A method for generating a bench test load spectrum based on a hybrid transmission

Abstract

The present invention relates to the technical field of vehicle testing, and specifically to a method for generating a bench test load spectrum based on a hybrid transmission, comprising the following steps: road condition definition, road route definition, road spectrum data acquisition, vehicle simulation, obtaining a reference cycle condition, damage calculation, and bench test load spectrum generation. This method uses a reference vehicle to collect actual road data, transfers the actual road data to the target vehicle through vehicle dynamics simulation of the target vehicle, calculates the damage under the life target for transmission-related failure modes, and generates a bench load spectrum by covering the damage target values of relevant failure modes. The load spectrum generated by this method can truly reflect the impact of the target vehicle model on the durability of the transmission during actual use, and solves the problem that it is difficult to define a reasonable and accurate durability test load spectrum due to the lack of a specification for generating a bench durability test load spectrum for hybrid transmissions.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle testing, and particularly to a method for generating a bench test load spectrum based on a hybrid transmission. Background Art

[0002] Before leaving the factory, vehicles must undergo various safety tests, such as transmission durability tests. Currently, there are national recommended standards or enterprise standards for bench durability tests of manual transmissions in China to verify the durability of transmissions. However, there are still no relevant standards for defining the bench test load spectrum of hybrid transmissions. Existing standards based on manual transmissions are difficult to meet the requirements of hybrid transmissions. The bench test load spectrum of existing manual transmissions usually requires a certain number of cycles for different gears and conducts durability assessment according to the maximum torque of each gear. However, for hybrid transmissions, it is necessary to consider the speed and torque balance between the engine and the motor, and it is necessary to improve the efficiency of the engine and the motor as much as possible according to the control strategy. Therefore, it is very difficult for hybrid transmissions to specify a certain number of cycles like manual transmissions. In addition, when conducting bench tests, it is necessary to consider the temperature rise of the motor, and it is also impossible to conduct bench tests completely according to the maximum torque.

[0003] Therefore, when developing hybrid transmissions, it is often difficult to accurately define the bench durability test load spectrum, which cannot ensure effective test verification of the transmission, resulting in design defects or over-design problems of components, restricting the independent development ability of hybrid transmissions.

[0004] Therefore, how to establish the development ability of the bench test load spectrum of hybrid transmissions is particularly crucial. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned problems of the prior art, and provides a method for generating a bench test load spectrum based on a hybrid transmission. By collecting actual road load information through road collection of a reference vehicle model, and transmitting the road load data to the target vehicle model through vehicle simulation based on the target vehicle model, the load information of the engine and the drive motor of the hybrid transmission can be obtained. Through damage calculation, it is ensured that the damage of each failure mode under the bench test load spectrum can meet the damage target value. Therefore, the generated load spectrum truly reflects the impact of the target vehicle model on the transmission durability during the entire life cycle in actual use, avoiding the problems of insufficient design or over-design of the transmission.

[0006] The above purpose is achieved through the following technical solutions:

[0007] A method for generating a bench test load spectrum based on a hybrid transmission includes.

[0008] Step 1 Road condition definition: Research the market information of target vehicles equipped with hybrid transmissions, and define the road distribution.

[0009] Step 2 Road route definition: According to the traffic characteristics in the road distribution described in Step 1, define the driving cities and driving routes as the road routes.

[0010] Step 3 Road spectrum data collection: Select a reference vehicle that matches the target vehicle, install and debug the test acquisition equipment on the reference vehicle, and collect the actual road load data according to the road routes described in Step 2.

[0011] Step 4 Vehicle simulation: Establish a dynamic simulation model of the target vehicle for loading the road load data described in Step 3.

[0012] Step 5 Obtain reference cycle conditions: Divide the road load data described in Step 3 into several typical reference conditions, and respectively perform simulations through the dynamic simulation model described in Step 4 to obtain the working data of the engine and drive motor in the hybrid transmission under each typical reference condition as the original road spectrum data of the hybrid transmission.

[0013] Step 6 Damage calculation: According to the original road spectrum data corresponding to each typical reference condition in Step 5, calculate the damage of the failure modes of all concerned parts in the hybrid transmission to obtain the damage target value.

[0014] Step 7 Generation of bench test load spectrum: Define the initial load spectrum conditions according to the boundary conditions of the hybrid transmission and the bench, and perform cyclic iterative optimization on the initial load spectrum condition parameters until the relative damage of each failure mode under the bench load spectrum meets the damage target value described in Step 6, thereby realizing the generation of the bench test load spectrum.

[0015] Furthermore, the market information of the target vehicle described in Step 1 includes market positioning, sales area, application scenarios, and transportation distance.

[0016] Furthermore, the vehicle simulation model of the target vehicle described in Step 4 includes an engine model, a transmission model, a motor model, a battery model, a vehicle model, and a controller model, and vehicle simulation is performed according to the control strategy of the hybrid transmission.

[0017] Furthermore, the damage calculation described in Step 6 needs to calculate the relative damage of relevant failure modes under each reference cycle condition, and extend each reference cycle condition to the design target of the hybrid transmission to define the damage target value of each failure mode including 95% of the reference cycle conditions as the damage target value for the generation of the bench test load spectrum.

[0018] Further, the design target of the hybrid transmission is 10 years or 600,000 kilometers.

[0019] Further, the relevant failure modes need to cover at least 95% of the damage of the reference cycle condition and not exceed 100% of the damage of the reference cycle condition under the bench test load spectrum.

[0020] Further, the definition of the initial load spectrum condition in step 7 needs to consider the allowable ranges of the engine and motor speeds and torques, the control capabilities of the bench for speed and torque, and the temperature rise effect of the motor.

[0021] Further, the bench load spectrum is generated by covering the damage target values of all concerned failure modes in the hybrid transmission, which can ensure that the generated bench load spectrum can reasonably represent the road spectrum.

[0022] Beneficial effects

[0023] A method for generating a bench test load spectrum based on a hybrid transmission provided by the present invention collects actual road data using a reference vehicle, transfers the actual road data to the target vehicle through vehicle dynamics simulation of the target vehicle, calculates the damage under the life target for the relevant failure modes of the transmission, and generates a bench load spectrum by covering the damage target values of the relevant failure modes. The load spectrum generated by this method can truly reflect the influence of the target vehicle model on the durability of the transmission during actual use, and solves the problem that it is difficult to define a reasonable and accurate durability test load spectrum due to the lack of a specification for generating the bench durability test load spectrum of the hybrid transmission. Description of the drawings

[0024] Figure 1 is a flowchart of a method for generating a bench test load spectrum based on a hybrid transmission according to the present invention;

[0025] Figure 2 is a schematic diagram of the gear bending fatigue failure principle of a method for generating a bench test load spectrum based on a hybrid transmission according to the present invention;

[0026] Figure 3 is a flowchart of generating a bench test load spectrum in a method for generating a bench test load spectrum based on a hybrid transmission according to the present invention. Detailed implementation manners

[0027] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0028] As Figure 1 shown, a method for generating a bench test load spectrum based on a hybrid transmission includes the following steps:

[0029] Step 1: Road condition definition. Conduct market research on target vehicles that can be equipped with a hybrid transmission, and define the road distribution. That is, comprehensively consider factors such as the market positioning, sales region, application scenario, and transportation distance of the target vehicle equipped with the developed product (i.e., the hybrid transmission), and define a reasonable road distribution, such as the proportion of urban, highway, and suburban roads throughout the life cycle.

[0030] Step 2: Road route definition. Define the driving city and driving route according to the traffic characteristics in the road distribution described in Step 1 as the road route. That is, select a suitable city as the data collection site based on factors such as the approximate vehicle speed and traffic characteristics of the target vehicle in road conditions such as urban, highway, and suburban roads, and further select a specific driving route as the road route for actual road spectrum data collection.

[0031] Step 3: Road spectrum data collection. Select a reference vehicle that matches the target vehicle, install and debug the test collection equipment on the reference vehicle, and collect actual road load data according to the road route described in Step 2. Specifically, usually in forward development, there is no physical product yet. Therefore, select a reference vehicle on the market that matches the target vehicle as the test vehicle for vehicle preparation, complete the installation and debugging of the test collection equipment, consider the influence of different load states such as vehicle unloaded, half-loaded, and fully-loaded, arrange the test collection plan according to the defined road route, and collect actual road data.

[0032] Step 4: Vehicle simulation. Establish a dynamic simulation model of the target vehicle for loading the road load data described in Step 3. Specifically, establish a vehicle dynamic simulation model of the target vehicle, including an engine model, a transmission model, a motor model, a battery model, a vehicle model, and a controller model. Use the collected road load data as the input of the vehicle model, conduct vehicle simulation based on the control strategy of the hybrid transmission, and transfer the collected road data to the target vehicle.

[0033] Step 5: Obtain the reference driving cycles. Divide the road load data described in Step 3 into several typical reference driving cycles, and perform simulations respectively through the dynamic simulation model described in Step 4 to obtain the working data of the engine and the drive motor in the hybrid transmission under each of the typical reference driving cycles, which are used as the original road spectrum data of the hybrid transmission. Specifically, divide the collected road data into several typical reference driving cycles (usually divided based on the parking state of the test vehicle. For example, in urban driving conditions, the vehicle stops every 0.5 - 1 hour; in suburban driving conditions, it stops every 1.5 - 2 hours; in highway driving conditions, it stops every 2 - 3 hours. The number of reference driving cycles depends on the test plan and the amount of data collected. If the number is too small, it cannot cover the actual needs of the target vehicle; if the number is too large, it will increase the development cycle and workload, and needs to be considered appropriately). Each reference driving cycle can be regarded as a kind of customer driving behavior. Through the vehicle simulation of the target vehicle model, information such as the rotational speed, torque, and gear position of the engine and the drive motor in the hybrid transmission under these reference driving cycles can be obtained, which are used as the original road spectrum data of the hybrid transmission;

[0034] Step 6: Damage calculation. Based on the original road spectrum data corresponding to each of the typical reference driving cycles in Step 5, perform damage calculations on the failure modes of all concerned parts in the hybrid transmission to obtain the damage target values (i.e., the damage target values of each failure mode). Specifically, conduct system analysis based on DFEMA (DFMEA is a reliability design and analysis technology focused on prevention. The application of this technology helps enterprises improve product quality, reduce costs, and shorten the R & D cycle) to define the transmission-related failure modes, establish the damage models of the failure modes through the analysis of the damage mechanism, perform damage calculations based on the typical reference driving cycles to obtain the relative damage of each failure mode under each reference driving cycle, extend each reference driving cycle to the design target of the hybrid transmission (such as 10 years or 600,000 kilometers), and define the damage target values of each failure mode including 95% of the reference driving cycles (i.e., including 95% of the customer driving behaviors, and generally in the industry, this proportion is considered to be able to meet the vehicle requirements), which are used as the damage target values for generating the bench test load spectrum. This part of the process is as shown Figure 3 on the left side in;

[0035] Step 7: Generate the bench test load spectrum. Define the initial load spectrum conditions according to the boundary conditions of the hybrid transmission and the bench, and perform cyclic iterative optimization on the parameters of the initial load spectrum conditions until the relative damage of each failure mode under the bench load spectrum meets the damage target values described in Step 6, thereby realizing the generation of the bench test load spectrum. Specifically, as shown Figure 3The following shows a method for generating a test bench load spectrum. Based on the results of damage calculation in Step 6, considering the boundary conditions of the transmission and the test bench, factors such as the allowable ranges of engine and motor speeds and torques, the control capabilities of the test bench for speed and torque, and the temperature rise effect of the motor, the initial conditions of the test bench load spectrum are defined. The relative damage of each failure mode under the initial conditions is calculated and compared with the corresponding damage target values. By iteratively optimizing the torque, speed, and time variables of the initial conditions until the relative damage of each failure mode under the test bench load spectrum can meet the corresponding damage target values, the final test bench test load spectrum is obtained.

[0036] The following takes the gear bending fatigue failure mode as an example to illustrate the process of damage calculation. The damage calculation principles for other failure modes are similar.

[0037] As Figure 2 shown, gear bending fatigue failure is caused by the gear root being subjected to bending stress during operation. Under the repeated action of the bending stress, damage is formed and accumulated, ultimately resulting in fatigue failure of the gear root fracture.

[0038] The principle of gear bending fatigue failure can be described by the following formula:

[0039]

[0040]

[0041] Among them, is the stress amplitude, C f is the fatigue coefficient, N is the number of load cycles, N E is the number of load cycles at failure, b f is the fatigue index. The fatigue index is obtained from the material SN curve (the SN curve is a curve with the fatigue strength of the material standard specimen as the ordinate and the logarithm of the fatigue life IgN as the abscissa, representing the relationship between the fatigue strength and fatigue life of the standard specimen under a certain cyclic characteristic, also known as the stress-life curve), D is the total damage, and i is the incremental step.

[0042] According to the above formula, the gear bending fatigue damage calculation formula can be obtained as follows:

[0043]

[0044] Because it is also necessary to calculate the damage of each failure mode for the generated test bench load spectrum conditions, and the evaluation index RAD is obtained through the ratio of the damage of each failure mode under the test bench load spectrum conditions to the damage target value, the constant is used as a common divisor and will be reduced. There is no need to determine the specific value. We define the damage result without considering the constant as the relative damage. Therefore, the gear bending fatigue damage calculation formula can be processed as follows:

[0045]

[0046]

[0047]

[0048]

[0049] Among them, D i，rel is the relative damage increment, D rel is the relative damage, n i is the rotational speed at a certain moment, Δt is the time interval, is the damage rate, t tol is the time corresponding to the reference cycle condition.

[0050] According to the damage calculation formula corresponding to the failure mode, damage calculation is carried out for the reference cycle conditions collected from the road. For the reference cycle conditions, after the whole vehicle simulation, the torque-time curve and rotational speed-time curve of the hybrid transmission engine and drive motor corresponding to each reference cycle condition can be obtained, that is, T engine (t), n engine (t), T EM (t), n EM (t). T engine (t), T EM (t) curve, each moment point on it is regarded as a working condition point (select a suitable time interval for calculation, such as 0.1 second). According to its torque value, the corresponding gear bending stress can be obtained, and then the bending stress-time curve corresponding to the gear under this reference cycle condition can be obtained (the gear stress result can be accurately obtained according to the transmission system simulation software, and data processing can be carried out by generating a stress nephogram through three-dimensional interpolation), that is, σ(t). Similarly, according to n engine (t) and n EM (t), the rotational speed-time curve n(t) of the gear can be obtained.

[0051] For the σ(t), n(t) curves at the same time interval, substituting the bending stress and rotational speed data corresponding to these moment points into the above gear bending fatigue damage calculation formula, the relative damage of the gear under this reference cycle condition can be obtained. Dividing the relative damage by the time of this reference cycle condition can obtain the relative damage rate, which refers to the damage corresponding to each hour of this failure mode under this reference cycle condition. Calculating the relative damage rate is mainly to facilitate the next calculation of the total relative damage when the reference cycle condition is extended to the life cycle.

[0052] Assume that the service life of the transmission is 600,000 km. According to the average vehicle speed of this reference cycle condition (obtained from test data), the time required to extend this reference cycle condition to 600,000 km is obtained. Multiplying this time by the relative damage rate can obtain the total relative damage of the failure mode based on this reference cycle condition extended to the entire service life.

[0053] Suppose there are n groups of reference cycle conditions, and n groups of relative damage values will be obtained. Define the damage target value of this failure mode as the damage value that can cover 95% of the reference cycle conditions. When generating the bench test load spectrum, it is necessary to cover the damage target values of each failure mode.

[0054] Figure 3 For the method of generating the bench load spectrum, based on the results of damage calculation, according to the boundary conditions of the transmission and the test bench, considering factors such as the allowable range of engine and motor speeds and torques, the control ability of the bench for speed and torque, and the temperature rise effect of the motor, define the initial conditions of the bench load spectrum, calculate the relative damage of each failure mode under the initial conditions, and compare it with the corresponding damage target value. Through iterative optimization of the torque, speed, and time variables of the initial conditions, until the relative damage of each failure mode under the bench load spectrum can meet the corresponding damage target value, thereby obtaining the final bench test load spectrum;

[0055]

[0056] Where D test is the relative damage corresponding to the bench test condition, and D ref is the damage target value. The generated bench load spectrum is evaluated by the RAD index to see if it meets the requirements. If not, the initial condition parameters are cyclically optimized until the conditions are met, thereby realizing the generation of the bench test load spectrum.

[0057] Where RAD refers to the relative cumulative damage, which is the ratio of the relative damage of each failure mode under the bench load spectrum to the damage target value, used to evaluate the relative magnitude of the damage caused by the converted bench load spectrum to the failure mode and the damage caused by the road spectrum;

[0058] 1 ≤ RAD ≤ max

[0059] The above formula is the requirement for RAD. When it is equal to 1, it means that the damage caused by the generated bench load spectrum is equivalent to the damage target value. max is the ratio of the relative damage including 100% of the customer driving behaviors to the relative damage including 95% of the customer driving behaviors. Therefore, calculate the RAD value for each failure mode so that the RAD value is between the lower limit and the upper limit, which can ensure that the failure modes of the parts of interest can meet the fatigue damage caused by at least 95% of the customer driving behaviors under the assessment of the bench load spectrum, and at the same time will not cause over-assessment. It should be noted that if a few failure modes cannot meet the requirements or in order to meet them will lead to too long bench test time, it can be considered to conduct the assessment through single-body tests.

[0060] As described above, it is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of by those who are familiar with the technology within the technical scope disclosed by the present invention are covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope protected by the claims.

Claims

1. A method for generating a bench test load spectrum based on a hybrid transmission, characterized in that Including: Step 1: Definition of road conditions. Conduct research on the market information of target vehicles equipped with hybrid transmissions, and define the road distribution. Step 2: Definition of road routes. Define the driving cities and driving routes according to the traffic characteristics in the road distribution described in Step 1 as the road routes. Step 3: Collection of road spectrum data. Select a reference vehicle that matches the target vehicle, install and debug the test acquisition equipment on the reference vehicle, and collect the actual road load data according to the road routes described in Step 2. Step 4: Vehicle simulation. Establish a dynamic simulation model of the target vehicle for loading the road load data in Step 3. Step 5: Obtain typical reference conditions. Divide the road load data in Step 3 into several typical reference conditions, and conduct simulations respectively through the dynamic simulation model in Step 4 to obtain the working data of the engine and drive motor in the hybrid transmission under each typical reference condition as the original road spectrum data of the hybrid transmission. Step 6: Damage calculation. According to the original road spectrum data corresponding to each typical reference condition in Step 5, calculate the damage of the failure modes of all key parts in the hybrid transmission to obtain the damage target value. Step 7: Generation of bench test load spectrum. Define the initial load spectrum conditions according to the boundary conditions of the hybrid transmission and the bench, and perform cyclic iterative optimization on the initial load spectrum condition parameters until the relative damage of each failure mode under the bench load spectrum meets the damage target value in Step 6, thereby realizing the generation of the bench test load spectrum. The damage calculation in Step 6 needs to calculate the relative damage of the relevant failure modes under each typical reference condition, and extend each typical reference condition to the design target of the hybrid transmission to define the damage target value of each failure mode including 95% of the typical reference conditions as the damage target value for the generation of the bench test load spectrum. The damage of the relevant failure modes under the bench test load spectrum needs to cover at least 95% of the damage of the typical reference conditions and not exceed 100% of the damage of the typical reference conditions.

2. The method for generating a bench test load spectrum based on a hybrid transmission according to claim 1, wherein The market information of the target vehicle in Step 1 includes market positioning, sales area, application scenarios, and transportation distance.

3. A method for generating a bench test load spectrum based on a hybrid transmission according to claim 1, characterized in that The vehicle simulation model of the target vehicle in Step 4 includes an engine model, a transmission model, a motor model, a battery model, a vehicle model, and a controller model, and conducts vehicle simulation according to the control strategy of the hybrid transmission.

4. A method for generating a bench test load spectrum based on a hybrid transmission according to claim 1, characterized in that, The design target of the hybrid transmission is 10 years or 600,000 kilometers.

5. A method for generating a bench test load spectrum based on a hybrid transmission according to claim 1, wherein The definition of the initial load spectrum conditions in Step 7 needs to consider the allowable ranges of the engine and motor speeds and torques, the control capabilities of the bench for speed and torque, and the temperature rise effect of the motor.

6. A method for generating a bench test load spectrum based on a hybrid transmission according to claim 1, characterized in that, The method of generating the bench test load spectrum in Step 7 is obtained by covering the damage target values of all concerned failure modes in the hybrid transmission, which can ensure that the generated bench load spectrum can reasonably represent the road spectrum.

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