the measured hydraulic oil temperature, the kinematic viscosity of the oil under the current operating conditions is calculated using the Vogel formula. Based on the kinematic viscosity, the theoretical leakage loss power is calculated using a function model related to the kinematic viscosity of the oil and the pressure difference. The mechanical friction loss is decomposed into churning loss related to the rotational speed and mechanical friction loss related to the load, and function models of the loss with respect to the rotational speed and torque are established respectively.

[0031] Specifically, the temperature of the hydraulic oil is measured to be 80°C by a temperature sensor. Substituting this temperature value into the preset Vogel viscosity-temperature relationship, the kinematic viscosity of the oil under the current operating conditions is calculated to be 15 mm² / s. Based on this viscosity value, and combined with the inlet and outlet pressure difference measured by a pressure sensor, for example 15 MPa, a pre-established function model related to viscosity and pressure difference is used to calculate the theoretical leakage power loss at this time as 1.5 kW.

[0032] The loss is decomposed into two parts: churning loss and load-related friction loss. For churning loss, a function model is established that is proportional to the cube of the rotational speed. Assuming the current rotational speed is 2500 rpm, the calculated churning loss power is 1.1 kW. For load-related friction loss, a function model is established that is proportional to the output torque. Assuming the current output torque is 200 Nm, the calculated loss power for this part is 1.3 kW. Adding the two parts of the loss together, the total mechanical friction loss power is 2.4 kW.

[0033] In an optional embodiment, defining the region where the efficiency value is lower than a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold as the efficiency-sensitive region includes:

[0034] Calculate the partial derivative of efficiency along torque and partial derivatives along rotational speed Through formula Calculate the modulus S of the partial derivative of the efficiency, where and The preset weighting coefficients will affect efficiency. The working area where the value is less than the first threshold and S is greater than the preset second threshold is determined as the efficiency-sensitive area.

[0035] Specifically, the first threshold for efficiency is set at 85%. For a specific operating point of the transmission system, for example, an input speed of 800 rpm and an input torque of 60 Nm, the measured efficiency is 82%. At this operating point, by referring to the universal efficiency characteristic diagram or performing numerical calculations, the partial derivative of efficiency along torque is found to be 0.2% per Nm, and the partial derivative of efficiency along speed is found to be 0.05% per rpm.

[0036] Set the weighting coefficients for torque and speed, for example... =1, The value is 30. The modulus S of the efficiency partial derivative is calculated using the weighted sum of squares and square root method. Substituting the above value, the calculated value of S is approximately 0.39. The calculated efficiency value and S value are compared with a preset threshold. Assume the preset second threshold is 0.30. Since the efficiency at this operating point is lower than the first threshold, and the modulus of the efficiency partial derivative is greater than the second threshold, this operating point is within the defined efficiency-sensitive region.

[0037] In an optional embodiment, the additional transient loss calculated based on the time-domain rate of change of the input speed and input torque includes:

[0038] Through formula Calculate the additional transient power loss; where, To add transient power loss, For input torque, Input speed, The input torque is the rate of change in the time domain. The input is the time-domain rate of change of rotational speed. and The preset transient loss coefficient is obtained through bench testing.

[0039] Specifically, to calculate the additional transient loss, a transient loss coefficient is obtained through bench testing calibration, for example, a set coefficient. The coefficient is 0.06. The value is 0.0015. Under a certain operating condition, assume that the controller issues a command within a 0.1s time interval to rapidly increase the input torque from 100 Nm to 120 Nm, while simultaneously decreasing the input speed from 2000 rpm to 1950 rpm.

[0040] Based on the above data, the absolute value of the time-domain change rate of the input torque is calculated to be 200 Nm / s, and the absolute value of the time-domain change rate of the input speed is 500 rpm / s. These data, along with the current input speed of 2000 rpm and preset coefficients, are substituted into the calculation model for the additional transient power loss. The total additional transient power loss is approximately 1.51 kW.

[0041] In an optional embodiment, the sensitive region compensation loss calculated based on a compensation function with the modulus of the partial derivative of the operating point efficiency as the independent variable includes:

[0042] When the operating point falls into the efficiency-sensitive region, it is achieved through a quadratic polynomial function. Calculate the power loss compensation in the sensitive area; where, To compensate for power loss in the sensitive area, S is the modulus of the partial derivative of the operating point efficiency, and a, b, and c are compensation coefficients determined by fitting experimental data.

[0043] Specifically, the compensation coefficients of the quadratic polynomial function are determined by fitting experimental data. For example, after fitting, the coefficients are determined to be 60, 120, and 30. When the current operating point is detected to fall into the predefined efficiency-sensitive zone, the calculation of this compensation loss is initiated. If the operating point does not fall into the efficiency-sensitive zone, the power meter for this compensation loss is zero.

[0044] Suppose an operating point is determined to be within the efficiency-sensitive region, and the modulus S of the efficiency partial derivative at that operating point has been calculated to be 0.8. Substituting the value of S into the function for calculating the power loss compensation in the sensitive region, we obtain a power loss compensation of 164.4 watts for that operating point.

[0045] In an optional embodiment, the step of superimposing the theoretical leakage loss, mechanical friction loss, and additional loss to obtain the comprehensive theoretical loss includes:

[0046] Through the power superposition formula Calculate the comprehensive theoretical power loss; where, To comprehensively consider theoretical power loss, For theoretical leakage power loss, Power loss due to mechanical friction To add transient power loss, To compensate for power loss in sensitive areas.

[0047] Specifically, assume that at a specific moment under a certain operating condition, all loss components have been calculated based on their respective models and real-time parameters. For example, the calculated theoretical leakage loss power is 1500 watts, and the mechanical friction loss power is 2400 watts.

[0048] Meanwhile, since the process is underway at this moment, the calculated additional transient power loss is 1512 watts. Furthermore, it has been determined that the operating point at this moment falls precisely within the efficiency-sensitive region, and the calculated sensitive region compensation power loss is 164 watts. A simple arithmetic summation of these four power losses yields a comprehensive theoretical power loss of approximately 5.58 kilowatts at this moment.

[0049] In an optional embodiment, the step of calculating the theoretical output power of the transmission system based on the comprehensive theoretical loss, and using the deviation between the theoretical output power and the measured output power to verify the efficiency of the transmission system, includes:

[0050] Through formula Calculate the theoretical output power, where The input power is calculated from the measured input speed and input torque; the theoretical output power is calculated. Compared with the measured output power relative deviation , Set a deviation threshold for successful verification; when If the deviation is less than the stated deviation threshold, the verification is considered successful.

[0051] Specifically, during verification, the input power is calculated based on the measured input parameters. For example, if the measured input speed is 2500 rpm and the input torque is 200 Nm, the calculated input power is approximately 52.36 kW. Simultaneously, based on the previously calculated comprehensive theoretical power loss under this operating condition, it is 5.58 kW. Therefore, the theoretical output power is the input power minus the comprehensive theoretical power loss, resulting in a theoretical output power of 46.78 kW.

[0052] The actual output power of the drive system is measured using a power sensor, assuming a measured value of 47.50 kW. The relative deviation between the theoretical and measured output power is calculated. The calculated relative deviation is approximately 1.52%. Since the preset verification pass deviation threshold is 5%, and the calculated deviation is less than this threshold, the verification passes.

[0053] In the second embodiment, the present invention also proposes an automotive hydraulic mechanical transmission efficiency verification system, comprising the following modules:

[0054] A construction module is used to obtain the input speed, input torque, output speed, output torque and hydraulic oil temperature of the hydraulic mechanical transmission system under preset working conditions; based on the working parameters and hydraulic oil temperature, a theoretical leakage loss and mechanical friction loss model of the transmission system taking into account the viscosity-temperature characteristics of the oil is established, and a full-condition efficiency map is constructed.

[0055] The definition module is used to calculate the partial derivatives of the efficiency value along the torque and speed coordinate axes at any operating point on the efficiency graph, and to define the region where the efficiency value is lower than a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold as the efficiency sensitive region.

[0056] The calculation module is used to calculate additional losses, which include: additional transient losses calculated based on the time-domain change rate of the input speed and input torque, and sensitive area compensation losses calculated based on a compensation function with the magnitude of the partial derivative of the efficiency at the operating point as the independent variable when the operating point falls into the efficiency sensitive area.

[0057] The verification module is used to superimpose the theoretical leakage loss, mechanical friction loss and the additional loss to obtain the comprehensive theoretical loss; calculate the theoretical output power of the transmission system based on the comprehensive theoretical loss, and use the deviation between the theoretical output power and the measured output power to complete the verification of the transmission system efficiency.

[0058] In an optional embodiment, establishing a theoretical leakage loss and mechanical friction loss model for the transmission system that takes into account the viscosity-temperature characteristics of the oil includes:

[0059] Based on the measured hydraulic oil temperature, the kinematic viscosity of the oil under the current operating conditions is calculated using the Vogel formula. Based on the kinematic viscosity, the theoretical leakage loss power is calculated using a function model related to the kinematic viscosity of the oil and the pressure difference. The mechanical friction loss is decomposed into churning loss related to the rotational speed and mechanical friction loss related to the load, and function models of the loss with respect to the rotational speed and torque are established respectively.

[0060] In an optional embodiment, defining the region where the efficiency value is lower than a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold as the efficiency-sensitive region includes:

[0061] Calculate the partial derivative of efficiency along torque and partial derivatives along rotational speed Through formula Calculate the modulus S of the partial derivative of the efficiency, where and The preset weighting coefficients will affect efficiency. The working area where the value is less than the first threshold and S is greater than the preset second threshold is determined as the efficiency-sensitive area.

[0062] In an optional embodiment, the additional transient loss calculated based on the time-domain rate of change of the input speed and input torque includes:

[0063] Through formula Calculate the additional transient power loss; where, To add transient power loss, For input torque, Input speed, The input torque is the rate of change in the time domain. The input is the time-domain rate of change of rotational speed. and The preset transient loss coefficient is obtained through bench testing.

[0064] In an optional embodiment, the sensitive region compensation loss calculated based on a compensation function with the modulus of the partial derivative of the operating point efficiency as the independent variable includes:

[0065] When the operating point falls into the efficiency-sensitive region, it is achieved through a quadratic polynomial function. Calculate the power loss compensation in the sensitive area; where, To compensate for power loss in the sensitive area, S is the modulus of the partial derivative of the operating point efficiency, and a, b, and c are compensation coefficients determined by fitting experimental data.

[0066] In an optional embodiment, the step of superimposing the theoretical leakage loss, mechanical friction loss, and additional loss to obtain the comprehensive theoretical loss includes:

[0067] Through the power superposition formula Calculate the comprehensive theoretical power loss; where, To comprehensively consider the theoretical power loss, For theoretical leakage power loss, Power loss due to mechanical friction To add transient power loss, To compensate for power loss in sensitive areas.

[0068] In an optional embodiment, the step of calculating the theoretical output power of the transmission system based on the comprehensive theoretical loss, and using the deviation between the theoretical output power and the measured output power to verify the efficiency of the transmission system, includes:

[0069] Through formula Calculate the theoretical output power, where The input power is calculated from the measured input speed and input torque; the theoretical output power is calculated. Compared with the measured output power relative deviation , Set a deviation threshold for successful verification; when If the deviation is less than the stated deviation threshold, the verification is considered successful.

[0070] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0071] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for verifying the efficiency of a hydraulic mechanical transmission of an automobile, characterized in that, Includes the following steps: The input speed, input torque, output speed, output torque, and hydraulic oil temperature of the hydraulic mechanical transmission system under preset working conditions are obtained. Based on the working parameters and hydraulic oil temperature, a theoretical leakage loss and mechanical friction loss model of the transmission system considering the viscosity-temperature characteristics of the oil is established, and an efficiency spectrum for all working conditions is constructed. Calculate the partial derivatives of the efficiency value along the torque and speed axes at any operating point on the efficiency graph, and define the region where the efficiency value is lower than a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold as the efficiency sensitive region; Calculate additional losses, which include: additional transient losses calculated based on the time-domain rate of change of the input speed and input torque, and sensitive area compensation losses calculated based on a compensation function with the magnitude of the partial derivative of the efficiency at the operating point as the independent variable when the operating point falls into the efficiency sensitive area. The theoretical leakage loss, mechanical friction loss, and additional loss are superimposed to obtain the comprehensive theoretical loss; the theoretical output power of the transmission system is calculated based on the comprehensive theoretical loss, and the efficiency of the transmission system is verified by using the deviation between the theoretical output power and the measured output power. The additional transient losses calculated based on the time-domain rate of change of the input speed and input torque include: The additional transient loss power is calculated by the formula ; wherein, is the additional transient loss power, is the input torque, is the input rotational speed, is the input torque time domain change rate, is the input rotational speed time domain change rate, and is a preset transient loss coefficient obtained through bench test calibration; The sensitive area compensation loss calculated based on the compensation function with the modulus of the partial derivative of the operating point efficiency as the independent variable includes: When the operating point falls into the efficiency-sensitive region, it is achieved through a quadratic polynomial function. Calculate the power loss compensation in the sensitive area; where, To compensate for power loss in the sensitive area, S is the modulus of the partial derivative of the operating point efficiency, and a, b, and c are compensation coefficients determined by fitting experimental data.

2. The method according to claim 1, characterized in that, The establishment of a theoretical leakage loss and mechanical friction loss model for the transmission system, taking into account the viscosity-temperature characteristics of the oil, includes: Based on the measured hydraulic oil temperature, the kinematic viscosity of the oil under the current operating conditions is calculated using the Vogel formula. Based on the kinematic viscosity, the theoretical leakage loss power is calculated using a function model related to the kinematic viscosity of the oil and the pressure difference. The mechanical friction loss is decomposed into churning loss related to the rotational speed and mechanical friction loss related to the load, and function models of the loss with respect to the rotational speed and torque are established respectively.

3. The method according to claim 1, characterized in that, The region defined as the efficiency-sensitive region, where the efficiency value is below a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold, includes: Calculate the partial derivative of efficiency along torque and partial derivatives along rotational speed Through formula Calculate the modulus S of the partial derivative of the efficiency, where and The preset weighting coefficients will affect efficiency. The working area where the value is less than the first threshold and S is greater than the preset second threshold is determined as the efficiency-sensitive area.

4. The method according to claim 1, characterized in that, The method of superimposing the theoretical leakage loss, mechanical friction loss, and additional loss to obtain the comprehensive theoretical loss includes: Through the power superposition formula Calculate the comprehensive theoretical power loss; where, To comprehensively consider theoretical power loss, For theoretical leakage power loss, Power loss due to mechanical friction To add transient power loss, To compensate for power loss in sensitive areas.

5. The method according to claim 1, characterized in that, The calculation of the theoretical output power of the transmission system based on the comprehensive theoretical loss, and the verification of the transmission system efficiency using the deviation between the theoretical output power and the measured output power, includes: Through formula Calculate the theoretical output power, where The input power is calculated from the measured input speed and input torque; the theoretical output power is calculated. Compared with the measured output power relative deviation , Set a deviation threshold for successful verification; when If the deviation is less than the stated deviation threshold, the verification is considered successful.

6. A system for verifying the efficiency of automotive hydraulic mechanical transmission, characterized in that, Includes the following modules: A construction module is used to obtain the input speed, input torque, output speed, output torque and hydraulic oil temperature working parameters of the hydraulic mechanical transmission system under preset working conditions; based on the working parameters and hydraulic oil temperature, a theoretical leakage loss and mechanical friction loss model of the transmission system taking into account the viscosity-temperature characteristics of the oil is established, and a full-condition efficiency map is constructed. The definition module is used to calculate the partial derivatives of the efficiency value along the torque and speed coordinate axes at any operating point on the efficiency graph, and to define the region where the efficiency value is lower than a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold as the efficiency sensitive region. The calculation module is used to calculate additional losses, which include: additional transient losses calculated based on the time-domain change rate of the input speed and input torque, and sensitive area compensation losses calculated based on a compensation function with the magnitude of the partial derivative of the efficiency at the operating point as the independent variable when the operating point falls into the efficiency sensitive area. The verification module is used to superimpose the theoretical leakage loss, mechanical friction loss and the additional loss to obtain the comprehensive theoretical loss; calculate the theoretical output power of the transmission system based on the comprehensive theoretical loss, and use the deviation between the theoretical output power and the measured output power to complete the verification of the transmission system efficiency; The additional transient losses calculated based on the time-domain rate of change of the input speed and input torque include: Through formula Calculate the additional transient power loss; where, To add transient power loss, For input torque, Input speed, The input torque is the rate of change in the time domain. The input is the time-domain rate of change of rotational speed. and The preset transient loss coefficient obtained through bench testing; The sensitive area compensation loss calculated based on the compensation function with the modulus of the partial derivative of the operating point efficiency as the independent variable includes: When the operating point falls into the efficiency-sensitive region, it is achieved through a quadratic polynomial function. Calculate the power loss compensation in the sensitive area; where, To compensate for power loss in the sensitive area, S is the modulus of the partial derivative of the operating point efficiency, and a, b, and c are compensation coefficients determined by fitting experimental data.

7. The system according to claim 6, characterized in that, The establishment of a theoretical leakage loss and mechanical friction loss model for the transmission system, taking into account the viscosity-temperature characteristics of the oil, includes: Based on the measured hydraulic oil temperature, the kinematic viscosity of the oil under the current operating conditions is calculated using the Vogel formula. Based on the kinematic viscosity, the theoretical leakage loss power is calculated using a function model related to the kinematic viscosity of the oil and the pressure difference. The mechanical friction loss is decomposed into churning loss related to the rotational speed and mechanical friction loss related to the load, and function models of the loss with respect to the rotational speed and torque are established respectively.

8. The system according to claim 6, characterized in that, The region defined as the efficiency-sensitive region, where the efficiency value is below a first threshold and the magnitude of the partial derivative of the efficiency value is greater than a second threshold, includes: Calculate the partial derivative of efficiency along torque and partial derivatives along rotational speed Through formula Calculate the modulus S of the partial derivative of the efficiency, where and The preset weighting coefficients will affect efficiency. The working area where the value is less than the first threshold and S is greater than the preset second threshold is determined as the efficiency-sensitive area.

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